File:Annual report of the United States Geological Survey to the Secretary of the Interior (1899) (14576795238).jpg

Identifier: annualreportofun2171geol (find matches)
Title: Annual report of the United States Geological Survey to the Secretary of the Interior
Year: 1880 (1880s)
Authors: Geological Survey (U.S.)
Subjects: Geological Survey (U.S.) Geology Water-supply Forest reserves Mines and mineral resources
Publisher: Washington : G.P.O.
Contributing Library: University of Illinois Urbana-Champaign
Digitizing Sponsor: University of Illinois Urbana-Champaign

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accessory. Thus the calcareous rocks of the Glen Rose forma-tion are partially arenaceous, especially at their base, the siliceousgrains being so tinely triturated that they are an almost impalpablepowder. This siliceous material gradually diminishes upward in thebeds, and the lime increases proportionately in both the indurated bedsand the marls. Toward the top of the Glen Rose the limestones areagain slightly arenaceous. The indurated beds consist of strata of brecciated crystalline, arena-ceous, magnesian, or chalky texture. They are white, yellow, and It is important to note that the Sycamore and Hensell sand beds axe Strikingly analogous to thewater-bearing beds denominated t1 and t2 on the deep-well descriptions, and that the Cow Creekbed corresponds in position to great thicknesses of limestone between the sands in the Austin. Belton.and Waco wells. 2See Bull. No. V, Geol. Survey of Texas, Austin, 1889, p. xiv. U. S. GEOLOGICAL SURVEY TWENTY-FIRST ANNUAL REPORT PART VII PL. XXI
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HILL.) THE GLEN ROSE FORMATION. 145 sometimes blue-gray on fresh fracture. Some are made up ofminute fragments of shells, which give them a granular pseudo-ooliticstructure. This is seen at Mount Bonnel, west of Austin, in manylayers of induiated stones and marls. Others, like the Orbitulitesbed, are chalky in character. The stratification of these beds is conspicuous in the landscape onaccount of the manner of weathering. The alternating beds of softmarls and hard limestones weather into numerous small cliffs andstratum plains, resulting in a compound terrace effect along theslopes and the many round hills and incised canyons of the LampasasCut Plain and the Edwards Plateau southward. The softer stratabetween the indurated layers readily disintegrate into a marly earth,yellow to white in color, while the harder layers weather into verticalledges, which break down into fragments as the softer bands fall awayfrom beneath them. Nearty all well-exposed sections of the Glen Rose formation

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