The impact of anoxia on pelagic macrofauna during the Toarcian Oceanic Anoxic Event (Early Jurassic) |
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| Authors: | Bryony A Caswell Angela L Coe |
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| Institution: | 1. Department of Environment, Earth and Ecosystems, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK;2. School of Environmental Sciences, University of Liverpool, Nicholson Building, Brownlow Street, Liverpool L69 3GP, UK |
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| Abstract: | Extreme environmental change during the Toarcian Oceanic Anoxic Event had widespread impacts on marine biota. This study provides new evidence, from the Yorkshire coast sections, UK, that the event was associated with periods of elevated fish and ammonite mortality. Using a synthesis of pelagic macrofaunal changes, benthic macrofaunal data and geochemical proxies we show that there are stratigraphical correlations between: (1) pelagic macrofaunal ranges and abundance, (2) benthic macrofaunal abundance, and (3) geochemical proxies that indicate deoxygenation. We identify eight stratigraphical intervals of differing character. Results suggest two major phases of relatively persistent deoxygenation with photic zone euxinia. The cyclostratigraphic timescale indicates that each phase lasted at least tens of thousands of years. Belemnite migration during the event probably resulted from increased seawater temperatures and low food supply similar to that observed for many marine taxa, including squid, within the present-day oceans. |
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| Keywords: | Oceanic anoxic event Environmental change Belemnites Ammonites Biogeographic range shift Fish mortality |
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