36 GEOLOGICAL SUEVEY OF THE TEREITOEIES. 



almost to tlie summit, are large quantities of drift material, and the 

 Tertiary marls appear to have been elevated nearly as high. Ail the 

 drift is local, as is usual in these mountain regions, and, by examining 

 it with care, fragments of the different kinds of rocks, brought to the 

 surface in the vicinity, may be found. Of course the later Tertiary beds 

 are made up of the eroded materials of rocks in the vicinity. Much of 

 the sediment was derived from the Carboniferous limestones, and 

 hence their marly character. The apparent inclination of these great 

 limestone ridges or mountains is in every direction, when examined 

 in detail, but the trend of the ranges is about northwest and southeast, 

 and the aggregate inclination northeast, although some of the strata 

 in the highest ridges incline north 60° to 70° 5 another i^ortion north- 

 west 15°. There is a somewhat x>eculiar feature about all the ridges 

 since leaving the Eocky Mountain " divide," and that is the evidence, 

 from their external a]3i)earance, of comparatively recent elevation. 

 The outcropping edges of the strata appear as if they had been 

 lifted up, without any of the usual proofs of wearing away by atmo- 

 spheric influences, and the debris on the sides and about the base would 

 indicate that the elevation had been prolonged up to the present 

 period. On the summits of these ridges, are great quantities of dead 

 pine-trees, scattered around without a trace of any younger trees or 

 shrubs to take their places. This is not an uncommon feature in many 

 portions of the Eocky Mountains. May it not be possible that these 

 mountain ridges are slowly rising at the present time ; that they have 

 reached an elevation that does not admit of the continued existence 

 of these pines, which evidently grew well under favorable conditions 

 which seem now to have entirely passed away*? On the north side 

 of Black-tailed Deer Creek, there is another exposure of the gneissic 

 rocks in a series of uplifted ridges, inclining about northeast, at angles 

 varying from 30° to 60°, (Fig. 6.) In the foreground are the modern ba- 

 salts, with an irregular columnar structure underlaid with modern 

 Pliocene deposits. It is a similar exposure, or, perhaps, a portion 

 of the same exposure on the south side i)reviously described, through 

 which Wildcat Canon passes to the valley. These exposures of the 

 gneissic rocks seem to be local, and are doubtless due to the stripping 

 off of the superincumbent formations. They undoubtedly form the 

 basis rocks of the whole country. In the mining regions they are 

 brought to the surface more frequently, and occupy much larger areas. 

 The broad, beautiful valley of the Black-tailed Deer Creek is worn out 

 of this belt of gneissic rbcks, and grows broader until it expands out 

 into the still wider valley of the Beaver-head Creek to the northwest, 

 about twenty miles below our road. In these granitoid rocks there is 

 the usual variety of texture, some composed of an aggregate of crys- 

 tals of feldspar, decomposing readily like sandstone ; others with a 

 schistose structure from their micaceous character 5 others so hard as to 

 resist the influences of the atmosphere — a kind of feldspathic quartzite in 

 large angular blocks. Are not these remnants of old mountain-ranges 

 that have resisted, to some extent, the powei"ful erosive influences that 

 have been brought to bear upon them for many geological ages ? 



From the valley of Black-tailed Deer' Creek we passed over the 

 " divide" to the sources of the Stinking Water. Our camp in the valley 

 was 5,973 feet, but the elevation of the divide is 6,657 feet. On our way 

 over we found here and there jjatches of basaltic rocks, fragments of the 

 great crust that once covered all the modern deposits of the valleys. On 

 the " divide," at the head of a cafion that leads into the valley of Stink- 

 ing Water, are some rather large exi)osures of the basalt, with a sort of 



