Taha, Z. Patrick1
(1) Rice University, Houston, TX
ABSTRACT: Fluvial Response to Base Level Change: The Role of Temporary Sediment Sequestering on the Brazos Alluvial and Coastal Plains
The significance of quantifying the volume and timing of continental sediment stored by the Brazos fluvial system is four fold: 1) to better understand how much sediment is sequestered during sea-level rise as accommodation space is generated, 2) to obtain long-term sediment flux values (calculated from sediment storage, chronostratigraphy, and rates of sea level rise), 3) to relate changes in sediment flux to climate variability, and 4) to generate a more integrated coupling of continental/marine sequence stratigraphy over one complete glacial-eustatic cycle.
Previous studies of the last glacial-eustatic cycle provide minimum values for delta volumes produced on the continental shelf by the Brazos River: 34.2 km3 for early highstand lobe (Stage 5e-5b); 3 km3, 9 km3, 22 km3, and 58 km3 for late highstand lobes (Stages 5a-3), and 13.4 km3 for lowstand wedge deposits (Stage 2). No volumes have yet been calculated for transgressive delta deposits.
Good seismic and stratigraphic control of flooded incised valleys in close proximity to the modern Brazos fluvial/deltaic system (Trinity, Matagorda, Corpus Christi) provide an approximate volume that could be contained within the fluvial-filled Brazos valley on the coastal plain (ex: Trinity ~ 15 km3). Current studies indicate the lower Brazos valley (within the coastal and alluvial plains) could contain as much as 50 km3 of sediment. This volume does not account for valley fill on the shelf nor the possibility of periodic valley purging caused by climatic events. On going research focuses on better defining the geomorphology and fill of the subsurface valley and climatic effects on the long-term sediment flux.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.