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|Title:||Testing post-IR IRSL luminescence dating methods in the southwest Mojave Desert, California, USA|
|Authors:||Carr, Andrew S|
Hay, Alex S.
|Citation:||Quaternary Geochronology, 2019 49, pp. 85-91|
|Abstract:||The Mojave Desert presents an array of Pleistocene lacustrine deposits and aeolian landforms to which, at times, it has proved challenging to apply luminescence methods. We tested the suitability of K-feldspar post-IR IRSL methods using two sites with independent radiocarbon dating – shorelines at Harper Lake and Silver Lake – considering: 1) overall performance of the post-IR IRSL 225 °C (pIRIR225) protocol, 2) effect of test dose size on pIRIR225 De, 3) anomalous fading correction of pIRIR225 ages; 4) preliminary single grain pIRIR225 results. We observe consistently good performance of the single aliquot pIRIR225 protocol, with good dose recovery, acceptable recycling ratios, low recuperation and low inter-aliquot scatter. The pIRIR225 ages for Silver Lake (8.8 ± 0.4 and 11.3 ± 0.5 ka) and Harper Lake (both 25.4 ± 1.4 ka) are in substantially better agreement with the independent dating than low temperature (50 °C) IRSL and quartz OSL ages. pIRIR225 fading rates are reduced to ∼2.0–2.5% per decade, but there remains a tendency for under-estimation when using uncorrected ages. A need for fading correction is further implied at Harper Lake via comparison with multi-elevated temperature (MET)-PIR age plateaus and pIRIR290 measurements, although at the younger Silver lake site these methods produce ages nearly identical to the uncorrected pIRIR225 ages. Preliminary single grain pIRIR225 measurements suggest a ∼25–30% usable grain yield. At Silver Lake the single grain and single aliquot ages agree well despite over-dispersion of the single grain equivalent dose distribution. At Harper Lake the single grain and single aliquot pIRIR225 ages also agree well, although a population of insensitive, lower De grains is observed. These grains are not associated with significantly higher fading rates.|
|Rights:||Copyright © the authors, 2018. This is an open-access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.|
|Appears in Collections:||Published Articles, Dept. of Geology|
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