EARLY CAMBRIAN STRATIGRAPHY. 
101 
The overlying shale series is the stratigraphic, lithologic, 
and faunal (?) equivalent of the Pioche formation in Nevada, 
and like that formation (see page 122) its first description 1 
listed fossils collected from Lower and Middle Cambrian zones 
a hundred or more feet apart. This mistake was corrected in 
189 1 2 when the formation was divided into two zones, a lower 
one with Olenellus which for convenience of description we shall 
call the Olenellus gilberti zone of the Pioche formation, and an 
upper one with “ Lingulella ella, Balhyuriscus producta,” etc., 
which for similar reasons will be called the Bathyuriscus pro - 
ductus zone of the Pioche formation. In Big Cottonwood can- 
yon, therefore, this unit is lithologic and includes both Lower 
and Middle Cambrian horizons. Indeed it includes the only 
Lower Cambrian forms so far discovered in the section and 
the placing below it of the line between the Lower and Middle 
Cambrian would remove from the underlying beds tiie very 
fossils upon which their age is predicated. For this reason 
that boundary is believed to be correctly assigned to a position 
above the Olenellus gilberti zone and it may be expected that 
subsequent work in the district will show this lower horizon to 
be properly separable as a lithologic member of the Pioche, 
more closely related to the underlying quartzite than to the 
overlying shale(see pages 124-125). Hintze 3 has proposed the term 
Alta shale for the strata between the quartzite and the “Ordo- 
vician” limestone to which he has applied the term Maxfield. 
The discovery, by Mr. F. B. Weeks and the writer, 4 of Middle 
Cambrian fossils in the type section of this limestone obliterates 
the “hiatus” at the top of the “Alta” and leaves that name 
so nearly the equivalent of the Pioche as hardly to warrant its 
adoption. 
Utah, Wasatch Mountains, Ogden Canyon.— The basal quartz- 
ite in Ogden canyon, Utah, is an apparently conformable series 
about 1,000 feet thick, which rests on gneisses and schists 
referred to the Archaean and is itself overlain by shales containing 
fossils that have been referred to the Middle Cambrian. Black- 
1 Walcott: Bull. U. S. Geol. Survey, No. 30, 1886, p. 39. 
2 Idem. No. 81, 1891, p. 319. 
3 Annals N. Y. Acad. Sci., vol. XXIII, 1913, pp. 104, 105. 
* Unpublished notes. 
