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Abstract

Hydrogen isotope ratios were measured on terrigenous alkanes (n-C-25 to n-C-31) extracted from recent lake surface sediments from the climatically and environmentally distinct basins Qiangyong Glacier Lake, Yamzho Lake, Nam Co Lake, Keluke Lake and Xiao Qaidam Lake along a S-N transect in the Tibetan Plateau to explore the climatic implication of these biomarkers. delta D values of these n-alkanes are compared to that of precipitation spanning a wide range from -167 parts per thousand to -51 parts per thousand and clearly correlate with delta D values of meteoric water, indicating that terrigenous alkanes record the precipitation signal. The fractionation between precipitation and n-C-25, n-C-27 alkanes cover a range from -45 parts per thousand to -70 parts per thousand whilst that between precipitation and n-C-29, n-C-31, alkanes varies from -70 parts per thousand to -95 parts per thousand, both being fairly constant along the S-N Tibetan transect with the mean at -57 parts per thousand and -82 parts per thousand respectively. By comparison with the fractionation of -130 parts per thousand along the S-N European transect, it implies that the hydrogen isotopic fractionation between meteoric water and terrestrial n-alkanes along the Tibetan transect represent distinct character. [References: 45]