The Oriskany sandstone and Onondaga formation are the principal producing formations in the 66 gas pools in the Appalachian area. Accumulation is due to favorable structural conditions in most of the pools. However, the areas of accumulation caused by stratigraphic trapping are more extensive and more than half of the total reserve of gas is in a large field in West Virginia which is productive because of interruption in porosity in an updip direction. Total reserves developed to date in the Oriskany and Onondaga gas pools are approximately 1½ trillion cubic feet.

Regional conditions have been important to accumulation. Early migration made some parts of the Appalachian basin more favorable than others for accumulation of gas in the Oriskany sand. Favorable structure seems to have had some effect on sand conditions, as well as providing a means of trapping.

In northern Pennsylvania and southern New York a producing province, including 34 pools, has been developed since 1930. These pools are structural traps caused by doming and thrust faulting along a series of prominent anticlines.

The province is described in some detail, and a structure map of the area is presented.