E-N-DLICH.1 GEOLOGY SAN LUIS DISTRICT, SECTION C. 347 



along the base of the range parallel to the river must have been depos- 

 ited by it, and not by any other means, provided lithological identifica- 

 tion of the drift-rocks admits of no contradiction. This latter does not 

 seem to be the case, however, and the accumulation of the greater por- 

 tion of the redeposited material I ascribe to the action of the Arkansas. 

 A number of creeks rnnniug out from deeply-cut ravines in the 

 mouutaius have cut in an almost straight line through the drift; a cir- 

 cumstance which is readily explained by the fact that its resistance was 

 so small as to necessitate no considerable deviation from a straight 

 line. As they have cut in deeply, however, forms stronglj^ resembling 

 moraines have not infrequently resulted, which might mislead. Oppo- 

 site station 4, the caiion of the Arkansas narrows and the drift-deposit 

 disappears. Along Tomichi Creek a considerable quantity of drift has 

 accumulated, covering about thirty to forty square miles, the material 

 for which was brought from the neighboring granitic and quartzitic hills. 

 Northwest of station 43 some drift has accumulated in the valley of the 

 Upper Gunnison, part of which is due to the action of glaciers. In a 

 long, narrow line, rnnniug from southeast to north'oest, raorainal de- 

 posits sweep down from the base of the high mountains to the valley. 

 Characteristic narrow but level valleys, bordered on either side by lat- 

 eral moraines, with a number of small glacial lakes, are found at the 

 points of emanation. Changing their course slightly^ these two moraines 

 extend down into the valley, leaving at every favorable locality small 

 lakes or swampy j)Iaces, and they terminate on the sides in moraines, 

 descending from 1,000 feet in height to 200. Eeaching the valley, the 

 ice melted and formed a large lake, at the place of which a swampy, low 

 country now is found, inhabited by hundreds of beavers. In these 

 moraines gold-washing has been carried on formerly, and is still carried 

 on in some of the neighboring gulches. This is the only instance through- 

 out our entire district where I could really recognize the action of 

 glaciers. 



Mineral deposits are found in only two localities of section c ; the one 

 on Mount Princeton, where a series of parallel veins are contained in 

 the granite, running between the strata, which are peculiarly well-defined 

 there. They are about 12,000 "feet above the sea, but several of them 

 have been worked to a small extent. Usually the strike is from north- 

 east to southwest, and the dip about 135° to the north, with slight varia- 

 tions of either. The ores contained in these lodes are mainly galenite, 

 sphalerite, and small quantities of fahlerz, resulting, when decomposed, 

 in the formation of azurite and malachite. Argentite was found in a 

 few specimens. According to report, assays that have been made are 

 favorable. In the valley of the Upper Gunnison, i. e., north and east 

 of the entrance of the canon, the drift contains gold, which has been 

 worked at intervals for some years. In Union gulch, adjoining the 

 valley, there were several miners at work at the time of our visit, appar- 

 ently well pleased with their results. Single nuggets of several dollars 

 in value are frequently washed out. Probably the drift-material of that 

 region may contain paying quantities of the precious metal, which some 

 day will most likely be turned to account by the enterprising western 

 miner. 



Resume of section c. — In this section we have the greatest variety of 

 granites met with thus far. Besides the red, middle to coarse-grained 

 rock, that I think may safely be regarded as the oldest, a repetition of 

 the type found in the two proceeding sections, we have another one, 

 composing the Sahwatch range, containing as its most jn'ominent peak 

 Mount Princeton : near that we have the i^rotogiue, possibly owing 



