HR: 08:00h
AN: PP51D-01 INVITED    [Abstracts]
TI: Novel Proxies for Continental Palaeo-temperature and Soil pH Reconstruction Based on Tetraether Membrane Lipids of Soil Bacteria
AU: * Weijers, J W
EM: johan.weijers@bristol.ac.uk
AF: Royal Netherlands Institute for Sea Research, Landsdiep 4, t Horntje - Texel, 1797SZ, Netherlands
AU: Schouten, S
EM: schouten@nioz.nl
AF: Royal Netherlands Institute for Sea Research, Landsdiep 4, t Horntje - Texel, 1797SZ, Netherlands
AU: Hopmans, E C
EM: hopmans@nioz.nl
AF: Royal Netherlands Institute for Sea Research, Landsdiep 4, t Horntje - Texel, 1797SZ, Netherlands
AU: Peterse, F
EM: fpeterse@nioz.nl
AF: Royal Netherlands Institute for Sea Research, Landsdiep 4, t Horntje - Texel, 1797SZ, Netherlands
AU: Sinninghe Damste, J S
EM: damste@nioz.nl
AF: Royal Netherlands Institute for Sea Research, Landsdiep 4, t Horntje - Texel, 1797SZ, Netherlands
AB: Several proxies based on organic compounds exist of which the Uk'37 and the TEX86 are now well established quantitative temperature proxies applied in the marine realm. Although biomarker proxies exist for the terrestrial realm, none of them can be used to quantitatively estimate continental temperatures. Here we introduce two new proxies based on terrestrial derived branched glycerol dialkyl glycerol tetraether (GDGT) membrane lipids to quantitatively estimate continental palaeo-temperatures and palaeo-soil pH. Branched GDGTs are abundant constituents of soils and peat bogs world wide and presumably of bacterial origin based on their stereo configuration. The distribution of individual branched GDGTs, varying in methyl branching and cyclopentanyl content, differs over the 150 soils analyzed. Principle component analysis showed a significant correlation between the degree of cyclisation of branched GDGTs (CBT) and soil pH. Another significant correlation was evident between the degree of methylation (MBT) and both soil pH and annual mean air temperature. This is explained by the fact that microorganisms adjust the composition of their cell membrane as an adaptation to changing environmental conditions. A focused study on soil transects off hot springs confirmed the temperature and pH dependence of the lipid distribution. Upon soil erosion and fluvial transport, branched GDGTs are deposited in near shore marine sediments. Being part of the marine sedimentary archive, branched GDGTs offer the opportunity to reconstruct long term river basin integrated temperature signals for the adjacent continent. A study of branched GDGT distributions in the Congo deep sea fan revealed a gradual temperature rise of 4°C over the last deglaciation in central Africa. Direct comparison with sea surface temperature estimates from the same core pointed to a dual influence of marine and terrestrial temperature development on the central African hydrological cycle. The presence of branched GDGTs in Palaeocene-Eocene sediments from the Arctic Ocean and in a German lignite of Early Cretaceous age, shows the potential of this new proxy on longer time scales.
DE: 0432 Contaminant and organic biogeochemistry (0792)
DE: 0473 Paleoclimatology and paleoceanography (3344, 4900)
DE: 0486 Soils/pedology (1865)
DE: 1055 Organic and biogenic geochemistry
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting