Geochemical characteristjcs of anoxic event bed in Qingshankou Formation from the Well Chao 73-87 of Songliao Basin
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摘要: 松辽盆地白垩纪青山口组下部广泛分布一套富含有机碳的黑色泥岩、页岩和油页岩沉积，是全盆地划分泉头组与青山口组的一级标志.朝73-87井青山口组黑色页岩、油页岩的地球化学特征研究表明：它具有干酪根碳同位素正偏和重排甾烷含量低，存在28，30一双降藿烷、伽马蜡烷生物标志化合物等有机地球化学特征，表征为白垩纪温室效应时间窗内古湖泊缺氧事件的产物.结合生物地层研究成果，认为青山口期缺氧事件层大体可与白垩纪古海洋Cenomanian-Turonian界线事件层进行对比，进而提出松辽盆地青山口组的时代归属晚白垩世晚cenomanian-Turonian期的新观点.Abstract: The Songliao Basin was a large lacustrine one during Late Cretaceous, where the dark mudstones, shales and oil-shales of Qingshankou Formation were distributed widely and oil-shales were considered as the primary marker beds of division and correlation in the basin.The dark mudstones and shales in Member 1, Qingshankou Formation from the Well Chao 73-87 were of high organic carbon and low diasteranes contents.Organic geochemical characters were illustrated by biomarkers of 28, 30-bisnorhopane and gammacerane, and positive excursion of kerogen isotopes.It was suggested that the dark mudstones and shales in Member 1, Qings-hankou Formation were products of lacustrine anoxic records in the extreme greenhouse climate period.Based on the study of biostratigraphy and anoxic event stratigraphy, it was proposed that the anoxic event might be corresponding to the oceanic anoxic event at Cenomanian-Turonian boundary in Cretaceous,and the age of Qingshankou Formation in the Songliao Basin should be Late Cenomanian to Turonian.
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Key words:
- Anoxic events /
- Dark shales /
- Carbon isotope /
- Biomarkers /
- Qingshankou Formation /
- The Songliao Basin
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