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Earliest Silurian faunal survival and recovery after the end Ordovician glaciation: evidence from the brachiopods

Published online by Cambridge University Press:  01 September 2007

L. Robin M. Cocks
Affiliation:
Department of Palaeontology, The Natural History Museum, London SW7 5BD, UK
Rong Jia-yu
Affiliation:
Institute of Geology and Palaeontology, Academia Sinica, 39 East Beijing Road, Nanjing, 210008 China

Abstract

Earliest Silurian (basal Llandovery) brachiopod faunas are surveyed and listed from around the globe, and divided between Lower Rhuddanian and Upper Rhuddanian occurrences. 60 genera are known from the Lower Rhuddanian within 20 superfamilies and there are 87 genera in 25 superfamilies in the Upper Rhuddanian. The 29 areas surveyed span the globe, both latitudinally and longitudinally. Only six superfamilies are Lazarus taxa which are known both from the Ordovician and Middle Llandovery (Aeronian) and later rocks but have not been recorded from the Rhuddanian. These are surprising results, since many previous studies have inferred that the Rhuddanian was a time of very sparse faunas. The global warming that followed the latest Ordovician (Hirnantian) ice age did not proceed quickly, with an ice-cap probably present through at least the Llandovery. There is a marked absence of Lower Rhuddanian bioherms even at low palaeolatitudes; however, the ecological recovery rate was far faster than that following the end-Permian mass extinction event. The partitioning of the Rhuddanian shelf faunas into well-defined benthic assemblages progressed slowly over the interval.

Type
Research Article
Copyright
Copyright © The Natural History Museum, London 2008

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