C

C’

New

River

0 4 8 MILES

0 4 8 KILOMETERS

PE-102

PE-101

DU-129

ON-269

ON-344

ON-229

ON-341

ON-346

ON-300

ON-358

ON-315

ON-356

ON-252

ON-278

ON-242

JO-089

JO-062

ON-233

ON-345

ON-285

JO-069

ON-283 JO-042

ON-314

ON-346

A

A’

A’ B’

B

B’

D

D’

E

E’

34o30’

34o

45’

77o

45’ 77o30’ 77o15’

35o

Atlantic

Ocean

EXPLANATION

Hydrogeologic cross section

Borehole not displayed 

in cross section

U.S. Marine Corps 

Base boundary

U.S. Marine Corps 

Camp Lejeune

Jacksonville

Richlands

Swansboro

Beulaville

Pink

Hill

Maysville

PENDER COUNTY

ONSLOW

COUNTY

JONES

COUNTY

CARTERET

COUNTYCRAVEN COUNTY

DUPLIN

COUNTY

LENOIR

COUNTY

LOCATION OF ONSLOW COUNTY, NORTH CAROLINA

Holly Ridge

Coastal Plain Piedmont

Blue Ridge

DU-129

SP

EXPLANATION

Borehole

Single point resistance

Contact uncertain

Other geophysical curve

SP - Spontaneous potential

G- Gamma-ray

0 5 10 MILES

0 5 10 KILOMETERS

VERTICAL SCALE GREATLY EXAGGERATED

SECTION

A–A’

PE-101 ON-344 ON-233 SECTION D–D’ SECTION B–B’ SECTION C–C’ON-278 JO-042

G

ON-356

PENDER COUNTY

ONSLOW COUNTY

ONSLOW COUNTY

JONES COUNTY

New R.

aquifer

Upper Castle Hayne aquifer

Lower Castle Hayne

aquifer

Basement

Peedee aquifer

Beaufort aquifer

Black Creek aquifer

Upper Cape Fear aquifer

Lower Cape Fear aquifer

E E’

ELEVATION, IN FEET ABOVE OR BELOW NATIONAL GEODETIC VERTICAL DATUM OF 1988

300

200

100

0

-100

-200

-300

-400

-500

-600

-700

-800

-900

-1,000

-1,100

-1,200

-1,300

-1,400

-1,500

-1,600

-1,700

Upper Castle Hayne

Peedee

Peedee

Lower Castle Hayne

Beaufort

G G

G G

ON-269

SECTION

A–D

ON-344

SP

ON-341 ON-229 ON-346

SECTION

E–E’

SECTION

A’–D’

SP

ELEVATION, IN FEET ABOVE OR BELOW NATIONAL GEODETIC VERTICAL DATUM OF 1988

300

200

100

0

-100

-200

-300

-400

-500

-600

-700

-800

-900

-1,000

-1,100

-1,200

-1,300

-1,400

-1,500

-1,600

-1,700

-1,800

aquifer

Upper Castle Hayne aquifer

Upper Castle Hayne

Lower Castle Hayne

Beaufort

Peedee

Black Creek

Lower Cape Fear

Lower Castle Hayne aquifer

Basement

Peedee aquifer Beaufort aquifer

Black Creek aquifer

Upper Cape Fear aquifer

Lower Cape Fear aquifer

B B’

System1 Geologic units

Yorktown Formation2

Belgrade Formation

River Bend Formation

Table 1. Correlation chart of North Carolina Coastal Plain geologic and hydrogeologic 

Quaternary

2

Tertiary

Eastover Formation2

Yorktown aquifer2

2

Pungo River Formation2

Castle Hayne Limestone

Upper Castle Hayne aquifer

Lower Castle Hayne aquifer

Beaufort Formation Beaufort aquifer

Peedee Formation Peedee aquifer

Black Creek Formation

Middendorf Formation2

Upper Cape Fear aquifer

Lower Cape Fear aquifer

Unnamed units2

 1

the age or ages of the principal geologic unit or units composing each hydrogeologic unit. 2Unit not present in the study area.

Cretaceous

Black Creek aquifer

Cape Fear Formation

Pungo River aquifer2

2

Lower Cretaceous aquifer2

Quaternary deposits

Hydrogeologic units

DU-129 SECTION A–A’ON-283 JO-089

G

SECTION

D–D’

JO-069

G

ON-300

G

G

SECTION 

B–B’

SECTION 

C–C’

ELEVATION, IN FEET ABOVE OR BELOW NATIONAL GEODETIC VERTICAL DATUM OF 1988

300

200

100

0

-100

-200

-300

-400

-500

-600

-700

-800

-900

-1,000

-1,100

-1,200

aquifer

Beaufort aquifer

Peedee aquifer

Basement

Upper Cape Fear aquifer

Lower Cape Fear aquifer

Black Creek aquifer

A D

Beaufort

Peedee

Black Creek

Lower Cape Fear

SECTION

A–D

SECTION

E–E’

SECTION

A’–D’

ON-300 ON-242 ON-356 ON-252 ON-315 ON-358

ELEVATION, IN FEET ABOVE OR BELOW NATIONAL GEODETIC VERTICAL DATUM OF 1988

300

200

100

0

-100

-200

-300

-400

-500

-600

-700

-800

-900

-1,000

-1,100

-1,200

-1,300

-1,400

-1,500

-1,600

-1,700

-1,800

aquifer

Upper Castle Hayne aquifer

Lower Castle Hayne

aquifer

Upper Castle Hayne

Basement

Peedee aquifer

Beaufort aquifer

Black Creek aquifer

Upper Cape Fear aquifer

Lower Cape Fear aquifer

C C’

Lower Castle Hayne

Beaufort

Peedee

Lower Cape Fear

G SP G G G

DU-129

G G G SECTION E–E’

PE-101 PE-102

DUPLIN COUNTY

PENDER COUNTY

SECTION

A’–D’

SECTION

A–D

Upper Castle Hayne aquifer

Lower Castle Hayne aquifer

Basement

Peedee aquifer

Black Creek aquifer

Upper Cape Fear aquifer 

Lower Cape Fear aquifer

ELEVATION, IN FEET ABOVE OR BELOW NATIONAL GEODETIC VERTICAL DATUM OF 1988

300

200

100

0

-100

-200

-300

-400

-500

-600

-700

-800

-900

-1,000

-1,100

-1,200

-1,300

-1,400

-1,500

A A’

ELEVATION, IN FEET ABOVE OR BELOW NATIONAL GEODETIC VERTICAL DATUM OF 1988

300

200

100

0

-100

-200

-300

-400

-500

-600

-700

-800

-900

-1,000

-1,100

-1,200

-1,300

-1,400

-1,500

-1,600

-1,700

-1,800

-1,900

-2,000

SECTION

E–E’

SECTION

A’–D’

SECTION

A–D

JONES COUNTY

ONSLOW COUNTY

aquifer

Upper Castle Hayne aquifer

Lower Castle Hayne aquifer

Basement

Peedee aquifer

Beaufort aquifer

Black Creek aquifer

Upper Cape Fear aquifer

Lower Cape Fear aquifer

D D’

Upper Castle Hayne Lower Castle Hayne

Beaufort

JO-089 JO-062 ON-285 ON-233 ON-345

G G

aquifer

Peedee

DUPLIN COUNTY

ONSLOW COUNTY

PENDER COUNTY

ONSLOW COUNTY

ONSLOW COUNTY

JONES COUNTY

SECTION

D–D’

SECTION

A–A’

SECTION

B–B’

SECTION

C–C’

PE-102 ON-346 ON-314 ON-358 ON-345

A’ D’

New R.

ELEVATION, IN FEET ABOVE OR BELOW NATIONAL GEODETIC VERTICAL DATUM OF 1988

300

200

100

0

-100

-200

-300

-400

-500

-600

-700

-800

-900

-1,000

-1,100

-1,200

-1,300

-1,400

-1,500

-1,600

-1,700

-1,800

-1,900

-2,000

aquifer

Peedee

Black Creek

Black Creek aquifer

Basement

Peedee aquifer

Beaufort aquifer

Lower Cape Fear aquifer

Upper Castle Hayne

Lower Castle Hayne Lower Castle Hayne

aquifer

Upper Castle Hayne aquifer

G G G G

Hydrogeologic Framework of Onslow County, North Carolina, 2008—Sheet 1 of 1

Fine, J.M., 2008, Hydrogeologic Framework of Onslow County, North Carolina, 2008

Prepared in cooperation with the

CITY OF JACKSONVILLE, ONSLOW WATER AND SEWER AUTHORITY, AND U.S. MARINE CORPS, CAMP LEJEUNE

Hydrogeologic Framework of Onslow County, North Carolina, 2008

By

Jason M. Fine

2008

Onslow Water & Sewer Authority

U.S. DEPARTMENT OF THE INTERIOR

U.S. GEOLOGICAL SURVEY

The unconsolidated sediments that underlie the Onslow County area are composed of interlayered permeable and 

impermeable beds, which overlie the crystalline basement rocks. The aquifers, composed mostly of sand and limestone, 

are separated by confining units composed mostly of clay and silt. The aquifers from top to bottom are the surficial, Castle 

Hayne, Beaufort, Peedee, Black Creek, and Upper and Lower Cape Fear aquifers. For this study, the Castle Hayne aquifer is 

informally divided into the upper and lower Castle Hayne aquifers.

The eight aquifers and seven confining units of the Tertiary and Cretaceous strata beneath Onslow County are 

presented in seven hydrogeologic sections. The hydrogeologic framework was refined from existing interpretations by using 

geophysical logs, driller’s logs, and other available data from 123 wells and boreholes. 

Introduction

For the past three decades, ground-water levels in the central Coastal Plain of North Carolina have declined as much 

as 200 feet from overpumping and depleting storage in the Cretaceous Black Creek and Upper Cape Fear aquifers (North 

Carolina Division of Water Resources, 2001). Because of these declines, the resulting increased potential for lateral saltwater migration along the coast and upward leakage of brackish water from deeper aquifers prompted the North Carolina 

Division of Water Resources (DWR) to institute the Central Coastal Plain Capacity Use Area (CCPCUA) rules for 15 

counties, effective August 1, 2002 (North Carolina Division of Water Resources, 2001). Under the CCPCUA rules, a 

ground-water withdrawal of more than 100,000 gallons per day from the Cretaceous aquifers is subject to a water-use 

reduction of as much as 75 percent over a 16-year period. 

The Black Creek aquifer is a major source of water for Onslow County. In order to meet the required reduction in 

withdrawals from the Cretaceous aquifers and continue to meet demand, water suppliers in Onslow and the surrounding 

counties have shifted withdrawals from the Black Creek aquifer to the Castle Hayne aquifer. 

The effects of increased development of the Castle Hayne aquifer and decreased use of the Black Creek aquifer in 

Onslow County are unknown. In 2007, the U.S. Geological Survey (USGS), in cooperation with the City of Jacksonville, 

Onslow Water and Sewer Authority, and the Marine Corps Base, Camp Lejeune, began an investigation to delineate and 

describe the ground-water flow system in the Onslow County area. As part of the initial phase of this study, a hydrogeologic 

framework has been delineated for all aquifers and confining units that underlie Onslow and parts of Duplin, Jones, and 

Pender Counties and is presented in this report. This hydrogeologic framework will form the basis of a digital ground-water 

flow model, which can be used to simulate and manage the ground-water flow system of Onslow County. 

Abstract

Study Area

Onslow County is located in the southeastern part of the Coastal Plain physiographic 

province of North Carolina (fig. 1). The Coastal 

Plain’s hydrogeology consists of an eastward 

dipping wedge of interbedded sand, clay, and 

limestone layers in the Quaternary to Cretaceous 

strata (table 1). The aquifers underlying Onslow 

County, in descending order, are the surficial, 

upper and lower Castle Hayne, Beaufort, Peedee, 

Black Creek, and Upper and Lower Cape Fear 

aquifers.

Methods

The hydrogeologic sections presented 

in this report were interpreted from geophysical 

logs, driller’s logs, water-level data, and waterquality data collected in 123 wells and boreholes. 

These interpretations came from this study, the 

DWR’s hydrogeologic framework database 

(J.C. Lautier, unpub. data, North Carolina 

Division of Water Resources, 2006), and

previous USGS studies that were conducted in

the area by Lyke and Winner (1990) and

Winner and Coble (1996).

Hydrogeologic interpretations were 

tabulated and displayed as point data using 

geographical information system (GIS) software. 

The GIS software then interpolated the point 

data into triangulated irregular networks (TIN), 

which fill in the gaps between the point data and

create planes representing the tops and bottoms 

of each aquifer and confining unit. The 

hydrogeologic cross sections were constructed 

from the created TINs (figs. 2–8)

Surficial Aquifer

The surficial aquifer is an important part of the ground-water flow system. This unconfined aquifer, composed mostly 

of sand, silt, and clay of Quaternary strata (table 1), is the primary source of recharge for the deeper aquifers and is the 

source of base flow for the area’s streams and rivers. With the exception of irrigation and private supply wells, the surficial 

aquifer generally is unused in the study area.

Upper and Lower Castle Hayne Aquifers

Tertiary marine sediments of the Belgrade, River Bend, and Castle Hayne Formations compose the Castle Hayne 

aquifer (Lyke and Winner, 1990). It is a highly productive aquifer composed of limestone and sand, with minor amounts of 

clay. The Castle Hayne aquifer is overlain by the Castle Hayne confining unit throughout most of the Onslow County area 

with the exception of the north and northeastern parts of the county, where it is unconfined and in direct contact with the 

surficial aquifer. For this study, the Castle Hayne aquifer has been informally subdivided into two aquifers, the upper and 

lower Castle Hayne, to better represent head differences that exist in the aquifer. The Castle Hayne aquifer is used

predominantly for water supply in Onslow County and will be a main source for future development. 

Beaufort Aquifer

The Beaufort aquifer is composed of Tertiary marine sediments and rocks of the Beaufort Formation, described by 

Lyke and Winner (1990) as fine to medium glauconitic sand, clayey sand, shell and limestone, and interbedded clay. Most 

of the study area is underlain by the Beaufort aquifer, with the exception of the western edge of Onslow County where the 

aquifer pinches out. The Beaufort confining unit separates the Castle Hayne aquifer from the Beaufort aquifer. The Beaufort 

aquifer is a relatively unused aquifer in Onslow County.

Peedee Aquifer

The Peedee aquifer consists of sediments of the Peedee Formation, which is the youngest Cretaceous formation in 

the study area. The Peedee Formation is composed primarily of sand with interbedded clay and silt layers, but limestone 

and partially consolidated calcareous sandstone are layered within the sands of the aquifer in some areas (Lyke and Winner, 

1990). The Peedee confining unit separates the Beaufort aquifer or the Castle Hayne aquifer (where the Beaufort aquifer is 

not present) from the Peedee aquifer. Because of high levels of iron and the presence of saltwater, the Peedee aquifer is only 

used for water supply in the northern part of Onslow County. 

Black Creek Aquifer

The Black Creek aquifer is composed of the Cretaceous Black Creek and Middendorf Formations (Winner and 

Coble, 1996). However, the Middendorf Formation is not present in the study area. The Black Creek Formation is composed 

of interbedded sand and clay layers, which contain shells, glauconite, and large amounts of organic matter (Lyke and Winner, 

1990). The Black Creek confining unit separates the Peedee aquifer from the Black Creek aquifer. The Black Creek aquifer 

is a source of high quality drinking water in the study area, but the presence of saltwater prevents the aquifer from being used 

for water supply in the southern half of Onslow County.

Upper and Lower Cape Fear Aquifers

The deepest Cretaceous aquifers in the study area are the Upper and Lower Cape Fear aquifers. These aquifers are 

composed of sand with minor amounts of clay, gravel, and limestone of the Cape Fear Formation. The Upper Cape Fear 

confining unit separates the Upper Cape Fear aquifer from the Black Creek aquifer, and the Lower Cape Fear confining 

unit separates the Upper Cape Fear aquifer from the Lower Cape Fear aquifer. The Lower Cape Fear aquifer is underlain by 

crystalline bedrock. The Upper and Lower Cape Fear aquifers are not used in the study area because of their depth and the 

presence of saltwater. 

Summary

The hydrogeologic framework of the Onslow County area is described as a series of eight generally eastward 

dipping and thickening wedge-shaped aquifers that are separated by seven confining units. The aquifers and confining units 

are composed mostly of sand, silt, clay, and limestone of Tertiary and Cretaceous strata. The aquifers from top to bottom are 

the surficial aquifer, upper and lower Castle Hayne aquifers, Beaufort aquifer, Peedee aquifer, Black Creek aquifer, 

Upper Cape Fear aquifer, and Lower Cape Fear aquifer. The Castle Hayne, Peedee, and Black Creek aquifers are the primary 

sources for water supply in the Onslow County area.

To better understand the hydrogeology of the study area, seven hydrogeologic sections were constructed from 

interpretations of data from 123 wells and boreholes. These interpretations were derived from geophysical logs, driller’s logs, 

water-level data, and water-quality data. This hydrogeologic framework can be used in the construction of a digital groundwater flow model to better understand the ground-water flow system of the Onslow County area.

References

Lyke, W.L., and Winner, M.D., Jr., 1990, Hydrogeology of aquifers in Cretaceous and younger rocks in the vicinity of 

Onslow and southern Jones Counties, North Carolina: U.S. Geological Survey Water-Resources Investigations

Report 89–4128, 49 p.

North Carolina Division of Water Resources, 2001, Central Coastal Plain Capacity Use Area Rules, accessed 

September 9, 2008, at http://www.ncwater.org/Permits_and_Registration/Capacity_Use/Central_Coastal_Plain/

CCPrulefinal5-10-2001.pdf.

Winner, M.D., Jr., and Coble, R.W., 1996, Hydrogeologic framework of the North Carolina Coastal Plain, Regional 

Aquifer-System Analysis—Northern Atlantic Coastal Plain: U.S. Geological Survey Professional Paper 1404–I, 

106 p. + 14 pls.

Figure 1. Locations of hydrogeologic cross sections in Duplin, Jones, and Pender Counties, North Carolina.

Figure 2. Hydrogeologic cross section A–A’ in Duplin and Pender Counties, North Carolina.

Figure 3. Hydrogeologic cross section B–B’ in Onslow County, North Carolina.

Figure 4. Hydrogeologic cross section C–C’ in Onslow County, North Carolina.

Figure 5. Hydrogeologic cross section D–D’ in Jones, and Onslow Counties, North Carolina.

Figure 7. Hydrogeologic cross section E–E’ in Pender, Onslow, and Jones Counties, North Carolina.

Figure 6. Hydrogeologic cross section A–D in Duplin, Onslow, and Jones Counties, North Carolina.

Figure 8. Hydrogeologic cross section A’–D’ in Pender, Onslow, and Jones Counties, North Carolina.