The Jackfork Group is a flysch deposit which crops out along the frontal Ouachita Mountains and the Athens Plateau of Arkansas. Along the frontal Ouachitas, the 5,400-ft section is 70 percent shale, most of which is contorted by soft-sediment deformation. The lack of siliceous shale zones within the Jackfork does not permit Oklahoma stratigraphic nomenclature to be used; therefore, two new formations of approximately equal thickness are proposed. On the Athens Plateau, the group is 6,000 ft thick and consists of 70 percent wackes and arenites. Pitkin Limestone exotics in the underlying Chickasaw Creek Formation suggest that the Jackfork was deposited during the formation of the Pitkin-Hale unconformity.

Differences in thickness, mineral composition, sedimentary structures, and sand-shale ratios allow the construction of a depositional model. Poorly sorted, indistinctly bedded rocks, considered to have been deposited as delta-front and prodeltaic sediment, are present along the southeastern Ouachitas. Sedimentation appears to have resulted chiefly from suspension and redistribution by weak tractional currents and slumping. Proximal turbidites, which developed very near the inception of turbidity flows, consist of thick-bedded sandstones generally with scoured bedding contacts, and are present throughout the eastern parts of the belts. Distal turbidites become more common westward, and are thinner bedded, poorly graded, laminated sandstones with abundant hieroglyphs. Beds disturbed and disrupted by soft-sediment deformation developed at the foot of a northern unstable slope. This allochthonous material entered at right angles to the basinal turbidites which flowed westward down the trough axis. Highest sand-shale ratios parallel the axis of the trough, whereas slope deposits contain higher pelitic contents that are commonly disturbed.