The Late Middle Pleistocene biostratigraphy of the Thames Valley, England:new data from eastern Essex

Coring investigations at East Hyde, near Tillingham, Essex. have revealed a sequence of fluvial and estuarine deposits infilling a channel incised int o London Clay. These deposits are of Thames origin and were deposited after the river's diversion into eastern Essex late in the Anglian Stage. The de tailed litho- and biostratigraphy of the deposits are described. Ostracod a nd molluscan data confirm that the lower parts of the sequence accumulated in a quiet, fluvial environment rich in aquatic vegetation. The upper sedim ents accumulated in an inner estuarine environment under conditions of risi ng sea level. Pollen assemblages from both units show strong biostratigraph ical affinities with the Hoxnian Stage, particularly with the Hoxnian late temperate substage. Ho III. The sequence has also yielded a rare assemblage of freshwater fluvial molluscs, the 'Rhenish' fauna, which migrated into t he Thames following a link with the rivers of continental Europe. The occur rence of Theodoxus serratiliniformis is exceptionally rare. representing on ly the second record of the species in the entire British Pleistocene. The molluscan assemblages show striking similarities with those at Clacton in n ortheast Essex and Swanscombe, Kent, and provide strong evidence that the t hree sites are contemporaneous and were connected in the same fluvial syste m. The timing of the migration of the 'Rhenish' fauna into Britain and the implications for sea-level reconstruction in the southern North Sea region are discussed. The episode of major climatic warmth and high eustatic sea l evel represented at East Hyde is correlated with Stage I I of the deep sea record. (C) 2001 Elsevier Science Ltd. All rights reserved.