The Bartlesville sand, which produces high-grade oil throughout a region 100 miles long and 50 miles wide, centering in Greenwood and Butler counties, Kansas, occurs in narrow, elongate lenses, each ranging from 50 to more than 100 feet thick, 0.5 to 1.5 miles wide, and 2 to 6 miles long. The lens-shaped bodies are systematically arranged approximately end to end, forming several systems, or trends, each 25 to 45 or more miles long.

Although some facts disclosed by the study appear to indicate somewhat conflicting conclusions, much evidence clearly indicates that the sands were deposited as two systems of offshore bars of slightly different age, bordering the western coast of a shallow sea which occupied much of eastern Kansas and northeastern Oklahoma in Cherokee (Pennsylvanian) time. Certain features in the trends of modern offshore bar systems, found to be characteristic of the Bartlesville trends, are important in extending oil production into unproved areas.

A map showing the thickness of the Cherokee shale in eastern Kansas is included to show the relationship of the ancient shore lines with the Nemaha granite ridge on the west and a broad land area which extended eastward through central-eastern Kansas and there formed a low barrier in parts of Cherokee time. The probable method of burial and preservation of the ancient offshore bars is described, and examples of burial of bars in recent time are cited.