Coastal Carolina Project 2001 - Kure Beach
Data

This borehole geophysical log graphic illustrates the use of various methods to describe hydrogeologic units, such as aquifers and confining layers.

The natural gamma ray log (GAM(NAT)) provides a measure of total gamma radiation passively detected within the corehole. The radiation is from naturally occurring radioisotopes, such as potassium-40 and daughter-products of the uranium-238 and thorium-232 decay series. In coastal North Carolina, natural gamma logs are used to identify increasing clay content (confining units for aquifers), phosphatic sands, and glauconitic lithologies.

The resistivity logs (RES(16) and LATERAL)) provide a measure of bulk formation resistivity and ground-water resistivity. For example, if the formation resistivity remains constant, and the resistivity log decreases, one may infer an increase in dissolved solids content in the ground water within the formation.

The fluid resistivity log (RES(FL)) is a direct measurement of the resistivity of the borehole fluid. In general, the dissolved solids content of the ground water flowing into the corehole from various aquifers is measured. Inflections in the fluid resistivity log indicate that ground water having different dissolved solids content is flowing into or out of the borehole. For example, the large decrease in fluid resistivity in the Kure Beach corehole from about 25 to 35 ft may indicate the presence of much higher dissolved solids in the ground water at this depth.

The temperature log (TEMP and DEL TEMP) is a direct measurement of the temperature of the borehole fluid. In general, the geothermal gradient is about 0.47 to 0.6 °Celsius per 100 ft of depth. However, if ground-water flow occurs within the borehole, inflections may be observed on the temperature log. For example, an overall decrease in borehole temperature is observed at a depth from about 106 to 116 ft in the Kure Beach corehole, which may indicate outflow of ground water from the corehole at that depth. The temperature difference log (DEL TEMP) helps isolate larger variations within the temperature log. These larger variations or measurements of delta temperature generally are observed where ground-water is moving into or out of the borehole.

Graph created in WellCAD by Melinda Chapman, USGS

This is a stratigraphic and paleontologic summary of the Cretaceous and Tertiary of the Kure Beach corehole. The geologic units listed in the "Group" column are provisional and do not necessarily reflect the opinions of all members of the Coastal Carolina Consortium. Calcareous nannofossil zonal picks are based on the zonations of Sissingh (1977) and Perch-Nielsen (1985), as calibrated to the timescale of Gradstein et al., (1995) by Burnett (1998). This figure is a work in progress.