178 GEOLOGICAL SURVEY OF THE TEEEITOEIES. 



Troublesome, while indications of former ones are said to exist in the 

 Lower Williams Elver. It is by no means improbable that, like the Hot 

 Sulphur Springs at the base of Mount Bross, these, also, have their out- 

 let between the Lower Cretaceous sandstones and the shales above; and 

 if so, indicate that these rocks, though now covered by lake-beds, still 

 occur beneath, and dip off northward and southward away from the 

 archsean area of the Grand. The relations of the Cretaceous to the west- 

 ern portion of this archsean area will be given shortly, when describing 

 the lower portions of the Muddy and Blue Elvers whore they join the 

 Grand. 



TnE VALLEY OF THE MUDDY. 



The Park range forms the western limit of the Middle Park drainage. 

 North of the Grand, and all along west of the Muddy Valley, it is by no 

 means a high and rugged mountain-range, but a great rolling, even- 

 contoured swell of archsean rock, on the gentle eastern slopes of which 

 rest the Lower Cretaceous quartzites, extending more or less far up on it, 

 and dipping off to beneath the Muddy Elver, which has excavated its 

 broad valley in the soft Middle Cretaceous shales. At the north, the 

 gentle eastern slopes of the valley are made up of the western edge of 

 the great northern lignitic area ; at the south, the low ridge of lake 

 beds lying between the Muddy and the Lower Troublesome Valley, limit 

 it on the east. The Cretaceous shales and sandstones of midvalley are, 

 however, nearly concealed by the long low terraces of lake-beds which 

 cover their upturned edges, and occupy nearly all of the main valley, 

 reachiug far up on either side, the underlying Cretaceous rocks being 

 exposed at innumerable points in the many ravines which cut through 

 the lake beds in all directions. The valley, however, is not wholly a 

 simple monoclinal. The Park range trends west of north, and from it, 

 at one or two points, low anticlinals run out in an east of north, or north, 

 direction for a few miles and then terminate, the beds flattening out at 

 their ends, the river meanwhile being forced more and more east, as it 

 passes around their northern ends. In the following more detailed de- 

 scription of the valley, reference should be made to the geological map 

 of the Middle Park, (Fig. 8,) and sections 2, 3, and 4, of Plate III, the 

 positions of which are indicated on the map. • 



The main source of the Muddy is the westernmost one, rising on the 

 long even massive slopes of the Park range, which are Iiere composed of 

 very coarse granite. The waters collecting on these granite slopes flow 

 down to a small north and south valley at their base, which is formed 

 by the westward facing edges of the Lower Cretaceous beds which lie on 

 the granites. Breaking through the ridge formed of these in a narrow 

 caiion, the stream flows out into the more open valley. (See west end 

 of section 2.) The lower beds are mostly soil-covered, but seem com- 

 I)Osed mostly of soft red sandstones, with a few harder beds, especially 

 at the top, where a prominent layer of hard, white, quartzitic sandstone 

 occurs. The estimated thickness of these beds is about 1,200 feet, or 

 nearly three times the thickness of the corresponding beds at the Hot 

 Springs, or about the same as the section noticed southeast of the Hot 

 Springs. Considerations as to whether a portion of the Jurassic may 

 be here represented, or whether all should be referred to No. 1, have 

 been given before. In the absence of fossils the latter is the most nat- 

 ural conclusion. They appear to become much thinner in their southern 

 extension, approaching the usual type and thickness of No. 1. Passing 

 east through the canon, the river flows across another little north and 

 south valley, and breaks through a smaller uniclinal ridge, likewise dip- 



