114 CABBONIFEEOUS FORMATIONS AND FAUNAS OF COLORADO. 



King soeiiis to take it tor siTiintcd tliat tlio siliceous bod at tlic ))as(> of tiio, Kawlings 

 Peak section is the same as that oreurring in a simihir position on tlie flanks of the 

 Laramie Mountains, ))ut as the hitter consists of r(>d sandstones and red limestones, 

 and the former of whitish quartzite without any limestone at all, there seems to lie 

 room for skepticism. If my conjectures prove at all true, the geologic ages of the 

 two ai-e entirely different. 



As previously noted, south of the forty-first parallel, the sti-ata bordering the 

 Archean nucleus and resting upon it belong to the well-known Rockj' Mountain lied 

 Beds of supposed Triassic age. Locally, at several points south of this parallel, and 

 more generallj' north of it, the Red Beds are underlain by strata of recognized Paleo- 

 zoic age. King states that the relative position of the Red Beds and Paleozoics is. 

 one of conformity, but from the marked overlap of the Red Beds, it seems clear that 

 the conformity can be onlj^ apparent. 



"The beds along the southern limit of the map, boi'dering the Big Thompson and 

 the Cache la Poudi'e, attain a thickness of 800 to 850 feet, thinning thence northward 

 and reaching a minimum in the region of Horse and Lodgepole creeks, where the_v 

 scarcely attain 300, but thickening again in the region of Chugwater and Bush creeks 

 to nearly 700 feet. 



"On the western borders of the range the conditions thus sketched are repeated. 

 North of the Union Pacific Railroad the soft, easily eroded beds of the Trias, vary- 

 ing from 400 to 800 feet in thickness, rest directly upon the uppermost limestones of 

 the Coal Measures. South of the railroad the Trias overlaps, and, as on the eastern 

 side of the range, comes in contact with the Archean. 



"Taken as a whole, and with the exception of the gypsum and limestone beds, which 

 nowhere within our field of observation exceed 40 feet in thickness, it is essentially 

 a sandstone series, for both clays and shales are exceedingly arenaceous, and the 

 dominant color is a brick red for the lower half of the series, and variable lighter 

 reds, pinks, and yellowish i-eds for the upper half. While this division of color holds 

 good in general, it is often varied by extremely brick-red, almost vermilion -colored, 

 beds apjaearing near the top, and light ones intercalated in the region of the heavy 

 red lower strata. 



"The Red Beds of Colorado Range have thus far yielded to our search no organic 

 remains, saving obscure pieces of half -petrified, half-carbonized wood, which crumbles 

 on exposure to the air, and displays no characteristic structure. " 



The distribution of the Triassic, so far as concerns the region discussed by King, 

 consists chiefly of two strips, one on the eastern and the other on the western side of 

 the Colorado Range, of an area of outcrops at Elk Mountain at the northern extremity 

 of the Medicine Bow Mountains, of another at Rawlins Peak, of a bordering of 

 outci'op on both sides of North Park near its northern end, and of one on both sides of 

 the Uinta Mountains. In North Park the thickness is nearl}^ 1,000 feet, and in the 

 Uinta Mountains in the region of Vermilion Creek it is 2,000 feet. 



