248 AMADEUS W. GRABAU 
the Virginia, western Tennessee, and Oklahoma occurrence of this 
series beginning with beds carrying a New Scotland fauna." 
The emergence of the North American continent at the end of 
Siluric time was accompanied by the first pronounced doming of the 
Cincinnati region and basining of the Michigan area. Local oscil- 
lations seem to have preceded this, but the first great movement 
apparently did not occur until the end of the Siluric. Between the 
Michigan basin and the Cincinnati dome were formed the Wabash 
anticline and the minor folds of Michigan, Ohio, and Canada. When 
these regions were again wholly submerged in Mid-Devonic time, 
the deposits of this later epoch came to rest on the beveled surfaces 
of various Siluric members (see Fig. 11). A subsequent movement. 
Northern Michigan 
Southern Michigan 
} Northern Ohio 
\ 
Central Ohio 
Southern Ohio 
mS ir a my 
SS ieee 
Fig. 11.—Section from northern Michigan to southern Ohio, showing the rela- 
tionship of the Middle Devonic to the Siluric and of the Upper to the Middle Devonic. 
O = Olantangy shale. 
in the same direction, at the end of Paleozoic time, threw the later 
beds into similar folds, while emphasizing those of the earlier series. 
A marked hiatus occurs between the Helderbergian and Oris- 
kanian. The former series is beveled, so that the Oriskany comes to 
rest, as it extends westward, upon lower and lower members of the 
Helderbergian, and finally upon the Manlius, and still farther west 
upon the Akron dolomite (Cobleskill). This beveling is in part due 
to retreatal “‘off-lap’’ but also to extensive erosion which indicates 
a time-period of some magnitude for the Oriskany. The deposi- 
tional equivalent of this hiatus is found in the Gaspe region of Canada, 
where 550 feet of Oriskanian (Grand Greve limestone) follows 
1 See Grabau, Bull. 92, New York State Museum. 
