Fluvial Response to Base Level Change: A Case Study of Two Incised Valleys Along the East Texas Coast

Patrick Taha¹, John B. Anderson¹, Alexander Simms¹, and Antonio Rodriguez^2
1 Rice University, Houston, TX
² University of Alabama, Tuscaloosa, AL

This study emphasizes the differences in fluvial response and valley fill architecture for the Brazos and Trinity, two adjacent East Texas fluvial/deltaic systems, over the course of the last transgressive and early highstand systems tracts (17-18 kyr). Numerous datasets, including 25 cores, 600 drillers' water well logs, 17 cone penetrometer tests, 60 radiocarbon dates, seismic and ground penetrating radar data were integrated using GIS software (ESRI's Arcmap).

The Brazos and Trinity incised valleys developed in response to base level fall. From the coast inland (~100 km) the depth and width excavated to create the incised valleys underlying the present lower reaches of both these fluvial systems appears to be similar, with the Brazos valley incised slightly deeper. Thus a strong similarity exists in fluvial response for both systems during sea level fall (highstand and lowstand systems tracts). Yet transgressive and earliest highstand aggradational fill of the Brazos and Trinity incised valleys represent the two end members of fluvial response to base level rise. The Brazos incised valley is overfilled (~50 km3) while the Trinity incised valley is underfilled (< 30 km3).

Ongoing research focuses on better defining the geomorphology and quantifying the fill of these two valleys, establishing the chronostratigraphy of the valley fill, and evaluating the role that antecedent topography and sediment supply play in suspended load sediment distribution within these two incised valleys.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005