100

break, so far as is known, into beds marked by the appearance of considerable thicknesses of limestone and of certain species associated with the Carboniferous fauna which have been referred to the Permian. These beds are shales, massive sandstones, conglomerates, and limestones, aggregating 1,500 feet (more or less) in thickness, of the type of those of the Neosho-Chase section of Kansas. These beds have been well studied in Kansas by Prosser, but little investigation has been made of their continuation south into Indian Territory. They are homotaxially the equivalent of the Coleman formation of Texas. In Texas the sedimental change indicating this formation is noted in the beds at the base of Tarr's Coleman division, which are included in the top of the Cisco division of Cummins and Drake. These transitional beds, for which, in the absence of a more satisfactory classification, the name Permo-Carboniferous may be provisionally retained, have a thickness of 1,500 feet in Kansas at the northern end of their strike, and 1,200 feet along the Colorado River of Texas. Their relation to the Ouachita uplift has not been studied or made out.

They uniformly occur in a belt along the western margin of the main bodies of the Carboniferous formation of the Muscogee, Palo Pinto, and Colorado districts, but do not occur in the Smithwick and Ouachita districts. They grade, so far as known without break, into the true Red Beds.

No Upper Carboniferous or later Paleozoic rocks have yet been discovered on the coastward (eastern and southern) side of the general Carboniferous area.

So far as known, the Permo-Carboniferous formations of the Central region, in southern Kansas, Indian Territory, and Texas grade upward without break into a series of sediments which have been spoken of throughout this report as the Red Beds, but which, in order that they may have a definite geographic name, might be defined as the Brazos series. This embraces all those rocks of Texas, Oklahoma, Kansas, and eastern New Mexico between the top of the conformable Coleman division of the Carboniferous beds below to the base of the unconformable Cretaceous above. The beds of this series have been called by various names in literature, such as Jura-Trias, Permian, etc.

These rocks underlie all the western half of the Central Province "

This name is selected on account of the development of these beds along the course of the Brazos River.

Inasmuch as in the whole of the Texas-New Mexican region east of the Rocky Mountains no evidence has been found that any of these beds are of Jurassic age the term Juratrias is not only inappropriate but misleading. It has been shown that by far the greater part of these beds is of undoubted Permian age, possibly succeeded by a thin Triassic formation. The term Permo-Trias is far more appropriate therefor if a compound name in necessary.