HR: 1340h
AN: PP43B-1275    [Abstracts]
TI: A Novel Tetraether Membrane Lipid Record from the Amazon Fan: The Influence of Changes in Sediment Supply on Estimates of Palaeo-Temperature, pH and Wetland Extent
AU: * Bendle, J A
EM: James.Bendle@ges.gla.ac.uk
AF: Geographical and Earth Sciences, University of Glasgow, Gregory Building,Lilybank Gardens, Glasgow, G12 8QQ, United Kingdom
AU: Weijers, J W
AF: Organic Geochemistry Unit, Bristol Biogeochemistry Research Centre, School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, United Kingdom
AU: Sinninghe-Damste, J S
AF: Royal Netherland Institute of Sea Research (NIOZ), P.O. Box 59, Texel, Den Burg, NL-1790 AB, Netherlands
AU: Maslin, M
AF: Environmental Change Research Centre, UCL, Department of Geography, University College London, 26 Bedford Way, London, WC1H 0AP, United Kingdom
AU: Ettwein, V
AF: Environmental Change Research Centre, UCL, Department of Geography, University College London, 26 Bedford Way, London, WC1H 0AP, United Kingdom
AU: Hopmans, E C
AF: Royal Netherland Institute of Sea Research (NIOZ), P.O. Box 59, Texel, Den Burg, NL-1790 AB, Netherlands
AU: Boot, C S
AF: Organic Geochemistry Unit, Bristol Biogeochemistry Research Centre, School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, United Kingdom
AU: Schouten, S
AF: Royal Netherland Institute of Sea Research (NIOZ), P.O. Box 59, Texel, Den Burg, NL-1790 AB, Netherlands
AU: Pancost, R D
AF: Organic Geochemistry Unit, Bristol Biogeochemistry Research Centre, School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, United Kingdom
AB: Reconstructing Amazon basin paleoclimatic change is important because the region is a major component of the global carbon and hydrological cycles. Moreover, the region's tropical wetlands represent a major source of atmospheric methane. In order to provide a multiproxy 35 kyr record of terrestrial paleoclimatic change from the Amazon basin, analysis of glycerol dialkyl glycerol tetraethers (GDGTs) was carried out on sediment recovered from Ocean Drilling Program (ODP) Site 942 (Amazon Fan). The GDGTs include those with methyl-branched alkyl components, derived from unknown terrestrial bacteria (present worldwide in peat bogs and soils) which have been fluvially transported from the Amazon basin and sequestered in the Amazon fan. The catchment area supplying sediment to the Amazon fan covers a large portion of South America, including vast areas of tropical forests and wetlands; hence proxy records from ODP 942 potentially provide a spatially averaged terrestrial signal of major significance. We use recently developed indices that predict changes in: the relative fluvial input of terrestrial organic material; annual mean air temperature (MAT) and soil pH. We also use the ratios of certain alcohols as qualitative proxies for the relative inputs of wetland material. The Amazon basin shows a glacial to interglacial temperature increase of around 5°C; consistent with pollen and other geochemical records. However, this is followed by an apparent drop of 11°C at the start of the Holocene. We discuss how this seemingly counter intuitive result may be explained by changes in sediment supply from the Andean region relative to the warmer eastern Amazonia. In the glacial the soil pH increases dramatically from 13 to 11 kyr; possibly related to an (inferred) ~40 percent decrease in effective moisture in the Amazon basin. A post-glacial increase in wetland biomarkers suggests that the propagation of tropical wetlands, on continental shelves, may have been a key source of the post-glacial increase in global atmospheric methane.
DE: 0473 Paleoclimatology and paleoceanography (3344, 4900)
DE: 0486 Soils/pedology (1865)
DE: 1055 Organic and biogenic geochemistry
DE: 4912 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 1615, 4805)
DE: 4926 Glacial
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting