PACKEK BASIN. 15] 



for long distances from one mountain to another. In this way it becomes 

 an easy matter to correlate strata in such blocks as Island and Leader 

 mountains and Sugar Loaf. The deep gorges penetrating the limestones 

 afford grand exposures. Sugar Loaf offers one of the best points of view 

 for gaining a clear understanding of the synclinal structure of the Silverado 

 Hills, the characteristic belts of sandstones and mottled limestones being 

 readily traceable from an easterly to a westerly dip. The summit of Sugar 

 Loaf is formed of Upper Devonian strata, with abrupt escarpments on all 

 sides. At the east base of this isolated mountain, the Rescue Canyon fault 

 may be traced crossing the ridge between the head of Rescue Canyon and 

 the faulted block of White Pine shales at Charcoal Canyon. From Sugar 

 Loaf northward to Packer Basin all the limestones on the west side of the 

 fault dip westerly, the fault following the line of contact between the 

 Nevada limestone and the White Pine shale. Opportunities for observing 

 these westerly dipping beds may be found in Charcoal and Ox Bow canyons, 

 the streams which cut the ravines crossing the strata nearly at right angles 

 to their strike. 



Packer Basin. Packer Basin is a small depressed block of Nevada lime- 

 stone lying between the northern end of the main ridge and the broad 

 basalt table, the abrupt wall of the latter shutting in the basin on the north. 

 As the basin lies on the very edge of a broad volcanic field, it has naturally 

 undergone a good deal of dislocation, and is much broken up by pumices 

 and tuffs, which partly fill the basin, having poured out along a fissure 

 on the west side of the faulted block. It is interesting to see here the same 

 association of pumices and tuffs, followed by a later outburst of basalt, in 

 all respects similar to those occurrences seen in so many other places 

 bordering the uplifted block. The limestone still maintains the north and 

 south strike and westerly dip of the main ridge to which it really belongs. 

 Its chief interest lies in the finding in a massive blue limestone a fauna 

 characteristic of a somewhat higher horizon than those observed at Wood- 

 peckers and Basalt peaks. Additional interest is derived from the disappear- 

 ance of the Rescue fault and the accompanying White Pine shales beneath 

 the basalts. 



