COCCOLITHS OF THE SPEETON CLAY AND SUTTERBY MARL

Abstract

Summary The Speeton Clay (Berriasian to Lower Albian) contains a much fuller succession of early Cretaceous coccoliths than has been described from beds of this age elsewhere. Most of the species are confined to the Lower Cretaceous and belong to three families which show a vigorous diversification in the Speeton Clay. Many of the rarer species are the forerunners of forms that are abundant in the Upper Cretaceous. There is a substantial break between Upper Jurassic and Lower Cretaceous assemblages, with very few species crossing the boundary. In the Berriasian beds a new flora begins to develop, very largely from Jurassic families. Most of these early forms are confined to the Speeton Clay and the first substantial appearance of Gault species is not until the Hauterivian; only a few of these continue into the Upper Cretaceous. When the Speeton assemblages are compared from an ecological point of view with communities living in modern seas, they are found to resemble most closely those of a land-locked gulf drawing its plankton, with some impoverishment, from the open ocean. Four new families, eleven new genera and forty-five new species are proposed.