THE UPPER PLEISTOCENE DEPOSITS AT CASSINGTON, NEAR OXFORD, ENGLAND

For much of the Middle and all of the Upper Pleistocene the Upper Tham es valley has remained outside the limit of ice advance. The main agen ts of landform evolution have been the River Thames and its tributarie s, which have cut down episodically and in so doing have abandoned a s eries of river terraces. This study reports the findings of an investi gation into exposures in the deposits underlying the Floodplain Terrac e at Cassington, near Oxford, England. The sequence exposed reveals a stratigraphy of basal, predominantly fine-grained, lithofacies overlai n by coarser gravel lithofacies. The fluvial architecture of these dep osits indicates a major change in fluvial style from a low-energy (mea ndering) to a high energy (braided) channel system. The flora and faun a from the lower fine-grained lithofacies display a marked change from temperate at the base, to colder conditions towards the top, indicati ng a close association between deteriorating climate and changing fluv ial depositional style. Amino acid and luminescence geochronology from the basal fine-grained lithofacies suggest correlation with Oxygen is otope Stage 5 and hence it is argued that the major environmental chan ge recorded at the site relates to the Oxygen-Isotope Stage 5-4 transi tion. Deposition of much of the overlying gravel sequence probably occ urred during Oxygen isotope Stage 4, suggesting that the latter half o f the Devensian may be less significant, in terms of fluvial landscape evolution in the Upper Thames valley, than was believed previously. ( C) 1998 John Wiley & Sons, Ltd.