W. Cross — New Devonian Formation in Colorado. 2-±9 



OP. FEET. 



Ignacio formation. 



5. Quartzite conglomerate with small pebbles, gray or 

 pink, hard and causing a distinct ledge (may belong 

 to Elbert) 3~| 



4. Quartzose sandstone and sandy shale, dark dull red, 



in layers 6 inches or less in thickness 5 



3. Quartzite, fine-grained, hard, gray, in beds 1 to 5 feet 

 in thickness with thin shale partings. Cross-bedding 

 common _ 24 



2. Sandstone and quartzite, fine and uneven grain in beds 

 2 or 3 feet thick, with red, sandy shale layers 

 between 17 



1. Crumbling shaly sandstone, dark, dull red in color, 

 mainly of quartz with some red feldspar grains. A 



coating of limonite on particles causes color " 2— J 



52- 

 Base of section is coarse biotite-granite. 



The quartzite formation, measuring 52 feet in thickness at 

 Devon Point, is called the Ignacio quartzite in the Silverton 

 folio (now in press) and it is believed to be of Upper Cambrian 

 age, since the only fossil thus far found in it is a small shell 

 which, according to Mr. Charles D. Walcott, is apparently an 

 Oholus, closely related to 0. Iqperi, known elsewhere in Colo- 

 rado. The strata between the quartzites and the Ouray lime- 

 stone, carrying fish remains at the base and also near the top, 

 seem unquestionably to form a lithologic stratigraphic and 

 faunal unit, and for these strata the name Elbert formation is 

 here proposed. The name is derived from Elbert creek, a 

 western tributary of the Animas, entering it just above Rock- 

 wood, which Hows for several miles on a broad bench between 

 the Animas canyon and the high scarp formed by the Hermosa 

 Upper Carboniferous formation. On this bench the Ignacio, 

 Elbert and Ouray formations are particularly well exhibited. 

 The first name is from the Ignacio lakes, lying on this bench 

 and drained by Elbert creek. 



The Elbert formation has been observed below the Ouray 

 limestone in several quadrangles of the San Juan region and 

 many exposures have been studied. While the reader is 

 referred for details to the Needle Mountains, Durango, Engi- 

 neer Mountain, and Silverton folios, now in press, or soon to be 

 completed, some statements of its characteristics may be made. 



Its general lithologic character is fairly well illustrated by 

 the section at Devon Point, although many of them have been 

 noted. The most persistent feature is the crumbling calcareous 



