The Cumberland oil field is on a closed, faulted anticline the discovery of which was the result of a coordinated program of surface, subsurface, magnetic, and seismic exploration. Comanche formations exposed in the area rest unconformably on the Springer formation of Pennsylvanian age. The stratigraphic section of Springer and older formations penetrated in drilling does not differ materially in thickness and character from the equivalent section exposed in the Arbuckle Mountains on the northwest. The closed faulted anticline is in a down-faulted block of sedimentary rocks on the south flank of the Arbuckle Mountains. The structure, probably formed in late Pennsylvanian pre-Permian time, is not reflected in the normally dipping Comanche beds. All oil produced to date fro this structural trap comes from sands of the Bromide, McLish, and Oil Creek formations of the Simpson group of Ordovician age. Total production as of January 31, 1947, was a little less than 22 1/2 million barrels of good average-grade Mid-Continent crude.