Evolution of the Toarcian (Early Jurassic) carbon-cycle and global climatic controls on local sedimentary processes (Cardigan Bay Basin, UK)

Weimu Xu, Micha Ruhl, Hugh C. Jenkyns, Melanie J. Leng, Jennifer M. Huggett, Daniel Minisini, Clemens V. Ullmann, James B. Riding, Johan W.H. Weijers, Marisa S. Storm, Lawrence M.E. Percival, Nicholas J. Tosca, Erdem F. Idiz, Erik W. Tegelaar, Stephen P. Hesselbo

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

The late Early Jurassic Toarcian Stage represents the warmest interval of the Jurassic Period, with an abrupt rise in global temperatures of up to ∼7 °C in mid-latitudes at the onset of the early Toarcian Oceanic Anoxic Event (T-OAE; ∼183 Ma). The T-OAE, which has been extensively studied in marine and continental successions from both hemispheres, was marked by the widespread expansion of anoxic and euxinic waters, geographically extensive deposition of organic-rich black shales, and climatic and environmental perturbations. Climatic and environmental processes following the T-OAE are, however, poorly known, largely due to a lack of study of stratigraphically well-constrained and complete sedimentary archives. Here, we present integrated geochemical and physical proxy data (high-resolution carbon-isotope data (δ13C), bulk and molecular organic geochemistry, inorganic petrology, mineral characterisation, and major- and trace-element concentrations) from the biostratigraphically complete and expanded entire Toarcian succession in the Llanbedr (Mochras Farm) Borehole, Cardigan Bay Basin, Wales, UK. With these data, we (1) construct the first high-resolution biostratigraphically calibrated chemostratigraphic reference record for nearly the complete Toarcian Stage, (2) establish palaeoceanographic and depositional conditions in the Cardigan Bay Basin, (3) show that the T-OAE in the hemipelagic Cardigan Bay Basin was marked by the occurrence of gravity-flow deposits that were likely linked to globally enhanced sediment fluxes to continental margins and deeper marine (shelf) basins, and (4) explore how early Toarcian (tenuicostatum and serpentinum zones) siderite formation in the Cardigan Bay Basin may have been linked to low global oceanic sulphate concentrations and elevated supply of iron (Fe) from the hinterland, in response to climatically induced changes in hydrological cycling, global weathering rates and large-scale sulphide and evaporite deposition.
Original languageEnglish
Pages (from-to)396-411
JournalEarth and Planetary Science Letters
Volume484
DOIs
Publication statusPublished - 15 Feb 2018
Externally publishedYes

Funding

We acknowledge funding from Shell International Exploration & Production B.V. , the International Continental Scientific Drilling Program (ICDP), the Natural Environment Research Council (NERC) (grant number NE/N018508/1 ), and the British Geological Survey . Clemens V. Ullmann acknowledges funding from Leopoldina, Germany National Academy of Sciences (grant number LPDS 2014-08 ). All authors thank the British Geological Survey (BGS), especially Scott Renshaw and Tracey Gallagher for enabling access to the Mochras core, and Steve Wyatt, Alice Barroll, Jonathan Wells and Phil Holdship (Oxford University) and Chris Kendrick (BGS) for laboratory assistance. Daniel Minisini thanks G. Gil for broadening the horizons. James B. Riding and Melanie J. Leng publish with the approval of the Executive Director of the British Geological Survey (NERC). This manuscript is a contribution to IGCP 655 (IUGS-UNESCO): Toarcian Oceanic Anoxic Event: Impact on marine carbon cycle and ecosystems , and IGCP 632 (IUGS-UNESCO): Continental Crises of the Jurassic: Major Extinction events and Environmental Changes within Lacustrine Ecosystems . Appendix A

FundersFunder number
Shell International Exploration & Production B.V.
National Academy of SciencesLPDS 2014-08
Natural Environment Research CouncilNE/N018508/1
British Geological Survey

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