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CAROLINA GEOLOGICAL SOCIETY
Guidebook for 1992 Annual Meeting
Pages 41-43
STRATIGRAPHIC RELATIONSHIPS IN EOCENE OUTCROPS ALONG UPPER THREE RUNS AT THE
SAVANNAH RIVER SITE
W. C. Fallaw
Department of Geology
Furman University
Greenville, South Carolina
David S. Snipes, J.S. Daggett, Lillian Furlow, April James, J.P. Moore, Sarah Price
Department of Earth Sciences
Clemson University
Clemson, South Carolina
Van Price
Westinghouse Savannah River Company
Aiken, South Carolina
Upper Three Runs, which flows southwest along strike
of the sedimentary strata toward the Savannah River, is the
major stream draining the Savannah River Site (SRS). Relief
is relatively low on its northwestern side but is up to about
200 ft on the southeast, perhaps because of migration of the
stream down the regional dip (Siple, 1967, p. 14). Eocene
sediments are exposed along northwesterly-flowing tributaries
to Upper Three Runs, in bluffs along Upper Three Runs,
and along the railroad paralleling the stream near F area and
C road (Figure 1). Sloan (1908) described sections along
Tinker Creek, a tributary to Upper Three Runs north of the
area studied in this report, and Siple (1967) mentioned outcrops
along Tinker Creek and Upper Three Runs. Exposures
in the area have been discussed recently by Dennehy and
others (1989), Nystrom (1989), Nystrom and others (1989,
1990, 1991), and Nystrom and Dockery (1992).
The sections described in this report are exposed at
Upper Three Runs Bluff, located about 2100 ft south of the
railroad bridge over Upper Three Runs and about 50 ft east
of the stream; in several outcrops along Waterfall Creek, a
tributary which flows into Upper Three Runs about 1500 ft
south of the bridge and extends upstream almost to F area; in
several outcrops along Copperhead Creek, a tributary which
passes under the railroad about 1800 ft northeast of the
bridge; and in the railroad cut about 2500 ft northeast of the
bridge (Figure 1). Thicknesses and elevations of the strata
were estimated by Jacob staff and hand level, measuring
from Upper Three Runs and the railroad. Composite sections
were constructed along the two streams. The sections
described in this report include the Congaree and Warley Hill
formations, the Santee Limestone and equivalent siliciclastics,
and the Dry Branch Formation, all of Eocene age, and
Quaternary () colluvial and fluvial deposits (Figure 2).
The Congaree is exposed at one place along the lower
part of Waterfall Creek where about 5 ft of orange, moderately
to well-sorted, fine to medium sand can be seen. The
thickness of the formation could not be determined. The
Congaree is early (to middle) Eocene and a correlative of
the Tallahatta of the Gulf Coastal Plain.
The Warley Hill, a middle Eocene lower Lisbon correlative,
is exposed at Upper Three Runs Bluff, Waterfall Creek,
and Copperhead Creek. It consists of orange, poorly sorted,
clayey and silty, medium to coarse sand with grayish clay
laminae overlain by dark green glauconitic clay and clayey
sand with very coarse sand, granules, and pebbles. The upper
clay unit is a little less than 2 ft thick. The thickness of the
formation is estimated to be about 15 ft.
The outcropping Santee Limestone (part of the
“McBean Formation” of other workers), a middle Eocene
upper Lisbon equivalent (and perhaps younger), occurs as a
silicified facies containing shell fragments and external and
internal molds of pelecypods and gastropods with Turritella
being especially common. A layer about 1.5 ft thick holds up
a waterfall about 2.5 ft high on Waterfall Creek and loose
blocks of the facies are common in the railroad cut. Fragments
of silicified limestone are also common in the strea
bed above the waterfall.
The Santee-equivalent siliciclastics (part of the
“McBean” of other workers) are interbedded with the silicified
carbonate facies and consist mostly of fine and very fine,
light gray, yellow, and orange well sorted sand with green,
white, gray, yellow, and tan laminae and beds common in
places. Ophiomorpha – type burrows approximately 0.5
inches to 1 inch in diameter, mostly vertically oriented and
lined with white clay, are abundant at some outcrops. Silicified
internal molds of Turritella are abundant, especially in
one exposure in Copperhead Creek. Prominent in the lower
part of the unit is a green glauconitic clay or very clayey
sand about 2 ft thick. The clay can be distinguished from the
dark green clayey bed of the underlying Warley Hill by a
paucity of coarse sand, granules, and pebbles abundant in the
older unit. In placed the two green clays are in sharp contact,
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