Salinity-redox covariation in Mississippian Bowland Shale (Craven Basin, UK) controlled by eustasy and climate

Jiao, Yu; Emmings, Joseph F.; Zhou, Lian; Algeo, Thomas J.; Feng, Lanping; He, Tao; Liu, Jinhua; Zhang, Daqian; Wang, Jianping. 2025 Salinity-redox covariation in Mississippian Bowland Shale (Craven Basin, UK) controlled by eustasy and climate. Chemical Geology, 674, 122572. 10.1016/j.chemgeo.2024.122572

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Official URL: https://doi.org/10.1016/j.chemgeo.2024.122572

Abstract/Summary

Changes in watermass properties can be monitored in real time in modern depositional systems, but reconstruction in deep-time systems is difficult. Here, we analyze long-term changes in salinity (B/Ga, Sr/Ba, and S/TOC) and redox conditions (FeHR/FeT, Fepy/FeHR, and Corg/P) in the upper unit of the Mississippian Bowland Shale Formation, Craven Basin, UK. Variations in paleosalinity and redox in the Upper Bowland Shale were tightly coupled to fourth-order glacio-eustatic cyclicity. At basinal sites (borehole MHD and outcrop HC), transgressive to highstand packages (‘marine bands’) were associated with weakly hypersaline to normal marine, euxinic bottom-water conditions. In contrast, falling-stage and lowstand packages were deposited under normal-marine salinity and fluctuating euxinic to ferruginous anoxic conditions punctuated by (sub)oxic events. HC, located within a bathymetric low, exhibits significantly higher Corg/P (∼100) than MHD (<50), located on an intrabasinal high, due to the more limited influence of oxygen-bearing hyperpycnal flows in the deep basin. A sharp shift to brackish conditions near the top of the HC section reflects the basinward progradation of the Pendle Paleodelta in response to long-term eustatic fall. In the relatively more proximal (landward) and stratigraphically younger COM borehole, the pattern of salinity-redox covariation in response to sea-level cyclicity is different: highstands were associated with normal-marine salinity and euxinic conditions, whereas lowstands exhibit shifts toward brackish, oxic bottom-water conditions, reflecting shoaling of this site into the ocean-surface layer and influence from the nearby Pendle deltaic system. The ultimate driver of late Mississippian sea-level fluctuations was growth and decay of Gondwanan icesheets during an early phase of the Late Paleozoic Ice Age, with interglacial stages potentially being marked by a shift toward stronger evaporation within the climatically sensitive zone occupied by the Craven Basin (∼10–15°S paleolatitude). Our findings provide new insights into the sea-level-redox-salinity dynamics of marginal-marine basins during a major ice age.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1016/j.chemgeo.2024.122572
ISSN:	00092541
Date made live:	27 Feb 2025 16:31 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/538981

Item Type:

Publication - Article

Digital Object Identifier (DOI):

10.1016/j.chemgeo.2024.122572

ISSN:

00092541

Date made live:

27 Feb 2025 16:31 +0 (UTC)

URI:

https://nora.nerc.ac.uk/id/eprint/538981