--> ABSTRACT: Foreland Structural Style and Hydrocarbon Occurrence: The Middle Urals (Russia) and Southern Appalachians (USA), by James H. Knapp, Konstantin O. Sobornov, Robert D. Hatcher Jr.; #91020 (1995).

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Foreland Structural Style and Hydrocarbon Occurrence: The Middle Urals (Russia) and Southern Appalachians (USA)

James H. Knapp, Konstantin O. Sobornov, Robert D. Hatcher Jr.

The Uralian orogen of central Russia and the Appalachian orogen of eastern North America are major collisional belts of Paleozoic age, whose culmination in late Paleozoic time resulted in assembly of the Pangean supercontinent. The stratigraphic section in the foreland of the Middle Urals is characterized by a thick (up to 7 km) Upper Proterozoic clastic sequence, and relatively thin (~3 km) Middle and Upper Paleozoic section. The Cambrian through Ordovician section is notably absent, and surface exposure of coal deposits suggest that ~1-1.5 km of section has been removed by erosion. In the Southern Appalachians, the entire Paleozoic section is ~3.5 km thick, and is missing the entire Devonian section. A thick Upper Proterozoic sequence is preserved to the east of the for land in the western Blue Ridge. Comparison of the foreland structural styles in the Middle Urals and the Southern Appalachians reveals a similar geometry of foreland-vergent imbrication of passive margin sediments with a ramp-flat geometry. The width of the deformed foreland in the Appalachians (180 km to the Hayesville fault) is considerably greater than in the Urals (40-75 km). Similarly, estimates for foreland shortening in the Southern Appalachians (180 km, Woodward, 1985) are substantially greater than those for the Middle Urals (50 km). Differences in amount of shortening may be related to the nature of continent-continent collision (Appalachians) versus extensive accretion of island-arc and microcontinental terranes (Urals). Major hydrocarbon accumulations (66 BBOE) in the Volga-U al basin of the Urals occur primarily in Devonian and Carboniferous reservoirs within the mildly deformed margin of the East European plate. In contrast, cumulative reserves in the Southern Appalachians are relatively minor, which may be related to (1) source rock potential and/or (2) maturation history. The foreland thrust belt of the Urals is presently underexplored, and seismic data here suggest new sub-thrust structural plays.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995