Abstract

Thematic set assembled by J. D. Hudson & D. M. Martill.

The Oxford Clay Formation is one of the classical units in British Jurassic stratigraphy. It crops out almost continuously in an arc running from the Dorset coast to Oxford, through the Midlands to Yorkshire. It was traditionally subdivided into Lower, Middle and Upper divisions, now formalized as the Peterborough, Stewartby and Weymouth Members, respectively (Cox et al. 1993). The Peterborough Member is organic-rich, the Stewartby and Weymouth Members more calcareous and generally organic-poor. Excellent ammonite faunas throughout the sequence are important in the international bio- and chrono-stratigraphy of the Callovian and Oxfordian Stages, and in correlation between the Tethyan and Boreal fauna1 realms. The Peterborough Member—‘the clay that burns’—supports Britain's largest brick industry.

Why study the Oxford Clay? Most obviously for its superb fossils, to be seen in museums the world over (Martill & Hudson 1991). The Peterborough Member also serves as an example of a potential petroleum source-rock, besides being an important current industrial resource. It has not yielded petroleum, because it has never been deeply buried. This means that the rocks and fossils preserve much of their original chemistry and thus help bridge the gap between studies of modern sediments and of conventional source rocks. In the papers in this thematic set we have tried to make use of these opportunities to show what modern methods and concepts can add to classical geological interpretation. We have studied mainly central and eastern England, the area of least burial, simplest structure, best fossil preservation, and, because of the

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