HR: 0800h
AN: PP31D-0653    [Abstracts]
TI: Coastal Lakes in South-Central Chile (38°S) – Archives of Holocene Climate and Fore-arc Tectonics
AU: * Blumberg, S
EM: sblumb@gfz-potsdam.de
AF: GFZ Potsdam, Telegrafenberg, Potsdam, 14473, Germany
AU: Arz, H W
EM: harz@gfz-potsdam.de
AF: GFZ Potsdam, Telegrafenberg, Potsdam, 14473, Germany
AU: Echtler, H P
EM: helle@gfz-potsdam.de
AF: GFZ Potsdam, Telegrafenberg, Potsdam, 14473, Germany
AU: Lamy, F
EM: flamy@awi-bremerhaven.de
AF: AWI Bremerhaven, Am Handelshafen 12, Bremerhaven, 27570, Germany
AU: Haug, G H
EM: gerald.haug@erdw.ethz.ch
AF: ETH Zuerich, Universitaetsstrasse 6, Zuerich, 8092, Switzerland
AU: Oncken, O
EM: oncken@gfz-potsdam.de
AF: GFZ Potsdam, Telegrafenberg, Potsdam, 14473, Germany
AB: The present study is based on sediment cores obtained from the two coastal lakes Lago Lanalhue and Lago Lleu Lleu, which are located on the western slopes of the Chilean Coastal Cordillera at approximately 38°S. Due to their near-shore location outside the influence of the Andean glaciation and volcanic activity, the lake sediments provide clear signals of continental rainfall changes that can be directly linked to offshore marine records. Both lakes are of tectonic origin and were cut off from the Pacific Ocean by raised marine terraces forming natural dams. For that reason their sediments do not only contain paleoclimatic information but also information about fore-arc tectonics and, in particular, about the regional uplift history. Sediment analyses so far include the lithological description, digital imaging, magnetic susceptibility measurements, X-ray fluorescence (partly high-resolution) scanning, carbon content detection and radiocarbon dating. Investigated piston cores of both lakes are extending back to the Late Pleistocene/Early Holocene and are showing mean sedimentation rates of 1.0 - 1.5 mm/a. First results of magnetic susceptibility measurements and XRF-scanning demonstrate a striking shift of the respective values at around 8000 yr BP in both lakes, which documents the transition from a marine to a lacustrine facies. Knowing the Holocene sea-level evolution and the present height of lake-levels we are able to calculate the mean regional uplift rate during the last 8000 yr (4.3 mm/yr). In the lacustrine part of the records we find higher terrigenous content during the Late Holocene (4300 to present) compared to the Middle Holocene (7600 – 4300 yr BP) consistent with generally more humid conditions in the late Holocene as known from other terrestrial and marine records in the region. On centennial time-scales a pronounced variability in elemental concentrations and magnetic suceptibility shows significant changes in the terrigenous sediment input to the lake, suggesting important hydrological fluctuations also on these time-scales.
DE: 1637 Regional climate change
DE: 3344 Paleoclimatology (0473, 4900)
DE: 4914 Continental climate records
DE: 4942 Limnology (0458, 1845, 4239)
DE: 9360 South America
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting