Abstract

Studying the lacustrine microbialites in the Western Qaidam Basin in the northeastern margin of the Qinghai–Tibetan Plateau may provide clues to the sedimentary record, the depositional model, and the hydrocarbon potential. Based on geological, geochemical, and seismic data, the sedimentary characteristics and hydrocarbon potential of Eocene lacustrine microbialites in Western Qaidam Basin are estimated. Three microbialites are identified In the Eocene lacustrine system of the Qaidam Basin, including the thick thrombolites in relatively high-energy near-shore settings, the small-scale stromatolites and thrombolites in extremely shallow water environment, and the laminates in relatively deep water of intrabasinal environments. Three sedimentary models have been established, including the marginal steep slope zone, the marginal gentle slope zone, and the intrabasinal deep-water zone, respectively. The framework pores, intergranular pores, dolomite intercrystalline pores, dissolved pores and interlayered fractures commonly composed the pore spaces of microbialites. The Fossil Group of Botryococcus (a lipid-rich algae) contributed the main source of hydrocarbons particularly in saline water in Western Qaidam Basin. The development of Eocene lacustrine microbialites on the northeastern Qinghai–Tibetan Plateau provides a new perspective to explore the complex mineralization processes and hydrocarbon potential of microbialites.