24:6 Dake — Episodes in Rocky Mountain Orogeny. 



brian granite included in the conglomerate involves the 

 erosion of part of the Cody (probably 1000 feet or more), 

 the Frontier (500 ft.), the Mowrv and Thermopolis (900 

 ft.), the Cloverly (100 ft.), the Morrison (500 ft), the 

 Sundance (500 ft.), the Chugwater (700 ft.), the Embar 

 (100 ft.), the Tensleep (100 ft.), the Amsden (200 ft.), the 

 Madison (1000 ft.), the Bighorn (300 ft.), and the Dead- 

 wood (800 ft. ) , all of which are known in the section within 

 ten miles of this point. This indicates a minimum total of 

 at least 6,000 feet of sediments ; probably much more if 

 the equivalent of the Mesa Verde, Meteetsee, and Ilo 

 (Lance) were at one time present, as they presumably 

 were, in the time before the pebbly sandstone was laid 

 down. At least they are known to underlie the Fort 

 Union in the Shoshone River section, just east of Cody. 

 Including these formations and assigning to them the 

 thicknesses known to occur within a few miles of this 

 locality (the Shoshone River Section) would bring the 

 grand total up to at least 11,000 feet. 



The removal of so great a thickness of beds by erosion, 

 in the interval before the laying down of the pebbly beds, 

 necessitates pronounced uplift of the region, and quite 

 probably involves the formation and truncation of sharp 

 folds. If more evidence is needed for this first phase of 

 the diastrophism, it is to be found in Sec. 34, T. 50 N., 

 R. 102 W., on the divide between Sage and Meteetsee 

 Creeks, where similar pebbly sandstones rest with slight 

 but distinct discordance. on Cody shales, the divergence in 

 dips being perhaps as great as ten degrees. The pebbly 

 sandstones in this latter locality are not continuous in out- 

 crop with those of the former area, but there can be little 

 doubt that they belong to the same formation. Still fur- 

 ther confirmation is probably to. be found in Sections 11 

 and 12, T. 50 N., R. 105 W., where similar pebbly sand- 

 stones rest, at nearly uniform elevation, in successive con- 

 tact against Cody, Frontier, and Thermopolis beds. The 

 area was not studied in detail, and the relations could con- 

 ceivably be those of faulting, but it is more than probable 

 that the situation represents unconformity, in which the 

 older beds occur in a truncated fold, buried by the pebbly 

 sandstone. Thus it seems probable that the first episode 

 of the diastrophism was marked not alone by broad uplift 

 and erosion but also by considerable folding, with accom- 

 panying truncation of the folds. 



