96 
MUSEUM BULLETIN NO. 2. 
wood Canyon, Highland Range, and Eureka District sections 
the two horizons were not separated by the field observers. 1 
The Lower Cambrian is represented by at least the lower 
portion of the Pioche formation (see page 121) but the relation 
of the underlying quartzite series, which has an exposed thickness 
of 350 feet, 2 to the Pre-Cambrian is unknown. Over 1,000 feet 
above the layers with Olenellus in the Highland Range section, 
occurs a fauna, No. 21 of the section, 3 which can be correlated 
with that of the Middle Cambrian portion of the “Pioche” 
in Big Cottonwood canyon and can be assigned to the Spence 
shale horizon 4 in northeastern Utah and Idaho and to the 
Ogygopsis zone of the Stephen formation in British Columbia. 
These faunas are discussed more fully in the section on the 
Pioche formation, pages 120-125. 
Nevada, Pioche . — The most thorough discussion of the stratig- 
raphy near Pioche, Nevada, is furnished by Pack 5 who gives 
the following section 6 : — 
1. Limestone 800 feet. 
2. Shale [ = Zacanthoides typicalis zone] . . 75 “ 
3. Limestone 600 “ 
4. Shale [ = Pioche formation] . 400 “ 
5. Quartzite 1500 “ 
The town of Pioche lies in the northwestern portion of a pitching 
anticlinal 7 which has been considerably disturbed by faulting, 
but in which there is a general concentric arrangement of the 
shale and limestone formations about the quartzite. Both 
shale horizons carry well developed faunas, that of the lower 
(400 feet) being the one quoted on page 120, and generally 
ascribed to the Pioche formation. 
1 Walcott: Bull. U. S. Geol. Survey, No. 81, 1891, p. 319. 
2 Idem, No. 30, 1886, p. 33. 
3 Idem, p. 34. 
4 The name Spence has been carried southward to the House range (Smithsonian 
Misc. Coll., vol. 53, No. 5, 1908, p. 183) where the rocks to which the name has 
been applied carry a fauna more closely analogous to that in the shales forming No. 21 
of the Highland Range section, but no name has as yet been applied either to those 
shales or to the Middle Cambrian shale outcropping near the mines in the Ely 
mountains near Pioche (No. 2 of the above section). 
6 School of Mines Quarterly, vol. XXVII, 1906, pp. 285-312. 
8 Idem, p. 295. 
7 Idem, pi. II, between pp. 290 and 291. 
