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29th International Meeting on Organic Geochemistry
- Conference date: September 1-6, 2019
- Location: Gothenburg, Sweden
- Published: 01 September 2019
1 - 100 of 396 results
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Source Constraints and Translocated Degradation of Terrestrial Organic Matter Using Siberian Arctic Shelves as Receptors
Authors Ö. Gustafsson, I.P. Semiletov, N. Shakhova, O. Dudarev, J. Vonk, B. van Dongen, T. Eglinton, T. Tesi, L. Bröder, A. Andersson, B. Wild, J. Martens and R. Wennström
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Organic Geochemical Perspectives on Hydrothermalism at Olduvai Gorge, 1.7 Mya
AbstractLandscape-scale geochemical reconstructions within the cradle of humanity may yield insights into the evolutionarily-relevant relationships between early hominins and their changing environments. While current geological interpretations of Olduvai Gorge 1.7 Mya suggest the presence of precession-driven wet-dry cycles atop a general aridification trend, the local environments early hominins experienced may have been varied and dynamic. Here, we analyse biomarkers to study the paleolandscape of a single deposition event, the 1.7 Myr old, Lower Augitic Sandstone (LAS) Bed II, at Olduvai Gorge. The discovery of the coexistence of two sets of stone tool technologies, Oldowan and Acheulean, during this depositional event at archaeological sites HWK and FLK-W, has revitalized the hypothesis that these hominin technologies may have been related to the exploitation of specific local resources.
New geochemical evidence from LAS sediments suggests the presence of resource-rich mosaic ecosystems, with groundwater-fed rivers and aquatic plants, revealed by the structural and isotopic characteristics of lipid biomarkers from microorganisms and vegetation. In this study, we employ data from lipids to illustrate an Olduvai environment populated by C3 aquatic plants and angiosperm shrublands, as well as plants that may have been edible.
We also found an unusual biomarker distribution of monoalkyl glycerol monoethers (MAGEs), isoprenoids, and fatty acids, consistent with the presence of hydrothermal features, which may have influenced early hominin behaviour. Similar distributions are reflected at active hydrothermal environments at Yellowstone National Park and New Zealand, though the study of hydrothermalism in ancient settings and its influence on hominin evolution has not yet been addressed. The hydrothermal features suggested by lipid biomarkers at Olduvai Gorge may have enabled early hominins to thermally process edible vegetation and animal matter, thus supporting the possibility of a pre-fire stage of human evolution.
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Molecular Characterization and Effect of Diagenesis and Maduration of Melanin in the Fossil Record
Authors J. Herrera, A. Sistiaga, J. Vinther, C. M. Brown, D. M. Henderson and R. E. SummonsAbstractDespite the fact that melanin is a ubiquitous pigment found in bacteria, fungi, plants and animals, little is known about its chemical preservation and its distribution in the fossil record. Melanins are polymeric phenolic compounds classified into two major groups based in their chemical structures and molecular precursors: eumelanin (dark brown-black in colour) and pheomelanin (orange-red in colour)1,2. Both eumelanin and pheomelanin are complex highly cross-linked biopolymers, being comparable to biomolecules like chitin that are resistant to microbial degradation and diagenetic alteration; which makes melanins potentially capable of maintaining their integrity for millions of years in the fossil record.
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Organic Matter Characterisation along a River Delta to Shelf Transect in Eastern Siberia
Authors D.J. Jong, L.M. Bröder, K.H. Keskitalo, T. Tesi, N. Zimov, A. Davydova, N. Haghipour, T.I. Eglinton and J.E. VonkAbstractThe Arctic Ocean receives an estimated amount of 40 × 1012 g organic carbon (OC) through inflow of rivers every year ( Holmes et al., 2012 ; McClelland et al., 2016 ). A large part of the Arctic Ocean watershed is underlain by permafrost that experiences widescale warming exposing more OC to thaw and degradation ( Biskaborn et al., 2019 ). Arctic Rivers will be increasingly affected by the hydrological and biogeochemical effects of thawing permafrost. During transport, permafrost-OC can be degraded into greenhouse gasses and potentially add to further climate warming (Schuur et al., 2015). However, a significant amount of this OC is transported all the way to the shelf and is buried in marine sediments, attenuating greenhouse gas emissions ( Vonk & Gustafsson, 2013 ).
The East Siberian Arctic Shelf is the largest and shallowest shelf in the Arctic Ocean (Stein & MacDonald, 2004). It receives significant amounts of terrestrial OC, delivered through coastal erosion and fluvial input ( Gustafsson et al., 2011 ; Sánchez-García et al., 2011 ; Vonk et al., 2012). This region is also warming rapidly, and is strongly affected by the loss of sea ice, increasing the open water extent and wave, storm and tidal impact on the coast ( Biskaborn et al., 2019 ; IPCC, 2014).
In this study, we focus on the biogeochemical cycling of OC along the river-shelf continuum of the Kolyma river, the largest river completely underlain by continuous permafrost. To quantify the flux of OC and to link its source to its potential sink in the East Siberian Sea, we have sampled dissolved OC, particulate OC and sediment OC along a transect from an active permafrost thaw site near Cherskiy towards the outer Kolyma delta near Ambarchik. On all of these samples isotopic (δ13C, Δ14C) and molecular (lipid biomarkers, lignin phenols) analyses will be used to characterise the OC and assess its degradation status. This, in combination with published data from the East Siberian Shelf close to the Kolyma delta and earlier studies on the Kolyma river, will give us insight in the complete pathway of permafrost-OC from the moment of thaw to degradation during transport and ultimate storage in marine sediments.
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