Molluscan and plant biostratigraphy of some Late Devensian and Flandrian deposits in Kent

Abstract

Sequences of calcareous slope and spring deposits (mainly tufa) are described from two localities in Kent (Folkestone and Wateringbury). They contain rich faunas of terrestrial Mollusca, allowing a detailed reconstruction of the local environments. The faunal changes also reveal an underlying common pattern, ascribed largely to the effects of climate and migration. Eight biostratigraphical assemblage zones are proposed, applicable to deposits of this general character in the area of southern England. The base of each zone is defined as follows: zone y first appearance of a molluscan fauna, dominantly of Pupilla, Vallonia and Vitrina ; zone z expansion of Abida and Trichia ; zone a decline of Pupilla , appearance of Carychium and Aegopinella ; zone b expansion of Carychium and Aegopinella , occurrence of Discus ruderatus ; zone c expansion of Discus rotundatus , suppression of Discus ruderatus ; zone d expansion of Oxychilus cellarius ; zone e re-expansion of Vallonia ; zone f appearance of Helix aspersa . Botanical evidence (pollen and seeds) and some radiocarbon dates allow a partial correlation of the zones with the standard Godwin pollen zones of the Late Devensian (late-glacial) and the Flandrian.