ALBERT

Description: 〈p〉Publication date: 15 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 218〈/p〉 〈p〉Author(s): Athanassios Athanassiou, Alexandra A.E. van der Geer, George A. Lyras〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Eastern Mediterranean islands, most of which belong to the Aegean archipelago, have a complex biogeographic history, which puts its stamp on their fauna and flora. A now extinct but most important faunal component, in terms of geographic spread and taxonomic diversity, are the elephants. The Eastern Mediterranean islands are particularly rich in Pleistocene endemic elephant localities, which preserve samples of extinct endemic populations. These were either descendants of the European straight-tusked elephant 〈em〉Palaeoloxodon antiquus〈/em〉 or the Southern mammoth, 〈em〉Mammuthus meridionalis〈/em〉. Their presence, history and palaeobiogeography has been documented only for Cyprus, Crete, Kasos, Rhodes, Tilos, Kýthera, Naxos, and Delos. For six other islands only anecdotal references exist in the literature: Kálymnos, Astypálaia, Milos, Sériphos, Kýthnos and Paros. Here, we provide an update on previously published specimens and taxa, describe previously undescribed specimens that were relocated in museum collections, as well as recently excavated specimens, and put these in the context of island palaeobiogeography. We conclude that dwarf elephants, endemic to their palaeo-island, lived on the islands of palaeo-Cyclades, Astypálaia, Crete, Kasos–Kárpathos–Saría, Tilos, Rhodes and Cyprus, whereas the elephants from Kephallenía, Kálymnos and Kýthera are indistinguishable on the species level from mainland 〈em〉Palaeoloxodon antiquus〈/em〉. Elephant fossils of unresolved taxonomic status are reported from five present-day islands. The Eastern Mediterranean endemic elephants likely derived from separate and independent colonisation events from the mainland. No island supported more than one proboscidean species at any time. We found that isolation had no effect on the degree of dwarfism, but that there exists a threshold of about 6–10 km distance between the island and the mainland, below which no dwarfism evolved, likely as a result of genetic contact with the mainland population. We also found that although island area is correlated with the degree of dwarfism in elephants, other factors, such as the level of interspecific competition, may limit this degree.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 218〈/p〉 〈p〉Author(s): Weizhe Chen, Dan Zhu, Philippe Ciais, Chunju Huang, Nicolas Viovy, Masa Kageyama〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Climate and atmospheric CO〈sub〉2〈/sub〉 strongly influence the vegetation distribution and the terrestrial carbon storage. Process-based dynamic global vegetation models (DGVM) are important tools for simulating past vegetation dynamics and carbon cycle; yet the link between spatial gradients of climate and vegetation cover in geological past has received less attention. In this study, we simulate the distribution of vegetation under three CO〈sub〉2〈/sub〉 levels for two climate states, the Last Glacial Maximum (LGM) and Pre-industrial (PI) climate with fire activated or deactivated using the ORCHIDEE-MICT DGVM. Results show that elevated CO〈sub〉2〈/sub〉 and warmer climate promote global total tree cover but the impacts are different between forest biomes. Regional tree cover is highly regulated by mean annual precipitation (MAP) especially in the tropics, and by temperature for the boreal-arctic tree line. Based on quantile nonlinear regressions, we analyze the MAP threshold at which maximum tree cover is reached. This threshold is significantly reduced with elevated CO〈sub〉2〈/sub〉 for tropical and temperate trees. With higher CO〈sub〉2〈/sub〉, increased tree cover leads to reduced fire ignition and burned area, and provides a positive feedback to tree cover, especially in Africa. Besides, in our model, increasing CO〈sub〉2〈/sub〉-induced enhancement of gross primary productivity (GPP) is more prominent for tropical trees than for temperate and boreal trees, and for dry regions than wet regions. This difference explains why CO〈sub〉2〈/sub〉 is the major factor influencing forest cover in the tropics. It also highlights that special attention should be paid to collect paleo-vegetation data across savannas-forest transition in dry regions.〈/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: 1 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 217〈/p〉 〈p〉Author(s): 〈/p〉

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: 15 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 218〈/p〉 〈p〉Author(s): Alexander M. Wilson, James K. Russell, Brent C. Ward〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Volcanic rocks erupted within glacial environments offer powerful paleoenvironmental insights. These glaciovolcanoes and their deposits serve as proxies that inform on the paleo-presence, distribution and thickness of past glaciers. We investigate the paleoenvironmental implications of three Mid to Late Pleistocene volcanic deposits in the Garibaldi volcanic belt of southwestern British Columbia, Canada. We use these data to inform a simple geometric model that constrains paleo-glacier distributions in the southern Canadian Cordillera. The three volcanoes are used to recover: i) a coalesced mountain ice sheet in late Marine Isotope Stage (MIS) 4, and possibly into MIS 3 (up to ∼49.1 ± 5.5 ka), ii) major and rapid degradation of glaciers during the late, MIS 6 to 5e transition (by 141 ± 12.9 ka), and, iii) a coalesced mountain ice sheet, or continental ice sheet that existed during MIS 15 (598 ± 7.5 ka).〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 221〈/p〉 〈p〉Author(s): Trine Kellberg Nielsen, Søren Munch Kristiansen, Felix Riede〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Preservation and exposure of sediments is a prerequisite for finding archaeological traces. Regional geological history plays a significant and potentially biasing role in the reconstruction of the biogeographical distribution of Pleistocene hominins, particularly in previously glaciated regions. Here we present a digital geoarchaeological approach to a qualitative assessment of this archaeological bias in southwestern South Scandinavia. First, we identify time periods where the region was accessible and suitable for past humans. Our results show that only the longer Pleistocene interstadials offered terrestrial access in combination with potentially suitable habitats. Second, we present an extended digital geoarchaeological prospection of lacustrine, fluvial and palaeosol deposits and relict landscape features. This review guides the identification of preserved sediments of Pleistocene origin and confirms that Pleistocene deposits and landscape features are present in the study area, however, generally in a poor state and low quantity/quality. Third, we map the modern occurrence of sediment exposure through natural processes and anthropogenic activities. Triangulating the cumulated results of these three steps we identify three target areas which offer promising combinations of these factors: A) the Holsted and Rødding hill islands in Central South Jutland; B) the moraine landscape of Central East Jutland, and C) the intersections of buried valleys on the east coast of Jutland. To test the robustness of our prediction, it is necessary to regularly survey open quarries and exposures in these target areas. This should be the aim of future studies, ideally conducted, we suggest, using citizen science approaches that include relevant stakeholders.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 221〈/p〉 〈p〉Author(s): Omotayo Anuoluwapo Fadina, Igor Martins Venancio, Andre Belem, Carla Semiramis Silveira, Denise de Castro Bertagnolli, Emmanoel Vieira Silva-Filho, Ana Luiza S. Albuquerque〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The sediment core GL-1248, collected from the continental slope off northeastern Brazil, was used to reconstruct mercury (Hg) variations in NE South American continental margin and understand its variability in response to paleoclimate changes over the past 128 ka. Mercury concentrations in GL-1248 ranged between 14.95 and 69.43 ng/g, showing a glacial-interglacial pattern with higher (lower) concentrations in the glacial period (interglacial period). Parallel trends of Hg and XRF-Fe plots suggest that following atmospheric Hg deposition onto the continent, Hg is incorporated with Fe compounds before transportation and eventual immobilization at the NE Brazil continental slope. Peaks of Hg and Fe/Ca ratio peaks occurred concurrently during certain Heinrich Stadials, indicating that Hg is transported from the continent alongside fluvial sediments during periods of increased precipitation and erosion in NE Brazil continent. Mercury concentrations varied with periodicities of 56 ka and 900 yr suggesting glacial-interglacial changes and millennial-scale variability, respectively. Total Hg and total organic carbon are poorly correlated, although the latter likely influenced Hg sequestration into marine sediments during millennial-scale events between 60 ka and 30 ka. Altogether, our results suggest that the atmosphere is the primary source of Hg to GL-1248 and glacial-interglacial climate variations were the major determinant of atmospheric Hg deposition. Furthermore, increased precipitation during millennial-scale events played a secondary role by enhancing Hg transport to the continental slope of NE Brazil.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 220〈/p〉 〈p〉Author(s): Nicole S. Khan, Benjamin P. Horton, Simon Engelhart, Alessio Rovere, Matteo Vacchi, Erica L. Ashe, Torbjörn E. Törnqvist, Andrea Dutton, Marc P. Hijma, Ian Shennan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Determining the rates, mechanisms, and geographic variability of relative sea-level (RSL) change following the Last Glacial Maximum (LGM) provides insight into the sensitivity of ice sheets to climate change, the response of the solid Earth and gravity field to ice-mass redistribution, and constrains statistical and physical models used to project future sea-level rise. To do so in a scientifically robust way requires standardized datasets that enable broad spatial comparisons that minimize bias. As part of a larger goal to develop a unified, spatially-comprehensive post-LGM global RSL database, in this special issue we provide a standardized global synthesis of regional RSL data that resulted from the first ‘Geographic variability of HOLocene relative SEA level (HOLSEA)’ meetings in Mt Hood, Oregon (2016) and St Lucia, South Africa (2017). The HOLSEA meetings brought together sea-level researchers to agree upon a consistent protocol to standardize, interpret, and incorporate realistic uncertainties of RSL data. This special issue provides RSL data from ten geographical regions including new databases from Atlantic Europe and the Russian Arctic and revised/expanded databases from Atlantic Canada, the British Isles, the Netherlands, the western Mediterranean, the Adriatic, Israel, Peninsular Malaysia, Southeast Asia, and the Indian Ocean. In total, the database derived from this special issue includes 5634 (5290 validated) index (n = 3202) and limiting points (n = 2088) that span from ∼20,000 years ago to present. Progress in improving the standardization of sea-level databases has also been accompanied by advancements in statistical and analytical methods used to infer spatial patterns and rates of RSL change from geological data that have a spatially and temporally sparse distribution and geochronological and elevational uncertainties. This special issue marks the inception of a unified, spatially-comprehensive post-LGM global RSL database.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 221〈/p〉 〈p〉Author(s): Xueqin Zhao, Lydie Dupont, Rachid Cheddadi, Martin Kölling, Hanane Reddad, Jeroen Groeneveld, Fatima Zohra Ain-Lhout, Ilham Bouimetarhan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Morocco is an area subject to recurrent severe droughts, desertification and an increasing land degradation. It is within a Mediterranean hotspot of biodiversity as it harbors many threatened endemic species such as the argan tree (〈em〉Argania spinosa〈/em〉). In this context, past climate records are needed to analyze the impact of climate variability on the occurrence and future persistence of these endemic species. In order to evaluate the impact of past climate changes on the endemic Argan tree in southern Morocco, we reconstructed its modern range using an extensive pollen dataset. The modern pollen distribution off southwestern Morocco was then utilized to interpret the high-resolution pollen record with complementary micro-charcoal and XRF element records from a marine sediment core GeoB8601-3 off Cape Ghir in southwestern Morocco covering the last three millennia. This multi-proxy study has shown clear evidence of wetter conditions resulting in higher fluvial input which could be correlated with a negative mode of the North Atlantic Oscillation (NAO), in contrast to the published pollen and XRF element records from another nearby core that showed limited effect of climate changes. On the other hand, clear opposite trend between the pollen occurrences of 〈em〉Argania spinosa〈/em〉 and the fire frequency was observed throughout our fossil record. The increase of 〈em〉Argania spinosa〈/em〉 pollen occurrences, along with herbaceous taxa, and lower fire frequency might suggest an increase in human impact on the landscape leading to a sparse vegetation cover and subsequently increased erosion. The reconstructed pollen-based vegetation, micro-charcoal-based fire activities and geochemical changes in our marine record suggest interplay of climate and anthropogenic effects on the landscape.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 221〈/p〉 〈p〉Author(s): Rivka Rabinovich, Gadi Herzlinger, Rani Calvo, Florent Rivals, Steffen Mischke, Gali Beiner〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Early sites along the Dead Sea Transform (southern Levant), among them the Erq el Ahmar Elephant Site, are key points in understanding hominin and mammal migration out of Africa and into Eurasia. The late Prof. Tchernov had begun an intensive campaign to expose the faunal remains at the site, but unfortunately was unable to conclude his study. Based on interim reports and geomorphological descriptions, we were aware of numerous elephant remains found and left 〈em〉in situ〈/em〉. The Erq el Ahmar Elephant Site is a controversial site. There are those who see it as the earliest Pleistocene hominin site in the area, while others consider it a paleontological site without any hominin involvement. We returned to the site to try to resolve this controversy. In a systematic excavation, we succeeded in exposing the previously uncovered elements, exposed more material and currently better understand the deposition sequence. However, the task was very challenging, since the skeletal elements were very fragile and required careful exposure and conservation, both 〈em〉in situ〈/em〉 and in the laboratory, before they could be studied. A series of elements were found partially superimposed. Several elements of the skull, an almost complete tusk, vertebrae, ribs, a scapula and limb bones were found. Mammoth diagnostic traits were identified in the teeth and tusk. However, very few skeletons of early mammoths are known from the region. Have we exposed the most complete 〈em〉Mammuthus rumanus〈/em〉 skeleton? Tooth microwear indicates leaf-browsing dietary traits, similar to that of other 〈em〉M. rumanus〈/em〉 of this period. In addition, the recent excavations have revealed the potential of the site in understanding the evolution and dispersal of proboscidean species out of Africa during the Plio-Pleistocene, adding another focal point to the southern Levant along this route.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 221〈/p〉 〈p〉Author(s): Sophie Montuire, Aurélien Royer, Anna Lemanik, Olivier Gilg, Natalya Sokolova, Aleksandr Sokolov, Emmanuel Desclaux, Adam Nadachowski, Nicolas Navarro〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The genus 〈em〉Dicrostonyx〈/em〉 (the collared lemming) is undoubtedly the small mammal best adapted to the extreme conditions of the arctic environment. The Palearctic collared lemming has been described in numerous European Late Pleistocene localities up to south of France and Croatia. This species experienced climate-driven changes through time, changes mainly observed as repetitive pulses of pan-continental migration, and it thus became a typical indicator of glacial conditions. Using geometric morphometrics on molars, we evaluate the shape changes occurring during the last 100 ky over some dispersal events in Western Europe. The results point out that 〈em〉Dicrostonyx torquatus〈/em〉 has a large intra-population variation with a homogenous morphology, regardless of the origin of the individuals. A temporal trend leading to a more complex tooth with a differentiated anterior loop on the first lower molar was observed. An additional effect of the distance from the core populations was also described with a more peculiar shape for the most western populations of France. These temporal and geographical trends might relate to the different migratory pulses documented from ancient DNA haplotypes.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 221〈/p〉 〈p〉Author(s): Michelle C. Langley, Chris Clarkson, Sean Ulm〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The pace of research undertaken in Sunda (Southeast Asia) through to Sahul (Greater Australia) has increased exponentially over the last three decades, resulting in spectacular discoveries ranging from new hominin species, significant extension to the age for first human occupation in the region, as well as the identification of what is currently the oldest known rock art in the world. These breakthroughs cast the archaeological record of complexity in Sunda, Sahul, and Wallacea in an entirely different light to that of several decades ago, placing it on an equal footingto that of Africa, Asia, and Europe. The archaeological record of these regions now points to rich and diverse early modern human (〈em〉Homo sapien〈/em〉) societies engaged in complex symbolic and technological behaviours demonstrating capacities for innovation and self-expression found in all modern human groups now around the globe. Here we provide a comprehensive review of all Pleistocene symbolic evidence reported for Sahul, Sunda, and Wallacea to date. We explore how recent findings have changed our perceptions of the first modern human colonists and our understanding of the origins and development of the rich and diverse cultures that arose in each region through time.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0277379118310023-fx1.jpg" width="500" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 221〈/p〉 〈p〉Author(s): Ali R. Vahdati, John David Weissmann, Axel Timmermann, Marcia S. Ponce de León, Christoph P.E. Zollikofer〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Understanding Late Pleistocene human dispersals from Africa requires understanding a multifaceted problem with factors varying in space and time, such as climate, ecology, human behavior, and population dynamics. To understand how these factors interact to affect human survival and dispersal, we have developed a realistic agent-based model that includes geographic features, climate change, and time-varying vegetation and food resources. To enhance computational efficiency, we further apply machine learning algorithms. Our approach is new in that it is designed to systematically evaluate a large-scale agent-based model, and identify its key parameters and sensitivities. Results show that parameter interactions are the major source in generating variability in human dispersal and survival/extinction scenarios. In realistic scenarios with geographical features and time-evolving climatic conditions, random fluctuations become a major source of variability in arrival times and success. Furthermore, parameter settings as different as 92% of maximum possible difference, and occupying more than 30% of parameter space can result in similar dispersal scenarios. This suggests that historical contingency (similar causes – different effects) and equifinality (different causes – similar effects) are primary constituents of human dispersal scenarios. While paleoanthropology, archaeology and paleogenetics now provide insights into patterns of human dispersals at an unprecedented level of detail, elucidating the causes underlying these patterns remains a major challenge.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 221〈/p〉 〈p〉Author(s): Elan J. Levy, Orit Sivan, Gilad Antler, Boaz Lazar, Mordechai Stein, Yossi Yechieli, Ittai Gavrieli〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉During the late Quaternary several hypersaline lakes occupied the tectonic depression of the Dead Sea Basin, depositing sequences of primary-evaporitic mineral phases: aragonite (CaCO〈sub〉3〈/sub〉), gypsum (CaSO〈sub〉4〈/sub〉·2H〈sub〉2〈/sub〉O) and halite (NaCl). Aragonite and gypsum were the dominant primary mineral phases during the glacial periods and their formation required significant import of bicarbonate (HCO〈sub〉3〈/sub〉〈sup〉−〈/sup〉) and sulfate (SO〈sub〉4〈/sub〉〈sup〉2−〈/sup〉) ions to the lake. While bicarbonate was likely derived from dissolution of calcite in the watershed, the sources of sulfate remained elusive. Here we investigate and quantify the long-term sulfate reservoir changes in the deep waters (hypolimnion) of Lake Lisan (the last glacial Dead Sea) using concentrations and stable isotopes of sulfur in pore-fluids from the cores that were drilled at the lake floor (2010–11) by ICDP (International Continental Drilling Program). From ca. 117ka, pore-fluid sulfate concentrations increased and the brine attained supersaturation with respect to gypsum, peaking during the last glacial maximum (LGM; ca. 20ka). Stable isotopes of pore-fluid sulfate (δ〈sup〉34〈/sup〉S and δ〈sup〉18〈/sup〉O) are similar to the values found in bulk sulfate minerals from the nearby Mount Sedom salt diapir. We suggest that relatively diluted and cool paleo-epilimnion water facilitated dissolution of halite and anhydrite (CaSO〈sub〉4〈/sub〉) of the Mt. Sedom salt diapir, resulting in a localized increase in solution density. Subsequently, this solution sank and mixed with saline hypolimnion water, simultaneously replenishing chloride, sodium and sulfate reservoirs, while diluting it with respect to other solutes. The mixing of the calcium-rich gypsum saturated hypolimnion and the sulfate-rich sinking brine from above resulted in gypsum supersaturation.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 221〈/p〉 〈p〉Author(s): Encarni Montoya, Jordi Pedra-Méndez, Esther García-Falcó, Miriam Gómez-Paccard, Santiago Giralt, Teresa Vegas-Vilarrúbia, Fred W. Stauffer, Valentí Rull〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Coastal wetlands have been proposed as highly threatened by the ongoing and future climatic change, including projected sea-level changes as an additional forcing factor compared to more inland locations. The limited knowledge generated to date in this topic has been primarily focused on those areas attaining a high population density, and rarely deals with long-term (〉50 years) dynamics. Here we present the first Holocene palaeoecological study carried in the Orinoco Delta, in NE Venezuela. The record presented here contains sediments from the last 6200 years and is located in a river-shore swamp dominated by the palm 〈em〉Mauritia flexuosa〈/em〉. Current human occupation is almost restricted to small settlements of the Warao indigenous culture, closely related to the use of 〈em〉M. flexuosa〈/em〉 and other palm species present in the zone. The results show the occurrence of three well-distinguished palynological zones: (i) from 6200 to 5200 cal yr BP, characterised by mixed rainforest and other taxa related to salinity (coastal-like), low (negative) values of magnetic susceptibility and magnetic grain size, absence of transported clays, and the highest macrocharcoal particles abundance; (ii) from 5200 to 2950 cal yr BP, marked by a replacement of the mangrove-like vegetation by a more inland mixed-swamp forest community with low levels of charcoal, and (iii) from 2950 cal yr BP to present-day, characterised by the establishment of the current vegetation community, dominated by 〈em〉M. flexuosa〈/em〉, and an increasing trend in the charcoal curve since the last 700 years. A combination of regional (climatic changes) and local (sediment ontogeny) has been proposed as the key drivers influencing the vegetation succession recorded. The stabilisation of the sea-level that occurred during the mid-Holocene would have favoured the transgression of the coastal line, with the migration of the coastal-like vegetation seawards. Synchronous to this event, a trend towards drier conditions has been reported in the close Cariaco record, that could have also influenced the vegetation replacement. Between 3800 and 2800 years ago, the increased ENSO variability registered in Cariaco may have played a key role in the expansion of the 〈em〉Mauritia〈/em〉 palm community. It is suggested that in our location, the potential inhabiting human populations were differently influenced by these environmental changes. First, the disappearance of the coastal resources could have favoured land abandonment, whereas the increase in the abundance of the palm might be influential for the arrival of other inland cultures that were previously used to manage 〈em〉Mauritia〈/em〉. This sequence shows the importance of the ecosystem services for the location inhabitants, highlighting the abandonment of the mid-Holocene culture coeval with the disappearance of its ecosystem. These results also provide information about the sensitivity and resilience in facing external stressors of both humans and vegetation, and will be valuable tools for managing the future of this ecosystem.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 22 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews〈/p〉 〈p〉Author(s): C. Rabouille, B. Dennielou, F. Baudin, M. Raimonet, L. Droz, A. Khripounoff, P. Martinez, L. Mejanelle, P. Michalopoulos, L. Pastor, A. Pruski, O. Ragueneau, J.-L. Reyss, L. Ruffine, J. Schnyder, E. Stetten, M. Taillefert, J. Tourolle, K. Olu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Carbon and silicon cycles at the Earth surface are linked to long-term variations of atmospheric CO〈sub〉2〈/sub〉 and oceanic primary production. In these cycles, the river-sea interface is considered a biogeochemical hotspot, and deltas presently receive and preserve a major fraction of riverine particles in shallow water sediments. In contrast, periods of glacial maximum lowstand were characterized by massive exports of sediments to the deep-sea via submarine canyons and accumulation in deep-sea fans. Here, we calculate present-day mass balances for organic carbon (OC) and amorphous silica (aSi) in the terminal lobe complex of the Congo River deep-sea fan as an analogue for glacial periods. We show that this lobe complex constitutes a megasink with the current accumulation of 18 and 35% of the OC and aSi river input, respectively. This increases the estimates of organic carbon burial by 19% in the South Atlantic Ocean in a zone representing less than 0.01% of the basin. These megasinks might have played a role in carbon trapping in oceanic sediments during glacial times.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 221〈/p〉 〈p〉Author(s): Marie Protin, Irene Schimmelpfennig, Jean-Louis Mugnier, Ludovic Ravanel, Melaine Le Roy, Philip Deline, Vincent Favier, Jean-François Buoncristiani, Georges Aumaître, Didier L. Bourlès, Karim Keddadouche〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Investigation of Holocene extents of mountain glaciers along with the related naturally-driven climate conditions helps improve our understanding of glacier sensitivity to ongoing climate change. Here, we present the first Holocene glacial chronology in the Mont-Blanc massif (Argentière glacier) in the French Alps, based on 25 〈em〉in situ〈/em〉-produced cosmogenic 〈sup〉10〈/sup〉Be dates of moraines and glacial bedrocks. The obtained ages from mapped sequences of moraines at three locations reveal that the glacier retreated from its Lateglacial extent and oscillated several times between ∼11.7 ka and ∼10.4 ka, i.e. during the Younger Dryas/Early Holocene (YD/EH) transition, before substantially retreating at ∼10.4 ka. Climate conditions corresponding to the past extents of Argentière glacier during the YD/EH transition (∼11 ka) and the Little Ice Age (LIA) were modelled with two different approaches: by determining summer temperature differences from reconstructed ELA-rises and by using a Positive Degree Day (PDD) mass-balance model. The ELA-rise reconstructions yield a possible range of temperatures for the YD/EH transition that were lower by between 3.0 and 4.8 °C compared to the year 2008, depending on the choice of the ELA sensitivity to temperature. The results from the PDD model indicate temperatures lower by ∼3.6–5.5 °C during the YD/EH transition than during the 1979–2002 period. For the LIA, our findings highlight the role of local precipitation changes, superimposed on the dominant temperature signal, in the detailed evolution of the glacier. Overall, this study highlights the challenge that remains in accurately inferring paleoclimate conditions from past glacier extents.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 221〈/p〉 〈p〉Author(s): Adi Torfstein〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉The history of Levant paleo-hydrology, which is expressed by the absolute water level record of the Dead Sea over the last 70 kyrs, has been shown to be closely coupled with global climate patterns, and specifically argued to be modulated by northern hemisphere climate systems. Here, this coupling is rigorously tested and the absolute lake level curve is compared with a variety of globally distributed climate archives and used to deconvolve the processes controlling regional climate and hydrology. Considering that different archives are based on different sampling resolutions, and hence might have inherently different recording sensitivities, each of the chosen archives was interpolated and then smoothed at varying temporal resolutions. The synthetic curves, ranging between temporal smoothing resolutions between 10 years and 15 kyrs were compared to the similarly processed lake level record over the last 60 kyrs. The best fit to the Dead Sea lake level was found to be with Antarctica temperatures and atmospheric CO〈sub〉2〈/sub〉 levels. Greenland temperatures and proximal archives such as the Soreq Cave and the Dead Sea lithological record, all yielded weaker correlations to the lake level curve.〈/p〉 〈p〉An exception to the strong correlation between Levant climate and atmospheric CO〈sub〉2〈/sub〉 concentrations, is observed during Marine Isotope Stage (MIS) 5e, at a time when the Dead Sea watershed was exposed to very weak Mediterranean westerly systems that imposed hyperarid conditions, and a superposition of southern derived systems that delivered short but intense precipitation to the region. At this time, Antarctic temperatures cross a temperature threshold beyond 1 °C above present. It is suggested that this exceptional warming phase induces a reorganization of global and regional climate systems influencing the Levant.〈/p〉 〈p〉These results have two important implications. The first is the understanding that global temperatures and atmospheric CO〈sub〉2〈/sub〉 concentrations impose the first order control over Levant climate. The second, is that the Antarctic records can be used as synthetic lake level proxies, extending the absolute lake level curve to ca. 800 ka, compared with its current span of 70 kyrs. Considering the importance of the Dead Sea lake level curve as a regional paleo-climatic-hydrologic recorder, the new synthetic curve provides a prominent proxy of Levant hydro-climate history.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 220〈/p〉 〈p〉Author(s): Jonathan Keinan, Miryam Bar-Matthews, Avner Ayalon, Tami Zilberman, Amotz Agnon, Amos Frumkin〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Levant region of Israel, located along the Eastern Mediterranean Sea, is characterized by Mediterranean climate, but sixty km eastwards towards the Dead Sea Rift Valley (DSRV), the region rapidly becomes a ‘rain shadowʼ desert. Speleothems from the Mediterranean climate zone continuously grew throughout several glacial/interglacial cycles, indicating that water was always available in the unsaturated zone. Their δ〈sup〉18〈/sup〉O variations match global and regional climate changes, with the Eastern Mediterranean Sea being the major control on their δ〈sup〉18〈/sup〉O values, as evident from the similarity between the speleothems and the planktonic foraminifer 〈em〉G. ruber〈/em〉 records. In contrast, speleothems along the central and southern segments of the DSRV grew mainly during last glacial periods coinciding with the higher stands of Lake Lisan, the precursor of the present-day Dead Sea. This paper discusses the newly discovered Zalmon Cave speleothems, located in the northern segment of the DSRV shedding light on the hydrological conditions along the rift during last glacial. Unlike speleothems located further south along the DSRV, Zalmon Cave speleothems grew both during glacial and interglacial periods. However, during last glacial their δ〈sup〉18〈/sup〉O values, shifted to lower values by ∼1–2‰ relative to speleothems from central Israel coinciding also with the largest difference in δ〈sup〉18〈/sup〉O values between Zalmon Cave speleothems and the marine record. The data suggest that a change of the westerlies' storm tracks occurred during most of the last glacial period, which resulted in increased rainfall in the northern DSRV providing freshwater input during the otherwise relatively ‘drierʼ glacial.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 31 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews〈/p〉 〈p〉Author(s): David J.A. Barrell, Aaron E. Putnam, George H. Denton〈/p〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 221〈/p〉 〈p〉Author(s): R. Belmaker, B. Lazar, M. Stein, N. Taha, R. Bookman〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The laminated sequences of the Holocene Dead Sea (DS) and its late Pleistocene precursor Lake Lisan comprise primary aragonite and fine detritus that record the hydro-climate conditions of the late Quaternary Levant. Several studies suggested that the primary aragonite precipitated due to mixing between runoff that brought bicarbonate to the lake and the lake's Ca-chloride brine. However, the factors controlling the aragonite precipitation were not robustly established. Here, we addressed this issue by measuring the chemical composition (pH, Na〈sup〉+〈/sup〉, K〈sup〉+〈/sup〉, Ca〈sup〉2+〈/sup〉, Mg〈sup〉2+〈/sup〉, Sr〈sup〉2+〈/sup〉, Cl〈sup〉−〈/sup〉, Br〈sup〉−〈/sup〉, B, alkalinity) of flood plumes where the mixing occurs. The results indicate that: (a) Na〈sup〉+〈/sup〉, Mg〈sup〉2+〈/sup〉, K〈sup〉+〈/sup〉 and Cl〈sup〉−〈/sup〉 are conservative during the floodwater-brine mixing whereas Ca〈sup〉2+〈/sup〉 and Sr〈sup〉2+〈/sup〉 adsorb on flood's suspended sediments; (b) Boron (an important alkalinity species in the DS) adsorption on flood's suspended load enabled the bicarbonate that entered the lake via runoff to react with the Ca〈sup〉2+〈/sup〉 thus facilitating aragonite precipitation (c) Dissolution of calcite dust blown from the Sahara during winter storm is the source of bicarbonate which is required for aragonite precipitation. These observations explain the occurrence of aragonite laminae both during the wet last glacial period and during the dry last 3000yr. Although the water input during these two periods was completely different, they both were characterized by high dust fluxes and a stratified lake configuration in which the boron concentrations in the epilimnion were low enough to enable the bicarbonate that entered the lake via runoff to react with the lake brine Ca〈sup〉2+〈/sup〉 and precipitate aragonite.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 220〈/p〉 〈p〉Author(s): Ye Yang, Cong-Qiang Liu, Jérôme Van der Woerd, Sheng Xu, Li-Feng Cui, Zhi-Qi Zhao, Qi-Lian Wang, Guo-Dong Jia, François Chabaux〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Based on Terrestrial Cosmogenic Nuclide (TCN) constraints from depth profiles of one granitic regolith from Wumingshan and five fluvial terraces from Xianshuihe and Zagunao rivers, we discuss the timing of the last deglaciation, the landscape-scale denudation and fluvial incision rates across the eastern Tibetan Plateau, in relation to previous work. We present a three-dimensional-graph visualization approach and corresponding constraints to better assess the feasibility and applicability of cosmogenic nuclides depth-profile dating. The exposure age (older than 19.4 ka) of the Wumingshan regolith corresponds to the retreat of the palaeo-Daocheng ice cap, which covered the Yidun terrane during the Last Glacial Maximum (LGM). Most basin-wide denudation rate data in the eastern Tibetan Plateau are lower than 130 mm/ka (47%, n = 90), which is consistent with the Wumingshan regolith denudation rate (lower than 52.8 mm/ka), and thus indicate that the landscape-scale denudation has been stabilized after the last deglaciation. Considering the reduction of integrated bulk density due to the accumulation of lower-density loess, we estimate mean exposure ages of Xianshuihe and Zagunao river terraces of 4.0 ± 0.7 ka, 5.9 ± 0.3 ka, 13.4 ± 2.0 ka, and 16.6 ± 1.4 ka. The observed increase in incision rate from 0.39 mm/yr over long timescale (∼600 ka) to 5.88 mm/yr over the last 15 ka at the Xianshuihe river site is probably due to the transition from glacial to interglacial climatic conditions. The fewer abandoned terraces along the Zagunao river after the Heinrich event 1 (H1) indicates that the climate change during the latest glacial-interglacial transition impacted less the landscape evolution in a relatively lower elevation area. Comparison with previously reported fluvial incision rates elsewhere across the eastern margin of the Tibetan Plateau indicates that incision rates are mainly influenced by abrupt climate change or intensified summer monsoon since the early Holocene, but probably controlled by regional tectonic uplift or fluvial headward retreat as the timescale increases. Overall, we propose a synthetic pattern of landscape evolution mainly dominated by long-term tectonic uplift together with fluvial headward erosion, episodically influenced by climatic change throughout the late Quaternary.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 220〈/p〉 〈p〉Author(s): Mingming Zhang, Zhaojun Bu, Ming Jiang, Shengzhong Wang, Shasha Liu, Qing Jin, Penghan Shi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The density of maar lake type peatlands in the Changbai Mountain areas, northeast (NE) China is among the highest in the world. These deposition systems include both peat and limnic deposits, providing valuable sites to study their evolutionary history shaped by their sensitivity to climate-forced state shifts. To investigate the maar lake-mire shift in response to hydroclimatic variability, we examined developmental history of the Jinchuan peatland based on sedimentary facies, grain-size, physical and chemical properites, plant macrofossils and peat basal age. The results indicate that the Jinchuan peatland mainly originated from paludification in a maar lake from approximately 7000 cal. BP. Its water level continuously increased since the Middle Holocene, reaching the peak during the period of 5000–4000 cal. yr BP. The outward expansions of Jinchuan peatland suggest a climate–driven model based on which water level variability superimposes the underlying basin morphology. The hydroclimatic variability and peatland development history can be divided into three periods. From 12 to 7 ka cal. BP, the increasing East Asian summer monsoon (EASM) was the major water vapor source of Jinchuan peatland. The strong evaporation effects induced by the strong Winter Asian winter monsoon (WAWM) and the maximum sea surface temperatures (SSTs) of Japan Sea might have changed the Jinchuan maar lake into dry upland. From 7 to 4 ka cal. BP, the maximum EASM and increasing Westerly jet (WJ) provided water vapor for the peatland. The decreasing EAWM and SSTs of Japan Sea resulted in decreased evaporation effects. The moisture and water level in Jinchuan peatland gradually increased. The peat covered 68.97% of the area during this period. Since 4 ka cal. BP, the decreased EASM and the maximum WJ provided water vapor for the Jinchuan peatland. The weak EAWM and the lower SSTs of Japan Sea induced lower evaporation effects. The moisture and water level in the peatland reached the maximum. Subsequently, peat area further expanded and covered the remaining 31.03% area. This study reveals a remarkable link between the maar lake-mire shift and hydroclimatic variability, which is significant for future prediction of maar lake-mire ecosystem shifts under global climate change.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0277379119304330-fx1.jpg" width="261" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 220〈/p〉 〈p〉Author(s): Andy I.R. Herries, Justin W. Adams, Renaud Joannes-Boyau, Brian Armstrong, Stephanie Baker, Alex F. Blackwood, Giovanni Boshian, Matt V. Caruana, Paul Penzo-Kajewski, Ashleigh Murszewski, Douglass S. Rovinsky〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Drimolen Palaeocave System in the ‘Fossil Hominid Sites of South Africa’ UNESCO World Heritage Site is well known for numerous remains of early hominins such as 〈em〉Paranthropus robustus〈/em〉 and early 〈em〉Homo〈/em〉. These hominin fossils, along with bone tools and notably diverse accumulation of non-hominin primates and fauna, have all been excavated from the 'Main Quarry' area of the site where extensive lime-mining took place. Here we report the first radiometric age of 1.712 ± 0.269 Ma for hominin bearing deposits associated with the DNH7 〈em〉Paranthropus robustus〈/em〉 cranium in the Main Quarry area of the site, which is consistent with recent biochronological estimates. This age is similar to recent estimates for Swartkrans Member 1 Hanging Remnant (somewhere between 2.3 and 1.8 Ma) which also contains 〈em〉Paranthropus〈/em〉 and early 〈em〉Homo〈/em〉. Simultaneously, we integrate the newly radiometrically dated Main Quarry deposits with a new fossil deposit, the Drimolen Makondo, discovered in 2013, that is situated some 50 m up the hill to the west from the Main Quarry. It has experienced only limited disturbance from mining but much more extensive erosion. Preliminary excavations and analysis have revealed that the Makondo infill is older than the Main Quarry, dating to 2.706 ± 0.428 Ma. Its greater age is confirmed by biochronology. The Makondo thus overlap with the suggested end of deposition of 〈em〉Australopithecus〈/em〉 bearing Sterkfontein deposits, although it is yet to yield any hominin remains. These new dates for the two Drimolen Palaeocave System deposits indicates that, contrary to prior age estimates, the Drimolen site as a whole records the critical hominin and faunal turnover in South African palaeocommunities that occurred around 2.3–1.7 Ma. Finally, as the Drimolen Makondo represents a rare example of a pre-2 Ma fossil bearing deposit in the Gauteng exposures of the Malmani dolomite, we also integrate our results into the greater South African record of palaeodeposit formation (most of which occur between ∼2.0 and 1.0 Ma). An analysis of the age of palaeocave infillings across the Malmani dolomite suggests that, as is classically the case with karst, the height within the dolomite is broadly correlated to their age, although with some notable exceptions that are likely related to localised geological features. Our analysis also indicates that most caves have undergone some form of secondary karstification related to a younger phase of cave formation, contrasting with models that suggest the cavities all formed at the same time and that infill is related to erosion and the opening up of cave passages. As such, the reason that few pre-2 Ma deposits have been identified in the Gauteng exposures of the Malmani dolomite is probably because these older caves have been eroded away. Identifying such early caves is critical in understanding whether earlier hominins may have once existed in South Africa or if erosion of older deposits (or an absence of speleogenesis at this time) has made such early periods absent from the geological record.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 221〈/p〉 〈p〉Author(s): Thaís Rabito Pansani, Fellipe Pereira Muniz, Alexander Cherkinsky, Mírian Liza Alves Forancelli Pacheco, Mário André Trindade Dantas〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In the present study, the paleoecology (diet and niche width) of Late Quaternary megamammals that inhabited the Brazilian Intertropical Region (BIR) was assessed at two sites in the states of Bahia and Mato Grosso do Sul. The δ〈sup〉13〈/sup〉C analyses suggest a generalist diet for 〈em〉Notiomastodon platensis〈/em〉, 〈em〉Palaeolama major〈/em〉, 〈em〉Holmesina paulacoutoi〈/em〉 and 〈em〉Glyptotherium〈/em〉 sp., while 〈em〉Equus neogeus〈/em〉 was a grazer with a diet consisting exclusively of C〈sub〉4〈/sub〉 grasses, and 〈em〉Eremotherium laurillard,〈/em〉 a predominant browser with a diet consisting predominantly of C〈sub〉3〈/sub〉 plants. A distinct diet pattern was inferred for one species: 〈em〉Toxodon platensis〈/em〉 with a mixed-diet preferring C〈sub〉4〈/sub〉 grasses in Mato Grosso do Sul but predominantly the C〈sub〉3〈/sub〉 feeder in Bahia. These results show a high ecological plasticity of this species and may suggest distinct ecological pressures or different vegetation configurations in the two regions. Diet reconstitutions based on δ〈sup〉13〈/sup〉C analyses suggest that an open savanna-like landscape predominated in both areas. The δ〈sup〉18〈/sup〉O values reveal that Mato Grosso do Sul could have experienced wetter climatic conditions than Bahia during the Late Quaternary, suggesting a humid corridor in midwestern Brazil, or that there were different contents of δ〈sup〉18〈/sup〉O of water sources between these areas. Hence, we assume that the same faunistic composition in different geographical areas is not enough to delimit the ecosystems of the BIR, and we recommend that the definitions of BIR should be revised to include more refined paleoclimate data. Other studies around the world should consider the same for delimitations of zoogeographic regions.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 221〈/p〉 〈p〉Author(s): Jernej Jevšenak〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉An extended European tree-ring network was compiled from various sources of tree-ring data from Europe, northern Africa and western Asia. A total of 1860 tree-ring chronologies were used to compare correlation coefficients calculated with aggregated day-wise and month-wise mean temperature, sums of precipitation and standardised precipitation-evapotranspiration index (SPEI). For the daily approach, climate data were aggregated over periods ranging from 21 to 365 days. Absolute correlations calculated with day-wise aggregated climate data were on average higher by 0.060 (temperature data), 0.076 (precipitation data) and 0.075 (SPEI data). Bootstrapped correlations are computationally expensive and were therefore calculated on a 69.4% subset of the data. Bootstrapped correlations indicated statistically significant differences between the daily and monthly approach in approximately 1% of examples. A comparison of time windows used for calculations of correlations revealed slightly later onset and earlier ending day of the year for the daily approach, while the largest differences between the two approaches arise from window lengths: Correlations calculated with day-wise aggregated climate data were calculated using fewer days than the monthly approach. Differences in the onset and ending dates of periods for the daily and monthly approaches were greater for precipitation and SPEI data than for temperature data.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 6 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews〈/p〉 〈p〉Author(s): Hayley C. Cawthra, Richard M. Cowling, Sergio Andò, Curtis W. Marean〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The South African Cape South Coast is bordered by one of the broadest continental shelves in Africa. The Agulhas Bank, inshore shelf and presently exposed coastal plain make up the Palaeo-Agulhas Plain (PAP), though our area of study extends beyond this limit and as far inland as the first mountain belt. Quaternary sea levels have been significantly lower than at present for ∼90% of the Pleistocene, exposing a terrestrial ecosystem on what is now the submerged shelf. The presently drowned component makes up 94% of the total area of the PAP. Past work has hypothesised a contrast in character of this submerged landscape when compared to the subaerial environment. Here, we assimilate newly-acquired geophysical and geological datasets to produce geological- and soil maps from the Last Glacial Maximum on a scale of 1:750,000, covering an area of ∼55,000 km. Three broad geomorphic zones are defined, including the Western section from Cape Agulhas to Cape Infanta, the Central section from Cape Infanta to Knysna and the Eastern section extending eastward of Knysna. We demonstrate that Mesozoic sedimentary deposits crop out near the surface on this current-swept shelf and soils derived from siltstone and shale bedrock are prominent when the coast is up to 64 km distant from the modern shoreline at its maximum point. Beyond this, weathered limestone dominates the substrate sequences on the Agulhas Bank. We show that the submerged landscape was a unique terrestrial environment and that there is no exact modern-day analogue in the region other than a small (∼70 km〈sup〉2〈/sup〉) area located at the edge of the Agulhas Plain near Cape Agulhas, and map major contrasts in the geological, topographic and edaphic nature of the landscape from the onshore to the offshore. The expansion of this plain is coupled with exaggerated floodplains, meandering shallowly incised rivers and wetlands. The submerged shelf is dominated by fertile soils compared to the dissected onshore belt, and extensive calcareous dunefields extending up to 10 km inland from their associated palaeoshorelines covered much of the emergent shelf. Sedimentary bedforms may have obstructed or slowed drainage as suggested by leached palaeosols and carbonate mixing observed in petrographic thin sections and grain mounts. The data show a low-relief “plains” landscape, which contrasts strongly to the topographically complex contemporary coastal foreland.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 219〈/p〉 〈p〉Author(s): Brian M. Chase, Arnoud Boom, Andrew S. Carr, Manuel Chevalier, Lynne J. Quick, G. Anthony Verboom, Paula J. Reimer〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Cape Floristic Region (CFR) is one of the world's major biodiversity hotspots, and much work has gone into identifying the drivers of this diversity. Considered regionally in the context of Quaternary climate change, climate stability is generally accepted as being one of the major factors promoting the abundance of species now present in the CFR. However, little direct evidence is available from the region, and responses to changes in global boundary conditions have been difficult to assess. In this paper, we present new high-resolution stable isotope data from Pakhuis Pass, in the species-rich western CFR, and contextualise our findings through comparison with other records from the region. Combined, they indicate clear, coherent changes in regional hydroclimate, which we relate to broader forcing mechanisms. However, while these climate change events share similar timings (indicating shared macro-scale drivers), the responses are distinct between sites, in some cases expressing opposing trends over very short spatial gradients (〈50 km). We describe the evolution of these trends, and propose that while long-term (10〈sup〉5〈/sup〉 yr) general climatic stability may have fostered high diversity in the region through low extinction rates, the strong, abrupt changes in hydroclimate gradients observed in our records may have driven a form of allopatric speciation pump, promoting the diversification of plant lineages through the periodic isolation and recombination of plant populations.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 220〈/p〉 〈p〉Author(s): Andrea Columbu, Christoph Spötl, Jo De Waele, Tsai-Luen Yu, Chuan-Chou Shen, Fernando Gázquez〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Here we present the first record of Marine Isotope Stage (MIS) 7 from Sardinia, based on a U-Th-dated speleothem from Crovassa Azzurra cave, which also grew during MIS 5. Carbonate precipitation was continuous during MIS 7, while two multi-millennial hiatuses interrupted growth during MIS 5. These hiatuses occurred during times of unstable climate, but local karst-specific conditions are considered to have played an important role as well. δ〈sup〉13〈/sup〉C values mostly reflect soil bioproductivity and vegetation density. During less humid periods these values reflect bedrock δ〈sup〉13〈/sup〉C values, because of a semi-closed system and/or sulphuric acid-driven bedrock dissolution. δ〈sup〉18〈/sup〉O changes were governed by the interplay of rainfall amount and moisture source. Disentangling these two effects was possible by comparing δ〈sup〉13〈/sup〉C and δ〈sup〉18〈/sup〉O values, whereby both isotopes co-vary during periods when δ〈sup〉18〈/sup〉O was dominated by the amount effect. Changes in the relative proportion of Atlantic and Mediterranean moisture sources was the main control on δ〈sup〉18〈/sup〉O at times when δ〈sup〉18〈/sup〉O was decoupled from δ〈sup〉13〈/sup〉C.〈/p〉 〈p〉δ〈sup〉18〈/sup〉O variations during MIS 5 are synchronous with Greenland stadials (GS) and interstadials (GI) GS 26, GI 25, GI-GS 22, GI-GS 21. With the exception of GS 22, these climate oscillations did not affect soil bioproductivity, and δ〈sup〉18〈/sup〉O mirrors the relative proportion of Atlantic and Mediterranean moisture sources. GS 22 was a prominent arid period in Sardinia, in accordance with other regional palaeoclimate archives.〈/p〉 〈p〉High soil bioproductivity is indicated by δ〈sup〉13〈/sup〉C values for MIS 7e and MIS 7c-a; the latter interval was characterized by a 30 kyr-long time span of warm and humid conditions in Sardinia. Soil bioproductivity decreased markedly during MIS 7d and the climate became drier. The latter period, also constrained by δ〈sup〉18〈/sup〉O data, lasted significantly shorter in Sardinia than in central Europe.〈/p〉 〈p〉As indicated by changes in δ〈sup〉13〈/sup〉C and δ〈sup〉18〈/sup〉O relationships, variations in moisture source are also recorded for MIS 7, with Mediterranean-dominated rainfall during MIS 7e and 7c followed by a shift toward Atlantic-dominated rainfall.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 1 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews〈/p〉 〈p〉Author(s): Zenobia Jacobs, Brian G. Jones, Hayley C. Cawthra, Christopher S. Henshilwood, Richard G. Roberts〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The site of Blombos Cave (BBC) is well known for archaeological remains that have advanced our understanding of the development of modern human behaviour during the Middle Stone Age (MSA). Occupation of the cave occurred against a backdrop of landscape-scale environmental and sedimentary processes that provide the broader context for finer-scale interpretations of the site-formation history and archaeological patterns detected in the cave deposits. Aeolian and palaeosol sequences are abundant in the vicinity of BBC and these provide a partial view of the past landscapes available to the inhabitants of the cave. An important extension to the palaeo-landscape around BBC currently lies submerged on the Agulhas Bank, as sea levels were lower than at present for the entire period of human occupation of BBC. In this paper, we revisit the optically stimulated luminescence (OSL) chronology for the full sequence of sediment deposition inside BBC, increasing the number of dated samples to a total of 40 and revising the period of MSA occupation to between 97.7 ± 7.6 and 71.0 ± 5.7 ka (uncertainties at 95.4% probability). We describe the geological successions at four main areas around BBC, estimate the time of sediment deposition using OSL, and describe and interpret three seismic profiles on the Agulhas Bank, offshore of BBC. By correlating these onshore and offshore geological sequences with the sedimentary deposits inside BBC, we place the archaeological record within a landscape-scale chrono-stratigraphic framework to examine how environmental changes may have regulated the presence or absence of humans in the cave and surrounding terrain between about 100 and 70 ka.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 220〈/p〉 〈p〉Author(s): Demet Biltekin, Francesc Burjachs, Josep Vallverdú, Warren D. Sharp, Regina Mertz-Kraus, M. Gema Chacón, Palmira Saladié, James L. Bischoff, Eudald Carbonell〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This study addresses the pollen record of Abric Romaní archaeological site and the climate evolution of the last interglacial and glacial stadials in the Iberian Peninsula. The new pollen record spans the interval from 110,000 to 55,000 years ago. In general, the glacial/stadial vegetation is characterized by a steppe and herbaceous communities indicating dry and cold climatic conditions, whereas the vegetation optimum of past interglacials can be described as pine-oaks with mediterranean forest indicating milder and moister climatic conditions. During the first half of the MIS 5a and the MIS 5c, the region was warmer, which is characterized by temperate forests. However, the existence of 〈em〉Artemisia〈/em〉 steppes during the second part of the MIS 5a indicates that the degree of continentality can be related to the low winter temperatures and precipitation. During MIS 4, a colder and dryer climate enabled the development of open vegetation (dominated by 〈em〉Artemisia〈/em〉 with Poaceae and other Asteraceae) around the study site.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 220〈/p〉 〈p〉Author(s): Peter D. Strand, Joerg M. Schaefer, Aaron E. Putnam, George H. Denton, David J.A. Barrell, Tobias N.B. Koffman, Roseanne Schwartz〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We undertook geomorphological mapping in conjunction with 〈sup〉10〈/sup〉Be surface-exposure dating in a previously unstudied sector of the left-lateral moraine sequence of the ice-age Pukaki glacier in the Southern Alps of New Zealand. The mapping and dating approach enabled the identification of six distinct moraine belts that were formed during maxima of glacier extent during the last glaciation. The chronology implies that ice recession occurred during Northern Hemisphere Heinrich stadials, while expansion occurred between Heinrich stadials. The ages of the moraine belts identified here are 44,000 ± 1000 yrs; 41,800 ± 1100 yrs; 36,450 ± 940 yrs 26,730 ± 740 yrs; 20,030 ± 460 yrs; and 18,000 ± 400 yrs. This moraine chronology is consistent with previous dating results from other sectors of the Pukaki moraine sequence, except that the c. 44,000 yr old moraine belt has not previously been detected elsewhere in the Pukaki moraines. Collectively with previously published 〈sup〉10〈/sup〉Be chronologies from the Pukaki glacier, and the adjacent Ohau glacier valley, the results demonstrate that there were several millennial-scale episodes of ice advance to full-glacial extent, and subsequent ice recession, during Marine Isotope Stages 3 and 2. This millennial-scale pulsebeat of oscillations of the Pukaki and Ohau glaciers in sympathy with the North Atlantic Heinrich episodes is further emphasized by rapid ice recession in the Southern Alps early in the last glacial termination, coeval with the onset of Heinrich stadial 1 (HS 1) in the Northern Hemisphere. That this pattern is widespread in mid-latitudes of the Southern Hemisphere is highlighted by similar chronologies of glacier variation for Andean ice lobes in the Chilean Lake District of South America.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 220〈/p〉 〈p〉Author(s): William E. Banks, Pascal Bertran, Sylvain Ducasse, Laurent Klaric, Philippe Lanos, Caroline Renard, Miriam Mesa〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Investigations of chronology play a key role in the majority of archaeological research endeavors and are particularly pertinent to examinations of culture-environment relationships, especially during periods characterized by rapid and marked climatic variability and environmental reorganization. Rigorous evaluations of available data and robust methods are required if one wishes to reconstruct reliable chronologies, and this is especially the case when examining periods that are associated with a relatively few radiometric measurements. Such is the case for the Upper Paleolithic archaeological record documented in present-day France from 32,000 to 21,000 calibrated years BP. We take into account critically examined radiocarbon measurements from contextually secure archaeological contexts and employ a recently-developed method of Hierarchical Bayesian Modeling to reconstruct the chronology of archaeological cultures from the Middle Gravettian to the Badegoulian. The calculated chronological intervals for each typo-technologically defined culture phase are compared to the Greenland ice core climatic record and a terrestrial paleoenvironmental record from Bergsee Lake (Southern Germany)—itself expressed in calendar years calculated with the same calibration curve employed in our age model—thereby permitting each archaeological culture to be correlated accurately with documented paleoclimatic variability.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 220〈/p〉 〈p〉Author(s): Scott A. Reynhout, Esteban A. Sagredo, Michael R. Kaplan, Juan Carlos Aravena, Mateo A. Martini, Patricio I. Moreno, Maisa Rojas, Roseanne Schwartz, Joerg M. Schaefer〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Alpine glaciers are sensitive indicators of changes in climate, and their ubiquity in mountainous regions make them valuable proxies for terrestrial climate reconstructions worldwide. However, the timing and extent of glacier change across the South American mid-latitudes through the Holocene are still poorly constrained relative to their counterparts in the Northern Hemisphere. Here we report a new 〈sup〉10〈/sup〉Be surface exposure-based chronology of moraines recording a series of progressively less-extensive glacier advances of Glaciar Torre (Argentina, 49.3°S/73.0°W) since the Last Glacial Maximum, with expansions culminating at 17,600 ± 900, 13,500 ± 500, 9700 ± 400, 6900 ± 200, 6100 ± 300, 4500 ± 200, and 530 ± 60 yr BP. The declining magnitude of Holocene glacier expansions parallels a gradual rise in local summer insolation intensity during the Holocene, while individual advances occurred during inferred negative Southern Annular Mode (SAM)-like states at centennial to millennial timescales. These observations suggest that (i) summer insolation intensity modulated antiphased trends in glacier extent in the polar hemispheres during the Holocene, and that (ii) centennial-scale ‘SAM-like’ temperature and precipitation anomalies paced glacier fluctuations throughout Patagonia. Given the persistence of the inferred ’SAM-like’ anomalies throughout the Holocene, the modern measured trend towards positive SAM index conditions could mark the onset of a fundamental shift in the climate of the Southern Hemisphere midlatitudes that warrants consideration in projections of future climate.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0277379119300745-fx1.jpg" width="500" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 16 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews〈/p〉 〈p〉Author(s): Robert A. Dull, John R. Southon, Steffen Kutterolf, Kevin J. Anchukaitis, Armin Freundt, David B. Wahl, Payson Sheets, Paul Amaroli, Walter Hernandez, Michael C. Wiemann, Clive Oppenheimer〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Ilopango volcano (El Salvador) erupted violently during the Maya Classic Period (250–900 CE) in a densely-populated and intensively-cultivated region of the southern Maya realm, causing regional abandonment of an area covering more than 20,000 km〈sup〉2〈/sup〉. However, neither the regional nor global impacts of the Tierra Blanca Joven (TBJ) eruption in Mesoamerica have been well appraised due to limitations in available volcanological, chronological, and archaeological observations. Here we present new evidence of the age, magnitude and sulfur release of the TBJ eruption, establishing it as one of the two hitherto unidentified volcanic triggers of a period of stratospheric aerosol loading that profoundly impacted Northern Hemisphere climate and society between circa 536 and 550 CE. Our chronology is derived from 100 new radiocarbon measurements performed on three subfossil tree trunks enveloped in proximal TBJ pyroclastic deposits. We also reassess the eruption magnitude using terrestrial (El Salvador, Guatemala, Honduras) and near-shore marine TBJ tephra deposit thickness measurements. Together, our new constraints on the age, eruption size (43.6 km〈sup〉3〈/sup〉 Dense Rock Equivalent of magma, magnitude = 7.0) and sulfur yield (∼9–90 Tg), along with Ilopango's latitude (13.7° N), squarely frame the TBJ as the major climate-forcing eruption of 539 or 540 CE identified in bipolar ice cores and sourced to the tropics. In addition to deepening appreciation of the TBJ eruption's impacts in Mesoamerica, linking it to the major Northern Hemisphere climatic downturn of the mid-6th century CE offers another piece in the puzzle of understanding Eurasian history of the period.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0277379119301465-fx1.jpg" width="156" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 221〈/p〉 〈p〉Author(s): Carl Regnéll, Jan Mangerud, John Inge Svendsen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉We present geomorphological evidence of large, previously undocumented, early Holocene ice-dammed lakes in the Scandinavian Mountains of northwestern Sweden. The lakes extents indicate that the last remnants of the Scandinavian Ice Sheet were located east of the mountain range. Some early pioneering works have presented similar reconstructions, whereas more recently published reconstructions place the last ice remnants in the high mountains of Sarek.〈/p〉 〈p〉Using high-resolution airborne LiDAR data we have mapped a large number of hitherto undocumented shorelines in some of the main valleys within the northern Scandinavian mountain range. Our results indicate that a larger system of ice-dammed lakes existed in this region than previously thought. The lakes were dammed between the main water divide to the west and the retreating ice sheet margin to the east. The shorelines dip towards the northwest with gradients ranging from 0.5 to 0.4 m/km, from the oldest to the youngest. Further, we have compiled Lateglacial and Holocene shoreline data along the Norwegian coast and from within the Baltic Sea basin and reconstructed the isostatic uplift along a 1400 km long northwest-southeast transect from the Norwegian Sea to Lake Ladoga. By comparing the measured ice-dammed lake shoreline gradients to the dated marine shorelines, we infer that the lakes may have existed for several centuries following 10.2 cal ka BP. We also describe large deposits and extensive erosive features, which demonstrate that a catastrophic glacial lake outburst flood (GLOF) took place eastward along the Pite River Valley. Based on cross-cutting relations to raised shorelines developed in the early Holocene Ancylus Lake (Baltic Sea basin) we conclude that the flood and thus the final phase of deglaciation took place within the time interval 10.3–9.9 cal ka BP.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 5 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews〈/p〉 〈p〉Author(s): Willem G.M. van der Bilt, Andreas Born, Kristian A. Haaga〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The timing and causes of Common Era (CE) glacier growth in the Arctic Atlantic region remain elusive. There is mounting evidence of advances that predate the Little Ice Age (1250–1850 CE); this challenges the view that 13th century volcanic eruptions triggered change by spurring sea-ice expansion. Recent climate model simulations indicate this response does not require external forcing under contemporaneous (Pre-Industrial) boundary conditions. Here, we try to reconcile these new insights by combining regional proxy evidence of glacier and sea-ice change with a climate model experiment. Collated recently published reconstructions demonstrate that regional climate shifted towards a colder mean state around 650–950 CE, a period marked by low radiative forcing. Unforced model simulations reproduce the time-transgressive evolution of this response, which emerged east of Greenland and progressed towards Svalbard. The inferred pattern is associated with sea-ice feedbacks, triggered by stochastic atmospheric cooling. We argue that this mechanism may explain the timing and pattern of CE glacier growth in the region.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 201〈/p〉 〈p〉Author(s): Matteo Vacchi, Matthieu Ghilardi, Rita T. Melis, Giorgio Spada, Matthieu Giaime, Nick Marriner, Thomas Lorscheid, Christophe Morhange, Francesc Burjachs, Alessio Rovere〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A recent suite of Relative Sea-Level (RSL) data for the past 12 ka BP has provided new insights into the sea-level histories of the western Mediterranean region. Our analysis of the chronostratigraphic context of sea-level indicators from Spain (Catalonia, the Balearic Islands and the Gulf of Valencia), France (Corsica Island) and Italy (Sardinia Island) has yielded 162 new sea-level index and limiting points. These data have considerably enhanced previous RSL compilations, in addition to improving the quality of spatio-temporal sea-level reconstructions and our capacity to estimate isostatic-related vertical motions in the western Mediterranean basin. The glacial and hydro-isostatic adjustment (GIA) pattern elucidated by the new database shows discrepancy with respect to those predicted by the available GIA models. In particular, the new results underscore a non-coherent isostatic response of the central portion of the western Mediterranean, with the Balearic Islands manifesting significant departures from the sea-level histories of Corsica, Sardinia and, more generally, along most of the western Mediterranean coast. Our results are a crucial contribution to defining both the pattern and the magnitude of the isostatic signal along the western Mediterranean coast. In fact, vertical isostatic motions represent a key to better assess any possible post-industrial acceleration in sea-level rise and to define future scenarios of coastal inundation in the context of global change.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 28 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews〈/p〉 〈p〉Author(s): Mariana Nabais, João Zilhão〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Optimal foraging theory and diet breadth models often place large mammals in top-ranking positions due to their high-energy return. However, mass collection of small prey can result in comparable return rates, and dietary diversity is nutritionally beneficial on its own right. A growing body of evidence recovered from several sites in the Mediterranean Basin confirms Neanderthal use of small size prey. Slow-moving, tortoises are an easy catch, and human collection and consumption is demonstrated by taphonomic analysis. In Portugal, two key Middle Palaeolithic cave sites, Gruta da Oliveira and Gruta da Figueira Brava, provide pertinent evidence. Based on an improved osteometric method, in which long bone measurements are standardised and analysed together using the Logarithmic Size Index (LSI), it is possible to better gauge the contribution of tortoises to the diet and the human impact on the species’ populations. At inland Gruta da Oliveira, a tendency towards the massive collection of tortoises, affecting the local population more severely, is apparent. At coastal Gruta da Figueira Brava, the data suggest opportunistic collection upon encounter, possibly due to the availability of a more diverse range of resources.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 May 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 211〈/p〉 〈p〉Author(s): Benjamin M.P. Chandler, Clare M. Boston, Sven Lukas〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Considerable research has been conducted in Scotland to reconstruct Younger Dryas glaciers and palaeoclimatic conditions, but our understanding remains incomplete. In this contribution, we examine the Gaick, a dissected plateau that extends over ∼520 km〈sup〉2〈/sup〉 in the Central Grampians, Scotland. The extent and style of Younger Dryas glaciation in the Gaick has been repeatedly contested, although a model of extensive plateau icefield glaciation has become generally accepted. This is despite well-documented issues with key elements of the plateau icefield reconstruction. We synthesise the results of recent geomorphological mapping in the Gaick and recognise a distinct morphostratigraphic signature in the upper parts of the western catchments. This differs markedly from sediment-landform associations in other parts of the area, and we argue this provides a strong indication of spatially-restricted Younger Dryas (∼12.9–11.7 ka) glaciation in the Gaick. Our interpretation is independently supported by glacierisation threshold analysis, which implies that the eastern Gaick was unable to nourish Younger Dryas ice. We therefore contest the accepted paradigm of extensive Younger Dryas glaciation in this area. Based on the geomorphological evidence and glacier surface profile modelling, we reconstruct a ∼42 km〈sup〉2〈/sup〉 plateau icefield that yields an equilibrium line altitude of 751 ± 46 m. Using this value, a sea-level precipitation value of 826 ± 331 mm a〈sup〉−1〈/sup〉 is inferred for the Younger Dryas, which suggests considerably drier conditions than at present. Using recalculated glacier-derived precipitation estimates from Scotland, we present regional climate analysis that corroborates arguments for a strong west-east precipitation gradient across Scotland.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 27 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews〈/p〉 〈p〉Author(s): Jordi Rosell, Ruth Blasco〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Fire represented a real revolution in human lifestyles, transforming the way food was processed and leading to a new way of organising settlements and interacting socially. Yet, it is one of the most debated and controversial issues in the field of Palaeolithic archaeology. The scientific community generally proposes that the regular and controlled use of fire occurred from 400 to 300 ka onward, and that the archaeological signal became well established in sites younger than 100 ka. Thus, the chronological range between 400 and 300 ka is crucial to exploring how this phenomenon and the associated behavioural changes occurred. Here, we examine the zooarchaeological signature this process left on the faunal record, including procurement techniques and animal processing (e.g., roasting). The data are compared to information from sites without fire that are framed within the same chronological period. Our objective is to collect zooarchaeological data on the process of dependence on fire as a central element in the new human mode of adaptation.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 May 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 211〈/p〉 〈p〉Author(s): Claire Archer, Paula Noble, Michael R. Rosen, Leonardo Sagnotti, Fabio Florindo, Scott Mensing, Gianluca Piovesan, Alessandro Maria Michetti〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Small lakes in low relief areas are atypical candidates for studies on paleoseismicity, but their sediments can contain seismically induced event layers (seismites) generated through strong ground shaking, sediment transport, hydrological reorganization and/or changes in groundwater chemistry and flow. Lakes Lungo and Ripasottile are shallow lakes (〈10 m deep) located in the tectonically active Rieti Basin in the central Apennines, Italy, where strong normal faulting earthquakes (Mw 6.5 to 7.0) regularly occur. Sediment cores from these lakes provide paleoseismic indicators for the past ∼1000 years. Sedimentological and geochemical analysis reveals four event layers identified in both lakes that correspond with documented large-scale earthquakes in 1298, 1349, 1639, and 1703 AD. Chronological correlation between earthquakes and paleoseismic features is reliable because of the resolution of sediment dating available for the studied cores. The common physical structure is a physically homogenous bed (homogenite) of re-suspended sediment consisting of a denser, high magnetic susceptibility (κ) clastic base, with organic matter concentrated above. Co-seismic to post-seismic chemical signatures are associated with some event layers and may represent abrupt or transient shifts to a groundwater-dominated system, or permanent changes in groundwater flow and/or spring discharge. Excursions in δ〈sup〉13〈/sup〉C〈sub〉org〈/sub〉 may represent disruptions or changes in carbon source. Not all event layers show the same features, a result attributed to differences in seismic processes as well as the lake attributes, and anthropogenic modification. The observations made here may provide a new means of detecting paleoseismicity and may be applied to other low relief lakes in seismically active areas.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 May 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 211〈/p〉 〈p〉Author(s): Camille Bréant, Amaëlle Landais, Anaïs Orsi, Patricia Martinerie, Thomas Extier, Frédéric Prié, Barbara Stenni, Jean Jouzel, Valérie Masson-Delmotte, Markus Leuenberger〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Each glacial – interglacial transition of the Quaternary occurs in a different orbital context leading to various timing for the deglaciation and sequence of high vs low latitudes events. Termination 3, 250 kyears before present (ka), is an unusual deglaciation in the context of the last 9 deglaciations recorded in the old EPICA Dome C (EDC) Antarctic ice core: it exhibits a three-phase sequence, two warming phases separated by a small cooling, the last phase suggesting a particularly rapid temperature increase. We present here new high resolution δ〈sup〉15〈/sup〉N and deuterium excess (d-excess) data from the EDC ice core to provide a detailed temperature change estimate during this termination. Then, we combined the δD and δ〈sup〉18〈/sup〉O to discuss the relationship between high and low latitude changes through the d-excess. We also provide the high vs low latitude sequence of events over this deglaciation without chronological uncertainty using low latitude ice core proxies. In agreement with previous studies based on speleothem analyses, we show that the first phase of Termination 3 (256–249 ka) is associated with small Heinrich like events linked to changes in ITCZ position, monsoon activity and teleconnections with Antarctica. In a context of minimum Northern Hemisphere insolation, this leads to a rather strong Antarctic warming, as observed in the δ〈sup〉15〈/sup〉N record in contrast to the relatively small δD increase. The second warming phase occurs during the rise of the Northern hemisphere insolation, with a large Heinrich like event leading to the characteristic Antarctic warming observed in the δ〈sup〉15〈/sup〉N and δD increase as for the more recent terminations.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 May 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 211〈/p〉 〈p〉Author(s): Zachary C. Dunseth, Daniel Fuks, Dafna Langgut, Ehud Weiss, Yoel Melamed, Don H. Butler, Xin Yan, Elisabetta Boaretto, Yotam Tepper, Guy Bar-Oz, Ruth Shahack-Gross〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This article presents a systematic methodological comparison of three archaeobotanical proxies (phytoliths, pollen and seeds) applied to an assemblage of dung pellets and corresponding archaeological refuse deposits from Early Islamic contexts at the site of Shivta. We set out with three main methodological questions: one, to evaluate the relative input of botanical remains from dung in refuse assemblages; two, to evaluate each archaeobotanical dataset and to test whether they are comparable, complementary or contradictory in their interpretations from dung; and three, infer herding practices at the site during the Early Islamic period. Our findings show that ovicaprine dung accumulated in Early Islamic Shivta during at least two periods: mid-7th–mid-8th centuries CE, and late-8th–mid-10th centuries CE. Methodologically, we see incomplete and incompatible reconstructions arise when each method is considered alone, with each proxy possessing its own advantages and limitations. Specifically, the amount of preserved seeds in dung pellets is low, which restricts statistical analysis and tends to emphasize small or hard-coated seeds and vegetation fruiting season; yet this method has the highest taxonomic power; pollen preserves only in uncharred pellets, emphasizes the flowering season and has an intermediate taxonomic value; phytoliths have the lowest taxonomic value yet complete the picture of livestock feeding habits by identifying leaf and stem remains, some from domestic cereals, which went unnoticed in both seed and pollen analyses. The combined archaeobotanical reconstruction from samples of the mid-7th–mid-8th centuries suggests that spring-time herding at Shivta was based on free-grazing of wild vegetation, supplemented by chaff and/or hay from domestic cereals. For the late-8th–mid-10th century samples, phytolith and pollen reconstruction indicates autumn-winter free-grazing with no evidence of foddering. Unlike the dung pellets, macrobotanical remains in the refuse deposits included domestic as well as wild taxa, the former mainly food plants that serve for human consumption. Plant remains in these refuse deposits originate primarily from domestic trash and are only partially composed of dung remains. The significance of this study is not only in its general methodological contribution to archaeobotany, but also to lasting discussions regarding the contribution of dung remains to archaeological deposits used for seed, pollen and phytolith analyses. We offer here a strong method for determining whether deposits derive from dung alone, are mixed, or absolutely do not contain dung. This has important ramifications for archaeological interpretation.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 May 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 211〈/p〉 〈p〉Author(s): Paul Szpak, James M. Savelle, James Conolly, Michael P. Richards〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Environmental change in the Arctic has been a primary topic of interest in recent years, particularly as it relates to the consequences of anthropogenic climate change. Sea ice is of particular importance in this context, both in terms of the effects of climate change in the Arctic, but also globally. Most studies examining the responses of various components of the biosphere to warming temperatures necessarily have a short temporal perspective. The purpose of this study was to use stable isotopes to examine long-term variation (c. 4000–500 yr BP) in the ecology of a ubiquitous Arctic marine mammal (the ringed seal, 〈em〉Pusa hispida〈/em〉) that is intimately linked to sea ice. We present 〈em〉δ〈/em〉〈sup〉13〈/sup〉C and 〈em〉δ〈/em〉〈sup〉15〈/sup〉N values for ringed seal bone collagen from archaeological sites in the central Canadian Arctic Archipelago as well as 61 new AMS 〈sup〉14〈/sup〉C dates from these sites. Ringed seal 〈em〉δ〈/em〉〈sup〉13〈/sup〉C values increased between the earliest sites in our study, Early Pre-Dorset (c. 4000 cal yr BP), through to the Late Dorset period (c. 800 cal yr BP) suggesting increasing primary productivity derived from sea ice relative to phytoplankton over this period and an overall cooling trend. Between the Late Dorset (1500–700 yr BP) and Thule (c. 700−500 yr BP) periods there was an abrupt decline in the contribution of sea ice algae to higher trophic levels, consistent with reduced sea ice extent and increased open water conditions. These data demonstrate the potential of using marine mammals from archaeological sites to reconstruct the changing importance of sea ice to food webs over time and offer insight into the consequences of climatic variation at higher trophic levels, which is difficult if not impossible to obtain with other proxy records.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 28 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews〈/p〉 〈p〉Author(s): Richard J. Payne, Fin Ring-Hrubesh, Graham Rush, Thomas J. Sloan, Chris D. Evans, Dmitri Mauquoy〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Falkland Islands in the South Atlantic Ocean contain extensive peatlands at the edge of their global climatic envelope, but the long-term carbon dynamics of these sites is poorly quantified. We present new data for ten sites, compile previously-published data and produce a new synthesis. Many peatlands in the Falkland Islands developed notably early, with a fifth of basal 〈sup〉14〈/sup〉C dates pre-Holocene. Falkland Islands peats have high ash content, high carbon content and high bulk density compared to global norms. In many sites carbon accumulation rates are extremely low, which may partly relate to low average rainfall, or to carbon loss through burning and aeolian processes. However, in coastal Tussac peatlands carbon accumulation can be extremely rapid. Our re-analysis of published data from Beauchene Island, the southernmost of the Falkland Islands, yields an exceptional long-term apparent carbon accumulation rate of 139 g C m〈sup〉−2〈/sup〉 yr〈sup〉−1〈/sup〉, to our knowledge the highest recorded for any global peatland. This high accumulation might relate to the combination of a long growing-season and marine nutrient inputs. Given extensive coverage and carbon-dense peats the carbon stock of Falkland Islands peatlands is clearly considerable but robust quantification will require the development of a reliable peat map. Falkland Island peatlands challenge many standard assumptions and deserve more detailed study.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 May 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 211〈/p〉 〈p〉Author(s): Thomas M. Urban, Jeffrey T. Rasic, Claire Alix, Douglas D. Anderson, Linda Chisholm, Robert W. Jacob, Sturt W. Manning, Owen K. Mason, Andrew H. Tremayne, Dale Vinson〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Magnetic survey methods have recently shown tremendous potential for the detection of archaeological hearths in Eastern Beringia, ranging from intermittent open-air camp fires to larger heat intensive activity areas. Here we present an overview of the method along with eight supporting case studies from seven U.S. National Park Service units in the U.S. state of Alaska, covering diverse geographic settings and time-periods. Together, these case studies demonstrate the capabilities of magnetic detection instruments in various modes of operation for finding datable archaeological deposits that span the breadth of known human occupation of this region. The examples range from the simplest use of the magnetometer as a single sensor reconnaissance instrument in a “search mode”, to use as a gradiometer in conjunction with other geophysical methods such as ground-penetrating radar, to record precise measurements and inform nuanced interpretations. Examples presented here range from the terminal Pleistocene to historic periods, spanning 12,000 years of human activity in Eastern Beringia, and encompassing the arrival, emergence, and expansion of multiple human groups or cultural traditions in the New World.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 May 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 211〈/p〉 〈p〉Author(s): Christophe Colin, Nadine Tisnérat-Laborde, Furu Mienis, Tim Collart, Edwige Pons-Branchu, Quentin Dubois-Dauphin, Norbert Frank, Arnaud Dapoigny, Mohamed Ayache, Didier Swingedouw, Jean-Claude Dutay, Frédérique Eynaud, Maxime Debret, Dominique Blamart, Eric Douville〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Variations in North Atlantic Ocean mid-depth circulation during the Holocene are poorly understood. It is believed that they had a significant influence on the properties of water entering the Nordic Sea by redistributing heat and freshwater, potentially affecting deep-water formation and climate. To improve our knowledge of the NE Atlantic mid-depth circulation, radiocarbon and neodymium isotope analyses have been then carried out on precisely dated (U-Th) 〈em〉L. pertusa〈/em〉 and 〈em〉M. oculata〈/em〉 coral fragments from two sediment cores taken at ∼750 m water depth on the SW Rockall Trough margin. Cold-water coral (CWC) εNd values vary between −12.2 ± 0.3 and −16.6 ± 0.4 and result from variable contributions of unradiogenic mid-depth subpolar gyre (mid-SPG) water (∼-15) and more radiogenic Eastern North Atlantic Water (ENAW) (∼-11) which is transported northward to the Rockall Trough by boundary currents along the European margin. Increased coral εNd reflects a westward contraction of the mid-SPG water and a higher proportion of ENAW. The mid-Holocene (from 8.8 to 6.8 ka BP) is marked by unradiogenic coral εNd (from −16.6 ± 0.4 to −14.6 ± 0.5) indicating a greater eastward extension of the mid-SPG. This is followed by a shift from 6.8 to 5 ka BP toward more radiogenic εNd values (from −15.4 ± 0.3 to −13.3 ± 0.2) suggesting a westward contraction of the mid-SPG and a higher proportion of ENAW. The mid-Holocene long-term change in εNd is characterized by millennial variations of up to 2.5 epsilon units well marked during the Late Holocene, indicating that eastward extension of the mid-SPG coeval with warm periods in northern Europe (e.g. the Medieval Climatic Anomaly and the Roman Warm Period). Most of the CWC-derived Δ〈sup〉14〈/sup〉C values match the global ocean values indicating that the water masses bathing the corals were generally well ventilated; the exceptions are a few short intervals of eastward extension of the mid-SPG, which are characterized by lower Δ〈sup〉14〈/sup〉C during the late Holocene. We propose that these minor Δ〈sup〉14〈/sup〉C fluctuations in the Rockall Trough may be related to local changes in the mixed layer depth or to variability in the advection of water from the Labrador Sea where deep convection gives rise to thermocline waters that are relatively depleted in terms of Δ〈sup〉14〈/sup〉C.〈/p〉 〈p〉The eastward extension of the mid-SPG between 8.8 and 6.8 ka BP is associated with the Holocene climatic optimum, concurrent with a maximum strength of the Iceland-Scotland Overflow Water (ISOW), which is indicative of an increase in the Atlantic Meridional Overturning Circulation (AMOC). This period is followed by a transition in the North Atlantic circulation, which occurred around 6.8 ka BP, and coincides with the onset of Labrador Sea Water formation, a decrease of the ISOW strength and a contraction of the mid-SPG leading to a greater intrusion of saline subtropical water into the subpolar Atlantic.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 204〈/p〉 〈p〉Author(s): Byron A. Steinman, Daniel B. Nelson, Mark B. Abbott, Nathan D. Stansell, Matthew S. Finkenbinder, Bruce P. Finney〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Multi-proxy sediment records from Castor Lake and Scanlon Lake, north-central Washington, provide a late Quaternary perspective on lake/catchment hydrologic and ecosystem responses to climate change and the Mazama volcanic ashfall event. Analyses of authigenic carbonate mineral oxygen and carbon isotope values, organic carbon and nitrogen content, and sedimentological facies were conducted on sediment from Castor Lake in order to reconstruct lake/catchment hydrologic balance, the source and abundance of organic matter, and variations in lake level. Sedimentary facies characterization was conducted on the Scanlon Lake sediment in order to provide supporting evidence for the lake-level shifts inferred from the Castor Lake data. Marked changes in Castor Lake proxy values occur from 12,860 to 11,440 calendar years before present (yr BP), suggesting lake/catchment responses to the Younger Dryas cold reversal including higher lake levels, substantial variability in productivity, and increased catchment erosion. High δ〈sup〉18〈/sup〉O values at 9630 yr BP indicate that lake levels were lower than at present and that the early Holocene was dry. Sedimentological analyses and δ〈sup〉18〈/sup〉O data demonstrate that subsequent to the Mazama climactic eruption (∼7600 yr BP), a transition to the lowest lake levels of the Holocene occurred over several centuries, with maximum δ〈sup〉18〈/sup〉O values at 7290 (90% uncertainty range: 7020–7500) yr BP and low lake levels persisting until 6190 (5960–6410) yr BP. Lithological changes in the Scanlon Lake record support these inferences. The lowest δ〈sup〉18〈/sup〉O values of the Holocene occur in sediment from ∼5000 yr BP, indicating high lake levels at this time, after which a secular trend toward higher δ〈sup〉18〈/sup〉O values and lower lake levels occurred. The prolonged lowstand in the centuries following the Mazama eruption suggests that catchment hydrologic characteristics were strongly impacted by the ashfall through effects on soil water retention capacity, that similar responses may have occurred in comparable settings within the Mazama ashfall zone, and that such volcanic events have the potential confound the climate signal in lake sediment records. Were a similar event to happen in the future, catchment hydrology, stream/river discharge, and lake/catchment ecosystem dynamics could be affected for centuries.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 205〈/p〉 〈p〉Author(s): Zhaojie Yu, Christophe Colin, Shiming Wan, Rajeev Saraswat, Lina Song, Zhaokai Xu, Peter Clift, Huayu Lu, Mitchell Lyle, Denise Kulhanek, Annette Hahn, Manish Tiwari, Ravi Mishra, Serge Miska, Anil Kumar〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Long marine sequences deposited in the Arabian Sea are suitable to study the orbital sensitivity of sediment dynamics from a source-to-sink perspective. The clay mineralogy and Sr〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉Nd isotopic compositions have been analyzed for the detrital fraction of sediments from IODP Site U1457 located in the Laxmi basin, eastern Arabian Sea to constrain the sediment sources and reconstruct a high-resolution record of sediment export to the Indus deep-sea fan over the past 600 kyr. The 〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr ratio (varying from 0.7154 to 0.7255) and εNd (varying from −12.9 to −9.5) imply a mixing of sediments derived from not only the Indus River but also the rivers draining the Deccan Traps. The variations in the smectite/(illite + chlorite) ratio combined with Sr〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉Nd isotopes permit the reconstruction of past changes in the relative proportions of sediments derived from the Indus River (mainly illite, chlorite and kaolinite) and the Deccan Traps (smectite). The wavelet and cross-spectral analyses further reveal that sediment transport to the eastern Arabian Sea since 600 kyr is mainly dominated by sea-level variations in the eccentricity (100-kyr) band, while the Indian summer monsoon might contribute moderately to the precession (23-kyr) band. The εNd and turbidite frequency indicate that more turbidite events are associated with Indus River-sourced sediments at IODP Site U1457 during sea-level lowstands, which might reflect a reconnection of deep-sea channels to the Indus River mouth and/or reworking of previously deposited Indus River sediments located northward.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 205〈/p〉 〈p〉Author(s): Richard S. Vachula, Yongsong Huang, William M. Longo, Sylvia G. Dee, William C. Daniels, James M. Russell〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Our understanding of the timing and pathway of human arrival to the Americas remains an important and polarizing topic of debate in archaeology and anthropology. Traditional consensus, supported by archaeological and paleoenvironmental data, favors a ‘swift peopling’ of the Americas from Asia via the Bering Land Bridge during the last Glacial termination. More recent genetic data and archaeological finds have challenged this view, proposing the ‘Beringian standstill hypothesis’ (BSH), wherein a population of proto-Americans migrated from Asia during, or even prior to the Last Glacial Maximum (LGM) and lived in Beringia for thousands of years before their eventual spread across the American continents. Using a sediment archive from Lake E5 (68.641667° N, 149.457706° W), located on Alaska's North Slope, we present new data supporting the BSH and shedding new light on the environmental impact of these early American populations. Fecal biomarkers support human presence in the environs of the lake, and our data demonstrate elevated biomass burning in this region during the last Glacial. Elevated burning defies the expectation that natural fires would be less frequent in the Arctic during the last Glacial, thereby suggesting human ignition as the likely culprit. Our data shed new light on the pathway and timing of human migration to the Americas and demonstrate the possibility of the sustainable coexistence of humans and the Ice Age megafauna in Beringia prior to their extinction.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 204〈/p〉 〈p〉Author(s): Mitch D'Arcy, Taylor F. Schildgen, Manfred R. Strecker, Hella Wittmann, Walter Duesing, Jürgen Mey, Stefanie Tofelde, Philipp Weissmann, Ricardo N. Alonso〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Advances in cosmogenic nuclide exposure dating have made moraines valuable terrestrial recorders of palaeoclimate. A growing number of moraine chronologies reported from the Central Andes show that tropical glaciers responded sensitively to past changes in precipitation and temperature over timescales ranging from 10〈sup〉3〈/sup〉 to 10〈sup〉5〈/sup〉 years. However, the causes of past glaciation in the Central Andes remain uncertain. Explanations have invoked insolation-modulated variability in the strength of the South American Summer Monsoon, teleconnections with the North Atlantic Ocean, and/or cooling in the Southern Hemisphere. The driver for these past climate changes is difficult to identify, partly due to a lack of dated moraine records, especially in climatically sensitive areas of the southern Central Andes. Moreover, new constraints are needed on precisely where and when glaciers advanced. We use cosmogenic 〈sup〉10〈/sup〉Be produced in situ to determine exposure ages for three generations of moraines at the Sierra de Aconquija, situated at 27°S on the eastern flank of the southern Central Andes. These moraines record glacier advances at approximately 22 ka and 40 ka, coincident with summer insolation maxima in the sub-tropics of the Southern Hemisphere, as well as at 12.5 ka and 13.5 ka during the Younger Dryas and the Antarctic Cold Reversal, respectively. We also identify minor glaciation during Bond Event 5, also known as the 8.2 ka event. These moraines register past climate changes with high fidelity, and currently constitute the southernmost dated record of glaciation on the eastern flank of the Central Andes. To contextualise these results, we compile 〈sup〉10〈/sup〉Be data reported from 144 moraines in the eastern Central Andes that represent past glacier advances. We re-calculate exposure ages from these data using an updated reference production rate, and we re-interpret the moraine ages by taking the oldest clustered boulder age (after the exclusion of outliers attributed to nuclide inheritance) as closest to the timing of glacier advance—an approach for which we provide empirical justification. This compilation reveals that Central Andean glaciers have responded to changes in temperature and precipitation. We identify cross-latitude advances in phase with insolation cycles, the last global glacial maximum, and episodes of strengthened monsoonal moisture transport including the Younger Dryas and Heinrich Stadials 1 and 2. Our results from the Sierra de Aconquija allow us to constrain the southerly limit of enhanced precipitation associated with Heinrich Stadials at ∼25°S. More broadly, our findings demonstrate at both local and regional scales that moraines record past climate variability with a fine spatial and temporal resolution.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 205〈/p〉 〈p〉Author(s): Christopher T. Hayes, Davin J. Wallace〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Despite evidence for an anti-correlation between African dust emissions and Atlantic hurricane activity in the instrumental period, there is debate as to whether there is any direct causal relationship between these two parameters. In this study, we provide a focused review of available African dust and storm activity records over 3 increasing timescales: the past 200 years, the past 3000 years and the past 12,000 years. In all three timescales, we find evidence for non-stationary, weak or unexpected relationships between African dust emissions and tropical cyclone activity. We suggest future storm record compilations that can better distinguish the relative frequency of storms generated in the eastern versus western development region of the tropical North Atlantic will provide a better test of the radiative impact of African dust over the past 3000 years and Holocene. Additionally, high resolution dust deposition records from the western Atlantic measured in the same cores used to derive storm records may provide much more detailed insight into how the variability in magnitude and spatial extent of the African dust plume has co-evolved with Atlantic storm tracks over recent millennia.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 204〈/p〉 〈p〉Author(s): Simon T. Belt〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Significant changes to Arctic and Antarctic sea ice in recent decades has prompted the development and application of novel approaches to the reconstruction of past sea ice conditions over much longer timeframes. One such approach is based on the variable distribution of certain source-specific highly branched isoprenoid (HBI) lipid biomarkers in well-dated marine sediment records. Thus, IP〈sub〉25〈/sub〉 and IPSO〈sub〉25〈/sub〉 have emerged as useful proxy measures of seasonal sea ice in the Arctic and Antarctic, respectively. An overview of the salient features of IP〈sub〉25〈/sub〉, IPSO〈sub〉25〈/sub〉 and related biomarkers is presented, together with aspects that are currently less well understood and potentially provide direction for future research.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 204〈/p〉 〈p〉Author(s): Yusuke Suganuma, Yuki Haneda, Koji Kameo, Yoshimi Kubota, Hiroki Hayashi, Takuya Itaki, Masaaki Okuda, Martin J. Head, Manami Sugaya, Hiroomi Nakazato, Atsuo Igarashi, Kizuku Shikoku, Misao Hongo, Masami Watanabe, Yasufumi Satoguchi, Yoshihiro Takeshita, Naohisa Nishida, Kentaro Izumi, Kenji Kawamura, Moto Kawamata〈/p〉

Description: 〈p〉Publication date: 1 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 205〈/p〉 〈p〉Author(s): Lee B. Corbett, Paul R. Bierman, Stephen F. Wright, Jeremy D. Shakun, P. Thompson Davis, Brent M. Goehring, Christopher T. Halsted, Alexandria J. Koester, Marc W. Caffee, Susan R. Zimmerman〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Constraining glacial history and process on Mt Mansfield, the highest peak in Vermont (1339 m a.s.l.), provides insight into how the Laurentide Ice Sheet shaped the underlying landscape, when latest Pleistocene ice retreated, and how upland and lowland glacial histories relate. Here, we quantify 〈em〉in situ〈/em〉 cosmogenic 〈sup〉10〈/sup〉Be in 20 bedrock and boulder surfaces, as well as 〈em〉in situ〈/em〉 cosmogenic 〈sup〉14〈/sup〉C in three of those surfaces, to assess subglacial erosion and exposure history. Isotopic concentrations indicate that Mt. Mansfield's lower elevations (∼400–1200 m a.s.l.) were deeply eroded by at least several meters during the last glaciation and then deglaciated rapidly; 〈sup〉10〈/sup〉Be ages across this elevation span are indistinguishable and average 13.9 ± 0.6 ka (n = 15), suggesting that 800 m of ice thinning occurred within at most about a millennium. Conversely, the higher elevations (〉1200 m a.s.l.) preserve a more complex geomorphic history. Mt. Mansfield's summit surfaces contain 〈sup〉10〈/sup〉Be from previous periods of exposure, indicating that the mountaintop landscapes were likely preserved beneath cold-based, weakly-erosive glacial ice. Exposure ages from the shorter-lived isotope, 〈sup〉14〈/sup〉C, are younger (9.7 and 11.7 ka), suggesting that Mt. Mansfield's summit was covered until the early Holocene, perhaps by snowfields, ice carapaces, and/or till. Our findings, in context of previous work, suggest that thinning Laurentide ice flowed through the valleys for at most hundreds of years following deglaciation of the uplands, but that the summit remained shielded by ice or sediment for millennia after the valleys became ice-free.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 205〈/p〉 〈p〉Author(s): G.M. Cárdenes-Sandí, C.R. Shadik, A. Correa-Metrio, W.D. Gosling, R. Cheddadi, M.B. Bush〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Last Interglacial (c. 128,000 to 115,000 years ago) was the last time when global temperatures may have been higher than those of the Holocene, but little is known about vegetation change or paleoclimate during that period in Central America. A new fossil pollen record from the lowland setting of El Valle, Panama, spanned the period from 137,000 to 98,000 years ago. We used multivariate analysis of modern and fossil pollen samples to provide the first regional quantification of Last Interglacial temperature and precipitation change and found mean annual temperatures were c. 1–2 °C warmer than modern, while precipitation was mostly similar to modern. The montane genus 〈em〉Quercus〈/em〉 was intermittently present throughout the interglacial period, leading to the inference that this dispersal-limited taxon was surviving in microrefugia. Both charcoal and the early successional genus 〈em〉Cecropia〈/em〉 were noticeably rare in the last interglacial compared with the Holocene. The modern absence of 〈em〉Quercus〈/em〉 from Central Panama does not appear to be the product of interglacial warming, but rather a result of dry conditions in the late Holocene and human activity. It is suggested that humans greatly increased fire frequency, thereby favoring 〈em〉Cecropia〈/em〉 and eliminating 〈em〉Quercus〈/em〉 from the lower portion of its elevational range.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 206〈/p〉 〈p〉Author(s): J. Shulmeister, G.D. Thackray, T.M. Rittenour, D. Fink, N.R. Patton〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper constitutes a review of the last (Otiran) glaciation in New Zealand, spanning marine isotope stages (MIS) 4-2. We highlight the nature of glaciation, which is characterised by exceptional sedimentation, relatively mild maritime climatic conditions and the widespread presence of water associated with proglacial settings. These conditions produce glacial systems characterised by extensive outwash fans and relatively small terminal moraines. Extensive recent geochronological work allows us to recognise at least eight glacial advances during the Otiran. These occurred at 65 ± 3.25ka, 47.5 ± 3 ka, 38.5 ± 2 ka, 31.5 ± 3 ka, 26.5 ± 2 ka, 20.5 ± 2 ka, 17 ± 2 ka and 13 ± 1 ka, which we term the Otira 1 to 8 advances, respectively. Though the analytical uncertainty ranges for some of these advances overlap, all are independently distinguished through moraine morphologic relationships and/or stratigraphic relationships in outcrop. Major advances appear to be associated with climate influences such as periods of Southern Hemisphere insolation minima (65ka, and 31.5 ka advances), the last glacial maximum cooling (LGM) (20.5 ka) and periods of Antarctic cooling (13ka). The timing of greatest glacial extent in the last glacial cycle is not simultaneous across New Zealand. The MIS 4 advance was the greatest in the southern South Island, while the MIS 3/2 advances (26.5 ka) were greatest in the central South Island. In the northern South Island and the North Island, MIS 4, MIS 3/2, and the last glacial maximum appear to be equivalent in extent. We attribute these spatio-temporal variations in the timing of maximum glaciation to precipitation changes related to a northward shift in the track of the westerlies.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 205〈/p〉 〈p〉Author(s): I. Hernández-Almeida, B. Ausín, M. Saavedra-Pellitero, K.-H. Baumann, H.M. Stoll〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Ocean net primary productivity (Npp) is a key component of the marine carbon cycle. Multi-model Npp projections based on a few decades of satellite data show large uncertainties, in particular at low latitudes (30°N−30°S). Calibration of sedimentary proxies with satellite-based Npp estimates allows for the quantitative reconstruction of this variable at longer time-scales. Relative abundance of deep-photic zone coccolithophore species 〈em〉Florisphaera profunda〈/em〉 in the fossil record can potentially be used as a quantitative proxy for Npp. However, the robustness of this proxy calibration has been tested in very specific oceanographic settings using surface sediment samples. Here, we use a global dataset of surface sediment (n = 1258) and sediment trap (n = 26) samples with relative abundance data of 〈em〉F. profunda〈/em〉 (%) to test the robustness of this proxy as a quantitative indicator of Npp. We study the modern and paleo-ecology of this species and the main factors affecting its latitudinal distribution. Results show that 〈em〉F. profunda〈/em〉 % is a strong indicator of Npp at latitudes between 30°N and 30°S, while at higher latitudes temperature-related variables are more important. We develop a global calibration model between satellite Npp estimates and 〈em〉F. profunda〈/em〉 for the latitudinal range between 30°N and 30°S, and we apply it to several low-latitude sediment cores with available 〈em〉F. profunda〈/em〉 counts covering the Late Glacial Maximum (LGM; 24–19 ka) and the Mid-to-Late Holocene period (MLH; 〈6 ka). Reconstructed Npp during the LGM is 15% higher than during the MLHdue to the intensification of trade winds that enhanced oceanic upwelling at low latitudes.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 205〈/p〉 〈p〉Author(s): M.F. Raczka, N.A. Mosblech, L. Giosan, B.G. Valencia, A.M. Folcik, M. Kingston, S. Baskin, M.B. Bush〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A new fossil pollen, 〈em〉Sporormiella,〈/em〉 and sediment chemistry record from Lake Llaviucu, Ecuador, spanning the period from 16,280–9000 years Before Present, provides a high-resolution record of paleoecological change in the high Andes. The deglacial transition from super-páramo through páramo grasslands, to Andean forest is traced, with near-modern systems being established by c. 11,900 years ago. It is suggested that forest elements probably existed in microrefugial populations close to the ice front. 〈em〉Sporormiella〈/em〉 is used as a proxy for megafaunal abundance, and its decline to background levels is inferred to indicate a local extinction event at c. 12,800 years ago. About 1800 years prior to the extinction, charcoal becomes a regular sedimentary component in this very wet valley. An early date for human activity in the valley is suggested, with the direct implication of humans in the extinction of the megafauna.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 21 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews〈/p〉 〈p〉Author(s): Gili Greenbaum, David E. Friesem, Erella Hovers, Marcus W. Feldman, Oren Kolodny〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The transition from the Middle Paleolithic (MP) to the Upper Paleolithic (UP), circa 40kya, is viewed as a major turning point in human evolution, in terms of the material culture, demography, and geographical expansion of modern humans. However, attempts to identify an origin of this so-called ‘revolution’ in the form of a particular stone-tool techno-complex, representing cultural modernity, which spread across the human range, have failed. Instead, the archaeological record of this period comprises multiple ‘transitional techno-complexes’, some associated with modern humans and others with Neanderthals. The cultures that these techno-complexes represent are characterized by precursors of the material cultures of the UP, often alongside features that suggest local cultural continuity. The broadly simultaneous appearance of these transitional cultures, despite a lack of a clear common origin, is puzzling. We suggest that these local ‘revolutions’ had a common underlying driver, which explains the simultaneous appearance of transitional techno-complexes, but that this driver did not determine the particular form of each local revolution. We propose that the driver of the transition to the UP was an increase in inter-population connectivity, both within- and between-species, which allowed local cultures to rapidly evolve and to attain greater complexity than ever before. We suggest that this change was driven by the interaction between modern humans and Neanderthals. In this article we outline processes that are likely to have influenced inter-population connectivity, bringing together evolutionary and ecological perspectives alongside insights from the field of cultural evolution.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 205〈/p〉 〈p〉Author(s): S. Nomade, F. Bassinot, M. Marino, Q. Simon, F. Dewilde, P. Maiorano, G. Isguder, D. Blamart, A. Girone, V. Scao, A. Pereira, F. Toti, A. Bertini, N. Combourieu-Nebout, M. Peral, D.L. Bourlès, P. Petrosino, S. Gallicchio, N. Ciaranfi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Understanding millennial and sub-millennial climate variability during past low eccentricity interglacials similar to the Holocene is important for forecasting the evolution of climate and natural variability. The 〈em〉Ideale section〈/em〉 (Montalbano Jonico, Southern Italy) studied here provides one of the best records of MIS 19c, the closest orbital analog to the Holocene. This exposed marine series covers Termination IX to the inception of MIS 18 with very high sedimentation rates (i.e. 90–200 cm/ka). We present 1) benthic δ〈sup〉18〈/sup〉O and δ〈sup〉13〈/sup〉C records at 90–200 year time-resolution, 2) a new 〈sup〉40〈/sup〉Ar/〈sup〉39〈/sup〉Ar age of 774.1 ± 0.9 ka for tephra layer V4 (Matuyama-Brunhes transitional period) and 3) new calcareous plankton, palynological and authigenic 〈sup〉10〈/sup〉Be/〈sup〉9〈/sup〉Be data. Our new Bayesian depth-age model suggests a 11.5 ± 3.4 ka (95% confidence) duration for the climatic optimum. The δ〈sup〉18〈/sup〉O series reveals millennial-scale oscillations (with sharp transitions 〈 200 years) between ∼774.0 and the onset of MIS 18 (∼757.0 ka) with a cyclicity of about 5.4 ka. Spectral analysis and band-pass filtering indicate that these climate oscillations existed throughout the entire MIS 19 period, although they were dampened during MIS 19c, which is chiefly controlled by orbitally-driven insolation. The amplitude of those sub-orbital oscillations increased towards MIS 18 as the climate became drier and cooler. The Ideale section reveals, with unprecedented detail, millennial-scale climatic oscillations of MIS 19b-a that have been observed worldwide. They highlight the response of the central Mediterranean area to North Atlantic climatic variation (i.e. oceanic circulation and atmospheric processes related to ice-sheet dynamics) during this low eccentricity interglacial.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0277379117310132-fx1.jpg" width="329" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 1 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 205〈/p〉 〈p〉Author(s): Jon Camuera, Gonzalo Jiménez-Moreno, María J. Ramos-Román, Antonio García-Alix, Jaime L. Toney, R. Scott Anderson, Francisco Jiménez-Espejo, Jordon Bright, Cole Webster, Yurena Yanes, José S. Carrión〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A new sediment core from Padul, Padul-15-05, provides a long and continuous sedimentary and paleoenvironmental record of the last ∼200 kyr. Here we present a detailed palynological study from this sedimentary sequence with new vegetation and paleoenvironmental data and a climatic interpretation for the last two climatic cycles from the southern Iberian Peninsula in the western Mediterranean region. Pollen analysis from this core shows orbital-scale vegetation oscillations (mainly forced by precession and eccentricity) pointing into insolation as the principal factor controlling vegetation changes at this latitude. The last two glacial-interglacial cycles (from MIS 6 to the present) as well as stadial and interstadial phases are well represented and characterized by significant oscillations in Mediterranean forest in the area, but several differences with respect to other Mediterranean long pollen records can be recognized. Some of these disparities between regions seem to be more related to different precipitation rates linked to the specific geographical features (e.g. strong topographic relief) than to latitudinal differences between the sites. In addition, a lake level reconstruction based on palynological data was developed and compared with the previous reconstruction from this record, representing local environmental changes in the Padul wetland that seems to be related to precipitation/evapotranspiration balance, and therefore, to changes in regional climate conditions. During glacial/stadial conditions recorded by maxima in xerophytes, the p/e increased due to very low evapotranspiration, resulting in high lake levels, while during warmer interglacial/interstadial phases (except for the MIS 5e), mainly represented in this record by maxima in the Mediterranean forest, water level decreased as a result of high evapotranspiration exceeding precipitation input. The comparison of the new Padul-15-05 pollen record with the two previous palynological studies from Padul shows significant differences mainly due to disagreements in the age control of the sequences. This study shows that an accurate age-depth model becomes essential when interpreting long paleoenvironmental and paleoclimate records.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 205〈/p〉 〈p〉Author(s): Margarita Caballero, Socorro Lozano-García, Beatriz Ortega-Guerrero, Alexander Correa-Metrio〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Diatom-based transfer functions for salinity, precipitation and temperature were developed using a training set that included data from 40 sites along central Mexico. These transfer functions showed good performance parameters and were subsequently applied to the previously published diatom record from lake Chalco, southern Basin of Mexico. Heinrich stadials (HS-3 to HS-0) were reconstructed as cold and dry events, with HS-2 representing the coldest and driest conditions, while HS-1 shows a complex bimodal cooling pattern. Orbital scale variability is also recorded. High and variable lake salinities from ∼34 to 29 ka BP (marine isotope stage 3, MIS-3) corresponded with times of maximum summer insolation and evidences of frequent fires. MIS-2 was identified as a cold period, with low lake salinity associated with low evaporation, with two cold intervals during the minima in spring (∼25.5 ka BP) and summer (∼20 ka BP) insolation. The ∼20 ka BP cold event together with HS-2 (24-23 ka BP), defined a bimodal maximum cooling during the last glacial maximum (LGM: 24.5–19.5 ka BP) within the range of pollen-based estimates, further supporting a maximum tropical cooling of 4–5 °C for the LGM. The deglacial (19.5–11.5 ka BP) showed the highest precipitation anomalies with three peaks that closely correlated with glacier advances in the nearby mountains (Iztaccihuatl). The early Holocene marked a change towards high lake salinities and the highest positive temperature anomalies (+3.5 °C) during a peak in summer insolation. Even though at orbital scale Chalco showed a nearly opposite trend to the record from the more southerly lake Peten-Itza (Guatemala), at millennial scale it showed a common pattern of cold and dry conditions during HSs, comparable to other tropical latitude sites in the northern hemisphere and further supporting the idea that there is a strong coupling between tropical and higher latitudes climates, in particular with the North Atlantic.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 205〈/p〉 〈p〉Author(s): Virgil Pasquier, Samuel Toucanne, Pierre Sansjofre, Yama Dixit, Sidonie Revillon, Zohra Mokeddem, Marina Rabineau〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study we use bulk sediment organic matter stable isotopes (δ〈sup〉13〈/sup〉C〈sub〉org〈/sub〉 and δ〈sup〉15〈/sup〉N) to examine the nature and timing of preserved organic matter in borehole PRGL1-4 from Northwestern Mediterranean Sea. This region is known as a transitional zone between the North Atlantic atmospheric circulation and the North African monsoon system. In the Gulf of Lion (SE France), increased inputs of organic matter from sediment-laden rivers occurred during warm substages of the last 200 kyr (MIS 5e, 5c, and 5a; MIS 6d, and 6b). Increased terrestrial organic matter are inferred from organic carbon isotopic composition (δ〈sup〉13〈/sup〉C〈sub〉org〈/sub〉), and are interpreted as resulting from enhanced rainfall over the Rhone river catchment area. Such increase in terrestrial organic carbon induced enhancement of the primary productivity leading to the formation of local oxygen minimum zone as demonstrated by ∼3‰ values in δ〈sup〉15〈/sup〉N. Comparison with regional paleohydrological records from the northern Mediterranean borderlands reveals the regional character of these pluvial events. Taking advantage of the location of PRGL1-4 borehole, out of Mediterranean cyclogenesis area, we suggest that the pluvial events recorded during warm substages of the last 200 kyr occurred in response to enhanced passage of North Atlantic atmospheric perturbation over the Gulf of Lion catchment area (especially over Rhone river watershed which represent 80% of the GoL catchment area), a scenario possibly similar to that encountered today during negative- NAO like conditions. At a regional scale, our data suggests that high rainfall events over the Gulf of Lion catchement area and the Rhone watershed occurred at the time of North African summer monsoon and the sapropel deposition in the Mediterranean basin, thus highlighting a close coupling between mid- (North Atlantic) and low-latitudes (monsoon) climate systems. Importantly, our geochemical evidence from the Gulf of Lion support an extra-Mediterranean source for the regional pluvial events described in many paleoclimatic records from the northern Mediterrean borderlands during warm substages of the last climate cycles. Consequently, we suggest that this region as a whole could provide, in addition to the river runoff from the North African sector, the necessary conditions for the sapropel deposition.〈/p〉〈/div〉 〈/div〉