ALBERT

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Water Resources, Volume 131〈/p〉 〈p〉Author(s): Maria Maza, Javier L. Lara, Iñigo J. Losada〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉With the aim of better understand and parameterize the physical processes involved in flow-mangrove interaction, wave attenuation and drag forces along a 1:6 scale fringe 〈em〉Rhizophora〈/em〉 mangrove forest are studied experimentally. The 26 m long forest is composed by 135 models built reproducing mature 〈em〉Rhizophora〈/em〉 mangrove trees with 24 prop roots. Hydrodynamic conditions are scaled using Froude similarity based on values collected in nature. Regular and random waves are tested and three water depths are considered to account for the influence of variable mangroves frontal area along the vertical. Wave decay analysis highlights the importance of considering the effect of flume bottom and walls friction. Neglecting this additional damping can result in a high overestimation of the mangrove dissipation capacity. It is proven that water depth, and the associated mangroves frontal area, and wave height are the dominant variables driving wave attenuation for short waves. The slope seaward the forest induces wave shoaling leading to an increase of wave steepness. Accordingly, the exerted forces on the mangroves also increase along the first 3–4 m of the forest. Smaller forces are recorded further into the forest where wave decay formulations fit well to the recorded wave heights. In general, analytical drag forces obtained by using mangrove trees induced damping coefficients compare well to the forces measured within the forest. However, analytical drag forces can lead to overestimations of up to double in some cases. This aspect is very important when experimental results are used to feed numerical or analytical models based on the introduction of a drag force in the momentum equation. These models should be calibrated using, whenever possible, direct force measurements.〈/p〉〈/div〉

Description: 〈p〉Publication date: August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Biomass and Bioenergy, Volume 127〈/p〉 〈p〉Author(s): Yunna Wu, Yudong Yan, Shiman Wang, Fangtong Liu, Chuanbo Xu, Ting Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Location decision of agroforestry biomass cogeneration (AFBC) project belongs to macro site selection, which is an important task in the pre-project planning stage and directly affects the subsequent economic benefits of the project. However, there are few studies on the site selection of biomass cogeneration projects. And the existing research equates the site selection of biomass cogeneration projects with that of biomass power generation projects, without distinguishing between the two, which is unreasonable. Therefore, in order to solve the above problems, this paper proposes a location decision framework for the AFBC project based on multi-attribute decision-making (MADM) method. Firstly, a special evaluation criteria system is constructed for the location decision of the AFBC project, which includes three main criteria consisting of social needs, resource supply and economic factors, as well as 11 sub-criteria. Then, considering the strong independence of the criteria in the AFBC project location decision, the subjective and objective weights are determined by best-worst method (BWM) and entropy method respectively. And then multiplicative integration method is applied to calculate the comprehensive weights of the criteria to ensure the rationality. Afterwards, Multi-Attributive Border Approximation area Comparison (MABAC) method is used to rank alternative locations and select the optimal. Finally, a case from Hebei Province of China is illustrated to verify the feasibility and validity of this location decision framework in practical applications.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 4 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Cretaceous Research〈/p〉 〈p〉Author(s): Guo Chen, Wenzhe Gang, Haizhong Tang, Gang Gao, Ning Wang, Lan Liu, Shangru Yang, Yifan Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Lower Cretaceous Xiagou Formation in Qingxi Sag consists of more than 1000 m of lacustrine sediments, including dolomitic mudstone/argillaceous dolomite and sandstone/mudstone, which is considered to be the most important source rock in the Jiuquan Basin. Power spectra, evolutionary fast Fourier transform (FFT), and correlation coefficient analyses of the gamma-ray (GR) series from four wells, including Liu 8 well, Long 14 well, Q2-36 well and Liu 9 well, through the Xiagou Formation reveal strong astronomical signals of long eccentricity (405 kyr), short eccentricity (100 kyr), obliquity (37 kyr) and precession (22 kyr). These provide an excellent opportunity to establish a floating astronomical time scales (ATS) then to determine variations in the sediment accumulation rate (SAR). Based on the floating ATS of the Xiagou Formation, the Xiagou Formation covers a 10.3 myr period depositional duration, and depositional duration of three members in the Xiagou Formation are 3.5 ± 0.1 myr, 3.1 ± 0.1 myr and 3.65 ± 0.15 myr, respectively. The high-resolution SARs of the Xiagou Formation vary from 8.5 cm/kyr to 19.8 cm/kyr. The different lithologies in the Xiagou Formation exhibit the same variation tendency in SARs, but the mechanisms of astronomical forcing that affect the SARs are different. In addition, the correlation between total organic carbon (TOC) and SARs can be used to investigate the impact of the SAR on organic matter abundance and conclude that relatively high SAR can protect organic matter and prevent oxidation, but rapid SAR can also dilute organic matter abundance of source rock.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Marine Systems, Volume 198〈/p〉 〈p〉Author(s): 〈/p〉

Description: 〈p〉Publication date: March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Climate Change Research, Volume 10, Issue 1〈/p〉 〈p〉Author(s): Rui-Qiang YUAN, Xin TAO, Xiang-Long YANG〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This study reviewed the urban passenger transportation (UPT) development of seven typical cities in China from 2000 to 2014, estimated the UPT CO〈sub〉2〈/sub〉 emission, analyzed the structure, and discussed the main factors of UPT CO〈sub〉2〈/sub〉 emission. Results showed that increases of GDP, population, and UPT scale of the cities have speeded up. The most significant development of UPT is that the growth of private vehicles is greatly faster than that of public transportation. The total and per-capita UPT CO〈sub〉2〈/sub〉 emissions both increased. The share of private vehicles emission to total UPT CO〈sub〉2〈/sub〉 emission has increased, with the share in range of 65%–88% in 2014, exponentially leading to the increases of total and per-capita UPT CO〈sub〉2〈/sub〉 emission. Although UPT CO〈sub〉2〈/sub〉 emission structure with more share of public transportation would slow down the UPT CO〈sub〉2〈/sub〉 emission increase, private vehicle CO〈sub〉2〈/sub〉 emission is recognized as the dominated driving factor. Contributions of driving factors, such as GDP, population, private vehicle CO〈sub〉2〈/sub〉 emissions, to UPT CO〈sub〉2〈/sub〉 emission are different among the cities. Private vehicle CO〈sub〉2〈/sub〉 emission is the dominated factor for UPT CO〈sub〉2〈/sub〉 emission in Beijing and Taiyuan. Besides private vehicle CO〈sub〉2〈/sub〉 emission, GDP also plays an important role in UPT CO〈sub〉2〈/sub〉 emissions of Chengdu, Shanghai, Guangzhou, and Urumqi. Contributions of private vehicle CO〈sub〉2〈/sub〉 emission and GDP to UPT CO〈sub〉2〈/sub〉 emission are almost same in Xi'an.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Climate Change Research, Volume 10, Issue 1〈/p〉 〈p〉Author(s): Shuai Gao, Meng-Yu Li, Mao-Sheng Duan, Can Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Article 6 of the Paris Agreement introduces two international carbon markets that receive extensive attention and are expected to play an important role in the post-2020 climate regime. Three key elements of the two international carbon markets, including the scope, the types of tradable units and the governance, are identified, as the basis to clarify their basic forms. Based on the key issues and their different designs identified in negotiations, this study analyzes the contributions and challenges for China to participate in international carbon markets. Considering the inherent needs of climate change mitigation, climate finance, the development of a green “Belt and Road” and the China South–South cooperation in climate change, along with the existing domestic capacities on market mechanisms, this study puts forward the short-, medium- and long-term development prospects of the two international carbon markets.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: June 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Climate Change Research, Volume 10, Issue 2〈/p〉 〈p〉Author(s): Shi-Chang Kang, Xiaoming Wang〈/p〉

Description: 〈p〉Publication date: June 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Climate Change Research, Volume 10, Issue 2〈/p〉 〈p〉Author(s): Shi-Jin WANG, Lan-Yue ZHOU〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Glacier tourism is an important type of nature-based tourism with great global potential. However, glacial landscapes and environments are seriously affected by global warming. This study used a scoping review method to explore integrated impacts of climate change on glaciers from the academic literature. All reviewed literature included a wide range of both research and non-research-based data or information. All literature was reviewed by summarizing findings of relevant research. It showed that climate warming has led to rapid melting and retreat of glacier landscapes, which has resulted in a huge impact on economic and social systems. The findings indicated that some glacial landscapes are declining in aesthetics or attractiveness while some landscapes face the prospect of sustained decline or even disappearance. This not only affects glacial cultural appreciation or mountain residents' beliefs, but increases the difficulty in entering and experiencing glaciers. Some points of tourism even face the risk of glacial disaster. Rapid glacial retreat or even disappearance will bring a loss of tourism revenues. At present, it is urgent to anticipate and adapt to these integrated impacts. In short, this study provides a general review of the impacts of climate change on glacial tourism and also some references for the adaptation of future glacial tourism to climate change.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: June 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Climate Change Research, Volume 10, Issue 2〈/p〉 〈p〉Author(s): Shu-Hua Yi, Bo Xiang, Bao-Ping Meng, Xiao-Dong Wu, Yong-Jian Ding〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Alpine grassland occupies two-thirds of the Qinghai-Tibetan Plateau (QTP). It is vital to project changes of this vulnerable ecosystem under different climate change scenarios before taking any mitigation or adaptation measures. In this study, we used a process-based ecosystem model, driven with output from global circulation models under different Representative Concentration Pathways (RCPs), to project the carbon dynamics of alpine grassland. The results showed the following: 1) Vegetation carbon (C) on the QTP increased by 22–38 gC m〈sup〉−2〈/sup〉 during periods of 1.5 and 2 °C warming under different RCPs when compared to the baseline period (1981–2006), while soil C increased by 85–122 gC m〈sup〉−2〈/sup〉. 2) The increases of vegetation C and soil C at the period of 1.5 °C warming were about 15 gC m〈sup〉−2〈/sup〉 and 40 gC m〈sup〉−2〈/sup〉 smaller than those at the period of 2 °C warming, respectively; increase of C was greater for alpine meadow than for alpine steppe. 3) Precipitation, radiation, and permafrost changed significantly and showed heterogeneous spatial patterns, and caused heterogeneous response of C dynamics. For alpine meadow in regions transformed from permafrost to seasonally frozen soil with medium annual precipitation (200–400 mm), vegetation C and net primary production decreased by 18.7 gC m〈sup〉−2〈/sup〉 and 3.1 gC m〈sup〉−2〈/sup〉 per year during 2 °C warming under RCP 4.5, respectively. This decrease can be attributed to the disappearing impermeable permafrost. Different from previous studies that indicated an unfavorable response of alpine grassland to climate warming, this study showed a relatively favorable response, which is mainly attributed to CO〈sub〉2〈/sub〉 fertilization.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: June 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Climate Change Research, Volume 10, Issue 2〈/p〉 〈p〉Author(s): Yang Yang, Xue-Jiao Wu, Shi-Wei Liu, Cun-De Xiao, Xiaoming Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Snow cover provides essential resources and services for human well-being and socioeconomic development in arid areas. With the change in snow cover resulting from climate change that causes concerns about its consequences, there is a pressing need to analyze and understand its impact on the benefits that people has been enjoying from snow cover. These can be derived from the variation in economic value of snow services, that are demanded to meet socioeconomic activities. Based on the average decline mass of snow cover from 1979 to 2016 in Irtysh River Basin, we use the approach by applying economic evaluation to estimate the annual value loss of snow services. Considering the decreasing trend of snow cover mass at rates of −10.2 Mt per year (〈em〉p〈/em〉 〈 0.05) or 0.3% per year, the annual service loss in Irtysh River Basin is currently worth up to CN¥196 million. Within it, the service loss of climate regulation contributes the most, or about CN¥84.7 million. The loss of freshwater service contributes only about 19%, implying that there would be a significant underestimation of service loss if only water supply would be considered. This may cause biased decision-making when we are facing the challenges of declining services as a result of climate change, impacting on the balancing of socioeconomic development and environment conservation for the sustainability over a long term.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: June 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Climate Change Research, Volume 10, Issue 2〈/p〉 〈p〉Author(s): Xiaoming Wang, Shi-Wei Liu, Jing-Lin Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉While the cryosphere may bring in adverse impacts on natural and built environment, it may also provide benefits resulting from cryosphere services. By looking into the effect of the cryosphere on human-being, the study develops a unified approach in the analysis of cryospheric risks and services, with one focusing on the adverse impacts by cryospheric hazards and another emphasizing on the benefits that people can obtain from the natural capitals in the cryosphere. Meanwhile, climate change could further alter and complicate the roles of the cryosphere, not only by the changes in risks to cryospheric hazards, but also the changes in services that could potentially add more risks. The study further proposed a risk-based approach for the development of climate adaptation in the cryosphere. The approach essentially takes options to reduce exposure and vulnerability of societies to cryospheric hazards, and to better manage natural capitals and demands together with enhancing utility of the cryosphere, so as to maintain the benefit of cryosphere services in a sustainable way. The study further addresses the role of cryosphere services in strengthening sustainable development in terms of its relation with the sustainable development goals (SDGs), and provides a preliminary results on how the services contributes to SDGs. Overall, the approach developed in this study creates a new way to comprehensively assess the effect of cryosphere changes on our society and identify measures to maximize the benefit while minimizing the risk in relation to the cryosphere.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Climate Change Research, Volume 9, Issue 4〈/p〉 〈p〉Author(s): Hong YIN, Ying SUN〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Based on the homogenized daily data in 2419 stations in China from 1961 to 2017, we calculated 26 extreme temperature and precipitation indices as defined by the Expert Team on Climate Change Detection and Indices (ETCCDI), and analyzed the characteristics of extreme temperature and precipitation in China in 2017. For China average, all the high temperature indices were above the 30-year average of 1961–1990 and the extreme low temperature indices are lower than their corresponding 1961–1990 average. The most extreme precipitations in 2017 were within the range of one standard deviation of precipitation change during 1961–2017. The annual minima of daily maximum temperature (TXn) and daily minimum temperature (TNn) reached the recorded highest level, while the number of cold nights (TN10p), cold days (TX10p), and cold spell duration index (CSDI) reached the recorded lowest values. Some indices were ranked at the second or third place since 1961, including annual maxima of daily maximum temperature (TXx) and of daily minimum temperature (TNx), warm nights (TN90p), frost days (FD), icing days (ID), summer days (SU), and growing season length (GSL). Other extreme temperature indices were ranked in the top 10 since 1961. Meanwhile, for the averaged extreme precipitation indices in China, seven out of the 10 extreme precipitation indices in 2017 were located within the range of one standard deviation, indicating a normal situation for extreme precipitation in 2017.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Climate Change Research, Volume 9, Issue 4〈/p〉 〈p〉Author(s): Xi-Liu YUE, Qing-Xian GAO〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, we conducted a literature review of relevant research and then statistically analyzed global greenhouse gas (GHG) emissions from natural systems, including forest fires, oceans, wetlands, permafrost, mud volcanoes, volcanoes, and earthquakes. Drawing on the Global Carbon Project (GCP) report, we also summarized the global anthropogenic GHG emissions. We then compared the global annual GHG emissions from natural systems with those generated by human activity. The results indicate that the global annual GHG emissions range approximately between 54.33 and 75.50 Gt CO〈sub〉2〈/sub〉-eq, of which natural emissions account for 18.13–39.30 Gt CO〈sub〉2〈/sub〉-eq, with the most likely value being approximately 29.07 Gt CO〈sub〉2〈/sub〉-eq. According to the GCP report, the global anthropogenic emissions have increased from 22 Gt CO〈sub〉2〈/sub〉-eq in 1990 to 36.2 Gt CO〈sub〉2〈/sub〉-eq in 2016. The amounts of natural and anthropogenic GHGs emissions are roughly of the same order of magnitude. Anthropogenic emissions account for approximately 55.46% of the total global GHGs emissions (2016 value), i.e., the ratio of natural to anthropogenic emissions is approximately 0.8. In addition, the annual amount of GHGs absorbed by Earth systems (ocean and terrestrial ecosystems) ranges between approximately 14.4 Gt CO〈sub〉2〈/sub〉-eq and 26.5 Gt CO〈sub〉2〈/sub〉-eq, with natural system GHG emissions and sinks also having roughly the same order of magnitude. This finding indicates that the GHG emissions generated by human activity exert extra pressure on what is otherwise a self-balancing Earth system.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 3 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Rock Mechanics and Geotechnical Engineering〈/p〉 〈p〉Author(s): Lamine Boumaiza, Ali Saeidi, Marco Quirion〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Among the methods used for evaluating the potential hydraulic erodibility of rock, the most common methods are those based on the correlation between the force of flowing water and the capacity of a rock to resist erosion, such as Annandale's and Pells' methods. The capacity of a rock to resist erosion is evaluated based on erodibility indices that are determined from specific geomechanical parameters of a rock mass. These indices include unconfined compressive strength (UCS) of rock, rock block size, joint shear strength, a block's shape and orientation relative to the direction of flow, joint openings, and the nature of the surface to be potentially eroded. However, it is difficult to determine the relevant geomechanical parameters for evaluating the hydraulic erodibility of rock. The assessment of eroded unlined spillways of dams has shown that the capacity of a rock to resist erosion is not accurately evaluated. Using more than 100 case studies, we develop a method to determine the relevant geomechanical parameters for evaluating the hydraulic erodibility of rock in unlined spillways. The UCS of rock is found not to be a relevant parameter for evaluating the hydraulic erodibility of rock. On the other hand, we find that the use of three-dimensional (3D) block volume measurements, instead of the block size factor used in Annandale's method, improves the rock block size estimation. Furthermore, the parameter representing the effect of a rock block's shape and orientation relative to the direction of flow, as considered in Pells' method, is more accurate than the parameter adopted by Annandale's method.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: June 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Climate Change Research, Volume 10, Issue 2〈/p〉 〈p〉Author(s): Xiao-Ming Xu, Qing-Bai Wu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Climate change has a substantial impact on infrastructures in the permafrost on the Qinghai-Tibetan Plateau (QTP). In this study, the mean annual ground temperature (MAGT) and permafrost evolution were investigated in both the historical (1950–2005) and projected (2006–2099) periods. Then, an allowable bearing capacity model was used to discuss the allowable bearing capacity change on the QTP. Results show that the MAGT increased by 0.36 °C during 1950–2005. The MAGT will increase by 0.40 (RCP2.6), 0.79 (RCP4.5), 1.07 (RCP6.0), and 1.75 (RCP8.5) °C during 2006–2099. In addition, the permafrost area has decreased by 0.195 × 10〈sup〉6〈/sup〉 km〈sup〉2〈/sup〉 in 1950–2005. The permafrost area will decrease by 0.232 × 10〈sup〉6〈/sup〉 (RCP2.6), 0.468 × 10〈sup〉6〈/sup〉 (RCP4.5), 0.564 × 10〈sup〉6〈/sup〉 (RCP6.0), and 0.803 × 10〈sup〉6〈/sup〉 (RCP8.5) km〈sup〉2〈/sup〉 during 2006–2099. With the degradation of permafrost, the allowable bearing capacity in permafrost zones would decrease accordingly. The decreasing trend is 6 kPa per 10 years in 1950–2005, and will be 0.6 (RCP2.6), 5 (RCP4.5), 7 (RCP6.0), and 11 (RCP8.5) kPa per 10 years during 2006–2099. The most remarkable trend would be observed under RCP8.5. Meanwhile, some scientific advices for the design, construction, operation and maintenance of permafrost engineering in the context of climate change were provided.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Climate Change Research, Volume 10, Issue 1〈/p〉 〈p〉Author(s): Vilas Nitivattananon, Sirinapha Srinonil〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Coastal areas in the eastern sub-region of Thailand, a popular destination in Southeast Asia, are facing rapid tourism-related urbanization and associated consequences of environment and climate change (CC). Thus, this study aims to analyze the relationships between tourism, coastal areas, the environment, and CC in the context of tourism urbanization; and recommend strategies for enhancing the governance of coastal areas. Three popular destinations were selected as study areas, Koh Chang, Koh Mak, and Pattaya. Group discussions, questionnaire surveys, interviews, and observation were used for primary data collection together with secondary data. The results show that the development of these destinations has been incompatible with the coastal environment and CC patterns. Rapid urbanization from tourism development is the main driver of environmental changes and makes the areas vulnerable to CC-related risks. While water scarcity and pollution are found the most critical environmental issues of the destinations, coastal areas are negatively affected in terms of increased air and water pollution and resource degradation. They have also been exposed to different CC-related problems while the risks of accumulative impacts of both environment and CC have not been adequately recognized or addressed. Although some measures have provided synergies of improved environment and increased climate resilience, possible conflicts and gaps were also found. Public infrastructure integration and optimization to enhance coastal areas’ environment and climate resilience are suggested.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geodesy and Geodynamics, Volume 10, Issue 4〈/p〉 〈p〉Author(s): 〈/p〉

Description: 〈p〉Publication date: August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Hydrology: Regional Studies, Volume 24〈/p〉 〈p〉Author(s): Dagnachew Daniel Molla, Tenalem Ayenew Tegaye, Christopher G. Fletcher〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈h6〉Study region〈/h6〉 〈p〉The volcano-tectonic lakes basin of Abaya-Chamo is part of the Main Ethiopian Rift system and exhibits large variations in geomorphology, physiography and climate between the rift floor and the plateau.〈/p〉 〈/div〉 〈div〉 〈h6〉Study focus〈/h6〉 〈p〉Despite the importance of streamflow for water resources management and planning in the basin, many of the rivers there are ungauged. To make quantitative estimates of streamflow for spatially resolved water availability in such a highly heterogeneous environment, therefore, requires numerical modeling. This study is the first to quantify the surface and shallow groundwater resources in Abaya-Chamo, and to validate the physically fully distributed hydrologic model WetSpass under highly data-limited conditions, in a complex two-lake environment.〈/p〉 〈/div〉 〈div〉 〈h6〉New hydrological insights〈/h6〉 〈p〉Simulated total river flow and estimated baseflow were verified at 15 gauging stations, with a good agreement. The WetSpass model is shown to be suitable for such a complex setting with a correlation coefficient of 0.95 and 0.97 for total flow and baseflow respectively at a statistically significant level (p-value 〈 0.05). The simulated annual water budget reveals that 74.6% of the 22.1 billion lit/yr in total precipitation in the basin is lost through evapotranspiration, 15.7% through surface runoff, and only 9.7% recharges the groundwater system. The simulations also revealed the surface runoff and groundwater recharge are the most sensitive to soil textural class, while evapotranspiration depends more strongly on land use.〈/p〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S2214581818302623-ga1.jpg" width="159" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: June 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Climate Change Research, Volume 10, Issue 2〈/p〉 〈p〉Author(s): Ling-Xing Xu, De-Wei Yang, Tong-Hua Wu, Shu-Hua Yi, Yi-Ping Fang, Cun-De Xiao, Hao-Xi Lin, Jin-Chuan Huang, Claudien Habimana Simbi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The degradation of the permafrost regions, resulting from intensive anthropogenic activities and global warming, has led to the loss of ecosystem services and is threating human well-being. Nevertheless, the real ecosystem service values and their complete zoning system in the permafrost regions have received insufficient attention. Research gaps between the identification of permafrost-based ecosystem services and ecosystem management are seriously constraining the development of cryospheric science. Thus, an ecosystem service zoning framework that links ecosystem services with human welfares is proposed to solve the abovementioned challenges in the permafrost regions of China. The three-tiered zoning framework for ecosystem services, consisting of zoning goals, principles, hierarchy, methodology, and nomenclature, is proposed for the permafrost regions of China. A combined method, i.e., GIS spatial tools, the location entropy analysis model, and ecosystem services assessment, was employed to distinguish ecosystem conditions, ecosystem service supply, and beneficiaries into these three-grade ecosystem service zones. Hierarchical and dynamic zoning could clarify protection priorities of ecosystems and ecosystem services in terms of regions, grades, and types. The framework could contribute to sustainable management of ecosystem services in the cryosphere.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil and Tillage Research, Volume 194〈/p〉 〈p〉Author(s): Kathryn L Page, Yash P. Dang, Ram C. Dalal, Steven Reeves, Greg Thomas, Weijin Wang, John P. Thompson〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉No-tillage (NT) has been widely adopted to assist in reducing soil erosion, lowering fuel costs, conserving soil water and promoting soil health. However, NT may also have a negative effect on yield depending on season and conditions due to inadequate weed/disease control, nutrient stratification and/or decreased soil temperatures. Therefore, to fully assess its impact, long-term studies are required to monitor changes over time. This study reports on the long-term effect of NT on crop yield and profitability (primarily for wheat, 〈em〉Triticum aestivum〈/em〉 L.) using results from an experiment that has been running for 50 years in a semiarid subtropical region of Australia. In this experiment, the effect of tillage (conventional till (CT) 〈em〉v〈/em〉 no-till (NT)), residue management (stubble burning (SB) 〈em〉v〈/em〉 stubble retention (SR)), and three rates of nitrogen (N) fertiliser (0, 30 and 90 kg N/ha) were measured in a balanced factorial experiment on a Vertisol (Ustic Pellusert). Over the period of the trial (1969–2018), NT with SR resulted in greater average soil water storage in the top 1.5 m of the profile than CT with SB (390 〈em〉v〈/em〉 346 mm). However, nitrate (NO〈sub〉3〈/sub〉-N) accumulation during the fallow period was generally lower with SR and this prevented wheat from fully capitalising of on the increased soil water storage. Consequently, while crop yield was greater under NT 〈em〉v〈/em〉 CT and more so under NT + SR 〈em〉v〈/em〉 CT + SR (particularly in years where in-crop rainfall was 〈˜300 mm), N fertiliser was required to maximise yields. Within the NT treatments, SR also resulted in greater yield in the presence of applied N. Prior to 1992, nematodes prevented wheat crops from capitalising on the increased soil water and reduced yields, however, the introduction of nematode-tolerant cultivars helped maximise crop production. In line with yield effects, gross margins were greater under NT than CT and for SR when N was applied. However, despite greater yield advantages for the 90 N treatments, gross margins were lower at 90 N compared to 30 N. Nitrogen use efficiency with 90 N was approximately half that with 30 N, likely due to greater losses of N at the higher rates of application. To maximise profitability techniques to reduce losses of N are thus desirable. Good disease control, or the use of tolerant/resistant cultivars, is also essential to allow the crop to capitalise on gains in soil water in NT systems.〈/p〉〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil and Tillage Research, Volume 194〈/p〉 〈p〉Author(s): Qi Chen, Pei-Qin Peng, Jian Long, Xin-Yang Li, Xianqing Ding, Hong-Bo Hou, Bo-Han Liao〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉While the evaluation of cadmium (Cd) phytoavailability in rice (〈em〉Oryza sativa〈/em〉 L.)–soil systems has attracted considerable attention in recent years, the results vary based on the evaluation method used. The objective of this work was to use field capacity-derived soil solution extraction (SSE) to evaluate the Cd phytoavailability in two typical paddy soils (purple paddy soil and red paddy soil) during an entire rice growth season. Compared to three conventional extraction methods diethylenetriaminepentaacetic acid (DTPA) extraction, toxicity characteristic leaching procedure (TCLP), and HCl extraction], field capacity-derived SSE resulted in the strongest correlation between extracted Cd and the Cd contents in different rice tissues (root, gem, leaf, ear, husk, and brown rice). When the data for the two soil types were combined, SSE was the best predictor of total accumulated Cd in rice, with linear correlation coefficients of 0.836, 0.831, 0.919, and 0.909 for the tillering stage, heading stage, filling stage, and mature stage, respectively. In contrast, TCLP was only suitable for predicting total Cd accumulation in the heading and mature stages (linear correlation coefficients of 0.813 and 0.931, respectively), while DTPA was only effective in the heading stage (linear correlation coefficient of 0.8306). These results demonstrate the potential of field capacity-based SSE to predict Cd phytoavailability in soil–rice systems with different soil types.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0167198719300418-ga1.jpg" width="345" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Carbon, Volume 152〈/p〉 〈p〉Author(s): Hongtao Guan, D.D.L. Chung〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The effect of macroscale planar arrangement (planar coil, unidirectional and crossply arrangements, with a gap between tow segments) of continuous polyacrylonitrile-based carbon fiber (7.0-μm diameter) 12 K tow on the electromagnetic interference shielding effectiveness for normal-incident unpolarized plane wave is reported at frequencies ranging from 200 to 2000 MHz. The planar coil configuration, which favors magnetic interaction, has not been previously reported for shielding with any material. For all arrangements, the total shielding effectiveness (〈em〉SE〈/em〉〈sub〉T〈/sub〉) is dominated by the absorption loss (〈em〉SE〈/em〉〈sub〉A〈/sub〉), whether the fiber is nickel-coated or not. The nickel coating (0.25-μm thick) increases 〈em〉SE〈/em〉〈sub〉T〈/sub〉 from 2‒6 dB to 13–26 dB for the planar coil configuration, but has little effect for the crossply/unidirectional configuration. Both 〈em〉SE〈/em〉〈sub〉T〈/sub〉 and 〈em〉SE〈/em〉〈sub〉A〈/sub〉 are greatly increased by the nickel coating, which also reduces 〈em〉SE〈/em〉〈sub〉A〈/sub〉's frequency dependence and increases the absorption's fractional contribution to shielding, particularly for the planar coil configuration below 1000 MHz (from 53%‒78% to 83%–94%). The advantage of the crossply configuration over the unidirectional configuration is greater without the nickel coating. Increasing the tow size from 12 K to 24 K (with the gap decreased from 3.0 to 2.0 mm) raises 〈em〉SE〈/em〉〈sub〉A〈/sub〉 for planar coil and unidirectional arrangements. The results agree essentially with electromagnetic theory.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S000862231930661X-fx1.jpg" width="262" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Carbon, Volume 152〈/p〉 〈p〉Author(s): Shang-Fa Pan, Jiang-Long Yin, Xue-Lian Zhu, Xiao-Jing Guo, Ping Hu, Xi Yan, Wan-Zhong Lang, Ya-Jun Guo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this work, a variety of microporous carbon nanospheres (MCNs) were synthesized by the in-situ approach, and used as metal-free catalysts for direct propane dehydrogenation (DPDH). Pristine MCNs showed excellent catalytic performances for DPDH with initial propane conversion of 26% and propylene selectivity of 87%–88%. Phosphorus (P) modifications with different P sources put different effects on the catalytic performances of MCNs in DPDH, i.e., triethyl phosphate exhibited a positive, while (NH〈sub〉4〈/sub〉)〈sub〉2〈/sub〉HPO〈sub〉4〈/sub〉 and H〈sub〉3〈/sub〉PO〈sub〉4〈/sub〉 showed a negative effect on the catalytic performances for the in-situ doping carbon catalysts. The amount of surface oxygenic groups and the graphitization extent of carbon materials are two important factors influencing the catalytic performances of MCNs in DPDH. These results indicate that P modification is an effective way to adjust the catalytic performances of MCNs in DPDH. While, except the dopant itself, the interaction between the dopant and other materials during the synthesis process also influences the surface oxygenic groups and the graphitization degree of carbon materials.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0008622319306827-fx1.jpg" width="260" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Carbon, Volume 152〈/p〉 〈p〉Author(s): Jing-Yang You, Xing-Yu Ma, Zhen Zhang, Kuan-Rong Hao, Qing-Bo Yan, Xian-Lei Sheng, Gang Su〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A structurally stable carbon allotrope with plentiful topological properties is predicted by means of first-principles calculations. This novel carbon allotrope possesses the simple space group C2/m, and contains simultaneously 〈em〉sp〈/em〉, 〈em〉sp〈/em〉〈sup〉2〈/sup〉 and 〈em〉sp〈/em〉〈sup〉3〈/sup〉 hybridized bonds in one structure, which is thus coined as carboneyane. The calculations on geometrical, vibrational, and electronic properties reveal that carboneyane, with good ductility and a much lower density 1.43 g/cm〈sup〉3〈/sup〉, is a topological metal with a pair of nodal lines traversing the whole Brillouin zone, such that they can only be annihilated in a pair when symmetry is preserved. The symmetry and topological protections of the nodal lines as well as the associated surface states are discussed. By comparing its x-ray diffraction pattern with experimental results, we find that three peaks of carboneyane meet with the detonation soot. On account of the fluffy structure, carboneyane is shown to have potential applications in areas of storage, adsorption and electrode materials.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0008622319306360-fx1.jpg" width="314" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Hydrology, Volume 576〈/p〉 〈p〉Author(s): Valentin Haselbeck, Jannes Kordilla, Florian Krause, Martin Sauter〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Growing inorganic and expansive hydrochemical datasets and large differences in the measured concentrations require methods that are capable of compressing data without the loss of critical information and subsequently displaying it in a condensed and comprehensive way. Here we train an artificial neural network, Kohonen’s self-organizing map (SOM), to model inorganic hydrochemical clusters and associate the salinity source with the distribution of the ionic concentration spatial variation at a former potash mining site. Kohonen’s self-organizing maps are applied to project the data onto a two-dimensional grid and the geometric relationship of the projected vectors is subsequently used to perform a hierarchical cluster analysis. The SOM clustering approach succeeded in assigning the groundwater samples automatically according to their inorganic chemical composition. Five different clusters, three geogenic and two anthropogenic, were identified. The final outcome is displayed and compared with the classification from Piper plotting of the same dataset. In order to see the SOM clustering results in the large scale hydrogeological context, the distribution of the clusters is displayed spatially. This approach is a tool for the hydrogeologist to quickly analyze large datasets and present them in a clear and concise format.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Atmospheric Environment, Volume 214〈/p〉 〈p〉Author(s): Weifeng Gao, Yunlong Yao, Dawen Gao, He Wang, Liquan Song, Houcai Sheng, Tijiu Cai, Hong Liang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In the context of global climate warming, spring thaw period had been changed in the permafrost regions, which significantly affect heat and water dynamics, along with soil microbial community structure and diversity, and microbially-mediated nitrogen cycle changes. However, 〈em〉in〈/em〉-〈em〉situ〈/em〉 N〈sub〉2〈/sub〉O emission research is scarce in the permafrost regions and the drivers of N〈sub〉2〈/sub〉O emission during spring thaw period remain unclear. We selected three type of swamp forests in the permafrost region to investigate the N〈sub〉2〈/sub〉O emissions during spring thaw period from 17 March to 23 May 2017. We found that N〈sub〉2〈/sub〉O emission ranged from −35.75 to 74.17 μg m〈sup〉−2〈/sup〉 h〈sup〉−1〈/sup〉 in the permafrost region during spring thaw period, and there was no significant large burst of N〈sub〉2〈/sub〉O emissions as observed in other ecosystems. The N〈sub〉2〈/sub〉O emission during spring thaw period were lower than those from growing season, which were significant affected by soil temperature. During spring thaw period, swamp forest types had no significantly influence on N〈sub〉2〈/sub〉O emissions, which mainly limited by NO〈sub〉3〈/sub〉〈sup〉−〈/sup〉-N content. Stepwise multiple linear regression indicated that the air temperature, thawing depth, soil temperature, soil moisture, pH, NH〈sub〉4〈/sub〉〈sup〉+〈/sup〉-N, NO〈sub〉3〈/sub〉〈sup〉−〈/sup〉-N, TOC, TN, and C/N ratio were the environmental factors which significant effecting the N〈sub〉2〈/sub〉O emissions. In the field campaign, cumulative N〈sub〉2〈/sub〉O emissions were mainly controlled by thawing depth, soil moisture, pH, NH〈sub〉4〈/sub〉〈sup〉+〈/sup〉-N, NO〈sub〉3〈/sub〉〈sup〉−〈/sup〉-N and TN during spring thaw period. Overall, the results demonstrate that in the permafrost ecosystems spring thaw period is an important source of N〈sub〉2〈/sub〉O emissions.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1352231019304510-fx1.jpg" width="336" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Marine Geology, Volume 416〈/p〉 〈p〉Author(s): Shili Liao, Chunhui Tao, Ágata Alveirinho Dias, Xin Su, Zhen Yang, Jianyu Ni, Jin Liang, Weifang Yang, Jia Liu, Wei Li, Chuanwan Dong〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The study of the hydrothermal component in oceanic sediments provides key data for locating active and inactive hydrothermal systems. In this work, we report the geochemistry of surface sediments collected in the newly discovered basaltic-hosted Duanqiao-1 hydrothermal field (DHF) on the Southwest Indian Ridge (SWIR). The sediments are mainly composed of a pelagic fraction (carbonate ooze) with minor clay contents, basaltic debris, Fe〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉Mn oxyhydroxides, and hydrothermal components. Hydrothermal elements in the DHF exhibit a precipitation sequence of Cu ≈ Co 〉 Zn ≈ Pb 〉 Fe 〉 Mn ≈ Ni ≈ As. Proximal sediments to the hydrothermal discharge area are characterized by high Cu, Pb, Zn, and Co concentrations and higher Cu/Fe and Zn/Fe ratios, decreasing abruptly within the first kilometer. After this proximal area, an evident increase of Mn concentrations and Mn/Fe ratios was observed, denoting higher oxidizing conditions of the hydrothermal plume. Hydrothermal derived Pb and Co precipitated together with the sulfide phases, whereas at the distal sediments Pb, Co, Ni, and As seem to be scavenged from seawater by oxyhydroxides. This was corroborated by increased REE/Fe ratios with distance to the discharge zone. The geochemistry of DHF sediments is consistent with an effective separation of metals during gradual cooling, and concomitant Eh and pH modifications, of the hydrothermal plume when in contact with seawater. This promotes the precipitation of Cu sulfides first, closest to the discharge area, followed by Cu〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉Zn and Fe sulfides and Fe〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉Mn oxyhydroxides, in more distal areas. A comparison of the DHF sediments with those from Dragon Horn, another hydrothermal site at the SWIR, suggests that the hydrothermal fluids responsible for mineral precipitation at DHF are less reduced, favoring the formation of sulfides and oxyhydroxides at shorter distances from the discharge zone. These findings are particularly valuable to the understanding of the variation in hydrothermal anomalies detected in sediments from proximal and distal areas of discharge zones, contributing to the development of tools for the discovery of hydrothermal fields.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0025322719300969-ga1.jpg" width="301" alt="Unlabelled Image" title="Unlabelled Image"〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 218〈/p〉 〈p〉Author(s): Taoliang Zhang, Rujian Wang, Leonid Polyak, Wenshen Xiao〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Distribution and composition of coarse particles (〉250 μm) were investigated in 13 sediment cores from the Chukchi margin, western Arctic Ocean. Petrographic clast identification is supplemented by XRF core scanning, EDS analysis of coal fragments, and AMS 〈sup〉14〈/sup〉C dating of planktic foraminifera for age control. Coal debris distribution is also investigated in surface sediments of the study region for provenance interpretation. The sediment-core study focuses on the interval between the Last Glacial Maximum and the Holocene for constraining provenance and timing of the deglacial discharge. We find that this interval is characterized by a distinct enrichment in sedimentary rock fragments, including coal. Comparison with longer stratigraphic records indicates that this composition is unique for the time interval since at least Maine Isotope Stage 5. Based on the timing, interpreted provenance, and geographic distribution of the coal enrichment, we conclude that the most likely primary source was the deglacial discharge from the Mackenzie drainage basin of the Laurentide Ice Sheet (LIS). The identified coal-bearing layer, also expressed in the XRF sulfur record, can be thus used as a stratigraphic marker for the LIS discharge to the Arctic Ocean during the last deglaciation.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Volcanology and Geothermal Research, Volume 384〈/p〉 〈p〉Author(s): Christian Pizarro, Miguel A. Parada, Claudio Contreras, Eduardo Morgado〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Villarrica volcano is one of the most active volcanoes of the Andes (rest cycles of 5.4 ± 3.9 years) and erupts products of basaltic to basaltic-andesite compositions and in styles from Hawaiian to Vigorous Strombolian. We compare whole-rock geochemistry and mineral abundances, textures and compositions of the most voluminous basaltic lavas of the 20th century, which were erupted in 1921, 1948 and 1971. The analyzed lavas show a restricted range in whole-rock compositions (51.7–52.4 wt% SiO〈sub〉2〈/sub〉), but there is an increasing trend of MgO content from 1921 (~5.3 wt% MgO) to 1948 (~7.0 wt% MgO) and a decreasing trend from 1948 to 1971 (~6.0 wt% MgO). Two groups of plagioclase compositions are observed in all lavas: An-poor (~An〈sub〉60〈/sub〉) and An-rich (~An〈sub〉80〈/sub〉). An-poor compositions are the most abundant in all lavas and were commonly formed in both the earliest (cores) and latest stages (external rims and small and nearly unzoned phenocrysts) of plagioclase crystallization, whereas An-rich plagioclase formed around An-poor cores during intermediate stages. Additionally, precipitation of An-poor plagioclase in both rims and cores could simultaneously have occurred in highly dissolved An-rich antecrysts. Equilibrium temperatures of plagioclase-olivine-clinopyroxene of about 1090 °C were obtained in crystal clots of the three lavas. Thermometry calculations obtained from MELTS simulations of plagioclase formation indicate a heating (thermal mixing) of the reservoir at ~0.5 kbar of up to 100 °C with respect to the crystal clots temperatures. Incorporation of small amounts of volatile-rich and hotter mafic magma of similar composition (cryptic mixing) into the Villarrica reservoir, could heat it, probably in a more efficient way than heat conduction alone. A longer interaction of the hot mafic magma within the reservoir could cause crystallization of An-rich plagioclase, dissolution of An-poor plagioclase (i.e. increase in An-rich/An-poor modal content ratios) and compositional modifications toward MgO-rich and volatile-rich compositions, that ultimately result in higher intensity of eruption.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 4 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Chemical Geology〈/p〉 〈p〉Author(s): J.K. Gorman, S.C. Penniston-Dorland, H.R. Marschall, R.J. Walker〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Traverses across amphibole-chlorite schist metamorphic reaction zones at contacts between meta-igneous and ultramafic rocks in high-pressure mélange zones were analyzed for highly siderophile element (HSE) concentrations and 〈sup〉187〈/sup〉Os/〈sup〉188〈/sup〉Os in two mélange zones (Catalina Schist, Santa Catalina Island, CA, and Attic-Cycladic Complex, Syros, Greece) in order to investigate the relative effects of mechanical mixing and diffusive and advective transport by fluids in subduction-related reaction zones. Results from Catalina Schist traverses show co-varying elevated concentrations of Os, Ir, Ru, Cr, and MgO and inversely correlated initial 〈sup〉187〈/sup〉Os/〈sup〉188〈/sup〉Os that display irregular patterns across the chlorite-actinolite schist reaction zones. These elements are strongly enriched in peridotite relative to mafic crust, and are relatively fluid immobile. The observations suggest that these components were added via mechanical mixing of mantle peridotitic material with material derived from mafic blocks. In a traverse across a Syros mafic eclogite block with a narrow chlorite schist reaction zone and broader glaucophane-rich reaction zone, the Os, Ir, Ru, and Cr concentrations in the chlorite schist are just barely higher than those in the eclogite block, while the initial 〈sup〉187〈/sup〉Os/〈sup〉188〈/sup〉Os ratio falls between the eclogite core and adjacent serpentinite. These compositions show a relatively minor metasomatic exchange between eclogite block and serpentinite. A second sample set from Syros was chosen across a contact zone between a meta-tuffite and a serpentinite because previous studies suggest it was not affected by mechanical mixing. This traverse contains a ~1 m wide complex metasomatic reaction zone that is used to study the relative contributions of diffusive and advective transport, respectively. The traverse reveals strong mobilization of Os, Ir, Ru and Pt beyond the scale of the outcrop, and minor advective enrichment of Re and Pd. This indicates that all HSE may be mobilized by fluid advection beyond the local scale in some subduction zone mélange zones.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Enzyme and Microbial Technology, Volume 130〈/p〉 〈p〉Author(s): Fernanda Valadares, Thiago A Gonçalves, André Damasio, Adriane MF Milagres, Fabio M Squina, Fernando Segato, André Ferraz〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Secretome evaluations of lignocellulose-decay basidiomycetes can reveal new enzymes in selected fungal species that degrade specific substrates. Proteins discovered in such studies can support biorefinery development. Brown-rot (〈em〉Gloeophyllum trabeum〈/em〉) and white-rot (〈em〉Pleurotus ostreatus〈/em〉) fungi growing in sugarcane bagasse solid-state cultures produced 119 and 63 different extracellular proteins, respectively. Several of the identified enzymes are suitable for 〈em〉in vitro〈/em〉 biomass conversion, including a range of cellulases (endoglucanases, cellobiohydrolases and β-glucosidases), hemicellulases (endoxylanases, α-arabinofuranosidases, α-glucuronidases and acetylxylan esterases) and carbohydrate-active auxiliary proteins, such as AA9 lytic polysaccharide monooxygenase, AA1 laccase and AA2 versatile peroxidase. Extracellular oxalate decarboxylase was also detected in both fungal species, exclusively in media containing sugarcane bagasse. Interestingly, intracellular AA6 quinone oxidoreductases were also exclusively produced under sugarcane bagasse induction in both fungi. These enzymes promote quinone redox cycling, which is used to produce Fenton’s reagents by lignocellulose-decay fungi. Hitherto undiscovered hypothetical proteins that are predicted in lignocellulose-decay fungi genomes appeared in high relative abundance in the cultures containing sugarcane bagasse, which suggests undisclosed, new biochemical mechanisms that are used by lignocellulose-decay fungi to degrade sugarcane biomass. In general, lignocellulose-decay fungi produce a number of canonical hydrolases, as well as some newly observed enzymes, that are suitable for 〈em〉in vitro〈/em〉 biomass digestion in a biorefinery context.〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Earth and Planetary Science Letters, Volume 522〈/p〉 〈p〉Author(s): Savannah Worne, Sev Kender, George E.A. Swann, Melanie J. Leng, Ana Christina Ravelo〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉High latitude deep water upwelling has the potential to control global climate over glacial timescales through the biological pump and ocean-atmosphere CO〈sub〉2〈/sub〉 exchange. However, there is currently a lack of continuous long nutrient upwelling records with which to assess this mechanism. Here we present geochemical proxy records for nutrient upwelling and glacial North Pacific Intermediate Water (GNPIW) formation in the Bering Sea over the past 850 kyr, which demonstrates that glacial periods were characterised by reduced nutrient upwelling, when global atmospheric CO〈sub〉2〈/sub〉 and temperature were also lowered. We suggest that glacial expansion of sea ice in the Bering Sea, and the simultaneous expansion of low nutrient GNPIW, inhibited vertical mixing and nutrient supply across the subarctic Pacific Ocean. Our findings lend support to the suggestion that high latitude sea ice and the resultant intermediate water formation, modulated deep water upwelling and ocean-atmosphere CO〈sub〉2〈/sub〉 exchange on glacial-interglacial timescales.〈/p〉〈/div〉

Description: 〈p〉Publication date: 1 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 217〈/p〉 〈p〉Author(s): 〈/p〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Planetary and Space Science, Volume 175〈/p〉 〈p〉Author(s): 〈/p〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Atmospheric Environment, Volume 214〈/p〉 〈p〉Author(s): O. Soupiona, S. Samaras, P. Ortiz-Amezcua, C. Böckmann, A. Papayannis, G.A. Moreira, J.A. Benavent-Oltra, J.L. Guerrero-Rascado, A.E. Bedoya-Velásquez, F.J. Olmo, R. Román, P. Kokkalis, M. Mylonaki, L. Alados-Arboledas, C.A. Papanikolaou, R. Foskinis〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this paper we extract the aerosol microphysical properties for a collection of mineral dust cases measured by multi-wavelength depolarization Raman lidar systems located at the National Technical University of Athens (NTUA, Athens, Greece) and the Andalusian Institute for Earth System Research (IISTA-CEAMA, Granada, Spain). The lidar-based retrievals were carried out with the Spheroidal Inversion eXperiments software tool (SphInX) developed at the University of Potsdam (Germany). The software uses regularized inversion of a two-dimensional enhancement of the Mie model based on the spheroid-particle approximation with the aspect ratio determining the particle shape. The selection of the cases was based on the transport time from the source regions to the measuring sites. The aerosol optical depth as measured by AERONET ranged from 0.27 to 0.54 (at 500 nm) depending on the intensity of each event. Our analysis showed the hourly mean particle linear depolarization ratio and particle lidar ratio values at 532 nm ranging from 11 to 34% and from 42 to 79 sr respectively, depending on the mixing status, the corresponding air mass pathways and their transport time. Cases with shorter transport time showed good agreement in terms of the optical and SphInX-retrieved microphysical properties between Athens and Granada providing a complex refractive index value equal to 1.4 + 0.004i. On the other hand, the results for cases with higher transport time deviated from the aforementioned ones as well as from each other, providing, in particular, an imaginary part of the refractive index ranging from 0.002 to 0.005. Reconstructions of two-dimensional shape-size distributions for each selected layer showed that the dominant effective particle shape was prolate with diverse spherical contributions. The retrieved volume concentrations reflect overall the intensity of the episodes.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Earth and Planetary Science Letters, Volume 522〈/p〉 〈p〉Author(s): Mariko Harada, Aki Nagano, Sota Yagi, Ryutaro Furukawa, Shin-ichi Yokobori, Akihiko Yamagishi〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The optimum growth temperature of ancestral cyanobacteria inhabiting the sea surface in the Neoproterozoic was estimated based on the thermal stability of experimentally reconstructed ancestral NDK enzymes. Ancestral NDKs of cyanobacteria that diversified ∼1.7, ∼1.0, ∼0.9, ∼0.7, ∼0.6, and ∼0.5 billion years ago were reconstructed and analyzed, and the unfolding midpoint temperatures (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈msub〉〈mrow〉〈mi〉T〈/mi〉〈/mrow〉〈mrow〉〈mi mathvariant="normal"〉m〈/mi〉〈/mrow〉〈/msub〉〈/math〉s) ranged from ∼65 °C to ∼70 °C. Among the host of analyzed NDKs, the ancestors of marine, planktonic 〈em〉α〈/em〉-cyanobacteria diversified ≤ ∼1.0 Ga are highly likely to have inhabited marine environments during the Neoproterozoic, while ancestral cyanobacteria diversified ∼1.7 billion years ago were possibly marine but the habitat is less constrained compared to the others. According to the calibration curves derived from extant organisms, the obtained 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈msub〉〈mrow〉〈mi〉T〈/mi〉〈/mrow〉〈mrow〉〈mi mathvariant="normal"〉m〈/mi〉〈/mrow〉〈/msub〉〈/math〉s of 〈em〉α〈/em〉-cyanobacteria diversified ≤ ∼1.0 Ga correspond to the range of optimum growth temperatures of around ∼33–48 °C. The temperature range agrees well with the long-term sea temperature trend during Neoproterozoic suggested by 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg"〉〈msup〉〈mrow〉〈mi〉δ〈/mi〉〈/mrow〉〈mrow〉〈mn〉18〈/mn〉〈/mrow〉〈/msup〉〈mi mathvariant="normal"〉O〈/mi〉〈/math〉 and 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si3.svg"〉〈msup〉〈mrow〉〈mi〉δ〈/mi〉〈/mrow〉〈mrow〉〈mn〉30〈/mn〉〈/mrow〉〈/msup〉〈mrow〉〈mi mathvariant="normal"〉Si〈/mi〉〈/mrow〉〈/math〉 records from marine cherts. Adaptation to the low temperature during the snowball glaciations in the late Neoproterozoic was not observed, implying that adaptation of optimum growth conditions to the episodic low temperature may not have been necessary. Therefore, ancestral marine plankton must have consistently adapted to the interglacial sea surface temperature in the Neoproterozoic, which was approximately 5–20 °C higher than that is today. They may have survived the glaciations by acquiring cold tolerance and/or by suppressing growth rate.〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Earth and Planetary Science Letters, Volume 522〈/p〉 〈p〉Author(s): Guilherme A.R. Gualda, Darren M. Gravley, Chad D. Deering, Mark S. Ghiorso〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The deposits of large volcanic eruptions provide the sole record of the architecture of magmatic plumbing systems in the moments when large pools of crystal-poor, eruptible magma are present in the crust. It is widely accepted that silicic magmas form by segregation of melt-rich, crystal-poor magma from a crystal-rich source; however, the depths at which segregation takes place and the distribution of the magma within the crust are not well constrained. We present a new approach to calculate pressures at which crystal-poor, eruptible magma is extracted from a crystal-rich source (i.e. mush). We apply the approach to a sequence of large (〉50 km〈sup〉3〈/sup〉) eruptions from the Taupo Volcanic Zone (TVZ), New Zealand, which were part of a volcanic flare-up. We compare the calculated extraction pressures with pre-eruptive storage pressures for the same units. Our results show that storage and extraction pressures do not always coincide. Instead, eruptible magma can be completely segregated from the crystal-rich source, and stored at shallower levels in the crust prior to eruption. In the case of the TVZ flare-up, repeated input of material and heat – probably coupled with tectonic extension – gradually conditioned the crust and allowed extraction of eruptible magma over a growing range of pressures with time. Our approach has the potential to reveal important information on the structure and distribution of magmatic systems within the shallow crust.〈/p〉〈/div〉

Description: 〈p〉Publication date: 20 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Chemical Geology, Volume 525〈/p〉 〈p〉Author(s): Rasesh Pokharel, Ruben Gerrits, Jan A. Schuessler, Friedhelm von Blanckenburg〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉To unravel the dissolution mechanisms of olivine by a rock-inhabiting fungus we determined the stable isotope ratios of Mg on solutions released in a laboratory experiment. We found that in the presence of the fungus 〈em〉Knufia petricola〈/em〉 the olivine dissolution rates were about seven-fold higher (1.04 × 10〈sup〉−〈/sup〉〈sup〉15〈/sup〉 mol cm〈sup〉−〈/sup〉〈sup〉2〈/sup〉 s〈sup〉−〈/sup〉〈sup〉1〈/sup〉) than those in the abiotic experiments (1.43 × 10〈sup〉−〈/sup〉〈sup〉16〈/sup〉 mol cm〈sup〉−〈/sup〉〈sup〉2〈/sup〉 s〈sup〉−〈/sup〉〈sup〉1〈/sup〉) conducted under the same experimental condition (pH 6, 25 °C, 94 days). Measured element concentrations and Mg isotope ratios in the supernatant solutions in both the biotic and the abiotic experiment followed a dissolution trend in the initial phase of the experiment, characterized by non-stoichiometric release of Mg and Si and preferential release of 〈sup〉24〈/sup〉Mg over 〈sup〉26〈/sup〉Mg. In a later phase, the data indicates stoichiometric release of Mg and Si, as well as isotopically congruent Mg release. We attribute the initial non-stoichiometric phase to the rapid replacement of Mg〈sup〉2+〈/sup〉 in the olivine with H〈sup〉+〈/sup〉 along with simultaneous polymerization of Si tetrahedra, resulting in high dissolution rates, and the stoichiometric phase to be influenced by the accumulation of a Si-rich amorphous layer that slowed olivine dissolution. We attribute the accelerated dissolution of olivine during the biotic experiment to physical attachment of 〈em〉K. petricola〈/em〉 to the Si-rich amorphous layer of olivine which potentially results in its direct exposure to protons released by the fungal cells. These additional protons can diffuse through the Si-rich amorphous layer into the crystalline olivine. Our results also indicate the ability of 〈em〉K. petricola〈/em〉 to dissolve Fe precipitates in the Si-rich amorphous layer either by protonation, or by Fe(III) chelation with siderophores. Such dissolution of Fe precipitates increases the porosity of the Si-rich amorphous layer and hence enhances olivine dissolution. The acceleration of mineral dissolution in the presence of a rock-dissolving fungus further suggests that its presence in surficial CO〈sub〉2〈/sub〉 sequestration plants may aid to accelerate CO〈sub〉2〈/sub〉 binding.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 4 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary International〈/p〉 〈p〉Author(s): Anamaria Roman, Tudor-Mihai Ursu, Sorina Fărcaş, Coriolan Horaţiu Opreanu, Vlad-Andrei Lăzărescu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The landscape at the Roman Archaeological Site from Moigrad-Porolissum, Romania, is nowadays mostly forested. But how did it look during the Roman period (106–275 AD)? Also, how can multispectral imagery and laser scanning be combined more effectively to detect the signatures of ancient sub-surface archaeological remains? This study employed WorldView2 satellite and LiDAR (Light Detection And Ranging) data to explore current remotely sensed vegetation and terrain proxies. These helped identify past anthropogenic signatures embedded within the landscape for reconstructing the ancient engineered environment. The spectral vegetation and terrain patterns revealed 227 marks (36256.22 m) relevant for the historical landscape, of which 182 correspond to ancient sub-surface features. In open landscapes, the two techniques had equivalent results, while LiDAR provided better detection rates in shrubland patches and forests. Their successive application is an advantageous strategy for optimizing costs. The satellite imagery is employed first, followed by the density analysis of the results, while the more expensive laser-based data collection can be focused on the problematic or promising areas. The vegetation and terrain marks revealed the intricate and extensive ancient defensive system that extended on over 24.5 km〈sup〉2〈/sup〉. Their strategic functions, requiring visibility between and around them, suggest large-scale deforestation (probably over 1 km around the structures). Thus, in contrast to the present forest dominance, it appears that in the 2nd and 3rd centuries AD, at Porolissum there was an anthropogenic open landscape covering over 2158 ha, with urbanization and intense military activity on 198.76 ha.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Earth and Planetary Science Letters, Volume 522〈/p〉 〈p〉Author(s): A.C. Ganzhorn, H. Pilorgé, B. Reynard〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Large earthquakes break the subduction interface to depths of 60 to 80 km. Current models hold that seismic rupture occurs when fluid overpressure builds in link with porosity cycles, an assumption still to be experimentally validated at high pressures. Porosities of subduction zone rocks are experimentally determined under pressures equivalent to depths of up to 90 km with a novel experimental approach that uses Raman deuterium-hydrogen mapping. Natural rocks (blueschists, antigorite serpentinites, and chlorite-schists) representing a typical cross-section of the subduction interface corresponding to the deep seismogenic zone are investigated. In serpentinite, and to a smaller extent blueschist, porosity increases with deformation, whereas chlorite-rich schists remain impermeable regardless of their deformation history. Such a contrasting behavior explains the observation of over-pressurized oceanic crust and the limited hydration of the forearc mantle wedge. These results provide quantitative evidence that serpentinite, and likely blueschist, may undergo porosity cycles making possible the downdip propagation of large seismic rupture to great depths.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 4 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary International〈/p〉 〈p〉Author(s): Weiwei Sun, Enlou Zhang, Rong Chen, Ji Shen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Organic carbon mineralization and storage in the inland water bodies is an important component of global carbon cycling. However, the mechanisms influencing carbon cycling in the inland water bodies remain uncertain. In this study, 〈em〉n〈/em〉-alkane data from a sediment core spanning the last glacial-interglacial cycle from Lake Xingkai in northeast China, were analyzed to determine response of regional carbon cycling to climate change. Prior to MIS 1 the sedimentary 〈em〉n〈/em〉-alkanes were mainly derived from terrigenous higher plants and helophytes in the wetland. By contrast, non-photosynthetic bacteria are probable major alternating source of sedimentary 〈em〉n〈/em〉-alkanes during MIS 1. The 〈em〉n〈/em〉-alkanes in the sediments are mainly influenced by the variations of lake level and deposition of mineral dust. The total organic carbon content (TOC) and TOC-normalized middle- and long-chain 〈em〉n〈/em〉-alkane concentrations increased during glacial times and decreased during interglacial periods, reflecting higher rates of organic matter decomposition under warmer climatic conditions. The temperature dependence of lacustrine organic matter mineralization suggests that the carbon burial potential of lakes in northeast China will decrease in the future as global warming intensifies.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of African Earth Sciences, Volume 158〈/p〉 〈p〉Author(s): Helmy S. Abuelnaga, Hamdy A. Aboulela, El-Sawy K. El-Sawy, Reda A.Y. El Qassas〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Hammam Faroun is one of the prominent hot springs; it is situated on the central zone of Gulf of Suez on the western side of Sinai Peninsula, Egypt. The main objective of the present study is to assess the structural setting controlling Hammam Faroun, using the available airborne magnetic and seismicity data, beside other ancillary geological information data. The interpretation of airborne magnetic data of the study area revealed that Hammam Faroun area appeared as a small down-lifted block, pulled down to its confinement between faults given in what is known as half graben and then pulled to the southeast direction and still in a depth of 2.0 km. The main structures controlling the study area mainly trend in the NNE-SSW, NW-SE, NE-SW and WNW-ESE directions. The analyses of the available seismic events ascertained the existence of the NW structural trend, parallel to the Gulf of Suez. These analysis revealed the existence of three seismic clusters, each of them is characterized by micro to light/small earthquakes, of magnitudes in the range of, (0.5 ≥ Ml ≤ 4.3) at the study area. Most events have focal depths that range between 2.0 and 40 km, within the upper Earth crust. The fault plane solutions of six recent events exhibit the variability of focal mechanism from site to site. It's characterized by strike-slip and oblique-slip motions with predominant dip-slip normal component. The stress pattern is convenient, with those of the Gulf of Suez events.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1464343X19302134-fx1.jpg" width="256" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of African Earth Sciences, Volume 158〈/p〉 〈p〉Author(s): Mohamed Abdelhamid Ghanmi, Ali Chaieb, Adel Zaafouri, Mohamed Sadok Ben Salem, Kais Aridhi, Mohamed Ghanmi, Fouad Zargouni〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In the North African Atlas, Triassic sedimentary rocks exhibit a variety of deformation styles that are caused by the interaction between halokinesis, tectonics and sedimentation. This paper aims to present an integrated study documenting the occurrence of salt-tectonic processes in the Maknassy-Mezzouna orogenic system. The interpretation of both, field mapping and seismic data suggests the existence of a complex tectonic evolution of these Triassic evaporites, with the occurrence of Mesozoic extensional/transtensional and Tertiary compressional/transpressional tectonic regime accompanied by sedimentary loading. This evolution took place along three major events of either lateral or vertical migration of Triassic evaporites. The first one is tectonic-driven and is related to the extensional/transtensional tectonic regime, which occurred during the break-up of Pangea and rifting of Neotethyan Ocean in the Early Jurassic. The second remobilization of salt Triassic rock developed during the Cretaceous. The initial mobilization of the Triassic salt was probably induced by sedimentary loading with a limited contribution of tectonic forces. During its third stage of evolution, salt Triassic rocks evolve into salt sheets due to the shortening deformation occurred during Tertiary and Quaternary in relationship with the closure of the Neotethyan realm. Salt migration controls subsidence, generates depocenter shifts and causes thickness variation of the entire post-Triassic sedimentary sequence. The signature of salt Triassic syn-sedimentary control is confirmed by thickness reduction and abrupt variation of structural dip that affects all the sedimentary pile in the flanks of salt sheets. In seismic sections the syn-sedimentary salt tectonic control is observed by geometries like pinching out, thickness reduction, onlap termination geometry as well as unconformities identified along the flanks of the salt sheets.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Geochemistry, Volume 108〈/p〉 〈p〉Author(s): Andri Stefánsson, Stefán Arnórsson, Árný E. Sveinbjörnsdóttir, Jan Heinemaier, Hrefna Kristmannsdóttir〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The isotope (δD, δ〈sup〉18〈/sup〉O, 〈sup〉3〈/sup〉H, δ〈sup〉13〈/sup〉C, 〈sup〉14〈/sup〉C) and chemical (B, Cl) compositions of cold (streams, rivers, soil- and groundwater) and low-temperature geothermal water from northern Iceland were investigated in order to delineate the origin, mixing, water-rock interaction and the age of the waters. The waters showed a large range in temperature (0–104 °C) and chemical composition (TDS 7–954 ppm). Based on the δD (−54.9 to −125‰), δ〈sup〉18〈/sup〉O (−7.8 to −16.7‰), B (0.001–1.57 ppm), Cl (0.3–500 ppm) content the waters were of meteoric origin that have been modified by primary rock leaching corresponding to rock to water ratio (ξ) of ∼0.001–0.1 kg of basalt dissolved per kg of water. At temperatures above ∼50 °C close to saturation was observed between the waters and common secondary minerals like clays, zeolites and oxides indicating these reactions control the concentrations of reactive elements. At lower temperatures deviation from equilibrium saturation was evident. The water age was constrained by 〈sup〉3〈/sup〉H and 〈sup〉14〈/sup〉C, the latter corrected for rock carbon using B, Cl and δ〈sup〉13〈/sup〉C〈sub〉DIC〈/sub〉 relations. Most waters displayed modern age. Exceptions were 1) some waters at high ground having lower tritium content and older radiocarbon age; the trend considered to result from mixing between old glacial melt water and modern meteoric water, and 2) some low-temperature geothermal waters in lowland areas considered to be a mixture of old ʽice-ageʼ water, originating from last glacial times 〉12,000 years ago and modern and/or few decades old meteoric water. Thus, the chemical and isotope composition of cold and low-temperature geothermal waters in the region display a complex story, with waters originating from different conditions and of different age and later mixed and affected by water-rock interaction. These processes need to be considered and understood in order to develop a hydrogeological model of a groundwater system.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Water Resources, Volume 131〈/p〉 〈p〉Author(s): Xiang Zeng, Tiesong Hu, Ximing Cai, Yuliang Zhou, Xin Wang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Optimizing a multi-reservoir system is challenging due to the problem of the curse of dimensionality. In this paper, rule-based improved dynamic programming (RIDP) and stochastic dynamic programming (RISDP) algorithms for the optimal operation of a system with a number of parallel reservoirs are proposed to alleviate the dimensionality problem. The improvement is based on a key property: the monotonic dependence relationship between individual reservoir carryover storage and system water availability, which is derived with the assumption of the non-decreasing storage distribution characteristic of a parallel reservoir system. Furthermore, a diagnosis procedure is employed to remove infeasible state transitions, which enables the application of the monotonic relationship within the feasible solution space. In general, the computational complexity of 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈msup〉〈mrow〉〈mo〉(〈/mo〉〈mrow〉〈mi〉N〈/mi〉〈mi〉S〈/mi〉〈/mrow〉〈mo〉)〈/mo〉〈/mrow〉〈msup〉〈mi〉n〈/mi〉〈mn〉2〈/mn〉〈/msup〉〈/msup〉〈/math〉 from DP can be reduced to (〈em〉NS〈/em〉)〈sup〉〈em〉n〈/em〉〈/sup〉 from RIDP (〈em〉NS〈/em〉 is the number of storage discretization for individual reservoirs, 〈em〉n〈/em〉 is the number of reservoirs in a parallel system), with controlled solution accuracy. The improved algorithms are applied to a real-world parallel reservoir system in northeastern China. The results demonstrate the computational efficiency and effectiveness of RIDP and RISDP.〈/p〉〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Petroleum Science and Engineering, Volume 181〈/p〉 〈p〉Author(s): Chinedu I. Ossai〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉To advance the prognosis of progressing cavity Pumps (PCPs) used for artificial lifting, the pump-off need to be identified to forestall failure. This study developed a new technique for determining the Pump-off events Activation Times (PATs) of the PCPs using the transient Water Discharge Rates (WDRs) from coal seam gas producing wells. The Gaussian distribution function parameters of the rolling standard deviations of the water discharge rate (RSWR) and the transition probability of the rolling standard deviations of the water discharge rate (TP_RSWR) were used to build the model. By determining the anomalies in the RSWR signals with the bottom-up segmentation technique and computing the statistical characteristics at the changepoint locations, the steady-state of the WDR signals was established. This steady-state signal, which represents the Operation Transition Level (OTL) between the Normal Operation (NOP) and the Pump-off Event (POE) was used for monitoring the transition of the PCPs' operating status. An algorithm was developed in Python and tested it on field data from 36 coal seam gas wells. The performance of my technique was determined with precision, recall and F1 score, which gave an average value of 94.94%, 92.63%, and 93.56% respectively. It is expected that the implementation of this technique in the real-time estimation of PATs will be vital for reducing PCPs faults seeing that poor PATs detection results in PCPs running dry and consequently failures due to the extreme temperatures and abrasions.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 CATENA, Volume 182〈/p〉 〈p〉Author(s): Donatella Magri, Alessandra Celant, Federico Di Rita〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The development and decline of alder floodplain forests and alder carrs along the Tyrrhenian coasts, in relation to sea level changes, geomorphological processes, human activity, and climate change are presented and discussed. A number of 22 pollen records, complemented by 〈em〉Alnus〈/em〉 macrofossil data, document the presence of widespread alder populations in the coastal Tyrrhenian floodplains throughout the Holocene, although with different density from one site to the other, mostly depending on local hydrological conditions. The role of climate changes in the dynamics of floodplain forests appears uncertain. In the last two centuries, major reclamation works disrupted this natural vegetation to obtain fertile plains that are now exploited for agricultural purposes, industrial activities, urban areas and related infrastructures. Only a few remnants of the original alder forests are preserved by international conservation conventions, as biodiversity reservoirs of severely endangered habitats. However, the vanished alder forests, which proved to be able to rapidly recover several times through the Holocene, may still have some potential to be restored.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geomorphology, Volume 343〈/p〉 〈p〉Author(s): Zhenwei Li, Xianli Xu, Jingxuan Zhu, Chaohao Xu, Kelin Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Due to the characteristics of the lithology and the complexity of the geomorphology, the karst areas of Southwest China are experiencing severe soil erosion. Knowledge of the effects of lithology and geomorphology on sediment yield are therefore essential for developing measures to effectively control sediment delivery in this region. The objective of this study was to investigate the relative importance of lithological and geomorphological factors for sediment yield in 40 selected karst mountainous catchments in Southwest China. Because of the high co-dependence of these variables, a partial least squares regression (PLSR) model was used to explore the quantitative relationships between annual sediment yield and 30 lithological and geomorphological factors. Results showed that the lithology and geomorphology were critically important to annual sediment yield and could explain 65.9% of the total variance in sediment yield. The dominant lithological and geomorphological factors controlling annual sediment yield were karst coverage, drainage density, basin relief, plane curvature, elevation, maximum elevation, average slope, dolomite coverage, relative relief, and catchment area. This importance or these contributions of lithological and geomorphological factors to annual sediment yield provides a good reference for selecting key factors when developing soil erosion models. This study yields a greater understanding of the influences of lithology and geomorphology on sediment yield, and is helpful for better catchment management in karst regions.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 30 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Chemical Geology, Volume 523〈/p〉 〈p〉Author(s): Xiaoping Feng, William J. D'Andrea, Cheng Zhao, Shouzhen Xin, Can Zhang, Weiguo Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The orogenic history of the Tibetan Plateau (TP) and surrounding mountain ranges continues to be a major source of disagreement among geologists, particularly concerning the uplift models for the Cenozoic evolution of the TP and estimates for when the highest and largest plateau on Earth reached its current elevation. Quantitative reconstructions of past elevation from geologic samples are necessary to document the uplift history of TP and examine the interactions between tectonic-relief and climate over geological time-scales. Several studies establishing lipid biomarker-based paleoaltimetry based on leaf wax δD values and brGDGTs have been reported in recent years for the TP and surrounding regions, but have yet to be synthesized into a regional framework for paleoelevation determination and uncertainty analysis. Here we report new leaf wax δD and brGDGTs data developed from surface soil samples along an elevation transect spanning ~1250–3900 m.a.s.l in the Hengduan Mountains on the southeastern edge of the TP. We find that the abundance-weighted mean leaf wax δD (〈em〉n〈/em〉-C〈sub〉27〈/sub〉, 〈em〉n〈/em〉-C〈sub〉29〈/sub〉 and 〈em〉n〈/em〉-C〈sub〉31〈/sub〉) values (〈em〉δ〈/em〉D〈sub〉wax〈/sub〉) lapse rates determined for the Hengduan Mountains and for five other nearby study locations are statistically indistinguishable, and can be combined to provide a regional 〈em〉δ〈/em〉D〈sub〉wax〈/sub〉 lapse rate of −1.97 ± 0.04‰ (1〈em〉σ〈/em〉)/100 m for use in regional paleoelevation studies across the southeastern TP. We also find a strong correlation (R〈sup〉2〈/sup〉 = 0.71) between brGDGTs and elevation-dependent mean annual air temperature, which contributes to a number of studies in the region that support the use of fossil brGDGTs as a paleoelevation proxy. Our results reveal that 〈em〉δ〈/em〉D〈sub〉wax〈/sub〉 and brGDGTs for the Hengduan Mountains provide similar empirical uncertainty in paleoelevation reconstruction, with standard errors of elevation estimation (〈em〉SE〈/em〉) of ±483 m (±1〈em〉σ〈/em〉) and ± 394 m (±1〈em〉σ〈/em〉), respectively. We propose a paleoaltimetric approach that combines 〈em〉δ〈/em〉D〈sub〉wax〈/sub〉 and brGDGT data, in order to derive paleoelevation estimates with lower uncertainties. In the Hengduan Mountains data set, the approach yields a 〈em〉SE〈/em〉 (±286 m; ±1〈em〉σ〈/em〉) that is 27–40% lower than when 〈em〉δ〈/em〉D〈sub〉wax〈/sub〉 values and brGDGTs are applied separately.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 30 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Chemical Geology, Volume 523〈/p〉 〈p〉Author(s): Fanqi Qin, Lauren E. Beckingham〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Imaging has emerged as a valuable means of geological sample characterization and parameterizing reactive transport simulations where image analysis can provide porosity, mineral composition and mineral accessible surface area data, for example. Images can be collected using a variety of techniques and at a range of resolutions, yet the impact of image resolution on measured properties is largely unknown. In this work, the impact of 2D image resolution on the calculated mineral abundances, accessibilities and effective surface areas are examined for a sample from the Paluxy formation, Kemper County, Mississippi. Scanning electron microscopy (SEM) backscatter electron (BSE) images of thin sections were captured at resolutions ranging from 0.3 μm to 6 μm. Images were segmented into pores and discrete mineral phases using ImageJ and algorithms developed in MATLAB. Porosity, mineral abundances and mineral accessibilities were calculated by counting pore and mineral pixels in the segmented image where accessible minerals were deemed as those adjacent to the pore space. A 3D X-ray computed tomography (CT) image of a core sample was collected, segmented, and analyzed to evaluate the 3D connected porosity. Cuboids with the same total area as the 2D image were randomly sampled and used to calculate the 3D connected surface area. This was then multiplied by mineral accessibility to calculate accessible mineral surface areas for non-clay minerals. Minimum variations were observed for mineral abundances calculated from images with varying resolutions. For high resolution images, 0.3 μm to 1 μm, mineral accessibilities agreed relatively well. For images with resolutions from 1 μm to 6 μm, the calculated accessibility of smectite/illite decreased with decreasing resolution while quartz accessibility increased. This in turn resulted in higher effective surface areas for quartz with decreasing resolution. No significant variations were observed for calcite, siderite and K-feldspar.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Chemical Geology, Volume 524〈/p〉 〈p〉Author(s): Taiyu Huang, Daizhao Chen, Yong Fu, Rumana Yeasmin, Chuan Guo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The early Cambrian was a critical interval in geological history and featured profound oceanic and biotic changes. To unravel the oceanic redox conditions, high-resolution analyses of iron speciation and redox-sensitive trace elements (Mo and U) within the framework of sequence stratigraphy were carried out on the Niutitang Formation (~528–521 Ma). The two examined sections, the Daotuo and Bahuang sections, were respectively located in a mid-upper slope setting and a lower slope to basin settings behind a seaward submerged sill on the middle Yangtze Block, South China. At Daotuo, the Fe〈sub〉py〈/sub〉/Fe〈sub〉HR〈/sub〉 values display moderate positive covariances with the total organic carbon contents (TOC) and the Mo/TOC ratios, notably in the basal part of the Niutitang Formation. Therefore, at this locality the euxinic water mass wedge was developed in association with a high primary organic productivity/burial rate, likely within a high-productivity zone. In contrast, at Bahuang, the Fe〈sub〉py〈/sub〉/Fe〈sub〉HR〈/sub〉 values show weak to negative covariances with the Mo/TOC ratios and TOC contents in the basal part, indicating that the biogeochemical cycles of Fe, Mo with C were decoupled in a lower-productivity, ferruginous deeper basinal setting. These spatial changes in marine redox structures and biogeochemical cycles can be reasonably explained by the existence of oceanic upwelling in the presence of strong offshore currents and a seaward submarine sill, reconciling the oxygen minimum zone (OMZ) in modern oceanic margins to some extent. This spatial redox pattern also accounts well for previous data based on which the euxinic state intermittently invaded upward onto the shelf margin and evolved into a ferruginous-dominant anoxia in the inner shelf subbasins. In addition, the euxinic wedge dynamically fluctuated upslope and downslope along the transect from the ferruginous outer shelf slope to the basin in response to rise and fall of sea-level. Consequently, the temporal evolution of the redox conditions was driven in part by eustatic variations. Moreover, the paleogeographic position of the Yangtze Block in the mid-lower latitudes suggests that the block was associated with relatively strong offshore currents induced by trade winds, which notably enhanced the oceanic upwelling near the transgression maximum. On the other hand, the dominance of deep ferruginous waters with the local occurrence of a euxinic wedge on the outer shelf slope indicates relatively low concentrations of seawater sulfate and atmospheric oxygen during the deposition of the Niutitang black shales. This redox model thus highlights the important roles of paleogeographic, paleoclimatic and eustatic sea-level changes in controlling the spatiotemporal fluctuations in marine redox conditions and biogeochemical cycling in the early Cambrian ocean.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 20 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Chemical Geology, Volume 525〈/p〉 〈p〉Author(s): Christian Grimm, Raul E. Martinez, Oleg S. Pokrovsky, Liane G. Benning, Eric H. Oelkers〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Particulate material plays a major role in the transport of sparingly soluble nutrients such as P and Fe in natural surface waters. Microbes might gain access to these nutrients either indirectly through particulate dissolution or directly through microbial attack. As such, it seems reasonable to expect a link between the particulate material concentration and bacterial growth in natural surface waters. To explore this link, a series of microcosm growth experiments were performed in the presence of a typical freshwater cyanobacteria, 〈em〉Synechococcus sp.〈/em〉, grown in dilute BG-11 culture media in the presence and absence of basaltic and continental riverine particulate material. Results demonstrate that riverine particulates can increase bacterial biomass by 1) triggering bacterial growth in otherwise unfavourable conditions, 2) increasing total maximum biomass concentration, and 3) inducing bacteria growth during the post-exponential phase. These effects are found to be enhanced by increasing particulate concentration. Results also indicate a positive feedback between the nutrient release from the particulates and growing bacteria, where dissolving particulates enhance bacterial growth, which further promotes particulate dissolution by altering fluid pH. Microscopic analysis showed direct physical contact between particulates and cyanobacteria, suggesting that bacteria attach directly on mineral surfaces to gain required nutrients. Furthermore, frequent bacteria clusters were observed associated with particulates, indicating an increasing aggregation of bacteria in the presence of particulate material, which may facilitate a higher burial efficiency of organic carbon.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 28 June 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Chemical Geology〈/p〉 〈p〉Author(s): P.L. Sullivan, G.L. Macpherson, J.B. Martin, R.M. Price〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉〈em〉Carbonate terrains〈/em〉 (CT) underlie one-fifth of terrestrial, ice-free land and are an important supply of potable water to the world's population, and yet processes endemic to CT critical zones (CZ) and responses of these processes to climatic and anthropogenic pressures are not well understood. Given the rapid dissolution rates and ability to generate well-developed networks of secondary porosity these landscapes can be highly sensitive to impacts from climate change (e.g., modifications of temperature, precipitation, sea level) and human disturbance (e.g., water withdrawal/diversions, changes in land use/land cover). This special issue includes 16 papers focused on CT-CZ processes and potential responses to climatic and human perturbations. Five major themes emerge from these papers, namely: (1) anthropogenic climate and land use changes alter CT-CZ weathering rate and diagenesis, (2) metal and carbon fluxes in CT-CZ will respond to increasing hydrologic variance caused by climate change, (3) endogenous and exogenous processes operating over short time periods (〈10,000 yrs) form landscape patterns in carbonate terrains, (4) rates of carbonate mineral dissolution depend on vadose zone and soil thickness, and (5) open systems may not always promote greater carbonate weathering rates in CT-CZ. These findings reflect the importance of carbonate minerals in Earth's CZ, both in terms of processes unique to carbonate minerals, as well as a predictor of future responses to anthropogenic and environmental changes.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Chemical Geology, Volume 524〈/p〉 〈p〉Author(s): Beichen Wang, Jian Yang, Hongchen Jiang, Guojing Zhang, Hailiang Dong〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉〈em〉N〈/em〉-alkane-based proxies are widely employed to reconstruct paleoclimate and paleoenvironment in lacustrine environments. However, little is known about the influence of microbially mediated alkane-degradation on 〈em〉n〈/em〉-alkane-derived proxies. In this study, the chemical composition of 〈em〉n〈/em〉-alkanes and microbially mediated 〈em〉n〈/em〉-alkane degradation potential were investigated in the surface sediment samples collected from seven lakes with a range of salinity from freshwater to salt saturation on the northern Qinghai-Tibetan Plateau (QTP). The results showed that the chemical composition of 〈em〉n〈/em〉-alkanes differed among the studied QTP lakes. Significant correlations were observed between salinity and some 〈em〉n〈/em〉-alkane-based paleoclimate and paleoenvironment proxies, such as ratio of C〈sub〉21〈/sub〉〈sup〉−〈/sup〉/C〈sub〉22〈/sub〉〈sup〉+〈/sup〉, average chain length (ACL) and carbon preference index (CPI). This suggested that salinity may affect the validity of some 〈em〉n〈/em〉-alkane-based paleoclimate and paleoenvironment proxies. Alkane-degrading bacteria were abundant and widespread in the studied freshwater and saline/hypersaline lakes but were minor or absent in salt-saturation lakes. The obtained alkane-degrading bacterial strains showed active ability to degrade 〈em〉n〈/em〉-hexadecane. This suggested that the salinity influence on the 〈em〉n〈/em〉-alkane distribution may be partially related to microbial degradation, which awaits further in-situ investigation. So salinity variation should be taken into account when using 〈em〉n〈/em〉-alkane-based proxies for reconstructing paleoclimate and paleoenvironment in lakes.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 30 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Chemical Geology, Volume 523〈/p〉 〈p〉Author(s): Pavel Pracný, Jiří Faimon, Dalibor Všianský, Antonín Přichystal〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Magnesium (Mg) and strontium (Sr) preserved in speleothems are among the terrestrial climatic proxies. The mechanism of their release from impurities in limestone bedrock is usually neglected in paleoclimatic studies mainly because it is not very well understood; most cation release studies focus on pure minerals instead of limestone. Therefore, the Mg and Sr released from six types of limestone from the Moravian Karst (Czech Republic) were studied experimentally and compared with the dripwater data coming from the Punkva Caves (Moravian Karst) formed in two of the studied limestone types. The dissolution data were used to calibrate a kinetic dissolution model. The results show an incongruent dissolution of Mg-calcite and dolomite, pronounced especially in advanced stages of the dissolution. According to the results, the trace element ratios in solution were dependent mainly on (1) the limestone composition (i.e., the Mg-calcite and dolomite availability and the stoichiometry of individual minerals) and (2) on the extent of limestone-solution interaction (controlled by dissolution dynamics). Modeling indicated that the dynamics depend on the ratios of the area of rock–water and air–water interfaces to the water volume. Moreover, modeling suggests that the dynamics and subsequently also the trace element ratios are influenced by (a) the fresh surface dissolution during the initial stages of interaction and by (b) the preferential release of trace elements from mineral surfaces (nonstoichiometric dissolution). The effects of disturbed surfaces and preferential leaching are limited by available fresh surfaces. Fresh surfaces are formed through rock crushing, e.g., during physical weathering (in the field) or sample preparation (in a laboratory). The dripwaters from Punkva Caves had trace element ratios with values between the ratios resulting from the experimental dissolution of the limestones present on the site, indicating a naturally mixed composition of waters.〈/p〉 〈p〉This study has shown that Mg/Ca and Sr/Ca ratios in dripwaters might be controlled by various climate-independent variables, which raises further questions about utilizing the ratios as paleoclimatic proxies.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Chemical Geology, Volume 524〈/p〉 〈p〉Author(s): Jennifer Thompson, Simon W. Poulton, Romain Guilbaud, Katherine A. Doyle, Stephen Reid, Michael D. Krom〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We report the development of a modified method for evaluating different reservoirs of sedimentary phosphorus (P) in ancient marine sedimentary rocks and in modern Fe-rich sediments. Utilising the existing SEDEX scheme for P partitioning in modern sediments, we initially demonstrate limitations in the application of the original scheme to sediments and rocks containing crystalline hematite and magnetite. We tested additional extractions for these crystalline Fe phases, using both synthetic minerals, and modern and ancient sediments. The addition of 6 h oxalate and 6 h citrate-dithionate-acetate extractions considerably enhanced the total recovery of synthetic magnetite and hematite to 88.7 ± 1.1% and 76.9 ± 3.8%, respectively. In addition, application of the 6 h oxalate extraction to synthetic P-containing magnetite recovered 93.9 ± 1.7% of the Fe present and 88.2 ± 12.8% of the co-precipitated P. Based upon these results we developed a modified SEDEX extraction scheme. The modified scheme was applied to modern Fe-rich sediments from Golfo Dulce, Costa Rica, which resulted in 16% higher Fe-bound P recovery. Application of the scheme to a variety of ancient marine rocks increased the recovery of Fe-bound P by up to 22%. We also highlight the potential for authigenic carbonate fluorapatite to convert to more crystalline apatite in ancient rocks during deep burial and metamorphism. We suggest that in such systems minimum and maximum estimates of the total reactive P pool may be calculated with and without the inclusion of crystalline P. It is noted that the application of the revised method may have important implications for understanding the cycling of P in ancient marine environments.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Chemical Geology, Volume 524〈/p〉 〈p〉Author(s): L. Millière, N. Gussone, T. Moritz, S. Bindschedler, E.P. Verrecchia〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Strontium (Sr) and calcium (Ca) isotopic compositions and Sr/Ca ratios have been analysed in different fractions of pedogenic needle fibre calcite (NFC) from the Swiss Jura Mountains (Villiers, Neuchâtel, Switzerland) in order to determine their Ca sources and to investigate the potential role of fungi in the origin of NFC. 〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr ratios have been measured to trace the Ca trapped within different pedogenic carbonate. This ratio was compared for previously identified microscopic morphological groups of NFC, the bulk soil fine earth (〈2 mm), the carbonate host rock (CHR), a late calcitic cement (LCC, another pedogenic carbonate precipitated physicochemically at the same depth as NFC in soil pores), the soil solution, and the throughfall. The 〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr indicated a mixing of weathered allochthonous minerals (an atmospheric component) and the dissolved CHR (the local geogenic component). Moreover, the comparison of 〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr ratios of the different types of NFC with LCC suggests that the contribution of Ca from the main Ca sources slightly differs between NFC morphotypes and LCC. In addition, the three NFC morphotypes displayed Sr isotopic compositions different from each other, emphasizing a direct relationship between the microscopic shapes of NFC and the processes involved in their respective formation, including the origin of the Ca. Strontium concentrations and δ〈sup〉44/40〈/sup〉Ca values of NFC and LCC crystals were used to determine possible differences in their growth rate and/or micro-environmental conditions during their formation. Crystals described micromorphologically as simple needles (SN) were enriched in 〈sup〉44〈/sup〉Ca and depleted in Sr compared to LCC, suggesting that the elongated shape of the SN crystal cannot be related to a rapid precipitation rate, but rather to a slow precipitation. Calculations applied to the soil solution evolution during calcite precipitation demonstrates the utilisation of large portions of the Ca pool for NFC formation within a closed system, e.g. inside an organic mould, such as fungal hyphae. The differences between the three microscopic groups can be explained by a mixing of the SN with a LCC-like compound originating from the soil solution.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0009254119303171-ga1.jpg" width="260" alt="Unlabelled Image" title="Unlabelled Image"〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 14 June 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Chemical Geology〈/p〉 〈p〉Author(s): Kenji Shimizu, Motoo Ito, Qing Chang, Takashi Miyazaki, Kenta Ueki, Chiaki Toyama, Ryoko Senda, Bogdan S. Vaglarov, Tsuyoshi Ishikawa, Jun-Ichi Kimura〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The lithophile elements and isotopic compositions of oceanic basalts suggest they derive from different mantle components. We present new analytical results of un-degassed deep-marine basaltic glasses from various regions, and we find strong linear correlations of R〈sup〉2〈/sup〉 ≥ 0.997 between H〈sub〉2〈/sub〉O and F as well as H〈sub〉2〈/sub〉O and Ce, for which we propose mantle trends. The mantle trends represent global variations of mantle components, ranging from a depleted dry peridotite of mid-ocean ridge basalt (MORB) (DMM, depleted MORB source mantle: H〈sub〉2〈/sub〉O = 100 ppm; H〈sub〉2〈/sub〉O/Ce = 200; H〈sub〉2〈/sub〉O/F = 10) to a hydrous peridotite of Hawaiian ocean island basalt (OIB) of deep mantle origin (FOZO, focal zone: H〈sub〉2〈/sub〉O = 750 ppm; H〈sub〉2〈/sub〉O/Ce = 200; H〈sub〉2〈/sub〉O/F = 18.5). Accordingly, we defined the correlation as a volatile DMM–FOZO trend. Based on our findings, we report novel H〈sub〉2〈/sub〉O–F–Ce systematics to discriminate the degree of water depletion in the source mantle and the rehydration of the mantle with recycled surface water through oceanic plate subduction. Using this method, most OIBs are distinguished clearly from the DMM–FOZO trend, and we find that the water in their sources originates from recycled water derived from the hydrated oceanic crust and sediment after various degrees of dehydration (75–95%) in subduction zones.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Chemical Geology, Volume 524〈/p〉 〈p〉Author(s): Luis Monasterio-Guillot, Fulvio Di Lorenzo, Encarnacion Ruiz-Agudo, Carlos Rodriguez-Navarro〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The kinetics of silicate carbonation in aqueous solutions are typically sluggish, especially at neutral to alkaline conditions. This hampers the complete understanding of the mechanisms and parameters that control mineral carbonation during carbon capture and storage (CCS). Here we study the hydrothermal dissolution and carbonation of pseudowollastonite (psw; 〈em〉α〈/em〉-CaSiO〈sub〉3〈/sub〉), one of the most reactive silicates known, under a range of geochemical conditions ranging from acidic to strongly alkaline pH, presence/absence of different background alkali metal ions and carbonate sources (K〈sub〉2〈/sub〉CO〈sub〉3〈/sub〉 and Na〈sub〉2〈/sub〉CO〈sub〉3〈/sub〉, pH ~13, or NaHCO〈sub〉3〈/sub〉 and KHCO〈sub〉3〈/sub〉, pH ~9). We show that in addition to amorphous silica precipitation, the formation of secondary Na + Ca- or K + Ca-silicates in the presence of Na〈sup〉+〈/sup〉 and K〈sup〉+〈/sup〉 background ions, respectively, fosters the progress of psw carbonation. However, the formation of Ca-containing secondary crystalline silicates and Ca-containing amorphous silica is shown to be a strong handicap for a fully effective carbonation. In all cases a higher conversion into CaCO〈sub〉3〈/sub〉 (up to ~70 mol%) is achieved when using bicarbonate salts (i.e., lower initial pH). By using a reactor with a pressurized CO〈sub〉2〈/sub〉-solution, with and without Na〈sup〉+〈/sup〉 or K〈sup〉+〈/sup〉 background ions, rapid and nearly complete conversion of psw with a CaCO〈sub〉3〈/sub〉 yield ~92 mol% is achieved because, in addition to the initial low pH (~3.7) that favored 〈em〉α〈/em〉-CaSiO〈sub〉3〈/sub〉 dissolution, abundant Ca-free non-passivating amorphous silica formed along with calcite. These results imply that the presence (e.g., use of sea water during CO〈sub〉2〈/sub〉 injection or mixing with saline formation solutions) or the release of different alkali metal ions (e.g., after feldspar and/or basaltic glass dissolution) in combination with a reaction-induced pH increase during in situ CCS scenarios may strongly limit carbonation due to the capture of alkaline-earth metals in secondary silicates and a reduction in reaction rates. In turn, our results show that the high conversion achieved in pure CO〈sub〉2〈/sub〉-aqueous systems, while relevant for ex situ CCS, may not reflect the actual conversion in multicomponent natural systems following reactive transport during in situ CCS. Moreover, the precipitation of secondary silicate and calcium carbonate phases have a direct cementing effect, which could be detrimental for in situ CCS, as it would likely reduce host rock permeability, but would be relevant and beneficial for the setting of novel CaSiO〈sub〉3〈/sub〉-based non-hydraulic cements with reduced CO〈sub〉2〈/sub〉 footprint.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Chemical Geology, Volume 524〈/p〉 〈p〉Author(s): Hong-Kun Dai, Jian-Ping Zheng, Suzanne Y. O'Reilly, William L. Griffin, Qing Xiong, Rong Xu, Yu-Ping Su, Xian-Quan Ping, Fu-Kun Chen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Crustal recycling is an important cause of mantle heterogeneity and can have significant control on basalt compositions. Recycled components from the subducted (Paleo-) Pacific slab have frequently been recognized in Cenozoic basalts from the eastern North China Craton (NCC). However, it still remains unclear if the subducted Paleo-Asian oceanic slab contributed to intraplate basalts in this Craton.〈/p〉 〈p〉In a search of evidence for the recycled components from this slab, we have studied the Ar〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉Ar age and elemental and Sr-Nd-Pb isotope compositions of newly-discovered basalts from the Langshan area and compiled a regional synthesis of Cenozoic alkali basalts from the northwest NCC. This region is far from the Pacific domain but near the suture zone of the Paleo-Asian Ocean. With a Late Cretaceous eruption age (~89 Ma), Langshan basalts have low silica and high FeO, MgO and alkali contents, high incompatible elemental concentrations, positive Sr, Eu, Ba, Nb, Ta and negative Pb and Ti anomalies with high Ce/Pb, Nb/U, Ba/Rb and low Rb/Sr ratios, superchondritic Zr/Hf ratios, and uniform radiogenic isotopes (ɛ〈sub〉Nd(t)〈/sub〉 = 2.20–2.51, 〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr〈sub〉〈em〉i〈/em〉〈/sub〉 = 0.703807–0.704348, 〈sup〉206〈/sup〉Pb/〈sup〉204〈/sup〉Pb〈sub〉〈em〉i〈/em〉〈/sub〉 = 18.200–18.384, 〈sup〉207〈/sup〉Pb/〈sup〉204〈/sup〉Pb〈sub〉〈em〉i〈/em〉〈/sub〉 = 15.470–15.515, 〈sup〉208〈/sup〉Pb/〈sup〉204〈/sup〉Pb〈sub〉〈em〉i〈/em〉〈/sub〉 = 38.007–39.430). These compositional characteristics are shared by the compiled Cenozoic alkali basalts from northwest NCC.〈/p〉 〈p〉The low silica and high MgO, FeO and alkali contents together with the positive Nb, Ta and negative Ti anomalies were probably controlled by silica-deficient garnet pyroxenite in the mantle source. The partial melting is estimated to have occurred in the asthenosphere under an average mantle potential temperature of 1300–1450 °C and a pressure of ~2.5 GPa. The positive Sr, Eu, Ba, Nb, Ta anomalies and the canonical indices (high Ce/Pb, Nb/U, Ba/Rb and low Rb/Sr ratios) indicate the involvement of a subducted oceanic igneous slab. Considering 1) the particular tectonic locality of the study region, 2) the inferred northward increase of silica-deficient pyroxenite in the mantle source of Cenozoic alkali basalts, 3) the evidence for strong lithospheric modification beneath the northwest NCC induced by slab-derived components, and 4) the longevity of subducted slabs in convecting mantle, the subducted Paleo-Asian oceanic materials could have introduced ubiquitous mantle heterogeneity beneath the northwest NCC and played a significant role in the generation of the Late Cretaceous to Cenozoic intraplate alkali basalts there.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Marine and Petroleum Geology, Volume 109〈/p〉 〈p〉Author(s): Haiyan Hu, Fang Hao, Xusheng Guo, Jizheng Yi, Zhiguo Shu, Hanyong Bao, Xiaoyu Zhu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Ten Longmaxi shale samples were collected from the Jiaoshiba area, China, where 5 billion cm〈sup〉3〈/sup〉/year of shale gas is produced. The samples were evaluated to characterize the pores of various shale lithofacies. Three shale lithofacies were determined in the Jiaoshiba area, Sichuan Basin, China, based on the shale mineral components, namely, siliceous lithofacies (SL), argillaceous lithofacies (AL), and mixed lithofacies (ML). Field emission scanning electron microscopy (FE-SEM), which was performed under high and low voltages, GRI porosity, and carbon dioxide and nitrogen adsorptions were used to investigate the bulk-shale porosity, pore type, pore size, pore morphology, and pore volume among the lithofacies. Lithofacies affects the shale total organic carbon (TOC), bulk-shale porosity, pore size, shape, and volume. SL and ML contain high porosity, high TOC, abundant organic-matter (OM)-hosted pores, and high OM porosity, whereas AL contains few OM pores and has low TOC and low porosity. In the same lithofacies, samples with various TOC values exhibit different pore morphologies. For SL, the low-TOC sample has a round and elliptical OM pore forms, whereas the high-TOC samples show linear and narrow pore shapes that are probably associated with gas expulsion. In ML, the higher TOC is related to spherical or near-spherical OM pores, whereas the OM pore shape collapses in the low-TOC shale. Therefore, lithofacies affect the shale reservoir, and the characteristic and evolution of OM pores should be considered as constraints in shale lithofacies. In SL, sections with a higher TOC value are prime targets despite the high expulsion efficiency, which does not affect the enrichment and high yield of the shale gas. Sections of ML and low-TOC SL should be considered as potential targets because of higher OM porosity and low expulsion efficiency, whereas sections of AL engender risk in exploration and development of shale gas.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Earth-Science Reviews, Volume 197〈/p〉 〈p〉Author(s): P. Bohorquez, P.J. Jimenez-Ruiz, P.A. Carling〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉In this work, we present a whole system model of megafloods from catastrophic ice-dam failure in the late Pleistocene that comprises the study of the dynamics of the glacial lake, the propagation of the flood wave downstream of the dam, and an approximation to the ice breach process. The ice-dam incision rate was simply considered an unknown constant, which was varied systematically to best fit the maximum altitude of the simulated water surface and the paleostage indicators in the downstream valley during the transient megaflood. Hence, the hydrograph resulting from the breach of the ice dam was not prescribed but was an output of the paleohydraulic reconstruction.〈/p〉 〈p〉By considering two possible configurations of the breach in the ice dam, i.e. full or partial removal of the ice, we constrained the incision rate in the narrow range of 28 − 42 m ⋅ h〈sup〉−1〈/sup〉. Two connected glacial lakes, Kuray and Chuja, released 95% of the stored water volume (i.e., 564 km〈sup〉3〈/sup〉) in 33.8 hours. A peak discharge of 10.5 M m〈sup〉3〈/sup〉 ⋅ s〈sup〉−1〈/sup〉 was required to form numerous giant bars and run-up deposits in the Chuja and Katun valleys. The peak streamflow occurred after 11 h when 45% of the available lake volume had been evacuated from the Kuray and Chuja basins. Further verification of the reconstructed megaflood was achieved by studying the computed hydraulic conditions during the lake draining that justify the existence and orientation of several fields of subaqueous gravel-dunes in the glacial lake. Complex spatiotemporal patterns during the recession stage of the flood built most of the fields of bedforms. In terms of nondimensional parameters, the Froude and Shields numbers that formed the dune fields were similar to those observed in large sandy rivers, but the flow was undoubtedly unsteady and two-dimensional.〈/p〉 〈p〉We conclude by noting that the extensions of the simulated area cannot be cropped or analysed by independent parts in order to predict the formation of the most relevant geological records due to the unsteady, two-dimensional nature of the flow motion and the development of backwater effects in the drainage network. Lastly, the paleohydrological reconstruction of a megaflood has helped not only to infer the dynamics of the event but also to retrodict the mean parameters of the ice-dam failure mechanism.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 10 May 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Chemical Geology〈/p〉 〈p〉Author(s): Jérôme Gaillardet, Damien Calmels, Gibran Romero-Mujalli, Elena Zakharova, Jens Hartmann〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Carbonate rocks are a peculiarity of the Earth relative to other planets in the solar system. Large terrestrial areas are covered by carbonate lithology, which actively reacts with atmospheric/biospheric CO〈sub〉2〈/sub〉. Although carbonate rocks represent a major component of the global carbon cycle, their intensity and rates of chemical weathering have been overlooked. In this study, we examine three global databases of rivers and springs draining carbonate regions under various climate conditions (from −15 °C to +30 °C). Using Ca〈sup〉2+〈/sup〉 + Mg〈sup〉2+〈/sup〉 concentrations as a proxy, we show that carbonate weathering intensity depends upon land temperature according to a boomerang-type relationship, with maximum dissolution between 10 and 15 °C. We show that this pattern is primarily controlled by thermodynamics if we assume that the partial pressure of CO〈sub〉2〈/sub〉 in soil (〈em〉pCO〈/em〉〈sub〉2〈/sub〉) increases from atmospheric-like levels under cold climate up to 100 times the present day atmospheric concentration under hot climate. The link between soil 〈em〉pCO〈/em〉〈sub〉2〈/sub〉 and land temperature is still not very well known, but by using three different published predictive soil 〈em〉pCO〈/em〉〈sub〉2〈/sub〉 vs. T curves, we show that the boomerang shape can be, at least qualitatively, reproduced.〈/p〉 〈p〉This study shows that more data on carbonate weathering in various environments are needed to predict with more accuracy the role that carbonate lithologies and overlying ecosystems could play in the Anthropocene.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 23 May 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Chemical Geology〈/p〉 〈p〉Author(s): Catherine A. Chamberlin, Thomas S. Bianchi, Amy L. Brown, Matthew J. Cohen, Xiaoli Dong, Madison K. Flint, Jonathan B. Martin, Daniel L. McLaughlin, A. Brad Murray, Andrea Pain, Carlos J. Quintero, Nicholas D. Ward, Xiaowen Zhang, James B. Heffernan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We constructed mass balances of both calcium and phosphorus for two watersheds in Big Cypress National Preserve in southwest Florida (USA) to evaluate the time scales over which its striking landscape pattern developed. This low-relief carbonate landscape is dotted with evenly spaced, evenly sized, shallow surface depressions that annually fill with surface water and thus support wetland ecosystems (e.g. cypress domes) embedded in a pine-dominated upland matrix with exposed bedrock. Local and landscape scale feedbacks between hydrology, ecological dynamics and limestone dissolution are hypothesized to explain this karst dissolution patterning. This hypothesis requires the region to be wet enough to initiate surface water storage, which constrains landscape formation to interglacial periods. The time scale therefore would be relatively recent if creation of the observed pattern occurred in the current interglacial period (i.e. Holocene), and older time scales could reflect inherited patterns from previous inter-glacial periods, or from other processes of abiotic karstification. We determined phosphorus stocks across four landscape compartments and estimated the limestone void space (i.e., wetland depression volume) across the landscape to represent cumulative calcium export. We calculated fluxes in (e.g., atmospheric deposition) and out (i.e., solute export) of the landscape to determine landscape denudation rates through mass balance. Comparing stocks and annual fluxes yielded independent estimates of landscape age from the calcium and phosphorus budgets. Our mass balance results indicate that the landscape began to develop in the early-mid Holocene (12,000–5000 ybp). Radiocarbon dating estimates implied similar rates of dissolution (~1 m per 3000–3500 years), and were in agreement with Holocene origin. This supports the hypothesis that ecohydrologic feedbacks between hydrology and vegetation occurring during the present interglacial period are sufficient to shape this landscape into the patterns we see today, and more broadly suggests the potential importance of biota in the development of macro-scale karst features.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 12 February 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Chemical Geology〈/p〉 〈p〉Author(s): Alan D. Wanamaker, David P. Gillikin〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In order to constrain spatial and temporal temperatures and environmental conditions in the North Atlantic Ocean during the Holocene, high-resolution (seasonal to annual) marine proxies with excellent chronological constraints are needed. The long-lived ocean quahog, 〈em〉Arctica islandica〈/em〉, which has the potential to provide a precise annually-dated record, via crossdating techniques, is a fairly well-developed and tested marine proxy archive. In particular, oxygen isotopes derived from 〈em〉A. islandica〈/em〉 shell carbonate have provided a wealth of information on marine climate and ocean circulation dynamics, however, shell-derived oxygen isotopes are influenced by both the isotopic source water signature (covarying with salinity) and seawater temperature. If seawater isotopic signature is not known, temperature reconstructions become challenging. Thus, an independent technique to estimate past seawater temperatures is highly desired, however based on previous studies on adult and juvenile clams, the utility of elemental ratios in 〈em〉A. islandica〈/em〉 shell material as environmental proxies remains questionable. To further evaluate the influence of seawater temperature on elemental and isotopic incorporation during biomineralization, 〈em〉A. islandica〈/em〉 shells were grown at constant temperatures under two regimes during a 16-week period from March 27 to July 21, 2011 at the Darling Marine Center in Walpole, Maine. Individual juvenile clams were stained with calcein and cultured at 10.30 ± 0.30 °C for six weeks. After this, the clams were again stained with calcein and cultured at 15.00 ± 0.40 °C for an additional 9.5 weeks. Average salinity values were 30.20 ± 0.70 and 30.70 ± 0.70 in the first and second phases of the experiment, respectively. Continuous sampling within and across the temperature conditions (from 10.30 °C to 15.00 °C) coupled with the calcein markings provided the ability to place each sample into a precise temporal framework and to establish exact average growth rates for the shells sampled. After accounting for changes in the isotopic composition of seawater, oxygen isotopes from one sampled shell effectively recorded seawater temperatures during the study and also gave confidence to the temporal fit of the data. Elemental ratios (Sr/Ca, Mg/Ca, Ba/Ca) from five aragonitic shells were determined via laser ablation inductively coupled plasma mass spectrometry. Sr/Ca and Mg/Ca data showed little coherence with temperature during the culture experiment, including the rapid 5 °C increase in seawater temperature. However, Ba/Ca ratios showed an inverse relationship with seawater temperatures although this relationship was noisy. Additionally, salinity interactions were present during the 15.00 °C treatment, further highlighting complex incorporation of elements during biomineralization. Incorporation of Sr, Mg, and Ba were strongly and variably impacted by growth rates. Combined, the results from these culture experiments demonstrate that Sr/Ca, Mg/Ca, Ba/Ca ratios in juvenile 〈em〉A. islandica〈/em〉 shell material are dominated by physiological processes and thus not reliable as environmental proxies.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 9 March 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Chemical Geology〈/p〉 〈p〉Author(s): Matthew D. Covington, Kiefer A. Vaughn〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Within numerical models of karst development, geochemical and hydrological boundary conditions are typically assumed to be constant. However, rates of calcite dissolution in natural karst systems can vary substantially in time. In particular, variation in carbon dioxide (CO〈sub〉2〈/sub〉) concentrations has been shown to produce time variability in dissolution rates in karst streams, but controls on CO〈sub〉2〈/sub〉 variation within karst systems are relatively poorly quantified. Here we analyze hourly in-situ measurements of dissolved CO〈sub〉2〈/sub〉, discharge, and specific conductance at a pair of karst underflow-overflow springs and examine potential drivers of variability in CO〈sub〉2〈/sub〉 and dissolution rates. The springs display strong seasonal variability in CO〈sub〉2〈/sub〉 and saturation state as well as moderate variation during storm events. Though both springs have elevated CO〈sub〉2〈/sub〉 concentrations in the summer season, the overflow spring experiences a substantial decrease in dissolved CO〈sub〉2〈/sub〉 below a critical discharge threshold. We hypothesize that this decrease results from ventilation within the overflow portion of the system as segments of the flow path transition from full pipe to open channel flow. The overflow spring experiences substantially lower average dissolution rates than the underflow spring, despite larger discharge and chemical variability during high flow events at the overflow spring. Though open systems are frequently presumed to have higher dissolution rates, because of their ability to replenish CO〈sub〉2〈/sub〉 that is consumed in the dissolution process, these data suggest that dissolution rates within the closed portion of the system may in some cases be higher due to the inability of closed flow paths to ventilate excess CO〈sub〉2〈/sub〉 to the atmosphere. Such conditions are likely to occur in conduits where CO〈sub〉2〈/sub〉 concentrations are elevated above atmospheric levels and average flow through times are short compared to the time scale over which water reaches equilibrium with respect to calcite.〈/p〉〈/div〉

Description: 〈p〉Publication date: 20 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Chemical Geology, Volume 525〈/p〉 〈p〉Author(s): Brendan A. Bishop, Shannon L. Flynn, Tyler J. Warchola, Md. Samrat Alam, Leslie J. Robbins, Yuxia Liu, George W. Owttrim, Daniel S. Alessi, Kurt O. Konhauser〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Marine bacterial plankton play a key role in elemental cycling through their ability to bind, assimilate, metabolize, and modify the redox state of trace metals in seawater. Of those processes, arguably the least studied are the mechanisms underpinning trace metal adsorption to planktonic marine bacteria, despite a plethora of literature pertaining to terrestrial species. Recently, Liu et al. (2015) demonstrated that the marine cyanobacterium 〈em〉Synechococcus〈/em〉 sp. PCC 7002 has the capacity to remove appreciable amounts of Cd〈sup〉2+〈/sup〉, a proxy for other divalent cations, from seawater by adsorption. In this study, we build on that work and employ a surface complexation modelling (SCM) approach using titration and pH adsorption edge experiments to calculate the thermodynamic binding constants of four bioessential transition metals (Co, Ni, Cu, Zn) to 〈em〉Synechococcus〈/em〉 in simulated seawater. Based on the titration results, the major functional groups involved in metal binding were carboxyl groups with a pK〈sub〉a〈/sub〉 of 5.59 and phosphoryl groups with a pK〈sub〉a〈/sub〉 of 7.61. Metal adsorption experiments indicate that 〈em〉Synechococcus〈/em〉 can bind considerable concentrations of Zn, Cu, Ni, and Co at pH 8. When all four metals are simultaneously added to solution, the same adsorption pattern of Zn 〉 Cu 〉 Ni 〉 Co is maintained, and accurately predicted by the SCM. Based on average marine cell densities and turnover rates of 〈em〉Synechococcus〈/em〉 cells in the photic zone, we calculate that 〈em〉Synechococcus〈/em〉, in the absence of competing ligands such as dissolved organic matter (DOM), has the theoretical capacity to remove nearly all of the free metal cations from seawater. These observations highlight the surface reactivity of marine cyanobacteria as a potentially important vector for the transfer of dissolved metals from the photic zone to deeper waters or the seafloor in modernoceans, but they also have implications for the Precambrian oceans as sinking cyanobacteria could have acted as an exit channel for trace elements into ancient sediments including banded iron formations (BIF).〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 22 September 2017〈/p〉 〈p〉〈b〉Source:〈/b〉 Chemical Geology〈/p〉 〈p〉Author(s): Melita Peharda, Julien Thébault, Krešimir Markulin, Bernd R. Schöne, Ivica Janeković, Laurent Chauvaud〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉High-resolution stable-isotope ratio data (δ〈sup〉18〈/sup〉O, δ〈sup〉13〈/sup〉C) were used to study growth strategies of two bivalve species, 〈em〉Pecten jacobaeus〈/em〉 (calcitic shell) and 〈em〉Glycymeris pilosa〈/em〉 (aragonitic shell) from the North Adriatic Sea. The principal objectives of this study were to identify the period of the year when the growth line is formed in the shell of two target species, to identify the main growing season of these two species, to identify the environmental drivers of shell growth, and to evaluate the potential applicability of δ〈sup〉18〈/sup〉O and δ〈sup〉13〈/sup〉C values for the reconstruction of environmental variability. Samples were collected from the North Adriatic Sea by commercial bean trawl (〈em〉P. jacobaeus〈/em〉, December 2013 and January 2014, N = 4) and SCUBA diver (〈em〉Glycymeris pilosa〈/em〉, March 2016, N = 3). Samples for the oxygen (δ〈sup〉18〈/sup〉O) and carbon (δ〈sup〉13〈/sup〉C) isotope composition of the calcium carbonate were collected by drilling the outer shell layer across several annual cycles. Temporal and spatial temperature and salinity values inside the investigated area were simulated using the 3D numerical ocean model - ROMS. The δ〈sup〉18〈/sup〉O cycles corresponded to the number of seasonal growth marks observed on the external shell surface of both target species, thereby confirming the annual periodicity of these growth patterns. In February 2012, extreme cooling of the water column accompanied by dense water formation occurred in the Adriatic Sea - an event recorded by 〈em〉P. jacobaeus〈/em〉 shells. This study indicates that 〈em〉P. jacobaeus〈/em〉 and 〈em〉G. pilosa〈/em〉 have contrasting shell growth strategies. 〈em〉Pecten jacobaeus〈/em〉 grows during winter and slows shell growth during the warmest part of the year, and thereby may be an interesting archive for winter conditions. Due to its longevity and continuous growth during the warmest part of the year, 〈em〉G. pilosa〈/em〉 is a promising archive for the reconstruction of summer seawater temperatures.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Marine and Petroleum Geology, Volume 110〈/p〉 〈p〉Author(s): Yan Detian, Chen Daizhao, Wang Zhuozhuo, Li jing, Yang Xiangrong, Zhang Bao〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Black shales deposited across the Late Ordovician and Early Silurian transition are considered to be the most important source rock and shale gas reservoirs in the Yangtze region of South China. However, the origin of these sediments remains contentious. In this study, we investigated the systematic changes in total organic carbon (TOC), organic carbon isotopes (δ〈sup〉13〈/sup〉C〈sub〉org〈/sub〉), major elements and trace elements on the Ordovician-Silurian boundary strata from Qiaoting, North Yangtze Sea, to reconstruct the climatic conditions, redox changes, primary productivity, and other factors there, promoting the understanding for the formation mechanism of the organic-rich black shales. Element compositions and their ratios suggest that the black shales studied here were dominantly sourced by the felsic igneous rock, which is similar to granodiorite in composition. Paleoclimatic proxies (CIA, CIW, δ〈sup〉13〈/sup〉C〈sub〉org〈/sub〉) suggest that the global climate system experienced significant changes from warm-humid to cold-dry and then to warm-humid climates during the Ordovician-Silurian transition. Paleoredox indices (S/C, U/Th, Ni/Co and V/(V + Ni) ratios) also demonstrate fluctuating redox variations from anoxic to oxygenated, and then to anoxic states during this interval in the Yangtze Sea, which describe an oxygenated Guanyinqiao strata sandwiched between the stagnant and anoxic Wufeng and Longmaxi black shales. Paleoproductivity parameters (TOC, Ba〈sub〉bio〈/sub〉 contents and P/Al ratio) suggest that the organic-rich Wufeng and Longmaxi black shales, were deposited with a high biological productivity, while the organic-lean Guanyinqiao sediments were deposited with a low biological productivity. These data demonstrate large climatic and oceanic fluctuations during the Ordovician-Silurian transition, providing essential controlling factors on the oceanic anoxia, primary productivity, and subsequent organic-rich black shale depositions in the Yangtze region during the Late Ordovician and Early Silurian intervals.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Lithos, Volumes 344–345〈/p〉 〈p〉Author(s): David Hernández-Montenegro, Christopher L. Andronicos, Carlos A. Zuluaga, Ruth F. Aronoff〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Two metasedimentary migmatite samples from the same outcrop in the northern margin of the Oak Creek pluton in the Wet Mountains, Colorado, have distinct mineralogy, textures and major and trace element geochemistry. Sample W6, a garnet-biotite migmatite, has trace element characteristics consistent with a sedimentary protolith, this sample is also rich in silica and lacks sillimanite and cordierite. Sample W6A, a garnet-sillimanite-cordierite migmatite, has strong heavy rare earth element (HREE) enrichment, low silica, and contains abundant aluminum-rich minerals. Both rocks are relatively oxidized, consistent with sedimentary protoliths for both. Based on textural and geochemical evidence, we interpret the differences in mineralogy between the two samples to be the result of differing degrees of melt extraction and variations in protolith composition. Such differences were assessed using isocon analysis and calculated 〈em〉P-T〈/em〉 phase diagrams. Melt retention in sample W6 resulted in the absence of sillimanite and cordierite, and back-reaction between minerals and melt in the peak assemblage. By contrast, melt extraction in W6A left garnet in the residuum, and imparted a strong heavy rare earth element enrichment on the sample, allowing preservation of the peak mineral assemblage. Consequently, W6A records peak conditions of 743 °C and ~7.6 kbar, whereas W6 yields lower 〈em〉P-T〈/em〉 estimates that may represent the prograde and retrograde metamorphic paths. Our results indicate that melt extraction can be heterogeneous even at outcrop scale, and differing mineralogy may reflect variable proportions of melt loss and local variations in the composition of the protolith. Moreover, at least at small-scale, migmatization of iron-rich protoliths is a plausible mechanism for the production of ferroan, alkaline granitic magmas.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Lithos, Volumes 344–345〈/p〉 〈p〉Author(s): Caue Rodrigues Cioffi, Mario da Costa Campos Neto, Andreas Möller, Brenda Chung Rocha〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Combining U-Pb geochronology and trace element characteristics of accessory minerals more reactive during metamorphism and deformation than zircon, such as titanite (CaTiSiO〈sub〉5〈/sub〉), is a powerful tool for elucidating pressure-temperature-time (P-T-t) evolution of orogenic basement complexes. This study reports in-situ titanite U-Pb and trace element data from upper-amphibolite facies metatexitic orthogneisses of the Pouso Alegre Complex in the basement of the Neoproterozoic southern Brasília Orogen, SE Brazil. The titanite data is combined with thermodynamic modeling, major phase compositions and U-Pb zircon dating and used to constrain the P-T-t path of the complex during the Neoproterozoic orogenesis. The investigated garnet amphibole gneisses record peak metamorphic conditions of 750–775 °C and 10.5–12.5 kbar, associated with partial melting and dated at ca. 630–620 Ma based on U-Pb analyses of HREE+Y depleted titanite cores, inferred to have crystallized in the presence of garnet near the peak P-T conditions. Extensive melt crystallization at ca. 616 Ma is constrained by U-Pb dating of leucosome zircons. The exhumation of the complex and re-equilibration to ca. 550–625 °C at 6–9 kbar led to widespread generation of biotite + epidote/clinozoisite, partially replacing amphibole + garnet along the main foliation. Trace element signatures of these retrograde net-transfer reactions are recorded in the titanite rims which are HREE+Y enriched, strontium depleted and were dated at 605.7 ± 6.2 Ma. The average zirconium contents of the titanite rims are higher than cores suggesting disequilibrium partitioning of zirconium into titanite during the retrograde path resulting in overestimated Zr-in-titanite temperatures for the rims. The exhumation of the complex was concomitant with the intrusion of folded and recrystallized leucogranite dykes dated at 607.0 ± 5.7 Ma, attesting the persistence of deformation after their intrusion. Assuming that the Pouso Alegre Complex is part of the São Francisco paleocontinent reworked during the Brasília orogeny, the data constrain the minimum age for the collision between the São Francisco paleocontinent and the Paranapanema block at ca. 620–630 Ma and agree with the idea of long-lived metamorphism and deformation in the southern Brasília Orogen.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0024493719302750-ga1.jpg" width="500" alt="Unlabelled Image" title="Unlabelled Image"〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 8 January 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Chemical Geology〈/p〉 〈p〉Author(s): Thomas J. Geeza, David P. Gillikin, David H. Goodwin, Scott D. Evans, Thomas Watters, Nathaniel R. Warner〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Freshwater bivalve shells may record inter-annual fluctuations in water chemistry, which in turn may archive variations in solute load due to pollution or discharge events. Here, using weekly surface water chemistry collected at two locations and shells of 〈em〉Lampsilis cardium〈/em〉 grown in the surface water we investigate if the Mg/Ca, Mn/Ca, Sr/Ca, and Ba/Ca ratios measured at high resolution in the shells on an intra-annual time scale consistently reflect the chemistry of the surface water. Two relationships appear highly correlated, Sr/Ca〈sub〉carb〈/sub〉 and Sr/Ca〈sub〉water〈/sub〉, and Mn/Ca〈sub〉carb〈/sub〉 and temperature. Ba/Ca〈sub〉carb〈/sub〉 correlated strongly with Ba/Ca〈sub〉water〈/sub〉 in one shell but temperature in another shell yielding inconclusive results. Mn/Ca〈sub〉carb〈/sub〉 and Mg/Ca〈sub〉carb〈/sub〉 were not strongly correlated with elemental ratios in the water, but Mn/Ca〈sub〉carb〈/sub〉 did show variable, weak to moderate correlation with pH〈sub〉.〈/sub〉 We found consistent partition coefficient (D〈sub〉Me〈/sub〉) values between individual shell samples grown in the same water with mean D〈sub〉Mg〈/sub〉 = 0.0006, D〈sub〉Mn〈/sub〉 = 17, D〈sub〉Ba〈/sub〉 = 0.13, and D〈sub〉Sr〈/sub〉 = 0.176. Sr/Ca〈sub〉carb〈/sub〉 and Sr/Ca〈sub〉water〈/sub〉 exhibited the strongest, most consistent correlation with partitioning coefficients that were consistent with published values, suggesting Sr/Ca〈sub〉carb〈/sub〉 can be used as a proxy for Sr/Ca〈sub〉water〈/sub〉 in freshwater mussels.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S000925411830007X-fx1.jpg" width="211" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 21 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Chemical Geology〈/p〉 〈p〉Author(s): Sophie M. Green, Jennifer A.J. Dungait, Chenglong Tu, Heather L. Buss, Nicole Sanderson, Simon J. Hawkes, Kaixiong Xing, Fujun Yue, Victoria L. Hussey, Jian Peng, Penny Johnes, Tim Barrows, Iain P. Hartley, Xianwei Song, Zihan Jiang, Jeroen Meersmans, Xinyu Zhang, Jing Tian, Xiuchen Wu, Hongyan Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Covering extensive parts of China, karst is a critically important landscape that has experienced rapid and intensive land use change and associated ecosystem degradation within only the last 50 years. In the natural state, key ecosystem services delivered by these landscapes include regulation of the hydrological cycle, nutrient cycling and supply, carbon storage in soils and biomass, biodiversity and food production. Intensification of agriculture since the late-20th century has led to a rapid deterioration in Critical Zone (CZ) state, evidenced by reduced crop production and rapid loss of soil. In many areas, an ecological ‘tipping point’ appears to have been passed as basement rock is exposed and ‘rocky desertification’ dominates. This paper reviews contemporary research of soil processes and ecosystems service delivery in Chinese karst ecosystems, with an emphasis on soil degradation and the potential for ecosystem recovery through sustainable management. It is clear that currently there is limited understanding of the geological, hydrological and ecological processes that control soil functions in these landscapes, which is critical for developing management strategies to optimise ecosystem service delivery. This knowledge gap presents a classic CZ scientific challenge because an integrated multi-disciplinary approach is essential to quantify the responses of soils in the Chinese karst CZ to extreme anthropogenic perturbation, to develop a mechanistic understanding of their resilience to environmental stressors, and thereby to inform strategies to recover and maintain sustainable soil function.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Asian Earth Sciences, Volume 181〈/p〉 〈p〉Author(s): Ponnusamy Saravanan, Anil K. Gupta, Hongbo Zheng, Mruganka K. Panigrahi, Muthusamy Prakasam〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Multi-proxy record of benthic and planktic foraminifera, total organic carbon and carbon and oxygen isotope ratios from Core SK291/GC15, off the coast of Goa, eastern Arabian Sea reveals significant paleoceanographic and paleoclimatic turnovers during ~6000 to 1700 calibrated years before the Present (cal yr BP). Benthic foraminiferal census data was analyzed with multivariate techniques including factor and cluster analyses of highest ranked species from the studied core that enabled to identify seven biofacies. The record suggests centennial to millennial-scale changes in the surface conditions driven by monsoon-linked upwelling in the eastern Arabian Sea during the studied interval. Various benthic biofacies combined with isotope and planktic foraminiferal data suggest that depletion of dissolved oxygen and increase in organic productivity in the study area was caused by intense monsoonal upwelling since the middle Holocene. The results suggest that during 5400–4700 and 3000–2500 cal yr BP the southwest (SW) monsoon was strong leading to intense upwelling in the study area as reflected by increased 〈em〉Globigerina bulloides〈/em〉 percentages. These were generally warmer intervals in the northern hemisphere. The SW monsoon significantly weakened (abrupt decrease in 〈em〉G. bulloides〈/em〉 population) during 4700–3400 cal yr BP roughly coinciding with a long arid phase in the Indian subcontinent and a cold interval in Europe. Our record suggests an abrupt increase in SW monsoon intensity during ~3000 to 2500 cal yr BP, when a pronounced change in benthic biofacies is also noted that suggests a major shift in the sub-surface conditions. Our data document a prolong weak SW monsoon phase beginning at ~4600 cal yr BP, little earlier than 4.2 ka event, in the eastern Arabian Sea.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1367912019302676-ga1.jpg" width="307" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 27 April 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Chemical Geology〈/p〉 〈p〉Author(s): Zita Kelemen, David P. Gillikin, Steven Bouillon〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Both climate change and land-use changes represent serious environmental issues throughout Africa, and are expected to lead to significant changes in river hydrology and geochemistry. Freshwater bivalve shell geochemistry may provide useful information about past river characteristics (discharge, geochemistry) providing a baseline to help understand modern environmental changes. Shells of two species of freshwater mussels (〈em〉Chambardia wissmanni〈/em〉 and 〈em〉Aspatharia dahomeyensis〈/em〉) were collected from two large African rivers (Oubangui and Niger Rivers) and were analyzed for Sr/Ca, Ba/Ca, Mg/Ca and Mn/Ca ratios along their maximal growth axis. Shell data were compared with geochemical data collected in these rivers every two weeks over a two-year period. To verify whether element ratios in shells were related to the host water, the elemental concentrations measured in the shells were set in a temporal context based on δ〈sup〉18〈/sup〉O〈sub〉shell〈/sub〉 cycles. Shells from the Oubangui River to some extent recorded water element ratios, with variations in water Sr/Ca ratios being reflected in all three bivalve specimens analyzed, while only the youngest specimen exhibited complete coverage. The two older specimens recorded only segments of the water data, which suggests an influence of growth rate. This relationship was not observed in 〈em〉A. dahomeyensis〈/em〉 shells from the Niger, suggesting a species-specific relationship between freshwater shells and water. The Ba/Ca and Mg/Ca record showed no similarity between the water elements and analyzed shells, but an ontogenetic decrease was observed in older specimens. Shell Mn/Ca ratios tracked pH in shells from the Oubangui, with a time-lag, which might be due to bivalves taking up the increased Mn via phytoplankton which are expected to show a similar time-lag. This relationship was not observed in shells from the Niger, where due to the high turbidity throughout the year we expect very low primary production rates. In conclusion, no consistent relationships between water chemistry and shell chemistry were observed. While Sr/Ca and Mn/Ca ratios in shells of 〈em〉C. wissmanni〈/em〉 from the Oubangui were most promising as proxies of water chemistry, the utility of element ratios as tracers is compromised by species-specific effects or by site-specific phenomena.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Weather and Climate Extremes, Volume 25〈/p〉 〈p〉Author(s): Mohammad Hossein Jahangir, Seyedeh Mahsa Mousavi Reineh, Mahnaz Abolghasemi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Flood is one of the significant natural disasters, which is treated as one of the main global concerns which increased occurrence has led to an increase in mortality rates and economic losses. Various methods have been developed and proposed for the analysis of this natural disaster. Iran is among several countries in the world, which faces severe problems of flood each year particularly in urban catchments. The present study aims to utilize GIS spatial analysis functions, data from Hydrometric and Rain-Gauge stations, satellite images, and thematic data layers in the form of Artificial Neural Network Algorithm for prediction of discharge values and spatial modeling of floods in Kan River Basin located in Tehran province. An optimized artificial neural network of 7 inputs, including slope, slope curvature, flow accumulation, NDVI, geological units, soil type, and rainfall data along with eight, sixteen and one neurons for the first, second and output hidden layers, respectively, were designed and developed. The output of the neural network was discharge values in stations. According to Table .2 in the result section, ANN method has one of the highest correlation and lowest RMSE in flood modeling. Precision parameters such as R〈sup〉2〈/sup〉, RMSE and MAE were used to show the efficiency of the proposed model which yielded the values of 0.82, 0.18, and 0.13, respectively. The results obtained by the present study can be employed in future environmental planning at local scale as a means for improving the management of environmental risks and crises. The present study showed that an integrated utilization of GIS spatial analysis function with neural network algorithm is one of the high efficiency methods for predicting the potential of natural disasters such as floods.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Marine Micropaleontology, Volume 151〈/p〉 〈p〉Author(s): Baptiste Suchéras-Marx, Gilles Escarguel, Jorge Ferreira, Øyvind Hammer〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Micropaleontologists often consider relative abundances of taxa to infer past ecological, environmental and climate conditions and dynamics. However, most published micropaleontological studies involving relative abundance data still do not routinely consider the counting uncertainty inherent to any sample, and thus simply ignore the statistical confidence interval (CI) related to a relative abundance or abundance-based ratio value. In an attempt to make this rather classic computation freely and easily available to the scientific community, we highlight here the calculation of binomial proportion CIs based on the ‘exact’ Clopper–Pearson method as implemented in the user-friendly PAST freeware. We also introduce a general solution for the computation of the CI related to any abundance-based ratio. In all cases, we strongly recommend that future studies involving taxonomic abundance-based data should systematically display the CIs associated to sample estimates, the only way to integrate sampling uncertainties into result interpretation.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 20 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Tectonophysics, Volume 765〈/p〉 〈p〉Author(s): R. Müller, T.G. Klausen, J.I. Faleide, S. Olaussen, C.H. Eide, A. Suslova〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉The Triassic-Jurassic transition marks an important change in the basin configuration of the Greater Barents Sea. A contiguous basin with km-thick sedimentary successions changed into a partitioned basin with uplift in the west and foreland basins in the east with significant implication for the basin infill history. Our study employs a range of different high-resolution datasets from a distal part of the basin which unravels the complex pattern of differential uplift and erosion in the basin during this period.〈/p〉 〈p〉We record for the first time distinct angular unconformities between Upper Triassic strata and overlying Lower Jurassic strata within the basin, showing that large parts of it formed topographic highs. Our study links these angular unconformities to compression induced by the Novaya Zemlya Fold and Thrust Belt. A heterolithic basement below a thick sedimentary succession where the fold belt developed created a complex uplift pattern in the basin, at the same time similar to but different from typical forebulge areas. Compression caused inversion of older basement rooted faults defining platforms and graben systems throughout western parts of the Barents Sea basin, in addition to salt remobilization that resulted in differential uplift and erosion. These local zones of uplift controlled the sediment distribution pattern to the basin at a time when the most important reservoir units in the basin were deposited. This new understanding of the basin development explains hitherto enigmatic sequence boundaries that has inspired complex paleogeographic models in the past.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Tectonophysics, Volume 766〈/p〉 〈p〉Author(s): Sebastián Carrasco, Javier A. Ruiz, Eduardo Contreras-Reyes, Francisco Ortega-Culaciati〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The September 16, 2015, M〈sub〉w〈/sub〉 8.4 Illapel, Chile earthquake is the first large event occurring in north-central Chile after the 1943 earthquake, filling a known seismic gap in the region. The earthquake took place in a complex tectonic region, nearby an area where transition from erosive to accretionary margin occurs due to the collision of Juan Fernandez Ridge (JFR) along the Chilean margin. We inverted the kinematic rupture process of the 2015 Mw 8.4 Illapel earthquake from the joint inversion of teleseismic body waves and near-field data. The relative weighting between datasets and the weighting of spatial/temporal constraints are objectively estimated by applying the Akaike's Bayesian Information Criterion. The coseismic slip model yields a total seismic moment of 4.92 × 10〈sup〉21〈/sup〉 Nm occurred over ~120 s. The rupture shows both downdip and updip propagation with slip extending along the thrust interface from ~50 km depth to shallow near-trench depths (〈15 km), with maximum slip of ~9 m located at shallow depths, where low average rupture speeds ~1.8–2 km/s are estimated. Outer-rise events, triggered within the oceanic Nazca plate after the mainshock, did not penetrate into the mantle and are related to preexisting faults due to both bending of Nazca plate and JFR uplift, which promotes a tensional stress regime in the surrounding area. This seismicity was triggered by static stress transfer from near-trench slip revealed by our source rupture modelling, suggesting outer-rise seismicity as a proxy for near-trench coseismic slip. Crustal seismicity within continental South American plate is observed prior to, and after, the mainshock, mainly related to extensional faulting within eroded and fractured wedge due to tectonic processes along erosive margins. We also show evidence of shallow seismicity after the mainshock associated with a long-lived crustal fault, which can represent a high seismic hazard for La Serena-Coquimbo conurbation.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 20 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Tectonophysics, Volume 765〈/p〉 〈p〉Author(s): Marcos Marcén, Teresa Román-Berdiel, Antonio M. Casas-Sainz, Ruth Soto, Belén Oliva-Urcia, Julia Castro〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉AMS and structural analysis are here applied to study the deformed zone associated with a large-scale, active normal fault in the central Betic Cordillera (Spain), namely the Baza fault system, to determine: i) the kinematics of structures and their relation with fault zone architecture and segmentation degree, ii) the correlation between deformational structures and the different types of magnetic fabrics and iii) the evolution of magnetic fabrics patterns, from sedimentary to shear-related, associated with normal faults. Five outcrops (969 samples) were analysed along the fault trace, which shows different degrees of segmentation along strike and strong localization of deformation along narrow fault zones. A first, main set of magnetic fabric data corroborates the normal kinematics of the Baza fault, showing magnetic lineations parallel to the dip-slip, transport direction. A second, secondary set of magnetic lineations, is parallel to the intersection lineation, and can be related to less intense deformation in the fault rocks. Furthermore, a detailed study (523 samples) of a trench excavated across the fault zone, where two fault splays tend to coalesce in a linkage relay zone indicates that i) lithology and distance to fault planes are two factors that control the development of extension-related magnetic fabrics in weakly deformed sediments, ii) the development of shear-related fabrics in fault zones entails the mechanical rotation of minerals, iii) different orientation of magnetic lineations are related to different intensity of bulk deformation and iv) magnetic lineation is useful to define local deviations of deformation axes produced by changes in the local extension direction (from fault-perpendicular to fault-parallel extension) in the linkage zone between adjacent fault splays.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Tectonophysics, Volume 766〈/p〉 〈p〉Author(s): J.F. Mescua, M. Barrionuevo, L. Giambiagi, J. Suriano, S. Spagnotto, E. Stahlschmidt, H. de la Cal, J.L. Soto, M. Mazzitelli〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We integrate field and wellbore data to discuss the stress field in the frontal sector of the Malargüe fold-and-thrust belt (Andes of Argentina). Surface observations indicate N-S thrusts and NW to WNW and ESE strike-slip faults are active in the study area. Inversion of fault kinematic indicators, combined with borehole breakout data and a mini-frac test within the study area, constrain the Quaternary to recent stress state, which is characterized by a subhorizontal, E-W oriented maximum stress, and by intermediate and minimum stresses with similar magnitudes that are locally interchanged, producing a setting in which reverse and strike-slip faults are alternatively active. The implications of the recognized structures for earthquake hazard are examined.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Tectonophysics, Volume 766〈/p〉 〈p〉Author(s): Jian Chang, Dan Li, Kyoungwon Min, Nansheng Qiu, Yao Xiao, Hang Wu, Nian Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Kalpin fold-and-thrust belt (FTB) was active during the Cenozoic and accommodated crustal shortening between the Tian Shan and Tarim Basin. To constrain the timing of thrusting in the Yimugantawu and Kepingtag thrust sheets from north to south in the central area of the Kalpin FTB, we performed apatite fission track (AFT) and apatite (U-Th)/He (AHe) dating, as well as sandbox experiments. The AFT central ages of the Yimugantawu and Kepingtag thrust sheets range from 93.0 to 148.7 Ma. Single grain AHe ages of the Kepingtag thrust sheet (10.7–27.1 Ma) are younger than those of the Yimugantawu thrust sheet (15.1–82.5 Ma), indicating a southward propagation of the Cenozoic deformation. Combined inverse and forward thermal modeling suggest that the Yimugantawu and Kepingtag thrust sheets underwent initial cooling and deformation at 25–20 Ma and 15–10 Ma, respectively. The sandbox experiments also suggest that the Yimugantawu thrust sheet underwent deformation before the Kepingtag thrust sheet was activated, confirming the sequence revealed by low-T thermochronology. This study provides new insights into the timing of deformation at the northern margin of the Tarim Basin, which can significantly enhance understanding of the tectonic evolution of Central Asia.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0040195119302495-ga1.jpg" width="301" alt="Unlabelled Image" title="Unlabelled Image"〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Tectonophysics, Volume 766〈/p〉 〈p〉Author(s): Hiwa Mohammadi, Mark Quigley, Sandy Steacy, Brendan Duffy〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Fault models are quickly produced and iteratively improved over weeks to years following a major earthquake, to characterise the dynamics of rupture, evaluate the role of stress transfer, and contribute to earthquake forecasting. We model Coulomb stress transfer (ΔCFS) between the largest foreshock (Mw 5.4; 1 year prior to first mainshock) and three Mw 6.1 to 6.5 earthquakes that occurred in a 12-hour period on January 22, 1988 in central Australia (Tennant Creek earthquake sequence) to investigate the role of static stress transfer in earthquake triggering relative to progressive source model development. The effects of fault model variance are studied using ΔCFS modelling of five different fault source model sequences (27 total models) using different inputs from seismic and geospatial data. Some initial models do not yield positive ΔCFS changes proximal to hypocentres but in all models, preceding earthquakes generate positive ΔCFS (≥0.1 bar) on ≥10 to 30% of the forthcoming receiver fault rupture areas. The most refined and data-integrative model reveals ΔCFS ≥ +0.7 to +13 bars within 2 km of impending hypocentres and large (≥30 to 99%) areas of positive ΔCFS. When compared to global compilations of threshold ΔCFS prior to impending ruptures (average = 3.71 bar, median = 1 bar), this suggests that Coulomb stress change theory adequately explains the Tennant Creek rupture sequence. In the most-refined model, earthquake inter-event times decrease as ΔCFS increases, suggesting that higher stress magnitudes may have more rapidly (within hours) triggered successive events, thus accounting for some temporal aspects of this sequence. ΔCFS analyses provide a useful framework for understanding the spatiotemporal aspects of some intraplate earthquakes. The progressive refinement of source models using emergent data may reduce epistemic uncertainties in the role of stress transfer that result from different model inputs, approaches, and results.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Tectonophysics, Volume 766〈/p〉 〈p〉Author(s): Filip Tomek, František Vacek, Jiří Žák, Michael S. Petronis, Kryštof Verner, Marine S. Foucher〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉An extensive early Carboniferous foreland basin (the Moravosilesian Culm Basin, MSCB) delineates the northeastern margin of the Bohemian Massif (Variscan orogenic belt). The basin overlays a complex suture between the outer Brunovistulia microplate, forming a promontory previously accreted to Laurussia, and inner Gondwana-derived units that form the remainder of the Bohemian Massif. Our structural, paleomagnetic and magnetic anisotropy data from the eastern portion of the MSCB indicate that its depositional architecture, internal fabric, and deformation by folding and faulting record a major switch from orthogonal convergence to orogen-oblique strike-slip shearing. First, the Brunovistulia microcontinent was subducted frontally towards W during ~346–335 Ma, followed by a shift of the subduction vector towards ~SSW at around 335–330 Ma. From ~330 Ma onwards, the underthrusting had ceased and the ~WNW–ESE dextral Elbe shear zone, related to the westward movement of Gondwana with respect to Laurussia, controlled deformation of this region. Displacement of the northerly Eastern Sudetes ‘block’ towards ~ESE produced regional ~WNW–ESE pure-shear shortening against the Brunovistulia indentor and resulted in an overall doubly-vergent structure of the MSCB. Simultaneously, the southerly Moldanubian unit was translated towards ~WNW, away from the Brunovistulian microplate, and likely contributed to an extensional regime related to orogenic collapse progressing outward from the internal domains of the Bohemian Massif. On a larger scale, we suggest that the MSCB is an illustrative example of a polykinematic foreland basin, where deposition, syn- to post-sedimentary deformation, and thus geodynamic processes changed significantly during basin evolution, starting off with microplate impingement into a continental margin reentrant and terminated by strike-slip shearing. Our data also do not support previous models for the tectonic development of the northeastern termination of the Variscan Belt, which suggested either a large-magnitude, vertical-axis oroclinal rotation of the foreland or its translation along an orogen-perpendicular strike-slip fault.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Tectonophysics, Volume 766〈/p〉 〈p〉Author(s): Victoria M. Buford Parks, Nadine McQuarrie〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Quantifying age, rate, and lateral variation of deformation and exhumation in convergent systems relies on integration of geologic map patterns, ag, and locations of reset thermochronometer systems, and synorogenic sediment distribution. The central Bolivian Andes provide an ideal location to examine the influence of variations in shortening and stratigraphic architecture on the structural evolution of the mountain range due to differential age and rates of shortening and distinct sedimentary basin geometries along strike. To quantify age and rate of shortening, we link thermokinematic modelling of sequentially deformed, forward-modelled, balanced cross-sections to synorogenic and thermochronologic histories. The preserved basin history in the Altiplano and Eastern Cordillera argues for an early fold-and-thrust belt located in the now-Western Cordillera, with subsequent propagation of shortening eastward around 40–50 Ma. Flexural modelling incorporating isostasy and erosion requires multiple basement thrust sheets with 35–97 km of displacement. A temporally evolving effective elastic thickness, as well as imposed subsidence in the foreland and uplift in the hinterland, is required to reproduce the surface geology, increase Subandean foreland basin depth, limit Altiplano sedimentation, and facilitate Altiplano uplift to modern elevation. Thermokinematic modelling is compatible with initiation of deformation at 50–40 Ma in a marked increase in Subandean velocities from ~5.5 to 8–10 mm/yr from ~12–10 Ma to present. Out-of-sequence thrusting at the westernmost limit of the Subandes is required to match measured young and partially reset zircon helium ages. Out-of-sequence faulting is supported by high Ksn values, indicative of active uplift, and was likely promoted by the abrupt eastern edge of the Paleozoic basin rocks, which limited forward propagation of structures, and/or increased erosion due to focused precipitation. Our results highlight the importance of incorporating detailed structural modelling in differentiating the geometry, kinematics, and timing of deformation to reproduce thermochronologic ages and basin histories.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Tectonophysics, Volume 766〈/p〉 〈p〉Author(s): Wei Lin, Michel Faure, Xian-Hua Li, Wenbin Ji〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Armorican Massif experienced a poly-orogenic evolution, represented by the Neoproterozoic Cadomian and the Devonian-Carboniferous Variscan tectonothermal events. In the southernmost part of the Armorican Domain (or Armorica microcontinent), the S〈sup〉t〈/sup〉-Georges-sur-Loire Unit consists of a block-in-matrix subunit, and a turbiditic subunit in the South and North, respectively. The S〈sup〉t〈/sup〉-Georges-sur Loire unit is interpreted as a remnant back-arc basin formed in Silurian-Early Devonian (ca. 440–400 Ma), and was deformed during the Variscan orogeny. Most of the sedimentary and magmatic blocks enclosed in clastic matrix are olistoliths derived from an assumed southern area called the “missing domain”, presently exposed as the Variscan Mauges Nappe composed of the Cadomian rocks and Early Paleozoic sedimentary cover. The “missing domain” was subducted beneath the Armorican massif during the Variscan collision. Detrital zircon age spectra from sandstones and siltstones from the olistostrome matrix reveal Neoproterozoic and Early Paleozoic age clusters, and less abundant Paleoproterozoic and Archean ages. Hf isotopic compositions of detrital zircons indicate dominantly negative ε〈sub〉Hf〈/sub〉 (t) values which are in agreement with a recycled continental source. Minor positive values correspond to a juvenile component that was formed during the Neoproterozoic Cadomian orogeny or Archean-Paleoproterozoic events. The Cambrian and Early Ordovician ages can be related to the pre-Variscan rifting of the Pannotia megacontinent that separated the Armorica microcontinent from Gondwana. Neoproterozoic ages imply a source of the magmatic rocks exposed in the Cadomian belt of the northern part of the Armorica microcontinent, and in the Mauges Nappe.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Desalination, Volume 467〈/p〉 〈p〉Author(s): Hyunkyung Lee, Jihun Lim, Min Zhan, Seungkwan Hong〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Preoxidation is gaining spotlight in the mitigation of ultrafiltration (UF) membrane fouling caused by algal organic matter (AOM). Although it is known to be beneficial in freshwater, its applicability in seawater treatment has barely been explored. This study first evaluated the effect of UV/permonosulfate (PMS) oxidation for UF process against marine harmful algal blooms (HAB). The transition of AOM released from 〈em〉Pseudo Nitzchia〈/em〉 was investigated which produces a neurotoxin, domoic acid (DA). Specifically, UV light emitting diodes (LED) were employed as UV source. The results indicated UV-LED/PMS treatment effectively reduces the fouling potential of AOM. However, the participation of abundant chloride ions generated free chlorine and disinfection byproducts, thus, PMS addition below 0.5 mM was suggested for seawater applications. With respect to PMS 0.5 mM, TOC and cake layer resistance were reduced by 10% and 85%, respectively, and this was followed by significant improvements in water permeability, flux reversibility and permeate quality of UF process. Furthermore, PMS exhibited significant reactivity for decomposing DA achieving rapid disappearance of 1 ppm of DA within a minute. The aforementioned results encourage the use of PMS as a bulk oxidant in seawater treatment to simultaneously mitigate membrane fouling and improve permeate quality.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0011916418325608-ga1.jpg" width="500" alt="Unlabelled Image" title="Unlabelled Image"〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Water Resources, Volume 130〈/p〉 〈p〉Author(s): Susana Garcia, Alfonso Mejia〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Virtual water flows have been extensively analyzed at the national level using complex network approaches. However, less is known about the regional structure of subnational virtual water flows, even though virtual water flows can vary greatly within a country. Additionally, subnational-level studies are needed since water policy and decision-making tend to be local or regional in scope. Here, we characterize and model virtual water flows for aggregated agricultural and industrial commodities at the US subnational level. Using subnational trade data for the US, we build and analyze unweighted and weighted, directed virtual water trade networks (VWTNs). To model and explore the drivers of subnational virtual water flows, we build and implement a gravity-type spatial interaction model. Using different network metrics, we find that the subnational VWTNs differ from previous well-studied networks, including national-level VWTNs. The network metrics also show a high connectivity for the unweighted VWTNs with no community structure, while the weighted VWTNs reveal spatially coherent communities of intense trade activity. The gravity model shows that the subnational weighted VWTNs are mainly controlled by distance, agricultural land, gross domestic product, and population. Despite the high connectivity of the VWTNs, the presence of community structure indicates that large volumes of virtual water are traded regionally. This suggests the possibility of having hydroeconomic boundaries that differ from known physical boundaries, e.g., watersheds and aquifers. Such boundaries could have implications for the design of consumption-based strategies for water sustainability.〈/p〉〈/div〉

Description: 〈p〉Publication date: 5 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Tectonophysics, Volume 766〈/p〉 〈p〉Author(s): Rasoul Ranjbar-Karami, Mojtaba Rajabi, Ali Ghavidel, Abdolvahab Afroogh〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The contemporary crustal stress pattern is important to several aspects of earth sciences such as reservoir geomechanics, neotectonic deformation and geodynamic modelling. The Persian Gulf Basin is a petroliferous region in southern Iran that hosts hundreds of petroleum wells and, hence, the knowledge of the present-day stress is critical for any exploration and production in this region. In addition to geo-resources, this region has a great economic importance and the in-situ stresses provide key insights on neotectonic and seismic hazard of the basin. However, there is limited in-situ stress information in the Persian Gulf region. In this study, we analyse 〉8 km of borehole image logs in 20 wellbores in the Persian Gulf in order to provide a clear picture of the stress pattern in this region. Our wellbore stress analyses provide 35 quality-ranked maximum horizontal stress orientations (S〈sub〉Hmax〈/sub〉) data records. In addition, we compile 27 earthquake focal mechanisms in the study region from different seismic catalogues and published literature, and present the first comprehensive quality-ranked in-situ stress map of the Persian Gulf Basin with 62 data records, which can be used as a valuable source of information for future exploration and seismic hazard assessment. The resulting database suggests that the S〈sub〉Hmax〈/sub〉 azimuth in central and western Persian Gulf is NE-SW (parallel to the Arabia-Eurasia tectonic plate convergence), which demonstrate the key role of relative plate motion in the present-day stress pattern of these areas. However, the S〈sub〉Hmax〈/sub〉 azimuth in the eastern part of the study area is NW-SE, which is different from the central and western Persian Gulf. The NW-SE S〈sub〉Hmax〈/sub〉 azimuth is consistent with other geological and geophysical observations that suggest an indentor model for Musandam Peninsula (Oman) in the Zagros-Makran syntaxis.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Tectonophysics, Volume 766〈/p〉 〈p〉Author(s): N. Espurt, F. Wattellier, J. Philip, J.-C. Hippolyte, O. Bellier, L. Bestani〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Provence Chain incorporated preexisting halokinetic and basement features which have played a key role in the structural evolution of the thrust systems. Field structural data, previously published geological maps and exploration well data have been used to interpret a new ~80 km-long balanced and restored cross section across the eastern Provence fold-thrust belt. The geological data and cross section construction suggest evidence for Mesozoic salt domes and minibasins embedded in the thin-skinned thrusts, and upper Paleozoic extensional structures transported on new thick-skinned thrusts. According to field data, pre-contractional palinspastic restoration suggests that salt domes and minibasins grew mainly during Rhaetien to late Jurassic times and intermittently until the early Santonian. Minibasins are mainly filled by carbonate systems associated with gravitational instabilities in minor normal faulting. Minibasin sinking into middle-upper Triassic evaporitic-carbonate succession has been mainly controlled by sediment loading. However, the initiation of salt movements might have been controlled by the initial geometry of the Triassic strata and probably extensional basement faulting. Preexisting salt structures have controlled thrust emplacements and their kinematics. Synorogenic deposits indicate a classical hinterland to foreland sequence of thrust inversion of the margin during the upper Cretaceous-Eocene Pyrenean-Provence compression. Diapiric structures were mainly eroded during and after the Pyrenean-Provence compression then reactivated during Oligocene extension and Miocene to present-day Alpine compression. Cross section balancing shows a total horizontal shortening of 28.5 km related to the Pyrenean-Provence and Alpine compressions. The eastern Provence fold-thrust belt integrates preexisting halokinetic folding which can be misinterpreted as resulting to compression. This suggests that a significant amount of folding in fold-thrust belts can results from an early halokinetic fold system developed during the pre-contractional passive margin evolution.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Tectonophysics, Volume 766〈/p〉 〈p〉Author(s): Min Liu, Hongyi Li, Zhigang Peng, Longbin Ouyang, Yuhu Ma, Jianxin Ma, Zhouji Liang, Yafen Huang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Lenglongling fault, located in the north Qilian fold zone along the northeastern margin of the Tibetan Plateau, plays an important role in accommodating the tectonic deformation between the Tibetan Plateau and the Alxa block. On 21 January 2016, the Ms 6.4 Menyuan earthquake occurred near the Lenglongling fault. In this study, we utilize the waveform matched filter technique and double-difference earthquake location algorithm to examine the spatial-temporal evolution of aftershocks following the Menyuan mainshock. Events from both China Earthquake Networks Center (CENC) routine catalog and relocated catalog are used as templates to scan through the continuous waveform data (21 January 2016 to 31 December 2016). We identify three and eleven times more events than listed in CENC routine catalog and relocated catalog, respectively. We find that the earliest aftershocks (e.g., in the first 10 min or so) mostly illuminated a steeply dipping plane, while aftershocks at later times outlined a near vertical dipping plane with mostly strike-slip focal mechanisms. The relocated aftershocks also suggest that the Menyuan mainshock occurred in a secondary fault rather than the major Lenglongling fault, which is consistent with geodetic and geological observations. Moreover, we find that aftershocks systematically expand with time along the fault strike and 16 repeating earthquake clusters occur in the rupture zone, which are likely driven by afterslip of the mainshock.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Marine Geology, Volume 416〈/p〉 〈p〉Author(s): Wei Yue, Shouye Yang, Baocheng Zhao, Zhongyuan Chen, Junjie Yu, Xianbin Liu, Xiangtong Huang, Bingfu Jin, Jing Chen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This study investigates heavy mineral assemblages in sediments of the modern Changjiang Delta (Yangtze River) and the Quaternary/Pliocene (Q/N) boundary strata within the delta area with the aim of deciphering changes in sediment provenance and the depositional environment during the Pliocene to Pleistocene transition. Major heavy mineral assemblages in the modern Changjiang sediments originate from their provenance rocks, while the distribution of unstable (amphibole), ultrastable (zircon, tourmaline, and rutile), and altered minerals (limonite, leucoxene) are closely related to the climate and the hydrodynamic environment within the catchment. The ratio of a certain unstable mineral (amphibole) to an altered mineral (limonite) is considered to be a sensitive indicator of the chemical weathering intensity that is largely affected by climate conditions. Heavy mineral data of core sediments reveal distinctly different environments and provenances between the upper (Quaternary) and lower (Pliocene) sedimentary strata in the Changjiang Delta. The Pliocene sediments are characterized by abnormally high contents of limonite (42%), leucoxene (8%) and zircon (15%), but an extremely low amphibole content (5%). Enrichment of zircon is indicated from the mid-lower Changjiang catchment, where granitoid rocks are widely distributed. The strong enrichment of altered minerals and the considerable great loss of unstable minerals suggest that Pliocene weathering was much stronger than it is nowadays. In contrast, high contents of amphibole, garnet, and pyroxene, and the low stable mineral content in the Quaternary strata indicate that sediment provenances may have extended to the upper Changjiang catchment, which underwent weak chemical weathering. These results imply that Changjiang as a large river system might have drained the East China's continental margin prior to the Q/N transition. The distinct heavy mineral assemblages found at the Q/N boundary in the Changjiang Delta are indicative of a drastic environment with provenance changes in response to intensive neotectonics. It is thus inferred that sensitive heavy mineral indices can be used to indicate the Q/N boundary in the Changjiang Delta, where reliable geochronological proxies have rarely reached an agreement.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Marine Geology, Volume 416〈/p〉 〈p〉Author(s): Ha Kim, Changyun Park, Myong-Ho Park, Yungoo Song〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉As the importance of reducing greenhouse gas emissions has attracted much attention, Pohang Basin has been identified as a CO〈sub〉2〈/sub〉 geological sequestration test site in Korea. This study aims to provide a better understanding of the diagenetic history of Pohang Basin through mineralogical and microstructural analyses, with a focus on tectonic evolution in the reservoirs offshore of the Pohang Basin during the East Sea (Sea of Japan) opening in the Miocene. We focused on two sections in the core that are considered to be target layers for CO〈sub〉2〈/sub〉 storage. Samples were analyzed for texture observation and chemical analysis. The major mineral components include quartz, feldspar, illite, chlorite, kaolinite and calcite, and the minor mineral components include pyrite, siderite, iron oxide, and titanium oxide. The detrital grains are composed of quartz and feldspar, and the primary pore is cemented with kaolinite (I), calcite, pyrite and chlorite. The analyzed chlorites are differentiated into five types by their textural characteristics, such as pore-filling (PF), pore-filling with kaolinite (PF-k), pore-lining (PL), replaced (RD), and detrital (DA) chlorites, and they were all categorized as either brunsvigite, diabantite, or ripidolite. Generally, the dissolution of feldspar is observed for all samples. The diagenetic temperature is estimated by chlorite geothermometry to be 170 °C on average, which is higher than the present temperature of Pohang Basin (55–60 °C). Considering all results together, the target layers have undergone diagenetic processes from early diagenesis (eogenesis) to late diagenesis (mesogenesis) and uplift-related diagenesis (telogenesis). After sedimentation of the Pohang Basin, kaolinite (I), calcite, and pyrite were cemented in the pore, and detrital mica was replaced with chlorite. As the burial depth increased, the dissolution of feldspar advanced. The high temperature resulting from the chlorite geothermometry could be influenced by the burial heat as source. Also, the Neogene volcanism and related tectonics (known as Eoil Orogeny) could become a heat source capable of high temperatures, and a high geothermal gradient and tectonically compressional environment may have influenced fluid flow. After the uplift, kaolinite (II) was precipitated in both an intergranular pore and intragranular pore as a result of dissolution. The effects of diagenesis, such as cementation and dissolution, in CO〈sub〉2〈/sub〉 reservoir rocks, could be an important factor in assessing the appropriacy of predicting potential charge after injection in carbon capture and storage project.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Atmospheric Environment, Volume 213〈/p〉 〈p〉Author(s): Steven T. Turnock, Oliver Wild, Alistair Sellar, Fiona M. O'Connor〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Tropospheric Ozone (O〈sub〉3〈/sub〉) is both an air pollutant and a greenhouse gas. Predicting changes to O〈sub〉3〈/sub〉 is therefore important for both air quality and near-term climate forcing. It is computationally expensive to predict changes in tropospheric O〈sub〉3〈/sub〉 from every possible future scenario in composition climate models like those used in the 6th Coupled Model Intercomparison Project (CMIP6). Here we apply the different emission pathways used in CMIP6 with a model based on source-receptor relationships for tropospheric O〈sub〉3〈/sub〉 to predict historical and future changes in O〈sub〉3〈/sub〉 and its radiative forcing over a 300 year period (1750–2050). Changes in regional precursor emissions (nitrogen oxides, carbon monoxide and volatile organic compounds) and global methane abundance are used to quantify the impact on tropospheric O〈sub〉3〈/sub〉 globally and across 16 regions, neglecting any impact from changes in climate. We predict large increases in global surface O〈sub〉3〈/sub〉 (+8 ppbv) and O〈sub〉3〈/sub〉 radiative forcing (+0.3 W m〈sup〉−2〈/sup〉) over the industrial period. Nine different Shared Socio-economic Pathways are used to assess future changes in O〈sub〉3〈/sub〉. Scenarios involving weak air pollutant controls and climate mitigation are inadequate in limiting the future degradation of surface O〈sub〉3〈/sub〉 air quality and enhancement of near-term climate warming over all regions. Middle-of-the-road and strong mitigation scenarios reduce both surface O〈sub〉3〈/sub〉 concentrations and O〈sub〉3〈/sub〉 radiative forcing by up to 5 ppbv and 0.17 W m〈sup〉−2〈/sup〉 globally, providing benefits to future air quality and near-term climate forcing. Sensitivity experiments show that targeting mitigation measures towards reducing global methane abundances could yield additional benefits for both surface O〈sub〉3〈/sub〉 air quality and near-term climate forcing. The parameterisation provides a valuable tool for rapidly assessing a large range of future emission pathways that involve differing degrees of air pollutant and climate mitigation. The calculated range of possible responses in tropospheric O〈sub〉3〈/sub〉 from these scenarios can be used to inform other modelling studies in CMIP6.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 218〈/p〉 〈p〉Author(s): Ebru Albayrak〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Although today the Asian elephant, 〈em〉Elephas maximus〈/em〉, exists in a number of fragmented and isolated populations in south and southeast Asia, its historical range was extended westwards as far as Iraq. Because 〈em〉E. maximus〈/em〉 is rarely preserved in fossil form and the remains from these peripheral ancient populations are scant, not much is known about their relationship to modern Asian elephant. The elephants in Tigris-Euphrates region, sometimes referred to as 〈em〉E. maximus asurus〈/em〉, had died out during the first half of the first millennium BCE. Some researchers have supported the idea that a living Asian elephant population inhabited the Euphrates-Tigris region in the late Holocene. The remains of ancient Asian elephant from the southeastern part of Turkey are known from several studies, and Gavur Lake Swamp (southeast Turkey) in particular is the only natural locality that yielded both dental and postcranial remains in southwest Asia. In this study new specimens including mandibles, isolated teeth, scapula, humeri and vertebras from Gavur Lake Swamp were studied. Moreover, the wear patterns of lower molars are examined in detail as they have an ambiguous pattern, which is mostly associated with 〈em〉Palaeoloxodon antiquus〈/em〉 and is not very common in recent Asian elephant. Comparisons with the recent Asian elephant teeth may point out that the extinct westernmost population of Asian elephant in Gavur Lake Swamp might have local or regional features in wear pattern in the lower molars.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Atmospheric Environment, Volume 214〈/p〉 〈p〉Author(s): Hiroyuki Ueno, Nobumitsu Tsunematsu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The sensitivity of ozone production to increasing temperature and a decreasing concentration of precursors, namely nitrogen oxides and non-methane hydrocarbon, has been estimated with probability theory using observation data for 2004–2015 for the Kanto region, Japan. The sensitivity of ozone, in terms of the number of high ozone concentration days, to temperature was higher at the beginning of the observation period when precursor concentrations were high but lower in more recent years when the precursor concentrations were lower. Analysis of the high ozone concentration days showed that a 10-percent reduction of both precursor concentrations yields a reduction in the number of high concentration ozone days of approximately 4 days per year, whereas a 0.2 °C temperature increase leads to less than a 1-day increase per year. This indicates that precursor concentration is more important than temperature for determining ozone concentration.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Atmospheric Environment, Volume 214〈/p〉 〈p〉Author(s): María C. Diéguez, Mariantonia Bencardino, Patricia E. García, Francesco D'Amore, Jessica Castagna, Francesco De Simone, Carolina Soto Cárdenas, Sergio Ribeiro Guevara, Nicola Pirrone, Francesca Sprovieri〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉This work provides the first continuous measurements of atmospheric mercury (Hg) at the EMMA Station in Patagonia (Argentina), within the Southern Volcanic Zone of South America. This monitoring site was set up by the Global Mercury Observation System (GMOS project) and is located inside Nahuel Huapi National Park (41°07′43.33″S, 71°25′12.03″W; 800 m a.s.l) in a forested valley of the Andes upwind of San Carlos de Bariloche city.〈/p〉 〈p〉This study aimed at describing atmospheric Hg levels and trends of variation using concentration data of Gaseous Elemental Mercury (GEM) collected from October 2012 to July 2017 and, Gaseous Oxidized Mercury (GOM) and Particle-Bound Mercury (PBM) recorded from March 2014 until July 2017. During the studied period the mean GEM concentration was 0.86 ± 0.16 ng m〈sup〉−3〈/sup〉; with the highest level in the austral spring (0.95 ± 0.13 ng m〈sup〉−3〈/sup〉) and the lowest in the autumn (0.80 ± 0.15 ng m〈sup〉−3〈/sup〉). Mean GOM concentration was 4.61 ± 4.00 pg m〈sup〉−3〈/sup〉, displaying the highest level in autumn (5.47 ± 4.39 pg m〈sup〉−3〈/sup〉) and the lowest in winter (1.24 ± 0.90 pg m〈sup〉−3〈/sup〉). Mean PBM computed for the whole period was 3.74 ± 3.41 pg m〈sup〉−3〈/sup〉; with the highest mean levels recorded in autumn (6.32 ± 3.41 pg m〈sup〉−3〈/sup〉) and the lowest in spring (1.18 ± 0.92 pg m〈sup〉−3〈/sup〉). Daytime levels of GEM, GOM and PBM were higher than nighttime concentrations, although in the case GOM and PBM similar levels were computed in autumn and summer, respectively. Westerly winds along with temperature and relative humidity influenced the dynamics of GEM, GOM and PBM at the EMMA Station. The HYSPLIT model showed that the area of the EMMA station was simultaneously affected by local and regional sources (forest fires and volcanoes) while the lowest values were recorded with the inflow of clean oceanic air masses coming from the free troposphere and corresponding to a long-range transport. Moreover, the Potential Source Contribution Function analysis showed that emissions in the Marine Boundary Layer, deriving from remote areas of Pacific Ocean, are sources of GEM and GOM.〈/p〉 〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1352231019304480-fx1.jpg" width="446" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 1 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Earth and Planetary Science Letters, Volume 521〈/p〉 〈p〉Author(s): Perach Nuriel, David M. Miller, Kevin M. Schmidt, Matthew A. Coble, Kate Maher〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Reconstructions of long-term fault activity are essential for understanding both the mechanisms controlling fault behavior and accurate earthquake hazard assessments. Increasing evidence for temporal variations in strain accumulation suggests non-uniform strain rates over a range of historic to geologic timescales. The paucity of long-term records of fault activity has limited our ability to resolve these variations. We present a method for constraining long-term fault activity based on U–Pb dating of fault-related opal from secondary fault segments within the Eastern California Shear Zone (ECSZ). The presence of sheared and breccia-cemented opaline silica within well-exposed faults at near-surface conditions suggest that opal formation is associated with high-magnitude earthquakes capable of surface rupture (〉6 M). Temporal constraints from massive and sheared syntectonic opal (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mi〉n〈/mi〉〈mo linebreak="goodbreak" linebreakstyle="after"〉=〈/mo〉〈mn〉74〈/mn〉〈/math〉) on related secondary faults from this study provide new insights on the timing of fault initiation, reactivation, and longevity. The oldest dates obtained indicate that ECSZ activity commenced at or before 10 Ma. Multiple deformation events dated within a single structure on episodically deposited and sheared opal (up to six generations), demonstrate that fault reactivation occurred over 10〈sup〉5〈/sup〉 yr timescales (0.7–0.1 Myr). Relative probabilities of dated deformation events can be used to evaluate changes in fault activity in the past 2.5 Ma (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg"〉〈mi〉n〈/mi〉〈mo linebreak="goodbreak" linebreakstyle="after"〉=〈/mo〉〈mn〉60〈/mn〉〈/math〉). This analysis indicates enhanced fault activity starting at 2 Ma and peaking around 1 Ma, possibly due to fault-interactions and distribution of deformation between the ECSZ and the San Andreas Fault.〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Atmospheric and Solar-Terrestrial Physics, Volume 193〈/p〉 〈p〉Author(s): Maryam Gharaylou, Majid M. Farahani, Morteza Hosseini, Alireza Mahmoudian〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉The electric POTential difference (POT) and the Lightning Potential Index (LPI) performance in predicting the lightning activity is investigated and the probable relationship between them is examined. These two indices have a similar dependency on microphysical variables such as ice, graupel mixing ratios, and also updraft characteristics within the cloud. Regardless of this similarity, the LPI directly calculated from WRF model is a more favorable parameter for predicting the lightning events in comparison with the POT, which requires an extra package (ELEC) model. Ten years' available data over the Tehran area were reviewed and four thundercloud cases with distinct characteristics (CAPE, time-frequency, intensity) were selected. In order to acquire the associated physical properties, four simulations have been done using the WRF-ELEC model, which is initialized with ERA-Interim data.〈/p〉 〈p〉The assessment conducted within both quantitative and qualitative themes to verify the potential probability of predicting lightning events. In qualitative evaluation framework, the horizontal distribution of LPI and POT were compared to the locations of lightning occurrence detected by WWLLN (The World Wide Lightning Location Network) data as well as the total lightning data obtained from LIS (Lightning Imaging Sensor) in the innermost simulation domain. This evaluation shows that the horizontal patterns of LPI and POT are well consistent with the locations of lightning occurrence. Moreover, in accordance with acquired values of correlation coefficients, it could be inferred that LPI has a better performance in the Number Of Lightning flashes (NOL) prediction than POT. Statistical review of our simulated data (LPI and POT) is performed to study the variation of LPI and POT which resulted in a good correlation between them and therefore, any information about lightning event using LPI values with less computational cost is preferable in the considered domain. Another comparison was carried out based on the calculated correlation coefficient between the simulated NOL and the NOL recorded by WWLLN that does not show any significant correlation between them for none of the cases. Since WWLLN has no observatory in the studied area, inconsistency of the simulated NOL with real atmosphere is justifiable.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Earth and Planetary Science Letters, Volume 521〈/p〉 〈p〉Author(s): James F.J. Bryson, Jerome A. Neufeld, Francis Nimmo〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Paleomagnetic measurements of ancient terrestrial and extraterrestrial samples indicate that numerous planetary bodies generated magnetic fields through core dynamo activity during the early solar system. The existence, timing, intensity and stability of these fields are governed by the internal transfer of heat throughout their parent bodies. Thus, paleomagnetic records preserved in natural samples can contain key information regarding the accretion and thermochemical history of the rocky bodies in our solar system. However, models capable of predicting these field properties across the entire active lifetime of a planetary core that could relate the processes occurring within these bodies to features in these records and provide such information are limited. Here, we perform asteroid thermal evolution models across suites of radii, accretion times and thermal diffusivities with the aim of predicting when fully and partially differentiated asteroids generated magnetic fields. We find that dynamo activity in both types of asteroid is delayed until ∼4.5-5.5 Myr after calcium-aluminium-rich inclusion formation due to the partitioning of 〈sup〉26〈/sup〉Al into the silicate portion of the body during differentiation and large early surface heat fluxes, followed by a brief period (〈12.5 Myr for bodies with radii 〈500 km) of thermally-driven dynamo activity as heat is convected from the core across a partially-molten magma ocean. We also expect that gradual core solidification produced compositionally-driven dynamo activity in these bodies, the timing of which could vary by tens to hundreds of millions of years depending on the S concentration of the core and the radius of the body. There was likely a pause in core cooling and dynamo activity following the cessation of convection in the magma ocean. Our predicted periods of magnetic field generation and quiescence match eras of high and low paleointensities in the asteroid magnetic field record compiled from paleomagnetic measurements of multiple meteorites, providing the possible origins of the remanent magnetisations carried by these samples. We also compare our predictions to paleomagnetic results from different meteorite groups to constrain the radii of the angrite, CV chondrite, H chondrite, IIE iron meteorite and Bjürbole (L/LL chondrite) parent bodies and identify a likely nebula origin for the remanent magnetisation carried by the CM chondrites.〈/p〉〈/div〉