. Annual report of the United States Geological Survey to the Secretary of the Interior . by Noland River and the Leon, the beds 21 geol, pt 7—01 14 210 BLACK AND GRAND PRAIRIES, TEXAS. have considerable thickness and are beautifully exposed as wide andfertile areas of agricultural lands. No measurements have been madeof their thickness within this region, however. Similar but less exten-sive areas occur in the valleys of the eastern portion of the Lampasasand at the falls of the San Gabriel River. The Walnut beds formagricultural lands as far south as Liberty Hill, Williamson County,and Bertr
. Annual report of the United States Geological Survey to the Secretary of the Interior . by Noland River and the Leon, the beds 21 geol, pt 7—01 14 210 BLACK AND GRAND PRAIRIES, TEXAS. have considerable thickness and are beautifully exposed as wide andfertile areas of agricultural lands. No measurements have been madeof their thickness within this region, however. Similar but less exten-sive areas occur in the valleys of the eastern portion of the Lampasasand at the falls of the San Gabriel River. The Walnut beds formagricultural lands as far south as Liberty Hill, Williamson County,and Bertram, Burnet County. In northern Bell, southern Lampasas, Williamson, and Travis coun-ties the Walnut beds have considerable exposure in fragmentary patchesalong the slopes of the various forks of the San Gabriel and Lampasasrivers. In the vicinity of Bertram and Bagdad the formation con-stitutes areas of agricultural land and has an estimated thickness of30 or 40 feet. Along the Lampasas it shows greater thickness andits general thickness increases from east to west, being nearly 80. Fig. 24.—A butte near the Blanco-Travis county line, Texas. (For explanation of lettering, sit ri. XVI, p. 110.) feet at Bachelors Peak and 55 feet at Twin Sisters Peak, in westernLampasas County. At Bachelors Peak it shows at the base bands offossiliferous limestone containing great numbers of Eeogyra marcoui, and Trigonia, alternating with thick layers ofyellow, argillaceous lime marl. Above this there are 15 feet of massiveshell agglomerate composed almost exclusively of Exogyra teaxrna,Gryphcea marcoui, and occasional specimens of Sr/doenbacMa aauto-carmata. Above this to the top there is a zone of chalky stratifiedlimestone, representing the base of the Comanche Peak beds. The Walnut subdivision at the edge of the Colorado Valley west ofAustin is from 10 to 15 feet thick. The formation is beautifully shownin the plateau region west of Austin. Here it makes a thin stratum of
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