Geology . by laterbeds, but are exposed at various points where the strata have beenelevated, and the overlying beds removed by erosion. The mosteasterly outcrops of the system are found in Texas,2 Indian Territory,3and South Dakota. The Triassic system may underlie the later for-mations west of these localities, and between them and the Rockies. 1 There is some doubt about the age of most of the beds formerly referred to thissystem. The tendency of later study has been to refer more and more of them tothe Permian. See references under Permian, and Hill, Physical Geography of theTexas Region,
Geology . by laterbeds, but are exposed at various points where the strata have beenelevated, and the overlying beds removed by erosion. The mosteasterly outcrops of the system are found in Texas,2 Indian Territory,3and South Dakota. The Triassic system may underlie the later for-mations west of these localities, and between them and the Rockies. 1 There is some doubt about the age of most of the beds formerly referred to thissystem. The tendency of later study has been to refer more and more of them tothe Permian. See references under Permian, and Hill, Physical Geography of theTexas Region, folio U. S. Geol. Surv. 2 See last foot-note. 3 Gould, Univ. of Kansas Quarterly. THE TRIASSIC PERIOD. 25 Throughout most of this area, the Triassic beds are red, and in theabsence of fossils, and of structural unconformity, are not readily differ-entiated from the Permian In Texas the beds generally regarded as Triassic underlie theStaked plains of the western part of the State, and outcrop along. Fig. 335.—Triassic sandstone five miles south of Lander, Wyo., showing characteristic cross-bedding. (Branson.) their eastern base. The deposits of this locality show that the waterin which they were laid down was shallow and fresh, and the beliefis that the sediments entered it from the In the Black Hills of South Dakota3 unfossiliferous, gypsiferousbeds (Spearfish) which are believed to be Triassic overlie the Permianconformably,4 and underlie the Jurassic unconformably. The rela-tions of the Triassic to the Permian and Carboniferous indicate thatthough the interruption of sedimentation at the close of the Paleozoicera was by no means complete in this part of the continent, the marinesedimentation of the earlier era gave place to salt-lake sedimentationin the later. A series of nearly unfossiliferous strata, among which are many Red beds occupying the stratigraphical position of the Triassicsystem, outcrop interruptedly along the eastern base of the Rockiesfrom Bri
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