Identification and tabulation of geological contacts in the Edwards aquifer, San Antonio area, Texas

Geological contacts were picked on logs of about 480 wells in the San Antonio area of the Edwards aquifer. The base of the Del Rio Clay is the most frequently picked contact because it is the top of the Edwards aquifer and also because it is easily identified on either gamma-ray or electric logs.

Other important formation contacts identified were the Austin Group, the Eagle Ford Group, the Buda Limestone, and the Glen Rose Formation. These contacts were usually easy to identify on either gamma-ray or electric logs.