Abstract: Jackfork Sandstones, Shallow Water Sequence Stratigraphy and Sedimentology, U.S. 259, La Flore County, Oklahoma

Roderick W. Tillman

The Morrowan Jackfork Group, where it crops out in the Ouachitas, has long been regarded as a deep-water, primarily turbidite, deposit. Recent work in southeastern Oklahoma indicates that at least two or more periods of significant shallowing occurred during the deposition of the Jackfork. Upper Jackfork outcrops along U.S. Highway 259, originally described by Lewis Cline and Frank Moretti in 1956, are herein interpreted as shelf, slope, and deltaic deposits.

These interpretations suggest that new and varied exploration plays exist in the Jackfork. The relatively shallow water deposits occur in the uppermost part of the Jackfork Group.

Several significant sequence-stratigraphic surfaces occur in the Jackfork Group. Relatively abrupt shallowing is evident at what are interpreted to be sequence boundaries at the base of the Prairie Mountain formation and at the base of the shelf and deltaic deposits that form the lower part of the Markham Mill formation. Significant flooding surfaces are observed between the slope and overlying shelf deposits in the upper Prairie Mountain formation and either in the upper part of the Markham Mill formation or at the base of the Wesley formation. A third flooding surface may occur at or near the base of the Game Refuge formation.

Slope, shelf, and deltaic deposits in the Jackfork Group are characterized by features distinctly different from those of the turbidites in the Wildhorse Mountain formation, which forms the lower two-thirds of Jackfork along U.S. 259.

AAPG Search and Discovery Article #90957©1995 AAPG Mid-Continent Section Meeting, Tulsa, Oklahoma