Mesozoic and Ccenozoic Geology and Palaeontology. 227 



with their opposite and considerable dips, but by supposing an uplift 

 of the intervening tract, such and so great, that if the movement were 

 now reversed, it would carry tliis swell of nearly 100 miles breadth 

 into a depression much below the present level of the troughs in which 

 these remnant fringes lie, so that there has been an erosion not only of 

 10,000 to 20,000 feet of the broken arch of Triassic beds over this area 

 but also of a considerable thickness of the underlying rocks on which 

 they had been deposited. 



The present area of Triassic in North Carolina is about 1,000 square 

 miles, about one third of which, it is estimated, is underlaid with coal. 



Prof. G. K. Gilbert* found a section of the Trias exposed by the 

 North fork of Virgin river, from the vicinity of Mountain Lakelet to 

 Rockville, in Southern Utah, 3,250 feet in thickness, and the Jurassic 

 at the same place 350 feet. The Triassic on the West Fork of Paria 

 Creek, 2.575 feet, and the Jurassic 740 feet. And the Triassic at 

 Jacob's Pool, Northern Arizona, 2,150 feet in thickness. E. E. Ho- 

 well estimated the Trias at Rock Canon, near Provo in the Wahsatch 

 Range, at from 4,000 to 5,000 feet, and the Jurassic from 6,000 to 

 8,000 feet. On Pine Mountain, the Trias at 4,650 feet, and the Jurassic 

 at 1,200 feet. 



On the Dirty Devil river in Northern Utah, the Jurassic is about 

 800 feet thick, on the southwest side of Escalante river, 60 miles far- 

 ther south, from 1,000 to 1,200 feet. The thickness of the Triassic in 

 New Mexico and Eastern Arizona is from 1,200 to 1,800 feet. This 

 gradually increases to the westward until near Pai'ia, it is 2,250 feet 

 Ninety miles to the northeast, on the Dirty Devil river, 1,700 to 1,900 

 feet, is found, while near St. George, farther west, the thickness is esti- 

 mated between 5,000 and 6,000 feet. 



J. J, Stevenson found the Triassic on Beaver Creek, a few miles 

 northeast of Canon Cit}^ 2,700 feet in thickness, and unconformable 

 with the Jurassic above, wherever it is observed in this region. 



Prof. G. M. Dawson, f separated the Triassic or Jurassic of the Rocky 

 Mountains, near the boundary monument, in des-cending order, into — 

 1st. Fawn-coloi'ed flaggy beds, 100 feet. 2d. Beds characterized by a 

 predominant red color, and chiefly red sandstone, but including some 

 thin greyish beds, and magnesian sandstones, the whole generally thin 

 bedded, though sometimes rather inassiA'e. Ripple marks, etc., weath- 

 ers to a steep rocky talus, where exposed on the mountain sides ; and 

 passes gradually down into the next series, 300 feet. 



'■■■ Geo. Sur. W. 100th Meridian, vol . 3. 

 t Rep. Geo. 49th Parallel. 



