218 AMADEUS W. GRABAU 
and regular one, but also necessitates the further assumption of an 
enormous erosion during the succeeding transgressive movements, 
which not only removed the greater part of several thousand feet 
of strata over the northern United States area, but also the whole of 
the extensive Canadian deposits of Beekmantown which must have 
reached far toward the Arctic regions, if the entire Beekmantown was 
deposited as a transgressional series. Aside from the fact that erosion 
would scarcely be very active during a positive diastrophic movement 
or transgression of the sea, it can hardly be assumed that such exten- 
sive erosion preceded the deposition of the St. Peter sandstone and 
the Chazy formation. Moreover, the intimate relation between the 
Lower St. Peter and the underlying Lower Beekmantown demands 
a close succession in deposition, the lower sand beds being probably 
deposited by the shoaling sea itself. If that is indeed the case, no 
higher dolomites of Beekmantown age than are now found ever 
existed in the Minnesota area. 
West of the Rocky Mountains, the basal Uinta quartzite is chiefly if 
not wholly a continental deposit of pre-marine Cambric time, 12,000 
feet or more in thickness. Upon this enormous basement series the 
eastward-transgressing Cambric sea laid down its progressively over- 
lapping strata, the upper beds of the series being reworked during the 
progress. The transgressing sea apparently did not reach the region 
of the eastern Uintas, where the basal quartzite is succeeded by the 
Lodore shales. From these shales Powell reported Carboniferous 
(Mississippic ?) fossils,' and he gives evidence of the existence of a 
disconformity between these shales and the basal sandstone. Weeks? 
identifies the Lodore with the Iron Creek shales of Berkey, which lie 
between the Uinta and the Ogden quartzites, and which Berkey 
correctly correlates with the Cambro-Ordovicic Ute limestone of 
the Wasatch. Weeks fails to recognize that, as Berkey has shown, 
the Ogden quartzite has united with the Uinta in the eastern section, 
the intervening shales having wedged out. The Lodore of the eastern 
Uintas thus lies above the Ogden horizon, and corresponds to a part 
of the overlapping Mississippic series (see Fig. 6). 
The Lower Ordovicic retreat is shown in the western section by the 
t Geology of the Uinta Mountains. 
2 Bull. Geol. Soc. Amer., Vol. XVIII, pp. 435, 436. 
