C. D. Waleott—Pre- Carboniferous Strata in Arizona. 441 
a flesh-colored granite, the layers of quartzite standing nearly 
vertical. ; 
_ The Pre-Tonto series is a remarkable one considering its 
geologic age. In the Chuar group limestones and shales suc- 
ceed each other with lithologic characters similar to the Tren- 
ton limestone and Utica shale. The parti-colored shales, in 
one belt 700 feet thick, recall the friable Permian clays. In 
fact there is no more evidence of metamorphism throughout 
the 12,000 feet of conformable beds than there is in the evenly 
bedded strata of the Trias and Cretaceous groups of Southern 
Utah. Ripple marks and mud cracks abound in many hori- 
zons, but not a trace of a fucoid or a molluscan or annelid trail 
was observed. But for the discovery of a small Discinoid 
triangularis and an obscure Stromatopora-like group of forms, 
the two and one-half months’ search for fossils in these groups 
would have been without result. They serve, however, to 
retain the group within the Cambrian and also point to a 
fauna that must be searched for elsewhere, as they alone could 
Scarcely have been the only representatives of the life in the sea 
at that time. 
As now known, the Grand Cafion and Chuar groups may be 
referred to the lower Cambrian. Their stratigraphic position 
1S essentially the same as that of the Keweenawan group of 
Wisconsin. Both series were originally deposited over the 
_ underlying Archean unconformably. Both were subsequently 
elevated, eroded, and buried beneath sediments that in each 
case uncomformably overlie them and also contain a fauna 
strikingly similar. : 
Professor Chamberlain, when speaking of the interval be- 
tween the elevation of the Keweenawan series and the eposi- 
hon of the Potsdam, suggests that, in part, at least, the Acadian 
period of the Atlantic border represents a portion of the work 
of the interval.* 
With relation to the interval between the elevation of the 
Grand Cafion groups and the deposition of the Tonto there is a 
section in the Eureka District of Central Nevada which passes 
rom the Tonto or Potsdam horizon down through 3,000 feet of 
conformably bedded limestones before reaching the Olenellus 
‘horizon. The latter in turn is underlaid conformably by a 
great belt of quartzite as far down as the section was exposed, 
These beds appear to have been those deposited in the Nevada 
sea during the period of land surface over the Grand Cafion 
area, and if the Keweenawan series correspond to the Grand 
Caiion group in time, as they certainly appear to do in geologic 
position, we would consider the interval of erosion before the 
* Geology of Wisconsin, vol. i, p. 94, 1883, 
