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Durham University

Department of Earth Sciences


Publication details for Professor David Harper

Armstrong, H.A. & Harper, D.A.T. (2014). An earth system approach to understanding the end-Ordovician (Hirnantian) mass extinction. In Volcanism, Impacts, and Mass Extinctions: Causes and Effects. Keller, G. & Kerr, A. The Geological Society of America. 287-300.

Author(s) from Durham


The Hirnantian mass extinction (HME) is recognized as the first of the “Big Three,” and along with the end- Permian and end- Cretaceous events results from an acceleration in biotic extinctions concomitant with a rise in originations. The HME is characterized by high taxonomic impact and within community extinctions. The HME is also unusual in that, a) it is associated with glaciation, but there is little evidence elsewhere in the younger Phanerozoic that glaciations have been a cause of mass extinction and, b) there is limited understanding of how glaciation directly causes mass extinction, particularly in the marine realm. In this review we argue coordinated extinctions occurred at the onset and termination of glaciation and, were due to climatically-induced changes in relative sea level, ocean redox stratification and sea surface temperature (SST) gradients. These earth system changes resulted in a reduction in prospective niche space both in the water column and on the seafloor, which in turn leadto increased competition and selection pressures leading to extinctions where the carrying capacities of particular ecological niches were exceeded. The long-term ventilation of the oceans broke the link between glaciation and mass extinction.


GSA Special Paper 505