In east-central Texas, or the area between the Colorado
and Trinity Rivers, the Wilcox Group (lower Eocene) is divided
into three formations. Up section they are the Hooper,
Simsboro, and Calvert Bluff. At Alcoa and Butler, lower Calvert

Geologic map that depicts the surface geology of Burleson, Lee, Washington, and Brazos Counties and parts of Burnet, Bell, Milam, Robertson, Madison, Grimes, Waller, Austin, Fayette, Bastrop, Caldwell, Hays, Travis, and Williamson Counties.

The stratigraphic record of the Lower Cretaceous Trinity Division in Central Texas, as revealed by extensive outcrop investigation, is that of a shallow sea transgressing the southern flank of the ancient Llano Uplift.

Based on need for convenient, small-scale cartographic units, the basal Cretaceous rocks in Texas from Red River to Burnet County and on the Callahan Divide are herein divided into three distinctive lithologic sequences.

Sediments of the Fredericksburg Division in south-central Texas were deposited on the slowly subsiding west flank of the Tyler basin. In this region there are three stratigraphically distinct areas. The southern area has a thick Edwards Limestone unit overlying a thin Walnut Formation.

The first entry in the Guidebook Series details a field excursion to the Eastern Llano Region of Central Texas in 1958. Retrace the footsteps of Virgil Barnes and the other state geologists in attendance: 

Stop 1. Honeycut Bend

Fourteen black-and-white geologic maps prepared in 1957 and 1959 and obtained from the Department of Geological Sciences, University of Texas, and sold by the Bureau of Economic Geology. Geology compiled by F. L. Whitney; drafted by S. Espey, W. M. Strong, or W. L. Brooks; edited by K. P.

The eastern part of Williamson County is in the black land belt of Texas where roads must be surfaced to be passable in wet weather. Road materials are scarce in this area, so much of the time spent on the mineral resource survey was concentrated on finding gravel.

During the latter part of 1930, several wells were drilled into serpentine in the vicinity of Kimbro in Travis County. One of these, on the Allen farm, drilled in December 1930, is reported to have obtained oil in commercial quantities.