Southern North America
The Gulf of Mexico basin on the southeastern margin of North America is one of the most extensively studied basins in the world. Most of this work, however, has been concentrated on the shallower parts of the thick sedimentary section around the periphery of the basin, primarily related to the search for oil and gas and other minerals. Although comparatively little is known about the details of the more deeply buried parts of the sedimentary section and the crust below, enough geological and geophysical data exist now to enable compilation of a reasonable framework for the entire basin and document the evolution of the crust in general terms. The crust in the region contains the record of three successive phases of plate motion:
1. Divergent motion. Late Precambrian to early Paleozoic rifted margin and early Paleozoic south-facing passive margin along the southeastern edge of the North American craton.
2. Convergent motion. Late Paleozoic diachronous Appalachian-Ouachita orogenic belt, including foreland thrust belts, interior belts, and accreted terranes.
3. Divergent motion. Early to middle Mesozoic rifted margin and middle Mesozoic to present passive margin centered around a small ocean basin (present Gulf of Mexico basin).
Mesozoic rifting introduced a new set of extensional faults, including a northeast-trending rift set and a northwest-trending transform set. Some faults used planes of weakness related to late Paleozoic compressional structures, and the Mesozoic transform system essentially duplicated an early Paleozoic transform system. Mesozoic extension resulted in a broad area of stretched or attenuated continental crust (transitional
Figures & Tables
This volume presents syntheses in twelve chapters of the tectonic evolution of continent-ocean transitions of North America (Canada-Mexico-U.S.A.) since the Precambrian. The syntheses are interpretations based on the 19 continent-ocean transects across North American margins published by GSA as part of its Decade of North American Geology (DNAG) series. The transitional region is the part of North America between the craton, little deformed in Phanerozoic time, and the modern ocean basins. The region developed heterogeneously within plate boundary zones that led to sequences of passive, collisional, and active margins that differ place to place. Nine chapters address individual segments of the transitional region, two consider active and passive margin tectonics topically, and one treats the evolution of Phanerozoic transitions of North America as a whole.