Paleosalinity and Its Association with Organic Matter: A Case Study from the Eocene Shahejie Formation, Laizhou Bay Sag, Bohai Bay Basin (China)  

作　　者：LIANG Haoran XU Guosheng YU Qing XU Fanghao WANG Deying CHEN Zhiyuan 

机构地区：[1]State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Chengdu University of Technology,Chengdu 610059,China [2]Bohai Oilfield Research Institute,Tianjin Branch,CNOOC Ltd.,Tianjin 300459,China [3]Shanghai Branch,CNOOC Ltd.,Shanghai 200335,China [4]Research Institute of Petroleum Exploration and Production,Southwest Petroleum Branch,SINOPEC,Chengdu 610041,China

出　　处：《Journal of Ocean University of China》2021年第4期741-754,共14页中国海洋大学学报（英文版）

基　　金：This study was supported by grants from the National Science and Technology Major Projects(No.2016ZX05024-002-007);the CNOOC Project(No.CCL2020TJ X0NST1271).

摘　　要：Paleosalinity is vital for the paleoenvironmental reconstruction and affects the formation of source rock.The lower-middle sections of the third member of Eocene Shahejie formation(Es3M-L)constitute the most important source rock layer in Laizhou Bay Sag.However,the paleosalinity of the depositional water in which Es3M-L submembers are deposited remains unclear.A series of integrated experiments,including major and trace elements,X-ray diffraction,total organic carbon,and Rock-Eval,was performed to reveal the paleosalinity and its relationship with organic matter(OM).Various inorganic proxies(Sr/Ba,Rb/K,B/Ga,Walker’s paleosalimeter,Adam’s paleosalimeter,and Couch’s paleosalimeter)were employed to determine the paleosalinity of samples.Prominent differences existed in the proxies.Couch’s paleosalimeter is the most reliable and qualitative approach for Laizhou Bay Sag.Samples from the lake center(depocenter)and margin showed paleosalinities from 4.92 wt‰to 9.73 wt‰,suggesting a ubiquitous brackish(oligohaline-mesohaline)water body in the paleolake.Molybdenum enrichment in samples indicates an oxygen-depleted(suboxic or anoxic)condition.The increase in salinity has a certain but non-significant positive correlation with oxygen reduction.This condition may be attributed to the weak stratification of the water column in brackish water bodies.Moreover,paleosalinity has a weak and indirect relationship with OM accumulation during the deposition of Es3M-L submembers in Laizhou Bay Sag.

关 键 词：PALEOSALINITY Laizhou Bay Sag Shahejie formation brackish lake major and trace elements 

分 类 号：P736.2[天文地球—海洋地质]