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The impact of anoxia on pelagic macrofauna during the Toarcian Oceanic Anoxic Event (Early Jurassic)

Caswell, Bryony A.; Coe, Angela L.


Angela L. Coe


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.

Journal Article Type Article
Publication Date 2014-09
Journal Proceedings of the Geologists' Association
Print ISSN 0016-7878
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 125
Issue 4
Pages 383-391
Keywords Oceanic anoxic event; Environmental change; Belemnites; Ammonites; Biogeographic range shift; Fish mortality
Publisher URL
Additional Information This article is maintained by: Elsevier; Article Title: The impact of anoxia on pelagic macrofauna during the Toarcian Oceanic Anoxic Event (Early Jurassic); Journal Title: Proceedings of the Geologists' Association; CrossRef DOI link to publisher maintained version:; Content Type: article; Copyright: Copyright © 2014 The Geologists’ Association. Published by Elsevier Ltd. All rights reserved.