Luminescence characterisation of quartz-rich cover sands from NE Thailand

The genesis of a several-meter-thick cover sand layer, which is widely distributed in mainland SE Asia has been the subject of much debate, being considered by some to be an aeolian mantle of late Pleistocene/early Holocene origin, and by others to represent a Holocene biomantle. Samples were collected from three sites in NW Thailand in 1998 to assess the potential of luminescence studies for characterisation and chronometric studies of the layer. The material is a quartz-rich, iron-stained sand, with high-luminescence sensitivities, a pronounced 325 degreesC TL peak, and high sensitivity to phototransfer and OSL. A number of methods for estimating stored dose were assessed, of which additive TL and regenerative OSL procedures produced good laboratory results. These methods have been used to produce stored dose and apparent age profiles for one of the sites. The data are consistent with a late Pleistocene/Holocene aeolian deposition process, possibly modified in the upper layers by bioturbation. However, the possibility that the recorded profiles are the result of heterogeneous mixing of bleached and unbleached grains within the biomantle model cannot at this stage be excluded. The material has excellent luminescence properties, and it is likely that further luminescence studies will be able to distinguish between the formation models, and contribute significantly to understanding of these regionally significant sediments. (C) 2000 Elsevier Science Ltd. All rights reserved.