80 GEOLOGICAL SURVEY OF THE TERRITORIES. 



tain, the quartzites rest directly on the granite uiiclens and flex over the 

 sides like a gently sloping roof. In the interval between the western 

 and middle ridges there are several small ridj^;es or uplifts of the gran- 

 ites that produced small anticlinals and. synclinals. There is one about 

 two miles above the Lower Canon and between it and the Middle Canon ; 

 the variegated beds form a well-marked synclinal. Scattered around 

 among the uplifted masses are depressions or basin-like valleys that are 

 filled with the modern lake-deposits. In the gorge of a little branch 

 that flows into the Grand from the south side, just above the Lower 

 Canon, there is a bluff-exposure of these modern deposits, mostly of a 

 deep drab or flesh color, and sometimes are 50 feet high, with three 

 layers of sandstone each 4 to 6 feet in thickness ; at another local- 

 ity 200 to 300 feet in thickness of these modern deposits, with a bed of 

 basalt near the summit. 



Like the modern lake-deposits in the valley of the Yellowstone, they 

 are very often capped with a basaltic layer. There is no doubt that dur- 

 ing the existence of the Pliocene or Post-pliocene lakes there were re- 

 peated eruptions of basalt, and probably there were hot springs which 

 dissolved the silica and feldspar, thus producing the fine materials 

 which have entered largely into the composition of these deposits. Be- 

 tween the west ridge and the middle ridge there is an interval of about 

 five miles. 



In this interval the variegated beds seem to have thinned out much 

 from the west toward the east, and here they rest directly on the gran- 

 ites. I call them variegated beds from the great variety of colors 

 they present. Whether they be Jurassic or Triassic age, or both, I 

 could not tell. I only know that the well-marked Cretaceous beds are 

 immediately above them. Immediately below the Middle Caiion the 

 Grand Eiver flows for about three miles through what I would call 

 a valley of depression ; the river cuts down into the granite base, and 

 at the lower portion of the little basin forms a narrow canon with ver- 

 tical sides or walls 50 feet high, while on either side granite hills rise 

 1,000 to 15,000 feet above. 



In the basin and resting upon this granite rock, but inclining at 

 various angles, is a considerable thickness of the variegated group. 

 Neither on the middle ridge nor in the valley of the Blue or the Grand, 

 east of this point, did we observe any of these red beds, and the quartz- 

 ites of the Dakota group rested directly on the granites. The entire 

 disappearance of from 4,000 to 6,000 feet of sedimentary beds within so 

 short a distance is certainly worthy of note. 



I have mentioned the parallel ridges that extend across the Middle 

 Park in a nearly north and south direction, through which the Grand 

 Eiver has carved out deep caiion s. 



On the west side of Blue Eiver there is one important ridge rather 

 convex in form, with a granitic nucleus. On the west side, near the 

 pass that leads over into the valley of the Blue Eiver, is a singular 

 mass of basalt, with a form so iDeculiar as to readily attract the atten- 

 tion of the traveler. It has much the shape of a huge steamboat. The 

 materials were effused in such a manner as to form a series of thin lay- 

 ers, flexed upward at each end, dish-like, with vertical sides 100 feet or 

 more. These dishes in the granite nucleus are very common. In some 

 instances the effusion of the basalt has changed the adjacent rocks, and 

 in many cases it has flowed out like water from a spring, producing no 

 change, but simply covering the surface for a greater or less distance 

 with the igneousrocks. On the high summits of the surrounding ridges 

 caps of basalt are common, giving them a partial table-like form. 



