570 



APPENDIX. 

 Section in West Central Colorado. 1 



Names of Formations. 



Thickness 

 in Feet. 



Characteristics. 



West Elk breccia. 



Unconformity -^^^ 



Ruby formation. 



-^- Unconformity^^- 

 Ohio formation. 

 (Local only.) 

 ^~~ Unconformity 



Laramie formation. 



3000 



2500 



200 



2000 



Upper part volcanic breccia; lower part fri- 

 able tuff, with sandstone beds. Material 

 mainly dark hornblende-andesite and pyrox- 

 ene-andesite, with some non-eruptive de- 

 bris in the lower part. 



Conglomerate, sandstone, and shale alternat- 

 ing; chiefly of igneous d6bris, with quartz 

 sand intermingled; conglomerate at base: 

 probably non-marine. 



Quartzose sandstone, with vari-colored jasper 

 and clay at base; probably non-marine. 



Sandstone and shale with workable coal-beds 

 in the lower 400 feet; arenaceous shale pre- 

 dominates in upper half. The coals are an- 

 thracite (subordinate), coking, and dry bitu- 

 minous. Sand and shallow- water deposits; 

 partly non-marine. 



Montana formation. 



2800 



Fine-grained yellow sandstone (Fox Hills) in 

 upper part, 300 feet; lead-gray shale, with 

 numerous lenticular bodies of limestone 

 (Pierre formation) below; marine. 



Niobrara formation. 



100-200 



Upper two thirds gray, calcareous shale ; the 

 lower third light-gray limestone; marine. 



Benton formation. 



150-300 



Black shale, with thin limestone-beds near top; 

 ironstone; marine. 



Dakota formation. 



40-300 



White quartzite; conglomerate at the base; 

 local fire-clays; non-marine in part at least. 



Gunnison formation. 

 Unconformity ^^^ 



Maroon 

 ate. 



conglomer- 



Possible unconformity 

 Weber limestone. 

 Unconformity 



350-500 



2500 



2000 



100-550 



Upper two thirds drab, green, yellow, and 

 pink clays, with thin beds of limestone. 

 Heavy white quartzite below; non-marine. 



Conglomerate and sandstone in heavy beds; 

 material chiefly from the Archean, but the 

 conglomerate contains limestone derived 

 from the earlier Carboniferous beds. Occa- 

 sional thin beds of fossiliferous limestone. 



— — ——-^Possible unconformity ~~— — 



Quartzose, conglomerate, grit, and sandstone, 

 with pebbles derived from Carboniferous be- 

 low. Thin beds of fossiliferous limestone. 



Dark-gray to black shale, with thin beds of 

 limestone carrying black chert. 



1 Emmons, Cross, and Eldridge, Anthracite and Crested Butte, Col., folio. U. S. Geol. Surv 



