JOHNSON: TALLULAH DISTRICT. 
219 
are numerous bosses of granite and dykes of diabase and diorite, the 
latter having a prevailing northwest-southeast strike, across the 
trend of the crystallines. Professor T. L. Watson (’01) has shown 
that the granites of this region are intrusive in character, and that 
many of the gneisses are simply foliated igneous granites. On the 
other hand, occasional beds of limestone and quartzite, of undoubted 
sedimentary origin, are found interfoliated with the gneisses and 
schists. The rocks of this belt have generally been considered of 
pre-Cambrian age, with the exception of the basic dykes, a part of 
which, at least, probably belong to the Jura-Triassic (McCallie, ’01). 
The presence of undoubted sediments shows that if the crystallines 
are correctly classed as pre-Cambrian, a part of them must be referred 
to the Algonkian. 
The 'paleozoic area .— The northwestern corner of Georgia is crossed 
by paleozoic sediments,— limestones, shales, sandstones, etc.,—which 
have been compressed into northeast-southwest folds and eroded 
to produce the ‘‘ridge and valley” type of Appalachian topography. 
This area, which is the southeastern portion of a great extent of 
4 
paleozoic rocks, is the smallest of the three geological provinces, 
and while it has been described in some detail by J. W. Spencer 
(’93), and by others, it is not of special importance in connection 
with the present paper. 
These three geological provinces, described above, are separated 
from each other by rather sharp, well defined boundaries. Between 
the coastal plain and the crystalline belt is located the “fall line,” 
which passes through Camden and Columbia, South Carolina; Au¬ 
gusta, Milledgeville, Macon, and Columbus, Georgia. It marks 
the somewhat irregular contact of the nearly horizontal coastal-plain 
deposits with the highly tilted crystallines which they overlap on 
the northwest. The crystalline belt is separated from the paleozoic 
area by a great physical break, the “ Cartersville fault,” which passes 
south to Cartersville, Georgia, and then a little south of west into 
Alabama. 
General Physiography. 
The studies of Hayes, Campbell, and others have made the general 
physiographic features of the southeastern United States so familiar 
that only a brief review is necessary in the present connection. In 
