Extending the time range of luminescence dating using red TL (RTL) from volcanic quartz

The potential of red thermoluminescence (RTL) emission from quartz, as a dosimeter for baked sediments and volcanic deposits, has received some attention over the past decade. While there have been some important observations relating to signal stability, saturation characteristics and emission wavebands, there has not been a systematic analysis of RTL properties of older (i.e., >1 Ma), quartz-bearing known age volcanic deposits. We have undertaken such an analysis using independently-dated silicic volcanic deposits from New Zealand, ranging in age from 300 ka through to 1.6 Ma. We observed a complex RTL emission in most volcanic quartzes, which consists of a number of discrete high temperature (i.e, >220 degreesC) TL peaks. Isothermal analysis indicates a stable dating trap (E = 2.03 eV; S = 4.20 x 10(15)) which is stable at ambient (c. 20 degreesC) temperatures for > 10(9) a. We confirm the slow onset of saturation with dose, acid the limited extent of sensitivity changes due to dosing and TL readout. As such, there is much potential for exploiting the dosimeter in dating studies and we present the results From a modified single aliquot regenerative (SAR) procedures which indicate that there is a good agreement between RTL dating and other methods over time scales 10(5)-10(6) a. This paper presents a summary of the most important related results of our findings and outlines the configuration of photomultiplier and filter combinations which maximizes RTL detection for temperatures up to 500 degreesC. (C) 2000 Elsevier Science Ltd. All rights reserved.