GEOPHYSICAL ANALYSIS OF THE LAURENTIAN BASEMENT UNDERLYING THE BLACK WARRIOR BASIN

The crustal structure of southeast Laurentia is related to processes that occurred from the Mesoproterozic to the Cretaceous. In the Mesoproterozoic, terrane accretion occurred during the formation of the granite rhyolite province. The subsequent Grenville orogeny that assembled Rodinia produced intrusions and crustal thickening along the eastern – southeastern margins, stretching from southeast Canada to northwest Alabama. The Neoproterozoic – earliest Cambrian rifting and fragmentation of Rodinia created the Laurentian basement outlined by the rift margins and segmented by transform faults. The AL-OK transform fault, which connects the Alabama and Texas promontories, is the southern end of the Reelfoot Rift, an early Paleozoic NE-SW striking aulacogen.

The early Paleozoic Laurentian passive margin accumulated transgressive sequences over the basement structures. During the Late Paleozoic Alleghenian orogeny, sediment deposition within the NE-SW trending Black Warrior Basin further buried the Laurentian basement. The basin homocline extends from the Nashville Dome to the syntaxial bend between the Appalachian and Ouachita thrust belts. The purpose of this project is to investigate the crustal structure of the Precambrian Laurentian basement underlying the Black Warrior Basin using gravity and magnetic data. Bouguer gravity and residual gravity anomaly maps indicate NE-SW trending gravity maxima with sources between 11.25 and 37.5 km based on upward continuation maps. These gravity maxima correlate with magnetic maxima on both reduced to the pole and residual magnetic maps which suggests the sources are linear mafic bodies underlying the Black Warrior Basin.

Keywords: Laurentia, Rodinia, gravity/ magnetic anomalies, Black Warrior Basin, Alleghenian orogeny, Reelfoot Rift