Organic and Trace-Element 

Content of Holocene Sediments 

in Two Estuarine Bays, 

Pamlico Sound Area, 

North Carolina

GEOLOGICAL SURVEY BULLETIN 1314-E

Organic and Trace-Element 

Content of Holocene Sediments 

in Two Estuarine Bays, 

Pamlico Sound Area, 

North Carolina

By HENRY L. BERRYHILL, JR., VERNON E. SWANSON, and A. HAROLD LOVE

CONTRIBUTIONS TO GEOCHEMISTRY

GEOLOGICAL SURVEY BULLETIN 1314-E

The distribution and interrelations of total 

organic matter and soluble organic 

components in sand and mud deposited in 

shallow brackish-water $ arts of the large 

complex Pamlico Sound estuarine 

environment

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1972
UNITED STATES DEPARTMENT OF THE INTERIOR 

ROGERS C. B. MORTON, Secretary

GEOLOGICAL SURVEY 

V. E. McKelvey, Director

Library of Congress catalog-card No. 72-600056

For sale by the Superintendent of Documents, U.S. Government Printing Office

Washington, D.C. 20402 - Price 25 cents (paper cover)

Stock Number 2401-2079
CONTENTS

Page

Abstract...................................................................................................................... El

Introduction................................................................................................................ 2

Acknowledgments. ................................................................... ........... . . 4

Field and laboratory methods.................................................................................. 4

Jarrett Bay................................................................................................................. 5

Bottom sediment..................................................~.....~..... ........................... 6

Organic and related materials.......................... ........ . ........... .- 11

Organic carbon........................................................................................... 11

Mineral carbon........................................................................................... 11

Sulfur........................................................................................................:.. 11

Bitumen........................................................................................................ 12

Alkaline-soluble humic substances.......................................................... 12

South River................................................................................................................. 20

Bottom sediment.... ........................ ................................................. . .. 20

Organic and related materials................. ............................................. ..... 24

Organic carbon..... ............................................................................. 24

Mineral carbon......................................................... ............................... 25

Sulfur.................................................................................... ... . 25

Bitumen.............................................................. .......................... 26

Alkaline-soluble humic substances.......................................................... 26

Comparisons and conclusions................................................................................... 28

References cited......................................................................................................... 32

ILLUSTRATIONS

Page

FIGURE 1. Index map of Pamlico Sound area, North Carolina, showing

location of Jarrett Bay and South River.................................. E3

2. Map showing sample localities and depths of water

in Jarrett Bay....... ............................. ........................................ 7

3. Map showing distribution of sediment by grain size

in Jarrett Bay.................................................................................. 8

4. Cumulative curves showing grain-size distribution in 

representative bottom-sediment samples from 

Jarrett Bay and South River........................................................ 9

5-9. Maps:

5. Organic-carbon content of sediment in Jarrett Bay...... 16

6. Content of alkaline-soluble humic substances

in sediment in Jarrett Bay............................................ 17

7. Sample localities and depths of water

in South River................. .......................................... 21

III
IV CONTENTS 

FIGURES 5-9. Maps Continued

8. Distribution of sediment by grain size in Page 

South River.......-.-...-........-.-..-....... ___.. E 23

9. Organic-carbon content of sediment in South River...... 27

TABLES

Page

TABLE 1. Summary of salinity and temperature of water at selected

localities in Jarrett Bay and South River.................................... E4

2. pH and Eh of bottom water and sediment at five localities

in Jarrett Bay.................................................................................... 6

3. Clay mineralogy of <2-micron fraction of selected samples

from Jarrett Bay and South River..............................-..-...... . 6

4. Semiquantitative emission spectrographic analyses of sediment 

samples and organic extracts of sediment samples from 

Jarrett Bay......--..............................-.-.-..--. .................... 13

5. Chemical and grain-size analyses of sediment from

Jarrett Bay......................................................................................... 14

6. Organic-element composition, on ash-free basis, of soluble

humic and fulvic fractions of sediment from Jarrett Bay...... 18

7. Chemical and grain-size analyses of upper 10-15 cm

(0.3-0.5 ft) of sediment from South River estuary.................. 22

8. Emission spectrographic analyses of sediment from

South River estuary.......................................................................... 25

9. Organic-element composition, on ash-free basis, of soluble

humic and fulvic fractions of sediment from South River...... 28
CONTRIBUTIONS TO GEOCHEMISTRY

ORGANIC AND TRACE-ELEMENT CONTENT OF

HOLOCENE SEDIMENTS IN TWO ESTUARINE BAYS,

PAMLICO SOUND AREA, NORTH CAROLINA

By HENRY L. BERRYHILL, JR., VERNON E. SWANSON, and 

A. HAROLD LOVE

ABSTRACT

Jarrett Bay and South River are small estuaries within the Pamlico Sound 

area, North Carolina. Jarrett Bay is an inland extension of the marine water 

of Core Sound; South River is a drowned tributary of the Neuse River, and 

its waters are brackish.

Most of the 102 samples from Jarrett Bay and the 53 samples from South 

River are of the uppermost 10-15 centimeters of sediment; some are from 

several cores about 60 centimeters in length that were also collected. Bottom 

sediments in both study areas, except for sediments in narrow belts of sand 

in the very shallow nearshore waters, typically are fine grained and poorly 

sorted. Clay-sized particles make up about 20 percent of the sediments in the 

deeper parts of both areas, but the mineralogy of clays differs markedly: 

Illite, chlorite, and chlorite-mica predominate in Jarrett Bay; kaolinite, illitemica, and aluminum-vermiculite predominate in South River. Marine macrofauna remains are abundant in Jarrett Bay, but only brackish-water clams 

were found in South River. Foraminifera in samples from Jarrett Bay are 

mostly arenaceous types; nine genera were identified, and the number of 

specimens per 10 cubic centimeters of sample material ranged from a few 

hundred to 3,000.

Organic-carbon content of the bottom sediments of Jarrett Bay is 0.1-4.4 

percent, and in South River it is 0.1-12.9 percent. The amount is typically 

highest in the finer grained sediments and lowest in the sands. The organic 

matter in both estuaries is high in alkaline-soluble humic substances (humic 

and fulvic fractions) and low in bitumen content, reflecting the major source 

of organic matter from nearby marshes and forests. The soluble humic fraction makes up as much as 2.68 percent of the sediment in Jarrett Bay and 

5.44 percent in South River; the fulvic fraction (organic substances remaining in solution after precipitation of humic fraction) is generally less than 

one-half the amount of the humic fraction from both areas. From headwaters 

to mouth in both estuaries, however, the ratio of the fulvic fraction to organic 

carbon increases and that of the humic fraction to organic carbon decreases. 

The range in bitumen content of the sediment in both areas is similar, 0.003- 

0.086 percent in Jarrett Bay and 0.006-0.086 in South River, and the bitumen 

content generally parallels the organic-carbon content of the sediment. Sand

El
E2 CONTRIBUTIONS TO GEOCHEMISTRY

has the lowest content of both organic carbon and bitumen, but the ratio of 

bitumen to organic carbon in the sand is about twice that in mud rich in 

organic matter.

Trace-element analyses of the whole samples indicate no anomalous concentrations of specific elements that might have environmental significance. 

Analyses of trace elements in the ash of the humic and the fulvic fractions 

show characteristic concentration of the metals Co, Cu, Mo, Ni, Pb, and V.

INTRODUCTION

Many sequences of ancient sedimentary rocks, perplexing in 

both vertical and lateral relationships, have strikingly similar 

counterparts in modern sediments in several coastal areas of the 

United States. The Pamlico Sound area of eastern North Carolina 

(fig. 1) is an excellent example of an area where diverse and 

complex sediment types and relationships can be studied today.

This area, which covers several thousand square miles, includes 

closely adjacent fluvial, lacustrine, estuarine, marsh, littoral, and 

marine depositional environments, where grossly different but 

time-equivalent sediments can be studied and mapped in detail. 

Fluvial sediments are being deposited in the Pamlico and Neuse 

Rivers and, toward their mouths, the fluvial sediments grade into 

the generally estuarine sediments of Pamlico Sound (fig. 1). 

Lacustrine fresh-water limy muds are being deposited in the 70 

square miles of Lake Mattamuskeet, less than 10 miles inland 

from Pamlico Sound. Lagoonal and estuarine sands and muds are 

being deposited in hundreds of square miles of Pamlico and Core 

Sounds, which are behind the ever-changing linear offshore bars 

of the Outer Banks that include Core Banks and Hatteras and 

Ocracoke Islands. Bay- and bayou-type estuaries, ranging in area 

from a few to many tens of square miles, adjoin these major 

bodies of marine and brackish water to form a maze of smaller 

areas where carbonaceous muds are being deposited. Adjacent to 

all these are tidal marshes, covering more than 1,000 square miles, 

where peat and carbonaceous mud are accumulating.

Two small bay-type estuaries, Jarrett Bay and South River, 

were selected in the Pamlico Sound area as representative of an 

environment, relatively rich in organic matter, that might yield 

knowledge on the genesis of organic fuels. Jarrett Bay is an inland 

extension of Core Sound, and South River is a drowned tributary 

of the larger Neuse River estuary (fig. 1). Both bodies of water 

are shallow, generally less than 12 feet (3.7 m) deep, and are 

fringed by many square miles of spear-grass marshes. Seasonal 

changes in the salinity and temperature of water are given in 

table 1; Jarrett Bay water has a general salinity range of 20-35 

parts per thousand, and South River 12-20 parts per thousand. 

Bottom sediments in Jarrett Bay and especially in South River
HOLOCENE SEDIMENTS, PAMLICO SOUND AREA, N.C. E3

are fine grained and poorly sorted, except for narrow nearshore 

belts of sand. These poorly sorted sediments have a fairly heterogeneous mineralogy, mainly derived from the lithologically complex metamorphic rocks of the Piedmont and the sedimentary 

Tertiary formations in central and eastern North Carolina.

76°30' 76°00' 75°30'

35°30'

35°00'

34-30' 

FIGURE 1. Index map of Pamlico Sound area, North Carolina, showing 

location of Jarrett Bay and South River.
E4 CONTRIBUTIONS TO GEOCHEMISTRY

This study is part of a broader investigation, concerned with 

the types and amounts of organic matter in sediments representing a variety of modern environments of deposition, that will add 

to our knowledge of the genesis of coal, petroleum, and related 

fossil fuels (Swanson and others, 1967; Palacas and others, 1968). 

The amount of organic matter that accumulates and is preserved 

in sediments is affected by the type of organic matter, type of 

sediment, and type of basin; by physiographic conditions in adjoining areas; by basin hydrography; and by physical and chemical conditions in the water. Similar data from a wide spectrum 

of modern depositional environments eventually will be compared 

and evaluated in detail as a means of understanding the chemical 

changes of the organic material in sediments through the general 

degradational and decompositional processes that take place during transport, deposition, and burial.

TABLE 1. Summary of salinity and temperature of water at selected 

localities in Jarrett Bay and South River

[Data are for the period June 15, 1952, through Dec. 31, 1953, and are from Williams (1955)]

Locality

Jarrett Bay (fig. 2) :

Williston Creek at Williston..... 

Wade Creek........................... ..........

South River (fig. 7) :

Mouth of Big Creek......................

Water 

depth

(ft)

..... 3

..... 3 

..... 3

...... 12

..... 8

..... 3

Bottom salinity Annual range of 

(parts per thousand) bottom temperature

Winter

24.9-26.0 

19.4-25.0 

19.1-25.5

H3.S 

H3.9 

!12.0

Summer

27.2-36.0 

27.4-36.2 

31.7-36.2

14.4-20.5 

13.9-16.5 

12.8-14.4

CC)

6.8-31.2 

6.6-30.2 

6.8-31.4

10.6-31.4 

11.0-31.4 

11.4-32.2

1 Average value.

This paper is a synthesis of factual information on estuarine 

deposits that eventually will be integrated with comparable information on nearby depositional environments. Interpretations and 

interrelations in this initial report on the Pamlico Sound area thus 

are minimal inasmuch as the studies of nearby areas have been 

temporarily postponed.

ACKNOWLEDGMENTS

Grateful acknowledgment is extended to Elmer Willis for loan 

of a skiff and motor for work in Jarrett Bay and to Stuart Berryhill who operated the skiff and assisted during work in South 

River. Foraminiferal data were supplied by Louise R. Berryhill. 

Special thanks are also extended to James G. Palacas for his 

detailed and constructive review of this paper.

FIELD AND LABORATORY METHODS

Field investigations in Jarrett Bay, in October 1965, and in 

South River, in July 1966, included the collection of a series of
HOLOCENE SEDIMENTS, PAMLICO SOUND AREA, N.C. E5

bottom-sediment samples and the determination of water depth, 

temperature of bottom water, and water salinity at each station 

sampled. Measurements of pH and Eh of the surface and bottom 

water and of the topmost few centimeters of sediment were made 

at several stations in Jarrett Bay. Samples of approximately the 

uppermost 15 cm (0.5 ft) of sediment were obtained by either a 

clam-shell grab sampler or a coring tube. Five cores, each about 

60 cm long, were also taken with a piston corer in Jarrett Bay. 

To prevent bacterial decay, the samples were frozen within a few 

hours after they were collected and were kept frozen until they 

were analyzed.

In order to determine the chemical characteristics of the bottom 

sediment, the following analyses were made: Total carbon, mineral 

carbon, organic carbon (by difference), bitumen, alkaline-soluble 

humic and fulvic fractions, total sulfur, and semiquantitative 

emission spectrographic analyses for trace elements. The organic 

composition of the humic and fulvic fractions of 11 representative 

samples was also determined by ultimate analysis. The laboratory 

procedures followed are those described by Palacas, Swanson, and 

Love (1968, p. C99-C100).

As used in this report, the alkaline-soluble humic substances 

are that part of the organic material in the sediment soluble in 

0.1 N NaOH. On acidification, the humic fraction is precipitated, 

and the organic substances remaining in solution are referred to 

as the fulvic fraction. These alkaline-soluble humic substances 

are believed to represent mainly the previously soluble organic 

substances in the natural tea-colored water that were precipitated 

or flocculated and incorporated in the sediment. These natural 

soluble substances are derived from decomposing land-plant debris.

To establish some understanding of the manner in which environmental factors influence organic material in recent sediments 

during movement, deposition, and burial, the physical properties 

of the sediments in selected samples were determined so that clues 

might be obtained and applied in studies of organic materials in 

ancient sediments. The grain size for the >0.062-mm fractions 

was determined by sieving; the particle-size distribution for the 

<0.062-mm fraction was determined by standard pipet method. 

Clay minerals for selected samples were identified by X-ray diffraction. Foraminifera were identified in some samples to complement other environmental and chemical data for the study sites.

JARRETT BAY

Jarrett Bay is elongate north to south; length is slightly more 

than 4 miles, and average width is about one-half mile. Its greatest 

depth, 8.3 feet (2.5 m), is in the south-central part (loc. 71, fig. 2).

454-767 O - 72 - 2
E6 CONTRIBUTIONS TO GEOCHEMISTRY

The bay has a generally symmetric bottom profile, and the deepest 

parts are along the axis of the bay. The water in the bay, as noted 

during the summer, is a very dark tea color, especially toward the 

north end of the bay. Salinity measurements of the bottom water 

during the period of field studies averaged 26.8 parts per thousand 

and ranged from 13.9 to 33.1 parts per thousand; the salinity was 

less than 20.0 parts per thousand at only one locality (loc. 9, fig. 2). 

The pH of the bottom water, measured a few centimeters above 

the sediment at five localities, ranged from 7.6 to 8.0 and averaged 

7.8; the water was reducing at two localities and oxidizing at three 

localities (table 2).

TABLE 2. pH and Eh of bottom water and sediment at five localities in

Jarrett Bay

Locality

(fig. 2)

7 

' 11 

39 

62 

84

Depth of 

water 

(ft)

2.6 

2.0 

3.5 

4.0 

3.8

Bottom water Bottom Sediment

Sediment type

Peaty silt.......................................

pH

........ 7.6

........ 7.7

........ 8.0

........ 8.0

........ 7.8

Eh 

(millivolts)

 155 

 180 

+125 

+150 

+100

pH

7.2

7.3 

7.2 

7.2 

7.5

Eh 

(millivolts)

 310 

-285 

 120 

 180 

 130

BOTTOM SEDIMENT

Bottom sediments were sampled at 102 localities in Jarrett Bay 

(fig. 2), and analyses of 62 of these samples are shown in table 5. 

The bottom sediment is largely a mixture of clay-, silt-, and sandsized particles. The percentage of sand decreases sharply from the 

shoreline toward the center of the bay, and clay-sized particles 

make up more than 20 percent of the bottom sediments in the 

deepest part of the bay (fig. 3). The most abundant clay minerals 

are illite, chlorite, and chlorite-mica (table 3). Slimy flocculated

TABLE 3. Clay mineralogy of <2-micron fraction of selected samples from 

Jarrett Bay and South River

[Leaders (....) in figure columns indicate amounts less than 10 percent. 

_________________Analysts, H. C. Starkey and P. D. Blackmon]_________________

Percentage of given clay type for indicated sample locality

_____ __ Jarrett Bay (fig. 2) ___ South River (fig. 7) 

Clay type__________1 2 13 30 32 33 39 88 91 92 98 99 3 10 17 38 48 49

Illite................................ 10 10 20 10 10 10 .... 10 .... 10 .... 10 .... .... .... .... .... ....

Illite-mica...................... .... .... .... .... .... .... .... .... .... .... .... .... 10 10 10 10 20 30

Chlorite.......................... 10 10 10 20 10 10 .... 10 .... 10 10 10 .... .... .... .... .... ....

Chlorite-mica................ .... 10 20 20 10 10 10 10 20 10 10 10 .... .... .... .... .... ....

Chloritemontmorillonite....... .... .... .... 10 20 10 10 10 .... 10 20 .... .... .... .... .... .... ....

Montmorillonite........... .... .... .... .... 10 .... .. . 10 10 10 .. 10 .... .... .... .... .... ....

Kaolinite........................ .... .... 10 .... .... .... 10 10 20 10 .... .... 50 60 60 40 50 40

Aluminumvermiculite................ .... .... .... .... .... .... ... .... .... .... .... .... 10 10 10 10 10 10

material high in organic matter forms a soupy transition zone as 

much as 30 cm (1 ft) thick between water and bottom sediment, 

except at those localities where the sediment is mainly sand. Cumu-
HOLOCENE SEDIMENTS, PAMLICO SOUND AREA, N.C. E7

76'30'

EXPLANATION

.21 

Basic data only

X60

Basic data and 

sedimentary analyses

®57

Basic data and Basic data and chemical 

chemical analyses and sedimentary analyses

Sample localities and numbers 

Basic data consist of sediment description and 

measurements of depth and salinity of water

34° 

47' 

30"

Water-depth contour 

Interval 2 feet

1 MILE

1 KILOMETER

FIGURE 2. Sample localities and depths of water in Jarrett Bay.

lative curves showing the distribution of grain size for five selected 

samples are shown in figure 4. The samples that consisted mostly
E8 CONTRIBUTIONS TO GEOCHEMISTRY

76°30'

EXPLANATION

X 

Grain-size Megascopic

analysis description

Sample localities

Area where <2ju particles exceed 

20 percent of sediment

Isopleth 

Showing amount of sand in sediment, in percent

I MILE

1 KILOMETER

FIGURE 3. Distribution of sediment by grain size in Jarrett Bay. For this 

report, clean sand contains more than 90 percent sand-sized grains, silty 

clayey sand contains 50-90 percent sand-sized grains, and mud contains less 

than 50 percent sand-sized grains.
HOLOCENE SEDIMENTS, PAMLICO SOUND AREA, N.C. E9

100

100

Sample 1

Sample 91

1.0 0.062 0.002

100

Sample 30

0 1.0 0.062 0.002 

GRAIN SIZE, IN MILLIMETERS

100 i r

Sample 93

0 1.0 0.062 0.002 0 1.0 0.062 

GRAIN SIZE, IN MILLIMETERS

0.002

100 I I 

Sample 31

So=5.00

I_____I

1.0 0.062 0.002

JARRETT BAY

100

75

50

25

10

0

i

100

75

50

25

10

0

Sample 43

1.0 0.062 0.002

100

75

50

25

10

0

Sample 17

0 1.0 0.062 0.002 

GRAIN SIZE, IN MILLIMETERS

100

75

50

25

10

0

Sample 49

0 1.0 0.062 0.002 0 1.0 0.062 

GRAIN SIZE, IN MILLIMETERS

0.002

100

Sample 38

1.0 0.062 0.002

SOUTH RIVER

FIGURE 4. Cumulative curves showing grain-size distribution in representative bottom-sediment samples (R. F. Gantnier, analyst). Sample localities 

in Jarrett Bay are shown in figure 2, those in South River, in figure 7. 

C, organic carbon, in percent; S, total sulfur, in percent; So, sorting index, 

based on the first and third quartiles.
E10 CONTRIBUTIONS TO GEOCHEMISTRY

of sand were very light brown; all the other samples were greenish 

gray. Eh readings for the upper 2.3 cm (0.1 ft) of bottom sediments at five localities ranged from 120 to 310 millivolts and 

averaged 205, indicating reducing conditions (table 2). The pH 

of these sediment samples ranged from 7.2 to 7.5 and averaged 7.3.

Spectrochemical analyses of 20 sediment samples from Jarrett 

Bay showed neither major value differences in elements among 

the samples nor anomalous concentrations of specific elements that 

might have environmental significance. Three representative analyses are shown in table 4. The amounts of B, Cr, Ga, and V shown 

by these analyses are within the range reported by Shimp, Witters, Potter, and Schleicher (1969, table 3) to be indicative of 

marine muds, although the amount of Ni is lower in the Jarrett 

Bay samples than the amount reported by those authors.

The percentage of heavy minerals in the bottom sediments of 

Jarrett Bay ranged from less than 0.01 to 2.0 in the sieved fraction (0.125-0.062 mm). The principal minerals are ilmenite, tourmaline, leucoxene, amphibole, and zircon.

Fragments of oyster and other marine mollusk shells are common, and plant debris is abundant. Most of the plant material is 

unidentifiable, but some grass, wood, and bark fragments and 

shreds were observed in samples from tributaries.

Foraminifera in a set of samples collected in the north half of 

Jarrett Bay were identified and counted by Louise R. Berryhill as 

an additional means of establishing the characteristics of the sediments. Arenaceous forms were either the predominant or the only 

Foraminifera in all samples, but many of the specimens were unidentifiable because they were very small or broken. The most 

abundant arenaceous genera were Ammotium and Ammobaculites; 

Miliammina, Trochammina, Arenoparrella, and Haplophragmoides 

were also present. At the north end of Jarrett Bay, calcareous 

forms of the genus Ammonia were abundant; these, together with 

Protelphidium, which were common, and a few Elphidium, were 

the only nonarenaceous Foraminifera in the samples studied.

Each sample processed for foraminiferal study had a volume of 

approximately 10 cm3 and was washed through 35-, 80-, and 200- 

mesh sieves. In the samples for which the total number of Foraminifera was counted, the number of specimens ranged from 200 to 

3,000. These counts are considerably higher than those recorded 

by Grossman (1967, p. 34) in samples from Nelson Bay, an 

estuarine environment similar to Jarrett Bay, 7 miles to the northeast. His counts ranged from 0 to 265 specimens in samples having 

a volume of 120 cm3 (12 times the volume used for this study), 

which he interpreted as indicating the relative scarcity of Foram-
HOLOCENE SEDIMENTS, PAMLICO SOUND AREA, N.C. Ell

inifera in the Pamlico Sound area. The most obvious factor contributing to the observed difference in abundance of Foraminifera 

was that Grossman used 20-, 40-, and 100-mesh sieves. Actually 

specimens in the less-than-100-mesh size far outnumber the larger 

ones.

ORGANIC AND RELATED MATERIALS 

Organic carbon

The amount of organic carbon (table 5) in the upper 10-15 cm 

(0.3-0.5 ft) of bottom mud (clay-silt content greater than 50 

percent) in Jarrett Bay (fig. 5) ranges from 1.0 to 4.4 percent 

and averages 2.1 percent. The highest organic-carbon values are 

generally for the mud samples from the northern and middle parts 

of the bay. In the relatively clean sand (clay-silt content less than 

10 percent), which is the common bottom sediment in the shallowwater nearshore areas, the organic-carbon content ranges from 

0.1 to 0.6 percent and averages 0.4 percent. In the silty sand (siltclay content 10-50 percent), the amount of organic carbon ranges 

from 0.5 to 2.9 percent and averages 1.3 percent. Wherever there 

appears to be an anomalously high organic-carbon content with 

respect to depth of water and grain-size distribution, the irregularity commonly is due to particulate organic substances such as 

grass and plant fragments in the sample.

Mineral carbon

The mineral-carbon, or carbonate, content of the sediment is 

generally less than 0.1 percent, but it ranges from less than 0.01 

to as much as 1.50 percent (table 5). The inclusion of mollusk 

shells or shell fragments in the samples probably explains all 

analyses for mineral carbon exceeding 0.1 percent. Mud and silty 

sand samples most commonly contain shell material.

Sulfur

Sulfur is a product of decomposition of organic remains in sediments and, volumetrically more important, a product of reduction 

of sulfate in interstitial water and, for some areas, in the bottom 

water. In general, the greater the amount of decomposing organic 

matter in the sediment, the greater the reducing action that results 

in precipitation of the sulfide ion. The reduced sulfur commonly 

combines with metal ions, particularly iron, to form metal sulfide 

minerals in the sediment. Sulfur minerals were not observed in 

the sediment samples studied but probably are finely dispersed in 

an amorphous hydrous form. In two cores (Iocs. 39 and 62, fig. 2), 

total sulfur increases with depth; at locality 39, for example, it 

increases from 0.10 percent in the upper 10 cm to 0.89 percent 

in the sample 40-50 cm below the sediment surface (table 5). The
E12 CONTRIBUTIONS TO GEOCHEMISTRY

total sulfur content of the upper 10-15 cm of sediment ranges 

from 0.02 to 0.95 percent sand contains an average of 0.06 

percent; silty sand, 0.29 percent; and mud, 0.48 percent (table 5). 

Very clearly, the smaller the grain size of the upper 10-15 cm of 

sediment, the greater the amount of organic carbon and total 

sulfur in the sediment.

Bitumen

The bitumen content of the upper 10-15 cm (0.3-0.5 ft) of 

bottom sediment ranges from 0.003 to 0.086 percent (table 5) and 

averages 0.0175 percent. This average value is very similar to the 

0.0170 average bitumen content of the estuary muds of Choctawhatchee Bay, Fla. (Palacas and others, 1971).

In Jarrett Bay, the average bitumen contents of sand, silty 

sand, and mud are 0.013, 0.014, and 0.020 percent, respectively. 

Thus, there is a slight increase of average bitumen content with 

decreasing grain size and, as previously noted, the aver age organiccarbon content also increases with decreasing grain size. The 

amounts of bitumen in the sediment are generally greater in the 

northern end of the bay, but the pattern of decrease southward 

is irregular. However, it should be emphasized that the individual 

values for bitumen, classified either by lithology, by organic-carbon 

content, or by geographic distribution, have very wide ranges. 

The analyses of samples from two cores (table 5) show no pattern 

of increase or decrease of bitumen content with depth.

Bitumen, as determined on the basis of ratios of bitumen to 

organic carbon, makes up an estimated average of 1 percent of 

the sparse organic matter in Jarrett Bay sand and about 0.5 percent in the silty sand. The bitumen fraction of the organic matter 

of the mud has a wide range, 0.1-2.0 percent, but also averages 

about 0.5 percent.

Alkaline-soluble humic substances

In most sediments of Holocene age, a large part of the organic 

matter has been decomposed so that it can be extracted in the 

laboratory by treatment with alkaline solutions. This organic matter, here termed soluble humic substances, is commonly divided 

in the laboratory into humic and fulvic fractions (table 5), by 

acidifying the solution. These soluble humic substances in the sediment of Jarrett Bay (fig. 6), calculated to an ash-free basis, range 

from 0.015 to 2.98 percent and generally parallel the total organic 

matter in the sediment, as indicated by the percentage of organic 

carbon (compare figs. 6 and 7). If the total organic matter is 

estimated by multiplying the percentage of organic carbon by the 

conversion factor of 1.9 (Palacas and others, 1968, p. C99), the
TABLE 4. Semiquantitative emission spectrographic analyses of sediment samples 

from Jarrett Bay

[Analysts, Harriet Neiman and A. L. Button. Leaders (....) in figure columns ind

Percentage of given element in sediment sample or extract of sed

Element

Whole 

sample

Si..................................

Al.. ...... .........................

Fe

Mg................................

Ca.... ......... .................. ..

Na.. ...............................

K... ................................

Ti.. .......... ......................

P..................................

Mn........................ ........

Ag.................................

B.............. ....................

Ba.................................

Ce............ ..................

Co.................................

Cr................ ..................

Cu... .................... ..........

Ga..... ....... ....... ............

La..... ........................... .

Mo..... ...........................

Nb.............. ...................

Ni.................................

Pb....... .........................

Sc...... ............................

Sn...... ................. ..........

Sr................... ...............

V....... ............................

Y...................................

Yb... .......... ...................

Zr.............. ....................

Nd.................................

Dy.................................

>10

......................... 5

......................... 2

......................... 1

........................ 2

....................... .3

........................ .015

........................ .01

........................ .03

........................ .0005

......................... .007

........................ .002

........................ .002

........................ .005

........................ .0003

......................... .0015

........................ .002

........................ .001

........................ .01

........................ .007

........................ .002

........................ .0003

........................ .02

Locality 3

Ash

Soluble 

humic 

fraction

10 

10 

7 

.5 

.05

1 

1 

.3 

1 

.005

.0002 

.01 

.01 

.015 

.0015

.03 

.03 

.007 

.005 

.03

.001 

.015 

.005 

.003 

.005

.003 

.03 

.003 

.0005 

.02

.015

Soluble 

fulvic 

fraction

3

7 

.015 

.1

10

.1 

3

.0003 

.02 

.001 

.0001 

.0005

.03 

.02 

.007 

.03 

.01

!"6"03 

.03 

.001 

.005

.003 

.5 

.02 

.002 

.005

.07 

.007

Whole 

sample

>10 

5 

3 

1 

.5

1.5 

2 

.3

!'6'2

.'05

.0005

.005 

.002 

.002 

.003

.001 

.0015 

.002 

.001

.01 

.007 

.003 

.0005 

.03

Locality 8

Ash

Soluble 

humic 

fraction

>10 

>10

7 

.7 

.07

10 

1.5 

.2 

.5 

.007

.0005 

.015 

.01

!6'02

.05 

.05 

.007 

.007 

.02

ibis

.001 

.002 

.007

.007 

.05 

.002 

.0005 

.015

.015
TABLE 5. Chemical and grain-size analyses, in percent, of sedim

[Carbon and sulfur analyses by I. C. Frost; grain-size analyses by R. F. Gantnier. Ash-free soluble and 

percentage of ash for 11 humic fractions (15.6 percent) and for 11 fulvic fractions (30.8 percent) fro

cate no analysis]

^fig*"? Sediment type

Depth 

of 

water 

(ft)

Chemical analyses

Alkaline-soluble humic 

. Bitumen substances

carbon

free)

Humic 

fraction 

(ash-free)

Upper 10-15 cm (0.3-0.5 ft)

1 

2 

3 

4 

8

12 

13 

15 

17 

22

23 

28 

29 

30 

31

32 

33 

37 

39 

43

44 

47 

50 

51 

52

56

57 

59 

62 

63

Mud........ .........................

........do.............................

........do.............................

..... ..do............ ................

Mud.................................

Sand................ ....... .......

........do.............................

Mud.................................

Mud... ..............................

........do.............................

........do.............................

Mud.................................

Mud............. ....................

........do.............................

Mud................................

... .....do....... .................. ...

Mud................................

........do............ ......... .......

........do...........................

........do....... .....................

.......... 4.5

.......... 4.2

.......... 3.9

.......... 2.3

.......... 3.6

.......... 3.5

.......... 4.6

.......... 2.6

.......... 3.6

.......... 4.6

.......... 4.0

.......... 3.7

........... 5.0

.......... 5.2

.......... 5.2

.......... 5.2

........... 2.9

.......... 4.7

.......... 3.5

.......... 1.4

........... 1.7

........... 4.4

........... 4.2

........... 5.4

.......... 3.3

3.4

........... 2.9

........... 4.0

........... 4.1

2.9 

4.4 

4.4 

3.5 

2.0

1.8 

2.1 

.3 

1.5 

1.8

1.8 

,1 

1.6 

2.4 

1.4

1.7 

.5 

1.9 

.8 

2.9

2.4 

1.9 

.6

1.7 

.7

1.2 

1.5 

1.0 

2.3 

1.8

0.035 

.030 

.071 

.030 

.036

.025 

.021

.015 

.008

.019 

.031 

.017 

.049 

.086

.029 

.019 

.006 

.009 

.034

.011 

.012 

.007 

.003 

.006

.007 

.010 

.004 

.015 

.010

1.35 

1.61 

2.58 

1.36

.88

.42 

.92

.43 

.41

.24 

.005 

.17 

.42 

.39

.48 

.03 

.38 

.18 

2.68

1.08 

.52 

.12 

.24 

.05

.24 

.56 

.13 

.23 

.37

Fulvic 

fraction

(ash -free)

carbo

of sediment

0.11 

.22 

.40 

.30 

.30

.41 

.32

.18 

.26

.12 

.01 

.12 

.17 

.16

.18 

.08 

.22 

.15 

.24

.35 

.40 

.16 

.23 

.10

.25 

.17 

.14 

.18 

.22

<0.01 

.02 

.01 

.04 

.03

.42 

.06 

.03 

.09 

.20

.15 

.03

!24

.14 

.38 

.23 

.04 

.04

.08 

.06 

.06 

.04 

.06

.0

.20 

1.50 

.0

.2
64

65

66

67

70

74

75

78

81

82

83

85

88

90

91

92

93

96

97

98

99

139

262

........ do....... ................................

........ do............ ...........................

........do....... ................................

Silty sand... .............................

........do............... ........................

Mud...................... .....................

........do...... ................ .........

Sand........ ................... ............. ..

Mud.............. ............ .................

........do............ ...........................

Silty sand.. ............................. ..

Mud ..... ........... ............. .

Sand ....................... ..............

Silty sand........ ........................

Sand........ ..................................

........do........ ...............................

Silty sand.... ............................

Mud ....................................

........do............ ......... ..................

Silty sand.............. ..................

Silty sand (0-10 cm) .

Shelly mud (10-20 cm)... 

Silty sand (20-30 cm).. .

Silty sand (30-40 cm) .

Silty sand (40-50 cm) . .

Silty sand (50-60 cm). ..

Mud (0-15 cm)... ....................

Mud (15-30 cm). .

Mud (30-45 cm) .......

Mud (45-60 cm).......... ...........

Mud (60-75 cm). ....................

4.3

4.1

4.7

3.0

4.2

4.9

1.8

3.9

3.4

6.7

5.2

4.4

4.9

3.3

6.6

4.2

2.8

6.9

6.6

6.5

5.4

1.8

1.9

2.0

.5

.5

1.5

1.6

1.7

.3

2.1

1.6

1.0

1.1

.3

1.3

.4

.6

1.7

1.8

1.2

.6

0.8

1.3

.8

- .8

.6

.5

2.3

2.2

2.4

2.5

2.1

.004

.015

.011

.009

.004

.007

.013

.016

.007

.014

.012

.011

.016

.007

.014

.011

.019

.014

.011

.016

.020

0.009

.008

.006

.007

.018

.009

.015

.028

.028

.021

.023

.40

.28

.65

.11

.24

.30

.70

.33

.02

.72

.30

.29

.23

.003

.17

.000

.003

.33

.46

.13

.12

Sediment cores

0.18

.09

.08

.16

.48

.02

.23

.37

.35

.24

.33

.25

.14

.31

.11

.25

.24

.33

.25

.03

.36

.24

.28

.22

.04

.15

.05

.03

.25

.26

.14

.15

0.15

.12

.11

.12

.07

.15

.18

.27

.24

.18

.22

.12

.08

.06

.04

.01

.08

.06

.06

.03

.10

.09

.03

.10

.02

<-01

.03

<-01

.06

.11

<-01

.01

0.04

1.44

.39

<C 0

.02

<.01

.05

.12

<.01

.0

<.01

'Core taken under 3.5 feet of water. 2Core taken under 4.0 feet of water.
E16 CONTRIBUTIONS TO GEOCHEMISTRY

76°30'

EXPLANATION

Sample analyzed for Crude estimate of ororganic carbon con- ganic-carbon content 

tent of sample based on

sediment description 

Sample localities

Isopleth

Showing organic-carbon content of sediment, 

in percent

I KILOMETER 

J

FIGURE 5. Organic-carbon content, in percent, of sediment in Jarrett Bay.

soluble humic substances generally constitute about one-fourth of 

the organic matter in the Jarrett Bay sediment, the organic mat-
HOLOCENE SEDIMENTS, PAMLICO SOUND AREA, N.C. E17

76'30'

EXPLANATION

Sample analyzed for soluble humic substances

Crude estimate of soluble-humic-substances 

content of sample 

based on sediment description 

Sample localities

Isopleth

Showing soluble humic substances extracted from 

sediment, in percent

1 MILE 

J

1 KILOMETER 

J

FIGURE 6. Content of alkaline-soluble humic substances, in percent,

in sediment in Jarrett Bay.

ter in the nearshore sand containing slightly less and the silty 

sand and muds slightly more.
E18 CONTRIBUTIONS TO GEOCHEMISTRY

The alkaline-soluble humic substances either are deposited as 

a dark-brown precipitate when the tea-colored water from the 

marshes encounters the saline water of the bay (Swanson and 

Palacas, 1965, p. 1), or they are formed in place from decomposing particulate matter within the bay sediment.

The amount of the soluble humic fraction in the samples, on 

an ash-free basis, averages 0.47 percent and is as much as 2.68 

percent of the sediment (table 5). Content of the humic fraction 

is lowest in the sand along the eastern part of the bay and is 

highest in the mud within the drowned channels of the creeks 

that enter the bay. Locally high concentrations are generally 

related to higher percentages of organic carbon in muds in the 

tributaries, for example at localities 2, 3, 43, and 44 (fig. 2).

Analyses for organic carbon and hydrogen were made for the 

soluble humic fractions of eight samples, and complete organic 

composition was determined by ultimate analysis for four of the 

eight samples (table 6). The samples analyzed were selected so

TABLE 6. Organic-element composition, in percent, on ash-free basis, of 

soluble humic and fulvic fractions of sediments from Jarrett Bay

[Average values for the elements are for samples with complete analysis only. All analyses by 

Huffman Laboratories, Inc., Wheatridge, Colo., except ash determinations for samples 3, 8, 

and 32 by I. C. Frost. Leaders (....) in element columns indicate no analysis]

Locality 

(fig. 2) Carbon Hydrogen Oxygen Nitrogen Sulfur

Carbonhydrogen 

ratio

Ash

Humic fraction

2.........................

3.........................

8.........................

13.........................

32.........................

65.........................

88............. ...........

91.........................

... 56.60

... 56.04

... 52.94

... 57.28

... 52.54

5.34 

5.13 

5.41 

5.59 

5.72 

6.23 

6.36 

6.17

5.9

32.54

30^20

35.67 

34.63

33.3

3.23

4^37

3i46 

4.88

4.0

2.29

2.56

2. 09 

1.25

2.0

10.6 

10.9 

9.8 

10.2 

9.4 

8.4 

8.3 

8.7

9.5

15.18 

12.8 

15.7 

14.32 

11.4 

29.47 

27.25 

11.35

17.2

Fulvic fraction

2..................... ..

3.........................

8.........................

13.........................

32.........................

65.........................

88.........................

91.........................

... 46.65

... 42.81

... 38.16

... 44.04

... 42.98

... 42.87

... 43.15

41 9

4.90 

5.11 

5.72 

5.74 

5.43 

5.68 

5.11 

7.49

5.5

44.18 

50^48

47.3

t.82 

3.' 78

4.3

1.22 

0.83

1.0

9.5

8.4 

6.7

7.7 

7.9 

7.6 

7.8 

5.8

7.7

30.59 

31.0 

32.2 

34.14 

27.3 

31.32 

17.34 

34.04

29.7

as to represent a north-south spread along the bay to determine 

if any chemical changes take place during transport and increase 

in distance from probable source areas. Some general trends in 

compositional change are indicated, but exceptions also are evident; for example, carbon and sulfur contents tend to decrease
HOLOCENE SEDIMENTS, PAMLICO SOUND AREA, N.C. E19

toward the mouth of the bay, and hydrogen content increases 

slightly southward.

Trace-element content of the ash of the soluble humic fraction 

in three representative samples is shown in table 4. The Fe, Ag, 

Co, Cr, Cu, Mo, Ni, Sn, and V contents are higher in the ash of 

the humic fractions than in the whole samples at the localities 

listed.

The amount of the soluble fulvic fraction in the sediment ranges 

from 0.01 to 0.41 percent and averages 0.21 percent (table 5). 

The distribution is similar to that for the soluble humic fraction; 

the smallest amounts are in sand, and the largest concentrations 

are near the north end of the bay and in the finer grained sediment having higher organic-carbon content in the middle parts 

of the bay.

Of the total soluble humic substances, the humic fraction is 

generally twice the amount of the fulvic fraction. However, the 

percentage of the fulvic fraction has a wide range, from less than 

10 percent to slightly more than 60 percent of the total alkalinesoluble material. The higher percentages of fulvic acid are generally confined to the cleaner sand, which has a relatively very 

low organic-carbon content. Beyond this general relation to grain 

size, there is also a general trend of increase of the fulvic fraction, 

as percentage of total soluble humic substances, from north to 

south, toward the mouth of Jarrett Bay. This trend is from 8 percent at Smyrna Creek (loc. 1, fig. 2), to 25 percent at the north 

end of Jarrett Bay (Iocs. 8 and 13), to 43 percent at the mouth 

of Jarrett Bay (average of data on samples from Iocs. 96, 97, and 

98). The logical explanation for this trend is that the most soluble 

fraction of the alkaline-soluble organic substances, the fulvic fraction, is transported farthest before precipitation and deposition.

Comparison of organic composition of the fulvic fraction with 

that of the humic fraction reveals significant differences (table 6). 

The main differences are in the average carbon content of the 

soluble humic and fulvic fractions, 54.8 and 41.9 percent, respectively, and in the average oxygen content, 33.3 and 47.3, respectively. Obviously, two major groups of molecular structures are 

represented by the two fractions.

Percentages of P, Ag, Cr, Cu, Mo, Pb, V, and Y are significantly 

higher in the ash of the soluble humic and fulvic fractions than in 

the whole sediment samples (table 4). This observation indicates 

that the cited elements are for the greater part associated with
E20 CONTRIBUTIONS TO GEOCHEMISTRY

the alkaline-soluble organic matter in the sediment, though this 

organic matter is only a small part of the whole sediment sample.

SOUTH RIVER

South River, which is about 10 miles southwest of the main 

part of Pamlico Sound, is a northwest-trending drowned creek 

channel about T1/^ miles long and Vi-% m^e wide; its outline and 

the sample localities are shown in figure 7. Depth of water along 

the axis of the channel averages about 11 feet (3.3 m) along twothirds of the stream and becomes shallower southeastward (fig. 7). 

A shallow sill of sand, having a narrow deep channel near its 

center, crosses the river mouth near its junction with the Neuse 

River. The linear channel of South River is U-shaped in profile 

and has shallow bordering shelves. The water, like that in Jarrett 

Bay, is dark tea colored, particularly in the southern part of the 

estuary. Salinity measurements for bottom water during the 

period of study in August 1966 averaged 10.5 parts per thousand 

and ranged from 8.9 to 18.0; most of the readings (86 percent), 

however, were in the range 9.0-11.0 parts per thousand. The 

seasonal averages for salinity and the annual range in the temperature of bottom water are shown in table 1, where comparison 

can be made with similar data for Jarrett Bay. Neither pH nor 

Eh measurements were made in South River because of malfunction of equipment.

BOTTOM SEDIMENT

Bottom sediments were sampled at 53 localities in South River 

(fig. 7), and 31 of the samples were analyzed (table 7). The upper 

10-15 cm (0.3-0.5 ft) of bottom sediment is in general very poorly 

sorted but mainly of silt size (fig. 4; table 7). Sand borders the 

channel on the shallow submerged shelves and forms shallowwater crossbars, or sills, across the mouths of the small tributaries 

to South River. Similarly, the mouth of the South River itself has 

a broad crossbar of sand that is cut by a very narrow channel.

Clay-sized particles compose more than 20 percent of the bottom 

sediment along the deepest part of the bay. The most abundant 

clay minerals are kaolinite, illite-mica, and aluminum-vermiculite 

(table 3). As in Jarrett Bay, a layer about 30 cm (1 ft) thick of 

soupy flocculated material high in organic matter forms an indefinite water-sediment interface in the deeper parts of the channel. Grain-size distribution of sediments is shown in figure 8.

Both calcareous shell fragments and living small clams are 

abundant in South River. A living specimen of a calcareous shelled 

worm similar to Spirorbis was attached to a fragment of tree bark
HOLOCENE SEDIMENTS, PAMLICO SOUND AREA, N.C. E21

76°32'30"

Basic data and chemical

and sedimentary analyses

Sample localities and numbers

Basic data consist of sediment description and

measurements of depth and salinity of water

Marsh Forested area

 5 

Water-depth contour

Interval 5 feet

I MILE

1 KILOMETER

FIGURE 7. Sample localities and depths of water in South River.

collected at locality 33. Wood fragments, particularly pine bark, 

and plant fibers are abundant in the sediment in many minor
TABLE 7. Chemical and grain-size analyses, in percent, of upper 10-15 ctn (0.3-0.5 f

[Carbon and sulfur analyses by I. C. Frost; grain-size analyses by R. F. Gantnier. Ash-free soluble hum

average percentage of ash for 11 humic fractions (15.6 percent) and for 11 fulvic fractions (30.8 pe

(....) in figure columns indicate no analysis]

Locality 

(fig. 7)

1

3

6

8

9

10

11

13

16

17

18

20

21

23

25

26

28

29

30

31

32

33

35

38

40

43

45

48

49

52

53

Sediment type

Sandy mud ....................

....... .do..... ....... .... .... ...........

........do.................. ...................

Sand............ .....................

Sandy mud... ... .... ...........

Mud .... ............ ........... .......

Silty sand .. ................

Mud..... ........ .... ..............

Sand ....... .... ......... ........

Mud................... ...............

........do................ ............

........ do............ .......... ...... .....

... .do ................ ..... .

Sand.......... ............ .....

Mud........ ......... ...... .... .....

Silty sand.......... ..... .... .....

Mud ... . ......

Sandy mud ............ .......

Mud ..... ....... .... ........ ...... 

 do ........ ........ .... 

Sand ............. ...... .

Sandy mud.. .............. 

Mud .......... ......... ..

...... ..do .............. .... .

Sandy mud... ....................

Mud........ ...

Silty sand .............. 

........do ........... ............

....... .do . ...... .. . Sand ........ ......... ..... ..

........do...... ........................

of 

water 

(ft)

4.0

13.2

14.6

1.9

9.6

10.4

6.3

2.4

8.6

11.3

12.1

4.3

6.5

6.4

10.9

4.7

3.9

8.3

12.1

8.5

3.0

4.8

6.8

11.4

2.6

9.4

3.3

7.6

6.6

6.8

2.8

Chemical analyses 

Alkaline-soluble humic

Organic 

carbon

2.7

1.2

1.9

.1

2.4

3.0

.2

9.3

.7

3.9

6.2

12.9

5.2

.8

5.9

7.3

10.1

4.1

6.5

3.6

.3

8.7

8.8

5.9

4.9

8.4

9.6

6.5

5.0

1.4

.4

Bitumen 

(sulfurfree)

0.017

.017

.021

.007

.015

.017

.007

.086

.006

.021

.027

.080

.033

.006

.032

.043

.055

.024

.034

.022

.007

.043

.046

.034

.024

.036

.069

.049

.029

.014

.008

substances

Humic 

fraction

(ash-free)

1.01

.39

.75

.02

1.05

1.14

.17

3.64

.18

1.64

1.90

5.39

2.40

.19

2.86

2.09

4.40

2.03

3.26

1.57

.02

3.46

4.96

2.94

2.26

4.15

5.44

3.24

2.75

.45

.15

Fulvic 

fraction

(ash-free)

0.33

.19

.27

.04

.31

.29

.11

.56

.09

.25

.18

.49

.31

.11

.28

.19

.38

.36

.20

.43

.06

.73

.47

.29

.39

.13

.76

.16

.15

.08

.07

- Mineral 

carbon

0.03

.02

.03

.01

.03

.04

.03

.08

.04

.03

.03

.10

.05

.04

.08

.06

<^.01

.02

.09

.02

.01

.04

.05

.13

.02

.07

<-01

.03

.04

<.01

<.01
HOLOCENE SEDIMENTS, PAMLICO SOUND AREA, N.C. E23

76°32'30"

34° 

57' 

30"

EXPLANATION

X 

Grain-size Megascopic

analysis description

Sample localities

Area where <2/u particles exceed 

20 percent of sediment

Isopleth 

Skoiving amount of sand in sediment, in percent

I MILE

1 KILOMETER

FIGURE 8. Distribution of sediment by grain size in South River. For this 

report, clean sand contains more than 90 percent sand-sized grains; all 

other sediment is either muddy sand or sandy mud.
E24 CONTRIBUTIONS TO GEOCHEMISTRY

depressions along the longer tributaries to South River. All sediments are greenish gray except the sand, which is very light 

brown; the odor of hydrogen sulfide was evident in most samples 

at the time of collection.

The chemical composition was determined for 25 samples from 

South River by semiquantitative emission spectrographic analysis, 

and the results for six representative samples are given in table 8. 

No conspicuous anomalies were noted but, comparing the 20 spectrographic analyses of Jarrett Bay samples with the 25 of South 

River samples, Fe, Ti, Ba, Co, Cr, Cu, Mo, Ni, Pb, and V are 

significantly higher in the clayey silts and sandy mud from South 

River than in sediments of similar grain size from Jarrett Bay.

The heavy-mineral content of sediment from South River is 

similar to that of Jarrett Bay; concentrations ranged from 0.3 to 

1.3 percent in the fraction < 0.125 and > 0.062 mm. Heavy minerals are most abundant in sands that form low sills across tributary channels.

ORGANIC AND RELATED MATERIALS 

Organic carbon

In South River, as in Jarrett Bay, of all the sediment types the 

sand (sediment greater than 90 percent sand) has the lowest 

organic-carbon content an average of 0.6 percent and a range 

of 0.1-1.4 percent* (table 7). In contrast to Jarrett Bay, however, 

the rest of the sediment in South River is very poorly sorted, and 

the general increase in organic carbon with decrease in grain size 

noted in sediments in Jarrett Bay and in many other aquatic environments is very erratic in South River sediment. Rather, the 

amount of organic carbon in the bottom mud (sediment less than 

50 percent sand) is related to geomorphic position in South River, 

here divided into the following three areas: (1) The mouth of the 

estuary, (2) the central linear part of the estuary where the 

water is more than 10 feet deep, and (3) the small tributaries. 

The mud near the mouth of South River (Iocs. 1, 3, and 6 in fig. 7) 

has a relatively very low organic-carbon content, which ranges 

from 1.2 to 2.7 percent and averages 1.9 percent. The organiccarbon content of mud along the central deep part of the bay 

averages 5.0 percent and ranges from 3.0 to 6.5 percent; in the 

tributaries it averages 9.2 percent and ranges from 5.2 to 12.9 

percent.

Undoubtedly, a detailed study of the mud samples from the 

three areas would reveal significant differences in the type and 

state of decomposition of the organic matter that would explain 

the different averages of 1.9, 5.0, and 9.2 percent organic carbon 

in these muds. From megascopic descriptions those samples with
HOLOCENE SEDIMENTS, PAMLICO SOUND AREA, N.C. E25

the higher organic-carbon contents contained a variety of organic 

substances, including grass and tree-bark fragments, minute wood 

shreds, some living and dead mollusks, mainly clams, and flocculent organic material that has a consistency of "liver mud." None 

of these materials, however, seemed to predominate or be confined 

to one geomorphic area or sediment type, though wood fragments 

were observed in almost all tributary sediment samples.

TABLE 8. Emission spectrographic analyses of sediments from 

South River estuary

[Analyst, G. W. Sears. Leaders (....) in figure columns indicate element not detected]

Percentage of given element in sediment sample

(Indicated are locality, shown in fig. 7 ; sediment type; and

organic-carbon content, in percent)

Si...................

Al...................

Fe..... .............

Mg.................

Ca....... ...........

K..... ...............

Ti...................

Mn.................

B....................

Ba..................

Be..................

Co..................

Cr.... ...............

Cu......... .........

Ga..................

La ................

Mo..................

Nb.......... ........

Ni. ..................

Pb.. ................

Sc.. .................

Sr.. .................

V..... ...............

Y...... .......... ...

Yb..................

Zr..... ..............

Locality 3 ;

sandy mud ;

1.2

>10

7

......... 3

........ .7

........ 1.5

........ 7

........ 2

........ .07

........ .015

........ .2

......... .0007

........ .007

........ .007

........ .003

........ .007

........ .002

........ .001

........ .005

........ .002

........ .03

........ .007

........ .003

........ .0007

........ .5

Locality 8 ; '. sand ;

0.1

10

3

2

.2

1

1.5

3

.07

.007

.1

.0015

.0007

.001

.002

.0007

.003

.001

.015

.003

.0003

Locality 17 ; '.

clayey silt ;

3.9

>10

>10

1.5

1.5

5

1.5

.07

.015

.15

.0003

.002

.01

.01

.007

.01

.001

.002

.007

.007

.003

AQ

.015

.005

.0007

Locality 38 ; 1

clayey silt ;

5.9

>10

>10

>10

3

2

7

1.5

.07

.02

.3

.0003

.002

.015

.015

.007

.01

.0015

.002

.007

.007

.003

.05

.015

.003

.0007

.05

Locality 48 ; 1

silty sand;

6.5

>10

7

5

1

2

1.5

1

.05

.001

.07

.0007

.003

.01

.0007

.001

.002

.0015

.005

.005

.002

.0003

Locality 53 ;

sand ;

0.4

>10

2

.7

.15

.5

.5

.015

.007

.07

.001

.007

.002

.0007

.005

.0015

.007

Mineral carbon

The mineral-carbon, or carbonate, content of the sediment, regardless of grain size, is relatively low; it averages less than 0.05 

percent and ranges from less than 0.01 to 0.13 percent. There is 

no specific correlation between organic- and mineral-carbon contents but, on the average, the mud in the tributaries and in deeper 

water in the middle of the bay contains 0.01-0.03 percent more 

mineral carbon than the more sandy nearshore sediment. This 

probably is a result of there being slightly more shell fragments 

in samples from these areas.

Sulfur

The total sulfur in South River sediment ranges from 0.06 to 

3.76 percent (table 7), and its distribution is somewhat analagous 

to that of organic carbon but not quite so clear cut as in Jarrett
E26 CONTRIBUTIONS TO GEOCHEMISTRY

Bay sediments. The sand contains an average of 0.28 percent total 

sulfur; and, as in the geomorphic areas described for organic 

carbon, the mud near the mouth of South River contains an average of 0.76 percent total sulfur; the mud along the central deep 

part of the bay, 1.94 percent; and the tributary mud, 3.08 percent.

Bitumen

The bitumen content of South River sediment clearly parallels 

the distribution of the organic carbon. In the six sand samples 

(table 7) the bitumen content averages 0.008 percent and ranges 

from 0.006 to 0.014 percent. The bitumen in the sediment, excluding the sand, also appears to be related to the three geomorphic 

positions in the estuary. The bitumen content of mud near the 

mouth of South River averages 0.018 percent and ranges from 

0.017 to 0.021 percent. In the mud in the deeper water along the 

axis of the estuary, it averages 0.026 percent and ranges from 

0.017 to 0.034 percent. In the tributary muds, which have the 

highest organic-carbon content and also the highest bitumen yield, 

the bitumen content averages 0.059 percent and ranges from 0.033 

to 0.086 percent. In South River, bitumen, as determined on the 

basis of ratios of bitumen to organic carbon, consistently makes 

up about 0.3 percent of the organic matter in the mud but about 

1 percent in the sand poor in organic matter.

Alkaline-soluble humic substances

The alkaline-soluble organic material in the bottom sediment of 

South River has a wide range in content, 0.06-5.88 percent, just 

as does the organic carbon in the sediment. These soluble organic 

substances constitute about one-fourth of the organic matter in 

the sediment, very similar to the amount of soluble humic substances derived from the organic matter in Jarrett Bay sediment. 

Because the pattern of distribution of alkaline-soluble humic substances almost exactly parallels that of organic-carbon content of 

sediments in South River (fig. 9), no separate map showing this 

distribution is included.

The soluble humic fraction makes up 70-97 percent of the 

alkaline-soluble organic material in South River sediment, except 

in the sand. The humic fraction in the six sand samples (table 7, 

Nos. 8, 16, 23, 32, 52, and 53) averages 57 percent of the alkalinesoluble material; these results, however, are possibly due to analytical error in analyses of sediment containing less than 1 percent 

organic carbon. For comparison, the humic fraction in the mud 

near the mouth of the estuary averages 72 percent of the soluble 

organic material; in the mud along the axis of the estuary, 87 

percent; and in the tributary mud, 89 percent.
HOLOCENE SEDIMENTS, PAMLICO SOUND AREA, N.C. E27

76°32'30"

34° 

57' 

30'

EXPLANATION

®

Sample analyzed for Crude estimate of ororganic-carbon con- ganic-carbon content 

tent of sample based on

sediment description 

Sample localities

Isopleth

Shelving organic-carbon content of sediment, 

in percent

1 MILE 

J

1 KILOMETER

FIGURE 9. Organic-carbon content, in percent, of sediment in South River.

Complete organic-element analyses of the humic fraction were 

made for three samples spaced from the upper reaches of South
E28 CONTRIBUTIONS TO GEOCHEMISTRY

River toward the mouth (table 9). The carbon content is almost 

identical in the three samples, the contents of hydrogen and nitrogen increase toward the mouth, and sulfur apparently decreases.

The amount of the fulvic fraction extracted from the sediment 

ranges from 0.04 to 0.76 percent. Highest concentrations are in 

sediment along the deepest part of the main channel of South 

River and in several of the tributary channels, and they correspond in general to the content of organic matter in the sediment.

A comparison of the organic-element composition of the fulvic 

fraction with that of the humic fraction (table 9) shows that the 

differences noted for Jarrett Bay also are evident for South River 

 for the fulvic fraction the carbon content is lower, the oxygen 

content is higher, and the amount of ash is considerably higher. 

Trace-element content of the ash of the fulvic and humic fractions 

was not determined for South River sediments.

TABLE 9. Organic-element composition, in percent, on ash-free basis, of 

soluble humic and fulvic fractions of sediments from South River

[Analyses by Huffman Laboratories, Inc., Wheatridge, Colo.]

Locality 

(fig. 7) Carbon Hydrogen Oxygen Nitrogen Sulfur

Carbonhydrogen 

ratio

Ash

Humic fraction

17....................

35........... ........

48........... ........

Avg. ...........

........ 57.17

........ 57.66

........ 57.97

........ 57.6

5.11 

4.59 

4.30

4.7

32.00 

32.76 

31.92

32.2

4.34 

3.80 

2.84

3.7

1.37 

1.17 

2.95

1.8

11.2 

12.6 

13.5

12.4

15.33 

12.72 

6.68

11.6

Fulvic fraction

17....................

35. ............... ....

48....................

........ 41.65

........ 41.98

........ 42.20

........ 41.9

4.68 

4.01 

4.75

4.5

48.66 

50.11

48.48

49.1

3.38 

2.54 

2.29

2.7

1.63 

1.35 

2.28

1.8

8.9 

10.5 

8.9

9.4

32.02 

36.59 

32.03

33.5

COMPARISONS AND CONCLUSIONS

The foregoing data and descriptions can be summarized and 

interpreted as follows in terms of the relationship of organic matter to the depositional environments:

1. The estuarine bottom sediments of both Jarrett Bay and South 

River are predominantly poorly sorted silt and fine sand that 

are mineralogically complex. The sand and silt content is 

consonant with the proximity and association of sediment 

types and distribution patterns in the river, the estuary, and 

the barrier-island environments of the Pamlico Sound area. 

Most of the organic matter in the bottom sediment of the 

two small estuaries is derived from plants in the large adjacent marsh areas and the predominantly pine and deciduous tree forests farther inland. The proportion of algal 

remains is unknown, though conspicuous "algal blooms"
HOLOCENE SEDIMENTS, PAMLICO SOUND AREA, N.C. E29

were observed during summer field studies. Especially indicative of plants being the primary source of the organic 

matter was the medium- to dark-brown color of the water 

in the estuaries; the very dark water in the upper reaches of 

the bays and in the many broad-mouthed tributaries was very 

similar to the waters in many peat bogs and tidal marshes.

Faunal remains associated with the bottom sediments are 

closely related to the environment. Arenaceous Foraminifera 

are typical of bays along the inshore side of lagoons and the 

associated marshes; oyster shells and remains of other marine mollusks indicate the direct connection of Jarrett Bay 

to the saline lagoon water of Core Sound. Small brackishwater clams are relatively abundant in South River. The 

salinity of Jarrett Bay water ranges from 20 to 35 parts per 

thousand, and the salinity of South River water ranges from 

12 to 20 parts per thousand.

It should be borne in mind that these two relatively small 

estuarine bodies of water lie but a few miles apart and are 

in many respects similar; they represent shallow estuarine 

extensions of broader environments in the interrelated and 

complex suite of depositional environments of the Pamlico 

Sound coastal area.

2. The amount of organic carbon in the upper 10-15 cm of sediment in Jarrett Bay and in South River averages 1.6 percent 

(51 samples) and 4.8 percent (31 samples), respectively. 

The higher content of organic carbon in the sediment of 

South River is probably best explained by the fact that South 

River is a narrower trough, separated from the Neuse River 

by a sand sill that partly prevents outflow of much of the 

suspended organic materials. Jarrett Bay, on the other hand, 

has a broad open mouth, and much of both the suspended 

and dissolved organic matter either entering the bay or generated in it is dispersed into Core Sound.

Generally, the percentage of organic carbon increases with 

decreasing grain size of sediment in both estuaries. In Jarrett Bay the sand, silty sand, and mud have average carbon 

contents of 0.4, 1.3, and 2.1 percent, respectively. This inverse correlation between organic-carbon content and grain 

size is markedly masked by geographic position of sediment 

in South River. This geographic control is best illustrated 

by the distinctly different organic-carbon content of the mud. 

The average organic-carbon content in mud is 1.9 percent 

near the mouth of South River, 5.0 percent along the axis of 

the bay, and 9.2 percent in the tributaries.
E30 CONTRIBUTIONS TO GEOCHEMISTRY

The sand forms the shallow-water sediment along the margins of both bay-type estuaries and generally contains 0.1-0.7 

percent organic carbon. Even this small amount of organic 

matter in the sand produces an anaerobic environment, a few 

centimeters below the sediment-water interface, having a 

negative Eh and an odor of hydrogen sulfide. The water several centimeters above mud rich in organic matter also can 

be reducing, even in water less than 3 feet (1m) deep.

No attempt is made here to relate the organic-carbon content of Jarrett Bay and South River sediment to that of 

recent sediment in many other depositional environments. 

It is interesting to note, however, that the carbon values for 

sediment types reported here are comparable to those reported for the much larger Choctawhatchee Bay estuary in 

northwest Florida, where the average organic-carbon content is 0.15 percent in sand and 3.6 percent in mud (James 

G. Palacas, written commun., 1970).

3. A high content of alkaline-soluble humic substances characterizes the sediment of both the Jarrett Bay and South River 

estuaries and indicates the large contribution of plant material from surrounding marsh and forest areas, relative to 

a low contribution of animal material. In South River, for 

example, sediment that has an organic-carbon content of 

more than 5 percent (14 samples, range of 5.2-12.9 percent) 

has a relatively low average bitumen content (0.048 percent), but the alkaline-soluble organic matter averages 3.9 

percent. In the same samples, the soluble humic fraction 

makes up an average of 91 percent of the alkaline-soluble 

organic material, and the fulvic fraction 9 percent. Similar 

relations would hold for a similar set of Jarrett Bay sediment samples, though all Jarrett Bay values would be about 

one-half those presented in the South River example. Thus, 

a high content of alkaline-soluble organic material, having 

an exceptionally high humic fraction, and a relatively low 

bitumen content are characteristic of these two marshbordered estuarine environments.

The data on samples from Jarrett Bay show a trend of 

increase in the proportion of the fulvic fraction, compared 

to the soluble humic fraction, from north to south. At the 

head, or north end, of Jarrett Bay, the fulvic fraction is 

8 percent of the total alkaline-soluble organic matter, and 

the percentage increases to 43 percent at the mouth of the 

estuary. The logical explanation for this trend is that the 

more soluble organic material, represented by the fulvic
HOLOCENE SEDIMENTS, PAMLICO SOUND AREA, N.C. E31

fraction, is transported farthest before precipitation and 

deposition.

4. The organic-element compositions of the extracted humic and 

fulvic fractions from both estuaries are quite different in 

several respects. The average composition of the humic fraction from Jarrett Bay sediment, in percent on an ash-free 

basis, is 54.8 C, 5.9 H, 33.3 0, 4.0 N, and 2.0 S; for South 

River, the average composition is 57.6 C, 4.7 H, 32.2 0, 

3.7 N, and 1.8 S. The slightly lower carbon content and 

higher hydrogen content of the humic fraction from Jarrett 

Bay are the obvious differences, but neither of these compositions is significantly different from those of humic fractions reported for other areas. (See Swanson and Palacas, 

1965, table 3; Palacas and others, 1968, table 2.) One apparently significant observation can be made, however, on the 

change in composition of the humic fraction from headwaters to the mouth of both estuaries namely, a very 

slight decrease in carbon content and an increase in hydrogen content.

Typically, the composition of the fulvic fraction greatly 

differs from that of the humic fraction, primarily in having 

a much lower carbon content and correspondingly higher 

oxygen content. The twofold difference in percentage of ash 

(see table 5) between the humic fraction (15.6) and fulvic 

fraction (30.8) is considered a result of the laboratory 

method used and thus is not of geochemical significance. 

The average composition of the fulvic fraction extracted 

from Jarrett Bay sediment, in percent on an ash-free basis, 

is 41.9 C, 5.5 H, 47.3 0, 4.3 N, and 1.0 S; for South River, 

the average composition is 41.9 C, 4.5 H, 49.1 0, 2.7 N, and 

1.8 S.

As in other areas, the soluble humic and fulvic fractions 

show concentration of certain metals. Analyses of the ash 

of these fractions from Jarrett Bay sediment show that the 

following metals are significantly concentrated: Ag, Co, Cr, 

Cu, Mo, Ni, Pb, Sn, and V. No comparable data were obtained on South River samples, but probably a similar suite 

of metals would be shown to be concentrated in the alkalinesoluble organic substances from South River sediment as well.

5. The clay minerals from the two areas represent two distinct 

suites which may indicate two different source areas involved 

in the delivery of clay minerals to the two areas. The clay 

minerals in sediments of Jarrett Bay probably are similar to 

those in sediment of the barrier islands which is transported
E32 CONTRIBUTIONS TO GEOCHEMISTRY

from the north by longshore currents in the Atlantic Ocean; 

clays in sediments of South River probably come principally 

from the Neuse River effluence whose drainage lies within 

the Piedmont and Coastal Plain physiographic provinces of 

North Carolina. As also shown by the differences in the 

macrof aunas, the marked difference in the clay-mineral suites 

of the two areas indicates the dissimilarities that can occur 

between two closely spaced estuarine environments in the 

Pamlico Sound coastal area.

REFERENCES CITED

Grossman, Stuart, 1967, Living and subfossil rhizopod and ostracode populations, part 1 of Ecology of Rhizopodea and Ostracoda of southern Pamlico 

Sound region, North Carolina: Kansas Univ. Paleont. Contr. 44, Ecology, 

art. 1, p. 1-82.

Palacas, J. G., Love, A. H., and Gerrild, P. M., 1971, Hydrocarbons in estuarine sediments of Choctawhatchee Bay, Florida, and their implications for 

the genesis of petroleum: Am. Assoc. Petroleum Geologists Bull, (in 

press).

Palacas, J. G., Swanson, V. E., and Love, A. H., 1968, Organic geochemistry 

of recent sediments in the Choctawhatchee Bay area, Florida A preliminary report, in Geological Survey research 1968: U.S. Geol. Survey 

Prof. Paper 600-C, p. C97-C106.

Shimp, N. F., Witters, J., Potter, P. E., and Schleicher, J. A., 1969, Distinguishing marine and freshwater muds: Jour. Geology, v. 77, no 5, 

p. 566-580.

Swanson, V. E., and Palacas, J. G., 1965, Humate in coastal sands of northwest Florida: U.S. Geol. Survey Bull. 1214-B, 29 p.

Swanson, V. E., Palacas, J. G., and Love, A. H., 1967, Geochemistry of deepsea sediment along the 160° W. meridian in the North Pacific Ocean, in 

Geological Survey research 1967: U.S. Geol. Survey Prof. Paper 575-B, 

p. B137-B144.

Williams, A. B., 1955, A contribution to the life histories of commercial 

shrimps (Penacidae) in North Carolina: Marine Sci. of the Gulf and 

Caribbean Bull., v. 5, no. 2, p. 116-146.

U. S. GOVERNMENT PRINTING OFFICE : 1972 O - 454-767