OSL of tephric loess and volcanic quartz in Japan and an alternative procedure for estimating De from a fast OSL component

Parameters of OSL components of quartz in volcanic ashes and in tephric loess from Japan were determined, and their characteristic in terms of recuperation was investigated. As a result, the medium and slowl components, which were the main components in the volcanic quartz, were also found in the quartz in tephric loess, while the OSL of quartz in tephric loess was dominated by fast component. This suggests that the medium and slowl components in tephric loess are probably coming from volcanic quartz. All the components in volcanic quartz appeared to give strong recuperation after preheating. In order to date tephric loess, the separation of fast component was essential, because only negligible recuperation was observed in the fast component. The equivalent dose (D-e) of tephric loess decreased significantly with the illumination time, while recuperation increased with illumination time. A plot of D-e versus recuperation indicated that D-e decreased exponentially as recuperation increased. Since the fast component is free from recuperation, the extrapolation of the exponential curve to the point that recuperation equals zero gives D-e, which entirely utilizes fast component. The agreement of the OSL ages with independent ages using the corrected D-e values provides strong evidence for the validity of the correction method. (C) 2003 Elsevier Science Ltd. All rights reserved.