ABSTRACT

Petrographic and geochemical analysis of recent fluvial, beach, and dune sediments derived from the same source terrane was carried out in the western Gulf of Mexico to show the usefulness of the these three environments in determining the tectonic setting of the source. Petrographic analysis showed that dunes concentrate the less heavy minerals and quartz grains by means of the selectiveness of the wind as a transport agent. In contrast, the heavier grains, such as the rock fragments remain in the beach and fluvial environments because of the high transport energy. Beach and dune sands do not define a particular tectonic setting because of the selective wind action of the backshore of the beach and the dune environments and the less intense chemical weathering. The fluvial sands are the most representative in terms of interpretation of tectonic setting because they reflect the volcanic domain of the source rocks of the Trans-Mexican Volcanic Belt. The geochemical results of all three sedimentary environments reflect the calcalkaline character of the igneous source rocks of the Trans-Mexican Volcanic Belt. The samples fall in a continental island-arc-margin field with basaltic and andesitic source rocks. A correlation and factor analysis indicates an alkali-basalt source that contributes to the composition of the beach, dune, and fluvial sediments. The geochemical analysis of the sediments more accurately reflects the tectonic setting regardless of the depositional setting of the sediments.