264 -. I. EMMONS — OROGRAPHIC MOVEMENTS. 



copied Webster park or Parkdale valley; if they < 1 i < 1 they have since been 

 very completely eroded away. 



Park range was probably isolated and formed an island, which was not 

 connected with the Colorado island. Along its present shore-lines the upper 

 Carboniferous beds are now so completely masked by subsequent Mesozoic 

 sediments that their original extent cannot be determined. They are dis- 

 closed, however, by the more recent uplift and erosion of the While river 

 plateau to the west, over which area sedimentation apparently went on con- 

 tinuously without leaving any very marked evidence of the movement. 



Sawatch Island. — Around the immediate shores of the Sawatch island sedi- 

 mentation apparently went on in unbroken continuity up to the time of the 

 Jurassic movement, no evidence having yet been detected in the remarkably 

 regular series of bed- that now surround it of any dynamic disturbance. The 

 character of these sediments Bhows, however, that shallow-water conditions 

 prevailed from the middle of the Carboniferous to the close of the Trias, 

 some small deposits of coal having been locally formed, and beds of coarse 

 conglomerates, containing pebbles that must have been derived from Bome 

 neighboring land-mass of Archaean rocks, constituting a very considerable 

 proportion of the section exposed. Alternating with these are occasional 

 bed- of limestone, which are of so frequent occurrence and have so little per- 

 sistence that they cannot be assumed to necessarily imply deep-water depo- 

 sition, but rather local changes in conditions of sedimentation. 



On the immediate western flanks of the Sawatch range, in the Elk mount- 

 ain-, were deposited at this time a thickness of not less than three thousand 

 feel of reddish conglomerates, characterized by a great abundance of lime- 



ne pebbles associated with those of Archaean rocks, of which no litholog- 

 ical correspondents are found in the beds encircling the Sawatch uplift. 

 These beds have been deposited over eroded surfaces of previously folded 

 Palaeozoic beds, and Carboniferous fossils have been found in some of the 

 pebbles. Theirmaterial must have been derived, therefore, from the abrasion 



- >me land-mass formed by the upheaval during this movement of an area 

 over which sedimentation had been going on during early Palaeozoic time. 

 They could not have come from the erosion of the Sawatch island, otherwise 

 the time correspondents of these beds around thai island would have con- 

 tained limestone pebbles also* 



A careful consideration of the present stratigraphieal conditions of the 



. ion -how- that this la ml -ma— inii-t have existed somewhere to the south 

 of the Klk mountains in the region about the head of the Gunnison valley 

 and possibly extended towards the northern end of the San Luis park. This 



land-m. I— may have been connected with the BOUthweSl end of the Sawatch 



island. 

 At the southeast end of this island is a Bhnilar unusual thickni irse 



