What besides redox conditions? Impact of sea-level fluctuations on redox-sensitive trace-element enrichment patterns in marine sediments  

作　　者：Junwen PENG 

机构地区：[1]Bureau of Economic Geology,Jackson School of Geosciences,The University of Texas at Austin,Austin,Texas 78713,USA

出　　处：《Science China Earth Sciences》2022年第10期1985-2004,共20页中国科学（地球科学英文版）

基　　金：supported by the State of Texas Advanced Resource Recovery (STARR) program at the Bureau of Economic Geology (BEG);minor financial support from the China Scholarship Council (Grant No. 201606440062);the Geological Society of America Graduate Student Research Grant (Grant No. 9244823)。

摘　　要：Concentrations of redox-sensitive trace-element(RSTE) in marine shales have long been interpreted simply as redox proxies. However, the impact of other non-redox factors(e.g., sea-level fluctuation and seawater chemistry) on the enrichment of RSTE, especially molybdenum(Mo) and uranium(U), in sediments has been rarely reported. This study presents newly obtained RSTE datasets from the Upper Pennsylvanian organic-rich Cline Shale in the silled Midland Basin, U.S., to illustrate the influence of sea-level fluctuation on the authigenic accumulation of RSTE in marine sediments. A previously established transgressive-regressive sequence of the Cline Shale, a well-constrained high-amplitude glacio-eustatic fluctuation curve, and an accompanying episodic resupply of aqueous RSTE from the Panthalassic Ocean provide an ideal stratigraphic framework for determining the spatial and temporal variations of sediment RSTE enrichment patterns that responded to the episodic variations of seawater chemistry in this marginal silled paleomarine basin. Results suggest that although slightly higher median RSTE concentrations were observed in sediments from more reducing environments, the overall variation ranges of RSTE concentrations largely overlap among sediments deposited from a wide redox spectrum(from oxic to euxinic conditions) or different sea-level statuses in the Cline Shale. In contrast to the sediment RSTE enrichment patterns, the variations of sediment Mo/TOC and U/TOC ratios are coupled with glacio-eustatic fluctuation. The highest Mo/TOC and U/TOC ratios are commonly observed in sediments deposited during the highest relative sea-level(RSTE resupply), whereas the lowest Mo/TOC and U/TOC ratios usually appear in sediments deposited during the lowest relative sea-level(RSTE depletion). Our findings suggest that the benthic redox conditions recorded in sediment Mo and U concentrations can be greatly obscured and weakened by depleted aqueous Mo and U concentrations in highly restricted basins. Thus, the use of sediment Mo a

关 键 词：Molybdenum Uranium Glacio-eustatic fluctuation PENNSYLVANIAN Cline Shale Midland Basin 

分 类 号：P736.41[天文地球—海洋地质]