260 S. r. EMMONS — OROGRAPHU MOVEMENTS. 



continuously along the flanks of the Medicine How range and across its ex- 

 tremity i" the Park range, but the ocean waters did not penetrate the North 

 and Middle parks which, up to post-Cretaceous time, formed a single con- 

 nected valley. On the east the shore-line probably reached higher and fur- 

 ther westward than the present hogbacks. Pike's peak stood out as a promon- 

 tory, or possibly as an island, the shore-line extending across the ridge to the 

 north of it into the bay now occupied by Manitou park, while to the south- 

 west the wato ra of the Canon City bay covered Webster park and portions 

 of the ridge through which the Royal gorge of the Arkansas is now cut, and 

 northwestward may have penetrated the South park depression. The main 

 connection of South park with the ocean was, however, from the northwest 

 around the northern point of the Sawatch uplift and across what is now the 

 northern portion of the Mosquito range. 



Further north the western shore of the Colorado island was formed by the 

 l'aik ran-'-. BO that its general outline was triangular with apex toward the 

 south and its width about 1<>I) miles at the broadesl part. 



s watch Island. — To the west of the South Park hay was the Sawatch 

 island, which included the west flanks of the present Mosquito range and the 

 upper valley of the Arkansas. The area of its present Archaean exposures 

 within the fringing reejf of Cambrian quartzites is about I'M) by 30 miles. 

 It was undoubtedly smaller at the time when these were deposited, hut their 

 outline probably preserves the general shape <>[' the original island, as they 

 resist erosion even better than the Aichaan rocks. 



Southern Areas. - -With regard to the southern portion of the region, ii i.- 

 di (lieu It to reconstruct the probable distribution of land ami sea at this lime, 

 partly on account of the uncertainty with regard to the outlines given on 

 the Harden map, and partly because observers have not hitherto discrim- 

 inated between upper and lower Carboniferous horizons. 



South of the latitude of < tanoa < 'ity and of the southern end of the Sawatch 

 i.-laml, the only region where the lower Palaeozoic rock- can with certainty be 

 -aid to have been deposited is ill the western portion of the San Juan mount- 

 ain-. AJong the Sangre de( !risto range the conglomerate series of the upper 

 Carboniferous is known to rest upon the Archaean in many places, and at the 

 southern end of this uplift Stevenson found lower beds which may belong to 

 the earlier series ; but in the presenl state of our knowledge of the Carbonif- 

 erous fauna of the R icky Mountain region the palseontologic&l evidence is 



not decisive. By analogy it would seem probable that the two exposures 

 of Carboniferous on the , ;asl flanks of the Wet mountain- belong to the 

 lower series. On the other hand, in the outlying regions of the [Jncom- 

 pahgre plateau, in western Colorado south of the Grand river, and at the 

 Xuni and Naciinieiito mountains in northern New Mexico, upper Carbon if- 

 i roua beds rest directly upon tin- Archaean, which U in bo tar an evidence of 



