Taphonomic and diagenetic implications of reduction spot formation in Cretaceous red beds from the Jiaolai Basin, Eastern China
Fu W, Turner P, Clements T, Spencer AR, Yu J, Yang Y, Guo B, Ning Z, Zhuo X, Riley MS, Hilton J (2023)
Publication Type: Journal article
Publication year: 2023
Journal
Book Volume: 243
Article Number: 105533
DOI: 10.1016/j.jseaes.2022.105533
Abstract
Green-grey coloured reduction spots are common in continental red beds through geological history and occur in a range of different lithologies and depositional environments, but their timing and mode of formation remain controversial. We investigate the Late Cretaceous to earliest Paleogene Jiaozhou Formation using borehole data from the Jiaolai Basin in Shandong province of eastern China, and consider the distribution, morphology, and geochemistry of reduction spots in these continental red beds to evaluate how the reduction spots formed. Here, we report a novel application of three-dimensional X-ray Computed Tomography (XCT) to analyse reduction spot morphology, composition and density. Our data show that individual reduction spots are spheroidal, tubular or irregular shaped, and often contain small, grey, dark brown or black organic cores, referred to as loci. Typically, reduction spots have a similar chemical composition to the host red beds, but with elevated levels of vanadium (V), lower levels of iron (Fe), and lower density. Isolated, small refractory fossils (e.g., charcoal) in the sediment alongside reduction spots but not within them indicates that microbial decay of organic labile (reactive) tissues in early diagenesis is an important control in reduction spot formation. We propose a new taphonomic model of reduction spot formation: post burial, during the primary sedimentary cycle in the groundwater zone, vanadium is released by intrastratal oxidation of titanomagnetite. Decay of organic matter creates localised reducing conditions resulting in the reduction of Fe3+ and the eventual depletion or removal of the resulting Fe2+ (altering the colour of the reduction spot). Simultaneously, the reduction of V4+ and the consequent lowering of the concentration of V as V2+ minerals occur in the reduction spot, explaining their lower density than the host sediment.
Authors with CRIS profile
Involved external institutions
Liaoning Technical University (LNTU) / 辽宁工程技术大学
China (CN)
Imperial College London / The Imperial College of Science, Technology and Medicine
United Kingdom (GB)
Shandong University of Science and Technology (SDUST) / 山东科技大学
China (CN)
Beijing Research Institute of Uranium Geology (BRIUG) / 核工业北京地质研究院
China (CN)
University of Birmingham
United Kingdom (GB)
China (CN)
Imperial College London / The Imperial College of Science, Technology and Medicine
United Kingdom (GB)
Shandong University of Science and Technology (SDUST) / 山东科技大学
China (CN)
Beijing Research Institute of Uranium Geology (BRIUG) / 核工业北京地质研究院
China (CN)
University of Birmingham
United Kingdom (GB)
How to cite
APA:
Fu, W., Turner, P., Clements, T., Spencer, A.R., Yu, J., Yang, Y.,... Hilton, J. (2023). Taphonomic and diagenetic implications of reduction spot formation in Cretaceous red beds from the Jiaolai Basin, Eastern China. Journal of Asian Earth Sciences, 243. https://dx.doi.org/10.1016/j.jseaes.2022.105533
MLA:
Fu, Wenzhao, et al. "Taphonomic and diagenetic implications of reduction spot formation in Cretaceous red beds from the Jiaolai Basin, Eastern China." Journal of Asian Earth Sciences 243 (2023).
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