FORMATIONS OF THE FRONT RANGE 427 



The formation is exposed at intervals from South Platte river to Colo- 

 rado City. A short distance north of the Gateway to the Garden of the 

 Gods its thickness is 130 feet, and the basal beds lying on the thick de- 

 posit of gypsum at the top of the Chugwater formation consist of ashy 

 gray massive shales with several thin limestone layers and a few streaks 

 of clay pebbles. These grade up into typical pale greenish and maroon 

 massive cla} 7 s with a few thin layers of fine grained light colored sand- 

 stone abruptly overlain by coarse grained buff colored " Dakota " sand- 

 stone. At Colorado City the Morrison beds are exposed in the railroad 

 cut. but only in part, the top and bottom members being covered by 

 talus. The dips are nearly or quite vertical. To the west are 55 feet of 

 pale greenish gray sandy shale, mostly massive, with thin layers which 

 are overlain (to the east) by a 15-foot bed of soft pale greenish gray 

 sandstone. The formation is cut off by the pre-Cambrian rocks south 

 of Colorado City, but appears again in the embayment north and north- 

 east of Canyon City. In Garden park on Oil creek it has a thickness of 

 about 350 feet, according to Cross* and consists mainly of greenish, 

 pinkish, or gray shales or marls with sandstone layers at various horizons. 

 It usually lies on the Fountain formation, but overlaps locally onto the 

 granite. In this region the formation has yielded large numbers of di- 

 nosaur remains. Hatcher f has recently described the formation and 

 its relations in the Garden Park area. He estimates the thickness at 450 

 feet, placing the upper limit higher than Cross, so as to include some 

 sandstones and shales containing dinosaur remains. The bones have 

 been obtained in largest number from a thick sandstone about 150 feet 

 above the base of the formation, but some occur 30 feet below this 

 stratum, and others have been found at various horizons above, both in 

 shale and sandstones. Just below the main bone-bearing sandstone bed 

 there is a layer of clay with thin limestone beds containing numerous 

 fresh water gasteropods, and in a marly layer, at a somewhat lower hori- 

 zon, occur abundant remains of Unios. These fossil shells have been 

 described by C. A. White, who classes them as Jurassic because they 

 occur with supposed Jurassic dinosaurs, but he states that otherwise 

 they might be regarded as much younger, so that they throw no light 

 on the age of the beds. Hatcher reports the discovery of an Inoceramus 

 at the Garden Park locality. 



South of Canyon City these beds do not reappear again until in the 

 vicinity of Beulah, southwest of Pueblo, where they extend for a few 



♦Whitman Cross,: Description of the Pike's Peak district. Geologic Atlas U. S., folio 7, U. S. 

 Geol. Survey, 1894, p. 2. 

 t J. B. Hatcher : Annals of Carnegie Museum, vol. 1, 1901, pp. 327-341. 



LV— Bom.. Geot.. Soc. Am., Vol. 15, 1903 



