HEAVY MINERAL ANALYSIS OF TRIASSIC SANDSTONE, 
DUNBARTON BASIN, SOUTH CAROLINA.

	HALL, M. H., and  THAYER, P. A., Dept. of Earth Sciences,
		University of North Carolina at Wilmington, 
		601 South College Rd., Wilmington, NC 28403-3297

The Dunbarton Basin, located 35 mi (~55 km) SE of the Fall Line 
beneath the  Savannah River Site (SRS), S.C., is one of the Triassic-
Jurassic rift basins of eastern North America.  The basin is about 30 
mi (~50 km) long and 6 mi (~10 km) wide; its axis trends N.57oE.  
Strata within the basin dip NW and are unconformably overlain by 
almost 1000 ft (~305 m) of Cretaceous and Tertiary Coastal Plain 
sediment.
	The deep rock borings (DRB), drilled at the SRS in the 1960's, 
encountered massive red mudrock, poorly to well sorted sandstone, 
and clast- and matrix-supported conglomerate.  Drill-core from these 
borings provide the least weathered samples of Triassic strata in the 
southeastern U.S.  Core from DRB-10, located near basin center, is 
fine- to very-coarse grained plagioclase arkose, lithic arkose and 
feldspathic litharenite interbedded with red mudrock and minor 
conglomerate.
	Sandstone samples utilized for this study contain relatively 
high percentages of heavy minerals, which on average comprise 6.5 
weight percent of the medium, fine, and very fine sand fraction.  To 
date, several non-opaque heavy mineral species have been identified. 
Abundant types include:   1) pink, orange, and colorless varieties of 
euhedral and subhedral garnet; 2) subrounded to well-rounded apatite; 
and 3) epidote group minerals.  Less common minerals include 
titanite, zircon, amphibole, chlorite, rutile, tourmaline and allanite; 
rare species are also present. This assemblage suggests a dominantly 
metamorphic provenance with minor contribution from granitoid rock.  
Ongoing microprobe study of the heavy mineral suite from Triassic 
sandstone and surrounding basement rock will provide more detailed 
provenance information.