The area described in this report comprises 712 square miles centered on the City of Austin. The area extends north almost to Round Rock, south to the vicinity of Buda, east to just beyond Manor, and west to about 5 miles west of Oak Hill.

Over 7,000 miles of lineations have been observed on aerial photographic mosaics of the Texas Coastal Zone. These lineations, in part, represent the surface traces of faults originating in the Tertiary sediments and propagating through the Quaternary sediments.