High-Resolution Sequence Stratigraphic Analysis of the Late Quaternary East Texas Continental Shelf and Upper Slope

Kenneth C. Abdulah, John B. Anderson, Sabrina Sarzalejo, Martin B. Lagoe, Lynette Y. Holdford

Sequence stratigraphic methodology has allowed us to unravel the late Quaternary evolution of the east Texas continental shelf and upper slope. The ability to date sequences, by radio-carbon methods, correlation with oxygen isotope records, and biostratigraphy, provides chronostratigraphic control for the major phases of fluvial/deltaic deposition. Three fluvial/deltaic systems, the Brazos, the Colorado, and the western Louisiana, contributed to the outbuilding of the east Texas continental shelf. High-resolution seismic data provide the means to correlate, and map, the major delta lobes associated with each of these fluvial/deltaic systems.

Our results show that the high sediment supply of the western Louisiana system can overwhelm the eustatic signal, while the Brazos and Colorado deltas have responded much more in phase with eustasy. During the rapid sea-level rise of the late Pleistocene-Holocene, the western Louisiana fluvial/deltaic system continued to prograde while the Brazos and Colorado fluvial/deltaic systems backstepped onto the shelf. Paleoenvironments and paleobathymetry for these areas are interpreted from benthic foraminiferal biofacies, diversity and the abundance of planktic foraminifera. Paleobathymetric curves from the western Louisiana and Brazos/Colorado areas support the concept of different depositional response based on the seismic.

Oxygen isotope records provide an independent guide to Quaternary sea-level, at least in terms of frequency of eustatic events if not always in magnitude. Correlation between the delta lobes of the Brazos and Colorado fluvial/deltaic systems, and the oxygen isotope records, indicates that major delta lobe development and switching are driven by fifth-order eustatic cycles.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995