EDO6117 - Chard Junction Quarry, Thorncombe; optical luminescence dating 2009

The deposits of the proto-Axe at Chard Junction Quarry potentially contain evidence of the earliest hominin occupation of southwest Britain and, along with Broom and Kilmington, represent one of the longest terrestrial records of Palaeolithic occupation in Britain. This project aimed to assess the reliability of the optical chronology of the sediment sequence within the Hodge Ditch excavations. The analytical properties of the age estimates are evaluation, with intrinsic measures and a tri-laboratory inter-comparison conducted to assess reliability. The raw optical chronology is refined substantially by rejection of those age estimates accompanied by analytical caveats, driven principally by poor recycling ratios in the high, saturating region of dose response. One of two inter-laboratory samples produced a significantly different age by one laboratory, which may be caused by the differencesin laboratory thermal treatment. The reliability of De:Dr plots may improve with increasing numbers of samples frrom equivalent stratigraphic units of divergent dosimetry, but having only two samples may lead to erroneous conclusions. Rapid sedimentation and deposition of artefacts between c.15.2m and 4.5m appears centred on a geometric mean age of 259A+/-10ka (MIS 7). There then followed relatively slow or pulsed sedimentation until 86ka (MIS 5a) beyond which the deposits were incised to form the current course of the River Axe.