STEVENSON— INTERRELATIONS OF FOSSIL FUELS. 73 



western border and deposition was apparently continuous in the 

 plains, Laramie covers or underlies great spaces. 



In the present state of knowledge, one may not assert or deny 

 the existence of Laramie beds in the important Trinidad-Raton field 

 of Colorado and New Mexico. Lee's discovery of an unconformity 

 by erosion in the mass, formerly regarded as Laramie, has made 

 the relations of the Raton formation, that above the unconformity, 

 somewhat uncertain. The plant remains appear to have Tertiary 

 affinities. The report by Lee and Knowlton on this field is still 

 unpublished. It would appear that the Laramie is present in the 

 isolated coal field on the Arkansas River, near Canyon City, Colorado. 

 Stevenson-^ in his first report referred all the coals of this field to 

 the Laramie ; but at a later date, he restricted that formation to the 

 upper part, 880 feet, which is in accord with the later measurement 

 by Washburne. This later observer obtained plant remains which 

 show that the rocks are equivalent to a part, at least, of the Laramie 

 as recognized farther north in the Denver Basin. The coal seams 

 are irregular in occurrence and appear to be mere lenses. The sand- 

 stones and shales are so variable that vertical sections, less than 100 

 yards apart, are wholly dissimilar. 



The Denver Basin extends along the eastern foot of the Front 

 Ranges almost to the northern boundary of Colorado. The Mesozoic 

 deposits were studied by Eldridge.-^ The Laramie, 600 to 1,200 

 feet thick, consists mostly of sandstones in the lower, but of clays in 

 the upper part. Coal seams in the higher beds are thinner and 

 much more irregular than those in the lower division, which is about 

 200 feet thick. Ostrea glabra, according to Eldridge, occurs in the 

 lower division, so that in the writer's opinion this sandstone is closely 

 allied to the Fox Hills, to which it is lithologically similar. Sections 

 throughout show great variation in the rocks as well as in the coal 

 seams, so that in any district, strict correlation of coals in different 

 mines is possible only where the workings are continuous. The coal 

 seams of the lower division are from 3 to 14 feet thick. A seam, 



2s J. J. Stevenson. U. S. Expl. W. of looth Mer., Vol. III., 1875, pp. 393- 

 397; Proc. Amer. Phil. Soc, Vol. XIX., 1881, pp. 505-521; C. W. Washburne, 

 U. S. Geo!. Survey, Bull. 381, 1910, pp. 341-378. 



29 S. F. Emmons, W. Cross, G. H. Eldridge, U. S. Geol. Survey, Monog. 

 27, 1896, pp. 51-74, 323-369- 



