96 GEOLOGICAL SUEVEY OF THE TERRITOEIES. 



and ill wliicli reel is so striking and predominant a color that they are 

 commonly known by the name of the " Eed Beds." Though shaly strata 

 are frequent, and the whole series may be quite soft, yet the general 

 thickness, or massiveness, of the strata forms another prominent and 

 characteristic feature. 



Most of these sandstones are of a normal red-sandstone type, varying 

 from coarse grits and moderately coarse sandstones, with fine examples 

 of cross-bedding, to quite fine-grained and shaly layers. The latter 

 occasionally may make up a considerable thickness, but though occurring 

 frequently they are generally so intercalated with the heavier beds, 

 that, as said before, a sort of massiveness characterizes the group. 

 Though conglomerates may occur anywhere in the series, they are 

 mostly confined to n'ear the base, where they are often plainly derived 

 from "the subjacent rock. It is in these lower parts, indeed, that the 

 beds are so directly made up of the material of older rocks near by that 

 a very little metamorphism has in some instances made it difficult to 

 distinguish small masses of sandstone from the underlying granites. 

 Dark red is the prevalent color, though light-red, yellow, and cream- 

 colored beds are frequent, and may, in places, quite predominate over 

 the red. This is more noticeable near the top, while the conglomerates 

 and beds directly composed of granitoid materials are also generally 

 gray or light in color. Sometimes, also, a peculiar character is shown 

 by sharply defined, often perfectly circular yellow or white spots up to 

 three-quarters of an inch in diameter scattered upon the deep-red back- 

 ground, as if drops of water in falling on the stone had worked the 

 color from it. This would not necessarily be characteristic of this for- 

 mation, though I did not see it elsewhere. 



Although the surface of the Archaean rocks below is more or less 

 smoothed, it is often irregular, and occasional bosses of granite, &c., 

 project into the sandstone, as in the accompanying instances, (fig. 2,) 

 observed by Mr. Gardner, near Turkey Creek. 



]S[ear the Big and Little Thompson's and Saint Yrain's Creeks, expo- 

 sures indicate a general shelving off or abutting of the edges of the 

 lower strata against the Archsean rocks, or "overlap," a point of inter- 

 est to which attention will be called later. 



Had opportunity offered, this feature would probably have been found 

 all along the base of the mountains. 



Local cMracters. — Toward the north end of the district the shaly 

 character is more marked than elsewhere. At the Little Thompson 

 (see Plate I, section 1) the series has a total thickness of about 750 

 feet, and is composed of soft granit^e sandstones and conglomerates be- 

 low, white to red, with coarse soft red sandstones above, followed by 

 two or three hundred feet of shaly sandstone, the whole capped by 

 massive red sandstones about 250 feet thick, but generally breaking 

 into from two to three prominent layers, with thin shaly strata between. 

 Farther north, the lower beds become much shalier than here, while 

 southward the shales grow heavier bedded. In this northern region, 

 the fact that the more massive beds are confined to the upper part of 

 the series, combined with a gentle eastern dip, causes the surface fea- 

 tures to differ somewhat from those farther south. The long, gentle 

 eastern slopes of the massive beds are denuded by erosion, often for 

 several miles to the east of the softer series of rocks which would lie 

 above them, (and yet to be described,) and the lower series, thus occur- 

 ring alone over considerable areas, has a sort of geographical individu- 

 ality given to it. It is this feature, a result of the more massive char- 

 acter of these beds as compared with those above, and this alone, which 



