PHYSICAL AND FAUNAL EVOLUTION 237, 
Niagaran fauna. ‘This fixes the age of the Queenston and Juniata 
as Richmond, so far as their major portion is concerned; though, as 
already noted, the lower part must be considered as Lorraine (see 
Fig. 10). 
In eastern Tennessee a second deposit of red sands of this period 
forms the Bays sandstone. This is from 1,100 to 1,300 feet thick 
in its maximum development near Loudon, but thins away by over- 
lap in all directions. In some localities, as at Walker Mountain, 
it is fossiliferous, carrving the late Lorraine fauna with Byssonychia 
radiata, Modiolopsis modiolaris, etc. Wherever the contact with 
the underlying Sevier shale is exposed, it is seen to be a gradational 
one, the fossils extending part way up into the red beds. The basal 
white bed, comparable to the Bald Eagle conglomerate, if it ever 
existed here, was overlapped by the Bays, the portion east of the 
overlapping edge having been removed by erosion. The Bays 
may be regarded as an independent fan, or group of fans, of red 
sedimentation with a distinct center of supply. 
The correlation of this series of continental sediments with the 
contraction of the sea known to have occurred in Upper Ordovicic 
time has not yet been attempted. It is not improbable that the 
initial uplift of the land which caused the retreat of the sea, also 
initiated the strong river-activities which resulted in the formation 
of the Bald Eagle conglomerate and sandstone. This probably 
corresponded to the period of folding of the Ordovicic and earlier 
strata in New England and northward. If that is the case, the emer- 
gence was probably post-Trenton, falling in early Lorraine (Frankfort 
or Eden) time and extending toward the end of Lorraine time. The 
period of red sedimentation in the east may have coincided with 
the pertod of erosion in the upper Mississippi and Rocky Mountain 
areas, and deposition of the Richmond in the narrow interior basins. 
The late Richmond expansion may coincide with the climatic change 
indicated by renewed river deposits of white quartzose material. 
D. THE LOWER SILURIC OR NIAGARAN 
The following divisions of the New York Niagaran are in common 
use as the North American standard: Guelph, Lockport, Rochester, 
Clinton. 
