Can glacial shearing of sediment reset the signal used for luminescence dating?

Abstract

Understanding the geomorphology left by waxing and waning of former glaciers and ice sheets during the late Quaternary has been the focus of much research. This has been hampered by the difficulty in dating such features. Luminescence has the potential to be applied to glacial sediments but requires signal resetting prior to burial in order to provide accurate ages. This paper explores the possibility that, rather than relying on light to reset the luminescence signal, glacial processes underneath ice might cause resetting. Experiments were conducted on a ring-shear machine set up to replicate subglacial conditions and simulate the shearing that can occur within subglacial sediments. Luminescence measurement at the single grain level indicates that a number (albeit small) of zero-dosed grains were produced and that these increased in abundance with distance travelled within the shearing zone. Observed changes in grain shape characteristics with increasing shear distance indicates the presence of localised high pressure grain-to-grain stresses caused by *Revised manuscript with no changes marked Click here to view linked References grain bridges. This appears to explain why some grains became zeroed whilst others retained their palaeodose. Based on the observed experimental trend, it is thought that localised grain stress is a viable luminescence resetting mechanism. As such relatively short shearing distances might be sufficient to reset a small proportion of the luminescence signal within subglacial sediments. Dating of previously avoided subglacial sediments may therefore be possible.

Optically Stimulated Luminescence Signal Resetting of Quartz Gouge During Subseismic to Seismic Frictional Sliding: A Case Study Using Granite‐Derived Quartz

“…Our results demonstrate that the OSL signal decreases drastically during high‐velocity friction experiments. Previous studies showed that the TL and OSL intensities of quartz grains decrease (or locally become zero) after slow slip rate ( V = 16 to 56 μm s −1 ) experiments (Bateman et al, 2018; Hiraga et al, 2004). Hiraga et al (2004) identify a reverse relationship between TL intensity and applied frictional work.…”

Demise of a Himalayan giant and the dramatic fate of the highest peaks on Earth

“…Infra-red stimulated luminescence (IRSL) dating on sheared deposits Although predominantly carbonate, TSS units may contain small amount of quartz and feldspar grains. It has been shown in previous studies that the luminescence signal can be reset (called triboluminescence) by heating, mechanical crushing or shearing 37 processes in intense sheared bands such as frictionnites.…”

Luminescence as a Sediment Tracer and Provenance Tool

“…Further inland, such as in mixing soils on hillslopes, bleaching occurs entirely by surface exposure where grains reach the surface via mixing processes and are then reburied (Reimann et al, ). Finally, in rare cases, bleaching can potentially occur via mechanisms such as pressure at the bottom of a glacier (Bateman et al, ). The wide variety in the extent of bleaching, and our limited understanding of the processes, shows that much is yet to be learned about the connections between luminescence and geomorphology.…”