WEST HUMBOLDT EANGB. 717 



but carrying- broad zones of quartzite. This limestone series is again con- 

 foiTnably overlaid, in the northeast corner of the range, by a series of lime- 

 stones and slates, which, for reasons expressed farther on, are referred to 

 the Jurassic age. The contact beds of the inferior quartzites with the low- 

 ermost beds of black limestone are considered to be the dividing line be- 

 tween the Koipato and the true Star Peak Triassic. 



On the west side of the range, and on the northwest side of the anti- 

 clinal, the Star Peak limestones first make their appearance near the mouth 

 of Sacramento Canon, where they form a feeble outcrop, standing vertically 

 and striking with the anticlinal about north 30° east. The strike, about a 

 mile north of the mouth of Sacramento Canon, makes a gradual curve 

 around to the west, until it becomes north 35° west, with a dip almost 

 vertical, but a little to the southwest. Two and one-half miles north of 

 Sacramento Cailon, it again describes a curve into parallelism with the axis, 

 and makes a strike of north 30° east, more and more of the formation 

 cropping out from under the Quaternary deposits, until there appears a 

 thickness of 600 or 800 feet. This northeast strike is continued until the 

 limestones approach very close to the body of granite already described, 

 where it is again curved to the northwest, and in extreme cases strikes due 

 west, dipping south. At the entrance of Wright's Canon, the prevailing 

 strike is north 15° to 25° west, with a dip of 30° to the southwest. Here 

 in the canon, in the axis of this sudden change of strike, the beds are much 

 contorted, folded up into loops, and in some cases thrown over into a 

 reversed dip. The contact between the limestones and granites is more or 

 less obscured by surface material and debris ; enough, however, can be seen 

 io found the belief that the granite was not an intrusive body, but that the 

 strata were deposited over and around it, and that the observed flexures in 

 the strike were developed by the thrust of this hard granitic mass. Directly 

 underlying these limestones, and quite conformable with them, all the way 

 from Sacramento Canon northward to Wright's Cation, there is a variable 

 zone of siliceous and argillaceous beds, having a more or less schistose 

 structure, nowhere over 200 feet in thickness, and consisting of rocks with 

 a prevailing felsitic base, but containing fragmentary crystals of quartz 

 and feldspar, with occasional but rare white mica. In hand- specimens, and 



