STRUCTURAL INTERPRETATIONS OF THE FRONTAL OUACHITA-ARKOMA BASIN TRANSITION ZONE IN WESTERN ARKANSAS

The Arkoma foreland basin was formed from a Late Paleozoic continent-continent collision between Laurentia and Gondwana (current-day North America and South America). The basin encompasses an area from south-central Oklahoma to central Arkansas adjacent along strike of the Ouachita fold and thrust belt. The stratigraphy of the transition zone is dominated by a thick sequence of Pennsylvanian clastics that exceed 30,000 feet. During the Pennsylvanian, sediments were accumulated in the basin which was bounded to the north by the continental margin of Laurentia and to the south by northward advancing thrust sheets. This clastic succession represents the evolution of the south-facing Precambrian to Pennsylvanian aged miogeoclinal rocks to a rapidly subsiding foreland basin that preserved a thick synorogenic wedge ahead of and deformed by the Ouachita Orogeny.

Constraining the structural geometry and magnitude of shortening within the frontal Ouachita-Arkoma Basin transition zone is fundamental to understanding the nature of thrust propagation into foreland settings. The transition zone between the highly-deformed Ouachita frontal thrust belt and the mildly-deformed Arkoma foreland basin is exposed at the surface in western Arkansas allowing field mapping techniques to be utilized in the structural interpretation. The Ione and Barber quadrangles are located at the intersections of Logan, Scott, Franklin, and Sebastian Counties in central-western Arkansas. A structural cross section based on field mapping, 2-D depth-converted reflection seismic profiles, and electronic petrophysical well logs across these quadrangles reveals mildly deformed Pennsylvanian aged formations creating the southern limb of the broad Washburn anticline, located between the north-vergent leading edge thrust of the frontal Ouachitas and the north-vergent Washburn fault.