REGIONAL CORRELATION OF THE PALEOZOIC STRATIGRAPHY OF THE OUACHITA SALIENT, AND IMPLICATIONS FOR TECTONIC HISTORY

Mostly buried beneath the Mesozoic-to-Recent Gulf Coastal Plain, imbricated and folded Paleozoic rocks of the Ouachita-Marathon orogen extend sinuously southwestward from eastern Mississippi to southwest Texas. The Ouachita salient is a sharp deflection in the Ouachita-Marathon orogen that extends northwestward from eastern Mississippi to eastern Oklahoma, and then southwestward to central Texas. The Ouachita Mountains of eastern Oklahoma and western Arkansas are the largest exposure of Paleozoic rocks within the Ouachita-Marathon orogen. Comparison of stratigraphy of predominantly deep-marine facies Paleozoic formations of the Ouachita Mountains with shallow-water correlative formations located in the foreland provides clues to regional tectonic history.

A new chronostratigraphic correlation chart based upon a compilation of published sources correlates shallow-water facies formations within the foreland of the Ouachita salient. Another new chronostratigraphic chart correlates shallow-water facies formations with deep-water facies equivalents. Deep-water facies formations can be placed in approximated restorated position. Regional unconformities of varying lateral extent separate the Paleozoic section into discrete packages. In some areas, unconformity surfaces are highly time-transgressive.

A generalized restored stratigraphic cross section constructed across the center of the Ouachita salient shows regional variations in formation thicknesses and lateral facies changes. The cross section extends in zig-zag trace from the Ardmore basin of eastern Oklahoma east to the Broken Bow uplift region, southeast to northern Louisiana and northward towards the southern flank of the Ozark dome. Stratigraphic columns of allochthonous deep-water facies rocks from several locations within the Ouachita Mountains are approximately restored relative to the autochthon. This new restoration suggests a Late Ordovician transgression of deep-water facies shales and cherts onto the Paleozoic carbonate platform of eastern Oklahoma (and to a lesser extent in Arkansas). The facies transition is near the southeastern edge of the Tishomingo anticline and may bend into the southeastern Ardmore basin.