ESR DATING OF THE TYPE CROMERIAN FRESH-WATER BED AT WEST RUNTON, UK

We performed ESR dating on tooth enamel from three in situ locations w ithin the West Runton Freshwater Bed (FW) bed, which is stratigraphica lly below fluvial sands of Anglian origin. The teeth contained little uranium, which made ESR ages essentially independent of the choice of uranium uptake model. However, this advantage was offset by a critical dependence of the FSR ages upon the moisture content of the sediments . Care was taken to account for self-shielding effects arising from th e large size of the elephant tooth. Using the value of 10% moisture co ntent observed during 1992 in sediments exposed on the cliff face, giv es ages of 346+/-55 (EU) and 350+/-52 (LU) ka, corresponding to the Ox ygen Isotope Stage 11/10 boundary. Additional moisture content measure ments of different parts of the EW bed in 1995 yielded a mean value of 25%. Using values of 20 and 30% moisture content, we obtain ages from 420+/-90 to 460+/-80 ka (EU, 1 sigma errors). Because the faunal and floral data indicate that the FW bed was an interglacial deposit, the ESR results suggest that the FW bed could have been deposited in eithe r isotope stages 11 or 13. However, independent faunal and stratigraph ic evidence favours a stage 13 age or earlier; this is discussed in re lation to the ESR data. These results are consistent with prevailing v iews (e.g. Bridgland, 1994) that the overlying Anglian deposits correl ate with oxygen isotope stage 12. Copyright (C) 1996 Elsevier Science Ltd