B'AUNAL EVIDENCE AKD COBRELATION. 235 



ELK MOUNTAIN KEGION. 



The Crested Butte quadrangle is that whose northwestern corner is made bj' the 

 intersection of the one hundred and seventh meridian and the thirty-ninth parallel. 

 It is a 15-minute quadrangle. The areal geologj', which forms part of the subject- 

 matter of the Anthracite-Crested Butte folio," was surveyed by G. H. Eldridge, by 

 whom most of the collections studied were made. Two Upper Carboniferous forma- 

 tions are recognized in the Anthracite-Crested Butte folio. The lower one is called 

 the Weber formation and the other the Maroon conglomerate. The Weber forma- 

 tion consists of shales and thin limestones, and varies in thickness from 100 to 550 

 feet. The Maroon conglomerate measures 4,500 feet, and is subdivided into two 

 portions. The lower division, which is 2,000 feet thick, is derived from the waste 

 of older sedimentary deposits; the upper, which contains 2,500 feet, is largely 

 derived from the waste of granites. Both series contain thin limestone beds. 



Thirty-three collections in all were obtained from the Upper Carboniferous beds 

 of the Elk Mountain region, and thirty of these were made in connection with the 

 areal work of the Anthracite-Crested Butte folio. These are from stations 2290- 

 2300, 2302-2308, 2310-2321. The following stations occur in the Weber limestone: 

 2307, 2308, 2312-2316, and 2320. The remainder occur in the lower portion of the 

 Maroon conglomerate, though the position of 2302 and 2303 is not quite certain.. No 

 fauna is at present known from the upper Maroon. The fossils from 2306, however, 

 can not properl}- be included with the Maroon fauna, since they were derived from 

 pebbles in one of the Maroon conglomerates where their presence is only secondary. 

 In the accompanying table the local faunas are set down, and in the two final columns 

 the composite faunas of the Weber formation and of the lower portion of the Maroon 

 conglomerate. 



aV. S. Geol. Sun-., Geol. Atlas U. B., folio 9, 1894. 



