Recognition that bedrock structure is reflected by modern topography in many areas has helped in successful exploration for petroleum reservoirs. However, application of this relation in other areas has proved unsuccessful. In such areas, older geologic patterns are concealed by divergent younger ones. Mapping of buried topography related to the older structural patterns may be an exploration technique deserving consideration.

Two established oil regions in Nebraska--one in the southern part of the panhandle (D-J basin) and the other in the southwestern part of the state (Cambridge arch area)--have no recognizable relation between modern topography and underlying petroleum reservoirs. However, mapping of buried unconformities shows a definite relation between the occurrence of oil fields and paleosurfaces. In western Nebraska, oil and gas fields producing from Cretaceous sandstones coincide with paleotopographic ridges on the pre-Tertiary surface with striking regularity. Similarly in southwestern Nebraska, oil fields producing from Pennsylvanian strata coincide fairly well with paleotopographic highs on the pre-Cretaceous surface.

This relation between established oil reservoirs and overlying paleotopography in 2 entirely different geologic regimes indicates a predictability pattern that should be utilized in future development in these and other petroleum-producing regions.

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