402 



quite abundaut vegetable forms, and at different localities one to three 

 ttiin seams of coal. Immediately over this saudstoae occurs the best 

 workable bed of coal yet known in this basin. This lower sandstone 

 may be regarded as the horizon between the coal group and the Creta- 

 ceous from Eaton Hills far north to Denver and probably farther. In 

 the laminated sandstones and arenaceous clay below the lower sand- 

 stone of the coal group for 200 to 300 feet, I searched in vain for any 

 trace of organic remains. Mr. J. N. Clark, a mining-engineer, for several 

 years in charge of the coal interests of the Denver and Eio Grande 

 Eailroad, informed me that he had examined the entire country from 

 CaSon City to the Eaton Hills, and that he had never found a marine 

 fossil within 200 feet of the first coal-bed. j^o fossils but plants have 

 yet been found in the Canon City group. 



The Eaton Hills come within the area assigned to Dr. F. M. Endlich, 

 assistant g'eologist, for geological examinations during the season of 

 1875, and I requested him to give special attention to the relations of 

 the coal-strata to the underlying beds. He reports an unconformability 

 ■extending along the base of the mountains for many miles. This fact 

 has not, to my knowledge, been previously observed. He says : — 



"Underlying the coal-bearing strata, we find older formations, the 

 youngest of which is the Cretaceous. As the divisions of this forma- 

 tion differ widely from those observed farther north, and a discussion 

 thereof would be out of place here, I will merely state that I regard 

 these strata as Cretaceous, in which I have found unmistakable inverte- 

 brate fossils which are acknowledged to belong to that geological period. 

 Overlying these strata unconformably, although the unconformability 

 is very much obscured at many places, the coal-bearing series of sand- 

 stones and shales begins. About 500 feet below the lowest coal-bed, I 

 found the highest Cretaceous fossils. All the intermediate strata 

 yielded no paleontological evidence whatever. A number of coal-beds, 

 varying in thickness in different localities, occur, separated from each 

 other by sandstones and shales. At Trinidad, the Lignitic, or coal-bear- 

 ing group, reaches a thickness of about 2,600 feet, containing a large 

 number of coal-beds and seams. As the development of the formation 

 is very typical at that locality, I have designated it as the ' Trinidad 

 Lignitic group.' 



"Taking into consideration the stratigraphical relation, the absence 

 of fossils that might weaken this evidence, and the observations made 

 upon the parallel group farther west, as well as its sharply-defined 

 characteristics, I have come to the conclusion that it certainly cannot 

 correctly be classed with the Cretaceous formation. As I am not sup- 

 plied with sufficient proof, based upon paleontological evidence, to regard 

 the Lignitic group as being of Tertiary age, I assign to it an interme- 

 diate position, between Cretaceous and Tertiary, showing, however, more 

 affinities to the latter than to the former." 



The Lignitic group is entirely absent from the Arkansas Eiver north 

 to Colorado Springs. Passing eastward over the rolling plain from 

 Colorado Springs, we gradually rise about 800 feet within a distance of 

 nine miles. The country is underlaid with Nos. 4 and 5. At one local- 

 ity, the characteristic fossils of No. 5 are very abundant and of consid- 

 erable variety. The usual calcareous concretions are scattered thickly 

 over the surface, which, when broken, reveal an abundance of Baculites 

 ovatus; Inoceramus, several species; ScapMtes Conradi; S. Clieyennsis; 

 and many others peculiar to No. 5, and some that are found abundant in 

 No. 4. From No. 5 there is a barren interval of 300 to 400 feet, very 

 similar to that at CaQon City. In the upper portion of these laminated 



