The Biomarker Characteristics and Sedimentary Environment of Lower Cambrian Niutitang Formation Source Rock in Northern Guizhou Province

详细信息   

• 责任者：Yang Ping (Chengdu Center ; China Geological Survey ; Chengdu 610081 ; Sichuan ; China) ; Wang Zhengjiang
• 刊名：Geological Bulletin of China
• 出版年：2012
• 卷期：31(11)
• 关键词：烃源岩 ; source rocks ; 贵州 ; Guizhou Province
• 页码：p.1910-1921
• 图表：5 illus., 4 tables, 47 refs.
• 分类号：1003
• issnNo：ISSN1671-2552
• isbnNo：CN11-4648/P

摘要

In order to investigate source material and sedimentary environment of Lower Cambrian Niutitang Formation source rock in northern Guizhou, the authors studied the biomarkers. The results show that they have the following characteristics： （1） OEP values of the n-alkanes are close to 1.0, showing no odd-even carbon dominance; N-alkanes mostly have bimodal performance（C18/C22）, and the ratios of （nC21＋nC22/（nC28＋nC29）are 0.54-1.01, indicating a dominant role of heavy hydrocarbon components; the average ratios of Pr/Ph vary from 0.51 to 0.82, showing phytane dominance.（2） According to the relative abundance, tricycfic terpane〉pentacyclic triterpane〉quart- cyclic terpane. The tricyclic terpane contents ofC21, C23 and C24 show inverted V-shaped distribution, and the ratios of Ts/ （Tm＋Ts） are between 0.45 and 0.50. （3） The average ratio of C27 and C29 of the sterane is slightly smaller than or close to 1. Aromatic compounds DBT/P are between 0.05 and 0.09. Based on these features combined with the isotope of kerogen and the isotope of the monomer hydrocar- bon composition and variation, the authors believe that the black rock of Niutitang Formation was formed in a reduction environment in shallow water in the Early Cambrian, with high degree of thermal evolution of organic matter, and the main sources were the bacte- ria, algae and other aquatic organisms. The constant index of MnO/TiO2, the trace indicators ofBa, Sr/Ba, U/Th, V/（V＋Ni）, and the combination oforgailic geochemical indicators depict the aquatic environment from Upper Sinian Dengying Formation to Lower Cam- brian Niutitang Formation and Mingxinsi Formation, and the source rocks of Niutitang Formation hydrocarbon are divided into three stages, the first stage being the initial rapid transgression stage in Early Cambrian, the second stage being a stage of deep-water reducing environment with high organic matter productivity, and the third stage being a stage of shallow waters with high organic matter productivity. The deposition period of Mingxinsi Formation nonhydrocarbon source rocks was a shallow water oxidation stage.