Influence of Mid-Continent Rift System on Occurrence of Oil in Forest City Basin

Marvin P. Carlson

The late Keweenawan Mid-Continent rift system (MRS) created a fracture pattern which has been reactivated and imprinted onto younger rocks. Studies of the MRS have focused on its depositional environments and internal structure. Also of importance to petroleum exploration was its effect on the facies and structural trends within Paleozoic rocks. The Southeast Nebraska arch, a post-Early Ordovician reactivation related to the MRS, is defined by Middle Ordovician (Simpson) overlap of Arbuckle equivalents. Continuing differential movement along the MRS within the North Kansas basin influenced the regional facies of both the Upper Ordovician (Viola) and the Upper Devonian (Hunton). Mid-Pennsylvanian compression from the Ouachita orogeny produced the Nemaha uplift and reactiva ed transcurrent faulting on the MRS. Extensions of these southeast-trending fractures created offsets on the Nemaha uplift/Humboldt fault system and enhanced structures which host oil production within the Forest City basin. Fields which lie upon these transform trends have produced from the Simpson (St. Peter), Viola, and Hunton. Analysis of the magnetic and gravity data provides an interpretation of the secondary structures within the MRS and, by extrapolation, an additional exploration tool not available from the subdued geophysical expression of the Paleozoic rocks. The MRS should be evaluated both as a frontier province internally and as a predictor for the occurrence of oil in younger rocks.

AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.