Abstract: Late Quaternary Stratigraphic Evolution of East Texas Mid-Outer Shelf and Upper Slope

S. Sarzalejo, S. A. Intevep, J.B. Anderson

The evolution of the low sediment-supply Trinity-Sabine incised valley system during the last glacial-eustatic cycle is documented. The dataset includes over 4500 km of high-resolution seismic data, 153 platform boring descriptions, and samples from two cores. Major surfaces and sedimentary packages were identified using sequence stratigraphic techniques.

Five phases of evolution were interpreted, two high sediment supply fluvial-deltaic systems, the Western Louisiana and the Brazos, acted in concert with the Trinity-Sabine system to produce a unique distribution of sandy facies in the study area. During Phase I, sea level fell and the Western Louisiana fluvio-deltaic system incised to the shelf edge. The Trinity-Sabine incised-valley system extended to the outer shelf, reincising its valley and eroding its previous fill. By the close of Phase I, the Western Louisiana system filled its incised valleys with sand and shifted slightly toward the east. Thick prodelta sediments were deposited on the shelf edge during Phase II.

Sea level reached its lowest position during Phase III. The Trinity-Sabine system formed a restricted delta at the shelf edge. Sand deposition occurred in a mouth bar behind a linear trend of salt uplifts. Some sediment bypassed these uplifts and were transported down slope. Initial sea-level rise at the onset of Phase IV resulted in the development of thick and complex shelf edge deltas. Sediment gravity flows occurred in response to tectonism and shelf edge instability. During Phase V, rapid sea-level rise resulted in backstepping of the Western Louisiana delta and backfilling of the Trinity-Sabine incised valley.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994