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The stratigraphic layers that currently make up the Petrolia Formation have been studied since 1890, when Cummins coined the "Wichita Beds" or Wichita Group. This original description of the group, it was a large, undifferentiated rock unit rather than multiple formations.^[1] The Wichita Group was later split into a total of seven formations by Plummer and Moore in 1921, though none of the formations coined by the authors are used today.^[2] The formation coined during this time that makes up a majority of the stratum now assigned to the Petrolia Formation was the Belle Plains Formation. Plummer and Moore originally defined the formation as the thick limestone strata between the Elm Creek Formation and the Bead Mountain bed.^[3] Between this 1921 publication and the late 1980's, the Belle Plains Formation was used to define these layers of rock in northern Texas. In 1988, however, Tucker F. Hentz published a complete revision of the Wichita Group which would cause the Belle Plains Formation to become an obsolete term for theses layers of rock. Instead of the seven formations defined in 1921, the Wichita Group was instead condensed into three formations: the Nocona, Petrolia, and Waggoner Ranch Formations. This revision placed the base of the formation as equivalent to the Elm Creek Formation rather than above it along with the undifferentiated Jagger Bend and Valera Formations. This change in the base of the formation causes some of the strata originally assigned to the upper Admiral Formation to also be included into the Petrolia Formation. However, unlike in the original interpretation, the Admiral Formation is strictly a part of the more southern Albany Group rather than being the basal-most formation of the Wichita Group.^[2] Since the 1988 paper by Hentz, the stratigraphy of the Petrolia Formation has stayed consistent, though the term "Belle Plains Formation" will be mentioned in papers covering fossils found in the past due to the now-obsolete name's long history of use.^[4]

The Petrolia Formation has had exposures found in both northern Texas and southern Oklahoma with the southern-most limit of the formation, like other formations within the group, being where the formations of the Albany formations begin. This cutoff is represented in the Brazos River within southern Baylor County. Exposures of the formation are found throughout drainage areas of the Red Rivers located in the Archer, Baylor, Clay, and Wichita counties of Texas along with the Jefferson county, Oklahoma. The stratotype of the formation is located in Wichita county, being represented by a mudstone escarpment that underlies the Beaverburk Limestone.^[2]

As a whole the Petrolia Formation, has a maximum depth of between 110–120 metres (360–390 ft). Within the group, the formation represents a transition between the more sandstone-rich underlying formations and the more mudstone-rich overlying formations. This is shown by the higher prevalence of mudstone when compared to the lower formations along with the presence of limestone that is only present in the upper formations. Even with this being the case, the sandstones seen within the formation have more similarities to the underlying Nocona Formation. The formation can be differentiated from other more continental portions of the red beds by the presence of the overlying Beaverburk Limestone, though this can only be used south of the South Fork of Buffalo Creek. Below are the descriptions of the constituent lithologies within the formation.^[2]

The strata that make up the Petrolia Formation represent both freshwater and marine environments with a coastal plain with evidence of meandering rivers, lakes, and marshes being present within the more continental areas of the formation. The muddy point-bar deposits are similar to what is seen in suspended-load rivers found in the midwestern US and eastern Australia. Along with these more permanent bodies of water, ephemeral streams are also found within the formation. These streams most likely represent a number of things such as tributaries, splay channels, and other more short-lived bodies of water. Though rare, only being present in the uppermost portion of the formation near Wichita County, marine environments are preserved within the formation. These represent the beach and shallow marine areas surrounding the more continental environment.^[2] Two separate floras are seen at the formation with those being a more water-dependent tree-fern-dominated assemblage and a more drought tolerant conifer-dominated assemblage. This is most likely due to the tree ferns being much more common near the margins of the rivers and marshes than outside of them.^[6] Based on this, the formation most likely represents a seasonally dry tropical environment. This would suggest a largely dry climate with short but extreme wet seasons, similar to what is seen in the slightly younger Clear Fork Group.^[7]