HULL, ROBERT A., University of Texas at Dallas, Richardson, TX

ABSTRACT: Downdip Regressive-Transgressive Sequences in the Claiborne Group

Origin of regressive-transgressive sequences within the Claiborne Group along the Texas and Louisiana coast have been variably attributed to eustatic sea level changes, autocyclic delta lobe switching, and changes in sediment sources. By using seismic, well logs, core data, sedimentological and stratigraphic principles, this project determines the sequence stratigraphic relationships within this Eocene group downdip. By understanding the sequence stratigraphic relationships within these formations, it is possible to advance our understanding of the regional changes in sea level along the Texas Gulf Coast as well as to highlight sedimentary relationships and models for this group.

The Claiborne Group in the Wharton, Colorado and Fort Bend counties area exhibits apparent features predicted by the Vail model for a changing sea-level. At least four major unconformity surfaces are recognized inseismic data acquired over this region of the Texas Gulf Coast from the San Marcos Arch to the Houston Embayment. These unconformity surfaces utilizing the chronology of Haq et al (1987), may be the 55, 42.5, 40.5, and 39.5 Ma sequence boundaries. It appears however that these unconformities are not evident on all seismic sections in the region. Whether this is due to variations in sediment supply and deposition, or seismic resolution is uncertain. A model is shown for a major erosional canyon feature that appears to have occurred around the 42.5 Ma sequence boundary in weste n Wharton County.

It appears there may be a relationship between a change in climate and the timing of the 40.5 unconformity surface. The relation between worldwide oxygen isotope data is shown.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.