File:Annual report of the United States Geological Survey to the Secretary of the Interior (1899) (14576836698).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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gradually loses its bituminous character and becomesmore and more calcareous with decreasing thickness southward fromRed River, until, at the San Gabriel, it finally ceases to form a recog-nizable horizon. PALEONTOLOGY OK THE KIAMITIA FORMATION. Apparently there is no other bed of rocks in the Texas Cretaceoushaving the extent and thickness of the Kiamitia clays which containsso few species of fossils. GrypTvam corrugata, 0. navia Hall (Exogyraforniculata White), ScJdoenbachia belknap-ii Marcou, and Exogyratexanq are the only known fossil forms in the Kiamitia clay proper(see PI. XXXV). Gryphcea <-rrti<j<it<i is the principal and charac-teristic fossil of this formation, occurring in great numbers in theclay and forming the mass of the indurated layers. Grypham cor-rugata occurs in the lower portion, rarely ranging higher than 6 feetabove the base. Exogyra texana (see PI. XXVII. fig. L) is rare, U. S. GEOLOGICAL SURVEY TWENTY-FIRST ANNUAL REPORT PART VII PL. XXXIV
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GRYPH/EA CORRUGATA BRECCIA, KI AM IT IA FORMATION, D EN I SO N , TEXAS. .LL/NO/S U1LL.J DUCK CEEEK FORMATION. 257 but its occurrence has heen noticed in the bluffs of Brazos River northof Greenock, Bosque County. Schloenbachia belknapii Marcou also occurs abundantly in theKiamitia formation. This ammonite ranges up into it from theFredericksburg division. In the transition bed at the top there are, besides S. belknapii andG. corrugata, Terebratula choctmcen«*\ Exoyynt plexa, G. imxhita,and Avicula leveretti. In considering some of its fossil remains, like Exogyra texana andSchloenbachia belknapii, Taff has expressed doubts as to whether thisformation in the areas of its marginal extension could be separatedsufficiently from the Fredericksburg division to give it the status of adistinct formation, although throughout a large area of northern Texasand southern Indian Territory it is a well-defined, conspicuous, andmappable unit. He therefore included it in the Fredericksburg divis-ion.

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