Distinguishing depositional setting for sandy deposits in coastal landscapes using grain shape

Several methods exist that use sediment properties to characterize depositional setting and related mechanisms of transport, including analysis of grain-size distributions, sediment petrology, micromorphology, and grain structure. Techniques that rely on electron or optical microscopy produce results with varying degrees of success and applicability. Here, a new method is presented and used to differentiate between littoral and eolian sands that were extracted from recently formed landforms, as well as landforms that are from mid to late Holocene in age. The method utilizes a standard optical microscope with a mounted digital camera, paired with freely available software (ImageJ) to characterize grain shape parameters. The method was tested on nearly 6000 sand grains from samples with varied transport histories, and it was found that grain solidity was the most distinguishable characteristic between eolian and littoral samples, differentiating them 86% of the time for calibration samples. The method was used to correctly identify the mechanism of transport for 76% of the samples. Patterns in the results indicated that this method could be extended to link potential sediment sources to various depositional basins, and future work includes testing the method in areas with a different mineralogy and/or landscape history.