LATE CRETACEOUS UPLIFTS OF THE NORTHERN AND NORTHWESTERN GULF OF MEXICO

Three types of uplifts in the Late Cretaceous of the northern and northwestern Gulf of Mexico can be defined, primarily by subsurface control. Type I Uplifts are closely associated in space and time with igneous activity. These uplifts are 20-130 km across with uplift of 100-2000 m, and include the Uvalde, Jackson and Monroe Uplifts. Type II Uplifts are broad domes (or portions of domes) with gentle flanks associated with a general locus of igneous activity. The largest uplift is the Southern Arkansas Uplift, which strips pre-Tuscaloosa strata from most of northern Louisiana. Its inferred diameter is 350 km and maximum uplift could reach 3000m. It is centered about at Little Rock, and may include much of Arkansas. A smaller, satellite uplift in east Texas (Rusk Uplift, pre-Austin) is not associated with known igneous rocks, but a buried intrusion is likely present. Type III Uplifts occur in central Texas along the trend of the San Marcos Arch, where at least five smaller unconformities occur from late Albian through earliest Cenozoic time. One larger unconformity, the Bigfoot Unconformity (mid-Maastrichtian) reaches farther south and truncates the northern rim of the Rio Grande Embayment. All three types of uplifts are associated with important petroleum and CO₂ accumulations.

Type I uplifts are likely the result of doming around crustal-level magma reservoirs and thermal effects caused by them. Type II uplifts must have a subcrustal origin, related to upwelling mantle (either deep plume or shallower convection cell). Type III uplifts are best explained as a forebulge related to subsidence in south Texas and adjacent Mexico, possibly a foredeep to Sierra Madre thrust loading.