Sediment Flux Variations Correlated with Climate Zones of the Gulf of Mexico for the Past 10kyr

Kristy Milliken¹, Patrick Taha⁴, Alex R. Simms², Antonio B. Rodriguez³, Jessica Maddox⁵, and John B. Anderson^1
1Earth Science, Rice University, Houston, TX
²Boone Pickens School Geology, Oklahoma State University, Stillwater, OK
³Institute of Marine Sciences, University of North Carolina, Morehead City, NC
⁴Chevron, Houston, TX
⁵Marathon Oil Company, Houston, TX

Modern day drainage basin characteristics of Gulf Coast rivers vary by an order of magnitude in size, relief, and precipitation. Some rivers terminate in bays (i.e. Trinity, Sabine/Neches, Calcasieu, Lavaca, Nueces) while others deposit deltaic sediment at the shoreline (i.e. Brazos). Drainage basin characteristics control sediment flux which explains the variation in depositional environments at the shoreline (bay versus delta).

This study focuses on the fluvial/delta/bay complexes of the northwestern Gulf. For each system we have quantified 1) the valley volume (accommodation space) created during low-stand incision, 2) the volume of fluvial, deltaic, and bay sediment that fills each valley, and 3) mass accumulation rates (sediment flux) for each valley. High-resolution seismic data coupled with continuous core provide the means to map facies variations and bounding surfaces within each valley. These data, along with robust radiocarbon chronologies, are then used to determine volume and MAR changes through time.

Comparison of drainage basin characteristics, accommodation space, and MAR show similarities between these variables. For example, the drainage basin area and relief, as well as accommodation space, of the Calcasieu river/valley is 5 times smaller than the Trinity - Galveston river/bay system. Furthermnore,mass accumulation rates for bay-head-delta facies are ~5 times less. For total bay-head delta deposition, the Calcasieu and Trinity-Galveston system sediment flux can be modeled as simple drainage basin geology scaling. But, comparison of the valley fill between the Brazos and Trinity valleys shows ~3 times greater MAR in the Brazos system for equivalent accommodation space. Climatic conditions, in conjunction with drainage basin geology, must control the efficacy of sediment delivery during the period of sea-level rise.

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas