Stratigraphic Facies Relationships and Structural Trends of the Spiro Formation, Frontal Ouachita Mountains, Southeastern Oklahoma

HINDE, LAWRENCE K., Baylor University, Waco, TX

The lower Atokan Spiro Formation is a well-known gas reservoir in the Arkoma basin. The recent explosion in gas exploration from the Spiro is providing valuable new data for a comprehensive stratigraphic study of this formation.

The Spiro Formation consists of laterally interfingering sandstone, shale, and limestone that can be categorized into bar crest, bar flank, bar margin, and interbar facies. The stacked shallow-marine shelf bars were derived from reworking of upper Morrowan Foster channel sandstones. In the eastern part of the outcrop belt, the Spiro primarily is sandstone with a thickness of up to 150 ft that represents predominantly bar crest, bar flank, and bar margin facies. To the west, the Spiro thins to about 60 ft in thickness and consists mostly of limestone with lesser amounts of sandstone. In this area, the sandstones exhibit sedimentary characteristics of bar margin and interbar facies. South of the present-day Pine Mountain fault, slope and basinal sediments accumulated, whereas east of th outcrop belt (along the frontal zone) the Spiro grades into a shale facies.

Late Pennsylvanian thrust faulting produced a narrow belt of several fault repeated sequences, which crop out only in the frontal Ouachita Mountains. Differences in thrusting styles between the eastern and western parts of the outcrop belt reflect variations in lateral lithologic character and perhaps subthrust structure. Palinspastic restoration of thrust sheets establishes a basis to determine paleodepositional trends and geometries.

AAPG Search and Discovery Article #91011©1991 AAPG Southwest Section Meeting, Abilene, Texas, February 9-12, 1991 (2009)