Salinity variation and hydrographic dynamics in the early Cambrian Nanhua Basin(South China)  

作　　者：Meng CHENG Zihu ZHANG Chengsheng JIN Wei WEI Haiyang WANG Thomas J.ALGEO Chao LI 

机构地区：[1]State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation&Institute of Sedimentary Geology,Chengdu University of Technology,Chengdu 610059,China [2]State Key Laboratory of Biogeology and Environmental Geology,China University of Geosciences,Wuhan 430074,China [3]International Center for Sedimentary Geochemistry and Biogeochemistry Research,Chengdu University of Technology,Chengdu 610059,China [4]College of Resource Environment and Tourism,Hubei University of Arts and Science,Xiangyang 441053,China [5]School of Earth Science,China University of Geosciences,Wuhan 430074,China [6]School of Earth Sciences and Engineering,Nanjing University,Nanjing 210023,China [7]State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences,Wuhan 430074,China [8]Department of Geology,University of Cincinnati,Cincinnati 45221-0013,USA

出　　处：《Science China Earth Sciences》2023年第6期1268-1278,共11页中国科学（地球科学英文版）

基　　金：supported by the Key R&D Project of Ministry of Science and Technology(Grant No.2022YFF0800100);the National Natural Science Foundation of China(Grant Nos.42072335,42002027,41825019,41821001,42130208);the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB26000000).

摘　　要：Despite intensive study of the early Cambrian Nanhua Basin(ECNB)in South China,its degree of connectedness to the open ocean remains uncertain,impeding analysis of contemporaneous oceanic redox evolution and its role in the Cambrian Explosion.We analyzed bulk-shale B/Ga,a newly proposed proxy for watermass salinity in ancient depositional systems,for three sections(Daotuo,Yuanjia,and Zhalagou)representing a range of water depths in the ECNB and spanning early Cambrian Stages 2 and 3.The B/Ga proxy records a salinity gradient in the basin,with increasing salinity from shallow-to deep-water areas,particularly during the deposition of black shales of the lower Jiumenchong/Niutitang/Zhalagou Formation.The gradient was probably due to the mixing of freshwater from adjacent landmasses with marine waters within a moderately restricted basin.All three study sections exhibit a monotonic rise in salinity over the~9-Myr study interval,reflecting increased watermass exchange with the open ocean due to regional tectonic and/or global sea-level changes.The improved watermass exchange may have weakened water-column stratification and reduced deep-water anoxia in the ECNB,contributing the enhanced oceanic oxygenation along with global environmental controls and further modulating the expression of the Cambrian Explosion recorded in Lower Cambrian sections of South China.Our study thus highlights the need for comprehensive analyses of hydrographic dynamics in marginal-marine settings that are used to explore co-evolutionary relationships between early animals and environmental oxygen levels.

关 键 词：B/Ga Boron GALLIUM Watermass restriction Cambrian Explosion CO-EVOLUTION 

分 类 号：P534.41[天文地球—古生物学与地层学] P333[天文地球—地质学]