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Late Cretaceous Magmatism and Source-to-Sink Configuration in the Northwestern Gulf of Mexico

Abstract

It has been demonstrated that emplacement of 92-108 Ma post-breakup alkalic magmatism and attendant structural culminations in Louisiana and Arkansas facilitated mid-Cretaceous surface uplift, development of unconformities in updip areas, and incision of fringing reefs along the northern Gulf of Mexico thereby promoting the development of depositional fairways that permited transport of Late Cretaceous coarse siliciclastic sediments into to the deep water gulf. Previous explanations for the mechanism driving this magmatism center on the passage of the North American plate above the “Bermuda” hotspot. The age and location of the Balcones igneous province in south Texas, however, do not support the hotspot model. To the west, the Balcones igneous province, exposed for 397 km from Austin to Carizo Springs, Texas, was emplaced between 83.5 and 72.4 Ma. It also roughly parallels the Balcones fault system, Llano uplift, and possibly the Luling uplift. Should the previously proposed hypothesis of the Sabine and Monroe uplifts in northern Louisiana providing the mechanism for incision and transport of siliciclastics past the fringing carbonate shelf prove true, the same effect could have occurred in south Texas. Breaching of fringing reefs associated with the magmatism may occur ca. 10-30 Myr later in the Late Cretaceous (83.5-72.4 Ma). This younger magmatism and structural domes along the San Marcos Arch predicts the development of basinward expansion of sand rich areas in the abyssal plain during the Campanian. Sediments younger than 80 Ma are predicted to have exploited and filled these incised valleys and presently are located in the Port Isabel and Perdido areas. Shear wave velocity models of the crust are used to construct an improved image of basement structures along the Texas Gulf Coast. Their spatial association with post-breakup magmatic alkali rocks suggests local surface uplift during the Campanian (Upper Cretaceous). Interpretation of GulfSPAN regional 2D seismic reflection profiles suggests the presence of south-facing incised valleys in the Lower Cretaceous Washita Group and Glen Rose Formation. This study incorporates the influence of magmatism and will shed light on the source-to-sink configuration in the NW Gulf of Mexico during the Late Cretaceous.