CLOSING PALEOZOIC MOVEMENTS. 263 



ica] divisions on maps, therefore, too much reliance has necessarily been 

 placed on distinctions derived from the character of the sediments. While 

 that of the upper part of the Trias seems to be persistent over this and the 

 adjoining regions, the earlier sediments only show a general prevalence of con- 

 ditions of rapid abrasion and shallow-water conditions. Whether the Permian 

 beds, recognized in the Wasatch and Grand Canon regions on the one side 

 and along the borders of the eastern continent and in Texas on the other, 

 are represented here seems still uncertain. Plants of Permian facies have 

 been found, but they are often associated with a Carboniferous fauna. It is 

 possible that the general elevation, which the shallow-water conditions imply, 

 may have shut out the ocean waters during part of this period ; this is 

 rendered probable by the evidence of a movement at the close of the Per- 

 mian said to exist in other regions. The erosion which took place at the 

 close of the next succeeding movement is known to have been locally very 

 great in the Rocky Mountains. Whether the marine Jura, as developed to 

 the west and north, was deposited in this region and has in great measure 

 been eroded away, or whether its elevation was such that the early Jurassic 

 ■* seas did not penetrate it, remains yet to be determined by future investiga- 

 tion. The only fact bearing upon this point is the observation by Mr. G. H. 

 Eldridge of an unconformity by erosion between the Trias and fresh- water 

 Jura along the foothills of the Colorado range near Denver. 



Late Palaeozoic Land. 



The outlines of the various land areas during the subsidence that fol- 

 lowed this movement were, as far as can now be determined, somewhat as 



follows : 



Colorado Island. — Along the eastern and northern shores of the Colorado 



island, no upper Carboniferous beds corresponding to the conglomerates of the 



Elk and Sangre de Cristo mountains have yet been recognized. The Triassic 



" Red Beds " now rest directly on an Archaean or lower Palaeozoic basement, 



as the case may be. Hence it may be assumed that during upper Carbon. 



iferous time these shore-lines were still above water, and that the subsidence 



had continued into Triassic time, so that what upper Carboniferous sediments 



might have been deposited were overlapped and buried from sight by those 



of the Trias. Triassic sediments invaded the depression of North park, but 



apparently did not extend far into the Middle park. 



South park was connected with the western ocean across the northern end of 



the Mosquito range, as in early Palaeozoic time, and received a complete and 



regular series of sediments. On the south the bays at Manitou and Canon 



City were probably not so deeply invaded as in early Paheozoic time, nor is 



there any evidence that upper Carboniferous or Triassic sediments ever oc- 



XXXV— Bull. Geol. Soc. Am., Vol. 1, 1889. 



