endlich.] CRETACEOUS NO. 2. 227 



tained. It will be of great importance now to obtain the relation of 

 these beds to the coal-bearing strata further east, which will probably be 

 accomplished during 1875. By that meansthe two horizons, if there are 

 two, can be definitely located, and the question as to the age of the East- 

 ern Colorado coal can be definitely solved. Mineralogically the coal is 

 a compact bituminous one, burning with flame. Specimens obtained 

 were taken from the surface only, as neither time nor facilities were at 

 hand to go down upon them. Therefore any analysis that might be 

 given would furnish a result that could not be regarded otherwise than 

 erroneous. 



Besides the Cretaceous formation in this region, it is developed on 

 the San Miguel and on the Bio Dolores. 



Ascending Bear Creek up to the pass leading over into the San Mig- 

 uel region, we pass through the red Carboniferous sandstones. Tra- 

 chyte overlying them is next met with, and on the west side of the divide 

 the Cretaceous beds are reached. East of Mount Wilson, Cretaceous 

 No. 1 appears in the canon of the San Miguel, and as its dip is in the 

 same direction with the.eourse of the river, it forms its beds for a long 

 distance. On either side the shales of No. 2 form the soil, reaching 

 eastward to the trachytic mountains of the main group, westward to 

 the Wilson group, and to the north far beyond the limits of our dis- 

 trict. On the way to Mount Sneffels, we had occasion to traverse these 

 two Lower Cretaceous numbers, and to observe their contact with the 

 volcanic rocks. Camp was made on a creek flowing in a southwesterly 

 direction into the San Miguel, and there it was observed that all the 

 shales of No. 2, as well as the upper beds of No. 1, had been changed 

 by the action of the volcanic material. The former were thoroughly 

 baked and turned into hard slate, while the upper sandstones of No. 1 

 presented the appearance of quartzites. In that region the Cretaceous 

 beds reach up into the narrow canons, and are usually overlaid by tra- 

 chyte. In the vicinity of the rivers and streams, No. 1 crops out, 

 iorming the almost inaccessible caiious through which they flow, A 

 section taken at the junction of the above-mentioned creek and Rio 

 San Miguel (Section VIII) will give some idea regarding the depth of 

 the canons and the distribution of strata. It will be noticed that the 

 creek at which this section was taken has flown scarcely five miles, 

 and nevertheless the depth of its canon amounts to 1,005 feet, accord- 

 ing to measurement. It seems, from the succession of strata, and the 

 fact that Inoceramus was found in the lowest one, that not the entire 

 No. 1 has there been developed. Beginning below, at the level of the 

 San Miguel, we find first 50 feet of dark-blue, partly shaly lime- 

 stones a, containing compressed specimens of Inoceramus. Above that 

 follow 390 feet of white to light-yellow sandstones, b, fine-grained, 

 and compact in structure, regularly stratified, having a straight dip to 

 the northwest, conformable with that of both over and unaer lying beds. 

 This is covered by 480 feet of light-brown sandstone, c, containing inter- 

 strata of greenish marls, underlying 40 feet of gray to yellow sandstone, 

 d, weathering in grotesque forms. Above that follow a series of sand- 

 stone and shales, interchanging. The stratum mark h, in the section, 

 shows indications of coal, consisting of very narrow seams of jet, and 

 numerous coaled remains of plants. Above this the gray shales of No. 

 2 occur, with Gryphcm and numerous fragments of Inoceramus. 



Although the question by what agents these comparatively deep 

 canons were formed cannot be definitely decided, without a very thor- 

 ough knowledge of all their occurrences, the presence of those just men- 

 tioned, in a region so near the main mass of mountains, attracts atten- 



