PETROLOGY OF THE SOUTH CAROLINA GRANIDES: 
THOMAS LEONARD WATSON 
Brooks Museum, University of Virginia 
OUTLINE OF THE GEOLOGY OF THE CRYSTALLINE AREA 
The South Carolina area of crystalline rocks extends northwest- 
ward from the fall-line, is roughly triangular in shape, and forms a 
part of the eastern crystalline area which extends southwestward 
from New York to northern central Alabama. 
Until the recently established State Geological Survey of Earle 
Sloan, this region had received almost no geological study since the 
state surveys of M. Toumey in 1844-47 (1848 date of final report) 
and of O. M. Lieber in 1855-60. 
The Blue Ridge crosses the extreme northwest corner of the state 
in a narrow mountainous belt, the higher peaks of which have an 
extreme elevation of 3,500 feet. Between this mountainous belt on 
the northwest and the fall-line on the southeast is included the greater 
part of the crystalline area—the Piedmont province. Its principal 
physiographic features, in common with the same province toward 
the northeast and southwest, are the broad rolling upland surface, the 
valleys carved in the upland, and the minor residuals which rise 
above the upland. The higher elevations over the region are stated 
by Sloan to range from 700 to goo feet above sea-level, with the beds 
of the major streams averaging 200 feet lower.’ 
Metamorphic crystalline rocks compose the principal part of 
this region. They include crystalline schists and gneisses derived 
from both igneous and sedimentary masses, altered chiefly through 
recrystallization and textural modifications, the most apparent of 
which is schistosity. The original rocks from which the schists and 
gneisses are derived are so extremely altered in many places that all 
trace of their characters is lost. 
Among the principal metamorphic igneous rocks are granite- 
gneisses, hornblende schists, and quartz-sericite schists. In com- 
1 Published by permission of the Director of the U. S. Geological Survey. 
2 South Carolina Geological Survey, 1908, Series IV, Bull. No. 2, p. 505. 
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