摘要
对巫溪地区田坝剖面五峰组—龙马溪组底部30件页岩样品开展了有机碳含量、微量元素地球化学等方面研究,分析了不同层段有机质富集特征及其控制因素,认为海平面升降控制着水体缺氧程度,从而影响该区有机质沉积富集程度.研究结果表明:1)五峰组—龙马溪组底部页岩中共识别出4个有机质沉积阶段,总有机碳(TOC)含量整体较高,TOC平均达到3.7%,但与古生产力(生源钡Babio含量)相关性不明显,指示着古生产力总体上不是该时期有机质沉积的主控因素;2)尽管不同有机质沉积阶段的水体氧化还原条件具有一定差异性,但与TOC变化总体上具有相关性,这表明这些时期有机质沉积主要受控于缺氧程度,其富集机理属于"保存模式";3)五峰组—龙马溪组早期有机质沉积模式为:海平面的升降控制着沉积水体的缺氧程度,海平面下降造成底水富氧,上升形成底水缺氧,从而控制着页岩中有机质富集程度.
30 samples of gas shale from the Wufeng formation to Lungmachi formation shale in Wuxi regions of Sichuan province were tested in terms of their organic carbon content （TOC）and trace element geochemistry.The characteristics of the organic matter enrichment and their controlling factors in different horizons were further analyzed.It is concluded that by controlling the hypoxia degree of sedimentary water,sea level changes affect the organic matter enrichment in shale.The results show that four different horizons of organic matter deposition are identified with high TOC of up to 3.7 % on average,but the correlation between TOC and palaeo-productivity （such as the content of Babio） is not obvious,implicating that the palaeoproductivity is not the major controlling factor.Although water redox condition varies in different sedimentary horizons,it has a good correlation with the TOC,indicating that the organic matter accumulation is mainly controlled by the degree of hypoxia,and the enrichment mechanism belongs to ＆quot;preservation mode＆quot;.In summary,the depositional model of organic matter in Wufeng-Lungmachi shale is that sea level changes control the hypoxia degree of sedimentary water.The sea level drop will lead to oxygen enrichment in the bottom water,while the sea level rise will cause hypoxia,thus affecting the organic matter enrichment in shale.
出处
《中国矿业大学学报》
EI
CAS
CSCD
北大核心
2017年第5期1134-1143,共10页
Journal of China University of Mining & Technology
基金
国家自然基金项目(41602119)
中国石油科学研究与技术开发项目(2016B-0302-01)
中石油勘探开发研究院项目(XN41601,XN41603)
