EARLIEE TERTIARY (EOCENE AND OLIGOCENE). 755 



J 12. PLATEAU PBOVINCE OF UTAH. 



In southwestern Utah the Cretaceous is overlain by Eocene (Wasatch) strata. 

 Richardson®*^^ says : 



The Cretaceous rocks are unconformably overlain by Eocene strata, which, as already 

 stated, outcrop in the Pink Cliffs and underlie the Markagunt and Paunsagunt plateaus. The 

 unconformity, marked by a basal conglomerate containing pebbles of the underlying rocks, is 

 emphasized by the absence of the upper members of the Cretaceous system, which are well 

 developed in other parts of the plateau province. The Eocene rocks consist of a variable 

 succession of shale, limestone, sandstone, and conglomerate that are characteristically vari- 

 colored. Shades of red and white predominate and are beautifully developed in the Pink Cliffs. 

 Fossils are extremely rare in these rocks and only a few fragments of Vivipara and Unio have 

 been obtained in this area, but the characteristic peculiarities of stratigraphy and coloring 

 of the rocks leave little room for doubt that, except possibly a few feet of basal beds containing 

 conglomerate of doubtful significance, they belong to the Wasatch formation of the Eocene 

 series, which is so largely developed in the High Plateaus of Utah and ftom which characteristic 

 fossils have been obtained in a number of places. 



J 12-13. SAN JTTAN BASIN, COLORADO AND NEW MEXICO. 



The Tertiary of the San Juan Basin of New Mexico and Colorado comprises 

 possibly the Animas formation and certainly the Puerco and Torrejon formations 

 (Eocene). The Animas formation is thus described by Cross: '*^* 



In the article already cited on the post-Laramie deposits of Colorado, the writer referred 

 to a series of strata occurring on the Animas River below Durango, which had been visited 

 by Mr. T. W. Stanton and found to be very similar to the Denver beds. In the summer of 

 1894 the writer was able to hurriedly examine this series of beds as exposed on the railroad 

 below Durango and found them to resemble the typical Denver beds in a very high degree. 

 These strata occur above the Laramie and below the Puerco and, as far as the present meager 

 observations show, are conformable with both of them where now preserved. The beds are 

 some 700 feet or more in thickness and are composed of yellowish-brown clays, tuffs, sandstones, 

 and congloinerates, in which andesitic material greatly predominates, and present a variety 

 rivaKng that in the Denver beds. 



A few fossil plants occur, but those found thus far arc poorly preserved, and the only 

 identifiable species collected is Magnolia tenuinervis Lx., a common Denver bed species originally 

 described from Table Mountain. No invertebrate fossils have been found as yet, but it seems 

 probable that a number of vertebrate species, described by Cope as from the Laramie of the 

 Animas River section, came out of the strata which so closely resemble the Denver formation. 



In an article discussing the relations of the Puerco and Laramie deposits Prof. Cope refers 

 to the succession of beds on the Animas River, saying: "Accordiag to the observations of Mr. 

 David Baldwin the Laramie beds succeed [the Puerco] downward, conformably it is thought 

 by Mr. Baldwin; and have a thickness of 2,000 feet at Animas City, N. Mex. [Colorado?]. A few 

 fossils sent from time to time by Mr. Baldwin identify the Laramie. This is especially done by 

 the teeth of the dinosaurian genus Dysganus Cope, which is restricted to the Laramie formation 

 elsewhere, also by the presence of the genera Lselaps and Diclonius, which in like manner do 

 not extend upward into the Puerco beds." 



According to the statement of Prof. Cope, made personally to the writer and quoted with 

 his permission, these fossils were collected incidentally to the investigation of the Puerco fauna 

 and for the purpose of identifying the underlying formation. He believes it most probable 

 that they came from what are here called the Animas beds, wlaich extend for several hundred 

 feet below the Puerco. Prof. Cope now regards the Dysganus and Diclonius as closely alhed 

 to the homed dinosaurs (Ceratopsidse Marsh, Agathaumidse Cope), which, as will be shown, 

 form the most characteristic element of the vertebrate fauna known in the Arapahoe and 

 Denver beds. 



