Sedimentary and Tectonic History of Ouachita Mountains: ABSTRACT

Abstract

The Ouachita Mountains of Oklahoma and Arkansas contain Paleozoic flysch-like geosynclinal rocks exposed by elongated east-west folds and thrust faults. Approximately 5,000 ft of Cambrian to Devonian flysch consists predominantly of dark slates and cherts, comprising a classical starved succession. Minor incursions of mature sands, apparently from the North American craton, invaded the trough at three different intervals. The succeeding Carboniferous, almost 40,000 ft thick, consists of proximal and distal turbidite sandstones, black shales, and minor interlayered wildflysch and volcanic ash. Sedimentary structures indicate southwestward, westward, and northwestward sand dispersal. Sandstone compositions suggest a cratonic, quartz-rich provenance as well as a fel spathic, lithic extracontinental source. The tectonic setting may well have been due to oceanic crust spreading northwestward, plunging under continental crust, and creating an island-arc-trench-subduction zone whose present location is overlapped by post-Paleozoic rocks. Northwest of the trench, a complex of slope, rise, and abyssal sediments formed upon the depressed outer margin of continental crust. East of the Ouachitas, continent-continent collision caused suturing of Africa and North America, which created source materials that were subsequently emplaced as a westward-building subsea cone during the Carboniferous. In the Ouachita area, continued subduction finally created a series of uplifted tectonic lands resulting in northward sliding of the sedimentary succession as continentward-directed folds and thrust sheets. ubsequent stress-field orientation changed so that the area then became dormant. End_of_Article - Last_Page 796------------