Descriptive, geologic, and borehole geophysical logs for 23 test holes in south-central Nebraska

This report presents logs for 23 test holes drilled in eight counties in south-central Nebraska as part of a study of the hydrogeology of the area. Five logs are presented for each of the test holes. The first is a written description summarizing the sediments penetrated during drilling; the second is a geological log providing a diagrammatic representation of the stratigraphic units; the remaining three show spontaneous potential, single-point resistance, and natural-gamma radiation measured in the test holes. The test holes penetrate silts, sands, and gravels of Quaternary age, and siltstones, sandstones , and silts of the Ogallala Formation of Tertiary age. Each test hole was drilled deep enough to penetrate about 20 feet of the underlying Cretaceous-age bedrock. (USGS)