. Annual report of the United States Geological Survey to the Secretary of the Interior . d the Navarro and Eoceneformation in the extreme eastern portion of the county. The entire county is underlain by the Trinity and Fredericksburg hill] ARTESIAN CONDITIONS IN WILLIAMSON COUNTY. 515 reservoirs. The Paluxy and Woodbine reservoirs do not extend intothis county. In the western part or district of the Lampasas Cut Plainthe Fredericksburg reservoir is not embedded, and hence need notbe considered. The Trinity reservoirs are available in the valleys ofthe many deeply-incised streams, such as the
. Annual report of the United States Geological Survey to the Secretary of the Interior . d the Navarro and Eoceneformation in the extreme eastern portion of the county. The entire county is underlain by the Trinity and Fredericksburg hill] ARTESIAN CONDITIONS IN WILLIAMSON COUNTY. 515 reservoirs. The Paluxy and Woodbine reservoirs do not extend intothis county. In the western part or district of the Lampasas Cut Plainthe Fredericksburg reservoir is not embedded, and hence need notbe considered. The Trinity reservoirs are available in the valleys ofthe many deeply-incised streams, such as the North and South Forksof the Salado, Barry Creek, the North and South Forks of the SanGabriel, and the headwaters of Brushy Creek, at depths of from 200feet on the western edge to 500 feet at the Balcones fault zone. The conditions in these valleys are very similar to those in theLampasas Valley in Bell County, already described, only the valleysare not cut quite so deep beneath the regional surface as is the valleyof that river, and hence the conditions for obtaining flowing wells are. Fig. 62.—Artesian map of Williamson County, Texas. Shaded portion indicates area where flowingwells may be obtained; 0, flowing wells from Trinity reservoir; Q, nonflowing wells from Trinityreservoir; figures indicate depths of wells in feet. inferior. In the district east of the Balcones fault line the Fred-ericksburg and Trinity reservoirs are both embedded, owing to thesudden downthrow of the geologic series of approximately 500 feetalong the fault line. At Round Rock, near the western border of thisdistrict, the lower Trinity reservoir is some 1,400 feet from the sur-face and more deeply embedded eastward, as shown in the discussionsof Bell County to the north and Travis County to the south. The conditions at the extieme eastern corner of the county are verysimilar to those at Marlin and Hubbard City, except that the Paluxyand Woodbine reservoirs encountered in those wells would not bereach
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