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Book Chapter

Purbeck–Wealden

By
David J. Horne
David J. Horne
Department of Geography, Queen Mary University of London, Mile End Road, London E1 4NS, UK and Department of Zoology, The Natural History Museum, Cromwell Road, London SW7 5BD, UK
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Published:
January 01, 2009

Abstract

The Purbeck-Wealden of the type areas in onshore southern Britain (Fig. 1) encompasses the Berria-sian-earliest Aptian stages of the Cretaceous, a time span of approximately 21 Ma. At least some of the lowest part of the succession belongs to the latest Jurassic (Portlandian); how much depends on where the Jurassic-Cretaceous boundary is placed. Ostracods are frequently diverse and abundant in the predominantly calcareous or argillaceous units (e.g. Purbeck Limestone Group, Wadhurst Clay Formation, Grinstead Clay Formation, Weald Clay Group), sometimes forming ostracod limestones, but in clays that have undergone pedogenesis and in arenaceous facies (e.g. Ashdown Beds Formation, Upper and Lower Tunbridge Wells Sand formations) they tend to be rare or poorly preserved. They are essentially non-marine faunas, with only a few convincing indicators of direct marine influence. Although their interpretation is difficult and has given rise to controversy, ostracods are undoubtedly the most useful biostratigraphical tool available in Purbeck-Wealden sequences. They have also been used with some success in correlations of the offshore ‘ Purbeck-Wealden’ facies of Portlandian-Barremian age found in the Celtic Sea and Fastnet basins between southern Ireland and SW England (Fig. 1).

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Contents

The Micropalaeontological Society, Special Publications

Ostracods in British Stratigraphy

J. E. Whittaker
J. E. Whittaker
The Natural History Museum, London, UK
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M. B. Hart
M. B. Hart
University of Plymouth, UK
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Geological Society of London
Volume
3
ISBN electronic:
9781862396210
Publication date:
January 01, 2009

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