Regional contour maps are shown on the surface of the Trenton in the western half of Ohio, and on the Berea and Clinton in eastern Ohio. The major structural features are the Cincinnati arch, as expressed by the Trenton, and less conspicuously, the syncline (Parkersburg) and adjacent Cambridge anticline as shown by the Berea in eastern Ohio. Structure contour maps are given for four areas in eastern Ohio. These are for the Berea in southeastern Meigs County and northeastern Muskingum County, for the Berea and shallow sands in the junction of Guernsey, Noble, Belmont, and Monroe counties, and for the Clinton sand in the Homer field of Knox and Licking counties.

The majority of the producing fields of eastern Ohio display some relationship to structure, although the relationship is ideal in but few cases. Structural highs are generally barren, the production lying on the flanks of anticlines or even in the upper ends of synclinal embayments. There is, then, a structural relationship, though not in the stricter sense in which the anticlinal theory was once applied. Most of the oil and gas accumulations are associated with some kind of structural irregularity. As a rule, there is a definite parallelism between the trend of production and the strike of the rocks. In a few places accumulation appears to be entirely a matter of lithology, notably in the Cow Run sand of the Chester Hill field, in Athens, Morgan, and Washington counties. In general, three factors appear to govern accumulation: local structure, water content and energy of movement in the sand, and the porosity of the sand. Since local structure exerts some influence on both water content and artesian conditions in a given sand, structure is regarded by the writer as the dominant factor.

These remarks as to accumulation apply to the Berea and higher sands. The Clinton has long been known as a sand practically devoid of water, although this classification can be accepted only as relative. Because of the lack of reliable key beds, the rapid divergence from surface beds, and the lenticularity of the Clinton, one cannot be sure of structure as mapped for the Clinton. Clinton production appears to be along a transition zone where the sand thins and is replaced to the west by shales.