Biomarker Records From Eocene Lacustrine Sequence in the Eastern Tibet Plateau and Its Implication for Organic Matter Sources

The Eocene is the initial stage of Cenozoic global cooling. Compared with abundant marine records, continental records are scarce. Throughout Eocene, a series continuous deposition gypsum and volcanic tuff-bearing red clastic sediments have developed in Nangqian Basin (NB). In this work, representative were collected from NB, lipid biomarkers compound-specific carbon isotopes n -alkanes analyzed. Based on robust paleomagnetic age–depth model, early to late isotopic compositions (δ 13 C 23 δ 25 ) increased sedimentary facies changed. At same time, relative proportion mid-chain length long-chain homologs (Paq) decreased, peak number (C max shifted 21 , 22 or 16 27 31 . We ascribed these variations climate drying water level turning high as indicated by lithology change fluvial lacustrine terrestrial inputs neighboring mountain belts middle–late Eocene. Moreover, we compared our -alkane results other TP sea benthic 18 O. found that nearly synchronous deformation eastern caused India–Asia collision was closely related arid conditions topographically changed northern TP. NB mainly controlled uplift affected Paratethys Sea long scale.