The Ouachita Embayment of Southern Laurentia in the Rodinia-Iapetus and Pangaea-Atlantic Wilson Cycles

The Iapetan Ouachita embayment is within a bend of the Grenville front in the Rodinia assembly. During late-stage continental rifting and breakup of Rodinia, the Ouachita rift and Alabama-Oklahoma transform framed the Argentine Precordillera microcontinent, which vacated the Ouachita embayment. Synrift and passive-margin deposits indicate earliest Cambrian rifting followed by post-rift thermal subsidence with complementary asymmetry on the conjugate margins (Texas promontory and Precordillera microcontinent). The Middle-Late Ordovician Ocloyic orogeny reflects terrane transfer and accretion of the peri-Laurentian Precordillera terrane to western Gondwana. On Laurentia, a passive margin extended around the Ouachita embayment by Late Cambrian and persisted until Mississippian. Taconic (Ordovician-Silurian) and Acadian (Devonian-Mississippian) orogenesis northward from the Alabama promontory is not expressed west of the corner of the Alabama promontory.

Tectonic loading (Ouachita orogeny) by accretion of a forearc complex began in the eastern Ouachita embayment (Black Warrior foreland basin) in Mississippian and migrated westward along the transform margin into the Ouachita embayment (Arkoma foreland basin) in Early Pennsylvanian. A wide sedimentary accretionary prism (Ouachita orogen) separates Laurentian continental crust from a continental-margin arc on the south, indicating no continental collision or terrane accretion within the Ouachita embayment. Post-orogenic shallow-marine deposits (Middle Pennsylvanian-Late Permian) mark the end of Ouachita orogeny in the embayment. Continental collision of African crust with the corner of the Alabama promontory drove Appalachian northwest-directed thrusting, which imbricated the easternmost part of the older Ouachita foreland and thrust belt. Suturing of African crust (Suwannee terrane and possibly Wiggins terrane) completed assembly of Pangaea along eastern Laurentia. Breakup of Pangaea and opening of the Atlantic and Gulf of Mexico followed a transform (Bahamas fracture zone) that reoccupied the trace of the Iapetan Alabama-Oklahoma transform. The Atlantic rift margin of the Florida promontory cut across the suture, leaving African crust (Suwannee terrane) attached to southeastern North America.