HR: 09:15h
AN: PP51D-06    [Abstracts]
TI: Reconstructing paleoaltimetry with D/H isotopic measurements on lipid biomarker
AU: * Polissar, P J
EM: ppolissa@geosc.psu.edu
AF: The Pennsylvania State University, Department of Geosciences, University Park, PA 16802, United States
AU: Freeman, K H
EM: kate@essc.psu.edu
AF: The Pennsylvania State University, Department of Geosciences, University Park, PA 16802, United States
AU: Rowley, D B
EM: rowley@geosci.uchicago.edu
AF: The University of Chicago, Department of the Geophysical Sciences, Chicago, IL 60637, United States
AU: Currie, B S
EM: curriebs@muohio.edu
AF: Miami University, Department of Geology, Oxford, OH 45056, United States
AB: Estimates of the paleoelevation in mountain regions is an important variable in tectonics and climate research. These estimates provide a benchmark to compare with models of mountain formation and records of uplift, erosion and climate. However, past elevation is a difficult variable to quantify. During orographic uplift of an airmass, isotopic distillation of the water vapor results in a predictable isotopic gradient with altitude. Using this gradient, paleoelevations can be calculated from reconstructions of the isotopic composition of precipitation at low- and high-elevations sites. Measurement of the deuterium/hydrogen isotopic ratio (δD) of lipid biomarkers preserved in mountain regions provides a method to reconstruct precipitation δD composition and elevation through time. Isotopic results indicate that the δD of plant leaf-wax n-alkanes preserved in both modern and ancient lake sediments can be used to reconstruct elevation. Lipid δD-based elevation estimates from the sediments of modern alpine lakes successfully predict the actual lake elevation. Elevations inferred from lipid δD analyses of lake basin sediments deposited on the Tibetan plateau over the past 40 million years are in close agreement with carbonate δ¹⁸O- and paleoflora-based estimates for the same sediments. Important variables to consider when interpreting n-alkane δD measurements for paleoaltimetry are the type of plants contributing leaf-wax compounds to the sediment, the aridity of the study site relative to the calibration sites for the lipid-water fractionation factor, and the thermal maturity of the organic matter.
DE: 0454 Isotopic composition and chemistry (1041, 4870)
DE: 0473 Paleoclimatology and paleoceanography (3344, 4900)
DE: 4914 Continental climate records
DE: 8177 Tectonics and climatic interactions
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting