. Annual report of the United States Geological Survey to the Secretary of the Interior . e Wichita Mountains, by H. FosterBain, has appeared. (See Bull. Geol. Soc. America, Vol. II, pp. 127-144, Rochester, March, 1900. i conclusions concerning the age of these mountains are as follows: It is evident that there was a pre-Cambrian land mass of igneous rocks, and that overthis was laid down an undisturbed sequence stretching from the Cambrian up to and including theTrenton. Then came the main upheaval and the intrusion of the granite. Around the edge of thenew mountains the Geronimo ser
. Annual report of the United States Geological Survey to the Secretary of the Interior . e Wichita Mountains, by H. FosterBain, has appeared. (See Bull. Geol. Soc. America, Vol. II, pp. 127-144, Rochester, March, 1900. i conclusions concerning the age of these mountains are as follows: It is evident that there was a pre-Cambrian land mass of igneous rocks, and that overthis was laid down an undisturbed sequence stretching from the Cambrian up to and including theTrenton. Then came the main upheaval and the intrusion of the granite. Around the edge of thenew mountains the Geronimo series was laid down. The shearing and faulting of the granite andthe presence of greenstone dikes cutting it, with the true though slight dip of the Geronimo be d-,indicate later disturbances of lesser degree. Since the intrusion of the granite, however, the mainhistory of the region has been one of vigorous and long-continued erosion, through which themechanical sediments of the Red Beds and later deposits were prepared and distributed. aproc. Am. Philos. Soc, Vol. XXXVI, 1808, p. OIS HILL.] CAMBRIAN STRATA. 89 been frequently considered an Archean nucleus, have been shown tobe of Algonkian age. It has been generally thought that the Ozarkuplift represented the survival of an ancient upland, but Marbut,Davis, Griswold, Keyes, and others who have recently given theregion special study from both the geographic and the geologic stand-point, agree in regarding the uplift as it now stands as a very modernfeature of relief, not earlier than middle or late Paleozoic Sedimentary Rocks. The sedimentary Paleozoic rocks of the Texas region, constitutingthe floor of the Cretaceous formations, belong to five great systems, theCambrian, Ordovician or Lower Silurian, Upper or true Silurian,Carboniferous, and Permo-Triassic. The Devonian may also haveinconspicuous representation in the complex of the Ouachita Moun-tains of Indian Territory, but need not be considered at present
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