EDO7564 - Broom Palaeolithic sites, Thorncombe; optical dating 2005

NRHE: The sand and gravel exposures at Broom, located on the River Axe, are of considerable significance in the context of the British Lower Palaeolithic and the fluvial terrace stratigraphy of southwest England. The archaeology is of both regional importance for the understanding of the Lower Palaeolithic (Acheulean) occupation of southwest Britain, and national significance with respect to the use of an atypical raw material (chert) in the manufacture of the majority of the lithic assemblage. The profilic assemblage of Acheulean artefacts is dispersed throughout this sequence and represents a mixture of in situ and derived material, with deposition of both components considered relatively contemporaneous with episodic occupation. The principle aim of this report is to assess the length of hominid presence through direct dating of the Broom sedimentary sequence. Fifteen conventional samples from matrix-supported units and three non-conventional interstitial sands with mean age estimates from matrix-supported samples suggests such age overestimation may be a product of partial bleaching. Bayesian analysis of the raw optical chronology demonstrates the stratigraphic ocnsistency of age estimates between major units and refines sedimentary succession into intervals of 324 to 282 ka (Middle Beds) and 292 to 205 ka (Upper Gravels). This might suggest a prolonged hominid presence from <325 ka to 205 ka, yet the minimum limit contradicts the chronology of sedimentary succession extrapolated by internal and stratigraphic consistency, the minimum optically derived age of the Broom sequence is accepted tentatively.