Abstract

The Stanley-Jackfork-Johns Valley-Atoka rocks of the Ouachitas and the Tesnus-Haymond sequence of the Marathons typify what Alpine geologists call black shale flysch. Wild flysch and calcareous flysch also are represented.

In late Mississippian and early Pennsylvanian time a minimum of 22,500 feet of alternating sandstones and shales was deposited in a rapidly subsiding, linear trough. During the cannibalistic stage of the Ouachita geosyncline, (sensu lato) the Oklahoma-Arkansas trough probably was but one part of an 1800-mile foldbelt stretching from the Marathons to the Appalachians. Deposition of fine pelitic muds and siliceous shales was interrupted hundreds of times by deposition of quartzose sandstones. The sandstones debouched from a shelf environment exhibit convolute bedding, graded bedding, sole marks and other features now commonly ascribed to turbidity current deposition.

The foldbelt is structurally complex, with several major thrust faults striking parallel to the axis of the foldbelt and thrust toward the craton. Where observed at the surface the thrusts emerge at high angles but some (at least) seem to flatten with depth and probably become bedding plane faults.

The facies patterns and structural characteristics compare closely with those of the Polish Carpathians, Swiss Alps, and Italian Apennines and the characteristic sedimentary features are duplicated in intricate detail in the four mountain systems. Direct comparisons will be made between the Ouachita flysch and that of the classical European areas.