The Texas Mud Blanket: Understanding Fine-Grained Sediment Flux in the NW Gulf of Mexico During the Previous Transgression

Robert Weight
Rice University Houston, Texas
[email protected]

The evolution of the Texas Mud Blanket is presented from 26 new radiocarbon dates and from ~3000 km of 2D seismic data. Sediment flux (km3/ka) was calculated from this combined dataset. XRD reveals that the mud blankets origins are local, coming mostly from the Colorado and Brazos Rivers.

Elevation differences between Stage 3 and Stage 2 shorelines created accommodation on the central Texas shelf. Between LGM and 17 ka reefs began to grow on Stage 2 deposits and terrestrial to marine sediments filled the deepest areas. 17-9 ka was a time of rapid eustatic rise (~7 mm/year) and low mud blanket sedimentation (0.4 km³/ka). By ~12 ka, the Brazos and Colorado rivers had formed delta’s on the shelf, but sediment flux to the mud blanket remained low (0.4 km³/ka). At 9 ka, sediment flux in the mud blanket increased to 41 km³/ka. At the same time, the Brazos and Colorado deltas were being ravined, producing ~61 km³ of sediment. Of this, ~58.3 km³ of fine-grained sediments were winnowed into the mud blanket. By ~5 ka, Texas was experiencing maximum temperature and minimum precipitation for the Holocene, which led to a reduction in significant sediment accumulation in the mud blanket. Since 5 ka, sediment supply to the mud blanket has been regulated by climate changes. During the last 3.5 ka the mud blanket received 172 km³ (57% of total volume) of fine-grained Colorado and Brazos sediments carried away by longshore coastal currents and transported offshore at the zone of convergence.

AAPG Search and Discovery Article #90094 © 2009 AAPG Foundation Grants in Aid