236 



GEOLOGICAL SURVEY OF THE TERRITORIES. 



The first one probably dies out to the southward of Station 45, or Sheep 

 Mountain. The country slopes off in that direction, and from station 45 

 there is a long ridge on the east side of a branch of the Little Platte, 

 which slopes toward the park. In following up the Little Platte to 

 Weston's Pass, I saw no indication of the first fault. The trend of the 

 fault at the point h in the illustration is about south 10° east. How 

 much farther it extends to the southward I was unable to determine for 

 want of time. The dip of the schists at the point d in the diagram is 

 toward the east. They are of a rusty-red color, with micaceous layers 

 in some places, and in others quartzitic beds with light-colored granites 

 below. These schists extend to the Arkansas Eiver, and it is through 

 them that the river cuts the caiion, to which I will refer further on. On 

 leaving the mouth of the canon on Four-Mile Creek and going eastward, 

 we find that all the underlying beds are covered. From a few indica- 

 tions of volcanic rock, however, I am inclined to believe that there is a 

 fault running toward the north, the line of which would pass east of 

 Mount Lincoln. We have seen (section 'No. 16) that on the ridge east 

 of Lincoln there is a line of volcanic rock. This probably represents a 

 line of faulting. On looking at the map we see that there is an abrupt 

 turn in the course of Four-Mile Creek directly on the prolongation of 

 this line, the course for a short distance being in a line with that of the 

 Platte west of the ridge where section No. 15 was made. 



In section No. 18, we have the Potsdam group in beds No. 11 to 19, a 

 thickness of 119 feet. This is repeated again in beds 78 to 79. The 

 estimated thickness here is greater, being 156 feet. In section No. 18, 

 made by Mr. Taggart, in Mosquito Gulch, the thickness is 160 feet. In 

 Buckskin Gulch it was estimated at over 200 feet in section No. 16. 

 This last is probably exaggerated, as the upper bed in the section was 

 estimated from a point some distance below it. The thickness of the 

 Potsdam group along this range probably averages about 150 feet. 

 The remainder of the Silurian layers will probably average about 200 

 feet in thickness. It is probably all referable to tbe Quebec group. 

 The lower layers are so beyond doubt. A comparison with the same 

 layers already treated of in the first chapter is given below : 





«« 



S.( 1 





o 



^s 





<B 



<D 





OJ 



03 





*« A 



«*H=f-l 





a i 



.a ° 





•rf :3 





Locality. 



OB '^ 



00 QO 



05 a . 





"^ -^ 



* •'- a 





°P 



a cs g 







.2 g s 





'2 



^ fi- 





H 



H 



Glen Eyrie . . .. ........ 



40 



73 



Trout Creek 



60 to 80 

 150 



100 to 150 



Range between South Park and Arkansas Valley. 



200 







There has, therefore, been an increase in tkickness as we have come 

 westward. The line between the Carboniferous beds and the Silurian is 

 in all probability the bed No. 68 or 69 of section 18. The lower part of 

 the Carboniferous contains a number of beds of limestone, with inter- 

 laminated black shales, more or less argillaceous. In no case do 

 these beds attain a great thickness, and between them are beds of. 

 micaceous sandstones, which are laminated. Their general color is a 

 greenish gray, with the mica especially noticeable between the laminse. 



