The Upper Cretaceous shale which has been called Carlile in the Laramie Basin, Wyoming, overlies the Frontier formation and is, in turn, overlain by the chalky beds of the Niobrara. The fauna of the upper part of the Frontier is of the same age as that of the upper type Carlile of Colorado, whereas the fauna of the “Carlile” of the Laramie Basin is of Niobrara age. It is believed, therefore, that the use of the name, Carlile, should be discontinued in the Laramie Basin and the name, Niobrara, extended downward to embrace the beds erroneously called Carlile. This basal Niobrara shale is correlated with the Sage Breaks shale member of the Niobrara of the Black Hills, and the name, Sage Breaks, is here substituted for the abandoned name, Carlile.

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