Echinoid distribution and sequence stratigraphy in the Cenomanian (Upper Cretaceous) of southern England

Abstract

Almost 3500 individual occurrences of echinoid have been recorded and correlated against a sequence stratigraphie framework for the entire Cenomanian and basal Turonian from three regions of southern England, representing onshore, mid-shelf and deeper-shelf habitats. There are marked differences in the composition and diversity of faunas both across the shelf at a single time interval and through time at the same locality, driven primarily by factors such as sedimentary facies, which are controlled by changing sea-levels. The ranges of individual taxa expand and contract across the shelf as sea-levels change. In mid-shelf environments more onshore taxa appear only near sequence bases, at times of lowest sea-level, while those from more outer shelf settings are found during highstand intervals, and this creates a cyclical pattern of diversity. By comparison with modern faunas, the Middle and Upper Cenomanian of the Sussex coast is likely to have been deposited in water depths of between 100 m and 150 m and the amplitude of sea-level change appears to increase through the Cenomanian.