ABSTRACT

The Jackfork Group is one of the major stratigraphic units of the Carboniferous flysch succession that is exposed in the central Ouachita Mountains of Oklahoma. In an idealized shelf-to-basin transect (northwest to southeast) the group thickens from 810 ft to 6900 ft, with sandstones being the dominant lithology.

Using the methodology of Morris and others (1979) flysch facies can be recognized in the field by rock composition and bedding characteristics. Facies show a northerly decrease in the number of thick, 3A facies sandstone-on-sandstone, rubble bed and fans (2B facies) and 2C facies.

The thicker successions of Jackfork sandstones are thought to have been confined in a basinal position by large-scale escarpments created by down-to-the-basin normal faults. This tectonic activity may also have generated rubble fans and beds within the Jackfork Group, intermittently stacking and commingling them with the westward-building deep-sea fan complex.