Stratigraphy is emphasized and discussed in some detail. Nomenclature follows that generally used along the Nemaha Ridge, where correlations between more closely spaced wells have recently been made by the writer and others. The remarkable lateral continuity of similar lithologic characteristics of the marine Permian is contrasted with the more variable beds in most of the Pennsylvanian. Under some conditions these lithologic variations form stratigraphic traps.

The most favorable conditions for the accumulation of oil in stratigraphic traps probably occur in the lower Pennsylvanian (Morrowan?) as wedge-outs updip in a part of the area. The reservoir rock is the basal Pennsylvanian sandstone which was deposited as a transgressive overlap on the Mississippian.

Structure is briefly discussed and illustrated. Apparently only minor variations occur on a monocline which dips southward into the Anadarko basin.

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