1. Evidence for transport mechanisms of soil derived branched GDGTs Hendrik Grotheer 1, Sabine Kasten², Gesine Mollenhauer 1,2 1 University of Bremen, FB5, Bremen Germany; 2 Alfred-Wegner-Institute for Marine and Polar Research, Bremerhaven Germany Marine Geochemistry Conclusion Southward shift of ITCZ during H1 led to increased precipitation and, therefore, enhanced erosion in the hinterland and terrestrial organic matter discharge into the ocean Correlation between GDGT concentration and precipitation, as well as terrestrial element content, propose two major transport pathways for soil GDGTs A) Precipitation triggered runoff erosion from anaerobic litter layer B) Leaching out in form of organo-metal complexes from podsol horizons Climate reconstruction Ti/Ca and BIT-value suggest increased discharge and, by inference, precipitation during H1 [3] Evolution of pH-values during H1 is in agreement with two-step vegetation change [4] in response to increased precipitation as suggested by previous studies I) Pollen data indicate a change from semi-arid to humid vegetation during phase 1 [4] II) Emergence of tropical rainforests during phase 2, causing a drop in soil-pH Co-evolution of SST [3] and MAT in NE Brazil, affected either by warming of Antarctica [5,6], or increase of pCO 2 [7] since H1 References 1. Hopmans, E.C., et al., Earth and Planetary Science Letters, 2004 2. Weijers, J.W.H., et al., Geochimica et Cosmochimica Acta, 2007 3. Jaeschke, A., et al., Paleoceanography, 2007 4. Dupont, L.M., et al., Global Change Biology, 2009 5. Anderson, K.K. et al., Nature, 2004 6. Meyer, H. et al., Nature, 2006 7. Monnin, E, et al., Earth and Planetary Science Letters, 2004 8. Bardy, M., et al., Geochimica et Cosmochimica Acta, 2007. 71(13) Transport of soil-derived GDGTs - Highest concentrations of soil-derived GDGTs during H1 (diamonds), enhanced concentrations during YD (squares)  Transport of soil GDGTs is directly linked to precipitation - Al, Fe and Ti concentrations showing clear correlation with amount of deposited GDGTs  Suggests formation of insoluble organo-metal complexes [8]  Increased soil acidification, due to rain forest growth, led to enhanced podsolisation  Anoxic and acidic conditions in podsols stimulate organo-metal complex formation Introduction Input of terrigenous material to the oceans is an important process in global element cycles. Therefore, many studies in the past have used either organic or inorganic proxies to quantify the terrigenous contribution. Among the more recently introduced proxies for export of soil-derived organic matter and the reconstruction of environmental conditions on land like mean air temperature (MAT) and soil pH, respectively, are the so-called BIT, MBT and CBT indices [1, 2], using abundance ratios of branched tetraether lipids (GDGTs) believed to derive from unknown soil-dwelling anaerobic bacteria. The habitat of these soil organisms, however, is not well constrained, nor is the association of these lipids with mineral grains exported to the ocean. We applied these proxies to sediment core GeoB3910-2 and compared them with solid phase element composition for the time interval between 20 and 10 ka BP, containing the Heinrich Event 1 (H1) and the Younger Dryas (YD). We investigated the effect of short term climate variability on the Brazilian hinterland and the associated discharge of organic matter to the ocean. GeoB3910-2: 4°14.7‘S/ 36°20.7‘W, 2362m water depth, 100km NE of Brazilian coast, deposition center of the Piranha River