CLIMATIC AND ENVIRONMENTAL RECONSTRUCTIONS BASED ON FOSSIL ASSEMBLAGES FROM MIDDLE DEVENSIAN (WEICHSELIAN) DEPOSITS OF THE RIVER THAMES AT SOUTH KENSINGTON, CENTRAL LONDON, UK

Fossiliferous silts within the Late Pleistocene Kempton Park Gravel, o f the River Thames Valley, were exposed in 1980 during foundation work s for the Ismaili Centre in South Kensington, London. The results of a multidisciplinary study of the geomorphology, sediments, fossil plant s, vertebrates, molluscs, ostracods and insects are reported. The silt s were deposited under two distinct climatic regimes; a lower unit acc umulated when the climate was arctic and an upper when the temperature s were at least as warm as those of the present day. Both these units occupy the same channel system and are separated from one another by l ess than a metre of sediment, implying that the climatic change was pr obably sudden and intense. The strongest evidence for this climatic di fference comes from a study of the Coleoptera, which show an almost co mplete replacement of the arctic element in the fauna by a suite of te mperate species. Palaeotemperature reconstructions using the Mutual Cl imatic Range method, based on the coleopteran assemblages from the low er unit, suggest that the mean temperature of the warmest month was 9/-2 degrees C and that of the coldest month -22+/-10 degrees C. For th e upper unit the mean temperature of the warmest month had risen to ab out 17 degrees C and that of the coldest month to about -4 degrees C. The episode represented by the lower unit, with its arctic climate, ha d not previously been recognized in the Thames Valley. The fauna from the upper, temperate, unit is very similar to that from other sites in the Kempton Park Gravel, such as that from Isleworth, 10 km upriver, which, like the upper unit at the Ismaili Centre, was characterized by the virtual absence of trees. It would appear that in such cases this treelessness does not indicate cold conditions, equivalent to those o f the modern tundra, but may instead result from a combination of ecol ogical and temporal factors. The value of multidisciplinary studies in reaching such conclusions is emphasized. The temperate episode descri bed here is correlated with the thermal maximum at the early part of t he Upton Warren Interstadial Complex. An earlier suggestion, based on amino acid epimerization ratios, that the Upton Warren Interstadial co rrelates with Oxygen Isotope Sub-stage 5a is not supported by the data , which show no evidence of the forested environments that characteriz ed this period in both Britain and the adjacent Continent. It is thoug ht that the temperate deposits at the Ismaili Centre belong to the Mid dle (Pleniglacial), rather than the Early, Devensian (Weichselian) and are equivalent to Oxygen Isotope Stage 3. (C) 1998 Published by Elsev ier Science Ltd. All rights reserved.