THE EVOLUTION OF THE GALVESTON BAY AND BARRIER COMPLEX

The Galveston Bay and Barrier complex currently occupies the ancestral incised fluvial valley of the Trinity and San Jacinto rivers. The bay was initially flooded prior to 11,000 years ago and began its history as a narrow bay with strong tidal influence. The early evolution of the bay was punctuated by dramatic landward shifts in bay environments as relatively flat fluvial terraces that flank the valley were flooded. The most dramatic events occurred 8,200 cal. yr. BP and 7,700 cal. yr. BP, when complete reorganization of bay environments took place. During the more recent event, the bay-head delta and barrier island shifted landward at rates of ~6.5 and ~2.0 km per century, respectively. Galveston Island did not form until after 5,500 cal. yr. BP and Bolivar Peninsula did not form until after 2,500 cal. yr. BP. These modern barriers formed only after the fluvial valley was mostly back-filled with bay and tidal deposits. Relatively slow westward accretion of Bolivar Peninsula resulted in diminishing tidal influence in the bay. The Peninsula was decapitated, probably by one or more major storms, after 900 cal. yr. BP.