EARLY CAMBRIAN STRATIGRAPHY. 
97 
The interpretation of such a fauna as properly belonging to the 
Lower Cambrian has, in addition to any doubt which might 
be occasioned by the association itself, been clouded by the 
reported occurrence 1 in “the Ely mountains, just east of the 
Highland range”, and, therefore, very near Pioche, of a Middle 
Cambrian shale (2 of the section, page 96) carrying several 
species identical with those in the “Lower Cambrian. ” Pioche 
lies on the north slope of the Ely mountains and the literature 
has thus come to indicate the presence near Pioche of two shales 
of more or less indefinite position, and with comparable faunas, 
the one referred to the Lower, the other to the Middle Cambrian 2 . 
F. J. Pack® was the first to point out the relationship between 
these two shale3, their typical outcrops being given as 5 or 6 
miles apart and separated by a stratigraphic interval of 1,000 
feet. 
The two localities may be closely defined as follows: (1) the 
shale which has been referred to the Lower Cambrian (4 of the 
section page 96) and for which the name “Pioche ” was proposed 4 
outcrops southeast of the town of Pioche on the road to Panaca, 
Nevada; 5 (2)the shale which has been referred to the Middle Cam- 
brian outcrops in the dumps of the Abe Lincoln, Chisholm, and 
Half Moon mines west and northwest of Pioche. 6 The second 
outcrop is upon the western flank of the anticline, the first 
upon the east. 
As thus defined the lowest shale (4 of section) represents the 
Pioche formation and appears to be divisible (see pages 121-123) 
into a basal Olenellus gilberti zone, and an upper portion or 
Crepicephalus zone which is believed to be Middle Cambrian in 
age and is in this paper (see page 127) correlated with the 
Albertella fauna in Montana and British Columbia and the 
Burton formation in southern British Columbia. The upper shale 
1 Walcott: Bull. U. S. Geol. Survey, No. 30, 1886, p. 35. 
2 Cf. localities 31 and 31a, Mon. U. S. Geol. Survey, vol. LI, 1912, p. 192. 
3 School of Mines Quarterly, vol. XXVII, 1906, pp. 292 and 294-296. 
4 Walcott: Smithsonian Misc. Coll., vol. 53, No. 1, 190S, pp. 11-12. 
* “On the east side of the anticlinal arch at Pioche:” Bull. U. S. Geol. Survey, 
No. 30, 1886, p. 35. 
“Southeast of Pioche on the road to Panaca, Utah:” Smithsonian Misc. Coll., 
vol. 53, No. 1, 1908, p. 11. 
"Southwest of Pioche on the Panaca Road:” Idem, No. 5, 1908, p. 184. 
* “In the Ely Mountains just east of the Highland Range, owing to mining opera- 
tions:” Bull. U. S. Geol. Survey, No. 30, 1886, p. 35. 
