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Molybdenum isotope evidence for global ocean anoxia coupled with perturbations to the carbon cycle during the Early Jurassic

Pearce, Christopher R.; Cohen, Anthony S.; Coe, Angela L. and Burton, Kevin W. (2008). Molybdenum isotope evidence for global ocean anoxia coupled with perturbations to the carbon cycle during the Early Jurassic. Geology, 36(3) pp. 231–234.

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Relatively brief periods of severe paleoenvironmental change during the Jurassic and Cretaceous were associated with the widespread accumulation of organic-rich marine deposits, termed oceanic anoxic events (OAEs). These intervals involved abrupt global warming of 5–10 °C, higher rates of continental weathering, elevated extinction rates, and large-scale perturbations to the global carbon cycle. The major OAEs also overlapped temporally the emplacement of large igneous provinces. However, despite being known as OAEs, the extent of seawater anoxia at those times is undefined and the causative processes remain unclear. Here we show how changes in seawater molybdenum isotope ratios (a proxy for seawater anoxia) during the Toarcian (Early Jurassic) OAE define the onset and expansion of oxygen deficient conditions. Our data also place constraints on the areal extent of marine anoxia during the event and demonstrate that anoxia expanded and contracted periodically, broadly in line with precession-driven changes in 13 Corg. Despite their intermittent occurrence over geological history, OAEs have an important contemporary relevance because the magnitude and high rates of environmental change then were broadly similar to those occurring at the present day.

Item Type: Journal Article
ISSN: 0091-7613
Keywords: Toarcian; Jurassic; molybdenum; oceanic anoxic event; carbon cycle
Academic Unit/Department: Science > Environment, Earth and Ecosystems
Interdisciplinary Research Centre: Centre for Earth, Planetary, Space and Astronomical Research (CEPSAR)
Item ID: 10605
Depositing User: Users 2315 not found.
Date Deposited: 16 Apr 2008
Last Modified: 14 Jan 2016 16:55
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