Geology of the Hardeeville NW Quadrangle and Parts of the Brighton and Pineland Quadrangles, Jasper County, South Carolina

By

Christopher S. Swezey, Arthur P. Schultz,1

 William R. Doar III,2 Christopher P. Garrity, Christopher E. Bernhardt, E. Allen Crider Jr., Lucy E. Edwards,1 and John P. McGeehin1

2019

Any use of firm, trade, or product names is for descriptive purposes only and does not imply

endorsement by the U.S. Government

For sale by U.S. Geological Survey, Box 25286, Denver Federal Center, Denver, CO 80225;

http://store.usgs.gov; 1–888–ASK–USGS (1-888-275-8747)

Suggested citation: Swezey, C.S., Schultz, A.P., Doar, W.R, III, Garrity, C.P., Bernhardt, C.E., Crider,

E.A., Jr., Edwards, L.E., and McGeehin, J.P., 2019, Geology of the Hardeeville NW quadrangle and

parts of the Brighton and Pineland quadrangles, Jasper County, South Carolina: U.S. Geological

Survey Scientific Investigations Map 3424, 2 sheets, scale 1:24,000, https://doi.org/10.3133/sim3424.

1

U.S. Geological Survey, retired. 2

South Carolina Geological Survey.

ISSN 2329-132X (online)

ISSN 2329-1311 (print)

https://doi.org/10.3133/sim3424

Age, in cal.

years BP

Age, in 14C

years BP

d13C, in

per mil (‰)

Sample depth

in core,

in meters

Surface elevation

of core,

in meters

Material

dated Latitude Longitude

Core

location

description

USGS

sample ID

WW8886

WW8887

WW8888

WW9477

WW9429

Map unit

Qsmp1

Qsmp1

Qsmp4

Qsmp1

Qsmp1

Core

C3

C3

C1

C3

C3

inter-hill

depression

inter-hill

depression

inter-hill

depression

inter-hill

depression

fluvial

channel

32.48710° N

32.48710° N

32.48710° N

32.48710° N

32.48282° N

81.20855° W

81.20855° W

81.20855° W

81.20855° W

81.15867° W

wood

wood

wood

8

8

8

8

5

1.81–1.83

0.46–0.48

1.37

1.03–1.05

2.13–2.14

-25

-25

-25

-29.6

-28.3

5,060±30

modern

41,890±930

887±35

8,275±30

modern

5,895–5,667

46,841–43,856

910–731

9,403–9,135

bulk

sediment

bulk

sediment

Table 3. Radiocarbon sample data and age results from vibracore (C3) and gouge core (C1).

[Core locations are shown on maps A and B. 14C analyses by John P. McGeehin. Explanation of table columns are as follows: "USGS sample ID" is the U.S. 

Geological Survey sample identification number from the radiocarbon laboratory in Reston, Va.; "Material dated" is the sample material that was used for 

radiocarbon dating; "Surface elevation of core, in meters" is elevation above sea level; "Sample depth in core, in meters" is the sample depth below surface; "d13C, 

in per mil (‰)" is the isotope carbon-13 (

13C) value used to correct radiocarbon ages due to isotope fractionation, according to Stuiver and Polach (1977); "Age, 

in 14C years BP" is the sample age in radiocarbon years before present with a 2-sigma standard deviation of age uncertainty using the Libby half-life of 5,568 

years, and 0 years BP being equivalent to A.D. 1950; "Age, in cal. years BP" is the sample age in calibrated years before present]

Estimated

age

Dinocystes

zone Preservation

Surface elevation

of drill core,

in meters

Latitude Longitude

Drill core

location

description

USGS

sample ID

R6709 F inter-hill

depression

32.48613° N 81.18845° W 8

Sample depth

in drill core,

in meters

7.74 to

7.59

good; no

single species

dominates

DN2 (subzone 2c)

of de Verteuil and

Norris (1996) and

de Verteuil (1997) 

lower Miocene

(probably lower

Burdigalian)

Dinoflagellate species identified

Apteodinium tectatum Piasecki 1980

Cleistosphaeridium placacanthum (Deflandre & Cookson 1955) Eaton et al. 2001

Dapsilidinium pseudocolligerum (Stover 1977) Bujak et al. 1980

Distatodinium paradoxum (Brosius 1963) Easton 1976

Exochosphaeridium insigne de Verteuil & Norris 1996

Heteraulacacysta Drugg & Loeblich 1967 sp.

Hystrichokolpoma rigaudiae Deflandre & Cookson 1955

Lejeunecysta Artzner & Dörhöfer 1978 spp.

Lingulodinium machaerophorum (Deflandre & Cookson 1955) Wall 1967

Operculodinium Wall 1967 spp.

Polysphaeridium zoharyi (Rossignol 1962) Bujak et al. 1980

Quadrina Bujak 1980 ? sp.

Selenopemphix nephroides Benedek 1972

Selenopemphix quanta (Bradford 1975) Matsuoka 1985

Spiniferites Mantell 1850 spp.

Spiniferites mirabilis (Rossignol 1964) Sarjeant 1970

Spiniferites pseudofurcatus (Klumpp 1953) Sarjeant 1970

Sumatradinium Lentin & Williams 1976 sp.

Sumatradinium soucouyantiae de Verteuil & Norris 1996

Tectatodinium pellitum Wall 1967

Tuberculodinium vancampoae (Rossignol 1962) Wall 1967

R6709 A inter-hill

depression

32.48613° N 81.18845° W 8 21.70 good; no

single species

dominates

DN2 (subzone 2b)

of de Verteuil and

Norris (1996) and

de Verteuil (1997) 

lower Miocene

(probably lower

Burdigalian)

Apteodinium tectatum Piasecki 1980

cf. Artemisiocysta Benedek 1972

Cerebrocysta satchelliae de Verteuil & Norris 1996 

Cleistosphaeridium placacanthum (Deflandre & Cookson 1955) Eaton et al. 2001

Cordosphaeridium cantharellus (Brosius 1963) Gocht 1969

Cribroperidinium tenuitabulatum (Gerlach 1961) Helenes 1984

Dapsilidinium pseudocolligerum (Stover 1977) Bujak et al. 1980

Emmetrocysta Stover 1975 sp.

Exochosphaeridium insigne de Verteuil & Norris 1996

Heteraulacacysta Drugg & Loeblich 1967 sp.

Hystrichokolpoma rigaudiae Deflandre & Cookson 1955

Lejeunecysta Artzner & Dörhöfer 1978 spp.

Lingulodinium machaerophorum (Deflandre & Cookson 1955) Wall 1967 

Operculodinium Wall 1967 spp.

Pentadinium sp. I of Edwards (1986)

Polysphaeridium zoharyi (Rossignol 1962) Bujak et al. 1980

Reticulatosphaera actinocoronata (Benedek 1972) Bujak & Matsuoka 1986

Selenopemphix nephroides Benedek 1972

Selenopemphix quanta (Bradford 1975) Matsuoka 1985

Spiniferites Mantell 1850 spp.

Spiniferites mirabilis (Rossignol 1964) Sarjeant 1970

Spiniferites pseudofurcatus (Klumpp 1953) Sarjeant 1970

Sumatradinium soucouyantiae de Verteuil & Norris 1996

Trinovantedinium papula de Verteuil & Norris 1992 [sensu amplo]

Tuberculodinium vancampoae (Rossignol 1962) Wall 1967

A single specimen of Homotryblium plectilum suggests reworking (range of

this species is middle Eocene to Oligocene).

Table 2. Dinoflagellate cyst species identification results and age estimates from samples R6709 F and R6709 A in drill core C2; sample depth locations within drill core C2 are shown in 

figure 2. The results provide the lower Miocene age estimate for the stratigraphic unit Nsm shown in figures 2 and 3.

["USGS sample ID" is the U.S. Geological Survey sample identification number; "Surface elevation of drill core, in meters" is elevation above sea level; "Sample depth in drill core, in meters" is the sample depth 

below surface. Dinoflagellate species identification analysis by Lucy E. Edwards. Abbreviations: N, north; W, west]

Table 1. Optically stimulated luminescence (OSL) sample data and age results from Swezey and others (2013).

[Explanation of table columns are as follows: "OSL sample ID" is the optically stimulated luminescence sample identification number; "Sample elevation, in meters" is the elevation of the sample location, in meters above sea level; "Sample depth, 

in centimeters" is the sample depth, in centimeters below surface; "Water, in percent" is the laboratory measured field moisture (water content) of the sediment at the center of each tube in which the sample was collected (sample saturation 

percentage is in parenthesis); "K, in percent" is the potassium concentration; "U, in ppm" is the uranium concentration, in parts per million; "Th, in ppm" is the thorium concentration, in parts per million; "CDA, in Gy/k.y." is the sample cosmic dose 

addition, in grays per thousand years, as calculated using the methods of Prescott and Hutton (1994); "Dose rate, in Gy/k.y." is the total dose rate, in grays per thousand years; "DE, in Gy (MAM)" is the sample equivalent dose, in grays, using the 

Minimum Age Model-3 (MAM); "DE, in Gy (weighted)" is the sample equivalent dose, in grays, using the weighted mean; "DE, in Gy (mean)" is the sample equivalent dose, in grays, using the mean; "nDE (mean)" is the number of replicated 

equivalent dose estimates used to calculate the mean value (number in parenthesis represents the total number of measurements of subsamples or aliquots, including failed runs with unusable data); "Dispersion, in percent" is the calculated average 

of the equivalent dose divided by the standard deviation of the equivalent dose, without evaluating the ranges of uncertainty; "OSL age, in ka (MAM)" is the determined age of the sample in thousands of years before present using the OSL Minimum 

Age Model-3 (MAM) for equivalent dose determination (preferred ages in bold); "OSL age, in ka (weighted)" is the determined age of the sample in thousands of years before present using the weighted mean OSL value for equivalent dose 

determination (preferred ages in bold); "OSL age, in ka (mean)" is the determined age of the sample in thousands of years before present using the mean OSL value for equivalent dose determination. OSL ages are given in years before A.D. 2010 

(the year of age determination), and are reported with a 1-sigma standard deviation of the age uncertainty. Preferred ages (in bold) follow criteria discussed in Swezey and others (2016) for the choice of statistical model that is thought to yield 

the most accurate OSL age. Following Swezey and others (2016), if the dispersion is <25 percent then the preferred age is that obtained by the weighted mean, and if the dispersion is ≥25 percent then the preferred age is that obtained by the 

Minimum Age Model-3 (MAM) (Galbraith and Laslett, 1993; Galbraith and others, 1999)]

OSL

sample ID Latitude Longitude

Sample

elevation,

in meters

Sample

depth, in

centimeters

Water, in

percent

K, in

percent

U, in

ppm

Th, in 

ppm

CDA, in

Gy/k.y.

Map

unit

GAW-03

GAW-04

GAW-05

GAW-06

GAW-07

GAW-08

GAW-09

GAW-10

GAW-11

Qs1

Qs1

Qs1

Qs1

Qs1

Qs1

Qs1

Qs1

Qs1

32.48457° N 81.20333° W 9 60 6 (38) 0.53±0.02 0.43±0.06 1.14±0.08 0.19±0.02

32.48911° N 81.18024° W 8 40 5 (34) 0.62±0.02 0.67±0.06 2.45±0.11 0.16±0.01

32.49084° N 81.19570° W 9 78 6 (37) 0.71±0.02 0.74±0.06 2.91±0.10 0.19±0.02

32.52192° N 81.23143° W 12 96 3 (30) 0.67±0.02 0.58±0.04 1.61±0.10 0.19±0.02

32.54423° N 81.26348° W 12 20 3 (28) 0.65±0.02 0.55±0.04 1.32±0.10 0.19±0.02

32.54423° N 81.26348° W 12 148 2 (30) 0.54±0.01 0.30±0.03 0.66±0.10 0.17±0.01

32.54332° N 81.26128° W 12 152 3 (29) 0.60±0.02 0.66±0.04 1.14±0.10 0.17±0.01

32.49416° N 81.19051° W 1 (24) 0.71±0.04 0.91±0.06 2.90±0.14 0.18±0.01

32.49416° N 81.19051° W 2 (22) 0.74±0.03 1.03±0.08 2.73±0.18 0.18±0.01

11

11

140

150

nDE

(mean)

20 (20)

20 (20)

19 (20)

23 (25)

20 (20)

25 (25)

29 (30)

4 (20)

DE, in Gy

(MAM)

7.4±0.37

25.6±1.10

19.1±0.69

27.5±0.96

20.0±0.92

20.0±0.90

23.9±1.08

22.2±0.60

22.8±0.63

26.8±0.66

28.1±0.33

25 (25)

OSL age,

in ka

(MAM)

10.2±0.7

28.4±1.5

18.5±0.1

29.9±1.4

22.3±1.3

29.3±2.0

28.2±1.7

18.6±0.1

19.1±0.1

21.5±1.0

22.6±0.9

Dispersion,

in percent

24.4

31.8

21.4

17.1

13.6

20.5

17.1

18.7

32.1

DE, in Gy

(weighted)

8.9±0.49

28.2±1.35

22.1±1.23

28.3±1.19

21.7±1.11

22.5±1.26

27.6±1.42

24.0±1.17

24.6±1.23

28.5±1.78

29.9±0.89

OSL age, 

in ka

(weighted)

12.2±0.8

31.3±1.8

21.5±1.3

30.8±1.6

24.1±1.5

32.9±2.5

32.7±2.1

20.1±1.2

20.6±1.2

22.9±1.7

24.0±1.2

OSL age,

in ka

(mean)

23.7±2.0

27.2±1.4

20.4±1.4

20.8±1.4

32.9±2.2

32.9±2.7

24.2±1.6

30.8±1.6

21.5±1.4

34.3±2.2

12.2±0.8

DE, in Gy

(mean)

8.9±0.46

30.9±1.70

22.1±1.37

28.3±1.13

21.8±1.16

22.5±1.35

27.8±1.53

24.5±1.47

24.8±1.49

29.5±2.11

33.8±1.18

Dose rate,

in Gy/k.y.

0.73±0.03

0.90±0.03

1.03±0.02

0.92±0.03

0.90±0.03

0.69±0.04

0.85±0.03

1.19±0.04

1.25±0.05

GAW-12

GAW-13

GAW-14

GAW-28

GAW-29

GAW-30

GAW-31

GAW-36

GAW-37

OSL

sample ID

GAW-03

GAW-04

GAW-05

GAW-06

GAW-07

GAW-08

GAW-09

GAW-10

GAW-11

GAW-12

GAW-13

GAW-14

GAW-28

GAW-29

GAW-30

GAW-31

GAW-36

GAW-37

Qs1 32.50996° N

Qs3

Ngsm

Qsmp3

Qs3

Qs1

Qs2

Qs1

Qs1

81.22414° W 11 82 3 (24) 0.42±0.01 0.58±0.05 2.38±0.17 0.19±0.02

32.48911° N 81.16963° W 8 183 6 (25) 0.50±0.01 0.41±0.05 1.25±0.17 0.16±0.01

32.55597° N 81.27906° W 8 640 15 (55) 1.33±0.05 3.58±0.21 14.1±0.60 0.16±0.01

32.55597° N 81.27906° W 8 549 1 (27) 0.56±0.02 0.51±0.06 1.93±0.22 0.18±0.01

32.54774° N 81.25823° W 12 61 15 (42) 0.49±0.02 2.06±0.12 7.35±0.23 0.19±0.02

32.54692° N 81.25918° W 12 84 16 (29) 1.80±0.02 2.7±0.06 10.6±0.23 0.19±0.02

32.44127° N 81.12888° W 8 70 8 (32) 0.79±0.02 0.96±0.07 3.08±0.10 0.19±0.02

32.43740° N 81.14857° W 8 90 4 (31) 0.66±0.03 0.67±0.06 2.09±0.02 0.19±0.02

32.42373° N 81.15730° W 8 80 2 (32) 0.51±0.02 0.43±0.06 1.24±0.08 0.19±0.02

20 (20)

19 (19)

10 (10)

30 (30)

29 (30)

30 (30)

20 (20)

17 (20)

18 (20)

17.3±1.04

75.7±5.45

>110

24.0±0.50

43.8±4.03

58.3±4.84

27.0±1.00

8.3±0.43

9.8±0.47

21.7±1.6

104±10

>46

27.9±1.9

33.2±3.2

20.9±1.8

22.3±1.0

8.6±0.5

17.4 13.3±0.7

21.3

22.8

13.7

15.1

13.2

20.9

15.6

16.3

18.6±1.21

79.0±6.72

>102

26.2±0.84

52.4±4.45

65.8±5.73

29.3±1.29

9.8±0.54

14.2±0.75

23.3±1.9

108±12.0

>43

30.5±2.2

39.7±3.6

23.6±2.1

24.2±1.2

10.3±0.7

19.2±1.2 13.4±1.0

12.3±0.9

25.0±1.4

23.7±2.1

43.5±5.9

37.1±2.8

>37

26.9±2.2

121±13

21.5±1.46

88.4±7.34

>88

31.9±1.16

57.4±7.58

66.1±5.68

30.3±5.12

11.8±0.59

9.9±0.56

0.80±0.04

0.73±0.05

2.37±0.08

0.86±0.06

1.32±0.04

2.74±0.06

1.21±0.02

0.96±0.05

0.74±0.03

EXPLANATION

[Predominant lithology]

Sand (sandstone, where lithified)

Sandy mud or muddy sand (mudstone or 

sandstone, where lithified)

Mud (mudstone, where lithified)

Pale-brown (5YR 5/2) clay; abundant monolete fern spores, decreased

abundance of Pinus and Nyssa pollen

Pale-brown (5YR 5/2) clay; increased abundance of Pinus,

Nyssa, Ulmus, and Ambrosia pollen (interpreted as indicative of post-colonial land clearance)

Pale-brown (5YR 5/2) to medium-gray (N5) clay, pollen assemblages

dominated by Pinus and Nyssa

Medium-dark-gray (N4) clay; pollen assemblage dominated by Nyssa (interpreted as

characteristic of seasonal flowing water)

Black (N1) silty sand; pollen assemblage dominated by Nyssa (interpreted as

characteristic of seasonal flowing water)

Grayish-black (N2) fine to medium sand; pollen assemblage dominated by Quercus, Poaceae,

Asteraceae, and Artemisia (interpreted as characteristic of regionally dry conditions); 

Nymphaea and Myriophyllum pollen are also present (interpreted as indicating locally wet

conditions with standing water)

WW8887

WW9477

WW8886

WW9429

Vibracore C3

32.48710° N

81.20855° W

0

1

.5

1.5

0

2

4

Gouge core C1

32.48282° N

81.15867° W

WW8888

Light-gray (N7) to olive-gray (5Y3/2), very fine to medium sand

Qsmp4

Qsmp1

Grayish-black (N2) sandy clay with plant debris

Medium-gray (N5), very coarse sand at base to medium sand at top; fining upward sequence

Dark-greenish-gray (5G 4/1) muddy sand; sand is very fine to fine

Medium-gray (N5), very coarse sand at base to medium sand at top; fining upward sequence

USGS sample ID and

radiocarbon age, in 14C years BP (see table 3)

USGS sample ID and

radiocarbon age, in 14C years BP (see table 3)

WW8887=modern

WW9477=887±35

WW8886=5,060±30

WW9429=8,275±30

WW8888=41,890±930

TD=2.33

meters

TD=1.37

meters

METERS FEET

0

1

.5

1.5

2

0

2

4

6

8

METERS FEET

Figure 4. Stratigraphic column descriptions of vibracore (C3) and gouge core (C1) with radiocarbon ages. Locations of cores C3 and C1 are 

shown on maps A and B. Color nomenclature (for example, 5YR 5/2) used in core descriptions is from Goddard and others (1963). 

Abbreviations: 14C years BP, radiocarbon years before present, where "present" is defined as A.D. 1950; N, north; TD, total depth of core from 

surface elevation; USGS sample ID, U.S. Geological Survey sample identification number; W, west.

Figure 3. Cross section B–B' constructed using auger core data. The lower Miocene age estimate for unit Nsm was determined from biostratigraphic data from drill

core C2 (fig. 2; table 2), and extrapolated to cross section B–B' located in the southern part of maps A and B. Auger core locations are shown with heavy dark vertical

lines; core widths are exaggerated to show lithologies. Dashed contacts in auger core HNW-34 are gradational. Abbreviations: HNW, Hardeeville Northwest; N, north;

P, sediment containing phosphate sand grains; TD, total depth of auger core from surface elevation; W, west.

0 250 500 750 1000 METERS

0 1000 2000 3000 FEET

VERTICAL EXAGGERATION ×120

EXPLANATION

[Predominant lithology]

Gravel or gravelly sandstone (conglomerate or 

conglomeratic sandstone, where lithified)

Sand (sandstone, where lithified)

Sandy mud or muddy sand (mudstone or 

sandstone, where lithified)

Mud (mudstone, where lithified)

Auger core

HNW-34

32.41876° N

81.16438° W

P

TD=9.22

meters

Auger core

HNW-33

32.43195° N

81.15246° W

Auger core

HNW-32

32.43648° N

81.14942° W

Auger core

HNW-31

32.43841° N

81.13920° W

Auger core

HNW-30

32.44088° N

81.12918° W

TD=19.95

meters

TD=16.91

meters

TD=12.30

meters

TD=15.37

meters

P

P

P

P

P

P

B B'

30

20

10

SEA LEVEL

10

20

30

40

50

WEST EAST

FEET

SEA LEVEL

5

10

15

5

METERS

SURFACE

Unconformity

Unconformity

Unconformity

Unconformity

BEND IN

SECTION

BEND IN

SECTION

BEND IN

SECTION

Nsm (lower Miocene)—Sand

and mud with phosphate grains;

shallow marine sediments

Ngsm (lower Pliocene?)—Gravel, sand, and mud;

fluvial to estuarine to marginal marine sediments

Qs3, Qs2, Qs1, Qsmp3, Qsm2, and Qsmp1

(Quaternary sediments, undivided)—Fluvial sand 

(Qs3 and Qs2); Eolian sand (Qs1); fluvial, 

swamp, and marsh sand, mud, and peat (Qsmp3); 

fluvial sand and mud (Qsm2); and interdune 

swamp sand, mud, and peat (Qsmp1)

0 500 1000 1500 2000 METERS

0 1000 2000 3000 4000 5000 6000 FEET

VERTICAL EXAGGERATION ×120

Figure 2. Cross section A–A' constructed using auger and drill core data. R6709 F and R6709 A are U.S. Geological Survey identification numbers for two samples from drill core C2 from which dinoflagellate species were identified for biostratigraphic age control (table 2). Auger and

drill core locations are shown with heavy dark vertical lines; core widths are exaggerated to show lithologies. Dashed contact in auger core HNW-9 is gradational. Abbreviations: HNW, Hardeeville Northwest; N, north; P, sediment containing phosphate sand grains; TD, total depth of auger

or drill core from surface elevation; W, west.

A A'

40

30

20

10

SEA LEVEL

10

20

30

40

50

Auger core

HNW-9

32.492611° N

81.223917° W

P

TD=12.30

meters

Auger core

HNW-6

32.485194° N

81.20750° W

P

P

TD=11.68

meters

Ngsm (lower Pliocene?)—Gravel, sand, and mud;

fluvial to estuarine to marginal marine sediments

Nsm (lower Miocene)—Sand and mud

with phosphate grains; shallow marine sediments

Drill core C2

32.48613° N

81.18845° W

P

P

R6709 F

R6709 A

P

P

P

P

P

P

TD=22.44

meters

Auger core

HNW-4

32.488139° N

81.178611° W

P

TD=23.06

meters

Auger core

HNW-2

32.472944° N

81.142028° W

WEST EAST

FEET

SEA LEVEL

10

5

10

15

5

METERS

P

TD=9.22

meters

EXPLANATION

[Predominant lithology]

Gravel or gravelly sandstone (conglomerate or 

conglomeratic sandstone, where lithified)

Sand (sandstone, where lithified)

Sandy mud or muddy sand (mudstone or 

sandstone, where lithified)

Mud (mudstone, where lithified)

Chert

Core not recovered

BEND IN

SECTION

BEND IN

SECTION

BEND IN

SECTION

SURFACE

SURFACE

Unconformity

Unconformity

Unconformity

Unconformity

Qs3, Qs2, Qs1, Qsmp3, Qsm2, and Qsmp1

(Quaternary sediments, undivided)—Fluvial sand 

(Qs3 and Qs2); Eolian sand (Qs1); fluvial, 

swamp, and marsh sand, mud, and peat (Qsmp3); 

fluvial sand and mud (Qsm2); and interdune 

swamp sand, mud, and peat (Qsmp1)

Figure 1. Measured section of an outcrop at Porters Landing on the west bank of the Savannah River, as 

described and interpreted by Sloan (1908), Cooke (1936), Malde (1959), and Huddlestun (1988). The outcrop 

is located approximately 7.4 kilometers (4.6 miles) northwest of the northwesternmost part of maps A and B. 

Note that different stratigraphic designations have been applied to the lithologic units identified at this 

outcrop by Sloan (1908), Cooke (1936), Malde (1959), and Huddlestun (1988). The term "phase" was used 

by Sloan (1908). For a discussion of the lithologic units and their relation to cross section A–A', see 

"SUMMARY OF MAP UNITS." Elevations shown on the scale are given as units above sea level. 

Abbreviation: P, sediment containing phosphate sand grains.

EXPLANATION

[Predominant lithology]

Sand (sandstone, where lithified)

Sandy mud or muddy sand (mudstone or 

sandstone, where lithified)

Marl (shells with sand)

Sloan

(1908) Outcrop description Cooke

(1936)

Malde

(1959)

Huddlestun

(1988)

Pleistocene

sediments

White, red, and yellow,

fine to coarse sand

with crossbedding

and some beds

of clay

Yellow to gray marl

Yellow sand and marl

with concretions of

sandy carbonate

Sand and sandstone

Shale and

sandy mud

Marl with oysters

Gray sandy mud

Miocene

Edisto phase

Miocene

Marks Head

phase

Oligocene

Parachucla

phase

Oligocene

Combahee

phase

Pleistocene(?)

Sunderland(?)

Formation

Upper Miocene

Duplin Marl

Lower Miocene

Hawthorn

Formation

Pleistocene

sediments

This study

Lower

Pliocene(?)

(Ngsm)

Lower

Miocene

(Nsm)

Miocene

Duplin Marl

Miocene

Hawthorn

Formation

Pliocene

Cypresshead

Formation

Lower

Miocene

Marks Head

Formation

Lower

Miocene

Porters

Landing

Member

Lower

Miocene

Tiger

Leap

Member

Parachucla Formation

Hawthorn Group

P

P

P

50

40

30

20

10

160

150

140

130

120

110

90

80

70

60

50

40

30

20

10

100

METERS

FEET

INTRODUCTION

This publication portrays the geology of the Hardeeville NW quadrangle and 

parts of the Brighton and Pineland quadrangles that are within Jasper County, South 

Carolina. This study area is located in the Atlantic Coastal Plain province, 

approximately 50 to 70 kilometers (km) inland from the coast. The data are compiled 

from geological field mapping, light detection and ranging (lidar) elevation data, 

cores, optically stimulated luminescence (OSL) ages, radiocarbon ages, and 

biostratigraphic interpretations. Most of the study area is occupied by the valley of 

the Savannah River, and exposures of geologic units are very limited. Traditional 

geologic mapping in this area is difficult because of limited access, subdued 

topography, extensive swamps, and abundant vegetation.

The Savannah River flows predominantly southeast, and forms most of the 

border between the States of South Carolina and Georgia. The river is approximately 

483 km long, and has a total drainage area of approximately 15,850 square km (km2). 

Although upstream tributaries drain the southeastern side of the Appalachian Blue 

Ridge province, the Savannah River begins in the Piedmont province and then flows 

across the Atlantic Coastal Plain province to the Atlantic Ocean. For much of its 

extent, the modern channel of the Savannah River is located on the southwestern side 

of the river valley, and the southwestern bank of the valley is the active cut bank.

Within the study area, the valley of the Savannah River trends southeast and is

relatively straight. The valley has relatively low relief, although the southwestern

valley wall is steeper and has greater relief than the northeastern valley wall.

Elevations within the valley mostly range from 3 to 15 meters (m) above sea level,

whereas elevations on the high terrace that forms the eastern margin of the Savannah

River valley are 15 to 20 m above sea level. The width of the valley is 6 to 7 km in

the northern part of the study area, and expands to 10 to 12 km farther south. The

modern river channel occupies the southwestern side of the valley, and some modern

(active) creeks enter the river from the west. Sand hills and low-relief terraces are

present to the east of the modern river channel, and the eastern side of the valley is

characterized by abandoned meandering and linear channels. Fan-shaped deposits of

sand and mud are present where relict (inactive) channels enter the eastern side of the

valley. Abandoned meandering channels of low relief (<3 m) are also present to the

east on the high terrace (>15 m elevation) that forms the eastern margin of the

Savannah River valley. Within the study area, most of the Savannah River valley is

covered by alluvial wetland community vegetation dominated by cypress and tupelo

trees, although sand hills within the valley are covered by xeric sand community

vegetation dominated by pine trees (Christensen, 2000; Bernhardt and others, 2012).

PREVIOUS WORK

Most early studies of the major geomorphological features of the Savannah 

River valley may be found in publications of broader studies of the geology of the 

Atlantic Coastal Plain (McGee, 1890, 1891; Veatch and Stephenson, 1911), and 

some early geomorphological descriptions may be found in publications of primarily 

botanical focus (Bartram, 1791; Harper, 1903, 1904, 1905). Nevertheless, most of 

these early studies provide general descriptions of the valley, and they report the 

presence of terraces, sand ridges, and sand hills.

Specific studies of terraces within the Savannah River valley are relatively few. 

In Aiken and Barnwell Counties, Siple (1967) noted the presence of terraces, and 

Leeth and Nagle (1996) described the following two mappable units within the 

valley: (1) a 6.7- to 13.7-m-thick unit of "modern" alluvial sediments on the western 

side of the flood plain, and (2) a 1.5- to 8.5-m-thick older alluvial terrace complex on 

the eastern side of the flood plain. The two units overlie an unconformity above 

Eocene strata, and the total thickness of these two units decreases towards the coast. 

In Jasper County, the U.S. Department of Agriculture (USDA) soil survey (Stuck, 

1980) characterizes the terraces within the Savannah River valley as primarily a 

mixture of sandy loam and clayey loam named the Santee association, whereas a few 

small areas are described as either a mixture of clayey loam and sandy loam named 

the Argent-Okeetee association or a mixture of sandy loam and sandy clay named the 

Eulonia association. 

In contrast with the terraces, the sand ridges and sand hills within the Savannah 

River valley have been the subject of more intensive study. McGee (1890, 1891) and 

Veatch and Stephenson (1911) reported the presence of sand hills and provided brief 

descriptions. In the USDA soil survey of Jasper County (Stuck, 1980), the area of the 

main sand hills within the Savannah River valley is mapped as a sandy soil named 

the Buncombe association, and the areas of isolated sand hills and ridges are mapped 

as a mixture of sandy soil and sandy loam named the Buncombe-Santee association. 

Pickering and Jones (1974) and Markewich and Markewich (1994) interpreted the 

sand hills as vegetated, parabolic eolian dunes. Leigh and others (2004) described 

south- to southeast-trending linear ridges in the Savannah River valley at 

approximately 32°22'50" north latitude, and they interpreted these features as fluvial 

"braid bars that have been reworked by the wind to produce parabolic dunes." They 

also described these features as "a braided terrace that is reworked and overlain by 

parabolic dunes." Bernhardt and others (2012) described pollen assemblages from 

Holocene sediment that had accumulated between sand hills (see vibracore C3 

location on maps A and B). Swezey and others (2013) published a detailed study of 

the sand hills, and they agreed with previous interpretations of the hills as parabolic 

eolian dunes that are derived from sand of the Savannah River and that are stabilized 

by vegetation under prevailing climate conditions. In addition, they published OSL

ages that suggested that most of the eolian dunes were active during the last glacial 

maximum (LGM) through early deglaciation, and they used a variety of data to infer 

paleoclimate conditions (wind direction, velocity, precipitation, evapotranspiration, 

vegetation cover) when the dunes were active. They also demonstrated that the 

Savannah River dunes are part of a larger assemblage of eolian dunes that were 

active in river valleys of the eastern United States during and immediately after the 

LGM.

Geologic maps of the South Carolina parts of the Brighton, Hardeeville NW, 

and Pineland quadrangles were published by Doar (2008, 2013a, b) as part of the 

STATEMAP component of the U.S. Geological Survey (USGS) National 

Cooperative Geologic Mapping Program. These maps show a variety of geologic 

units including terraces, marsh and swamp deposits, fluvial and alluvial sediments, 

and eolian dune ridges and hills. However, the work for these maps was completed 

before the widespread use of lidar imagery, and therefore they do not display the 

amount of detail that is visible in the lidar shaded-relief image (map B). This 

publication adds details to the existing geologic maps by Doar (2008, 2013a, b), and 

provides additional data derived from geologic field mapping, lidar elevation data, 

cores, OSL ages, radiocarbon ages, and biostratigraphic interpretations.

SUMMARY OF MAP UNITS

[Abbreviations: "14C yr BP" indicates radiocarbon years before present, where "present" is 

defined as A.D. 1950; "cal yr BP" indicates calibrated radiocarbon years before present. 

Preferred OSL ages are shown in bold fonts in table 1 and explained in the table 1 headnote. 

Conversions from radiocarbon years to calibrated radiocarbon years were made using the 

program CALIB 6.1.1 (accessed at http://calib.qub.ac.uk/calib/), in conjunction with Stuiver

and Reimer (1993) and Reimer and others (2009)]

Within the study area, the various map units are grouped into the following five 

broad categories on the basis of age and sediment composition:

(1) Quaternary (Holocene) sand and mud, with or without peat (Qsmp1, 

Qsmp2, Qsm1, and Qsm2) are interpreted as fluvial and swamp deposits. Some of 

the sediments in this category have accumulated in topographic depressions among 

the sand hills, and thus must be younger than the sand hills that have yielded 

preferred OSL ages ranging from approximately 35.4 to 18.0 ka (kilo-annum, or 

thousand years before present) (table 1). Samples from vibracore C3 (maps A and B) 

in one of these depressions have yielded radiocarbon ages ranging from 8,275±30 

14C yr BP (9,403 to 9,135 cal yr BP) to modern (fig. 4; table 3). Other sediments in 

this category consist of fluvial sediments and swamp sediments associated with the 

lowest and westernmost terrace (Qt0), which is the terrace that is closest to the 

modern Savannah River. The Holocene age for these units is provided by the 

observation that meandering channels on terrace Qt0 have cut laterally into the 

western margins of both the sand hills and terrace Qt1.

(2) Quaternary sand (Qs1) that forms sand hills is interpreted as degraded 

eolian dunes stabilized by vegetation under prevailing climate conditions. Detailed 

descriptions and analyses of these sand hills are given in Swezey and others (2013). 

Sediments in this category generally form one relatively continuous group of sand 

hills that is located at distances of 0 to 5 km from the modern river channel, and 

covers an area that is approximately 15 km long and 0.2 to 3.2 km wide. Where 

discernible, the morphologies of individual hills range from parabolic shapes (with 

tails pointing west) to isolated circular and linear shapes. In addition, several isolated 

sand hills and northwest-trending ridges are present in the southern part of the study 

area at distances of 2 to 6 km east of the modern river channel (maps A and B). As 

discussed in the following section, the lidar image (map B) shows that the relatively 

continuous group of sand hills (Qs1) overlies parts of terraces Qt1 through Qt5, 

implying that the terraces are older than the sand hills. Using the preferred OSL ages 

given in bold in table 1 and taking into account the reported ranges of uncertainty, 13 

samples from 11 locations within the relatively continuous group of sand hills have 

yielded OSL ages ranging from approximately 35.4 to 18.0 ka, and two samples from 

relatively isolated sand hills have yielded preferred OSL ages ranging from 

approximately 11.0 to 9.5 ka (GAW-13 and GAW-11; table 1).

(3) Quaternary (Pleistocene) sand and mud, with or without gravel or peat 

(Qgsm, Qsm5, Qs3, Qsmp4, Qsmp3, and Qs2) are interpreted as alluvial, fluvial,

and swamp deposits. The sediments of this category lie within the Savannah River

flood plain to the east of the lowest and westernmost terrace (Qt0). Some of the units

of this category form distinct terraces (Qt1 through Qt5), whereas others form 

alluvial fans on the east margin of the flood plain, and yet others occupy abandoned 

fluvial channels that are truncated by younger sediments. These sediments are 

thought to be Quaternary in age, spanning a time that ranges from older than the sand 

hills (eolian dunes, Qs1) to coeval with the sand hills. For example, the lidar image 

(map B) shows that the relatively continuous group of sand hills overlies parts of 

terraces Qt1 through Qt5, implying that the terraces are older than the sand hills. 

Indeed, one sample of sand (GAW-37; table 1) collected from a depth of 183 

centimeters (cm) below the surface of terrace Qt4 yielded a preferred OSL age of 

approximately 108±12.0 ka, which is much older than the preferred OSL age range 

of 35.4 to 18.0 ka for the sand hills (table 1). However, some of the preferred OSL

ages from the terraces are coeval with the preferred OSL ages from the sand hills. For 

example, (1) a sample of sandy mud (GAW-29; table 1) collected from a depth of 61 

cm below the surface of terrace Qt5 yielded a preferred OSL age of 39.7±3.6 ka, (2) 

a sample of sand (GAW-14; table 1) collected from a depth of 70 cm below the 

surface of terrace Qt4 yielded a preferred OSL age of 24.2±1.2 ka, and (3) a sample 

of sandy mud (GAW-28; table 1) collected from a depth of 84 cm below the surface 

of terrace Qt4 yielded a preferred OSL age of approximately 23.6±2.1 ka. In addition 

to the terraces, sediment in this category is found in the southern part of the lidar 

image (map B), where a 50- to 130-m-wide southwest-trending channel (Qsmp4) is 

incised into terraces Qt1 through Qt5, and is buried by the sediment of terrace Qt0. 

Gouge core C1 that was drilled in the upper reaches of this channel (maps A and B; 

fig. 4) recovered 1.37 m of sand, sandy mud, and muddy sand. A sample of wood 

(WW8888; table 3) from muddy sand at the base of gouge core C1 yielded a 

radiocarbon age of 41,890±930 14C yr BP (46,841 to 43,856 cal yr BP). This age 

approaches the older limit for radiocarbon dating, and therefore may be a minimum 

age for the sample (and a minimum age for the channel).

(4) Neogene (lower Pliocene?) mottled gray, brown, and orange gravel, sand, 

and mud without phosphate grains (Ngsm). Sediments of this category are exposed 

at one outcrop on the Savannah River near the northwesternmost part of the geologic 

map (map A) and lidar image (map B) (sample location GAW-31; photographs 1 and 

2), and were encountered at depth in drill core C2 and all auger cores (figs. 2 and 3). 

At this outcrop on the river (described in greater detail in Swezey and others, 2013), 

a 4-m-thick unit of sand (sand hill, Qs1) overlies an unconformity that caps a 

1.5-m-thick unit (Ngsm) of partially indurated, mottled reddish-brown to light-gray, 

fine-grained quartz sand with a few thin beds and laminations of gray to white mud. 

This unit of reddish-brown to light-gray sand and mud, overlies a >1-m-thick unit of 

partially indurated, dark-yellowish-orange, poorly sorted, coarse to fine quartz sand 

with crossbedding. At this location, sample GAW-31 (table 1) from the

reddish-brown to gray sand (Ngsm) beneath the sand hill yielded an OSL age of

>43 ka. A similar occurrence is present in drill core C2, where 2.6 m of sand of the

sand hills (Qs1) overlies an unconformity that caps a 1.4-m-thick unit (Ngsm) of

partially indurated, mottled light-gray to reddish-brown sandy mud (fig. 2). This 

unit of sandy mud overlies a >1.2-m-thick unit of partially indurated, 

pale-reddish-brown to dark-yellowish-orange fine to coarse quartz sand.

The sediments of unit Ngsm also comprise the high terrace (>15 m elevation) 

that forms the eastern margin of the Savannah River valley (east of terrace Q5). In 

the lidar image (map B), this high terrace displays a series of relict meandering 

channels and it is presumed that these channels are filled with Quaternary sand and 

mud (Qsm3 and Qsm4). The sizes of the relict meandering channels are similar to 

those of the modern Savannah River, suggesting similar flow regimes.

There is some uncertainty about the stratigraphic name that should be applied to 

mapped unit Ngsm. The strata are similar in both appearance and stratigraphic 

position to strata that have been described on the west bank of the Savannah River. 

For example, at Sisters Ferry Landing on the west side of the river (immediately west 

of auger core HNW-9), Lyell (1845) reported the presence of Cenozoic brick-red 

loam, red and gray clay, and beds of steatitic clay. At an outcrop at Porters Landing 

on the west bank of the Savannah River, approximately 7.4 km northwest of the 

northwesternmost corner of Jasper County (northwestermost point on maps A and 

B), several geologists have provided descriptions of measured sections but have 

assigned different stratigraphic names to the units (fig. 1). At this Porters Landing 

outcrop, there is an upper unit of white, red, and yellow, fine to coarse sand with 

crossbedding and some beds of clay that has been assumed to be Pleistocene in age 

by geologists who have worked primarily in South Carolina (Sloan, 1908; Cooke, 

1936; Malde, 1959). Cooke (1936) tentatively assigned these strata at Porters 

Landing to the Pleistocene(?) Sunderland(?) Formation. This formation was named 

by Shattuck (1901) after a site in Calvert County, Maryland, but the name is now 

considered to apply only to a geomorphic feature and has been abandoned as a 

stratigraphic term (Huddlestun, 1988). In contrast, Huddlestun (1988) worked 

primarily in Georgia, and he designated this unit of fine to coarse sand at Porters 

Landing as the Pliocene Cypresshead Formation, which has its type locality in 

Wayne County, Georgia (Huddlestun, 1988). More recently, Doar (2008) mapped 

these strata of post-Miocene and pre-Quaternary fine to coarse sand in the 

Hardeeville NW quadrangle as the Pleistocene Ladson Formation, which has its type 

locality in Charleston County, South Carolina (Malde, 1959). However, Doar 

(2013b) mapped these strata of post-Miocene and pre-Quaternary fine to coarse sand 

in the Pineland quadrangle as the Pleistocene Penholoway Formation. This 

formation was named by Cooke (1925) after a site in Wayne County, Georgia, but the 

name is now considered to apply only to a geomorphic feature and has been 

abandoned as a stratigraphic term (Huddlestun, 1988). Furthermore, Huddlestun 

(1988) stated that the Penholoway terrace is an erosional terrace that has been cut on 

the Cypresshead Formation. In summary, different stratigraphic names have been 

applied to post-Miocene and pre-Quaternary fine to coarse sand at different 

locations, and it seems likely that some or all of these names refer to the same unit. 

(5) Neogene (lower Miocene) sand and mud with phosphate grains (Nsm). 

Sediments of this category are not exposed in outcrop within the study area, but they 

were encountered in drill core C2 and all auger cores (figs. 2 and 3). These sediments 

are capped by an unconformity, above which lies lower Pliocene(?) mottled 

light-gray and pale-reddish-brown sand and mud (Ngsm). The lower Miocene age of 

this unit is indicated by biostratigraphic data from sample R6709 A (table 2).

Like the overlying lower Pliocene(?) unit Ngsm, there is some uncertainty about

the stratigraphic name that should be applied to mapped unit Nsm. The strata are

similar in both appearance and stratigraphic position to strata that have been

described at the outcrop at Porters Landing, although geologists have given different

names to the strata at this outcrop (fig. 1). At Porters Landing, the lower units of the

outcrop are predominantly sandy mud and muddy sand with phosphate grains, and

were designated by Cooke (1936) and Malde (1959) as the lower Miocene Hawthorn

Formation (which has its type locality in Alachua County, Florida; Dall and Harris,

1892) and the overlying upper Miocene Duplin Marl (which was named for outcrops

in Duplin County, North Carolina; Dall, 1898). Malde (1959), however, noted that the

Duplin Marl has distinct marine fossils but very little lithologic uniformity, and he

recommended that the name be abandoned. Likewise, Blackwelder and Ward (1979)

noted that the Duplin Marl was defined on biostratigraphic data rather than lithologic

data, and they recommended that the name be abandoned in favor of the name

Yorktown Formation (which has its type locality in York County, Virginia; Clark and

Miller, 1906). In contrast, Huddlestun (1988) designated the lower units at Porters

Landing as lower Miocene strata of the Parachucla Formation (which has its type

locality in Effingham County, Georgia) and the overlying Marks Head Formation

(which also hasitstype locality in Effingham County, Georgia; Sloan, 1908). Both the

Parachucla Formation and the Marks Head Formation are mapped by Huddlestun

(1988) as part of the Hawthorn Group.

DISCUSSION

The sediments and strata preserved in the study area reveal an interesting 

history of landscape evolution since the Miocene. The lower Miocene unit of sand 

and mud with phosphate grains (Nsm) is interpreted as a shallow marine deposit that 

accumulated when sea level was high enough to flood the study area. The presence 

of phosphate in the Miocene strata may be attributed to the reworking of older 

phosphate-bearing strata and (or) to the warming of phosphate-rich marine water that 

would have caused a subsequent loss of CO2 and an increase in pH. Such conditions 

of warm phosphate-rich marine water tend to occur in shallow-water areas of 

upwelling in the trade wind zone (Cook and McElhinny, 1979; Föllmi, 1996). The 

unconformity above the lower Miocene strata may or may not be regional in extent. 

Brief but significant falls in eustatic sea level during the middle Miocene and late 

Miocene have been identified in studies by Haq and others (1987), Van Sickel and 

others (2004), Miller and others (2005), and Swezey (2009). The overlying lower 

Pliocene(?) gravel, sand, and mud (without phosphate grains) (Ngsm) is interpreted 

as a fluvial to estuarine to marginal marine deposit. As such, it represents the 

progradation of terrigenous sediment into the study area. An early Pliocene age is the 

best interpretation for this unit, with the overlying unconformity being the result of a 

major eustatic sea-level fall caused by the onset of glaciation in the northern 

hemisphere. As outlined by Shackleton and others (1984), Haug and others (1999), 

Prueher and Rea (2001), and Maslin and others (1998, 2001), the sudden increase in 

ice-sheet extent in the northern hemisphere occurred at approximately 3.1 to 2.5 Ma 

(mega-annum, or million years before present). After the onset of glaciation, the 

study area would have become a site of sediment bypass and erosion, as sediments 

were carried farther east to the new (lower) sea-level position. Any exposed 

sediments in the area would have been subjected to weathering (which would 

account for the mottled appearance of the lower Pliocene(?) gravel, sand, and mud) 

and bioturbation by plants (which would account for lack of obvious primary 

sedimentary structures in many of the mapped units of the study area). During the 

past 2.5 million years, ice sheets have waxed and waned, but the only sediments 

preserved in the study area from this time interval are (1) Quaternary eolian dunes 

and various fluvial and alluvial sediments that date from approximately the Last 

Glacial Maximum (LGM), and (2) Holocene sand and mud that are predominantly 

fluvial and swamp deposits. As outlined by Swezey and others (2013), most of the 

Quaternary eolian sediments were active during the LGM when the climate was 

more arid, wind velocities were much greater, and vegetation cover was less dense. 

During this time, the Savannah River is thought to have been active enough to have 

mobilized and deposited some fluvial sediment, but this activity was more ephemeral 

than at present. During the Holocene, however, as ice sheets have retreated and sea 

level has risen, the study area has changed from an area of fluvial sediment bypass 

and erosion to an area of fluvial (and swamp) sediment accumulation. As these 

changes have occurred, the climate has become more humid, wind velocity has 

decreased, and vegetation cover has increased. As a result, the eolian sediments have 

become stabilized by vegetation.

ACKNOWLEDGMENTS

An early draft of this publication benefitted from reviews by U.S. Geological 

Survey (USGS) geologists Helaine W. Markewich and C. Scott Southworth, and a 

later draft was reviewed by USGS geologists Ronald C. Counts and David S. Powars.

The publication also benefitted from map editing by David A. Shields (USGS).

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