The McPherson anticline trends NNE-SSW and traverses the arch between the Salina and Cherokee basins in Kansas. It extends 50 miles and contains ten multi-pay oil and gas fields that produce from reservoirs in Paleozoic rocks. Subtle structural movement occurred throughout Paleozoic time, but the anticline is primarily a Late Mississippian - Early Pennsylvanian feature. It has a steeply dipping down-to-the-west fault on its western flank that has up to 400 feet of throw. Culminations (and greater vertical offsets along the flanking fault) are generally adjacent to N-S-trending fault segments. Lesser vertical offsets along the flanking fault and structural sags are associated with NNE-SSW-trending fault segments. Reverse faulting is indicated by repeated stratigraphic sections encountered in wells, thus an overall right-lateral NNE-SSW wrench-fault regime can account for the distribution of structural traps.
The cross-fault juxtaposition of the Devonian-Mississippian
Chattanooga Shale against a given pay zone may affect the chemical
characteristics of the produced oils. Oils produced from Mississippian
strata, relatively high in the section, have chemistries that
suggest a mature Chattanooga Shale source rock and south-to-north
migration up the crest of the anticline. Similarly, oils produced
from pay zones in Ordovician rocks, where the Chattanooga Shale
across the fault is shallower than the pay zone, are typical "Ordovician"
oils of low relative maturity. If, however, because of faulting,
an Ordovician-age pay zone is located above or directly against
the Chattanooga Shale, then oils produced from the Ordovician
pay zone may have compositions indicating mixing of Chattanooga-Shale
oils with "Ordovician" oils.