Tectonic Setting and Structure of Pre-Salt, Mesozoic Rift Basins in the Northeastern Gulf of Mexico

Abstract

The northeast-trending Apalachicola rift (AR) in the northeast Gulf of Mexico (GOM) is ~220-km- long and contains 5-7 km of undrilled clastic and volcaniclastic deposits inferred to be a syn-rift of Late Triassic-Early Jurassic age. Previous workers have interpreted pre-salt (Triassic-Early Jurassic), basinward-dipping reflectors in the AR as either: (1) clastic sedimentary fill with volcanic intrusives that are contained and tilted within Mesozoic half-grabens, or (2) as layered, igneous units ("seaward-dipping reflectors") erupted during GOM phase 1 rifting of late Triassic- early Jurassic age. I integrate mapping results from a five-layer, 3D gravity inversion model to determine the crustal thickness of the GOM and the southern continental of North America. From this regional crustal thickness map, I can trace the northwest-trending Florida lineament for over 740-km along a 35-km-wide corridor of thinned continental crust ranging in thickness from 23- to 26-km that abruptly truncates northeast trends of the Appalachian fold belt, the Paleozoic Suwannee Basin and Suwanee Suture Zone, the Mesozoic South Georgia rift system, and the Apalachicola rift described here. The Florida lineament aligns precisely with the 450-km-long Pickens-Gilbertown-Pollard fault zone that truncates the southeastern edge of the Appalachian orogenic belt in the Mississippi Valley. This extensive Florida-to-Arkansas northwest strike-slip zone likely formed as a right-lateral indenter fault along the eastern edge of the Yucatan block during Late Paleozoic collision and was reactivated as a left-lateral transfer fault during Late Triassic-Early Jurassic continental rifting.

AAPG Datapages/Search and Discovery Article #90369 © 2020 AAPG Hedberg Conference, Geology and Hydrocarbon Potential of the Circum-Gulf of Mexico Pre-salt Section, Mexico City, Mexico, February 4-6, 2020