STANTON: UPPER CRETACEOUS STRATIGRAPHY 63 



5300 to 6800 feet thick; the coal-bearing Frontier formation with 

 yellow and gray sandstone, yellow, gray and black carbonaceous 

 shales and numerous coal beds, 2200 to 2600 feet thick; the Aspen 

 shale, 1500 to 2000 feet thick; and the fresh- and brackish-water 

 Bear River formation which attains a thickness of 5000 feet. 



For the present purpose the chief interest in this great section 

 lies in the fact that it is so unlike the sections in areas a short 

 distance to the east, as at Rock Springs, 70 miles east, described 

 by Schultz,^- and in the Rawlins district, 80 miles farther east, 

 described by Veatch,!^ Ball,^^ and E. E. Smith. ^^ In these more 

 eastern sections the Bear River is absent as might be expected. 

 Its place in the section is occupied by a thin representative of 

 the Dakota sandstone. The Frontier is faintly recognizable in 

 a comparatively thin sandstone-bearing formation without coal. 

 It is overlain by a great mass of dark clay shale, sandy shale 

 and shaly sandstone 4000 to 5000 feet thick followed by a thick 

 and very important coal-bearing formation and a marine shale 

 for which the names Mesaverde and Lewis, respectively, have 

 been brought in from Colorado. Assuming that Mesaverde is 

 here correctly identified the logical treatment would be to apply 

 the name Mancos to all the rocks between the Mesaverde and 

 the Dakota but on account of the great thickness of those beds 

 and their partial differentiation into members that have come 

 in from other areas on the east and west this has not yet been 

 done. The Mesaverde and Lewis together apparently represent, 

 in part at least, the Hilliard shale of the Uinta County section. 

 Both these sections show very great thickening so that the total 

 sediments from the base of the Mancos or Colorado up, amount 

 to more than 10,000 feet. The chief difference lies in the fact 

 that the Uinta County section develops a great coal-bearing 

 formation of sandstone and shale in the lower part witliin the 

 equivalent of the Colorado group, while the Rock Springs and 

 more eastern sections have no coal in that part of the column but 



12 U. S. Geol. Survey, Bull. 341, pp. 256-282. 

 13' Ibid., Bull. 316, pp. 244-260. 

 " Ibid., Bull. 341, pp. 243-255. 

 15 Ibid., Bull. 341, pp. 220-242. 



