522 DESCRIPTIVE GEOLOGY. 



value. In the region of Independence Spring are a series of low quartzite 

 hills, which, in passing north, are overlaid by patches and fragments of lime- 

 stone, which dip generally to the northwest. 



As already mentioned, the quartzite has been referred to the Weber, 

 and as the limestone, wherever observed, is seen invariably overlying it, the 

 latter has all been placed in the Upper Coal-Measure series. 



Organic remains, generally too poorly preserved for specific determi- 

 nation, but which undoubtedly belong to Coal-Measure forms, are found in 

 many localities. The following species have been determined: 



Productus subhorridus. 

 Athyris subtilita. 



North of Independence Spring were also found, not over 100 feet from 

 the quartzite, undetermined species of Bryozoa^ belonging to the genus Tre- 

 matopora. 



East of Euclid Peak occurs a peculiar outburst of volcanic rock, which, 

 although not a typical trachyte, has been regarded as belonging to that 

 group. It stands remote from all other trachytic bodies, the other acidic 

 volcanic rocks of the region, so far as observed, belonging to the rhyolites. 

 It forms a long north and south ridge inclined to the eastward, and is cut 

 through by Peoquop Creek, offering a good exposure of the mass. It is an 

 exceedingly dense, tough rock, breaking with difficulty. In color, it is yel- 

 lowish-brown, derived from the decomposed earthy material which makes 

 up the base. Macroscopically, in its mineralogical composition, it shows 

 only well-developed monoclinic and triclinic feldspars; the latter, appar- 

 ently predominating, are brilliant and characteristic. Hornblende, very 

 much decomposed, may be recognized from its form. The rock carries 

 small cavities and druses, many of them completely filled by secondary 

 products, as calcite and chalcedony. A chemical analysis was made of this 

 rock by Mr. E. W. Woodward with the following result : 



Silica. 67.81 67.60 



Alumina 15.83 15.74 



Ferrous oxide 3.41 3.47 



Lime 3.66 3.76 



