Identification of partial resetting using De as a function of illumination time

Modem age samples from various depositional environments were examined for signal resetting. For 19 modem aeolian/beach samples all D-e values obtained were <0.5 Gy, with similar to70% having D-e<0.2 Gy. For 21 fluvial/colluvial. samples, all D-e values were <5 Gy with similar to80% being <1 Gy. D-e as a function of illumination (OSL measurement) time (D-e(t)) plots were examined for all samples. Based on previous laboratory experiments, increases in D-e(t) were expected for partially reset samples, and constant D-e(t) for fully reset samples. All aeolian samples, both modem age and additional 'young' samples (<1000 years), showed constant (flat) D-e(t) while all modem, non-zero D-e fluvial/colluvial samples showed increasing D-e(t). 'Replacement plots', where a regenerated signal is substituted for the natural, yielded constant (flat) D-e(t). These findings support strongly the use of D-e(t) as a method of identifying incomplete resetting in fluvial samples. Potential complicating factors, such as illumination (bleaching) spectrum, thermal instability and component composition are discussed and a series of internal checks on the applicability of the D-e(t) for each individual aliquot/grain level are outlined. (C) 2003 Elsevier Ltd. All rights reserved.