Marine Geology, South Texas Outer Continental Shelf: A Processes Approach

Although the South Texas Outer Continental Shelf (OCS) has been aseismic, crustal movements have been virtually continuous. The two principal types of movement have been seaward subsidence of the shelf and folding of strata by a combination of seaward creep and diapiric movement of low density material. Faulting has been extensive and has migrated seaward. Surficial benthic sediments are typically fine-grained (<0.063 mm). The average rate of deposition over the past 18,000 years seems to have been about 1 meter per thousand years. Sediment modification by infaunal activity ranges from high on the inner OCS to low on the outer part. Concentrations of cadmium, chromium, lead, and vanadium are highest in an area of suspected gas seeps at the shelf edge. Higher amounts of barium on the inner shelf are associated with petroleum fields.