Application of Luminescence Techniques to Coastal Studies at the St. Joseph Peninsula, Gulf County, Florida

Abstract

<p>The main objectives of this study are to use optically stimulated luminescence (OSL) to date quartz samples collected from dune ridges on the St. Joseph Peninsula, to test the feasibility of dating quartz from heavy mineral layers as a solution to the problems associated with the low luminescence signal inherent to young samples and to use the natural residual thermoluminescence (NRTL) signal in littoral zone quartz to study sediment transport in the nearshore zone.</p> <p>All samples were collected from the St. Joseph Peninsula, part of a barrier island chain that stretches across the northern Gulf of Mexico. Dune ridge samples and offshore samples were collected from various locations along the length of the peninsula.</p> <p>Frequency histograms, showing the distribution of equivalent doses (D_E'S), were plotted for each of the dune ridge samples. Several samples have large D_E'S relative to their D_E distributions. There are two ways of obtaining grains with large doses and, therefore, large D_E'S. The first is by proximity to other grains that are delivering high doses. The second is by incomplete zeroing. These possibilities are explored.</p> <p>Based on the geometry of the ridges on the peninsula, the youngest dune ridges should be closest to the gulf side of the peninsula and the oldest ridges should be on the bay side. This is tested by obtaining OSL dates for a series of samples from the north end of the peninsula.</p> <p>Two samples from storm deposits of a known age were collected. Results show that it is possible to date young samples by using quartz collected from heavy mineral layers. The high radiation dose delivered to the quartz by the heavy minerals makes it possible to obtain accurate dates on "modem" deposits.</p> <p>The natural residual thermoluminescence (NRTL) signal of the littoral samples was analysed for trends related to grain size and sample position relative to longshore drift. This study shows that NRTL is a useful tool in studies of sediment transport in the nearshore and can be used as an alternative to other sediment tracing methods.</p> <p>The results of this study are a significant contribution to both luminescence dating and coastal geology.</p>