EARLIER TERTIARY (EOCENE AND OLIGOCENE). 757 



The coal field between Gallina and Raton Spring, N. Mex., in the San Juan coal 

 region, is described by Gardner ^^^^ as follows : 



In the vicinity of Gallina and to the south beyond Lajara the variegated shales of the 

 Wasatch rest horizontally against the foot of the Sierra Nacimiento, covering the highly inclined 

 strata of the Cretaceous, and lower sedimentary rocks. The Wasatch bears many fragments 

 of vertebrates, and collections were sufficient to permit its positive identification. 



In the southern portion of the area, along the mountain foot* northeast of Cuba and along 

 the headwaters of Rio Puerco, the Wasatch is underlain by a mass of variegated bituminous 

 shale, with two beds of massive sandstone. The sandstones form prominent escarpments, 

 the upper immediately west and the lower about 10 miles southwest of Cuba. The entire 

 thickness of these beds is about 800 feet. They are highly inchned along the mountains, and 

 northeast of Cuba they are overturned and dip toward the mountains at about 70°. The high 

 dips of the massive sandstones are in marked contrast to the unconformable horizontal shale 

 of the overlying Wasatch. The prominent sandstone escarpments swing westward from Cuba, 

 the lower being traced across the area beyond the hmits of the present mapping. The upper 

 escarpment could not be traced with certainty. The prominent escarpment of the Wasatch 

 to the north follows in a general way parallel to these escarpments. Near a small pond, about 

 7 miles N. 76° E. of Ensino Spring, vertebrate fossils were collected from 25 feet of dark and 

 gray argillaceous sand and shale immediately overljdng the basal escarpment sandstone. A 

 careful study of these fossils has been made by J. W. Gidley, of the United States National 

 Museum, and the specimens have been compared with original material in the American Museum 

 of Natural History, New York. This comparison definitely places them in the Torrejon 

 formation." The Laramie reappears from beneath the lower escarpment, striking almost at 

 right angles with it, 'thus bringing out a marked unconformity between the two. It does not 

 follow from the fossils that the lower escarpment is of Torrejon age. It is probable that there 

 is an unconformity between the Puerco and the Torrejon. Tliis accounts for the Torrejon 

 fossils immediately above the basal escarpment sandstone, which is in all probabihty the low- 

 est member of the Puerco. It is certainly at the base of an 800-foot mass below the Wasatch, 

 exposed along the headwaters of Rio Puerco, as originally described by Cope.* Along Rio 

 Puerco the base of the Wasatch is 750 feet above the top of the basal Puerco sandstone. At 

 the point where the Torrejon fossils were collected the base of the Wasatch, as determined by 

 both stratigraphic relationship and fossil evidence, is only 135 feet above the top of the same 

 sandstone. Hence the 800 feet of the original Puerco is represented by only the basal sandstone,, 

 from 30 to 50 feet thick, unconformably overlying the Laramie. This sandstone is uncon- 

 formably overlain by 110 feet of Torrejon, above which, also unconformably, Hes the Wasatch. 



J 13. GREAT PLAINS OF COLORADO. 



In the plains southeast of Denver the Oligocene and possibly part of the Eocene 

 are represented by the Monument Creek formation. Darton ''*° describes it as — 



an extensive deposit of conglomerates, sand, sandstone, gravel, and clay, known as the Monu- 

 ment Creek formation. It lies on the Laramie formation to the east and the Arapahoe formation 

 to the west, and at Palmer Lake it abuts against the granite at the foot of the mountain. There 

 are two members, a lower one of sands and clays and an upper one of conglomerate and sand- 

 stone. The latter caps numerous buttes and plateaus in the high region west and north of Calhan 

 and north of Monument. 



Fossil bones of Titanotherium have been discovered by the writer " and Mr. C. A. Fisher 

 in the upper member of the region north of Calhan and southwest of Elizabeth, which indicate 



a Torrejon is a name proposed by J. L. Wortman (Bull. Am. Mus. Nat. Hist., vol. 9, 1897, pp. 260-261) for a fossil 

 zone at the top of the original Puerco of Cope. 



A Cope, E. D., Rept. Chief Eng., 1875, pt. 2, p. 1008. 



c Darton, N. H., Age of the Monument Creek formation: Am. Jour. Sci., 4th ser., vol. 20, 1905, pp. 178-180. 



