Testing an approach to OSL dating of Late Devensian glaciofluvial sediments of the British Isles

Abstract

2009. Testing an approach to OSL dating of Late Devensian glaciofluvial sediments of the British Isles.ABSTRACT: In the British and Irish Isles, the understanding of expansion and retreat of the last ice sheet in Marine Isotope Stage (MIS) 2 has been hindered by a lack of chronological control for the timing of its maximum extent and subsequent retreat stages. In this research, a suite of lithofacies from a former distal ice marginal sandur at Orrisdale, Isle of Man, were identified and selected for optically stimulated luminescence dating. Different-size fractions of quartz grains were extracted from selected lithofacies types with the aim of identifying which depositional environments and grain size fractions are best suited for optical dating. Tests have been undertaken to identify the luminescence properties of this quartz, including preheat dose recovery and constant-wave optically stimulated luminescence (OSL) decay curve fitting. Equivalent dose distributions for all samples were wide and positively skewed, indicative of heterogeneous bleaching. A comprehensive statistically based decision-making protocol has been defined in order to find the appropriate statistical model for burial dose estimation. Ages in the range of 17-14 ka have been obtained which agree with the expected geologically constrained chronology. The Orrisdale Formation is contemporaneous with Heinrich Event 1 and the Killard Point Stadial identified in eastern Ireland ca. 16.4 ka. The suggested approach for OSL dating of glaciofluvial sediments has the potential for much wider application to high latitude or temperate areas where there is an abundance of such sediments and where improved chronological control is much needed.

The effect of fluvial environments on sediment bleaching and Holocene luminescence ages — A case study from the German Alpine Foreland

“…Hence, the decision process, originally designed for single grains of quartz can be applicable to multiple grain analyses under the premise that only a small percentage of luminescent grains are present in the samples. This finding supports the previous work of Thrasher et al (2009b). Hence, for our samples, the decision process proved to be a powerful tool to detect incomplete bleaching and to decide on the mode of D e calculation.…”

“…However, a range of studies showed that in insensitive samples, only very few grains contribute to the overall OSL signal of a multiple grain disc and as a consequence, a multiple grain distribution can be very similar to that of single grains (e.g. Thrasher et al, 2009b;Cunningham and Wallinga, 2012). Calculated D e values are based on a minimum of 30 aliquots in case of coarse grain analysis and 5 aliquots for fine grain analysis.…”

Extent and timing of the Last Glacial Maximum (LGM) in Britain and Ireland: a review

“…There researchers have employed radiocarbon, luminescence and cosmogenic dating techniques to firmly secure the advance to maximum limits Ó Cofaigh and Evans, 2007;McCarroll et al, 2010;Ó Cofaigh et al, 2010a), and for various retreat marginal positions on the west and east coast of the Irish Sea (e.g. McCabe, 2008a;Thrasher et al, 2009;McCarroll et al, 2010;Ó Cofaigh et al, 2010b). Securing a robust independent chronology for the sectors of the continental shelf showing strong morphological evidence for glaciation that underpins the shelf-edge LGM limit should be a research priority.…”

Realizing the potential of fluvial archives using robust OSL chronologies

“…Rittenour et al, 2005;Rodnight et al, 2005;Busschers et al, 2007), the degree of partial bleaching in the data is minimal. The appearance of partial bleaching in a dataset necessitates some statistical processing, although the selection and application of 'age models' is a frequent source of discussion (Bailey and Arnold, 2006;Rodnight et al, 2006;Thrasher et al, 2009). …”