ABSTRACT

The facies architecture and evolution of modern and Holocene tidal-delta deposits were examined using high-resolution seismic (chirper) data, sediment cores, and boring descriptions. During the last transgression (18,000 yr. BP to present) the Trinity/Sabine incised valley backfilled with continuous fluvial and bay-head delta facies and discontinuous middle-bay and tidal delta facies. The tidal delta facies preserved within the valley extend up to 22 km in dip-direction and are up to 12 m thick. The modern Bolivar Roads tidal delta complex is similar in size to those preserved within the offshore portion of the valley, and is a mud-dominated system. The overall size of the tidal delta complex decreased around 1,500 yr. BP as the peninsula accreted and the inlet grew narrower. Prior to this time the tidal delta complex was two times larger.

The tidal delta seismic facies is characterized by stacked landward and seaward dipping reflectors overlain by a ravinement surface. Lithofacies have been described using sediment cores for the Holocene tidal delta complexes. Isopach maps of these tidal deltas provide reservoir analogs for subsurface exploration and production.