The last sea-level highstand (between 125,000 and 40,000 yrs BP) resulted in the deposition and preservation of a wide variety of depositional environments on the northern Gulf of Mexico shelf. A combination of studies, spanning from west Florida to south Texas and utilizing a database of over 20,000 km of high-resolution seismic data and hundreds of industry platform boring descriptions, have yielded strike- and dip-oriented cross-sections and paleogeographic maps that illustrate profound lateral variability in highstand deposits across the shelf.

High sediment supply, bedload-dominated systems, such as the Rio Grande, produced sandy delta lobes; whereas, suspended load-dominated fluvial systems, such as the Brazos River and western Louisiana drainage system, produced muddy delta lobes. Low sediment supply, bedload-dominated systems fed by shallow braided streamplains formed large sandy delta lobes on the West Florida/Alabama shelf. Non-fluvial, interdeltaic regions, such as the central Texas shelf, exhibit highstand barrier-bar shoreline sand bodies, which are sourced by longshore and nearshore wind-driven currents. The highstand deposits range in thickness from 10 to greater than 200 m, and the sand bodies associated with different depositional systems are upwards of several thousand square km in area.

The styles of highstand deposition over repeated glacial eustatic cycles and within a given segment of the shelf exhibit repetitive patterns. This implies that depositional models that incorporate such factors as amount and type of sediment supply, shelf width and gradient, subsidence, and tectonics can be used to predict reservoir character and distribution.

Paleogeographic map of highstand depositional environments in the Gulf of Mexico

Gulf Bottom Imagemap

Comments, questions? Contact us at gulf@gulf.rice.edu.