Numerous new geologic and geophysical data collected in recent years in the Ouachita province by industry, government, and academic institutions allow an updated synthesis of events that shaped the southern margin of North America in the Paleozoic.

Some new key observations include: (1) radiometric data indicate both Devonian and late Paleozoic metamorphic events affected the core areas of the Ouachita Mountains; (2) long-suspected pre-Desmoinesian orogenic uplift that supplied detritus into the foreland basins of the Ouachita system is well displayed on seismic data and has been confirmed by the drill. Weakly deformed Desmoinesian and younger, shallow marine to continental successor basin sediments overlie with angular unconformity the folded and thrusted Ouachita facies rocks beneath the Gulf coastal plain as far south as the Sabine uplift; (3) high-quality field work, especially in Arkansas, has yielded ample data that support a polyphase deformation in the core areas of the Ouachita Mountains. Movements consisted of at least one north-vergent thrust and fold phase primarily of Pennsylvanian age. Initial folding and thrusting were followed (probably in Permian time) by a south-vergent overturning of previous geometries, additional folding and thrusting, and the development of north-dipping cleavage; and (4) plate tectonic reconstructions of the opening and closing of the Iapetus Ocean and the formation and breakup of Pangea have added to the understanding of the events that led to the origin of the Ouachita system. Nevertheless, big data gaps remain.

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