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OUTCROPS IN THE VICINITY OF THE SAVANNAH RIVER SITE
Altamaha and of fluvial deposits in general. A few miles to
the east, the Altamaha is truncated by the Orangeburg scarp.
Pliocene marine deposits occur to the east of the scarp
(Colquhoun, 1988).
There is evidence of deformation in the sediments at the
northern end of the cut. The deformed zone is several feet
wide and strikes approximately north-south across the highway.
Two northeasterly-striking, down-to-the-northwest
faults have been mapped from subsurface control in Allendale
County by Oldham (1981) and Colquhoun and others
(1983). Is the Miocene Altamaha Formation affected by the
deformation at this outcrop
B. Bluffs along Savannah River and tributaries, Georgia
Power Company Plant Vogtle, Burke County, Georgia, off
River Road.
The “Blue Bluff” unit or member (Huddlestun and
Hetrick, 1986, p.4), a middle Eocene carbonate cliff-former,
crops out in bluffs along the river and in tributary valleys on
the Georgia side. “Blue Bluff” sediments are light gray, and
pale green and weather to gray, olive gray, and tan. They are
mostly glauconitic calcilutite and calcarenite with thin layers
and nodules of indurated limestone and quartz sand laminae.
Shell layers occur sporadically. Cream colored carbonates
(McBean facies”) of the middle Eocene Santee Limestone
also occur here. Outcrops of the “Blue Bluff” are at least 40
ft high in places.
Slump blocks of the middle or upper Eocene Utley
Limestone Member of the Clinchfield Formation and the
upper Eocene Griffins Landing Member of the Dry Branch
Formation occur at river level. The Utley is composed of
indurated limestone, glauconitic in places, with abundant
Periarchus (sand dollars) and molds of pelecypods and gastropods.
Shells of Crassostrea gigantissima from the Griffins
Landing are also common on the slopes.
C. Bank on the southwest side of US 278, 100 yd southeast
of the intersection of US 178 and county road 57; southeast
of Hollow Creek, 0.3 mi southeast of Petticoat Junction,
Aiken County, South Carolina.
The massive, color-mottled clay at the base of the outcrop
is similar to the oxidized clay found at the top of the
Cretaceous in outcrops and in cores from SRS. It is tentatively
assigned to the Upper Cretaceous.
A sample from a roadside ditch beside county road 57 a
short distance southwest of the intersection with US 278
yielded an early Paleocene age (see Nystrom and others,
1991, p. 224). The thinly bedded or laminated, tan, red, and
brown clay above the mottled clay at our outcrop is tentatively
assigned to the Paleocene. It overlies the Cretaceous
() clay with a sharp contact. Behind the nearby store,
coarse, cross-bedded sand lies on the Cretaceous () mottled
clay.
Several palynological samples from wells at SRS, about
4 mi to the southeast, indicate that late Sabinian (early
Eocene) deposits of the Fourmile Formation lie between
Paleocene strata and the early (and middle) Eocene Congaree
Formation. The interbedded sands, pebbly sands, and
clays at this outcrop are tentatively correlated with the Fourmile
on the basis of stratigraphic position. A quartz pebble
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