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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dby the occurrence of the fossils contained in it and by the character of the rock.Its chalky whiteness, as it occurs at Round Rock, is a contrast to the dull-blueflagstones below and to the Kiauiitia and Fort Worth limestone above. Thisbed is about 6 feet thick. The rocks of this bed are involved in the disturbanceincident to the great fault along the line of their outcrop. Hence in but fewlocalities has it been possible to study them satisfactorily. In the valley of theSan Gabriel they have been totally concealed by the downthrow of the fault. The total thickness of the Edwards limestone described in this .sectionl>v Mr. Taif is 188 feet. The writer is inclined to believe that, owingto difficulties in connecting the outcrops, this thickness is underesti-mated by at least -AO feet. Northward from the Colorado River in Travis County the variable,arenaceous, flinty strata of the upper part of the Edwards limestone U. S. GEOLOGICAL SURVEY TWENTY-FIRST ANNUAL REPORT PART VII PL. XXXII
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UNOIS hill.) VARIATIONS OF THE EDWARDS LIMESTONE. 237 thin out and become more chalky, and finally lose their hard and sandycharacter as the immediate valley of Brazos River is approached. The Edwards limestone on Brazos River in McLennan, Hill, andBosque counties is composed of homogeneous strata with little varia-tion, ranging in thickness along the river basin from east to west from10 to 33 feet. Fossil Bequienia and Budistes occur throughout, butare not very abundant. At the summit there is a narrow band of lime-stone bearing Caprma crassifibm and associated forms en masse. Thehorizon of Requienias crops out in the bluffs of the Brazos oppositeGreenock, Bosque County, in the base of Coon Creek, in the bluffs ofRocky Creek north of Greenock, in the low bluffs at the edge of theBrazos River basin east of Towash, Hill County, and in the. bluffs ofNolands River from its mouth to a point 4 miles above Blum, JohnsonCounty. In the valley of the Clear Fork of Trinity River, as seen 2 mile

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