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
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
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
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