AGATE PASS. 575 



these quartzitic sandstones, which is of the older type, and in all probability 

 Archaean. The frequent outcroppings, through this deep sedimentary series, 

 of gi-anite and schist summits of the Archsean age are sufficient to account 

 for the presence of angular conglomerates in any of the subsequent rocks. 



The quartzite series and the before-mentioned limestone series dip 

 toward each other at an angle of about 30°. Of the limestones, as has been 

 seen, there are 1,500 feet exposed, and of the quartzites about 4,000. They 

 represent the two sides of a synclinal, of which the western side has prob- 

 ably been faulted downward, and the diorite then burst up through the fis- 

 sure. The quartzitic series, from its character and thickness, has been 

 refen'ed to the Weber Quartzite, and the limestones to the Upper Coal- 

 Measure group. There is nothing, however, to prove that these do not 

 represent the upper members of the Wahsatch limestone, in which case it 

 must be the rocks to the east side of the synclinal that are depressed. Be- 

 sides the yellow conglomerate beds, near the summit of the quartzite series, 

 is a bluish-gray quartzite, made up of very fine grains of quartz, with very 

 little orthoclase and a few crystals of calcite. This is, however, a very 

 unimportant member of the series. There is a very close resemblance 

 between the yellow conglomerates and grits of this series and those under- 

 lying the Upper Carboniferous limestone of Moleen Peak, which will be 

 described in the next section. 



At the summit of Agate Pass, the quartzite series is cut through by 

 innumerable basaltic dikes, and overflowed by sheets of fine black basalt, 

 which flow down the eastern slope, and mask the whole range, from the 

 region of Mount Tenabo to Wagon Canon, a distance of 28 miles. As 

 observed along Agate Pass, these basalts are of a fine doleritic type, con- 

 sisting of plagioclase, augite, olivine, and rather coarse magnetite, between 

 which are small spots of dark bluish-gray globulitic base. There is consid- 

 erable variety in these basalts, as to the coarseness of their crystalline ingre- 

 dients, and the proportion of secreted crystals to the globulitic base. There 

 are some specimens in the uppermost flows which are as fine-grained as 

 hornstone, and have quite a resinous lustre in the fresh fracture. These 

 contain a larger proportion of glassy matter, and their crystals are very 

 minute. A characteristic of these basalts is the presence of a great quantity 



