Abstract

A southern proximal and a northern distal flysch facies are recognized in Mississippian lower Stanley strata over an area of 5,000 sq mi in the Ouachita Mountains of Oklahoma and Arkansas. Four widespread tuffs, each with distinctive lithologies, are interbedded with deep-marine turbidite sandstones and shales and serve as key units for detailed correlations of 8 sections 500 to 1,500 ft thick. The lower Stanley flysch is an ancient analog to one or more modern deep-sea fans and adjacent basin deposits. The lithologic character, sedimentary structures, bedding styles, fan-like geometry, ratio of sandstone to shale, and stratigraphic relationships of promixal and distal facies of the lower Stanley Group are similar to middle and outer margins of modern deep-sea fans and associated basin sediments off the coast of western North America. A proximal turbidite facies (probably a channeled suprafan) was deposited in the Hot Springs area of Arkansas at the same time a deep-water shale-rich facies accumulated in the southern and central Ouachitas of Oklahoma. During later Stanley time a proximal flysch facies prograded over the shale-rich facies of the southern Ouachitas of Oklahoma and represents deposition of a middle fan facies over an outer fan and basin plain facies. This proximal facies laterally changes to a distal flysch facies of apparent outer fan and basin plain deposition in the central Ouachitas of Oklahoma. The source area for lower Stanley strata was to the south-southeast, probably a northeastern continuation of the buried upper plate of the Luling thrust of Texas.

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