Geology, climate and water circulation of the Galveston Bay system

The geology of the Galveston Bay System reflects its location in one of the world's largest depositional basins, the northwest Gulf Coast Basin, as well as changes in the rates and balance among sea level, sediment influx and basin subsidence. Sedimentary deposits of two ages dominate the surficial geology surrounding the bays. Deposits of the most recent interglacial period of the Pleistocene Epoch include (1) river sands and flood basin muds of a deltaic plain and (2) sands of a barrier island system. Modern (Holocene) sediments that entrench and overlie the older strata are (1) fine sand and mud in rivers and bayhead deltas; (2) mud in the bays; (3) oyster reefs in the bays; and (4) sand composing the youngest barrier islands. Galveston Bay is extremely shallow (10-12 feet deep) compared with its large areal extent of 600 square miles. Sediment samples, collected a mile apart, are mud in most of the bays; samples coarsen shoreward where sand and reworked shell (gravel) dominate. Geochemical analyses of sediment samples indicate that abnormally high concentrations of barium, boron, chromium, copper, lead, nickel and zinc are products of anthropogenic activities and pollutants.