The Joins, Oil Creek, McLish, Tulip Creek, Bromide, and Corbin Ranch Formations of the Simpson Group were correlated throughout the subsurface of Oklahoma in order to (1) establish formational equivalents between measured surface sections in the Arbuckle and southwestern Ozark Mountain regions, (2) determine erosional or depositional limits of each of the formations, (3) illustrate suspected existing interformational regional disconformities, and (4) provide basic operational units from which thickness and gross lithologic data could be derived quantitatively for construction of a series of isopach and facies maps.

A technique of lithofacies expression based on the classifying function ("D-function") is advanced. The method was conceived by Pelto (1954) as a means of mapping multicomponent systems alternative to methods devised by Krumbein and Sloss (1951). With one exception (Forgotson, 1960, p. 88), the classifying function technique generally has not been utilized in practical application. Simplicity of map design, compared with corresponding composite maps based on percentages and ratios, the extreme rapidity with which the maps are constructed, and the facility of tectonic and environmental interpretation justify recognition of this method as a usable mapping tool.

Detailed subsurface correlation and faunal evidence substantiate the thesis that the thin lower Tyner-Burgen sequence cropping out along the southwestern flank of the Ozark uplift is equivalent to at least the lower part of the thick Oil Creek Formation of the Arbuckle region. The middle Tyner shale is considered by the writer to be McLish, and the upper Tyner dolomitic limestone and Fite Limestone are herein correlated conjunctively with the Corbin Ranch Formation. A distinct break in sedimentation between the upper and middle Tyner beds represents a significant hiatus during which time Tulip Creek and Bromide strata were eroded from the Ozark area.

The Simpson Group contains many interformational unconformities and onlap pinchouts of both regional and local magnitude. Intraformational discontinuity on a lesser scale is suspected but not confirmed. The Joins and Tulip Creek Formations are limited essentially to the southern half of Oklahoma as a result of non-deposition and only locally by erosion. The Tulip Creek and superjacent Bromide Formation are absent from eastern Oklahoma owing to erosion from the Ozark uplift in Black Riveran time. Absence of the Corbin Ranch Formation locally below Viola strata in the Arbuckle and eastern Wichita Mountains is evidence that minor incipient tectonism of these elements occurred in post-early Trenton time.