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Basement Structures Beneath Thrust Ouachita Rocks

Jan Golonka

The Ouachita foldbelt in Arkansas and Oklahoma involves a very complex structure. Generally all the exposed rocks in the Ouachita Mountains are strongly allochthonous and have been thrust as far as 50 mi northward from their former position. The overthrust surface is steep in the northern part of orogene, southward it is low angle, nearly horizontal, with two major elevated zones. The slope of the southwest surface is strongly dependent on the basement configuration.

The seismic surveys and well data indicate uplifted and depression-graben zones in the basement beneath overthrust Ouachita rocks. The northern uplift is the continuation of the Arbuckle Mountains. It is bordered on the north by the Anadarko basin. The axis of the uplift trends northeast through Oklahoma and Arkansas beneath the Potato Hills-Benton zone and beyond. The depths to basement range from 5 to 7 km. The southern uplift establishes a continuation of the Wichita Mountains. It trends east and northeast through northeastern Texas, Oklahoma, and south Arkansas and is connected with the Broken Bow zone. The depth to basement ranges from 5 to 7 km. In the depression zone, which lies between the two uplifts, the depth to basement is 9-17 km. This zone is a continuation of the Anadar o-Ardmore basin and probably of the Mississippi graben. The strong connections between autochthonous and allochthonous structural features proves a renewal of basement activity during the overthrusting of the Ouachita orogenic belt and afterward during the Late Pennsylvanian.

AAPG Search and Discovery Article #91034©1988 AAPG Southwest Section, El Paso, Texas, 21-23 February 1988.