136 GEOLOGY OF THE EUKEKA DISTRICT. 



cal position, a search which was rewarded by finding a limited and imper- 

 fect fauna, characteristic of the Trenton period. The finding of this group- 

 ing of fossils is important, as it carries the comformable Silurian limestones 

 overlying the Eureka quartzite down into beds generally regarded as lower 

 Silurian, whereas, elsewhere in the district there is no paleontological evi- 

 dence of strata older than the Niagara or Hall/site* beds above the quartzite. 

 Some description of this fauna will be found on page 59. 



The dark limestones which have been referred to the Trenton at this 

 point measure, according to the best estimates that can be made, about 300 

 feet; that is to say, this is approximately the thickness from the Eureka 

 quartzite on Wood Cone to the strata having the characteristics of the 

 horizon found elsewhere and regarded as of Lone Mountain age. These 

 dark limestones extend northward to the low saddle over which the wagon 

 road passes, beyond which the light colored, pearly limestones come in. 

 Westward and northward of the granite-porphyry a second locality was 

 found yielding a similar fauna, proving the extension of the horizon in 

 that direction. Here the Trenton beds, or those assigned to that epoch 

 upon lithological grounds, appear somewhat thicker than those obtained near 

 the first mentioned locality. Passing up the slope of the peak over the Lone 

 Mountain beds, north of Wood Cone, the strata generally referred to the 

 Nevada limestone make their appearance at the base of the first abrupt 

 slope of the long spur from Combs Peak, and from here to the top of the 

 prominent hill south of the peak the ridge offers an excellent section across 

 the limestones. The beds strike across the ridge and dip toward the peak, 

 with varying angles. A number of the observed strikes and dips will 

 be found recorded on atlas sheet ix. On the top of the hill a few fossils 

 may be found, indicating that the beds at the top of the northerly dipping 

 rocks still belong to the Lower Nevada limestone. Between this hill and 

 the summit of Combs Peak occurs a sharp syncline, the axis of the fold 

 lying in the saddle at the base of the steep slope of the peak. The lime- 

 stones on both summits strike about N. 55 west; those 011 the peak dipping 

 25 southwesterly, and those on the spur 35 northeasterly. The amphi- 

 theater of Combs Canyon has been eroded out of the beds lying within 

 the synclinal fold. 



