ALBERT

Description: The global impacts of river floods are substantial and rising. Effective adaptation to the increasing risks requires an in-depth understanding of the physical and socioeconomic drivers of risk. Whereas the modeling of flood hazard and exposure has improved greatly, compelling evidence on spatiotemporal patterns in vulnerability of societies around the...

Description: Severe changes in ocean redox, nutrient cycling, and marine productivity accompanied most Phanerozoic mass extinctions. However, evidence for marine photic zone euxinia (PZE) as a globally important extinction mechanism for the end-Triassic extinction (ETE) is currently lacking. Fossil molecular (biomarker) and nitrogen isotopic records from a sedimentary sequence in western Canada provide the first conclusive evidence of PZE and disrupted biogeochemistry in neritic waters of the Panthalassic Ocean during the end Triassic. Increasing water-column stratification and deoxygenation across the ETE led to PZE in the Early Jurassic, paralleled by a perturbed nitrogen cycle and ecological turnovers among noncalcifying groups, including eukaryotic algae and prokaryotic plankton. If such conditions developed widely in the Panthalassic Ocean, PZE might have been a potent mechanism for the ETE.

Description: A new framework for automatically tracking subsurface tracers in electrical resistivity tomography (ERT) monitoring images is presented. Using computer vision and Bayesian inference techniques, in the form of a Kalman filter, the trajectory of a subsurface tracer is monitored by predicting and updating a state model representing its movements. Observations for the Kalman filter are gathered using the maximally stable volumes algorithm, which is used to dynamically threshold local regions of an ERT image sequence to detect the tracer at each time-step. The application of the framework to the results of 2-D and 3-D tracer monitoring experiments show that the proposed method is effective for detecting and tracking tracer plumes in ERT images in the presence of noise, without intermediate manual intervention. This article is protected by copyright. All rights reserved.

Description: Large collections of well-preserved specimens of the ammonite Baculites inornatus Meek ( 1862 ) from two lower to middle Campanian localities on the Pacific coast of North America are analyzed quantitatively to examine both variability and evolutionary change of species-level distinguishing characters. To this end, we present a new method of describing the morphology of the biostratigraphically important Upper Cretaceous zonal index fossil Baculites , using five independent shell characters that can be measured quantitatively. We then use this method to test hypotheses of phyletic evolutionary change in B . inornatus specimens collected from Sucia Island, Washington, USA, and Punta San Jose, Baja California, Mexico. The greatest observed character change is in mature shell size: baculitids from the older of the two outcrops (Sucia islands) show a smaller mean diameter at maturity compared to those of the younger of the two outcrops (Punta San Jose). Other than this phyletic size increase, no other directional changes were observed from specimens collected at sub-meter precision from the 90 m-thick measured stratigraphic section of the Rosario Formation located at Punta San Jose. Importantly, neither the younger nor older baculitid assemblages show a size distribution of mature specimens that can be attributed to sexual dimorphism. We observed fluctuating proportions of individuals with ribs and/or keels through this section; since both characters have been used in previous taxonomic studies to define, or differentiate between, other Baculites species, our results indicate that no single character is sufficient to discriminate species within this lineage, and that there is far more variation of these characters than has previously been accepted. Our methodology can also be used to assess morphologic variation and taxonomic assignments of Baculites species in other biogeographic provinces, as well as to evaluate ecological influences on population variation and to test hypotheses of lineage evolution.

Description: Economically viable concentrations of mineral resources are uncommon among the predominantly silicate-dominated rocks in Earth's crust. Most ore deposits that were mined in the past or are currently being extracted were found at or near Earth's surface, often serendipitously. To meet the future demand for mineral resources, exploration success hinges on identifying targets at depth, which, on the one hand, requires advances in detection and interpretation techniques for geophysical and geochemical data. On the other hand, however, our knowledge of the chain of events that lead to ore deposit formation is limited. As geoscience embraces an integrated Earth systems approach, considering the geodynamic context of ore deposits can provide a step change in understanding why, how, when and where geological systems become ore-forming systems. Contributions to this volume address the future resources challenge by: (i) applying advanced microscale geochemical detection and characterization methods; (ii) introducing more rigorous 3D Earth models; (iii) exploring critical behaviour and coupled processes; (iv) evaluating the role of geodynamic and tectonic setting; and (v) applying 3D structural models to characterize specific ore-forming systems.

Description: The Ilomantsi greenstone belt is a Neoarchaean, c. 2.75–2.70 Ga volcanic–sedimentary complex in which metamorphic grade increases from staurolite grade in the SW of the belt to sillimanite grade in the NE. In the staurolite zone, prograde garnet zoning indicates pressure and temperature increases from 480–500°C at 2–4 kbar to 560–570°C at 6–7 kbar. Within the sillimanite zone temperatures peaked at 660–670°C at pressures of around 6 kbar. The U–Pb age determinations on monazite from the sillimanite zone yielded both Archaean and Proterozoic ages. One sample contains an exclusively Archaean monazite population of 2620±24 Ma, while another sample has two generations of monazite, with ages of 2664±33 Ma and 1837±13 Ma. The monazite data confirm that the Ilomantsi greenstone belt was metamorphosed simultaneously with the surrounding Neoarchaean migmatite complexes. The apparent clockwise PT path and medium P / T -type metamorphism are consistent with collisional tectonic settings, but the two distinct metamorphic events recorded by monazite indicate that a second, Palaeoproterozoic thermal event caused recrystallization and new mineral growth, in line with previous evidence from other isotopic systems. Accordingly, great care is necessary in defining metamorphic evolutionary P–T–t paths in rocks with complex mineral assemblages, to ensure correct identification of truly coeval mineral assemblages.

Description: The Istituto Nazionale di Geofisica e Vulcanologia (INGV) leads an international project funded by the Italian National Program for Antarctic Research (PNRA), called DemoGRAPE, in partnership with Politecnico di Torino, Istituto Superiore Mario Boella, and with SANSA (South African National Space Agency) and INPE (the Brazilian National Institute of Space Physics), as key collaborators. DemoGRAPE, a Demonstrator of GNSS Research and Application for Polar Environment, is a new prototype of support for the satellite navigation in Antarctica. Besides the scientific interest, the accuracy of satellite navigation in Antarctica is of paramount importance since there is always the danger that people and vehicles can fall into a crevasse during a snowstorm, when visibility is limited and travel is restricted to following specified routes using satellite navigation systems. The variability of ionospheric delay and ionospheric scintillation are two of the primary factors which affect the accuracy of satellite navigation. The project will provide a demonstrator of cutting edge technology for the empirical assessment of the ionospheric delay and ionospheric scintillations in the polar regions. The scope of the project includes new equipment for the recording and dissemination of GNSS data and products installed at the South African and Brazilian bases in Antarctica. The new equipment will facilitate the exchange of software and derived products via the Cloud computing technology infrastructure. The project portal is accessible at: www.demogrape.net . We report the first Global Navigation Satellite System (GNSS) signal scintillations observed in Antarctica.

Description: The Hattu schist belt is an emerging gold-producing ore district in the western part of the Archean Karelian Province of the Fennoscandian Shield. The belt consists of 2.76 to 2.70 Ga tonalite, granodiorite, and leucogranite intruded into a mafic-felsic epiclastic-volcanic sequence of an only slightly older age. Complex and successive folding, shearing, and hydrothermal processes affected these rocks prior to the lower amphibolites facies peak metamorphism (550° ± 50°C; 3–5 kbar) at ca. 2.70 Ga. Orogenic gold deposits are hosted by the highly strained zones that developed during the Archean deformation of the belt. However, previous K-Ar and Rb-Sr geochronological studies indicated that a second tectonothermal overprint affected the Hattu schist belt between 1.7 and 1.8 Ga during the Svecofennian orogeny. Results of our field, mineralogical, textural, and Pb isotope studies suggest that ore deposition at Pampalo was initiated by hydrothermal processes at the time of the emplacement of feldspar porphyry and tonalite intrusions and dikes, at around 2.72 Ga. Albitization and quartz-tourmaline-biotite-muscovite veining characterize this hydrothermal activity. The major stage of gold ore deposition can be confined to the subsequent development of high-strain zones in an intermediate-felsic tuffaceous unit (mafic schist) characterized by biotite-carbonate-pyrite alteration. Ar-Ar studies revealed the complete resetting of the Ar-Ar system in muscovite and biotite due to the Svecofennian orogeny, with closure of the isotopic system at 1.81 Ga. Results of Pb isotope studies of hydrothermal K-feldspar, galena, and altaite by laser ablation-inductively coupled plasma-mass spectrometry indicate that K-feldspar alteration and remobilization of metals also took place during the Svecofennian reactivation of high-strain zones. The petrographic manifestation of this process is the replacement of albite by hydrothermal K-feldspar. Fluid inclusion data from hydrothermal K-feldspar suggest that carbonic-aqueous, low-salinity fluids interacted with the Archean ore at 350° to 400°C and 1.8 to 2.4 kbar during the Svecofennian overprint. Results of mass transfer calculations indicate that potassium gain correlates with increase of gold concentrations in the mafic schist and feldspar-porphyry units. Therefore, the Svecofennian overprint locally also enhanced the grade of gold mineralization, mostly along competency differences of the mafic schist and feldspar porphyry blocks/dikes. Later percolation of relatively low temperature (〈300°C) saline basin fluids in some fractures of the crystalline basement also left their Pb isotope and fluid inclusion signatures on the mineralization while further modifying the composition of the ore. Occurrences of hydrothermal proto-ores, as well as fluid flow events along structures reactivated by overprinting orogenic processes, are not exceptional features in Archean orogenic gold provinces. This study shows that the combination of in situ Pb isotope studies of U-poor alteration minerals and Pb-rich ore minerals, together with evaluation of relationships between gold enrichment and hydrothermal alteration and fluid inclusion studies, can be very useful in determining the significance and conditions of overprinting processes, as well as their potential implications for genetic and exploration models.

Description: 〈p〉The last extended time period when climate may have been warmer than today was during the Last Interglacial (LIG; ca. 129 to 120 thousand years ago). However, a global view of LIG precipitation is lacking. Here, seven new LIG climate models are compared to the first global database of proxies for LIG precipitation. In this way, models are assessed in their ability to capture important hydroclimatic processes during a different climate. The models can reproduce the proxy-based positive precipitation anomalies from the preindustrial period over much of the boreal continents. Over the Southern Hemisphere, proxy-model agreement is partial. In models, LIG boreal monsoons have 42% wider area than in the preindustrial and produce 55% more precipitation and 50% more extreme precipitation. Austral monsoons are weaker. The mechanisms behind these changes are consistent with stronger summer radiative forcing over boreal high latitudes and with the associated higher temperatures during the LIG.〈/p〉