AGE OF THE ARAPAHOE AND DENVER. 217 



post-Laramie group they testify to the extent of the orographic disturbances 

 and volcanic eruptions of the time immediately succeeding the Laramie. 



Formations of the Huerfano Basin. ( Ml till" eastern side 111' tile 1 1 1( lllllt flillS, ill 



Huerfano Basin, Mr. K. ( '. Hills lias tumid and described' a series of strata 

 which he subdivided as follows: 



I Huerfano beds, 3,300 feet = Bridger group. 



Huerfano series. ...■'. ( 'uchara beds, 300 feet. > 



_..„,, Lower Eocene. 



V Poison Canyon beds. 3,500 feet. ' 



Great angular unconformity exists between the Laramie and the Poison 

 Canyon beds, but none has been detected between the several members of 

 the new series. The Huerfano beds are assigned to the Bridger Eocene 

 from the presence of Tillotherium, Hyrochyus, Glyptosaurus, Palaeosyops, 

 and other vertebrates. TheCuchara and Poison Canyon beds are separated 

 on hthological grounds, and no fossils have been found in them. Theformer 

 formation consists of "pink and white massive sandstones;" the latter of 

 "soft sandstones and line conglomerates of a yellowish tinge, with occasional 

 bands of yellow clay or marl." It is believed by Mr. Hills that the Cuchara 

 and Poison Canyon beds are probably contemporaneous with some of the 

 other post-Laramie formations here referred to. 



The Animas River beds. — In the article already cited on the post-Laramie 

 deposits of ( "olorado, the writer referred to a series of strata occurring on the 

 Animas River below Durango, which had been visited by Mr. T. W. Stanton 

 and found to lie very similar to the Denver beds. In the summer of 1894 

 the writer was aide to hurriedly examine this series of beds as exposed on 

 the railroad below Durango, and found them to resemble the typical Denver 

 beds in a very high degree. These strata occur above the Laramie and 

 below the Puerco, and, as far as the present meager observations show, 

 are conformable with both of them where now preserved. The beds are 

 some 70() feet or more in thickness, and are composed of yellowish-brown 

 clays, tuffs, sandstones, and conglomerates, in which andesitic material 

 greatly predominates, and present a variety rivaling that in the Denver beds. 



'The recently discovered Tertiary beds of the Huerfano River Basin, Colorado: Proc. Colo. 

 Sci. Soc, Vol. Ill, 1888, \>. 148. 



Additional notes on tin- llnerl'ano beds: ibid., Vol. Ill, 1889, p. 217. 

 Remarks on the classification of tin- Huerfano Eocene: ibid., Vol. IV. 



