Abstract

Two stages of regional cross-fold jointing reflect the rearrangement of a lithospheric-plate-scale stress field during the Ouachita (i.e., Alleghanian) orogeny. These joints overprint northward-verging thrust-related folds in the Ouachita foreland. Stage-one jointing during the Ouachita orogeny is associated with a stress field recorded by an Atokan and earlier regional joint set, which has a NNE strike. Stage-one jointing is separated into two phases in the central Ouachita salient, where a second-order recess is marked by a prominent bend in the Windingstair fault below the forelandmost sheet of the central thrust belt. The Big Cedar recess developed when the Windingstair sheet overrode the frontal imbricate zone, thereby causing the Big Cedar pinch zone, a structure reflecting fold-parallel shortening proximal to localized dextral transpression in the Choctaw thrust sheet. A later regional joint set, representing the second stage of jointing during the Ouachita orogeny, affects rocks in the Arkoma foreland as well as in the fold belt. Stage-two jointing records a stress field associated with NNW-directed closure during the final stage of plate convergence; this stage persisted into the Desmoinesian.

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