Using simple portable OSL measurements and laboratory characterisation to help understand complex and heterogeneous sediment sequences for luminescence dating

摘要

Many applications of luminescence dating to geo-archaeological and environmental systems face the challenges of complex depositional sequences with heterogeneous and incompletely bleached samples. Laboratory procedures can help to identify such samples, and rapid laboratory profiling developed over recent years can assist in forming a detailed appreciation of the luminescence stratigraphy of complex sites. However to assist with well-directed sampling, and with field interpretation of sediment sequences, such information is needed during the fieldwork period as well. This paper outlines the development of simple battery-powered IRSL/OSL readers at SUERC which have been designed to assist with field sampling for luminescence dating. The use of simple luminescence intensities, depletion rates and signal ratios is introduced which act, together with field gamma spectrometry, as proxies for underlying luminescence age, sensitivity and dosimetry within stratified sequences. Two case studies; the first summarizing experience derived from the 2004 Indian Ocean tsunami and subsequent fieldwork, the second concerning Neolithic ditch fills from the Tavoliere district in southern Italy are presented. In both cases simple luminescence field measurements were extremely useful in helping to understand the depositional mechanisms and in identifying sediments with significant residual signals at time of deposition. Subsequent laboratory work has confirmed the utility of the data and approaches in both these cases.