The Sedimentary Geochemical Characteristics and Geological Significance of the Wufeng-Longmaxi Formation Accumulation of Organic Matter Black Shale on the Southeastern Sichuan Basin, China

At present, the understanding of sedimentary paleoenvironment and organic matter enrichment law black shale in Wufeng-Longmaxi Formation is still insufficient. This time, we investigated total carbon (TOC) content, X-ray diffraction mineralogical composition, major trace element abundances newly recovered cores three gas exploration wells Changning, Qianjiang, Xiushan areas which were, respectively, selected to discuss compare varying paleoenvironmental conditions factors that control accumulation, such as terrigenous input, redox conditions, primary productivity, degree water retention basin. The results show siliceous lithofacies, gray-black silty gray argillaceous siltstone shell marl lithofacies are mainly deposited southeastern Sichuan Basin. Organic-rich concentrated lower part Wufeng Longmaxi Formation. continuous thickness content greater than 2% Changning area 32 m, Qianjiang 22 11 m. hydrocarbon generation potential gradually weakens from west east. identification geochemical behavior characteristics elements shows section Changning-Qianjiang-Xiushan formation anoxic-moderate mass restriction environment with high productivity less detritus input under low hydrodynamic conditions. However, correlations detrital proxies Ti/Al, V/Cr, Ni/Co, paleoproductivity Babio TOC contents a favorable for organic-rich affected by Wuling underwater uplift; deposits becomes thinner; adjacent Xuefeng uplift, deposition accumulation deteriorate, unfavorable exploration.