MSc Research

My MSc research at Oxford University, supervised by Dr. Stephen Stokes and done in conjunction with Prof. Warren Wood of the US Geological Survey, involved using optically stimulated luminescence (OSL) to date lunette deposits from the Southern High Plains of the United States. The Southern High Plains (SHP) are a semi-arid elevated plateau in the southwest, which have undergone major environmental change during the Quaternary period. The landscape is sensitive to changes in moisture and wind regime, and features such as sand dunes and lunettes have undergone periodic reactivation related to regional climatic change. In this study, a chronology of aeolian activity is presented based on OSL dating and granulometric analysis of lunette sediments from Yellow Lake, a large playa lake system in the Southern High Plains.

Lunettes form on the lee sides of playas, the internally drained closed depressions that are ubiquitous in the Southern High Plains of Texas. The lunette sediments are dated by measuring the luminescent signal retained in quartz grains, a signal that is proportional to the time that has elapsed since the grain was last exposed to light. OSL is particularly suited to dating lunette sediments - they tend to be high in mineralogically mature quartz, are well-bleached, and are derived from a single source.

Drilling at Yellow Lake

The results show that aeolian activity and sediment deposition was not an isolated phenomenon on the SHP, but was part of a wider, continental-scale trend in desert reactivation and aridity in the middle and late Holocene. Within this broad-scale trend, there are regional variations. The period of aeolian activity in the last millennium observed in Great Plains records is not generally seen in the SHP. This is explained as a function of local groundwater levels, which control lunette deposition, being locally high in the SHP at this time. Thus deposition is ultimately climatically controlled, but locally supply-limited. It is concluded that groundwater levels on the SHP have undergone regionally coherent changes in the Holocene, which have been generally related to large-scale climate over the Great Plains.

Yellow Lake Lunette

The SHP are a sensitive geomorphic environment and are shown to have undergone major landscape changes in response to relatively modest climatic forcing in the Holocene. This has possible implications for future conditions on the SHP the latest IPCC report suggests that climate is currently predicted to become drier and warmer in the region, potentially leading to a decline in groundwater levels (and consequent reduction in agricultural capacity), and the reactivation of currently stable desert landforms.

The principal findings of this study are currently in preparation and will be published in due course.

Science and Engineering at The University of Edinburgh

School of GeoSciences

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