Data from Stratigraphic Test Holes Drilled at the U.S. Marine Corps Air Station, Cherry Point, North Carolina, 1994–2001, and Periodic Water Levels, 2000–2003

Open-File Report 2004–1434
By Beth M. Wrege and Philip S. Jen

Abstract

Nine stratigraphic test holes, from 158 to 305 feet deep, were drilled at the U.S. Marine Corps Air Station at Cherry Point, North Carolina, between 1994 and 2001 by the U.S. Geological Survey. These test holes and subsequent wells provide information about the lithology, stratigraphy, and geology at the Marine Corps Air Station. In addition, ground-water-level data were collected at the Air Station through 2003. The U.S. Geological Survey also conducted high-resolution marine and land seismic surveys during this investigation. The ground-water-level data and locations of the seismic survey lines are included in this report. The stratigraphic data combined with the seismic data provide a basis for the delineation of paleochannels beneath the Air Station as well as information for the management of water resources at the Air Station.

Introduction

The water supply for the U.S. Marine Corps Air Station (MCAS) at Cherry Point, North Carolina, has been derived from the Castle Hayne aquifer since the Air station was established in 1941 (Grossnick and Armstrong, 1997). The MCAS, which is in the Coastal Plain Physiographic Province (fig. 1), is underlain by five freshwater-bearing aquifers—the surficial, Yorktown, Pungo River, and the upper and lower Castle Hayne aquifers (Daniel and others, 1996). The upper Castle Hayne aquifer is composed of sand and sandy shell beds of the Pungo River Formation and limestone of the River Bend Formation. In localized areas, the lower part of the Pungo River Formation is not the confining unit between the Yorktown and underlying aquifers, as is the case in other areas of the Coastal Plain. This lack of hydrologic separation is attributed to the development of paleochannels. Locating these paleochannels will better define the hydrogeologic framework beneath the MCAS.

Purpose and Scope

This report presents hydrogeologic and ground-water-level data collected by the U.S. Geological Survey (USGS) at the request of the MCAS, Cherry Point, North Carolina, from 1994 to 2003. The report includes lithologic data from stratigraphic test-hole drilling, borehole geophysical data, well-construction data, and the locations of marine seismic surveys and high-resolution land seismic surveys. The purpose of this report is to provide data to aid in locating paleochannels beneath the MCAS. The existence of paleochannels may affect the ground-water supply by providing a conduit for contaminant movement at the Air Station.

Nine stratigraphic test holes, designated Strat-1 through Strat-9, were drilled at the MCAS, Cherry Point. The first four test holes, Strat-1 through Strat-4, were drilled in 1994 and 1995. Interpretations and data analysis of these four test holes are presented in Daniel and others (1996). The Strat-5 through Strat-9 test holes were drilled in 2000 and 2001.

The hydrogeologic data presented in this report include summarized data from Daniel and others (1996) for Strat-1 through Strat-4 and the data collected during this investigation for Strat-5 through Strat-9. The data are organized sequentially from Strat-1 through Strat-9. Descriptions of the stratigraphic test holes include the following:

1. Background data for each test-hole drilling site,

2. Location maps, including directions to the drilling sites,

3. Borehole geophysical logs prepared at identical scales for comparison purposes,

4. Well-construction reports for monitoring wells installed in the stratigraphic test holes,

5. Water-level data,

6. Hydrographs of periodic water-level measurements, and

7. Photographs of selected data-collection methods and core samples.

Continuous water-level monitoring data were archived and can be accessed at http://waterdata.usgs.gov/nc/nwis/.

High-resolution seismic data were collected at the MCAS during four separate field surveys between September 1994 and March 2000. A map showing the line locations for these investigations is presented in this report.

Description of Study Area

The MCAS at Cherry Point is located in Craven County, North Carolina, in the Neuse River basin (fig. 1). The study area is just north of the town of Havelock in the southeastern part of the county. The area is bounded to the north by the Neuse River, to the east by Hancock Creek, to the south by State Highway 101, and to the west by an irregular boundary about 1 mile west of Slocum Creek (fig. 1). The MCAS encompasses an area of about 19 square miles (mi²).

Figure 1. Location of the U.S. Marine Corps Air Station, Cherry Point, North Carolina.

Previous Investigations

The USGS has conducted several hydrogeological investigations at the MCAS, Cherry Point, since 1986. This investigation is a continuation of the work begun by Daniel and others (1996). Reports of previous investigations by the USGS in cooperation with the MCAS, Cherry Point, are listed in Appendix table 1-1.

Hydrogeologic Setting

The hydrogeologic framework underlying the MCAS at Cherry Point consists of five freshwater aquifers and associated confining units—the surficial, Yorktown, Pungo River, and upper and lower Castle Hayne. These aquifers are recognized as geologically separate units ranging in age from Quaternary-Holocene to Tertiary-Eocene (fig. 2; Daniel and others, 1996). The aquifers, however, may not be hydrologically distinct near the MCAS because of erosional truncations and paleochannels beneath the Air Station. Most municipal water-supply wells in the study area tap the Castle Hayne aquifer of Tertiary age and are completed in either the River Bend-Oligocene or the Castle Hayne-Eocene Formations.

The sedimentary deposits that form the upper three aquifers—the surficial, Yorktown, and Pungo River—range in age from Holocene through Miocene (Daniel and others, 1996, fig. 3). These deposits are composed mostly of sand with lesser amounts of gravel and limestone that are separated by locally discontinuous clay layers and lenses. The deeper Castle Hayne aquifer primarily consists of limestone with substantial thicknesses of interbedded sands.

Paleochannels are remnants of river and stream channels that have been filled with sediment and are overlain by younger units. The existence of paleochannels that breach one or more of the confining units above the Castle Hayne aquifer could provide a conduit for contaminants to penetrate from the land surface to the water supply.

Figure 2. Stratigraphic units beneath the U.S. Marine Corps Air Station, Cherry Point, North Carolina (Wrege and Daniel, 2001).

Acknowledgments

High-resolution land seismic data for this investigation were collected by Richard D. Miller, Joe M. Anderson, David R. Laflen, Choon B. Park, and Dr. Jianghai Xia of the Kansas Geological Survey, Lawrence, Kansas. Lithologic descriptions of the core samples for three wells were prepared by Dr. Charles C. Daniel, III (retired), USGS, Raleigh, North Carolina, who was the project chief during much of the investigation. TheUSGS borehole and well-drilling crew, Eugene Cobbs, II (retired), and Eugene Cobbs, III, from Reston, Virginia, provided excellent technical and professional support under adverse conditions. Geophysical logs for Strat-1 through Strat-4 were collected by Gerry Idler (retired), USGS, Atlanta, Georgia. Logistical support was provided by Ken Cobb of the MCAS, Cherry Point.

Data Collection Methods

Geological and geophysical methods were used to locate paleochannels that breach one or more of the confining units above the Castle Hayne aquifer. Stratigraphic test holes were drilled for the collection of core material and the installation of observation wells (Wrege and Daniel, 2001). Drilling of these test holes began with Strat-1 in 1994 and concluded with Strat-9 in 2001. The test holes range in depth from about 158 to 305 feet (ft) below land surface. The mean depth of the nine test holes is about 222 ft below land surface. The target depth of the test holes was the top of the Castle Hayne aquifer. Observation wells were installed in selected test holes. Strat-1, 2, 3, 4, and 6 are located on the east side of the MCAS (fig. 3). Strat-5, 7, 8, and 9 are located west of Slocum Creek on the west side of the MCAS (fig. 3). Selected records and borehole geophysical logs for each stratigraphic test hole are listed in table 1. Well-construction information for the eight installed monitoring wells is presented in table 2.

Figure 3. Locations of stratigraphic test wells, vertical seismic profile wells, and seismic surveys at the U.S. Marine Corps Air Station, Cherry Point, North Carolina.

Samples from Strat-1 through Strat-4 were collected by using a 2-inch diameter split-spoon sampler. Collection of cores was limited to targeted intervals. Using this drilling method, a 2-ft section of core was collected at regular intervals or when facies change was anticipated. Core-collection intervals initially were set for 10 sections, 2-ft each, per 100 ft drilled. The remaining test holes, Strat-5 through Strat-9, were drilled by using a wire-line core rig and were continuously cored. Detailed information on this method is given in the description for Strat-5.

Observation wells were installed in eight of the nine stratigraphic test holes to monitor ground-water levels (table 2). The Strat-4 well, however, was not suitable for monitoring because of a bulge in the polyvinyl chloride (PVC) pipe. A well was not installed in the Strat-9 test hole. One well, Strat-5, was equipped with a hydrologic data-collection platform (DCP) to collect and transmit near real-time water-level data.

Data collected from each of the stratigraphic test holes include lithologic descriptions (cuttings and core samples), vertical seismic profiles (VSPs), and borehole geophysical logs. Of the nearly 1,995 ft drilled, about 1,245 ft were continuously cored, and 750 ft were intermittently cored. The core material was analyzed for information on geologic contacts, age,lithology, relative hydrologic properties, and to correlate stratigraphic relations with those of the other test holes.

Borehole geophysical well logs were collected by USGS personnel using Century, Mount Sopris, and Geometrics equipment. The VSPs were collected by the Kansas Geological Survey (KGS). Seismic study design and identification of hydrogeologic units were a combined effort of the USGS and the KGS.

Stratigraphic Test Hole Descriptions and Data

Information about the nine stratigraphic test holes drilled at the MCAS, Cherry Point (fig. 3), is presented in this section. Descriptions include available background data, location maps, lithologic logs, borehole geophysical well logs, monitoring-well construction diagrams, and ground-water-level data and hydrographs. Water-level data for some of the wells were published previously in USGS annual data reports (Howe and others, 2002, 2003).

Strat-1

The Strat-1 well is located north of State Highway 101 and east of Cunningham Boulevard (fig. 4). The well is on the east side of the road behind the tree line. A detailed location map is provided in figure 4.

The Strat-1 test hole was drilled by the U.S. Army Corps of Engineers (USACE) drilling crew. Drilling began on November 1, 1994, and was completed on November 4, 1994. A reverse mud-rotary drilling method was used to reach a total depth of 163 ft. The cored intervals for this stratigraphic test hole totaled 76 ft, of which 78.2 percent was recovered. Forty separate split-spoon core runs were made, and each sample was collected in a 2-ft long tube. Lithologic descriptions were recorded from the cuttings and core samples (table 3). A general lithologic description of the core is included in this report.

Strat-1 was geophysically logged on November 16, 1994. The abbreviated lithology and digitized borehole geophysical logs are shown in figure 5. Logs collected at Strat-1 include the driller's penetration log (blow counts), a lithologic log, a hydrologic log, natural gamma radiation, and acoustic velocity. A monitoring well was installed in the borehole, and installation was completed on November 4, 1994. A diagram of the well construction, including placement of the well screen, is shown in the monitoring-well construction report (fig. 6).

The Strat-1 well was assigned North Carolina (NC) county number CR-617 and USGS station number 345318076541001. Periodic water-level measurements were made in the monitoring well between September 2000 and August 2002. Water levels ranged from 13.83 to 16.74 ft below land surface (table 4; fig. 7).

Strat-2

The Strat-2 well is located between runways on the south side of the MCAS and on the north side of an unimproved road (fig. 3). Although access to this location is limited, a detailed location map is provided in figure 8.

The Strat-2 test hole was drilled by the USACE drilling crew. Drilling began on November 5, 1994, and a total depth of 158 ft was reached on November 15, 1994. A reverse mud-rotary drilling method was used. The cored intervals of this stratigraphic test hole totaled 91 ft, of which 92.7 percent was recovered. The core was collected in 2-ft long tubes. Lithologic determinations were made from the cuttings and core samples, and are described in table 5. For a more detailed analysis, see Daniel and others (1996).

After the test was drilled, geophysical logs were run in the open borehole, which was logged on November 15, 1994. Logs collected at Strat-2 include the driller's penetration log (blow counts), a lithologic log, a hydrologic log, natural gamma radiation, acoustic velocity, single-point resistance, spontaneous potential, guard log (focused resistivity), caliper, and temperature. Vertical seismic profiling (VSP) included a hydrophone log and aholelock geophysical log. The VSP survey was completed November 23, 1994, in the Strat-2 borehole. The abbreviated lithology and borehole geophysical logs are shown in figure 9. A monitoring well was installed in the borehole to a depth of 152.06 ft. A diagram of the well construction, including placement of the well screen, is shown in the monitoring-well construction report (fig. 10).

The Strat-2 well was assigned NC county number CR-618 and USGS station number 345335076530701. Periodic water-level measurements were made in the monitoring well between September 2000 and August 2002. Water-level data ranged from 11.51 to 16.53 ft below land surface (table 6; fig. 11).

Strat-3

The Strat-3 well is west of Cunningham Boulevard, north of Stte highway 101, and south of the railroad tracks at the MCAS (fig. 3). A detailed map is provided in figure 12.

The Strat-3 test hole was drilled by the USACE drilling crew. Drilling began on November 17, 1994, and reached a total depth of 204 ft on November 25, 1994. Using are reverse rotary drilling method, drilling was initiated with a 7 3/8-inch drag bit (fishtail) and a 150-pound hammer. At 174 ft, the drag bit was changed to a roller cone (tri-cone) bit. Of the total 204 ft drilled, 17 cores were collected and 80 percent were recovered. The cored intervals and amounts are listed in table 7. (Note: When clay is recovered, it can expand to a length greater than the initial interval cored, resulting in a recovery length that exceeds the drilling interval.) Lithologic determinations were made from the cuttings and core samples, and are described in table 8. A more detailed core description is given in Daniel and others (1996).

After the test hole was drilled, geophysical logs were run in the open hole. The VSP logs were collected on November 25, 1994, and included the driller's penetration log (blow counts), a lithologic log, a hydrologic log, natural gamma radiation, acoustic veolocity, single-point resistance, spontaneous potential, guard log (focused resistivity), caliper, and temperature. VSP included a hydrophone log and a holelock geophysical log. The abbreviated lithology and digitized borehole geophysical logs are shown in figure 13. A monitoring well was installed in the borehole, and a diagram of the well construction, including placement of the well screen, is shown in the monitoring-well construction report (fig. 14).

The Strat-3 well was assigned NC county number CR-623 and USGS station number 345312076540701. Periodic water-level measurements were made in the monitoring well between February 2001 and August 2002. Water-level data ranged from 14.09 to 17.11 ft below land surface (table 9; fig. 15).

Strat-4

The Strat-4 well is on the northwest side of the intersection of Access Road and Range Road (fig. 3). A detailed location map is provided in figure 16.

The Strat-4 test hole was drilled by the USACE drilling crew. Drilling began on March 27, 1995, and reached a total depth of 225 ft on March 29, 1995. A reverse rotary drilling method was used. Of the total 225 ft drilled, 11.4 ft were cored, with a targeted 2-ft interval (out of 10 ft) and a 93-percent core recovery. The cored intervals and amounts are listed in table 10. Lithologic determinations were made from the cuttings and core samples and are described in table 11. A more detailed core description is given in Daniel and others (1996).

The test hole was logged on March 30, 1995. Logs collected at Strat-4 included the lithologic log, a hydrologic log, natural gamma radiation, single-point resistance, spontaneous potential, and caliper. VSP included a hydrophone log and a holelock geophysical log. The abbreviated lithology and the borehole geophysical logs are shown in figure 17. A monitoring well was installed in the borehole, and a diagram of the well construction, including placement of the well screen, is shown in the monitoring-well construction report (fig. 18).

Strat-4 was assigned NC county number CR-619 and USGS station number 345539076524201. Periodic water-level measurements were made in the monitoring well between September 2000 and May 2002. Water-level data ranged from 21.56 to 23.12 ft below land surface (table 12; fig. 19).

Strat-5

The Strat-5 well is located in a grove of pine trees on the north side of the intersection of State Highway 70 and Slocum Road (fig. 3). Although the monitoring well is outside the gated area of the MCAS, it is on MCAS property. A detailed location map is provided in figure 20.

The Strat-5 test hole was drilled by the USGS corerecovery team. Drilling began on March 9, 2000, and reached a total depth of 235 ft on March 15, 2000. Continuous core was collected with a mud-rotary wire-line core rig (fig. 21). The entire section was cored, and all recovered samples were boxed. This method of sample recovery increased the accuracy of the depth and thickness determinations.

Lithologic determinations were made from drill cuttings, driller's penetration reports, and core samples, and are described in table 13. After the borehole was drilled, borehole geophysical surveys were collected. The abbreviated lithology and digitized borehole geophysical logs are shown in figure 22.

A monitoring well was constructed to target a specific hydrogeologic unit based on the aquifer determinations made on location. As a result, the well was installed in the borehole and was completed in the Castle Hayne aquifer of Oligocene and Eocene age. A diagram of the well construction, including the placement of the well screen, is shown in the monitoring well construction report (fig. 23). The Strat-5 well was assigned NC county number CR-616 and USGS station number 345504076562801. Periodic standard tape-down water-level measurements were made in the monitoring well between September 2000 and May 2002. Water-level data during this period ranged from 15.36 to 18.16 ft below land surface (table 14; fig. 24). Land-surface datum at Strat-5 is 26 ft (referenced to National Geodetic Vertical Datum of 1929), and the water-level measuring point was the top of the 2-inch pipe, which is parallel to the top of the instrument shelter floor 2.79 ft above land surface.

A hydrologic DCP was installed at Strat-5 to demonstrate the collection of continuous near real-time water-level data. The instrumentation included satellite telemetry and a solar energy battery supply panel. Continuous recording began in December 2000 (table 15, 16), and water levels were collected at 60- minute intervals. Continuous water-level data are stored in the USGS National Water Information System (NWIS) database and can be accessed from the USGS Web site http://waterdata.usgs.gov/nc/nwis/.

For the 2002 water year (October 1, 2001, through September 30, 2002), the highest water level was 16.48 ft below land surface, and the lowest water level was 18.63 ft below land surface (table 16; fig. 25). Water levels for the entire period of record are shown in figure 26. Rapid tree growth in the vicinity of Strat-5 interfered with solar energy power for the DCP and resulted in the loss of data.

Figure 21. Mud-rotary wire-line core rig used to drill the Strat-5 borehole.

Strat-6

The Strat-6 well is near the marina on Hancock Creek (fig. 3) about 20 ft west of a stand of pine trees. A detailed location map is provided in figure 27.

The Strat-6 test hole was drilled by the USGS corerecovery team. Drilling began on August 11, 2000, and reached a total depth of 305 ft on August 19, 2000. Continuous core was collected by using a wire-line rotary core rig. Lithologic determinations were made from cuttings and core samples, and are described in table 17.

Geophysical surveys were collected after the test hole reached its total depth of 305 ft. The abbreviated lithology and borehole geophysical logs are shown in figure 28. The Strat-6 test hole was the deepest test hole drilled during this study. Two sets of geophysical data are presented—one with a 250-ft scale (fig. 28A) and the other with a 300-ft scale (fig. 28B). The 250-ft scale allows an overlay comparison of the geophysical data with the other stratigraphic well logs in this series; the 300-ft scale provides complete data.

Core samples and geophysical logs were used to make aquifer determinations and to design the well. The Strat-6 test hole penetrated an unconformity. A diagram of the well construction, including the placement of the well screen, is shown in the monitoring-well construction report (fig. 29). A monitoring well was installed in the corehole and completed on August 20, 2000, with a flush-mounted well cap.

The Strat-6 well was assigned NC county number CR-620 and USGS station number 345613076513701. Periodic waterlevel measurements were made in the monitoring well between September 2000 and August 2002. Water-level data ranged from 10.78 to 13.61 ft below land surface (table 18; fig. 30). The initial water level was 12.09 ft below land surface, and the well was pumped for 20 minutes at a rate of 6.67 gallons per minute until the water ran clear. The water level declined to 110 ft; when the pumping stopped, the water level recovered to 11.99 ft below land surface.

Strat-7

The Strat-7 well is near the intersection of Slocum Road and Buncombe Road, west of Slocum Creek (fig. 3). The well is east of an unpaved trail and has a concrete pad and bollards protecting it. A detailed location map is provided in figure 31.

The Strat-7 test hole was drilled by the USGS corerecovery team. Drilling began on August 2, 2000, and reached a total depth of 265 ft on August 8, 2000. Continuous core was collected by using a wire-line rotary core rig. Field determinations of the lithology and hydrology were made on location from cuttings and core samples, and are described in table 19.

After the test hole was drilled, geophysical surveys were collected. The abbreviated lithology and borehole geophysical logs are shown in figure 32. Lithology, cores, and geophysical logs were used to determine the aquifers and design the monitoring well. A diagram of the well construction, including the placement of the well screen, is shown in the monitoringwell construction report (fig. 33).

The Strat-7 well was assigned NC county number CR-621 and USGS station number 345510076544901. Periodic waterlevel measurements were made in the monitoring well between September 2000 and May 2002. Water-level data ranged from 16.71 to 18.74 ft below land surface (table 20; fig. 34).

Strat-8

The Strat-8 well is in a secured, fenced, northwest area of the MCAS (fig. 3). A detailed location map is provided in figure 35.

The Strat-8 test hole was drilled by the USGS core recovery team. Drilling reached a total depth of 220 ft on February 12, 2001. Continuous core was collected by using a wire-line rotary core rig. Field determinations of the lithology were made on location from cuttings and core samples and are described in table 21.

After the test hole was completed, borehole geophysical surveys were collected. The abbreviated lithology and borehole geophysical logs are shown in figure 36. Lithology and geophysical logs were used to determine the aquifers and design the monitoring well. A diagram of the well construction, including the placement of the well screen, is shown in the monitoring-well construction report (fig. 37).

The Strat-8 well was assigned NC county number CR-622 and USGS station number 345707076553501. The water level was measured on May 15, 2002, at a depth of 22.91 ft below land surface.

Strat-9

The Strat-9 test hole is north of State Highway 70 and south of Slocum Creek (fig. 3). A detailed location map is provided in figure 38.

The Strat-9 test hole was drilled by the USGS corerecovery team. Drilling began on February 14, 2001, and reached a total depth of 220 ft on February 18, 2001. Continuous core was collected by using a mud-rotary wire-line core rig. Lithologic determinations were made from cuttings and core samples and are described in table 22.

After the test hole was completed, borehole geophysical surveys were collected. The abbreviated lithology and borehole geophysical logs are shown in figure 39. No monitoring well was installed at this location. The test hole was pressure grouted from the bottom (220 ft) to the land surface using type-I Portland cement and abandoned in compliance with State regulations (North Carolina Department of Environment, Health, and Natural Resources, 1976).

Seismic Data

Marine and high-resolution land-seismic surveys were conducted for stratigraphic interpretations and paleochannel delineation from 1994 to 2001. The locations of the seismic data lines (fig. 3), the surveyed elevation inflection points, and the dates of data collection are provided herein.

The seismic profiles were used to delineate structures and correlate stratigraphy of the subsurface geology. Marine seismic data were collected in Slocum Creek, Hancock Creek, and in the Neuse River by the USGS in 1994 and 1998. The high-resolution land-seismic data were collected by the KGS. The data collected through 1998, analyses, and data-collection methods were published previously in Daniel and others (1996), Miller and Xia (1996), Cardinell (1999), and Wrege and Daniel (2001).

As part of this current study, two objectives were addressed with the acquisition of high-resolution land-seismic data: (1) to detect and delineate the subsurface trace of the Eocene and younger paleochannels inferred to underlie the MCAS (Mixon and Pilkey, 1976), and (2) to determine the feasibility of acoustically imaging and correlating the subsurface geology to existing geologic, hydrogeologic, and geophysical data. Initial short-line surveys were conducted and then extended with longer geophysical surveys sufficient to provide linear coverage across most of the Air Station. This approach was intended to provide an acoustic signature of the subsurface geology. The following discussion documents seismic data-collection activities from 1994 through 2001.

Marine Seismic Data

The locations of the 1994 marine seismic data lines are shown in figure 3. A detailed discussion of the 1998 marine seismic study is provided in Cardinell (1999). The marine seismic survey provided additional information for delineating the channels along the northern border of the MCAS.

Land Seismic Data

High-resolution seismic data were collected to support detailed interpretation of the underlying geology of the MCAS for water-supply management. The KGS collected the geophysical surveys during four separate field surveys (table 23).

Three methods were used as part of the land seismic surveys to acoustically image, correlate, and extend the borehole and point data beyond the test holes and across the MCAS. The first method combines walk-away noise tests, velocity check shots, and VSP to determine the signal-to-noise ratio of the upper 90 meters (m) of the geologic units. Seismic surveys were collected during September 1994 along 13 short (73 m) seismic lines, totaling approximately 240 ft. These common midpoint (CMP) lines are designated lines 1A–13A (Miller and Xia, 1996). The locations of the seismic lines and elevations by station are listed in table 24. The line locations were carefully selected to correlate with projected paleochannel locations from marine seismic and stratigraphic information. These profiles allowed data-collection parameters and equipment to be maximized for each site and enhanced placement so areal coverage of the longer continuous profiles could be optimized (Miller and Xia, 1996). The methods development phase of this investigation has been presented by Miller and Xia (1996).

The second seismic application method correlates the geologist's formation determinations with seismic acoustic properties using VSP. Based on the first 13 CMP surveys, three boreholes were drilled and geophysically logged for ground truth and to allow a series of time-domain walk-away VSPs to be acquired in each of the boreholes (Miller and Xia, 1996). The geologist's formation determinations were correlated with the VSPs.

The third seismic data method used at the MCAS after the initial calibration of acoustic properties and determination of local formations was to extend the data collection along 12-fold CMP seismic-reflection surveys (fig. 3). The longer CMP surveys were collected during separate field trips (table 23). A more extensive discussion of the three methods and the data collected prior to February 1995 can be found in Miller and Xia (1996).

In February 1995, seismic lines 1B, 2B, and 3B were run (fig. 3). These three 12-fold CMP seismic-reflection profiles had total linear lengths of about 2,160 m, 1,460 m, and 1,450 m, respectively (table 23), and provided boundary coverage to the south and north across the MCAS. The surveys cross the Air Station from the west near Slocum Creek to the east near Hancock Creek (fig. 3). Line 2B is a northeast-trending line beginning near the south-central boundary of the MCAS, generally paralleling the runway.

In July 1999, seismic lines 1C, 2C, and 3C were run (fig. 3). Line 1C is on the west side of the MCAS and extends along the eastern portion of Slocum Road. Line 2C, or the "Gas Mask" line, is a north-south line beginning near State Highway 101 at the southern boundary of the MCAS. Line 3C, or the "Runway" line, lies along the northeastern extent of the MCAS runway.

In March 2000, seismic lines 1D, 2D, and 3D were run (fig. 3). Line 1D is on the west side of the MCAS and extends along the western portion of Slocum Road (west of line 1C). Line 2D runs from southwest to northeast and nearly parallels C-Street. Line 3D also runs from southwest to northeast along Rifle Range Road in the northeast area of the MCAS. The datacollection methodology evolved with each new period of data collection as a result of improvements in knowledge, understanding, and technology. Acoustic velocity signatures were developed in each of these locations.

Several seismic lines have stratigraphic test holes near their terminus (fig. 3). VSPs, a borehole geophysical method, were run in the test holes. The VSPs provide a link to the highresolution seismic profile, serve as calibration for the land seismic surveys, and can be correlated with the lithologic units in the test hole. After the VSP parameters are determined for a test hole, the lithologic unit velocities can be used to interpret data along the seismic line. The seismic section shown in figure 40 was taken from the central part of the Slocum line (line 1D, fig. 3). The multiple returns in this example of raw data are of a 12-fold CMP stacked section of the line on the eastern side of the Slocum Road profile. A travel time of 150 minutes per second is equal to a depth of 377 ft (R.D. Miller, Kansas Geological Survey, written commun., 2000). The geophone (receiver) location is critical in the interpretation of data. Seismic survey lines have vertical and limited horizontal dimensions. Elevation surveys were collected along the seismic lines to provide elevation inflection points at the linear stations (table 24). Changes in elevation inflection points provide guidance for depth determinations of the subsurface elevation of the geological formations.

Figure 40. Section of seismic data collected along the Slocum line (line 1D, fig. 3), U.S. Marine Corps Air Station, Cherry Point,
North Carolina (courtesy J. Xia, Kansas Geological Survey).

Summary

Nine stratigraphic test holes were drilled and cored at the U.S. Marine Corps Air Station, Cherry Point, North Carolina, between 1994 and 2001.The lithologic summary data and the borehole geophysical data collected from these test holes are included in this report, including the drilling and samplecollection methods. Water-level monitoring wells were installed in eight of the nine test holes, and the water-level data collected from seven of the eight wells are included in this report along with the well-construction records. Also included are the locations of the high-resolution seismic surveys conducted in conjunction with this stratigraphic investigation.

AccessibilityFOIAPrivacyPolicies and Notices
U.S. Department of the Interior, U.S. Geological Survey Persistent URL: http://pubsdata.usgs.gov/pubs/of/2004/1434/report.html Page Contact Information: USGS Publishing Network Last modified: Saturday, January 12 2013, 11:40:40 PM

---