Laura A. Banfield¹, John B. Anderson²
(1) BP Amoco, Houston, TX
(2) Department of Geology and Geophysics, Rice University, Houston, TX

Abstract: Examination of the depositional environments on the continental shelf and slope associated with the transition from the lowstand to transgressive systems tract in the late Quaternary Rio Grande system, offshore South Texas

An earlier study of the evolution of the ancestral Rio Grande system in western Gulf of Mexico examined how deposition on the continental shelf responded to fluctuations in sea level and sediment supply over the past 120,000 years. The addition of approximately 800km of high resolution, single channel seismic profiles over the outer shelf and slope provides the opportunity to examine the relationship between shelf and slope deposits. This relationship is important as it defines the pathway of sediments from the shelf, down the slope, and onto the basin floor. The imaging window is limited due to the high frequency content of the dataset. Therefore, the additional data are most helpful in supplying insight into how depositional environments stepped back up the slope and onto the outer shelf during the transition between the most recent lowstand and transgressive systems tracts. Examination of this change in depositional environments is critical to understanding how the high sediment supply Rio Grande system switched from depositing a greater than 100 meter thick lowstand systems tract unit at the shelf edge to depositing transgressive systems tract deltaic deposits on the inner and middle shelf.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana