216 GEOLOGICAL SURVEY OF THE TERRITORIES. 



from both its character and its position, I refer it, with hut little doubt, 

 to the age of the Niagara limestone of the Upper Silurian. It may, 

 however, have been deposited continuously from the era of the Upper 

 Silurian to the commencement of the Carboniferous age. The bed 

 forms tall, castellated cliffs along the caQons wherever it is exposed, 

 adding much to the beauty of the scenery. This is followed, in descend- 

 ing order, by about 400 feet of a blue, very impure, thin-bedded and 

 partly shaly limestone, much of which is a mass of pebbles, and from 

 the lower i)ortion of wbich Mr. Taggart and I, after long-continued 

 search, were able to obtain a few fragments of trilobites, of the genera 

 ConocorypJie and Bieelloceplialus ( f) These would not be sufficient of 

 themselves to determine the precise age of the strata, but, taken in con- 

 nection with the lithological character of the beds and the identification 

 of i)recisely similar layers only a short distance to the southward, they 

 justify the conclusion that this limestone is of Quebec Group age. The 

 thin lamination of the strata causes their easy weathering; so that they 

 generally present slopes of debris rather than bluffs of solid rock. In 

 many places, however, these debris are more or less thoroughly reconsoli- 

 dated by a cement of the lime first dissolved and then redeposited by 

 percolating rain-water. The rock is somewhat cavernous, and gives 

 passage to numerous streams flowing from the melted snows, which 

 escape in large springs at several points in the caSon. The water at 

 these points is still very cold, reaching only 38° and 40°, while the air 

 was at 72°. One of these springs was intermittent; but its periods were 

 not ascertained. At another outcrop of these limestones, they are 

 immediately underlaid by about 300 feet of partly compact and partly 

 shaly glauconitic sandstones, which are evidently equivalent to the so- 

 called Knox sandstones of Safford, which form, in Tennessee, the lower 

 part of the Quebec groui). No fossils were seen in these beds. They 

 are apparently unequally distributed, since no corresponding beds 

 appear along the caiion of West Teton Creek. Beneath them, and often 

 present when they are absent, we generally find from 50 to 75 feet of a 

 very compact ferruginous quartzite, which must represent the Potsdam, 

 though this also is sometimes wanting. 



Where these lower limestones are first encountered, near the mouth 

 of the caQou, they are nearly horizontal ; but, as we pass in toward the 

 center of the mountain, we find them rising considerably, until they 

 reach angles of 15°, 20°, and even 30°, dipping westerly and south- 

 westerly, and resting uncouformably upon the edges of granites which 

 dip in various directions. At the forks of West Teton Creek, where the 

 granites are first seen, their bedding dips 35° N. 78° E. Up the left- 

 liand fork they rise rapidly, causing beautiful cascades a hundred feet 

 or more in height, and finally occupying the whole upper basin of that 

 stream and reaching the very crest of the ridge. They also occupy the 

 vallej^ of the right-hand fork for a considerable distance, forming smooth, 

 bare cliffs on the left as we ascend, and finally are exposed in broad 

 surfaces on its floor. The right-hand wall of the caiion is abrupt for 

 1,200 feet or more, reaching well up into the Carboniferous limestones, 

 the upper parts of which form crests here reachiag more than 3,000 feet 

 above the caiion and about 10,000 feet above the sea. 



The granites, gneisses, and schists, which form the central nucleus of 

 the mountain, vary greatly in character and position. They are partly 

 micaceous, partly hornblendic, and partly talcose and cliloritic. No 

 regular succession was ascertained. The granites are mostly white or 

 tinged with pink, and occur in thick, solid beds. The other rocks are 

 much broken up and tilted in various ways, and are crossed in every 



