Geologic map of the Squaw Creek Quadrangle, Gillespie and Mason Counties, Texas

The Squaw Creek quadrangle is partly within the Llano region and partly within the Edwards Plateau province. The Edwards Plateau is continuous along the southern border of the quadrangle, but erosion has dissected it until long fingers extend northward, the most important being between Mormon and Squaw Creeks and east of Squaw Creek. The geology of the Squaw Creek quadrangle is shown on a planimetric map, and the only topographic map available is the reconnaissance 30-minute Kerrville quadrangle. Elevations ranging between 1,721 and 2,207 feet were determined during traversing for control, but neither the highest nor the lowest elevation was reached. However, it is estimated that the relief within the quadrangle is about 620 feet, ranging between about 1,600 and 2,220 feet in elevation. The quadrangle is almost entirely within the Llano River drainage basin and is drained by Squaw Creek and Threadgill Creek and its tributaries Mormon and Dry Mormon Creeks. The water reaches Llano River by way of Beaver Creek. A small area in the northeastern corner of the quadrangle is drained by Pecan Spring Branch and reaches Llano River through Marshall Creek and Hickory Creek. An extremely small area in the southeastern corner of the quadrangle drains into Pecan Creek and reaches Pedernales River by way of Live Oak Creek. Squaw Creek quadrangle is high on the southern side of the Llano uplift, and rocks of Cambrian and Ordovician age outcrop in the northern part of the quadrangle. Faults in these rocks are related to the Ouachita orogeny. The Cretaceous rocks are essentially horizontal, dipping northward perhaps a few feet per mile. A small fault in the Cretaceous is exposed in a road cut 3 miles east of Doss. Broader discussions of the stratigraphic, structural, economic, and geophysical problems of the region cannot be given in the space available. References cited below deal with some of these problems. This publication on the Squaw Creek quadrangle is one of a series of similar publications, an index to which is shown on the opposite page. The reader is referred to this index map to locate other quadrangles mentioned in the present text.