Lower Severn Valley: Piloting Optical Dating of Terraces

Author(s): A G Brown, R Jackson, A Mann, Dr P S Toms

This study contributes to Stage 2 of the English Heritage project ‘Evaluating and Enhancing the Geoarchaeological Resource of the Lower Severn Valley’. It aims to assess the potential of Optical dating of terraces in the project area as part of a prospection toolkit that will increase the effectiveness of archaeological mitigation strategies within the particular environment of the Severn Valley. Twelve samples of sediments associated with terraces were collected from active quarry sites at Frampton, Clifton and Ball Mill. Each yielded sufficient datable mass and signal to generate Optical age estimates. The terrace deposits at Frampton and Clifton formed after the Last Glacial Maximum of Marine Isotope Stage (MIS) 2 and prior to mid MIS 1. Those at Ball Mill were created between MIS 5e and early MIS 4. Most of the age estimates are accompanied by analytical caveats though are on the whole consistent with their relative stratigraphic positions. The occurrence of samples at Frampton and Clifton exhibiting traits of partial bleaching suggests that future Optical dating of terraces 1 and 2 should draw upon single grain approaches to acquire ages more consistent with the burial period. Intrinsic assessment of reliability would also be improved by obtaining at least two samples from each unit to be dated that have distinct dose rates, identified either by profiling before or prioritising after sampling.

Report Number:
36/2011
Series:
Research Department Reports
Pages:
34
Keywords:
Geochronology Optically Stimulated Luminescence

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