Abstract

The early Miocene was a period of major continental margin progradation in the Gulf of Mexico Basin that accompanied prominent tectonic and climatic changes in North America. However, sediment pathways from continental upland sources to deep basinal sinks remain poorly constrained. This study presents 2192 new detrital zircon U-Pb analyses from 19 Lower Miocene samples spanning the entire northern Gulf of Mexico margin to elucidate early Miocene sediment provenance and paleodrainage systems. The U-Pb age patterns indicate that the Great Plains, southern Rocky Mountains, and mid-Cenozoic volcanic field were the major source terranes for the western-central Gulf of Mexico coast, whereas the Appalachian foreland basin and Appalachian Mountains mainly contributed sediment to the eastern Gulf of Mexico coast. Local source terranes included the Llano uplift and Edwards Plateau in central Texas and the Ouachita Mountains and foreland basin in Oklahoma and Arkansas. A comparison to previous detrital zircon studies around the Gulf of Mexico indicates that sediment recycling was important during the early Miocene.

Sediment associated with major paleorivers, including the Rio Bravo, Rio Grande, Houston-Brazos, Red, Mississippi, Tombigbee, and Apalachicola Rivers, can be differentiated using the detrital zircon U-Pb analyses. These data help to better define the early Miocene source-to-sink system in the northern Gulf of Mexico, by relating the basin fill to hinterland tectonic and geological evolution. In comparison to the Paleocene–Eocene Wilcox drainage system, the early Miocene drainage system of the northern Gulf of Mexico was smaller and received less input from western Mexico arc terranes and Archean basement in Wyoming. This drainage area reduction, related to regional thermal uplift and Basin and Range–Rio Grande rifting, likely explains the reduced sediment volume of the Lower Miocene strata in the Gulf of Mexico relative to the Paleocene–Eocene Wilcox Group.

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