STRATIGRAPHY AND STRUCTURE OF PART OF FRONTAL OUACHITA MOUNTAINS, ARKANSAS

Geologic mapping locates major faults and folds and shows the distribution of major stratigraphic units in the frontal Ouachita Mountains of Arkansas. The units constitute a thick Carboniferous flysch sequence with gradational depositional contacts. Three major high-angle, east-west-trending thrust faults cross the area and probably flatten out to become bedding-plane thrusts. At one folded fault plane, the upper plate apparently has been eroded away, exposing the lower plate for almost 30 mi along the upwarp. Folded thrust planes have not been described previously in the frontal Ouachitas of Arkansas and the exposed window in the map area comprises the largest such structure anywhere in the Ouachita Mountains. Tables, plates, maps, and diagrams illustrate formations.