THE APPLHCATEON OF RADIO FIELD
RNTENSITY MEASUREMENTS TO MAPPING

PREC-AMBRHAN GEOLOGICAL STRUCTURES

THESIS FOR THE DEGREE OF M. S.

MICHIGAN STATE UNIVERSITY
CHARLES EDWARD KERMAN
1968

«HESIS

 

LIBRARY

Michigan State
University

 

 

 

THE APPLICATION OF RADIO FIELD
INTENSITY MEASUREMENTS TO MAPPING

PRECAMBRIAN GEOLOGICAL STRUCTURES

By

Charles E. Kerman

A THESIS

Submitted to
‘Michigan State university
in partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE

Department of Geology

1963

3043470
4/57/64

ABSTRACT

A radio field intensity survey was conducted in the
Marquette, Iron‘MOuntain, Ironwood and Keweenaw areas of
the northern peninsula of Michigan. The purpose of this
study was to determine the applicability of radio field
intensity measurements to mapping Precambrian geological
structures in the Lake Superior region.

This method of geological mapping operates on the
principle that a change in the underlying geology in-
fluences the intensity of radio waves at that point. These
changes in intensity were permanently recorded on paper
charts at the time the variations were observed. The re-
cording was done continuously while the vehicle was in

7 motion.

It is concluded that when a radio station can be
received and there is a minimum of cultural interference,
the radio field intensity method is applicable to geologic

'mapping in the Lake Superior region.

ii

ACKNOWLEDGEMENTS

The successful completion of this study was greatly
facilitated by the unselfish assistance of many organic
sations and individualso The author wishes to eXpress
his sincere appreciation to them; i

The Ford Motor Company Fund which generously financed
this research in the summer of 19620

Mro Victor Kral and Mrs Thomas Lawler of the Ford
lotor Company who were helpful in this researcho

Dro Villiam Jo Hinze who suggested the study and
under whose guidance the study was undertakeno

Dro Justin Zinn and Dro James Trow of the Geology
Department, Michigan State University, for their support
of this research projecto

The Department of Registration and Education,
Division of the State Geological Survey, State of Illinois,
for the loan of the radio field intensity equipmento

The McClure Oil Company for sponsoring the investi»
gation during the summer of 1961.

Dr. Lawrence Frymire aner0 John Blakeslee of WKAR,
lflchigan State university Radio, for their generous
technical assistance during the research projecto

The Bendix Corporation, Systems Division, Ann Arbor,'
.Hichigan, for calibrating the field intensity metero

Hr, Walter Io Dobar, for the loan of the tape recorder

iii

which greatly facilitated the field procedureso

Hr, Robert Reed, Michigan Department of Conservation,
Geological Survey Division, for his information about the
geology of the areas investigatedo

Hr, James Wheeler, WBEMC, Iron mountain, for his sug»
gestions and generous offer and loan of antenna equipmento

Er, Gerald Shideler for his help in the field and
laboratory during the initial stages of this investigationo

iv

TABLE OF CONTENTS

Ab“ tr‘c. t O O O O O O O O O O O O O O O O O O

Achmledgman t3 e e e e e e e e e e e e e e
In trOduCtim e e e e e e e e e e e e e e e e
meatim e e e e e e e e e e e e e e e e e e

Previous Investigations . . . . . . . .

Physics of Radio waves . . . . . . . . . . .
ImtE’O‘flthim e e e e e e e e e e
Factors Affecting Field Strength . . .

iatr@du¢3tim e e e e e e e e e e e
Geometrical Spreading . . . . . .
Absorption of Energy . . . . . . .
Reflection and Refraction'oithin t
Eund‘ugtiié‘im e e e e e e e e o e e e
Surface Enviroment . . . . . . .
Penetration into the Earth . . . ,., .
Pertinent Rock Properties . . . . 0.‘ .

Emimenteeeeeeeeeeeeeeeee
Iatr©ducti©fn e e ~e e e e e e e e e e e
Radio Field Intensity‘neter . . . . . .
PW: Supply a e e e e e e e e e e e e
R‘CGDEereeeeeeeeeeeeeee
”CWeeeeeeeeeeeeeeee

F101d ROCCdUirCO e e e e e e e e e e e e e a

Results and Interpretations . . -. . . . . .
Introduction e e e e e e e e e e e e e
TheMerquetteArea ..........
Th. WCRCW Ar.‘ 0 e e e e e e e e e e

.The IronMountainArea ........
The IrWQQd Area e e e e e e e e e e e
.Conditions Under Which the Method Fails

melmion.e‘Jeeeeeeeeeeeeeee
Race-endations for Further Investigation .

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Page
ii
iii

INDEX OF TABLES

Page

Table l. Pertinent Electrical Properties of Rocks
Encountered in This Survey . o . . . . . o o o 26

vi

1.
2.

3.
h.

5.
6.

7.

9.
10.
11.
12.

13.
1h.

15.
16.
17.
18.
19.

INDEX OF FIGURES

Location of the Area 0 . . o o o . o . o o o o 0
Relation between Frequency, Resistivity,
Dielectric Constant, and Percent Absorption of
”d19W‘VCCeoeeooooooooooooooo
Schematic of Power Supply . . o . o o . . . o o .

Schematic Showing Electrical Connections between
V‘rioua PiQCOB Of Equipent o o o o o o o o o o o

Schematic of Tuned‘Whip Antenna . . o o o o . o 0
Equipment behind(Fbont Seat of Vehicle 0 o o o o
Generalised Stratigraphic Column of the.Harquette

Ar...oooooooooooooooooooooo

Record No. 38 . o o . o o o o o o o o o o . o . 0
Record No. 50 o o o . o o o . o o . o o o o o o 0
Record No. 51 . o o . . o o o o o . o o o o o o 0
Record No. 63 o . o . . o . . . . o o . . o o o o

Generalised Stratigraphic Column of the Keweenaw

Ar.‘ 9 0 O 0 O O O 0 O O O O O 0 O O 0 0.0 0 0 0

RCCON N00 h“ 0 O 0 O 0 ‘0 0 0 O O O O O O O O O 0

Generalised Stratigraphic Column of the Iron
Mountain Area . . . . . o . . o . . o o . o . o 0

Record No. 5 . o . o o o . o o o . o o . o o o 0
Record No. 10 . . . . . . . . o . . o . . o . o 0
Record No. 13-8 and 13=E . o o o o . o o o o . .
Record No. Zh-A . o o o . . . . . o o o . . o o .

RecordNo. 65, 66, 67~A and 67=B . o o . o o o 0

vii

Page
, 4

. 33

. 38

<.44
..46
.,48
. 50
o 52

o 58
o 60
o 62

Figure
20. Record No. 21 . . . . . . . . . . . . . . . . . .
21. Record No. 77 . . . . . . . . . . . . . . . . . .
22. Generalised Stratigraphic Column of the Ironwood
Area . . . . . . . . . . . . . . . . . . . . . .
23. Record No. 25 . . . . . . . . . . . . . . . . . .
2h. Record No. 29 . . . . . . . . . . . . . . . . . .
25. Record No. 30 . . . . . . . . . . . . . . . . . .
26. RecordNo.32,33and35............
27. Record No. 37, Unsuitable Response . . . . . . .
28. Record No. 62, Too Many Wires . . . . . . . . . .
29. Record No. 26, Concrete-Dirt Road . . . . . . . .
30. Specific Locations of Traverses . . . . . . . . .
'1: i Wm} gm
I; E“ i m
R Li: 5? E“ f“? {is so:

 

viii

Page

. 80
. 83
. 85
. 87
. 89
. 94

. in
pocket

INTRODUCTION

The increased demand for mineral resources has spurred
the search for new mineral deposits. Geophysical exploe
ration methods, which detect hidden ore bodies or
structures favorable for the occurrence of ore, have been
the primary tools employed in this search because the vast
majority of ore deposits that outcrop have already been
found and eXploited. A great variety of geophysical
techniques are now being utilised in the search for mineral
deposits. Although they all have their optimum place in
the orploration industry, the reconnaissance methods which
quickly and economically isolate favorable areas for
intensified geophysical and geological studies have been
the most useful.

The airborne magnetic and lowefrequency electromag=
netic methods have been particularly useful in
reconnaissance orploration for mineral deposits. However,
these methods do have limitations. The magnetic method
is only applicable to the detection of horizontal varies
tions in the magnetic susceptibility of rocks. Therefore,
the method is limited to the detection of those ore
bodies which are associated with concentrations of high
magnetic susceptibility minerals such as magnetite,
ilmenite, and pyrrhotite. Of course, not all mineral

deposits are associated with detectable differences in

these minerals. The low-frequency electromagnetic methods
have been successful in detecting hidden ore bodies that
have a high electrical conductivity in contrast with the
country rock. It is limited, however, to investigations
on feet which are slow, or airborne studies which are very
costly. In addition, the method is based on mapping
variations in an electromagnetic field which is artifi-
cially generated and, therefore, requires a power source.
Another geophysical method which is potentially a
valuable reconnaissance tool has not been fully investi-
gated to determine its applicability to the detection of
mineral deposits and geological structures. This is the
radio field intensity method. It is based upon the
measurement of the variations in the intensity of the
signal carried by the surface wave from commercial broad-
cast band radio stations. The intensity of this wave is
a function of, among other things, the electrical
conductivity, dielectric constant, and magnetic permea-
bility of the underlying earth formations. Therefore,
unlike the airborne magnetic method, this technique is
capable of detecting variations in the conductivity of
earth material, and unlike the electromagnetic method,
radio field intensity measurements can be made continu-
ously from a moving vehicle, either ground or airborne,

without having to produce the field which is investigated.

The purpose of this study was to determine the
application of radio field intensity measurements in
mapping Precambrian geological structures in the Lake
Superior region.

This study was designed as a reconnaissance investi-
gation of areas believed to be particularly well suited
to this type of mapping. In the course of this study,
during the summer of 1962, 350 miles of continuous field
intensity records were made in northern Michigan and
Visconsin over a great variety of rock types and struc-
tures .

Some of the features investigated include the
Keweenaw fault, granitic intrusions into lava flows, iron
formations, the Hakefield fault, faults and Precambrian
metasediments in a variety of locations in the Marquette
syncline and adjoining areas, faults and metasediments in
the Iron Mountain region, dikes and sills, and strongly

magnetic features.
LOCATION

The field work was conducted in selected areas in the
western half of the Northern Peninsula oflflichigan and in
adjacent parts of northern Wisconsin. The general
locations of the areas of investigation are shown in Figure
l, and the specific locations of the traverses are given on

the map in the folder at the back of the thesis.

    
  

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The specific areas investigated were selected for a
number of reasons. First, the geology is relatively well
known. As the study was to determine the feasibility of
geological mapping with radio field intensity measurements
in this region, a good deal of geological control was
needed to verify the results.

Second, geologic formations and structural features
dip at high angles as a result of the intense structural
deformation. In this type of mapping, it is desirable to
have sharp contacts between adjacent rock types so the
change in rock properties that affect the radio field will
be abrupt and thus cause a distinctive change in the
intensity.

Third, the glacial drift is thin in the areas investi-
gated. The theoretical depth penetration of radio waves
into the earth is limited, therefore the waves might not
penetrate through thick drift to the bedrock. The
desirability of thin drift in radio field intensity
studies was pointed out by Gibbs (1939). On the basis of
a survey in the Southern Peninsula of Michigan, he con-
cluded that lithologic variations in the glacial drift
were responsible for significant intensity changes.

The general level of geological knowledge, the sharp
rock contacts, and the thin glacial drift provided

excellent conditions for evaluating this method. In

addition, no comprehensive study of this method had been

made in this area, and this method is potentially valuable
in exploiting the mineral resources of highly deformed
mineral districts.

PREVIOUS INVESTIGATIONS

Experimentation with radio waves in the earth began
in the nineteen’twenties. lbch of the first work dealt
with the problem of radio communications within mines.

As early as 1928, the 0.3. Bureau of Mines published two
technical papers on this subject; "Experiments in Under-
ground Communications Through Earth Strata' by Ilsley,

et al., and "Geophysical Prospecting: Some Electrical
Methods" by Eve and Keys. Ilsley, et al., found evidence
of radio wave penetration through seventy feet of earth,
but were skeptical of the method of penetration. Eve and
Keys, working at the Caribou magnetite line, fifty miles
from Denver, Colorado, found that KFEL, Denver, could be
received at depths of 200 feet, and were of the opinion
that there might be some reception at depths as great as
500 feet.

Eve, et al. (1929) continued their experiments in
the Rbunt Royal Tunnel, Montreal, Canada. The most
significant result of this work was the realisation that

long radio waves penetrate rock to a much greater extent

than short waves. That is, the lower the frequency, the

greater the response deep in the tunnel. Later, Eve, Keys

and Lee. conducted similar experiments in the

elammoth Caves of Kentucky. The investigators thought that
this would be a better test of the radio wave penetration
because these caves did not have the wires, cables, and
rails that were present in the lount Royal Tunnel. Their
work demonstrated that broadcast frequencies could pene-
trate at least 350 feet of rock.

Ernst Cloos (l93b) accidentally noticed some distur-
bances in the reception on his car radio which did not
seen to be related to cultural features such as power
lines, steel bridges or telephone lines. As a result of
this, he carried out a series of experinents in an attempt
to relate these disturbances to the underlying geology.
This was done using his automobile radio as a detection
device, and listening for volume changes. He found that
the results of his work agreed quite well with the known
geology. He postulated that if the same area were run
time and time again, and if the same non-cultural dis-
turbances were recorded each time, then these might be a
reflection of the underlying geology. Cloos found that
there were 'dead spots' associated with faults and steeply
dipping contacts. The results that Cloos obtained were
excellent considering the type of equipment he used.

'Vith the control of automobile traffic becoming a
problem, the Ohio State Police had Higgy and Shipley (1936)
run a radio transmission survey of Ohio to determine the
best location, or locations, for their radio communica-
tions antennas. When the results of their work were
plotted on a map of Ohio and the areas of similar conduc-
tivity shaded in, there was a remarkable correlation
between this map and the geologic map of Ohio. The areas
of best transmissive properties were underlain by
Ordovician, Silurian, and Devonian limestones. The area
with the next best properties was over Devonian and

lississippian shales. An area largely composed of
I Pennsylvanian and Permian sandstones was the third best
area. A small section around Cleveland with thick
Pleistocene deposits was the poorest area. This was pro-
bably the first time that the effects of the underlying
rocks over a large area were fully realised.

Gibbs (1939) did a field intensity survey over the
Howell Anticline in southern lichigan. In his conclusion
he states that the bedrock had no effect on the field
intensity because the glacial drift was too thick to allow
penetration, and further, that the drift masked the bed-
rock response by its own changes in lithology.

B. F. Howell, Jr. (19h3) ran radio field surveys over

areas in southern California and New Jersey. He was not

too optimistic about the method because he found that
some faults had weak fields associated with them but

others did not. He was not able to determine the cause
of the erratic response. He also stated that in popu-
lated areas there were too many man-made disturbances to
render a good indication of the geology.

Larkin Kerwin (l9t6) was able to locate a dike with
radio gear, and was then able to verify the location by
field work. He also located several other anomalies and
was optimistic about the future of the radio wave method
of mapping. He concluded that topography had little
effect on the field intensity in an area where the hills
are gently rolling.

In 19t8,1chlwain and Wheeler presented a paper to
the convention of the Institute of Radio Engineers on
the propagation of radio waves through the earth. Only
the abstract of their report is available and in it they
state: "The results show the limitations of radio waves
for deep geophysical prospecting, though they may be
useful for related exploration”.

Haycock, et al., (l9h9) discussed the possibility of
using radar for locating discontinuities within the earth.
Their conclusion was that it probably would not be
feasible to do this. However, they did think a phase

shift measurement from a frequency modulated transmitter

10

might be of some value in this type of study.

Barrett (l9h9, 1952, 1953, and 1959) has done a con-
siderable amount of work with a radio exploration method
that he calls Radoil. In a demonstration at the Hleer Salt
line at Grand Saline, Texas, he showed that radio waves
with a frequency of 1,602 kc could penetrate 700 feet of
earth materials.

The last major report in this field was by W. H.
Pullen (1953). Pullen attempted to evaluate this method
‘ in all respects. He had a fair amount of success in
mapping geology in Illinois using a method of continuous
recording. Some of the features over which he found radio
field intensity changes are the Shawneetown-Rough Creek
fault, a cryptovolcanic structure, the Hicks dome, and the
Inman East fault. In Illinois he found conflicting re-
sults over ore bodies of pyrite, sphalerite, and mnrcnsite.
He found little or no effect from soil or loose over
glacial drift.

A major change that differentiates the nore recent
work from the older work is that since Kerwin (19t6) all
of the investigators have used a continuous recording
method, and used only relative variations in the field
intensity.

This research differs from that of Pullen's in that
this is an attempt to determine the potential of the radio

11
field intensity method in the Precambrian areas around Lake
Superior. This is, of course, a completely different
geologic province than that in which Pullen made his in»
vestigations. Another difference, is that a tuned whip

antenna was used whereas Pullen and most of the others used

a loop antenna.
PHYSICS OF RADIO WAVES

INTRODUCTION

In the radio field intensity method of geological
mapping the intensity of radio fields produced by
commercial A.M. broadcast stations are measured. many
things affect the intensity of radio waves, one of these
is the geology. By measuring variations in the intensity
of the field, local changes in the underlying geology can
be determined. These variations are caused by the inter-
action of the radio waves with the physical properties of
the earth.

The radio waves that are utilised in this type of
geological napping are one form of electromagnetic radia-
tion. Like the other forms, e.g. light, they travel at
300,000,000 meters or 186,000 miles, per second in free
space.

When radio waves leave the transmitting antenna they

can be classified into a number of waves depending on how

12

they are affected by the earth, and the path they travel in
reaching the receiving antenna. The primary waves are the
sky wave and the ground wave. The sky wave is that portion
of the total wave that is directed toward the upper
atmosphere. Depending on the time of day and the fre-
quency of the radio signal this wave may or may not be
reflected back to the earth by the ionosphere. This is
primarily a nighttime phenomenon. is this wave does not
interact with the earth it is of no interest to this in-
vestigation.

The ground wave is directed along the surface of the
earth, is not reflected off the ionosphere, and is composed
of one or more of the folldwing waves: 1. the direct
wave, 2. the ground-reflected wave, 3. the surface wave,
and h. the ground-refracted wave.

1. The direct wave is that conponent of the ground
wave that travels directly to the receiving antenna from
the transnitting antenna. This wave is primarily a line-
of-sight wave. However, it can undergo a slight amount of
diffraction in the atmosphere.

2. The ground-reflected wave is that portion of the
ground wave which reaches the receiving antenna by reflec-
ting off the earth. This wave is primarily important in
short distance communication. When this wave is reflected

it undergoes a phase reversal of 180 degrees, therefore at

13

close distances the ground-reflected wave and the direct
wave may nearly cancel each other.

3. The surface wave is that portion of the ground
wave that travels along the surface of the earth and
follows the curvature for moderate distances. At near
distances the direct wave and the ground-reflected wave
can nearly cancel each other so that the primary form of
transmission is by the surface wave. This wave is
affected by the conductivity of the ground over which it
passes. .

A. The ground-refracted wave, for the purposes of
this discussion, is that portion of the ground-reflected
wave which enters the earth. This wave is refracted by the
earth and travels within the earth until it is absorbed or
until it is refracted or reflected back into the atmosphere.
This wave is strongly affected by the electrical and
magnetic properties of the earth.

As these waves are a form of electromagnetic radiation
they follow the general laws of light. That is they can be
diffracted, polarised, and reflected, and in accordance

with Snell's law, they can be refracted.
FACTORS AFFECTING FIELD STREHGTH

Introduction

As the radio waves are emitted from the antenna they

14

spread out in accordance with the_directiona1 properties of
the antenna. These waves consist of two fields, neither

of which can be transmitted separately. These two fields,
the electric and the magnetic, are mutually perpendicular

to each other. The electrical field is vertically polarised
and the magnetic field is horisontally polarised in waves
emitted from commercial radio broadcast stations.

The intensity of these fields decreases as the wave
travels away from the transmitting antenna as a result of
the geometrical spreading of the wave and the absorption
of the wave's energy. In addition, the intensity is
affected locally by waves that are reflected and refracted
within the earth. The surface environment including
cultural, meteorological and terrain features, and secondary

fields induced by the radio waves, also affect the intensity.

Geometrical Spreading

Geometrical spreading causes a decrease in the power
per unit area, and therefore inifhe intensity of the waves
as they travel outward from the antenna. when a wave is
emitted from a transmitter it has a certain amount of power,
and it is confined to a small area. As the waves spread
out this initial power must new cover the increasing area
thereby reducing the power per unit area. The power of

these waves falls off as the square of the distance, while

15

the intensity decreases proportionally to the distance.
In this investigation an attempt was made to orient the
traverse at right angles to the direction of propagation,
so that geometrical spreading would not unduly affect the

results.

Absorption of Energy
‘As the waves travel away from the transnitting antenna

the earth exerts an influence on them. Part of their
energy is absorbed by the earth and is dissipated as heat.
This loss of energy can be great and as a result of this
the surface wave transmission is limited to moderate dis-
tances. As the surface wave travels along the surface of
the earth it gives up energy to the earth and as a result
there is a retardation of the wave front along the surface
causing it to bend forward in the direction of propagation.
Therefore the antenna does not pick up the maximum intensity
of the electrical field, but rather a component of it,
because the antenna is no longer parallel to the electric
field vector. This tilting of the wave front has been
measured and is as much as 32° from the vertical at broad-
cast frequencies.

Poorly conducting ground surfaces cause a greater
dissipation or absorption of the radio wave energy than good

conducting surfaces, hence a greater tilt of the wave front.

16

In an attempt to account for this absorption of energy

by the earth Sommerfeld (Byrne, 1932) advanced the following

equation:
5 ‘= ya) 5:33; (1)
where E . field strength in millivolts/meter at a distance
of d miles
ya)- Sommerfeld's integral to account for earth
effects

P - doublet antenna power in watts
d - distance in miles from transmitter to point of
measurement.
Sommerfeld's integral, y(0(), was approxinated by Van der

Pol to the following:

 

 

= .2+a3dfi__
3(4) .2 M + and: (2)
where
_., 8.38!/o”°c/
0‘ ,(2 O. (3)

where A II wave length in meters
- earth conductivity in can
d - distance in miles.

We can see from equation 3 that the conductivity is
one of the earth's properties that affects the intensity.
This conductivity is the total effect of all the various
conductivities of the rocks over which the wave has passed.
If a traverse should cross a particularly poor conducting

body there will be an additional absorption and tilting of

17

the wave which will cause a further decrease in intensity.

Reflection and Refraction within the Earth

The intensity of the surface wave is also affected by
waves that return to the surface after they have been re-
flected and refracted by discontinuities within the earth.
The intensity of these waves which pass through the earth
is rapidly attenuated by absorption of energy during propa-
gation, and by dissipation of energy on reflecting and re-
fracting interfaces within the earth.

The effect the ground-refracted wave will have on the
surface wave upon recombination in the atmosphere is
determined by the path within the earth, and by its velocity.
The velocity of the electromagnetic radiation through a
material is a function of the dielectric constant and the
magnetic permeability of that material. The velocity of
the wave within a medium can be expressed in terms of its
speed in free space by the following equation which assumes
a fixed frequency:

 

0,”. = W (h)

where cI - velocity in the medium in meters/second .
c I 300,000,000 meters/second, velocity in free space
[I - magnetic permeability
k - dielectric constant.

If the ground-refracted wave returns to the surface it

may or may not be in phase with the surface wave because of.

18

the path it has followed and the subsequent change in
velocity. If'it is 180 degrees out of phase there will
be attenuation and an intensity low. If, however, the
ground-refracted wave is in phase with the surface wave
there will be a reinforcement and hence an intensity
high. The path length is determined by the angle of
incidence with which the radio wave impinges on the dise
continuity, and the electrical properties of the medium
through which it travels.

Induction
An electromagnetic field is induced in the conducting

rocks where the radio waves enter the earth. As this field
is 180 degrees out~of phase with the inducing field it
causes some attenuation of the surface wave and hence an .
intensity low over this location. The better the conductor,
the stronger the induced field, and the lower the intensity.
As the conductivity of the rocks decreases so will the
strength of the induced field and therefore the amount of

attenuation.

Surface Environment
The earth is only one of many things that affect the
radio field intensity in this type of mapping. In general,

the more pronounced and spectacular changes in field

19

intensity are caused by surface features. Fortunately
these can be accounted for by close observation on the part
of the operator.

Iflost noticeable of these effects are those caused by
overhead wires of various types. Electric wires cause the
largest changes in the intensity, telephone and guy wires
cause changes of a lesser degree. Bridges, railroads and
metallic culverts under the road also cause changes in the
field intensity. In general, any metallic object that can
act as an antenna will usually cause some sort of abnormal
response in the meter, although wire fences along the
road did not cause any noticeable changes in the intensity.

The type of response experienced by the meter from any
given type of wire or object is not constant. It varies
as a result of a number of factors. If the disturbing
factor is an electric wire the strength of its field
depends on how much current it is carrying. The amount of
disturbance also depends on the relationship between the
wire, the transmitting antenna location, and the vehicle's
.motion in relatioa.to these factors. When driving in one
direction under a wire the response may be large, however
there may be little or no response from the same wire when
driving in the other direction, or it may be in the
opposite direction to the first response, even with the

same station. See Figure 28.

26

In most cases the disturbance caused by a wire builds

up as the wire is approached and drops off as the wire is
left behind, with the greatest disturbance coming directly
under the wire. This however, is not inviolable. There
are some wires that give all of their effects on one side,
regardless of the direction of the transmitter or the
direction driven. This is the exception rather than the
rule.

Topography may also affect the intensity if it is
severe and close to the road. There seems to be some
effect from swamps, but this is not something that can be
relied upon. 'Woods were continuous on both sides of most
roads and did not present any problems for this investi-
gation although it is possible that they might affect the
intensity under other circumstances.

The reinforcing in modern concrete highways has the
effect of shielding the underlying geology so that the
geology has little effect on the radio waves.

.meteorological conditions have been found to affect
radio waves by Gracely (1959). He has shown that as the
temperature increases the intensity decreases, and there
is a specific temperature for which each individual fre-
quency is attenuated the most. In this project the
temperature had no affect because most of the traverses

were short in distance and therefore in time. Pullen (1953)

21

states that meteorological effects are noticeable at low
frequencies over long time intervals, or at high frequencies
in short time periods. There are changes during the year,
the winter apparently being the best time of year for
reception. There seems to be no relation between magnetic
storms and long wave field intensity. There does, however,
seem to be a relation between intensity and sunspots, for .
as the activity of sunspots increases so does the intensity.
The last two statements do not hold for short waves. All
wave lengths are affected by bolts of lightning which

result in erratic responses.

PENETRATION OF RADIO'WAVES INTO THE EARTH

The depth to which radio waves penetrate the earth is
primarily a function of their frequency. The higher the -

. frequency the less the penetration. This is one reason why
radar which utilises very high frequency waves will not
work in this type of investigation.

The relationship between the frequency and the depth‘c
of penetration of radio waves in the earth is controlled by
the phenomenon called the skin effect. The skin effect is
the crowding of current toward the earth's surface with
increasing frequency. This is caused by the radio field
inducing in the rocks another field that is 180 degrees

outabfephase. As the frequency of the radio wave increases

22

the intensity of the field that is induced in opposition
also increases. As the intensity of this field becomes
greater the current is limited to increasingly shallow
depths.

Joyce (1931) has related the absorption of electro-
magnetic radiation in the earth to the frequency of the
wave, the dielectricconstant, the resistivity and the
magnetic permeability of the earth. He has expressed this
as a ratio of the amplitude of the wave at a depth, d, to
the amplitude of the wave at sero depth. This ratio is

called the transmission factor and may be expressed as

elf—4341”“ (5-)) * (3%)}? "9f (5)

TE:

where - depth in on

d

c - velocity of light in cm/sec

k - dielectric constant

f - frequency in cps

)9 - resistivity in e.s.u.

[U'- magnetic permeability.
Joyce has made calculations using this relationship to
show the percent absorption of the signal with varying
dielectric constants, resistivities, and frequencies. Some
of his results are shown in Figure 2. The depth for which
these calculations were made is 12h feet, and the magnetic
permeability is considered to be equal to 1. It can be

seen from Figure 2 that as the frequency increases the

23

,.
"1, |
L‘Q“J-

 

 

 

 

IC)O

9C)

8()

7 0

6'0

 

 

5 O

 

4 O

 

3 O

 

2 O

 

l O

 

 

 

 

 

 

 

l
I

i

 

 

Frequency in egg.

(After.Joyce,l93l,poge 4)

J. (o ' H

 

7 O
D

Broodcastronqc

Absorpnon

Per cent

24

amount of absorption increases. It can also be seen that
as the resistivity decreases, and as the‘dielectric con-
stant decreases, the amount of absorption increases.

For a given frequency and resistivity the dielectric,

constant plays an important role, e.g., at f - 106 cps
and 1° - 106ncm, doubling k reduces the absorption by

almost 10 percent.
a

PERTIIEHT ROCK PROPERTIES

The radio field intensity method of mapping measures,
to some extent, all of the electrical and magnetic pro-
perties of the earth. The distribution and the nagnitude
of the current induced in the subsurface depends on the
type of electrical and magnetic properties the rocks possess.
The most important of these properties is the resistivity.
Resistivity,/°, is defined as the resistance in ohms between
parallel faces of a unit cube. This is usually measured
in ohm-centimeters. The inverse of resistivity is conduc-
tivity. The conductivity, J,'is often used in equations
.expressing electromagnetic relationships. It is usually
measured in mho-centimeters. Table 1 shows the range of
values these two important physical properties have in some
of the rocks encountered in this survey. Rocks that have

3

resistivity values of 10- to 10 ohm-centimeters are con-

sidered good conductors, 100 to 10"9 are intermediate, and

25

10'10 to 10-17 are poor conductors.

Another electrical property to be considered is the
dielectric constant of the rocks and ninerals. The
dielectric constant is a measure of the rocks ability to
be polarised in an electric field. With an impressed
electrical field, E, there is P, polarisation per unit
volume that is proportional to E, and E, the electrical
susceptibility. This is expressed as the total electric
flux Etf per unit area in the following equation:

(6)

5%, =' (E‘*‘¢fl'fl’ on [aflfii4flvgfl

The term (1 + ATTE) is called the dielectric constant, k.
The dielectric constant is an important electrical
property when considering general electromagnetic wave
theory, as seen from Joyce's curve, Figure 2.

The magnetic permeability is another rock property
that must be considered. The magnetic permeabilityflfl,
of a substance is the ease with which magnetic flux can
be established in a material, or the ratio of the number
of lines of force passing through the material to the

number of lines in a like cross-section of air,
=.§.
,u H (7)

where H - intensity of field
B - flux density.

The magnetic permeability is a consideration in determining

26

Thble 1

Pertinent Electrical Pro rties

 

 

 

of Rocks Encountered in t s Survey*
Rock Type Resistivity Conductivity
ohm-centimeters mho-centimeters

Basalt 2:105 0.52:10“6
Diabase 2:103 to 2x106 0.5x10'3 to 0.5110”6
Gneias 2x10“ to 3.Lx106 0.5110" to 0.29:10'6
Granite 3:10“ to 106 0.33:10-5 to 10'6
Quartsite 103 to 2x107 10-3 to 0.5x10'7
Schist 5:102 to 105 0.5x10'2 to 10"
Syenite 10b to 107 10" to 10"7
Trap Rock 1.5x10‘ to 3x105 0.66x10“ to 0.33x10-5
Glacial Drift 8x10'2 to 9.51105 0.125x102 to 0.05:10’5
Conglomerate 2 . 5x103 ‘ to ' 1. 5x106 0.1.x10“3 to 0 .66x10'6
Sandstone 3x103 to 107 0.33x10'3 to 10'7
Hematite 5x10h to 107 0.2x10" to 10'7
.lhgnetite » 0.6 to 5:163 1.66 to 0.2119‘3

 

 

 

* Source of Data J. J. Jakosky'&,F. Birch

 

Table

27

1 (continued)

 

 

 

Rock Type Magnetic Permeability Dielectric Constant
Basalt 1.0085 to 1.079 12
Diabase 1.0009 to 1.0526 --
Gneiss 1.0012 to 1.012 8 to 15
Granite 1.0012 to 1.012 7 to 12
Quartsite 1.0000 7
Schist 1.0012 to 1.012 11 to 12
Syenite -- 13 to lb
Trap Hock -- 18 to 39
Glacial Drift -- --
Conglomerate 1.0012 to 1.012 --
Sandstone 1.0006 9 to 11
Hematite 1.000h8 to 1.0012 25
Magnetite 26.0 to 1.5 --

 

 

 

 

28

Athe velocity with which an electromagnetic wave will pass
through a substance.

Table 1 gives the range of values of these physical
properties for some of the rock types encountered in this

survey 0

The exact manner in which the electrenagnetic waves
interact with the subsurface is not known. Therefore, by
necessity, some of the considerations in this section are

tentative and subject to further investigation.
EQUIPMENT

INTRODUCTION

The major components of the equipment employed in this
investigation were borrowed from the Illinois Geological
Survey. This equipment, which was used by Pullen in his
investigations,-was obtained in the summer of 1961. Field
studies with the equipment were initiated at this time.
These studies included 1. investigating the optimum speeds
at which traverses should be run, 2. types of antennas best
suited for this type of work, 3. the effect of cultural
disturbances on the intensity of the radio field and A.
general operational procedures. As this was a continuing
project technical problems that arose with the equipment

during the summer were solved the following school year.

29

RADIO FIELD INTENSITY HETER

The major component of the method is the R.C.A. 308-3
Radio Field Intensity Meter. This is a six band receiver
covering the frequency range from 120 kc to 18 me. The
meter contains, besides the receiving circuits, calibrating
circuits to enable the operator to make absolute field
intensity measurements. This meter is calibrated in
microvolts per meter. This is defined as the voltage in-
duced in a conductor 1 meter long when held so that it
lies in the direction of the electric field, and at right
angles to the direction of propagation and to the direction
of the magnetic field. These circuits were not used,
however, because relative variations are all that is needed
for the purposes of this method and because the type of
antenna used would not permit absolute measurements to be

made.

POWER SUPPLY

The 308-3 field intensity meter is normally powered
by a 135 volt wet cell battery. Since there was no way of
conveniently charging the battery in the field, a power
supply was constructed that could be powered by a 12 volt
automobile battery. This power supply was similar to one
built by WKAR, Michigan State University Radio for an
identical meter. The circuit diagram of this power a:

30

supply is shown in Figure 3.

The power supply consists of three parts: an auto-
mobile battery, a converter, and a rectifier. A special
12 volt auto battery was procured with an extra 6 volt
terminal. This battery was kept charged by connecting it
in parallel with the vehicle's battery when the equipment
was not in use. This battery ran the converter which
took the 12 volts DC and converted them into 115 volts AC.
The converter is a 90 watt A.T.R. (American Television and .
Radio Company) converter. The rectifier plugged into the
converter. The rectifier changed the 115 volts AC to 135
volts DC and 90 volts DC to operate the plates and the
screens, respectively, of the tubes in the 308-3. Fila-
ment power came from the special 6 volt DC terminal on
the battery. The ground for the equipment came from the
negative terminal of the battery. However, the filaments
needed a positive ground and therefore had to be isolated
from the car body while the charging of the equipment
battery was in process. If this was not done a short
circuit developed. This can be seen in Figure A which
shows a schematic diagram of the connections between the
various components. These power supplies, in addition to
two 7.5 volt batteries in the meter, completed all of the

necessary energy to operate the equipment.

31

RECORDER

The recorder used in this investigation was an
Esterline-Angus, model AW, DC milliammeter. Full scale
deflection of the meter was provided by a current of 10
milliamperes. (The record of intensity changes is produced
as an ink pen which is connected to the meter movement
noves across a paper chart which is fed through the meter
at a speed which is proportional to the speed of the
vehicle. The synchronization of the vehicular speed and
the chart is acconplished through the use of a Clark
Speedometer Too. The speedometer cable is disconnected
from the back of the speedometer and is connected to the
Tee. From the Tee there are two cables, one of which
goes back to the speedometer and the other which goes to
the recorder. This drives the recorder at a speed that
is proportional to the vehicle's speed. In this investi-
gation four inches of paper represented one mile of
traverse. .

Within the recorder there is, in addition to the re-
cording pen, an event marking pen. This pen is activated
by a 115 volt AC solenoid which is controlled by a key
that was operated by the driver. This pen was used to
mark cultural features that might disturb the radio field .

and also to mark features that were used to establish the

32

>nm;

30.
qu

 

T>om .Ro

n oh:u_m

>Jaa3m «mica

'hl'

 

e nmo

 

 

.smm
swear

 

 

 

 

 

 

 

 

 

¢>n

 

 

 

 

2<mo<_o oz_m_>’

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

>9. .ce>u d ogzwflu
!\\\!
_W L
:28 .23.. . A
.2200 a
dozen
. J
a W
amu.0uom _ .nfi -
maocd .031 35:02: 0.07; 3:02.00 >N. (
-ostfmu m-m0m 4.0.x .de r01
1)
1) ll
«pom 3.0; :om 5CO
e o - a.
6 TH

occo.c<

 

 

 

 

 

 

 

 

 

 

 

 

34

location of the traverse, e.g., road junctions, railroads,

and county lines.

ANTENNA

One of the results of the investigations conducted
during the summer of 1961 was the decision to use an
omnidirectional antenna, rather than the loop antenna that
is normally used with the 308-3. Even though the loop
antenna has greater sensitivity than the omnidirectional
whip antenna it must be kept oriented in a fixed position
relative to the radio field. This would have been im- .
possible in a oneoman operation such as this one.

A number of experiments were carried out on the
possibility of spinning the loop to avoid having to orient
it. This proved impractical with the equipment available.
The next best type of antenna was the omnidirectional whip.
The exact configuration of the whip was not decided upon
until the field operations were initiated. The final
choice was the tuned whip which is shown in Figure 5.

v
105"'Whip Antenna
n/ .

Condenser
50 ,u farads

 

  

 

To Meter

35

The antenna was attached to the back of the vehicle
via a bumper mount. The antenna was kept rigid because if
it swayed it caused an unwanted response on the record.
This was done by use of a wooden pole to which the antenna
was attached, and this was in turn fixed to the vehicle.
This wooden pole also served as a mounting place for the
coil in the antenna circuit. The condenser used to tune
the antenna was fixed on top of the meter inside the

'ChiClCo
FIELD PROCEDURES

This was a one man operation, therefore driving,
observing, operating the event key and taking notes had
to be done simultaneously. To alleviate this condition
a magnetic tape dictaphone was used to record the field
notes. The dictaphone was powered by a 30 watt A.T.R.
converter that plugged into the cigarette lighter of the
vehicle. The dictaphone was a DeJur Magnetic Tape
Stenorette.

The general areas to be investigated were selected
in the office on the basis of the conditions previously
cited. On arrival at an area a general reconnaissance
was made to determine whether radio broadcast stations
were detectable and which roads were most suitable for

traverses o

36

Investigations were carried out in the Marquette
area, the Iron mountain area, the Ironwood area, the
Keweenaw area, and selected areas in Wisconsin. Examples
of all traverses in these areas where the intensity
changes correlated with the geology are shown and dis-
cussed in the section dealing with results and interpre-
tations. Representative areas where the radio field
intensity variations failed to correlate with the geology
are also shown.

Sone of the specific areas initially chosen were
later changed because of the inability to receive radio
stations, or because of cultural interferences.

The field procedure for making a traverse is given
below.

1. The road previously selected for investigation
was located.

2. A reconnaissance of the road was made to see if
it was feasible to make the traverse. The
presence of many overhead lines was justification
for disregarding a road.

3. If the traverse was feasible the equipment was
warmed up and a station selected. A preferred
station was one which gave a reading of mid-scale
on the milliameter in the 308-8.

6. As the traverse was run events were marked on the
record with the event marking pen, and notes were
recorded on the dictaphone. The events narked
and the notes describing these events included
orientation marks, culture, outcrops if any, and
pertinent comments about other surface features.

5.

6.

7.

8.

37

At the end of each traverse an evaluation of the
traverse was made to determine the success, and
to see if there was a particular area in which
closer visual observations should be nade.

A re-run was then made using a different station
if one could be received. There are only nine
stations in the northern peninsula in the area

in which the investigations were carried out, and
these are all low power.

If a third station could be received successfully
then the road was run again, etc.

Many times outcrops were available within easy
access of the road, and the operator would get
out and make a determination of the lithology
and record it appropriately.

A.
B.
C.
D.
E.
F.

38

Figure 6

Equipment Mounted in Vehicle

R.C.A. 308-3 Field Intensity Ieter
Hilliammeter

Esterline-Angus Recorder

Clark Speedometer drive

Control Panel

Event Key

 

 

39

RESULTS AND INTERPRETATIGNS

INTRODUCTION

The results of this investigation are shown on the
following pages. Not all of the records that were made are
shown. These shown are the ones most indicative of the
successes and failures of the method. Sometimes the changes
in the intensity and hence the geology, stand out very well.
In other cases this is not so.

As this investigation was carried out in an area where
the geology is relatively well known little attempt was
made to introduce formations not on the present maps. At
the same time, valid significant changes in the intensity
level were not ignored. 'When more than one geological
interpretation of an area was available the interpretation
which best fit the intensity record was used. In every
case an attempt was made to identify the geologic changes
on the records before the geological maps were consulted.
The final interpretation, however, was based on the naps
available. The most detailed maps available were used in
all cases.

The results are presented in groups from areas which
have the same general stratigraphic sequence. The general-
ised geologic column showing stratigraphy and lithologies

for each area is presented prior to the discussion of each

40

section. In the description of the records only the

stratigraphic names are used. The basis for the strati-

graphy was the Centennial Geologic Map of the Northern
Peninsula of Michigan; (1939), publication 39, series 33.
In the discussion of each record the following

information is given.

Number

Date

Name

Location

Radio station

General topography

Road type

Vegetation

A numerical sequence for
cataloguing.

Day on which the particular tra-
verse was run.

A geographical title for use in
the field by the author.

The ran e and township, and
sectionis) of the particular
traverse. Sometimes it was more
convenient to use the name or
number of the road if the traverse
is long and winding. In this case
the location of the starting point
is given.

This identifies the radio station
used, giving call letters, fre-
quency power, city, and distance
and azimuth from the starting
location of the traverse.

This is a general explanation of
the topography if the topography
is much the same along the entire
traverse. Significant changes in
the topography are noted.

The material with which the road
is surfaced .

The type of vegetation along the
traverse.

Geology and source

Interpretation

Comments

Scale

41

Geology refers to the formations
and structures encountered along
the road with the mileage given
from the start of the traverse to
the geologic feature.

Source indicates the authority on
which the geology is based.

A discussion of the correlation
of the intensity changes with the

geology.

Additional information on the
record or its interpretation.

A inches - 1 mile all records.

In the interpretation of the records it is important

to know why the event key was operated. On every record

just off the scaled paper is the trace of the event key.

This is always on the low intensity side. The reason the

key was operated is indicated by the coded letter next to

its mark.

1. - Start of traverse.

w¥§fi§“§*’”

- Bridge.

- Road junction.

- Power line crossing road.
- Telephone line crossing road.

- Railroad with its wires.

- Side road to the north.
Side road to the east.
- Side road to the south.
- Side road to the west.

gamut

TPL

42

Of no importance in interpretation.

Guy wire crossing road.

Traverse turns or bends north.

Traverse turns or bends east.

Traverse turns or bonds south.

Traverse turns or bonds west.

Telephone lines start parallel to traverse.
High hill next to traverse.

Operator adjusted meter.

End of run.

43

THE NNRQUETTE AREA

The Harquette area was chosen for investigation because
the geology is well known, there are a variety of rock types,
and there is considerable structural deformation. Geologi-
cally this area is a series of subparallel synclines, which
trend generally east-west.

In this area there are three radio stations: WDNJ,
1320 kc, 1 kw in Hhrquette; W013, 970 kc, 5 kw, and WJPD,
12A0 kc, 1 kw, in Ishpeming. Unfortunately no two stations
could be used on the same traverse. Host of the traverses
in this area were run using'WJAN, because of its high power
and low frequency. The others were used where possible.

Generally the topography in the larquette area is rugged.
An attempt was made to pick traverses in level areas but

this was not always possible.

44
Figure 7

Generalised stratigraphic column for the Marquette area.
(After The Centennial Geological Mhp of the Northern

Peninsula of Michigan, 193)

 

#’

. 2mm...

+

1EOAMERUUIor*
3trmxammunn

AHMHEIAH

“*t

annnan

 

-4rrt

 

8
0
8
.p
3.
.93
m
tenants
q,‘f‘uiJacobsville
o sandstone
g H
5
m
*aserss
Nichigamme
slate
ar 3 urg
§. GTEenwood
8'
Goodrich (
Ne aunee
g 8
g o
-« .
s --» ---------- --
g Siamo
Ajibik
*** unconformity*

Nmnmxin

 

 

Glacial outwash and drift

unconformityeeaaeaaasesaeass*asasazeeeee*ee**eeeta

Red and brown sandstone with
mottlings of white and rey.
Red arkosic with a cong omerate
at the base.

conformity*8**********#**********************#*#

Grey slate, darquuarts slate to

 

hitic slate and re acke
EEsIc voIcanIcs and pyrocIastics

 

Wewe slate

with interbedded ra acke.
Magnetic slaty quartsites, sIaEy
iron formation, magnetic grunerite
with laminae of green amphibole.

 

Hainly massive vitreous quartzite
with jasper conglomerate at baseo~

uwasunconfornityssasassenate*aaeeeaaaesssstetcassettes

Iron formations. Silica and iron
oxides hematite and limonite; thin
jaspillite; dominantly ferruginous
cherts

Mainly thinbedded slates, locally
with ferruginous quartsite.

Quartsite; schists, granitic gneiss-
*******a*****aansasaaeaasaaasaaasaaa

Slate interlaminated with graywacke
and quartsite.

 

 

 

 

H — —=—— -------------- --
,§ Kona Massive and banded cherty dolomite
Ilesnard Quartsite, dense, light-colored and
vitreous; conglomerate at base.
afieeasuncon:ornity*#a***********************asaaataaesss
Laurentian Shistose and gneissic intrusives in
3 the Keewatin
+5 fiewatin 3381c intrusives,1:Igny metamor-
E phoned.
Kitchi
3 Mona

 

 

 

Number
Date
Name

Location

Radio Station
General topography
Road type

Vegetation.

Geology and source

Interpretation

Comment

45

Figure 8

38
June 21, 1962
Deer Lake-5

On the road that goes thro h Sections-
33, ,g2, ,29, 28, 21, and 16, T. A N., R.27W.,
Mic e

'WJAN 970 ksWS kw, Ishpeming,.Michigan,
3mi es 320 from starting point in NW
1 9f SOCo 33

Very hilly.
Blacktop.
Wooded on both sides of road.

1. start over Kitchi Schist.

2. 1.15 miles Kitchi-Ajibik contact

3. 1.31 miles Ajibik-Peridotite contact
A. 1.96 miles Peridotite-Kitchi contact
5. 2.95 miles Kitchi-Ajibik 7 contact

6. 3.A0 miles Ajibik-Siamo ? contact

7. 3.78 miles Siamo-Michigamme ? contact
8. b.05 miles and of traverse

U.S.G.S. monograph IIVIII and LII

Some of these contacts do not show up
toowell but others show up very well

and agree with the geology. The reasons
could be changing drift thickness, the
effect of tepography, or unmapped dikes
or sills. Where the changes in intensity
are not conclusive the geology is put in
about where the maps show it to be. It
is this uncertainty that is indicated by
the question marks.

A repeat traverse was run with nearly
identical results.

  
    
    
       

THE ESTERLINE-ANGUS CO. INDIANAPOLIS, mu, u. s. A. CHART NO. 4331-X

 

 

c_-_.

   

- 7 ‘e O — —-——4— -- r&——~ v ~. , —7 4--
l
,

      

Kitchi

- .+_ -,...

   

Kitchi} "peridotite-_,dikes

, _--_

peridotite AJLLiK T

,__, __ 5___...

v '

 

 

 

 

 

Number
Date
Name

Location

Radio Station
General topography
Road type

Vegetation

Geology and source

Interpretation

Comment

47'

Figure 9
51
June 30, 1962
IN - 7

On Marquette county read 553 from the
junction of 553 and A80 north for 5.37
miles. The road junction is in Section
15, T.A7N., R.25W., Much.

WJAN, 970 kc, 5 kw, Ishpeming, Mich.
1A miles west of road junction and
starting point.

Very hilly.
Blacktop; very winding.
‘Wooded on both sides of road.

1. start over Cambrian sandstones
2. 2.38 miles Lk. Superior-Granite
3. 2.65 miles Granite-Mesnard

4. 2.82 miles Mesnard-Kona

5. 4.32 miles Kona-Hesnard

6. 4.Al miles Nesnard-Lake Superior
7. 5.47 miles end of traverse

U.S.G.S. Monograph XIVIII, Atlas plates
XXXVIII and IIIIV.

The changes in intensity correlate very
well with the mapped geological contacts.
The fluctuation on this record could be
due to topography as the traverse was
very hilly. There were also a great
number of telephone and guy wires which
hgd only minor variations associated with
t on.

There was a repeat traverse which was nearly
identical.

The spot marked I (1.25 miles) may be due

to a change in drift or sandstone lithology
or a hill in the granite basement covered

up by later sediments. The latter is most
probable, because there is a field of high
intensity associated with both and the base-
ment rock undulates quite a bit as the
outcrops indicate.

 

Id;

H

H

m
.—‘-H~Twunql—V\

ex~n

\\\~4E\l\\.

   

unoe m u. s. A. THE ESTERLINE-ANGUS Co. mommpous, 1m... u. s. A.

THE ES‘TERLINE-ANGUS Co. mommpous, mm, 11.3. A. Cr

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7- >— ~-§-~— +- - ,
—- ~r~-—4‘-————~—--- **_H"
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P,

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1.1L 0 -__-_.rrr_d., --—-—--——--t———4—-—-~-
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Number
Date
Name

Location

Radio station

General topography
Vegetation

Geology and source

Interpretation

Comment

49

Figure 10
50
June 30, 1962
NI- 6

OnIHarquette county road A80 from the
junction of 553 and A80 north-west for
4.9 miles. The road junction is in
acetion 15, Totem-e, ReZSWo, MCho

WJAN 970 kc, 5 kw, Ishpeming, Mich.
lA miles west of road junction and
starting point.

Flat to gentle hills.
Wooded on both sides of road.

1. start at junction over Cambrian
sandstone

2. 1.29 miles Lake Superior-Mesnard

3. 2.50 miles.Nesnard-Kona

A. 2.63 miles Kenn-Wewe

5. 3.A3 miles Wewe-Ajibik

6 o 3 o 59 .1198 Ajibik-Siamo

7. 3.79 miles Siamo-Ajibik

8. A.32 miles Ajibik-Siamo

9. 5.05 end of run

U.S.G.S.IHonograph.IXVIII, Atlas plates
XXIVIII and IIIVII

This is an excellent example of how well
the field intensity measurements can be
applied to geologic mapping. The corre-
lation between the geology and the
intensity variations on this record are
excellent. The small changes in intensity
in the Wewe could be a facies change.

The traverse was repeated with nearly
identical results.

)3

NO.

 

 

4331-X

CHART No.

INDIANAPOLIS, IND., U. S. A.

THE ESTERLINE-ANGUS Co.

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‘n

 

Number
Date
Name

Location

Radio station
General topography
Road type
Vegetation

Geology and source

Interpretation

Comments

51

Figure 11

63
July 1, 1962
Old I a 35

On Marquette County read 510 from Midway,-
in Section 23, T.A8N., R.26W., to Big Bay,
Michigan. Complete traverse not shown.

'WJAN, 970 kc, 5 kw, Ishpeming, Mich.
Very hilly.

Black top to start with, then gravel.
Heavily wooded.

The geology along the road is not well
known. The traverse crosses the end of

the Dead River Basin about where the bridge
is located.

1. start over syenite.

2. 1.61 miles syenite-Huronian sediments?

3. 2.10 miles bridge -

4. 2.30 miles Huronian sediments-greenstone?

5. 3.00 miles fault along south side of
Clark Creek Basin; Huronian
sediments-Mona ?

$.00 miles Mona-dike? ‘ -

7. A.1O miles dikeéMona-T

A.25 miles fault 7 -
9. A.A0.miles blacktop road ends.

10. 10.76 miles south edge Clark Creek Basin
11. ll.A5 miles north edge Clark Creek Basin

Before and after the Clark Creek Basin the
rocks are greenstones and granites. The
reception was poor along most of this
traverse.

The geology here is speculation by Dr.
Justin Zinn and the author. There has been
no recent work done in the area and the
only known map (1936) is unavailable.

 

 

 

  

X'IEEV 'ON ”nag-L53 3H,], 'V'B'n m sown

 

53

THE KEWEENAW AREA

The Keweenaw area was chosen for the presence of the
Keweenaw fault. Geologically the area consists of the fault
trending generally north-east -- south-west. The "Lake
Superior Sandstone“ (Cambrian or Precambrian?) lies to the
south, and the Keweenawan sediments lie to the north. The
north side of the fault has moved up and all the Keweenawan
sediments dip toward the north-east.

In the northern part of this area there are two radio
stations. ‘WHDF, lAOO kc, 250 watts, is in Houghton, and
WNPL, 920 kc, 1 kw, is in Hencock. As WNPL was more power-
ful and lower in frequency it was used exclusively. East of
the Eagle River no station could be received with this
equipment.

The topography is quite varied in this area but it was

generally level where the traverses were run.

54

Figure 12

Generalised stratigraphic column for the Keweenaw area.

(After the Centennial Geolo
Peninsula of Michigan, 1936

gical flap of the Northern

 

”Mutt

g

ALGOIKIAI '

 

 

Pleistocene

***#****

Reweenawnn

Tune

Superior Ss.

.Hiddle

 

Jacobsville
sandstone

Freda sandstone

Nonesuch shale
e ore. aps

. ---------------- ”d

Great Conglomerate

****unconformity**
Eagle River and
Ashbed groups.

 

o. 8 Conglomerate
Bohemia Range group

Glacial outwash and drift

4****uncenfornity***T*************************

Red and brown sandstone
with mottlings of white
and grey. Red arkosic
with a conglomerate at
th. base 0

reasveeeTeeeewsenynncenforlicy?safessssasssaeestssssssasees

A

Conglomerates.) Red sand-
stone, arkoses, shales.

 

Dark shale and sandstone
"This SasaItic Iava rows,
anygdaloidal.

Coarse heavy conglomerate
and quartsite
sassassassstessasaasasass
Basic lava flows with
many conglomerates and

a few sandstone beds
iiinly basic lava rows,
intrusions of basic ig-
neous racks and granite.

 

Nhsnard e idote
lflCentraI fiine group

 

 

Number
Date
Name
Location

Radio station
General topography
Road type

Vegetation

Geology and source

Interpretation

Comment

55

Figure 13

44

July 13, 1962

Laurium - 2

Sections 10 and 3, T.55N., R.33W., Mich.
WMPL, 920 c, l kw, Hancock, Mich. 6.5

miles 8.54 . of starting point in SW A
of Section 3. 1

Very gently downhill to the south.
Gravel.
Open fields.

1. start over sandstone
2. 0.A miles Keweenawan fault
3. 1.0 miles and of run.

U.S.G.S. lenograph LII

We see here a completely different type
of response over the Keweenawan con-
glomerates. This may be due to various
thin beds of conglomerates. The change
in field intensity agrees very well with
the mappedlocation of the fault.

The traverse was repeated with nearly
identical results.

 

 

 

lava flows sand stone

4—4...—
-_ 4 .

_.*_

_._..

_‘.-- - 4..__ +_._

 

-- 4 - *f — «—
——«-—~»+-«.—
—- \

—---- -$_-——-§——'
.————~—-—~——_._*—.*7 -

-4.__.q-—-——~———+——

 

‘3': van “am ‘sI'Io-IVNVIONI ‘03 snowy-annuals: 3H1

57

THE IRON.MOUNThIN AREA

Geologically the Iron Nbuntain area consists of a
parallel series of faults trending east-west. This
faulting gives rise to repetition of beds from north to
south. Host of the formations dip at very high angles in
this area. The knowledge of the geology and the steeply
dipping beds were the main factors governing the choice
of the Iron mountain area.

In Iron Mountain there is one radio station, WHIQ,
1A50 kc, 250 watts. Even considering its low power WHIQ
seemed to have abnormally poor areal coverage. This
might be accounted for by the fact that the transmitter
is located on highly conductive iron formation. However,
it was possible to receive WDBC, 680 kc, 1 kw, Escanaba,
Ndchigan A8 miles east of Iron Mountain. These two
stations were used in this area wherever possible, and
provide a good check of the effects of varying transmitter
frequencies and distances. One excellent example of this
is seen in Figure 19.

The topography in the Iron Mountain area is quite
varied. The land ranges from very hilly with woods, to

very flat with open fields.

‘r.‘ e

58

Figure 1A

Generalised stratigraphic column for the Iron.Nountain
(After the Centennial Geological lap of the
Northern Peninsula of Michigan. (1936).

 

1*

E

 

AIGONKIAN

a
a

 

 

Keewatin

leietocene

*P

E

Laurentian

.3

'U
'U

i!

T*****

H

3
.3

 

Glacial outwash and drift

Jesseaweuncanger-1emanatesaassessessesssessseeseeaeaese

 

 

 

 

 

H Jacobsville -Red and-brown-sandstone with
3 sandstone mottlings of white and grey.
3 9' Red arkosic with a conglomerate
~ :83' g b‘..j_
3 “t: “V
g g Badwater Greens tone
(3‘s s
its: seesseeassunconfornit assasssaassssssssessaseasssssssss
‘Michigamme l-Grey slate, dark quartslslate--.-
slate to graphitic slate and gray-
“ wacke. '
& Guinnesec Basic volcanic‘rocks, Schists
3' schist and greenstones. Intruded by
the Hoskins Lake granite 7),
and sills of metagabbro. Wise.)

itseasssnnceuro-.1syneeseessssssssss*ssssesessseeeseaas

Silica and
hematite and
Interbedded slates.

**#*******************************

 

Laurentian

 

 

Upper -Iron formations.
5 slate iron oxides
o ---=.--‘ limonite.
g Brier
Trader
**unconformit
«Randville lassive and banded cherty dolo-
mite and marble, with beds of
greenish slate and graywacke.
Sturgeon Dense vitreous light colored

quartsites with conglomerate at
base.

Vsaeqeeaqeessseeuncsafer-1cyhas*aasaseasssaesexsseesscassettes:

-Shistose and gneissic intrusives
in the Keewatin. Masses of syen-
ite schist and gneiss rich in
hornblend.

 

 

1)th

location

Radio station

General topography
Road type
Vegetation
Geology and source

Interpretation

Cc-ents

59

Figure 15
5
June 14, 1962
#5

0n Dickinson County read 607 from Badwater
Lake in the south to Randville in the
north. The traverse starts in NE 9; of
Section 12, T.40N., 2.309)., Mich. .

WHIQ, 1450 kc, 250 watts, Iron Mountain,

. Mich. 4 miles 8.20%.er start.

Hilly in the south, flat in the north.
Poor blacktop and gravel. .
Wooded on both sides of the road.

1. start over Badwater reenstones

2. 1.46 miles Badwater- iks

3. 1.65 miles dikeaBadwater

4. 2.10 miles Badwater-Hichiga-e

5. 4.12 miles Michigan‘s-granite fault -

6. 6.21 miles ranite-Nichiga-e
7. 7.82 miles ch a-e-quartsite fault
traverse

8. 10.00 miles and o

0.8.0.8. professional paper 310.

Host of these changes in intensity are
easil seen. The lace marked x (0.30
miles may be snot er dike. North of Iron
Mountain, once the Badwater had been left,
the reception of WHIQ was very poor as can
be seen on this record. This break was
very abrupt. This hold true on all of the
runs just to the north of Iron Mountain.

One repeat traverse nearly identical .

   

’_.___ _._—.._..———..

t.. - _+._. 4..- -_..._...

      
 
      
          
     

4. “4‘-.——+v—.—.~—-

 
 

V-”,4_- .4... 4
- f.-__+__-_+

-.- .- +~-- -

.-._
._§ V _-,-..‘,___‘i.

5. —~- «§——v-?-

       

~-_ .‘. -~‘.-——~.—»-

\
a.» H-.—*¢—-§~_

, .-n H--b--—- F—-—~——-—»r. -.

   
 

   
   
   
   
    

-_*_.

       
 

_--,

 

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IONI '03 ‘00 SHDNV'INIM IHJ.

lumber
Date
Name

Location

Radio station

General topography
Road type

Vegetation

Geology.and source

Interpretation

Co—ents

61

Figure 16

19
June 11, 1962
Quinnesec #1

Sections 21, 28, 27, and 3h, T.40l.,
n.3ow. , Rich.

VHIQ, 1&50 kc, 250 vattsa Iron Mountain,
Hichigan. 2 miles 3.50 . froa start of
traverse in section 21 at road junction.

Gently dosn hill to the south-east.

Blacktop with shallow curves to the
south-east.

‘Uooded on both sides of road.

1. start over Upper Slates

2. 0.50 miles Upper Slate-lichi same

3. 1.65 miles Michigamne-Bandvi 1e fault
4. 2.80 miles end of run.

U.S.0.8. Monograph XII

The Upper Slates are poor conductors as
indicated by the high level of intensity.
There is a sharp drop in intensity as
the Michigamme is approached and a still
further decrease as the Randville is
approached and crossed.

Point 21 (1.50 miles) on the record may ~
ha e significance. The possible orplana-
tions are, in order of probability, as
follows:

1. the fault

2. the Cambrian sandstone {inching out
3. the drift changing thic ess

4. the soil type changing.

Six repeat traverses were run, all very
sini lar.

 

 

 

 

 

 

 

 

 

 

 

blight,

ichir—

Jul

VJ

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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\

 

 

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Number
Date
Name

Location

Radio station-

General topography
Road type
Vegetation

Geology and source

Interpretation

Comment

63

Figure 17

13-B and 13-E

June 1a, 1962

13 a 14

Town line road between Breitung, T.LON.,
H.30U. and Norway T.AON., R.29W., north
from U.S. 2 for 3; miles, Michigan

WMIQ, 1L50 kc, 250 watts, Iron Mountain,

and WDBC, 860 kc, 1 kw, Escanaba, Mich.
‘IMIQ's transmitter is 5 miles due west of

,traverse start at Escanaba, and WDBC's

transmitter is #2 miles due east of start.
Very hilly.

Blacktop straight north.

Farm land, open fields.

1. start over Brier‘

2. 0.18 miles Brier-Trader.

3. 0.30 miles Trader-Upper Slate

4. 0.38 miles Upper S1ate-Randville fault
5. 0.66 miles Randvilleéflichigamme fault
6. 1.63 miles Michiganme-Trader

7. 1.70 miles Trader-Upper Slate

8. 1.82 miles Upper Slate-Randville fault
9. 2.15 miles Randville-Upper Slate

10. 2.32 miles Upper Slateqflichigamme
11. 2.92 miles fault in.Nichigamme
12. 3.25 miles and of traverse

U.S.G.S. open file report on Southern
Dickinson County

This record shows the changes in. the geolo y
quite well. WIIQ's traverse is not too go
because the station is quite weak here. One
mile further west it could not be received.
WDBC is very strong at this location.

A repeat traverse was run with nearly
identical results.

433LX

CHART No.

INDIANAPO‘ S, "40., U.$. A.

THE ESTERLINE-ANGUS Co.

 

 

 

 

 

 

 

 

 

 

      

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,—
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.—1p—

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Michigamme

16

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Number
Date
Name

Location

Radio station

General topography
Vegetation

Geology and source

Interpretation

Comments

66

Figure 18

24 A
June 16, 1962
Cowboy Lake

Pro: Power Plant in Section 3 along the
township line between Sections 34 and 35,
T.40N., R.19E., and sections 3 and 2,
T.39N., R.19E., Much. Traverse turns
south at the north é corner of section 2,
Just west of Iron Mbuntain, Mich.

WMIQ, 1450 kc, 250 watts, Iron ountain,
.Mich. Transmitter 4 miles N.78 E. from
start of traverse at Power Plant.

Flat except for a low hill where traverse
turns south.

Open fields except for hill where traverse
turns south.

1. start over Quinnesec

2. 0.83 miles Quinnesec-Michigamme
3. 1.25 miles turn south

4. 1.65 miles Nichigamme-Quinnesec
5. 2.00 miles end of traverse

0.8.0.8. Monograph LII, plate XXVI.

There is some question as to the exact
location of this contact. However, the
intensity low seen on these records
agrees very well with the place-out by
monograph LII.

The low level of intensity at the start

of the record is probably due to the power
station and its associated wires by Cowboy
Lake. The probable reason that the inten-
sity over the contact is not the same on
both records is that there was a minor fluo-
tuation in the power of the station. This
change in intensity is only 0.8 milliamperes.

Michiganun' ’e -'
. . 7.7 f -lfie

9 »

 

’— h ‘ A Q

l 21...»; z —-

-- - a—___ V .
.. _, . 4..__-._~-V_- f—A
- 4—-_~——_._~.r___‘_

.__,7_ —-—«7» - .

 

~93 .v '3 11 “am ‘snoavuvnaul '01) SflSNV‘SNI'lhEJSQ 3H,]. ’V ‘3'“ III Ila"!

 

 

 

 

 

 

 

 

   

Location

Radio station

General topography
Road types
Vegetation
Geology and source

Interpretation

68

Figure 19

65, 66, and 67-A and 3
June 14, 1962
Lake Antoine 2, 3, and 4.

No. 65 8: 66 start in the 88 k of section 21,
T.4ml.,.R.30w., Mich an. No. 67 starts
at U.S.-2 in section 9, and runs through
sections ’20, 17 and 8, T.40R., a.3ow., Rich.

No. 55 and 66; me, 1450 kc, 250 «cu,
Iron Hountain, Mich. no. 67-A- 91410
No. 67-3; WDBC, 680 kc, 1 law, Escanaba, Rich.

Hilly.
Blacktop, and gravel.

Generally wooded all along the roads.

No. 65

1. start over Randviue

2. 0.70 miles Randville-uichiga-ae fault
3. 1.72 miles end of traverse

No. 66

1. start over Randville

2. 0.70 miles Randville-Hichiga-e fault
3. 1.00 miles end of traverse

NO. 67"

1. start over Randville oing north

2. 1.35 miles lsndville-gadwater fault
3. 3.15 miles and of traverse

No. 67-8 is a rerun starting over the
Badwater going south

0.8.6.8. open file report on Southern
Dickinson County

In all of these records we see that the
Hichigame has a much lower level of in-
tensity associated with it. The fault does
not show up too well on No. 65. Also
notice that this fault does not give the
same kind of response that Cloos and Howell
have show.

69

Figure 19 - Continued

The X (0.58 miles) on record 67-A.is where
the operator had to increase the gain of
the meter. Notice the difference between
679A.and B‘with the different radio sta-
tions. The response of the fault in 67-8
is more like Cloos experienced in that
there was a large change from the normal.
In this particular instance the field of
the fault was large.

Michigamme

 

 

_. Randville

+ l

_ Micnigaume

I

     

H3 'V '8 'fl "CHI ‘SI'IOJVNVIONI

'03 snouv—aunaalsa EHJ.

 

          

if,

‘badwater-rv

4— -

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annavnlle

 

7,:

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—4,

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I>

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X18817

 

 

 

 

 

Huber
Date

Name
Location

Radio station

General topography
Road type

Vegetation

Geology and source

Interpretation

74

Figure 20

69
July 9, 1962
Lake Antoine - 6

Sections 26, 23, and 13, T'.40M., R.31W.,
Mich. Starts at 0.8. 2 via Section 13.

1. .VMIQ, 1450 kc, 250 watts, Iron
Mountain, transmitter 3 miles S.20°E.
from start of traverse in sec. 13.

2. VDBC, 680 kc 1 low, Escanaba, Mich.
transmitter 48 miles due east from
start of traverse.

Flat except for Pine Mountain at the
south end of the traverse.

Poor blacktop with shallow curves to the
northaeast

Open fields.

1. start over Badwater Greenstone in North.
2. 0.60 miles BadwateroMichi some

3. 1.77 miles Mich sane-Ran ville fault
4. 2.40 miles Randv 11e=Upper Slate

5. 2.43 miles Upper Slate-Trader

6. 2.49 miles TraderoBrier

7. 2.52 miles BrieroRandville fault

8. 2.57 miles Randvilleavpper Slate
9. 2.61 miles Upper Slateo’rrader
10. ' 2.66 miles TraderwBrier

11. 2.69 miles BrieraMichigan-e

12. 3.20 miles end of traverse

U.S.G.8. Open file report on Southern
Dickinson County

‘while the geologic factors do not show up

to any great extent, this is still a very
interesting set of records. These two re-
cords show very well the effect of frequency,
distance and topography. Record 1 is verz
erratic. This s probably caused by the igh
frequency of WMIQ, the traverse's nearness

to the transmitter and in part, the effect of

Co-ents

75

Figure 20 - Continued

Pine Mountain at the south end of the
traverse. Under these conditions the in-
tensity reacted more strongly to the
rock's electrical roperties than WDBC,
which is much furter away and therefore
has a weaker field. Pine Mt. absorbed
more of WMIQ's signal than WDBC's.

~ This points out the advantage of using

stations more than a few miles from the
traverse.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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4331-X

CHART NO.

INDIANAPOLIS, IND., U. S. A.

   

 

 

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4331-X

CHART NO.

INDIANAPOLIS, IND., U. S. A.

   

 

 

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III-her
Date
8-.
Location

Radio station

General topography
Reed €790
Vegetation
Geology and source

Interpretation

77

Figure 21

77
July 9, 1962
Wisconsin #3.

Sections 8 and 17 T'.38M., R.20£. on
County Road '0', \‘iisconsin.

WDBC, 860 kc l kw, Escanaba, Michigan.
Transmitter 48 miles dueeast from start
of traverse in section 17 et RM 1128.

Rolling.
Blacktop, generally straight, north-south.
Open fields.

1. start over Metadiorite

2. 0.31 miles metadiorite-Roskinslake
granite

3. 0.55 miles Hoskinsleke-Quinnesec

4. 0.90 miles Quinnesec-Horseface sill

5. 1.08 miles and of traverse

U.8.G.S. open file report on Southern
Dickinson County ‘

The metadiorite is a good conductor. The
Roskinslake Granite seems to be a poor
conductor as indicated by the high level
of intensity. The Quinnesec is only _
slightl better than the metadiorite, and
the sil seems to be a little better than
the Quinnesec.

m repeat traverses were run, both of
which are nearly identical to the original.

- F0 I -
Quinne s c me tech 0 1'1
3 ' Lake ‘6

Grani t e

A __.-_

 

'03 ShDNV-ENI'IHSJSS 3H,]. 'V '8 11 HI ndvu

79

THE IRONWOOD AREA

Geologically the Ironwood area consists of beds trending
generally east-west and tilted toward the north giving rise to
a cross-section of the Huronian sediments. To the north of
the Huronian sediments there is an unconformable contact with
the Keweenawan sediments. There are also faults in the area
which were investigated. 8

In Ironwood there is one radio station, UJMS, 630 kc, l
kw, which was used. This was the only station that the equip-
ment could pick up in this area.

The topography in the Ironwood area was generally level

where the traverses were run.

80

Figure 22

Generalised stratigraphic column for the Ironwood area.
(After The Centennial Geological Map of the Northern
Peninsula of Michigan, 1936.)

 

|**** ****fl***

Phnstmume

 

    
 
  
    

Jacobsville
sandstone

WDHEISmmuior

Eagle River and
Ashbed groups.

    
 
  

Glacial outwash and
drift.

etssnnconfor.1tysee#eeeseeesseseeee*eeeeseese

Red and brown sandstone
with mottlings of white
and grey. Red arkosic
with a conglonerate at i
the base.

as *eesuncenfor.1tyssedesesessssssesssseeetestes

Basic lava flows with
many conglomerates and

a few sandstone beds ‘
fiiInIy Basic lava flows,
intrusions of basic ig-
neous rocks and granite.

*esunccarer-1tyeeseeeeeseeeseeeesseeesseesee

Acidic intrusives, granb
its and granite gneiss
with some diorite and"
syenite.

 

 

 

 

Ramadan

3 .9: Mesnard e idote.
a» 3 entra ne group
3 E o. 8 Conglomerate
:3 Bohemia Range group
assess
a 5 Killarney Granite
a (Presque Isle
3 Granite)
m
8 4:
53‘:
Tyler slate ‘—

H

8.
8'

***d****unconformity***

Ironwood

 

(con't)

 

a
333;?“ """"" *

raywaEEe and slate
locally very ferruginous.
Chert with associated
beds of siderite; black

carbonaceous slates .
ssesesssssseesssseesesees

i

Iron formations. Silica
and iron oxides, hematite
and limonite; some slates
interbedded. .............
Fine silty thin bedded

green argillaceous slate
with a clear, vitreous

 

quartsite.

**J****uncenter-1ty¥**]*********************#***

 

 

81

Figure 22 (Con't)

Generalised stratigraphic column for the Ironwood area.
Continued.

 

 

keessheeeuncQatar-1tys+esessetsetetssseseseeseeee

Bad River Massive and banded
cherty dolomite and
marble, with beds of
greenish slate and
graywacke.

P----------------d i- ------------------------

Sunday Dense vitreous light
colored quartsites

gith conglomerate at
‘ICe

asstsesseeesasweesuncouter-1tysaseeesessstseesssssessessss

AIGOIKIAI (con't)
Ramadan
Lower

Laurentian Shistose and gneissic
intrusives in Keewatin,
masses of syenite schist
and gneiss rich in horn-
blend-

 

fl.

Keewatin Basic extrusives, highly
aetamorphosed.

 

 

 

 

AEEEAR
KemeJnIUnuentnun

 

 

Location

Radio station

General topography

Road type
Vegetation

Geology and source

Interpretation

82

Figure 23

25
June 19, 1962

watersmeet - 1

0n U.S. 45 from 11.5 miles north to
4 miles south of Watersmeet, Mich.

VBRL, 930 kc, Eagle River, Wisconsin,
ap roximately 24 miles south of starting
po nt at north end of traverse.

North of Vatersmeet gently rolling, south
of Watersmeet quite illy.

Blacktop

North of Watersmeet open fields, south
wooded.

1. start over Cambrian sedimcnts

. 1.9 miles Cambrian-Bohemian Range Group
. 3.83 miles Bohemian R.G.-Michigame

. 8.75 miles Michigame-Killarney granite
. 10.63 miles Killarney-Michi ame

. 14.10 miles Michigame-Undi ferentiated

Precambrian
U.S.G.S. Monograph LII

The correlation between the intensity changes
and the geology are excellent. The interest-
ing thing about this record is the depth of
the bedrock, about 150'-200'. This is, how-
ever, a rare example of drift penetration. A
magnetic anomaly of 10's of thousands of
gammas lies not south of U.S. 2. There does
not seem to c any indication of this anomaly.
The contact between the Michi me and the
undifferentiated Precambrian s not shown on
the Centennial Geologic Map of the Northern
Peninsula of Mich an. Th 8 change is too
great to be ignore , it does show on the source
map.

O‘U‘IkUN

 

          

'ifferentiated Precambrian

 

Number
Date
Name

Location

Radio station
General topography
Road type
Vegetation

Geology and source

Interpretation

Comments

84

Figure 24

29
June 20, 1962
Ironwood - 2.

Section 36, T.48N., R.47W., and Sections
1, 12, and 13, mum, 3.1711,, Mich.

WJMS, 630 kc, 1 kw, Ironwood, Rich. 2
miles 8.35°U. from start at 3unction of
US-Zo

Gentle hills.
Gravel.
Open fields.

1. start at Tyler slates
2. 1.32 miles Keweenawan fault
3. Keweenawan lavas and conglomerates.

The fault itself does not seem to have

any field change associated with it but

the different lithologies of the beds on
either side of the fault show up very well.
These changes correlate very well with the
mapped position of the fault.

Notice that on this record the Keweenawan
formations have a low level of intensity,
while on No. 30, Fig. 25, the Keweenawan
has a high level of intensity. This is
probably due to changes in the Tyler slate.
The Tyler slate can be clay slates, gray-
wacke and graywacke slates, or mica schist
and mice slates.

 

 

 

 

 

l in

-_.. _ .._ ___-,;._

T— -—---.— ~—fi;—

.i__;_-,

 

X‘ISEV 'ON wVHO 'v '3 '0 "am ‘snoavuwam ‘03 SflSNv-SNI'IEEJSB 3H1

:
y
l
I

 

 

 

 

.u‘im.‘ -Nax‘.¢-

 

Number
Date
Name
Location

Radio station

General topography
Road type
Vegetation

Geology and source

Interpretation

Comment

86
Figure 25

30

June 20, 1962

Ironwood - 3.

Sections 5 and 8, T.47N., R.46U., Mich.

WJMS, 630 kc, 1 kw, Ironwood Mich. 5
miles 8.55°U. from start at 68-2.

L0" hill. e
Gravel, oiled.
Open fields.

1. start in Tyler slates

2. 0.5 miles fault ” ~ x

3. stop in Keweenawan lava and con-
glomerates

U.S.G.S. Monograph LII, p. 266.

The fault itself does not seem to have

any field change associated with it but
the different lithologies of the beds on
either side of the fault show up very well.
These changes correlate very well with the
mapped position of the fault.

We see here a high level of intensity
associated with the Keweenawan formation.
0n record 29 the Keweenawan has a low
level of intensity. This is probably due
to fihangzs in the Tyler slate as discussed
on o. . e

The traverse was repeated with nearly
identical results.

Kewe enawan

 

X' ICE?
H

V

Number
Date
Name

Location

Radio station

General topography
Road type
Vegetation

Geology and source

Interpretation

Comments

88

Figure 26

32. 33, and 35.
June 20, 1962
Ironwood 5, 6 and 8.

No. 32 1-5 Section 23 T.47N., R.4SV.,
No. 33 BIZ?" Sections 2 and 26, T.47l.,

No. 35 (Its) Sections 21 and 25, T.47N.,
R.45W. , Michigan.
All start in the north and run south.

‘WJMS, 630 kc l kw, Ironwood,.Mich. approx-
imately 1L miles due west of traverse.

Flat for all three traverses.
Gravel for all three.
Mostly open fields, some woods.

1. start over basic intrusives
2. fault
3. end in Laurentian granite.

Centennial Geologic Ma of the Northern
Peninsula of Michigan 71936) and the
Geologic flip of Lake Superior Region,
Leith, Lund and Leith (1935).

It is interesting to note on these
records that on 32 the fault shows an
intensity low, while on 33 and 35 the
fault shows an intensity high. This is
similar to the kind of results Howell
obtained. This could be caused by a
change in the gouge material of the
fault or in the moisture content.

This is a good example of how this method
can be used for tracing a feature.

One traverse was repeated for each, all
were nearly identical to the original.

intrusives

 

 

47*“.—

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- o..— v. f .
- ._—_?-——¢— < r—- v Q -—’
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r +---

intrusives *

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"”*.' r-“t—
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l .

,‘ -4~_-.‘_ fi‘+-

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'03 309NV°3NHU3413 1H,], W's 'n w: roves

 

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~m‘—. Md

  

_- ._1_~__.w_1~
,._11 _._~_ _1~- -

 

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repeat run

_ 1- --r_'—-_._.1_rr_1_._r__
M

   

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92

CONDITIONS UNDER WHICH THE METHOD FAILS

0n the following pages are given examples of how certain
conditions affect the records undesirably. These conditions
include road type, presence of wires, and inadequate radio
reception. Also included is an example of the method's failure
to locate highly magnetic features.

All of the areas in Wisconsin were failures except in

the lron‘Mountain Area. The records are not included.

These areas are:

1. Pine Lake, T.44N., R.3E., sections 28, 21, and 20.
Highly magnetic feature, no significant change in
intensity. I

2. Butternut, T.41N., a.1w., section 29. Highly
magnetic feature, no significant change.

3. The McCa‘slin Mountain area. Could not receive a
radio station with the equipment.

A possible source of failure, not knowingly experienced

in this investigation, is where the rocks on either side of
a fault or contact do not have significantly different

electrical and magnetic properties to cause field intensity

variations.

Huber
Date
Name
Location

Radio station

General topography

Road type
Vegetation

Geology and source

Interpretation

Co-ent

93

Figure 27

37
June 20, 1962
Norwich - 1

Sections 14°13, 11912, and 2, T.49N.,
R.4lVI., Mich.

WJMS, 630 kc, 1 kw Ironwood Mich.
approximately 40 miles 8.7 from
fiafiing point on section line between

Level to hilly, except where we pass
through the Keweenaw fault scarp.

Gravel .

Open south of fault, wooded north of
ault.

f

1. start over Jacobsville sandstone

«2. 2.10 miles Reweenaw fault

3. end of run, over Keweenaw basic lava
flows. Cmplete traverse now shown.

The Centennial Geologic Map of the Northern
Peninsula of Michigan

On this traverse the fault face could be
seen clearly but there was no indication
on the record. The fault face stood about
200 feet above the road.

This is s end example of a weak radio
field not teracting with the rocks to
any measurable extent. '

 

 

 

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Number
Date
Name

Location

Radio station

General topography
Road type
Vegetation
Geology and source

Interpretation

Comments

95
Figure 28

62
June 21, 1962
Deer Lake - 1

Section 29 and 32, T.48N., R.27V. and
Sections 4 and 5, T.h7N., R.27W., Mich.

NJAN 970 kc, 5 kw, Ishpeming, Mich.
2} miles S.15°W. from start in section
29 at junction with Co. Rd. 573.

Very hilly.

Blacktop.

Wooded on both sides of road.
Undetermined.

This is‘a fine example of what too many
electric, telephone, and guy wires can
do. The needle never has time to estab-
lish a level of intensity between wires,
and thus the record is unusable.

Repeat traverse shown: observe that the

changes in intensity during the south to

north traverse are not as great as the

north to south run. The event pen marked

{11“ location of the telephone ad power
HCBo

     

,-1__+.1
/

4 - 7+ - -
, .. _1._1,',_111_.1,_ 1
—~—+ 4—7-14 —
1111_ 111-
1 1

Start inhorth? ': _ 1 Startrin Southmat

 

J.

11 1111 '1 11

 

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—. ——L\.———._+_~‘—‘__1 -.—~————

0 /‘/ 0 2. O
"V'S'n "UNI ‘SnOdVNV'ONl '03 ShSNV-ENI'IBBLSE 3H_L 'v 's 11 Nl aovw 2.: . x-lgep 'ON Law-43 'V’S'n "am ‘SI‘IOdVNVICINI '03 snSNv-ENI'THBJJ

    

 

   

Number
Date
Name

Location

Radio station

General topography
Road type

Vegetation

Geology and source

Interpretation

Comments

97

Figure 29

26
June 19, 1962
UoSoFeSo - 116

Sections 13 14, 15, and 23 T.45N.,
n.11w.,.n1c£., junction of 6.3. 2 and
u.s.r.s. 116.

WBRL, 930 kc, Eagle River 'Nisconsin,
approximately 20 miles S.35°E. from
Junction.

Flat.

U.S. 2, concrete
U.S.F.8. 116, gravel

‘Vooded
High magnetic area

Robert C. Reed, Michigan State Geological
Survey

The author experienced no success over
magnetic featurai Other traverses besides
this one have been run and the results are
all the same.

‘What is particularly interesting about
this set of traverses is the vast dif-
ference in response over the two roads,
0.8. 2 and USPS 116. The reason for

this difference is that U.S. 2 is a
reinforced concrete road. The reinforcing
mesh acts as an electrical shield for the
rocks beneath. All we measured on U.S. 2
is the field intensity with very little
effect from the geology.

0

One repeat traverse was run with nearly
identical results... ...“.

 

CONCLUSIONS

As a result of the radio field intensity survey conducw
ted in the Lake Superior region the following conclusions were
reached.

1. It is readily apparent that the radio field intensity
method of geologic mapping can be of significant value. Gen-
erally speaking, in areas that were amenable to this type of
mapping, the correlation between the changes in the intensity
and the changes in the underlying geology was excellent.

2. There are several factors that make an area unsuited
for this mapping method.

a. Before anything else is considered, if the road
paving material is reinforced concrete there will be little
or no success. This was postulated by Pullen and is here
verified. (Figure 29)

b. Another factor is the intensity of the radio
field at the area to be investigated. If there is not suffia
cient field strength the geology will not cause intensity
changes. (Figure 27).

c. A third factor which interferes with this method
is the presence of too may overhead wires. Just how many
wires are too many is difficult to state. This is something
which the operator must experiment with and learn to Judge.
The effect of many wires can be seen in Figure 28. At the

same time we can observe from Figure 9 that sometimes a

99

t: 100

large number of wires does not disturb the record. Therefore,
unless there is an extremely high concentration of wires the
traverse must be attempted before a Judgement can be made.

d. The fourth, and most difficult factor to evaluate,

is the topography. About all that can be done is to try and

run traverses where the ground is level. If this is not
possible it may be worthwhile to attempt a traverse as fair
results can sometimes be obtained.

e. A fifth factor to be considered is the thickness
of the drift. The theoretical depth penetration of radio
waves, leads one away from attempting this method in heavily
drifted areas. The'Vatersmoet record (Figure 23) is an
exception.

3. There are a few traverses in which a fault or a con-
tact has a field associated with it, e.g., Figure 26. IHost
of the time the only change noticed in passing over a fault
or contact was in the lovel of intensity which correlated
with differing formations on either side. It is possible
that if the beds on either side of a fault or contact did
not differ significantly no change in the level of intensity
would occur.

A. It was also concluded that the transmitter should
not be too close to the traverse. In some cases ten miles is
too close. This depends primarily on the power of the
station. The best results in this investigation were obtained

101

with stations of low power, 250 watts to 5 kilowatts, at
distances greater than ten miles. Figures 21, 17, 10, and 9.

Pullen states that the best stations are ones 5-50 miles
distant, depending on the frequency, and with a power of 250
to 1000 watts. He concluded that this was because weak fields
are affected more by the geology than strong fields. This
investigation found, on the contrary, that strong fields were
affected more by geology than weak fields. Figure 22. Notice
also the north ends of Figure ll and Figure 15. These are
weak field areas. Other examples are available but these are
representative.

5. A number of highly magnetic features were inves-
tigated. The radio field does not seem to be affected by
these fields.

Summary

Where field conditions are suitable, the radio field
intensity method of geologic mapping offers pronise of an
economical and rapid method of reconnaissance mapping. It
also has potential as a device for tracing and extending
faults, contacts, and formations. Assuming the other condi-
tions for suitability are met, the presence of glacial drift

is the most serious drawback.

RECOMMENDATIONS FOR FURTHER INVESTIGATIONS

As a result of this investigation the following recom-
mendations can be made.

1. Before further studies are initiated in this field
the equipment should be modernised. With the recent advances
in electronics it should be possible to make the equipment
lighter, more compact, more sensitive and with a lower power
demand .

2. If in future investigations a whip antenna is used,
it should be matched perfectly with the receiving meter. The
antenna used in this study was the best the author could
devise with the funds available and it worked very well, but
possibly it is not the best arrangement.

3. ‘With the improved equipment there are a number of
intensity experiments that could be conducted which would be
of value. O

a. Rerun and expand the areas investigated in this
study to see if results would be comparable, and if results
in some areas could be improved.

b. ‘With improved sensitivity it is possible that
the low frequency (120 to 550 kc) aircraft range markers could
be used as stations to be monitored.

c. This equipment might be suitable for airborne
studies. This type of study is particularly appealing to the

102

103

author because it might eliminate the concern with cultural
features, and would also make areas accessible which can not
be reached by road.

d. Make a reconnaissance study of an unknown area
and follow up with geological field work, to determine the
value of the method.

REFERENCES

Atwood, 8.8., (19L9) Electric and Magnetic Fields, John Wiley
and Sons, Inc., New York.

Barrett,".l. (19h9) Earth Penetration by Radio‘flaves Proved
by Salt Mine Tests, Iorld Oil, larch.

(191.9) Exploring The Earth With Radio Waves,
NorIH Petroleum, April.

(1952) Note on The Radio-Transmission Demon-
stragion at Grand Saline, Texas, Geophysics, Vol. 17,
no. .

 

(1953) Radoil Survey of the New Hope Field,‘
FranEIIn County, Texas; A Case History,‘W.Ht Barrett,
Inc., Shreveport, Louisiana.

(1959) Radoil's Approach to Porosity-Trend
flipping, The Oil and Gas Journal, August 25 edition.

Bayley ‘V.S. (190A) The lbnominee Iron-Bearing District of
Michigan Department of Interior, united States Geologic
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Birch, F., Schairer‘& Spicer (l9h2) Handbook of Physical
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Blackburn,ll.3. (19h?) Radiographic thhod of Geophysical
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Byrne J.F. (1932) Radio Transmission Characteristics of
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Cloos E. (193A) Auto-Radio - an aid in Geologic lapping,
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Department of the Army (1953) Antennas and Radio Propagation,
‘ TI 11-666, February.

Dewitt, J.H., and Omberg, (1939) The Relation of the Carrying
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Engineers, vol. 27, no. 1.

104

105

Eve, A.S., Keys, and Lee (1928) The Penetration of Rocks by
Electromagnetic waves and Audio Frequencies ‘Proceedings
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(1929) Reception Experiments in It.
EeyaI TunneI, Proceedings of the Institute of Radio
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Eve, A.S., and Keys (1928) Geophysical Prospecting: Some
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Gibbs, C.J. (1939) The Influence of Sub-Surface Geology Upon
the Propagation of Electromagnetic Waves unpublished
Masters Thesis, Department of Geology, chigan State
University.

Gracely, F33. (19A9) Temperature Variations of Groundéiave
Signal Intensity at Standard Broadcast Frequencies,
groceedings of the Institute of Radio Engineers, vol.

7' n00 1.0

Haycock, 0.0., and Hurst (19A9) Propagation of Electromagnetic
waves Through the Earth, Geophysics, vol. 1h, no. 2.

Higgy, R.C., and Shipley (1936) Radio Transmission Survey of
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Station, Bulletin 92.

Howell, B.F. (l9h3) Some Effects of Geologic Structure on
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Ilsley, L.C., Freeman, and Zellers, (1928) Ex eriments in
Underground Communication Through Earth trata Depart-
ment of Interior, lines Bureau, Technical Publication #33.

James H.L. Clark, Lamey, and Pettijohn (1961) Geology of
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Survey, Professional Paper 310.

Jakosky, J.J. (1960) Exploration Geophysics, TriJa Publishing
Company, Newport Beach, California.

Joyce J.U. (1931) Electromagnetic Absorption by Rocks, United
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Kerwin, L. (19h?) Use of Broadcast Band in Geologic lapping,
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106

EcGehee, F.M. (195A) Propagation of Radio Frequenc; Energy
Through the Earth, Geophysics, vol. XIX, no. .

EcIlwain, Knox and Wheeler (19A8) Propagation of Radio Haves
Through t e Ground, Proceedings of the Institute of
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Peters, L.J., and Bardeen (19A?) Some Aspects of Electrical -
Prospecting Applied in Locating Oil Structures, Physics,
V010 20

Pratt, R.B. (1953) New Oil Findinglflethod Tested, World 011,
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Pritchett, v.0. (1952) Attenuation of Radio Frequency waves
Through the Earth, Geophysics, vol. XVII, no. 2, April.

Pullen, NEW. (1953) Geologic Aspects of Radio wave Trans-
mission, Illinois State Geological Survey, Report of
Investigations, no. 162.

Spieker, E.E; (1936) Radio Transmission in Geology, American
Association of Petroleum Geologists, Bulletin, vol. 20,
pto 20

Terman, E.S. (19h3) Radio Engineers Handbook, HcGraw-Rill Book
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Van Hise, C.R., Haley, and Smyth (1897) The Ear uette Irena
Bearing District of lichigan,-Department o Interior,
United States Geologic Survey, lbnograph XXVIII.

Van Rise, C.R., and Loith (1911) The Geology of The Lake
Superior Region, Department of Interior, United States
Geologic Survey, lonograph LII.

 

 

 

 

 

 

MICHIGAN STATE UNIVER I Y L 8

III Hilillilli
74

3 1293 030 1

RARIES

004