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North America |
Hudnall Professor and Chairman, Department of Geology, 252 Bowman Hall, University of Kentucky, Lexington, Kentucky 40506, USA
The Alleghenian-Variscan-Hercynian orogeny in eastern North America has five structural domains: (1) Newfoundland-Maritime (northern) platform; (2) northern Appalachian Maritime-New England Variscan belt; (3) Alleghenian platform; (4) central-southern Appalachian (Alleghenian) orogen; (5) Ouachita belt. Connections between these domains are generally faulted or unexposed and the domains are heterogeneous.
There is a major discontinuity between the northern Appalachians and central-southern Appalachians. In the northern Appalachians the Variscan orogeny is distinct from the Acadian, but not so in the central-southern Appalachians. The Alleghenian overthrusting of the southern Appalachians is still to be traced to the north where the whole of southern Nova Scotia may be totally allochthonous.
Also, the northern but not the southern belt appears to have suffered in Devonian to Carboniferous times a sinistral strike-slip movement of about 2000 km. By taking this movement into account it is suggested that the four Appalachian domains have been assembled in Devonian-Lower Carboniferous time by transcurrent faulting and deformed in the late Carboniferous-Permian times by subduction-related processes.
The geology of the Ouachita belt is different from the southern Appalachians and their unexposed connection is still enigmatic. The timing of orogenic events in the two domains also differs.
It is possible that the Ouachitas were deformed by collision with the South American plate, while the Appalachians were deformed by collision with the African plate.
