PROVENANCE OF SEDIMENTS IN THE CENTER OF THE 
DURHAM SUB-BASIN, NORTH CAROLINA

	GILMER, James P. III, TEXTORIS, Daniel A., Department of 
		Geology, University of North Carolina, Chapel,Hill, 
		NC 27599
	WATSON, Mary E., North Carolina Geological Survey, 	
		Raleigh, NC, 27607
	
The study area lies within the central portion of the Upper Triassic 
Durham sub-basin, a half-graben structure bounded to the southeast 
by the syn-depositional Jonesboro fault system (probably step-faulted) 
and to the west by nonconformities and post-depositional faults.  
Surrounding the sub-basin are metamorphic rocks of the Carolina 
Slate Belt to the west and higher grade metamorphic rocks and silicic 
intrusives of the Raleigh Metamorphic Belt to the east.
	The study was undertaken in order to determine the specific 
source terrane of the arkoses and lithic arkoses which were deposited 
in a meandering and axial river system which drained to the 
southwest.
	The lithic grains within the sandstones and the pebbles consist 
of schists, gneisses, slates, phyllites, and metavolcanics in order of 
higher to lower abundance.  Many of the lithic constituents contain 
index minerals, such as garnet, magnetite, myrmekitic feldspar, and 
epidote, that provide estimates of source terrane metamorphic grade.  
From the metamorphic grade estimates, lithologic character of the 
pebbles and sandstone lithic grains, maturity of texture to determine 
distance of transportation, paleocurrent data, and general outcrop 
information which suggest distal alluvial fan inflow, it is concluded 
that the sands and pebbles were derived predominantly from the east 
side of the sub-basin.
	The present-day terranes of the Raleigh Metamorphic Belt 
were the major source.  Sandstone point count data indicate a triple 
source:  1) a basement uplift of continental crustal granitic rock, 2) a 
dissected volcanic arc, and 3) a mixed source of basement rock, 
volcanic arc, and recycled orogen rock.
	Compatible source rocks are present within the major exposed 
terranes of the Raleigh Metamorphic Belt.  The Carolina terrane 
consists of low metamorphic grade slates and schists of volcanic arc 
origin.  The Rolesville batholith, the Falls Lake melange, and the 
Nutbush Creek fault zone consist of gneisses, granites, and 
leucogneiss of continental crust basement and mixed crust and 
recycled orogen origin.  The Crabtree terrane consists of garnet-
bearing gneisses of crust/recycled orogen origin.