--> Abstract: The Late Quaternary Evolution Of The Rio Grande System, Offshore South Texas: Differentiating The Controls Of Sediment Supply And Eustasy, by L. A. Banfield and J. B. Anderson; #90928 (1999).

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BANFIELD, LAURA A.1 and JOHN B. ANDERSON2
1BP Exploration, Houston, TX
2
Rice University, Houston, TX

Abstract: The Late Quaternary Evolution of the Rio Grande System, Offshore South Texas: Differentiating the Controls of Sediment Supply and Eustasy

A seismic and sequence stratigraphic investigation of the Rio Grande system provides information concerning: (1) the distribution of depositional units relative to the last glacioeustatic cycle (120,000 ybp to present); (2) the spatial and temporal distribution of sand-prone units; and (3) whether the control of eustasy and sediment supply (climate?) can be differentiated. The combination of biostratigraphic data (formaninferal abundances and extinctions), oxygen isotope startigraphy, and radiocarbon ages in the Rio Grande area provides the chronologic control for the study. The depositional unit dataset consists of 1850 kilometers of highresolution seismic reflection profiles, 14 platform boring descriptions, and sediment samples from one platform boring.

The study of the Rio Grande system identified 7 units that are interpreted as fluvially and wave dominated deltas and a shelf mud deposit. Within a sequence stratigraphic framework, they are interpreted as 2 highstand systems tract, 1 lowstand systems tract, and 4 transgressive systems tract deposits. The integration of a strong chronologic framework, a high-resolution sea level curve, and a series of isochron maps of the units produced an understanding of the timing of deposition relative to sea level fluctuations and sediment supply. Although eustasy is the dominant control during highstand and lowstand systems tract deposition, transgressive systems tract deposition primarily is controlled by sediment supply.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas