Abstract

A regional analysis of adjacent beach and foredune variability was conducted along the Texas barrier system. Evaluated parameters include beach morphology, dune internal structures, and comparative textural and heavy mineral characteristics. The most variable element of beach morphology is backshore width. Foredune-ridge height increases southward and is climatically controlled. Dune cross-bedding is highly variable in terms of both dip angles and azimuth distributions, indicating the presence of polygenetic cross-strata. The azimuth distribution modes indicate the presence of both pyramidal dune structures generated by seasonal wind variations, and storm-related structures resulting from multiple episodes of ridge erosion and rebuilding phases. Regional constraints on foredune-ridge orientation imposed by the coastline have some polarizing influence on the cross-bedding azimuth distributions. Beach textures are greatly influenced by she admixtures and show relatively high local variability. In contrast, dune textures are not significantly influenced by shell admixtures and show a low degree of local variability, thus allowing the detection of regional trends. Foredune deposits show a northward reduction in grain size and improved sorting; from a regional reduction in energy level and competency range of the eolian regime. The foredunes generally contain higher total heavy mineral concentrations and higher proportions of dense opaque minerals than the beach population. No apparent difference occurs in the proportion of elongate minerals. Beach and foredune heavy mineral assemblages show regional trends in total concentrations and opaque mineral content that correlate with similar trends on the adjacent continental shelf, indicating a constancy of provenance and regional dispersal patterns during the Holocene transgression.--Modified journal abstract.

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