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