U.S. DEPARTMENT OF THE INTERIOR

U.S. GEOLOGICAL SURVEY

Structural Controls on Ground-Water Conditions 

and Estimated Aquifer Properties near 

Bill Williams Mountain, Williams, Arizona

Prepared in cooperation with the

CITY OF WILLIAMS

By Herbert A. Pierce

Tucson, Arizona

2003

(First printing, 2001)

Water-Resources Investigations Report 01—4058
For additional information write to:

District Chief

U.S. Geological Survey

Water Resources Division

520 N. Park Avenue, Suite 221

Tucson, AZ 85719–5035

Copies of this report can be purchased from:

U.S. Geological Survey

Information Services

Box 25286

Federal Center

Denver, CO 80225–0046

The use of firm, trade, and brand names in this report is for identification purposes only and does not constitute 

endorsement by the U.S. Geological Survey.

Information about U.S. Geological Survey programs in Arizona is available online at http://az.water.usgs.gov.

U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director
Contents iii

CONTENTS

Page

Abstract .............................................................................................................................................................. 1

Introduction .......................................................................................................................................................... 1

Purpose and scope....................................................................................................................................... 4

Physical setting............................................................................................................................................ 4

Previous investigations................................................................................................................................ 7

Methods of investigation...................................................................................................................................... 8

Gravity measurements................................................................................................................................. 8

Aeromagnetic measurements ...................................................................................................................... 8

Audiomagnetotelluric soundings ................................................................................................................ 8

Square-array resistivity ............................................................................................................................... 12

Thematic-Mapper data ................................................................................................................................ 16

Aerial photography...................................................................................................................................... 17

Digital elevation model data ....................................................................................................................... 17

Well data ..................................................................................................................................................... 17

Hydrogeologic units ............................................................................................................................................. 17

Structural controls on ground-water conditions................................................................................................... 22

Interpreted depth to ground water in the regional aquifer.................................................................................... 23

Estimated aquifer properties ....................................................................................................................... 29

Summary and conclusions.................................................................................................................................... 34

Selected references............................................................................................................................................... 34
iv Contents

FIGURES

Page

1. Maps showing location of study area and locations of wells, selected springs, 

gravity stations, audiomagnetotelluric sites, square-array resistivity sites, 

and faults and fault systems near Williams, Arizona ........................................................................... 2

2. Map showing Laramide folds in Cretaceous rocks on the southwestern flank of the 

Colorado Plateau .................................................................................................................................. 5

3. Map showing overview of southwestern edge of the Colorado Plateau, Mogollon Rim, 

and Grand Canyon, and location of surface waters bounding the study area in 

northern Arizona................................................................................................................................... 6

4. Graph showing variation in annual precipitation, city of Williams, Arizona, 1897–1998 .................. 7

5. Simple Bouguer gravity anomaly map generated from the 2-kilometer grid of the 

U.S. Geological Survey and new gravity data near Williams, Arizona ............................................... 9

6. Aeromagnetic anomaly map generated from the 2-kilometer grid of the 

U.S. Geological Survey, Universal Transverse Mercator projection, 

near Williams, Arizona......................................................................................................................... 10

7. Graphs showing scalar audiomagnetotelluric sounding data and model for data 

collected near the A-1 well site near Williams, Arizona

A. Scalar audiomagnetotelluric sounding data.................................................................................. 13

B. Layered earth model and smooth model....................................................................................... 13

8. Graphs showing tensor audiomagnetotelluric sounding data and model for data showing 

electric and magnetic field coherencies better than 0.8 recorded in Davenport Lake (dry) 

site (EMI-3) about 10 kilometers east of Williams, Arizona

A. Tensor audiomagnetotelluric sounding data ................................................................................. 14

B. Phase audiomagnetotelluric sounding data................................................................................... 14

C. Layered earth model (dashed line) and smooth model (solid line) .............................................. 14

9. Landsat Thematic-Mapper image of the study area near Williams, Arizona....................................... 16

10. Mosaic of four 7.5-minute U.S. Geological Survey digital elevation models near 

Williams, Arizona................................................................................................................................. 18

11. Diagram showing rock formations and hydrogeologic units for the Williams area, Arizona.............. 19

12. Diagram showing Lithologic logs derived from well cuttings analyzed every 6.1 meters 

in two wells near Williams, Arizona .................................................................................................... 24

13. Geophysical logs and lithology for Bard Spring #2 well, Williams, Arizona...................................... 25

14. Map showing depth to water, Williams, Arizona................................................................................. 27

15. Map showing Altitude of the water table, Williams, Arizona.............................................................. 28

16–19. Graphs showing:

16. Square-array resistivity sounding data and estimated aquifer properties from the site 

at Airport Road, Williams, Arizona.............................................................................................. 30

17. Square-array resistivity sounding data and estimated aquifer properties from the site 

at Bard Spring, Williams, Arizona................................................................................................ 31

18. Square-array resistivity sounding data and estimated aquifer properties from the site 

at McDougal Flat, Williams, Arizona........................................................................................... 32

19. Square-array resistivity sounding data and estimated aquifer properties from the site 

at Poquette Homestead, Williams, Arizona.................................................................................. 33
Contents v

TABLES

Page

1. Data for selected wells that discharge water from the regional aquifer near 

Williams, Arizona................................................................................................................................. 23

2. Dry wells near Williams, Arizona ........................................................................................................ 23

3. Data from audiomagnetotelluric and square-array resistivity sites, and estimated 

water levels near Williams, Arizona .................................................................................................... 41

CONVERSION FACTORS AND DATUMS

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F = 1.8(°C)+32

Sea level: In this report, “sea level” refers to the National Geodetic Vertical Datum of 1929 (NGVD of 1929)—A geodetic 

datum derived from a general adjustment of the first-order level nets of the United States and Canada, formerly called Sea 

Level Datum of 1929. Altitude, as used in this report, refers to distance above or below sea level.

ABBREVIATED WATER-QUALITY UNITS 

Chemical concentration and water temperature are given only in metric units. Chemical concentration in water is given in 

milligrams per liter (mg/L) or micrograms per liter (μg/L). Milligrams per liter is a unit expressing the solute mass 

(milligrams) per unit volume (liter) of water. One thousand micrograms per liter is equivalent to 1 milligram per liter. For 

concentrations less than 7,000 milligrams per liter, the numerical value is about the same as for concentrations in parts per 

million. Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (μS/cm at 25°C). 

Multiply By To obtain

millimeter (mm) 0.03937 inch

meter (m) 3.281 foot

kilometer (km) 0.6214 mile

square kilometer (km2) 247.1 acre

liter per second (L/s) 15.85 gallon per minute

square meter (m2) 10.76 square foot

radian (rad) 0.017453 degree

milligal (mGal) .00001 Gal
vi Contents

ABBREVIATED GEOPHYSICAL TERMS

Ampere is the International System (S.I.) unit of electric current measured as one coulomb per second or one volt per ohm. 

Ohm is the International System unit of electrical resistance equal to that of a conductor in which a current of one ampere is 

produced by a potential of one volt across its terminals. Ohm meter (Ω•m) is a unit of resistivity, also written as ohm meter 

squared per meter (Ω•m2/m), and is the resistance of a meter cube to the flow of current between opposite faces. Farad is the 

International System unit of capacitance equal to the capacitance of a capacitor having a charge of 1 couloumb on each plate 

and a potential difference of 1 volt between the plates. Henry is the International System unit of electrical inductance in which 

an induced electromotive force of one volt is produced when the current is varied at the rate of one ampere per second. Radian 

is a unit of angular measure equal to the angle subtended at the center of a circle by an arc of length equal to the radius of the 

circle. Gamma is a unit of magnetic field equal to one nanotesla, the preferred International System name (1 gamma=10-5

gauss=10-9 tesla). Milligal (mGal) is a unit of acceleration used in gravity field measurements. Hertz is a unit of frequency 

equal to one cycle per second. Kilohertz is a unit of frequency equal to 1,000 hertz. The weber is the magnetic flux which, 

linking a circuit of one turn, produces in it an electromotive force of one volt as it is reduced to zero at a uniform rate in one 

second.
Abstract 1

Structural Controls on Ground-Water Conditions and Estimated 

Aquifer Properties near Bill Williams Mountain, Williams, Arizona 

By Herbert A. Pierce

Abstract

As of 1999, surface water collected and stored in reservoirs is the sole source of municipal water for 

the city of Williams. During 1996 and 1999, reservoirs reached historically low levels. Understanding the 

ground-water flow system is critical to managing the ground-water resources in this part of the Coconino 

Plateau. The nearly 1,000-meter-deep regional aquifer in the Redwall and Muav Limestones, however, 

makes studying or utilizing the resource difficult.

Near-vertical faults and complex geologic structures control the ground-water flow system on the 

southwest side of the Kaibab Uplift near Williams, Arizona. To address the hydrogeologic complexities in 

the study area, a suite of techniques, which included aeromagnetic, gravity, square-array resistivity, and 

audiomagnetotelluric surveys, were applied as part of a regional study near Bill Williams Mountain. 

Existing well data and interpreted geophysical data were compiled and used to estimate depths to the 

water table and to prepare a potentiometric map. Geologic characteristics, such as secondary porosity, 

coefficient of anisotropy, and fracture-strike direction, were calculated at several sites to examine how 

these characteristics change with depth.

The 14-kilometer-wide, seismically active northwestward-trending Cataract Creek and the 

northeastward-trending Mesa Butte Fault systems intersect near Bill Williams Mountain. Several northsouth-trending faults may provide additional block faulting north and west of Bill Williams Mountain. 

Because of the extensive block faulting and regional folding, the volcanic and sedimentary rocks are tilted 

toward one or more of these faults. These faults provide near-vertical flow paths to the regional water 

table. The nearly radial fractures allow water that reaches the regional aquifer to move away from the 

Bill Williams Mountain area.

Depth to the regional aquifer is highly variable and depends on location and local structures. On the 

basis of interpreted audiomagnetotelluric and square-array resistivity sounding curves and few well data, 

depths to water may range from 450 to 1,300 meters.

INTRODUCTION

Currently (1999), the city of Williams, Arizona, 

supplies its residents with water exclusively from 

surface reservoirs. During periods of drought, surface 

runoff is negligible or may not occur at all. Infiltration 

and evaporation reduce runoff from Bill Williams 

Mountain and further reduce reservoir storage once the 

water is contained in the reservoirs. Most of the 

reservoirs have been lined to reduce infiltration, 

however, evaporation continues to reduce storage.

Population growth and the drought of 1995–96 

prompted the city to explore the possibility of using 

ground water as a backup to the surface-water system. 

Few wells have been drilled because the depth to water 

in this part of northern Arizona is nearly 1,000 m. 

The lack of wells limits the knowledge of the 

hydrogeology of the regional ground-water system. 

Williams is near the intersection of two roughly 

orthogonal fault systems (fig. 1). The fault systems are 

wide zones of subparallel faults. The fault zones (Mesa 

Butte and Cataract Creek Fault systems) intersect at 
2 Structural Controls on Ground-Water Conditions and Estimated Aquifer Properties near Bill Williams Mountain, Williams, Arizona

22'30''

30'

37'30''

35°45' 22'30'' 15'

15'

7'30''

35°

0 5 10 KILOMETERS

0 5 MILES

Base from U.S. Geological Survey

digital data, 1:100,000, 1983

Universe Transverse Mercator

projection, zone 12 

C

Syca ore m reek

180

180

89

Ash Fork

Pine Springs Bill

Williams

Mountain

Sitgreaves

Mountain

Bard

Spring

Red Lake

17

36

16

15

Quivero

Valle

Klinke well

Santa Fe

Santa Fe #1

Valle 3 Valle 2

Ash Fork 2

Ash Fork 1

C

ata act r C

S

W

V a a ey ll

sh

pring

r

H

Can on y

ell

eek

40

7'30'' 112°

Williams

Quivero

112°30'

64

64

Polson Dam Fault

Lo Draw Fault

Mesa Butte

Fault System

Cataract Creek

Fault System

Area of enlargement

Unnamed

fault

Figure 1. Location of study area and locations of wells, selected springs, gravity stations, 

audiomagnetotelluric sites, square-array resistivity sites, and faults and fault systems near 

Williams, Arizona.
Introduction 3

15'

10'

35°5'

35°20'

0 5 KILOMETERS

0 3 MILES

C

S yca ore m reek

Pine Springs

Bard Spring

15' 10' 5'

14

18

7

112°'20' 112°

McDougal

Flat

McDougal

Flat

Bard Spring

Dogtown Reservoir

Bard

Spring#2

Poquette Homestead

64

31

13

3

22

23

33

4

5

35

21

34 29

32

9

10

12

37

30

6

26

25

25

38

20

19

39

11

2

24

8

28

Airport Rd.

27

El Paso Gas

Gonzales A-1

Santa Fe #3

Kaibab

Lake

Davenport

Lake

D

Wash o own gt

40

H

Canyon

ell

36°

34°

32°

EXPLANATION

Area enlarged

WELL—Annotation, Quivero,

 denotes well name

GRAVITY STATION

SQUARE-ARRAY RESISTIVITY

 SITE—Annotation, McDougal Flat,

 denotes site name

AUDIOMAGNETOTELLURIC

 SITE—Number, 25, is identifier

 (see Supplemental Data at back

 of report)

Quivero ARIZONA

Williams Flagstaff

Phoenix

112°

Co o rad

l

114° 110°

revi

o

R

City Reservoir

Santa Fe Reservoir

Cataract Lake

Figure 1. Continued.
4 Structural Controls on Ground-Water Conditions and Estimated Aquifer Properties near Bill Williams Mountain, Williams, Arizona

Bill Williams Mountain and create a weak spot in the 

crust as reflected by the volcanic activity of Tertiary 

age (Newhall and others, 1987). These fault systems 

are near-vertical faults zones, are seismically active 

(Shoemaker and others, 1978), and probably provide 

conduits for water from the near surface to the regional 

aquifer. This study by the U.S. Geological Survey 

(USGS), in cooperation with the city of Williams, was 

done during 1995–99 to provide information about the 

structure, lithology, and flow system of the regional 

aquifer.

This report was revised in March 2003 to eliminate 

minor editorial errors that were detected following the 

first printing in 2001. Fault labels and lines shown on 

figures 5, 6, 9, and 10 were revised to match the 

discussions of these figures in the text. In addition, 

figures 14 and 15 and the azimuth plots in figures 16–

19 were revised to show only data points, and the 

water-level altitude for the A-1 well was revised to the 

correct value of 1,178 m. No changes, however, were 

made to the interpretations presented in the report.

Purpose and Scope

This report describes the hydrogeologic units and 

ground-water conditions in the regional aquifer near 

Williams, Arizona, identifies regional geologic 

structural features that in part control ground-water 

conditions in the regional aquifer, and presents 

estimated properties of the regional aquifer determined 

from surface-geophysical surveys. This study included 

reviews of previous geologic and hydrologic studies, 

databases, and published geologic information. In 

addition, geophysical data, digital elevation models 

(DEMs), aerial photography, and Thematic-Mapper 

(TM) images were analyzed. A shallow well was 

drilled and logged on the west side of Bill Williams 

Mountain. In addition, data were collected from 

30 gravity stations, 13 scalar audiomagnetotelluric 

(AMT) soundings, 25 tensor AMT soundings, and 

4 square-array direct-current resistivity (SAR) 

soundings. Data from the geophysical investigations 

provided information about local faults and provided 

the basis for estimates of depth to the water table.

Physical Setting

Williams is in north-central Arizona near the 

southern edge of the Colorado Plateau. Within the 

2,510-km2 study area, altitudes range from 1,981 m 

along Cataract Creek to 2,821 m at the top of Bill 

Williams Mountain. Bill Williams Mountain is near the 

western edge of the San Francisco volcanic field. This 

volcanic field along the southern edge of the Colorado 

Plateau is predominantly basaltic in composition. The 

basalt flows bury an erosional surface of Tertiary age, 

which cuts across a sedimentary sequence of Paleozoic 

age that is composed of limestone, dolomite, dolomitic 

limestone, dolomitic sandstone, sandstone, and 

mudstone. Near the study area, rocks of Paleozoic age 

are about 975 to 1,128 m thick. Along the southern 

edge of the Colorado Plateau, the Paleozoic rocks are 

as much as 1,524 m thick. Beneath the consolidated 

Paleozoic sediments are undifferentiated rocks of 

Proterozoic age that include granites, metavolcanics, 

and gneisses.

In and near the study area, the western edge of the 

San Francisco volcanic field generally is coincident 

with the western flank of the Kaibab Uplift. This uplift 

forms a broad, low, domal upwarp (fig. 2). The upwarp 

trends approximately north-south from the WilliamsFlagstaff area to the Kaibab Plateau north of Grand 

Canyon. South of Grand Canyon, the uplift is called the 

Coconino Plateau. The San Francisco volcanic field 

and the Coconino Plateau are part of the 2,134-meterhigh Kaibab Uplift. A few miles west of Williams, the 

San Francisco volcanic field and the Kaibab Uplift end, 

and the general altitude of the Colorado Plateau drops 

off abruptly to an average altitude of about 1,520 m.

The Colorado River is the largest surface-water 

feature near the study area (fig. 3). To the north and 

northwest of the study area, the Colorado River flows 

from east to west, then southwest and divides and 

drains the Coconino and Kaibab Plateaus. To the west 

and south, Chino Wash and the Verde River flow 

southeast and then south into the Phoenix area where 

they join the Salt River. To the east, the Little Colorado 

River flows northwestward to its confluence with the 

Colorado River.

Cataract Creek is the main drainage in the study 

area and is a major influence on the hydrogeology of 

the region. Although Cataract Creek is ephemeral for 

much of its course, the coincident fault zone and 

ancillary structures funnel ground water to the 

northwest toward Havasu Spring, which is the terminus 

of the Cataract Creek Fault system. Havasu Spring is 

the major ground-water discharge point for the western 

half of the Coconino Plateau. Several reservoirs on 

Cataract Creek and its tributaries serve as the municipal 

water supply for Williams.
Introduction 5

Base from U.S. Geological Survey

digital data, 1:100,000, 1982

Universal Transverse Mercator

projection, Zone 12 

Figure 2. Laramide folds in Cretaceous rocks on the southwestern flank of the Colorado Plateau. The Kaibab Uplift and a synclinal 

feature associated with the Grand Canyon Embayment are two geologic features that affect ground-water flow near Williams, Arizona.
6 Structural Controls on Ground-Water Conditions and Estimated Aquifer Properties near Bill Williams Mountain, Williams, Arizona

The average monthly temperature varies with 

altitude. In Williams, average monthly temperatures 

range from 1.0°C in January to about 20.3°C in July, 

and average monthly temperature extremes range from 

-5.6°C to 28.1°C in January and July, respectively 

(National Climatic Data Center, NOAA, accessed June 

2000). Precipitation in this cold, temperate climate is 

sufficient to support large stands of yellow pines and 

aspen groves in high, wet areas and piñon-juniper trees 

and meadow grasses in the lower and drier areas.

Williams has two wet seasons each year—

December to March and July to August. Reservoir 

recharge occurs during March and April when the rains 

melt the snowpack. Williams receives an average of 

560 mm of precipitation each year, but the amount can 

vary considerably from year to year (fig. 4). 

The San Francisco Peaks volcanic field near 

Williams mantles the area and fills older valleys with 

volcanic deposits of Tertiary age (Damon and others, 

1974). Bill Williams Mountain is near the intersection 

of Mesa Butte, Cataract Creek, and Lo Draw Faults. 

Volcanic rocks cover the faults but postdepositional 

Colorado

Plateau

Base from U.S. Geological Survey

digital data, 1:100,000, 1982

Universal Transverse Mercator

projection, Zone 12

S

C

River

olo ra d o

alt

River

Gila

Figure 3. Overview of southwestern edge of the Colorado Plateau, Mogollon Rim, and Grand Canyon, and location of surface 

waters bounding the study area in northern Arizona.
Introduction 7

–60

1995

2000

100

80

60

40

20

0

–20

–40

YEAR-ON-YEAR VARIATION OF PRECIPITATION

FROM MEDIAN, IN PERCENT

19551960196519701975198019851990

Average precipitation is 560 millimeters,

median precipitation is 527 millimeters

189519001905

19101915

1920192519301935194019451950

Figure 4. Variation in annual precipitation, city of Williams, Arizona, 1897–1998. The mean monthly precipitation was used for 

any month with 26 or more days of missing record, and a yearly total then was calculated. (Western Region Climate Center 

database, accessed 1996; data for 1996–98 from National Climatic Data Center, 1996–98).

deformation from seismic activity on the near-vertical 

and throughgoing Mesa Butte and Cataract Creek Fault 

systems is observable (Shoemaker and others, 1978). 

Northwest of Williams, the Cataract Creek Fault 

system trends southeast-northwest and forms a graben. 

The volcanic rocks cover the graben within the study 

area and thin to extinction to the north and northwest.

Previous Investigations

The city of Williams and the USGS have 

cooperated on water-resources projects since the early 

1960s. Data from streamflow-gaging stations and creststage gages provided some of the first long-term 

information for the Dogtown Reservoir and Kaibab 

Lake on the Dogtown Wash drainage 7 km southeast 

and 5 km northeast of Williams, respectively. Thomsen 

(1969) completed a surface-water study near Williams, 

and although the primary focus of that study was 

surface water, Thomsen observed high rates of 

infiltration and evaporation in and around Williams. 

The porous and extensively fractured volcanic rocks 

provide a path to the underlying fractured consolidated 

sediments of the Coconino Plateau. Detailed 

descriptions of the geology of the study area are 

available in Darton (1910), McKee (1938, 1954), 

Metzger (1961), Shoemaker and others (1978), Blakey 

(1979, 1990), Billingsley and others (1980), Ulrich and 

others (1984), Blakey and Knepp (1989), and Sorauf 

and Billingsley (1991). 

Errol L. Montgomery and Associates, Inc. (1996) 

assessed hydrogeologic conditions on the Coconino 

Plateau and defined a north-northwestward-trending 

oblate structural subbasin that begins near Williams on 

the south and trends north to the south rim of Grand 

Canyon. They defined the subbasin using many of the 

northwestward-, northeastward-, and northwardtrending geologic structures mapped by Breed and 

others (1986), Billingsley and Huntoon (1983), 

Huntoon and Billingsley (1981), Loughlin and 

Huntoon (1983), and Shoemaker and others (1978). 

Errol L. Montgomery and Associates, Inc. (1996) 

grouped the Redwall Limestone, Temple Butte 

Formation, and the Muav Limestone within the 

subbasin into a single geohydrologic unit called the 

Redwall-Muav aquifer. Thiele (1964a, b) assessed the 

deep aquifers. The interpreted geophysical curves did 

not indicate methods used or provide original data; 

therefore, the curves were not used in this study.
8 Structural Controls on Ground-Water Conditions and Estimated Aquifer Properties, Williams, Arizona

METHODS OF INVESTIGATION 

Gravity and magnetic-potential field methods were 

used to identify variations in rock density and magnetic 

susceptibility. The objective was to associate density 

and magnetic-field variations with differences in the 

areal and vertical distribution of rock types and 

structures. A TM image, aerial photographs, and a 

DEM were used to complement observations from the 

geology, hydrology, and potential-field data. The large 

spatial coverage provided by these data sets allowed an 

overview of the study area and information on largescale regional structures. Square-array and electromagnetic soundings provided information on the 

subsurface-resistivity structure and estimates of depths 

to the water table.

Well data were collected and used to provide 

ground truth and augment the interpreted depth-towater estimates generated by the soundings. During the 

course of the study, a well, Bard Spring #2, was drilled 

on the west side of Bill Williams Mountain. Geophysical and lithologic logs were compiled from Bard 

Spring #2 and were used to provide ground truth for 

electrical soundings on the west side of the study area.

Gravity Measurements

Gravity measurements were made at 40 sites near 

the intersection of the Mesa Butte and Cataract Creek 

Fault systems (fig. 1) to supplement the gravity data 

taken from the USGS 2-km simple Bouguer gravitydata grid (Phillips and others, 1993). Gravity measurements were made using a LaCoste & Romberg 

Model D gravity meter (Model D-76) with loops back 

to the USGS absolute-gravity station (WaltBM) in 

Flagstaff. These new data were merged with the 

existing data set and then plotted (fig. 5). The data 

provide improved resolution on the gravity-anomaly 

map for the area southeast of Williams near the 

intersection of the Mesa Butte and Cataract Creek Fault 

systems. 

Aeromagnetic Measurements

The aeromagnetic data (for 2,134 km2) used in this 

survey were extracted from the United States 2-km grid 

of the USGS (Phillips and others, 1993), converted to a 

Universal Transverse Mercator (UTM) projection, and 

contoured every 50 gammas (fig. 6). Aeromagnetic 

surveys measure magnetic field anomalies caused by 

changes in the magnetic fields of geological bodies that 

are superimposed on the Earth’s magnetic field. The 

magnetic effects of a rock, or the intensity of 

magnetization, is complex in that it has a magnitude 

and a direction. In aeromagnetic prospecting, variations 

in the intensity of some component of the field usually 

are measured. After the Earth’s magnetic field is 

removed, the residual field is used to interpret the 

rocks. Rocks rich in magnetite, pyrrhotite, or illmenite 

have the most pronounced effects and generate the 

largest anomalies. Magnetic gradients near the edges of 

magnetic anomalies often indicate the location of faults 

or other boundaries.

Audiomagnetotelluric Soundings

AMT soundings (13 scalar and 25 tensor) were 

collected during the course of the study (fig. 1). Both 

types of soundings were used to provide depth-to-water 

estimates. The station names, locations, and estimates 

of depths to water in the regional aquifer are given in 

the section entitled “Supplemental Data” at the back 

of the report.

Natural-source AMT is an electromagnetic (EM) 

sounding technique in which the variation in resistivity 

of the ground as a function of depth is measured (Keller 

and Frischknecht, 1966). Soundings are obtained by 

measuring the magnitude of coherent signal peaks in 

the electric and magnetic fields. These peaks are 

generated by lightning and other atmospheric 

disturbances that provide a range of electromagnetic 

signals at various frequencies measurable at land 

surface. As an EM signal passes over a point on the 

Earth, a small amount of energy is transmitted 

vertically into the ground. The part of the EM signal 

that is transmitted attenuates exponentially with depth. 

The lower-frequency signals are less attenuated and 

penetrate farther than the higher-frequency signals. 

EM measurements made over a range of frequencies 

give information about resistivity variations with depth. 

EM measurements made at and below a frequency of 

1 hertz are called magnetotelluric (MT). EM measurements made within the audio-frequency range are 

called AMT (typically 1 hertz to 30 kilohertz).
Methods of Investigation 9

– 19 9 –1

–1

–196

–191

–192

–

–

1

18

–182

–176

–178

6

88

–190

98

–190

–19

– 19 8

9

–174

–191 –190

–190

–

–

2

2

–208

–206

–204

–202

–200

09 –20

–2 0

–

5

2 0 3

– 2 01

7

10

–175

–188

681–

481–

281–

0

871–

81–

EXPLANATION

–180 LINE OF EQUAL SIMPLE BOUGER GRAVITY

 DATA —Interval, 1 milligal

NOTE: Dashed white line denotes

 assumed fault trace or

 inferred fault

15'

 35°20'

10'

35°5'

112°25' 20' 15' 10' 5' 112°00' 111°55'

–177

177 –

– 1 7 6

–178

7

– 1

–19

9 3 0

–189

–189

–184

–18

–178

0

–187

–185

–183

–181 –191

–19 5

–178

– 17 9

177 –

7

Polson

Dam Fault

Lo Draw Fault

Williams

Cataract

Creek

System

Fault

Mesa Butte

Fault System

Base from U.S. Geological Survey

digital data, 1:100,000, 1983

Universe Transverse Mercator

projection, zone 12 

0 5 10 KILOMETERS

0 5 MILES

Figure 5. Simple Bouguer gravity anomaly map generated from the 2-kilometer grid of the U.S. Geological Survey and 

new gravity data near Williams, Arizona. Cooler colors are gravity lows; warmer colors are gravity highs. Fault 

identification and orientation based on gravity data.
10 Structural Controls on Ground-Water Conditions and Estimated Aquifer Properties near Bill Williams Mountain, Williams, Arizona

–35

– 3 00

0

–150

–250

200

–100

–150

–150

–150

–150

100

– 50

1– 0

–150

0

–100

–1 05

– 250

–

–

30 0

2 00 –50

50

100

1–

00

1– 50

2– 50

2 – 00

150

0

0

0

50

50

51

0

52

0

53

0

4

550 50

5 6 0

100

10

1

0

5

15 0

2 5 0

0

200

200

300

400

500

600

700

50

0

0

–50

50

EXPLANATION

–150 LINE OF EQUAL MAGNETIC INTENSITY—Interval

 50 gammas

15'

 35°20'

10'

35°5'

112°25' 20' 15' 10' 5' 112°00' 111°55' Polson Dam Fault Lo Draw Fault

Williams

Cataract

Creek

System

Fault

Mesa

Butte

Fault

System

Base from U.S. Geological Survey

digital data, 1:100,000, 1983

Universe Transverse Mercator

projection, zone 12 

0 5 10 KILOMETERS

0 5 MILES

NOTE: Dashed white line denotes

 assumed fault trace or

 inferred fault

Figure 6. Aeromagnetic anomaly map generated from the 2-kilometer grid of the U.S. Geological Survey, Universal 

Transverse Mercator projection, near Williams, Arizona. Warmer colors represent magnetic highs; cooler colors 

represent magnetic lows. Fault identification and orientation based on aeromagnetic data.
Methods of Investigation 11

Scalar AMT is a method in which one electric 

component (Ex) and one orthogonal magnetic 

component (Hy) are used to define the apparent 

resistivity (Sheriff, 1991). The vector electric field (E) 

in volts per meter and the vector current-density field 

(J) in amperes per square meter are related by the 

resistivity tensor (ρa) in which E=ρa J. If the material 

sampled is isotropic, then ρa is a scalar value. Scalar 

AMT is applicable to areas such as basins where 

isotropic horizontal layering can be assumed. The 

scalar AMT technique gives only an approximation of 

the true resistivity in areas with complex geology. 

Cagniard (1953) discusses MT theory, 

interpretation, and potential applications and provides a 

formula for calculating Cagniard resistivity:

, (1)

where

Tensor AMT methods are better suited to areas 

with complex geology. The tensor method measures 

two orthogonal horizontal electric and magnetic fields. 

These fields are: Ex, electric field in the x direction; Ey, 

electric field in the y direction; Hx, magnetic field in the 

x direction; and Hy, magnetic field in the y direction. 

The impedance matrix (Z), therefore, can be described 

as a complex tensor to account for anisotropy and twodimensional structures. The impedance is the apparent 

resistance, in ohms, to the flow of alternating current 

analogous to resistance in a direct-current circuit. 

Impedance is complex and of magnitude, Z, and has a 

phase angle, γ. These terms can be expressed in terms 

of resistance (R), inductive reactance (XL=2πvL), and 

capacitive reactance (XC=1/2πvC):

, (2)

where

, (3)

where

In tensor AMT exploration, if Ex is the electricfield component in an arbitrary horizontal direction, 

and Hy is the associated orthogonal horizontal magnetic 

field, the surface impedance Zsurface is:

. (4)

Measurements of surface impedance and frequency 

can be interpreted in terms of the electric properties of 

the subsurface. Vozoff (1986, 1991) discusses 

fundamental principles, data processing, analysis, 

noise, modeling, inversion, instrumentation, data 

acquisition, and case histories for the tensormagnetotelluric method. The same techniques can be 

applied to the tensor-AMT method. The traditional 

technique for interpreting EM soundings is to find a 

model that closely reproduces the observed data (Spies 

and Frischknecht, 1991). Models can be found by curve 

matching, by interactive trial-and-error matching using 

a computer, or by automated computer programs. 

Techniques are available that use partial-curve 

matching or mathematical relations. The degree to 

which the physical model corresponds to the actual 

model depends on the type, completeness, and quality 

of the data, as well as on the geology.

Inverse-computer modeling allowed a starting 

layered-earth model to be adjusted to best fit the data. 

Ridge regression (Inman, 1975) was used to iteratively 

adjust the values of resistivity and thickness for the 

starting model using a least-squares fit. The starting 

layered-earth model can have as many as eight layers 

and can be constrained if some values of resistivity and 

thickness are known or can be estimated before 

inversion.

ρa = apparent resistance, in ohm-meters;

ν = frequency in hertz;

Ex = magnitude of the electric field in the 

x direction, in millivolts per kilometer; 

and 

Hy = magnitude of the magnetic field in the 

y direction, in gammas.

ρa

0.2

ν

-------     Ex

Hy

---------     2

=

Z R2 XL XC ( ) – 2 [ ] +

1/2 =

R = resistance, in ohms;

L = inductance, in henrys; 

C = capacitance, in farads; and

γ = phase angle, in radians.

γ tan–1 XL XC ( ) – 2 [ ]

1/2 =

Zsurface E

x

/H

y =
12 Structural Controls on Ground-Water Conditions and Estimated Aquifer Properties near Bill Williams Mountain, Williams, Arizona

Smooth modeling also has been used to 

automatically interpret the MT amplitude and 

impedance-phase sounding data in terms of a smooth 

model. The model depths are spaced logarithmically 

and are generated from a minimum and maximum 

depth on the basis of a Bostik one-dimensional 

inversion or William of Occam’s smooth inversion 

(Constable and others, 1987). 

Estimated depth of exploration is a function of 

frequency (ν) and resistivity (ρa) and is approximated 

by the skin depth (δ) of the electromagnetic waves. 

The skin depth is the depth at which the fields have 

decreased to 37 percent (1/e) of their surface value and 

is:

, (5)

where

Bostick (1977) provides for the calculation of 

depth (Dmeters) to conductors. This one-dimensional 

inversion technique is given as:

. (6)

Bosticks’s equation gives a practical estimate of 

depth of exploration particularly if a well-defined 

descending branch (a conductor) is observed on a 

sounding curve. Because the Earth is being sampled 

laterally as well as vertically at the measuring station, 

simple one-dimensional model interpretations provide 

only an approximation of the true geoelectric section. 

If low-resistivity layers are encountered in the shallow 

subsurface, the curves may not reflect the true verticalresistivity distribution because of signal attenuation 

and lateral effects caused by three-dimensional 

geologic structures.

Scalar-AMT sounding setup and data collection 

requires an electric dipole with nonpolarizing 

electrodes and an orthogonal magnetic sensor. Ten or 

more coherent electric and magnetic signals are 

digitized at each of 16 sampled frequencies (2.7, 4.5, 

7.5, 14, 27, 45, 75... up to 14,000 hertz). The twochannel scalar AMT receiver used in this study used a 

25-meter dipole and 1.3-meter magnetic coil. The 

scalar AMT receiver is a portable unit suitable for use 

in rugged terrain or in areas where vegetation prohibits 

the use of long lengths of wire. Cagniard (1953) 

resistivity values were calculated using appropriate 

instrument calibration and gain corrections (Long and 

Pierce, 1984). Application and details of the scalar 

AMT method are given by Strangway and others 

(1973). Hoover and others (1976, 1978) and Hoover 

and Long (1975) provide details about the USGS scalar 

AMT system used in this study.

Tensor AMT soundings require two electric 

dipoles with four nonpolarizing electrodes and two 

orthogonal-magnetic sensors (three if the vertical 

magnetic field, Hz, is measured). The tensor system 

used was a 10-channel receiver manufactured by 

Electromagnetic Instruments Incorporated (EMI, 

Berkeley, California). The EMI (MT-1) system collects 

coherent signals and calculates phase and impedance 

for as many as 60 equal log-spaced frequencies from 

2.2 to 24,000 hertz. Scalar and tensor soundings 

(examples shown in figures 7 and 8) were modeled 

using the EMIXMT software by Interpex Limited 

(1993). Interpreted curves for each sounding were used 

to estimate depth to the water table.

Square-Array Resistivity

A recent study near Flagstaff, Arizona, included 

SAR and seismic-reflection work (Bills and others, 

2000). The SAR provided a means to estimate fracture 

strike direction and depth to water. The high-resolution 

seismic-reflection profiles confirmed the SAR strike 

direction and the near-vertical nature of the faults on 

the Coconino Plateau. The fractures associated with 

faulting serve as pathways for ground-water flow and 

strongly influence the ground-water flow patterns near 

Flagstaff. On the basis of this experience, four SAR 

soundings were completed in the Williams area near 

Poquette Homestead, McDougal Flat, Williams Airport 

Road, and Bard Spring (fig. 1).

The SAR method is similar to that for traditional 

collinear arrays. The location of the array is the center 

of four electrodes that are laid out in a square pattern.

μ = μ0 = 4π x 10-7, in weber per 

ampere meter.

δ ρa

( ) μπν = ---------------

Dmeters 355 ρa

ν

-----     =
Methods of Investigation 13

RESISTIVITY,

IN OHM METERS

105 1 104 103 102 101

APPARENT RESISTIVITY, IN OHM - METERS

DEPTH BELOW LAND SURFACE, IN METERS

103

FREQUENCY, IN HERTZ

A.

B.

102

102

103

102 101

103

104

10 1 4 105

101

101

Figure 7. Scalar audiomagnetotelluric sounding data and model for data collected near the A-1 well site near Williams, Arizona. 

A, Scalar audiomagnetotelluric sounding data. B, Layered earth model (dashed line) and smooth model (solid line).
14 Structural Controls on Ground-Water Conditions and Estimated Aquifer Properties near Bill Williams Mountain, Williams, Arizona

RESISTIVITY,

IN OHM METERS

105 1 104 103 102 101

APPARENT RESISTIVITY, IN OHM - METERS PHASE, IN DEGREES

DEPTH BELOW LAND SURFACE, IN METERS

101

103

FREQUENCY, IN HERTZ

102

101

103

102 101

102

103

10 1 4 105

1

90

1

0

45

30

15

75

60

A.

C.

B.

Figure 8. Tensor audiomagnetotelluric sounding data and model for data showing electric and magnetic field coherencies better 

than 0.8 recorded in Davenport Lake (dry) site (EMI-3) about 10 kilometers east of Williams, Arizona. A, Tensor audiomagnetotelluric sounding data. B, Phase audiomagnetotelluric sounding data. C, Layered earth model (dashed line) and smooth model 

(solid line).
Methods of Investigation 15

The square size is equal to the length of one side of the 

square (A). Resistivity measurements are collected in 

three directions, two measurements in the two orthogonal directions along the sides of the square and one 

diagonal measurement collected as a check measurement. The array then is expanded by a factor of 

(Habberjam and Watkins, 1967) so that the sounding 

can be interpreted as a function of depth. Estimates of 

the depth of exploration in isotropic homogeneous 

material are roughly equal to the length of the side of 

the square (A). The square is expanded until the desired 

size is reached. The wire is reeled in, and the orientation of the square is rotated usually by 10 to 15°. The 

process is repeated until the data have been collected 

through 180°. In this study, a 15°-rotation increment 

was used, providing 12 orientations.

Apparent resistivity values are calculated using the 

equation:

, (7)

where

The 12 azimuthal soundings are averaged; the 

points are translated by a factor of 1.172 (Habberjam, 

1979) to the right to generate a Schlumberger (1920) 

resistivity curve and are processed using ATO, which is 

a computer program developed by Zohdy and Bisdorf 

(1989). Several plots from SAR soundings collected in 

a study by Bills and others (2000) showed a resistivity 

maximum usually followed by a resistivity low. 

The measured depth to the water table usually equaled 

the resistivity high (rollover point) just before the 

resistivity low caused by the more conductive watersaturated rocks (Bills and others, 2000).

Resistivity data from SAR soundings are plotted 

for each square size (A) using polar coordinates after 

Taylor and Fleming (1988). The plots allow the 

investigator to visually pick the dominant fracture 

trend, which is normal to the major ellipse axis. Lane 

and others (1995) and Habberjam (1979) demonstrated 

that fracture direction, coefficient of anisotropy, and 

secondary porosity can be calculated from square-array 

soundings. Alternatively, a least-squares fit of an 

ellipse to the data can provide the ellipse maxima and 

minima necessary for the calculation of the coefficient 

of anisotropy and secondary porosity as follows:

, (8)

where

λ can be calculated for the rock unit given by the 

ratio of major-axis resistivity to minor-axis resistivity 

and the true resistivity normal to joint direction. 

An azimuthal-resistivity survey provides the effective 

bulk-resistivity values parallel to the joint and (or) 

fracture strike (ρx) and normal to the joint and (or) 

fracture strike (ρy). 

Lane and others (1995) modified Taylor and 

Fleming’s (1988) equation for use with a square-array 

accounting for the geometric differences between the 

square and collinear arrays:

, (9)

where

, (10)

ρa = apparent resistance, in ohm-meters;

K = calculated as is 

the geometric-correction factor for the 

square (Habberjam and Watkins, 1967), 

and A is equal to one side of the square, 

in meters;

∆V = potential difference, in volts; and

I = current, in amperes.

A 2

ρa = K∆V I⁄

K = 2πA ⁄ ( ) 2 2 –

λ = coefficient of anisotropy.

φ = secondary porosity, in percent;

N = effective vertical anisotropy;

C = specific conductance of ground water 

in microsiemens per centimeter at 

25°C;

ρmax = maximum apparent resistivity, in ohm 

meters; and

ρmin = minimum apparent resistivity, in ohm 

meters.

λ ρy ρx = ( ) ⁄

φ 3.41 104 ( ) × ( ) N – 1 N2 ( ) – 1

N2

C ρmax ρmin ( ) –

= --------------------------------------------------------------------

N 1 λ2 ( )α – 1 2 = ( ) + sin
16 Structural Controls on Ground-Water Conditions and Estimated Aquifer Properties near Bill Williams Mountain, Williams, Arizona

where

If the fractures are vertical, then N=λ. These 

formulas enable calculations of apparent resistivity for 

several directions; apparent fracture strike angle, θ (in 

degrees); coefficient of anisotropy; and secondary 

porosity for each crossed square-array set of apparent 

resistivity values at each square size. Properties 

obtained from these formulas are used to characterize 

aquifer conditions and ground-water flow.

Thematic-Mapper Data

A 3,108-km2 area approximately centered on 

Williams was analyzed using Landsat TM data (fig. 9). 

The Landsat 5 TM satellite collects radiation in seven 

spectral bands. Bands 1, 2, and 3 record data in the 

blue, green, and red parts of the visible spectrum, 

respectively. Band 4 collects in the near infrared, and 

bands 5 and 7 in the middle infrared. Band 6 collects 

radiation in the thermal infrared. The data collected in 

bands 1–5 and band 7 have a ground resolution of 

30 by 30 m; the data collected in band 6 have a ground 

resolution of 120 by 120 m. These data commonly are 

resampled to a nominal ground resolution of 28.5 by 

28.5 m.

The Landsat TM data used in this analysis were 

acquired on May 10, 1993 (USGS EROS Data Center 

Scene ID numbers LT5037035009313010 and 

LT5037016009313010). These data were enhanced 

digitally to emphasize the geomorphic and (or) 

topographic expression of faults and other large surface 

fractures. This enhanced digital image was analyzed 

visually to identify and map continuous linear to 

curvilinear alignments of natural landscape features 

that indicate bedrock faults and other large surface 

fractures (Dr. J. Dohrenwend, consultant, Above and 

Beyond, Inc., written commun., 1998).

α = dip of the fractures, in degrees.

Williams

Dogtown

Reservoir

Kaibab

Lake

Davenport

Lake

Santa Fe

Reservoir

Bill

Williams

Mountain

Cinder

cones

Lost

Canyon

Unnamed fault

Cataract

Creek

System

Fault

Mesa

Butte

Fault

System

McDougal Flat

0 5 KILOMETERS

0 3 MILES

N

Figure 9. Landsat Thematic-Mapper image of the study area near Williams, Arizona. The northwestward-trending unnamed 

fault south and east of Williams was detected by square-array resistivity and audiomagnetotelluric soundings in McDougal Flat 

and intersects several cinder cones, Lost Canyon, and the Santa Fe Reservoir. Fault identification and orientation based on 

Thematic-Mapper data.
Hydrogeologic Units 17

Aerial Photography

Photographs of an area of about 1,554 km2 that 

extends north about 48 km and west about 32 km from 

Bill Williams Mountain were examined for indications 

of fracturing. Two sets of panchromatic, vertical, aerial 

photographs were used in the analysis: (1) National 

High Altitude Program (NHA) photographs that were 

taken in the summer and early fall of 1980 at an altitude 

of about 12,200 m (nominal scale of 1:80,000); and 

(2) National Aerial Photograph Program (NAPP) 

photographs that were taken in the summer of 1992 at 

an altitude of about 6,100 m (nominal scale of 

1:40,000).

These aerial photographs were examined using a 

stereoscope with 3X binocular magnification. Such 

examination enables the resolution of features as small 

as 2 by 2 m on the 1:40,000-scale photographs. 

The resolution is 225 times smaller than the smallest 

features that can be resolved using the Landsat TM 

images. Linear to curvilinear alignments of natural 

landscape features that may indicate bedrock faults and 

other large surface fractures were identified and 

mapped using these photographs (Dr. J. Dohrenwend, 

consultant, Above and Beyond, Inc., written commun., 

1998).

Digital Elevation Model Data

DEM is the terminology adopted by the USGS to 

describe terrain elevation data sets in a digital raster 

form. The 7.5-minute DEM provides coverage in 7.5- 

by 7.5-minute blocks. Resolution is 30- by 30-meter 

spacing on a UTM projection. The 7.5-minute DEM 

provides the same coverage as a standard USGS 

7.5-minute quadrangle.

Many of the large structural features in the 

Williams area have a topographic signature. To assess 

these features, a DEM image for the area was compiled 

from four 7.5-minute USGS DEM quadrangles 

(fig. 10). The image covers 178 km2.

Well Data

A total of 14 wells were located in the USGS 

ground-water site inventory (GWSI) database and the 

Arizona Department of Water Resources well-registry 

database. Seven of these wells are deep enough to yield 

water from the regional aquifer.

During the study, two wells near Williams were 

drilled, and lithologic sections were constructed from 

the drill cuttings. The A-1 well was drilled during 

1995–96 by a private water company, and Bard Spring 

#2 well was drilled and logged in 1998 by the USGS 

Western Region drill rig. Lithologic information, 

geophysical logs, and depth-to-water data were used to 

provide ground truth for the geophysical-sounding 

methods.

HYDROGEOLOGIC UNITS

At the base of the hydrogeologic section are 

undifferentiated rocks of Precambrian age (fig. 11). 

Above the Precambrian rocks are consolidated 

sediments of Paleozoic age. These rocks extend over 

much of the Colorado Plateau Province (Fenneman, 

1931). The geologic units include the Tapeats 

Sandstone, Bright Angel Shale, Muav Limestone, 

Temple Butte (Martin) Formation, Redwall Limestone, 

Supai Group, Hermit Formation, Schnebly Hill 

Formation, Coconino Sandstone, Toroweap Formation, 

and the Kaibab Formation. Saturated rocks include the 

Tapeats Sandstone, Bright Angel Shale, Muav 

Limestone, Redwall Limestone, and the bottom part of 

the Supai Group. Water quality in the Tapeats 

Sandstone and the Bright Angel Shale is too saline for 

most uses. A water sample from the Quivero well 

(1,123 m in depth) that is completed in the Tapeats 

Sandstone had a dissolved-solids concentration of 

11,200 mg/L and a specific conductance of 

18,000 μS/cm (Baroid, Inc., written commun., 1970). 

Water from the regional aquifer above the Tapeats 

Sandstone is used as drinking water in the communities 

of Valle and Tusayan, Arizona.

The regional aquifer in this study includes the 

Muav Limestone, the Redwall Limestone, and the base 

of the Supai Group. The total thickness of this 

sedimentary section varies but generally is about 

1,100 m (Billingsley and others, 1980). Basaltic 

volcanic rocks of the San Francisco volcanic field 

mantel the entire study area.

Rocks of Precambrian age form the base of the 

hydrogeologic section. These rocks, where exposed in 

Grand Canyon, have low permeability and porosity and 

form the basal confining layer below the consolidated 

sediments.
18 Structural Controls on Ground-Water Conditions and Estimated Aquifer Properties near Bill Williams Mountain, Williams, Arizona

0 1 2 KILOMETERS

0 1 MILE

Lo Draw Fault

N

Unnamed fault

Polson Dam Fault

Mesa

Butte

Fault

System

Cataract

Creek

System

Fault

Williams

Figure 10. Mosaic of four 7.5-minute U.S. Geological Survey digital elevation models near Williams, Arizona. The unnamed 

fault in the eastern part of Williams was detected by square-array resistivity and audiomagnetotelluric soundings. Other 

faults were identified and oriented on the basis of digital elevation model data.
Hydrogeologic Units 19

PRECAMBRIAN ROCKS

TAPEATS SANDSTONE

KAIBAB FORMATION

TOROWEAP FORMATION

WATAHOMIGI FORMATION

MANAKACHA FORMATION

BASALT

REDWALL LIMESTONE

Modified from Billingsley and others (1980) and McKee (1982)

Supai Group

0–122

15–91

200–500

0–244

91–213

16–91

30–146

0–182

0–30

Limestone

water-bearing

zone

Solution

channels

and caves

RELATIVE THICKNESS, IN METERS

COCONINO SANDSTONE

SCHNEBLY HILL FORMATION

ESPLANADE SANDSTONE

WESCOGAME FORMATION

HERMIT FORMATION

TEMPLE BUTTE (MARTIN) FORMATION

MUAV LIMESTONE

BRIGHT ANGEL SHALE

Figure 11. Rock formations and hydrogeologic units for the Williams area, Arizona.
20 Structural Controls on Ground-Water Conditions and Estimated Aquifer Properties near Bill Williams Mountain, Williams, Arizona

The Tapeats Sandstone of Early Cambrian age is 

separated from the Precambrian rocks by an erosional 

unconformity (Hereford, 1975, 1977). The Tapeats 

Sandstone is the basal formation of the Tonto Group in 

the Grand Canyon area in Mohave and Coconino 

Counties, Arizona, and in the Colorado Plateau. 

The Tapeats Sandstone typically is between 53 and 

55 m thick in the western part of Grand Canyon where 

the massive section is purple to buff, coarse-grained, 

thick-bedded, cross-laminated quartzite to quartzitic 

sandstone and the overlying transitional unit is a 

brown, coarse-grained, thin-bedded, ledge-forming, 

cream- to-brown quartzite or sandstone with some 

conglomerate beds and lenses near the base.

The Bright Angel Shale of Middle and Early 

Cambrian age is recognized as the middle formation of 

the Tonto Group within the Colorado Plateau (McKee, 

1945). The fossiliferous shale is between the 

underlying Tapeats Sandstone and the overlying Muav 

Limestone and has gradational top and bottom 

contacts. The Bright Angel Shale is characterized by 

thin, platy laminations, green-buff color, glauconitic 

beds, and an abundance of worm markings. The Bright 

Angel Shale weathers to a slope or bench and ranges 

from 98 to 147 m in thickness in measured sections. 

Near Grand Canyon, the unit is green shale, platy, 

brown-spotted siltstone, and platy, micaceous, gray 

siltstone. This unit also may function as a basal or 

partial confining layer for the overlying regional 

aquifer near Williams.

The Muav Limestone, which is the upper formation 

of the Tonto Group, is Middle Cambrian in age. 

The formation is mapped on the north and south sides 

of the Colorado River and is recognized on cross 

sections and in measured sections from Mohave 

County to east of the Little Colorado River in the 

Colorado Plateau (McKee, 1945). The formation 

overlies and intertongues eastward with the Bright 

Angel Shale of the Tonto Group and unconformably 

underlies the Redwall Limestone. The section 

measures 139 m in thickness in Bass Canyon where the 

formation is composed of mottled-gray and buff, 

impure shaly and sandy limestone interbedded with 

fine-grained, buff sandstone. The formation forms 

steep slopes and cliffs and has coralloid and fucoidal 

markings but lacks fossils (Noble, 1914). The Muav 

Limestone is saturated and forms part of the regional 

aquifer near Williams.

The Temple Butte (Martin) Formation is Devonian 

in age (McNair, 1951; Teichert, 1968; Poole and others, 

1967). In Arizona, this formation extends from the 

Basin and Range Province to the Black Mesa Basin and 

from the Colorado Plateau to the Pedregosa Basin. 

Poole and others (1967) have divided it into a lower 

unit, the Beckers Butte Sandstone Member of early 

Middle or possibly Early Devonian age, and an upper 

unit, the Jerome Member of Late Devonian age. The 

formation is light gray to dark gray. This formation also 

has been called the Martin Limestone or Martin 

Formation. Within the study area, it was not possible to 

distinguish this formation from the Redwall and Muav 

Limestones.

The Redwall Limestone of Mississippian and 

Pennsylvanian age unconformably overlies the Muav 

Limestone in Coconino County and in the Colorado 

Plateau (Noble, 1914; Armstrong and Holcomb, 1989). 

The Redwall Limestone is a dense, blue-gray 

crystalline limestone that forms a single cliff and 

underlies the Supai Group. This limestone ranges in 

thickness from 168 m on the trail near Grand Canyon 

station to 293 m east of Seligman, Arizona, on the east 

side of the Kaibab Plateau, and is 296 m thick in the 

Kanab Valley. Within the study area, the Redwall 

Limestone is saturated and forms part of the regional 

aquifer.

The Supai Group of Pennsylvanian to Permian age 

unconformably lies on the Redwall Limestone and 

similarly underlies the Hermit Formation. The group is 

a series of marine transgressional sediments deposited 

in an embayment of a Pennsylvanian sea. The group is 

recognized through most of the Arizona part of the 

Colorado Plateau, comprises four formations, and 

ranges in total thickness from about 200 to 530 m 

(McKee, 1982). The marine Watahomigi Formation, 

the lowest unit, is largely carbonate in composition and 

ranges from chert and flint gravels to fine-grained 

limestones. The Manakacha Formation overlies the 

Watahomigi Formation, grades from marine to 

continental from west to east, and is considerably 

sandier than the underlying Watahomigi Formation. 

The Wescogame Formation unconformably overlies the 

Manakacha Formation and, like the underlying unit, 

grades from marine to continental from west to east. 

This formation is sandier still than the Manakacha 

Formation and includes a basal conglomerate that 

partially fills erosional channels and depressions and 

blankets much of its depositional extent. The Permian 

Esplanade Sandstone overlies the Wescogame 
Hydrogeologic Units 21

Formation and is the thickest and most extensive part of 

the Supai Group. This shelf deposit ranges from thickbedded limestones and sandstone in the west and east, 

respectively, that sit atop a basal mudstone or siltstone. 

In the A-1 well near Williams, the potentiometric 

surface is 2 m below the contact between the Supai 

Group and the Redwall Limestone.

A red shaly siltstone, the Hermit Shale, was 

deposited on an eroded, unconsolidated Supai surface 

(Noble, 1923). This formation was not observed in drill 

cuttings from wells in the Williams area.

The Schnebly Hill Formation of Early Permian age 

is named for exposures on the south side of Casner 

Canyon in Coconino County. The unit overlies the 

Supai Group in the Williams area and underlies the 

Coconino Sandstone at Fossil and Carrizo Creeks, at 

Fort Apache, and in the southern part of the Defiance 

Plateau. The formation includes sandstone, siltstone, 

mudstone, evaporites, and carbonates and ranges from 

0 to 274 m in thickness. The unit is absent at Chino 

Point and at Grand Canyon, thickens toward the 

southeast, and is thickest (274 m) in the Holbrook 

Basin. The unit is present in the subsurface in wells 

east of Grand Canyon and is exposed on the Mogollon 

Rim, Mount Elden near Flagstaff, Defiance Plateau, 

and in some quarries north of Williams (Blakey, 1990). 

The Schnebly Hill Formation is unsaturated near 

Williams.

The Coconino Sandstone of Early Permian age 

extends across all of northern and central Arizona from 

the Defiance Plateau and the Monument Upwarp to 

northeastern Arizona. The lower part of the Schnebly 

Hill Formation intertongues with the Coconino 

Sandstone near Williams. The Coconino Sandstone is a 

cross-stratified, noncalcareous quartzarenite of eolian 

origin (Blakey, 1990). The unit ranges in thickness 

from 91 m at Bass Trail to 213 m in an escarpment 

24 km southwest of Bill Williams Mountain (Darton, 

1910). The formation is unsaturated near Williams.

The Toroweap Formation of Early Permian age 

overlies and intertongues with the Coconino 

Sandstone. The formation unconformably underlies 

the Kaibab Formation in the Sycamore Canyon-Sedona 

area in Yavapai County. The Toroweap Formation is 

recognized west of a line that runs from Sycamore 

Canyon north through Marble Canyon of Grand 

Canyon (Blakey, 1990). West of the study area near 

the Hurricane Cliffs in Mohave County, the Toroweap 

Formation is 131 m thick (Sorauf and Billingsley, 

1991); and near Williams, the Toroweap Formation 

is 76 to 91 m thick (Bills and others, 2000). 

The formation is unsaturated.

The Kaibab Formation of early Permian age 

overlies the Toroweap Formation. The Kaibab is 

divided into the Fossil Mountain Member (base) and 

the Harrisburg Member (top) west of a north-south line 

in Arizona from Page in Coconino County in the 

Colorado Plateau to the Verde Valley and Prescott areas 

in Yavapai County in the Basin and Range Province. 

East of the north-south line, the formation consists of 

calcareous sandstone and sandstone and is not divided. 

The formation ranges from 30 to 250 m in thickness 

where it overlies the Toroweap Formation and 

unconformably underlies the Moenkopi Formation. 

The Fossil Mountain Member consists of fossiliferous 

limestone, white chert, and a yellow sandstone bed. 

The Harrisburg Member consists of interbedded 

limestone, gypsum, dolomite, chert, and sandstone, and 

has fossil brachiopods and gastropods. Total thickness 

for the Kaibab Formation near Williams is 146 m 

(Sorauf and Billingsley, 1991), and the formation 

generally is unsaturated although some small perched 

zones exist.

Newhall and others (1987) mapped and dated the 

basaltic rocks of Cenozoic age exposed in the Williams 

area. These basaltic flows cover an area of about 

5,200 km2 and vary in thickness from 0 to 300 m. 

Although andesitic, dacitic, and rhyolitic rocks also are 

found in the volcanic field, these rocks are concentrated 

in the larger volcanic centers (such as Bill Williams and 

Sitgreaves Mountains). The smaller, more numerous 

vents (mostly cinder cones) and associated flows are 

composed primarily of basalt, basaltic andesite, and 

benmoreite. These basalt flows typically are 

unsaturated although exceptions do exist. The truck 

stop at Beaumont, east of Williams on Interstate 40, has 

a productive well completed in basalt. Several springs 

near Bill Williams Mountain appear to be associated 

with brecciated flow bottoms, near-vertical joints, or 

faults. Springs on the flanks of Bill Williams Mountain 

are due to discontinuous fine-grained ash flows and 

tuffs that restrict the vertical flow of water locally.

Shallow alluvial wells in Pittman Valley and other 

topographically low areas yield water to ranches and 

homes. During extended periods of drought, the springs 

and the thin, discontinuous, and shallow aquifers have 

dried up because of pumping and infiltration.
22 Structural Controls on Ground-Water Conditions and Estimated Aquifer Properties near Bill Williams Mountain, Williams, Arizona

Errol L. Montgomery and Associates, Inc. 

(1996) state that the Redwall-Muav aquifer is:

“...considered the only aquifer of regional 

extent that is capable of consistently yielding 

large quantities of groundwater to wells and 

springs...” 

They estimated that 98 percent of the water from 

this part of the Coconino Plateau discharges from the 

regional aquifer at Havasu Springs, which has a flow of 

1,830 L/s. The remainder of the water discharges from 

smaller springs, usually at rates of less than 19 L/s, 

along the south rim of Grand Canyon.

STRUCTURAL CONTROLS ON GROUND-WATER 

CONDITIONS 

The southwestern part of the Colorado Plateau has 

been affected by large-scale folds of Laramide age 

(Kelley, 1958; Chapin and Cather, 1981; Nations and 

others, 1985; and Davis and Kiven, 1975). The 

resulting large synclinal basins, anticlinal uplifts, and 

many smaller folds generally trend to the northwest in 

the study area and have been found in New Mexico and 

Utah (fig. 2). Examples of undulating basin uplift 

structures from west to east in northern Arizona are the 

Grand Canyon Embayment (a synclinal basin 

northwest of Bill Williams Mountain), the Kaibab 

Uplift, Black Mesa Basin, and the Defiance Uplift.

Within the study area, the synclinal Grand Canyon 

Embayment northwest of Bill Williams Mountain is the 

most important basin. The basin is bounded on the 

southeast by the Mesa Butte Fault system and on the 

east by the Kaibab Uplift. Two large fault systems cross 

the study area at right angles. The Mesa Butte Fault 

system trends northeast across the study area, and the 

Cataract Creek Fault system trends to the northwest 

(figs. 1, 5, 6, 9, and 10). These large throughgoing fault 

systems are as much as 14 km wide in some places and 

intersect near Bill Williams Mountain. The two fault 

systems are so pervasive that multiple subparallel 

fractures can be identified easily from gradients in the 

aeromagnetic and gravity data sets or from linear or 

curvilinear features on the TM and DEM images. Two 

smaller mapped faults, the Lo Draw and Polson Dam 

Faults, to the north and to the west, respectively, strike 

north and south (fig. 10).

These fault trends and other lineaments have been 

mapped using gravity (fig. 5), aeromagnetic (fig. 6), 

Landsat TM image (fig. 9), aerial photograph, DEM 

(fig. 10), and other surface-geophysical techniques. On 

a smaller scale, aerial photographs were used to 

identify or delineate north-south trending linear 

features on the west side of Bill Williams Mountain 

near Bard Spring before the Bard Spring #2 well was 

drilled.

The gravity map (fig. 5) shows a 10 Mgal low 

in the northeastern part of the study area. The 

northeastward- and southwestward-trending gravity 

low is bounded by the Mesa Butte Fault system on the 

northwest, the Cataract Creek Fault system on the 

southwest, and an unmapped feature on the southeast 

that probably is a fault. This gravity low is thought to 

be a fault-bounded graben or small subbasin filled with 

volcanic rock.

The aeromagnetic map (fig. 6) shows the Mesa 

Butte and Cataract Creek Fault systems. These fault 

systems, the Polson Dam Fault and an unnamed fault, 

are closely associated with the locations of magnetic 

gradients. On the basis of interpretation of 

aeromagnetic data, Shoemaker and others (1978) 

suggest that as much as 8 km of right lateral offset can 

be inferred from the basement-aeromagnetic 

anomalies.

The enhanced digital TM image (fig. 9) was 

analyzed visually to identify and map continuous linear 

to curvilinear alignments of natural landscape features 

that indicate bedrock faults and other large surface 

fractures. The large fault systems have been mapped on 

the image to show locations.

DEMs (fig. 10) show the two north-south trending 

faults, Polson Dam and Lo Draw, mapped by Newhall 

and others (1987) and one unnamed fault interpreted 

from the SAR and AMT sounding data. The image 

shows surface traces of the two major fault systems as 

they cut through Bill Williams Mountain. Several other 

subparallel fractures associated with the 

northwestward-trending Cataract Creek Fault system 

and the northeastward-trending Mesa Butte Fault 

system can be seen on figure 10.

The highly fractured and block-faulted rocks limit 

the occurrence and extent of shallow perched aquifers. 

The fault blocks, though nearly horizontal, usually are 

in contact with near-vertical, throughgoing and active 

faults that may provide vertical flow paths to the 

regional aquifer. The near-vertical (<10°) nature of the 

faults has been imaged on seismic-reflection profiles 

by Catchings and others (1997) west of the study area 

in Flagstaff, Arizona.
Interpreted Depth to Ground Water in the Regional Aquifer 23

INTERPRETED DEPTH TO GROUND WATER IN THE 

REGIONAL AQUIFER

Wells in the study area.—Only seven wells near 

the study area are completed in the regional aquifer 

(fig. 1; table 1); one of these wells is bridged, and one 

well yields water of poor quality for most uses. Only 

the 1,067-meter-deep A-1 well (table 1) is completed in 

the Redwall and Muav Limestones in Williams. The 

Gonzalez and the Klinke wells were drilled into the 

graben on the Cataract Creek Fault system in Williams 

(table 2). These two dry, 762-meter-deep wells were 

completed in the Supai Group. Four wells along State 

Highway 64 to the north toward Grand Canyon are 

completed in the regional aquifer. The Quivero well is 

29 km north of Interstate 40 along State Highway 64 

near the intersection of the highway and the Black 

Mesa Pipeline. As of 1999, the community of Valle has 

three wells. The Valle 1 well is 549 m deep and yields 

water from a perched zone above the regional aquifer. 

East of Williams along Interstate 40, the Santa Fe well 

(near the Klinke well) is completed in the regional 

aquifer, and the community of Ash Fork has two wells 

that are completed in the regional aquifer. Measured 

depth-to-water data from these wells were used in 

conjunction with interpreted sounding estimates for the 

water-table interpretation.

The A-1 well is bridged at about 884 m below land 

surface and above the water table in the Redwall 

Limestone. Before bridging occurred, the driller 

indicated that water could be air lifted at a rate of about 

9.5 L/s. A lithologic log was compiled from cuttings 

collected every 6.1 m (Bradley Baum and D.J. Bills, 

hydrologists, USGS, written commun., 1998). This 

well provided lithologic information and a local depth 

to water in the regional aquifer (fig. 12). In addition, a 

video log was completed to 150 m before large solution 

caverns and unstable rock in the Kaibab Formation 

halted the work. An unexpected observation from the 

A-1 well cuttings was halite crystals in the Supai 

Group. Although no halite was observed in wells near 

Flagstaff, Aiken and Sumner (1972) noted halite in the 

evaporites of the upper part of the Supai Group near 

Holbrook, Arizona. 

Table 1. Data for selected wells that discharge water from the regional aquifer near Williams, Arizona

[Minus signs on longitude values indicate west longitude]

Well name Latitude Longitude

Water-level altitude, 

in meters

Date water level 

measured

Quivero 35°31'34" -112°09'49" 1,014 12–16–1969

Valle 2 35°39'20" -112°08'25" 1,068 12–28–1994

Valle 3 35°39'29" -112°07'50" 1,050 6–15–1994

Santa Fe (near Klinke well) 35°15'46" -112°25'26" 1,058 10–1–1931

A-1 well 35°14'56" -112°07'28" 11,178 3–1997

Ash Fork 1 35°12'49" -112°28'37" 1,248 1–1988

Ash Fork 2 35°12'07" -112°28'37" 1,254 10–17–1997

1Altitude at which water was first encountered during drilling. Hole later collapsed.

Table 2. Dry wells near Williams, Arizona

[Minus signs on longitude values indicate west longitude]

Location Latitude Longitude

Altitude of the bottom 

of hole, in meters Year drilled

Santa Fe #1 35°19'24" -112°21'18" 1,186 1952

El Paso Gas 35°18'19" -112°03'30" 1,357 1978

Klinke well 35°14'44" -112°27'58" 1,250 1941

Gonzalez well 35°15'29" -112°11'51" 1,291 1963

Bard Spring #2 35°12'16" -112°16'07" 1,621 1998

Santa Fe #3 35°15'13" -112°10'49" 1,762 1960
24 Structural Controls on Ground-Water Conditions and Estimated Aquifer Properties near Bill Williams Mountain, Williams, Arizona

Data from geophysical surveys in the Bard Spring 

area indicate perched ground-water conditions in a 

small basin west of Bill Williams Mountain. An 

exploration hole was drilled in 1998 near Bard Spring 

to test the observations and provide stratigraphic and 

borehole-geophysical information. The Bard Spring #2 

well is 401 m deep and did not reach the regional 

aquifer. A lithologic log (fig. 12) was compiled from 

cuttings taken every 3.0 m (Bradley Baum and D.J. 

Bills, hydrologists, USGS, written commun., 1998). 

In May 1998, induction-borehole-conductivity logs 

were collected and show that the basalt has a mean 

conductivity of 140 μS/m (standard deviation of 

36.7 μS/m). The Kaibab Formation below the basalts 

has a mean conductivity of 3.9 μS/m (standard 

deviation of 0.64 μS/m). The Toroweap Formation has 

slightly higher and more variable conductivity values 

and a mean of 8.6 μS/m (standard deviation of 

5.6 μS/m). The Coconino Sandstone has a mean 

conductivity of 3.8 μS/m (standard deviation of 

0.3 μS/m). The high conductivity values in the basalts 

may be caused by water or altered zeolites. Two video 

logs recorded on May 14, 1998, and on July 24, 1998, 

show moisture on the basalt in the well bore from near 

the end of the casing at 46 m below land surface to 

200 m below land surface. The accumulated moisture 

on the well bore does not provide any usable flow, and 

the formations below the basalt are dry (fig. 13).

An estimated depth-to-water map and an estimated 

water-table map were compiled using data from several 

sources. Measured water levels from wells completed 

in the regional aquifer were augmented with SARderived depth-to-water estimates and with AMT depthto-water estimates from layered-earth models (figs. 14

and 15). The SAR estimates are based on interpreted 

curves derived from a computer program (ATO) 

developed by Zohdy and Bisdorf (1989). The AMT 

depth-to-water estimates are based on layered-earth 

models generated from the apparent resistivity values 

and sampled frequencies. The general direction of 

water flow is to the northwest from Bill Williams 

Mountain toward the Cataract Creek Fault system and 

the main northern discharge point at Havasu Springs. 

The apparent ground-water gradient between A-1 well 

in Williams and the Valle wells is -0.003 to the north. 

ALTITUDE ABOVE SEA LEVEL, IN METERS

2,110.6

2,038.4

1,000

BASALT

TOROWEAP FORMATION

COCONINO SANDSTONE

LITHOLOGY

Bard Spring#2 well A-1 well

West East

Bottom

of hole

SCHNEBLY

HILL

FORMATION

SCHNEBLY

HILL

FORMATION

SUPAI

GROUP

REDWALL

LIMESTONE

Water table

COCONINO SANDSTONE

Bottom

of hole

2,000

1,500

1,900

2,100

1,800

1,700

1,600

1,400

1,300

1,200

1,100

HARRISBURG MEMBER

FOSSIL MOUNTAIN

MEMBER

KAIBAB

FORMATION

Figure 12. Lithologic logs derived from well cuttings analyzed 

every 6.1 meters in two wells near Williams, Arizona. Bard 

Spring #2 well is 4.82 kilometers west of Bill Williams Mountain 

near Pine Springs, and A-1 well is 8 kilometers east of the city of 

Williams along Interstate 40. Water table is at an altitude of 

1,178 meters above sea level.
Interpreted Depth to Ground Water in the Regional Aquifer 25

CONDUCTIVITY,

IN MICROSIEMENS

PER METER

10 100 50 0 100 150

RESISTIVITY,

IN OHM METERS

0 300

NATURAL GAMMA,

IN COUNTS

PER SECOND

ALTITUDE ABOVE SEA LEVEL, IN METERS

2,038.4

1,600

2,000

200

1,700

1,650

1,800

1,750

1,900

1,950

1,850

100 300 200

Figure 13. Geophysical logs and lithology for Bard Spring #2 well, Williams, Arizona. The borehole data include 

natural gamma, conductivity, resistivity, caliper, and two temperature logs.
26 Structural Controls on Ground-Water Conditions and Estimated Aquifer Properties near Bill Williams Mountain, Williams, Arizona

15 20

TEMPERATURE,

IN DEGREES

CELSIUS

10

ALTITUDE ABOVE SEA LEVEL, IN METERS

2,038.4 

2,000 

1,600 

0 28

CALIPER

MIRROR, IN

CENTIMETERS

May 

1998

September 1998

28

LITHOLOGY

1,950 

1,900 

1,850 

1,800 

1,750 

1,700 

1,650 

BASALT,

cased

BASALT

HARRISBURG

MEMBER; KAIBAB

FORMATION

TOROWEAP

FORMATION

COCONINO

SANDSTONE

FOSSIL

MOUNTAIN

MEMBER;

KAIBAB

FORMATION

Figure 13. Continued.
Interpreted Depth to Ground Water in the Regional Aquifer 27

Williams

0 5 10 KILOMETERS

0 5 MILES

Base from U.S. Geological Survey

digital data, 1:100,000, 1983

Universe Transverse Mercator

projection, zone 12 

 30'

 25'

 35°35'

20'

 15'

 35°10'

112°25' 20' 15' 10'762 777 112°5'

EXPLANATION

WELL AND DEPTH TO WATER,

 IN METERS

865

865 SQUARE-ARRAY RESISTIVITY

 SITE AND DEPTH TO WATER,

 IN METERS

628

933

950

900

950

940

700

1,000 303

304

900

750

800

850

800

775

875

700

800 775

450

900

650 750

1,000

750

725

900

850

600 700

600

600

800 500

500

900

1,025

1,025

850

1,050

1,000

800

900

850

850

1,300

1,000 AUDIOMAGNETOTELLURIC

 SITE AND DEPTH TO WATER,

 IN METERS

Figure 14. Depth to water, Williams, Arizona. No altitude corrections have been applied. Data are from 7 wells, 4 square-array 

resistivity soundings, 25 tensor audiomagnetotelluric soundings, and 11 scalar audiomagnetotelluric soundings. 
28 Structural Controls on Ground-Water Conditions and Estimated Aquifer Properties near Bill Williams Mountain, Williams, Arizona

0 5 10 KILOMETERS

0 5 MILES

Base from U.S. Geological Survey

digital data, 1:100,000, 1983

Universe Transverse Mercator

projection, zone 12 

 30'

 25'

 35°35'

20'

 15'

 35°10'

112°25' 20' 15' 10' 112°5'

EXPLANATION

Williams

1,050

1,068

WELL AND ALTITUDE OF

 WATER TABLE, IN METERS

1,014

SQUARE-ARRAY RESISTIVITY SITE

 AND ALTITUDE OF WATER TABLE,

 IN METERS

1,058

1,050

1,178

1,110

1,186

1,244

1,146

1,275

1,285

1,252

1,439

1,139 1,248

1,254

1,455 1,299

1,340

1,390

1,415

1,343

1,295

1,197 1,320

1,500

1,086

1,416 1,277

1,027

1,256

1,376

1,190

1,403

1,450

1,545

1,256

1,275 1,505

1,530

1,120

908

1,005

929

814

872

1,230

840

1,027 AUDIOMAGNETOTELLURIC SITE

 AND ALTITUDE OF WATER TABLE,

 IN METERS

1,026

1,463

Figure 15. Altitude of the water table, Williams, Arizona. Data are from 7 wells, 4 square-array soundings, 25 tensor 

audiomagnetotelluric soundings, and 11 scalar audiomagnetotelluric soundings. 
Interpreted Depth to Ground Water in the Regional Aquifer 29

Estimated Aquifer Properties

Secondary porosity values estimated from the four 

SAR soundings varied from 0.1 to 9.6 percent. 

The coefficient-of-anisotropy values ranged from 

1.01 to 1.34. SAR mean resistivity, coefficient of 

anisotropy, secondary porosity, and fracture-strike 

azimuth were plotted against depth for each of the four 

sites (figs. 16–19).

The 980-meter-deep SAR sounding at the Williams 

Airport Road site has a mean resistivity curve that 

gradually increases with depth from about 140 Ω•m 

near the surface to more than 500 Ω•m at depth 

(fig. 16). The coefficient of anisotropy, secondary 

porosity, and strike azimuth can be divided into an 

upper half and a lower half for the sounding. The upper 

500 m of the sounding has the largest coefficient of 

anisotropy (1.3 for the 0- to 40-meter-depth range) and 

the highest secondary porosity (7 percent). A value of 

1.04 over the lower 500 m of the sounding indicates 

little fracturing and secondary porosity of generally 

less than 0.5 percent at this site.The upper 500 m of the 

sounding has fracture strikes that are almost due east. 

Below 500 m, the fracture-strike direction is 

predominately to the northwest. The northwestward 

trend calculated from the SAR data is in line with the 

Cataract Creek Fault system.

The mean resistivity curve for the SAR sounding at 

the Bard Spring site increases rapidly from 150 Ω•m 

near the surface to 300 Ω•m at a depth of 50 m 

(fig. 17). Resistivity gradually decreases to about 

110 Ω•m at a depth of 300 m. The decrease probably is 

due to the moisture content in the basalts and the finegrained volcanic material as observed in the Bard 

Spring #2 well. The coefficient of anisotropy averages 

about 1.1 from 0 to 350 m, which indicates abundant 

fracturing. The ratio then drops to 1.04 from 500 to 

850 m. At 1,000 m, the coefficient of anisotropy has a 

small peak at 1.08. Secondary porosity follows the 

coefficient of anisotropy pattern of high-low-high. 

Secondary porosity reaches a high of 2.5 percent in the 

0- to 350-meter range, drops to less than 1 percent for 

the 500- to 850-meter range, and then recovers to 

1 percent at 1,000 m. The strike direction gradually 

changes from due north at the surface to northwest at a 

depth of 650 m. At 850 m, the strike direction is rotated 

due north again and is rotated back to the northwest at 

1,150 m.

The mean resistivity curve for the SAR sounding at 

McDougal Flat increases from 28 Ω•m near the surface 

to about 400 Ω•m near a depth of 1,300 m, which 

indicates a smoothly increasing electrical section 

(fig. 18). The coefficient-of-anisotropy ratio increases 

from near unity at the surface to 1.12 at a depth of 

350 m. The ratio then remains near 1.12 to a depth of 

1,300 m. Secondary porosity is near zero at the surface, 

near 4 percent at 125 m, then gradually tapers down to 

about 1 percent at a depth of 1,300 m. The strike 

direction for this sounding is northwest from 0 to 

200 m and then predominantly N. 60° W. from 500 to 

1,300 m. The strike direction matches an unnamed fault 

and a line of cinder cones that trend northwestward to 

the Santa Fe Reservoir. Analysis of aerial photography 

also indicates a lineament that trends in this direction.

The mean resistivity curve for the SAR sounding at 

Poquette Homestead increases from 40 Ω•m at the 

surface to about 600 Ω•m near a depth of 1,150 m, 

which indicates a resistive electrical section (fig. 19). 

The coefficient-of-anisotropy ratio is 1.0 at 50 m, 

increases to 1.22 at 350 m, and then is constant until 

1,000 m. At 1,000 m, the ratio increases to 1.34, which 

is the highest measured in the Williams area. 

Secondary porosity is 9.5 percent near the surface, but 

at a depth of 50 m, the secondary porosity is near zero. 

The secondary porosity increases to near 2 percent for 

the 150- to 1,150-meter depth range. The strike 

direction swings from due east at the surface to due 

north by the 100-meter depth, then swings back to the 

northeast in the 250- to 1,150-meter depth range, and 

follows the trend of the Mesa Butte Fault system.
30 Structural Controls on Ground-Water Conditions and Estimated Aquifer Properties near Bill Williams Mountain, Williams, Arizona

COEFFICIENT

OF ANISOTROPY

RATIO

10 100 1.4 1,000 1 1.2

SECONDARY

POROSITY,

IN PERCENT

0 5 10

AZIMUTH,

IN DEGREES

–90 0 90

MEAN RESISTIVITY,

IN OHM METERS

DEPTH BELOW LAND SURFACE, IN METERSDEPTH BELOW LAND SURFACE, IN METERS

100

200

0

50 

300

400

500

600

700

800

900

1,000

950

850

750

650

550

450

350

250

150

50

0 

100 

150 

200 

250 

300 

350 

400 

450 

500 

550 

600 

650 

700 

750 

800 

850 

900 

950 

1,000 

Figure 16. Square-array resistivity sounding data and estimated aquifer properties from the site at Airport Road, 

Williams, Arizona.
Interpreted Depth to Ground Water in the Regional Aquifer 31

COEFFICIENT

OF ANISOTROPY

RATIO

10 100 1.4 1,000 1 1.2

SECONDARY

POROSITY,

IN PERCENT

0 5 10 –90 0 90

MEAN RESISTIVITY,

IN OHM METERS

DEPTH BELOW LAND SURFACE, IN METERSDEPTH BELOW LAND SURFACE, IN METERS

100

200

0

50 

300

400

500

600

700

800

900

1,000

1,100

1,200

1,300

1,250

1,050

950

850

750

650

550

450

350

250

150

50

1,150

0 

100 

150 

200 

250 

300 

350 

400 

450 

500 

550 

600 

650 

700 

750 

800 

850 

900 

950 

1,000 

1,050 

1,100 

1,150 

1,200 

1,250 

1,300 

AZIMUTH,

IN DEGREES

Figure 17. Square-array resistivity sounding data and estimated aquifer properties from the site at Bard Spring, Williams, Arizona.
32 Structural Controls on Ground-Water Conditions and Estimated Aquifer Properties near Bill Williams Mountain, Williams, Arizona

COEFFICIENT

OF ANISOTROPY

RATIO

10 100 1.4 1,000 1 1.2

SECONDARY

POROSITY,

IN PERCENT

0 5 10 –90 0 90

MEAN RESISTIVITY,

IN OHM METERS

DEPTH BELOW LAND SURFACE, IN METERSDEPTH BELOW LAND SURFACE, IN METERS

100

200

0

50 

300

400

500

600

700

800

900

1,000

1,100

1,200

1,300

1,250

1,050

950

850

750

650

550

450

350

250

150

50

1,150

0 

100 

150 

200 

250 

300 

350 

400 

450 

500 

550 

600 

650 

700 

750 

800 

850 

900 

950 

1,000 

1,050 

1,100 

1,150 

1,200 

1,250 

1,300 

AZIMUTH,

IN DEGREES

Figure 18. Square-array resistivity sounding data and estimated aquifer properties from the site at McDougal Flat, Williams, Arizona.
Interpreted Depth to Ground Water in the Regional Aquifer 33

COEFFICIENT

OF ANISOTROPY

RATIO

10 100 1.4 1,000 1 1.2

SECONDARY

POROSITY,

IN PERCENT

0 5 10 –90 0 90

MEAN RESISTIVITY,

IN OHM METERS

DEPTH BELOW LAND SURFACE, IN METERSDEPTH BELOW LAND SURFACE, IN METERS

100

200

0

50 

300

400

500

600

700

800

900

1,000

1,100

1,200

1,300

1,250

1,050

950

850

750

650

550

450

350

250

150

50

1,150

0 

100 

150 

200 

250 

300 

350 

400 

450 

500 

550 

600 

650 

700 

750 

800 

850 

900 

950 

1,000 

1,050 

1,100 

1,150 

1,200 

1,250 

1,300 

AZIMUTH,

IN DEGREES

Figure 19. Square-array resistivity sounding data and estimated aquifer properties from the site at Poquette Homestead, 

Williams, Arizona.
34 Structural Controls on Ground-Water Conditions and Estimated Aquifer Properties near Bill Williams Mountain, Williams, Arizona

SUMMARY AND CONCLUSIONS 

In the area near Bill Williams Mountain, the 

volcanic and sedimentary rocks are cut pervasively by 

near-vertical, laterally continuous, and active normal 

faults. Most of these faults trend N. 45° W. and 

N. 45° E.; however, some faults trend north and south 

and at least one fault trends N. 60° W. These faults are 

evident in the magnetic, gravity, TM, and DEM 

images. The faults have broken the near-horizontal 

consolidated sediments that restrict the vertical 

movement of water to the regional aquifer. The active 

faults probably improve the vertical-hydraulic 

conductivity by providing many open near-vertical 

conduits to the regional aquifer. Below the regional 

water table, the near-vertical faults in the Redwall and 

Muav Limestones provide lateral flow to the discharge 

points. The lateral flow may be enhanced by solution 

features along fractures in the limestone aquifers.

Estimated depth to water in the regional aquifer 

varies with location on the basis of interpreted AMT 

and SAR sounding curves and few well data. Estimated 

depth to water ranges from 450 to about 1,300 m. 

Estimated altitudes of the water table range from about 

814 to 1,545 m above sea level.

The coefficient of anisotropy calculated from the 

four SAR soundings ranged from 1.01 to 1.34. 

The highest coefficient-of-anisotropy value is at the 

bottom of the sounding for Poquette Homestead. 

Secondary porosity values estimated from the SAR 

soundings varied from 0.1 to 9.6 percent. The highest 

secondary porosity calculated at the surface of the 

sounding at Poquette Homestead is associated with 

fractured volcanic rocks. Mean resistivity from the 

SAR soundings varied from less than 30 Ω•m to more 

than 600 Ω•m. Strike direction depends on proximity 

to major structures. For example, the N. 45° E. trend 

was expected for the fractures at Poquette Homestead 

because the sounding was within 1 km of the 24-meter 

Mesa Butte Fault scarp near Dogtown Reservoir. 

The northwestward trend at McDougal Flat was 

unexpected. A previously unmapped fault that trends 

N. 60° W. was detected first by the AMT and SAR 

soundings then confirmed or verified on aerial 

photographs and DEM images by cinder-cone 

alignment. The northward-trending strike direction 

measured at the SAR site at Bard Spring coincides with 

the Polson Dam Fault north of Interstate 40. 

The N. 45° W. trend in the lower 500 m of the sounding 

at the site at Airport Road was due to the 

northwestward-trending Cataract Creek Fault system.

Because much of the data derived in this study 

were from surface techniques rather than well 

information, the inferred water levels should be viewed 

strictly as estimates. Additional wells in the area would 

provide data that could strengthen the limited control of 

the existing well data. Continued collection of well 

data as it becomes available is essential to add to the 

understanding of the hydrology of this part of the 

Coconino Plateau. Because of potential water-quality 

issues associated with the halite in the Supai Group and 

high dissolved solids in the lower part of the regional 

aquifer, the following approaches for further study of 

the area in and around Bill Williams Mountain may 

need to be considered in order to provide information 

to evaluate the ground-water quality in the area.

 1. Continue to collect lithologic data from wells 

completed in the regional aquifer to refine the 

stratigraphic interpretations.

 2. Determine the chemistry of well water 

collected from wells completed in the various 

formations along State Highway 64 north to 

Grand Canyon.

 3. Describe the chemistry of water for all 

discharge points in the study area.

 4. Estimate the age of water in the regional 

aquifer to improve the present understanding 

of recharge and ground-water flow paths.

 5. Estimate the age of water from the volcanic 

springs and seeps to determine residence time 

in volcanic rocks of Tertiary and Quaternary 

age.

SELECTED REFERENCES

Aiken, C.L.V., and Sumner, J.S., 1972, A study of regional 

geophysical data in the Holbrook area, Arizona: 

Arizona Geological Survey Publication OG–23, 42 p. 

[Formerly published as Oil and Gas Conservation 

Commission Report of Investigations RI–2].

Armstrong, A.K., and Holcomb, L.D., 1989, Stratigraphy, 

facies and paleotectonic history of Mississippian rocks 

in the San Juan Basin of northwestern New Mexico and 

adjacent areas, in Evolution of sedimentary basins, 

San Juan Basin: U.S. Geological Survey Bulletin 1808–

D, p. D1–D21.
Selected References 35

Bills, D.J., Truini, Margot, Flynn, M.E., Pierce, H.A., 

Catchings, R.D., and Rymer, M.J., 2000, Hydrogeology 

of the regional aquifer near Flagstaff, Arizona, 1994–

97: U.S. Geological Survey Water-Resources 

Investigations Report 00–4122, 143 p.

Billingsley, G.H., and Huntoon, P.W., 1983, Geologic map of 

the western Grand Canyon Formation, Arizona: Grand 

Canyon, Arizona, Grand Canyon Natural History 

Association map sheet.

Billingsley, G.H., Barnes, C.W., and Ulrich, G.E., 1985, 

Geologic map of the Coconino Point and Grandview 

Point quadrangles, Coconino County, Arizona: U.S. 

Geological Survey Miscellaneous Investigations Map I–

1644, 1 sheet, scale, 1:62,500.

Billingsley, G.H., Breed, W.J., and Beasley, D., 1980, 

Geologic cross section along Interstate 40–Kingman to 

Flagstaff, Arizona: Chandler, Arizona, Pagosa Press, 

Petrified Forest Museum Association in cooperation 

with the Museum of Northern Arizona, map sheet.

Blakey, R.C., 1979, Stratigraphy of the Supai Group 

(Pennsylvanian-Permian), Mogollon Rim, Arizona, in

Beus, S.S., and Rawson, R.R., eds., Carboniferous 

stratigraphy in the Grand Canyon Country, northern 

Arizona and southern Nevada: Falls Church, Virginia, 

American Geological Institute Guidebook Series No. 2, 

Ninth International Congress of Carboniferous 

Stratigraphy and Geology, p. 89–104.

____1990, Stratigraphy and geologic history of 

Pennsylvanian and Permian rocks, Mogollon Rim 

region, central Arizona and vicinity: Geological Society 

of America Bulletin, v. 102, no. 9, p. 1189–1217. 

Blakey, R.C., and Knepp, R., 1989, Pennsylvanian and 

Permian geology of Arizona, in Jenney, J.P., and 

Reynolds, S.J., eds., Geologic Evolution of Arizona: 

Arizona Geological Society Digest 17, p. 313–347. 

Bostick, F.X., Jr., 1977, A simple and almost exact method 

of MT analysis: Salt Lake City, University of Utah, 

Geothermal Workshop Report, p. 175–177.

Breed, W.J., Huntoon, P.W., and Billingsley, G.H., 1986, 

Geologic map of the eastern part of the Grand Canyon 

National Park, Arizona: Grand Canyon, Arizona, Grand 

Canyon Natural History Association, map sheet, 

scale 1:62,500.

Cagniard, Louis, 1953, Basic theory of the magnetotelluric 

method of geophysical prospecting: Geophysics, v. 18, 

no. 3, p. 605–635.

Catchings, R.D., Jaasma, M.N., Goldman, M.R., and Rymer, 

M.J., 1997, Seismic images beneath the Continental 

(Bottomless Pits) area of Flagstaff, Arizona: U.S. 

Geological Survey Open-File Report 97–76, 29 p.

Chapin, C.E., and Cather, S.M., 1981, Eocene tectonics and 

sedimentation in the Colorado Plateau-Rocky Mountain 

area, in Dickinson, W.R., and Payne, W.D., eds., 

Relations of tectonics to ore deposits in the southern 

Cordillera: Tucson, Arizona Geological Society Digest, 

v. 14, March 19–20, 1981 Meeting, Tucson, Arizona, 

p. 173–198.

Constable, S.C., Parker, R.L., and Constable, C.G., 1987, 

Occam’s inversion—A practical algorithm for 

generating smooth models from electromagnetic 

sounding data: Geophysics, v. 52, no. 3, p. 289–300.

Damon, P.E., Shafiqullah, Mohammed, and Leventhal, J.S., 

1974, K-Ar chronology for the San Francisco volcanic 

field and rate of erosion of the Little Colorado River, in

Karlstom, T.N.V., Swann, G.A., and Eastwood, R.L., 

eds., Part 1 of Geology of Northern Arizona: 

Geological Society of America Guidebook for Rocky 

Mountain Section Meeting, Flagstaff, Arizona, v. 6, 

no. 5, p. 221–235.

Darton, N.H., 1910, A reconnaissance of parts of 

northwestern New Mexico and northern Arizona: U.S. 

Geological Survey Bulletin 435, 88 p.

Davis, G.H., and Kiven, C.W., 1975, Tectonic analysis of 

folds in the Colorado Plateau of Arizona: Tucson, 

University of Arizona, Office of Arid Lands Studies 

Bulletin 9, 68 p.

Doe, T.W., Long, J.C.S., Endo, H.K., and Wilson, C.R., 

1982, Approaches to evaluating the permeability and 

porosity of fractured rock masses, in Goodman, R.E., 

and Hueze, F.E., eds., Issues in Rock Mechanics: New 

York, American Institute of Mining, Metallurgical and 

Petroleum Engineers, Inc., Proceedings of the TwentyThird Symposium on Rock Mechanics, Berkeley, 

California, August 25–27, 1982, p. 30–38. 

Fenneman, N.M., 1931, Physiography of western United 

States: New York, McGraw-Hill, 534 p.

Fetter, C.W., 1980, Applied hydrogeology: Columbus, Ohio, 

Charles E. Merrill Publishing Company, 488 p.

Habberjam, G.M., 1972, The effects of anisotropy in squarearray resistivity measurements: Geophysical 

Prospecting, v. 20, no. 2, p. 249–266. 

____1979, Apparent resistivity observations and the use of 

square-array techniques: Berlin, Germany, Bebruder 

Borntraeger, Geoexploration Monograph Series 1, 

no. 9, 152 p.

Habberjam, G.M., and Watkins, G.E., 1967, The use of a 

square configuration in resistivity prospecting: 

Geophysical Prospecting, v. 15, no. 3, p. 445–467.

Hereford, Richard, 1975, Chino Valley Formation 

(Cambrian?) in northwestern Arizona: Geological 

Society of America Bulletin, v. 86, no. 5, p. 677–682.

____1977, Deposition of the Tapeats Sandstone (Cambrian) 

in central Arizona: Geological Society of America 

Bulletin, v. 88, no. 2, p. 199–211. 
36 Structural Controls on Ground-Water Conditions and Estimated Aquifer Properties near Bill Williams Mountain, Williams, Arizona

Hoover, D.B., and Long, C.L., 1975, Audio-magnetotelluric 

methods in reconnaissance geothermal exploration 

[abs.]: Proceedings of the Second United Nations 

Symposium for the Development of Geothermal 

Resources, San Francisco, California, May 20–29, 

1975, p. 1059–1064.

Hoover, D.B., Frischknecht, F.C., and Tippens, C., 1976, 

Audio-magnetotelluric soundings as a reconnaissance 

exploration technique in Long Valley, California: 

Washington, D.C., American, Geophysical Union, 

Journal of Geophysical Research, v. 81, no. 5, p. 801–

809.

Hoover, D.B., Long, C.L., and Senterfit, R.M., 1978, Some 

results from audio-magnetotelluric investigations in 

geothermal areas: Geophysics, v. 43, no. 7, p. 1501–

1514.

Huntoon, P.W., and Billingsley, G.H., 1981, Geologic map of 

the Hurricane Fault zone and vicinity, western Grand 

Canyon, Arizona: Grand Canyon Arizona, Grand 

Canyon Natural History Association, map sheet.

Inman, J.R., 1975, Resistivity inversion with ridge 

regression: Geophysics, v. 40, no. 5, p. 798–817.

Interpex, Inc., 1993, EMIX MT, v. 2.0, Magnetotelluric data 

interpretation software: Golden, Colorado, Interpex 

Limited.

Keller, G.V., and Frischknecht, F.C., 1966, Electrical 

methods in geophysical prospecting: London, Great 

Britain, Pergamon Press, 519 p.

Kelley, V.C., 1958, Tectonics of the Black Mesa Basin region 

of Arizona, in Anderson, R.Y., and Harshbarger, J.W., 

eds., 9th Field Conference Guidebook of the Black 

Mesa Basin, northeastern Arizona: New Mexico 

Geological Society, p. 146–150.

Lane, J.W., Jr., Haeni, F.P., and Watson, W.M., 1995, Use of 

a square-array direct-current resistivity method to 

detect fractures in crystalline bedrock in New 

Hampshire: Groundwater, v. 33, no. 3, p. 476–485.

Long, Carl, and Pierce, H.A., 1986, BASIC program to 

reduce audio-magnetotelluric data and calculate 

apparent resistivity: U.S. Geological Survey Open-File 

Report 86–200, 17 p.

Loughlin, W.D., and Huntoon, P.W., 1983, Compilation of 

available ground-water quality data for sources with the 

Grand Canyon of Arizona: U.S. National Park Service, 

unpublished report prepared under contract 

PX8210Z0883. 

McKee, E.D., 1938, The environment and history of the 

Toroweap and Kaibab Formations of northern Arizona 

and southern Utah: Washington, D.C., Carnegie 

Institution of Washington Publication 492, 268 p.

____1945, Stratigraphy and ecology of the Grand Canyon 

Cambrian, Part 1—Cambrian history of the Grand 

Canyon region: Carnegie Institution of Washington 

Publication No. 563, p. 1–170.

____1954, Stratigraphy and history of the Moenkopi 

Formation of Triassic age: Geological Society of 

America Memoir 61, 133 p.

____1982, The Supai Group of the Grand Canyon: U.S. 

Geological Survey Professional Paper 1173, 504 p.

McNair, A.H., 1951, Paleozoic stratigraphy of part of 

northwestern Arizona: American Association of 

Petroleum Geologists Bulletin, v. 35, no. 3, p. 503–541.

Metzger, D.G., 1961, Geology in relation to availability of 

water along the south rim Grand Canyon National Park, 

Arizona: U.S. Geological Survey Water-Supply Paper 

1475–C, p. 105–138.

Milsom, John, 1989, Field geophysics, in Cox, Keith, ed., 

Geological Society of London Handbook: New York, 

John Wiley & Sons, 181 p. 

Montgomery, Errol, L., and Associates, Inc., 1996, 

Assessment of hydrogeologic conditions and potential 

effects of proposed groundwater withdrawal for Canyon 

Forest Village, Coconino County, Arizona: Tucson, 

Arizona, E.L. Montgomery and Associates, Inc., 64 p. 

National Climatic Data Center, 2000, NCDC climate data 

online: U.S. Department of Commerce, National 

Oceanic and Atmospheric Administration, National 

Climatic Data Center, URL, http://cdo.ncdc.noaa.gov/ 

plclimprod, accessed June 2000.

____1996, Climatological data annual summaries, Arizona: 

U.S. Department of Commerce, National Oceanic and 

Atmospheric Administration, National Climatic Data 

Center, v. 100, no. 13.

____1997, Climatological data annual summaries, Arizona: 

U.S. Department of Commerce, National Oceanic and 

Atmospheric Administration, National Climatic Data 

Center, v. 101, no. 13.

____1998, Climatological data annual summaries, Arizona: 

U.S. Department of Commerce, National Climatic Data 

Center, v. 102, no. 13.

Nations, J.D., Wilt, J.C., and Hevly, R.H., 1985, Cenozoic 

paleogeography of Arizona, in Flores, R.M., and 

Caplan, S.S., eds., Cenozoic Paleogeography of the 

West-Central United States, Rocky Mountain 

Paleogeography Symposium 3: Society of Economic 

Paleotologists and Mineralogists, p. 201–224.

Newhall, C.G., Ulrich, G.E., and Wolfe, E.W., 1987, 

Geologic map of the southwest part of the San 

Francisco volcanic field, north-central Arizona: U.S. 

Geological Survey Miscellaneous Field-Studies Map 

MF–1958, scale, 1:50,000, 58 p.

Noble, L.F., 1914, The Shinumo quadrangle, Grand Canyon 

district, Arizona: U.S. Geological Survey Bulletin 549, 

100 p.
Selected References 37

____1923, A section of the Paleozoic Formations of the 

Grand Canyon at the Bass Trail, in Shorter 

contributions to General Geology, 1922: U.S. 

Geological Survey Professional Paper 131–B, p. B23–

B73.

Phillips, J.D., Duval, J.S., and Ambrosiak, R.A., 1993, 

National geophysical data grids—Gamma-ray, 

magnetic, and topographic data for the conterminous 

United States: U.S. Geological Survey Digital Data 

Series DDS-9, 1 CD-ROM.

Poole, F.G., Baars, D.L., Drewes, Harald, Hayes, P.T., 

Ketner, K.B., McKee, E.D., and Teichert, Curt, 1967, 

Devonian of the southwestern United States, in Oswald, 

D.H., ed.: Alberta Society of Petroleum Geologists, 

International Symposium on the Devonian System, v. 1, 

Calgary, Alberta, Canada, p. 879–912.

Ragozin, E.I., 1903, The use of electricity in investigations 

of ore bodies: St. Petersburg, Russia, I. Goldberg, s. 4, 

442 p.

Schlumberger, Conrad, 1920, Essais de prospection 

électrique du sous-sol: Académie Science Comptes 

Rendus, v. 170, no. 9, p. 519–521.

Sheriff, R.E., 1991, Encyclopedic dictionary of exploration 

geophysics: Tulsa, Oklahoma, Society of Exploration 

Geophysicists, Geophysical References Series 1, 376 p.

Shoemaker, E.M., Squires, R.I., and Abrams, M.J., 1978, 

Bright Angel and Mesa Butte Fault systems of northern 

Arizona, in Smith, R.B., and Eaton, G.P., eds., 

Cenozoic Tectonics and Regional Geophysics of the 

Western Cordillera: Geological Society of America 

Memoir 152, p. 341–367.

Sorauf, J.E., and Billingsley, G.H., 1991, Members of the 

Toroweap and Kaibab Formations, Lower Permian, 

Northern Arizona, and Southwestern Utah: Rocky 

Mountain Association of Geologists, The Mountain 

Geologist, v. 28, no. 1, p. 9–24.

Spies, B.R., and Frischknecht, F.C., 1991, Electromagnetic 

sounding, in Nabighian, M.N., ed., Electromagnetic 

Methods in Applied Geophysics: Tulsa, Oklahoma, 

Society of Exploration Geophysicists, Investigations in 

Geophysics no. 3, v. 2, part A, p. 285–407.

Strangway, D.W., Swift, C.M., Jr., and Holmer, R.C., 1973, 

The application of audio-frequency magnetotelluric 

(AMT) to mineral exploration: Geophysics, v. 38, no. 1, 

p. 139.

Taylor, R.W., 1984, The determination of joint orientation 

and porosity from azimuthal resistivity measurements, 

in Nielsen, D.M., and Curl, Mary, eds., Proceedings of 

the National Water Well Association and U.S. 

Environmental Protection Agency Conference on 

Surface and Borehole Geophysical Methods in GroundWater Investigations: Worthington, Ohio, National 

Water Well Association, San Antonio, Texas, February 

7–9, 1984, p. 37–49. 

Taylor, R.W., and Fleming, A.H., 1988, Characterizing 

jointed systems by azimuthal resistivity surveys: 

Groundwater, v. 26, no. 4, p. 464–474.

Teichert, Curt, 1968, Stratigraphic nomenclature in 

Devonian of central Arizona: The Mountain Geologist, 

v. 5, no. 4, p. 179–180.

Thiele, H.J., 1964a, Groundwater hydrological survey—

Deep aquifers: Williams, Arizona, City of Williams 

consultant report, 30 p.

____1964b, Groundwater survey report within 3-mile 

radius—Shallow aquifers: Williams, Arizona, City of 

Williams consultant report, 73 p.

Thomsen, B.W., 1969, Surface-water supply for the City of 

Williams, Coconino County, Arizona: U.S. Geological 

Survey unnumbered report, 50 p.

Ulrich, G.E., Billingsley, G.H., Hereford, Richard, Wolfe, 

E.W., Nealey, L.D., and Sutton, R.L., 1984, Map 

showing geology, structure, and uranium deposits of the 

Flagstaff 1°x2° quadrangle, Arizona: U.S. Geological 

Survey Miscellaneous Investigations Series Map I–

1446, 1:250,000. 

Vozoff, Keeva, 1986, Magnetotelluric methods: Society of 

Exploration Geophysicists, Geophysics, Reprint Series 

No. 5, p. 763.

____1991, The magnetotelluric method, in Nabighian, M.N., 

ed., Electromagnetic Methods in Applied Geophysics: 

Tulsa, Oklahoma, Society of Exploration 

Geophysicists, Investigations in Geophysics, No. 3, 

v. 2, part B, chap. 8, p. 641–712.

Wenner, Frank, 1915, A method of measuring earth 

resistivity: Washington, D.C., U.S. Department of 

Commerce, Bureau of Standards Bulletin 12, Paper 

258, p. 469–478.

Western Region Climate Center, City of Williams 

precipitation data 1897–1996: Reno, Nevada, Desert 

Research Institute, at URL http://www.wrcc.dri.edu, 

accessed 1996.

Wolfe, E.W., Ulrich, G.E., Holm, R.F., Moore, R.B., and 

Newhall, C.G., 1987, Geologic map of the central part 

of the San Francisco volcanic field, north-central 

Arizona: U.S. Geological Survey Miscellaneous Field 

Studies Map, MF–1959, 1:50,000.

Zohdy, A.A.R., and Bisdorf, R.J., 1989, Programs for the 

automatic processing and interpretation of 

Schlumberger sounding curves in QuickBASIC 4.0: 

U.S. Geological Survey Open-File Report 89–0137–A, 

64 p.
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SUPPLEMENTAL DATA
Page 40, Blank
Supplemental Data 41

Table 3. Data from audiomagnetotelluric and square-array resistivity sites, and estimated water levels near Williams, Arizona

[Minus sign on longitude indicates west longitude; N/A, not applicable]

Site number 

(See figure 1) Sounding name Latitude (decimal) Longitude (decimal)

Sounding altitude, 

in meters

Estimated depth to 

water, in meters

Estimated altitude 

of water table,

in meters

Tensor soundings

2 EMI-2 35.2042 -112.2683 2,027 750 1,277

3 EMI-3 35.2494 -112.0831 2,125 850 1,275

4 EMI-4 35.1642 -112.1581 2,140 800 1,340

5 EMI-5 35.1542 -112.1703 2,190 775 1,415

6 EMI-6 35.2753 -112.1108 2,130 900 1,230

7 EMI-7 35.3169 -112.1536 2,030 1,025 1,005

8 EMI-8 35.3133 -112.1925 2,020 900 1,120

9 EMI-9 35.2611 -112.2239 2,253 850 1,403

10 EMI-10 35.2642 -112.2642 2,140 1,300 840

11 EMI-11 35.2067 -112.2641 2,066 650 1,416

12 EMI-12 35.2392 -112.3031 2,006 750 1,256

13 EMI-13 35.1936 -112.0794 2,194 950 1,244

14 EMI-14 35.3319 -112.2347 1,933 1,025 908

15 EMI-15 35.4192 -112.3142 1,864 1,050 814

16 EMI-16 35.4275 -112.2975 1,779 850 929

17 EMI-17 35.4292 -112.2853 1,872 1,000 872

18 EMI-18 35.2772 -112.2175 2,101 725 1,376

19 EMI-19 35.1144 -112.2358 1,986 900 1,086

20 EMI-20 35.1258 -112.2697 1,997 800 1,197

21 EMI-21 35.1453 -112.2977 2,095 775 1,320

22 EMI-22 35.2231 -112.1239 2,152 900 1,252

23 EMI-23 35.1733 -112.1181 2,205 750 1,455

24 EMI-24 35.1703 -112.1839 2,079 850 1,229

25 EMI-25 35.1714 -112.2117 2,218 875 1,343

26 EMI-26 35.2939 -112.1292 2,075 800 1,275

Scalar soundings

27 Poquette 

Homestead

35.2028 -112.1278 2,139 700 1,439

28 Airport Road 35.2933 -112.1926 2,030 500 1,530

29 A-1 well 35.2500 -112.1217 2,135 850 1,285

30 Kaibab Lake 35.2703 -112.1542 2,145 600 1,545

31 Lost Canyon 35.2281 -112.1733 2,150 700 1,450

32 FS124 and P 35.2833 -112.2394 2,090 900 1,190

33 Siever F 35.1936 -112.1681 2,190 800 1,390

34 APR1-40 35.2625 -112.1867 2,060 950 1,110

35 John’s H 35.2467 -112.2272 2,063 600 1,463

36 Valle 35.6456 -112.1375 1,826 800 1,026

37 McDougal Flat 35.2119 -112.0672 2,086 900 1,186

38 FS122 and 108 35.1603 -112.2875 1,950 450 1,500

39 FS122 and 42 35.1494 -112.2450 1,995 700 1,295

Square-array resistivity soundings

N/A Poquette 

Homestead

35.2028 -112.1278 2,139 1,000 1,139

N/A Airport Road 35.3125 -112.1836 2,005 500 1,505

N/A McDougal Flat 35.2119 -112.0672 2,086 940 1,146

N/A Bard Spring 35.2042 -112.2683 2,027 1,000 1,027