St. Joseph Peninsula is located in Florida, along the northeast coast of the Gulf of Mexico. Natural residual thermoluminescence (NRTL) analysis of quartz grains extracted from sands at eight localities showed a gradual reduction in NRTL intensity from south to north, which is also the accepted direction of longshore transport. Differences in NRTL reduction were also noted between grain size fractions, indicating either differential response to light exposure during travel, or different amounts of exposure between grain sizes. Laboratory experiments using simulated sunlight exposure in air and seawater were combined with natural exposure experiments, wherein differences in residence time in the swash zone between grain size fractions were quantified. In this study, sediment residence times in the swash zone along the St. Joseph Peninsula were estimated to vary from ∼25 days to ∼9 days depending on grain size. A 67% variance in littoral zone residence between 90–150-µm and 150–212-µm grains is revealed. The results of this study indicate the significance of NRTL as a novel method of sand transport analysis.

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