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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said to constitute a mappableunit in the counties of Grayson, Cooke, Denton, Tarrant, and Johnsononly, and is therefore of less areal importance than other subdivi-sions of the Washita division. Its lithologic identity fades out to thenortheast in Indian Territory, but is distinctly recognizable in theChickasaw Nation northwest of Marietta. It continues as a recog-nizable formation as far south as the Brazos, being exposed 4 milesnorth of Blum and south of Rio Vista. South of the Brazos thisformation loses its lithologic and paleontologic identity, its positionbeing occupied on the Colorado by the lithologic phase of the George-town limestone in that direction. These beds have a total estimatedthickness of about 194 feet at Denison and about 40 feet at FortWorth.1 1 The Duck Creek fossils occur in the base of a bluff north of the public square. This containsGvyphxanavia, Hamites fremonti, and Iaehydiscu* brazoensis. U. S. GEOLOGICAL SURVEY TWENTY-FIRST ANNUAL REPORT PART III PL. XXXV
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UfflVffWTY of ILLINOIS HILL.) LOWER CRETACEOUS BEDS AT FORT WORTH. 259 FOKT WORTH FOUMATIOX. DEFINITION AND GENERAL CHARACTER. The term Fort Worth formation as originally applied by the writerwas used for a conspicuous white limestone and marl formation whichmay be traced almost entirely across Texas. For reasons which willbe apparent in the following pages, this name will hereafter be usedin a more restricted sense for that portion of the formation lyingnorth of the Brazos, and the term Georgetown formation will be usedfor its modified continuation south of that stream. The Fort Worth formation, as exposed in the railway cuts north ofthe Union Station at Fort Worth (see fig. 31), and underlying all the

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