Geology and Geohydrology of the Sitgreaves Mountain Area, Coconino County, Arizona

Geology and geohydrology of the Sitgreaves Mountain area, Coconino County, Arizona

Item Type Thesis-Reproduction (electronic); text

Authors Gilman, Chandler Robbins,1933-

Publisher The University of Arizona.

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Link to Item http://hdl.handle.net/10150/191462 GEOLOGY AND GEOHYDROLOGY OF THE SITGREAVES MOUNTAIN AREA, COCONINO COUNTY, ARIZONA

Chandler R. Gilman

A Thesis Submitted to the Faculty of the DEPARTMENT OF GEOLOGY

In Partial Fulfillment of the Requirements For the Degree of MASTER OF SCIENCE

In the Graduate College

THEUNIVERSITY OF ARIZONA

19 6 5 STATEMENT BY AUTHOR

This thesis has been submitted in partial fuif ill- merit of requirements for an advanced degree at The Universi- ty of Arizona and is deposited in the University Library to be made available to borrowers under rules of the Library.

Brief quotations from this thesis are allowable without special permission, provided that accurate ac- knowledgment of source is made. Requests for permission for extended quotation from or reproduction of this manu- script in whole or in part may be granted by the head of the major department or the Dean of the Graduate College when in his judgment the proposed use of the material is in the interests of scholarship. In all other instances, however, permission must be obtained from the author.

SIGNED:OW w

APPROVAL BY THESIS DIRECTOR

This thesis has been approved on the date shown below:

((II/óS Dat Acknowledgments

I want to thank Dr. John W. Harshbarger for pointing out the problem and his help in attacking it.

The Museum of Northern Arizona made mea grant, and the various members of the Museum staff were very helpful,

especially William J. Breed, Curator of Geology. At the University of Arizona, faculty and graduate students assisted greatly in discussions of general and particular aspects of the work. Dr. E. M. P. Lovejoy and Mr. Philip

Matter made many constructive criticisms of both form and content.

iii TABLE OFCONTENTS

Page

INTRODUCTION 1

Method of Treatment 1 Geologic and Geographic Setting 2 Method of Specifying Locations 4

GEOLOGY 5

Regional Stratigraphy 5 Precambrian 5 Cambrian 5 Ordovician and Silurian 6 Devonian 6 Mississippian 6 Pennsylvanian and Perrnian 7 Perrnian 8 Hermit Shale 8 Coconino Sandstone 8 Toroweap Formation 9 Kaibab Formation 11 Triassic 12 Triassic-Tertiary Interval 13 Late Tertiary and Quaternary 14 Volcanic Rocks 14 Local Stratigraphy 16 Pennsylvanian and Permian 19 Permian 19 Hermit Shale 19 Coconino Sandstone 19 Toroweap Formation 21 Kaibab Formation 22 Triassic 23 Tertiary and Quaternary 23 Rocks of felsic and intermediate composition 23 Geomorphic classification of basalts . . . 24 Stage I 25 Stage II 28 Stage III 29 Stage lIla 29 Stage IlIb 30 Stage IlIc 31

iv V TABLE OF CONTENTS (Continued)

Page

Quaternary 32 Alluvium 32 Soil 33 Regional Structure 33 Local Structure 35 Elongate Cones 35 Alignments 36 Rocks of fe].sic and intermediate composition 39 Stage II 39 Stage lIla 39 Stage IlIb 40 Stage IlIc 40 Summary 40 Faulting 42

GROUND WATER 52

Regional 52 Ground Water Conditions near Flagstaff 52 Structural Control of Ground Water 54 Recharge 55 Hydrologic Properties of Strata 60 Alluvium and Soil 60 Volcanic Rocks 60 Moenkopi Formation 60 Kaibab and Toroweap Formations 60 Coconino Sandstone 61 Supai Formation 61 Redwall Limestone 61 Martin Limestone 62 Tonto Group 62 Ground Water of the Area 62 Local Structural Control 64 Summary and Conclusions 65 Recommendations 67

APPENDIX 69

REFERENCES CITED 85 LIST OF FIGURES

Figure Page

Index Map 3

Southern Wells 17

Northern Wells 18

Principal Alignments of Cinder Cones . . in pocket

Cones of Stage II 37

Cones of Stage lIla 37

Cones of Stage IlIb 38

Cones of Stage IlIc 38

Rose Diagram, Spring Valley, Unfaulted Flow . 44

Rose Diagram, Spring Valley, East End, North Side 45 Rose Diagram, Spring Valley, West End, South Side 46

12. Rose Diagram,Schoolhouse Valley, North Side 47 Rose Diagram, Schoolhouse Valley, South Side 48 Rose Diagram, Scarp North of Spring Valley 49

Rose Diagram, Duck Lake Scarp 50 Calculated Actual Evapotranspiration and Precipitation, Coconino County 56

Geologic Map of the Sitgreaves Mountain Area in pocket

vi LIST OF TABLES

Table Page 1.Criteria forDistinguishing Ages of Cones 26 2.Criteria for Distinguishing Ages of Flows 27

vii GEOLOGY AND GEOFLYDROLOCY OF THE SITCREAVESMOUNTAIN AREA, COCONINO COUNTY, ARIZONA

Chandler R. Gilman

ABSTRACT

The Sitgreaves Mountain area is in the northwest

part of the San Francisco volcanic field, northeast of Williams, Arizona.

The surface rocks in the area are the Kaibab and Moenkopi Formations in the northwest, and volcanic rocks of felsic and intermediate composition near the center, but most of the area is covered by basalt. The basalt flows arid cinder cones are divided into Stages on the basis of weathering and erosion. Three basalt domes are present in the mapped area. Maps of the volcanic vents of individual Stages indicate persistent trends of N3OW, N1OE, and N6OE, and a major alignment in one Stage of

N8OW. The center of the effusive activity moved westward and died out toward the south. Many of the assymmetric cones are elongated N30-50W.

Bore holes penetrate the volcanic rocks of Qua- ternary and Tertiary age, the Permian Kaibab, Toroweap,

viii ix and Coconino Formations, and the Pennsylvanian and Permian

Supai Formation. The Triassic Moenkopi Formation is recognized in two holes.

Evidence from driller's logs of the holes indicates that the upper Supai and Coconino Formations are not water bearing in the area north and east of Williams, though these formations are the principal source of ground water in the area near Flagstaff. Fractures associated with the faults and alignments of volcanic vents permit the ground water to move more rapidly downward. INTRODUCTION

This study was undertaken as an attempt to gain knowledge of the hydrologic conditions in the area northeast of Williams, Arizona, and to evaluate the possibilities of developing a ground water supply. Structure and lithology are the principal controlling factors, and both were studied.

Method of Treatment

The area was mapped on U.S. Geological Survey topographic pre-release sheets now published as the Williams,

Valle, and Ebert Mountain quadrangles, and on an enlarged portion of the 1913 Flagstaff quadrangle. Aerial photo- graphs were used in the field as aids to accurate location and for the tracing of lava flow boundaries. Well samples and records at the Museum of Northern Arizona, Flagstaff, and the Arizona Bureau of Mines, Tucson, were studied and logs were prepared. Strikes and dips of joints were measured along features which are interpreted as faults.

Thin sections of both representative and distinctive basalts were prepared and examined. An unsuccessful attempt was made to obtain quantitativefigures for recharge of the ground water body by a method of calculating evapotranspiration.

1 2

Geologic and Cecgraphic Setting

The San Francisco volcanic field is at the southwestern edge of the Colorado Plateaus. This report covers the area of the field within these approximate boundaries: north of U.S. Highway 66, east of State Highway 64, south and east of the boundaries of the Kaibab National Forest.

(See Fig. 1). Most of the surface is covered by Tertiary and

Quaternary volcanic rocks. Underlying strata are Triassic

to Devonian and Cambrian in age. The southern end of the East Kaibab monocline is

several miles northeast of the area, and the San Francisco

anticline terminates at the eastern edge. North of the

area is the Coconino Plateau which extends to the Grand

Canyon, about seventy miles north. About 20 miles south

of the area, the Mogollon Rim exposes about 2,000 feet of

strata. The surface of the plateau adjacent to the volcanic

field has little relief. The highest mountains of the field rise more than 5,000 feet above the plateau, but most of the cinder cones are only a few hundred feet in height. Ephemeral streams have cut gullies and canyons in some of the basalt flows, in other areasthe streams lose

their identity in broad flat valleys. 3

d c0

Cocoriino Cameron Plateau

COCONINO COUNTY FranciSCo Mtn.

Williams

Flagstaff YVAPAI COUNTY

Sedo n a Clarkd ale

Figure I. Index Map, Sitgreaves Mountain area is hachured, 4 Method of Specifying Locations

The system adopted for identifying locations is that of the U.S. Geological Survey, Ground Water Branch.

The initial letter "A" signifies the point to be located is north and east of the Gila and Salt River Principal Me- ridian and Baseline. The two numbers within the paren- theses are the township and range numbers. The number following the second parenthesis is the section number. The first letter indicates in which quarter the point is located. The northeast quarter is "a", "b" is the northwest, "c" is the southwest, and "d" is the southeast quarter. The second letter subdivides the quarter into quarter- quarters in a similar manner, and the third letter indicates in which part of the quarter-quarter the point is located. For example, A(22-5)lOabc indicates a point in SW, NW, NE, sec.lO, T22N, R5E. GEOLOGY

Regional Stratigraphy

Precambrian

The oldest rocks underlying the area are probably similar to those exposed in the Grand Canyon to the north.

There the Older Precambrian rocks include schist, quart- zite and inetavolcanics of the Vishnu series intruded by granite and diabase. These rocks may be overlain by the Younger Precambrian Grand Canyon series of sandstones, shales and limestones.

Cambrian

The middle and lower Cambrian Tonto group, consist- ing of the Tapeats Sandstone, Bright Angel Shale, and Muav Limestone, thins southeastward from the Grand Canyon, but because it crops out south of the Mogollon Rim it may underlie the area. Wilson (1962, p.26) states that the Muav Limestone and the Bright Angel Shale wedge out at about latitude350 (approximately the location of the Mogollon Rim) and that the Tapeats "wedges out abruptly ... in Gila

County". McKee (1951, P1.1, A) indicates a total thickness of 200 to 500 feet of Cambrian deposits in the thesis area.

5 6

Ordoviciari and Silurian

Rocks of Ordovician and Silurian age do not Occur in this part of Arizona (Wilson, 1962, p.27-28).

Devon ian

Rocks of Late Devonian age are present both north

and south of the area. In eastern Grand Canyon the Temple Butte Limestone occurs in erosion channels ofthe under-

lying Muav Limestone (Metzger, 1961, p.117). Its occur-

rence is so limited that it is notdepicted on the Arizona Bureau of Mines' Geologic Map of Coconino County. Lehner (1958, p.523) reports the MartinLimestone

to be 455 feet of mostly dolomiticlimestone, with cherty, sandy, and shale layers, in theClarkdale quadrangle.

Mississippian

Overlying the Martin Limestone is theRedwall Lime-

stone of lower Mississippian age. Lehner (1958, p.259-260)

reports 241 feet ofRedwall exposed in Sycamore Canyon. In eastern Grand Canyon, theRedwall is about 400 feet thick

(Wilson, 1962, p.32). It is a finely- to coarsely-crystal-

line, thin- to thick-beddedlimestone exhibiting many solu-

tion features. 7 Pennsylvanian and Permian

In eastern Grand Canyon, along the Mogollon Rim and in Verde Valley the Supai unconformably overlies the Redwall

Limestone. The Supai has a thickness of 950 feet in the

Grand Canyon (Metzger, 1961, p.118), 1,665 feet in Sycamore

Canyon, and somewhat less in other parts of Verde Valley

(Lehner, 1958, p.533). The rocks of the Supai are of varying shades and intensities of reddish brown with limonite and calcite cement. Grain sizes generally range from silt to fine sand though claystones, coarse sandstones, limestones, and cherts have been reported from various parts of the formation (Jackson, 1951; Lehner,1958; Winters, 1962; Akers, 1962; Twenter and Metzger, 1963). In the Clarkdale quadrangle (Lehner, 1958, p.533-

540) the lower member is about 600 feet thick,mostly siltstone, shaley mudstone, and very fine- tofine-grained sandstone. The top of the lower member is composed predominantly of the smaller sand sizes. The middle member of the Supai, about 300 feetthick, is principally of dark reddish brownsiltatone. Beds of limestone occur but are rare. The 650 to 750 foot thick upper memberof the Supai

Formation forms most of the red cliffsand buttes of the "Red

Rock Country" around Sedona, Arizona. The sandstones of 8

the upper memberare medium- to coarse-grained, andcross- laminated on a large scale.

On the basis of fossil evidenceand lateral correla-

tion, the Supai Formationis Pennsylvanian and Permian.

Permian

Hermit Shale. The Hermit Shale crops out in the

Grand Canyon in disconformablecontact with the Supai Forma-

tion. It consists of about 300 feet of dark brown silt-

stone at the type locality. In eastern Grand Canyon it

thins, becoming coarser grained and isnot readily differ-

entiated from the Supai (Metzger, 1961, p.118). The

Hermit is not recognized along the Mogollon Rim. Baars

(1962, diagram, p.188-189) has placed an inferredzero isopach for the Hermit in an east-west direction about 20 miles north of Flagstaff and Williams.

Coconino Sandstone. The Coconino Sandstone, which overlies the Hermit Shale, is 600 feet thick in Grand Canyon. The contact is abruptly disconformable except in

eastern Grand Canyon where it is gradational. In Sycamore Canyon the Coconino is 750 feet thick (Lehner, 1958, p.541).

Here the lower contact is gradational with beds of Coconino aspect intertonguing with Supai in a transition zone of 50

to 150 feet (Twenter and Metzger, 1963, p.48). Locally the Supai and Coconino are lithologically very similar because the large-scale torrential cross-bedding of the 9 upper Supai closely resembles the sweeping cross-beds of the

Coconino. The contact is commonly placed at the top of the uppermost flat-bedded siltstone as there are no known siltstones in the Coconino (Lehner, 1958, p.538). Other use- ful criteria are a color change and a difference in cement- ing material (Akers, Cooley and Dennis, 1962, p.7). The Coconino Sandstone consists of very fine- to fine-grained quartz sand, ranging from white to yellow to moderate reddish orange. Generally a cliff-former, it shows great wedge-shaped cross-beds interpreted asthe £ ore- set beds of sand dunes formed bynortherly and westerly winds (Reiche, 1938). The cement of the Cocontho is chiefly silica; McKee (1934, p.81) states that this is a diagnostic feature which he contrasts withother units having calcite or iron oxide or both ascementing material. Although the Coconino contains no diagnostic fossils, its position between middlePermian formations leaves no doubt about its age.

Toroweap Formation. TheToroweap Formation con- formably overlies the Coconino inboth eastern Grand Canyon and Sycamore Canyon. The contact is remarkably smooth, with the beveled cross-beds ofthe Coconino covered by an ubiquitous red sandstone. McKee (1938, p.15) reasoned

that this is a conformablerelationship because the bevel- ing of the top of the Coconino tosuch a flat surface 10 without deposition of an overlying conglomerate must have

occurred before lithification of the Coconino. Lack of relief on the Coconino indicates exposure to erosion for a

rather short interval of time. McKee (1938, p.17-28) divided the Toroweap into two

phases, eastern and western, and the latter (from the top

down) into three members, Alpha, Beta and Gamma. The Alpha

and Gamma Members are largely soft friable elastic sediments, mostly red beds, and the Beta Member is a resistant lime-

stone. The limestone member thins toward the east and

disappears; the red beds interfinger with white cross-

laminated sandstones. Finally, in the eastern phase, the transition to sandstone becomes complete and members can no

longer be differentiated. The transition from western to eastern phases is exposed in Sycamore Canyonwhere the

lithology alternates seven times. Lehner (1958, p.543-545) divided the Toroweap in

the Clarkdale quadrangle into three units totalling 150

feet. The lowest unit is medium- to fine-grained calcareous or argillaceoussandstone. The middle unit grades from a 15 foot, highly calcareous sandstonein the east to

a 75 foot, very sandylimestone in the west. The top unit

is a sequence of sandstone, si].tstone,and shaley mudstone

in the west, grading eastward intolight colored non-

calcareous sandstone. 11

Exposures of the eastern phase of the Toroweap in eastern Grand Canyon are 280 feet thick at Bright Angel

Trail, thinning eastward (McKee, 1938, p.200-201). The quartz sandstones are medium- to very fine-grained, pale orange to white, and are gnarly- or cross-bedded. The

Toroweap has been assigned to the lower middle Permian on

the basis of its faunal assemblage.

Kaibab Formation. The Kaibab Formation was deposited disconformably on a slightly deformed and eroded

Toroweap surface. The time interval represented by the unconformity is small as evidenced by similarities of

faunas within the two formations as well as by the incomplete lithification of Toroweap fragments in overlying

Kaibab (McKee, 1938, p.35). The Kaibab, like the Toroweap, has been divided

into three members (from the top downwards): Alpha, Beta,

and Gamma, each of which exhibits various facies. The upper two members are exposed in easternGrand Canyon with

a thickness of 432 feet. The Beta Member is composed of sandy limestone, liiney sandstone, and bedded chert. The

Alpha Member is sandy magnesian limestone and cross-bedded

sandstone. Exposures in Sycamore Canyon of the same two members have an aggregate thicknessof 358 feet. The

Alpha Member dtffers lithologically inthis area, being composed of sand-free magnesian limestone(McKee, 1938, p.l86-19fl. 12

The Kaibab is the surface rock over most of the area from the northern edge of the San Francisco volcanic field to the Grand Canyon. Solution caves in the Kaibab, described by Colton, (1938, p.29-32), indicate that it has been subjected to extensive solution.

On the basis of fossils, the Kaibab is assigned to the middle Permian system (McKee, 1938; Brady, 1962).

Triassic

Unconformably overlying the Kaibab in scattered out- crops (where they have been spared byerosion) are the red beds of the Moenkopi Formation. Moenkopi crops out south of Gt'and Canyon at Red

Butte and at Cedar Mountain. The Cedar Mountain exposure (Noble, 1922, p.72) consists of 480 feet of partially cross- bedded, red, fine-grained, sandstone and shale. Gregory's type section of the Moenkopi for theLittle Colorado Valley, 20 miles southeast of Cedar Mountain (Gregory, 1917,p.24), has generally similar lithology but is about 90feet thinner.

In Sycamore Canyon, Price (1949,p.49-51) describes two sections .of 33.0 and 239feet of claystone, siltstone, and sandstone. The Moenkopi has been assigned by McKee(1954) to lower and possibly medial Triassic age onthe basis of the contained fossils. 13

Triassic-Tertiary Interval

There are no rocks of early Triassic to late Ter- tiary age in the vicinity of the thesis area. The

Shinarump and Chinle Formations may have been deposited here, but no exposure of them is found nearer than the valley of the Little Colorado River. Robinson (1913, p.26-27) reports almost 700 feet of Moenkopi several miles northeast of the thesis area, and McKee's isopach maps

(1951) indicate about 1,000 feet of Triassic sediments. McKee's maps indicate that the thesis area was marginal to basins of deposition in Jurassic and Cretaceous time. Uplift along the Mogollon Rim probably took place in middle Tertiary if correlations by Hunt (1956) and

Wilson (1962) are correct. Strata above the resistant Kaibab Formation were removed except where they were preserved locally beneath early Pliocene lava flows or because of structure. The resulting stripped surface on the Kaibab is a major erosion surface.

Late Tertiary and Quaternary

Volcanic Rocks. The volcanic rocks of the San Francisco volcanic field are describedin publications by

Robinson (1913), Colton (1950),Sabels (1962), Cooley (1962), and Babbitt (1964). Robinson's work is primarily concerned 14 with rocks of felsic and intermediate composition, Colton's work with basalts. Sabels, Cooley, and Babbitt correlated the rocks.

The San Francisco volcanic field covers some 4,000 square miles, mostly in south-central Coconino County. It

is bordered on the west by the Mount Floyd volcanic field and on the south by the Mormon Mountain volcanic field.

The volcanic rocks of the San Francisco field can be

separated into two major groups based on composition. One

group consists of lavas of felsic andintermediate composition, generally forming the higher elevations within the

area, e.g. those of San Francisco,Bill Williams, Sitgreaves, Kendrick, O'Leary, and Eldon Mountains. The other group

consists of rocks of basaltic composition making upthe

cinder cones and the flows which cover mostof the volcanic

field. The maximum ages of the volcanicrocks, as presently

known, are given by Sabels (1962,p.100) and Cooley (1962,

p.101+). The oldest basalts are of late Miocene age. Cooley assigned the age byinterpretation of fossil evidence

found in the Hopi Buttes countryand extension to the San

Francisco field by geomorphiccorrelations. Sabels deter-

mined the same age (14 millionyears) by the potassium-

argon age-datingtechnique. Volcanic activity continued intermittently until almost historictime. The most recent 15 activity is dated by dendrochronologic studies (Smiley,

1958) as 1064-65 A.D. Most of the basalts of the San

Francisco field are late Pliocene and Quaternary in age according to Cooley (1962, p.111-112). Robinson divided the volcanic activity into three periods: the First General Period, during which material of basaltic composition was ejected; the Second General Period, during which material of felsic to intermediate composition was ejected; and the Third General Period in which more basaltic material was ejected (Robinson, 1913, p.38). Cooley states that the main mass of felsic material was formed during a cessationof basaltic activity. Colton divides the cones and flows into five stages of eruption, numbered I to V (from oldest toyoungest), dis-

tinguished by the amount of erosion andweathering. Colton's criteria, modified to fit the area understudy,

are presented in Tables1 and 2. Cooley (1962, p.l08-ll2)

found this chronology (withColton's Stage I subdivided) to be correlative with erosionalsurfaces of the Little Colo- rado River area to the east. From these relationships he concludes that Stage I flows arelate Pliocene to early Pleistocene, Stages II and III rangefrom middle to late

Pleistocene, and Stage IV rangesfrom very late Pleistocene

to early Recent. Babbitt's findings are notin complete agreement

with Cooley's correlation. Babbitt (1964) found some of 16 the flows, mapped by Cooley as Stage II, to be reversely magnetized, indicating an age of late Pliocene or earliest

Pleistocene (0.99 to 1.9 m.y.). He also found an older group of flows, mapped by Cooley as early Stage I, to be reversely magnetized, correlating them with the next previous reversal (3.4 m.y.) of the Pliocene. Koons (1945, p.l56-l57), in studying the geology of the Uinkaret Plateau north of the Grand Canyon, applied Colton's classification to cones and flows in that area.

Basalt cones and flows occur at elevations from below

2,000 to above 8,000 feet, with annual precipitation ranging from 8 to 30 inches. Within any given Stage, he found no difference in weathering and erosionof the flows extending from one elevation to another or amongthe cones

at different elevations. Koons' findings appear to sup-

port the validity of Colton'scriteria for determination of different Stages of volcanic activity, evenunder widely

varying climatic conditions.

Local Stratigraphy

Well logs made by the authorand logs from various

sources are givenin the Appendix. Figures 2 and 3 are generalized graphic sections ofthe wells, and location

maps. 17

R3E I R4E R5E R6E 3 N T 9 miles 22 N

-I- 1-

T 21 N 10

7000 - Thm 7 Pk 9 Pt

a) 6000 - IPPs C.) 0.4 .

5000-

Figure2. Location and lithology of the I southern wells. (Key on Figure 3). fletailed descriptions inAppendix. 18

R1E R2E limes tone

T siltstone 27 9 miles N 15 sands tone + 13 volcanic rocks T 26 sandy N / silty

Eleva- [1calcareous t ion 13 no samples 6000- Pk W- -L static water level

5000 Pc

]PPs

Figure 3. Location and lithology of the northernwells. Detailed descriptions in Appendix. 19

Pennsylvanian and Permian

The Supai Formation does not crop out in or near the thesis area, but samples are available from seven wells, none of which penetrate the entire formation. It is of sandstone, silty sandstone and sandy siltstone in most of the samples. Calcareous cement is generally present. Colors are usually varying shades of reddish brown, red, and less commonly pink and orange.

Permian

Hermit Shale. In the two northernmost wells examined (A(27-l)29 and A(26-2)1O) dark brown to dark grayish red, fine siltstone occurs at the top of the Supai.

This is probably the southernmost extension of the Hermit

Shale. Coconino Sandstone. The Coconino Sandstone crops out at one location and samples areavailable from six wells. The formation has very uniformlithology throughout the area. It is a well sorted sandstone consistingof very fine- to fine-, lesscommonly to medium-sized, quartz sand grains cemented with silicaand minor calcite. The grains are subrounded torounded and anhedral to subhedral. The larger grains are frosted, betterrounded, and lighter colored than the smaller oneswhichare more susceptible to 20 secondary crystalline overgrowth. The formation is usually light reddish tan or orange-tan.

There is a slight westward thinning trend in the southern wells as shown by wells 10, 5, and 3. Samples

from well number 8 of the southern group show an anomolous

thickness of Coconino. Probably the samples are not representative, as an abrupt thickening of more than 500

feet in three miles is unlikely. However, logs for wells

number 8 and number 9 supplied by John McCarthy(personal communication, 1965) of the El Paso Natural Gas Co.show

a similar abrupt thickeningof the Coconino. A small part of this abnormal thickness may becaused by the difficulty

of picking the Toroweap-CoconinO contact. In the northern wells, theCoconino thins northward

and northwestward. The surface exposure of Coconinois at the bottom

of a large uplifted block atthe northern end of Squaw

Mountain. The thick cover of grass,scrub and talus hides the attitude of theformation; exposures of rock in place

are limited to thinledges and small blocks. The thin- bedded sandstone is veryfine- to fine-grained. Color of

fresh surfaces is lightreddish tan. The rock is firmly

cemented by silica, withcrystalline overgrowths common.

A minimum of 200 feetof sandstone is exposed abovethe

covered base. 21

Toroweap Formation. The Toroweap Formation crops out at one surface location and is completely penetrated in seven wells, with samples available from six.

The samples show the bottom of the Toroweap to be reddish, calcareous sandstone and shale. Overlying this basal portion are sandstones and limestones. In the southern wells the lower part of this section has the lithology of the transition zone between the eastern and western phases. The top of the formation is calcareous sandstone and shale in the north; in the south it is silty limestone. The finer grained clastic sediments are reddish brown; the sandstones are light shades of yellow-tanand pink; the limestones are gray ortannishgray. Thickness varies from 200 to 400 feet. The surface exposure of Toroweap is atthe Squaw

Mountain locality. The lower contact of the formation was not located. The lowest exposure consists of aboutfive feet of silty, calcareous, palereddish brown, fine-grained sandstone. Overlying this lowermost exposure is amassive 15 foot unit of buff weathering tanlimestone, very fine- grained and moderately dolomitic,which forms a ridge.

Two thin zones within itcontain outlines of pelecypods that are completely replacedby crystalline calcite. Calcite also fills the many discontinuousfractures which cut the 22 rock mass. Locally overlying the limestone is a thin reddish brown calcareous mudstone. The minimum thickness of exposed Toroweap is about 20 feet.

Kaibab Formation. The Kaibab, which crops out

over an area of about 10 square miles in the northern part

of the thesis area, is exposed or reported in 11 wells.

Samples are available from nine wells, seven of which com-

pletely penetrate the formation. In the southern wells, the Kaibab Formation con-

sists of a series of calcareous sandstones and lirnestones.

The very fine-grained limes tones are usually dolomitic and

partly sandy or cherty. They are yellowish to tannish gray and the chert is usually alighter shade of the ac-

companying limestone. The sandstones range from very

fine- to mediuru-grained, commonly areyellowish tan. The

northern wells are similar, except thatthey have little

sandstone. The thickness of the Kaibab is 200 to400 feet in the southern wells, 220 to 360feet in the northern ones. The best surface exposure ofKaibab is in the 60

foot deep canyon of Spring ValleyWash, where it is thin-

to thick-bedded, dolomitic,partly sandy and cherty lime-

stone. A few sink holes havebeen developed locally. Elsewhere the surface is flat orundulating with thin resis-

tant ledges of limestoneoccurring on slopes. 23

Triassic

The Moenkopi Formation forms the surface rock over about six square miles in the northern part of the area and

is represented by cuttings from two wells. The samples

are pale to medium reddish brownsiltstone and sandy silt-

stone with much calcite cement. The best surface exposure is in a canyonof Miller

Wash. About 40 feet of red-brown and red-purplesiltstones is exposed which contains a smallproportion of very fine

and fine sand. The surface of the Moenkopi hasgently rounded forms and since it disintegrates80easily, out-

crops are rare. The contact with theunderlying Kaibab is not exposed, and the contactwith the overlying basaltsis

without relief in the few exposureswhere it is visible.

Tertiary and Quaternary

Rocks of felsic andintermediate composition. Be- and inter- cause of Robinson'sthorough work on the felsic mediate rocks, previouslyknown occurrences were not re- examined or mapped indetail for the present work,other

than to distinguish their areasof outcrop. There are twolocalities of felsic andintermediate previous rocks within the thesis areawhich are not noted in (Fig. 17) literature. Two miles southof Government Hill latite. is a cone (A(22-4)1O)of light reddish gray 24

Examination under the binocular microscopeshows the rock to be glassy, graywhere non-vesicular and reddishwhere finely vesicular. Crystals of fresh clear plagioclase and cloudy white orthoclase arepresent in about equal pro-

portions, totaling perhaps15 percent of the rock. Flakes

of biotite are common andlie subparallel to thered and

gray layers. At the west base ofSitgreaveS Mountain(Fig. 17)

is a low range ofhills (A(23-3)34a, 27cand d, 35) of vitro- light to medium gray, veryvesicular to pumiceouS out to long thintubes. phyre. The vesicles are drawn largest cross-sectional They are somewhatflattened with the smallest of micro- dimensions about 2 mm.by 1 mm. and the and brown biotite. scopic size. PhenocrystS are feldspar are The feldspar occursin subhedralcrystalswhich show albite generally much fractured. A few of the grains feldspar is plagioclaSecannot twinning; whether all the It is possible that be determined withoutoptical tests. orthoclase. Small (less many of theuntwinned grains are biotite lie parallel to than 0.5 mm.)hexagonal plates of

the elongate directionof the vesicles. reddish gray, with a The rock weatherstO a dull reflecting its extremevesicularity. peculiar surface texture basalts. H. S. Colton Geomorphicclassification of archeological worknortheast (1950), primarilyinterested in 25 of San Francisco Mountain, presents a classification of the

cones and flows in that area based on the degree of erosion

and weathering which they exhibit. This classification

divides the cones and flows into five main stages of erup-

tive activity, as given (in modified form) in Tables 1

and 2.

Evidence was not found to demonstrate the precise

age relationships of the basalts to the intermediate and

felsic rocks. Cooley (1962, p.111-112) believes the bulk of the felsic and intermediate rocks were erupted in an

interval between Stages I and II. The two exposures of

latite and vitrophyre described above would have been

mapped as Stage II except for their composition.

Stage I. Cones of this stage would be represented

only by plutonic plugs. None were found. Flows assigned to this stage occur only alongthe

northwest edge of the volcanic field. The characteristics

of Stage I flows are given in Table 2. The basalt has a medium gray,finely vesicular

groundmass. It contains scattered pheriocrystsof con-

spicuous clear plagioclase, commonlyabout 2 mm. in dia-

meter, and smaller gray plagioclase. The thin sections examined show the groundmass to becomposed of plagioclase

laths and pyroxene in equal proportions,with about 15

percent opaques. MicropheflOCrysts of olivene with the Table 1. Criteria for distinguishing age of cones. (Modified from Colton, 1937). Stage V Original outline Cone shape Degree of erosionNo erosion. oxidizedNot appreciably or al- Weatheriflg No gullies. Gullying Remarks IV perfectlypreserved.Originalserved. pre- outline No erosion. oxidized,Surfacetered to materialclays. enough Noany gullies part ofon Musttinguishflow see to dis- it hUe Original outline preserved .Gener- erosion.Essentially no vegetationoxidized,claySurface to support on materialin flats. part any part of Nocone. gullies on from hlic. IlIb Original outline moundallypreserved, small,shaped. often Slight erosion. oxidized,alteredSurface to materialmuch clays, cone. Gullyon north or gullies or lila Most original shape preserved. inSomeLittle upper have erosion. parts. dikes Similaraltered to Ilib.clays, northeast side. Gullieson all cutsides. II resistanted.ShapesoutlineOriginal destroy- smoothpartsreflect materialMuchdikesexposing fragmental and removed lavaridges Muchmaterialtofragmental ofclay. the altered I Awithin plutonic(dikes, the etc.)plug.cone materialAllHeight fragmental reduced. removed. plugsNofound. basaltic have been StageTable 2. Flow outlines Criteria for distinguishing age of flows. General surface Small features (Modified from Colton, 1937). Gullies and Canyons IV V TrueTrueis visible.edge edge of of flow visibleSurfacepreservedOriginal erosion. very surfacewithout rough AllfaceOriginalserved.features original features pre-lava sur- gullies.NogulliesNo canyons canyons except or or flows visible. and broken. placedweathering.andpresent,smoothed somewhat by frostbut by dis- majorrado(e.g.Little drainagesRiver). Colo- III usuallyorpreservedOriginal in part.Sources determin- edges wholly ModeratedeeplySurfaceamountsirregular, eroded. rough toof largenotbasalt and subdued.originalprominentpressureSpatter conesoutlines ridgesbut and yonsGulliespresent. may andbe can- II erodedOriginalablegeneralcovered. if back, not edgesoutline but basalt,Erodedcular,in soil, smooth.inmay etc.soil be .Densevesi-More rarelyandTraces spatter preserved.of ridges cones present.Gulliescanyons and may shallow be preserved.Originaltooften determine. difficult Sources edges Deeplyered.basaltof vesicular lesseroded, weath- uppermuch AllbasaltFewoutcropsor outcropsremoved.surfaces. on interi-of ofFewba- Deepcanyons gullies couon. and undetermined.outliersandMayeroded remainbe far"cut .Sources back.as off" basaltdense,surface.Relativelyportion inweatheredremoved. Onlysoil. smooth little saltsurfaces. on interior 28 edges altered toiddingsite make up about five percent. This red rim of iddingsite onthe olivine crystals is

common in thebasalts of all stages. The groundmass plagioclase in one thin sectionexamined was labradorite other thin section was (Ab42An58). The groundmass in the the plagio- too fine-grained topermit identification of

clase type. The Michel-Levy method wasused to determine the In every case the plagioclase type inall thin sections. Plagio- plagioclase identifiedis that in thegroundmass. thin section for clase phenocrysts aretoo scarce in Michel-Levy'S method to beapplicable. of Stage II occur Stage II. Cones and flows is shown throughout the thesisarea. Their distribution II cones and flows in Figure 5. Characteristics of Stage

are given inTables 1 and 2. dark gray and some The basaltflows are light tO phenocrySts. Clear plagio- of them have verysmall olivine distributed, less clase phenocrySts arewidely but sparsely usually make up a conspicuOUS smaller grayfeldspar grains

greater proportionof the rock. One of them, Three thinsectiOnS wereexamined. about 10 percentolivine and from a flow inA(22-4)32b, has phenocryStS. The groundmass a few grainsof augite as in equal proportions consists of pyroxefleand plagioclaSe olivine. with lesser opaqueminerals and minor 29

The other two sections arefrom opposite ends of

Moritz Hill, an erodedbasalt dome at A(24-4)35. They are distinctive in that they havemicrophenocryStS ofbasaltic completely replace, hornblende. Opaques rim, and sometimes of pyrox- the hornblende. A few rounded microphenocrYStS ene appear in oneof the sections. The groundmass is very material, 10 fine, composed of about 25percent microlitic predominantly of labra- percent augite, andthe remainder

dorite (approximatelyAb45). subdivided on the Stage III. Stage III cones are The Stage III basis of theirerosion and weathering. general "younger flowscannot besubdivided except on a the source ofthe looking" or "olderlooking" basis, unless particular cone. Character- flowcan beattributed to a are given inTables I is tics of StageIII cones andflows

and 2. Stage lila occurthroughout Stage lila. Conesof central portion (Fig.6). the area, exceptin the west usually a middleshade The basaltofStage lila is conspicuous clearplagio- of gray, commonlywith olivine, plagioclase phenocryStS. clase, and lessconspicuous gray phenocryStSofplagio- Examination in thinsection discloses groundmasSofplagioclase clase, olivine,and augite in a and opaques. laths withinterstitial pyroxene 30

Squaw Mountain, a double basaltdome, is unusual.

Field evidence indicates that thesouthern part of the mountain is the older of the two domes. The Coconino and Toro- weap Formations areuplifted in the younger northerndome, which has pierced the edge ofthe southern dome. The basalt of the southerndome contains about25 plagio- percent augite phenocrysts,with minor olivine and minor clase in a groundmass oflabradorite (Ab46), opaques, pyroxene and trace amountsof glass. The basalt of the

northern part has phenocrystsof olivine and plagioclase of pyroxene with only a trace ofaugite, in a groundmass (Ab46) and no glass. with lesser opaquesand labradorite composition of the two Thus the differencein mineralogical that this is a basalts corroboratesthe field evidence

double dome. Stage lila, it Although SquawMountain is mapped as in the state of aggre- may well beolder. The difference cinder cones wouldhave gation of the basaltdomes from the weathering. The domes, changed the ratesof erosion and in contrast withMoritz however, are verysymmetrical apparent erosionand Hill, and on thebasis of their

weathering areclassed as Stagelila. Ilib are almost twice Stage Ilib. Cones of Stage other stages. Their distribution as common asthose of the is shown in Figure7. 31

The basalt of Stage IlIb conesand flows is generally medium to dark gray. It is commonly porphyriticwith olivine and the usual clearand gray plagioclasepheno- distinguish crysts. Small phenocrysts ofaugite are often present in able in hand specimenand, though not always in the basalts 11Th flows, arecharacteristically uncommon made from Stage of other stages. Of nine thin sections in amounts flub basalts, five haveaugite phenocrystS Of two greater than 10percent and oneother has a few. pyroxene in the thin sections whichlack recognizable groundmass, one ismostly microlitic. Ilic are generally Stage Ilic. The cones of Stage often less steepthan somewhat smaller andtheir slopes are An explanation maybe those of Stage lilaand Ilib cones. spread on the surface that the earlycinder ejections are material is needed to and a minimum amountof time and cone shape. If vol- achieve thetypical straight-sided before this lastcondition is reached, canic activity ceases Many of theIlic cones are a moundshape mightresult. with the relativescarcity and mound shaped,which, coupled seems toindicate a waning small size ofthe Ilic flows, in this part ofthe San intensity ofvolcanic activity

Francisco field. IV within the area, There are noflows of Stage associated flows aredesignated hence all the coneswithout 32

Stage Ilic and Stage as Ific; in Colton's classification, examination of IV cones cannot bedistinguished without associated flows. few or no The basalts of StageIlIc generally have Two thin sections phenocrysts. The lavas are dark gray. plagioclase examined have microphenocryStsof olivine and opaques, in a groundmasS ofplagioclase laths, pyroxene, and rare olivine.

Quaternary

mapped as alluviumoccurs Alluvium. The material what are locallyreferred tO in valleys,generally forming flat valley bottomsbarren as "parks" or"prairies" - broad of them are asdeep as six of trees. GulleyS in some

feet. bulldozing a pitfound a In SpringValley a rancher Milton Wetherill(oral skull at a depthof eight feet. Museum ofNorthern Arizona cOmmUTliCatiOfl,1963) of the of a youngdomestic sheep. identified theskull as that introduced tonorthern Arizona Though domesticsheep were they did notbecome common by the Spanish asearly as 1629, until 1850 to1870 (Towne and in this partof the Plateau This gives afigure for Wentworth, 1945,p.88, 154). of alluviumin the last century. possible localaccumulation 33

The alluvium is generally light to dark yellowish or grayish brown. It is composed of minor clay, sandy silt, and silty sand, with pebbles occurringin lenses.

Soil. Soil, which is not mapped as alluvium,has developed on the surfaces of the flowsand contains relatively unaltered material from theflow. Though no measurements were made, thethickness of this soil averages about two feet according to RobertMitchell (oral communication, 1962) of the Flagstaffoffice of the Soil Conservation

Service who is studying thesoils of Coconino County. Soil is also developed on the conesfrom the weathering of thesis area have suf- the cinders. All the cones in the ficient soil to support grassand tree growth.

Regional Structure

south- The San Franciscovolcanic field is on the flat anti- western end of theColorado Plateaus, on a very Cooley dine trending aboutN3OW (Robinson, 1913, p.33). as a "structur- (1962, p.lO3) hasreferred to this structure with the Kaibab al shelf" connectingthe Mogollon slope

uplift. East Kaibab monocline The Mesa Buttesegment of the faults at Mesa Butte. These merges with apair of parallel and Cedar Ranchfaults, con- two fractures,the Mesa Butte the older lavas,and dis- tinue southwest,offset some of of Mesa Butte. appear about sevenmiles southwest 34

Northwest of the line of the Mesa Buttefault and the monocline, the sedimentsdip to the west and southwest

(Babenroth and Strahier, 1945,p.112). Babenroth and Strahler (1945)mapped and described a number of grabens,varying in length from two toeight miles, generally about a quarterof a mile wide. Most of

these grabens predate lavaswhich have flowed intothem, a

few of the lavas are faultedby later movement and one throw. graben is entirely post-lava,with 80 to 100 feet of which Colton This last graben offsetsthe Tappan Wash flow, (1937) has classified as aStage II flow.

On the basis ofstratigraphic relationships ex- the structure hibited near the northend of the monocline, 1945, p.148-149) asearly is dated (Babenrothand Strahler, also state Tertiary (Laramide). Babenroth and Strahier follow three that most of the majorand minor structures

trends, N30-40E,N25-40W, and north. general periods Lehner (1958,p.568-57l) found two formations in theClarkdale of deformationof the Paleozoic these took placeafter the time quadrangle. The earlier of deposited and before the when the MoenkopiFormation was (post-Lower Triassic- deposition of theHickey FormatiOn penecOntemPorafleouslY Pliocene?), possiblyin Laramide time Kaibab monocline. The later with formationof the East of Hickey period of deformationfollowed the time 35 accumulation but preceded the depositionof Verde and

Perkinsville Formations (latePliocene-Pleistocene).

The earlier deformationtilted the rocks to the

northeast and displaced them byfaults which strike N5OW

and N45E with near-verticaldips and throws of 50 to150 Price feet; vertical joint systemsparallel the faults. with (1950) notes similar faulttrends in Sycamore Canyon produce the northwesterly faults morecommon, tending to

graben structures. The later period ofdeformation resultedin block trend north to faulting and uplift. The major faults north-northwest, are steepto verticalwith the west sides of steeply dip- more commonlyuplifted. A large number with the north ping transverse faultsstrike northwest throw in a sides commonlyuplifted. The stratigraphic 400 feet in thenorthern few of the majorfaults exceeds

part of thequadrangle.

Local Structure

Elongate Cones -

cinder cones Breed (1964,p.66-68) has classified volcanic field as coneswith symmetri- of the San Francisco craters, coneswith cal craters, coneswith assymetrical crater), and cones cleft "craters",mounds (no apparent explosion or collapse. All but with cratersenlarged by 36 the first one are, or maybe, elongated, a conditionwhich he ascribes to linear ventscaused by fractures in the underlying rocks. Of 17 elongate cones inthe area, ten belong to tendency for Stage II. This may indicate a stronger it may fissure types oferuption during that stage, or by exposure of indicate differentialerosion controlled the Stage dikes within the older cones. Because nine of quadrant and six are II cones have trendsin the northwest not random. about N30-40W, it seemsthat these trends are stages, sixhave Of the seven elongatecones of other of which are about trends in the northwestquadrant, four

N40-50W. indeed controlledby If theseelongations are of relatively structure they maybe controlledby features later. shallow depth aswill be discussed

Alignments

of volcanic conesin The numberand distribution alignment ofthree or more cones the area issuch that an arbitrarily chosendirection. can befound in almost any demonstrated, however. Certain preferredtrends can be of cones belongingtO each of Maps showingthe distribution (Figs. 4, 5,6, 7, 8) suggest the four basalticstages persisted, but thatthe positions of that trenddirections changed throughtime. the eruptivefissures R3E R4E I R5E R3E R4E RSE K; 0 25 N 0 25 NT 0 24 TN 24 NT 23 TN a 23 NT 0 22 N 0 3 22 TN Figurt 5. ConesUseHWMn = HowardwithMoritzof Stage Figure Mesa.Hill II. 4 White Hill (overlay). Figure 6. 0 UseConesS with of StageFigure lila. 4 (overlay). Squaw Mountain. I R5E - NI R3 R4E R5E 25 T R3E R4E 25 NT Q N 0 T 0 O°0 0 0 0 24 NT 24 N 2 0 0 0 23 NT a 0 0 0 23 NT c' V 0 22 NT 0 '3 oot 0 22 NT Figure 7. UseCCones with of FigureStage tub.4 Cedar Mountain. (overlay). Figure 8. UseCones with of StageFigure Ilic. 4 (overlay). 39

Rocks of felsic and intermediate composition. Sit- greaves, Kendrick and Bill Williams Mountains lie on a line trending N55E (Fig. 17). About three miles southeast of Sitgreaves is a parallel line of three smaller cones of similar composition (Fig. 17). Two of these cones, Government Hill and the peak west of it, are younger than

Sitgreaves Mountain and may be younger than Stage II. Stage II basalt occurs south of these cones on the southeast slope of Sitgreaves with no basaltic vent exposed.

The vent may have been covered by later formation of the

two felsic cones (see Fig. 17).

Stage II. The earliest basalt cones are Stage II and three trends are prominent (Figs. 4,5): an arcuate alignment curving from north to northeast; a straight

alignment running N6OE from Howard Mesa, ara1lel to the Kendrick-Sitgreaves-Bill Williams trend; and three paral-

lel alignments bearing N3OW whichinclude Moritz Hill and

White Hill. Near the south edge of the map areseveral cones which do notbelong to any trend in the mapped area.

Stage lila. The cones of Stage lila form a very

prominent belt, two miles wide,trending N1OE through Squaw

Mountain. Within this belt fall mostof the cones of the arcuate alignment of StageII. A shorteralignmentof

three cones in the southeast cornerparallels this belt.

An alignment of one Stage IIand four Stage lila cones extends southeast from the largelila cone on the southflank 40 of Sitgreaves Mountain, with a trend of N6OW paralleling the White Hill alignments. Two cones fall on the N6OE line from Howard Mesa, four cones on the N3OW White Hill alignments and one cone on the N55E Government Hill alignment.

Stage Ilib. Bordering the Squaw Mountain belt on the west, and parallel to it, is a second belt two miles wide. An alignment of five cones 14 miles long parallels the belts to the east. Similarly a line of cones passing just north of Cedar Mountain parallels the White Hill alignments. A new trend appears in an alignment bearing NSOW which passes north of Sitgreaves Mountain. There is

also a suggestion of an alignment paralleling the Howard Mesa line running N6OE from just north of Cedar Mountain.

Stage Ilic. The cones of Stage Ilic occur as con- tinuations of previous alignments except in the southwest

portion where an alignment roughly parallels the Kendrick- Sjtreaves-Bil1 Williams trend. Another line extends the Government Hill alignment toward thesouthwest. Other

cones continue earliertrends parallel to the Squaw

Mountain belt.

Summary. A remarkable feature of thesealignments,

except the arcuate Stage IIalignment, is their linearity.

Many more short alignments may besuggested, and if arcs or

curves are used, still morepossibilities present themselves. 41

Analysis of the cone alignments from individual stages indicates major trends of N1OE, N3OW and N6OE, and one prominent alignment of N8OW. Except for the latter trend which occurs almost entirely with Stage Ilib cones, all stages have alignments parallel to the major trends.

The common trends of north, east, northeast, and northwest

(Mayo, 1958, p.1169) is matched almost perfectly if these

trends are rotated 100 counter-clockwise. The particular alignments shifted in space through

time, with activity moving progressively westwardand with

the last activity in the south. The area studied is too small for tectonic synthesis but it seems likelythat analysis of a larger area of the field might provefruit-

ful; features of such magnitude as these musthave their origins deep within the crust. The tendency for the elongate cones totrend

N30-50W is somewhat at variancewith trends of cone align-

ments. If Breed's conclusion(1964, p.70) that assynimetric shapes are determined by thedirection of underlying joints

and faults, theircomparatively small scale indicates a relatively shallow control,while the large scale of the

alignments indicatescorrespondingly deeper control. 42 Faulting

A few features in the area suggest faulting since the period of volcanic activity. In the northwestern part of the area, Spring Valley is a straight, alluvium-filled valley a fourth of a mile wide and six miles long trending

N5OW. About lmiles of its length is filled with a Stage Ilib flow through which a canyon has been cut. Thus, this part of Spring Valley can be determined as post-Stage II and pre-Stage Ilib. Though no direct evidence of dis- placement was found, this valley has been interpreted as a graben, primarily because it looks like one in aerial photo- graphs and in the field; no other explanation is rational to the author. Similarly, near Schoolhouse Tank (A(23-3)20) there is a narrow straight-sided valley between Stage Ilibflows, about half a mile long on the south and lmiles on the north side, which is interpreted similarly, thoughwith

less confidence, as a graben. The Schoolhouse feature bears N7OW and is post-Stage Ilib as it occursin flows of

that age. Two linear scarps areinterpreted as fault scarps

and for similar reasons. One of the scarps is north of the Spring Valley "graben" and is morethan a mile long bearing N20w. The maximum relief alongthe scarp is about 65 feet and occurs on a StageI flow. The other 43 scarp which forms the northwest side of Duck Lake (A(22-3)24) has a minimum length of three miles, with maximum relief of about 60 feet and bears N4OE. It occurs on a Stage III flow. These inferred grabens and faults are shown in Figures 1? and 4.

As no direct evidence of movement can be demonstrated in these valleys and scarps, strikes of joints along their sides were recorded and rose diagrams and stereo net plots were prepared. From 90 to 152 strikes were used in each diagram. As most of the dips exceed 600, the stereo net plots are not reproduced here.

The author believed that, though basalt flows tend to be strongly jointed, the orientation of the strikes of

the joints would be random. The rose diagram of joints

from theunfaulted basalt which flowed into Spring

Valley (Fig. 9) shows random orientation. The two diagrams constructed from data collectedalong the uplifted

sides of the proposed bounding faults suggest preference of

strike directions (Figs. 10 ançl 11), although the causeis not obvious. Data collected at the Schoolhouse7tgrabenPt show more definite evidence ofpreferred strike directions

(Figs. 12 and 13), though their interpretationis likewise

obscure. Rose diagrams of jointsalong the scarp north of Spring Valley (Fig. 14) and theDuck Lake scarp (Fig. 15) 44

Figure 9. Rose diagram of the strike of 132 joints. Spring Valley, unfaulted flow. 45

Figure 10. Rose diagram of the strike of 103 joints. Spring Valley, east end,northside. 46

Figure 11. Rose diagram of thestrike of 99 joints. Spring Valley, westend, south side. 47

Figure 12. Rose diagram ofthe strike of 152 joints. Schoolhouse Valley,north side. 4

ot Ae 49

Figure 14. Rose diagram of thestrike of 98 joints. Scarp north of SpringValley. 50

the strike of 90joints. Figure 15. Rose diagram of Duck Lake Scarp. 51 also show preferred orientations andare difficult to interpret.

The cause of the observed joint sets is not obvious.

Possibly these joints are related to stresses present at the time of solidification of the basalt rather than to the inferred movement of graben formation, although the unfaulted flow in Spring Valley shows random joints.

The diagrams are presented here as partial support of the author's contention that the features cited are faults, though the interpretation is questionable. GROUND WATER

Regional

Ground water discharges from springs near the Grand

Canyon and at the base of the Mogollon Rim. The principal springs along the Rim are in Oak Creek and Sycamore Canyons.

In Oak Creek Canyon, most springs discharge from the

Coconino and Supai Formations; in Sycamore Canyon most of the water comes from the Redwall Limestone (Feth and Hem,

1963, p.H30, 1146). In the Grand Canyon area only one small (less than 1 gpm) spring issues from the Supai Forma-

tion, the rest are in the Muav and the RedwallLimestones

(Metzger, 1961, p.l68).

Groundwater Conditions near Flagstaff

Groundwater conditions near Flagstaff aredescribed

in reports by Akers (1962) andAkers, Cooley, and Daniels

(1964). Parts of these reports are reviewedbriefly be-

cause of theirpertinence to conditions in the thesis area. The principal aquifer discussedis the upper Supai

and the Coconino Formations inthe area bounded by the Oak Creek fault on the west and theAnderson Mesa fault on the

east. The block between thefaults has moved relatively down, juxtaposing the permeablerocks of the aquifer with

52 53

the impermeable beds of theSupai. The silty parts of the

Supai Formation actas the bottom aquiclude in theareas where the upper Supai andCoconino are water-bearing.

The report by Akers (1962,p.99) contains a contour

map of the regional water table in thearea near Flagstaff.

Water recharged from Rodgers Lakeand Lake Mary forms

groundwater mounds near the lakes. The groundwater divide

coincides with a line drawn between themounds and the

water table slopes downward to the northeastand southweit.

The water table is inclined southwardat about 35 feet per

mile where it is in the relativelypermeable Cocormino Sand- stone, and at about 100 feet per mile northeastward where

the water moves in the less permeableupper Supai.

Highly fractured, locally pulverized, rocks in the vicinity of the major faults transmit 10 to 50 timesas much water as do the same rocks where unfractured.

Although the authors do not point it out, thecon- tours near the Woody Mountain well field show the water table to be descending very steeply northward along the fault. The aquifer in the well field is highly permeable, hence the steepness of the water table must indicate a steep groundwater gradient through the generally low permeable part of the Supai. Intense fracturing has shattered the parts of the formations penetrated by the wells. This fracturing must have affected the underlying siltstones, rendering them more permeable, also. 54 A large amount of recharge (as shown by the groundwater mound) is channeled into the area of the well field from the west (uplifted) block by a cross-fault. Rodgers Lake, though usually dry, serves as a collecting basin and intake area for the cross-fault (Akers, 1962, ps99-102).

Small perched water bodies occur locally above the Moenkopi Formation or above soil zones interbedded with the bas1ts. As they are dependent on seasonal precipitation for recharge they are generally undependable sources of water (Akers, Cooley and Dennis, 1964, p.8-16).

Structural Control of Ground Water

Except in the Flagstaff area, described above, the location and configuration of the water table are not known.

If the ground water were confined to the Coconino and upper

Supai, investigations of the structure of the region would indicate the directions of ground water movement. The water would move down-dip, away from axis of the San

Francisco anticline. Evidence from the Flagstaff area indicates that fracturing associated with faulting renders the Supai siltstones permeable. The water which passes downward through the Supai will then be controlled by the hydraulic gradient established above the next effective aquiclude. The Kaibab

Formation dips away from the crest of the San Francisco - 55 anticline at less than 20 according to Akers, Cooley and

Dennis (1964, p.21), and less than10 according to Robinson

(1913, p.33-34). Slight local changes in thicknesses of the Kaibab, Toroweap, Coconino, and Supai Formations could have large effects on the attitudes of these and deeper formations. Data of thinning rates and direction are not available in sufficient detail to make meaningful predic- tions about structure at depth.

Recharge

Normally, major losses from recharge are runoff and evapotranspiration. There is apparently no runoff from the area as a whole, though ephemeral streams mayflow after summer rains or spring thaw; the water infiltrates within a few miles and probably little waterleaves the

San Francisco Plateau on thesurface. EvapotranspiratiOn is difficult to measurein natural conditions. Thornthwaite (1948) has given a method f or calculatingpotential and actual evapotranspiration based on the mean soil waterstorage, the mean monthly precipitation, and anempirically derived relation-

ship between mean air temperatureand potential evapo-

transpiration. Buol (1964, p.19) haspublished a map of calculated

actual evapotranspiration forArizona. Figure 16 combines 56

i Baker Ranch V11e 7 Fort Valley Flagstaff Williams 15

13 10 20sh. 13 2 16 _Isograms of calculated actual evapotranspiration for soils with 4 inches available water holding capacity (from Ariz. Ag. Exp. Station Tech. Bull. #162, 1964,p. 19). - Precipitation Map of Arizona (from Ariz. Ag. Exp. Station Bull. #279, 1956, p. 56).

Figure 16. Calculated actual evapotranspiration and precipitation, Coconino County. Thesis area outlined. 57 the Coconino County part of Smith's precipitation map(1956, p.56) and Buol's calculated actual evapotranspiration map. The southern third of the thesis area receives wore than 20 inches of precipitation, the middle third between15 and

20 inches,and the northern third about12 to 15 inches, The thesis area lies between the 16-inch and 13-inch evapotranspiration isograms. The southern third may be assumed to have a calculated actual evapotranspirationof 15 inches, the middle third, 14 inches, and the northernthird, 13 inches. In the absence of appreciable runoff, thesurplus of precipitation over the calculatedactual evapotranspiration should represent the amount ofrecharge.

Meanann. Caic. actual Surplus Precip. Evapotrans.(recharge) Northern third 10 13 0 Middle third 15 14 1 Southern third 20 15 5

The recharge availablefrom the middle third of the

area may beneglected because one inch isprobably within

the margin of error. The present authorcalculated the evapotranspiration

from temperature and precipitationfigures given for Flagstaff, Fort Valley, andWilliams in the report bySmith inches re- (1956). Surpluses were 3½,5-3/4, and

spectively. These figures agreeroughly with those derived 58 from Buol's and Smith'smaps. Calculations from incomplete or short-term records for Baker Ranch published by Colton

(1959) and Valle Airport supplied by P. C.Kangeiser,

State Climatologist (written communication, 1963)gave results which also agree with Buol's and Smith'smaps. If the apparently conservative figure of four inches of annual recharge is applied to the southern third

(100 square miles) of the thesisarea, the estimated annual recharge is 21,000 acre-feet (ac-f t).

A comparison of this recharge rate with the discharge of the major springs north and south of the area should indicate its validity. The thesis area may be considered typical in geology and climate of an extensive region along the Rim which should have similar recharge rates.

The large springs south of the thesis area emerge from the Redwall Limestone in Sycamore Canyon. They have a combined flow of about 4,700 gallons per minute (gpm)

(Feth and Hem, 1963, p.H46) or 7,300 ac-ft/year, about one third the estimated recharge from the thesis area alone.

The combined flow of all the springs west of Fossil Creek

(about 10 miles west of Payson) is 37,500 gpm (Feth and

Hem, 1963, p.H46-47) or 60,000 ac-ft/year. The estimated recharge from the thesis area is one third of this total. If, as is probably the case, the thesis area lies north of the ground water divide, it would discharge to 59 one of two places in the Grand Canyon area. Metzger (1961, p.l3l) gives discharge rates of 66 cubic feet per second

(cfs) at Havasu Springs and 220 cfs at Blue Springs.

These are 50,000 and 170,000 ac-ft/year, respectively.

However, to reach Blue Springs, the water would have to cross a structural high which passes northwestward through the region of Kendrick Mountain (Robinson, 1913, p.33).

These discharges are too small for the size of their drainage areas if the thesis area is typical of the portions near the Mogollon Rim. The estimated recharge rate is too large for even approximate agreement with known discharge. Three possibilities might explain the discrepancy: (1) the discharge takes place at some unknown area; (2) equilibrium is not established and water is entering storage; (3) the basic assumptions on which the estimates were made are not valid. The amount of water unaccounted for is too large to go un- noticed in a dry state like Arizona. Attainment of equilibrium conditions is not proved in the San Francisco

Plateau area, but it seems likely. Thus it appears that the basic assumptions of this method of estimating recharge are in error. These assumptions are: Thornthwaite's empirically derived relation- ship between evapotranspiration and mean monthly temperature is valid and accurate in this environment; runoff is negligible and the surplus is recharged. 60 Hydrologic Properties of Strata

Alluvium and Soil

The generally coarse alluvium is permeable, although small perched water bodiesmay form on lenses of silt and clay. The soil surfaces, especially in the forested areas, are excellent for receiving infiltration.

Volcanic Rocks

The basalt flows are strongly jointed and permeable.

Occasional interbedded soil zones underlie small perched water bodies which locally supply small wells. The cinder deposits forming cones and interbedded with basalt flows are extremely permeable.

Moenkopi Formation

The Moenkopi acts as an aquiclude. Probably some wells obtain water from the basalts overlying the Moenkopi.

Kaibab and Toroweap Formations

The Kaibab Formation is principally brittle dolomitic limestone which is fractured and shows evidence of solution. The Toroweap Formation is similar to the Kaibab except that it is somewhat more sandy. The Kaibab and

Toroweap are above the regional water table and no wells 61 obtain water from them, but they permit water to pass downward.

Coconino Sandstone

The Coconino Sandstone is one of the principal aquifers of the southwestern Colorado Plateaus. In the area along the Mogollon Rim the Coconino is an aquifer where it is below the water table and where the underlying aquiclude is not permeable because of fracturing. Yields from the Coconino are generally low because of the low permeability, but are greater where the formation is fractured.

Supai Formation

The upper portion is commonly sand and resembles the Coconino lithologically and hydrologically. The middle and bottom parts are silty and act as a bottom aqui- dude. Fracturing may cause the silty portions to become more permeable and solose their ability to restrict vertical water movement.

Redwall Limes tone

The Redwall Limestone andunderlying formations have not been tested by wells northof the Mogollon Rim. The high permeability of the Redwall isdemonstrated by the 62 occurrence of the large springs which issue from it in Grand Canyon and Sycamore Canyon and the solution features it commonly exhibits in outcrop. It should produce good yields in fractured areas where it is below the water

table.

Martin Limestone

The Martin Limestone may be hydrologically similar

to the Redwall, and large springs emerge from it southeast

of the thesis area at the base of the Mogollon Rim.

Tonto Group

The Muav Limestone is the source of many springs in

the Grand Canyon. If it extends as far south as the thesis area it should serve as an aquifer withgood permeability. The Bright Angel Shale would probably serve as an aquiclude.

The sandy portions of the Tapeats Sandstone would be a

poor aquifer because of theirgenerally fine grain size, and the upper silty portions would act as an aquiclude.

Ground Water of the Area

Figure 2 shows the five deep wells inthe south of

the area. Well number 1 is structurally high and the

water table is in the upper SupaiFormation. Well number 8

is three miles to the north in approximatelythe same 63 structural position if the samplesare correct (the sudden thickening of the Coconino is unexplained). The water stands almost 400 feet lower, just above theCoconino-Supai contact in this well.

These two wells give the only information available about the water table in thearea. The water table appears to descend northward with a gradient of about 130 feet per mile; the same gradient prevails in the water table north of the groundwater divide in the Flagstaffarea. All other wells are reported dry.

Well number 5 is only l miles southeast of well number 8 and more than 300 feet deeper, but is dry. The probable explanation is that the well lies on line with a fault which is exposed about four miles south. The north end is covered by flows, but it probably continues northward. Fracturing of the bottom aquiclude may have drained the ground water from the upper Supai.

Well number 3 is the deepest well and has the greatest stratigraphic penetration, but is reported dry.

It lies directly on the Bill Williams-Sitgreaves-Kendrick alignment. Probably fractures associated with this major alignment occur in the Supai and serve to drain the overlying formations.

Well number 10 is structurally high and apparently not deep enough to penetrate the water table. 64 In other parts of the region, the location of the water table is unknown. Figure 3 shows the locations and lithologies of the three deep wells northwest of the thesis area. Records at the Museum of Northern Arizona for well number 15

(A(27-l)29) in the northwestern part of the area indicate

2½ gph at the depth of a dark reddish brown siltstone strata which the author believes to be Hermit Shale. There are no water records for the two other northernwells though a local rancher reported all three to be dry holes.

All three are abandoned.

Local Structural Control

The structures which control groundwater movements are the San Franciscoanticline and faulting. As was pointed out in a previous section, the SanFrancisco anti- dine, as expressed at the surface,has dips of at most20.

The effect of slight local changesof thickness will have a large influence on the structure atdepth. Local faults may have the effect onground water which is evident in the Woody MountainWell Field - render-

ing the siltstones permeable andcausing the water to drain

to greater depth. Even if this is not the case,the traces of faults

in the thesis area are subparallel tothe probable dip of 65 the Kaibab Formation. If the Supai has the same dip, the faults do not raise impermeable rocks across the path of groundwater movement to cause local entrapment.

Summary and Conclusions

The evidence from mapping indicates many lines of deep-seated structural weakness, as shown by the alignments of cones. The depth of dry well number 3 suggests that the major trend of the Bill Williams-Sitgreaves-Kendrick alignment has associated fracturing which has drained the

Coconino- Supai aquifer. The evidence at the Woody Mountain well field and at well number 5 in the thesis areaindicates that fractures associated with faulting increase the permeability ofboth the aquifer and the aguiclude. The increased permeability of the aquiclude can permit ground water to passto greater depth. The large amount of recharge from RodgersLake serves to maintain watersupply to the aquifer. Without this concentrated recharge, theaquifer might be dry. Evidence of minor folds and faultswhich might cause small local entrapmentof ground water is difficult to detect in the area mappedbecause of the cover of young volcanic rocks. The orientations of the few structures interpreted as faults are approximatelyparallel to the dip direction away from the San Franciscoanticline, and 66 so would not cause entrapment of ground water - even if the

Supai remains impermeable.

In the lack of this particular combination of conditions, it is very unlikely that large groundwater supplies in the Coconino-Supai aquifer will be found within the area investigated. There is only one small lake, Smoot Lake, in the area, and no faults are known nearby. Formations beneath the Supai have not been tested by wells. Water might be found in the Redwall Limestone if the underlying Martin Limestone and other formations are saturated. A test for water below the Supai would involve drilling a minimum of 3,000 feet. Wells along faults or at intersections of faults would take advantage of fractures and possible solution openings, which arethe principle conduits for ground water in limestonereservoirs.

The springs in the Redwall Formationwhich discharge in Sycamore Canyon have an elevationof 3,750 feet. This is the elevation of the watertable at that point. The water table should rise tothe north, though the gradient is unknown. Drilling in areas removed fromfaults and known alignments, may develop water supplies atdepths and with yields similar to wells number 1 andnumber 8. The large number of alignments and their probableassociated fractures 67 suggests that in most of the area the Coconino-Supai aquifer is drained or does not store water.

Recommendations

In view of the depth to water below the Supai Forma- tion it is recommended that the possibilities of developing surface catchment basins be investigated as an alternative to drilling0

A survey of the drainage patterns of the area will indicate those drainages which appear to have the most runoff. Gauging stations should be established at suitable points in the selected drainages and records kept for a period of years to establish the amount of runoff available and the variations. If records show suitable runoff from a drainage system, storage in conditions with minimum evaporation or leakage is necessary. Such storage conditions could be developed by constructing a suitable dam and spillway, lining the reservoir with c1ay or bentonite, and filling the reservoir with cinders. Cinders exposed in most of the cones have little clay or ash beneath the surface and probably have a porosity of at least 50 percent. No data are available for specific retention of these cinders. It probably is small, and after the first wetting will be of minor importance in water losses. 68 The disadvantages of such a storage facility will be: added cost of construction; cost of maintenance of a surface with high infiltration capacity; cost of plant control to prevent transpiration; and loss of about 50 percent of the reservoir's capacity. The advantage, of course, will be reduced water losses. The potential evaporation from the water surface of an open reservoir is high. The protection afforded by the cinders should reduce evaporation losses to almost nothing. If study shows surface development to be impracti- cable, the exploration for water supplies from the Redwall

Limestone should be undertaken. APPENDIX

Abbreviations Used in Descriptions of Drill Cuttings

ABM Arizona Bureau of Mines ovg overgrowth ang angular Pc Coconino sandstone anh anhedral. Ph Hermit Shale bik black Pk Kaibab Formation bot bottom Pt Toroweap Formation brn brown I'Ps Supai Formation

c coarse q quartz

cal calcareous QTv volcanic rocks

cern cement md rounded subangul.ar cli chert s-ang subbedral dlc dark sb-h

dol dolomitic sd(y) sand(y)

euh euhedral sil silica slt(ly) slight(ly) f fine subrounded gm grain s-md sandstone gry gray SS

lm limonite StS siltstone silt(y) LS limestone st(y) Moenkopi Formation it light Trm very in medium, moderately v variable MNA Museum of Northern var Arizona

69 70 Abbreviations Used in Descriptions of Drill Cuttings (Continued)

MudSmuds tone w with or orange wht white xl crystal 71 Well #1 Navajo OrdnanceDepot #1 Location: A(21-5)llccb Elevation: 7,050 feet Samples from MNA, Flagstaff.

Forma- Depth tion (in feet)

QTv 0-105 basalt

Trm(?) 105-125 StS, f st and clay; red-brn.

Pk 125-210 LS, vf, ch, dol; gry-tan to yel-tan.

210-295 LS, vf, ch, dol; tan-gry. sdy top 20'.

295-310 Cal SS, vf to m, mostly f; tan gry.

310-390 ch LS, vf, m dol; tan-gry. gry to brn ch. no ch top 20'.

390-437 SS, vf to m, mostly f; cal cern; buff.

Pt 437-555 LS sltly dol, vf; tan-brn. v ch 440-55', 45-79'. sty bot 30'. 555-601 SS, mostly f; v cal; ittan to itgry. top5'is StS. 601-665 SS m to vf,sty.si].and cal cern; it pink. f and vf gmhave q ovg.

665-760 SS, mostlyf, some m and c; tanandit tan, somebuff. StS,red-bmn in top 30'.

760-780 SS and StS. SS, f; it tan (top) to dk red (bot). StS, dk red.

Pc 780-795 SS, mostly m; tan and red-tan; frost. larger gm have the color.

795-910 SS, vf to in; mostly tan, but yei-tan, gry, pink. vf and f gm often ovg,ingm often frost. im spots bot 60'. larger gm have the color. 72 Well #1 (Continued)

Pc 910-1100 SS, f to m, mostly f (top half seem coarser than bot); yel-tan. similar ovg and frost to above, larger gm have the color.

1100-1130 SS, vf to m, mostly yE and f, pink-buff. some m gmfrost, some glassy. less ovg, more color on vf and f gm.

PPs 1130-1155 SS, vf to f; it red-tan to yel-tan. some m toward bot.

1155- 1240 SS and StS. SS, vf to f; it yel-tan to red-tan. StS, m red to dk red-brn, minor amounts,

1240-1290 SS, vf to f, few chips of m; yel-tan, red-tan, dk bmn.

1290-1430 SS and StS. SS, vf to f, little m; tan to red-tan. StS, bmn, minor amount.

1430 -1520 sty SS and StS. SS, vf to f, m 1450-65'; bmn and red-bru. StS, brn; about half.

1520- 1625 sty SS, mostly f; it red-brn. v sty at bot.

1625-1654 sty SS and StS. SS, vf to 1, few m; or- tan to it red-tan. StS, brn, about a fourth.

1654 Total Depth. Static level 1 273. Yields "about lo gpm". (U.S.G.S. Tucson files). 73 Well #3 El PasoNatural Gas Co., Williams #1 Location: A(22-3) lOabd Elevation: 6,957 feet No samples available. Log from El Paso Natural Gas Co.(McCarthy, personal communication, 1965) Forina- Depth tion (in feet)

P1< 455

Pc 1055

2705 Total Depth. Dry hole. Plugged and abandoned.

Log from MNA files

QTv 0-380 Location given as A(22-2)32 P1< 380-850 named E.P.N.C. #1 Samples on file at MNA Pt 850-1040 do not agree with this log at all. Pc 1040-1380

IPPs 1380-2340

2570 Total Depth. Boundaries determined by E. D. McKee in June,1953

Log from U.S. Geological Survey, Tucson Office:

0-3 Top soil

3-20 Malapais

20-55 Cinder

55-97 Broken malapais

97-114 Coarse sand

114-135 Sand and gravel 74 Well #3 (Continued)

135-150 Malapais boulders

150- 260 Sand

260-380 Malapai a

380-440 Limes tone

440-445 Kaibab Sand

445-935 Limes tone

935-940 Sand

940-1055 Limes tone

1055-1059 Coconino sand

1059-1115 Limes tone-sand

1115- 1260 Red sand

1260- 129 2 Limes tone

1292-2507 Sand

Well #5 El Paso Natural Gas Co., Williams #4 Location: A(22-5)36bd Elevation: 7,250 feet Samples from ABM, Tucson

Forma- Depth tion (in feet)

QTv 0-620 basalt to 490', rhyolite and agglomerate to 620'.

Pk 620-660 LS, vf, sitly dol; yel-tan. ch, tan w dk brn streaks, top 10'.

660- 720 sty SS, m to at, cal;red-purple. q ad gm are md and frost. 75 Well #5 (Continued)

720-810 LS, f, dol var sit to m; yei-tan; vuggy in parts. ch 780-810'.

810-860 v cal sty SS. f to st; yel-gry. it gry ch 830-40', 850-60'.

860-870 chy LS, f; tan, it gry ch.

870-1060 v cal sty SS, f to at, yel-gry. ch, tan, 870-80', 950-57', 990-1010'. 1010-20' all ch.

1060-1070v chy LS, dense; gry. ch, tan-gry.

Pt 1070-1140v cal sty SS, f to st, yel-gry. scattered wht ch.

1140-1150 StS, cal; it brn. some md f sd.

1150-1210v sdy LS, f, yel-gry. ad, f to m, md and frost.

1210-1290 sdy StS, v cal; m pink and tan-gry. ad, vf to f.

Pc 1290-1360 SS, f to vf, some ovg; buff.

1360-1450SS, f to vf, some ovg; it buff.

1450-1520 SS, m to vf. m and f 30%, md, frost.

1520-1750 SS, f to vf, some ovg; it buff.

PPs 1750-1780 SS, vf to at, cal; dk red-brn.

1780-1800 SS, f to vf, some ovg; it buff.

1800-2200No samples

2200 Total Depth. Dry hole, plugged and abandoned. (McCarthy, personal conmiunication, 1965). 76 Well #6 Unnamed Location: A(22-5)23 Elevation: 7,350 feet

Samples from MNA, Flagstaff (460'- 550' only). Forma- Depth don (in feet)

QTv 460-490 basalt,

490-500 StS, it red-brn.

Pk 500-550 LS, vf, it or-pink.

550 Total Depth.

Well #7 El Paso Natural Gas Co., Williams #2 Location: A(22-5)26abc Elevation: 7,300 feet

No samples available. Log from El Paso Natural Gas Co. No tops given.

Depth (in feet) 0-6 Top soil

6-417 Volcanics 417-510 red SS

510-560 gry LS 560-630 sdy LS 630-670 yel LS 670-840 gry LS 840 Total Depth. Dry hole, plugged and abandoned. (McCarthy, personal coimnunication, 1965). 77 Well #8 El Paso Natural Gas Co., Williams #5 Location:A(22-5)26adc Elevation:7,232 feet Samples from MNA, Flagstaff, and ABM, Tucson. Forum- Depth t ion (in feet) 0-460 No samples Pk 460-520 LS, vf, dol; v it or-tan, sltly sdy, vf. 520- 550 sty SS, f to vf, cal and sil cern; it or-pink. 550-620 LS, vf, dol; it or-pink to buff. 620-630 sty SS, f to vf, cal; buff,large q xis. Pt 630-670 LS, f to in, dol; it or-pink to buff; few vugs.little ch. 670- 770 StS and little LS.StS, m red-brn. LS, f, buff. 770-905 sty SS, little LS and ch.StS, cal; red-or.LS, tan. Pc 905-1400SS, vf to f, little in, sitly cal near top, md,inred bmn to it red. 1400-1900SS, vf to f, md; tan to it or-pink. PPs 1900-2000SS, vf to f, md, friable, cal; dull or. 2000-2100SS, vf to f, md, friable; dull or. 2100-2130SS, vf to f, s-ang; tan to v it or. 2130-2140sdy StS, brn.sd, vf; dk or. 2140-2210SS, vf to f, cal, md; or. 2210-2230SS, vf to in, cal, md; tan. 78 Well #8 (Continued)

PPs 2230-2350 SS, vf to f, some in, sitly cal, md to ang; it brn and it red-brn.

2350 Total Depth Water at 2027 Static level 1900 Pumped 25 gpm Plugged and abandoned (McCarthy, personal communication, 1965).

Well #9 El Paso Natural Gas Co., Williams #6 Location: A(22-5) 26adc Elevation: 7,230 feet

Only samples available are contradictory and valueless.

Log from El Paso Natural Gas Co.(McCarthy, personal communication, 1965) Forma- Depth tion (in feet)

Pk 502

Pc 930

EPPs 1920

2350 Total Depth. Water at: 2010 2100 2142 Static level 1900 Pumped 25 gpm Plugged and abandoned. 79 Well #10 Flagstaff Well #2 Location: A(22-6)26a Elevation: 7,335 feet Samples from MNA, Flagstaff

Forma- Depth tion (in feet)

QTv 0-290 basalt w interbedded soil at 100', 140- 165', 190-210', 217-290'.

Trm 290-302 sdy StS, cal cern; it brn. sd, vf.

302-480 StS, cal cern; red-brn.

Pk 480-495 LS, vf; it red.

495-510 LS, vf; it red, sty.

510-573 LS, vf; gry red, a cal xl. sd grns, rare, md, vf.

573-680 LS, vf, sitly dol; it red. bot 20' it or-pink, larger chips.

Pt 680-740 SS, f to vf, cal cern; it red-or.

740-770 cal StS, rn red-brn.

770-910 ch and sdy LS1 vf; it red-or to it red- bmn, top 40 ch, rest sdy.

910-920 cal StS, it gry-red. little ch.

920-930 LS, vf, in red-bmn. little vf sd and St.

930-940 SS, f to vf; gry-pink.

940-990 sdy LS and cal SS. SS, f to st, cal; it gry-red. LS, sdy to sty in red-or.

Pc 990-1140 SS, f to vf, (in to f 1110-20'), s-md to s-ang, anh to sb-h, sil and little cal cern; gry-or to it or-brn.

1140-1370 SS, f to vf, texture like above; gry-or to it or-bmn, urn spots in ?ianes or scattered except 1170-1210 , 1250-1320'. 80 Well #10 (Continued)

Pc 1370-1490 SS, f to st, texture like above;gry-or to it orsbrn. in spots like above bot 60'.

PPs 1490-1520 sdy StS; sd, vf; red-or. cal cern.

1520-1530 SS, like 1370-1490' but red-or, more cal.

1530-1542 sty SS, vf to st, sit cal cern; rn red-or.

1542 Total Depth.

Driller's log at MNA, Flagstaff, notes 20 gprn water in QTv, lost in crevasses in Pk; "little" water in top StS of Pt, lost in Pc.

Well #12 Unnamed Location: A(25-5)2lc Elevation: 7,350feet

Samples from MNA,Flagstaff.

Forma- Depth tion (in feet)

QTv 0-310 basalt

Pk 310-320 LS, vf; it gry-or.

320 Total Depth. Reported dry (MNA, Flagstaff, files). 81 Well #13 TWA #2 (Valle) Location: A(26-2)10 Elevation: 6,050feet

Samples from MNA,Flagstaff Forma- Depth don (in feet)

Pk 0-140 LS, vf, var dol; wht to or-pink to it brn. ch, wht, 20-40', 80-100', 120- 140'.

140-160 dol LS, vf, v dol; wht. little ch.

160-220 LS, vf, v dol; it or-pink, much gry ch.

220- 240 ch dol LS, vf, v dol, v ch; it or-pink.

240-260 LS, vf, dol,inor-pink, little sd, in, md, frost. ch.

260-300 cal SS, f to vf, s-md, s-ang; it or- pink.

300-360 LS, vf, dol; gry-pink. son ch, gry.

Pt 360-420 cal SS, f to vf, it pink to it or-pink.

420-440 LS, vf, dol;inor-pink, little vf sd. little ch.

440-580 StS, cal, it red-brn. little sd, vf throughout. quite sdy 440-60', 500- 520'.

580-680 LS, vf,indol; it toinred-bmn. little ad, vf 640-660'.

680-700 SS vf, some f, sitly cal.

Pc 700-1440 SS, vf to f scattered m, pure q, usually v alt cal cern, large gmns md andanh, small grns ovg and sb-h; color var, mostlyinor-pink, also gry-or, v it or, it brn.

Ph (?) 1440-1460 StS, vf, in cal; gry-red. 82 Well #13 (Continued)

PPs 1460-1680 StS, sdy StS, sty SS. changes lithology every 20 to 40'. Generally cal. sd £ and mostly vf. colors mostly red-brn and red-or.

1680-1740 SS, f, mostly vf, v cal; it red-brn.

1740-1817 StS, sdy StS, sty SS. like 1460-1680. 1817 Total Depth. Reported dry(local rancher). Abandoned.

Well #14 Vaile Airport (TWA) Location: A(26-2)26 Elevation: 6,000 feet Samples from NNA, Flagstaff.

Forma- Depth tion (in feet)

0-100 Missing.

Plc 100-120 LS, vf, sitly dol; lt or-pink.

120-300 LS, vf, little wht ch, dol; it pink to it brn. v ch 240-260'.

300-320 LS, vf, dol; m or-pink.

3 20-340 LS, vf; lt or-gry. ch, lt gry.

3 40-420 LS, vf, dol; v it red to pink-brn.

Pt 420-500 SS vf, few £ and in, some st, cal cern, it red brn.

500-640 LS, vf, doi 540-600',it yel-brn çtop) to it or-pink (bot) sdy bot 20

640- 720 SS, vf and st, few fand m, cal cern; it or-pink. 83 Well #14 (Continued)

Pc 720-940 SS f to vf, some in, s-md and sb-h, littlecal, au cern and ovg; it bmn to inred-or.

940-1140 SS, similar to above, but noin.

PPs 1140-1280 StS, little vf ad, sitly cal;inred-bmn.

1280-1300 SS, f to st, sitly cal;inor-pink.

1300-1320 StS, little vf sd, sitly cal;inred-bmn.

1320 Total Depth. Reported dry (local rancher).Abandoned.

Well #15 Smith #3 Location: A(27-1)29 Elevation: 5,750 feet

Samples from MNA, Flagstaff

Fortna- Depth tion (in feet)

Pk 10-15 LS, vf, dol; gry or. some ch.

15-50 sdy LS, vf, dol; v it or. ad, vf to f.

50-80 LS, vf, dol; gry-or.

80-95 LS, vf, dol; sitly sty; it yel-brn.

95-145 LS, vf, v dol; v it gry. ch to 132', wht.

145- 212 LS, vf, sitly ch;inor-pink. doi bot 8'.

212-255 SS and LS. SS, f and vf, cal cern; v it or. LS, vf, dol; it gry.

255- 297 LS, vf, doi, v ch; it gry.

297-330 SS, f to vf, cal cern; v it or.

330-368 LS, vf, ch;inor-pink. 84 Well #15 (Continued)

Pt 368-414 SS,into vf, cal; gry-or.

414-510 SS, vf to f (to in below 470'), calcern; it red-brn.

510-625 LS, vf, dol, it brn to or-pink. SS chips 547-560'. MudS chips 590-600'.

625-640 ss,into vf, sitly cal; gry or.

Pc 640-1276 SS, f to vf, v sit cal cemj or-pinkto or-red. urn spots 694-795

Ph 1276-1282 StS, v little vf Sd; red-brn.

IPPs 1282-1355 sdy StS, sitly toincal; it red and red- brn. some SS, vf.

1355-1432 SS, f to vf,into non-cal;inbrn toinor- pink. StS, 1367-1384', non-cal;inbrn.

1432-1460 sty SS, vf; it brn toinor-pink. 1460 Total Depth. Reported dry (local rancher). MNA files report 2½gph seep at 1279 (Ph). Abandoned. REFERENCES CITED

Akers, J, P., 1962, Relation of faulting to the occurrence of ground water in the Flagstaff area, Arizona: U.S. Gaol. Survey Prof. Paper 450-B, p. 399-B102. Cooley,M. E.,and Dennis, P. E., 1964, Synopsis of ground-water conditions on the San Francisco Plateau near Flagstaff, Arizona: U.S. Geol. Survey open-file report.

Baars, D. L., 1962, Permian system of the Colorado Plateau: Am. Assoc. Petroleum Geologists Bull., v. 46, p. 149- 218. Babbitt, Bruce E., 1964, A Palcomagnetic chronology of the San Francisco volcanic fields: Contributions to the geology of northern Arizona, Major Brady Memorial, Museum of No. Ariz. Bull, no. 40, p. 11-14.

Babenroth, D. L., and Strahier, A. N., 1945, Geomorphology and structure of the East Kaibab monocline, Arizona and Utah: Geol. Soc. America Bull., v. 56, p. 107-150. Brady, L. F., 1962, Note on the "Alpha" Member of the Kaibab Formation: New Mexico Geol. Soc., in cooperation with Ariz. Geol. Soc., Guidebook to the Mogollon Rim region, east central Arizona, p. 92. Breed, W. J., 1964, Morphology and lineation of cinder cones in the San Francisco volcanic field: Contributions to the geology of northern Arizona, Major BradyMemorial, Museum of No. Ariz. Bull., no. 40, p. 65-71.

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alignment fault

"belt" of Stage II "belt" of and lila Stage Ilib

Figure 4. Principal alignments of cinder cones. Overlay for Figures 5, 6, 7, 8. Gilman, C. R., 1965, Geology and geohydrology of the Sitgreaves Mountain area, Coconino County, Arizona. EXPLAN AT)O N I (- 26 \ y_---_ \ N. SEDIMENTARY ROCKS VOLCANIC ROCKS N >'<

Stage LII basalt flowa

Alluvium > - < cc- - V - c Stage U basalt flows

Moenkopi Formation Felsic and intermediate volcanic rocks I. 25 Kaibab Formation Stage I basalt floovs (Includes Toroweap and C000nino N. Formations undifferentiated at Squaw Mountain)

SYMBOLS / -S Arrow shows generalized lava movement Ephemeral stream from source, where determinable Paved road Contact (dashed where approximateor inferred) Dirt or gravel road N Inferred fault

Basalt veet (dome or cinder cone) and stage

,is Ii- -w -' Ii -z )- 1 -'-g -

24 N. # /1=,,' P 4 S I II S - '...'-w. S

- I / 4 23 N.

.To Willows 5- C Base from U. S. Geological Survey topographic sheets, Williams, Valle, Ebert Mountain, and Flagstaff quadrangles R 2 E. FL 3 E. R. 4 E. R. 5 E. Geology by Chandler ft. Oilman. t965

0 2 3 4 5 9Miles

I L I I Contour interval 200 feet

FIGURE 17.--GEOLOGIC MAP OF THESITGREAVES MOUNTAIN AREA, 0000NINO COUNTY, ARIZONA.