Abstract: Foreland Deformation and Hydrocarbon Potential Resulting from Rotational-Oblique, then Head-on Continent-Continent Collision in the Appalachian Orogen

Robert D. Hatcher Jr.

The Appalachians are the product of Carboniferous to Permian initial oblique collision followed by rotational head-on continent-continent collision between Africa and Laurentia. Initial oblique contact between the two continents in the north (Carboniferous) resulted in dextral strike slip throughout the orogen. Clockwise rotation of Africa (+/- counterclockwise rotation of Laurentia) produced head-on collision (Late Carboniferous-Permian) in the southern half of the orogen. This resulted in the Blue Ridge-Piedmont megathrust sheet and foreland deformation of the Precambrian-Paleozoic rifted margin, carbonate platform, and clastic wedges (Ordovician, Devonian-Early Carboniferous, Late Carboniferous-Permian). Hydrocarbon reservoirs developed in primary (intergranular) and secondary (fra ture) porosity in both the Alleghanian (Carboniferous-Permian) and Acadian (Devonian) clastic wedges. An unexplored region of known natural gas seeps and abundant late methane fluid inclusions exists within the western Blue Ridge thrust sheet in Tennessee, North Carolina, and Georgia, where surface geologic and seismic reflection data indicate the Paleozoic platform has been overthrust >200 km. 3-D palinspastic reconstructions of the foreland and Blue Ridge thrust sheet indicate appreciable thicknesses of fractured unmetamorphosed platform sedimentary rocks could be present beneath the sheet. The Appalachians are a useful analog for exploration in less well-known collisional orogens.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994