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The latest Ordovician Hirnantian brachiopod faunas : new global insights.

Jiayu, Rong and Harper, D.A.T. and Bing, Huang and Rongyu, Li and Xiaole, Zhang and Di, Chen (2020) 'The latest Ordovician Hirnantian brachiopod faunas : new global insights.', Earth-science reviews., 208 . p. 103280.


The temporal and spatial distribution of Hirnantian brachiopod faunas are reviewed based on a new, comprehensive dataset from over 20 palaeoplates and terranes, a revised correlation scheme for Hirnantian strata and numerical methods including network analysis. There were two successive evolutionary faunas: 1. the widespread and diachronous Hirnantia Fauna related to the glacial acme in the early−mid Hirnantian, including shallow, deeper and deep-water communities that diversified in much more complicated environmental conditions than hitherto envisaged; and 2. the Edgewood-Cathay Fauna (new term) thrived during post-glacial, warmer, shallow-water regimes with both carbonate and siliciclastic facies from low latitudes in the late Hirnantian−early Rhuddanian. The two survival faunas can occur in the same order in different regions, immediately following the first and second phases of the Hirnantian crisis, respectively. This faunal succession records two climatic perturbations, one with a glaciation, associated with climatic cooling and a global low-stand, during which the Hirnantia Fauna flourished, and a second characterized by melting ice, global warming, and sea-level rise (with global anoxia), aligned to the development of the Edgewood-Cathay Fauna and the repopulation of the seas by many animals adapted to warmer water, e.g., metazoan reefs, massive tabulates, and sponges. Changes in many properties of the Hirnantia Fauna may have resulted from the heterogeneity of global climate change in time and space; contrasts in the Edgewood-Cathay faunas record differences between carbonate and siliciclastic deposition, respectively, at low latitudes. Intense climate changes, sea-level fluctuations, and oceanographic ventilation and anoxia, had important roles in brachiopod evolution through the Hirnantian extinctions as first taxa confined to warm-water and then cool-water conditions were the main victims. During the Hirnantian, higher originations of new taxa may have been a response to crises, which increased the rate of phyletic evolution due to extreme climatic conditions.

Item Type:Article
Full text:(AM) Accepted Manuscript
Available under License - Creative Commons Attribution Non-commercial No Derivatives.
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Publisher statement:© 2020 This manuscript version is made available under the CC-BY-NC-ND 4.0 license
Date accepted:06 July 2020
Date deposited:14 July 2020
Date of first online publication:11 July 2020
Date first made open access:11 July 2021

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