45 2 STUDIES FOR STUDENTS 



These constitute the only true Huerfano deposits. (2) That the 

 Cuchara and Poison Canyon beds are unconformable with the 

 Huerfano beds and older than the Eocene, probably marine cre- 

 taceous as partly determined by the presence of a species of 

 Bacnlites in the yellow sandstone of the typical Poison Canyon 

 section. (3) That the present canyon of the Huerfano River cuts 

 through the base of the main anticlinal axis of post-Laramie 

 origin, which formed the eastern boundary of the lake. This 

 axis extended to the south so as to include the base of Silver 

 Mountain toward the Cuchara divide ; but it lies from three to 

 seven miles west of the anticlinal axis described by Professor 

 Hills. (4) That the Huerfano lake deposition did not extend as 

 far to the east or south as Spanish Peaks, and that the variegated 

 beds observed there are of older origin. This would materially 

 affect the geological age of the prominent neighboring laccoliths." 



From the above conclusions it will be observed that the 

 Huerfano beds are much more restricted geographically than 

 was supposed by Hills. They occupy a part of the basin of the 

 upper part of Huerfano River, between the Wet Mountains on the 

 northeast and the Sangre de Cristo and Culebra ranges on the 

 west and south. Osborn thinks the beds were formed by the 

 damming of the Huerfano River by a post-Laramie axis of 

 uplift which was afterward trenched by the river. The lake was 

 thus drained. 



It appears from Osborn's conclusions that the two divisions 

 of the Huerfano beds represent the two substages of the Bridger 

 stage of Scott. The name Huerfano should be restricted to one 

 of these divisions. The other division should receive a new 

 name. 



the uinta formation (=Brown's Park group of Powell). 



The Uinta formation was named by King from the Uinta 

 Mountains, on the flanks of which its outcrops occur. The Uinta 

 is described as follows 1 : ". ... it is possible that this group 

 was deposited continuously, at least in part, with the Bridger 



"Quoted by Clark, loc. cit., p. 143. 



