fl1 /'"""I * 1 *

bnorter Contributions 

to Geophysics, 

1979

GEOLOGICAL SURVEY PRO? E S SIOK AX PAPEB
Shorter Contributions 

to Geophysics, 

1979

Mountain Breathing Preliminary Studies of Air-Land Interaction 

on Mauna Kea, Hawaii

By ALFRED H. WOODCOCK and IRVING FRIEDMAN

Porosity and Density of Kilauea Volcano Basalts, Hawaii 

By GORDON R. JOHNSON

Diabase Dikes in the Haile-Brewer Area, South Carolina, and 

Their Magnetic Properties

By HENRY BELL III, KENNETH G. BOOKS, DAVID L. DANIELS, 

WILLIIAM E. HUFF, JR., and PETER POPENOE

Aerial Gamma-Ray Survey in Duval, McMullen, Live Oak, and 

Webb Counties, Texas

^JOSEPH S. DUVAL and KAREN A. SCHULZ

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1123-A-D

UNITED STATES GOVERNMENT PRINTING, WASHINGTON: 1980
UNITED STATES DEPARTMENT OF THE INTERIOR 

CECIL D. ANDRUS, Secretary

GEOLOGICAL SURVEY

H. William Menard, Director

Library of Congress Catalog-card No. 80-600006

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

Washington, D.C. 20402

Stock Number 024-001-03277-5
CONTENTS

[Letters designate the separate chapters]

(A) Mountain breathing preliminary studies of air-land interaction on Mauna Kea, Hawaii, by Alfred H. Woodcock and 

Irving Friedman.

(B) Porosity and density of Kilaeua Volcano Basalts, Hawaii, by Gordon R. Johnson.

(C) Diabase dikes in the Haile-Brewer area, South Carolina, and their magnetic properties, by Henry Bell III, Kenneth G. 

Books, David L. Daniels, William E. Huff, Jr., and Peter Popenoe.

(D) Aerial gamma-ray survey in Duval, McMullen, Live Oak, and Webb Counties, Texas, by Joseph S. Duval and Karen 

A. Schulz.
CONVERSION FACTORS

Metric unit Inch-Pound equivalent

Length

millimeter (mm) 

meter (m) 

kilometer (km)

= 0.03837 inch (in) 

= 3.28 feet (ft) 

= .62 mile (mi)

Area

square meter (m2 ) 

square kilometer (km2 ) 

hectare (ha)

= 10.76 square feet (ft2 ) 

= .386 square mile (mi2 ) 

= 2.47 acres

Volume

cubic centimeter (cm3 ) 

liter (L) 

cubic meter (m3 ) 

cubic meter 

cubic hectometer (hm3 ) 

liter 

liter 

liter 

cubic meter

cubic meter

= 0.061 cubic inch (in3 ) 

= 61.03 cubic inches 

= 35.31 cubic feet (ft3 ) 

= .00081 acre-foot (acre-ft) 

= 810.7 acre-feet 

= 2.113 pints (pt) 

= 1.06 quarts (qt) 

= .26 gallon (gal) 

= .00026 million gallons (Mgal or 

10" gal) 

= 6.290 barrels (bbl) (1 bbl = 42 gal)

Weight

gram (g) 

gram 

metric tons (t) 

metric tons

= 0.035 ounce, avoirdupois (oz avdp) 

=: .0022 pound, avoirdupois (Ib avdp) 

= 1.102 tons, short (2,000 Ib) 

= 0.9842 ton, long (2,240 Ib)

Specific combinations

kilogram per square 

centimeter (kg/ cm2 ) 

kilogram per square 

centimeter 

cubic meter per second 

(ms/s)

 0.96 atmosphere (atm)

 .98 bar (0.9869 atm) 

= 35.3 cubic feet per second (ft3/s)

Metric unit

Specific

liter per second (L/s) 

cubic meter per second 

per square kilometer 

[(m3/s)/km2 ] 

meter per day (m/d)

meter per kilometer 

(m/km) 

kilometer per hour 

(km/h) 

meter per second (m/s) 

meter squared per day 

(m2/cl) 

cubic meter per second 

(m8/s) 

cubic meter per minute 

(ms/min) 

liter per second (L/s) 

liter per second per 

meter [(L/s)/m] 

kilometer per hour 

(km/h) 

meter per second (m/s) 

gram per cubic 

centimeter (g/cm3 ) 

gram per square 

centimeter (g/cm2 ) 

gram per square 

centimeter

Inch-Pound equivalent

combinations Continued

= .0353 cubic foot per second 

= 91.47 cubic feet per second per 

square mile [(ft3/s)/mia ]

= 3.28 feet per day (hydraulic 

conductivity) (ft/d)

= 5.28 feet per mile (ft/mi) 

 .9113 foot per second (ft/s)

 3.28 feet per second

= 10.764 feet squared per day (ft2/d) 

( transmissivity ) 

= 22.826 million gallons per day 

(Mgal/d) 

= 264.2 gallons per minute (gal/min)

= 15.85 gallons per minute

= 4.83 gallons per minifte per foot 

[(gal/min) /ft]

 .62 mile per hour (mi/h)

 2.237 miles per hour

= ©2.43 pounds per cubic foot (lb/ft3 ) 

= 2.048 pounds per square foot (lb/ft2 ) 

= .0142 pound per square inch (lb/in2 )

Temperature

degree Celsius (°C) 

degrees Celsius 

(temperature)

= 1.8 degrees Fahrenheit (°F) 

= [(1.8X°C)+32] degrees Fahrenheit
Mountain Breathing Preliminary Studies of 

Air-Land Interaction on Mauna Kea, Hawaii

By ALFRED H. WOODCOCK and IRVING FRIEDMAX

SHORTER CONTRIBUTIONS TO GEOPHYSICS, 1979

GEOLOGICAL SURVEY PROFESSIONAL PAPER 112 3 A

CONTENTS

Page

Abstract ____________________________________________ Al

Introduction ___________________________________________________ 1

Acknowledgments ______________________________________ 2

Observations ______________________________________________________ 3

Latent heat loss to the air _________________________________ 5

Source of heat ________________________________________ 5

Sensible heat of inflowing air as source of latent heat in outflowing air _ 5

Conduction of heat into the mountain ______________________ 5

Snow and rainwater as a sensible heat source ______________________ 6

Discussion and speculations ________________________________ 6

Conclusions ____________________________________________________ 8

References cited _________________ _____________________ 8

ILLUSTRATIONS

Page

FIGURE 1. Photograph showing north-northeast view over Mauna Kea summit area ________________ A2

2. Graph showing time-related differences in average direction and volume of airflow in the drill holes,

summit cone of Mauna Kea, Hawaii ____________________________________ __________ ___ 3

3. Graph showing temperature versus depth over time in a summit-cone drill hole over a period of about 6

months, Mauna Kea, Hawaii __________________________________________________ 4

TABLES

Page

TABLE 1. Comparative temperature, water vapor, and speeds of motion of air flowing out of the drill hole on the

summit cone and in the free air above, Mauna Kea, Hawaii ___________________________________ _ A3

2. Deuterium in water vapor from 2-liter samples of nearly saturated air flowing from the summit-cone drill

hole, Mauna Kea, Hawaii ___________________________________ __ 4

3. Deuterium in snow, graupel, permafrost, and lake waters of the Mauna Kea summit area, Hawaii ______ 7

ill

SHORTER CONTRIBUTIONS TO GEOPHYSICS, 1979

MOUNTAIN BREATHING PRELIMINARY STUDIES OF 

AIR-LAND INTERACTION ON MAUNA KEA, HAWAII

By ALFRED H. WOODCOCK 1 and IRVING FRIEDMAN

ABSTRACT

Air moves in and out of the porous ash and cinder of the 

summit of the dormant volcano Mauna Kea, Hawaii (altitude about 4200 m), presumably in response to pressure 

changes in the atmosphere. Measurements have revealed an 

average airflow of about 20 kg m~2 d'1 . The air enters the 

porous ash relatively dry and leaves nearly saturated; the 

excess water vapor averages about 6.6 gm kg~\ This vapor 

flow produces an estimated average latent heat loss to the atmosphere from the interior surfaces of the mountain of about 

3.9 W nr2 (0.94 cal m~" s'1 ). Thus it appears that a sensible heat source, which is probably geothermal, exists within 

the mountain. A negative thermal gradient in the summit 

cone and deuterium analyses of exhaled water vapor indicate 

that the vapor source is, in part, permafrost.

INTRODUCTION

The summit cinder cone on Mauna Kea, Hawaii, 

is the site of several astronomical observatories of 

the Institute for Astronomy, University of Hawaii. 

Figure 1 shows an aerial view of this and other 

cones which lie well above the moist trade-wind air 

of the lower atmosphere on the island of Hawaii 

(lat 19°49'34" N., long 155°28'20" W.). Preparatory to the construction of the Mauna Kea observatory buildings in 1967 and 1975, exploratory holes 

were drilled about 12 m down into the cinder at the 

sites. These holes (76 and 100 mm in diameter) 

presented an opportunity to obtain the vertical temperature distribution in the summit cone.

In March 1967 the first author visited the first 

of these holes to make a series of temperature-depth 

measurements. At the time a rapid flow of air out of 

the drill hole was noted. This flow was so interesting 

that the temperature study was delayed and instead 

measurements were made in the hole of the speed, 

direction, temperature, and water vapor of the flowing air. Unfortunately the observatory construction

1 Present address is Department of Oceanography, Hawaii Institute of 

Geophysics, Honolulu, HI 96822.

program in 1967 required that the hole be filled 

after a short time, thus preventing the accumulation 

of comprehensive amounts of information about the 

flow.

In 1975 two more drill holes (100 mm in diameter and 12 m deep) in the summit cone were made 

available for study by the Institute for Astronomy. 

One was used to continue the airflow (air breathing) study, and the other was used to measure the 

temperature changes with depth and time. Again 

the time interval between the drilling and construction at the site was too short to permit conclusive 

results. However, the combined exploratory data 

collected during these two intervals are sufficiently 

interesting and unique to warrant publication 

now. We hope that the results will lead to a more 

complete study of the interaction of alpine atmospheres and mountain regions such as the Mauna 

Kea summit.

The occurrence of pressure-induced breathing of 

air through porous earth is well established but its 

role in the transfer of water vapor and latent heat 

to dry atmospheres remains unexplored. Penetration 

of air through cave surfaces into porous limestone 

has been studied (Wigley, 1967), and there is evidence of atmospheric-pressure effect upon watertable levels in soils (Peck, 1960; Turk, 1975). Yen 

(1963) has done much experimental work on vapor 

transport through porous snow, and Geiger (1971) 

reported that moist air adds water to porous dry 

sandy soils as they breathe about 22 m3 m~2 d-1 

under the influence of wind-produced pressure 

changes.

This paper presents the preliminary observations 

made in the Mauna Kea drill holes and estimates of 

their meaning in terms of water vapor and latent 

heat flow from the mountain to the atmosphere. 

Previous work near the top of Mauna Kea (WoodAl
A2 SHORTER CONTRIBUTIONS TO GEOPHYSICS, 1979

cock, 1974) revealed a deep layer of permafrost, 

although the mean air temperature (about 4°C) 

had been thought to be too high for the occurrence 

of permafrost there. Also, a negative temperature 

gradient was found in the sediments under nearby 

Lake Waiau (fig. 1) (altitude 3970 m), a surprising 

find near the top of a dormant volcano in the tropics 

(Woodcock and Groves, 1969). Study of the loss of 

latent heat from the mountain may eventually aid 

in explaining these anomalous phenomena.

ACKNOWLEDGMENTS

Lother Ruhnke and Bernard Mendonca of the 

Mauna Loa observatory, U.'S. National Oceanic and 

Atmospheric Administration, also made a series of 

measurements of the flow in the Mauna Kea drill

holes. These data are included in the average quantities presented in figure 2. We thank the staff of 

the Institute for Astronomy and the Infra-red Telescope Facility of the University of Hawaii for making the drill holes available. The vane and hot-wire 

anemometers were loaned to us by C. M. Fullerton 

and R. C. Taylor of the Cloud Physics Laboratory, 

Hilo, and the Meterology Department, University of 

Hawaii, Honolulu, respectively. Kenneth Hardcastle 

of the U.S. Geological Survey, Denver, Colo., carried 

out all the deuterium measurements, and R. L. 

Soroos of the U.S. Geological Survey made the drillhole ash samples available to us. Kerry Wilson of 

the Cloud Physics Laboratory derived the free-atmosphere mixing-ratio values from the Hilo radiosondes, and Paul Ekern aided our literature search. 

The gas analyses were carried out under the direcFIGURE 1. View north-northeast over Mauna Kea summit area, showing some of the many pyroclastic cones there. Waiau 

Cone and Waiau Lake are in the foreground, and the summit cone, Puu Wekiu, and the observatory of the Institute for 

Astronomy are in the middle distance to the right. (Photograph by A. J. Abbott.)
MOUNTAIN BREATHING, OF AIR-LAND INTERACTION OF MAUNA KEA, HAWAII A3

tion of J. J. Naughton, Department of Chemistry, 

University of Hawaii. G. P. Wollard, recently deceased former Director of the Hawaii Institute of 

Geophysics, long encouraged and supported the work 

on Mauna Kea. These studies have been supported 

in major part by the U.S. Office of Naval Research. 

Hawaii Institute of Geophysics contribution no. 828.

OBSERVATIONS

Flow in and out of the holes in the summit cone 

was measured with a calibrated sensitive Taylor 

(Biram's type) totalizing vane anemometer with 

100-mm inside diameter, which was carefully fitted 

into the top of the holes for each measurement 

period. A correction of + 12 percent, determined 

from calibration runs at the Hilo Cloud Physics 

Observatory, was found to be required when the 

vane anemometer registered flow into the hole (that 

is, when the anemometer vane reversed). At airflow 

rates too low to be registered correctly by the vane 

anemometer, a hot-wire anemometer was used.

The speed and direction of air motion in the holes 

was measured for a total of 111.5 hours, including 

two 24-hour periods, during which the mean flow 

was derived from 274 separate readings. Figure 2 

presents an average of the volume and direction of 

flow per unit of interior surface area of the two 

drill holes (that is, 2.93 and 3.8 m2 ). The average 

outflow was 26.9 m3 m~2 d -1, derived from the sums 

of the product of the units of flow and its duration

O 1 5

4 8 12 16 20 

NOON

HOURS, LOCAL STANDARD TIME

FIGURE 2. Time-related differences in average direction and 

volume of airflow in the drill holes, summit cone of Mauna 

Kea, Hawaii. In histogram each block represents average 

volume derived from totalizing anemometer readings during 

time interval. Black dots show representative semidiurnal 

air pressures at Mauna Kea observatory.

(fig. 2). This outflow amounts to 21.0 kg m~2 d- 1 , 

based upon a mean air density of 0.78 kg m^ 3 at a 

pressure of 623 millibars (List, 1951, p. 298) or 

62,300 pascals.

TABLE 1. Comparative temperature, water vapor, and speeds of motion of air flowing out of the drill holes on the summit

cone and in the free air above, Mauna Kea, Hawaii

[! , dry-bulb temperature; T.,, wet-bulb temperature; RH, relative humidity; W, mixing ratio; %, about; L, liter]

Free air

Date and

local standard

time

May 5, 1967, 0920--

July 25, 1967, 0830

Aug. 7, 1967, 1400-

Auq. 8, 1967, 0730-

Sept. 9, 1967, 1035

Oct. 15, 1975, 1506

Nov. 18, 1975, 1240

Nov. 19, 1975, 1300

Dec. 17, 1975, 1315

Jan. 21, 1976, 1150

Jan. 22, 1976, 1155

Mar. 9, 1976, 1424-

Mar. 10, 1976, 1520

Apr. 7, 1976, 1338-

May 6, 1976, 1457--

May 7, 1976, 1428 

T D

(°C)

8.0

5.4

6.7

.5

7.9

5.5

8.2

6.7

- .4

-3.7

- .2

- .8

-3.0

5.8

3.4

2.2

TW

(°c)

-1.8

.9

.4

.0

-1.1

-1.4

-2.6

-1.8

-5.8

-5.7

- .6

-1.6

-4.4

-3.5

.9

-1.8

RH

(percent)

27

53

39

93

18

31

7

20

31

69

94

88

78

11

72

53

W

(g kg'')

3.1

5.0

4.0

6.2

2.0

3.0

.8

2.1

1.9

3.4

6.0

6.0

4.0

1.1

5.9

4.0

Wind

(m s' 1 )

7.2

6.9

4.2

^8

8.9

 ^4

^3

( l )

3.0

7.0

2.3

3.3

9.0 \,5

7.6

5.2

TD

(°C)

3.8

4.3

3.6

4.0

5.7

7.8

6.7

7.6

6.2

5.0

5.3

5.0

4.8

5.2

6.2

6.2

Tw

(°c)

3.8

4.2

3.6

4.0

5.0

7.2

6.6

7.3

5.8

4.7

5.0

5.0

4.6

4.7

5.5

5.5

Out-flowing air

RH

(percent)

100

99

100

100

93

94

99

97

95

97

96

100

97

94

93

93

W (g'kg' 1 )

8.5

8.7

8.3

8.6

9.0

10.5

10.3

10.7

9.5

8.9

9.0

9.2

8.8

8.8

9.3

9.3

Flow

volume

(L s' 1 )

5.6

14.1

2.4

3.7

2.7

2.3

3.5

3.8

4.7

19.8

6.9

5.3

6.2

6.3

5.6

4.4

Flow rate

(m s' 1 )

0.71

1.8

.3

.5

.9

.29

.45

.49

.61

2.53

.88

.68

.79

.80

.72

.56

Near calm.
A4 SHORTER CONTRIBUTIONS TO GEOPHYSICS, 1979

A sling- psychrometer was inserted into the drill 

hole during outflow to measure the wet-bulb (Tw ) 

and the dry-bulb (TD ) temperatures during the 1967 

period (table 1). Because of the relatively low flow 

rates, the Stevenson Screen hygrometric formulation, adjusted for atmospheric pressure effects, was 

used to derive relative humidities and mixing- ratios 

(Great Britain Meteorological Office, 1964). However, for all the 1975 and 1976 Tw and TD measurements during outflow in the drill hole, an Assmann 

ventilated psychrometer was used. The free-air Tw 

and TV readings were made from a shielded sling 

psychrometer. The standard psychrometric formulation (List, 1951, p. 365) was used to derive relative humidity and mixing ratios from the Assmann 

and sling psychrometer readings.

CO 

DC

LLJ

CL

LU 8 

Q

10

12

Temperature taken in

1975

A Nov. 19

O Dec. 1 7

1976

A Jan. 21

 Mar. 9

o Apr. 7

D May 7

246

TEMPERATURE, IN 

DEGREES CELSIUS

10 18

PERCENT 

WATER

FIGURE 3. Temperature versus depth over time in a summitcone drill hole over a period of about 6 months, Mauna 

Kea, Hawaii. Annual thermal wave not evident below 8 m. 

To avoid confusion below 7 m, observations at same depth 

that correspond within 0.1 °C or less are represented by 

closed circles. Adjacent digits show number of observations represented by closed circles. Graph at right shows 

percent water (weight H2 0/weight dry ash) in drill-hole 

core samples taken October 15, 1975.

TABLE 2. Deuterium in water vapor from 2-L samples 

of nearly saturated air flowing from the summit-cone 

drill hole, Mauna Kea, Hawaii

(Deuterium analyses were made using conventional techniques. The water vapor 

was converted quantitatively to hydrogen gas by reaction with hot uranium 

metal. The gas was analyzed by a double collecting 6 in. (204 mm) 60° 

Nier-type mass spectrometer. Analyses are reported relative to Vienna 

Standard Mean Ocean Water (SMOW), having a 2 sigma of 0.5 permil. 60 °/oo = 

R. __, - R sample standard

R

standard 

and the standard is Vienna SMOW.

x 1000 where R , = D/H , , R . . . sample sample standard D/Hstandard'

Date Time

1330

1450

1148

1327

1505

1428

1430

1432

Water content

(mg)

15

15

13.6

14.1

13.1

17.2

16.8

16.2

SO 7 oo

-174

-182

-156

-159

-159

-163

-163

-166

-177

Sampl ing 

depth in hole

(m)

2.5

2.5

2.5

2.5

2.5

3.3

6.1

11.9

Table 1 shows only a part of the numerous psychrometric data used to estimate the net latent heat 

flow from the holes. For the sake of brevity, the data 

from which the mean local free-air mixing ratio 

(2.62 g kg- 1 ) was derived are not shown. This mixing ratio is based upon a total of 86 readings of 

TD and Tw, at least five readings on different days 

in each month of the year. They included the local 

free-air mixing ratio (W) values shown in table 1. 

The mean local free-air mixing-ratio value is about 

1 g kg~ l greater than the mean mixing ratio at 4.2 

km in the atmosphere away from the influence of 

Mauna Kea. This free-atmosphere average was derived from 3 years of twice-daily radiosonde data 

(1972, 1973, 1974) at the National Weather Service, 

Hilo, about 30 km east of Mauna Kea. Upslope 

winds during part of the day probably account for 

this 1 g kg- 1 increase in water vapor at the Mauna 

Kea summit (J. Z. Jefferies and D. R. McKnig-ht, 

written commun., 1968).

The above local air-temperature measurements 

and those of ground temperature made by thermistor in a third drill hole (fig 3) are corrected, 

where necessary, for instrumental errors. These 

errors are discussed in a publication concerning 

other recent uses of the instruments (Woodcock, 

1974).

To learn more about the origins of the water 

vapor coming from the drill holes, samples for deuterium analysis were taken in 2-L (liter) evacuated 

stainless steel flasks. A plastic tube, lowered into 

the hole and drained of surface air during rapid outflow of air, was then attached to the flask valve. 

While taking the outflow air samples, the valve was
MOUNTAIN BREATHING, OF AIR-LAND INTERACTION OF MAUNA KEA, HAWAII A5

opened slowly to avoid condensation effects due to 

rapid pressure changes. The deuterium concentrations of the air samples were measured at a laboratory of the U.S. Geological Survey at Denver, Colo. 

(table 2).

LATENT HEAT LOSS TO THE AIR

From the data of figure 2 and table 1, and the 

mean local air-mixing ratio (that is, 2.62 g kg- 1 ), 

we estimated the average amounts of latent heat 

coming out of the drill holes. This evaporative heat 

loss from the interior of the holes (He ) is proportional to the mixing-ratio difference (AW), as noted 

below.

where #P = heat loss in W m~ 2 or watts per square

meter, 

L = latent heat of water vaporization

(2.49x10° J kg- 1 or joules per kilogram) (see footnote 2),

APF = average difference in water- vapor content between entering and exiting air 

(about 6.6 g kg- 1 ), and 

M = average weight of exiting air (about 21 

kgm- 2 d- 1 ).

Using the above relationships, taken from the mean 

data of table 1 and figure 2, we found that an 

average of 3.9 W m-- (0.94 cal m~2 s" 1 ) left the 

interior surfaces of the drill holes, representing 

about 137 g m- 2 d- 1 water (about 50 mm yr- 1 ).

It may seem unreasonable to suggest a mean 

annual exchange from extrapolation of these few 

days' observations, because we do not know how representative the quantity may be. However, we believe 

that it is useful to do so at this exploratory stage in 

the study, as a flow of dry air in and moist air out 

as the air pressure changes is almost certainly a 

long-term fact in this summit region.

SOURCE OF HEAT

In suggesting that the mountain is the source of 

the sensible heat represented by the loss of water 

vapor to the atmosphere, it is necessary to show that 

other potential sources of heat are inadequate.

SENSIBLE HEAT OF INFLOWING AIR AS SOURCE OF 

LATENT HEAT IN OUTFLOWING AIR

Transport of sensible heat into the mountain interior due to airflow (HH ) is proportional to the tem2 This quantity becomes 2.82 X 10" J kg-1 if permafrost proves to be the 

only vapor source. However, until more is known about the source, we 

assume the conservative value of 2.49 X10" J kg-1 .

perature excess of the inflowing air over that of the 

outflowing air and is derived as follows:

H» = CP (ATM),

where H* = sensible heat transport (cal m~2 d-1 ),

Cp = specific heat capacity of dry air (about

1004 joules per kilogram kelvin), 

AT = temperature excess of inflowing air over

outflowing air (°C), and 

M = weight of flowing air (21.0 kg m- 2 d -1).

Using the above equation, we estimate that the air 

entering the mountain (that is, 21.0 kg m~2 d -1 ) 

should have a mean temperature exceeding that of 

the air leaving the mountain by 16.1°C in order to 

supply the mean latent heat found in the air coming 

out of the mountain. The average temperature of 

the exiting air is estimated to be about 5°C (table 

1), which means that the average temperature of 

the entering air should be about 21°C. In other 

words, if the interior of Mauna Kea were dry, the 

exiting air would have a mean temperature of about 

21 °C. Actually, the mean air temperature at the 

Mauna Kea summit is about 4°C (Woodcock, 1974). 

Thus the sensible heat of the air is an unlikely 

source of the latent heat in the outflowing air. The 

fact that airflow into the mountain seems confined 

to the evening and night hours (fig. 2) when the air 

is colder (J. Z. Jefferies and D. R. McKnight, written 

commun., 1968) makes it probable that the air is, 

on the average, a sink rather than a source of 

sensible heat.

CONDUCTION OF HEAT INTO THE MOUNTAIN

Until more is known about the thermal conductivity of the ash, cinder, and lava flows of Mauna 

Kea summit cones, this source of sensible heat cannot be estimated. However, a brief consideration 

causes us to conclude that it is almost certainly 

negligible. Even if we assume that the mountain is 

solid basalt (thermal conductivity about 0.005 cal 

cm-1 cm~ 2 s-1 °C~1 ), a mean negative temperature gradient of about 2.0°C m- 1 would be required 

for conduction to transfer 3.9 W m~ 2 (0.94 cal m~2 

s- 1 ) into the mountain. A negative gradient is 

present on the summit cone (fig. 3), but it is only 

about 0.1°C m- 1 . This is about twice that found under Lake Waiau, where downward heat flow of about 

1/xcal cm~ 2 s~ L (4.18xlO~2 W m~-') has been estimated (Adams and others, 1976). Actually, the 

Mauna Kea summit area is made up largely of 

porous vesiculated ash and cinder, which have a 

very much lower thermal conductivity than solid 

basalt. Thus, conduction of sensible heat into Mauna
A6 SHORTER CONTRIBUTIONS TO GEOPHYSICS, 1979

Kea is discarded as a source of the latent heat coming out in the air.

SNOW AND RAINWATER AS A SENSIBLE 

HEAT SOURCE

The few years of data available indicate that precipitation at the Mauna Kea observatory is only 

about 250 mm yr" 1 , largely in the form of snow. 

If no evaporation or sublimation occurred at the 

surface and all this water seeped into Mauna Kea 

at a temperature of 10°C, it would carry in less 

than 10 percent of the heat coming out as latent 

heat. As melt-water temperatures on Mauna Kea 

are found to be near 0°C, it is more likely to be a 

sink for sensible heat within the mountain than 

a source.

DISCUSSION AND SPECULATIONS

The sums of the daily outflow amounts, derived 

from the product of the average rates and the times 

in figure 2, exceed the inflow by a factor of about 

1.7. Also, the direction of flow seems to have little 

if any relationship to the local semidiurnal pressure 

changes. At this stage in the study we can only 

assume that these effects are due to horizontal pressure gradients across the summit region and that 

these gradients are caused perhaps by local differences in winds, air temperature, and summit-cone 

surface and subsurface conditions. Pyle (1959) has 

indicated the variability of local diurnal pressures 

arising from island mountain effects in Hawaii.

In deriving the estimates of average flow in and 

out of the summit cone, we have simply summed the 

daily in-and-out flow amounts from the holes and 

divided by two. Thus, we have assumed that the 

total inflow and outflow observed (about 53 800 L 

m~2 d -1 or liters per square meter per day) occurred generally over the summit cone and that the 

local inflow deficiency was balanced approximately 

by a proportional excess of inflow elsewhere on the 

mountain summit.

In making these estimates of airflow and water 

vapor flow into and out of the summit cone, we also 

assumed that the flow through each square meter of 

the walls of the drill holes was the same as the 

average flow from a square meter of the mountaintop surface. This may not be a valid assumption, 

because the porosity of the pyroclastic cones of the 

summit area probably differs horizontally from 

place to place, and perhaps vertically as well. 

(Porter, 1972a, b, discussed the morphology of 

Mauna Kea cones.) However, we have no reason to 

think that the area of our drill holes in the summit

cone is either more or less porous than elsewhere on 

the summit cone. In this respect it was encouraging 

to find that the flow in the second drill hole, about 

100 m from the first, corresponded closely to that 

in the first hole. However, we are unable to answer 

the question of whether the flow in these two holes 

is representative of the average air and vapor motion in and out of the mountaintop. Clearly, more 

work is required.

The depth of penetration of air into the mountain 

structures is not known, but the possibilities for 

internal transport of heat and water via the airpenetration mechanism are apparent. This transport 

will be a function of differences in the pressure and 

temperature of the water-saturated air as it moves 

from place to place within the mountain. The air 

will extract heat and water vapor from wet, warmer 

surfaces and will add heat and water to colder surfaces. These exchanges will be superimposed upon 

adiabatic processes as the air moves up and down. 

The trend should be one of smoothing out differences in temperature and water distribution within 

the mountain. (For example note in figure 3 the 

rather uniform distribution of water despite the 

preceding 9-month dry period.)

The water-vapor flow out of the summit seems to 

require a large heat source. We note that the heat 

loss due to the excess vapor flow 3.9 W m~ 2 

(94xlO~° cal cm- 2 s" 1 ) is many times the earth's 

mean geothermal flow in oceanic areas near Hawaii 

(about 1 or 2xlO-(i cal cm-- s- 1 or 4.2-8.4X1Q- 2 W 

m~ 2 ; Lee and Uyeda, 1965, p. 129). Perhaps it is a 

heat flow normal for the top of a long-dormant 

oceanic volcano. (Porter, 1972c, discussed dates of 

most recent eruptions on Mauna Kea.) Clearly more 

work of this nature at other locations on Mauna Kea 

is needed to see how general this latent heat outflow 

is.

The role of synoptic atmospheric pressure 

changes in forcing air in and out of the mountain 

has not been considered. These pressure changes are 

thought to average only a small fraction of the 

semidiurnal or diurnal pressure changes in Hawaii 

mountain locations (Pyle, 1959).

Winds obviously altered the flow of air in the 

hole, presumably due to their effects on local pressures. The vane anemometer was occasionally observed to reverse direction momentarily, during inflow, as wind gusts passed over the summit cone. 

The hot-wire anemometer revealed short-poriod 

variability of 1.5 to 2 times in the speed of flow in 

or out, as the wind strength changed, but these were
MOUNTAIN BREATHING, OF AIR-LAND INTERACTION OF MAUNA KEA, HAWAII A7

transitory effects superimposed upon the consistent 

general flow.

A gas sample was taken from the drill hole during- slow outflow at 0800 on August 8, 1967, and 

later was found to be air. From the data of figure 2, 

we now know, however, that the air sample should 

have been taken at the end of the exhalation period, 

when air with the deepest penetration of the mountain should have been emerging. If subterranean 

processes (for example, oxidation and degassing) 

alter the air inhaled, the differences should be most 

evident in the air emerging near the end of the 

outflow period.

It is unfortunate that the ground-temperature 

series (fig. 3) could not have been extended for a 

full year, in order to show the negative gradient 

more completely. However, enough of the annual 

cycle is represented to show that we have probably 

penetrated below the local depth of near-zero annual 

amplitude, and that the negative sign is real. At 

four other locations on Mauna Kea, temperaturedepth measurements taken over more than a year 

have also shown this near-zero amplitude at depths 

between 5 and 9 m. Two of these four series of 

measurements also show a negative gradient.

The hole used for the temperature measurements 

was drilled on October 14, 1975, without the use of 

water and apparently without production of much 

sensible heating. This low level of heating was 

judged from the fact that the temeprature near the 

12-m level was reduced from 5.5°C, as measured on 

October 15, to only 4.9° C on November 19, where 

it remained practically constant (fig. 3).

The decrease in the deuterium concentration of 

the water vapor with increasing depth in the hole 

or with duration of outflow (table 2, April 7 and 

May 6 observations3 ) suggests that the snowmelt is 

not the source of the lightest water but that the 

source lies farther down in the mountain. The presence of the negative thermal gradient and of the 

thick layer of permafrost nearby causes us to think 

that the source of the lightest vapor is melt from 

permafrost.

The deuterium of evaporate from melt waters of 

the known permafrost nearby (SD or delta deuterium of melt, 88 permil; Woodcock, 1974) is about 

 190 permil, and the SD of evaporate from old sn<j>wmelt (SD about 66 permil; Woodcock, 1974) is 

about -160 permil (Friedman and others, 1964). 

The observed SD values of the exhaled vapor fall

3 These samples were taken in the presence of slow melting of old 

snow, whereas the December 17 samples were taken near the end of a 

9-month dry period in which only 30 mm of rain fell at Mauna Kea 

observatory.

TABLE 3. Deuterium in snow, graupel, permafrost, and 

lake waters of the Mauna Kea summit area, Hawaii

[Deuterium analyses were made using conventional techniques. The water vapor 

was converted quantitatively to hydrogen gas by reaction with hot uranium 

metal. The gas was analyzed by a double collecting 6 in. (204 mm) 60° 

Nier-type mass spectrometer. Analyses are reported relative to Vienna 

Standard Mean Ocean Water (SMOW), having a 2 sigma of 0.5 permil. «D %,„ =

sample " standard .. ,„„„ ..,..._.

n

standard 

and the standard

Date

Nov. 27, 1973

Mar. 4, 1974-

Mar. 3, 1976-

Mar. 4, 1976-

Mar. 16, 1976

Mar. 17, 1976

Apr. 1, 1976-

Oct. 1972----

Nov. 21, 1954

Sept. 4, 1970

Apr. 10, 1971

is Vienna SMOW.

Description

Graupel ——

—— do ----

---- do - —

---- do-- —

—— do ——

—— do— -

---- do— -

Permafrost

Water ———

—— do ——

—— do — --

p = 

sample

60 °/

-77

-69

-169

-39

-147

-189

-169

-73

-82 to

-23

-18

-52

D/Hsample' "standard D/Hstandard>

0 Remarks

average in drift

1.5 m deep.

Falling as sampled.

Do

Recently alien.

Do

Do

Do

Do

-93 8 samples from

depths between

0.4 and 14 m.

Lake Waiau, level

not recorded.

Lake Waiau, level

unusual ly low.

(0.8 m below sill

depth).

Lake Waiau, overflow 91 m3 d'>.

very nearly between these limits (table 2), as would 

be expected if the average vapor source were a mixture of evaporate from old snowmelt and permafrost melt. We assume that fractionation occurs and 

that the residual (heavier) liquid, from which vaporization has occurred, does not accumulate but 

drains away to greater depths. The light exhaled 

vapor might also be explained if the vapor (relative 

humidity 50 percent) is light when it enters the 

mountain (that is, 8D = 250 permil), and if the 

SD value of the vapor added by sublimation of 

permafrost is about -90 permil. The final SD value 

of the vapor would be about -175 permil. Because 

measurement of the deuterium of a local air sample 

from Mauna Kea (Friedman and others, 1964, p. 

199-200) revealed the expected relatively heavy 

value of 160 permil, the preceding explanation is 

unlikely. Waters from deep within Mauna Kea, originating from low-altitude precipitation, are excluded 

as a possible vapor source as they are all much 

heavier (Friedman and Woodcock, 1957).

Four factors incline us to regard permafrost as 

the most probable source of the light vapor: (1) 

ice is the only known adequate local source of such 

light vapor (table 3); (2) the SD decreases with 

depth and duration of outflow, indicating a deeper 

light-vapor source (table 2); (3) after a long dry 

summer we found the lightest vapor exhaled (Dec. 

17 samples, table 2) ; and (4) we found a negative 

temperature gradient in the summit cone (fig. 3). 

Thus, it appears that deuterium and temperature
A8 SHORTER CONTRIBUTIONS TO GEOPHYSICS, 1979

measurements both indicate the presence of permafrost below the observatory site. Extrapolation of 

the temperature curve below the depth of near-zero 

annual amplitude (fig. 3) suggests that 0°C and ice 

occur at about 60-m depth.

In the future, with more data available on the 

average of 3D of snow and on the proportions of 

light and heavy water in the outflowing vapor, we 

may be able to estimate the rate of melting of the 

permafrost from the latent heat loss in this vapor.

CONCLUSIONS

A source of heat in the Mauna Kea summit cone 

of nearly 4 W m~- (1 cal m~- s" 1 ) is indicated 

by the net outward flow of water vapor due to 

mountain breathing. Most, if not all, of this heat is 

apparently derived from within the mountain and 

not from the atmosphere at the summit. The source 

of the water vapor appears to be melt from old 

snow and from permafrost.

REFERENCES CITED

Adams, W. M., Watts, George, and Mason, George, 1976, 

Estimation of thermal diffusivity from field observations of temperature as a function of time and depth: 

Am. Mineralogist, v. 61, nos. 7-8, p. 560-568.

Friedman, Irving, and Woodcock, A. H., 1957, Determination 

of deuterium-hydrogen ratios in Hawaiian waters: 

Tellus, v. 9, p. 553-556.

Friedman, Irving, Redfield, A. C., Schoen, Beatrice, and 

Harris, Joseph, 1964, The variation of the deuterium 

content of natural waters in the hydrologic cycle: Rev. 

Geophysics, v. 2, no. 1, p. 177-224.

Geiger, Rudolph, 1971, The climate near the ground: Cambridge, Mass., Harvard University Press, 611 p.

Great Britain Meteorological Office, 1964, Hygrometric tables, 

Part II (2d ed.) : London, England, Pub. 265b.

Lee, W. H. K., and Uyeda, Seiya, 1965, Review of heat flow 

data, Chapter 6 in Terrestrial heat flow: Am. Geophys. 

Union Geophys. Mon. Ser. No. 8 (Natl. Acad. Sci.-Natl. 

Research Council Pub. 1288), p. 87-190.

List, R. J., 1951, Smithsonian Meteorological Tables (6th revised ed.) Smithsonian Misc. Colln., v. 114 (pub. 4014), 

527 p.

Peck, A. J., 1960, The water table as affected by atmospheric 

pressure: Jour. Geophys. Research, v. 65, no. 8, p. 2383- 

2388.

Porter, S. C., 1972a, Buried caldera of Mauna Kea volcano, 

Hawaii: Science, v. 175, no. 4029, p. 1458-1460.

———1972b, Distribution, morphology, and size frequency of 

cinder cones on Mauna Kea volcano, Hawaii: Geol. Soc. 

America Bull., v. 83, no. 12, p. 3607-3612. 

-1972c, Holocene eruptions of Mauna Kea volcano,

Hawaii: Science, v. 172, no. 3981, p. 375-377.

Pyle, R. L., 1959, The diurnal pressure oscillation on a heated 

mountain island: Jour. Meteorology, v. 16, no. 5, p. 467- 

482.

Turk, L. J., 1975, Diurnal fluctuations of water tables induced by atmospheric pressure changes: Jour. Hydrology, v. 26, p. 1-16.

Wigley, T. M. L., 1967, Non-steady flow through a porous 

medium and cave breathing: Jour. Geophys. Research, v. 

72, no. 12, p. 3199-3205.

Woodcock, A. H., 1974, Permafrost and climatology of a 

Hawaii volcano crater: Arctic and Alpine Research, v. 

6, no. 1, p. 49-62.

Woodcock, A. H., and Groves, G. W., 1969, Negative thermal 

gradient under alpine lake in Hawaii: Deep-Sea Research, supp. v. 16, p. 393-405.

Yen, Yin-Chao, 1963, Heat transfer by vapor transfer in 

ventilated snow: Jour. Geophys. Research, v. 68, no. 4, 

p. 1093-1101.
Porosity and Density of 

Kilauea Volcano Basalts, Hawaii

By GORDON R. JOHNSON

SHORTER CONTRIBUTIONS TO GEOPHYSICS, 1979

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1123-B

Tabulation of data and comparison of the 

densities and porosities of samples 

from two depositional environments

CONTENTS

Page

Abstract _______________________________________ ___ Bl

Introduction ______________________________________________________ 1

Techniques _______________________________________________ _ ___ 1

Basalts of Kilauea Iki ___________________________________ 3

Basalts of the east rift zone ________________________________ 4

Summary and conclusions ___________________________________________ 6

References cited _________________________________________ 6

ILLUSTRATIONS

Page

FIGURE 1. Locations of Kl-76-1 and HGP-A drill holes, Island of Hawaii __________________________ Bl 

2. Porosities of basalt from drill hole Kl-76-1, Kilauea Iki, Hawaii ________________________ 4

TABLES

Page

TABLE 1. Densities and porosities of basalt from Sandia Corporation drill hole Kl-76-1, Kilauea Iki, Hawaii ____ B3 

2. Densities and porosities of basalt from University of Hawaii drill hole HGP-A, east rift zone of Kilauea

Volcano, Hawaii _______________________________________________ 5

ill

SHORTER CONTRIBUTIONS TO GEOPHYSICS, 1979

POROSITY AND DENSITY OF KILAUEA VOLCANO BASALTS, HAWAII

By GORDON R. JOHNSON

ABSTRACT

Bulk-density and grain-density measurements were made 

on samples of basalt from the Kilauea Volcano region of 

Hawaii. Samples were obtained from two drill holes: a shallow hole at Kilauea Iki pit crater, and a deep hole at the 

lower east rift zone. Water-accessible porosities were calculated from calipered measurements of bulk density and 

measurements of grain density made using Archimedes' 

principle. Helium-accessible porosities were calculated from 

calipered measurements of bulk density and measurements of 

grain density made using helium pycnometry. Grain density 

apparently decreases with depth in the Kilauea Iki drill hole 

owing to (1) rapid cooling and simultaneous trapping of 

heavy minerals in the upper material and (2) settling of 

heavy minerals from the deeper material that was cooled 

at a much slower rate. No such relationship can be determined from grain-density measurements of east rift zone 

drill-hole samples. Helium-accessible porosities and corresponding water-accessible porosities of most individual 

samples from the Kilauea Iki drill hole are nearly the same. 

In contrast, helium-accessible porosities of many individual 

samples from the east rift zone drill hole are much greater 

than corresponding water-accessible porosities. The sample 

depths involved for the two drill holes and the depositional 

environments of the rocks probably account for the relationships between helium-accessible porosities and water-accessible porosities determined for one hole differing from 

those determined for the other.

INTRODUCTION

Sixty-eight samples of Hawaii basalts were collected from cores of two drill holes, one (Kl-76 

1) in Kilauea Iki pit crater and the other (HGP-A) 

in the lower east rift zone of Kilauea Volcano (fig. 

1) ; both are on the island of Hawaii. Data about 

the porosity, dry bulk density, and grain density of 

the samples are tabulated in tables 1 and 2. The 

Kilauea Iki samples are tholeiitic basialts from magma deposited in December 1959. The measured 

Kilauea Iki core samples were collected at 1-m intervals from near the ground surface to a depth of 

43 m. The samples from the east rift zone drill hole 

came from cored intervals at depths of 139 to 

1965.5 m.

155°

FIGURE 1. Locations of Kl-76-1 and HGP-A drill 

holes, Island of Hawaii.

TECHNIQUES

At U.S. Geological Survey laboratories in Denver, 

Colo., the cores were drilled and trimmed with 

diamond tools to obtain uniform cylindrical samples 

25.4 mm in both diameter and length. These samples 

were then dried overnight in a vacuum oven and 

weighed to an accuracy of 0.001 g. The sample 

weights, recorded as Wdry, were later used to calculate grain volume and grain and bulk densities.

Grain volumes were determined on the small 

samples using two techniques: (1) helium pycnomBl
B2 SHORTER CONTRIBUTIONS TO GEOPHYSICS, 1979

etry and (2) the buoyancy, or Archimedes', principle. Basically, helium pycnometer measurements 

utilize an inert gas to compare the pressure-volume 

relationship of a sample with that of a steel ball of 

known volume. Accepting the validity of the perfect 

gas law with the imposed conditions, the unknown 

volume of the sample can be derived. Helium is used 

because it is an inert, nonadsorbing gas and has a 

small molecular diameter that allows it to penetrate 

easily into minute sample pores. A method using 

Archimedes' principle consists of weighing a watersaturated sample suspended from a fine wire and 

stirrup in a water bath. Before weighing, the 

samples are soaked in a partial-vacuum environment 

for several days to attain complete saturation. Grain 

volume VtJ is /then calculated as

W, ——W 7, jy _ '' dry '" sub /1 \ 

P

where W8M6 is the submerged or suspended weight 

and p is the density of water. To obtain grain volumes by either of the above methods assumes that, 

depending on the method, helium or water completely invades all sample pores.

The bulk volume of a solid consists of the total of 

the volumes of solid material and of voids. Bulk volumes for these samples were determined by measuring the length and diameter of each cylindrical 

sample. An average of several readings, each accurate to 0.1 mm, was used to calculate bulk volume. 

Bulk volumes were also obtained using submerged 

weights and saturated sample weights. The saturated samples were towelled to a surface-dry condition and weighed in air. Bulk volumes were calculated using the equation

(2)

where Wsat were saturated surface-dry weights.

Grain and dry bulk densities of the samples were 

obtained from the volume determinations. Dry bulk 

density (DBD) was calculated as the ratio of Wary 

to the calipered volume, whereas bulk density determined by Archimedes' principle (DBA) was calculated as the ratio of Wdry to V&. Grain density was 

also calculated two ways: (1) the ratio of Wdry to 

the grain volume obtained by helium pycnometry 

(SGH) and (2) the ratio of Wdrv io Vg (SGA).

True measurements of grain volumes, and hence 

of grain densities, require that all pores are helium 

or water saturable. If complete saturation is not 

achieved, then measurements of grain volume will be 

erroneously large, and apparent grain density will

be correspondingly low. In contrast, DBA calculations are not affected by incomplete saturation but 

rather by the size and quantity of pores that occur 

at the surface of samples. When saturated samples 

are removed from water to be weighed in air, the 

effects of towelling and the low surface tension of 

water result in all but the very small surface pores 

becoming unsaturated. Thus Wsat will be reduced, 76 

will be abnormally low, and DBA will be greater 

than the actual dry bulk density.

Helium-accessible and water-accessible apparent 

porosities were determined from measurements of 

DBD, DBA, SGH, and SGA. Apparent porosity (Pfl ) 

is commonly expressed as

where Vp is the volume of fluid-accessible pores and 

F6 is bulk volume. However, because grain volume, 

measured both by Archimedes' principle and helium 

pycnometry, includes those pores that are isolated 

to either water or helium, Vp may be expressed as

Vp = Vb — Vg, (4)

where Vg is grain volume. 

By substitution,

P« = 10o(l 5^-Y (5)

\ VT> /

and expressed in terms of bulk and grain density,

(6)

where Db is either DBD or DBA, and Dg is either 

SGH or SGA. Because values of SGH are nearly the 

same as intrinsic grain densities in many rock types, 

helium-accessible porosities in these rocks will ap^ 

proach total porosities. Total porosity may be expressed as

P, = 100f 1- (7)

as in equation 5, except that in this case V,, is the 

volume of grains only, not that of grains and isolated 

pores.

In many rocks, such as clean sandstones, wateraccessible porosities are equivalent or nearly equivalent to total porosities, because the interstices between grains are large enough to permit easy penetration by water. In other rocks, such as the basalt 

from Kilauea Volcano, porosity is controlled mainly 

by fractures that act as capillaries interconnecting 

larger vesicular pores. This association of largediameter pores with restricted openings (fractures)
POROSITY AND DENSITY OF KILAUEA VOLCANO BASALTS, HAWAII B3

is one type of so-called inkwell pores. If the fractures 

are not too restrictive to water penetration, then 

saturation can be easily achieved by capillarity. 

However, if the fractures are so tight as to resist 

water penetration, then saturation can be achieved 

only if sufficient pressure is applied to overcome the 

restrictive effects of the surface tension of water. 

Nevertheless, water-accessible porosities are measrured on samples that have been saturated at pressures of about 1 atmosphere, and these porosities 

miay therefore be much less than helium-accessible 

porosities measured on the same samples. Conversely, the water-accessible porosity of a sample 

cannot truly be greater than its helium-accessible 

porosity.

BASALTS OF KILAUEA IKI

Because of the vesicularity of most of the basalt 

samples of Kilauea Iki, values of DBA are, for many 

samples, much greater than corresponding values of 

DBD. The obviously vesicular samples listed in table 

1 have noticeably high values of DBA, but other 

samples have values of DBA that are as much as 

0.09 g/cm3 greater than corresponding DBD values. 

Consequently only DBD was considered when calculating water-accessible porosities, because porosities calculated using values of DBA would be 

erroneously low and, when compared with heliumaccessible porosities, would lead to the false assumption that most of the basalts of Kilauea Iki have 

significant quantities of isolated pores. Figure 2 

compares the helium-accessible porosities with the 

water-accessible porosities of the basalt samples of 

Kilauea Iki. Whereas a direct comparison indicates 

that porosity as a function of depth is apparently 

about the same for both types of porosity (fig. 2A), 

the ratio of PHe to PHo0 plotted for all samples (fig. 

2B) shows an interval at 32 to 35 m where samples 

have isolated pores and another probably similar 

zone below a depth of 41 m. Additionally, a single 

sample at 7 m has a significant amount of isolated 

porosity. Otherwise, the helium- and water-accessible 

porosities are more or less equivalent in these 

samples.

Because values of SGH for many samples are in 

the upper range of grain density of basalts (3.1- 

3.2 g/cm3 ), helium porosities in these samples are 

probably about equivalent to total porosities. However, grain density apparently decreases somewhat 

with depth. This decrease in grain density is probably real but could be due to the effect of porosity 

that is isolated to both helium and water invasion.

TABLE 1. Densities and porosities of basalt from Sandia 

Corporation drill hole K1-76-1, Kilauea Iki, Hawaii

[DBD, dry bulk density using calipered volume; DBA and SGA, dry bulk density 

and grain density using bulk and grain volume determined from Archimedes' 

principle; SGH, grain density using volume obtained by helium pycnometry. 

PU , helium-accessible porosity, in percent; P H „, water-accessible 

porosity, in percent, g/cm 3 = Mg/m 3 ] 2

Depth 

of core, 

in meters

0.99

1.91

2.87

3.73

4.70

5.59

6.53

7.39

8.31

9.22

10.13

11.00

11.96

12.88

13.84

14.71

15.62

16.56

16.56

17.45

18.31

19.30

20.57

21.65

23.24

24.16

25.07

25.96

27.20

28.32

28.93

29.90

30.99

32.54

33.45

34.47

35.38

36.60

37.57

39.04

39.80

41.17

42.11

43.03

DBD

1.860

2.342

2.405

2.342

2.695

2.655

2.872

2.811

2.699

2.549

2.678

2.767

2.416

2.821

2.793

2.789

2.782

2.248

2.730

2.821

2.794

2.643

2.655

2.568

2.451

2.714

2.575

2.758

2.782

2.751

2.804

2.764

2.782

2.849

2.867

2.847

2.788

2.781

2.677

2.645

2.844

2.877

2.882

2.811

DBA

'2.359

'2.614

'2.615

'2.558

'2.732

'2.770

2.890

2.876

'2.827

'2!657

2.745

2.830

'2.566

2.846

2.798

2.811

2.825

'2.578

2.783

2.822

2.838

2.726

2.706

2.649

'2.638

2.746

'2.665

2.790

2.802

2.764

2.837

2.790

2.835

2.873

2.880

2.851

2.802

2.807

2.717

2.714

2.859

2.894

2.895

2.852

SGA

(g/cm 3 ) 

3.046

3.169

3.095

3.147

3.118

3.056

3.014

3.215

3.196

3.164

3.208

3.180

3.158

3.113

3.117

3.104

3.104

3.035

3.073

3.095

3.103

3.074

3.025

2.938

2.994

3.057

3.023

3.008

3.023

3.027

3.016

3.008

3.027

2.981

2.991

2.982

2.972

3.004

2.994

3.024

2.995

3.013

3.019

2.957

SGH

3.144

3.198

3.196

3.197

3.139

3.109

3.099

3.217

3.192

3.193

3.235

3.205

3.192

3.139

3.117

3.119

3.104

3.055

3.092

3.120

3.117

3.098

3.053

2.954

3.013

3.078

3.035

3.052

3.081

3.054

3.046

3.084

3.062

3.094

3.092

3.052

3.044

3.037

3.023

3.050

3.007

3.059

3.047

3.038

P He 

- ]00 ^-?G

40.8

26.8

24.7

26.7

14.1

14.6

7.32

12.6

15.4

20.2

17.2

13.7

24.3

10.1

10.4

10.6

10.4

26.4

11.7

9.58

10.4

14.7

13.0

13.1

18.7

11.8

15.2

9.63

9.70

9.92

7.94

10.4

9.14

7.92

7.28

6.72

8.41

8.43

11.4

13.3

5.42

5.95

5.42

7.47

P H 2 0

) i e\n.t -i DBD \

,n 100(1 -SGA }

38.9

26.1

22.3

25.6

13.6

13.1

4.71

12.6

15.6

19.4

16.5

13.0

23.5

9.38

10.4

10.1

10.4

25.9

11.2

8.85

9.96

14.0

12.2

12.6

18.1

11.2

14.8

8.31

7.97

9.12

7.03

8.11

8.09

4.43

4.14

4.53

6.19

7.42

10.6

12.5

5.04

4.51

4.54

4.94

Averages--- 3.061 3.098

'Denotes DBA of samples with noticeably large vesicles.

If isolated porosity does in fact exist in samples 

from greater depth, powdered samples will then exhibit higher values of grain density than will their 

solid counterparts, because isolated pores are destroyed in the process of pulverization. Nevertheless, 

the SGH of a powdered split of the 21.65 m sample 

was determined to be 2.934 g/cm3 , or nearly the 

same value as the SGH of the 21.65 m solid sample 

(table 1).

The most probable explanation for the decrease 

in grain density with depth is that the near-surface 

lava cooled rapidly, thus trapping heavy minerals,
B4 SHORTER CONTRIBUTIONS TO GEOPHYSICS, 1979

03 

OC 

LUILU

LU 

O

LJL 

OC

Z) 

03

LJJ 

CD

Q_

LU 

Q

o»

o 

o •

10

© 

o

o

r 20 o* 

o

o

30

o 

o

o

40 -

o 

o 

o

o

O'

o

EXPLANATION

• Helium-accessible porosity, PHe 

o Water-accessible porosity, PH2 o

50 i i i i

10 20 30

POROSITY, IN PERCENT

40 501.0

B

1.5 2.0

FIGURE 2. Porosities of basalt from drill hole Kl-76-1, Kilauea Iki, Hawaii. A, Porosity values and their relationship to 

depth. B, Porosity values as a function of technique, showing zones of isolated porosity.

while the deeper lava cooled much more slowly, 

allowing heavy minerals to settle at some level below 

the depth of the drill hole. Richterand Moore (1966) 

reported extreme variability, from 2 to 37 percent, 

in olivine content in samples from another drill hole 

at Kilauea Iki; the amount of olivine phenocrysts 

also affects the chemical composition and results in 

a corresponding increase in magnesia. Because both 

olivine and magnesia have specific gravities of about 

3.2, their relative abundance from sample to sample 

should account for the differences in SGH and SGA 

values shown on table 1.

BASALTS OF THE EAST RIFT ZONE

In contrast with the samples from the Kilauea Iki 

drill holes, most of the samples from the drill hole 

on the lower east rift zone are dense, fine-grained 

basalts. According to Kingston and others (1976), 

all cores collected below 914.4 m show some degree 

of chloritic alteration. Samples taken near the surface are normal olivine-bearing tholeiitic basalt. 

However, none of the samples measured in the laboratory contains large vesicles to the extent that 

erroneous values of DBA would be expected. Accordingly, most values of DBA are within 0.02 g/cm3 

of their corresponding DBD, and for only one 

sample, collected from 139.3 m, is the DBA as much 

as 0.07 g/cm3 higher than its value of DBD. For 

these samples either DBD or DBA could be used 

with comparable results to calculate water-accessible 

porosity, but to be consistent, only porosities calculated from values of DBD are shown on table 2.

Unlike Kilauea Iki samples, porosity-depth relationships and porosity ratios for the east rift zone 

samples are not graphed, because these samples are 

from widely spaced cored intervals; thus, the values 

of porosity do not necessarily represent a continuous 

function with respect to depth. The ratios of heliumaccessible to water-accessible porosities (table 2) 

show that at core intervals at depths greater than
POROSITY AND DENSITY OF KILAUEA VOLCANO BASALTS, HAWAII B5

TABLE 2. Densities and porosities of basalt from University of Hawaii drill hole HGP-A, east rift zone of Kilauea Volcano,

Hawaii

[DBD, dry bulk density using calipered volume; DBA and SGA, dry bulk density and grain density 

using bulk and grain volume determined from Archimedes' principle; SGH, grain density using volume 

obtained by helium pycnometry. .P., , helium-accessible porosity, in percent; P , water-accessible

porosity, in percent, g/cm 3 = Mg/m 3 ]

H

Depth 

cf core, 

in meters

138.99

139.29

139.60

681.23

682.14

682.29

682.75

876.60

877.37

1117.55

1118.46

1120.14

1355.44

1356.97

1358.19

1644.85

1645.46

1647.14

1838.40

1839.16

1839.32

1840.08

1964.89

1965.50

DBD

2.810

2.603

2.696

2.546

2.892

2.908

2.810

2.560

2.348

2.767

2.614

2.719

2.811

2.503

2.666

2.799

2.822

2.682

2.883

2.856

2.826

2.843

2.397

2.418

DBA

2.838

2.669

2.709

2.538

2.884

2.893

2.801

2.566

2.355

2.758

2.615

2.697

2.815

2.511

2.663

2.807

2.816

2.688

2.866

2.843

2.826

2.865

2.385

2.411

SGA 

• (g/cm 3 ) ————

3.038

3.019

3.026

2.837

2.966

2.964

2.948

2.740

2.960

2.937

2.910

2.829

3.078

2.786

3.138

2.970

2.980

2.914

2.945

2.948

2.953

2.954

2.960

2.946

SGH

3.046

3.042

3.077

2.949

!2.917

^.909

1 2.878

2.894

1 2.869

3.013

3.041

3.053

!2.942

2.996

1 2.995

3.142

2.983

2.981

3.003

3.096

3.122

2.991

3.067

2.971

P He 

innn DBCS 100(1- SGH )

7.74

14.4

12.4

13.7

0.86

0.03

2.36

11.5

18.2

8.16

14.0

10.9

4.45

16.4

11.0

10.9

5.40

10.0

4.00

7.75

9.48

4.94

21.8

18.6

P H 2 0 

100(1- DBD )

iuuu SGA ;

7.50

13.8

10.9

10.3

2.49

1.89

4.68

6.57

20.7

5.79

10.2

3.89

8.67

10.2

15.0

5.76

5.30

7.96

2.11

3.12

4.30

3.76

19.0

17.9

P He

P H 2 0

1.03

1.04

1.14

1.33

0.34

0.02

0.50

1.75

0.88

1.41

1.37

2.80

0.51

1.61

0.73

1.89

1.02

1.26

1.90

2.48

2.20

1.31

1.15

1.04

Denotes SGH of samples with noticeably large vesicles.

139.60 m, water-accessible porosity is, in most 

samples, much less than helium-accessible porosity. 

Only samples collected from the core interval at 

about 139 m, a single sample at 1645.46 m, and those 

at 1964.89 m and 1965.50 m, near the bottom of the 

drill hole, have nearly equivalent water-accessible 

and helium-accessible porosities.

Unfortunately, reliable SGH measurements could 

not be made on those samples that are footnoted 

in table 2. Unstable and nonreproducible instrument 

readings indicated that the permeabilities of the 

samples were so tight that they resisted invasion by 

helium. However, these same samples were apparently more water saturable than helium saturable, 

because their SGA values in all cases were greater

than their corresponding SGH values. Paradoxically, 

accurate values of SGH must always be equal to or 

greater than corresponding values of SGA.

According to the Hawaii Geothermal Project Well 

Completion report HGP-A (Kingston and others, 

1976), all samples collected below 366 m to a depth 

of 1219 m contain secondary zeolites that are moderately abundant. One possible explanation for the 

obviously low SGH values of the samples footnoted 

in table 2 is that certain zeolites act as molecular 

sieves (Evans (1964), among others) and thereby 

are permeable to small molecules in such a way that 

excess amounts of helium would be held in the 

crystal lattices. Thus, when measured on these 

samples, grain volumes could be larger than actual
B6 SHORTER CONTRIBUTIONS TO GEOPHYSICS, 1979

grain volumes, and values of SGH would be correspondingly low.

This explanation assumes the mineralogy of the 

zeolite to be that which would act as a molecular 

sieve to helium molecules. If so, then this type of 

zeolite is in significant abundance in three core intervals: (1) from 681.23 to 682.75 m, (2) from 

876.60 to 877.37 m, and (3) from 1355.44 to 1358.10 

m. Obviously, helium-accessible porosities are much 

toio low in all the footnoted samples from these three 

core intervals, and it is possible, although indeterminable, that the values of SGH for other samples 

taken from these intervals are also erroneous. Because values of SGH for such samples from these 

core intervals cannot be relied on, helium-accessible 

porosities must be considered therefore to be erroneously low.

SUMMARY AND CONCLUSIONS

The porosity relationships graphed in figure 2B 

show that the fractures in the basalt of Kilauea Iki 

are, for the most part, open and accessible to water 

penetration. The few samples that exhibit wateraccessible porosity that is anomalously low compared 

with helium-accessible porosity might represent 

layers of basalt that have tight fractures, although

under an increased hydrostatic pressure these fractures could be open to water penetration. In contrast, many samples from the drill hole at the east 

rift zone have porosities that are isolated to water 

penetration. Most of the tight east rift zone lavas 

are presumed to have been formed subaerially 

(Kingston and others, 1976), whereas the lavas of 

Kilauea Iki were formed at or near ground surface. 

A general decrease in grain density with depth 

indicated by the Kilauea Iki samples is probably due 

to a near-surface concentration of heavy minerals 

and possibly to a settling and depletion of heavy 

minerals in the deeper zones. No such relationship 

is evident from grain density measurements of 

samples from the east rift zone drill hole.

REFERENCES CITED

Evans, R. C., 1964, An introduction to crystal chemistry: 

Cambridge, Cambridge University Press, 410 p.

Kingston, Reynolds, Thorn, and Allardice, Ltd., 1976, Hawaii 

geothermal project well completion report HGP-A: 

Honolulu, University of Hawaii Research Corp., and 

U.S. Energy Research and Development Administration, 

34 p.

Richter, Donald H., and Moore, James G., 1966, Petrology of 

the Kilauea Iki lava lake, Hawaii: U.S. Geological Survey Professional Paper 537-B, p. B1-B26.
Diabase Dikes in the

Haile-Brewer Area, South Carolina,

and Their Magnetic Properties

By HENRY BELL III, KENNETH G. BOOKS, DAVID L. DANIELS, 

WILLIAM E. HUFF, JR., and PETER POPENOE

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1123-C

Paleomagnetic poles are calculated for 

Upper Triassic and Lower Jurassic dikes 

revealed by magnetic data

CONTENTS

Page

Abstract __________________________________———___— Cl

Introduction ___________________________—_———————— 1

Magnetic setting ____________________________________—___ — — — — _ — __ 2

Geologic setting ______________________________________________ — — _ 9

Diabase dikes ________________________ — __ ——— ————— 10

Sampling procedures _______________________________—————— 11

Laboratory procedures ___________________________________________ — _ — - 13

Results ___________________________________________— 14

Conclusions ____________________________________________________ 17

References cited ________________________________ — _———— 17

ILLUSTRATIONS

Page

FIGURE 1. Sketch map of the Appalachian region of the Eastern United States, showing the location of the HaileBrewer area, South Carolina, known occurrences of dikes of Triassic and Jurassic age, and areas of 

outcrop of the Newark Group ____________________________________________- C2

2. Aeromagnetic map of the Camden-Kershaw area, north-central South Carolina ______________ 4

3. Geologic map of the Haile-Brewer area, South Carolina ___________________________——— 6

4. Profiles obtained by means of an airborne magnetometer carried at 122-m elevation and profiles obtained by

means of a truck-mounted magnetometer __________________________________ 8

5. Two-dimensional magnetic profiles of a simulated geologic profile calculated for 4.6 m and 122 m elevation 9

TABLES

Page

TABLE 1. Major- and minor-oxide composition, trace-element content, and normative mineralogy of a large diabase

dike. Lancaster County, S.C. _____________________________________________________________ C12

2. Magnetic properties and normative magnetite and ilmenite contents of a large diabase dike, Lancaster

County, S.C. ___________________________________________________________ 13

3. Definition of terms used in the sampling hierarchy ___________________________ — ___ 13

4. Results of spinner-magnetometer measurements on specimens of diabase dikes from the Haile-Brewer area, 

South Carolina, untreated and after cleaning by subjection to alternating magnetic fields of intensities 

of 100, 200, and 300 oersteds ________________________________________________ 14

5. Paleomagnetic directions and paleomagnetic pole positions for diabase dikes and dike swarms in the

Haile-Brewer area, South Carolina ____________________________ — _—————————— 16

6. Summary of magnetic data and paleomagnetic pole positions for diabase dikes and dike swarms in the

Haile-Brewer area, South Carolina _____________________________________— 17

III

SHORTER CONTRIBUTIONS TO GEOPHYSICS, 1979

DIABASE DIKES IN THE HAILE-BREWER AREA, SOUTH CAROLINA, 

AND THEIR MAGNETIC PROPERTIES

By HENRY BELL III, KENNETH G. BOOKS, DAVID L. DANIELS, 

WILLIAM E. HUFF, JR., and PETER POPENOE

ABSTRACT

The aeromagnetic map of the Haile-Brewer area, eastcentral South Carolina, shows numerous strong narrow 

northwest-trending anomalies that are associated with diabase dikes. These diabase dikes were sampled by means of 

core-drilling equipment to obtain oriented samples on which 

magnetic properties were measured for paleomagnetic orientation. The pole positions calculated for the various dikes are 

in two groups that are close together but that have opposing 

polarity. The paleomagnetic pole positions calculated are 

within the range of those obtained from diabase intrusive 

rocks in eastern North America that are considered to be 

Late Triassic and Early Jurassic in age.

INTRODUCTION

Sedimentary and igneous rocks of the Newark 

Group (Upper Triassic and Lower Jurassic) in the 

Eastern United States crop out in extensively 

faulted narrow basins. The igneous rocks are predominantly diabase and gabbro that have been emplaced as dikes and sills. Commonly, the diabase 

dikes are emplaced in faults cutting not only fossiliferous sedimentary rocks within the basins but also, 

as in the Haile-Brewer area, South Carolina, Paleozoic or Precambrian crystalline rocks in areas 

widely distributed beyond the basins, as P. B. King 

has emphasized (1961, 1971). The igneous rocks, 

including the diabase dikes, that are in these basins 

have been much studied, particularly in regards to 

their petrography, structural setting, and relation 

to the rifting that preceded continental drift and 

the opening of the Atlantic Ocean.

In West Africa, particularly Mauritania and 

Liberia, and in northern South America, in Brazil, 

Guyana, Surinam, and French Guiana, there are 

diabase dikes and dike swarms very similar in appearance and probably in age to the widespread 

diabase dikes in eastern North America. P. R. May

(1971, fig. 1) has pointed out that the orientation of 

all these dikes is such that if the continents surrounding the Atlantic Ocean were restored to a precontinental-drift configuration, these widely separated dikes would all seem to radiate from a 

common center located somewhere near the southeast coast of the United States and perhaps on the 

Blake Plateau.

In the Eastern United States, particularly in 

Pennsylvania, these diabase intrusive rocks are associated with deposits of iron, copper, and other 

minerals, but the relation of the diabase to the 

mineralizing process is obscure. In the Haile-Brewer 

area, South Carolina, diabase dikes cut gold-bearing rocks but appear to be younger than the mineralizing processes. Although the diabase dikes are 

not known to be related to the mineralization in 

South Carolina, they are nevertheless part of the 

geologic environment where investigations into the 

geologic, geochemical, and geophysical setting of the 

gold mines have been carried out.

Aeromagnetic data indicate that the dikes are 

even more abundant and widespread than previously 

believed from geologic reconnaissance mapping of 

mining areas. They may indicate areas of abundant 

pre-Mesozoic fracturing, or perhaps other features, 

as yet unrecognized, that might lead to favorable 

areas for ore deposits. Paleomagnetic studies offer 

a method for placing the diabase dikes in the HaileBrewer area more precisely into the context of the 

geologic and chronologic framework of Mesozoic 

rocks in eastern North America. For this purpose, 

many of the dikes have been sampled, and their 

magnetic properties and paleomagnetic-pole positions have been obtained. The results are summarized in this report. Figure 1 shows the location of

Cl
C2 SHORTER CONTRIBUTIONS TO GEOPHYSICS, 1979

EXPLANATION

Diabase dikes of Triassic and Jurassic 

age— Mainly in Piedmont province 

of Appalachian region; unmapped 

in many areas

Outcrops of Newark Group of Late 

Triassic and Early Jurassic 

age—Mainly sedimentary rocks but 

including intrusive stocks and sills in 

most areas, and interbedded lava in 

some northern areas

— —— Normal faults—At borders of areas 

of outcrop of Newark Group

Boundaries of major geologic 

provinces

FIGURE 1.—Sketch map of the Appalachian region of the Eastern United States, showing the location of the Haile-Brewer 

area, South Carolina, known occurrences of dikes of Triassic and Jurassic age, and areas of outcrop of the Newark 

Group. (Modified from King 1961.)

the Haile-Brewer area in South Carolina, the wide 

distribution of diabase dikes in the Appalachian 

region, and areas where the dikes cut sedimentary 

rocks of Late Triassic and Early Jurassic age.

MAGNETIC SETTING

A total-intensity magnetic map of part of South 

Carolina, including the area of the Haile and Brewer 

mines, is shown in figure 2, which is modified from 

a map by the U.S. Geological Survey (1970). The 

data were acquired by means of airborne instruments along flight traverses that were about 122 m 

above the ground, approximately 0.8 km apart, and 

oriented east and west. The Doppler system Was 

used for navigational location. The data, contoured 

relative to an arbitrary datum, show the totalintensity magnetic field in gammas.

The aeromagnetic map (fig. 2) shows numerous 

areas of anomalies that are closely spaced, moderately high in amplitude, linear, and positive; the 

anomalies reflect sharp, narrow variations in the 

intensity of the Earth's magnetic field. Many of
DIABASE DIKES IN THE HAILE-BREWER AREA, SOUTH CAROLINA C3

these linear positive anomalies are conspicuously 

alined, trend northwest, and have steep gradients 

that reflect sources having tops near the surface of 

the ground. The anomalies are clearly related to 

diabase dikes that crop out in the area. The flight 

lines trending approximately due east are particularly well oriented for revealing these narrow, linear magnetic anomalies. If the flight lines had been 

oriented parallel to the anomalies, their recognition 

would have been much more difficult for several reasons; for example, the anomalies might have been 

between flight lines and might not have been recorded, or the large differences in magnetic response 

between adjacent flight lines might have been interpreted as an instrumental or other technical difficulty.

The steep northwest-trending anomalies are not 

evident either on the northwest part of the map or 

on the southeast part, In a large part of the area 

shown on the magnetic map (fig. 2) centered near 

lat 34°30' N., long 80°45' W., the level of magnetic 

intensity is so great that the magnetic contrast due 

to the linear anomalies is lost. The geologic map of 

the Haile-Brewer area shows that the Liberty Hill 

quartz-monzonite pluton is in this area (fig. 3) and 

that it is cut by diabase dikes, at least locally and in 

the peripheral parts of the pluton. Apparently the 

magnetic intensity of the quartz monzonite is nearly 

the same as that of the diabase dikes. The highintensity magnetic anomalies in the southeastern 

part of the map area near lat 34° 15' N., long 80°37' 

30" W. also obscure the dike anomalies. There, 

broad northeast-trending anomalies coincide with 

a steep gradient in gravity data and may reflect 

faulting in subsurface rocks (Popenoe and Bell, 

1975). Strong linear northwest-trending magnetic 

anomalies have been recognized southeast of the 

area shown in figure 2; these anomalies have been 

interpreted as reflecting diabase dikes deeply buried 

beneath Coastal Plain sedimentary rocks (Popenoe 

and Zietz, 1977).

The widths of the northwest-trending linear aeromagnetic anomalies indicate tabular magnetic 

sources, which are inferred to be wider or less 

steeply dipping than field experience and reconnaissance mapping show the diabase dikes to be. In 

order to locate the magnetic anomalies as precisely 

as possible on the ground and to confirm that the 

anomalies overlie diabase dikes, as inferred, a 

ground-magnetometer survey was made using truckmounted equipment. Traverses were made along 

roads that crossed the anomalies shown by the airborne survey. The equipment, described by Zablocki 

(1967), consists of an encapsulated flux-gate magnetometer suspended from 3 to 4.6 m above the 

ground on a boom behind the vehicle. Kane, Hairwood, and Hatch (1971) used similar equipment in 

New England to test and map magnetic anomalies 

previously located by airborne surveys.

The results of the ground traverses in South Carolina were similar to the results in New England 

and indicated that the sources of several anomalies 

were diabase dikes not previously discovered. In 

addition, the ground traverses showed that in a few 

places where data from airborne instruments indicate a broad anomaly, the ground traverse shows 

many small anomalies not evident in the data from 

the airborne survey (fig. 4). These smaller anomalies in the ground data commonly seem to result 

from closely spaced thin dikes, which are not indicated as individual anomalies in data from the 

airborne-magnetometer survey. In Meriwether 

County, Ga., a single linear magnetic anomaly detected by airborne methods proved to be as many as 

four distinct diabase dikes when studied at ground 

level (Rothe and Long, 1975). In New England, 

Kane and others (1971) found that airborne equipment could not detect single rock units having 

thicknesses of less than about 15 m.

By means of a two-dimensional technique, magnetic profiles were calculated to test the assumptions 

that broad magnetic anomalies result from closely 

spaced thin dikes; a small part of profile A—A' 

in figure 4 was used as a model. The model, shown 

in figure 5, consists of tabular bodies simulating 

diabase dikes ranging from 7.6 to 30.5 m in thickness, extending an infinite length perpendicular to 

the profile, dipping at 80° W. or 80° E., extending 

to an infinite depth, and having parallel contacts. 

The magnetic properties used to calculate the profiles were chosen to be representative of all the 

known diabase dikes in the Haile-Brewer area and 

were in some cases averages of as many as 37 dikes. 

Two profiles were calculated, at 4.6 m above the 

ground and at 122 m, and they were compared with 

the observed profiles obtained from the airborne and 

truck-mounted magnetometers.

The results, illustrated in figure 5, show calculated profiles that resemble closely the observed profiles. The results suggest that many of the linear 

magnetic anomalies shown on the aeromagnetic map 

(fig. 2) likewise may represent an unknown number 

of dikes of various thicknesses and spacings, all 

trending at any particular location in nearly the 

same direction. On the aeromagnetic map (fig. 2), 

all the anomalies that have identifiable diabase-like 

outcrops are shown as a dike or dike swarm. In
C4 SHORTER CONTRIBUTIONS TO GEOPHYSICS, 1979

80°37'30" 

34°40'-

Index map showing location 

of Camden-Kershaw area

-'\A •''. ^ ^\''V^l^-^\^^\^^<^^s-^^'"^^^

Approximate boundary 

of aeromagnetic survey

34=15' 

80°52'30" 80°37'30"

FIGURE 2.—Aeromagnetic map of the Camden-Kershaw area, north-central South Carolina. (Modified from U.S. Geological Survey, 1970.)
DIABASE DIKES IN THE HAILE-BREWER AREA, SOUTH CAROLINA

22'30" 80°15'

C5

34W

76-20

A'

EXPLANATION

Magnetic contours—Showing total intensity magnetic field of the earth in 

gammas relative to arbitrary datum. Hachured to indicate dosed areas of 

lower magnetic intensity, dashed where data are incomplete. Contour 

intervals are 20 and 100 gammas

Flight path—Showing location and spacing of data

NOTE—Aeromagnetic survey flown 122 m above ground, 1967

Linear magnetic anomaly associated with diabase dike or inferred to be 

associated with diabase dike or dike swarm—A, B, 676, etc. refer to dike 

or dike swarm discussed in text and listed in table 6

Site of one or more drill cores for paleomagnetic studies—Showing number 

listed in table 5

Truck-mounted magnetometer traverses and aeromagnetic profiles shown 

in figure 4

i i i

10 15 20 KILOMETERS

10 MILES

FIGURE 2.—Continued.
C6 SHORTER CONTRIBUTIONS TO GEOPHYSICS, 1979

34°45' 81-00* 80M5' 35°00'

34°00' 80-30' 34-15' 80°15' 

DESCRIPTION OF MAP UNITS

80-00'

GRAVEL, SAND, CLAYEY SAND, AND CLAY (HOLOCENE TO CRETACEOUS)—Coastal Plain deposits with 

Middendorf Formation (Upper Cretaceous) at the base 

overlain by younger upland deposits; deeply weathered, and 

much redistributed by leaching, colluvial and aeolian processes. 

Middendorf Formation probably absent where less than 50 

feet thick

DIABASE (TRIASSIC AND JURASSIC)—Black to dark-gray 

dikes from less than 0.3 m to 342 m thick; numerous dikes in 

Kershaw County projected on the basis of close-spaced airborne 

and ground geophysical data

CONGLOMERATE, SANDSTONE, SHALE, AND CLAYSTONE (TRIASSIC)—Various shades of red, brown, purple, 

and gray undif ferentiated. Conglomerates in southernmost 

outcrops contain many fragments of argillite, pbyllite, and 

schist derived from nearby sources in the Carolina slate belt

GABBRO (UPPER PALEOZOIC)—Coarse-grained, dark, 

divine-bearing, grades to diorite locally, noritic in part. Includes the Dutchmans Creek Gabbro of McSween (1972)

QUARTZ MONZONITE (BIOTITE QUARTZ MONZONITE, 

GRANODIORITE, TONALITE, AND GRANITE) (CARBONIFEROUS)—Pink and gray porphyritic, coarse-grained, includes fine-grained and subporphyritic facies; commonly with 

abundant inclusions near contacts

GRANITOID ROCKS UNDIVIDED (LOWER PALEOZOIC TO 

UPPER PRECAMBRIAN)—Includes the Great Falls granitic 

phiton of Fullagar (1971) and quartz porphyry in Lancaster Co.,S.C.

CAROLINA SLATE BELT UNDIFFERENTIATED (PALEOZOIC AND UPPER PRECAMBRIAN)—Argillite, tuffaceous 

argillite, and graywacke, includes felsic and mafic volcaniclastic rocks and volcanic flows. Metamorphic rocks, predominantly in greenschist or lower greenschist facies. North

FIGURE 3.—Geologic map of the Haile-Brewer area, South Carolina. (Modified from Bell and Popenoe, 1976.)
DIABASE DIKES IN THE HAILE-BREWER AREA, SOUTH CAROLINA C7

80C 30' 35°15' 80" 15'

s Geology compiled from Overstreet and 

Bell (1965 a. b); Stuckey (1958); 

Randazzo. Swe and Wheeler 

(1970); Waskom and Butler (1971); 

McSween (1972); Nystrom (1972); 

and others

CORRELATION OF MAP UNITS 

QKu Holocene to 

Cretaceous

Carolina 

slate belt

mg

.•amJurassic and

Triassic

Paleozoic

Paleozoic and(or) 

Precambrian

———— Contact—Dotted where concealed

—=-|j—— Fault—Dashed where largely a shear zone; dotted 

where concealed or projected on geophysical 

data. U, up thrown side; D, downthrown side

——|—>• Major anticline—Dashed where projected

FV Bearing and plunge of fold axes in tightly folded 

rocks

Strike and dip of beds—

->& Inclined

-*- Vertical

Strike and dip of foliation—. 

_£ Inclined

-*- Vertical

J^J Strike and dip of foliation— 

i, inclusion in igneous rock

Strike and dip of fracture cleavageLittle or no recrystallization in plane of cleavage

-cf5 Inclined

-fr- Vertical

-£> Bearingvmd plunge of lineation—

Variety of linear feature shown by letter; 

c, crinkles on bedding, foliation, or cleavage; 

x, intersection of bedding and cleavage

5? Mine, mining area, or prospect 

4___4' Line of section shown in Bell and Popenoe (1976)

34°30' 79-45' 34-45' 79-30' 

DESCRIPTION OF MAP UNITS

of the Jonesboro fault extended, includes the McManus Formation of Conley and Bain (1965)

MICA GNEISS (PALEOZOIC AND UPPER PRECAMBRIAN)—Layered biotite gneiss and biotite schist, hornblende 

gneiss and hornblende schist with granitic layers common. 

Probably equivalent to large parts of the Carolina slate belt 

north of the Jonesboro fault extended except the metamorphic 

grade is almadine-amphibolite

ARGILLITE AND SLATE (LOWER PALEOZOIC)—Gray 

and greenish-gray, thinly bedded and laminated argillite and 

slate

VOLCANICLASTIC ROCKS (LOWER PALEOZOIC)—Tuffs 

and flows are common near Kershaw. Muscovite, chlorite, 

phyllite, and muscovite-quartz schist, largely felsic but with 

some interbedded mafic units. Probably equivalent, at

least in part, to the Wildhorse Branch and Persimmon Fork 

Formations of Secor and Wagener (1968)

AMPHIBOLITE (LOWER PALEOZOIC)—Dark-green, gray, 

and black amphibolite, includes some hornblende schist and 

hornblende gneiss, diorite, and metagabbro

GRANITOID GNEISS (LOWER PALEOZOIC AND UPPER 

PRECAMBRIAN)—Undivided granitoid gneisses, gneissic 

granites, and schists characteristic of the Charlotte belt

HORNFELS AND CONTACT METAMORPHIC ROCKS—Includes dark saccharoidal rocks at the contact of the Liberty 

Hill and Pageland plutons; biotite gneiss with some sericite 

schist adjacent to the Lilesville pluton. Around the Liberty 

Hill pluton mapped largely on the basis of geophysical data

INTENSELY SILICIFIED ROCKS—Vicinity of the Brewer 

mine; contains massive topaz locally

FIGURE 3.—Continued.
'C8 SHORTER CONTRIBUTIONS TO GEOPHYSICS, 1979

Part of profile

shown in figure 5

76-B

Data from airborne magnetometer

Data from truck-mounted magnetometer

1200-

800-

400-

0

B

B'

1600-'

1200-

800-

400-

0

Data from airborne magnetometer

Data from truck-mounted magnetometer

500 1000 1500 METERS

I I I I I 

0 1000 2000 3000 4000 FEET

EXPLANATION

76-B

Diabase dike—Sotid symbol indicates outcrop, number indicates paleomagnetic sample site 

included in table 5; open symbol indicates location projected from nearby outcrop or inferred from 

aeromagnetic data

FIGURE 4.—Comparison of profiles obtained by means of an airborne magnetometer carried at 122 m elevation 

with profiles obtained by means of a truck-mounted magnetometer. Locations of profiles are shown on figure 

2.
200-i

100-

0—

DIABASE DIKES IN THE HAILE-BREWER AREA, SOUTH CAROLINA C9

Calculated magnetic profile at 122 m elevation

Observed magnetic profile from airborne 

magnetometer at 122 m elevation

600—1

500^

400-

300-

200-

100-

o—

100 -I

Calculated magnetic profile at 4.6 m elevation

Observed magnetic profile 

obtained by means of a 

truck-mounted magnetometer 

at 3-4.6 m elevation

Simulated geologic profile (part of profile A-A' shown in figure 4) striking N. 60° E., showing dikes dipping 80° E. or 80° W. 

Dikes are 7.6,15.2, or 30.4 m thick and are of infinite length and depth. Magnetic properties used are: magnetic vector with 

azimuth of 84°, inclination 25°, and intensity 0.0027 emu (electromagnetic unit). Con version 2.7 X 10-6 A/m 

(2.7 X 10-3 emu/cc)

500

I

1000 METERS

500 1000 1500 2000 2500 3000 FEET

FIGURE 5.—Two-dimensional magnetic profiles of a simulated geologic profile calculated for 4.6 m and 122 m

elevation.

addition, all comparably long anomalies are shown 

as a dike or dike swarm, even though no outcrop of 

diabase has been found. Other less pronounced or 

less continuous anomalies that may also be thin 

diabase dikes are not identified on figure 2. All these 

anomalies indicate that the total number of diabase 

dikes in the area is very much larger than previously known.

GEOLOGIC SETTING

The geologic map of the Haile-Brewer area (fig. 

3) shows that diabase dikes seen in outcrop or interpreted from the aeromagnetic map are not uniformly distributed. The dikes tend to be particularly 

abundant in parts of Kershaw and Lancaster 

Counties and along the Wateree River near the
CIO SHORTER CONTRIBUTIONS TO GEOPHYSICS, 1979

boundary between Kershaw and Fairfield Counties. 

There the dikes are cutting metamorphosed volcaniclastic rocks and argillites of the Carolina slate belt 

and to a lesser extent the coarse-grained Liberty Hill 

pluton, which intrudes rocks of the slate belt. The 

Pageland pluton, however, is cut by several diabase 

dikes, including a dike more than 300 m thick.

Included within the volcaniclastic unit in the 

Haile-Brewer area are sparse dark metamorphosed 

dikes, perhaps originally of andesitic or basaltic 

composition, which are not reflected in the aeromagnetic data. Neither were they detected by the 

truck-mounted magnetometer, perhaps, because they 

are thin, are discontinuous in outcrop, and are probably low in magnetite content.

Figure 3 shows diabase dikes extending as far as 

the limit of aeromagnetic data into areas where 

Coastal Plain sedimentary rocks are at the surface. 

Diabase dikes in the Haile-Brewer area are not 

known to cut either Cretaceous or younger sedimentary rocks. The strong magnetic anomalies extending from known diabase in areas of crystalline 

rocks into areas covered by rocks of the Coastal 

Plain reveal that the dikes extend beneath the overlying sedimentary rocks, where their orientation and 

extent can be interpreted from the magnetic data.

DIABASE DIKES

The dikes in the Haile-Brewer area are all olivinebearing tholeiitic diabase that is commonly intergranular or subophitic, is less commonly porphyritic, 

and contains feldspar or olivine phenocrysts. Megascopic variations in the dikes are mainly variations 

in grain size, texture, and abundance of olivine and 

feldspar phenocrysts. The average modal analysis of 

16 thin sections of diabase from South Carolina reported by Chalcraft (1976) is given as follows:

Volume 

(percent)

Alteration products

Total

53.3

30.9

11.2

2.5

Trace X 3.3

101.2

1 Average of 13 thin sections containing more than traces of alteration products.

In the field, the black to dark-gray diabase commonly has a weathering rind of characteristic 

orange-brown soft residuum. Many of the dikes 

weather spheroidally, and cores of the weathering 

spheroids, called core stones, are displaced as float

and are commonly found scattered on the ground 

surface below the dike outcrop. In some thin dikes, 

a columnarlike jointing is perpendicular to the dike 

walls, and some dikes have distinct fine-grained 

chilled margins.

No systematic thickness measurements of diabase 

dikes have been made; thus, neither the average 

thickness nor the most common thickness is known. 

However, the thickness of a dike sampled in the 

present study was measured or estimated wherever 

the dike contacts could be at least approximately 

located. The thicknesses range from a few centimeters to more than 300 m. The most common thicknesses appear to be about 3 m and about 15 m. The 

largest dike, carefully measured by Steele (1971) 

where it is exposed in a deep road cut in Lancaster 

County, is 1,123 feet (342.3 m) thick. Dikes of this 

thickness appear to be very rare. Several artificial 

outcrops, perhaps as long as 100 m, were found 

where as many as nine dikes ranging in width from 

less than 15 cm to as much as 22 m crop out. Where 

several thin dikes are close together, correlation of 

specific dikes from outcrop to outcrop is complicated 

by the similarity in appearance of the dikes, their 

nearly parallel strike, and their apparently anastomosing character.

Steele (1971), as a result of his studies of the 

thick dike in Lancaster County, concluded that the 

unusual thickness of that dike resulted from two 

injections of magma. The bifurcated character of 

the long aeromagnetic anomaly associated with the 

dike may indicate that, indeed, more than one dike 

did coalesce to produce an exceptionally thick dike. 

The dike probably coalesced before the magma in 

either dike cooled, because no textural indication of 

chilling between them is obvious.

In general, the diabase dikes in the Haile-Brewer 

area have the conspicuously oriented trend of about 

N. 45° W. that is characteristic of these dikes in the 

southeastern piedmont (fig. 1). However, the strike 

of individual dikes is locally varied. The dip of the 

dikes is commonly vertical, or nearly so.

In the Wadesboro Triassic and Jurassic (?) basin 

a short distance northeast of the Haile-Brewer 

area, diabase dikes trending northeast, as well as 

those trending northwest, appear to be common 

(Randazzo, Swe, and Wheeler, 1970; Randazzo and 

Copeland, 1976). Some of the northwest-trending 

diabase dikes are cut and offset by faults that parallel the southeastern border faults of the Wadesboro 

basin. At least two episodes of diabase-dike emplacement in the Wadesboro basin seem to be clearly indicated ; therefore, several episodes of dike emplace-
DIABASE DIKES IN THE HAILE-BREWER AREA, SOUTH CAROLINA Cll

ment in the nearby Haile-Brewer area might also 

be expected, but they have not been recognized.

Although diabase dikes similar to dikes in the 

Triassic and Jurassic basins have been recognized 

and mapped in the Haile mine and elsewhere in the 

Haile-Brewer area, the airborne-magnetometer survey shows that the dikes are very much more numerous in the deeply weathered rocks than previously 

realized. Most commonly, the dikes crop out in 

stream beds, where dense unweathered diabase 

makes an obstruction that diverts the course of the 

stream. These obstructions and diversions produce 

local topographic expressions that reveal the trend 

of the dikes. Other outcrops along ridges or on interfluvial areas commonly are poorly exposed pavements or consist of clusters of boulders or cobble^- 

size fragments. Bouldery ridges and trails of float 

cobbles are clear indications in areas of residual 

weathering that at least one diabase dike is present 

in the immediate vicinity, but the true nature and 

attitude of the dike or dikes are generally concealed. 

Detailed mapping of the dikes is impeded not only 

by deeply weathered country rocks in which the 

dikes are found but also by the common deeply 

weathered condition of the dikes themselves and by 

the heavily vegetated countryside. In these areas, 

the aeromagnetic map is particularly helpful as an 

aid to mapping.

In petrographic and chemical studies, Ragland, 

Rogers, and Justus (1968), Weigand and Ragland 

(1970), and Smith, Rose, and Lanning (1975) have 

divided the Triassic diabase into groups differing in 

chemistry, probable origin, and age. Weigand and 

Ragland (1970) separated eastern North American 

diabase dikes into three varieties. These are an 

olivine-normative diabase, a high-Ti02 group, and a 

Iow-Ti02 group. They further divided the high-Ti02 

rocks by recognizing a subgroup of dikes having a 

high iron-oxide content. Smith and others (1975, 

p. 945) found that in Pennsylvania, copper and 

titanium contents were reliable indicators of diabase 

type. They divided the diabase intrusive rocks into 

three groups—Rossville, York Haven, and Quarryville types—having differing mineralogy and chemistry and corresponding approximately to the three 

varieties of Weigand and Ragland (Smith and 

others, 1975, p. 949-950). The Quarryville type corresponds to the olivine-normative variety, the York 

Haven type corresponds to the high-Ti02 quartznormative variety, and the Rossville type corresponds to the Iow-Ti02 quartz-normative type. Table 

1 gives the chemical composition, trace-element content, and normative mineralogy of eight oriented

samples of the 342.3 m-thick dike in Lancaster 

County that were collected for magnetic studies. 

Most samples are quartz normative, but those collected near the margins are olivine normative. Table 

2 summarizes the magnetic properties, measured 

during this study, of the eight samples for which 

chemical data are presented in table 1. Steele (1971) 

gave detailed analytical and petrographic data for 

95 samples from this same dike.

The magnetic properties closely reflect the normative mineralogy. Both the induced magnetism and 

the remanent magnetism are distinctly lower near 

the western margin than in the central part of the 

dike. The sample from near the eastern margin of 

the dike is similar to the sample from the western 

margin in content of normative olivine, magnetite, 

and ilmenite; the magnetic properties are also> similar, except that the remanent magnetism of the 

sample from the eastern margin is unaccountably 

high.

Using K-Ar age determinations of samples of 

Triassic diabase intrusive rocks collected in Connecticut and New Jersey, Armstrong and Besancon 

(1970) attempted to test the hypothesis that more 

than one period of intrusion occurred in the Newark 

Group rocks. They reviewed previous work of a 

similar nature that seemingly indicated that the ages 

of the volcanic rocks in the Newark Group (Upper 

Triassic and Lower Jurassic) are about 190 to 195 

m.y. (million years). Armstrong and Besancon 

found that K-Ar age determinations on diabase dikes 

gave results that were consistently and statistically 

older than the rocks the dikes cut. They (1970, p. 25) 

came to the conclusion that the diabase dikes in 

eastern North America are not suitable for "defining 

a point on the geologic time scale," either because of 

a loss of Ar from low-grade metamorphic rocks: at 

zeolite or prehnite-pumpellyite facies conditions or 

because of extraneous excess Ar.

SAMPLING PROCEDURES

The diabase dikes were sampled for study of 

paleomagnetic properties, beginning with the large 

dike in Lancaster County in 1969; a few dikes were 

sampled in 1975, and most of the remaining dikes 

described in this report were sampled in the spring 

of 1976. All the samples except those collected in 

1969 were obtained by drilling outcrops using the 

methods described by Doell and Cox (1965) and 

using equipment similar to that they described.

The nature of the outcrops in the Haile-Brewer 

area and the general thinness of the dikes required
C12 SHORTER CONTRIBUTIONS TO GEOPHYSICS, 1979

TAJBLE 1.—Major- and minor-oxide composition, trace-element content, and normative minerology of a large diabase dike,

Lancaster County, S.C.

[Rapid rock analysis by P. L. Elmpre, Gillison Chloe. James Kelsey, Lowell Artis, Hezekiah Smith, and J. L. Glenn, all of the U.S. Geological

i across the dike; sample 677 

leadered where not calculated]

Survey. Spectrographic analysis by J. L. Harris, U.S. Geological Survey. Samples are approximately equally spaced across the dike; sample 677 

is near the west margin, and sample 683 is near the east margin of the dike. L, present but below limit of detection; I

Sample __ _ _____ __ _ _ _ 677 €76 678 679 680 681 682 683

Major- and minor-oxide compositions

[Rapid rock analyses, in weight percent]

SiO2 _ _ __ -_ _ _

A1203 __ ________ _

Fe.03 _ __ _ ___

FeO _ __ __ _ _ _ MgO ____ _ ___

CaO _ __ _ ______ _

Na2O _ _ ___

K20 _ _ _ ____ _

H2 0+ __ __ ___ __

H20- __ _ ___________

Ti02 _ _ _ __ ___ _ _

P205 __ __ _ _

MnO

C02 _ _ _ ____ __ __

Total _

. - 50.0

. — 18.3

. - 1.2

7 1

. - 6.5

190

9 4

.62

- - .89

.21

.56

.05

.15

<.05

100

50.5 

17.3 

2.5 

7.8 

5.5 

10.4 

2.5 

.91 

.82 

.28 

.76 

.10 

.17 

<.05

100

51.1 51.0 

17.0 17.2 

2.4 2.0 

7.9 7.7 

5.5 5.8 

10.5 10.9 

2.5 2.4 

.99 .87 

.74 .97 

.26 .23 

.76 .67 

.10 .09 

.17 .18 

<.05 <.05

100 100

51.4 

16.9 

2.3 

7.4 

6.0 

10.7 

2.4 

.90 

.63 

.25 

.72 

.09 

.19 

<.05

100

51.0 

17.0 

2.5 

7.8 

5.8 

10.4 

2.2 

.87 

.76 

.44 

.76 

.10 

.19 

<.05

100

51.2 

17.2 

2.9 

6.8 

6.1 

11.2 

2.4 

.85 

.12 

.25 

.65 

.09 

.18 

<.05

100

50.4 

17.9 

1.2 

7.6 

6.2 

11.7 

2.2 

.66 

.95 

.25 

.60 

.07 

.15 

<.05

100

Trace-element contents

[Spectrographic analyses, in parts per million]

Ag _ _ __ _ _

Ba

Co ___ ____ — _

Cr ____ ______ _ _

Cu ______ __ ___ ___

Mo _ __ _ _ _

Ni ____ __ __ _

Pb

Sc _____ ______ _

Sr _ _ _____ ______

V _ _ _ _ __ _

Y

Zr ________ _____ __

Ga _____ __ ______

Yb _ _________________

L

150

70

500

70

5

150

3

70

150

200

30

50

10

3

L 

150 

30 

200 

100 

5 

100 

10 

70 

200 

200 

30 

70 

15 

3

L L 

200 200 

50 30 

300 200 

100 70 

5 5 

100 100 

7 3 

70 70 

200 200 

200 200 

50 30 

100 70 

15 10 

5 3

L 

200 

30 

200 

100 

5 

100 

3 

70 

200 

200 

30 

70 

10 

3

L 

200 

50 

200 

100 

5 

100 

3 

70 

200 

200 

50 

100 

10 

5

L 

100 

20 

150 

100 

3 

70 

3 

30 

150 

100 

20 

30 

10 

2

L 

150 

30 

300 

70 

5 

100 

3 

50 

150 

150 

30 

70 

15 

3

CIPW mineral norms

[In weight percent]

Quartz _ __ _ _

Orthoclase

Albite

Anorthite

Diopside _ _

Wollastonite _

Enstatite

Ferrosalite _ _ _

Hypersthene _ _ __

Enstatite - _____

Ferrosalite

Magnetite _ _ _ _

Ilmenite __ _ _ _ _ __

Apatite _ _ __ _

Olivine _ _ _ _ _

Forsterite _ _

Fayalite _ __ _ _

Calcite _ _ _ _

Total

3.67

20.34

37.40

17.67

(9.02)

(5.08)

/q K7\

U KQ

(6.80)

I A 7Q\

1.74

1.06

12

5.41

(3.04)

(2.36)

.12

99.11

1.01 

5.42 

21.30 

33.53 

14.35 

(7.29) 

(3.87) 

(3.19) 

18.13 

(9.93) 

(8.20) 

3.65 

1.45 

.24

.11

99.18

1.30 .99 

5.87 5.15 

21.22 20.34 

32.33 33.65 

15.58 16.12 

(7.91) (8.19) 

(4.16) (4.38) 

(3.52) (3.55) 

17.68 18.28 

(9.58) (10.09) 

(8.10) (8.19) 

3.49 2.90 

1.45 1.28 

.24 .21

.11 .11

99.26 99.04

1.79 

5.34 

20.37 

32.79 

16.01 

(8.17) 

(4.55) 

(3.30) 

18.03 

(10.44) 

(7.59) 

3.34 

1.37 

.21

.11

99.38

2.81 

5.17 

18.72 

34.14 

13.77 

(7.01) 

(3.79) 

(2.98) 

19.18 

(10.74) 

(8.44) 

3.65 

1.45 

.24

~~11

99.24

1.57 

5.04 

20.36 

33.74 

17.16 

(8.80) 

(5.18) 

(3.19) 

16.24 

(10.06) 

(6.19) 

4.22 

1.24 

.21

.11

99.89

3.91 

18.68 

37.14 

16.68 

(8.48) 

(4.57) 

(3.63) 

19.18 

(10.70) 

(8.49) 

1.74 

1.14 

.17 

.29 

(.16) 

(.14) 

.11

99.05

that special care be taken to insure that the rock 

drilled was in its original place and not rotated or 

moved by erosion or other disturbances. Outcrops of 

diabase in the beds of streams, along the shores of 

Wateree Lake, and in deep road cuts where both 

contacts between dike and country rock are exposed

gave the greatest confidence that the dikes were suitable for sampling. Other outcrops on bouldery ridges 

or flat pavement outcrops inspired less confidence 

that they were undisturbed. At these places, it was 

not always possible to1 determine that an outcrop 

was not a large spheroidal weathering boulder
DIABASE DIKES IN THE HAILE-BREWER AREA, SOUTH CAROLINA C13

TABLE 2.—Magnetic properties and normative magnetite and ilmenite contents of a large diabase dike, Lancaster County, S.C.

[wt. percent, percent by weight. K, Ji, Jr, and Jr + Ji are in 1Q-4 emu (electromagnetic units)/cm3. Jfc0.554K. Koenigsberger ratio: Q—Jr/Ji}

Sample

677 __ __ _.

676 __ _ __

678 _

679 _ _

680 _

681

682 __ _

683

Normative 

magnetite 

plus 

ilmenite 

(wt. 

percent)

2.80

5.10

. _ 4.94

4.18

4.71

5.10

5.46

2.88

Proportions, 

normative 

magnetite 

plus ilmenite

magnetite 

(percent)

62

72 

71 

69 

71 

72 

77 

60

ilmenite 

(percent)

38 

28 

29 

31 

29 

28 

23 

40

Magnetic 

susceptibility, K

0.67 

17.90

14.60 

10.70 

15.00 

15.8 

13.4 

10.2

Induced 

magnetization, Ji

0.37 

9.91 

8.08 

5.92 

8.31 

8.75 

7.42 

5.65

Remanent 

magnetization, Jr

6.06 

9.96 

6.88 

3.36 

9.14 

3.40 

3.04 

19.0

Koenigsberger 

ratio, Q

16.37 

1.01 

.85 

.57 

1.10 

.39 

.41 

3.36

InclinaTotal tion of 

magnetiza- reman en t 

tion, magnetiJr + Jt zation 

( degrees )

6.43 

19.87

14.96 

9.28 

17.45 

12.15 

10.46 

24.65

7 

20 

20 

44 

38 

-25 

20 

18

slumped from its original position or that the outr 

crop was not part of a large mass of colluvium that 

had 'slumped or slid as a unit. Probably some such 

disturbed outcrops were sampled and may be the 

cause of unrealistic results and a source of error.

An attempt was made at each site location to obtain at least three drill cores spaced about a meter 

apart. At some sites, the outcrop of diabase was too 

small to be conveniently drilled more than once or 

twice, or the diabase proved to be too deeply 

weathered to provide satisfactory samples. At other 

locations, only the fine-grained, chilled margin of the 

dike proved to be sufficiently unweathered to drill. 

Cores were obtained from a total of 39 sites. Of 

these, only 27 were used in statistical calculations 

and measurements of remanent magnetism, for the 

various reasons just mentioned. All sites drilled, 

however, are shown on figure 2.

In the laboratory, the drill cores were cut into as 

many 23-mm-long specimens as possible. Usually 

one to five specimens were cut from each core, and 

the total number of specimens involved is 163. These 

were all measured and compared to obtain a single 

direction and intensity of remanent magnetism for 

each core. Table 3 shows the hierarchy of names 

used in the sampling and statistical calculations.

TABLE 3.—Definition of terms used in the sampling hierarchy

Dike or dike swarm. Diabase dike or several closely spaced 

dikes associated with a linear magnetic anomaly on which 

there is at least one drilling site. Labeled "Dike A," "Dike 

B," etc.

Site. Outcrop of diabase suitable for drilling by means of a 

portable diamond drill and from which a drill core was 

collected. Labeled "76-1," "75-2," "676," etc.

Core or drill core. Drill core obtained at a site; 1-3 cores 

obtained at each site; each core 20-40 cm long. Labeled 

"a," "b," "c," etc. Label follows site designation.

Specimen. One to five 23-mm-long pieces cut from individual 

drill cores; magnetic properties were measured on these 

specimens. Labeled "A," "B," "C," etc. Label was added to 

site and core designations but is not included in tables.

LABORATORY PROCEDURES

Measurement of NRM.—In the laboratory, the 

specimens were given random sequential numbers, 

and their natural remanent magnetism (NRM) was 

measured. The instrument used and the procedures 

followed were the same as those described by Doell 

and Cox (1965). The data obtained from the spinner 

magnetometer were reduced, and the declination and 

inclination of the magnetic fields of the specimens 

were plotted by various computer programs (R. W. 

Bowen, R. R. Doell, and C. S. Gromnie, unpublished 

computer program, 1966).

Alternating-field cleaning.—The plot of the data 

from the spinner magnetometer showed that there 

is much scatter in the NRM of the specimens. In 

order to decrease the dispersion in the data not 

related to the paleomagnetic field, all specimens were 

subjected to an alternating field of 100 Oe (oersteds) 

to remove the extraneous magnetism. One hundred 

oersteds was chosen as the best level for cleaning all 

specimens, after specimens from several locations 

had been cleaned at incremental steps from 37 Oe 

to as much as 500 Oe. The 100-Oe level of cleaning is 

close to the 150-Oe level found to be satisfactory by 

Beck (1972) and deBoer (1967, 1968) for samples 

of diabase from Pennsylvania and New England.

Calculation of paleomagnetic-pole positions.—In 

order to interpret the data obtained, most researchers of paleomagnetism rely on parametric statistics for dispersion on a sphere (Fisher, 1953). In 

order to calculate a paleomagnetic-pole position, the 

variations inherent in the specimens have been averaged for each hierarchy in the sampling- program. 

The specimens from each site where at least three 

cores were obtained have been averaged to produce 

the mean declination and mean inclination of the 

NRM. These data together wtih the mean declinations and mean inclinations calculated after the 

specimens had been cleaned at 100, 200, and 300 Oe
C14 DIABASE DIKES IN THE HAILE-BREWER AREA, SOUTH CAROLINA

TABLE 4.—Results of spinner-magnetometer measurements on specimens of diabase dikes from the Haile-Brewer area, South

[D, declination, in degrees; I, inclination, in degrees; k, estimate of Fisher's (1953) precision parameter;

Latitude N. 

(degrees)

34.33

34.40

34.40

34.40

34.39

34.52

34.51

34.52

34.55

34.60

34.61

34.58

34.55

34.40

34.40

34.40

34.40

34.40

34.40

34.40

34.40

34.41

34.42

34.45

34.65

34.57

34.60

Site

Longitude W. 

( degrees )

80.67

80.72

80.72

80.72

80.69

80.59

80.59

80.57

80.60

80.59

80.60

80.56

80.53

80.81

80.82

80.82

80.81

80.83

80.83

80.83

80.83

80.85

80.85

80.86

80.50

80.60

80.60

No. of Natural remanent magnetism

No.

76-1

76-2, a

76-2, b

76-3, a

76-3, b

76-4, a

76-4, b

76-8

76-9, a

76-9, b

76-10

76-12, a

76-12, a

76-12, b

76-13

76-15

76-17

76-19, a

76-19, b

76-20

76-21

76-22, a

76-22, b

76-22, b

76-23

76-24

76-25

76-26, a

76-26, b

76-27

76-28, a

76-28, b

76-29

76-30, a

76-30, b

76-31

676

75-1

75-2, a

75-2, b

corep ———————— 

averaged D

3 18.9

355.5

354.8

50.6

41.3

341.7

__ 346.4

5 341.7

C)

_ __ 59.9

4 162.6

__ 10.3

8.2

2.1

4 9.6

4 13.2

4 15.1

__ 149.0

__ 200.7

4 319.2

6 87.3

__ 174.9

__ 184.8

__ 162.6

__ 178.5

4 161.3

3 115.0

__ 235.6 ( 1 )

3 197.5

__ 96.0

__ 100.3

5 102.9

__ 303.0

__ 145.3

5 52.6

9 7.6

__ 311.6

__ 77.2

__ 3.0

I

10.6

-7.1

-15.0

-20.6

-20.0

15.2

24.3

27.3

C)

14.0

-58.0

32.9

31.5

40.0

24.0

68.8

38.5

42.5

28.1

18.4

17.0

12.8

72.7

70.7

21.3

39.5

-15.2

9.8

16.5

29.5

26.6

-62.8

22.0

32.7

2.8

19.9

45.1

39.9

30.6

k

27.9

____

____

____

____

____

_

4.3

____

____

13.2

____

____

____

41.9

12.7

10.7

____

2.6

1.3

____

____

____

_ _

2.5

1.1

____

17.7

____

1.8

____

106.6

40.4

____

____

——

«95

23.8

____

____

____

____

____

41.6

____

____

26.2

____

____

____

14.4

26.8

29.5

____

_

72.7

__ __

____

____

____

____

74.4

0.0

____

___

30.2

____

___

85.6

____

7.4

8.2

____

____

——

1 Not measured.

are shown in table 4. Data from specimens, cleaned 

at 100 Oe, from sites on the same linear magnetic 

anomaly (fig. 2), and therefore presumably on the 

same diabase dike, have then been averaged to produce a mean virtual geomagnetic-pole (VGP) position for individual dikes. Data from sites on closely 

spaced thin dikes in a dike swarm have been combined and used to calculate a VGP for the dikes in 

that swarm. The paleomagnetic direction, paleopole 

position, and statistical parameters for each dike, 

calculated from data derived from specimens cleaned 

at 100 Oe, are shown in table 5. No correction for 

structural rotation or folding of the rocks in which 

the dikes are emplaced has been applied to the data.

RESULTS

The VGP calculated for each dike or dike swarm 

(table 5) results from combining data having various reliabilities. For instance, the calculated pole for 

dike A is a combination of data from three sites on 

an aeromagnetic anomaly (fig. 2) that extends about 

16 km in the volcaniclastic unit near the contact with 

the Liberty Hill pluton. The data from these three 

sites give conflicting results. One site, 76-10 (table 

4), is an outcrop in the bed of a stream; it has ample 

area for core drilling and yields significant statistical 

results. The second site, 76-9 (table 4), is a roadcut, 

0.32 km to the northwest, where only two cores were 

obtained; perhaps as a result of undetected disturbance by road builders, these two cores yield 

divergent results that are not significant for pole 

calculations. The third site, 76-13, is 2.74 km northwest of the second site. Although also an artificial 

exposure, it yields results that are within acceptable 

statistical limits but have a magnetic direction 

that is nearly 180° from that of site 76-10 on this
DIABASE DIKES IN THE HAILE-BREWER AREA, SOUTH CAROLINA C15

Carolina, untreated and after cleaning by subjection to alternating magnetic fields of intensities of 100, 200, and 300 oersteds

a95, radius of cone of confidence at 95 percent probability level, in degrees; Oe, oersted]

Magnetism remaining after cleaning at the indicated intensities

100 Oe

D

6.8

12.8

15.6

41.7

43.0

349.4

0.1

238.3

5.5

11.8

175.8

16.6

10.1

4.5

3.5

11.7

9.1

169.7

197.2

234.3

33.0

187.3

179.3

179.6

184.2

196.4

153.0

205.9

183.3

190.4

111.7

140.7

179.7

358.3

182.8

15.0

5.6

22.1

94.0

10.0

I

4.6

-12.4

-19.8

-26.4

-24.9

13.2

3.0

53.7

16.3

12.7

-24.4

33.1

27.2

32.4

20.2

60.1

32.4

44.4

28.0

66.0

63.9

13.4

61.0

62.1

14.0

52.0

47.6

11.0

11.3

6.7

21.8

21.0

-3.5

42.4

32.3

9.7

17.9

36.7

35.3

35.4

fc

81.4

~~2~2

~~3~6

1~2~6~8

158.8

39.4

~~3~2

2.5

~~2~2

1.4

5~673

2.0

3~2~0~4

30.1

——

«95

13.8

68.4

____

~5~6~6

~~8~2

7.3

14.8

~6~0~9

54.4

~82~3

0.0

16~6

~7~5~3

~4~.3

9.5

____

D

359.1

____

2~19".6

174.3

3~5~7~6

15.6

2.4

2645

10.4

19~9~8

157.4

182.0

162.2

167.8

175~2

16.8

Yf.8

101.0

11.4

200 Oe

I

-0.9

____

~39~8

~4~6

Y7~9

58.2

36.2

~64~8

68.2

~52~2

48.8

0.4

9.2

-11.9

25.2

5.2

~3~6~6

34.5

35.1

fc

101.3

____

~Y.6

____

5.2

~3~6~8

104.3

17.1

~Y.6

1.9

~Y.4

1.4

~2~3~.l

"l"6

Y5~7

----

«95

12.3

____

____

61.1

~2~0~6

7.5

22.9

YT"!

~~o~6

0.0

26.3

~~o~6

~2~4~6

____

____

- —

D

353.4

____

____

1~5~7~.6

____

__

184.4

3~4~0~8

22.3

336.2

3~0~2~8

343.7

209~6

198.9

194~5

____

____

____

114~5

1.1

300 Oe

I

-21.8

____

____

~5~7~6

____

20~6

Y3~4

46.3

50.8

~5~9~5

68.0

55.6

65.5

2.8

____

____

____

____

29.3

37.4

fc

5.9

____

"Y.4

5.8

Yf.7

15.4

5.3

~2~4

2.2

1.5

1.5

56.6

____

— —

a95

56.1

____

____

o.o

56.6

37.8

17.6

44.2

____

0.0

0.0

0.0

16.5

——

aeromagnetic anomaly. The reason the data are so 

divergent is not known, but it may be that unrecognized multiple dikes are present or that the aeromagnetic anomaly or some other factor has been misinterpreted. The consequences of combining data 

from these sites are reflected in a large radius of the 

cone of confidence for the paleomagnetic direction 

and a small precision parameter, k, for the VGP 

from this dike.

Dike B (fig. 2) is a 28.2-km-long segment of an 

aeromagnetic anomaly on which three sites were 

drilled. Suitable cores were obtained from only two 

of the sites, which were 2.09 km apart. The VGP 

obtained by combining data from all specimens from 

these two sites yielded a pole position having a small 

cone of confidence at the 95-percent level, a large 

precision parameter, k, and normal polarity. It seems 

likely therefore, at least for the distance between

the two sites, that this aeromagnetic anomaly results 

from a diabase dike for which the VGP is reliable.

Data from two sites on Dike C produced a reliable 

VGP with reverse polarity. The diabase drilled at 

the two sites, however, differs in lithology in both 

hand specimens and thin section. At one site, the 

rock is porphyritic and contains abundant feldspar 

phenocrysts, which in thin section are much clouded 

with opaque alteration products and calcite. The 

other site, in contrast, is a more typical nonporphyritic diabase. Apparently the appearance of the 

diabase changes along strike.

On Dike D, four sites were drilled, but only two 

sites provided the required cores and specimens that 

when combined met accepted reliability criteria. 

Dike 676 is the dike in Lancaster County that is 

more than 305 m thick. The data for this dike give 

a reliable VGP.
C16 SHORTER CONTRIBUTIONS TO GEOPHYSICS, 1979

TABLE 5.—Paleomagnetic directions and paleomagnetic pole positions for diabase dikes and dike swarms in the Haile—Brewer

area, South Carolina

[a95, radius of cone of confidence at 95 percent probability level; k, estimate of Fisher's (1953) precision parameter; Lat. and Long., latitude and 

longitude of the virtual geomagnetic pole (VGP); P, polarity; N, north-seeking (reverse) polarity; S, south-seeking (normal) polarity; 5m and 

5p, semiaxes of the confidence oval about the VGP]

Paleomagnetic direction

Dike 

(sites included)

A (76-9, 76-10, 76-13) _ __ _

B (75-2, 76-17)

C (76-19, 76-20) __ _

D (75-1, 76-12) _ _

676 _ _

E (76-22 to 76-30 inclusive) __ 

F (76-15) _ _ _ __

G (76-31) __ __ __ __ __ _

H (76-2, 76-3, 76-4) _

I (76-1) _______________________

Mean 

declination 

(degrees)

6 

12 

190 

13 

3 

182 

11 

15 

16 

7

Mean 

inclination 

(degrees)

23 

36 

43 

32 

16 

19 

60 

9 

-12 

5

a95

52 

15 

17

8 

8 

14 

7 

4 

23 

14

k

2 

25 

29 

116 

49 

5 

158 

320 

9 

81

Paleopole position

Lat. N. 

( degrees )

67.13 

72.18 

29.32 

69.37 

63.44 

45.37 

78.76 

57.34 

46.70 

57.37

Long. E. 

(degrees)

83.55 

58.48 

88.38 

61.49 

91.45 

96.03 

331.07 

70.62 

75.24 

86.73

p 5m 5p 

( degrees ) ( degrees )

S

S 

N 

S 

S 

N 

S 

S 

S 

S

56 

18 

21 

9 

8 

15 

11 

4 

23 

14

30 

10 

13 

5

4 

8 

8 

2 

12 

7

EXPLANATION

A. Dike, weathered, probably about 14 m thick; core stones sampled; fine to very fine grained; abundant olivine, some much altered; opaque minerals conspicuous; intergranular texture.

B. Dike, probably about 15 m thick; fine to medium fine grained; olivine bearing, partly altered; opaque minerals sparse.

C. Dike, outcrop in road gutter and stream bed; no contacts seen; in part porphyritic; in thin section, possible relict olivine; pyroxene altered; all 

plagioclase much clouded with opaque alteration material; some clots of calcite with very fine quartz; sparse chlorite; opaque minerals abundant.

D. Dike, outcrops as bouldery ridge and on flood plain; about 23 m thick; fine grained; olivine sparse, altered; intergranular texture.

676. Dike, sampled in deep road cut; about 342 m thick; described by Steele (1971); contains as much as 5 percent olivine and 4 percent 

opaque minerals; intergranular texture.

E. Group of closely spaced thin dikes; most range in thickness from 0.6 m to 2.7 m but group includes one dike 21 m thick; most dikes are 

well exposed at location site; some have abundant transverse joints; dike trends range from N. 3° W. to N. 27° W.

F. Dike, weathered outcrops are crumbly; fine to medium grained; abundant large unaltered olivine; abundant opaque minerals both fine and very 

fine; intergranular texture.

G. Dike, weathered; core stones sampled; strikes N. 30° W., dips vertically; abundant transverse joints; about 3 m thick.

H. Group of 3 closely spaced thin dikes, 1 m, 3 m, and 3.4 m thick, respectively; crops out in road gutter; some dikes show unweathered very fine 

grained chilled margins and have coarser grained weathered interiors.

I. Dike, outcrop in road cut, weathered; core stones sampled.

In table 5, E represents a dike swarm of as many 

as nine closely spaced dikes ranging in thickness 

from 0.6 m to 2.7 m; the swarm also includes one 

dike about 21 m thick. Because these dikes are so 

closely spaced and because they have similar trends 

and similar appearances, they have been considered 

as if they were the result of a single intrusion of 

magma along closely spaced fractures. The paleomagnetic direction that results from combining 

data from these sites meets the standards for reliability; the data provide a cone of confidence within the 95-percent probability level at 14°. The dike 

swarm, however, has a reverse, north-seeking, 

polarity.

Data are used from only one site on each of the 

dikes F, G, and I, but the results of paleomagneticdirection and paleopole-position calculations give 

small cones of confidence and large precision parameters, k.

In table 5, H represents a dike swarm of as many 

as six dikes, ranging from about 0.2 m to about 

3.6 m in thickness, emplaced in the coarse-grained 

Liberty Hill pluton. Only three of the dikes, however, 

were suitable for core drilling. Possibly one of these 

thin dikes may be represented by a small anomaly in 

each of the aeromagnetic profiles (fig. 4, southwesternmost open-dike symbol in each profile) obtained by means of a truck-mounted magnetometer.

The VGP's calculated for the dikes designated A 

through I and 676 seem to fall into three groups on 

the basis of their positions and polarities (table 5). 

The average positions of the paleopoles of each of 

these three groups are presented in table 6, which 

consists of two parts, A and B. The pole positions 

given in part A are calculated by using all the data 

listed in table 5, including some from sites where 

fewer than three cores were obtained and which 

therefore yield data that do not meet the statistical 

standards of data used from other sites. Part B 

shows pole positions calculated by using only data 

that meet the strictest statistical standards applied 

to these data.

The number of specimens from which data are 

used in the calculations for part B of table 6 is less 

than half the number from which data are used in 

part A, but part B shows the probably more reliable 

pole positions. The paleomagnetic pole positions 

shown in table 6, part B, for groups 1 and 2 are very 

close, but the poles show opposing polarity. Group 3 

consists of specimens from only one site, and 

although the statistical parameters indicate that 

confidence should be placed in the results of the calculations, the positions calculated are so> far from 

expected Mesozoic or Paleozoic paleopole positions
DIABASE DIKES IN THE HAILE-BREWER AREA, SOUTH CAROLINA C17

TABLE 6.—Summary of magnetic data and paleomagnetic pole positions for diabase dikes and dike swarms in the HaileBrewer area, South Carolina

[Group 1, specimens from dikes A, B, D, 676, G, and I; group 2, specimens from dike C (part A) and dike swarms E (parts A & B) and H (part 

A); group 3, specimens from dike F. x, number of sites from which data are combined; y, number of specimens used; Decl., mean declination; 

Incl., mean inclination; a95, radius of cone of confidence at 95 percent probability level; k, estimate of Fisher's (1953) precision parameter; Lat. N. 

and Long. E., north latitude and east longitude of the virtual geomagnetic pole (VGP); P, polarity; N, north-seeking (reverse) polarity; S, southseeking (normal) polarity; 8m and 8p, semiaxes of the confidence oval about the VGPJ

Paleomagnetic direction Paleopole position

Specimens x/y Decl. 

(degrees)

Incl. 

( degrees )

«95 

( degrees )

k

Lat. N. 

( degrees )

Long. E. 

( degrees )

P

8m 

( degrees ) ( degrees )

Part A—all sites:

Group 1 ____ 10/37 9.8 17.3 13.6 4 63 78 S 14 7 

Group 2 ____ 14/37 177.1 43.4 28.0 2 30 102 N 35 22 

Group 3 ____ 1/4 11 60 7 158 79 331 S 11 8

Part B—only sites

yielding signficant

VGP's:

Group 1 ____ 5/25 7.7 14.7 6.3 22 62 83 S 6.5 3.3 

Group 2 ____ 1/3 190.4 6.7 16.6 56.3 51 82 N 16.6 8.4 

Group 3 ____ 1/4 11 60 7 158 79 331 S 11 8

that they are not paleomagnetically or geologically 

realistic and should probably be disregarded.

CONCLUSIONS

The diabase dikes in the Haile-Brewer area asso^ 

ciated with aeromagnetic anomalies yield paleomagnetic poles that are statistically acceptable at 

either 62° N., 83° E., normally polarized, or 

51° N., 82° E., reversely polarized. These poles seem 

to be close to the mean Late Triassic paleomagnetic 

pole given as 68° N., 97° E. by McElhinny (1973, 

p. 202, table 16) and as 66° N., 95.5° E. by Beck 

(1972, p. 5684) for eastern North America Upper 

Tria,s$ic igneous rocks. The mean pole of 68.6° N., 

100.9° E., calculated by Smith (1976, p. 604, table 3) 

for his data from diabase intrusions in Connecticut, 

Maryland, and southern Pennsylvania is less than 

20° from the pole positions calculated for the South 

Carolina dikes. The South Carolina paleomagnetic 

poles differ by a maximum of 22.5° from the 62° N., 

104.5° E. pole that Beck (1972, p. 5680, and table 2) 

considered to be the best estimate of the Late Triassic geomagnetic pole derived from his samples of 

southeast Pennsylvania diabase intrusions. The 

South Carolina dikes, therefore, are likely to have 

been emplaced during the same time interval as 

these other diabase intrusions in the Late Triassic. 

No other group of distinctively different poles was 

found that might be related to the various chemical 

and petrographic groups recognized by Smith and 

others (1975) and Weigand and Ragland (1970). 

However, not enough dikes, sites, or cores were 

included in the study for us to be entirely satisfied 

that a group of dikes yielding some other paleomagnetic pole does not exist in the Haile-Brewer area.

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18-20, 1968: South Carolina Division of Geology Geologic Notes, v. 12, no. 4, p. 67-84.

Smith, R. C., II, Rose, A. W., and Lanning, R. M., 1975, 

Geology and geochemistry of Triassic diabase in Pennsylvania: Geological Society of America Bulletin, v. 86, 

no. 7, p. 943-955.

Smith, T. E., 1976, Paleomagnetic study of lower Mesozoic 

diabase dikes and sills of Connecticut and Maryland: 

Canadian Journal of Earth Science, v. 13, no. 4, p. 

597-609.

Steele, K. F., Jr., 1971, Chemical variations parallel and perpendicular to strike in two Mesozoic dolerite dikes, North 

Carolina and South Carolina: Chapel Hill, N.C., University of North Carolina Ph.D. dissertation, 213 p.

Stuckey, J. L., 1958, Geologic map of North Carolina: 

Raleigh, North Carolina Division of Mineral Resources, 

scale 1:500,000.

U.S. Geological Survey, 1970, Aeromagnetic map of the Camden-Kershaw area, north-central South Carolina: U.S. 

Geological Survey open-file map, scale 1:24,000.

Waskom, J. D., and Butler, J. R., 1971, Geology and gravity 

of the Lilesville Granite batholith, North Carolina: Geological Society of America Bulletin, v. 82, no. 10, p. 

2827-2844.

Wiegand, P. W., and Ragland, P. C., 1970, Geochemistry of 

Mesozoic dolerite dikes from eastern North America: 

Contributions to Mineralogy and Petrology, v. 29, no. 3, 

p. 195-214.

Zablocki, C. J., 1967, Results of some geophysical investigations in the Wood Hills area of northeastern Nevada: 

U.S. Geological Survey Professional Paper 575-B, p. 

B145-B154.
Aerial Gamma-Ray Survey 

in Duval, McMullen, Live Oak, 

and Webb Counties, Texas

By JOSEPH S. DUVAL and KAREN A. SCHULZ

SHORTER CONTRIBUTIONS TO GEOPHYSICS, 1979

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1123-D

A presentation of aerial gamma-ray data 

as apparent surface concentrations of 

potassium, equivalent uranium, and 

equivalent thorium

CONTENTS

Page

Abstract ___________________________________ ——— -——————— Dl

Introduction _________________________________________----_--------——- 1

Survey description ________________________________—_______________-_-_--- 1

Geology of the surveyed area _________________________________________—-__ 3

Expected radiometric signatures _________________________ — ________ — ____— 3

Presentation of the data _________________________________ — ______ — _____ 5

Discussion of the data __________________________________ — _________ — ___ 8

Conclusions _____________________________________________—____________ 9

References cited ___________________________ — __ —— — —— - 11

ILLUSTRATIONS

Page

FIGURE 1. Geologic map of the area covered by the aerial survey near Freer, Tex _____________________ D2

2. Contour maps of the apparent surface concentrations of potassium, equivalent uranium, and equivalent

thorium _____________________________________________________________________________ 4

3. Contour maps of the total count data, eU/eTh, eU/K, and eTh/K ________________________ 6

4. Graph showing frequency distributions of the radioelement concentrations for the Oakville Sandstone __ 8

5. Anomaly map of eU and eU/eTh anomalies where the values exceed the expected ranges ___________ 10

TABLES

Page

TABLE 1. List of the energy windows used in the measurement of the radiometric data _______________________ D3

2. Average values and indicated range of expected values of the radiometric data for the mapped geologic

units ___________________________________________________________________________________ 9

in

SHORTER CONTRIBUTIONS TO GEOPHYSICS, 1979

AERIAL GAMMA-RAY SURVEY IN DUVAL, MCMULLEN, LIVE OAK, AND

WEBB COUNTIES, TEXAS

By JOSEPH S. DUVAL and KAREN A. SCHUL.Z

ABSTRACT

High-sensitivity gamma-ray data have been obtained for 

an area of about 3300 km2 in Duval, McMullen, Live Oak, 

and Webb Counties, Tex. Contour maps of the aerial gammaray data show the apparent surface concentrations of the 

radioelements potassium, uranium, and thorium. The different geologic units within the survey area have the following average values: 1.2 percent K, 1.8 ppm (parts per 

million) eU (equivalent uranium), and 5.6 ppm eTh (equivalent thorium) for the Goliad Sand; 1.5 percent K, 1.9 ppm 

eU, and 6.5 ppm eTh for the Oakville Sandstone; 1.5 percent 

K, 2.3 ppm eU, and 9.7 ppm eTh for the undivided Catahoula 

Tuff; 1.9 percent K, 2.9 ppm eU, and 9.9 ppm eTh for the 

Frio Clay; 1.5 percent K, 2.8 ppm eU, and 9.7 ppm eTh for 

the Jackson Group. A comparison of anomalies defined on the 

map of eU with those defined on the map of eU/eTh indicates that the ratio is the more effective function for locating 

areas where known mineralization occurs.

INTRODUCTION

If research is to be done to improve the interpretation and understanding of aerial gamma-ray data, 

high-quality data must be obtained over an area 

where the surface geology and mineralization occurrences are known and also where surface disturbances due to man's activities are minimal. The 

U.S. Geological Survey has obtained such data for 

an area of about 3300 km2 in south Texas.

This paper presents those data in terms of apparent surface concentrations of the radioelements potassium, uranium, and thorium, and the data are 

discussed relative to the known lithology. Use of the 

data to detect areas of known mineralization is also 

discussed.

SURVEY DESCRIPTION

The data presented are from a survey flown for 

the U.S. Geological Survey by Geodata International,

1 Any use of trade names in this publication is for descriptive purposes 

only and does not constitute endorsement by the U.S. Geological Survey.

Inc. 1 , in Duval, McMullen, Live Oak, and Webb 

Counties, Tex., near Freer, Tex. (fig. 1).

High-sensitivity aeroradiometric data were obtained continuously along flight lines spaced at 

1.6-km intervals. The flight lines were oriented northwest-southeast at an angle of about 34° west of 

north. Fifty-two lines each 40 km long were flown, 

resulting in 2,080 line-kilometers of data. The nominal altitude of the aircraft during the survey was 

120 m above the ground surface.

The radiometric data were measured using eight 

Nal(Tl) (thallium-activated sodium iodide) detectors. The detectors were right cylinders 29.2 cm in 

diameter and 10.2 cm thick, and the total detector 

volume was 54.4 L. An additional Nal(TI) detector 

(with the same dimensions as the other eight detectors) was shielded from the ground radiation by 

about 10 cm of lead. This detector was used to 

monitor Bi 214 in the atmosphere. A radar altimeter 

was used to measure the altitude of the aircraft 

above the ground surface. The aircraft location was 

determined from the output of a doppler radar navigation system, and a cross check was provided by a 

35-mm film with pictures of the ground below the 

aircraft. One picture was taken every 3 seconds, and 

at the nominal airspeed of 192 km/h, each picture 

had a 15 to 20 percent overlap of both the previous 

and succeeding pictures,

Various corrections were applied to the data. 

Background counts due to cosmic rays, aircraft contamination, and airborne Bi214 were subtracted from 

the observed radiometric count rates. The counts due 

to cosmic rays were determined by monitoring the 

gamma-ray spectrum from 3.0 MeV (million electron 

volts) to 6.0 MeV. The aircraft contamination was 

measured by flying at altitudes higher than 1,000 m, 

where radiation from the ground is negligible. The

Dl
D2 SHORTER CONTRIBUTIONS TO GEOPHYSICS, 1979

00°

99°

EXPLANATION

QUATERNARY 

ALLUVIUM

TERRACE DEPOSITS

TERTIARY 

GOLIAD SAND (PLIOCENE)

OAKVILLE SANDSTONE (MIOCENE) 

CATAHOULA TUFF, UNDIVIDED (MIOCENE)

Chusa Member

Soledad Member

Fant Member

FRIOCLAY (OLIGOCENE?) 

JACKSON GROUP (EOCENE)

Known uranium mineralization 

Fault

98°

rr

10

I

20 KILOMETERS 0 16 32 KILOMETERS 

I I I

FIGURE 1.—Geologic map of the area covered by the aerial survey near Freer, Tex.

airborne Bi214 was measured by the shielded detector. 

The radiometric data were also adjusted to a common altitude of 122 m using a standard equation for 

the exponential attenuation of gamma rays. The 

corrections for Compton scattered gamma rays in 

the potassium and equivalent uranium (eU) energy 

windows were the final corrections applied to the 

radiometric data. Table 1 lists the radioelements 

(potassium, equivalent uranium, and equivalent

thorium) and the energy windows that were used to 

obtain the count rates that are proportional to the 

concentrations of the elements. Two energy windows 

were used to measure eU. The second, lower, energy 

window, which includes the 1.12 MeV gamma ray of 

Bi214 , increases the net eU count rate by a factor 

approximately equal to 2.8 times the count rate obtained with the higher energy window alone. The 

total count window is also listed in table 1.
AERIAL GAMMA-RAY SURVEY; DUVAL, MCMULLEN, LIVE OAK, WEBB COUNTIES, TEXAS D3

TABLE 1.—List of the energy windows used in the measurement of the radiometric data

Element Energy window 

(MeV)

eU -----

eU -----

_ rpT— .

- - - - - 1.34-1.65

1.07 1.33

I

ff O / O 

. 66-2 .42

- - - - - 2.44-2.81

Total count ------ .40-3

GEOLOGY OF THE SURVEYED AREA

The survey was flown over the surface exposures 

of a sequence of Texas Gulf Coast Tertiary rocks 

ranging from the Pliocene Goliad Sand to the Eocene 

Jackson Group. The stratigraphy from youngest to 

oldest, as given by Eargle, Dickinson, and Davis 

(1975), is as follows:

Pliocene: 

Goliad Sand:

Sandstone, light-gray, calichified, fine- to 

medium-grained in upper part, medium- to 

coarse-grained near base; and pink, calcare^ 

ous clay.

Miocene:

Fleming Formation:

Claystone and minor sandstone, gray, pink, red, 

and light-brown; red color increases upward 

in unit.

Oakville Sandstone:

Sandstone, gray to light-reddish-brown, fine- to 

coarse-grained; contains clay pebbles, silt, 

clay, and calcite cement.

Catahoula Tuff: 

Chusa Member:

Claystone, pink, calcareous, tuffaceous, montmorillonitic; and a basal sandy conglomerate containing pebbles of volcanic rock, 

siliceous limestone, and sandstone.

Soledad Member:

Conglomerate, sandy volcanic; contains

boulders of amygdaloidal rhyolite, trachyte,

and trachyandesite as large as 30 cm in

diameter. 

Fant Member:

Tuff, white to light-gray, zeolitic, montmorillonitic; and interbedded sandstone.

Oligocene (?) :

Frio Clay:

Clay, light-gray to green, montmorillionitic, zeolitic, tuffaceous; and channel-sandstone beds.

Eocene (upper) :

Whitsett Formation (of Jackson Group) : 

Fashing Clay Member:

Clay and tuff, gray, calcareous, montmorillonitic, zeolitic, fossiliferous; and some 

beds of lignite, coquina, and sandstone. 

Callihan Sandstone Member (Ataslosa County) 

and its approximate equivalent the Tordilla 

Sandstone Member of the Whitsett in Karnes 

County:

Sandstone, yellowish-gray, fine-grained, 

arkosic, tuffaceous, fossiliferous.

Dubose Member:

Clay and siltstone, gray, montmorillonitic, 

tuffaceous; and minor amounts of sandstone and lignite. 

Deweesville Sandstone Member:

Sandstone, gray, fine-grained, arkosic, crossbedded; contains burrows of Ophiomorpha 

sp. and root impressions and a few beds of 

fossiliferous siltstone and claystone.

Conquista Clay Member:

Mudstone, gray, tuffaceous, montmorillonitic, 

fossiliferous, opalitic, zeolitic, carbonaceous; and a few thin beds of fine-grained 

arkosic sandstone.

Dilworth Sandstone Member:

Sandstone, light-gray, very fine to mediumgrained, arkosic, crossbedded to weakly 

laminated; contains burrows of Ophiomorpha sp. and root impressions.

The geologic map shown on figure 1 was adapted 

from the Laredo and Crystal City Atlas Sheets of the 

Texas Bureau of Economic Geology, Austin, Tex. 

(1976). If the Fleming Formation is present in the 

survey area, it has not been recognized as a separate 

unit on the Atlas Sheets.

EXPECTED RADIOMETRIC SIGNATURES

Because lithologically different materials have 

both physical and chemical differences, prediction 

of the relative radioactivity levels and the expected 

concentrations of potassium, uranium, and thorium 

should be possible, given typical values for rocks having similar lithologies. Duex (1971) gives average 

values for the exposed Catahoula Tuff as 1.1 percent 

K, 3.1 ppm (parts per million) eU, and 9.4 ppm eTh
D4 SHORTER CONTRIBUTIONS TO GEOPHYSICS, 1979

10 20 KILOMETERS B

10 20 KILOMETERS

-1.4- Apparent surface concentration of K, in percent. 

Contour interval 0.2 percent

-3.2- Apparent surface concentration of eU, in ppm. 

Contour interval 0.4 ppm

FIGURE 2.—Contour maps of the apparent surface concentrations of A, potassium; B, Equivalent uranium; C, Equivalent

thorium.

(equivalent thorium). Duval and others (1972) give 

concentrations of 0.6 percent K, 1.1 ppm eU, and 

2.9 ppm eTh for a sandstone in the area of the Llano 

Uplift in central Texas.

Because the Frio Clay, the Catahoula Tuff (excepting the Soledad Member), and the upper members of the Whitsett Formation are lithologically 

similar, in that they are of volcanic origin and are 

tuffaceous, they can be expected to have similar

radiometric signatures. Inherent in the preceding 

statement are the assumptions that the original average concentrations of the radioelements in the sediments did not differ by more than a few parts per 

million and that all the sedimentary rocks have 

undergone similar weathering. In the Soledad Member, the concentrations of potassium and uranium 

should be higher than those in the other volcanic 

sedimentary rocks, because weathering processes
AERIAL GAMMA-RAY SURVEY; DUVAL, MCMULLEN, LIVE OAK, WEBB COUNTIES, TEXAS D5

EXPLANATION

GOLIAD SAND (PLIOCENE) 

OAKVILLE SANDSTONE (MIOCENE) 

CATAHOULA TUFF, UNDIVIDED (MIOCENE)

Chusa Member

Soledad Member

Fant Member

FRIO CLAY (OLIGOCENE?) 

JACKSON GROUP (EOCENE)

Geologic contact. Dashed where approximate

Fault

Known uranium mineralization

10

I

20 KILOMETERS

-9.0- Apparent surface concentration of eTh, in ppm. 

Contour interval 1.8 ppm

FIGURE 2.— (For caption, see facing page.)

should be less effective in leaching" potassium and 

uranium from the conglomerate than from the 

tuffaceous sedimentary rocks.

Because the Oakville Sandstone and the Goliad 

Sand are sandstones of continental origin, they 

might be expected to have radioelement concentrations similar to those of sandstone of continental 

origin stuied by Duval and others (1972). If the 

source rocks for the sandstones are very different or

if differences in weathering exist, this assumption 

will not hold true. The Oakville and Goliad should 

have similar radioelement concentrations, and they 

should have lower concentrations than any of the 

volcanic sedimentary rocks.

PRESENTATION OF THE DATA

The data from the aerial survey are presented in 

the form of contour maps in figures 2 and 3. These
D6 SHORTER CONTRIBUTIONS TO GEOPHYSICS, 1979

-38.2- Total count. Contour interval 1.8 ur eU/eTh. Contour interval 0.056(ppm eU/ppm eTh)

FIGURE 3.—Contour maps of A, The total count data; B, eU/eTh; C, eU/K; D, eTh/K.

maps were adapted from maps produced by an automatic contouring computer program. The fully corrected count-rate data were converted to represent 

the apparent surface concentrations of K, in percent, 

eU, in parts per million, and eTh, in parts per million (fig. 2), using the calibration constants given 

by Duval, Schultz, and Pitkin (1977). The units 

used for the total-count map (fig. 3A) are defined 

such that 1 ur (radioelement unit, International 

Atomic Energy Agency, 1976) is equal to the total

count that would be measured by a detector being 

carried at an altitude of 122 m over a broad source 

of gamma rays that has an apparent surface concentration of 1 ppm eU but lacks potassium and thorium. The value of 1 ur=55 cps (counts per second) 

adopted for this aerial survey was determined by 

using a linear regression fit to establish the relationship between the total count and the radioelement 

concentrations.
AERIAL GAMMA-BAY SUEVEY; DUVAL, MCMULLEN, LIVE OAK, WEBB COUNTIES, TEXAS D7

c

10 20 KILOMETERS D

10 20 KILOMETERS

• 2.0 ———— eU/K. Contour interval 0.4(ppm eU/percent K' ——

EXPLANATION 

GOLIAD SAND (PLIOCENE) 

OAKVILLE SANDSTONE (MIOCENE) 

CATAHOULA TUFF, UNDIVIDED (MIOCENE) 

Chusa Member 

Soledad Member 

Fant Member

-5.4——— eTh/K. Contour interval 0.9(ppm eTh/ percent K)

FRIO CLAY (OLIGOCENE?) 

JACKSON GROUP (EOCENE)

Contact—Dashed where approximate

Fault

Known uranium mineralization

FIGURE 3.— (For caption, see facing page.)
D8 SHORTER CONTRIBUTIONS TO GEOPHYSICS, 1979

DISCUSSION OF THE DATA

Before the data can be discussed relative to the 

mapped geology, the normal or expected values for 

each geologic unit must be determined. Because 

geologic formations are not necessarily uniform in 

radioactivity, calculations of mean values and of 

standard deviations can be in error. A better method 

to determine the average value for a unit is to plot a 

frequency distribution of the number of data points 

with a given value versus the value. Figure 4 shows 

the frequency distributions of the radioelement concentrations for the Oakville Sandstone.

Once the frequency distributions have been 

plotted, the expected values for each geologic unit 

can be defined either by fitting a mathematical function, such as a normal distribution, to the curves or 

by visual inspection. Table 2 lists the average values 

of the radiometric data for each geologic unit plus 

or minus a value representative of the normal range 

of values. The average values were determined by 

inspection of the frequency distribution curves. The 

plus or minus deviation from the mean value was 

defined as 0.75 times the full width of the curve at

one-half of the peak number of data points. The 

values given for the Oakville Sandstone are shown in 

figure 4.

As expected, the radioactive characteristics (particularly eU, eTh, and eTh/K of fig. 3D) of the 

Goliad and the Oakville are significantly different 

from those of the more tuffaceous sediments; however, the concentrations given by Duval and others 

(1972) for the sandstone in central Texas are also 

significantly different. This difference suggests that 

care must be taken to avoid classifying geologic 

units on the basis of such physical parameters as 

grain size when the purpose of the classification is 

to predict expected radioelement concentrations.

The differences between the Goliad and the Oakville are subtle, and the values given in table 2 could 

not be used to distinguish them. However, the contour maps indicate that some of the mapped Goliad 

has lower values for K, eTh, and total count. This 

fact could provide aid for geologic mapping.

The differences among the Catahoula, Frio, and 

Jackson sedimentary rocks are also subtle; the greatest differences are in eTh, total count, and eU/eTh.

600

1.0

FIGURE 4.-

1.4 1.6 1.8 

K, IN PERCENT

2.0 2.2 1.3 1.5 1.7 1.9 2.1 2.3 2.5 

eU, IN PARTS PER MILLION

2.7 4.0 5.0 6.0 7.0 8.0 9.0 

eTh, IN PARTS PER MILLION

10.0

-Frequency distributions of the radioelement concentrations for the Oakville Sandstone. The mean value is represented by the open circle; the expected range of values, by the bar.
AERIAL GAMMA-RAY SURVEY; DUVAL, MCMULLEN, LIVE OAK, WEBB COUNTIES, TEXAS D9 

TABLE 2.—Average values and indicated range of expected values of the radiometric data for the mapped geologic units

Geologic unit K elJ 

(percent) (ppm)

eTh Total eU/eTh 

(ppm) count (ur)

iU/K

1 Member of Catahoula Tuff.

eTh/K

Goliad Sand ——

Oakville

Sandstone — -

Catahoula Tuff

(undivided) -

/TI 1

L/riUod.

Q -1 1 1 1

Frio Clay ————

Jackson Group -

1.2+0.3

1.5+0.3

1.5+0.4

2.0+0.3

1.2+0.5

2.0+0.3

1.9+0.6

1.5+0.7

1.8+0.4

1.9+0.4

2.3+0.8

2.7+0.9

2.8+0.6

3.3+0.6

2.9+0.7

2.8+0.9

5.6+1.7

6.5+1.2

9.7+3.0

11.9+2.7

12.8+1.9

11.7+2.7

9.9+2.7

9.7+2.4

32.8+6.8

35.4+2.7

28.2+6.8

45.5+4.1

47.3+4.1

38.2+6.4

35.5+7.0

30.0+8.9

0.31+0.09

0.27+0.07

0.23+0.06

0.22+0.07

0.22+0.09

0.25+0.10

0.28+0.08

0.28+0.07

1.4+0.5

1.2+0.3

1.4+0.6

1.4+0.4

1.3+0.3

1.5+0.5

1.4+0.6

1.7+0.8

3.3+0.8

3.3+0.8

4.9+1.3

4.6+0.8

4.0+1.3

4.1+1.0

4.0+0.7

4.7+2.2

The Catahoula in the northeastern part of the survey 

area, where it is undivided, has values of K, eU, eTh, 

and total count that are significantly lower than the 

values of the divided members of the Catahoula in 

the southwestern part of the survey area. Also, the 

undivided Catahoula can be more readily distinguished from the divided Catahoula than can either 

the Frio or the Jackson. This difference within the 

Catahoula suggests a facies change, and such a 

change would reflect a difference in the depositional 

environment. Galloway and others (1977) show a 

channel facies that correlates at least in part with 

the area of the divided Catahoula and a floodplain 

facies that correlates with the undivided Catahoula.

Another difference between the Catahoula and the 

other sedimentary rocks is that the eU/eTh is significantly lower in the Catahoula (fig. SB). The 

lower eU/eTh could be indicative of a greater relative leaching of uranium from the Catahoula. Moxham (1964) and Duex (1971) suggest that uranium 

has been leached from the Catahoula sedimentary 

rocks, and Galloway and others (1977) have analytical data that support a hypothesis that extensive 

leaching of the uranium occurred soon after the sediments were deposited.

Although the differences among the radiometric 

characteristics are interesting and useful for geologic mapping, they do not provide any direct indicators for specific areas of uranium mineralization. 

The values in table 2 can, however, be used to define 

anomalous radiometric values. Figure 5 shows eU 

and eU/eTh anomalies mapped as areas where the

measured values exceed the maximum expected 

values, as given in table 2. Figure 5 also shows generalized locations of known uranium mineralization. 

An examination of figure 5 shows that most of the 

known mineralized areas occur within 10 km of a 

eU/eTh anomaly. The mineralized areas coincide 

reasonably well with eU anomalies within the Catahoula; however, there are no eU anomalies within 

the Oakville.

CONCLUSIONS

Relative radioactivity levels for a sequence of sediments can be predicted using the lithologic descriptions; however, the absolute concentration levels 

cannot be accurately estimated at present. More accurate estimates of the concentration levels would 

require knowledge of the mineral assemblage in the 

sediment and better information on known concentrations in similar sediments. In order to establish 

a table of known concentrations in similar sediments, a classification scheme will be necessary. Such 

a classification scheme should only use characteristics that are directly related to chemical or mineralogical properties.

Almost all sedimentary rocks, particularly those 

fluvial in origin, have facies changes along strike 

that can have distinctive radiometric characteristics, 

as is true of the differences between the channel 

facies and the floodplain facies in the Catahoula 

Tuff. The possibility that similar differences may 

occur within other sedimentary rocks raises doubt
DlO SHORTER CONTRIBUTIONS TO GEOPHYSICS, 1979

10 20 KILOMETERS

EXPLANATION

GOLIAD SAND (PLIOCENE) 

OAKVILLE SANDSTONE (MIOCENE)

CATAHOULA TUFF, UNDIVIDED (MIOCENE)

Chusa Member

Soledad Member

Fant Member

FRIO CLAY (OLIGOCENE ?) 

JACKSON GROUP (EOCENE)

Geologic contact. Dashed where approximate

Fault

Location of known uranium mineralization

eU anomaly 

eU/eTh anomaly

FIGURE 5.—eU and eU/eTh anomalies where the values exceed the expected ranges.

concerning- the validity of expressing- radiometric 

characteristics in terms of mapped geologic 

formations.

One approach that would eliminate the limitations 

imposed by displaying- the data in terms of mapped 

geology is to define radiometric map units. A radiometric unit should have relatively homogeneous 

radioactive characteristics and be geographically 

continuous. Duval (1976) presents a method utilizing- factor analysis that mig-ht be used to define

radiometric units, and Duval, Pitkin, and Macke 

(1977) present a method using- color images, which 

also mig-ht be used. However, both of the cited 

methods appear to require further development, and 

such questions as the definition of relative homog-eneity must be resolved.

If the concept of radiometric anomalies is to be 

applied to aerial gamma-ray data, normal expected 

values should be defined using- frequency histograms 

of the values measured over mapped geologic units
AERIAL GAMMA-RAY SURVEY; DUVAL, MCMULLEN, LIVE OAK, WEBB COUNTIES, TEXAS Dll

or radiometric units. The application of the anomaly 

concept to the eU and ell/eTh (fig. 3C) data presented here indicates that within the Catahoula Tuff, 

both eU and eU/eTh are useful as indicators of 

uranium mineralization; however, within the Oakville Sandstone only eU/eTh provides some indication of uranium mineralization.

REFERENCES CITED

Duex, T. W., 1971, K/Ar age dates and U, K geochemistry 

of the Gueydan (Catahoula) formation of south Texas, 

Final Report: U.S. Atomic Energy Commission research 

contract AT(05-1)-935, p. 101-145.

Duval, J. S., 1976, Statistical interpretation of airborne 

gamma-ray spectrometric data using factor analysis, in 

International Atomic Energy Agency, Exploration for 

uranium ore deposits—a symposium: International 

Atomic Energy Agency, IAEA-SM-208, p. 71-80.

Duval, J. S., Pitkin, J. A., and Macke, D. L., 1977, Composite 

images of radiometric data from south Texas and Wyoming, in U.S. Geological Survey, Short papers of the U.S. 

Geological Survey uranium-thorium symposium: U.S. 

Geological Survey Circular 753, p. 21-22.

Duval, J. S., Schulz, K. A., and Pitkin, J. A., 1977, Calibration constants for the Geodata International, Inc., and 

Texas Instruments, Inc., high sensitivity systems used for

the ERDA aerial gamma-ray surveys: U.S. Geological 

Survey Open-File Report 77-159, 15 p.

Duval, J. S., Worden, J. M., Clark, R. B., and Adams, J. A. 

S., 1972, Experimental comparison of Nal(Tl) and solid 

organic scintillation detectors for use in remote sensing 

of terrestrial gamma rays: Geophysics, v. 37, no. 5, p. 

879-888.

Eargle, D. H., Dickerson, K. A., and Davis, B. O., 1975, South 

Texas uranium deposits: American Association of Petroleum Geologists Bulletin, v. 59, no. 5, p. 766-779.

Galloway, W. E., Murphy, T. D., Belcher, R. C., Johnson, B. 

D., and Sutton, S., 1977, Catahoula Formation of the 

Texas coastal plain; depositional systems, composition, 

structural development, ground-water flow history, and 

uranium distribution: Texas University Bureau of Economic Geology Report of Investigations 87, 63 p.

International Atomic Energy Agency, 1976, Radiometric reporting methods and calibration in uranium exploration: 

International Atomic Energy Agency Technical Report 

Series 174, 57 p.

Moxham, R. M., 1964, Radioelement dispersion in a sedimentary environment and its effect on uranium exploration: Economic Geology, v. 59, no. 2, p. 309-321.

Texas University Bureau of Economic Geology, 1976, Crystal 

City-Eagle Pass Sheet: Geologic Atlas of Texas, scale 

1:250,000.

————1976, Laredo Sheet: Geologic Atlas of Texas, scale 

1:250,000.

* U.S. GOVERNMENT PRINTING OFFICE: 1980 O— 311-344/11