Paleo-sedimentary environmental restoration and its significance of Chang 7 Member of Triassic Yanchang Formation in Ordos Basin,NW China

• 作者: FU Jinhua LI Shixiang NIU Xiaobing XU Liming
• 来源期刊: 石油勘探与开发:英文版
• 学科: 地球科学
• 关键词: paleo-climate paleo-salinity paleo-redox conditions element geochemistry paleo-sedimentary environment CHANG 7 MEMBER Upper TRIASSIC ORDOS Basin
• 年，卷（期）: 2018,（6）
• 页码范围: 998-1008
• 页数: 11页
• 分类号: P618.13

摘要

Paleo-sedimentary environment of Chang 7 Member of Upper Triassic Yanchang Formation in Ordos Basin, including the paleoclimate, paleo-salinity and paleo-redox conditions were restored through geochemical elements analysis of 289 samples collected from the outcrop sections around and wells drilled in the basin and using a series of identification indexes of paleo-climate, paleo-salinity and paleo-redox conditions, such as CaO/MgO?Al2 O3, Sr/Cu, Rb/Sr, Rb/K2 O, Th/U, V/(V+Ni), the content of element B tested from the mudstone. Comprehensive analysis shows that in sedimentary period of the Chang 7, the paleo-climate was warm temperate to subtropical climate with temperature higher than 15 ?C, the water body was continental brackish water to freshwater, and the sediments were deposited under strong reduction conditions. Suitable temperature, extensively deep lake basin and strongly reductive paleo-sedimentary environment led to the blooming, enrichment and preservation of organic matter in the submember Chang 73. As a result, a set of high-quality source rock was formed, laying material foundation for large-scale accumulation of shale oil.