Geology of the Prescott and 

Paulden Quadrangles, Arizona 

By 1\IIEDORA H. KRIEGER 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 467 

A detailed discussion of the stratigraphy 

and structure and a brief description of 

the geography, physiography, and mineral 

and water resources 

BnN! • . r: -~; .. ,JcAL 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1965 

[LITL!G 

CE.NTRAL kEGION 
UNITED STATES DEPARTMENT OF THE INTERIOR 

STEWART L. UDALL, Secretary 

GEOLOGICAL SURVEY 

Thomas B. Nolan, Director 

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

Washington, D.C. 20402 
CONTENTS 

Page 

Abstract___________________________________________ 1 

Introduction____________________________ ___________ 3 

Acknowledgments_________________________ _ _ _ _ _ _ 3 

Previouswork__________________________________ 3 

Economic and physical geography_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 4 

General geology _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 7 

Older Precambrian rocks_________________________ 7 

Yavapai Series-Alder Group________________ 7 

Texas Gulch Formation ___ -------------- 11 

Indian Hills Volcanics______________ _____ 14 

Spud Mountain Volcanics________________ 15 

Chaparral Volcanics_____________ ________ 16 

Green Gulch Volcanics_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 17 

Unnamed volcanic rocks of the Alder(?) 

Group______________ __ _______________ 18 

Mazatzal Quartzite_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 20 

Intrusive rocks_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 28 

Gabbro and related rocks__ ______________ 29 

Government Canyon Granodiorite________ 34 

Prescott Granodiorite_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 35 

Alaskite and related rocks_______________ 40 

Coarse-grained granite____________ _ _ _ _ _ _ _ 44 

Dells Granite___________________________ 44 

Fine-grained granite_____________________ 47 

Other intrusive rocks______ ______________ 47 

Quartz porphyry____ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 4 7 

Rhyolite dikes______________________ 48 

Veins, silicified zones, and alteration 

General geology-Continued Page 

Cenozoic rocks-Continued 

Upper Tertiary(?) rocks~Continued 

Thickness _________ ----- ___ __ ------_- __ - 74 

Age___________________________________ 75 

Stratigraphic relations and correlations____ 81 

Quaternary deposits ___ ----------_----------- 85 

Pleistocene gravels ___________ - ----- _- __ - 85 

Recent alluvium________________________ 86 

Age___________________________________ 87 

Structure___ ___________________________________ 87 

Structure of older Precambrian rocks ____ -- ___ - 87 

Structure of the Alder Group ___ ------- __ - 88 

Structure east of the Chaparral zone__ 88 

Stru'cture west of the Chaparral zone__ 89 

Structure in the Chaparral zone-the 

Chaparral Volcanics and Chaparral 

and Spud faults ______________ -_-- 90 

Structure of the Mazatzal Quartzite_______ 91 

Structure in the intrusive rocks___________ 92 

Structure of Paleozoic and Cenozoic rocks______ 94 

Older structure ______________ ------_- __ - 94 

Monoclines________________________ 94 

Faults ___________________ --- ___ -_-- 96 

Joints_____________________________ 97 

Younger structure ___________ ----------- 97 

Structure formed by intrusion of andesite plugs _____________ - ______ ---- 97 

Faults ______________ - - ___ ---------- 98 

zones____________________________ 48 

Conclu~ons_ __________________________ 49 

Age_______________________________ 49 

Relations ____________ -_____________ 49 

Unconformity at the base of the Paleozoic rocks ____ 50 

Paleozoic sedimentary rocks __ ~______ ____________ 50 

General features _______________________ _____ 50 

Tapeats Sandstone______________________ __ __ 51 

Martin Limestone_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 57 

Red wall Limestone____________ ______________ 60 

Supai Formation____________________________ 61 

Coconino Sandstone_________________________ 64 

Unconformity at the base of the Cenozoic rocks____ 64 

Cenozoic rocks_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 65 

Andesite dikes______________________________ 65 

Upper Tertiary(?) rocks_______ ______________ 65 

Distribution________ ____________________ 66 

Age of the structures______ ______________ 98 

Monoclines _____________ --- ---- ---- 98 

FauUs_____________________________ 99 

Conclusions _____________ -----_----- 99 

Physiography_ _________________________________ 99 

General features __________________ ---------- 99 

Mountains ______________________ --- ____ ---- 100 

Pediments_____________ _________ ___________ 100 

Drainage_______________ ______________ _____ 102 

Chino-Lonesome Valley__________________ 102 

Northeast of Chino-Lonesome Valley__ _ _ _ _ 102 

Economic geology __________________ ________________ - 104 

Ore deposits ___________________________________ - 104 

History____ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 104 

Mineralogy________________________________ 104 

Hypogene minerals _____________________ - 104 

Ore minerals_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 104 

Basalt_____________ ________________ 66 

Andesite ______ ~ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 66 

Sedimentary rocks__________________ 66 

Gangue minerals ___________ ________ - 105 

Supergene ore minerals__________________ 106 

General characteristics______________________ 106 

Litho logy__ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 6 7 

Basalt_________________ _______ _____ 6 7 

Andesite___ _______________ _________ 70 

Massive sulfide deposits __________________ --- 106 

Fissure-vein deposits ____________ __ -----_---- 107 

Post-Paleozoic mineralization_________________ 107 

Sedimentary rocks_ __________ _______ 71 Placer gold deposits________ _________________ 109 

III 
IV CONTENDS 

Economic geology-Continued Page Economic geology-Continued Page 

Ore deposits-Continued Water resources of tne Prescott area-Continued 

Descriptions of individual deposits________ ____ 109 Occurrence of ground water__________________ 118 

Iron King mine____ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 1 09 Precambrian rocks______________________ 118 

Fissure veins in the southern part of the Upper Tertiary(?) rocks_________________ 118 

Prescott quadrangle___________________ 110 Quaternary deposits ____________ -----____ 119 

Fissure veins in Mineral Point district and Movement of ground water__________________ 119 

adjacent areas___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 111 Source of ground water______________________ 119 

Lynx Creek placer district_____________ __ 112 Water-bearing properties of valley fill_________ 120 

History of operations and production__ 112 

Geology and occurrence of the gold___ 113 

Other placer deposits____________________ 114 

Nonmetallic deposits____________________________ 114 

Building stone____ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 114 

Limestone__ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 114 

Quality of water____________________________ 120 

Collection and analyses of samples________ 120 

Chemical character of the water__________ 120 

Surface water______ ________________ 120 

Ground water______________________ 121 

Water resources of the Prescott area______________ 115 Conclusions________________________________ 122 

History of use of ground and surface water_____ 115 References cited____________________________________ 122 

Ground-water resources_____________________ 118 Index-----------------~--------------------------- 125 

ILLUSTRATIONS 

[Plates are in pocket] 

PLATE 1. Geologic map and sections of the Prescott quadrangle, Arizona. 

2. Geologic map and sections of the Paulden quadrangle, Arizona. 

3. Map of Chino-Lomesome Valley and surrounding areas, Arizona, showing location of wells, springs, and geologic 

sections. 

4. Geologic map and sections showing distribution and relations of upper Tertiary and lower Quaternary(?) volcanic 

and sedimentary rocks in the Prescott-Paulden-Jerome-Clarkdale area, Arizona .. 

5. Structure-contour map on base of the Red wall Limestone, Paulden, Clarkdale, and Mingus Mountain quadrangles, 

Arizona. 

Page 

FIGURE 1. Index map of the study area---------------------- ------------------- --------------------------------- 5 

2. Photograph showing a view to the east-northeast along the Verde River_______________ _____________________ 6 

3. Generalized stratigraphic section, Prescott-Paulden area _________________________ - ------------------------ 8 

4-5. Maps showing: 

4. Distribution of conglomerate in the Texas Gulch Formation, Prescott quadrangle ___ - __ -- _--- _-------- 13 

5. Location of outcrops of Mazatzal Quartzite------------------------------------------------------- 21 

6. Photograph showing the lower conglomerate in the Mazatzal Quartzite _______________ ---------------------- 25 

7. Variation diagrams of quartz-bearing intrusive rocks and gabbro____________________________ _______________ 32 

8. Map showing the distribution of Government Canyon Granodiorite _________ -_----------------------------- 34 

9. Diagram showing modes and norms of Government Canyon Granodiorite _______ ----_----------------------- 35 

10. Map showing the distribution of Prescott Granodiorite--------------------------------------------------- 36 

11. Diagrams showing modes and norms of the Prescott Granodiorite ______________ ---------------------------- 38 

12. Map showing the distribution of granitic rocks______ ____________________________________________________ 41 

13. Diagrams showing the modes and norms of granitic rocks_________________________________________________ 43 

14. Aerial photograph of Granite Dells and Glassford HilL___________________________________________________ 45 

15. Photograph showing the checkerboard appearance formed in Dells Granite ____ ---------- ------------------- 46 

16. Map showing the approximate distribution of Cambrian formations ______________ -------- ------------- ----- 54 

17. Fence diagram of Precambrian and lower Paleozoic formations in the Paulden quadrangle_- -- ------------- --- 55 

18-19. Photographs showing: _ 

18. The conglomerate at the top of the Tapeats Sandstone____________________________________________ 56 

19. Andesite plug or dome remnants _______________________________________ __________ ,______________ 66 

20. Structure-contour map of the top of buried basalt in Chino artesian basin _________ - __ ---------------------- 69 

21. Photograph showing volcanic and sedimentary rocks of late Tertiary(?) age near Granite Creek_-------------- 72 

22-24. Maps showing: 

22. Probable configuration of the Chino-Lonesome basin________ ______________________________________ 74 

23. Approximate minimum thickness of volcanic and sedimentary rocks of late Tertiary(?) age_----------- 75 

24. Structural contour of the base of basalt flows of late Tertiary(?) age north of Prescott-_-------------- 84 

25. Photograph showing Recent alluvium in a channel cut into fine-grained sedimentary rocks of late Tertiary(?) age_ 87 
CONTENTS v 

Page 

FIGURE 26. Contour diagram of joints in the Dells Granite-------------------------------------------------------- 93 

27. Diagram showing variations in monoclines____________________________________________________________ 94 

28. Photograph showing the pediment east of Glassford Hill________________________________________________ 100 

29-31. Maps showing: 

29. Distributibn of pediment remnants in Chino-Lonesome Valley___________________________________ 101 

30. Drainage pattern in Lonesome, Chino, and Williamson Vaileys_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 103 

31. Approximate thickness of Paleozoic and Cenozoic rocks, Paulden quadrangle_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 108 

TABLES 

Page 

TABLE 1. Location of Indian ruins and pictographs in the Prescott-Paulden area______________________________________ 4 

2. Temperature, humidity, and precipitation, Prescott area___________________________________________________ 6 

3. Mineralogy of argillite from the Mazatzal Quartzite, Paulden quadrangle____________________________________ 26 

4. Chemical analysis of argillite from the Mazatzal Quartzite, Paulden quadrangle_______________________________ 26 

5. Semiquantitative analysis for minor elements in argillite from the Mazatzal Quartzite, Paulden quadrangle_______ 26 

6. Alkali ratio in argillite from the Mazatzal Quartzite, Paulden quadrangle ________________________________ ~____ 27 

7. Modn.l composition of quartzose intrusive rocks, Prescott-Paulden-Jerome area_______________________________ 29 

8. Chemical analyses of quartzose intrusive rocks and gabbro, Prescott-Jerome area_____________________________ 30 

9. Semiquantitative analyses for minor elements in quartzose intrusive rocks, Prescott-Jerome area________________ 30 

10. Normative composition of quartzose intrusive rocks and gabbro, Prescott-Jerome area________________ _________ 31 

11. Thickness of Paleozoic formations in north-central Arizona_________________________________________________ 51 

12. Well-log data in Chino-Lonesome Valley_________________________________________________________________ 76 

13. Diatoms from fossiliferous limestone of late Tertiary(?) age_________________________________________________ 81 

14. Value of gold, silver, and copper recovered from the Mineral Point district, 1932-57_____ ______________________ 112 

15. Value of gold and silver production of the Lynx Creek Placers, 1914-51-------------------------------------- 113 

16. Recorded production of placer gold from Granite Creek, 1931-57------------------------------------------- 114 

17. Record of wells and springs, Prescott area___________________ __ __________________________________________ 116 

18. Analyses of water from wells and springs and of surface water, Prescott area__________________________________ 121 

GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

By MEDORA H .. KRIEGER 

ABSTRACT 

The Prescott and Paulden 15-minute quadrangles in northcentral Arizona were mapped as pal'lt of a program to determine 

the regional setting of the massive sulfide deposits at Jerome 

and Humboldt. The structure and stratigraphy of the older 

Precam.brian, Paleozoic, and Cenozoic rocks were studied, and 

data on the minel'ial and water resources of the area were 

collecoted. The approximate thickness of the Paleozoic and 

Cenozoic cover above the Precambrian rocks and the probable 

extent of the Precambrian Mazatzal Quartzite beneath this cover 

were determined. Both are import'ant economically, as known 

ore deposits of the area are Precambrian in age, but the Mazatzal Qual'itzite is not mineralized. 

The older Precambrian consists of volcanic rocks of the Alder 

Group, the Mazatzal Quartzite, and intrusive rocks that range 

from gabbro to granite. The volcanic and intrusive rocks are 

extensively exposed along the southern border and in the eastcentral pal'lt of the area. The Mazatzal Qu'artzite crops out in 

a few places in the northern half. 

The Alder Group is part of the Yavapai Series. It consists 

largely of basaltic, andesitic, and rhyolitic flows •and tuffaceous 

rocks. The group has been separated into five named formations and into isolated masses of unnamed basaltic flows and 

tuffaceous rocks, probably of the Alder Group. The n•amed 

formations are (1) the Texas Gulch Formation, composed 

largely of rhyolitic tuff, ( 2) the Indian Hills Volcanics, composed largely of rhyolitic and basaltic or andesitic flows, ( 3) 

the Spud Mountain Volcanics, composed of andesitic breccia and 

tuff, ( 4) the Ch•aparral Volcanics, composed of rhyolitic and 

·andesttic tuffs, and ( 5) the Green Gulch Volcanics, composed 

of tuffaceous rocks and basaltic flows. The first · three are arranged in probable order of decreasing age. The stratigraphic 

position of the other formations is unknown. Original textures 

and structural fe•atures have been preserved in places. .These 

include ( 1) pillow and flow struC'tures, amygdules, vesicles, and 

phenocrysts in the flows, (2) crystal, lithic, and vitric fragments, 

( 3) relict bedding, and ( 4) abrupt changes in composition across 

the strike in tuffaceous rocks. Textures and structural features indicating original form were lacking or l'a'ter destroyed 

by deformation or metamorphism in some rocks, bu't these rocks 

can in places be traced along the strike into rocks that contain 

diagnostic features. As the bedded deposits contain no limestone or sandstone and very little slate, they are probably 

largely volcanic in origin. The formations have been metamorphosed largely to the green schist facies but locally to a 

higher grade of metamorphism. The thicknesses of individual 

formations are not known, but the total thickness of the group 

is probably at least 20,000 feet. 

·The Mazatzal Quartzite consists of about 4,000 feet of quartzite, conglomerate, and very little argillite. l't is in fault contact with the Alder Group, and neither the top nor the bottom 

is exposed. In central Arizona the quartzite is considered older 

Precambrian in age because it is older than the deformation 

and igneous intrusions that separate older from younger Precambrian rocks in that area. In the Prescott-Paulden area the 

quartzite seems younger than the intrusive rocks and the major 

deformation that affected both the Alder Group and the intrusive rocks. The grade of metamorphism is very low; the 

rocks are not foliated, and the argillite is composed principally 

of (1) quartz •and pyrophyllite, (2) kaolinite, or (3) quartz and 

mixed-layered mica-montmorillonite. No quartz veins or 

granite dikes cut the formation, and the conglomeratic portion 

contains 'abundant pebbles and cobbles of vein quartz that must 

have come from a granitic terrane. 

The intrusive rocks, part of what has been called the Bradshaw Granite, include gabbro, Government Canyon Granodiorite, Prescott Granodiorite, alaskite, and Dells Gl'ianite, listed 

in probable decreasing order of age. The relations are obscure 

bee a use (1) mafic intrusions include lithologically inseparable 

gabbro and diabase, some of which is older and some younger 

th'an the quartzose intrusive rocks, (2) most of the intrusions 

have been cut by dikes of granodioritic to apli'tic composition 

whose correlations with a certain intrusive body is uncertain, 

( 3) many contacts are mechanical owing to intense distributive shear, and ( 4) the various masses mapped as Prescott 

Granodiorite m1ay not be consanguineous, although their modal, 

chemical, and normative compositions are so similar as to suggest this conclusion. All the intrusive rocks probably belong 

to the Precambrian. A Precambrian age is assumed for those 

that are not overlain by Paleozoic rocks because of (1) similarity to intrusive rocks of known Precambrian age, (2) the 

ill'tense deformation they have undergone, and (3) the leadalpha determination of Precambrian age of zircon in one of the 

relatively urideformed granodiorites. 

The Paleozoic rocks, which are separated from the Precambrian rocks by a m•ajor unconformity, are the Tapeats Sandstone, Martin and Redwall Limestones, Supai Formation, and 

Coconino Sandstone. The basal Paleozoic sandstone has, in 

the past, been considered either Cambrian or Devonian in age. 

Although basal sandstone of Devonian age occurs locally, it 

is not the same as an older sandstone that, on the basis of present evidence, is the Tapeats of Cambrian age. The Tapeats is 

0--150 feet thick and consists of a lower unit of sandstone and 

an upper unit of shale. The Martin Limestone of Middle(?) 

and Late Devonian age overlies the Tapeats with apparent conformity. Its thickness ranges from less than 50 feet, where it 

cuts out around the topographic high of Mazatzal Quartzite, 

to about 440 feet. The form'ation consists largely of dolomitic 

limestone and can be subdivided into four units. The Redwall 

Limestone of Early Mississippian age is about 220 feet thick and 

consists of four units, all of which are quite pure limestone, 

except for one unit that is cherty. Minor disconformities sepa1 
2 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

rate the Redwall from the underlying and overlying formations. 

The Supai Formation of PennsylVianian and Permian age is 

largely a red-bed deposit; it consists of three members-lower, 

middle, and upper-that total about 1,600 feet in thickness. 

The formation is conformably overlain by 'the eolian Coconino 

Sandstone of Early Permian age ; it has been eroded from all 

but the northeastern corner of the 'area, where less than 400 

feet of its original thickness of more than 500 feet remains. 

The three members of the Supai Formation have been mapped. 

The units into which the other formations can be subdivided 

have not been mapped but were helpful in recognizing stratigraphic separations on small faults and monoclines. Erosion 

since the close of the Paleozoic Era has stripped all the Paleo·zoic 

rocks from the southern half of the area and much of the 

younger Paleozoic formations from the northern half. The 

youngest Permian formations, the Toroweap Formation and 

Kaibab Limestone, have been completed removed. 

Cenozoic rocks consist of Tertiary ( ? ) andesite dikes, volcanic 

and sedimentary rocks of late Tertiary ( ?) age, and Quaternary 

gravel and alluvium. The andesite dikes cut Precambrian 

rocks in the southern part of the area ; they are probably 

older than the upper Tertiary(?) rocks. The upper Tertiary ( ? ) rocks consist of ( 1) fanglomerate and channel gravels, 

sand, silt, and clay of fluviatile and lacustrine origin, (2) 

basalt flows and cinder cones, and ( 3) andesitic :flows, plugs, 

breccias, tuffs, mud flows, and gravels. Locally andesite separates older from younger gravel and basalt. Elsewhere relative ages of the various rocks are uncertain. The rocks of late 

Tertiary ( ?) age are westward continuations of rocks mapped 

as the Hickey and Perkinsville Formations in the ClarkdaleJerome area. These two formations were separated largely 

on the basis of relation to structure: the Hickey Formation of 

Pliocene(?) age, being older and the Perkinsville Formation 

of Pliocene ( ? ) to Pleistocene ( ? ) age, younger than the major 

post-Paleozoic deformation. In the Prescott-Paulden area all 

the rocks of late Tertiary ( ? ) age appear to be younger than 

the major post-Paleozoic structure, and no clear-cut separation 

into two formations could be made. The Quaternary rocks 

are Pleistocene pediment and terrace gravels and Recent gravel 

and alluvium, which conceal large areas of the upper Tertiary(?) rocks in Chino-Lonesome Valley. 

Structually, many rocks of the Alder Group and later intrusive rocks have been intensely deformed, but the Mazat~al 

Quartzite and younger rocks have been only mildly deformed. 

The Precambrian deformation produced isoclinal folds, foliation parallel to bedding, and strike faults in rocks of the Alder 

Group and foliation and shear planes in intrusive rocks. The 

rocks of the Alder Group have been separated into isolated 

blocks by faults and igneous rocks, and the stratigraphic relations and the broad structural pattern are uncertain. Lithologic trends of intrusive rocks, in general, parallel those in 

volcanic rocks. Structural features trend northward, except 

for a northeast-trending discordant fault zone that is characterized by distributive shear. Deformat,ion of the Mazatzal 

Quartizite produced open folds and local zones of small, tight 

folds and small-scale thrusts but no foliation. The major 

structure consists of two northeast-trending anticlines that. 

plunge gently southward and are separated by a fault. The 

western anticline has apparently been folded so that on the 

south end it plunges north and its limbs diverge abruptly. 

The gentle regional north and northeast dip of the Paleozoic 

rocks in the general area is interrupted in the Paulden quadrangle by sharp monoclines and by two anticlines, having opposing northwest and southeast plunges, that meet in the 

central part of the quadrangle. The Paleozoic rocks are also 

cut by high-angle faults. Structural relief caused by the regional dip is about 3,200 feet; that caused by monoclines, anticlines, and faults is in some places 1,000-2,700 feet. Most of 

the deformation apparently preceded deposition of the volcanic 

and sedimentary rocks of late Tertiary(?) age, but faults having small displacement locally cut these rocks. East of the 

Paulden area the major post-Paleozoic deformation occurred 

after deposition of the Hickey Formation. 

The major physiographic feature is Chino-Lonesome Valley, 

which extends from the southeastern part of the area for 60 

miles to the northwest. The valley is an erosional and structural basin that was filled with upper Tertiary(?) rocks. 

Exterior drainage commenced when the basin was filled sufficiently for water to spill over a low point into the Verde River 

drainage. This point is near the center of the nort}Jeastern 

boundary, not at one end as in a normal valley. A temporary 

base level along the Verde River resulted in a gravel-strewn 

pediment that covered much of the valley. The northward 

drainage of the southern part of the valley was captured by 

headward erosion of the south-flowing Agua Fria River, and 

much of the pediment is dissected. Granite Creek, the major 

tributary to the Verde River, is a superimposed stream and has 

been let down onto resistant Precambrian rocks from the over~ 

lying upper Tertiary(?) rocks or pediment gravels. The surface forms are largely erosional. The mountains and hills are 

of several types, depending on the rocks and structure involved. 

Erosion of the schistose volcanic and intrusive rocks of the 

Bradshaw Mountains along the south border produced long 

sharp ridges separated by north-trending gulches. The topographic form of the isolated Dells Granite is controlled by nearly 

vertical joints. Flat-topped mesas and buttes are remnants 

of pediments or of nearly horizontal Paleozoic rocks or basalt 

flows. Hogbacks formed locally on steeply dipping Paleozoic 

rocks and the Mazatzal Quartzite. A few remnants of volcanic ~ones and plugs or domes dot the landscape. Except for 

the southwest-facing escarpment of Black Mesa in the northwest corner and the escarpment of the Colorado Plateau in the 

extreme northeast corner, much of the area northeast of ChinoLonesome Valley has low relief and is deeply dissected only 

along the Verde River and its tributaries. 

The Iron King lead-zinc massive sulfide deposit in the southeast corner of the area near Humboldt is the only operating 

mine in the area. The mine was studied by S. C. Creasey, and 

a detailed report is included in a 1958 report on the Jerome 

area by C. A. Anderson and S. C. Creasey. Many of the rocks 

of the Alder Group and the intrusive rocks have been mineralized slightly or are cut by mineralized veins, but except for the 

Iron King mine, no important deposits have been found. The 

Lynx Creek placers have contributed a considerable part of the 

placer gold of the State; the principal production was before 

1900, but the deposits have been operated intermittently since 

then. Rocks of the Prescott Granodiorite and Mazatzal Quartzite and some upper Tertiary(?) tuffs have been used for building stone. The Coconino Sandstone and part of the . upper 

member of the Supai Formation are quarried for :flagstone. 

The pure units of the Redwall Limestone have been used for 

cement and lime. The Chino artesian basin supplies water to 

the city of Prescott and for irrigation near the village of Chino 

Valley. 
INTRODUCTION 3 

INTRODUCTION 

The study of the Prescott and Paulden quadrangles 

was made as part of a program of the U.S. Geological 

Survey to determine the regional geological setting of 

two important copper mines: the United Verde and 

United Verde Extension at Jerome, Ariz., and the Iron 

King lead-zinc mine at Humboldt, Ariz. Anderson and 

Creasey (1958) mapped the Jerome area, which included the Mingus Mountain quadrangle, a small part 

of the Clarkdale quadrangle north of the United Verde 

mine, and small parts of the Mayer and Mount Union 

quadrangles near Humboldt (fig. 1). 'The geologic map 

of the southeast corner of the Prescott quadrangle was 

also included in their report. Creasey ( 1950 and 1952; 

Anderson and Creasey, 1958, p. 155-169) mapped the 

surface and underground geology of the Iron King 

mine. Lehner (1958) mapped the Clarkdale quadrangle. The Clarkdale, Paulden, Prescott, and Mingus 

Mountain quadrangles compose the old Jerome 30-minute quadrangle. 

Geologic mapping of the Prescott-Paulden area furnished information on the older Precambrian sedimentary, volcanic, and. intrusive rocks, on Paleozoic stratigraphy, on the upper Tertiary (?) sedimentary and 

volcanic rocks, and on structural features that affected 

these rocks. Information was also obtained on the mineral deposits and on the approximate thickness of the 

Paleozoic and Cenozoic cover over the Precambrian 

rocks, which are the principal host rocks for ore deposits 

in the area. Data on ground-water resources supplied 

by personnel of the Water Resources Division of the 

U.S. 'Geological Survey are incorporated into this 

report. 

ACKNOWLEDGMENTS 

Fieldwork in the Prescott quadrangle was carried on 

during the summers of 1947-49 with the assistance of 

W. E. Bergquist and during the summer of 1950 with 

the assistance of R. L. Kupfer. It was completed during 1951 and 19'52. About 12 months were spent in 

fieldwork in the Paulden quadrangle during the summers of 1953-55; I was assisted by the following persons 

for varying periods: J. H. Wallace, E. L. Markward, 

Virginia Remy, M. J. Ebner, Kathleen McQueen, N. C. 

Pearre, M. H. Miller, Dorothy McKenney, June Waterman, and Rosina Yoder. 

Mr. S. F. Turner of the Geological Survey supplied 

data on the ground-water resources of the city of Prescott. Well-log data for the area were obtained from 

Mr. Turner, from Dr. H. C. Schwaller of the Irrigation 

Department, State Land Department, University of 

Arizona, Tucson, from the Museum of Northern Arizona, and from ranchers and well drillers. E. D. Wilson 

kindly loaned his unpublished geologic map of the 

Jerome 30-minute quadrangle. 

PREVIOUS WORK 

No detailed reports on the geology of the area have 

been published execept for stratigraphic studies of the 

Red wall Limestone. The discovery and early workings 

of gold placer deposits on Lynx Creek are mentioned in 

several reports on the resources of the southwest, especially in those by Raymond ( 187 4) and Hamilton 

( 1883). The earliest mention of the geology is by 

Blandy (1883), who published a map showing granitic 

rocks, schist, and slate along the southern boundary of 

the area. He made specific mention of the scarcity and 

unimportance of the quartz veins in granite near Prescott. 

The geology and ore deposits of Jerome were described by Reber ( 1922, 1938), who subdivided the Precambrian rocks. His rna p extends into the eastern part 

of the Prescott quadrangle. Wilson ( 1922, 1939) reported on and published maps of the area underlain by 

the Mazatzal Quartzite in the Paulden quadrangle. 

The first published map to show the general distribution of formations in the two quadrangles is the "Geologic Map of the State of Arizona" (Darton and others, 

1924). 'This part of the map was compiled largely from 

an unpublished map of the Jerome 30-minute quadrangle prepared for the State by L. F. Reber, Jr., and 

Olaf Jenkins and from later reconnaissance by Wilson. 

The map by Reber and Jenkins was later published in 

Lindgren's report (1926·, pl. 1) on the ore deposits of 

the Jerome and Bradshaw Mountains quadrangles. 

Lindgren's report contains information on mines and 

prospects of the area but only briefly discusses the regional geology. 

Tenney (1928, p. 109) mentioned limestone quarries 

near Cedar Glade (now Drake). Descriptions of the 

Lynx Creek placer deposits and operations were summarized by Wilson and Tenney (1932) and Wilson 

( 1937, 1952) . Mills ( 19'41) first briefly described the 

Iron King mine and later ( 1947) published an excellent 

short account of the geology of the mine, especially of 

the character of the ore shoots. 

'Gutschick ( 1943) and Easton and Gutschick ( 1953) 

made stratigraphic and faunal studies of the Redwall 

Limestone in the area. McNair (1951) presented evidence which he believed indicated that the basal sandstone near Jerome is Devonian and not Cambrian. A 

preliminary statement on Precambrian stratigraphy 

and structure in the Jerome-Prescott area was given by 

Anderson (1951). 
4 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

ECONOMIC AND PHYSICAL GEOGRAPHY 

Location.-The Prescott-Paulden area includes about 

490 square miles and is bounded by the meridians 112°-

15' and 112°30' W., and the parallels 34°'3{)' and 35°00' 

N. (pis. 1, 2). 'Most of the area is in Yavapai County, 

central Arizona (fig. 1) ; about 8 square miles o:f the 

northeast corner is in Coconino County. 

Population and industry.-The city o:f Prescott, 

which now includes Forbing Park and Miller Valley, 

is the county seat and the largest settlement in Yavapai 

County; in 1956 its population was estimated at more 

than 11,000. Prescott is the shopping center :for ranching and mining in the county and contains a :few small 

light industries; together with the higher pine-clad 

hills to the south and west, it is a resort area during 

the summer months. The Veterans Hospital at Whipple and a small Indian settlement, Yavapai Indian Reservation, are adjacent to the city. The village o:f Chino 

Valley, west o:f Granite Creek, lies on the boundary between the quadrangles and is a :farming and ranching 

settlement. Drake, a railroad junction in the northern 

part o:f the area, is the cutting and shipping center of 

the local flagstone industry; the quarries and camps 

o:f the quarrymen lie to the northeast, mostly outside 

the study area. Except :for these settlements and :for 

dwellings at Granite Dells, Prescott Municipal Airport, 

Paulden, and a :few ranches, a large part o:f the area i~ 

uninhabited. 

Indian ruins.-Small Indian ruins, pictographs, and 

Apache :forts are scattered throughout the area; some 

o:f them are listed in table 1. The site o:f the ruin on 

the west side of Granite Creek, where the creek enters 

the Mazatzal Quartzite (pl. 2, 1,380,000 N ., 359,800 E. 1 ), 

was undoubtedly chosen because o:f its proximity to 

outcrops o:f argillite used :for artifacts. 

TABLE 1.-Location of some Indian ruins and pictographs in the 

Prescott-Paulden area 

Older Indian ruins 

(mostly Pueblo type) : 

Prescott quadrangle : 

1,276,600 N., 325,500 E . 

1,279,300 N ., 384,600 E . 

1,286,800 N., 358,500 E. 

1,300,200 N., 370,300 E. 

1,301,200 N., 348,200 E. 

1,309, 700 N., 343,500 E. 

Paulden quadrangle : 

1,380,300 N., 3.59,800 E. 

1,411,500 N., 378,900 E. 

1,40.2,200 N., 340,2.00 E. 

1,412,100 N., 369,200 E. 

Indian pictographs : 

Prescott quadrangle : 

1,283,300 N., 358,800 E. 

1,2>85,600 N., 361,300 E. 

1,303,600 N., 343,700 E. 

Paulden quadrangle: 

1,388,400 N., 352,800 E. 

Apache forts : 

Prescott quadrangle : 

1,280,500 N., 333,600 E. 

1,310,200 N., 327,500 E. 

Mining and quarrying.-Base and preciOus metals 

and some nonmetallic materials have been mined or 

quarried in the area. The only operating mine, and 

1 The 10,000-foot grid of the Arizona (Central) rectangular coordinate system has been placed on the maps, and many references to this 

coordinate system are made in the discussions of specific localities and 

geologic features. 

the only important one developed, is the Iron King 

lead-zinc mine in the extreme southeast corner o:f the 

area. Gold has been recovered :from placer deposits, 

principally along Lynx Creek in the south-central part. 

The Precambrian rocks, except the Mazatzal Quartzite, 

have been widely prospected and have yielded minor 

amounts o:f metals, mostly gold. Some prospecting has 

been done in slightly mineralized Paleozoic rocks near 

the Verde River at the east edge o:f the area (pl. 2). 

The Supai and Coconino Formations are quarried :for 

flagstone; several :formations are used locally :for building and construction. The Red wall Limestone has been 

quarried :for cement and lime. Four unproductive 

wildcat oil wells were drilled north o:f Paulden. The 

Chino-artesian basin supplies water :for irrigation near 

the village o:f Chino Valley; Prescott obtains much o:f 

its water supply :from this source. 

Accessibility.-Prescott and Drake are served by a 

branch o:f the Santa Fe Railroad, which runs :from the 

main line at Ash:folk, 50 miles north, to Phoenix, the 

State capitol, 100 miles south of Prescott. Branch 

lines :from Drake and :from north o:f Prescott serve 

Clarkdale (Jerome) and the Iron King mine (fig. 1) . 

Many roads traverse the area (fig. 1). Route 89 

crosses the western part :from north to south, passing 

through Drake, Paulden, and Chino Valley, and connecting Prescott with east-west highways to the north 

and south. Route 89 Alternate leaves Route 89 about 

6 miles northeast o:f Prescott and joins Prescott with 

Jerome, the Verde Valley, and Flagstaff to the northeast. State Route 69, the Black Canyon Highway, connects Prescott with the Iron King mine and Phoenix. 

County roads to ranch, mine, and resort areas, and other 

roads and trails provide access to all parts o:f the area ; 

no outcrop is more than 1 or 2 miles :from a road passable 

by truck or jeep. 

Physical .features.-The Prescott-Paulden area lies 

mostly in the mountain region of Arizona (Ransome, 

1903, p. ~5), a zone o:f north- and northwest-trending 

ranges and broad valleys. To the northeast lies the 

plateau region; to the southwest, the desert region (fig. 

1, inset). 

The scenery is varied. More than half the area is occupied by the intermontane Chino-Lonesome Valley 

(figs. 22, 23, 29, 30), which extends to the northwest :for 

60 miles :from the southeast corner. It was filled with 

fluviatile and lacustrine deposits that were eroded into 

a broad gravel-strewn pediment, which has since been 

dissected. The northern part of the rugged Bradshaw 

Mountains extends :for a :few miles into the area (fig. 1) . 

From the northeast side of Chino-Lonesome Valley to 

the Colorado Plateau margin, which lies mostly north 

of the Paulden quadrangle, the area is relatively low-
ECONOMIC AND PHY·SICAL GEOGRAPHY 

112°45' 112.00' 

35.15'r-----------~~~~~------~T---------~~--~------------~ ·~~~~~ ~~=------------, 

35 •oo• SIMMONS 

.. /· /. 

\ 

/ 

45' IRO~SPRINGS 

_.-/ 

\ 

· ... / 

·-./(_. 

l- ~ ~- ll 

~: 

\ 

\ 

/; PAULDEN ::: 

/// ,, ..... 

/ 1 II I\\\ 

\ 

~ 

(:C 

)_~ .·~ 

·.\ 

~. ( ·"'--· . ·\.__ .. 

R D E 

--~ ~ j.S 

Walker 

\!) 

~ .,. 

~ 

10 15 20 MILES 

~ 

< , ' (' 

1- l 

"" 1- e 

., , u 

< ~ 

\ < 

\!) 

I -E 

\ ~ 

§ "" 

u 

FIGURE 1.--The study area. Inset shows location of the two quadrangles in relation to Yavapai County and 

the State and the approximate position of the three topographic regions. 

5 
6 GEOLOGY OF THE PRESCO'IT AND PAULDEN QUADRANGLES, ARIZONA 

lying but is related to the plateau by its flat-lying Paleozoic rocks. The southwest-facing escarpment of Black 

Mesa, largely northwest of the area, is part of, but not 

continuous with, the plateau margin to the east. Granite Creek has been deeply incised into the resistant 

Mazatzal Quartzite (pl. 2), and gorges have been cut in 

Paleozoic rocks and overlying basalt flows by the Verde 

River (fig. 2) and its tributaries. An isolated block of 

.granite northeast of Prescott has been eroded into rectangular and pictu,resque forms owing to strong joint 

control (fig. 14). Other forms include volcanic cones, 

andesitic plugs (fig. 19), buttes and mesas, which are 

remnants of once more extensive basalt flows of Paleozoic rocks, and a few narrow hogback ridges formed by 

erosion of monoclinally folded sedimentary rocks. 

FIGURE 2.-The view is to the east-northeast along the Verde River, 

Paulden quadrangle, from near 1,410,500 N., 384,300 E. The following units are exposed: Precambrian quartz diorite (qd), Tapeats Sand- · 

stone (£t), Martin Limestone (Dm, units A-D), and Redwall Limestone 

(Mr). Note figure (arrow) for scale. 

Altitudes range from 6,968 feet near the south margin 

of the area (pl. 1) to about 3,875 feet along the Verde 

River in the northeastern part (pl. 2). Much of the 

area is between 4,500 d 5,500 ·feet in altitude. High~ 

est altitudes in surrounding areas are between 7,500 and 

8,000 feet. 

Drainage.-The Verde River and parts of two of its 

tributaries are the only perennial streams. The principal tributaries of the river (fig. 30) are Granite Creek, 

which flows northward across the area, and the washes 

in Hell Canyon and Big Chino and Williamson Valleys. 

The southeastern part is drained by the Agua Fria 

River and its major tributary, Lynx Creek. Dams impound water to form Sullivan Lake-the head waters 

of the Verde River (pl. 2)-and Watson Lake and Willow Creek Reservoir in the Granite Dells north of Prescott (pl. 1). 

Olimate.-Arizona has a wide range in climatic conditions owing to a wide range in surface altitudes. 

The Prescott-Paulden area lies between the extremes 

of both altitude and climate. Only rarely does the temperature reach 100°F in Prescott, where below-zero temperatures are not common. Incomplete weather reports 

are available for Prescott since 1872 and for the Prescott Municipal Airport, 8 miles north of Prescott, since 

1942. These data are summarized in table 2. Summer 

and winter are the periods of greatest precipitation. 

TABLE 2.-Temperature, humidity, and precipitation in the 

Prescott area 

[Unless otherwise noted, length of record is as follows: For temperature and humidity Prescott, 40 years; Prescott Municipal Airport, 10 years. For precipitation: Prescott, 28 years; airport, 10 years] 

Temperature, in degrees Fahrenheit: January average _________________ _ July average ____________________ _ 

Annual average _________________ _ Maximum ______________________ _ Minimum ______________________ _ 

Summer average _________________ _ Winter average __________________ _ 

Humidity, in percent: Annual average ____________ - _____ _ December average _______________ _ June average ____________________ _ 

Average precipitation, in inches: January ________________________ _ February ________________________ . March __________________________ _ 

ApriL May ____ -_-_------------------- ___________________________ _ June ___________________________ _ July ____________________________ _ August _________________________ _ September ______________________ _ October ________________________ _ ~ovember ______________________ _ December ______________________ _ Annual _________________________ _ Snowfall ________________________ _ 

J Length of reeord: 80 years. 

Prescott 

35 

72.5 

1 54 1 105 1 -21 

70 

36 

1. 80 

2.20 

1. 56 

1. 20 

.44 

. 34 

2.62 

3.39 

1. 98 

.99 

1. 08 

2.38 

19.98 

Airport 

35.6 

75 

57 

102 

-5 

47 

66 

26 

1. 19 

. 69 

. 88 

.71 

.19 

.11 

2.69 

2.81 

1. 20 

. 64 

. 60 

1. 31 

13.02 

20 

July and August are generally the wettest months of 

the year, most of the precipitation falling during 

local thunderstorms. Snowfall is common above an 

altitude of 5,000 feet. but rarely accumulates at 

this altitude. The average winter snowfall at the airport is 20 inches. Compared with lower altitudes, 

higher altitudes have cooler summer and colder winter 

temperatures and greater accumulations of snow and 
GENEHAL GEOLOGY 7 

somewhat greater rainfall. Recorded precipitation at 

the airport is lower than at Prescott because of the airport's lower altitude and greater distance from the 

mountains and also because the airport records were 

taken during a period of drought. 

Vegetation.-Pine forests, pinyon-juniper woodland, 

grassland, and chaparral constitute the four types of 

vegetation in the area. Pine forests are limited to the 

southern part of the area, mostly above an alitude of 

5,500 feet. Sparse pinyon-juniper woodland (fig .. 2) 

covers a large part of the northern half and a little of 

the southern half. The chaparral areas (southwestern 

brush- or shrub-type vegetation) occur principally in 

the southern part along the margin of Chino-Lonesome 

Valley. Most of Chino-Lonesome Valley (figs. 19, 28) 

and the area east and south of Drake is in grassland. 

For a more detailed account of the vegetation of adjacent areas, see Anderson and Creasey ( 1958, p. ·5-6) 

and Lehner (1958, p. 518-519). 

GENERAL GEOLOGY 

Rock formation in the Prescott and Paulden quadrangles belong to the Precambrian, Paleozoic, and Cenozoic Eras. The distribution and structure of these formations are shown on plates 1 and 2. The formations 

are shown diagrammatically in figure 3. The older 

Precambrian formations consist of volcanic, sedimentary, and intrusive rocks. Volcanic rocks belong to the 

Alder Group of the Yavapai Series; the sedimentary 

rocks belong to the Mazatzal Quartzite. The Mazatzal 

Quartzite is in fault contact with the Alder Group. 

Precambrian igneous rocks intrude the Alder Group 

but not the Mazatzal Quartzite. The intrusive rocks 

consist of gabbro, granodiorite, granite, and alaskite 

of Precambrian age and are probably closely related in 

time. 

Paleozoic rocks of Cambrian and Devonian through 

Permian ages presumably overlay the Precambrian 

rocks throughout the area but have been stripped from 

the southern half. Mesozoic rocks, with the possible 

exception of the Moenkopi Formation of Triassic age, 

were not deposited here. The Cenozoic rocks consist of 

andesite dikes of Tertiary (?) age, volcanic and sedimentary rocks of late Tertiary ( ? ) age, and Quaternary 

gravel and alluvium. The sedimentary rocks of late 

Tertiary ( ? ) age consist of gravel, sand, silt, clay, and 

thin beds of rhyolite tuff and freshwater limestone of 

fluviatile and lacustrine origin. The interbedded volcanic rocks are basaltic flows, tuffs, and cinder cones 

and andesitic plugs, domes, flows, breccias, mud flows, 

tuffs, and gravels. The sedimentary and volcanic rocks 

filled Chino-Lonesome Basin and covered much of the 

area northeast of the basin. These rocks are westward 

extensions of Pliocene ( ? ) -Pleistocene ( ? ) rocks, which 

are separated to the east into the older Hickey and 

younger Perkinsville Formations on the basis of relation to structure (Anderson and Creasey, 1958; Lehner, 

1958). Locally in the Prescott-Paulden area andesite 

separates older from younger gravel and basalt, but 

elsewhere no clear-cut division of an older and a 

younger formation could be mad_e. ' 

Rocks of the Alder Group have been intensely deformed; in most places bedding and :foliation are about 

parallel, and the :formations dip steeply. Many of the 

Precambrian intrusive rocks have also been intensely 

deformed. Distributive shear characterizes much o:f the 

older Precambrian deformation. The Mazatzal quartzite, however, although :folded, has not been intensely 

deformed in this area. Paleozoic and late Cenozoic 

rocks, most of which are nearly horizontal, have locally 

been displaced by high-angle :faults, and the Paleozoic 

rocks have been :folded into sharp monoclines. 

OLDER PRECAMBRIAN ROCKS 

The Precambrian rocks of Arizona have been divided 

into older and younger Precambrian (Butler and Wilson, 1938, p. 11) on the basis of a major unconformity. 

The older Precambrian rocks include the Pinal Schist 

in southeastern Arizona, the Yavapai Schist and the 

Mazatzal Quartzite and associated formations in central Arizona, the Vishnu Schist in the Grand Canyon 

region, and the granitic rocks that intrude the schist 

and quartzite. Wilson (1939, p. 1153) correlated the 

quartzite in the Paulden area with the Mazatzal and 

recognized only one period of deformation and intrusion, which occurred after the deposition of the Mazatzal. In the Paulden quadrangle, evidence suggests that 

the quartzite is younger than deformation of both 

schist and granitic rocks; the quartzite was not intruded 

by granitic rocks or deformed to the extent that the 

schist and granite were. Younger Precambrian rocksthe Grand Canyon Series to the north and the Apache 

Group to the southeast-are not present in the PrescottPaulden area. The regional correlation of the Precambrian rocks was discussed by Anderson and Creasey 

( 1958, p. 44-45). 

YAVAPAI SERIES-ALDER GROUP 

In the Jerome area Anderson and Creasey ( 1958, p. 

9) recognized two groups (Alder and Ash Creek) in 

rocks previously called the Yavapai Schist. They 

therefore redefined the Yavapai as a series. Only the 

Alder Group is represented in the Prescott-Paulden 

area. 

Rocks of the Alder Group were described by Anderson and Creasey ( 1958, p. 20-32), who redefined strata 

previously called the Alder Sreies ("\Vilson, 1939, 
8 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

SYSTEM SERIES FORMATION AND MEMBERS THICKNESS 

(FEET) 

-c 

<11 

(.) 

> <11 

0:::: 0:::: 

< "C 

z c Pediment and terrace 0-50+ 0:::: 1'0 

LIJ <11 gravels and alluvium,Qg of each type 1- c < <11 of deposit ;::) (.) 

0 .s 

en 

·a:; 

a: 

UNCONFORMITY 2 

,...... t;. ..... ~ Sedimentary rock~. Ts 

> 1'0 Volcanic rocks: 0:::: :e < <11 Andesite, Ta 0-1700+ i= 1- Basalt, Tb 0:::: .... LIJ <11 

1- Q. Basaltic cinder cone, Tc Q. 

;::) 

~UNCONFORMITY 3 

Coconino Sandstone, Pc 400+ 

4 

c 

1'0 

z ·~ Upper member, Psu 700± < 

i <11 Supai ~ 

0:::: .... Formation LIJ <11 ~ ~ 

0 ...J 

5 

Middle member, Psm 250± 

6 

~- Lower member, PIPsl 600± 

UNCONFORMITY ·z .... ' c 7 ~< (1)-

(/)Q.. ~·~ ·~ Redwall Limestone, Mr 219± -Q.. 0·- Q. 

:::E(ij ...J ~ ·u; ~ UNCONFORMITY J 

c 8 "Cftl 

z c ·-

:5 1'0 c 0 

z ,...... > ..... <11 

0 Q)o Martin limestone, Om >50-439 > =c .... LIJ "C <11 0 ·- Q. ~Q. ;::) 

Tapeats 

UNCONFORMITY 

Sandstone, £t 

~ 

0-154 9 

ANGULAR UNCONFORMITY 10 z Intrusive rocks < Mazatzal Quartzite dg, al, pg, gg, gb Mazatzal 

o:::ii: Quartzite LIJCQ mq, rna 1 , ma 2 Alder Group of 0~ mc 1 , mc 2 Yavapai Series 4000+ ...J< 

ou av,. gv, cv, ik, sv, iu, tu Alder Group LIJ 

0:::: Fault contact, Mazatzal may be unconformable 30,000± ~ above Alder Group and intrusive rocks 

FIGURE 3.-GENERALIZED STRATIGRAPHIC SECTION, 
2 

OLDER PRECAMBRIAN ROCKS 9 

GENERAL DESCRIPTION AND REMARKS -l 

Gravel veneer on pediment surfaces; gravel, sand, and silt on terraces; alluvial and colluvial material on slop~ and valley bottoms; sand and coarse gravel in stream channels. Unconsolidated except where locally cemented by caliche 

Sedimentary rocks: fanglomerate, coarse to fine gravel, sand, silt, clay of fluviatile and lacustrine origin, thin 

beds of fresh-water limestone, and minor amounts of interbedded rhyolitic tuff, Ts ; volcanic rocks: andesite 

flow, plug, breccia, mud flow, tuff, and gravel composed largely of andesite fragments, Ta; basalt flow, Tb; 

basaltic cinder cone, Tc. In places andesite separates older from younger sedimentary and basaltic rocks 

------·----------------------------------------------------------------------------------------------------- ~ 3 

4 

7 

8 

Massive pale-oran~e to grayish-orange sandstone characterized by crossbedding on a large scale. In most 

places forms a sheer cliff 

Chiefly strongly crossbedded reddish-orange sandstone separated by horizontally bedded and thinly laminated 

fine-grained pale-reddish-brown sandstone and siltstone; forms cliffs, buttresses, and pinnacles 

Comprises four units: unit 1 consists of 0 - 35 feet of thin-bedded reworked Devonian material and 23 feet of 

bluish-gray oolitic limestone; unit 2 consists of 80 feet of fine-grained cherty limestone; unit 3 consists of 

81 feet of coarsely crystalline limestone; and unit 4 consists of 35 feet of bluish-gray micro-oolitic to pellety 

limestone, locally underlain by crystalline and cherty limestone and by a solution breccia. Formation 

forms a cliff in most places 

Comprises four units: unit A is 0- 21 feet of cliff-forming crossbedded impure clastic dark-gray dolomitic 

limestone; unit B is 0- 97 feet of slope-forming light-gray thin-bedded lithographic limestone with shale 

partings; unit C is 0- 75 feet of thicker bedded mottled cliff-forming dark-gray dolomitic limestone; unit D 

is less than 50 to 255 feet of alternate thin beds similar to units A, B, and C, with some siltstone, shale, and 

sandstone; forms a steep, steplike slope 

~-------------------------------------------------------------------------------------------------·----------

9 

10 

Comprises two units: a lower unit of cliff-forming dark-reddish-brown and buff cr:ossbedded sandstone 0- 142 

feet thick that averages at least two-thirds of the total thickness, and an upper unit of slope-forming 

reddish- to yellowish-gray mudstone, siltstone, and shale, and locally conglomerate, 0- 22 feet thick 

Intrusive rocks: (from oldest to youngest) gabbro, gb; Government Canyon Granodiorite, gg; Prescott Granodiorite, pg; alaskite, al ; and Dells Granite, dg; (not shown are coarse-grained granite, fine- grained granite, 

and younger diabase and fine-grained gabbro-diorite). 

Mazatzal Quartzite: includes lavender, reddish, and grayish massive to crossbedded fine- to coarse-grained 

quartzite and minor granule conglomerate, mq; interbedded lower and upper red argillite, ma 1 and ma 2 ; 

and lower and upper conglomerate containing quartz and jasper pebbles, cobbles, and small boulders, interbedded with quartzite, mc 1 and mc 2 

Alder Group rocks: unnamed basaltic flows and tuffaceous rocks of the Alder(?) Group, av; Green Gulch Volcanics, 

basaltic flows, breccias and tuffs, and rhyol itic and basaltic tuffs and flows, gv; Chaparral Volcanics, andesitic and rhyolitic tuffs, cv; Iron King Volcanics (not exposed), andesitic tuffs and andesitic or bas a I tic flows, ik; 

Spud Mountain Volcanics, andesitic breccia and andesitic tuffs, sv; Indian Hills Volcanics, rhyolitic and andesitic or basaltic flows, a few tuffaceous rocks, iu; Texas Gulch Formation, largely rhyolitic tuffaceous 

sedimentary rocks, some rhyolite flows or massive tuffs, andesitic flows and tuffs, and minor amounts of 

conglomerate and jasper-magnetite beds, tu 

PRESCOTT-PAULDEN AREA, ARIZONA. 
10 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

p. 1121, 1159). In general the group consists of basaltic, 

andesitic, and rhyolitic flows and tuffaceous sedimentary rocks. Of the six formations described by Anderson and Creasey, five were recognized in the PrescottPaulden area; these are the Texas Gulch Formation 

a~d the Indian Hills, Spud Mountain, Chaparral, and 

Green Gulch Volcanics. The sixth formation, the Iron 

King Volcanics, is beneath Cenozoic deposits in the extreme southeast corner of the area (pl. 1, sec. E-E'). 

In addition, isolated masses of basaltic flows and tuffaceous rocks probably belong to the Alder Group but are 

not given formation names or assigned to one of the 

previously named formations. 

The Alder Group has been regionally metamorphosed, and many of the textures, structural features, 

and mineral assemblages are typical of rocks of the 

green schist facies; some are the result of higher grade 

metamorphism. The principal metamorphic minerals 

are chlorite, actinolitic hornblende, epidote, clinozoisite 

(zoisite), albite, sericite,2 and quartz. Microcline is 

a common stable relict mineral in the rhyolitic rocks. 

Biotite, muscovite, hornblende, oligoclase-andesine, 

garnet, and staurolite ( ~) indicate local higher grade 

metamorphism. 

Although the Alder Group has been metamorphosed, 

unravelling its stratigraphy and structure was of greater importance in the search for clues to ore deposits in 

the Precambrian rocks than was the study of metamorphic features. A careful search was therefore 

made for relict textures and structural features.. 

If relict amygdules or pillow structures can be recognized in chlorite or hornblende schist, the rocks are 

classed as andesite or basalt. Rocks of the same general composition that show relict bedding are called 

andesitic or basaltic tuffs or tuffaceous sedimentary 

rocks; those containing abundant phenocrysts or crystal fragments of plagioclase are called andesite. Sericitic schists or fine-grained rocks composed of quartz 

and alkalic feldspar and containing flow structures and 

phenocrysts of quartz and feldspar are classed as rhyolite; similar rocks having relict bedded structures are 

classed as rhyolitic tuff or tuffaceous sedimentary rocks. 

Siliceous-looking flows containing a greater amount of 

mafic minerals and calcic plagioclase than normal rhyolites are called dacites. Some fine-grained rocks originally lacked features indicating that they were a volcanic flow, massive tuff, or a fine-grained intrusive rock. 

The original textures and structures in other rocks 

have been obliterated by intense deformation, higher 

2 Although muscovite and sericite are the same mineral, in this report the term "sericite" is used for fine-grained metamorphic or secondary muscovite ; the term "muscovite" is used for the primary igneous 

mineral and also f()r the larger (generally more than 2 mm) crystals 

formed by higher grade metamorphism. 

grade metamorphism, or later retrograde metamorphism. Fortunately, many of the rocks in which original 

diagnostic features were lacking or were later destroyed 

can be traced along the strike into rocks in which relict 

textures and structural features indicate the original 

character of the rock. 

Because of the almost complete absence of sedimentary rocks such as limestone, sandstone, and shale and 

because of the abundance of volcanic material in the 

Precambrian rocks in this area, much of the bedded material has been interpreted as of tuffaceous, rather 

than terrigenous, origin. Bedded tuffs and a few pillow lavas indicate deposition in water, probably in a 

marine environment. 

Attempts to work out the stratigraphy and structure 

of the Alder Group in the area met with little success. 

The rocks have been isoclinally folded and foliated. 

They are separated into isolated masses by faults and 

intrusive igneous rocks or are exposed only in windows 

in Paleozoic and Cenozoic rocks. Some masses may 

lack internal continuity; a displacement may not have 

been recognized because it paralleled lithologic trends 

and brought similar rocks of different formations into 

apparent continuity, or because it had been injected by 

igneous rocks. 

Little evidence was found to indicate the direction 

in which tops of beds face. In many places where the 

orientation of a bed could be determined, only the local 

rather than the regional structure was indicated because of known or inferred isoclinal folding. 

Rocks of the Alder Group were injected by and 

caught up in intrusive igneous rocks. Where mixing 

of volcanic and intrusive rocks is difficult to show on 

the map (pis. 1, 2), a stippled pattern has been placed 

over the pattern used for the principal rock type in the 

area. Data on these complex areas are given in sections 

on the principal rock type involved. 

The formations of the Alder Group dip so steeply 

that outcrop widths ~ould approximate stratigraphic 

thickness except for several complications: ( 1) Isoclinal 

folds and small unmapped masses of igneous rocks 

cause outcrop widths to be greater than stratigraphic 

thickness, and ( 2) flowage, shearing out of beds, and 

unmeasured amounts of rocks of the Alder Group in 

adjacent intrusive rocks cause outcrop widths to be less 

than stratigraphic thickness. 

Because of these complications and because neither 

the top nor the bottom of the Alder Group is exposed, 

the thickness of the group is not kno,vn; however, it is 

probably at least 20,000 feet. In the Jerome area Anderson and Creasey ( 1958, p. 20) estimated the Alder 

Group to be 20,000-30,000 feet thick. Their figures include thicknesses of the Spud Mountain, Chaparral, 
OLDER PRECAMBRIAN ROCKS 11 

and most of the Green Gulch Volcanics in the southeastern part of the Prescott quadrangle but not thick-

~esses of the unnamed volcanic rocks that are probably 

Ill the Alder Group and thicknesses of additional units 

in the Texas Gulch Formation and Green Gulch and 

Indian Hills Volcanics. 

TEXAS GULCH FORMATION 

DISTRIBUTION 

The Texas Gulch Formation was named and described 

by Anderson and Creasey ( 1958, p. 28-30) for exposures 

in Texas Gulch in the southwestern part of the Jerome 

area. The principal exposure of the Texas Gulch Formation in the Prescott-Paulden area is in the southcentral part (pl. 1) . Three small exposures are in the 

northern part along Granite Creek about 1 mile south 

of its junction with the Verde River (pl. 2; fig. 5). 

Li~ho~ogic units have not been mapped, except for four 

units In the largest exposure (pl. 1). They are units 

containing respectively, jasper-magnetite beds, andesite 

flows and tuffs, rhyolite crystal tuffs, and rhyolitic flow 

?r massive tuff. The andesitic rocks have been mapped 

In three places; the other units, in only one area each. 

THICKNESS, ,STRATIGRAPHIC RELATIONS, AND CORRELATION 

The thickness and stratigraphic relations of the Texas 

Gulch Formation are not known. Structural and stratigraphic features suggest that the main mass occupies 

a south-plunging syncline within which are small folds 

the top and the bottom are both absent, the oldest bed~ ~re on the ~~st and west sides, and the youngest part 

IS the rhyolitic flow or massive tuff unit near the center 

of the o.utcrop. This interpretation is based on jaspermagnetite float and beds of rhyolite tuff, slate, and conglomerate in the western part· of the mass that may be 

correla:ti.ve with similar beds on the east; on generally 

west-faCing beds in the eastern part ; and on southplunging lineation, interpreted as the b axis of the structural coordinate system. 

The greater outcrop width of the formation (about 

~2,000 ft) alo~g the southern border of the quadr.angle, 

In contra~t with a narrower width (less than 5,000 ft) 

about 2 miles to the north, is probably due to duplication 

of be~s by folding and to the southward plunge of the 

synchne. The formation must be 3 000-4 000 feet thick . h' ' ' In t Is area. 

No normal stratigraphic contacts of the Texas Gulch 

Formation wi,th other Precambrian formations are exposed. Its western contact with unnamed basaltic flows 

of the Alder(~) Group appears to be a fault or shear 

zone (pl. 1). To the north and east the Texas Gulch 

Formation is -intruded by igneous rocks. The eastern 

contact is sharp, but the granite adjacent to it contains 

abundant inclusions of volcanic rocks, which probably 

,7,58-447 0-65-2 

are part of the formation. One small outcrop is in fault 

contact with the Mazatzal Quartzite (pl. 2). 

Anderson and Creasey's interpretation ( 1958, p. 28) 

of the regional structure of the Alder Group in the 

Jerome area is that the Texas Gulch Formation is the 

oldest formation in the group. Whether it directly underlies the Indian Hills volcanics or is separated from it 

by other formations is not known, as the two are not in 

contact. 

In the Jerome area Anderson and Creasey ( 1958, p. 

28) applied the name Texas Gulch Formation to roc.ks 

formerly referred to as quartz-sericite schist, conglomerate, and slate by Lausen (1930) and as arkosic sandstone, squeezed conglomerate, and slate by Wilson (1939, 

p. 1157-1158). Wilson correlated these rocks with his 

Alder Series in the Mazatzal Mountains. In the southern part of the Prescott-Paulden area, many of the rocks 

mapped as Texas Gulch Formation are lithologically 

similar to those in the type locality. Similarities include the abundance of fine- to coarse-grained rhyolite 

tuff that locally grades into lithic tuff, the considerable 

amounts of slate, and a distinctive conglomerate. Not 

all the lithologic types are found in both areas. Thin 

beds or layers of marble occur in the Jerome area; none 

occur in the Prescott area. Thin beds of jasper-magnetite and scattered jasper-magnetite pebbles in conglomerate occur in the Prescott area but not in the 

~ erome area. In the Prescott area the slate is gray; 

111 the Jerome area it is chiefly purple or maroon and 

only locally gray or green. Another difference is the 

presence of dacite( n and andesite in the Prescott area 

but not in the Jerome area. If rocks in the Prescott 

and Jerome areas are correctly correlated, these differences may be because neither area contains a complete 

section. Near Granite Creek (pl. 2) the abundance of 

quartz-sericite schist that may represent metamorphosed 

slate and rhyolitic tuff suggests a correlation with the 

Texas Gulch Formation to the south. Also Wilson ' (1939, p. 1153) termed these rocks "phyllite and argillaceous sandstone of Alder type." Inclusion of rocks 

here called Texas Gulch .Formation in the Alder Group 

and their correlation with the Texas Gulch Formation 

in the Jerome area are both tentative but the best that 

can be done on the basis of present know ledge . 

LITHOLOGY AND INTERNAL STRUCTURE 

The Texas Gulch Formation is composed largely of 

rhyolitic tuff but it includes rhyolite flows ( ~), andesite 

tuffs and flows, slate, conglomerate, dacite ( ~) flows and 

tuffs, and jasper-magnetite beds. Much of the descriptive material in the section on undifferentiated rocks 

applies to rocks in differentiated units; some rocks are 

described only under an individual unit. 
12 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

The rocks are variably foliated; the finer grained ones 

have a smoother, more regular foliation than the coarser 

grained ones; conglomerates have a hackly foliation. 

Lineation, which is widespread, results from elongation 

of sericite or chlorite flakes, elongation of pebbles, and 

intersection of cleavage and bedding. Except for mineral streaking, which is parallel to the a axis, most lineation is parallel to the plunge of minor drag folds and 

to the b axis of the structural coordinate system. 

Thickening on crests and thinning on limbs of small 

drag folds is characteristic of the jasper-magnetite beds. 

Some pebbles in conglomerates are attenuated to lengths 

as much as 10 times widths. 

The rhyolite tuffs are various shades of gra:y. Many 

of them are very fine grained and finely laminated, 

especially in the area extending 1,500 feet west of the 

unit containing jasper-magnetite beds. Relict bedding 

is preserved in pll:\ces. Some tuffs are coarse grained or 

contain sparse to abundant crystal or lithic fragments. 

Lithic fragments range from about 1 mm to 15 em in 

length. In some beds, crystal or lithic fragments are 

massed almost without matrix. The tuffs grade into 

slate and into sandstone and conglomerate of questionable tuffaceous origin. The matrix of the tuff consists 

of quartz, sericite, alkalic feldspar, and lesser amounts 

of biotite, chlorite, museovite, epidote, and sparse actinolite. Magnetite is a fairly abundant accessory 

mineral in some tuff. Most fragments in the lithic tuffs 

have the same composition as the matrix-mainly rhyolite-but some are composed of quartz, chalcedony, 

or andesite. Except for a distinctive conglomerate, 

discussed in the next paragraph, the lithic tuffs are 

most abundant west of the rhyolite flow or massive tuff 

unit. 

A distinctive conglomerate lies east and west of the 

unit containing jasper-magnetite beds (fig. 4). Similar 

conglomerate is exposed near the western edge of the 

largest exposure (1,285,400 N., 352,600 E.). West of 

the unit containing jasper-magnetite beds, the conglomerate is a maximum of 50 feet thick; east of this unit 

the conglomerate is mostly less than 10 feet thick. The 

conglomerate is similar to rhyolitic lithic tuffs except 

for the presence of pebbles and cobbles of red chalcedony 

and jasper-magnetite; the conglomerate also contains a 

few fragments of andesite and of graphic intergrowths 

of quartz and alkalic feldspar. 

Gray slate, which may be a normal terrigenous sedi 

ment,3 is associated with the jasper-magnetite beds and 

with conglomerate and tuffaceous rocks for about 1,500 

3 Anderson and Creasey (1958, p. 29-30) C()nsidered purple slate in 

the Jerome area to be terrigenous on the basis of a higher alumina 

content and a higher ratio of potash to soda as compared with rhyolite 

tuft's of the area. 

feet west of the jasper-magnetite beds. Quartz-sericite 

schist, associated with lithic tuffs (pl. 1; near 353,500 

E., north of 1,281,500 N.) and with micaceous quartzite 

in the two western outcrops near Granite Creek (pl. 2), 

may be metamorphosed gray slate. Some of these 

schists are spotted. In the southern exposures the spots, 

as much as 2 em by 0.6 em, are pseudomorphs after 

staurolite ( ~) and now consist of sericite, magnetite, and 

chlorite in a matrix of quartz, sericite, chlorite, magnetite, and some alkalic feldspar. In the northern exposures the spots are biotite metacrysts as much as 3 mm 

in diameter that poikilitically enclose quartz grains. 

Dacite ( ~) rocks, probably flows and tuffs, occur west 

of the rhyolite flow or massive tuff unit (south of 

1,281,000 N.). They interfinger with rhyolitic lithic 

tuff and with rocks of uncertain origin. The dacite ( ~) 

is medium dark gray and well foliated. Some contain 

large amygdularlike areas of granular quartz; others 

contain fragments of a slightly different composition; 

some are bedded. The very fine grained matrix or 

groundmass consists of sericite, quartz, alkalic feldspar, 

chlorite, minerals of the epidote group, and abundant 

magnetite. Altered plagioclase grains are mostly less 

than 2 mm long; many are less than 0.5 mm long. 

Rocks of uncertain origin are characterized by sparse 

to 3Jbundant flattened white fragments of feldspar(?) 

or rhyolite. The fragments are angular and are randomly oriented in the plane of foliation, but they are 

somewhat augenshaped at right angles to foliation. 

Many of them are as large as 1.5 em by 0.4 em; some 

are much larger. They consist of a mixture of zoisite, 

epidote, sericite, alkalic feldspar, quartz, and a little 

chlorite. The matrix is composed of alkalic feldspar, 

quartz, ·chlorite, epidote-zoisite, and magnetite. 

Unit containing jasper-magnetite beds.-The unit 

that contains thin beds of jasper-magnetite consists of 

tuffaceous sedimentary rocks composed of ·rhyolite, 

some andesite, and a little gray slate; jasper-magnetite 

beds form a very minor part of the unit. Thin interbeds of jasper-magnetite are concentrated in layers 25-

50 feet thick, which are separated by at least 100 feet of 

tuffaceous rocks free of jasper-magnetite. Individual 

jasper-magnetite beds range from paper thin to about 

an inch in thickness. They are dark gray to blackish 

red-except for iron-poor, silica-rich interbeds, which 

are a lighter gray. A few beds have been traced along 

the strike for as much as 1,000 feet. The jaspermagnetite beds are composed of very fine grained magnetite-locally of hematite or the specular variety of 

hematite-in a matrix of microcrystalline quartz and 

variable amounts of quartz, sericite, albit~, chlorite, and 

minerals of the epidote group. These beds resemble the 

Precambrian iron formation of the Lake Superior region 
OLDER PRECAMBRIAN ROCKS 13 

(Leith and others, 1935, p. 21) and probably had a 

similar origin. James (1954) concluded that the high 

iron content of the iron formation is the product of 

iron-rich sedimentation in marine waters. 

Andesite flow·s and tuffs.-The eastern mass of andesite is largely tuff; the middle one is largely flow, and 

the western one is largely a porphyritic rock of uncer-

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360,000E 

0 

tain origin. Much of the andesite, in both differentiated and undifferentiated areas, is very fine grained and 

well bedded; some is medium grained and massive. 

The andesite is medium dark to medium greenish gray. 

Some is porphyritic or contains clusters of large flattened plates of saussuritized plagioclase. A few of the 

coarser grained rocks are vesicular or contain quartz 

EXPLANATION 

D 

Younger rocks 

· · · tu · · · .))) tj ::}}}: tc 

I

. · · · ·r<·:-:-:-:·: :::::::::::::::1 1 

. • • • • · .. • .. > ::: ::::::::::::: DC 0 0 tib 0 

Texas Gulch Formation 

tu, undifferentiated Texas Gulch Formation 

tj, unit containing jasper-magnetite beds 

tc, conglomerate beds in undifferentiated 

Texas Gulch Formation and unit containing 

jasper-magnetite beds 

Contact 

Dashed where approximately located; 

dotted where concealed 

Fault 

~ 

Strike and dip of beds 

Direction in which top of bed faces, based on 

graded bedding, channelling, beddingfoliation relations, or pattern of drag folds 

APPROXIMATE MEAN 

DECLINATION, 1965 

1 MILE 

FIGURID 4.-Distribution of conglomerate in the Texas Gulch Formation, Prescott quadrangle. 
14 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

or calcite amygdules. Small crystal fragments or 

phenocrysts of saussuritized plagioclase are erratically 

distributed through some of the rock. The andesite 

consists of chlorite, albite, and variable amounts of 

sericite, epidote, actinolite, calcite, quartz, m·agnetite, 

and ilmenite. Chlorite and sericite (from rhyolitic 

detritus) are abundant in the finer grained fissile rocks; 

actinolite, in the coarser grained ones. Hornblende 

( actinolitic) forms some metacrysts. The porphyritic 

rock contains plagioclase, actinolitic hornblende, epidote, magnetite, and sphene. 

Rhyolite crystal tuff.-Rhyolite crystal tuff is fine to 

coarse grained. Quartz and feldspar crystal fragments, as much as 2 mm in diameter, are sparse to 

abundant; either mineral may predominate; locally 

they are absent. Lithic fragments are composed of 

rhyolite and chalcedony. The matrix consists of 

quartz, sericite, alkalic feldspar, and a little chlorite 

and epidote. 

Rhyolite flmo or massive tuff.-The rhyolite flow or 

massive tuff is dark to medium gray or pale red to 

pinkish gray; it weathers pinkish gray to light brownish gray. The dark-gray rocks are very fine grained 

and dense, almost flinty in appearance. Massive rhyolite grades into and interfingers with foliated rhyolite, 

but the micaceous minerals have a preferred orientation, even in massive-appearing rhyolite. Most of the 

rock lacks features that might indicate whether it is a 

flow or massive tuff; its length does not support a flow 

origin. The tiny phenocrysts or fragments of quartz 

and albite and a few of orthoclase are not conspicuous 

or abundant; they are mostly less than 1 mm in diameter. The matrix consists of quartz, alkalic feldspar, 

and sericite. Green biotite~ magnetite, pyrite, epidote, 

or irregular aggregates of biotite, calcite, and magnetite 

were observed in some of the rhyolite. Muscovite 

forms metacrysts in some of the coarser textured rock. 

INDIAN HIL-LS VOLCANICS 

DISTRIBUTION 

The Indian Hills Volcanics, named by Anderson and 

Creasey (1958, p. 20) for exposures in the Indian Hills 

in the western part of the Jerome area, extend into the 

east-central part of the Prescott-Paulden area, where 

they crop out north of Route 89A: (pl. 1) and in four 

places south of 1,381,000 N. and east of 395,000 E. (pl. 

2). The formation consists of interbedded andesitic 

and rhyolitic flows. The two units are differentiated 

on plate 1 but not on plate 2. Tuffaceous material, in 

areas mapped as contaminated Indian Hills Volcanics 

and in adjacent contaminated intrusive rocks, is included in the formation; tuffaceous rocks are not part 

of the formation in the type section. 

THICKNESS AND STRATIGRAPHIC RELATIONS 

The maximum outcrop width of the Indian Hills 

Volcanics within the area is about 4,000 feet. The 

thickness is probably less than outcrop width because 

the formation is probably folded and because the outcrop includes a considerable amount of granodiorite 

and gabbro too small or too poorly exposed to map. 

In places sheets and pods of gabbro compose as much 

as one-third of an area mapped as rhyolite. Gabbro 

may be as abundant as andesite in some areas mapped 

only as andesite, but it is not as apparent as in the rhyolite. In areas mapped as contaminated Indian Hills 

Volcanics, the volcanic rocks appear to make up about 

half of the outcrops. Granodiorite and some alaskite 

and gabbro, however, may be more abundant but are 

not apparent because the volcanic rocks crop out better. 

The volcanic rocks occur as angular to lenticular xenoliths in the intrusive rocks and as large masses into 

which the intrusive rocks were intimately injected. 

In the Prescott-Paulden area the Indian Hills Volcanics are not in contact with other formations of the 

Alder Group. In the · Jerome area (Anderson and 

Creasey, 1958, p. 21) the Indian Hills and Spud Mountain Volcanics appear conformable, but the direction 

in which tops of beds face was not determined. Because 

the Iron King Volcanics probably overlie the Spud 

Mountain Volcanics, the Indian Hills Volcanics were 

interpreted as underlying the Spud Mountain Volcanics. Although the base of the Indian Hills Volcanics 

is not exposed, Anderson and Creasey interpreted the 

volcanic rocks as presumably overlying the Texas Gulch 

Formation. 

LITHOLOGY AND INTERNAL STRUCTURE . 

Interbedded andesitic and rhyolitic flows and some 

tuffaceous sedimentary rocks make up the Indian Hills 

Volcanics. The main exposures of the flows are in the 

Jerome area; they are described in detail by Anderson 

and Creasey ( 1958, p. 21). 

The rocks are foliated but less so than other formations of the Alder Group. Foliation is absent in some 

outcrops in the Jerome area; it is more pronounced to 

the west, especially in the areas of fine-grained bedded 

tuffs. Some contacts between rhyolite and andesite 

flows are shear zones. 

Rhyolitic flows.-The rhyolitic flows are grayish 

orange pink to light gray or greenish gray, except for 

dense siliceous, almost flinty rhyolite, which is medium 

gray to medium dark gray. Textures and structural 

features typical of rhyolite flows-such as flow banding, 

flow breccia, amygdules, and vesicles-occur locally but 

are generally inconspicuous. Phenocrysts consist of 

quartz, albite, and a little potassium feldspar; few of 
OLDER PRECAMBRIAN ROCKS 15 

them are conspicuous. Most phenocrysts are less than 

1.0 mm long; where abundant, they may be more than 

2 mm long. The groundmass is composed of microcrystalline aggregates of alkalic feldspar, quartz, and 

a little sericite; accessory minerals are chlorite, minerals of the epidote group, and magnetite. Sericite is 

abundant in the more sheared rocks. In some northern 

outcrops (pl. 2), biotite is concentrated in widely scattered thin layers and lenses, and quartz phenocrysts 

are recrystallized. 

Andesitic and basaltic flows.-The andesitic and 

basaltic flows are greenish black. The flows are blocky, 

except where they are somewhat fissile owing to foliation or shearing. Amygdules, composed of minerals of 

the epidote group, and vesicles are widely distributed. 

Phenocrysts of altered plagioclase and less commonly 

of hornblende are widespread and are as much as 2 em 

long. The holocrystalline commonly fine-grained 

groundmass consists of granular albite and minerals 

of the epidote group, small flakes of chlorite, and som.e 

biotite, magnetite, and calcite. Most chlorite has a 

slight preferred orientation; some is well oriented. 

Tuffaceous sedimentary rocks.-Most of the andesitic 

and rhyolitic tuffaceous sedimentary rocks are finegrained fissile foliates of light to dark color. Graded 

bedding and drag folds were observed in a few places. 

Mafic minerals are more abundant in some siliceous 

tuffs than in the rhyolite flows. Quartz, alkalic feldpar, and variable amounts of sericite make up the rhyolitic tuffs. Albite, minerals of the epidote group, 

chlorite, and some actinolitic hornblende compose the 

andesitic tuffs. Epidote is conspicuous in many of the 

rocks, even those composed largely of rhyolitic detritus. 

SPUD MOUNTAIN VOLCANICS 

DISTRIBUTION 

The Spud Mountain Volcanics (Anderson and 

Creasey, 1958, p. 21-26) were named for excellent exposures on Spud Mountain, in the extreme southeast 

corner of the area (pl. 1), where they crop out as one 

large and several smaller masses. An outcrop of breccia, mapped with the Indian Hills Volcanics but probably part of the Spud Mountain Volcanics is in the eastcentral part of the area (pl. 2,1,367,500 N., 398,100 E.). 

The breccia is faulted against Indian Hills Volcanics 

and Martin Limestone. In the type locality the formation consists of two units: ( 1) andesitic tuff lying east 

of ( 2) andesitic breccia. Elsewhere in the Jerome area, 

some rhyolitic tuff and andesite flows are intercalated 

in the andesitic tuff and breccia units. 

THICKNESS AND STRATIGRAPHIC RELATIONS 

The thickness and stratigraphic relations of the Spud 

Mountain Volcanics are uncertain because the formation is cut off on the west by the Spud fault and buried 

to the north and east by Cenozoic rocks. It has an 

outcrop width within the area of about 5,500 feet, of 

which about 4,000 feet is the breccia unit and 1,500 feet, 

the tuff unit. The tuff unit may be approximately 1,500 

feet thick in this area; the breccia unit may not be more 

than 2,000 feet thick, as the structure of the unit may be 

anticlincal (pl. 1, sec. E-E'), as interpreted by Anderson and Creasey ( 1958, p. 72). 

To the southeast the volcanics appear to be conformably and gradationally overlain by the Iron King Volcanics (pl. 1, sec. E-E') (Anderson and Creasey, 1958, 

p. 23). The andesitic breccia is interpreted as occupying the lower part and the andesite tuff, the upper part 

of the formation. 

LITHOLOGY AND INTERNAL STRUCTURE 

The Spud Mountain Volcanics are various shades of 

grayish green to greenish gray; actinolitic hornblende 

produces the darker shades. Lighter shades are due 

to sericite from admixed rhyolitic detritus. The rocks 

weather brown or reddish brown to yellowish gray. 

Most of the breccia within the map area is foliated, 

but it does not readily break parallel to this foliation because of abundant fibrous actinolitic hornblende. Finegrained tuffs in any one locality are more intensely 

foliated than coarser grained crystal tuffs or breccia 

beds. Some fragments in the breccia facies show little 

or no evidence of stretching; others, even in adjacent 

beds, have been attenuated to lengths as much as 12 

times the widths. 

Relict bedding is preserved in some tuffaceous beds. 

Graded bedding, brought out by the distribution and 

size of plagioclase grains, can be recognized in places. 

The principal constituents of both breccia and tuff are 

chlorite, albite and albite-oligoclase, minerals of the epidote group, some carbonate, and accessory magnetite, 

sphene or leucoxene, and apatite. Clinozoisite (or 

zoisite) is more abundant than epidote; actinolitic hornblende is found only in the andesitic breccias. The distribution of quartz is very erratic. Except in saussuritized plagioclase, sericite is largely confined to finer 

grained tuffs and was derived probably from admixed 

rhyolitic detritus. 

Andesitic breccia.-Included within the breccia facies 

of the Spud Mountain Volcanics are beds of. breccia, 

granular crystal tuff, and fine-grained tuffaceous sedimentary rocks. The unit is predominantly andesitic in 

composition. Breccia beds, which range from less than 

1 foot to possibly 500 feet in thickness, are more abundant than the tuffs in the breccia facies. 

The fragments, from less than 1 inch to 18 inches 

long, are sparsely to abundantly distributed throughout the breccia beds. Within individual beds most of 
16 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

them are rather uniform in size. Their shape, which 

is generally subrounded, is due, in some places, to the 

original form or, in other places, to later deformation. 

Fragments in the breccia are composed largely of 

porphyritic andesite. A few andesite fragments are 

amygdaloidal or vesicular. Other fragments consist of 

rhyolite, fine-grained dark rocks of undetermined origin, and mixtures of quartz and epidote of probable 

metamorphic origin. Rhyolitic fragments are locally 

abundant on the west side of Spud Mountain. Phenocrysts in the andesite fragments occur as individual 

crystals and clusters of crystals. They consist principally of equant saussuritized plagioclase and have a maximum size of 1 em. The character, size, and distribution 

of the phenocrysts are identical .in many places with 

those of the crystal fragments in andesitic crystal tuff, 

which forms the matrix of some of the breccia. Elsewhere the matrix is fine-grained andesitic tuff. Finegrained tuff and crystal tuff similar to the matrix occur 

as interbeds in the breccia and are identical with 

andesitic tuff described in the following paragraphs. 

Andesitic tutf.-The contact between the tu:tf and 

breccia is gradational and is arbitrarily located. Away 

from the contact, breccia or conglomerate and coarse 

crystal tuff beds are thin and ~ess abundant, the fragments are smaller, and finer grained tuff beds are more 

prevalent. Conglomerate beds as much as 10 feet thick 

are common in the part of the tuff within the Prescott 

quadrangle; however, to the east and presumably higher 

in the section, coarse-grained crystal tuff beds and associated conglomerates are much less abundant, and 

more of the unit is fine grained (Anderson and Creasey, 

1958, p. 24-25). 

The andesitic tuft' is a sedimentary rock composed 

largely of andesitic volcanic· detritus. Most individual 

beds are not more than a few inches thick; grain size 

varies from bed to bed. The particles range from clay 

to cobbles, but most of them are between silt and coarse 

sand in size. Some variation in grain size is due to differential shearing, but most of it is probably a primary 

sedimentary feature. 

Visible minerals in the tuff are chlorite, saussuritized 

plagioclase, and variable amounts of quartz and sericite; saussuritized plagioclase is the most conspicuous 

mineral. The plagioclase grains give the rock a pcrphyritic appearance or bring out its bedding depending 

on their distribution. 

The finer grained facies are phy Hites or slates. Chlorite and some sericite produce a sheen on cleavage surface that is characteristic of these rocks. Small grains 

of quartz or saussuritized plagioclase can be seen with 

a hand lens in some of these beds. Fissility is more pronounced and regular than in the coarser grained tuffs. 

CHAPARRAL VOLCANICS 

DISTRIBUTION 

The Chaparral Volcanics (Anderson and Creasey, 

1958, p. 30-31), named for exposures in Chaparral 

Gulch (1,277,000 N., 392,000 E.), trend northeastward 

for about 3 miles across the southeast corner of the area 

(pl. 1). 

The volcanics consist of two lithologic units: rhyolitic 

tuff and andesitic tuft'. Most of the andesitic tuff lies 

east of the rhyolitic tu:tf. A narrow layer of rhyolitic 

tuff occurs in andesitic tuff (pl. 1), and a narrow layer 

of andesitic tuff that tapers to a point from a width of 

about 50 feet occurs in rhyolitic tuff (shown only on 

pl. 1 of the Jerome report, Anderson and Creasey, 19'58). 

At the north, the outcrop of the rhyolitic tuff is split 

into three parts by the south-tapering masses of Prescot Granodiorite and alaskite. South of the tongues of 

intrusive rocks, the separate belts of rhyolite join to 

form a single belt. At the many places where quartzsericite schist was formed at the contact between rhyolitic tuft' and intrusive granitic rocks, the location of 

the contact is indefinite because the schist that was produced by intense distributive shear could have originated from either the tuff or the granitic rocks. 

THICKNESS AND STRATIGRAPHIC RELATIONS 

No estimate of the thickness of the Chaparral Volcanics can be made, and its stratigraphic relations to 

other formations are unknown. The formation is separated from adjacent formations by major faul~ that 

are occupied by intrusive igneous rocks (pl. 1). The 

Chaparral fault separates it from the Green ·Gulch 

Volcanics on the northwest, and the Spud fault separates it from the Spud Mountain Volcanics on the 

southeast. Structural complications-isoclinal folding, 

strong phyllonitization (Knopf and Ingerson, 1938, p. 

190), and shearing out of beds-make an attempt to 

estimate original thickness hopeless. 

The formation has an outcrop width of 1,50(}-2,600 

feet. At the north end the distance between the two 

bounding faults is about 3,800 feet, but approximately 

1,500 feet of this distance is occupied by intrusive rocks. 

The outcrop width of the rhyolitic tuff is much greater 

than that of the andesitic tuff at the north but less than 

that of the andesitic tuff to the south. The stratigraphic 

relation of andesitic tuff to rhyolitic tuff is not known, 

as the direction in which tops of beds face was not 

determined. 

Although lithologically some of the Chaparral Volcanics resemble parts of other formations of the Alder 

Group, evidence currently available is insufficient to 

justify any correlation. The faults and shears in the 

area suggest that the Chaparral Volcanics may have 
OLDER PRECAMBRIAN ROCKS 17 

been moved for a long distance and may not even· be 

part of the Alder Group. 

LITHOLOGY AND INTERNAL STRUCTURE 

Rhyolitio tuff.-The rhyolitic tuff is a fine-grained 

predominantly sedimentary rock that ranges from fissile, finely laminated foliates to more massive rocks. 

The rocks included in the rhyolitic tuff grade from compartively pure rhyolite to those containing added andesitic material. On a broad scale the rhyolite tuff consists of three types ; each variety predominates in a 

separate area, but some interbedding of and gradation 

between the types occur. The eastern belt consists 

mostly of white fissile quartz-sericite schist; the western 

belt, of massive pink rhyolite; and the middle belt, of 

finely laminated greenish -gray tuff having contorted 

bedding. A single belt composed largely of white tuff 

occurs south of the tongues of intrusive rocks. 

Rhyolitic tuff of the eastern belt is very light gray 

to yellowish gray, very fine grained, and finely laminated. Scattered tiny grains of quartz and a few of 

feldspar are the only visible minerals, fl,lthough the 

sheen of the rock attests to the presence of sericite and 

a green tinge indicates admixed chlorite. Most of the 

feldspar grains are albite; a few are orthoclase. The 

matrix is composed of quartz, sericite, and variable 

amou~ts of alkalic feldspar. 

Much of the rhyolitic tuff in the middle belt is a finely 

laminated greenish-gray to dark greenish-gray rock. 

Fissility is less well formed than in the rocks of the 

eastern belt. Contorted beds and small drag folds are 

common. The rock contains some epidote, actinolite, 

and biotite or chlorite; sericite is less abundant than in 

rocks of the eastern belt. 

Rhyolitic tuff of the western belt is largely a massive pale-red rock; some is yellowish gray. Some grains 

o£ quartz and feldspar are a little larger and more 

abundant than those in the tuffs of the east. The matrix 

is mainly quartz and feldspar; a little epidote occurs 

locally. In much of this belt, no textures or structural 

features resembling primary flow or bedded features 

were found. The massive rhyolite is interpreted as a 

massive tuff on the basis of its extremely long strike 

length in contrast to its width; most rhyolitic flows are 

lenticular. 

Andesitio tuff.-The andesitic tuff is fine grained, well 

foliated, and fissile, except for interbeds of more massive, coarser grained tuff. The finer grained tuff is 

commonly greenish gray to olive green; some is blotched 

and streaked with variegations of light yellowish green. 

Much of the lighter color is due to admixed rhyolitic 

material; where crosscutting, it is due to alteration. 

The matrix is composed of chlorite, sericite, albite, epidote, and quartz. The coarser tuff, in beds 1-50 feet 

thick, is more plentiful in the eastern than in the western part of this unit. It is grayish green and less well 

and more irregularly foliated than the finer grained 

tuff. Its principal constituents are chlorite, albite, and 

epidote. Feldspar grains are saussuritized. 

GREEN GULCH VOLCANICS 

DISTRIBUTION 

The Green Gulch Volcanics (Anderson and Creasey, 

1958, p. 31-32) were named for excellent but incomplete 

exposures along Green Gulch (between 1,282,000 N., 

393,500 E. and 1,281,900 N., ·386,500 E.). The formation crops out in the southeast part of the area (pl. 1) 

west of the Chaparral fault. Scattered outcrops protrude above the Cenozoic cover north of the main exposures. The formation is cut out near the south border 

o£ the area by the fault and by gabbro. It is not exposed elsewhere in the Prescott-Paulden area or the 

Jerome area. The formation has been divided into a 

basaltic flow unit and a tuffaceous unit; the basaltic flow 

unit lies east of the tuffaceous unit, which is split into 

two parts by intrusive rocks. 

THICKNESS AND STRATIGRAPHIC RELATIONS 

If outcrop widths approximate thickness, the formation must be more than 5,000 feet thick; the outcrop 

width of the basaltic flow unit is 7,000 feet, and that 

of the tuffaceous unit is 4,500 feet. 

The stratigraphic relations could not be determined 

as the Green Gulch is not in normal contact with other 

formations of the Alder Group. Except locally, the 

lithology of the ·Green Gulch Volcanics is not sufficiently 

like that of any other formation in the group to permit 

a correlation. 

Although beds face east and west in the basaltic flow 

unit, west-facing beds are more prevalent than eastfacing ones. For this reason, the tuffaceous unit is believed to overlie the basaltic flow unit. 

LITHOLOGY AND INTERNAL STRUCTURE 

B asaltio flow unit.-The basaltic flow unit consists of 

flow, breccia, tuff, and conglomeratic tuff. Most of these 

rocks are medium to dark gray and have a green cast. 

Rocks rich in metamorphic hornblende are dark bluish 

gray; those rich in chlorite are grayish green. 

Relict pillow and breccia structures, amygdules, vesicles, and bedding are preserved here and there and are 

well exposed in the water-polished exposures in the 

larger gulches. Pillows were recognized only in Green 

Gulch and the next gulch to the south (indicated by 

symbol on pl. 1). Many of the pillows are attenuated 

to as much as 15-20 times the width. Amygdules, composed of quartz and quartz-epidote, and vesicles are 

more widespread than the pillows. Relict bedding and . 

drag folds are preserved in tuffaceous interbeds separat-
18 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

ing flows and breccias. Bedding symobls in the basaltic 

flow unit on plate 1 indicate the location of some of these 

interbeds. Fragments in the breccia and conglomeratic 

tuff are composed of rhyolite and more abundant andesite or basalt and of crystal fragments from these rocks. 

The fragments range from less than 1 mm to about 

15 em. Some are attenuated; lengths in places exceed 

widths by as much as 10 times. Some fragments are 

angular to sub angular. 

Small saussuritized plagioclase phenocrysts and 

porphyroblasts or aggregates of hornblende are the most 

rubundant megascopic minerals. Some phenocrysts (or 

fragments in the tuffs) are clustered. Chlorite is visible 

locally. Relict felty texture was recognized in one 

place, but metamorphism has obliterated many original 

textures. 

The principal constituents are actinolitic hornblende, 

albite, and epidote; chlorite and carbonate are abundant 

where the rocks were highly sheared. Higher grade 

metamorphism in the northeasternmost expesures produced hornplende, oligoclase, and some brown biotite, 

sphene, and apatite. Here narrow veinlets that resemble ptygmatic folds consists of minerals of the epidote 

group and some quartz, chlorite, plagioclase, sphene, 

and muscovite, all of which were probably formed by 

metamorphic diffusion. 

The predominance of mafic constituents and the lack 

of abundant plagioclase phenocrysts suggest that this 

unit is basaltic rather than andesitic. The presence of 

pillows likewise suggests a basaltic composition; Satterly (1941) pointed out that most of the analyzed pillow lavas of Canada are basalts, and an analysis of the 

Iron King Volcanics (Anderson and Creasey, 1958, p. 

27), which contains pillow lavas, indicates a basaltic 

composition. 

Tuffaceou.s unit.-The tuffaceous unit consists of tuffs 

and breccias and very minor rhyolitic flows. The clastic rocks are principally rhyolitic and admixed rhyolitic 

and andesitic in composition, but a few are mafic. The 

mafic tuffs and breccias are identical to the tuff and 

breccia in the basaltic unit and predominate for about 

1,000 feet west of the arbitrarily located contact between 

the two units. 

Most of the rhyolitic rocks are dark gray ; some have 

a green, olive, or pink cast; they weather olive gray or 

pinkish gray. A few are light-gray porcelaneous slates. 

In the eastern exposures those that weather olive gray 

have a characteristic sheen due to abundant sericite 

and a little chlorite. Here the rhyolitic tuffs are fine 

grained and range from finely laminated fissile foliates 

to more massive locally coarser grained rocks. Relict 

. bedding and drag folds are apparent in water-worn outcrops along Green Gulch. An additional indication of 

the sedimentary origin of at least the eastern part of the 

unit is the abrupt variation in composition and texture 

across the trend of the unit. No relict bedding was 

observed in the western ·outcrops; flow banding was observed in one place ( 1,280,800 N ., 382,200 E.). 

Phenocrysts and crystal fragments are visible in many 

places, but few of them are more than 1 mm long. They 

consist mostly of clear albite-oligoclase, quartz, and 

magnetite. Some plagioclase has saussuritized centers; 

larger ones are completely saussuritized. The groundmass or matrix is composed of quartz, orthoclase, albite, 

sericite, minerals of the epidote group, magnetite, 

sphene, and sporadic chlorite and actinolite or actinolitic hornblende. Saussuritized plagioclase, epidotegroup minerals, and magnetite are locally abundant. 

The plagioclase and epidote minerals together with 

chlorite and actinolite probably represent admixed andesitic or basaltic detritus. The rhyolitic tuffs in the 

eastern outcrops are composed largely of quartz and 

sericite. In the western outcrops quart.z and alkalic 

feldspar are the principal constituents. 

The unit ontains a few rhyolitic breccias. Fragments are composed of rhyolite and andesite or basalt; 

some are angular, others are rounded. They range from 

a fraction of an inch to 10 inches in length. 

UNNAMED VOLCANIC ROCKS OF THE ALDER(l) GROUP 

DISTRmUTION 

Volcanic rocks that may belong to the Alder Group, 

but which could not be correlated with known formations in the group, are mapped as two lithologic units; 

basaltic flows and tuffaceous rocks. These rocks crop 

out in four places along the southern border of the 

area (pl. 1) and in two places in the northern part 

(pl. 2). They are referred to as (1) the southwestern 

basaltic flows and tuffaceous rocks, (2) the southcentral basaltic flows, ( 3) the south-central tuffaceous 

rocks, ( 4) the southeastern basaltic flows and tuffaceous 

rocks, ( 5) the northern tuffaceous rocks, which extend 

south-southeastward from upper King Canyon (1,392,-

500 N., 381,000 E.), and (6) the northern basaltic flows, 

which form six small outcrops (fig. 5) east and southeast of the Pinnacle ( 1,400,000 N ., 353,000 E.). Small 

unmapped amounts of these lithologic units occur in 

adjacent intrusive rocks. 

THICKNESS AND STRATIGRAPHIC RELATIONS 

On the basis of outcrop widths, individual masses of 

these unnamed volcanic rocks are estimated to be 1,000-

3,000 feet thick, but the relations are unknown. No 

correlation of individual masses with one another has 

been made. Lithologically some or all of the masses of 

tuffaceous rocks could be stratigraphic equivalents, as 

could some of the basaltic flows. 
OLDER ·PRECAMBRIAN ROCKS 19 

Where mapped, the individual masses are surrounded 

by younger rocks. Many of them occur only as roof 

pendants or lenses in intrusive rocks (pl. 1, sec. B-B' 

and E-E'). Only the south-central basaltic flows are 

adjacent to another formation of the Alder Group, but 

a fault or shear zone separates the two. The southwestern basaltic flows and tuffaceous rocks interfinger or are 

repeated by folds along the contacts between the two 

units. The relations of the southeastern basaltic flows 

and tuffaceous rocks is not known; on the east, along, 

and west of Charcoal Gulch, a fault or shear zone probably separates the two units. 

LITHOLOGY AND INTERNAL STRUCTURE 

Basaltic flows.-Rocks mapped as unnamed basaltic 

flows comprise basaltic flow, breccia, tuff, and some 

interbedded rhyolitic tuff. The basaltic rocks are 

medium to dark gray with a slightly green or blue cast. 

Foliation except in some sedimentary breccia and 

tuff, is variable but generally less well defined than in 

most of the formations of the Alder Group. Intense 

shear has produced zones of retrograde metamorphism 

and abundant chlorite. The northern basaltic flows and 

some of the southeastern and southwestern ones are 

poorly foliated to nonfoliated. 

Amygdules, vesicles, agglomeratic structures, and pillows ( ? ) indicate a flow origin for some rocks. Bedding, 

a fragmental character, and abrupt changes in lithology 

indicate or suggest a sedimentary origin for others. 

Amygdules are composed of quartz, epidote, or calcite. 

Pillows ( ? ) were noted in the southwestern basaltic flows 

(especially near 1,276,100 N., 337,900 E.). The closely 

packed rounded, ellipsoidal, or irregularly shaped pillow ( ?) , mostly l~ss than 1 foot long, have thin finegrained dark selvages, which are probably chilled bor~ 

ders. The irregular shape and small size are suggestive of bombs, lapilli, ·and other agglomeratic fragments, 

but triangular chalcedonic fillings are reminiscent of the 

chalcedonic fillings between most pillows in the area. 

The enclosing matrix is rich in zoisite (or clinozoisite). 

The northern basaltic flows consist largely of closely 

packed fragments having the same composition as the 

enclosing matrix. Some of these fragments resemble 

the smalllapilli and bombs of an agglutinate (Tyrrell, 

1931, p. 66). 

Sedimentary breccias are largely confined to the 

south-central basaltic flow. Fragments in the breccias 

are 1 mm to 15 em long and consist of saussuritized 

plagioclase, basalt, and a little rhyolite. The fragments are angular, rounded, or attenuated. Recognizable tuff interbeds are confined to the south-central and 

to the western parts of both the southeastern and southwestern basaltic flows. 

Much of the rock is massive, fine grained, and nondescript; it has no features that indicate a flow, tuff, or 

intrusive origin. Scattered saussuritized plagioclase 

phenocrysts, crystals fragments, or clusters of them, 

are generally visible and may be abundant. Many of 

them are about 1 mm in size; some are as much as 7 mm. 

Most of them are equant to lath-shaped. In distribution 

and abundance the phenocrysts in fragments are similar to, or contrast with, those in the matrix. 

Saussuritized plagioclase and magnetite are generally 

the only relict primary minerals, but a little relict pyroxene was observed in the northern and southeastern 

basaltic flows. Some unaltered zoned plagioclase laths 

occur as phenocrysts and in the groundmass in the 

northern and south-central basaltic flows. The felty to 

diabasic texture and subparallel orientation of plagioclase laths are interpreted as primary. 

Most minerals and textures are metamorphic. The 

rock is composed of a granular assemblage of albite or 

oligoclase, actinolite or aetinolitic hornblende, minerals 

of the epidote group, and some quartz, chlorite, calcite, 

sericite, and accessory magnetite, sphene, and apatite. 

Hornblende or actinolitic hornblende forms sparse to 

abundant large porpJ:lyroblasts, poikiloblasts, or aggregates. Hornblende, brown biotite, and muscovite are 

common in areas of higher grade metamorphism. A 

subparallel dimensional orientation of actinolitic hornblende and variations in the relative proportions of 

hornblende and plagioclase in thin layers are probably 

metamorphic features. 

Tuffaceous rocks.-The unnamed tuffaceous rocks are 

principally a sedimentary series composed of volcanic 

detritus of basaltic (or andesitic) and rhyolitic composition; some may be terrigenous siliceous sediments. A 

few small unmapped basaltic flows and questionable 

flmvs are included with the tuffs. The tuffs are mostly 

fine grained, finely laminated, and well foliated; where 

micaceous minerals are abundant, the tuffs cleave readily. Mineral streaking, plunge of drag folds, and intersection of cleavage and bedding give some of the rock 

a pronounced lineation. Some pebble- to cobble-sized 

fragments have the same composition as the enclosing 

matrix; the composition of other fragments contrasts 

with the matrix. 

The basaltic or andesitic tuffs are medium dark to 

dark gray and have a green or blue cast; some layers are 

light yellowish or greenish gray. Some tuffs contain 

visible crystal fragments of saussuritized plagioclase; 

others contain poikiloblastic or porphyroblastic actino-
20 GEOLOGY OF THE PRESCO'IT AND PAULDEN QUADRANGLES, ARIZONA 

litic hornblende as much as 1 em long. The matrix is 

composed of metamorphic albite or oligoclase-andesine, 

actinolitic hornblende, and minerals of the epidote 

group. Accessory minerals are magnetite, apatite, 

sphene, and pyrite. Quartz, potassium feldspar, biotite, chlorite, muscovite, or sericite sporadically occur. 

Zoisite or clinozoisite is more abundant than epidote. 

Much of the quartz and feldspar represent admixed 

rhyolitic detritus, but some may have been derived from 

granitic veinlets that cut the tuff. Except for sericite 

formed from alteration of plagioclase, micaceous minerals are generally absent unless the rocks contain rhyolitic detritus or have been sheared. The typical finely 

laminated rocks are composed of layers of different 

combinations and proportions of the principal minerals; hornblende is especially abundant in the dark 

layers; and zoisite, or clinozoisite, in the light-colored 

layers. Some light-colored layers contain abundant 

tremoli te-actinolite. 

Many rhyolitic tuffs are medium-dark to light shades 

of bluish, greenish, or yellowish gray; some are nearly 

white; others are pale or grayish red to grayish orange 

pink. They are composed of quartz, variable amounts 

of alkalic feldspar, muscovite, sericite, biotite, chlorite, 

minerals of the epidote group, and accessory magnetite, pyrite, and sphene. The tiny angular to subrounded crystal fragments, some visible in hand specimen, are composed of quartz, potassium feldspar, and 

albite; a few are composed of saussuritized plagioclase. 

Many of the rocks are quartz-sericite schis s, but higher 

grade metamorphism of the southwestern tuffaceous 

rocks has formed some quartz-biotite and quartz-muscovite schists. In the southeastern exposures some tuffaceous rocks are composed of quartz and alkalic feldspar but contain little or no sericite. In one place along 

Bannon Creek (near 1,274,200 N., 336,200 E.), pseudomorphs after poikilitic tremolite ( ? ) are now composed 

of biotite, chlorite, epidote, sphene, and a little relict 

amphibole. They are as much as 1 em long and enclose many quartz and feldspar grains. Tremolite(?) 

metacrysts are unusual in a rock composed largely of 

quartz and calcitic albite. Some schists contain magnetite metacrysts as much as 4 mm in diameter; others 

(near 1,290,500 N., 375,800 E.) contain tiny red garnets. 

Garnet-epidote-quartz alteration zones and quartzmagnetite veins or alteration zones are common in the 

southwestern and south-central areas of tuffaceous 

rocks; some occur in the southeastern areas. The 

quartz-magnetite veins are discussed under veins and 

silicified and alteration zones in the section on older 

Precambrian intrusive rocks (p. 48). 

The garnet-epidote-quartz alteration formed largely 

in the mafic tuffs as concordant and crosscutting thin 

layers and lenses and locally, as knots and ptygmaticlike veinlets. The minerals formed during the alteration are epidote, grayish-red garnet, and quartz in varying proportions. Sparse to abundant zoisite, tremolite, 

sericite, sodic plagioclase, magnetite, and sphene occur 

in various combinations in the alteration zones. 

MAZATZAL QUARTZITE 

DISTRIBUTION 

The Mazatzal Quartzite, named by Wilson ( 1922, p. 

299; 1939, p. 1124) for exposures in the Mazatzal Mountains (southeast of Pine, inset, fig. 1), crops out south 

of the Verde River in the central part of the Paulden 

quadrangle (pl. 2), where it is referred to as the Del 

Rio area. Within an area of about 23 square miles, the 

quartzite forms 1 large and 21 small outcrops (fig. 5), 

which total about 3 square miles in area. 

THICKNESS AND STR.ATIGRAPHIC RELATIONS 

About 4,000 feet of Mazatzal Quartzite was measured 

in the Del Rio area, but the total thickness is not known, 

as neither the top nor the bottom of the formation is 

exposed. Wilson (1939, p. 1155) measured only 1,780 

feet, but he believed the formation to be cut by a thrust 

fault. 

The stratigraphic position of the Mazatzal is not 

known. The quartzite is in fault contact (fig. 5) with 

the Texas Gulch Formation (1,402,500 N., 347,000 E.) 

and with basaltic flows of the Alder(?) Group (near 

1,393,500 N., 353,300 E.). Quartzite apparently surrounds the basaltic flows to the north, but contacts are 

covered. The probable stratigraphic position of some 

of the small outcrops of the formation is shown in 

figure 5. 

The Mazatzal Quartzite is unconformably overlain 

by the Tapeats Sandstone, or Martin Limestone, of 

Paleozoic age or by Cenozoic rocks. 

LITHOLOGY AND INTERNAL STRUCTURES 

The Mazatzal Quartzite comprises a series of fine- to 

coarse-grained quartzite, granule to boulder conglomerate, and a little argillite. In ascending order the 

formation consists of quartzite, 260 feet (0-1); lower 

conglomerate, 440 feet ( 2-5) ; lower argillite, 50 feet 

(6); quartzite and minor conglomerate, 940-1,100 feet 

(7-11); upper argillite, 60 feet (12); quartzite and 

minor conglomerate, 835 feet (13-17); upper conglomerate, 1,150 feet (18-26) ; and quartzite, 325 feet (27-

28). (Figures in parentheses refer to units described 

in the measured section.) The formation is described 
OLDER PRECAMBRIAN ROCKS 

1,410,000 r---------------.----------------.---------------,--------~------,---------------,----------------. 

345,000 

Mazatzal Quartzite 

me 2 , upper con{;lomerate 

rna 2 , upper argillite 

rna 1, lower argillite 

me 1, lower conglomerate 

0 

Stratigraphic position of me (conglomerate) 

and ma (argillite) unknown 

350,000 

Unnamed basaltic flows of the Alder(?) 

Group 

Pinnacle 

ab 

t~ 

J

mc 

0 

mq 

355,000 

EXPLANATION 

11111 11 111:~: ::111 111111 1 Texas Gulch Formation 

Contact 

Dashed where approximately located; 

dotted where concealed 

Fault 

Dashed where approximately located; 

dotted where concealed 

Thrust fault 

Saw teeth on upper plate 

Amq 

• W ·a···.m····· .. \····\.• rna lv

v 

365,000 370,000 

/3+-+-----

Anticline 

Showing plunge; dashed where 

approximately located 

+ 

Minor fold 

Nearly horizontal, or plunge unknown 

50 ____!___ 

Strike and dip of beds 

-+ 

Strike of vertical beds 

Area of jointed rock 

FIGURE 5.--0utcrops of the Mazatzal Quartzite and of Precambrian rocks adjacent to the Mazatzal in the Paulden quadrangle. 

The structure and probable correlation of isolated outcrops to the main mas:s of the Mazatzal are shown. 

21 
22 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

Mazatzal Quartzite, Del Rio area, Arizona-Continued 

Section 3-Continued 

in detail in the following sections (note that two different figures, sections 1 and 1a, were obtained for units 

7-11): Thickne8B 

(feet) 

Mazatzal Quartzite, Del Rio area, Arizona Upper conglomerate ( 18-26) -Continued 

24. Sandstone, sandy and micaceous, and 

[Color terms and numerical designations are those used in the "Rock 

Color Chart," National Research Council, 1948] 

shale, grayish-red ( 10RP 5/3-5R 4.5/3), 

fine-grained to silty, weakly cemented, 

Section 3 locally ripple-marked, slope-forming ; 

[Top located at 1,395,600 N., 347,600 E.] 

Top eroded and covered by Cenozoic deposits. 

Quartzite (27-28) : 

28. Quartzite and a little granule conglomerate, 

pale red-purple (5RP 6/2), mediumgrained, thin bedded (beds are about 6 in. 

thick), cross-laminated, well-indurated 

(quartz cement); conglomerate contains 

subrounded to subangular granules of 

quartz and a few of red chalcedony ____ _ 

27. Quartzite and a little granule to smallpebble conglomerate, grayish-red (5R 4.5/ 

2), rarely pale-red (7R 5/2) ; weathers 

dusky red to very dark red (5R 3/4-

2/6) ; medium-grained, thin-bedded (6 in. 

to 1 ft), cross-laminated, well-indurated 

(quartz cement); contains a few very 

thin partings of red argillite and micaceous sandstone, granules and small pebbles of quartz, a little red chalcedony, 

and, locally, red argillite llh in. across __ 

Total thickness of exposed quartzite (27-

28>------------------------------------

Upper conglomerate ( 18-26) : 

26. Conglomerate and medium- to coarsegrained quartzite, grayish red-purple to 

grayish-red (5RP 4/2-5R 5/2); unit 

weathers very dusky red (lOR 2/2); 

very thin to thin bedded, well-indurated; 

subrounded granules and pebbles (as 

large as 3% by 2 in.) of quartz, red and 

dark-gray chalcedony, grayish and reddish quartzite, and quartz porphyry ; 

some angular red chalcedony pebbles ; 

conglomerate beds 6 in. to 2 ft thick; 

pebbles at least as abundant as matrix 

in one 15-ft intervaL __ _______________ _ 

25. Quartzite, medium- to coarse-grained, less 

abundant granule to pebble conglomerate; light brownish-g~ay, very pale 

brown to brownish-gray (5YR 6/1-6/2-

4/1), mostly thin-bedded ( 1 ft to rarely 

7ft), cross-laminae accentuated by black 

hematite; quartzite contains scattered 

pebbles ( %-% in. in size) of quartz and 

a few of red chalcedony ; most pebbles in 

conglomerate are of quartz and less than 

1 in. in diameter; a few cobbles (as much 

as 1 ft in diameter) occur near base in a 

very coarse grained matrix ___________ _ 

estimated thickness, less than _________ _ 

Thickness The same conglomerate bed (23) that forms the 

<teet) top of section 2 forms the bottom of section 3. 

[Bottom of sectlon located at 1,395,000 N., 348,100 E.] 

Section 2 

,[Top located at 1,391,500 N., 347,200 E.] 

23. Conglomerate and a few reddish-brown 

quartzite interbeds as much as 1ft thick, 

light brownish-gray (5YR 6/1)-locally 

50 light olive-gray (5Y 6/1) and pale red 

(7R 5/2)-grayish red-purple (5RP 4/2) 

near base; weathers blackish red to 

dusky-red ( 5R 2/2-3/2) ; some black hematite grains concentrated in laminae; 

medium to very coarse grained, thin (6 

in.) to thick-bedded; pebbles of subrounded to subangular quartz, and a few 

of quartzite, quartz porphyry, and angular red chalcedony; red and dark-gray 

chalcedony more abundant toward base ; 

275 pebbles, generally as abundant as matrix, mostly less than 1 in. in size near 

top, mostly about 2 in. near base; largest 

325 pebbles ( 3-4 in. in size) in middle ; a few 

triangular fragments of blackish-red 

( 5R 2/2) chalcedony and grayish quartzite are 6 by 4 in. in size ______________ _ 

22. Quartzite, medium-grained, and granule to 

small-pebble conglomerate; weathers 

dark, like base of unit 23; thin layers 

(as much as 1 ft thick) of coarser conglomerate like lower part of unit 23----

21. Pebble conglomerate and a little quartzite; 

weathers very dusky red to grayish 

bro~ (lOR 2/2-5Y R 3/2) ; pebbles of 

red chalcedony and quartz about equally 

abundant ; a few of quartzite, quartz 

porphyry, and gray chalcedony and some 

angular fragments of grayish-red ( 5R 

30 4/2) argillite (as much as 1ft in size) __ 

20. Conglomerate, chiefly quartz pebbles and 

small cobbles generally 2 in. in size ; a 

few as much as 8 in. across ___________ _ 

19. Conglomerate and some quartzite; weathers light brownish gray to light olive gray 

(5YR 6/1-5Y 6/1) near base; some finer 

grained beds weather dusky red (5R 

3/4-3.5/5) ; pebbles composed of quartz, 

red chalcedony, or a little quartzite and 

quartz porphyry ; pebbles are mostly less 

than 2 in. in diameter but range from 

granules to cobbles, smaller ones near 

base ; some finer grained beds are cross 

230 laminated--------·--------------------

5 

140 

50 

25 

5 

448 
OLDER PRECAMBRIAN ROCKS 23 

:Mazatzal Qua.rtzite, Del Rio area, Arizona-Continued 

Section 2-Continued 

18. Quartzite, granule conglomerate, and 

some thin beds of small-pebble conglomerate; unit weathers dusky red; some 

beds in the middle of the unit weather 

to a lighter color _____________________ _ 

Total thickness of the upper conglomerate 

(18-26) -------------------------------

A saddle near the middle of the ridge separates 

the predominantly conglomerate beds (above) on 

the west from the predominantly quartzite beds 

(below) on the east. 

Quartzite ( 13-17) : 

17. Quartzite and granule conglomerate, 

largely grayish-red (5R 4/2-5/2) to 

slightly red-purple; finer and more even 

grained beds are dark reddish-brown 

(5R 3/5) ; cross-laminated; quartz 

grains in a reddish matrix ___________ _ 

16. Quartzite and granule conglomerate, very 

pale red-purple ( 5RP 7/2), grayish 

orange-pink (5YR 7/2), and pale-red 

(lOR 6/2), cross-laminated ___________ _ 

15. Conglomerate; pebbles (as much as 2 in. in 

size) of quartz and some red chalcedony; a few other rock fragments _______ _ 

14. Quartzite, pale-red (lOR 6/2), fine to very 

coarse grained, crossbedded'; a .few somewhat friable medium-grained beds; some 

interbeds as much as 5 ft thick contain 

quartz pebbles (less than 1 in. in diameter)----------------------------------

13. Quartzite and sandstone, pale reddishbrown (lOR 5/4), moderate-red (5R 5/4-

4/6), grayish-orange-pink (lOR 7/3-

5YR 7/2), thin-bedded (less than 6 in.), 

cross-laminated, medium- to coarsegrained ; basal beds contain angular 

pieces of red argillite. Approximate 

thickness----------------·-------------

Total thickness of quartzite ( 13-17) -------

Upper argillite (12) : 

12. Argillite (very fine grained mudstone) , 

some micaceous shale and sandstone ; 

various shades of red (mostly 6R 4/6-7 R 

4/6; some 5R 4.5/5-3.5/3-4.5/3) ; weathers lighter shades, numerous light spots 

due to leaching of iron oxide ; massive 

to very thinly laminated. 

Estimated thickness of argillite (12) -------

Thickness 

(feet) 

220 

1,153 

35 

95 

25 

602 

75 

832 

25-60 

NOTE.-Bottom of section located at 1,391,800 N., 349,600 E. 

:Mazatzal Quartzite, Del Rio area, Arizona-Continued 

Section la 

[Top located at 1,386,500 N., 349,700 E.] 

Top overlain by upper argillite (unit 12). 

Quartzite (7-11) : 

11. Quartzite (the typical lavender quartzite 

of the Mazatzal) and well-indurated 

sandstone, pale-red ( 5R 6/2-5.5/3-5/2), 

very pale red-purple (5RP 7/2), to light 

brownish-gray (5YR 6/1) ; weathers 

light brownish gray, light olive gray, yellowish gray, to very pale yellowish brown 

(5YR 6/1-5¥ 6/1-5¥ 7/2-lOYR 7/2); 

medium- to fine- and eYen-grained, locally 

cross-laminated; composed almost entirely of quartz ; redder quartzite is fine 

to medium grained and well sorted; lavender quartzite is slightly coarser and 

less well sorted. Thickness approximate, it grades down into unit 10 ______ _ 

10. Quartzite and a few beds (as much as 1 

ft thick) of granule and pebble (as 

much as half an inch in size) conglomerate, light brownish-gray (5YR 6/1-7/1) ; 

weathers pale yellowish brown with a 

rough surface, locally, pale red (lOR 6/2-

7/1) ; medium to very coarse grained, 

cross-laminated; grades upward into 

medium- to fine-grained lavender quartzite (pale-red, 5R 7/2, to very pale redpurple, 5RP 7 /2) ----------------------

9. Conglomerate, light olive-gray (5Y 6/1) 

to light brownish-gray (5YR 6/1) ; 

rounded to subangular pebbles as much 

as half an inch in diameter------------

8. Sandstone, well-cemented; some quartzite 

and a few thin beds of granule and 

small-pebble (as much as 1 in. in size) 

conglomerate; pale-red ( 5R 6/2) to light 

brownish-gray (5YR 6/1) ; weathers 

pale red (lOR 6/2) ; cross-laminated 

(less so than is unit 7C) ; dark-gray 

hematite grains in some cross laminae __ 

7C. Quartzite; weathers medium gray to 

brownish gray (5N-5YR 4/1-3/1), lo-

;cally grayish red (7R 5/4) ; medium- to 

coarse-grained; scattered (locally abundant) granules and small pebbles (as 

much as 1 in. in size) of quartz and a 

few of red chalcedony ; prominently 

cross-laminated; cross laminae accentuated by abundant grains of dark-gray 

hematite ----------------------------- 7B. Conglomerate ~nd some quartzite lenses 

as much as 6 in. in thickness; pebbles 

and cobbles (as much as 3'% in. in size) 

of subrounded quartz, subrounded to 

subanguler red and dark-gray chalcedony, and, a few of quartzite and quartz 

porphyrY-----------------------------

Thickness 

(feet) 

408 

330 

4 

67 

27 

4 
24 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

Mazatzal Quartzite, Del Rio area, Arizona-Continued 

Section !a-Continued 

Mazatzal Quartzite, Del Rio area, Arizona-Continued 

Section 1-Continued 

Quartzite (7-11)-Continued 

7 A. Quartzite, light brownish-gray to pale 

grayish-red (5YR 6/1-5/1-5R 6/1); 

weathers pale brown (5YR 5/2) with a 

rough surface; weathers darker brownish-gray near top ; coarS"e to very 

coarse grained ; scattered granules and 

very small pebbles; cross-laminated ___ _ 

Total thickness of quartzite ( 7-11) , as meas- ured in section 1a _____________________ _ 

Thickness 

(feet) 

Lower conglomerate ( 2-5) -Continued 

3. Conglomerate; red and gray chalcedony 

fragments are more abundant than in 

unit 2; weathers dusky red (5R 3/4) __ _ 

2. Conglomerate and a little quartzite, palered ( 5R 6/2) to grayish orange-pink 

(5YR 7/2); rounded to angular quartz 

265 and some angular red chalcedony, ranging in size from granules to cobbles 6 

in. long ______________________________ _ 

1,105 

Total thickness of lower conglomerate 

Thickness 

(feet) 

100 

20 

[Bottom of section is located at 1,384, 7100 N., 350,800 E. and is 

underlain by lower argillite ( 6) ] (2-5) ----------------------------------- 440 

Section 1 

[Top located at 1,383,900 N., 356,200 E.] 

Top overlain by upper argillite (unit 12). 

Quartzite ( 7-11) : 

11. Quartzite (same as unit 11, section 1a), 

lavender, becoming reddish at top; 

crossbedded, even-grained ____________ _ 

10. Quartzite and some granule to small-pebble conglomerate; weathers light brownish gray ( 5YR 6/1) -------------------

9. Conglomerate, same as unit 9 of section 1a_ 

8. Quartzite and some small-pebble (as much 

as a quarter of an inch in size) conglomerate, pale-red (5R 6/2-5/3), 

coarse-grained, cross-laminated; some 

laminae accentuated by hematite grains_ 

7. Quartzite, poorly exposed ; some is like 

unit 7C of section 1a _________________ _ 

Total thickness of quartzite (7-11), as meas- ured in section !_ ______________________ _ 

Lower argillite ( 6) : 

6. Sandstone, micaceous, sandy micaceous 

shale, and a little argillite; grayish-red 

(5R 4/2-5/2) to pale reddish-brown (8R 

5/4), white or light-colored spots due 

to leaching of iron oxide, medium- to 

fine-grained ; angular to subrounded 

closely packed grains of quartz and some 

muscovite in a r:eddish matrix. 

Thickness of lower argillite, estimated ____ _ 

Lower conglomerate ( 2-5) : 

5. Conglomerate and quartzite; weathers 

brownish gray ( 5Y R 4/1) at top ; pebbles are smaller, and beds of quartzite 

are thicker and more abundant than in 

unit 4--------------------------------

4. Conglomerate; lighter colored than unit 

3; contains abundant cobbles and small 

boulders (as much as 12 in. in size) of 

quartz and a few of red chalcedony ___ _ 

Quartzite ( 0-1) : 

1. Quartzite, grayish orange-pink (5YR 7/2) 

to very pale red (5R 7/2) ; weathers yellowish gray, light brownish gray, light 

olive gray, to pale yellowish brown (5YR 

8/1-5YR 6/1-5Y 6/1-10YR 6/2) : 

medium- to coarse-grained and very 

480 coarse grained, mostly well-indurated; 

massive, bedding is indistinct_ ________ _ 208 

0. Quartzite, weathers dark reddish brown 

230 at base; unit was not measured, but is 

4 exposed below unit 1; approximate thickness---------------------------------- 50 

Total exposed thickness of quartzite ( 0-1), approximate ___________________________ _ 258 

40 

Base concealed by Cenozoic deposits. 

188 [Bottom of section located at 1,382,700 N., 3M,900 E.] 

942 

25-50 

305 

15 

Total thickness exposed, approximate ______ 4, 000-4, 200 

Section 1a was measured as a check on the correlation 

of the western and eastern outcrops of upper argillite 

and on the stratigraphy of the rocks between the upper 

and lower argillite in the two areas. The difference in 

measured thickness (about 160 ft out of a total of 

about 1,000 ft) could be due to several factors: ( 1) 

errors in measuring caused in part by the gentler dip of 

the rocks in section 1a; (2) original differences in thickness; and ( 3) the fact that upper and lower contacts of 

the two argillites in section 1a were covered and may 

actually have been farther west and therefore higher up 

in the section than estimated. 

QUARTZITE AND CONGLOMERATE 

Most of the quartzite and conglomerate are hard 

vitreous rocks that form cliffs and rugged topography, 

but some beds are less resistant. The fresh rock is various shades of red, grayish pink, and brown to pale red 

.purple; much of it has a lavender tint. The rock 

weathers dark to light shades of gray, red, and brown. 

From a distance the outcrops are dark colored. 
OLDER PRECAMBRIAN ROCKS 25 

Bedding ranges from thin to thick or massive and 

from indistinct to conspicuous. Crossbedding is common in much of the finer grained rocks and is sporadic 

in conglomerate. Most lamination planes are 1 foot or 

less in length; some are as much as 3 feet long. In 

places grains of dark-gray hematite accentuate cross 

/ laminae and some bedding planes. Some laminae, composed principally of hematite, are more than 5 mm thick. 

The hematite grains, which are subrounded and mostly 

less than 0.5 mm in diameter, represent original concentrations, not later replacement. 

Textures range from fine grains to boulders 12 inches 

in diameter (fig. 6) . Most of the lavender quartzite 

below the upper argillite (unit 11, measured sections) 

is even grained, but elsewhere much of the material is 

poorly sorted. Pebbles are very sparsely distributed to 

closely packed. Many of them are subrounded, but 

some large pieces of argillite and red chalcedony are 

subangular to angular. The pebbles are milky quartz, 

variable amounts of red, reddish-black, and dark- and 

light-gray chalcedony, a little grayish and reddish 

quartz porphyry and quartzite, schistose and more massive dark volcanic rocks, and argillite. Argillite fragments are common immediately above the upper argillite. No granitic pebbles were seen. The quartzite 

and matrix of the conglomerate are composed of quartz 

and a little chalcedony, black hematite, argillite, and 

muscovite. Grains of magnetite and ilmenite, observed 

in most thin sections, are rounded to angular; smaller 

grains are more angular. 

ARGILLITE 

Argillite forms thin partings in the Mazatzal Quartzite and two thicker beds-lower (unit 6) and upper 

(unit 12) argillite. The lower argillite, consisting of 

micaceous sandstone, sandy micaceous shale, and a little 

argillite, forms two narrow bands in the central part of 

the main mass of the formation. _ The upper argillite, 

consisting of argillite, micaceous sandstone, and sandy 

micaceous shale, forms three bands in the main massa western, a central, and an eastern one. 

The argillites crop out poorly and form grassy slopes 

and flats over which small chips of the material are 

scattered. The upper argillite was first noted and 

mapped because of small pits dug on it by Indians, who 

used the material for pendants. Most of the pits are on 

the two eastern outcrops; only one was noted on the 

western outcrop. The argillite is similar to the pipestone or catlinite used by Minnesota Indians for pipes 

of peace and other artifacts. 4 

The argillite is shades of grayish red, reddish brown, 

and red purple. It weathers moderate orange pink; 

much of it contains numerous spheroidal-, ellipsoidal-, 

and disk-shaped spots that are the same color as the 

weathered surface or very light gray. The spots range 

from less than 1 to 10 mm in diameter; they are formed 

by leaching of iron oxide from the matrix. Scattered 

small white grains are also visible. 

The argillite ranges from a very fine grained, dense 

rock to one composed of rounded and ellipsoidal grains 

as much as 1.5 mm in diameter. Much of the argillite 

is massive, but some is thinly laminated; the slightly 

darker laminae are about 1 mm thick, and the lighter 

colored ones are 3-10 mm thick. The laminated rock 

tends to break parallel to the bedding, but it does not 

split readily. The massive rock has a very irregular 

fracture, except where cut by numerous closely spaced 

joints. Slickensides have formed where the rock has 

been shattered, but the argillite shows no internal evidence of having been deformed. 

Micaceous sandstone and sandy micaceous shale grade 

into argillite and into quartzite. These rocks are medium to fine grained, thinly bedded (2-3 em), and in 

places ripple marked. The color is similar to that of 

the argillite. The rock is composed of grains consisting 

of quartz, residual muscovite, aggregates of fine sericite, 

and minor amounts of chalcedony, tourmaline, magnetite, and ilmenite in a fine-grained reddish matrix 

that is composed principally of sericite and iron oxide. 

Many quartz grains are angular, and most of them are 

less than 0.2 mm long; a few are as much as 1 mm 

long. 

FIGURE 6.-Lower conglomerate in the Mazatzal Quartzite, Granite 4 According to Laudermilk (1944), the source of all red pipestone was 

Creek (near 1,388,200 N., 353,600 E.) believed to be in Minnesota until the Del Rio locality was discovered. 
26 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

Although quantitatively unimportant, the argillite is 

discussed in some detail because of its interesting mineralogical composition and the light its composition 

may throw on its probable origin and on the age of 

the Mazatzal Quartzite. 

The mineralogy of five specimens of argillite .was 

determined by use of X-rays (table 3). Specimens 

from the central outcrop (Nos. 1, 4, and 5, table 3) are 

composed of quartz, pyrophyllite, and minor amounts 

or traces of mica, chlorite, and hematite. One specimen (No. 3, table 3) from the western outcrop consists of kaolinite and minor pyrophyllite and hematite; 

the other (No.2, table 3) consists of quartz, mixed layered mica-montmorillonite, and traces of hematite. 

The fine-grained finely laminated argillite (No. 4, 

table 3) from the central outcrop contains angular to 

rounded colorless grains and aggregates of a mineral 

having a moderately high birefringence. The grains, as 

much as 0.1 mm in diameter, are enclosed in a finegrained ferruginous matrix that, where iron oxide has 

been leached, has birefringence similar to that of the 

larger grains; both probably are pyrophyllite. The 

elongated grains in the argillite from. the western outcrop (No.3, table 3) are composed of cryptocrystalline 

material of very low birefringence, presumably kaolinite. No quartz was recognized in thin sections of 

either specimen. 

TABLE B.-Mineralogy of argillite from the Mazatzal Quartzite, 

Paulden quadrangle 

[Analyses based on X-ray studies. Analysts: J. C. Hathaway, H. C. Starkey, and 

P. D. Blackmon, U.S. Geol. Survey. Tr., trace] 

Specimen_------------ 2 3 4 5 

Fraction after grind- ing __________________ Clay Silt Clay Silt Clay Silt Clay Silt Clay Silt 

Percent of sample_____ 24 76 20 80 21 79 28 72 21 78 

-------1-------------------

Estimated amount of 

minerals present, in 

parts in ten: Pyrophyllite______ 6 4 ______ _____ Tr. Tr. 6 5 6 6 

Quartz____________ 3 5 2 6 ______ _____ 2 5 2 4 

N;:aiiie========= :R: --ri- ---ri- --ri- ----i- ---i- Tr~ :R: Tr~ :R: 

Mixed layered 

mica-montmor- illonite 1 ________ ------ _____ 8 3 ________________________________ _ Kaolinite___________________________________ 8 9 _____________________ _ Chlorite __________ ------___________________________ Tr. _____ Tr. ____ _ 

t About 20 percent montmorillonite layers. 

1. Massive fine-grained argillite, central outcrops (1,381,000 N., 359, 400 E.). Lab. 

No. 266397. 

2. Massive fine-grained purplish argillite, western outcrops (1 ,388,200 N ., 350,000 E.). 

Lab. No. 266396. 

3. Massive granular argillite, western outcrops (1,388,200 N., 350,000 E.). Lab. 

No. 266395. 

4. Finely laminated fine-grained argillite, central outcrops (1,381,000 N., 359,400 E.). 

Lab. No. 266394. 

5. Massive fine-grained argillite, central outcrops (1,381,000 N., 359, 400 E.). Lab. No. 266393. 

The chemical composition of one specimen (No. 1, 

table 3) is given in table 4 and compared with the 

chemical composition of other argillaceous rocks; the 

minor elements in specimen 1 are given in table 5. 

TABLE 4.-0hemicaZ analysis of argilUte from Mazatzal Quartzite, Paulden quadrangle, compared with analysis of other 

argillaceous rocks 

Sample __ --------------------- 2 3 

--------1----------------

Si02- _ ------------------------ 77.5 62.2 60.96 60.15 61.54 

AbO a __ ----------------------- 15.3 19.4 16.15 16.45 16.95 

Ti02- ------------------------- . 27 . 75 . 86 . 76 . 82 

Fe20a_ ------------------------ 1. 2 7. 5 5.16 4. 04 2. 56 Feo___________________________ . 06 . 30 2. 54 2. 90 3. oo 

MnO__________________________ . 01 . 02 . 07 Trace 

MgO_ ------------------------- . 26 1. 6 3. 06 2. 32 2. 52 cao __ ------------------------ .15 . os . 71 1. 41 1. 76 

Na20-------------------------- .13 1. 3 1. 5 1. 01 1. 84 K20--------------------------- 1. 3 3. 6 5. 01 3. flO 3. 45 

P205_ ------------------------- . 04 • 20 . 23 .15 ---------- Ignition _______________________ ---------- 3. 3 ---------- ---------- ----------

H20-_ -----------------------} 3 {--------- .17 .89 } 3 47 

~!g~---~====================== ---------- -========= 3: ~ 3: ~ -------~-- SOa_ -------------------------- ---------- ---------- ---------- . 58 ---------- Nll3 __ ------------------------ ---------- ---------- . 01 ---------- ---------- C02___________________________ <. 05 ---------- . 68 1. 46 1. 67 

s__________________ c----------------------------- ____________ ---------- <. o1 ----------_______________________________________ ---------- . 88 ----------_ 

TotaL___________________ 99 100. 25 100. 23 100. 46 100.48 

1. Rapid analysis of argillite from Mazatzal Quartzite, Paulden quadrangle (1,381,000 

N., 359,400 E.). Analysts: P. L. D. Elmore, S.D. Botts, K. E. White, U.S. 

Geol. Survey. Lab.No.l48371. 

2. Rapid analysis of purple slate, south of Shylock mine (1,312,900 N ., 418,500 E.), 

Mingus Mountain quadrangle. Analysts: S.M. Berthold and E. A. Nygaard 

From Anderson and Creasey (1958, table 10). 

3. Purple slate, Castleton, Vt. From Clarke (1924, p. 554). 4. Composite analysis of 51 Paleozoic shales by H. N. Stokes. From Clarke (1924, 

p. 552). 5. Average composition of pelitic rocks. From Shaw (1956, table 10). 

TABLE 5.-Semiquantitative analysis for minor elements ·in argillite 

from Mazatzal Quartzite, Paulden quadrangle 

(Analyst, H. J. Rose, Jr., U.S. Geol. Survey. Lab. No. 148371] 

Element 

Cu _______________ _ 

Pb _______________ _ 

~n _______________ _ 

Co _______________ _ 

Ni _____ - _--- ------- Fe ________________ _ 

Cr ________________ _ 

y ________________ _ 

AI ________________ _ 

Ga _______________ _ 

Sc ________________ _ 

1{ ________________ _ 

Percent 

0. 001 

. 001 

. 01 

. 001 

. 003 

1. 0 

. 001 

. 001 

10.0 

. 003 

. 001 

. 003 

Element La _______________ _ 

Ti ________________ _ 

Zr ________________ _ 

Nb _______________ _ 

Be _______________ _ 

~g _______________ _ 

Ca _______________ _ 

Sr ________________ _ 

Ba _______________ _ 

Na _______________ _ 

B ________________ _ 

Percent 

0.003 

. 1 

. 01 

0 

. 0003 

.3 

. 1 

. 003 

. 01 

. 1 

. 003 

Looked for but not found: Ag, Au, Hg, Ru, Rh, Pd, Os, Ir, Pt, Mo, W, Re, Ge, 

Sn, As, Sb, Bi, Zn, Cd, Tl, In, Ce, Nd, Hf, Th, Ta, U, P. 

The silica content is higher (about 17 percent) in the 

argillite than in other argillaceous rocks. This higher 

content makes the other components of the argillite 

seem lower, but they generally retain the same relative 

proportions as the other argillaceous rocks. The alkali 

ratios of the five specimens are given in table 6. 

All have a high ratio of potassium oxide to sodium 

oxide. The amount 9f sodium oxide varies only slightly 

(0.04-0.18 percent) and is lowest in the kaolinite-rich 

sample (No.3, table 6). The amount of potassium oxide 

is more variable; it ranges from 0.96 to 1.6 percent in 

the specimens composed of quartz and pyrophy llite 

(Nos. 1, 4, and 5, table 6); it is lowest (0.11 percent) 

in the kaolinite-rich sample (No.3, table 6) and highest 
OLDER PRECAMBRIAN ROCKS 27 

(2.9 percent) in the specimen containing the mixedlayered (mica-montmorillonite) clay mineral component (No. 2, table 6), where it is contained mostly 

in the mica mineral structure. 

TABLE 6.-Alkali ratio in five specimens of argillite from Mazatzal 

Quartzite, Paulden quadrangle 

[Specimens 2-5.-Rapid analyses for NazO and K20 only. Analyst, I. H . Barlow, 

U.S. Geol. Survey] 

NazO KzO 

Specimen (percent) (percent) 1 __________________________________ _ 0. 13 1. 3 

2------------------------ ----------- . 14 2. 9 3 __________________________________ _ . 04 . 11 4 __________________________________ _ . 18 1. 6 

5----------------------------------- . 15 . 96 

1. Massive fine-grained argillite, central outcrops (1,381,000 N., 359,400 E.). From chemical analysis 1, table 4. 

2. Massive fine-grained, argillite, western outcrops (1,388,200 N., 350,000 E.) . Lab. No. 15337. 

3. Massive granular argillite, western outcrops (1,388,200 N ., 350,000 E .). Lab. No. 15336. 

4. Finely laminated fine-grained argillite; central outcrops (1,381,000 N., 359,400 E.). 

Lab. No. 15335. 

5. Massive fine-grained argillite, central outcrops (1,381,000 N ., 359,400 E.). Lab. No. 15334. 

Kaolinite, montmorillonite, and pyrophyllite are unexpected constituents in older Precambrian rocks. 

Grim ( 1953, p. 356), pointed out that montmorillonite 

is generally absent in sedimentary rocks older than the 

Mesozoic, whereas it is abundant in many Mesozoic and 

Cenozoic rocks, in Recent marine sediments, and 

in present-day weathering products; kaolinite is less 

abundant in rocks older than the Devonian than in 

younger ones. Montmorillonite and kaolinite are generally not formed under the same conditions (Grim, 

1953, p. 355-356). All three minerals are common products of mild hydrothermal alteration in nature. Pyrophyllite forms at higher temperatures (above 350° C) 

than does kaolinite, according to laboratory experiments 

by Remley ( 1959) ; at a low pH it forms at a lower 

temperature than does mica. The significance of these 

minerals is not understood. There is no evidence that 

they formed under hydrothermal conditions, though 

possibly the higher temperature represented by pyrophyllite may be related to late Tertiary (?) andesite 

plugs; kaolinite and montmorillonite may represent 

products of weathering. The relation of temperature 

of formation or degreee of metamorphism indicated by 

pyrophyllite to that of the formation of the green schist 

facies common in rocks of the Alder Group is not 

known. 

The high KzO to N a20 ratio of the argillite may indicate derivation from normal terrigenous clay, as this 

ratio is typical of normal clays (table 4, Nos. 2-5) ; Precambrian rhyolite tuffs of the area have a high Na2 0 to 

KzO ratio. On the other hand, montmorillonite is common in bentonitic clays derived from volcanic ash. Extensive leaching of the argillite is indicated by the high 

silica content, but it must have occurred under different 

weathering conditions than exist today. 

758-44'7 0----<65-3 

Laudermilk (1944) stated that specimens of argillite 

from the Del Rio locality had the same general chemical 

composition as the pipestone from Minnesota: SiOz, 

Al20 3 , Fe20 3 • FeO, and minor amounts of CaO, MgO, 

Na 20, K20, and rare elements. However, he stated that 

a different alkali ratio (high K zO to N azO in the Minnesota material; a reverse ratio in the Del Rio material) 

and different amounts of certain other elements (copper, 

silver, calcium, strontium, and barium) distinguish the 

material from which Minnesota and Arizona artifacts 

were made. Laudermilk's conclusions were based on 

spectrographic and petrographic studies 'by Howell 

(1940, p. 51), who stated: "Potassium, a constant constituent of the northern material, is either extremely 

minute or entirely missing in the southern samples examined. Sodium and lithium show a similar decrease 

between specimens from these two sources." Howell 

stated further ( p. 55) that the Minnesota material is 

"composed predominantly of pyrophyllite, hematite, 

and a sericite-like mineral as against a predominance of 

kaolinite for the Arizona shales." The present X-ray 

and chemical studies of Del Rio material (tables 3-6) 

do not agree with Howell's results. His material may 

have come from the eastern outcrop, which was not examined chemically or by X-ray during the present 

study, or from variations that may occur across or along 

the strike of an outcrop band. 

AGE AND CORRELATIONS 

The Mazatzal Quartzite in the Del Rio area is older 

than the Tapeats Sandstone. It may be younger than 

the metamorphism of the Alder Group and than the 

granitic intrusions that cut the Alder Group. 

The composition of the argillite, the absence of foliation, and the unstrained character of quartz grains in 

folded quartzite indicate that the Mazatzal in this area 

was at most only slightly metamorphosed. In contrast, 

rocks of the Alder Group have been foliated and metamorphosed to green schist and higher grade facies. A 

granitic terrane older than the Mazatzal is indicated by 

the abundance of pebbles, cobbles, and small boulders 

of vein quartz in the conglomerate and by the absence 

of quartz veins or granitic rocks intruding the Mazatzal ; quartz veins and granitic rocks are abundant in 

the Alder Group. Although lack of granitic pebbles 

and feldspar grains in the quartzite might indicate 

deposition prior to the granitic intrusions, their absence 

may be attributed to vigorous and long-continued erosion that removed particles of earlier granite or reduced 

them to clay-sized particl~s, now represented by thin 

argillaceous partings in the quartzite. 

Southeast of Pine (fig. 1, inset) the Mazatzal Quartzite is assigned to the older Precambrian because it was 

folded, intruded by granite, and eroded prior to depo-
28 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

sition of the younger Precambrian Apache Group. This 

deformation and granitic intrusion mark the Mazatzal 

Revolution (Wilson, 1939, p. 1134), which separates 

older from younger (Apache Group and Grand Canyon 

Series) Precambrian .rocks (Butler and Wilson, 1938, 

p. 11). 

Wilson (1922, p. 299) first correlated the quartzite in 

the Del Rio area with the Mazatzal Quartzite in the 

Mazatzal Mountains and adjacent areas. Although a 

correlation from Pine Creek to the Del Rio area, a distance of more than 60 miles, may be open to question, 

the lithology of the thick quartzites and conglomerates 

in the areas mapped as Mazatzal is similar, and the 

correlation does have merit. According to E. D. McKee 

(oral commun., 1957), the quartzite in the Del Rio area 

resembles the Shinumo Quartzite of the Unkar Group, 

which is the older of the two groups that make up the 

younger Precambrian Grand Canyon Series in the 

Grand Canyon, more than 90 miles north of the Del 

Rio area. The fact that younger Precambrian rocks 

overlie the Mazatzal to the southeast does not preclude 

the possibility that the Mazatzal is equivalent to the 

Shinumo Quartzite, as the relative ages of the younger 

Precambrian rocks north and southeast of the Del Rio 

area are unknown. 

Because of the possibility that the Mazatzal Quartzite in the Del Rio area has been moved along faults 

from an area of very low grade metamorphism that 

was not intruded by granitic rocks, the formation has 

been left in the older Precambrian. The quartz cobbles and pebbles in the Del Rio area may have been derived from a terrane older than the Alder Group, such 

as is now known to have existed (see footnote 7, p. 49), 

and the granitic intrusions that cut the Mazatzal to the 

southeast may be younger than the granitic intrusions 

in the Prescott-Paulden area. Age determinations 

made by analysis of enclosed zircon grains in granitic 

rocks, in quartzite in the Grand Canyon, Del Rio, and 

Mazatzal Mountain areas, and in rhyolitic tuff in the 

Alder Group may eventually help to solve this problem 

of age relations. 

INTRUSIVE ROCKS 

Jaggar and Palache (1905) proposed the name Bradshaw Granite for most of the quartzose intrusive rocks 

south of the Prescott-Jerome area, and Lindgren ( 1926, 

p. 16, pl. 2) extended the term Bradshaw Granite to 

rocks in the Prescott-Jerome area. Lindgren considered the "diorite" and some quartz diorite or granodiorite to be younger than the Bradshaw Granite and 

believed that younger quartz-bearing intrusive rocks 

were possibly Laramide in age. Studies in the Jerome 

and Prescott-Paulden areas show that (1) the so-called 

Bradshaw Granite consists of several different intrusives ranging from granodiorite, which is the most 

abundant, to granite and alaskite, (2) much of the 

"diorite," now called gabbro, is older than the Bradshaw Granite, and (3) one of the "younger quartz diorite or granodiorite stocks" is Precambrian in age and 

older than at least some of the Bradshaw Granite. 

In this report the name Bradshaw Granite is abandoned and new names are assigned to some of the intrusive rocks that formerly were part of the "Bradshaw 

Granite." The major intrusives in the Prescott-Paulden area, and their probable age relations from oldest to 

younge8t, based largely on field evidence, are : ( 1) gabbro and quartz diorite, (2) Government Canyon Granodiorite, ( 3) Prescott Granodiorite, ( 4) quartz monzonite and alaskite, ( 5) coarse-grained granite, ( 6) Dells 

Granite, and (7) fine-grained granite. 

The relationships of the various intrusive masses are 

obscure for the following reasons: 

1. The gabbro includes diabase and fine-grained gabbroic to dioritic rocks, some of which are younger 

than quartzose intrusive rocks but cannot be distinguished from the older gabbroic rocks petrographically or in the field in most places. 

2. Mafic volcanic rocks of the Alder ( ~) Group may 

have been misidentified as fine-grained gabbro 

older than the quartzose intrusive rocks. 

3. Dikes of granodiorite, granite, alaskite, and aplite 

cut the intrusive rocks, but correlation of these 

dikes with a given intrusive mass is doubtful or 

impossible in some places; in addition, the aplites 

are of more than one age. 

4. Compositional and textural features of the quartzose intrusive rocks differ from place to place, 

some of the differences being due to contamination of the magma by the intruded rocks; therefore, a mass may be erroneously assigned to a 

different intrusion. 

5. Intense shearing masked and destroyed primary features of some rocks and resulted in mechanical 

rather than normal intrusive contacts; most of the 

north-trending contacts are zones of shear, and 

many contacts were located arbitrarily because of 

mechanical mixing of adjacent rocks. 

6. The various masses mapped as the Prescott Granodiorite are not contiguous, and their relationships 

to one another could not be determined exactly in 

the field; they are considered consanguineous because of similarities in modal, chemical, and normative compositions. 

7. Some of the quartzose intrusive rocks may possibly be 

pre-Alder Group in age (see footnote 7 on p. 49). 
OLDER PRrCAMBRIAN ROCKS 29 

The available modal, chemical, and normative data 

o.n the_intrusive rocks are given in tables 7-10. Va ia­ tion diagrams show the modal and normative quartzorthoclase-plagioclase composition of the different 

groups of intrusive rocks. Figure 9 represents the Gbvernment Canyon Granodiorite; figure 11, the various 

~a~ses of Prescott Granodiorite; and figure 13, the granitiC rocks. Modes, norms, and average mode ~re 

plotted. Figure 7 shows (A) the quartz-orthocla!seplagioclase norm and average mode of all the rocks, 

(B) modal and normative quartz-feldspar-mafic 3!lld 

accessory minerals, (C) plots of oxides on Si02-K20 · 

N a20-FeO · Fe203 · MgO · CaO diagrams, and (D) Jxides plotted against Si02. The distribution of the various masses is shown in figures 8, 10, and 12. Included 

in these tables and figures are data on gabbro from the 

Mingus Mountain quadrangle and north-central part 

of the Mayer quadrangle, on granodiorite of the "\Valker 

area (Lindgren, 1926, p. 21) in the north-central part 

of the Mount Union quadrangle, and on the quahz 

diorite of the Jerome area (Anderson and Creasey, 19;;>8, 

p. 40, table 13). The quartz diorite is considered part 

of the Prescott Granodiorite and is referred to as the 

Yarber Wash, Big Bug Creek, and Chaparral masses 

(fig. 10). The Big Bug Creek mass (McCabe a~ea 

of Lindgren, 1926, p. 21, pl. 2) and the wanodiorite of 

the Walker area are among the "younger granodiorit~s" 

of Lindgren. Modes and norms agree fairly w~ll. Most average modes, however, are lower in orthocl31se 

than are the norms, because in the norm all potash hias 

been assigned to orthoclase whereas in the mode some 

potash is tied up in the micas. 

GABBRO AND RELATED ROCKS 

DISTRIBUTION 

Gabbro and related rocks are widely distributed 

throughout the Precambrian rock outcrops of the 

Prescott-Paulden area. They form two large and several smaller bodies. Innumerable lenticular to dikelike masses, m·any of them too small to show on the geologic maps, intrude the Alder Group and quartzose 

intrusive rocks. 

The largest mass extends from the southern border 

of the area (pl. 1, west of 370,000 E.) northward for 

nearly 5 miles. The second largest mass forms the 

high ridge east of Prescott and extends from the southern border of the area (pl. 1, near 344,000 E.) northward for 3~4 miles. 

Scattered gabbro masses, the largest occupying not 

more than 1 square mile, are in the southeastern (pl. 1) 

and east-central (pis. 1, 2) pa.rts of the area. Dikelike 

masses occur in the Chaparral and Spud faults (pl. 1). 

A small mass of quartz diorite, probably a facies of 

gabbro, crops out along the Verde River (pl. 2, between 

375,500 E. and 390,000 E.) and is the northernmost 

exposure of Precambrian rocks in the area. 

Diabase dikes cut the Alder 'Group and some of the 

intrusive rocks but have not been mapped. They are 

abundant in the alaskite porphyry near Charcoal Gulch 

(pl. 1, between 377,000 E. and 378,000 E.) and in the 

TABLE 7.-Modal composition of quartzose intrusive rocks in the Prescott-Paulden-Jerome area 

[See figs. 8, 10, and 12 for locations; figs. 9, 11, and 13 for plots of norms and modes on Qu-Or-Pl diagrams; fig. 7 for other triangular and variation diagrams; table 8 for chemical 

and table 10 fof normative composition] 

Map 1 2 3A 3B 3C 4 5 6 symboL _______________________ qd gg pgy-1 pgy-2 pgy-3 pgs pgc pgl 

---------- 1- --------- Quartz ___________________ 17 16 27 26 27 32. 0 29. 0 28 Orthoclase ________________ 5 14 9 4 7 5. 0 8. 0 10 Plagioclase ________________ 54 52 56 61 58 52. 0 56.0 52 Hornblende _______________ Mica 16 8 2 4 3 ------ ------ ------ 2 ___________________ 5 7 5 4 4 10. 0 4. 0 7 Epidote a _________________ 2 2 ------ ------ ------ 1.0 3. 0 2 Accessory minerals _________ 1 1 1 1 1 <.5 <. 5 1 ------------------------ TotaL _____________ 100 100 100 100 1~0 100. 0 100. 0 100 ------ --~ ---__ , _ ------- - -

Percent of feldspar that is orthoclase _______________ 8 21 14 6 10 9 12 16 

. . ~ Approxima~e COIJ?.PO~ItiOn based. on X-ray diffraction, An15 = 5 • 

3 Largely white mica; ~ncludes pnmary and meta~orphic biotite, chlorite, and muscovite-sericite. 

Mostly secondary epidote denved from mafic mmerals; includes some derived from plagioclase. 

7 8 9 pgp pgm qm 

---------

28. 0 22 23 

10. 0 9 28 

54. 0 56 1 37 

------ 3 --- - --

6. 0 7 7 

2. 0 2 4 

<.5 1 1 --------- 100. 0 100 100 ---- - - ---

16 14 43 

10 

al 

---

35.0 

26. 0 

38.0 

------ 1.0 

<. 5 ---

100.0 

---

40 

11 

cg 

---

33. 0 

19. 0 

39. 0 

------

9. 0 

<.5 

---

100. 0 ---

33 

12 

dg 

3 

2 

2 

6 

8 

5 

------9 

2 ---

100 ---

53 

1. Quartz diorite_, Verde River, Paulden quadrangle, average of two thin sectiGns 

(not shown m figs. 8, 10, or 12). 

6. Lynx Creek mass, Prescott Granodiorite, average of eight thin sections. 

2. Government Canyon Granodiorite, average of 14 thin sections. 

3. Yarb~r w.ash mass, Prescc;>tt Granodiorite: 3A,,western facies, average offour tfuin 

sectiOns, 3B, ea~tern facies, average of five thm sections; 3C, average of western a!ld eastern faCies (Anderson and Creasey, 1958, table 13). 

4. Salida Gulch mass, Prescott Granodiorite, average of 11 thin sections. .5. Chaparral mass, Prescott Granodiorite, average of six thin sections. 

7. Prescott mass, Prescott Granodiorite, average of seven thin ~ections. 

8. Mineral Point mass, Prescott Granodiorite, average of four thin sections. 

9. Quartz monzonite, average of two thin sections. 

10. Alaskite, average of four thin sections. 

11. Coarse-grained granite, average of seven thin sections. 

12. Dells Granite, average of four thin sections . 
30 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

TABLE 8.-Chemical analyses of quartzose intrusive rocks and gabbro of the Prescott-Jerome area 

[See figs. 8, 10, and 12 for location, figs. 9, 11, and 13 for plots of norms and modes on Qu-Or-Pl diagrams, fig. 7 for other triangular and variation diagrams, table 7 for modal· 

and table 10 for normative composition. Analyst: W. W. Brannock and others, U.S. Geol. Survey, rapid rock analyses, except for granodiorite of Walker area (from Lind: 

gren, 1926, p. 21, No. 3) and gabbro (from Anderson and Creasey, 1958, p. 38, table 12, No.8)] 

1 2 3 4 5 6 7 8 9 10 11 Map symboL _______ gb gg wg pgy pgs pgl pgp pgm al cg dg Lab. No ____________ ------------ 148366 ------------ 148361 148362 148363 148364 148365 148369 148368 148370 

Si02---------- 48.57 61.4 65.74 65.6 69.5 70. 1 67.7 64.5 77.9 76.3 76.2 

Al20a---- _-- __ 20.32 16.7 16.76 16.2 16.0 16.6 15.8 17.4 13.2 13.4 13.7 Fe20a- ________ -------- 2.6 3.99 2.5 1.3 1.2 2.0 1.6 . 61 .8 . 69 FeO __________ 8.87 2.7 -------- 2.3 1.5 . 81 1.6 2.2 . 06 . 48 . 17 MgO __________ 4.87 2.8 1. 70 1.7 1.1 . 72 1.5 2. 1 . 05 . 26 .10 CaO __________ 9. 15 4.7 3.78 4.6 3.2 2.9 3.3 4.5 . 22 . 49 . 50 

N a20 _ - - - - - - - - 2.66 4.2 3.37 3.6 4.3 4.7 4.0 4.4 4. 1 3.9 4.2 

K20- - - - -- - - - - . 34 3.4 3.55 2. 1 2. 1 2.0 2.6 1.9 4.5 3.7 4.5 

TiOll---- _- _- __ . 64 . 69 -------- . 38 . 23 . 20 . 41 . 36 .11 .10 . 04 

P20s---------- -------- . 35 -------- .14 . 09 . 05 . 13 . 15 . 00 . 02 . 00 Mn 0 _________ . 12 . 08 -------- . 08 . 04 . 05 . 06 . 06 . 00 . 01 . 03 

H20---------- 4.02 . 62 . 99 . 84 . 70 . 67 . 64 1.0 .30 . 50 . 56 

C02----------- -------- . 06 -------- . 07 . 34 . 24 . 28 . 16 . 08 . 32 . 13 

Total Sulfur 

as s_------- -------- <.01 -------- <.01 <.01 <. 01 . 04 <. 01 <.01 <.01 <.01 

TotaL __ 99.56 100 99.88 100 100 100 100 100 101 100 101 

1. Gabbro, composite of five specimens from loc. 49 and one . from loc. 50 (fig. 10). 2. Government Canyon Granodiorite (loc . .5, fig. 8). 

3. Granodiorite of Walker area (Joe. 48, fig . 10). 

7. Prescott mass, Prescott Granodiorite (loc. 7, fig. 10). 

8. Mineral·Point mass, Prescott Granodiorite (loc. 36, fig. 10). 

9. Alaskite noc. 16, fig. 12). 

4. Yarber Wash mass (western facies), Prescott Granodiorite (loc. 47, fig. 10). 

5. Salida Gulch mass, Prescott Granodiorite (loc. 23, fig. 10). 

10. Coarse-grained granite (Joe. 13, fig. 12). 11. Dells Granite (loc. 1. fig. 12). 

6. Lynx Creek mass, Prescott Granodiorite (loc. 12, fig. 10). 12. Fine-grained granite (Joe. 6, fig. 12). 

TABLE 9.-Semiquantitative analyses for minor elements in quartzose intrusive rocks of the Prescott-Jerome area 

[See table 8 for explanation of map symbols. Analyst: H. J. Rose, Jr., U.S. Geol. Survey] 

Prescott Granodiorite 

Government --- Coarse- Dells 

Canyon Alaskite grained Granite 

Grano- Yarber Salida Lynx Prescott Mineral granite 

diorite Wash Gulch Creek mass Point mass mass mass mass 

---------- ------------------- Map symboL _________________ gg pgy pgs pgl pgp pgm al cg dg Lab. No _______________________ 148366 148361 148362 148363 148364 148365 148369 148368 148370 

-------------- Cu __________________ 0. 003 0. 003 0. 001 0. 0003 0. 003 0. 001 0 0. 001 0. 0001 Pb __________________ . 001 . 001 . 001 . 001 . 003 . 001 . 001 . 001 . 003 Mn __________________ . 03 . 03 . 03 . 03 . 03 . 03 . 01 . 01 . 03 Co __________________ . 001 . 001 . 0003 . 0003 . 001 . 001 0 0 0 N i ___________________ . 003 . 001 . 001 . 001 . 001 . 003 0 0 0 Fe ___________________ 3 3 3 3 3 3 .3 .3 .3 

Cr--------------~---- . 001 . 001 . 0003 . 0003 . 001 . 001 0 . 001 0 v ___________________ . 01 . 01 . 003 . 003 . 003 . 003 . 001 . 001 . 003 AI ___________________ 10 10 10 10 10 10 10 10 10 Ga __________________ . 003 . 001 . 001 . 001 . 003 . 003 . 003 . 003 . 003 Sc ___________________ . 001 . 001 . 0003 . 0003 . 001 . 001 0 . 001 0 y ___________________ . 003 . 001 . 001 . 001 . 003 . 001 . 003 . 003 . 01 La ___________________ . 003 . 001 . 003 . 001 . 003 . 001 . 001 . 003 . 001 Ti ___________________ .3 .3 . 1 . 1 . 1 . 1 . 03 . 03 . 01 Zr ___________________ . 01 . 003 . 001 . 001 . 003 . 001 . 001 . 003 . 003 Nb __________________ 0 0 0 0 0 0 0 0 . 01 Be ___________________ . 0003 . 0001 . 0001 . 0001 . 0001 . 0001 . 0003 . 0003 . 0003 Mg __________________ 3 1 1 1 1 1 . 03 . 1 . 1 Ca __________________ 3 3 1 1 1 3 . 1 .3 .3 Sr ___________________ . 1 . 03 . 03 . 03 . 1 . 1 . 001 . 01 . 001 Ba __________________ . 03 . 03 . 03 . 03 . 03 . 03 .. 003 . 03 . 003 Na __________________ 3 3 3 3 3 3 3 3 3 

B------~------------ 0 0 0 0 o· 0 0 0 . 003 

Looked for but not found: Ag, Au, Hg, Ru, Rh, Pd, Os, Ir, Pt, Mo, W, Re, Ge, Sn, As, Sb, Bi, Zn, Cd, Tl, In, Ce, Nd, Hf, Th, Ta, U, P. 

12 

fg 

148367 

78.2 

13.0 

.6 

. 35 

. 10 

. 74 

4.4 

1.9 

. 06 

. 00 

. 01 

. 39 

. 36 

. 02 

100 

Finegrained 

granite 

---

fg 

148367 

--

0. 001 

- 001 

. 01 

0 

0 

.3 

. 000 3 

. 001 

10 . 001 

. 000 3 . 001 

. 003 

. 03 

. 01 

0 

. 000 1 . 1 

.3 

. 01 

. 03 

3 

. 001 
OLDER PRECAMBRIAN ROCKS 31 

TABLE 10.-Normative composition of quartzose intrusive rocks and gabbro of the Prescott-Jerome area 

[See figs. 8, 10, and 12 for locations; figs. 9, 11, and 13 for plots of norms and modes on Qu-Or-Pl diagrams; fig. 7 for other triangular and variation diagrams; table 7 for modal 

composition and table 8 for chemical composition] 

1 2 3 4 5 6 7 8 9 10 11 12 

Map symbol ___ --------------------- gb gg wg pgy pgs pgl pgp pgm al eg dg fg 

---- --------------- Quartz ___________________ 5. 64 10. 68 21. 96 24. 00 27. 90 28. 14 24. 96 18. 36 36. 30 38. 10 33.24 43. 7 4 

2 

0 

1 

0 

Orthoclase ______ ::. _________ 1. 67 20. 02 21. 13 12. 23 12. 23 11. 68 15. 57 11. 12 26. 69 21. 68 26. 69 11. 1 Albite ____________________ 22. 53 35. 63 28. 30 30. 39 36. 15 39. 82 34. 06 37. 20 34. 58 33. 01 35. 63 37. 2 Anorthite ____ __ ___________ 42. 53 16. 68 18. 90 21. 96 15. 01 13. 62 15. 57 21. 41 1.11 2. 50 2. 50 3. 6 

Hypersthene ______________ 11. 50 7. 05 1 4. 20 5. 88 4. 25 1. 93 4. 36 7. 44 1. 10 . 73 1 . 20 1. 2 

- Diopside ________ _________ 2.38 3. 77 ------- ------- ------- ------- ------- ------- -------- ------- ------- ------ Magnetite ________________ 8. 12 3. 71 ------- 3. 71 1. 86 1. 86 Ilmenite __________________ 1. 22 1. 37 ------- . 76 . 46 . 46 Apatite ___________________ ------- . 67 ------- . 34 . 34 . 34 Corundum ________________ ------- ------- . 51 ------- 1. 22 1.73 

3. 02 2. 32 --------

. 76 . 76 . 15 . 34 . 34 -------- . 61 . 31 1. 12 

1. 16 . 46 . 15 -------

------- ------- 2. 04 . 92 

.9 

. 1 

------ 2. 3 

3 

5 

5 Hematite _________________ ------- ------- 4. 00 ------- ------- ------- ------- ------- . 64 ------- . 32 ------ ------------- - Total ______________ 95. 59 99. 58 99. 00 99. 27 99. 42 99. 58 99. 25 99. 26 100. 69 99. 37 99. 96 99. 3 0 ---------------------- ------ Percent of feldspar that is 

orthoclase ______________ 2. 5 28 31 19 19 21 24 16 43 38 41 21 

Plagioclase composition _____ 2An65 3An 32 4An 40 4 An 42 3An 29 3An 25 3 An31 4 An 37 5 An 3 5 An 7 5 An7 5 An 

1 Iron free (enstatite). 2 Labradorite-bytownite. 

a Oligoclase-andesine. 

4 Andesine. 

6 Albite. 

1. Gabbro, composite of 5 specimens from United Verde mine at Jerome and 1 from 

Yarber Wash (locs. 49 and 50, fig. 10). In the chemical analysis, iron is reported as FeO; in calculating norm ratio of Fe20s, FeO is arbitrarily taken as 5:3. 2. Government Canyon Granodiorite. 

3. Granodiorite of Walker area. 4. Yarber Wash mass (western facies), Prescott Granodiorite. 

5. Salida Gulch mass, Prescott Granodiorite. 

Prescott Granodiorite west of the largest mass of gabbro, but they are sparse in the Government Canyon 

Granodiorite and in the mass of Prescott Granodiorite 

that is north of the largest m.ass of gabbro (one was 

noted near 1,279,800 N., 333,700 E., and another near 

1,300,000 N., 268,000 E.). Diabase dikes are probably 

abundant in gabbro but are not as obvious as in the 

granitic rocks, where they contrast in color. Larger 

masses of di:iibasic rock are included with gabbro because 

of the difficulty in distinguishing diabase from gabbro 

and because of the uncertainty as to age relationships 

between the rock types. 

GENERAL CHARACTER 

Gabbro.-The gabbro is a variable generally darkcolored granular rock. Where fresh, much of it is 

medium dark to medium gray, but the color ranges 

from nearly black to light gray, greenish gray, and 

grayish green. Much altered gabbro is green tinted. 

Weathered outcrops are various shades of brown. 

Grain size ranges from coarse to fine. Most of the 

gabbro is medi urn grained, the crystals ranging from 

2 to 5 mm. Crystals in coarse-grained rocks are 5-10 

mm long; some euhedral pyroxene crystals are several 

inches across. Rocks that may have been coarse 

grained are now finer grained because of cataclastic 

deformation. Some are now coarse grained because 

6. Lynx Creek mass, Prescott Granodiorite. 

7. Prescott mass, Prescott Granodiorite. 

8. Mineral Point mass, Prescott Granodiorite. 

9. Alaskite. 

10. Coarse-grained granite. 11. Dells Granite. 12. Fine-grained granite. 

of the development of more or less equant porphyroblastic or poikiloblastic hornblende several inches 

across. 

Textures include the ophitic (or poikilophitic), hypidiomorphic-granular, diabasic, and porphyritic textures of intrusive rocks and the foliated, cataclastic, 

granularly recrystallized, or porphyroblastic to poikiloblastic textures of metamoprhic rocks. Most of the 

younger diabase has well-defined diabasic texture and 

chilled margins. Some is porphyritic or contains large 

saussuritized plagioclase xenocrysts. 

The gabbro in some parts of the two largest masses 

is layered. Many of the pyroxene-rich, plagioclase-rich, 

and locally olivine-rich and magnetite-rich layers 

range from 1,4 inch to 3 inches in thickness. Some layers probably resulted from crystal settling. Where 

alternating layers are now composed of metamorphic 

minerals-dark -colored hornblende and light-colored 

zoisite (or clinozoisite) and tremolite (or anthophyllite )-the origin of the layering is in doubt. 

Original minerals in the gabbro were plagioclase and 

monoclinic pyroxene (augite?) ; accessory magnetite, 

ilmenite, apatite, and zircon; and some pyrite and allanite. Olivine and quartz are erratically distributed. 

Metamorphism has saussuritized the plagioclase, replaced pyroxene by amphibole, and serpentinized the 

olivine. 
32 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA . 

A, Plots of norms ( •) and average 

modes (.) on quartz-orthoclaseplagioclase diagram 

C, Plots of oxides on Si0 2-Na 2 0, 

K20-Fe0, Fe 203, MgO, CaO diagram 

.gb 

Qu 

FeO, Fe 2 0

3

'--.:.t...._ _ _,_ _ _,._ _ __y__ _ ___,..'-------'"----"----"---'"-----" K2 0 

Mafic and 

accessory minerals 

B. Plots of norms ( •) and average 

modes (.) on quartz- feldsparmafic and accessory mineral 

diagram (included with the 

mafic minerals in the mode are white mica and epidote) 

gb. 

1-

~ 6 u 

ffi 4 Q_ 

50 55 60 65 70 

PERCENT SILICA 

D, Plots of oxides against silica 

dg cgal fg 

75 

MgO, CaO Na20 

gb Gabbro 

qd Quartz diorite (not located in fig. 10) 

gg Government Canyon Granodiorite 

wg Granodiorite of Walker area 

pgp Prescott mass, Prescott Granodiorite 

pgl Lynx Creek mass, Prescott Granodiorite 

pgs Salida Gulch mass, Prescott Granodiorite 

pgc Chaparral mass, Prescott Granodiorite 

pgm Mineral Point mass, Prescott Granodiorite 

pgy Yarber Wash mass, Prescott Granodiorite 

q m Quartz monzonite 

al Alaskite 

cg Coarse-grained granite 

dg Dells Granite 

fg Fine-grained granite 

FIGURE 7.-Variation diagrams of quartz-bearing intrusive rocks and gabbro in the Prescott-Paulden-Jerome area. See figures 8, 10, and 12 for location of masses; 

figures 9, 11, and 13 for quartz-orthoclase-plagioclase plots of individual thin sections; and tables 7, 8, and 10 for modal, chemical, and normative analyses. 

Plagioclase in parts of the two largest masses forms 

euhedral to anhedral clear unaltered crystals that range 

in composition from andesine to labradorite or more 

calcic plagioclase. Some of it is packed with minute 

unidentified inclusions (probably magnetite, spinel, 

and others) . In fresh diabase the plagioclase is zoned. 

Much of the plagioclase has been partially to completely 

altered to a granular aggregate of clinozoisite and 

zoisite associated with albitic plagioclase and sericite; 

some has recrystallized to clear granular oligoclaseandesine. 

Pyroxene is preserved in diabase dikes and in a few 

places in the two largest masses of gabbro. Most of it 

is partly to completely replaced by amphibole. The 

amphibole ranges from actinolite to hornblende; most 

of it is actinolitic hornblende. Actinolite forms fibrous 

masses and needles; hornblende forms fine to coarse 

equant crystals or grains. 

Olivine, much of it altered to serpentine, occurs in 

the northern part of the second largest mass (mostly 

north of 1,285,000 N.) and in small amounts elsewhere. 

Some rocks that may have had the composition of 
OLDER PRECAMBRIAN ROCKS 33 

periodotite are now composed largely of either antigorite and narrow chrysotile veinlets or of talc, serpentine, and a few unaltered olivine remnants. 

Interstitial quartz and potassium feldspar occur as 

original, minor constituents, but some quartz and microcline were derived probably from granitic emanations 

that locally permeated the gabbro. Quartz appears to 

be much less common as an original constituent in the 

largest masses than in some of the smaller ones, but its 

source in the more sheared rocks is problematic. 

A little primary ( ? ) biotite was noted in some of the 

least altered gabbro; much of the biotite is metamorphic 

and intergrown with magnetite. Chlorite replaces 

pyroxene, amphibole, or biotite, commonly forming rims 

around these minerals or forming aggregates with epidote, quartz, and other minerals. It is most abundant 

along shear zones. 

Locally, more or less feathery masses of tremolite, 

anthophyllite, and zoisite, or clinozoisite) have partly 

to almost completely replaced plagioclase and pyroxene 

in the two largest masses of gabbro. The thermal metamorphism that formed these minerals was caused by 

adjacent quartzose intrusive rocks. 

Some gabbro has been extensively epidotized, and 

some of it in the southwestern part of the second largest 

mass contains piedmontite as veinlets and disseminations (seep. 105). 

Iron-rich gabbro occurs in parts of the two largest 

masses and in small masses (near 1,288,700 N., 37 4,000 

E., especially the one near 1,290,500 N., 374,500 E.). 

Locally, layers are composed almost entirely of magnetite and ilmenite. Plagioclase is the principal silicate mineral, almost to the exclusion of pyroxene or 

hornblende in some of these rocks. Apatite is generally 

abundant. Although euhedral magnetite crystals are 

common in the gabbro, in the iron-rich rock most magnetite and ilmenite occupy interstitial positions between 

and are molded on plagioclase and pyroxene. The 

granular intergrowths of magnetite and ilmenite are of 

secondary or late-stage origin and replace pyroxene and 

hornblende. Magnetite appears to be later than ilmenite in iron-rich rocks but earlier than ilmenite in the 

more normal gabbro.5 

Chemical analyses of gabbroic rocks from the area 

have not been made. The average silica content 

(Anderson and Creasey, 1958, table 12, No. 8, p. 38) of 

5 The magnetic susceptibility of several specimens of gabbro from the 

Prescott quadrangle was tested in the Physical Properties Laboratory 

of Newmont Exploration, Ltd. The susceptibility of most of the specimens ranges from 4,200 X 10-ecgs to 7,100 X 1o~cgs (1,68Q--2,84() 

gammas). The susceptibility of some specimens of light-colored altered gabbro and of serpentine ranges from 19 X 10-e to 200 X 10-ecgs 

(7.6-;-80 gammas). A specimen rich in magnetite and ilmenite gave a 

reading of 13,000 X 10-ecgs (5,200 ga:mmas). The susceptibility of the 

gabbro is sufficiently high to give rise to magnetic anomalies (U.S. Geol. 

Survey, 1950) over gabbro areas. 

five specimens from the United Verde mine at Jerome 

and one from southeast of the Preqcott quadrangle (see 

fig. 10, table 8, and also fig. 7 and ta;ble 10) is 48.57 

percent compared with a silica content of 48.24 percent 

for average gabbro and 56.7·7 percent for average diorite (Daly, 1933, p. 16-17). Much of the least metamorphosed parts of the two largest masses appears to be 

a saturated gabbro in which the plagioclase is at least 

as calcic as labradorite; it is likely that most of the 

smaller more metamorphosed masses had a similar composition. The presence of olivine in some and quartz 

in others indicates a range from undersaturated to oversaturated rocks. Quartz gabbroic to quartz dioritic 

facies occur, but only the quartz diorite along the Verde 

River is large enough to map and describe separately. 

Quartz diorite.-Quartz diorite along the Verde River 

is a medium- to coarse-grained rock composed principally of light pinkish-gray feldspar and greenishblack to dark olive-gray hornblende and some biotite. 

Grain size of much of the rock is 4-5 mm, but some hornblende crystals are as large as 5 by 10 mm. The rock 

varies slightly in relative proportions of dark and light 

minerals and in the amount of quartz and potassium 

feldspar (largely microcline). The plagioclase is sericitized or saussuritized. Chlorite replaces hornblende 

and biotite. The rock contains some coarse epidote and 

accessory magnetite, apatite, zircon, sphene, and allanite. Because the quartz content is greater than 10 percent (table 7; fig. 7 A), the rock is classed as quartz 

diorite. The higher content of hornblende, biotite, and 

epidote suggests correlation with gabbro rather than 

with one of the granodiorites. 

RELATIONS TO OTHER ROCKS 

Gabbroic rocks are younger than the Alder Group, 

as they clearly intrude the volcanic rocks and contain 

xenoliths of them. The large-scale intrusive relations 

are illustrated on the geologic map (see pl. 1, near 

1,283,000 N., 350,000 E.). Most of the gq,bbroic rocks 

are older than the quartzose intrusive rock, but some 

are younger. 

'Gabbro is cut out by Prescott Granodiorite (for 

example, at the northern end of the largest mass of 

gabbro) . It is brecciated, and fractures are filled with 

granitic to aplitic material, especially along the sides 

of some of the masses and in some areas of contaminated gabbro and Prescott Granodiorite. In the eastcentral part (northeast part, pl. 1) intrusive breccia, 

formed by the invading Prescott Granodiorite and 

aplite, are common. The east side of the largest mass 

and the southwest part of the second largest mass of 

gabbro have been contact metamorphosed, and zoisite 

(or clinozoisite) and tremolite (or anthophyllite) extensively replace primary plagioclase and pyroxene. 
34 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

Mainly because of spatial relations, the intrusive rocks 

that probably produced both the alteration and the 

veinlets are thought to bf} alaskite, quartz monzonite, 

and Government Canyon Granodiorite. 

Some gabbroic rocks, mostly diabase, have intruded 

gabbro, alaskite porphyry, and some masses of Prescott 

Granodiorite. The dikes in gabbro fill clean fractures 

and have chilled borders. Larger masses of fine-grained 

mafic rocks, especially in areas mapped as contaminated 

gabbro and Prescott Granodiorite in the south-central 

part of the area, contain xenoliths or xenocrysts of 

granodiorite. These xenoliths, however, could have 

come from a pre-Alder ·Group intrusive rock (see foot-: 

note 7, p. 49). Much of what is shown as contaminated gabbro in the westernmost lenses in this area 

may be volcanic in origin. 

GOVERNMENT CANYON GRANODIORITE 

DISTRIBUTION 

The Government Canyon Granodiorite, herein named 

for good exposures along Government Canyon ( 1,280,-

000 N., 341,000 E.), forms two masses in the southwestern part of the area (pl. 1 ; fig. 8) . The western mass, 

which is separated into two parts by Cenozoic rocks, 

must end somewhere between its northernmost exposures and the Dells Granit~, less than 2 miles to the 

north. Minor amounts of granodiorite, too small to 

show on the geologic map, occur in the southern part of 

the adjacent unnamed volcanic rocks of the Alder( n 

Group. 

GENERAL CHARACTER 

The Government Canyon Granodiorite forms topographic lows, many of which are covered with pine 

forest. The rock weathers light yellowish brown to 

light brown. It disintegrates to a sandy soil, through 

which protrude scattered more or less spheroidal boulders of relatively fresh rock. The fresh rock is medium 

to medium light gray and has a salt and pepper appearance. 

The granodiorite ranges from a massive rock to one 

having a fairly pronounced planar and linear structure. 

Primary planar and linear flow structures are brought 

out by alinement of xenoliths, of plagioclase, hornblende, and biotite crystals, and in places of porphyritic and nonporphyritic layers; A secondary foliation 

locally cuts the western mass. 

Xenoliths of various sizes are abundant in the western 

mass. In the eastern mass xenoliths, mostly less than 

6 inches long, are rather sparsely but uniformly distributed, except near the contacts with the volcanic rocks, 

where they are abundant and of many sizes. The xenoliths are composed largely of mafic volcanic rocks and 

of fine-grained gabbro(~). 

330,000E 

0 2 3 MILES 

Government Canyon Granodiorite 

Contacts dashed where overlain by younger rocks 

FIGURE B.-Distribution of the Government Canyon 

Granodiorite in the Prescott and Mount Union quadrangles, showing location of specimens used for modal, 

chemical, and n()rmative analyses. No. 13 is from a 

small mass in schist. 

Typical granodiorite is a medium-grained rock having a seriate texture. Some of it is porphyritic. The 

maximum length of plagioclase, hornblende, and biotite crystals is about 1.5 em. In addition to these minerals the rock contains orthoclase, quartz, epidote, and 

accessory minerals (see tables 7, 8, 9, and 10, and figs. 7 

and 9 for modal, chemical, and normative composition). 

Plagioclase is somewhat zoned and has an average 

composition of sodic andesine;~ normative plagioclase 

is An32 • The plagioclase forms euhedral to anhedral 

grains. The centers of most crystals are slightly sericitized or saussuritized; a few are highly altered. 

Microcline and perthite fill interstices and locally form 

poikilitic grains 3 mm in diameter. Quartz is interstitial to plagioclase and mafic minerals. Most of it shows 

wavy extinction, but little of it is granulated. G~een 

hornblende and greenish-brown biotite are in euhedral 

crystals and in very ragged grains and aggregates. 
OLDER PRECAMBRIAN ROCKS 35 

EXPLANATION 

Mode of individuJI thin section Qu 

Average mode of mass 

Norm 

10 

FIGURE 9.-Government Canyon Granodiorite. Plots of modes and 

norms on quartz-orthoclase-plagioclase diagram. Numbers refer to 

individual thin sections or to chemically analyzed specimens; location of numbers is shown in figure 8. See also figure 7 and tables 

7, 8, and 10. 

Some are intergrown with other mafic and accessory 

minerals or altered to chlorite. Some hornblende is 

poikilitic. Sphene is commonly conspicuous as wellformed crystals as much as 1.7 mm long and as ragged 

and poilkilitic grains. Apatite and magnetite form 

euhedral crystals less than 0.4 mm in size. Biotite contains tiny zircons. A few euhedral epidote crystals 

were observed; much of the epidote is secondary and 

forms intergrowths with mafic and accessory minerals. 

Veins and disseminations of piedmontite occur locally 

(seep. 105). 

RELATIONS TO OTHER ROCKS 

The Government Canyon Granodiorite is younger 

than unnamed volcanic rocks of the Alder(?) Group; 

the intrusive relations are manifested by the very irregular contact between the two rocks (south of 1,284,000 

N.), by widespread intrusive breccias, and by granodiorite injected along bedding, fracture, and foliation 

planes in the volcanic rocks. Erratically and conformably oriented volcanic xenoliths from a few feet to 3,500 

feet long are abundant in the southern part of the western body of granodiorite. The granodiorite is probably 

younger than gabbro (see the discussion in the preceding section) . 

The western mass of Government Canyon Granodiorite is cut by many dikes of Prescott Granodiorite 

and occurs as xenoliths in the Prescott Granodiorite; 

however, no dikes of Prescott Granodiorite were noted 

in the eastern mass of Government Canyon Granodiorite. The possibility that the eastern and western 

masses are not part of the same intrusion or that the 

western mass contains two granodiorites has been considered, but no supporting field evidence was observed. 

The eastern mass is the northern part of what Lindgren 

(1926, p. 21-22 and pl. 2) called the Groom Creek area 

of granodiorite, which he considered probably Late Cretaceous to early Tertiary in age. The lead/alpha age 

of zircon in the granodiorite, however, is Precambrian 

(seep. 50). 

PRESCOTT GRANODIORITE 

DISTRffiUTION 

The Prescott Granqdiorite, herein named for extensive exposures in the western part of the city of 

Prescott, forms isolated masses in the southern and eastcentral parts of the Prescott-Paulden area. For ease 

in discussion, the various masses are given locality 

names: the Prescott, Salida Gulch, Lynx Creek, Chaparral, and Mineral Point masses (fig. 10). Small outcrops, dikes, and lenses and much granodiorite in areas 

of contaminated rocks are part of the Prescott Granodiorite. The quartz diorite of the Jerome area (Anderson and Creasey, 1958, p. 38--41) is considered to be part 

of the Prescott Granodiorite and is referred to as the 

Yarber Wash and B.ig Bug Creek masses. The Chaparral mass was also called quartz diorite by Anderson 

and Creasey. In the present report, a rock is considered to be a granodiorite if more than 10 percent of the 

feldspar is orthoelase. On this basis, only the eastern 

facies of the Yarber Wash mass is a quartz diorite; 

the Salida Gulch mass is on the dividing line between 

quartz diorite and granodiorite (fig. 7, 11). As the 

Prescott mass, which gives its name to these rocks, is a 

granodiorite and as the norms of all the rocks fall 

within the granodiorite field, the term granodiorite is 

used. 

The Prescott mass forms a triangular-shaped outcrop 

in the southwest corner of the area. The Salida Gulch 

mass is a long, narrow north-trending body in the southcentral part. The Lynx Creek mass lies at the north 

end of the largest body of gabbro. All of these masses 

are buried to the north or northeast by Cenozoic deposits, and their extent beneath these deposits is unknown, except that the Prescott mass cannot extend for 

more than 2 miles to the northeast before it is cut out by 

or faulted against the Dells Granite (pl. 1, sees. 0-0' 

and F-F'). Two narrow north-northeast-trending 

bodies of granodiorite in the Chaparral zone form the 

Chaparral mass. The larger one, whose extent to the 

northeast is unknown, is in the Chaparral Volcanics; 

the smaller one occurs along the Spud fault. The Mineral Point mass is in the east-central part of the area 
36 

1,390,000 

1,260,000N 

GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

v-Pgi 

t'>.---:'l:r? 

pgi-C) '\:.Y 

' (Pii~ 

PAULDEN QUADRANGLE 34 {s CLARK nALR OTTAnRAN r..LF. & 

1-'KI~;:scUTT QTT A nR .<\NGLE ~Y -MOUNTAIN gb~ / ( -QUADRANGLE 

>(pgi ll' (" ~<,o36 

1~~ T~'& ,; 

~ 1\ + + + + + +\ + + 

I' ~ + + + + 

/ + + + + -1 I~ ~,o- I ++~ j +. + + + -1 -1 

ft 42+ -+ + + ) 

~ + -1- + + -1 

~~ J- ~ 10~~ 1 + + I+ + -+ + + + + 

I \._-: 

;~ ~pgp 

,~ i4~ + + i+ + -t ~ N· + + ft + -+ + +( lld-1 + pgy + Je41 + + + + 

I.J -t:J + +3_;.~ + + + +43J- + + ~ 

47 + + + + + + +,...-..--

I.J~ __, 1-\ ~ 3~ + + + + + ~45 + f41 + + + 

pgci,o: 

+ +40+ + + + + _j j ~~\ ~gi~ + 

·-""~ +. + + 

~ I~ ~ ~gi + -'C + + + 

I_J/ + + + .+ + ........ rz..-.: 3_1 ---

I.J~ a pg~~ 0 ?2,33 

bY MT U NION Ql ·AnRAN~LF. ~ MAYER QTT A nR ANGLE 

330,000E 

Prescott mass 

Numbers 1-8; number 8jrom a 

dike 

[ +p!y+ J 

Yarber Wash mass 

Western facies, numbers 38-41, 

4 7; eastern facies, numbers 

42-46 

ln..~ (~ ;.; ~ ~~ ~ 

Lynx Creek mass 

Numbers 9-16 

Big Bug Creek mass 

No data available 

ON 

Salida Gulch mass 

Numbers 17-27 

Miscellaneous outcrops, 

lenses, and dikes 

Probably related to Prescott 

Granodiorite 

• 

I 

t 

Chaparral mass 

Numbers 28-33 

? 

I 

Granodiorite of Walker 

area 

Number 48 

Contact Location of specimen 

Dashed where overlain by 

younger rocks 

t 

I 

f T 4 MILES I 

I 470,000 

Mineral Point mass 

Numbers 34-37 

Gabbro 

Composite of jive specimens 

from number 49 and one from 

number 50 

FIGURE 10.-Distribution of masses of the Prescott Granodi()rite, showing location of specimens used for modal, chemical, and normative 

analyses ; locati()ns of granodiorite of the Walker area and of gabbro samples are also shown. 
OLDER PRECAMBRIAN ROCKS 37 

(pis. 1, 2) and is exposed intermittently for about 10 

miles. Its extent to the south and southwest beneath 

Cenozic deposits is unknown. 

GENERAL CHARACTER 

The various masses of Prescott Granodiorite have 

been correlated on the basis of similarity in modal, 

chemical, and normative composition (figs. 7, 11; tables 

7, 8, 9, 10). The Prescott mass is the least altered and 

deformed and is described in detail; brief mention of 

differences in the other masses are also given. 

Weathering of the Prescott mass characteristically results in large erosional mounds of relatively fresh rock 

surrounded by sand flats formed by accumulation of 

angular fragments, some of crystal-grain size. Disintegration along joints results in piles of rounded 

boulders, some balanced, whose form depends largely 

on the spacing and attitude of joints. 

The Prescott mass is a fine- to medium-grained massive slightly altered rock, having a poikilitic, hypidiomorphic-granular texture. Fresh granodiorite is 

medium gray, light gray, or greenish gray. Slightly 

darker or lighter shades are principally a function of 

grain size, but lighter shades in places are due to less 

abundant biotite or to the opaque character of the more 

altered plagioclase. The weathered surface is grayish 

orange pink to grayish orange; some is reddish brown 

owing to baking by basalt or is light brown owing to 

weathering of introduced pyrite. 

The granodiorite contains plagioclase, quartz, potassium feldspar, biotite, epidote, and accessory minerals. 

Most plagioclase is translucent to greasy; some is glassy, 

and some is chalky or greenish. Individual grains are 

hard to distinguish in hand specimen. The plagioclase 

forms zoned subhedrallaths and anhedral grains, mostly 

less than 1 mm long. A few euhedral laths are 2 mm 

long; sparse phenocrysts are larger. Some plagioclase 

encloses other mineral grains ; the margins of some are 

intergrown with quartz and microcline. Cloudy sodic 

plagioclase surrounds microcline in places. The centers 

of the plagoiclase, which is about andesine in composition, are cloudy because of slight argillization, sericitization, or saussuritization. The margins are clear 

albite (An5 _ 10 ). Normative plagioclase in this mass is 

An31 ; it ranges from An31 to An25 in the other masses. 

Quartz occurs as glassy colorless to light-gray slightly 

strained anhedral grains, mostly less than 1 mm in 

diameter. Some of it forms myrmekitic or graphic 

intergrowths with plagioclase. Where microcline is not 

abundant, quartz is interstitial to plagioclase. 

Most of the potassium feldspar is microcline, but some 

occurs as orthoclase and as perthitic or microperthitic 

intergrowths. Microcline forms clear, colorless square 

to rectangular, poikilitic crystals having irregular 

margins. The crystals average about a quarter of an 

inch long; some are as much as 1 Y2 inches across. The 

poikilitic microline is scattered sparsely to abundantly 

throughout the rock and encloses the other minerals. 

Commonly, the inclusions are distributed rather evenly 

through the microcline; some are so abundant that the 

enclosing microcline is easily overlooked. Locally the 

inclusions are concentrated around the margins of the 

microcline. 

Biotite forms greenish-black flakes, books, and granular aggregates, which average about 0.5 mm ~ 

diameter; a few are as much as 1-2 mm. Pleochroic 

halos around zircon are common. Some biotite is replaced by magnetite (or ilmenite), epidote, or chlorite. 

Epidote is widely distributed, from minor quantities 

to amounts nearly as abundant as biotite. Some grains 

are euhedral, but epidote is probably metamorphic; it 

also occurs in veinlets. V einlets and disseminated 

grains of piedmontite (seep. 105) are abundant in the 

granodiorite north west 'and west of Prescott. 

Accessory minerals are sphene, magnetite, ilmenite(?), apatite, and zircon. Sphene forms euhedral 

crystals as much as 0.6 mm long and granular rims 

around magnetite. Leucoxene has formed from sphene 

and from ilmenite or titaniferous magnetite. 

Although most of the Prescott mass is uniform, some 

of it is spotted, layered, or altered. Contamination 

from mafic rocks produced sparse to abundant rounded, 

irregular, or angular spots (especially near 1,295,500 N., 

340,500 E.; and 1,294,000 N., 336,000 E.). Most of the 

spots are about a quarter of an inch in diameter. They 

are composed of green biotite and minor amounts of 

epidote, sphene, magnetite, apatite, and leucoxene. 

Parallel dikes of aplite and pegmatite produced layered rocks in a few places (1,296,400 N., 334,500 E.; 

1295 500 N., 340,800 E.; and 1,308,000 N., 327,300 E.). ' ' . The layers strike north-northeast and dip about vertically. Individual layers average 1-3 feet wide, but 

range from 1 inch to more than 10 feet. Some can be 

traced along the strike for several hundred feet. Some 

layers consists of compound dikes, the centers being 

aplitic and the margins pegmatitic, or vice versa; others 

are made up of irregular aplitic and pegmatitic zones. 

The layers are cut by younger pegmatite and aplite 

dikes. 

Most of the Prescott mass has been altered by mild 

regional metamorphism. For about 3 miles north of the 

southern border of the area, a more intense alteration 

is probably the result of hydrothermal solutions associated with quartz, quartz-tourmaline, and tourmaline 

veins. It formed a mafic-poor aplitic-looking rock 

containing dark specks composed of granular mixtures 
38 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

Qu . Qu 

PIL---~--~--~L-~--~~~L_J_~--~--~--~or PIL---~--~--~

33~1L--~--~--~~~--~--~~~or 

10 331h 66% 73 

MINERAL POINT MASS (pgm) YARBER WASH 

Qu 

COMPOSITE 

EXPLANATION 

Mode of individual thin section 

Average mode of mass (Yarber Wash mass: 

.y-1, average of western facies; 

y-2, average of eastern facies; 

y-3, average of mass) 

Norm (no norm of pgc) 

FIGURE H.-PRESCOTT GRANODIORITE. PLOTS OF MODES AND NORMS . ARE ON QUARTZ-ORTHOCLASE-PLAGIOCLASE 

OF NUMBERS AND EXPLANATION OF LETTER SYMBOLS ARE 
OLDER PRECAMBRIAN ROCKS 

Qu Qu 

Pl~--1~0--~--~3~3~~~--~--~-6~6~%~--~--~--~ar PIL---1~0--~--~3~3~~~L_~L---~6~6~%~--~--~--~or 

PRESCOTT MASS (pgp) LYNX CREEK MASS (pgl) 

Qu Qu 

Pl~--1~0--~--~3~3~~~~~~--~-66~%~--~--~--~or PIL---1~o--~--~3~3~~~L-~L---~6~67.%~--~--~--~or 

SALIDA GULCH MASS (pgs) CHAPARRAL MASS (pqc) 

DIAGRAMS. NUMBERS REFER TO INDIVIDUAL THIN SECTIONS OR TO CHEMICALLY ANALYZED SPECIMENS: LOCATION 

SHOWN IN FIGURE 10. See also figure 7 and tables 7, 8, and 10. 

39 
40 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

of magnetite, specular hematite, and leucoxene that are 

pseudomorphic after magnetite, pyrite, or original 

mafic minerals. The saussuritized centers of plagioclase have been replaced by coarse sericite. Microcline 

is somewhat mottled owing to intergrowth or replacement by sodic plagioclase or myrmekitic quartz. Specular hematite occurs as veinlets, and coarse sericite coats 

fractures in places. 

Except for small parts of the Lynx Creek and Mineral Point masses, the other masses do not resemble the 

Prescott mass. They are more deformed and altered, 

lack poikilitic microcline, and are generally coarser 

grained. The northern part of the Salida Gulch mass 

is intensely foliated quartz-feldspar-biotite schist and 

augen gneiss. Much of the Chaparral mass is a cataclastically deformed mafic-poor rock. Grain size in 

undeformed parts of these masses ranges from 1 to 5 

mm, but the size of some of the feldspar augen suggests 

an original coarse-grained or porphyritic rock containing feldspar crystals more than 8 mm long. The calcic 

cores of plagioclase are highly saussuritized. Quartz 

occurs as granular aggregates or is drawn out ir~.to long 

thin plates. Potassium feldspar forms fine intergrowths or granular mixtures with quartz and albite. 

Hornblende was observed only in the Mineral Point 

mass; allanite, in the Salida Gulch, Chaparral, and 

Mineral Point masses. 

No primary mafic minerals are preserved in the 

Salida Gulch and Chaparral masses, with the possible 

exception of a few large biotite flakes. Most boitite 

and chlorite occur as granular aggregates associated 

with epidote and accessory minerals. In the intensely 

foliated rock in the northern part of the Salida Gulch 

mass, metamorphic brown or greenish-brown biotite is 

concentrated in plates or thin lenses. In the less foliated 

rock to the south, the biotite is green or brownish green. 

This part of the Salida Gulch mass contains more 

chlorite than the more schistose rock to the north. In 

the Chaparral mass mafic minerals have been largely 

sheared out and completely altered to chlorite, epidote, 

calcite, and leucoxene. 

RELATIONS TO OTHER ROCKS 

The conclusion that the rocks mapped as the Prescott 

Granodiorite are part of the same intrusion is based 

primarily on similarities in modal, chemical, and normative composition, but this correlation is open to 

question. Refinements in age determinations may prove 

or disprove this conclusion. On the basis of the amount 

of deformation the rocks have undergone, the Prescott, 

Yarber Wash, Big Bug Creek, Mineral Point, and 

Lynx Creek masses could be interpreted as younger 

than the Salida Gulch and Chaparral masses. 

Field relations prove that most of the masses of Prescott Granodiorite intrude the Alder Group or contain 

xenoliths of the Alder Group, but because of intense 

deformation and mechanical mixing, relations are obscure in some places. The Lynx Creek mass clearly 

intrudes tuffaceous rocks of · the Alder ( ~) Group and 

gabbro. The Mineral Point and Yarber Wash masses 

also intrude gabbro; most of the other masses contain 

xenoliths of gabbroic( n rocks. The Prescott mass 

intrudes the western mass of ·Government Canyon 

Granodiorite. Pink aplite dikes, some spatially related 

to alaskite, cut all the masses; coarse-grained alaskite 

cuts the Mineral Point mass. The Salida Gulch mass 

is cut by coarse-grained granite, fine-grained granite, 

and fine-grained gabbroic to diabasic rocks. A few 

diabase dikes also cut the Lynx Creek mass, but nonE} 

cut the other masses. The Dells Granite and Prescott 

Granodiorite are not in contact, but the Prescott mass 

is cut by dikes of aplite and pegamatite and veins of 

quartz, quartz-tourmaline, and tourmaline that are 

probably related to the granite; the granite contains 

xenoliths that resemble the granodiorite. 

The fine-grained granite rather thoroughly permeated some of the Salida Gulch mass. This mass contains numerous dikelike bodies, too small to map, and 

larger irregularly shaped bodies of mafic rocks that are 

mapped as gabbro. Some of the bodies may be older 

volcanic or gabbroic rocks; others have a diabasic texture, cut the granodiorite, contain xenoliths of granodiorite, or ha-ve chilled margins against the granodiorite. 

The granodiorite bodies in the Chaparral-Spud fault 

zone parallel the regional foliation within the zone. 

The bodies were intruded prior to final deformation 

within the zone or, more probably, were dragged into it. 

Postintrusive deformation produced augen gneiss and 

mylonite in the granodiorite and obscured the original 

relations of granodiorite to Chaparral Volcanics and 

to gabbro. The contacts are gradational, and the granodiorite may nowhere be in contact with rocks that it 

originally intruded. 

ALASKITE AND RELATED ROCKS 

DISTRmUTION 

Alaskite and related rocks crop out in the southeastern and east-central parts of the Prescott-Paulden area 

(pis. 1, 2; fig. 12). These rocks are mapped as quartz 

monzonite, alaskite, and alaskite porphyry; the alaskite 

porphyry includes aplitic alaskite and aplite. 

Quartz monzonite lies west of the eastern mass of the 

Green Gulch tuffaceous. unit. It is separated into two 

parts and buried to the north by Cenozoic deposits. 
OLDER PRECAMBRIAN ROCKS 41 

PART 

1,320,000~----+-----------~--~------+-----------~----------~---------+----------1---------~ 

330,000E 390,000 

EXPLANATION 

~ + dg + ~ i __ +_±_j El 

Dells Granite 

Numbers 1-5; number 5/rom boulder 

in gravel 

Fine-grained granite 

Number 6 

Coarse-grained granite 

Numbers 7-13 

Contact 

Alaskite and related rocks 

al, alas/cite; numbers 14-18 

ap, alas/cite porphyry and aplite 

qm, quartz monzonite; numbers 19-20 

Dashed where overlain by younger rocks 

FIGURE 12.-Distribution of granitic rocks, showing location of specimens used for modal, chemical, and normative analyses. 

Alaskite forms two large and several small discrete 

bodies in the southeastern part of the area, all of them 

east of the largest mass of gabbro. Five small lenses 

and pods, one of them occurring largely south of the 

map area, are in the southwestern part of the tuffaceous 

rocks of the Green Gulch Volcanics; a long, narrow body 

of alaskite is in the Chaparral Volcanics. Eight small 

bodies of alaskite extend south-southeast from Upper 

King Canyon (pl. 2, 1,396,500 N., 379,100 E.). Unmapped sheets, pods, and irregular dikes of alaskite are 

found in the Prescott Granodiorite and gabbro south of 

these exposures. 

Alaskite porphyry forms one large mass in the southeastern part of the area. Two narrow masses of aplitic 

alaskite occur in the northern part of the Green Gulch 

tuffaceous unit, and an elongated lens lies immediately 

east of Chaparral fault. Unmapped aplite dikes, 

probably related to alaskitic rocks, are common in the 
42 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

Mineral Point and Lynx Creek masses of the Prescott 

Granodiorite (fig. 10) and cut other intrusive rocks. 

GENERAL CHARACTER 

Alaskite and alaskite porphyry are resistant rocks. 

In the southern part of the area the largest masses form 

high ridges having local steep to precipitous slopes. 

The crests of the ridges that extend northward from the 

wider parts of the larger alaskite masses are occupied by 

narrow dikelike masses of alaskite augen gneiss. A subdued topography, formed on alaskite in the east-central 

part of the area and on the quartz monzonite, is the 

result of proximity to old erosion surfaces-pre-late 

Tertiary on the quartz monzonite and pre-Paleozoic on 

the alaskite. 

Quartz monzonite.-Quartz monzonite is medium 

grai~ed, locally coarse grained or porphyritic, and has a 

mass1veto foliated structure. The rock is mottled olive 

gray and light brownish gray and is composed of microcline, plagioclase, quartz, and mafic and accessory minerals. The modal composition is given in table 7. The 

Plagioclase is a somewhat zoned oligoclase ( An15• 5 as 

~etermin~~ ?Y X-ray diffraction). The cores are partially sericitlzed and saussuritized. Chlorite, less abundant biotite, epidote, and muscovite, and a few relics of 

hornblende form irregularly shaped aggregates. Accessory minerals are magnetite, apatite, zircon and allanite. ' 

Alaskite and alaskite porphyry.-The alaskitic rocks 

are similar in color and composition. They differ in 

degree of deformation and amount of contamination but 

principally in texture. Textural gradations between 

alaskite and alaskite porphyry occur in a few places. 

. Most alaskitic rocks are pale red to grayish orange 

pink, some are moderate red, and some are nearly white 

because of alteration. The rocks weather light shades 

of brown; exceptions are the northern part of alaskite in 

the Chaparral Volcanics and some of the aplitic alaskite 

east of Chaparral fault, which weather dark to moderate 

reddish brown. 

Alaskite ranges from a massive rock through augen 

gneiss to mylonite. Augen gneiss is chal"acteristic of 

many of the narrow dikelike masses 8Qme unmapnAd . ' r~ ' In gabbro and volcanic rocks; it forms only narrow 

zones in the large masses. Alaskite in the Chaparral 

Volcanics is mostly equigranular a;t its northern end 

and augen gneiss in the middle; its southernmost 1 000 

feet is a tail of mylonite less tham. 50 feet wide. Much 

of the granitic-textured alaskite is medium grained. 

In augen gneiss, however, the size of some feldspar 

augen suggests that some of the original rock was coarse 

grained or porphyritic. 

Most alaskite porphyry is massive and fine grained. 

Its sparse to abundant phenocrysts, 2-6 mm in diameter, 

consist of feldspar and quartz. Aplite wd aplitic 

alaskite are fine grained and have a sugary texture. 

Slight recrystallization of mylonite may also have 

formed a sugary texture. Some aplitic alaskite, especially on the eastern edge of the large mass of alaskite 

porphyry, contains phenocrysts of quartz and :feldspar, 

generally less than 1 mm and rarely as much as 2 mm in 

diameter. 

Modal, chemical, and norma;tive compositions of 

medium-grained equigranular alaskite are given in 

tables 7, 8, 9, and 10, and figures 7 and 13. The rock 

consists of potassium feldspar, albite, quartz, a little 

mica, and accessory minerals. 

The feldspar is albite, microcline, orthoclase, and 

perthite. Some potassium feldspar has been ·partly 

replaced by late albite. Most of the augen are potassium feldspar. Albite, in many places, is sligptly 

sericitized; most potassium feldspar is fresh. Normative albite is An3 • 

Quartz is strained, crushed,. or granulated in most 

alaskite but is only slightly strained in the finer grained. 

rocks. In augen gneiss it forms lenticular or plate-li~e 

aggregates or granular mixtures with feldspar. 

In unsheared and uncontaminated alaskitic rocks 

poor in mafic minerals, primary biotite, muscovite, 

magnetite (or ilmenite), zircon, and sphene are sparse. 

In some of the sheared rocks, aggregates of fine flakes 

of biotite, chlorite, or sericite are concentrated in thin 

plates or lenses. In some intensely deformed alaskite in 

the Chaparral zone, mafic minerals have boon completely sheared out. 

Contaminated alaskitic rocks contain sparse to 

abundant biotite, chlorite, amphibole, and epidote, 

which were derived from mafic volcanic rocks and 

gabbro that have been sheared into the alaskite or were 

picked up by it from the intruded rocks. The aggregates 

of chlorite, sericite, epidote, leucoxene, and some calcite 

were derived from orig,inal or xenolithic biotite or other 

mafic minerals. Biotite has altered to chlorite. Tiny 

pyrite cubes are abundam.t in some alaskitic rocks and 

appear to be related to mild sericitization. 

RELATIONS TO OTHER BOCKS 

Alaskite, alaskite porphyry, and quartz monzonite are 

prdbably consanguineous; the alaskite porphyry is 

slightly younger, and the quartz monzonite is slightly 

older than the alaskite. If consanguineous, then alaskite and related rocks are all younger than the gabbro 

and the granodiorites but older than some diabase. 

.Quartz monzonite.-Quartz monzonite probably intrudes gabbro. Many pink aplite dikes in quartz monzonit'3 suggests that is a slightly older facies of the alaskite 

and alaskite porphyry. 
OLDER PRECAMBRIAN ROCKS 43 

Qu Qu 

PIL---~--~--~~~~--~--~L_~~--~--~L_~or PIL---~--~--~LL~~--~--~L_-L~--~--~L-~or 

10 33lh 66% 10 

DELLS GRANITE (dg) 

Qu 

PI~--1~0~--~--~33~¥;~3~~--U---~-6-6~%~--~--~L-~or 

COARSE-GRAINED GRANITE (cg), QUARTZ MONZONITE (qm) 

EXPLANATION 

Mode of individual thin section 

Average mode of mass (no mode of fg) 

Norm (no norm of qm) 

ALASKITE (al) 

Qu 

COMPOSITE 

FIGURE 13.~ranitic rocks. Plots of modes and norms are on quartz-orthoclase-plagioclase diagrams. Numbers refer to individual thin 

sections or to chemically analyzed specimens; location of numbers and explanation of letter symbols are shown in figure 12. See also 

figure 7 and tables 7, 8, and 10. 

758-447 0-65--4 
44 GEOLOGY OF . THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

Alaskite.-The larger masses of alaskite intrude the 

unnamed volcanic rocks of the Alder( n Group. Although the actual contacts are poorly exposed, the outcrop pattern of the basaltic flows that separate the two 

largest bodies of alaskite indicates intrusion by alaskite, 

an indication strongly supported by the many aplite 

dikes in the basaltic flows. Part of the outcrop pattern 

of the tuffaceous rocks northeast of these alaskite masses 

is due to intrusion of the alaskite. In upper King 

Canyon (pl. 2) alaskite is clearly intrusive into the 

tuffaceous rocks. 

Unmapped masses of alaskite in gabbro north of the 

largest masses of alaskite and alaskite porphyry have 

dikelike form. They are 1-50 feet wide and as much as 

half a mile long. The margins are zones of shear, and 

the alaskite is an augen gneiss, but much of the adjacent 

gabbro is relatively massive. Presumably shearing was 

taken up in alaskite rather than in gabbro. 

Alaskite porphyry.-Alaskite porphyry and aplite 

clearly intrude unnamed basaltic flows of the Alder ( ~) 

Group and form distinctive intrusive breccias, especially 

along Green Gulch (near 1,284,500 N., 378,300 E.; and 

1,284,400 N., 381,100 E.) and along Charcoal Gulch 

(near 1,283,200 N., 377,700 E.; and 1,277,800 N., 377,400 

E.) . The elongated subrounded to angular xenoliths 

are alined roughly parallel to the regional trend of the 

foliation and range from individual biotite or hornblende crystals or aggregates a fraction of an inch long 

to masses measured in tens of feet. Some xenoliths are 

dikelike in form. Xenoliths make up about 40 percent 

of some outcrops, and in these places many ~f them are 

about 3 feet long. Narrow diabase dikes in alaskite 

porphyry along Charcoal Gulch are also paraliel to the 

regional north-trending foliation. 

Narrow dikes of aplite intrude gabbro and the Lynx 

Creek and Mineral Point masses of Prescott Granodiorite in the southeastern and east-central parts of the 

area. Although most of the alaskite and alaskite 

porphyry masses parallel the regional formation, some 

aplite dikes are crosscutting. 

COARSE-GRAINED GRANITE 

DISTRmUTION 

Coarse-grained granite forms a long narrow northtrending mass in the south-central part of the area (pl. 

1,284,500 N., 359,500 E., and fig. 12). Adjacent areas 

mapped as contaminated Prescott Granodiorite and 

contaminated fine-grained granite contain some coarsegrained granite. 

GENERAL CHARACTER 

Coarse-grained granite is a medium-light-gray to 

light-gray rock. Where intensely foliated it has a 

silvery sheen due to abundant sericite. The rock is 

medium to coarse grained and locally porphyritic, containing phenoorysts as much as 1 em long. Most of the 

massive rock has an equigranular granitic texture. 

Some of the foliated rock is augen gneiss. The granite 

is composed of plagioclase, quartz, microcline, biotite, 

sericite, chlorite, and accessory minerals (see tables 7, 

8, 9, and 10, and figs. 7 and 13 for chemical, modal,· and 

normaHve compositions). 

Quartz is strained, granulated, or drawn out into 

thin, platelike, fine granular masses. Microcline and 

mircrocline-perthite are subordinate to albite, which 

shows slight replacement by or altera.tion to coarsegrained sericite. Normative plagioclase is An1. Some 

of the rock contains a few large altered plagioclase 

(oligoclase-andesine) crystals. Epidote is generally 

lacking. Metamorphic biotite occurs as aggregates of 

small flakes or is concentrated in lenticular areas or as 

thin plates. In most places it is not abundant and is 

generally subordinate to the white mica, most of which 

is also of secondary origin. Accessory minerals are 

zircon, magnetite, apatite, and sphene( ~), which is now 

largely altered to leucoxene. 

RELATIONS TO OTHER ROCKS 

In a few places coarse-grained granite clearly intrudes the Salida Gulch mass of Prescott Granodiorite 

and is intruded by fine-grained granite. Most contact 

between coarse-grained granite and granodiorite, however, are gradational and arbitrary. Because biotite, 

epidpte, and saussuritized plagioclase gradually increase 

in abundance toward the granodiorite contact, it was 

difficult in the field to distinguish the granite from the 

granodiorite. Prescott granodiorite may occupy more 

of the area mapped as coarse-grained granite, or coarsegrained granite may occupy more of the areas mapped 

as contaminated granodiorite. Modal, chemical, and 

normative analyses of the granite resemble those of both 

alaskite and the Dell Granite, but the coarse-grained 

granite has been mapped separately because it does not 

resemble either rock megasoopically and because the 

analyses do not clearly indicate that it belongs to either 

the alaskite or the Dells Granite. 

DELLS GRANITE 

DISTRIBUTION 

The Dells Granite, herein named for the Granite Dells, 

lies about 5 miles northeast of Prescott (pl. 1 ; fig. 12). 

It forms a somewhat triangular-shaped mass about 5 

square miles in area. Its extent beneath the surround- . 

ing Cenozoic cover is probably limited by faults on the 

southeast and southwest to a mile or less (pl. 1, sees. 

B-B', 0-G', D-D', and F-F'); its extent to other directions is unknown. 
OLDER PRECAMBRIAN ROCKS 45 

FIGURE 14.-Aerial photograph (Cou-8-73) of Granite Dells and Glassford Hill, showing joint pattern in the Dells Granite (dg) and the 

overlying rocks of late Tertiary' ( ?) age: basalt flows (Tbl, lower; Tbm, middle; Tbu, upper) ; sedimentary and tuffaceous rocks (Ts) ; cinder 

cone (Tel ; branching dike (Td) ; and andesite flow (To). Light areas east and north of Glassford Hill are caliche. 

GENERAL CHARACTER 

The form of the bold outcrops of the Dells Granite 

is controlled by joints and shows up well in aerial photographs (fig.14) and on the topographic map, where contour lines make right-angle bends. In two places, 

northeast of Storm Ranch (1,308,800 N., 354,300 E.) 

and between Entro (1,312,000 N., 353,500 E.) and Route 

89, N. 15°-40° W. joints have exerted more control on 

the topography than the principal set, which is N. 25° 

E. and N. 70° W. (fig. 26). Where the rocks are more 

disintegrated, especially northwest of Storm Ranch, 

bold hills and pronounced valleys are absent, and the 

area is more extensively covered by trees and brush. 

Weathering along joints has formed large and small 

rounded boulders, some balanced boulders, and other 

unusual forms. It has also produced a checkerboard 

appearance (fig. 15) where iron oxide has migrated inward from horizontal, vertical, and sloping joint surfaces. Successive migrations of iron oxide resulted in 

concentric envelopes that become more spherical inward. 

The weathered surface is rough owing to rounded knobs 

or pits. The knobs consist of masses or individual large 
46 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

FIGURE 15.-Checkerboard appearance formed in t•he Dells Granite due 

to weathering along joint planes; southwest of Willow Creek Reservoir (1,310,000 N., 343,900 E.). 

crystals of pegmatitic minerals or of xenoliths of schist 

or gneiss. The pits, 3-6 inches deep and 1-2 feet in 

diameter, noted northwest of Watson Lake, are formed 

by weathering along joints or by removal of pegmatitic 

minerals or of xenoliths. Much of the granite is crumbly because its present surface is near an old erosion 

surface. A green claylike material coats joints and is 

disseminated through the rock near the surface in some 

places. 

The Dells Granite is a fairly uniform massive 

medium- to coarse-grained rock having a granitic 

(seriate), locally porphyritic, texture. The principal 

minerals generally range from 2 to 5 mm in diameter. 

Phenocrysts of feldspar are erratically distributed and 

are almost completely absent in some areas. The phenocrysts have a maximum size· of about 2 inches and 

average from % to 1 inch in length. Most of them, 

and the larger ones, are microcline ; some are 

albite. Fresh surfaces of the granite are very light 

gray to almost white, and weathered surfaces are various shades of orange pink and light brown. The 

granite is composed of white feldspar, light smoky-gray 

quartz, and variable amounts ofbiotite. Black tourmaline, purple fluorite, magnetite, specular hematite, and 

a little apatite occur either as accessory minerals or as 

introduced hydrothermal minerals. The modal, chemical, and normative compositions are given in tables 7, 

8, 9, and 10, and in figures 7 and 13. 

Quartz occurs as rout:1ded, anhedral, slightly strained 

grains, many containing inclusions of other minerals. 

Microcline is the principal potassium feldspar. It 

forms interstitial anhedral grains; some of it poikilitically encloses albite, quartz, and biotite; some phenocrysts have poikilitic margins. Perthite forms irregular areas in the microcline. Albite occurs as subhedral 

crystals, perthitic intergrowths, and a few phenocrysts. 

Some of it encloses other minerals, especially around 

the margins. It ranges from about An1s to An4; 

normative plagioclase is An7 • A few phenocrysts show 

slight zoning. Much of the albite is slightly cloudy 

because of minor sericitic or argillic a1ter3!tion. 

Locally in the northeastern part of the mass, darkgreen biotite forms books ranging from 1 to 4 mm in 

size, but in much of the rock, biotite is bleached and 

forms smaller flakes that have a ragged outline and a 

pale-olive color. Under the microscope this mica is 

nearly colorless and nonpleochroic or slightly pleochroic. Darker pleochroic halos occur around some of 

the tiny zircons. The index of refraction on cleavage 

flakes is slightly less than 1.61, 6 in contrast to the index 

of the fresh mica, which is nearly 1.64. The 2V of this 

colorless mica is too small for muscovite. Alternate 

platelike areas of iron oxides (magnetite, specular hematite, ilmenite, and leucoxene) occur in some of the 

bleached biotite. The bleaching appears to he associated with the introduction of deuteric or hydrothermal 

fluorite. Most of the specimens used for modal analyses contain bleached biotite; the chemically analyzed 

specimen contained fresh biotite. Alteration of the 

rock might account for the poor agreement between the 

norm and average mode of the granite (figs. 7, 13) . 

Accessory minerals are magnetite, specular hematite, 

and some leucoxene. V einlets and granular masses of 

individual crystals generally less than 1 mm in diameter 

of purple to colorless fluorite can be seen in most thin 

sections and in .many hand specimens. Crystals of black 

tourmaline range from less than 0.1 mm to more than 

5 em in length; some are concentrated in irregular areas 

as graphic intergrowths with quartz and feldspar. 

Tiny red garnets a.re present in some places but are more 

abundant in some aplites that cut the granite. A few 

diamond-shaped reddish areas, now largely altered to 

hematite ( ? ) and leucoxene ( ? ) , probably represent 

original sphene. 

LATE-STAGE PRODUCTS OF. CRYSTALLIZATION 

Deuteric and hydrQ:thermal alteration slightly 

sericitized albite, bleached biotite, and introduced pegmatitic and aplitic minerals and quartz, quartz-tourmaline, and tourmaline veins. The abundance of these 

minerals, together with fluorite, suggests that the 

e The index checks reasonably well with partly altered biotite from 

Santa Rita (Kerr and others, 1950, p. 321). 
OLDER PRECAMBRIAN ROCKS 47 

granite was rich in water and mineralizers. These minerals are erratically distributed and do not appear to be 

as abundant in the northeastern part and along the 

northwestern border as elsewhere. 

Pegmatitic material permeated the granite and 

formed dikes, irregular veins, pods, and individual 

crystals. Many of the dikes are only a few feet wide; 

individual microcline crystals are as long as 12 inches; 

pods of quartz and tourmaline and individual tourmaline crystals are several inches long. The dikes are 

composed of coarse quartz and microcline, some finer 

grained graphic or platelike intergrowths of quartz and 

albite (about An6 ), dark-green biotite, muscovite, and 

tourmaline. Some dikes contain alternating layers of 

pegmatite and aplite; the aplite is fine grained, sugary, 

and white to grayish orange pink. 

RELATIONS TO OTHER ROCKS 

The Dells Gram.ite is surrounded and unconformably 

overlain by Cenozoic rocks (fig. 14). The concealed 

oontact between the granite and the Precambrian volcanic and intrusive rocks southeast of the Granite Dells 

is thought to be a fault trending north-northeast that 

passes beneath Glassford Hill (pl. 1, sees. B-B', D-D'). 

The concealed contact between the granite and the Government Canyon and Prescott Granodiorites southwest 

of the Granite Dells may be a fault trending west-northwest close to the southwestern outcrops of the granitethat is, between the granite outcrops and a 1,000-foot 

well in late Tertiary ( ? ) deposits (pl. 1, sees. 0-0', 

D-D', F -F'). The granite is probably younger 

than the Prescott Granodiorite, as discussed on page 40. 

FINE-GRAINED GRANITE 

DISTRIBUTION 

Two areas of fine-grained granite are found in the 

south-central part of the area (pl. 1, fig. 12). One is 

east of the Texas Gulch Formation and extends north 

from the southern border of the area for about 4 miles. 

The other is north of the Texas Gulch Formation am.d 

west of the unit containing jasper-magnetite beds. It is 

separated into two parts by a surficial cover of Cenozoic 

rocks. 

GENERAL CHARACTER 

Fine-grained granite is greatly contaminated with 

older rocks. The granite is massive, light, slightly 

pinkish, yellowish, or greenish gray. Individual grains 

are mostly less than 1 mm long. The granite is composed of plagioclase, orthoclase, quartz, and traces of 

m·afic and accessory minerals. Chemical and normative 

compositions of what appeared to be a relatively uncontaminated sample from the eastern area are given in 

tables 8, 9, and 10, and in figures 7 and 13. The composition falls in the granodiorite field (fig. 7), but the 

plagioclase is albite; therefore the rock is a granite. 

The following petrographic data were obtained from 

study of thin sections of specimens from the eastern 

mass. Much of the ql}artz occurs as graphic or myrmekitic intergrowths, in places having a radial arrangement; some quartz encloses plagioclase. The irregular 

margins of the plagioclase are sodic albite, but the more 

or less euhedral centers of some are more calcic and 

slightly sericitized. Normative plagioclase is An9 • 

Large quartz grains as much as 5 mm in diameter, large 

saussuritized and sericitized plagioclase, and erratically 

distributed lenticular aggregates of mafic and accessory 

minerals probably were picked up from intruded quartz 

porphyry, the Prescott Granodiorite, gabbro, and the 

Alder Group. The mafic and accessory minerals are 

biotite, chlorite, epidote ( zoisite), magnetite, apatite, 

sphene, leucoxene, actinolitic hornblende, zircon, calcite, 

and pyrite. Same granite in the western area resembles 

the aplitic alaskite or aplite in texture and in the almost 

complete absence of mafic and accessory minerals. 

RELATIONS TO OTHER ROCKS 

Fine-grained granite intrudes the Texas Gulch Formation, quartz porphyry, gabbro, the Salida Gulch mass 

of the Prescott Granodiorite, and coarse-grained granite. In places it thoroughly permeates older rocks. 

The aplitic material in the western outcrops may not be 

related to the fine-grained granite of the eastern area; it 

may be older, as indicated by local foliation. The eastern mass may not be consanguineous with the other 

quartzose intrusive rocks; its chemical and normative 

composition (tables 8, 10; figs. 7, 13) differs from that 

of the other rocks. 

OTHER INTRUSIVE ROCKS 

Quartz porphyry and rhyolite dikes, too small to 

show on the geologic map, occur in the south-central 

part of the Prescott-Paulden area, mostly in areas 

mapped as contaminated Prescott Granodiorite and 

contaminated fine-grained granite. 

QUARTZ PORPHYRY 

Quartz porphyry intrudes the Alder Group and is 

intruded by the Prescott Granodiorite, coarse-grained 

granite, and fine-grained granite. It is a light gray 

porphyritic rock; some of it has a primary flow structure and embayed pheonocrysts, but much of it has 

been intensely foliated. It is composed of quartz and 

albite phenocrysts as much as 10 mm long in a groundmass composed of quartz, alkalic feldspar, variable 

amounts of sericite, a little biotite or chlorite, a little 

epidote or zoisite, and accessory magnetite and apatite. 
48 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

Some intensely foliated quartz porphyry consists of alternating layers of sericite and quartz-sericite; but some 

of the augen of quartz in the layers show little strain or 

granulation. 

RHYOLITE DIKES 

Rhyolite dikes are confined largely to the southern 

part of the area of fine-grained granite east of the 

Texas Gulch Formation. The dikes intrude the Alder 

Group and fine-grained granite. The rhyolite is fine 

grained, massive and light to medium light bluish to 

greenish gray; it weathers white. Quartz and albite 

phenocrysts are as much as 3 mm in size. Quartz is 

euhedral or resorbed. Some albite crystals are clustered. Large areas of epidote are scattered erratically 

through the rock. The groundmass is quartz, alkalic 

feldspar, and very minor amounts of epidote, sericite, 

and chlorite. 

VEINS, SILICIFIED ZONES, AND ALTERAT.ION ZONES 

Veins, silicified zones, and alteration zones include 

quartz, quartz-tourmaline, and tourmaline veins ( identified on pl. 1 by the letter q), quartz-magnetite veins or 

replacements (identified on pl. 1 by the symbol m), and 

to avoid the use of a separate symbol, silicified and 

alteration zones (identified on pl. 1 by the symbol si). 

The silicified and alteration zones include silicified 

breccia zones and economically important mineralized 

and alteration zones; many quartz veins have been mineralized. Mineralized veins and zones are discussed , 

in the section on "Economic geology," page 104. 

Quartz veins are widely distributed in the Precambrian rocks, except in the Mazatzal Quartzite. They are 

especially abundant in the east-central and southeastern 

parts of the area. Quartz-tourmaline and tourmaline 

veins cut principally the Dells Granite, Government 

Canyon Granodiorite, Prescott and Lynx Creek masses 

of Prescott Granodiorite, and the aplite and pegmatite 

dikes in these rocks. 

The veins fill shear zones and a few joints. Some 

are parallel to and others are at an angle to the foliation 

in the host rock. The veins, pods, and lenses of quartz 

range in width from a few inches to, rarely, 50 feet. 

They are generally discontinuous within a shear zone. 

The longest quartz vein, about 1,000 feet, is in quartz 

diorite north of the Verde River (pl. 2, 1,413,500 N., 

382,300 E.) ; other large veins and pods are found in the 

extreme southwest corner of the area and in alaskite in 

the Chaparral zone (pl. 1, 1,284,000 N ., 398,000 E.). 

The largest tourmaline vein seen is 5 feet by about 100 

feet. Some tourmaline veins form thin coatings on 

joints. 

The quartz veins consist principally of milky or white 

quartz. Some contain appreciable amounts of tourmaline and grade into veins composed principally of tour- ' 

maline. Others contain minor amounts of gold, and 

many of them contain sufficient pyrite, chalcopyrite, or 

other metallic minerals to have induced prospectors to 

dig many shallow pits and adits. Few of the quartztourmaline and tourmaline veins contain enough metallic minerals to encourage exploration. The tourmaline ranges from hairlike needles to thicker crystals 2 

mm long. The crystals form a network or mesh containing minor amounts of quartz. 

Quartz-magnetite veins, pods, and lenses are most 

abundant in the southwesternmost and south-central 

masses of unnamed tuffaceous rocks of the Alder 

Group ( ? ) , but they occur also in the Spud Mountain 

Volcanics and the basaltic flow unit of the Green Gulch 

Volcanics. Those in intrusive rocks are probably part 

of a xenolith of volcanic rocks. The veins are parallel to 

foliation or bedding in the host rock and do not appear 

to have any stratigraphic significance. Some are en 

echelon, an eastern one lying to the north of an adjacent 

western one. They range from a few inches to 20 feet 

in width.; a few fill all but a minor part of a 50-foot zone. 

Some have been traced as much as 1,500 feet. 

The quartz-magnetite is medium gray to medium 

dark gray and has a purple or blue cast. Most of it is 

finely laminated; some is massive. Laminae range from 

paper thin to several feet in width and are formed by 

variations in amount and grain size of quartz · and magnetite. Minute magnetite grains, 0.01-0.4 mm in 

diameter, are scattered or occur in ramifying streaks 

and bands, some of them more than 1 mm long. Most 

quartz grains are elongate and range from 0.01-0.8 mm 

in length, except in magnetite-free layers, where the 

individual grains are as much as 4 mm long. Small to 

large variations in the proportions of quartz and magnetite are common; the layers range from pure quartz. 

to almost pure magnetite. Some veins enclose minerals 

characteristic of the host rock. The quartz-magnetite 

zones may represent recrystallized sedimentary jaspermagnetite beds or, more probably; a replacement of the 

tuff by hydrothermal quartz and magnetite. In the 

Prescott quadrangle portion of the Jerome area, these 

veins are referred to as jasper veins. by Anderson and 

Creasey ( 19·58, p. 43), but the veins here are more 

crystalline than the jasper veins farther east. 

Silicified breccia zones occur in the Dells Granite west 

and northwest of Storm Ranch and in the Prescott and 

Lynx Creek masses of Prescott Granodiorite (pl. 1) . 

Most zones are narrow, ranging from less than an inch 

to a few inches or feet wide. A number of narrow zones 

may be concentrated to form a wider zone, such as the 
OLDER PRECAMBRIAN ROCKS 49 

one in the Prescott mass (1,301,000 N., 329,000 E., to 

1,305,300 N., 327,800 E.). The widest breccia zone has 

a maximum width of 50 feet and was traced intermittently for about half a mile (from 1,295,800 N., 370,700 

E., to 1,297,700 N., 369,000 E.). This zone contains 

fragments of Precambrian volcanic and intrusive rocks, 

some of which are more than a foot long, and smaller 

ones of quartz, feldspar, tourmaline, and other minerals. 

The fragments are cemented by chert and other forms of 

silica. Limonitic areas suggest alteration of introduced 

pyrite or other iron oxide or sulfide-bearing minerals. 

CONCLUSIONS 

AGE 

The Precambrian quartzose intrusive rocks in Arizona 

have generally been thought to belong to one period of 

orogeny that occurred before the deposition of the ~{azatzal Quartzite, although Hinds ( 1936, p. 100) suggested two periods, one prior to and one after deposition 

of the Mazatzal. Until the recent discovery of a granodiorite older than the Texas Gulch Formation, 7 all the 

intrusive rocks of the Prescott-Paulden area were considered younger than the Alder Group. As relations 

are obscure in many places, the possibility exists that 

locally pre-Alder Group rocks may have been included 

in the Government Canyon or Prescott Granodiorites. 

No evidence, however, of intrusion of any granitic rocks 

into the Mazatzal Quartzite was found in the area. 

Gabbro and the Yarber vVash mass of Prescott 

Granodiorite in the Jerome area, quartz diorite in the 

northern part (pl. 2), and alaskite and the Mineral 

Point mass of the Prescott Granodiorite in the eastcentral part (pis. 1, 2) of the Prescott-Paulden area are 

unconformably overlain by lower Paleozoic rocks. 

Elsewhere Paleozoic rocks are absent, and the Precambrian age of the intrusives is less certain. The lead/ 

alpha age of zircon in the Government Canyon Granodiorite (see p. 50), however, is Precambrian. The 

intense deformation of some intrusive rocks in the 

southern part of the area-especially alaskite, coarsegrained granite, and the Chaparral and Salida Gulch 

masses of the Prescott Granodiorite-likewise indicates 

a Precambrian age for these rocks. If the correlation 

of the Yarber Wash and Mineral Point masses with the 

Prescott mass is correct, then the Prescott mass also is 

Precambrian, even though it has undergone only mild 

regional metamorphism. Also the Prescott mass 

1 Mapping in the Mount Union quadrangle about 10 miles southsouthwest of the southeast corner of the Prescott quadrangle by P. M. 

Blacet of the U.S. Geol(}gical Survey in the summer of 19·61 has shown 

that t he Texas Gulch Formation rests unconformably on an older 

granodiorite (quartz diorite) (C. A. Anderson, oral commun., 1962). 

This is the first known occurrence of granitic rocks older than the 

Alder Group. 

resembles granodiorite that is overlain by Ta peats 

Sandstone in the southeastern part of the Simons 

quadrangle (fig. 1). The age of the massive Dells 

granite is less certain, but it is considered Precambrian 

because it is cut by quartz and tourmaline veins, which 

have not been found cutting Paleozoic rocks to the 

north, and because it resembles granite that is overlain 

by Cambrian rocks in the Camp Wood quadrangle (see 

fig. 16) about 25 miles to the northwest. Fine-grained 

granite is considered Precambrian only because it is cut 

by diabase dikes, which have not been obserwed cutting 

Paleozoic rocks; its massive uP.altered character suggests that it may be younger. The massive rhyolite 

dikes were intruded after regional deformation ; they 

may be related to upper Tertiary rhyolite tuff, but be, 

cause they are more altered than the rhyolite lapilli in 

the tuff, they are included in the Precambrian instrusive 

rocks. Quartz, tourmaline, and quartz-magnetite veins 

are presumably Precambrian; none were observed 

cutting Paleozoic rocks. They were formed probably 

after the major Precambrian deformation, as they are 

fractured but otherwise undeformed. The fragmental 

character of the breccia zones implies that brecciation 

occurred close to the surface in very late Precambrian 

or, possibly, in post-Precambrian tLmes. 

RELATIONS 

The various masses of the Prescott Granodiorite are 

correlated on the basis of modal, chemical, and normative compositions (tables 7-10, figs. 7, 9, 11, 13, 15). 

The similarity in hand specimen between some of the 

masses is less striking. The Prescott mass is finer 

grained than all the other masses except parts of the 

Lynx Creek mass; it is characterized by large poikilitic 

microcline; the others are not. The Lynx Creek mass 

consists of finer and coarser grained rocks that are considered to be facies but conceivably represent different 

intrusions. The Yarber Wash and Mineral Point 

masses both have hornblende; no hornblende was observed in the Prescott and Lynx Creek masses, and if 

originally present in the Salida Gulch and Chaparral 

masses, it was destroyed during shearing. 

. The composition of most of the Prescott Granodiorite 

is sufficiently different from that of the Government 

Canyon Granodiorite-lower in modal and normative 

quartz and in total silica, higher in modal and normative mafic and accessory minerals (fig. 7)-to conclude 

that the two granodiorites .are not part of the same intrusion. The presence of hornblende in the Yarber 

'V ash and Mineral Point masses suggests a possible 

correlation with the Government Canyon Granodiorite, 

as does the somewhat lower quartz content of the Mineral Point mass compared with that of the other masses 
50 · GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

of Prescott Granodiorite. The amount of contamination of the Mineral Point mass, however, makes inadvisable any firm conclusion that it is consanguineous 

with either the Prescott or the Government Canyon 

Granodiorite or that more than one granodiorite is 

present. 

The lead/alpha age of zircon in the Government Canyon Granodiorite is 930 million years and that of the 

Yarber Wash mass is 1,045 million years. These ages 

were determined by H. W. Jaffe of the U.S. Geological 

Survey in 1954. The ftlge of the Government Canyon 

Granodiorite was reported as 910 and that of the Yarber 

Wash mass as 1,050 million years by Anderson and 

Creasey (1958, p. 39'). The change in age is due to 

slight revision in the constants used in the calculations 

(Jaffe, written commun., 1957). The results indicate 

only that these rocks are Precambrian ; they should not 

be considered as indicative of the relative a.ges. If the 

Yarber Wash mass is a facies of the Prescott Granodiorite and if both areas mapped as Government Canyon 

Granodiorite are the same age, then the Government 

Canyon Granodiorite is older than the Yarber Wash 

mass. Because alaskite and some masses of Prescott 

Granodiorite were intensely deformed, they appear to 

be older than Government Canyon Granodiorite and the 

Prescott mass of Presoott Granodiorite. 

Alaskite, coarse-grained granite, and the Dells 

Granite are similar in modal, chemical, and normative 

composition, but megascopically alaskite is too different 

from the two granites to be oonsidered correlative; the 

amount of deformation and metamorphism of coa~­

grained granite compared with that of the Dells Granite appears to preclude a correlation of the two 

granites. 

All or most of the intrusive rocks of the area may 

have been derived from the same parent magma.. The 

gradual shift of points from the plagioclase oorn.er of 

the field towards the center of the field in figure 7 A 

conforms to expedmental data on silicate melts. The 

curves of oxides plotted against silica in figure 7 D are 

relatively smooth and likewise conform to curves that 

would be expected from differentiation of a ·magma. 

Both are in general agreement with relations established 

in the field. As the point representing the potassium 

oxide content of fine-grained granite does not fall on 

the curve, this granite may have had a. different source. 

New and additional age determinations using the 

potassium/argon and strontiumjrubidium methods to 

be made on Government Canyon Granodiorite, the 

Yarber Wash and Prescott masses of Prescott Granodiorite, and the Dells Granite may resolve some of the 

uncertainties. 

UNCONFORMITY AT THE BASE OF THE PALEOZOIC 

ROCKS 

The older Precambrian rocks of north-central Arizona are separated from Paleozoic formations by a 

major angular unconformity. Paleozoic rocks were 

laid down on the eroded edges of the older Precambrian 

volcanic, sedimentary, and intrusive rocks. Where local 

hills or monadnocks stood above this surface, the basal 

Paleozoic formations were deposited a.round them. In 

most places these hills rise to heights of little more than 

50 feet above the general level, but part of the area 

underlain by the Mazatzal Quartzite (southwest-central 

part, pl. 2) was so high that about 500 feet of lower 

Paleozoic beds (Cambrian and most of the Devonian) 

are absent (fig. 17). 

PALEOZOIC SEDIMENTARY ROCKS 

GENERAL FEATURES 

Paleozoic rocks are largely limited to the area northeast of Chino-Lonesome Valley, where they are widely 

exposed but are concealed in many places by Cenozoic 

rocks. Their presence beneath these deposits in ChinoLonesome Valley is uncertain. 

The southernmost exposures of the Paleozoic rocks 

(northeast corner, pl. 1) consist of the Tapeats Sandstone of Cambrian age and the basal beds of the'Martin 

Limestone of Devonian age. Successively younger 

formations appear to the north. They are the upper 

beds of the Martin Limestone, the Redwall Limestone 

of Mississippian age, the Supai Formation of Pennsylvanian and Permian age, and the Coconino Sandstone of 

Permian age. The youngest Permian formations, the 

Toroweap Formation and the Kaibab Limestone, crop 

out northeast of the area. 

The present distribution of Paleozoic rocks is due to 

uplift of the area to the southwest, which resulted in 

gentle titling of the rocks to the northeast, in local 

modifications of the northeast structure by faults and 

sharp warps, in burial by upper Tertiary ( ~) rocks ; and 

in erosion prior to and after accumulation of the upper 

Tertiary ( ~ ) rocks. Northeast of the basin this distribution is illustrated in part by the maps showing the 

structure contours of the base of the Red wall Limestone 

(pl. 5) and the map showing the present thickness of 

Paleozoic and Cenozoic rocks (fig. 31). 

The Tapeats Sandstone can be divided into two units; 

and the Martin and Red wall Limestones, into four units 

each. These units have not been mapped, but their 

recognition is helpful in working out offsets along monoclinal structures and faults of small displacement. The 

three members of the Supai Formation, a red-bed deposit, have been mapped (pl. 2). The Paleozoic rocks 

are probably about 2,800 feet thick in the northeast 
PALEOZOIC SEDIMENTARY ROCKS 51 

corner of the area. The thicknesses of the formations 

and their units in north-central Arizona are shown in 

table 11. 

TAPEATS SANDSTONE 

DISTRIBUTION 

Outcrops of the Tapeats Sandstone are limited to the 

extreme northeast corner of the Prescott quadrangle 

and to the southern part of the Paulden quadrangle 

(fig. 16). Northeast of the outcrops, the formation 

probably lies beneath younger Paleozoic rocks; it was 

not deposited in much of the area that is underlain by 

the Mazatzal Quartzite (fig. 17). 

The southernmost exposures of the Tapeats Sandstone 

are on the hill near 1,364,000 N., 3.92,500 E. (pl. 1), and 

near the eastern margin of the quadrangle between 

1,357,900 N. and 1,361,100 E. An outcrop, too small to 

show on the geologic map, occurs beneath basalt near 

1,358,000 N., 398,500 E. 

The most continuous exposures of the Tapeats (see 

pl. 2) are along the Verde River east-southeastward 

from Hubbel Ranch (1,417,500 N., 374,500 E.), in the 

headwaters of King Canyon (1,390,000 N., 383,000 E.), 

and north and northwest of St. Mathews Mountain 

( 1,370,000 N., 399,000 E.). The sandstone forms isolated exposures along the Verde River west of Hubbel 

Ranch, near the mouth of Granite Creek (1,403,000 N., 

346,000 E.), in upper and lower Bull Basin Canyon 

(south of Hub bel Ranch), in the head waters of Gold 

Basin Canyon (1,398,000 N., 382,000 E.), and 3-31h 

miles south-southwest of Paulden (near 1,398,000 N., 

330,000 E.). The last occurrence is the only outcrop 

within the area that is not northeast of Chino-Lonesome 

Valley. About 100 feet of mudstone, siltstone, and 

sandstone of the Tapeats was penetrated about 1,150 

below the surface in a wildcat oil well (No. 1, sec. 20, 

T. 18 N., R. 2 "\V.; pl. 1, sees. B-B', 0-0') about 31h 

miles northwest of Paulden. 

TABLE 11.-Thickness, in feet, of Paleozoic formations in north-central Arizona 

[Inc., incomplete: Abs., absent because of nondeposition or erosion; U, undifferentiated or unrecognizable. Figures given 1n parentheses are approximate range of thickness 

In the quadrangles involved; they are listed because the thickness of the formation or unit at the indicated section is not given. See figs. 16 and 17 for approximate locations. The sections in Paulden quadrangle were measured by Krieger] 

Section ___________________________ _ 2 4 5 6 8 9 10 11 12 13 14 

---·---------1----1---------------1-----1---

CoconinoSandstone ___________________________________________________________________________________ (500--650) (500--650) ------------ ------------ ________ 1,000 

Supai Formation: 

~~die~~====================== Lower_________________________________________ ======== ======== --~~~~- 1150 ____________________________________________ ======== ======== ======== ============ ======== (580-625) ~~~&=~ggj 758 

329 

2578 

1,140 

390 

2670 

----1-----1-----1--- Total Supai Formation_______ ________ ________ 1,155 Inc. 2,200 

RedwallLimestone: ===l===l===l===l===l===l====l=== 

1,550 1, 665 

Unit4 ________________________________________ _ 51 -------- -------- -------- ------------ 35 

81 

80 

23 

(40) 

(100) 

(55-80) 

(25-55) 

<40) ------------ } 151 (Inc.) (100) ------------ Unit 3 ________________________________________ _ 140 {-------

Unit 2 ____ --------------------- _______________ _ 

Unit L ______ ---- _ ------------- -------- -------- ------ Total Redwall Limestone ___ _ Inc. Inc. ------ Martin Limestone: UnitD _______________________ _ u u Unit C _______ _________________ _ u u UnitB _______________________ _ u u Unit A _______________________ _ u u 

100 

103 

21 ---

275 ---

u 

u 

u 

u 

---

Inc. ---

u 

u 

u 

u 

---

Inc. Inc. ---

} 3 315 { <50 

0 

55 0 

20 0 

Inc. 219 252 

(55-80) ------------ 74 (25-55) ________ c___ 30 

54 

92 

----1-----1-----1---

241 Inc. 256 (Inc.) 286 

3 325 218 (260-270) (260-270) 255 260 250 

65 (65-80) (65-80) 75 63 78 90 97 (80-110) (80-110) 88 89 79 

20 15 (20-50) (20-50) 21 53 34 

30 

------------------1-----1--- ----1-----1-----1---

Total Martin limestone _____ _ 332 324 385 381 350 <50 --------------- Cambrian formations: 

Muav Limestone _____________ _ Bright Angel Shale ____________ _ Tapeats Sandstone ____________ _ 

297 50 Abs. Abs. Abs. Abs. 

112 135 Abs. Abs. 5 612 Abs. 

317 223 7 279 7 114 7 142 Abs. --------------- Total Cambrian ____________ _ 726 408 279 114 154 Abs. 

1 Part of all of the lower unit is correlated with the Callville Limestone of Penn· 

sylvanlan age. 2 J;'art or all of the lower unit is correlated with the Naco Formation of Pennsyl- vaman age. 3 Contact between the C and D units is gradational. 

l. Fort Rock, about 25 miles northwest of section 2. McNair (1951, p. 510-511, 517). 

2. Juniper Mountains (Walnut Creek), Camp Wood quadrangle. McNair (1951 

p. 507, 511, 515). 

3. Black Mesa. Supai Formation: Hughes (1949; 1952; 1950, The stratigraphy of 

the Supai formation, Chino Valley area, Yavapai County, Arizona: Arizona 

Univ. M. S. thesis); northeast corner of Turkey Canyon quadrangle. Red wall 

Limestone: Gutschick (1943); northeast corner of Simmons quadrangle. 

Martin and Tapeats Formations: Hughes (1950 [see above]); southeast quarter of Picacho Butte quadrangle. 

4. Simmons, southeastern part of Simmons quadrangle. McNair (1951, p. 507, 515, 517-518). 

5. Verde River-Granite Creek, Paulden quadrangle, between 1,407,700 N., 351,500 

E., and 1,403,000 N., 347,000 E. 

6. Granite Creek, Paulden quadrangle, near 1,385,000 N., 356,500 E. 

7. Verde River, south of Bald Hill, Paulden quadrangle, between 1,416,100 N., 

368,200 E., and 1,414,700 N., 368,000 E. 

435 395 444 480 439 465 441 '390 

Abs. 618 53 (Inc.) 

71 (Inc.) 

Abs. 6 21 

125 

146 

Abs. 

6 (0-20) 

(0--40) 

50 

Abs. Abs. 6 (0-20) 6 20 

(0-40) 29 (Inc.) 

50 49 (Inc.) 

Abs. Abs. Abs. 

6 (0-20) fi (0-20) u 

(0-40) (0-40) u 

55 50 

' The formation locally cuts out against hills composed of Precambrian rocks, as in section 6. · 6 Pebble to boulder conglomerate. e May be equavilent to the Bright Angel Shale. 1 Contains pebbles of limestone and sandstone. 

8. Verde River, south of the mouth of Hell Canyon, Paulden quadrangle, ne!lr 

1,415,700 N., 368,200 E. The Redwall Limestone was mea!>ured .about 1 mlle to the north; the Tapeats Sandstone, about halfway between sectwns 7 and 8. 

9. Verde River-Mormon Pocket-Henderson Flat, Clarkdale quadrangle. Lehner 

(1958). s . 10: Verde River-Packard Ranch-Sycamore Canyon, Clarkdale qu!ldrangle. upa1 Formation: McKee (oral commun., 1953). Redwall, Martm, and Tapeats 

Formations: Lehner (1958). 11. Upper King Canyon, Paulden quadrangle, near 1,392,500 N., 385,900 E. 

12. Little Coyote Canyon, northwestern part of Mingus Mountam quadrangle. 

Anderson and Creasey (1958, p. 49, 51; unpub. data). 13. Haynes Gulch, south-central part of Clarkdale quadrangle. Anderson and , Creasey (1958, p. 49, 51; unpub. data). 14. Pine area, 30-45 miles southeast of Jerome. Coconino Sandst<:me: McKee (1933, 

p. 82). Supai, Redwall, Martin, and Tapeats Format1ons: Huddle and 

Dobrovolfl.y (1945). 
52 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

THICKNESS AND STRATIGRAPHIC RELATIONS 

The Ta peats Sandstone ranges from zero to about 

150 feet in thickness. The thickest sections are in the 

central part of the Paulden quadrangle. To the east 

(Clarkdale and Mingus Mountain quadrangles), the 

Tapeats has a maximum thickness of about 100 feet and 

in a few places is more than 60 feet thick. The thickness of the formation and of its two units in northcentral Arizona is given in table 11 (see also figs. 16, 17). 

In the Paulden-Jerome area-as used in the discussion 

of the Paleozoic rocks, the Paulden-Jerome area refers 

to the Clarkdale, Paulden, Prescott, and Mingus Mountain quadrangles-the lower unit generally makes up 

about two-thirds of the total thickness, except where it 

is cut out against topographic highs on the Precambrian 

surface. Along the Verde River (pl. 2) the lower unit 

mak~s up more than four-fifths of the total thickness. 

The Tapeats Sandstone rests unconformably on Precambrian rocks. Where the underlying rocks are composed of older Precambrian intrusive or volcanic rocks, 

the surface on which the sandstone was deposited is one 

of low relief but has rounded hills protruding into or 

through the sandstone for little more than 100 feet. 

Where the underlying rocks are composed of the resistant Mazatzal Quartzite, sharp ridges and hills as much 

as 500 feet high protrude through the sandstone and 

into or nearly through the Martin Limestone (fig. 17). 

The Tapeats Sandstone is overlain with apparent conformity by the Martin Limestone. The contact between 

the two formations has been arbitrarily placed at the 

base of the first massive limestone bed that overlies the 

limy siltstone and marl of the upper part of the normally shaly upper unit. Near the junction of Granite 

Creek and the Verde River, the lower unit, which is 

sandstone, grades up into and interfingers with a pebble 

to boulder conglomerate (fig. 18) that is equivalent to 

the shale unit to the east. The conglomerate has a 

maximum thickness of about 12 feet. A thin bed of 

reworked(~) sandstone (well exposed near 1,404,700 N., 

344,800 E.) locally overlies the conglomerate. This 

sandstone is probably basal Devonian. 

LITHOLOGY 

Two lithologic units comprise the Tapeats Sandstone 

in the Paulden-Jerome area: a lower cliff-forming unit 

of sandstone and an upper slope-forming unit of shale 

and mudstone and, locally, of conglomerate. 

The lower unit consists of medium- to coarse-grained 

sandstone, lenses of granule to pebble conglomerate, and 

a little siltstone, which forms shaly partings. Most of 

the pebbles are less than one-half inch long, but some, 

chiefly near the base, are as much as 2 inches long. Individual beds range from 1 inch to 15 feet. Small-scale 

' 

cross-laminations are well formed in many beds, and 

cut-and-fill channels are common, especially in poorly 

sorted beds. The crossbedding is typical of the Tapeats 

of the Grand Canyon area. As described by McKee 

( 1945, p. 125-126), it "consists of repeated layers or beds 

each containing series of short, uniformly sloping 

laminae truncated by flat surfaces ab<;>Ve and below 

* * *. [The laminae] vary in length according to the 

thickness of the bed * * * but rarely * * * exceed 3 or 

4 feet and in places are only a matter of inches." Current ripple marks are widespread. Grain size is rather 

uniform in some medium-grained beds, but in most beds 

it is variable. Alternation of well-sorted and poorly 

sorted material, abrupt changes in grain size, and 

changes in the amount of ferruginous cement give the 

unit a heterogeneous appearance. Grains and pebbles 

range from angular to rounded, but most of them are 

subrounded to subangular. Most of the bonding material is siliceous-ferruginous cement, but some is calcareous. Where ferruginous cement is abundant, the 

rock is friable. Much of the basal part of the unit, as 

well as most oithe unit in thinner sections, is dusky red 

or grayish red to dark reddish brown because of the 

high iron content of the cement, but much of the upper 

part in thicker sections is buff (very pale orange to 

moderate orange pink or grayish orange pink) . 

Spherical, lenticular, and irregular dusky-red areas are 

scattered throughout the buff sandstone, and similarly 

shaped buff areas occur in the red sandstone, a fact suggesting that the light color is due to leaching of iron 

oxide. According to McKee (1945, p. 129), however, . 

basal beds of the Tapeats in the Grand Canyon area that 

were deposited in protected areas (depressions or "island 

embayments") are redder in color than those in unpro· 

tected areas. Quartz makes up all but a small proportion of the mineral grains and many of the pebbles in 

much of this unit. Minor constituents are chalcedonic 

quartz, feldspar, quartz porphyry, rocks of the Alder 

Group, granitic rocks, and, in the Granite Creek area, 

sandstone and limestone pebbles of unknown derivation. 

Pebbles of the Mazatzal Quartzite were not observed in 

this unit. 

The upper, slope-forming unit of the Tapeats is 

poorly exposed and consists principally of mudstone 

3tnd siltstone. Where observed it can be divided into 

two parts: the lower is a dusky-red to dark reddishbrown locally slightly fissile mudstone; the upper part 

is greenish shale that is intercalated with buff to greenish or reddish mudstone, siltstone, and marl. Some of 

the siltstone is highly micaceous. Marl and dolomitic 

limestone weather shades of red, are more abundant 

near the top, and in places are intercalated with sandstone. Except for the basal red mudstone in which beds 
PALEOZOIC SEDIMENTARY ROCKS 53 

may be thicker, beds are less than 6 inches thick; shaly 

partings are common in the upper part o£ the unit. The 

conglomerate (fig. 18) th~t overlies the lower unit near 

the mouth of Granite Creek (within an area bounded 

by 1,400,000-1,410,000 N. and 340,000-350,000 E.) consists o£ subrounded to subangular pebbles to small boulders, composed of quartzite and conglomerate from the 

Mazatzal, in a sandy, calcareous matrix. Pebbles o£ 

Mazatzal Quartzite in a sandy matrix near the base of 

the shaly unit :farther east (in King Canyon, near 

1,936,500 N., 379,200 E.) and the stratigraphic position 

and slope-forming character of the conglomerate .suggest that the conglomerate is a local :facies of the upper 

unit. Sandstone that interfingers with the conglomerate lacks the typical crossbedding of the lower unit; this 

sandstone and conglomerate may represent a continental deposit formed during a temporary withdrawal o£ 

the sea. 

AGE AND CORRELATION 

Northwest of the area, the basal Paleozoic rocks are 

the Tapeats Sandstone, Bright Angel Shale, and Muav 

Limestone, all Cambrian in age (McKee, 1945, p. 11-

36). Within the Paulden-Jerome area and for more 

than 100 miles to the southeast, the age and correlation 

of the basal Paleozoic sandstones are in doubt. Fearing 

(1926, p. 757-759) and McNair (1951) concluded that 

the basal sandstone at Jerome is Devonian in age and 

equivalent to the basal Devonian s~ndstone in the Pine 

area (fig. 1, inset) (Stoyanow, 1926, p. 311-313; 1936, 

p. 499-500; 1942, p. 1268-1269). Reber (1922), Ram.-

some ( 1932), Stoyanow ( 1936, p. 462), and McKee 

(1951) interpreted it as probably equivalent to the 

Tapeats Sandstone in the Grand Canyon. The principal arguments in support o£ a Devonian age are the 

apparent conformity and lithologic gradation £rom the 

sandstone_ unit through the shale unit to the basal 

Martin and the thinning o£ the Cambrian formations 

and their overlap by the Martin as one goes £rom the 

Grand Canyon towards Jerome (figs. 16, 17; table 11). 

Evidence in :favor o£ a Cambrian age are the stratigraphic position and lithologic similarities, especially 

the type o£ crossbedding. Although Anderson and 

Creasey (1958, p. 48-49) and Lehner (1958, p. 522, 523, 

525) :found little supporting evidence other than local 

sandstone beds in the upper part o£ the shale unit and 

a discontinuous sandstone bed at the base o£ the Martin, 

they £a.vored a Cambrian age £or most o£ the basal 

sandstone but referred to it as Tapeats( ~). Additional 

evidence £rom the Paulden quadrangle supports a 

Cambrian age £or most o£ the basal sandstone. 8 

Some basal Paleozoic sandstone and conglomerate 

beds in the Paulden quadrangle and where I have observed it to the southeast in the Pine area are o£ known 

Devonian age ( Stoyanow, 1936, p. 497-498), but in these 

areas they are distinct £rom other basal Paleozoic sandstone whose Cambrian age has been questioned. In the 

:following discussion these Cambrian sandstones will be 

referred to as Tapeats ( ~) to distinguish them £rom 

unquestioned Tapeats to the northwest. The basal Devonian sandstone and conglomerate interfinger with 

known Devonian limestone; they abut against and surround topographic highs o£ the Mazatzal Quartzite, in 

contrast to the sheetlike :form o£ the known and the 

questionable Tapeats. They differ £rom known and 

questionable Tapeats by lacking typical crossbedding, 

by lacking the dusky-red color characteristic o£ basal 

Tapeats, and by being more flaggy and thin bedded. 

The Tapeats ( ? ) Sandstone always underlies the lowest 

(A) unit o£ the Martin Limestone, and the sandstone 

unit is generally separated £rom the Martin by the shale 

unit. The shale unit resembles and may be equivalent 

to the Bright Angel Shale to the northwest. 

McNair (1951, p. 516} considered the sandstone at 

Simmons to be· the Caanbrian Tapeats and that at 

Jerome to be basal Devonian-he stated that the clastic 

beds at Jerome "do not resemble the Ta peats excepting 

in their stratigraphic position." Sandstone in the many 

outcrops (fig. 16) between Simmons and Jerome, however, belong to the same £ormation; the buff sandstone 

near the mouth o£ Granite Creek is identical with that 

at Simmons, and dusky-red sandstone, similar to that 

at Jerome, underlies the buff sandstone at both the Simmons and Granite Creek localities. Furthermore, the 

Tapeats at Simmons and the Tapeats( ~) at Granite 

Creek underlie identical beds o£ reworked(?) sandstone 

that McNair (1951, p. 516-518) considered to be basal 

Devonian at Simmons. 

A Cambrian age £or the sandstone at Simmons has not 

been proved, owing to the absence o£ :fossils or o£ overlying Bright Angel Shale or Muav Limestone; however, the presence o£ worm-borings in the sandstone 

suggests a Cambrian age. According to E. D. McKee 

(written commun., 1957), this type o£ marking is extremely common in the known Tapeats. McKee stated 

that although any :fossil as universal in character as a 

worm-boring cannot be restricted to any geologic age, 

this particular type is extremely common in the Cambrian o£ northern Arizona and has not been :found in 

younger rocks in the region. 

sIn the basal Paleozoic sandstone on Mingus Mountain (Jerome 

area), Curt Teichert found a bed crowded with U-shaped burrows of 

the Corophioides type. This evidence supports the Cambrian age of the 

rocks formerly called questionable Tapeats, as these burrows are abundant in the undoubted Tapeats of Juniper Mountains and are p·robably 

indicative of marine conditions. Teichert did not o'bserve these burrows 

in the basal Devonian sandstone, which he considered fluviatile or at 

least nonmarine, in the Salt River Canyon area (Teichert, written 

commun., June 1961 ; Averitt, 1961, p. A33). 
54 

3) 

(1) 

(2) 

Fort Rock 

1\{Cross Mtn) 

1 1 <I> <2> 317ft (409ft) 

GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

o Seligman 

~1) (2) 

~(2) ' 

CAMP WOOD 

PICACHO 

BUTTE 

Simmons 

114 ft\J 

SIMMONS 

o ASHFORK 

Ashfork 

o Williams 

Chino Valley\'',,~~ ~\ 

.................. l, 

0 Prescott '',-!) 

L---------------------~11_~1~3~0~'----------, 

SHERIDAN o Camp Verde 

34 o 30 r-~B=A~G~D~A~D--~--~M~T~N~--~IR~O~N~S~P~R~I~N~G~S4-~P~R~E~S~C~O~T~T~~M~I~N~G~U~S~M~T~N~----~''----------~-----+----------~ "ZURRET PEAK PINE 

CONGRESS KIRKLAND MT UNION MAYER 

'\..... t), 

j. Limestone 

~Hills 

10 0 10 20 30 MILES 

L_------~------~------~----~ 

-"""Fort Rock 

Exposures of Cambrian formations 

with locality name 

(1) 

Cambrian fossils reported 

(2) 

Includes Bright Angel Shale and 

(or) Muav Limestone 

(3) 

Continuous outcrops from here to 

Grand Canyon, increasing to over 

1000 feet in thickness 

(4) 

Cambrian and basal Devonian 

sandstones both present 

Locally no Cambrian and little 

Devonian was ckposited 

EXPLANATION 

317 ft 

Thickness of Tapeats Sandstone 

Dashed line encloses areas within 

which thickness averages 50 or 

150jeet 

(409ft) 

Thickness of overlying Cambrian 

formations 

See table 11 for sources of data. 

Compiled from geologic maps of 

the Paulden-Jerome area; reconnaissance by the author from 

near Seligman to Camp Verde; 

the geologic map of Arizona 

(Darton and others, 1924); and 

the geologic map of Yavapai 

County (Wilson and others, 1958) 

FIGURE 16.-Approximate distribution and thickness of Cambrian formation in central Arizona. 

oPine 

(4) 
113°45' 

I 

PICACHO BUTTE QUADRANGLE 

113°30' 113°15' 

ANGLE ASHFORK QUADRANGLE 35• 

CAMP WOOD QUADRANGLE PAULDEN QUADRANGLE CLARKDALE QUADRANGLE 00' 

EXPLANATION 

D m .1--------1 IZ 

<( 

Dma 1 

Martin 

Dmd, D 

Limestone 

unit ~~ Dmc, Cunit 

Dmb, Bunit 

Dma, A unit 

R££1m±4 

H Muav Limestone 

~§j Bright Angel Shale ,0 

fTI~TITI Tapeats Sandstone 

£t 2 , upper unit, largely 

shale except for coarse 

conglomerate near sec 4 

£t 1 , lower sandstone unit 

ft.~t~E!I Mazatzal Quartzite 

Schist and granite 

0::: 

Ill 

~ 

<( 

0 

}I 

SIMMONS 

QUADRANGLE 

PRESCOTT 

QUADRANGLE 

~0 

~400 I 

VERTICAL I SCALE 

[

800 

1200 FEET 

2 0 2 4 6 8 MILES 

HORIZONTAL SCALE 

MINGUS MOUNTAIN QUADRANGLE 

FIGURE 17.-Preca'mbrian and lower Paleozoic formations in the Paulden quadrangle and adjacent areas: the topographic high formed by the Mazatzal Quartzite is shown. Sections 

3 and 11 cannot be connected, as no Paleozoic rocks crop out along or south of this line except in the extreme northeast corner of the Prescott quadrangle. (See table 11 

for location of sections, thicknesses of formations and units, and sources of data.) 

""d 

~ t';j 

0 

N 

0 

8 

UJ. 

t';j 

t::1 

~ 

~ 8 

> 

~ 

~ 

~ 

0 

~ UJ. 

Of 

Of 
56 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

Evidence of a break in deposition between the Tapeats ( ? ) Sandstone and the Martin Limestone can be 

seen near the mouth of Granite Creek. The contact between the conglomeratic facies of the shale unit and the 

overlying A unit of the Martin is sharp and indicates 

an abrupt change in conditions of deposition. The surface on which the A unit-that is, the discontinuous bed 

of reworked ( ? ) sandstone-was deposited locally bevels 

slightly the underlying conglomerate. The surface is 

relati"\7ely smooth and even, but small irregularities pro1trude a few inches to a foot above it (fig. 18). The 

overlying limestone .abuts against and dips away from 

these protruding masses; the dips are probably due to 

a combination of compaction and initial dip. 

FIGURE 18.---'Conglomerate at the top of the Tapeats Sandstone (£t), 

and the overlying Martin Limestone ( Dm) ( 1,403,500 N., 345,000 E.). 

Note the abrupt change from conglomerate to limestone, the relatively 

flat surface cut on the conglomerate, the local irregularities where 

cobbles in the conglomerate protrude into the overlying limestone, and 

the compaction and initial dip of the limestone around the irregularities. See hammer for scale (arrow) . 

About four-tenths of a mile (near 1,402,800 N ., 34 7,-

000 E.) east-southeast of the exposures of conglomerate 

shown in figure 18, the Tapeats ( ? ) Sandstone rests on 

the Texas Gulch Formation of the Alder Group. The 

basa:l 20 feet of dusky-red sandstone grades upward 

into buff sandstone about 127 feet ~thick. Except in 

color and the presence of some calcareous cement, the 

buff sandstone differs little from the underlying sandstone. Pebbles of limestone and sandstone, in addition 

to the pebbles normally found in the sandstone, occur 

near the base of the buff sandstone; however, no pebbles 

derived from the Mazatzal were observed in the section, .although a topographic high of Mazatzal cuts out 

the sandstone less than 500 feet to the east. The upper 

4 feet of sandstone at the Simmons section immediately 

below the reworked sandstone contains similar limestone 

and sandstone pebbles, as does the upper 50 feet of 

sandstone in the Black Mesa section. 

The origin of these pebbles is an enigma. If the 

pebbles were derived from Cambrian formations (Tapeats and Muav to the northwest), then the sandstone 

that contains them must be Devonian, and probably all 

the sandstone in the area is also Devonian. However, 

a Devonian .age is not necessary and is not considered 

likely, because the limestone pebbles do not resemble 

the Muav and because a thickness of sandstone, such 

as occurs at Black Mesa (279ft) has not been reported 

elsewhere in the Devonian in northern Arizona. The 

limestone pebbles do not resemble thin beds of marble 

in the Texas Gulch FormaJtion of the Jerome area.-the 

only other known pre-Devonian carbonate rock nearby. 

The limestone and sandstone pebbles may have been 

derived from the younger Precambrian Grand Canyon 

Series or Apache Group. Limestone and sandstone 

form part of these younger Precambrian rocks, and, 

according to E. D. McKee (oral commun., 1957), a 

thick sequence of limestone has been reported in a drill 

hole underlying the Tapeats in the Grand Canyon. Because the area from the Grand Canyon to Paulden is 

covered by younger deposits, the southwestward extent 

of the Grand Canyon Series is unknown. Likewise, because of deep erosion of the Precambrian rocks in preand post-Paleozoic times south of here, the former extent of the younger Precambrian rocks is unknown. 

Immediately east of the thick section of sandstone 

just described, the Texas Gulch Formation is in fault 

contact with the Mazatzal Quartzite, and the Mazatzal 

and adjacent schist form a topographic high. The 

sandstone is absent east of the fault, and the conglomerate that overlies 140 feet of sandstone west of the 

fault rests directly on the Mazatzal Quartzite east of the 

fault. The area near the fault is largely talus covered, 

so the relation of the Tapeats(?) to the Mazatzal is not 

obvious, but one small exposure proved that the sandstone is in depositional contact with a small sliver of 

the quartzite that lies just west of the main fault between the two Precrumbrian formations. The sandstone, therefore, is not older than the fault, as might be 

assumed from its absence east of the fault and from the 

absence of Mazatzal pebbles in the sandstone immediately west of the fault. According to E. D. McKee 

(oral commun., 1957) this deposition of Tapeats Sand-
PALEOZOIC SEDIMENTARY ROCKS 57 

stone against a quartzite high is typical of the situation 

in the Grand Canyon, where the Shinumo Quartzite of 

the Grand Canyon Series forms sharp peaks surrounded 

and buried by Tapeats Sandstone; the sandstone may 

contain a few angular fragments of quartzite close to 

the contact but contains none within a short distance 

of it. The outcrops of Mazatzal that supplied the 

rounded pebbles and cobbles in the overlying conglomerate may not have been expoood at the time the sandstone was deposited. The amount of rounding of the 

resistant pebbles and cobbles of quartzite and conglomerate from the ~Iazatzal indicates that this material was 

derived from some distance away and not from the 

nearby outcrop of the Mazatzal. The similarity between the relation of the Tapeats ( ~) Sandstone to the 

Mazatzal and of Tapeats to the Shinumo Quartzite in 

the Grand Canyon area contrasts with the relation of 

known Devonian sandstone to the Mazatzal Quartzite 

in the Paulden quadrangle; this contrast also suggests 

that the questionable sandstone in the Paulden-Jerome 

area is Cambrian. 

In view of the foregoing evidence, the Cambrian age 

of the basal Paleozoic sandstone in the Paulden-Jerome 

area is no longer questioned. 

MARTIN LIMESTONE 

DISTRIBUTION 

Outcrops of the Martin Limestone are found mostly 

northeast of the Tapeats Sandstone and are more extensive than those of the Tapeats. Northeast of ChinoLonesome Valley, the formation is widely distributed 

across the northern part of the area (pl. 2) along a 

northwest-trending strip that has a maximum width of 

about 9 miles. The formation is exposed almost continuously ( 1) along the Verde River from Stewart Ranch 

Headquarters (1,406,000 N., 341,500 E.) nearly to the 

mouth of Hell Canyon, ( 2) from the southeast corner to 

the Verde River, principally east of King Canyon (1,-

397,000 N., 378,000 E.), and (3) along the southwest 

side of Black Mesa for 5 miles from the northwest 

corner of the study area. The Martin is buried by 

younger rocks northeast of a line running parallel to 

but at lea.st a mile southwest of Hell Canyon. It is not 

exposed in or west of Chino Valley, except for two small 

outcrops south-southwest of Paulden (near 1,397,000 N., 

330,000 E.). A wildcat oil well (No. 1, sec. 20, T. 18 N., 

R. 2 W.) northwest of Paulden cuts more than 400 feet 

of the Martin beneath about 700 feet of Cenozoic deposits. The southernmost exposures of the formation 

are in the same area as those of the Tapeats; a small 

outcrop, too small to show on plate 1, occurs near 

1,359,000 N., 397,200 E. 

THICKNESS AND STRATIGRAPHIC RELATIONS 

The Martin Limestone thins to less than 50 feet over 

the topographic high of the Mazatzal Quartzite (fig. 

17). Elsewhere in the Paulden-Jerome area the formation has a relatively uniform thickness of 390-479 feet, 

as it does for many miles to the northwest and southeast 

(table 11). Four units, from botton to top the A, B, C, 

and D units, 9 are recognizable in the southeast of the 

Paulden-Jerome area; they are less distinct northwest 

of the area. The units thin and are successively cut out 

around the topographic high of Mazatzal Quartzite. 

A way from the topographic high, the A unit is 15-21 

feet thick, and the B unit is 55-97 feet thick. The C and 

D units are 65-75 feet and 218-255 feet thick, respectively, in the eastern part of the area, but to the west the 

position of the contact between the two units is 

uncertain. 

Except where topographic highs on the Precambrian 

surface cut out the Ta peats, the Martin Limestone rests 

on the Tapeats, as described on page 52. The aMrtin is 

overlain disconformably by the Redwall Limestone of 

Mississippian age; the maximum relief on the ~fartin 

surface is about 35 feet and averages 10-15 feet. 

LITHOLOGY 

The Martin Limestone comprises dolomite, dolomitic 

limestone, limestone, disseminated argillaceous and 

arenaceous material, and minor amounts of limy siltstone and sandstone. The dark color, thinly and evenly 

bedded character, and steplike slopes to which the formation weathers serve to distinguish it from the overlying Redwall Limestone. 

Some beds in the C and D units are fossiliferous, and 

fish plates have been reported from sandstone beds near 

the top of the B unit near Jerome. The fauna of the 

Martin at Jerome was described by Stoyanow ( 1936, p. 

495-500). 

A UNIT 

The A unit is largely dolomitic limestone, but near 

Granite Creek (1,402,800 N., 347,000 E.), it contains 

interbedded sandy and conglomeratic layers and is 

underlain by a 2-foot bed of reworked ( n sandstone. 

Lehner (1958, p. 525) reported a similar, nonpersistent 

basal sandstone in the Clarkdale quadrangle. The well 

sorted medium to coarse grained sandstone is composed 

principaily of well-rounded frosted grains of quartz. 

It is light gray or light olive gray to nearly white and 

has local limonitic spots. 

u The units were so designated by Lehner ( 1958, p. 525) but were 

called lower, lithographic, middle, and upper units by Anderson and 

Creasey (1958, p. 50). 
58 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

The A unit is a very impure quite uniform clastic 

cliff-forming dolomite and dolomitic limestone that 

emits a strong fetid (petroliferouslike) odor when 

freshly broken. According to Curt Teichert (written 

commun., 1956), the rock contains no hydrocarbons, and 

the odor may be due to ammoniacal salts. The rock is 

light brownish gray to light olive gray and weathers to 

slightly darker shades. Coarser beds are, in general, 

darker than the finer grained beds. Impuritieslargely clay and silt-impacrt a pink or yellow cast. 

Most beds are medium to coarse grained, but some are 

fine grained. Dolomite forms larger grains than does 

calcite. The weathered surface is pitted because of the 

weathering out of scattered coarse calcite grains, as 

much as 1 can in diameter, whose origin is uncertain. 

The beds range from Vs inch to 4 feet in thickness. 

The clastic character of the unit can be observed where 

etching has revealed crossbedding, channels, or fragments. Massive beds are coarse grained, possibly owing 

to recrystallization. The upper part of the A unit nea.r 

Granite Creek (especially near 1,403,000 N., 347,000 E.) 

is coarser grained and lighter <'A>lored. In places it is 

a breccia abundantly and irregularly replaced by darkbrown chert-the chert may be related to late Tertiary ( ~) basalt flows. At this place the basal 4 feet of 

the unit is the typical dark dolomitic limestone, but it 

contains many sand grains and small pebbles derived 

from the Mazatzal Qua.rtzite. East of the fault that 

separates the Texas Gulch Formation from the Mazatzal, the coarse-grained light-colored limestone rests directly on the conglomerate bed at the top of the Tapeats. 

B UNIT 

The B unit (fig. 2) contrasts sharply with the olivegray A and C units. It is an aphanitic evenly and thinly 

bedded light-colored slope-forming dolomitic limestone 

containing shale partings. 

The limestone beds are pinkish gray, locally darker 

gray or lavender, and weather light gray to white. 

Beds range from 3 inches to 3 feet and average about 8 

inches in thickness. Few of them show internal stratification. The beds are separated by shaly partingsfrom thin films to 3 inches thick-which are exposed 

only in. road cuts and cliffs. The shale is dark gray 

to grayish yellow green and pale yellowish green. The 

unit, which is more calcite than dolomitic, is very fine 

grained; it is virtually a lithographic limestone. The 

weathered surface is smooth, except where disseminated 

grains of sand project above the surface and where it 

has a wrinkled appearance because of solution along 

joints. Light-yellow and dark-gray chert, as nodules, 

lenses, and thin layers parallel to the bedding, is fairly 

abundant in some of the beds. 

A persistent sandstone, locally called the red marker 

bed, lies within a few feet of the top of the unit. Even 

though in places it is represented by only thin sandy 

lenses in the limestone, this horizon marker was recognized wherever the upper part of the unit is exposed in 

the Paulden-Jerome area. It ranges from a few inches 

to about 61;2 feet in thickness. Locally it consists of 

several beds of sandstone, of scattered sand grains, or 

of lenses of sandstone interbedded in aphanitic limestone through an interval of more than 10 feet. In 

places the rock is more nearly an orthoquartzite. Ripple marks and crossbedding are locally conspicuous. 

The sandstone is generally various shades of light reddish brown to pale red; some is buff to light gray. At 

one place in the southeastern part of the Paulden quadrangle the sandstone contains fragments of aphanitic 

limestone as much as 8 inches in maximum size. Near 

the mouth of Granite Creek and in an exposure as far 

east as Bull Basin Canyon (1,401,500 N., 373,700 E.), 

small pebbles as much as 21;2 inches in diameter of Mazatzal Quartzite occur in the sandstone or in limestone 

immediately below the sandstone. 

Much of the upper part of the B unit beneath the red 

marker bed in the Granite Creek area is a yellowishbrown chert that weathers very light gray to white. 

The origin of this chert is in doubt, but in the southeastern part of the quadrangle, the local association of 

. similar chert beds in the unit which late Tertiary ( ~) 

basalt flows suggests that the chert is a replacement associated with volcanism. West of Hubbel Ranch 

(1,417,700 N., 374,500 E.) the upper part of the B unit, 

below the red marker bed, contains beds of a very light 

gray massive friable medium-grained sugary limestone 

or dolomite that weathers light yellowish or reddish. 

Some beds are as much as 8 feet thick and lack internal 

stratification, except for a few greenish sandy, shaly 

partings. C UNIT 

The C unit (fig. 2) is darker colored, coarser grained, 

and thicker bedded than the B unit; it forms weak 

cliffs. The typical rock of the unit is light to moderate 

olive-gray dolomitic limestone mottled by fine-grained 

light-pinkish-gray areas. The mottled areas, which are 

due to recrystallization, are irregular in size and shape 

but, in general, are several inches long. Beds range 

from less than 1 inch to 4 feet in thickness; few of them 

show internal stratification. Beds that resemble those 

of the A unit and have the same fetid odor occur in the 

C unit, especially near the base. A bed of light-weathering aphanitic limestone, similar to beds in the B unit, 

commonly lies 7-12 feet above the base of the C unit. In 

the southeastern part of the Paulden quadrangle, the 

contact between the C and D units is placed below the 

first bed of aphanitic white-weathering dolomitic lime-
PALEOZOIC SEDIMENTARY ROCKS 59 

stone (B-unit type) at the top of the typical beds of the 

C unit. West of Hub bel Ranch the contact between the 

C and D units occurs either about 35 or 65 feet above 

the base of the C unit-about 30 feet of mottled limestone ( C-unit type) overlie one or more beds of aphanitic 

light-weathering limestone (B-unit type), which are 

about 35 feet above the base of the C unit. 

D UNIT 

The D unit is characterized by diverse lithology. It 

comprises alternating beds typical of the three lower 

units and some interbedded calcareous shaly siltstone. 

mudstone, and sandstone. 

Much of the lower part of the D unit consists of interbedded rocks of A, B, and C lithologies. The bottom 50 

feet or so of the unit in upper King Canyon contains 

beds, as much as 5 feet thick, of A and C lithologies and 

a few beds of B lithology. Above this part of the D 

unit, the beds are thinner (ranging from a few inches to 

2 ft.) and contain more abundant aphanitic beds that 

weather light gray, bluish gray, lavender, and purple. 

The upper part of the unit contains some shaly mudstone, platy siltstone, and a few thin beds of sandston~. 

Some beds contain chert. In places, the top of the unit 

is a grayish-orange-pink medium-grained dolomitic 

limestone. 

Where the uppermost beds of the unit overlap the 

Mazatzal Quartzite (near 1,382,500 N., 358,000 E.), numerous beds of sandstone and conglomerate derived 

from the Mazatzal interfinger with beds typical of the 

D unit. The beds dip gently to steeply away from the 

Mazatzal because of initial dip or compaction. In 

places only the sandstone and conglomerate are exposed-as on the east side of the largest mass of Mazatzal Quartzite and the two small outcrops near the south 

side of this mass (northeast of 1,380,000 N., 362,500 E. 

and at 1,382,300 N., 357,200 E. and 1,384,000 N., 353,700 

E.) -but these beds can be distinguished from the 

Tapeats(n by their thin-bedded, flaggy character and 

darker, but not red, color. 

Several distinctive beds can be used as key or marker 

horizons, 3!t least for short distances. One is a massive 

bed, generaHy about 2 feet thick, which is olive gray 

mottled with conspicuous yellow to orange colorations 

on weathered surfaces. 

AGE AND CORRELATION 

The Devonian limestone at Jerome was originally 

named the Jerome Formation by Stoyanow (1930) and 

later described by him in detail ( 1936, p. 49·5-500). 

Stoyanow (19·36, p. 503) considered the Temple Butte 

Limestone (named by Walcott, 1800, p. 50) of the Grand 

Canyon as correlative with his Jerome Formation. In 

the southeastern part of the state, the Devonian lime7158-4417 0----65~5 

stone was named the Martin Limestone by Ransome 

(1904, p. 33). According to Stoyanow the Devonian 

rocks thin towards and are largely absent from the area 

between Pine (fig. 1, inset) and Theodore Roosevelt 

Lake ( 60 miles southeast of Pine) . Because of certain 

differences in lithology and in sequence, Stoyanow 

( 1936, p. 495) postulated a land mass-Mazatzal Land~ 

to separate the Devonian seas northwest of Mazatzal 

Land from those southeast of it. He considered the 

upper part of his Jerome Formation to be equiv.alent 

in age to the Martin Limestone. 

Huddle and Dobrovolny ( 1945) found that in spite 

of local thinning the Martin Limestone could be traced 

from Globe into the Pine area, even though it is locally 

only 30 feet thick in the areas Stoyanow called Mazatzal Land. They pointed out that the lithologic similarities and the indication of original continuity of the 

Devonian rocks are sufficient to justify the extension 

of the name Martin Limestone into the Pine area. They 

believed that the Martin can be traced into the Temple 

Butte Limestone of the Grand Canyon region. 

Because the Martin Limestone in the Pine ar~a, as 

described by Huddle and Dobrovolny, is without doubt 

the same as the Devonian rocks in the Jerome area, 

Anderson and Creasey (1958, p. 51) applied the name 

Martin to these rocks at Jerome. 

McNair (1951, p. 516) correlated the Devonian rocks 

of Jerome with those at Hurricane Cliffs in the western 

part of the Grand Canyon and called them all Martin 

Limestone. Huddle and Dobrovolny (1945; 1952, p. 

73) subdivided the Martin Limestone in the Pine a.rea 

into three members. Their lower member apparently 

includes the A and B units and a basal sandstone. Their 

upper members differ from the C and D units in containing greater amounts of sandstone and shale. Where 

I have observed the form3!tion in the Pine area, ·the 

four units can be recognized in sections where the formation is not adjacent to or partly cut out by topogra.-

phic highs of the Mazatzal Qua.rtzite. According to 

Curt Teichert (oral commun., 1956), the four units can 

be recognized as far as Theodore Roosevelt Lake, although they become less distinct southeast of Pine. 

Northwest of the Paulden quadrangle, the A unit was 

recognized during reconnaissance, but the other units 

were not recognized much beyond the western boundary 

of the quadrangle. At Fort Rock and farther northwest, the formation consists entirely of cyclothems, each 

of which comprises one or more of six broadly defined 

lithologic types and phases, according toW. H. W ood.10 

Huddle and Dobrovolny (1952, p. 67 and 86) placed 

the Martin Limestone of central Arizona in the Upper 

Devonian, except for the lower part, which may be 

to Wood, W. H., 1956, The Cambrian and Devonian carbonate rocks 

at Yampai Cliffs, Mohave County, Arizona: Arizona Univ. Ph. D. thesis. 
60 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

equivalent to the lower part of the Devils Gate Limestone (Middle and Upper Devonian) of Merriam (1940, 

p. 16--17) in central Nevada. The Martin in the Prescott and Paulden area, therefore, is assigned a Middle ( ~) and Late Devonian age. 

REDW ALL LIMESTONE 

DISTRIBUTION 

The distribution of the Redwall Limestone is about 

the same as that of the Martin Limestone, except that 

its outcrops extend farther to the northeast. Its most 

extensive exposures in the Paulden quadrangle are in 

the north western part, the east-central part, and along 

the Verde River in the central part. Its most northeasterly exposures are along Hell Canyon and along 

the Verde River east of its junction with Hell Canyon. 

THICKNESS AND STRATIGRAPHIC RELATIONS 

The Redwall Limestone is about 220 feet thick where 

measured in the Paulden quadrangle and somewhat 

thicker in the Clarkdale and Mingus Mountain quadrangles (table 11) . To the north west towards the Grand 

Canyon, it thickens to 500 feet (MeN air, 1951, p. 515, 

519). To the southeast it thins locally to about 30 feet 

in the Pine area (Huddle and Dobrovolny, 1945) . 

The Redwall Limestone lies unconformably between 

the Martin Limestone of Devonian age and the Supai 

Formation of Pennsylvanian and Permian age. The 

relief on the Martin surface is low and gently undulatory; the Martin and Red wall therefore appear conformable. Depressions on the Martin surface are filled 

with material derived from the Martin and not readily 

separable from the Martin. For mapping purposes, the 

base of a massive light bluish-gray oolitic limestone 

that overlies the Martin or the reworked Martin was 

used as the contact between the Martin and Redwall. 

In many places the relief on the Red wall surface is 

more than 50 feet in a horizontal distance of little more 

than 100 feet. 

LITHOLOGY 

The Redwall Limestone is a cliff-forming massive, 

thick- to thin-bedded, white to light-gray coarsely 

crystalline to aphanitic limestone. Solution channels 

and caverns, in places collapsed or filled, are common. 

The filling consists of fragments of limestone or chert, 

or both, cemented with a bright red clay like sediment or 

with silica. In several places large blocks of the Supai 

Formation rest on the lower part of the Red wall or even 

on the upper part of the Martin. Some of these blocks 

may have been let down along faults, but some probably 

were let down as a result of solution and collapse within 

the Red wall. Much of the limestone is fossiliferous, but 

local zones are barren. 

In the Jerome area Wooddell (Stoyanow, 1936, p. 512-

513) divided the Red wall Limestone into six members. 

Gutschick ( 1943; see also Easton and Gutschick, 1953), 

who studied the Red wall from the Pine area northwestward to beyond Seligman (fig. 1, inset), subdivided it 

into four member~ designated, from oldest to youngest, 

members I, II, III, and IV. His members II and III 

are about the same as Wooddell's members 3 and 4. 

Gutschick's four members have been recognized in the 

Paulden and Clarkdale (Lehner, 1958, p. 530-531) quadrangles· and are called units 1, 2, 3, and 4. In the Jerome 

area Anderson and Creasey (1958, p. 52) did not distinguish between units 3 and 4. 

UNIT 1 

Unit 1 consists of two parts: reworked Martin Limestone and oolitic limestone. The lower part, 0-40 feet 

thick according to Gutschick (1943), consists of thinbedded clastic dolomitic limesto:p.e, arenaceous limestone, 

and calcareous sandstone that resembles the Martin. 

The beds are finely crystalline and light to very light 

brownish gray and olive gray, locally tinged with pink 

or lavender because of impurities. 

Much of the upper part of the unit is a conspicuous, 

massive aphanitic very light bluish-gray oolitic limestone. In most places in the Paulden quadrangle it 

forms a slope or bench between the weak cliff-formi;ng 

lower part of unit 1 (or the upper part of the Martin 

Limestone) and the cliff-forming unit 2; it is 23 feet 

thick where measured. Locally the bed grades laterally 

into crystalline limestone. A bed of finely crystalline 

darker limestone or dolomitic limestone that resembles 

the Martin lies 2-5 feet above the base of the oolitic 

limestone in many places. The top of the unit is a 

coarsely crystalline fossiliferous limestone, generally 

only a few feet thick. Fossils include cup corals, 

brachiopods, and gastropods. 

UNIT 2 

Unit 2 is 80 feet thick where measured and is a fineto medium-grained porous limestone containing 

abundant chert nodules, lenses, and layers. The limestone ranges from nearly white or very light gray to 

yellowish gray. The chert is white, grayish yellow, 

and locally dark gray; it weathers reddish brown. 

Beds are 2-5 feet thick. Fossils are scarce and consist 

of corals, crinoids, and brachiopods. Solution and collapse have produced widespread breccias, especially in 

the southeastern part of the area. The breccia consists 

of fragments of chert and a few of limestone that are 

cemented by silica or by a red cla.ylike sediment. Some 

of these breccias resemble fault breccias, except in their 

blanketlike distribution. 
PALEOZOIC SEDIMENTARY ROCKS 61 

UNIT 3 

Unit 3 is 81 feet thick where measured and is a thickbedded coarsely crystalline massive fossiliferous pure 

limestone of uniform character. It is yellowish gray to 

very light gray and weathers yellowish gray; the 

weathered surfac-e is rough owing to the unit's coarse 

grain size and to the abundance of crinoid discs. Corals 

are relatively abundant; other fossils include bryozoa, 

blastoids, gastropods, trilobites, and fish ( Gutschick, 

1943). 

UNIT 4 

A solution breccia and overlying light-gray limestone 

compose unit 4, which forms weak cliffs. ·The solution 

breccia consists of irregular cobble- to boulder-sized 

limestone fragments surrounded by red silty material. 

Most of the limestone resembles that of the upper pa,rt 

of unit 1, except that much of it is micro-oolitic to 

pellety. In the northwestern part of the area, the 

limestone is partly crystalline in the lower part and 

partly cherty in the middle part. Local fossil zones 

contain corals, gastropods, cephalopods, pelecypods, 

fish teeth, formanifera, and ostracodes ( Gutschick, 

1943, written commun. to Lehner, 1955; Easton and 

Gutschick, 1953). Gutschick interpreted the solution 

breccia to be a residual deposit representing an unconformity. I am not sure of its significance. Lehner 

did not 01bserve the breccia or the crystalline and cherty 

beds and placed the contact between units 3 and 4 at 

the base of the oolitic limestone. The oolitic limestone 

is better exposed in the Paulden quadrangle than are 

the underlying beds of the unit. Where measured, the 

breccia is 15 foot thick, and the oolitic limestone is 20 

feet thick. 

AGE AND CORRELATION 

Mississipian rocks in the Jerome area were called 

Redwall by Ransome (1916, p. 162), Lindgren (1926, 

p. 9), Stoyanow (1936, p. 512-514), and Gutschick 

( 1943). The name Red wall was first applied to Mississipian limestone in northern Arizona by Gilbert 

(1875, p. 162, 177-186), who included rocks older and 

younger than Mississippian. Later, Noble (1922, p. 

54) restricted the name Red wall to rocks of Mississippian age. In southeastern Arizona, limestone of 

Mississippian age was called Escabrosa Limestone by 

Ransome ( 1904, p. 42), and this term has been widely 

used in that part of the state. According to Stoyanow 

( 1936, p. 505), the Escabrosa and Red wall "are not 

exactly taxonomic equivalents * * * but, rather, overlap each other." He stated that the deposition of the 

Redwall began somewhat later than that of the Escabrosa. In central Arizona, Huddle and Dobrovolny 

( 1952, p. 86) found that the two formations are probably a continuous, mappable unit, which they called the 

Redwall Limestone. 

Fossils collected by Ransome (1916, p. 162) indicate 

an early Burlington age (lower Osage series), and those 

collected by Wooddell ( Stoyanow, 1936, p. 514) indioate 

a late Kinderhook to Keokuk age (largely late Kinderhook and Burlington). Gutshick (written commun. 

to Lehner, 1955) placed unit 1 in the Kinderhook and 

the other members in the Osage. He correlated unit 2 

with the top of the Alamogordo and base of the N unn 

Members of the Lake Valley Formation of Laudon and 

Bowsher (1941, 1949) of New Mexico. He correlated 

unit 3 with the Burlington Limestone of the Mississippi 

Valley. He tentatively placed unit 4 in the uppermost 

Osage (Keokuk affinity) but stated that it may be 

Meramec, especially if the "conspicuous solution 

bouldery ~one" between units 3 and 4 does represent a 

break in the sedimentary sequence. The Red wall Limestone in this area is considered to be Early Mississipian 

In age. 

SUPAI FORMATION 

DISTRIBUTION 

The Supai Formation, principally a red-bed deposit, 

is confined to the northeastern half of the Paulden 

quadrangle. The southeasternmost exposure lies about 

4.3 miles north of the southeast corner of the quadrangle. 

The most extensive exposures are in the northeastern 

parrt, north of Limestone Canyon in the northwestern 

part, and north and south of the Verde River in the 

central part. The formation comprises three members 

(pl. 2); the middle and upper members have been 

eroded from all but the northeastern corner of the area. 

THICKNESS AND STRATIGRAPHIC REL.AITIONS 

The thickness of the Supai Formation is not known, 

as faults cut out some of the upper member and a continuous section of the middle member is not exposed, 

although most of this member is problably exposed in 

Red Butte. In the northeast part, the formation is presumably about as thick as in the east part of the Clarkdale quadrangle, where it is 1,550-1,665 feet thick 

(Lehner, 1958, p. 533; E. D. McKee, oral commun., 

1953). It probably thins to the northwest, as Hughes 

( 1949, p. 33; 1952, p. 643) measured about 1,100 feet 

in Black Mesa about 20 miles northwest of the Paulden 

quadrangle. The forma,tion thickens to the southeast 

(table11). 

The three members into which the Supai Formation 

can be subdivided have been recognized to the east and 

southeast. In the Clarkdale quadrangle (Lehner, 1958, 

p. 535-537), the lower member is 580-625 feet thick; 

t,he middle member, 250-300 feet; and the upper member, 650-750 feet. In Blaek Mesa, Hughes (1949, p. 
62 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

33; 1952, p. 643) recognized only two members; the lower 

is about 150 feet thick, and the upper, about 1,000 feet. 

In the northwestern part of the Paulden quadrangle, 

the exposures include the lower part of his upper member and probably his lower member. 

The Supai Formation unconformably overlies the 

Redwall Limestone, as described on page 60. The contact is generally marked by a basal limestone or a chert 

breccia or conglomerate in a red-purp1le to grayish-red 

mudstone and silty shale. In the northwestern part 

of the area, however, the contact between the Redwall 

and Supai, because of poor exposures, was arbitrarily 

considered to be at the base of a light-gray to lavender 

limestone that has been partly to completely replaced 

by chert. At least 25 feet of the formation probably 

underlies the cherty limestone. Along Limestone Canyon about 3 miles northwest of the quadrangle boundary (Ashfork quadrangle, NWl!.t, sec. 17, T. 19 N., R. 

2 W.), the sequenoo between the top of the Redwall and 

the cherty limestone is (1) chert breccia, (2) olive-gray 

fetid limestone, (3) light-bluish-gray to lavender noncherty limestone, and ( 4) a thin zone of red beds. The 

cherty limestone and underlying beds probably correspond to the lower unit of Hughes ( 1952, p. 643), 

which comprises interbedded limestone, red siltstone, 

and basai conglomerate. 

The contact of the Supai Formation with the overlying Permian Coconino Sandstone is gradational and 

intertonguing. In the upper part of the Supai, torrential-type and some eolian-type cross-laminae occur 

in thick sandstone beds. These cross-laminae a.re beveled and covered by thinly laminated horizontally 

bedded siltstone and fine-grained sandstone. The Coconino Sandstone has large-scale eolian-type crossbedding and lacks the horizontal silty layers. Because 

where examined- at close range the crossbedding in the 

sandstone of the upper member of the Supai resembles 

that in the Coconino, it may be impossible to determine 

to which formation isolated outcrops belong. The contact can locally be determined by color, as most of the 

Coconino is buff and the Supai is reddish. Some Coconino, however, has the same color as the Supai, and 

vice versa. Hughes ( 1952, p. 642), like Huddle and 

Dobrovolny (1945), considered the contact to be"* * * 

at the base of the lowest massive sandstone with welldeveloped Coconino-type crossbedding." McKee (oral 

commun., 1953), on the other hand, arbitrarily placed 

the upper limits of the Supai at the top of the uppermost flat-bedded siltstone or sandstone. McKee's criterion was used to map the contact in the Paulden and 

Clarkdale quadrangles. In the Grand Canyon area 

the Hermit Shale separates the Coconino Sandstone 

from the Supai; there the contact between the Hermit 

Shale and the Supai FormaHon is an erosional unconformity (Noble, 1922, p. 61

3-64). 

LITHOLOGY 

The Supai Formation, largely a red-bed deposit, consists of sandstone, siltstone, shaly mudstone, and minor 

amounts of limestone and chert near the base. The 

limestones are marine in origin, as northwest of the 

area they contain a brachiopod-pelecypod fauna 

(Hughes, 1952, p. 639, 652-656). The detrital material is deltaic or flood:-plain in origin, according to McKee (1940, p. 822). McNair (1951, p. 532) suggested a 

marine mud-flat environment. 

LOWER MEMBER 

The lower member comprises sandstone, siltstone, 

minor amounts of shaly mudstone, some limestone 

beds-especially in the lower part-and basal chert 

breccia or limestone conglomerate. It forms a steplike 

topography, except for a cliff of sandstone at the top. 

The basal chert breccia is almost universally present. 

It consists of angular to subangular fragments of chert 

and some of limestone as much as several inches across. 

The chert is gray, black, and red; it occurs in a very 

dusky purple, dusky-red, or black shaly, silty, or sandy 

matrix, some of which is hematitic. Limestone conglomerate occurs locally at the base and is also interbedded with red beds higher in the section. It contains 

chert, limestone, and siltstone pebbles as much as 4 

inches in diameter in a light-gray to brownish-gray 

limestone that weathers pale reddish brown. Chert in 

siltstone and sandstone occurs as nodules a~d more or 

less spherical concretionary masses. These masses reach 

dimensions of 31;2 by 2 feet and are composed of alternating concentric bands of white chert and red silt. The 

limestone, which occurs in beds 1-6 feet thick, is mostly 

fine grained to aphanitic and olive gray, light gray, or 

light bluish, yellowish, or brownish gray. 

In the northwestern part of the area, especially south 

and east of Rock Butte (1,453,000 N., 342,500 E.) and 

about 41;2 miles east-northeast of Paulden (near 

1,424,000 N., 356,500 E.), some light-gray and lavender 

limestone has been partially to completely replaced by 

chert. Some of the chert is banded white, lavender, 

purple, and red. The chert forms thin layers and irregular stringers parallel to the bedding. V einlets of red 

and white chert cut the bedded chert. 

Most of the member in the eastern part of the area and 

the beds that overlie the cherty limestone in the northwestern part consists of alternating siltstone, very fine 

grained sandstone, some mudstone, and some silty and 

cherty limestone. Sandstone is more abundant in the 

upper part. These rocks are pale to dark reddish brown 

and have a somewhat orange cast. 
PaLEOZO]C SEDIMENTARY ROCKS 63 

MIDDLE MEMBER 

The middle member remains only in the northeastern 

part of the area (north of 1,435,000 N., and east of 392,-

000 E.). This member contrasts with the underlying 

and overlying members, especially in topography and 

color. It forms slopes having a few subdued rounded 

ledges and some rounded hills-such as Red Butte 

( 1,436,500 N ., 394,500 E.). The color is generally grayish red to reddish brown ; the weathered surface has a 

purple cast that contrasts with the more orange red 

color of the other members. 

The principal constituent is siltstone; minor constituents are conglomerate, sandstone, and a very little 

limestone. Beds range from less than 1 inch to about 

3 feet in thickness. Some siltstone is calcareous or con-:-

tains calcareous nodules and grades laterally into }.imestone. Conglomerates are composed of a pale-red to 

reddish-brown siltstone and pebbles as much as 5 inches 

long composed of pale-brown to pale-red siltstone and 

some light brownish-gray to medium-gray limestone. 

The beds are typical "intraformational conglomerates." 

The few sandstone beds are 5-10 feet thick, light brown 

to pale reddish brown, and fine grained. They form 

rounded ledges. Some are calcareous and prominently 

cross-laminated. The limestones are very light brownish gray, cross-laminated to structureless, aphanitic, and 

sandy or silty. 

UPPER MEMBER 

The upper member of the Supai Formation crops out 

in the extreme northeast corner of the area. It contrasts 

sharply with the middle member in topography, lithology, and color and consists of sandstone and a little 

siltstone that form cliffs, buttresses, and pinnacles. The 

sandstone is medium to coarse grained; some is finer 

grained. Current cross-lamination is conspicuous in 

the sandstone beds; the cross-laminae are generally 

larger than those in the middle member. Near the top 

some of the cross-laminae are eolian. A reddish -orange 

color characterizes this member, but some of it is light 

brown or moderate reddish brown. It weathers to slabs 

and plates or to a sandy soil. Some sandstone is calcareous. Bedding is massive; some sets of beds, according to Lehner ( 1958, p. 538) , are 150 or more feet thick. 

Siltstone beds are a few feet to 30 feet thick but average 6-8 feet. The siltstone is pale reddish brown and 

has irregular wavy laminae. Some is cross-laminated 

on a small scale. It weathers to smoothly rounded 

ledges that, together with its horizontal beds, contrast 

markedly with the large.:scale crossbedding of the 

sandstone. 

AGE AND CORRELATION 

The name Supai Formation was applied by Darton 

(1910, p. 25-27) to red sandstone and shale occurring 

between the Red wall Limestone and overlying Coconino 

Sandstone in the Grand Canyon area. Noble ( 1922, p. 

59) redefined the Supai by removing from the top about 

300 feet of red shale and sandstone of Permian age, 

which he called the Hermit Shale, and by adding about 

250 feet of red shale, purple and gray limestone, and 

calcareous sandstone to the bottom. These lower beds 

are Pennsylvanian in age and had previously been included in the Redwall Limestone. Noble (1922, p. 62) 

regarded the 'Supai as probably Pennsylvanian in age. 

Darton ( 1925, p. 72, 89) believed that most if not all of 

the red beds are Permian in age, except for the lower 

beds that Noble had included in the formation. 

Much of the Supai Formation outside the Grand 

Canyon area includes beds of known or inferred Pennsylvanian age as well as those of Permian age. Wherever possible in recent years, these Pennsylvanian beds 

have been separated from the Supai or have had their 

probable Pennsylvanian age pointed out. In the Paulden-Jerome area, lack of fossils and of a distinctive 

lithology makes this separation impossible, although it 

is probable that the lowest beds are Pennsylvanian. 

In northwestern Arizona the Supai Formation is 

underlain by and interfingers with the Callville Limestone, named by Longwell (1921, p. 46-47) for limestone lying between Mississippian rocks and Permian 

red beds in the Muddy Mountains of Nevada. Longwell 

placed the Callville in the Pennsylvanian but later 

stated (1949, p. 930) that the Callville contains some 

Permian strata. MeN air ( 1951, p. 520) restricted the 

name Callville in northwestern Arizona to Pennsylvanian limestones and removed from the Callville the overlying dolomitic limestones of Permian age. The basal 

member of the Supai in Black Mesa northwest of the 

Paulden quadrangle (Hughes, 1952, p. 654-656) contains 

brachiopods, pelecypods, and trilobites; these fossils indicate marine conditions this far to the southeast. The 

fossils are not diagnostic as to age, but the beds containing them may be equivalent to the upper part of the Callville (Upper Pennsylvanian) or to lower part (Lower 

Pennsylvanian), depending on whether the seas were 

transgressive (McNair, 1951, p. 520), or regressive 

(Hughes, 1952, p. 656, fig. 10). 

In southeastern Arizona the name Naco Limestone 

was applied by Ransome (1904, p. 44) to Pennsylvanian 

rocks. In central Cochise County the Naco has been 

assigned to a group and subdivided into several formations of Pennsylvanian and Permian age (Gilluly, 

Cooper, and Williams, 1954, p. 15-42). Beds of Naco 

Limestone interfinger with Supai red beds to the north 
64 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

and northwest of the type locality. Huddle and 

Dobrovolny ( 1945) extended the name Naco to beds 

at Fossil Creek and at Fort Apache ( 40 and 140 miles, 

respectively, southeast of Jerome). In these two areas, 

R. L. Jackson 11 (1951) and Winters (1951) likewise 

applied the name Naco to beds of Pennsylvanian age 

that had been included in the Supai. E. D. McKee 

(oral commun., 1953) correlated the bottom 332 feet 

of the lower member of the Supai in Sycamore Canyon 

(Clarkdale quadrangle) with the Naco and placed the 

boundary between it and the overlying Supai Formation along an arbitrary plane. 

Huddle and Dobrovolny ( 1945) stated that the Supai 

transgresses time lines and probably varies in age from 

Des Moines (Middle Pennsylvanian) through Leonard 

(Early Permian') -and that the lower member in southeastern Arizona differs in age from place to place and 

probably ranges from :Qes Moines through W olfcamp 

(Early Permian). Huddle and Dobrovolny assigned 

the middle member to the W alfcamp ( ~) and Leonard 

and correlated it with the Abo Formation of New Mexico. It may represent the main part of the Supai Formation and the Hermit Shale of the Grand Canyon. 

They stated that the upper member is Leonard in age 

and is about equivalent in age to the Y eso Formation 

in New Mexico. 

The Supai Formation of the Paulden quadrangle is 

assigned a Pennsylvanian and Early Permian age to 

conform to usage immediately to the east and northwest, 

although the basal part eontains no diagnostic fossils 

and cannot be definitely correlated with either the Callville or the Naco Formations. 

COCONINO SANDSTONE 

DISTRIBUTION 

The Coconino Sandstone is found only in the extreme 

northeastern corner of the Paulden quadrangle. These 

exposures are its south westernmost limit in this area; 

the formation underlies much of the Colorado Plateau 

in northern Arizona. In the Paulden quadrangle about 

half the area underlain by the sandstone is covered by 

basalt of late Tertiary ( ~) age. 

THICKNESS AND STRATIGRAPHIC RELATIONS 

Less than 400 feet of Coconino Sandstone is exp<>sed 

because of faulting and because of removal of the upper 

part of the formation prior to its burial by late Tertiary ( ~) basalt. In the Clarkdale quadrangle the 

formation is 500-650 feet thick (Lehner, 1958, p. 541). 

It thickens to the southeast (table 11) and thins and 

11 Also see Jackson, R. L., 1951, The Stratigraphy of the Supai formation along the Mogollon Rim, Central Arizona: Arizona Univ. M.S. 

thesis. 

pinches out to the north and northwest (MeN air, 

1951, p. 532-534; Noble, 1922, p. 67). 

The Coconino Sandstone conformably overlies the 

Supai Formation and intertongues with it as described 

on page 62. Northeast of the quadrangle the sandstone 

is beveled by the Toroweap Formation along a sharp, 

remarka:bly smooth contact. McKee (1938, p. 15) concluded: "Extensive truncation of sloping Coconino 

laminae to a perfectly flat surface can be accounted for 

only by beveling of the sediments while still unconsolidated." 

LITHOLOGY 

The Coconino Sandstone is a homogeneous massive 

fine-grained sandstone having conspicuous large-scale 

crossbedding. Most of it is very pale orange to grayish 

orange or grayish orange pink. Quartz is the major 

constituent; clay and iron oxides and traces of feldspar 

and heavy minerals are very minor constituents. The 

quartz grains are rounded to subangular. Many of 

them are frosted and pitted; some are stained with iron 

oxide; a few are clear. Silica forms the cement. Some 

beds are nearly as resistant as quartzite; some aro 

friable, but many of them are moderately firm. The 

crossbedding is eolian and individual laminae are as 

much as 50 feet long. The sandstone weathers to slabs 

and block~; it splits readily along bedding planes. 

Ripple marks and tracks are common. 

AGE AND CORRELATION 

The Coconino Sandstone was named by Darton ( 1910, 

p. 21 and 27) for exposures in the Grand Canyon,_ 

where it is underlain by the Hermit Shale of late Early 

Permian age (White, 1929). To the southeast the 

Coconino is underlain by the upper member of :the 

Supai Formation which is Leonard in age. As the 

Kaibab Limestone (as redefined by McKee, 1938, p. ,12) 

is likewise Leonard in age, the underlying Toroweap 

and Coconino Formations are also considered to be 

Leonard (Early Permian) in age. 

UNCONFORMITY AT THE BASE OF THE CENOZOIC 

ROCKS 

A major· unconformity and long period of erosion 

separate the Paleozoic rocks from the Cenozoic rocks 

in north-central Arizona. Although the thickness 

(about 300 feet) of the Triassic Moenkopi Formation 

in Sycamore Canyon ( Price/2 1949), about 17 miles 

east-northeast of the Paulden quadrangle, indicates that 

the formation extended farther south and west, no other 

formations .are known to have been deposited in this 

part of Arizona until late Tertiary; the oldest known 

uSee also Price. W. E., Jr., l948, Rim rocks of Sycamore Canyon, 

Arizona: Arizona Univ. M.S. thesis, 92 p. 
CENOZOIC ROCKS 65 

Cenozoic rocks reported from this area are early Pliocene (20 miles south of Prescott, J. F. Lance, oral commun., 1950).. During this period more than 3,000 feet 

of Paleozoic rocks and an unknown amount of Precambrian rocks were eroded from the southern part of the 

Prescott-Paulden area, and lesser amounts were eroded 

from the northern part. 

Recurrent uplift and erosion probably occurred in 

Late Triassic, Late Cretaceous to early Tertiary, and 

possibly other times. McKee (1937) cited the Shina.-

rump Conglomerate of Late Triassic age and the gravel 

deposits of Pliocene ( ~) age beneath the basalt flows on 

the Colorado Plateau as evidence of extensive uplift 

in central Arizona prior to these times. Both contain 

pebbles and cobbles ranging from Precambrian to Permian in age that could only have come from the southwest. 

The uplift tilted the Paleozoic rocks northward a few 

degrees and erosion beveled them; so, successively older 

Paleozoic rocks and finally Precambrian rocks are found 

beneath basalt of late Tertiary ( ~) age as one goes 

southward across the Prescott-Paulden area. 

CENOZOIC ROCKS 

Cenozoic rocks in the Prescott-Paulden area consist 

of andesite dikes of Tertiary ( ~) age, sedimentary and 

volcanic rocks of late Tertiary ( ~) age, and gravel and 

alluvium of Quaternary age. 

ANDESITE DIKES 

DISTRIBUTION 

Andesite dikes cut the Precambrian rocks in the southern part of the area (pl. 1). They range from a few 

inches to more than 50 feet in width; some were traced 

for more than 2 miles. The dikes trend mostly northward or east-northeastward. The longest ones trend 

(1) northward in the Texas Gulch Formation, (2) eastnortheastward across the largest mass of gabbro, alaskite, and alaskite porphyry, and (3) northward in the 

eastern mass of unnamed tuffaceous rocks of the 

Alder( n Group. 

LITHOLOGY 

The dike rocks are distinctive in appearance. They 

are light gray to medium light gray or, rarely, very light 

or medium dark gray. Fairly fresh outcrops are characteristically light brownish gray; brown, yellow, or 

red shades are typical of weathered surfaces. Mafic 

minerals may weather out leaving well-defined molds 

or may alter to limonite. Plagioclase is chalky on 

weathered surface. 

Phenocrysts are conspicuous and range from about 

1 to 10 mm in length, averaging a little less than 5 mm. 

plagioclase phenocrysts are generally more abundant 

and larger than mafic phenocrysts. Most plagioclase 

is zoned; some has been resorbed. It ranges from about 

An50 to An20 • Locally phenocrysts of hornblende and 

biotite are mor~ abundant than those of plagioclase; 

some dikes contain only hornblende phenocrysts. Tiny 

magnetite and apatite crystals are generally present. 

The groundmass is aphanitic and consists of plagioclase microlites and tiny laths in a cryptocrystalline 

base. The texture is felty. Flow structure, where present, is brought out by the arrangement of microlites. 

Some dikes have been slightly altered-the groundmass 

to calcite, the plagioclase to sericite, and the mafic minerals to chlorite, calcite, and magnetite or to limonite. 

Part of the north -trending dike in the eastern mass 

of the unnamed tuffaceous rocks of the Alder(~) Group 

is a pebble dike locally packed with fragments of Precambrian rocks ranging from less than 1 to more than 

60 mm in length. 

AGE 

The andesite dikes are younger than the P~ambrian 

and older than the upper Tertiary ( ~) rocks. They have 

been intruded along faults, shear zones, and joints in 

Precambrian rocks, but none were observed cutting the 

upper Tertiary ( ~) rocks. Other evidence in support of 

a pre-late Tertiary ( ~) age are ( 1) the pebbles of dike 

material in fanglomerate beneath basalt south of Glassford Hill (near 1,294,400 N., 358,200 E.) and south of 

Willow Creek (near 1,304,250 N., 335,400 N.), (2) the 

apparent cutting off of a dike by the andesite plug south 

of Glassford Hill, (3) the lithologic dissimilarity between dikes and andesite plugs and flows-most of the 

dikes contain large plagioclase and hornblende or biotite J?henocrysts, whereas the plugs and flows lack 

plagioclase phenocrysts and have generally small mafic 

phenocrysts-and ( 4) the slight propy litic alteration 

of some dikes in contrast to the general lack of alteration of the flows and plugs. 

The andesite dikes intrude faults which may have immediately preceded the accumulation of the upper Tertiary ( ~) rocks. On the other hand, uplift and faulting 

prdbably occurred intermittently between Late Triassic 

and late Tertiary ( ? ) times, and the dikes may have been 

intruded at one of these times. A late Precambrian 

age is unlikely because of the relatively fresh, unrecrystallized character of the groundmass. On the other 

hand, they have not been reported cutting Paleozoic 

rocks to the north and east. The andesitic dikes are 

tentatively assigned a Tertiary ( ? ) age. 

UPPER TERTIARY(?) ROCKS 

The rocks of late Tertiary ( ? ) age in the PrescottPaulden area are westward extensions of rocks mapped 

as the Hickey Formation in the Jerome area (Anderson 
66 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

and Creasey, 1958, p. 56-61, 79-83) and the Hickey and 

Perkinsville Formations in the Clarkdale quadrangle 

(Lehner, 1958, p. 549-557,563-566, 571-579). The terms 

Hickey and Perkinsville, however, are not used in this 

report because of uncertainties as to correlation. East 

of the Prescott-Paulden area the Hickey and Perkinsville Formations were distinguished largely by structural and physiographic evidence, the Hickey Formation being older and the Perkinsville Formation younger than the last major post-Paleozoic deformation. No 

such distinction was possible in the Prescott-Paulden 

area, where all the rocks appear to be younger than the 

major post-Paleozoic deformation. 

The upper Tertiary ( ~) rocks filled Chino-Lonesome 

basin and covered most if not all of the area northeast 

of the basin. They consist of ( 1) fanglomerate and 

channel gravel, (2) sand, silt, and clay of fluviatile and 

lacustrine origin, ( 3) basaltic flows, dikes, and cinder 

cones, ( 4) andesitic flows, plugs, breccias, tuffs, and 

gravels, and ( 5) some rhyolitic tuff. Andesite locally 

separates older gravel and basalt from younger gravel 

and basalt. Elsewhere, relations of the various lithologic types, as well as the significance of the andesite 

and its relation to the Hickey and Perkinsville Formations, are uncertain. Plates 1 and 2 show only the lithology of the upper Tertiary ( ~) rocks. Some stratigraphic relations and possible correlations with rocks 

to the east are shown on plate 4. 

DISTRIBUTION 

Upper Tertiary ( ~ ) rocks at one time covered most of 

the Prescott-Paulden area and now occupy about threefourths of it, although they are largely concealed 

throughout much of Chino-Lonesome Valley by thin 

Quaternary deposits. 

BASALT 

The most extensive exposures of basalt flows are in 

the northeastern part of the area, in the north-central 

part from Paulden southeastward to St. Mathews 

Mountain, and in the southwestern part. One cinder 

cone is in the northern part west of the Pinnacle 

(1,401,000 N., 351,000 E.); two cones are in the southern 

part-the cone that makes up the central part of Glassford Hill (fig. 14) and an older cone to the south-southwest. One basalt dike has been mapped in the northcentral part (near the center of pl. 2) ; and four in the 

southwestern part (two a short distance southwest of 

Granite Dells and one cutting each of the cinder cones, 

pl. 1). 

ANDESITE 

Andesite is widely distributed in the northern part of 

the Prescott-Paulden area, especially in a belt that extends northwestward from St. Mathews Mountain, a 

volcanic cone, in the southeast 'COrner (pl. 2) . The isolated peaks (fig. 19) east of Granite Creek on the northeast side of Chino Valley are plugs or plug domes. 

Thick ~ccumulations of andesitic gravels, tuffs, mud 

flows, breccias, massive flows, and plugs or domes extend northwest then west from these peaks. Small 

plugs and remnants of flows, mud flows, tuffs, and andesitic gravels are found north and south of the main exposures. The northernmost outcrops are on and east of 

Red Butte (1,436,500 N., 394,500 E.). 

Five isolated masses of andesite are in the Prescott 

quadrangle-three in the southern part and two in the 

northern part. A small plug is found south of Glassford Hill, and a flow remnant (fig. 14) is found on the 

northeast side of the Granite Dells; the form of the 

other masses is unknown. 

The various forms of andesite are not differentiated 

on the geologic maps, although the location of some mud 

flows and gravels are shown (pl. 2). The best exposures of the fragmental rocks are west (fig. 21), east, 

and south of the Pinnacle (1,400,000 N., 353,000 E.). 

SEDIMENTARY ROCKS 

The sedimentary rocks that filled Chino-Lonesome 

basin (pis. 1, 2) are best exposed in the southern part. 

FIGURE 19.-Andesite plug or dome remnants, north side of Chino Valley. The view is to the north-northeast from east of Granite Creek 

(near 1,36-8,500 N., 370,000 E.). The dark rocks at the left are the southernmost exposures of Mazatzal Quartzite. The rocks at the 

extreme right are Precambrian and Paleozoic formations. Photograph by Museum of Northern Arizona. 
CENOZOIC ROCKS 67 

Northeast of the basin they are well exposed from near 

Puro (1,391,000 N., 342,500 E.) northeastward to Hell 

Canyon but are generally less well exposed elsewhere. 

They are more abundant than the volcanic rocks at the 

surface, except locally in the southwestern part, in the 

northeastern corner, and in a northwest-trending belt 

im·mediately northeast of the basin. Available data 

from deep wells (table 12) indicate that sedimentary 

material is also more abundant than volcanic material, 

except in the Chino artesian area near the village of 

Chino Valley. 

Unmapped remnants of thin but widespread rhyolitic 

tuffs occur mainly in the southwestern part of the basin. 

These tuffs are more widespread than would appear 

from outcrops, as they are easily masked by pediment 

gravel and alluvium. They are best exposed in small 

gullies, prospect pits, and roadcuts-notably the cut at 

the top of the hill on the new alinement of State Route 

69 (pl.1, 1,292,100 N., 352,100 E.). 

Thin unmapped beds of fresh-water limestone are 

rather widely distributed in gravels northeast of the 

basin, especially ( 1) south and locally north of the 

Verde River eastward from its junction with Hell 

Canyon, (2) along Hell Canyon for about 4 miles southeast of Drake, where the limestone forms a very thin 

bed above gravel and below basalt, and (3) south of 

Granite Creek (1,386,200 N., 353,600 E.) and about 1.2 

miles to the northeast ( 1,390,500 N ., 358,000 E.). In 

the southwestern part of the basin a little fresh-water 

limestone is below the uppermost basalt flow on the 

ridge south of Willow Creek (near 1,305,500 N., 339,700 

E.) and beneath basalt on the south side of Glassford 

Hill (near 1,300,800 N., 360,500 E.). 

LITHOLOGY 

BASALT 

Flow'S and dikes.-Basalt flows in and northeast of 

the basin are similar; those in the south western part 

were studied and are described in more detail than the 

flows elsewhere. The basalt spread out as sheets, 10-20 

feet but locally 50 feet or more thick. Most flows are 

nearly horizontal and maintain a fairly uniform thickness for considerable distances. Many individual flows 

stand out clearly, but in some places no evidence of individual flows or their attitude can be observed. Remnants of a thick sequence of many thin flows can be 

seen on Glassford Hill (pl. 1; fig. 14), on the north side 

of St. Mathews Mountain (southeast corner of pl. 2), 

and elsewhere; but in many places only a few thin flows 

accumulated between sedimentary rocks, or the overlying sequence of flows has been eroded. Few source areas 

were observed; most of the basalt probably came from 

dikes. Much of the basalt in the northern part flowed 

from the Colorado Plateau rim north of the area along 

drainage lines into the Hell Canyon-Verde River lowland. Some flowed into this lowland from Black Mesa, 

northwest of the area. Some of it may have flowed 

northward towards the Verde River. 

The basalt is typical of plateau basalts. Most of it is 

medium dark to dark gray; some is lighter or darker 

gray or shades of red. The weathered surface is dark 

gray or brownish black to very light gray, brown, or 

olive. 

Most of the flows have massive interiors and blocky, 

brecciated tops and bottoms that may be vesicular to 

scoriaceous or agglomeratic. Thicker, more massive 

flows generally form steep-walled cliffs along canyons. 

A few inches of basaltic tuff underlie ma~y flows. 

V e.."icles range from microscopic openings to almondshaped ones more than 3 inches long; they are rounded, 

elongated, flattened, and irregular. Many vesicles are 

filled with calcite; others, with quartz, opal, chalcedony, 

cristobalite, zeolites, and (or) epidote. Cristobalite 

spherules are generally about 0.2 mm in diameter; a few 

are 1 mm. Flow structure is brought out in places by 

alinement of vesicles and by alternating layers of vesicular and nonvesicular basalt; it indicates only local flow 

direction but not the direction from which a flow came. 

Splatter cone type of accumulations are associated 

with some flows. On the east end of the ridge south of 

Willow Creek (pl. 1, 1,306,500 N., 341,000 E.), vesicular basalt grades upward into brecciated and ropy lava 

that contains abundant lava fragments and bombs. The 

largest bomb seen was 3 feet long. The bombs may have 

been carried for some distance on the surface of a flow, 

possibly from the Glassford cinder cone, as there is no 

evidence of explosive activity at this place sufficient to 

eject bombs of this size. 

Columnar, platy, and spheroidal joints occur in many 

places in the basalt. Prominent columnar joints are in 

basalt on the north side of the tilted flow remnant or 

plug(~) south of Prescott (pl. 1, 1,281,000 N., 333,700 

E.), along Hell Canyon, and along the Verde River 

west of Stewart Ranch (pl. 2); crude columnar joints 

are widespread. Platy and spherical joints are especially abundant in the thicker finely vesicular or nonvesicular portions. Gently dipping platy joints in the 

basal part of some flows are replaced upward by 

columnar joints. Linear striations on some platy joints, 

especially along the gulch east of the east-trending 

ridge south of Willow Creek, resemble grooves on slickensides. Spheroids in this gulch are as much as 6 feet 

long. 

The basalt contains phenocrysts of olivine, magnetite, 

augite, and plagioclase (listed in general order of decreasing abundance). Phenocrysts make up 5 to rarely 
·' 

68 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

25 percent of the rock. Except for those of magnetite, 

which are generally smaller, the phenocrysts average 

'about 1 mm in size, but some are as long as 7 mm. 

Along Hell Canyon, especially near King Spring (near 

Gila and Salt River Meridian), large augite and olivine 

phenocrysts and clusters of phenocrysts measure as 

much as 4 em across. The large augites are black and 

have a vitreous luster. In thin section they are light 

brownish gray, whereas the augite of most of the basalt 

is colorless to light greenish gray. Some basalt northeast of the basin contains elongated black pyroxene 

phenocrysts that in hand specimen resemble hornblende. 

In other places, especially west of the Pinnacle and beneath the andesite 2,000 and 3,000 feet northeast of St. 

Mathews Mountain, the basalt contains phenocrysts of 

light-green pyroxene. These elongated and green 

pyroxene phenocrysts and a few phenocrysts of biotite 

make distinguishing basalt from basaltic andesite difficult in places. Much of the olivine is fresh, yellowish 

or greenish, transparent to irridescent; some is partly 

altered to iddingsite or less commonly to serpentine and 

magnetite. Much of it is euhedral, some is resorbed or 

skeletal, and some is zoned. Plagioclase phenocrysts 

are zoned; the centers are calcic labradorite, and the 

margins are sodic labradorite. 

The groundmass, which is fine grained or microcrystalline, is felty; some is int~rgranular or trachytic. 

It is composed of plagioclase needles in a base of mafic 

material, which, where it can be resolved, consists of 

augite, olivine, magnetite, and a little apatite. 

The volcanic rock penetrated in water wells is report~d as basalt or "mala pais" ("malpais"), a term used 

for m·afie volcanic rock-s. · It may be basalt, or some or 

all of it may be andesite. Most of this volcanic rock is 

described as red or black and as "coarse" or "porous"-

water in the Chino artesian basin comes from "porous 

malapais." The volcanic material is interbedded with 

clastic material, some of which is undoubtedly pyroclastic in origin; some pyroclastic material probably 

was reported as sand and gravel, and some as "malapais." The weH-log data suggest that the upper surface 

of the basalt ( ~) is fairly even and slopes gently upward 

from the northeast side of the basin to southwest of the 

village of Chino Valley (fig. 20). This surface should 

merge near where basalt masses protrude above the 

Quaternary cover. The buried volcanic rocks, however, 

may not be part of the outcropping basalt, and the upper 

surface of the buried volcanic rocks may not have been 

formed completely by related rocks. 

Basaltic dikes are lithologically similar to the flows. 

Platy joints and flattened vesides occur parallel to their 

chilled margins. The interior of the branching dike or 

neck that cuts the Glassford cinder cone is coarser 

grained than most flows and dikes and has a diabastic 

texture. 

Cinder oones and tuffs.-The cinder cone west of the 

Pinnacle (1,401,000 N., 351,000 E.) is well exposed in 

the west-flowing gulch that partially dissects the co·ne. 

Beds dip 15°-55° away from its probable center. The 

rock is moderate brown, moderately dark reddish brown, 

or very dusky red. It is composed principally of fragments of porphyritic, vesicular to scoriaceous basalt. 

The phenocrysts of greenish pyroxene and brownish altered olivine, as much as 2 mm in diameter, are enclosed 

in a finely vesicular, frothy dark-colored unresolved 

groundmass. 

The einder cone which forms the eenter of Glassford 

Hill (1,307,000 N., 362,000 E.) is exposed only around 

the eraterlike depression at the top of the hill and along 

the northeast-trending gulch that has cut through the 

overlying basalt and partially dissected the cone (pl. 1, 

see. D-D'; fig. 14). Beds dip away on all sides from 

the dike or neek that is exposed in the depression. No 

interbedded flows or sills of basalt were observed. This 

cone was probably built up to a height of about 700 

feet and then completely buried by basalt flows, some 

of which issued from the T-shaped dike or neck near 

the top. The basalt is conformable to the underlying 

cinder cone where exposed. Elsewhere around the hill 

the eroded edges of flows are exposed, and where their 

attitude could be d~~ermined, they are nearly horizontal. On the south side (near 1,301,400 N., 359,500 E.) 

the flows dip gently northward. The thick sequence of 

nearly horizontal to gently northward-dipping flows 

_ on the south side of the hill were at one time continuous 

with the thick sequence on the ridge to the south. The 

northward dip of the flows and the surface on which 

they are deposited (fig. 24 A and B) appears to be a normal feature related to basin filling. This surface sloped 

gently away from the southern margin of the basin. If 

the cinder cone was nearly buried by basalt from the 

south, as appears likely, then the present shape of 

Glassford Hill is due largely to erosion. The material 

that makes up the einder eone is pale to dark reddish 

brown, grayish red, or pale red. It is well indurated, 

generally well bedded, and composed of erystal, lithic, 

and vitric fragments derived from basalt. The basaltic 

particles are fine ash (shards and pumice) , lapilli, 

bombs, and blocks; large bloeks and bombs are common. 

A tilted and eroded cinder cone (1,300,000 N., 357,000 

E.) southwest of Glassford Hill is largely concealed by 

float from overlying basalt, but it is well exposed 

through a vertical distance of about 150 feet in a few 

gullies. Beds in the lower part dip steeply northward 

or are nearly vertical ; beds in the upper part dip 25 °-

40°-a:bout normal for cinder eones. The cinder cone 
T. 

17 

N. 

T. 

16 

N. 

4240. 4246• 

4230 

.4255 

" " "'-... 

.4476 

.4440 

"'-... 

CENOZOIC ROCKS 

R. 2 W. 

.3925 

4070. 3906. 3888 

.4049 

.4304 

• 4274 .4351 

"'-... ......._ 

4090. 

~054 4000. 

.4330 

"' 4440 • "' • 4349 

440'5-- • 4250 

• ""'"'.4366 

'-............._ .4480 .4500 ------

--- 4458. • 4459 • 4450------

r--------

1 

I 

I 

I 

I 

I 

.3954 

4530? . 

4285 • 

----------- 4537. .4442 .4361 .......... " 

34045'~~~~~~~----------~4~5~00~_--- __ 2-~~-----·~4~4~5~0~------------------~~--------~ 

T. 

15 

N. 

··························· 

0 4450 

112°30' 

•4563 .4568 

.4650 

.4590 

··································· 

.4650 

4700 

············(11_ •.•.•.•. -•.•.••.. ·. ·~-·~ ; . ... ···..... 'Boo Z0 ~ ·· ··· ~9o0 

0 2 

36 

3 MILES 

69 

EXPLANATION 

:-~.:.:>J 4900 

Outcrop of basalt 

4750 -

0utcrop of Mazatzal Quartzite 

x475o 

Altitude of outcrop 

.4054 

Well 

Number indicates reported altitude of top of basalt. Some wells 

also reported basalt at higher 

or lower altitudes, separated 

by sedimentary deposits. Wells 

which were not deep enough to 

reach basalt or for which no log 

is available have been omitted 

---- 4200 ______ ,, 

Structure contour on top of 

buried basalt 

Dotted where projected from 

southernmost wells to basalt 

outcrops 

FIGURE 210.-Structure-contour map of the top of buried uazsalt in Chino artesian basin. 
70 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

material ranges from well to poorly sorted and from 

friable to fairly well indurated. The lower part is soft, 

prdb:tbly because of thermal alteration. In contrast to 

the Glassford cone, the material that makes up this cone 

ranges from yellowish gray through yellowish brown to 

pale or light brown and has a somewhat mottled appearance. It consists of well-bedded basaltic ash, lapilli, 

blocks, and small bombs. The fragments range from 

less than 1 to more than 60 mm long and are of two 

types: ( 1) yellowish or brownish lapilli -and shards of 

basaltic pumice and (2) medium-gray to medium-darkgray lapilli of scoriaceous, vesicular, and some nonvesicular basalt. Some beds are cemented by calcite; 

others contain tiny cristobalite spherules. The cinder 

cone is older than the surrounding basalt and gravel, a 

fact proved by its more altered character and by its 

steep dip in contrast to the nearly horizontal attitude of 

the basalt and gravel that bury it. The cone is not part 

of the Glassford cone, as it dips steeply north. Its rela.-

tion to the nearby andesite plug is unknown. 

Some basaltic tuffs are similar to the material that 

composes the cinder cones, but they are generally finer 

grained. These tuffs are gray, brown, reddish brown, 

or red, depending on the color of basaltic lapilli, scoria, 

and pumice or on the abundance of calcite cement. 

ANDESITE 

The topographic expression of the andesitic rocks 

varies from a subdued rubble-covered surface to sharp 

peaks, such as the Pinnacle and the peaks east of Granite 

Creek (fig. 19). The rubble-covered surface formed 

from fragmental andesite-gravel, mud flow, breccia, 

and agglomerate-and may make recognition of the 

form of an andesite mass difficult or impossible. The 

sharp peaks are composed of massive to flow-banded or 

platy-jointed andesite or of consolidated flow breccia or 

rugglomerate. Some weathered surfaces are lumpy due 

to abundant inclusions or to autobrecciation. 

Prominent columnar joints were observed only in the 

flow remnant northeast of the Granite Dells-one of the 

few recognizable flows in the area. Flow hands and 

platy joints, mostly steeply dipping and parallel, but in 

places fan shaped, are common in much of the nonfragmental andesite; flow bands are visible in some 

blocks in fragmental rook. Phenocrysts, plagioclase 

microlites, and some basic inclusions are parallel to the 

flow or platy structure but may have random orientation within t:he plane of flow. 

Fragments in mud flows are angular to rounded; 

most of those in breccia and agglomerate are subangular. 

They range from little larger than groundmass particles to several feet or even tens of feet in size; many 

rounded ones in mud flows are about 2 feet in diameter. 

Angular to subrounded basic inclusions are abundant 

in and near source or probable source areas. They are 

as much as 5 inches long and consist of ( 1) granular 

aggregates of light-green pyroxene ( diopsiden containing or lacking reddish garnet, ( 2) aggregates of 

biotite containing minor plagioclase, (3) large crystals 

of dark-colored pyroxene, mostly altered to aggregates 

of coarse hornblende, ( 4) greenish-brown hornblende, 

( 5) basaltic ( ? ) hornblende containing or lacking magnetite, and (6) various mixtures of the foregoing minerals. 

The andesite consists of hornblende andesite, biotite 

andesite, and basaltic andesite. Gradations are common between biotite and basaltic andesite; most contacts between basaltic and hornblende andesite are 

abrupt. Lithologic types have not been separated on 

the maps. Biotite andesite is most abundant, especially 

on St. Mathews Mountain and on some of the peaks 

east of Granite Creek. The most extensive biotite-andesite mud flow is east of the Pinnacle and underlies 

hornblende andesite mud flow near the base of the section. Hornblende andesite is confined principaUy to 

the area south of the Verde River for about 5 miles 

east of Route 89 (pl. 2) and to the andesite (pl. 1) 

northeast of the Granite Dells and west of Granite 

Creek (near 1,359,000 N.). As many as three hornblende andesite mud flows interfinger with andesitic 

gravel and tuffaceous deposits beneath andesite breccia 

and massive andesite in the southwest-trending gulch 

south of the Pinnacle. The principal areas of basaltic 

andesite are west of the headquarters of King Canyon 

and about 11;2 miles east-southeast of the Pinnacle (pl. 

2, near 1,384,000 N., 380,000 E., and 1,397,900 N., 360,-

300 E.), each area occupying about half a square mile. 

The scarcity of mafic minerals (low color index) suggests that the hornblende andesite may be a dacite rather 

than an andesite. The index of refraction of obsidian 

and of some white pumice tuff associated with andesitic 

gravel is about 1.50; it indicates andesite or dacite 

(George, 1924, p. 368). 

Hornblende andesite.-The hornblende andesite is a 

medium light gray to medium dark gray dense siliceouslooking rock containing phenocrysts of hornblende. 

Some glassy rocks are nearly black and have tiny hornblende needles; others have light grayish-brown zones, 

probably caused by slight devitrifi.cation, that gives a 

brecciated appearance. 

Vesicles are generally lacking. The flow on the northeast side of the Granite Dells (pl. 1), however, contains 

miarolitic cavities with small transparent light olivegray hornblende prisms .about 1 mm long associa.ted with 

orthoclase and spherules of cristobalite. 

Hornblende is the only megascopic mineral, except 
CENOZOIC ROCKS 71 

for minerals in basic inclusions and for scattered lightgreen pyroxene crystals. The hornblende crystals are 

0.1-5 mm and rarely 1 em long. Some crystals are 

clustered. Most hornblende is fresh, but some is partly 

to completely altered to aggregates of granular magnetite. Some is resorbed or skeletal. Most of it is pleochroic in shades of green to brown, but some is reddish 

brown to yellow. 

Microscopic phenocrysts are of unzoned plagioclase 

0.1 to 0.3 mm long and minor amounts of magnetite or 

ilmenite, apatite, sphene, pyroxene, and, in a few places, 

quartz, possibly as xenocrysts. Pyroxene is colorless or 

slightly green in plain polarized light. The groundmass is cryptocrystalline to glassy and contains microlites and small laths of plagioclase, mostly less than 0.01 

mm long. 

Biotite andesite.-Included in the discussion of biotite andesite-more properly biotite-pyroxene andesite-is much andesite that contains little or no biotite 

but that otherwise resembles biotite andesite. Biotite 

andesite is various shades of gray to nearly black. Much 

of it has a brownish or olive cast; some is reddish. 

Some biotite andesite mud flow is light brown to yellowish orange. A mottled appearance is due to alteration 

or devitrification of glassy groundmass or to differences 

in abundance of small vesicles. Vesicles are flattened 

and alined parallel to flow banding or to platy joints. 

Calcite, chalcedony, cristobalite, opal, quartz, tridymite, 

or zeolites (or combinations of these minerals) line or 

fill the cavities. 

Phenocrysts are of pyroxene, which is generally the 

most abundant, biotite, magnetite, apatite, and, very 

rarely, plagioclase. Pyroxene phenocrysts are 0.1-1 mm 

or, rarely, 1 em in maximum dimension. Larger crystals and glomeroporphyritic aggregates are probably 

inclusions or basic segregations, not phenocrysts. Most 

pyroxene is light green, glassy, and granular. 

Few biotite crystals are larger than 1 mm in diameter 

by 0.1 mm thick, but some are twice that size. Most 

biotite is pleochroic, ranging from greenish brown to 

light yellow; some is reddish brown. Biotite is fresh, 

altered around the margins, or completely altered to 

aggregates of granular magnetite. Tiny needles and 

plates composed of granular magnetite are common in 

some andesite that contains no unaltered biotite. Some 

of these aggregates have the shape of hornblende. Magnetite phenocrysts are rarely as much as 0.5 mm in 

diameter. 

The groundmass is aphanitic to glassy and composed 

of glass, devitrified glass, or an unresolved cryptocrystalline base containing plagioclase microlites or 

laths. The laths are mostly less than 0.1 by 0.11 mm 

in size; many are less than 0.02 mm long. Pyroxene 

and magnetite can be recognized in the groundmass in 

a few thin sections. The texture is hyalophitic or felty 

and locally trachytic. Some groundmass has been partially replaced by calcite. 

B asaltie andesite.-The mineralogy of the basaltic 

andesite is for the most part similar to that of the 

biotite andesite, but both light-green pyroxene and biotite may be absent from some of the rock. The basaltic 

andesite is darker than much of the biotite andesite. 

Olivine phenocrysts are common in rock that may or 

may not contain needlelike or platelike aggregates of 

granular magnetite, light-green pyroxene, or basic inclusions. Some olivine is partly to completely altered 

to iddingsite or to iddingsite having centers of antigorite ( ~). Some is unaltered or only slightly altered, 

even in rocks that contain the aggregates of granular 

magnetite. Altered olivine, biotite, hornblende ( ~),and, 

rarely, pyroxene are reddish or orange in these rocks. 

Some basaltic andesite has a speckled appearance caused 

by abundant phenocrysts as much as 1 em across 

composed of light-green pyroxene and other mafic minerals. 

Origin of the andesite.-The andesite was probably 

extruded and spread out from volcanic domes-endogenous and exogenous domes and plug domes (Williams, 1932). Evidence for this conclusion includes 

the steep to vertical flow planes and platy joints---:some 

fan-shaped-the abundance of basic inclusions in andesite close to source and probable-source areas, and the 

abundance of fragmental material that in many places 

grades upward through andesitic gravel, tuff, and breccia to massive andesite (fig. 21). Basic inclusions probably represent early segregations from the magma and 

not xenoliths, as they are similar over widely scattered 

areas. Forceful intrusion of andesite is suggested in 

several places; an example is the plug east of the Pinnacle that is partly surrounded by steeply dipping Paleozoic rocks (pl. 2, sec. F -F'). The attitude of a steeply 

dipping zone of tuff and glassy welded or fused tuff 

that is conformable to the north side of a hill of Paleozoic rocks (near 1,378,800 N., 377,800 E.) is probably 

due to flow of a mass of the nuee-ardente type against 

the limestone hill. Fragments of limestone in the tuff 

are bleached and altered owing to the high temperature 

of the tuff. SEDIMENTARY ROCKS 

The exposed sedimentary rocks in the southern part 

of Chino-Lonesome basin consist of fanglomerate, mud 

flows, and some interbedded rhyolitic and basaltic tuffaceous material around the margins; in the interior of 

the basin these sedimentary rocks include channel 

gravel, sand, silt, clay, and marl and some rhyolite tuff. 

From the exposed Precambrian rocks to the south, the 

fanglomerate grades outward and upward into finer 
72 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

FIGURE 21.-Volcanic and sedimentary rocks of late Tertiary(?) age near Granite Creek (1,401,500 N., 348,300 E.). Tab, massive andesite 

breccia; Tas, lighter colored bedded tuff, breccia, and andesitic gravel; Tb, basalt flow; and Tg , gravel. 

particles; some interfingering of coarse and fine material occurs. Most of the material that is 1-2 miles a way 

from the Precambrian rocks is fine sand, silt, clay, and 

marl. The coarse and fine materials are not shown 

separately on the geologic map (pl. 1), but their approximate distribution is indicated on plate 4. Logs 

of wells in Chino Valley show a large amount of fine 

material, either "clay" or "volcanic ash." In the northwestern part of the area (pl. 2), the sedimentary material is so poorly exposed that little about its character is 

known with certainty. Both coarse and fine material is 

exposed locally. Northeast of the basin most of the 

sedimentary material is coarse grained and accumulated 

in channels; some (southwest of Drake) resembles the 

finer grained beds in the interior of the basin. 

The sedimentary rocks have a wide range of color. 

Many gravels are various shades of greenish or yellowish gray, but in the northeastern part of the area, many 

of them are shades of red owing to abundant material · 

derived from the Supai Formation; others are gray 

owing to abundant basalt fragments. Mud flows are 

generally pale red to yellowish brown (buff); the 

rhyolitic tuffs are white, buff, pale red, or shades of 

orange pink, reddish orange, and reddish brown. The 

clay, silt, and fine sand of the interior of the basin are 

pale orange to moderate or grayish orange pink; the 

interbedded marly layers are very pale orange to nearly 

white. 

Gravels in the southern part of the area are composed 

of Precambrian fragments, generally a heterogeneous 

mixture, except close to a source area, where the fragments may be largely of one kind. Where granitic 

rocks were deeply weathered, . .the overlycing gravel con-·· 

tains little granite. Northeast of the basin many 

gravels, especially south of the Verde River, are composed of about 'equal amounts of fragments of Precambrian and Paleozoic rocks, but locally, rocks of one era 

may predominate almost to the exclusion of rocks of the 

other era. The Precambrian fragments in this area are 

largely from the Alder Group but include intrusive 

rocks and Mazatzal Quartzite; the Paleozoic rock fragments are largely from the Martin and Red wall. In the 

northeastern part of the area the Paleozoic fragments 

are largely from the Supai and Coconino Formations. 

Scattered basalt fragments, composing generally less 

than 1 percent of the gravels at any one locality, are 

widely distributed in the coarser sedimentary rocks, 

especially in the southern part of the basin. Basalt 

fragments, however, may be very abundant in some 

gravels that are interbedded with or overlie basalt flows, 

and some of these were derived from penecontemporaneous flows. In the northeastern part of the area, much 

of .the gravel is composed largely of basalt. Basaltic 

gravels have been reported in deep wells. 

The fragments are angular to subrounded; many are 

subangular, but channel gravels are generally more 
CENOZOIC ROCKS 73 

rounded. Those composed of schistose Precambrian 

rocks are platy; many of those from the Coconino Sandstone are slabby. The degree of sorting varies from bed 

to bed and from one locality to another. Some beds or 

lenses, especially along Hell Canyon, consist of closely 

packed pebbles or cobbles and a minimum amount of 

fine-grained material; others consist largely of sand or 

silt and only a few scattered pebbles, cobbles, or boulders. Some of the material, especially in the southwestern part, accumulated as mud flow on alluvial fans. 

Some mud flows are composed largely of tuffaceous material. Accumulation as mud flows is suggested by the 

local chaotic jumbling of cobbles and by scattered boulders, some more than 6 feet long, in nonbedded and nonsorted fine sand, silt, or clay. A good example of finegrained mud flow is exposed in the gulch east of the road 

to Williamson Valley and Simmons (pl. 1; 1,313,500 

N., 326,000 E.). 

A way from the margins of the basin the nearly horizontal well-bedded fine-grained character of much of the 

sedimentary material (fig. 25), the intercalated crossbedded sands, and the sand- and pebble-filled channels 

indicate a lacustrine origin, possibly in playa lakes. 

This material is well exposed along lower Lynx Creek 

and the Agua Fria River and in roadcuts along the new 

alinement of State Route 69 near Fain Ranch (pl. 1; 

1,298,000 N., 397,000 E.). 

The sedimentary rocks are variably cemented, some 

sufficiently enough to form cliffs; others are almost completely unconsolidated. Consolidated and unconsolidated material is interbedded in places. Along Hell 

Canyon the gravel is virtually a conglomerate and is so 

firmly cemented that it breaks across pebbles. Chalcedony, opal, or zeolites, probably formed by hot springs 

associated with volcanism, cement some gravels and 

tuffs. Much of the cement in gravels is calcium carbonate, but little or no calcium carbonate, silica, or zeolites cements the clay, silt, and many of the rhyolitic 

tuffs. Some rhyolitic tuffs, however, have a calcareous 

cement, and calcite crystals that poikilitically enclose 

grains of tuff are as much as 1 em in diameter. Spherical concretions in sandy tuff a short distance south of 

the Granite Dells (1,306,400 N., 347,300 E.) are 8-10 em 

in diameter and consist of an exterior shell of sandy 

tuff in which the calcite cement has a radial arrangement. The centers (about 4 em in diameter) of the concretions consist solely of coarsely crystalline calcite. 

Tuffaceous rocks-Relatively pure tuffs that are rhyolitic in composition and mixed tuffaceous sedimentary 

rocks form part of the sedimentary sequence; most of 

them are associated with the basin deposits. The pure 

tuffs are much less abundant than the mixed tuffaceous 

rocks, which may contain basaltic material. Some silt 

and clay in the southeastern part of the area and probably some so-called clay and volcanic ash reported from 

deep wells in the Chino Valley area is rhyolitic tuff. 

The tuffs and tuffaceous rocks are variable in texture, 

composition, color, degree of sorting, bedding, consolidation, and type of cement. Interbedding with and 

gradations into nontuffaceous rocks are common. The 

tuffaceous rocks range from clay to gravel and locally 

contain scattered cobbles and boulders. Most tuffaceous 

. deposits observed are 1-2 feet thick; some are as much 

as 25 feet thick. 

Most pure rhyolitic tuffs are white, except where they 

are shades of red owing to baking by overlying basalt; 

some are buff. They are massive to thinly bedded, locally crossbedded, well to poorly sorted, and fine to coarse 

grained; they contain lapilli as much as 5 em long. 

_Most particles are angular, but some quartz grains 

(original phenocrysts? ) ·are rounded. The tuffs are 

composed of vitric, crystal, and lithic fragments. The 

vitric fragments are shards, grains, and pumice lapilli; 

the lithic fragments are gray rhyolite lapilli; the crystal 

fragments are quartz, orthoclase, plagioclase, and a little 

biotite and magnetite. These same minerals occur as 

phenocrysts in pumice and rhyolite lapilli. The plagioclase is about An10 ; some is zoned. The groundmass of 

the rhyolite is cryptocrystalline to glassy; some has been 

devitrified. The index of refraction of the shards is 

about 1.485 and suggests a rhyolite (George, 1924, p. 

368). A prominent 10-foot thick bed of gray tuff, used 

for building stone, is well bedded, locally crossbedded, or 

massive. The medium-grained, coarse- to fine-sand 

particles consist of round gray vitric grains (index of 

refract!on of 1.495) and sparse to abundant shards, dust, 

and tiny pumice lapilli. Some thin layers resemble 

sandstone and are composed of well-sorted pumice and 

rounded vitric grains; the vitric grains appear to be 

molded on each other and on scattered crystal grains. 

The best exposures of this rock are near 1,305,000 N., 

331,800 E. (pl.1). 

An orange-colored tuffaceous sedimentary rock from 

a few inches to about 10 feet thick generally underlies 

the "middle" basalt flows north and northeast of Prescott (fig. 24A). It grades downward into pure white 

rhyolite tuff or into fanglomerate and upward into basaltic tuff. The "orange tuff" contains fragments common to these rocks. Its color is due in part to altered 

mafic, lithic, and crystal fragments, to basaltic scoria, 

pumice, lapilli, and shard, and, in part, to limonitic and 

hematitic staining of the matrix caused by baking. 

Fresh-water limestone.-The fresh-water limestone, 

which ranges in thickness from a few inches to about 

10 feet, is thinnest along Hell Canyon and near Granite 

Creek and thickest along the Verde River, where more 

than one bed occurs in gravel. Some of the limestone 
74 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

is more resistant to erosion than is the gravel; it forms 

weak cliffs and breaks into very angular chunks. Clastic 

grains and pebbles of quartz and other mineral and rock 

fragments are common and abundant where the limestone grades into grayel. The rock weathers rough, 

owing to exposed pebbles and grains or to holes left by 

their removal. The dense limestone has a very low 

siliceous content and contains microfossils, gastropods, 

and stem molds ( ? ) • Much of the limestone is massive, 

but some is finely laminated. It ranges from white to 

shades of gray and very pale yellowish brown; some is 

mottled. The dark-gray color, characteristic of some 

limestone along Hell Canyon, is due to amorphous organic material. The fossils indicate deposition in shallow tern perate to cold fresh to brackish or saline water 

(seep. 80). 

THICKNESS 

The thickness of the upper Tertiary ( ? ) rocks in 

Chino-Lonesome basin was probably at least 2,000 feet 

in the deepest portion before the top was removed by 

erosion. Gravel-strewn pediment remnants and the 

superposition of Granite Creek across the Dells Granite 

and Mazatzal Quartzite (pls. 1, 2; figs. 29, 30) prove 

that the upper surface of the upper Tertiary ( ? ) rocks 

is one of erosion ; the creek was let down from the overlying upper Tertiary ( ? ) rocks or from pediment 

gravels cut on them. That some of the local thick accumulations of basalt originally were more extensive is 

indicated by the eroded edges of thin nearly horizontal 

flows. The greatest known thickness of sedimentary 

material is· about 1,000 feet, and the thickest uninterrupted basalts are about 500 feet. Much of the information on the thickness of the basin fill has been 

obtained from logs of wells. Deep wells near the center 

of the basin have not penetrated bedrock; the basin 

apparently becomes deeper towards the northwest at 

least as far as the headwaters of the Verde River. The 

distribution of the wells is shown on plate 3; the probable configuration of the basin, in figure 22 ; and the 

present mini:rp.um thickness of deposits, in figure 23. 

The well-log data are summarized in table 12. 

About half a mile southwest of the Granite Dells, 

well1 in sec. 14, T. 14 N., R. 2 W. (1,306,200 N., 345,000 

E.), penetrated 1,013 feet of sedimentary material but 

did not reach bedrock. Above the collar of the well, 

about 325 feet of interbedded basalt flows and sedimentary rocks are exposed to the top of the east-trending 

ridge ( 1,305,500 N., 336,500 E.). Thus a total of at 

least 1,338 feet is indicated in this area. The uppermost 

flow on this ridge was at one time continuous with the 

uppermost flow (1,301,500 N., 350,000 E.) east of Granite Creek (pl. 1, sec. B-B'). More than 300 feet of 

basalt may have overlain this uppermost flow if the 

112'15' 

EXPLANATION 

Contact between Precambrian and Paleozoic 

basement rocks (lined pattern) and upper 

Tertiary(?) volcanic and sedimentary rocks 

---4500---

Contour showing probable configuration of 

Chino-Lonesome basin as extrapolated 

from outcrops and well data 

FIGURE 22.-Probable configuration of Chino-Lonesome basin in which 

volcanic and sedimentary rocks were deposited. 

nearly horizontal basalt flows that form the ridge southsouthwest of Glassford Hill extended westward. 

In the southeastern part of the area, about 800 feet 

of nearly horizontal sedimentary material is exposed intermittently from near the point where Clipper Wash 

leaves the quadrangle ( 1,291,300 N.) to the base of the 

basalt flow on the south side of Glassford Hill. East 

of the southern part of the rna p area, a well (No. 1, sec. 

11, T. 13 N., R. 11 E.; 1,282,300 N., 405,500 E.) entered 

Precambrian bedrock about 7 40 feet below the lowest 

exposures on Clipper Wash; the total amount of sedimentary material, therefore, may be 1,600 feet. 

Near the village of Chino Valley, many wells that 

tap the Chino artesian area bottom in upper Tertiary ( ? ) 

rocks as much as 768 feet below the surface; some of 
CENOZOIC ROCKS 75 

EXPLANATION 

,%~'-..W..'-..~'-..'..~~~"~W..~'-..'0:: 

Contact between Precambrian and Paleozoic 

basement rocks (lined pattern) and upper 

Tertiary(?) volcanic and sedimentary rocks 

D 

0-500 

500-1000 

More than 1000 

Present minimum thickness, in feet, based 

on well data 

FIGURE 23.-Approximate present minimum thickness of volc{lnic and 

sedimentary rocks of late Tertiary ( ?) age in and adjacent to ChinoLonesome basin. 

them cut as much as 500 feet of "malpais." One well 

(No. 1, sec. 17, T. 16 N., R. 1 W.) is reported to have 

bottomed in basalt 1,085 feet below the surface. A 

wildcat oil well (No. 1, sec. 32, T. 18 N., R. 2 W.) re17 58-447. 0--166-------6 

portedly entered ·bedrock about 1,000 feet below the 

surface. Another wildcat oil well (No. 1, sec. 20, T. 18 

N., R. 2 W.) closer to the margin of the basin entered 

bedrock 600 feet below the surface. An additional 200 

feet or more of sedimentary material remains a:bove the 

collars of some of these wells and below the pediment 

gravels that cap nearby hills. Erosion has been greater 

in this area, which is the headwaters of the Verde River, 

and at the southeast end of the basin than elsewhere. 

North west of the Prescott-Paulden area, the deepest well 

for which I have a record is 700 feet. 

Northeast of the basin, the upper Tertiary ( ?) rocks 

are thinner, except for thick accumulations of volcanic 

rocks, probably around vents. Basalt ranges from 10 

to more than 500 feet in thickness (at the north side of 

St. Mathews Mountain) ; accumulations of 200-300 feet 

are on the mesa about 3 miles northwest of St. Mathews 

Mountain, near the headwaters of Muldoon Canyon 

( 1,395,000 N., 366,500 E.), and south of Stewart Ranch 

(1,407,300 N., 354,500 E.). The maximum known thickness of andesite is 850-1,000 feet on the Pinnacle, St. 

Mathews Mountain, and the two peaks between them; 

some thick accumulations may represent plug or domal 

material intrusive into earlier andesite. About 300 feet 

of massive andesite breccia underlain by breccia, tuff, 

and andesitic gravel is exposed (fig. 21) along Granite 

Creek south of the Verde River. Gravel in the central 

part of the area northeast of the basin filled shallow depressions and local channels and is mostly less than 200 

feet thick. It is thickest near the low land along the 

Verde River, where it may have been down warped when 

the structural low was formed rather than have accumulated in the lowland. The top of the gravel, which 

is a relatively level surface beneath basalt or andesite, 

may be erosional. Northeast of Hell Canyon the maximum thickness of combined basalt and gravel is about 

300 feet, but in many places, especially along Hell 

Canyon, it is less than 150 feet thick. Basalt generally 

makes up most of the known thickness. The gravel 

portion is very thin; some gravel along Hell Canyon 

forms a sheetlike deposit less than 50 feet thick. 

Thicker sections of gravel are in the general area where 

the gravel is most extensively exposed-in the neighborhood of Bar Heart Ranch and Schwanbeck Tank. 

AGE 

During Cenozoic times volcanic and sedimentary 

rocks accumulated throughout Arizona. Volcanic activity was dominant at various times and places, deposition of clastic material was dominant at others, and 

at still other times volcanic and sedimentary material 

were deposited in nearly equal amounts. Discovery of 

diagnostic fossils or physiographic and structural relations locally indicate that many of these rocks are 
76 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

TABLE 12.-Summary of well-log data in Chino-Lonesome Valley, Arizona 

[Compiled from data supplied by H. C. Schwallen, State Land Office, University of Arizona, Tucson, Ariz., and by drillers and ranch owners and from data on file with 

the U.S. Geological Survey. Not all data are reliable, and the table reflects the author's interpretation of the available data. Some well altitudes are approximate. Basalt refers to volcanic rocks reported in logs as "malapais (malpais)," "lava," and "basalt"-some may be andesite; where more than one figure is given for altitudes 

of the top and bottom of basalt, the lavas are separated by clastic deposits; figures for some thin beds of clastic deposits have been omitted from the calculations. Where 

the figure for the bottom altitude of a well is underlined and followed by the symbol "br," the well entered bedrock at the given altitude] 

Section and well 

Sec. 22, 9well !_ L---------------1 ______________ _ 

Sec. 20, well!_ ______________ _ 

32, well !_ ______________ _ 

Sec. 26, well !_ _______________ 

2 ________________ 

34, well L _______________ 

2 ________________ 

3 ________________ 

4 ________________ 

5 ________________ 

35, well !_ _______________ 

2 ________________ 

3 ________________ 

Sec. 1, well!_ _______________ 2, well!_ _______________ 

2 ________________ 

3, well!_ _______________ 2 ________________ 

3 ________________ 

4---------------- 5 ________________ 

6 ________________ 

7 ________________ 

8 ________________ 

9 ________________ 10 ________________ 

Well 

Altitude (feet above sea level) 

Top 

4,450 

4,417 

4,500 

4,385 

4,446 

4,489 

4,500 

4,500 

- 4, 500 

4,514 

4,515 

4,508 

4,525 

4,510 

4, 591 

4,550 

4,550 

4,532 

4,574 

4,575 

4,575 

4,582 

4,584 

4,r592 

4,575 

4,597 

4, 602 

I Bottom 

3,750 

3,917 

2,440 

Depth (feet) 

T. 18 N., R. 3 W. 

700 

500 

T. 18 N., R •. 2 W. 

2,600 

3, 900br? 

3,385br 1,000 

T. 17 N., R. 2 W. 

4, 171 275 

3,986 503 

4, 188br? ------------

3,925 575 

4,115 385 

3,9'13 "587 

3,792 722 

3,795 720 

3,778 730 

3,808 717 

4, 190 320 

T. 16 N., R. 2 W. 

3,891 700 

3,988 562 

3,830 720 

4,016 516 

4, 045 529 

4,075 500 

4,075 500 

4, 050 532 

3,918 666 

4,010 582 

4,034 541 

4,010 587 

4,013 589 

Basalt 

Altitude (feet above sea level) 

Top I 

Thickness (feet) 

Bottom 

1

------------I------------I------------I ------------ ------------ ------------

4,441 4,429 12 

4,416 4,408 8 

4,396 4,388 8 

4,486 4,469 17 

4,457 4,447 10 

4,427 4,417 10 

4,325 4,314 11 

3,986 3,925 61 

------------ ------------ ------------ 4,290 (?) 377? 

4,070? (?) ------------ 4,291 4,229 62 

3,906 3,792 114 

3,925? 3,904? 21? 

4,446 4, 108 338 

3,888 3,808 80 

3,801 3,778? 11? 

4,090 4,075 15? 

4,060? 3,815? 245? 

------------ ------------ ------------

3,954 3,891 63 

4,054 4,048 6 

(?) (?) (?) 

4,049 4, 016 33 

------------ ------------ ------------ 4,202 4, 185 17 

4,099 4,075 24 

4,225 4, 075? 150? 

4,262? 4,259? 3? 

4,095? 4,059? 36? 

4,049? 3,918 131? 

4, 142 4, 010? 132? 

4, 132 4,034 98 

4, 162 4, 010 152 

4, 120? 4,013? 107? 

Thickness, in feet 

of overlying (a), intervening, and 

underlying (b), 

sedimentary deposits 

(?) 

700 

500 

600 

5a 

13 

12 

217b 

3a 

12 

20 

229 or 431b 

175a 

328 

-----------

----------- ----------- 223a 

323 

590? 

109? a 

b 

62a 

220 

7 

12? b 

435a 

15? 

7? b 

320 

637a 

496a 

60b 

550a 

(?) 

483a 

------------ 373a 

86 

350a 

320?a 

164? 

9?b 

535a 

450a 

443a 

435a 

482?a 
CENOZOIC ROCKS 77 

TABLE 12.-Summary of well-log data in Chino-Lonesome Valley, Arizona-Continued 

Well Basalt Thickness, in feet 

of overlying (a), 

Section and well Altitude (feet above sea level) 

intervening, and 

Altitude (feet above sea level) underlying (b), 

Depth (feet) Thickness (feet) sedimentary 

I I 

deposits 

Top Bottom Top Bottom 

1T. 16 N., R. 2 W.-Continued 

Sec. 4, well!_ _______________ 4, 568 3,948 620 4, 068 4,038 30 500a 

3,993? 3,948 45? 45? 2 ____________ ____ 4,600 4, 100 500 4, 110? 4, 100 to 490?a 3 ________________ 4,600 4, 115 485 4,240 4,210 30 360a 

4, 150 4,115 35 60 

4---------------- 4, 600 3,900 700 4,436 4,420 16 164a 

4,246 3,900 346 174 5 ________________ 4, 600 4, 040 560 4,230 4,200 30 370a 

4, 140 4,115 25 60 

75b 6 ________________ 4,600 3,988 612 7 ________________ ------------ ------------ ------------ ------------ 4,600 4,020 580 4,240 4, 210 30 360a 

190?b 8 _________ _______ 4, 600 4,080 520 4,240 4,220 20 360a 

4, 150 4,080 70 70 9 ________________ 4, 650 3,882 768 4, 340 4,320 20 310a 

4,255 4, 140 115 65 

3,985 3,915 70 155 

33b 

5, well!_ _______________ 4,567 3,870 697? ------------ ------------ ------------ 697? 

9, well!_ ______________ _ 4, 650 3,885 765? 4,278 3,885 393 372a 

10, well!_ _______________ 4,650 4,050 600 4,352? 4,064 288? 298a 

14b 2 ________________ 4, 600 3,919 681 4,000 3, 919 81 600?a 

3---------------- 4,654 3, 954 700 4,304 4,204 100? 350a 

250?b 4 ________________ 4, 633 4,037 596 4,309 4,037 272 324a 

11, well L _______________ 4, 621 3, 921 700 4,231 3, 921? 310? 390a 2 ________________ 4, 560 4,000 560 ------------ ------------ ------------ 560 3 ________________ 4, 611 4, 111 500 4,261 4, 111 150? 350?a 4 ________________ 4, 600 3,956 644 4,050? 3,986 64 550?a 

3-0?b 5 ________________ 4, 628 3, 989 639 6 ________________ ------------ ------------ ------------ ------------ 4, 600 4,065 535 4,210 4, 138 72 390a 

4, 135 4,065 70 3 7 ________________ 4,600 3, 980 620 4, 185 3,980 205 415a 8 ________________ 4,582 4, 042 540 4, 382 4, 042 340? 200a 9 _________ ___ ____ 4, 600 4,020 580 4, 185 4,020 165 415a 10 _______________ 4,600 3,900 700 4,000? 3, 900 100? 600a 

12, well!_ __________ . _____ 4,600 3,956 644 4, 150 3,970 180 450a 

14b 2 ________________ 4, 600 3, 856 744 4,285 3,856? 429 315a 

3---------------- 4, 700 3, 740? 960? 4,530 3, 740? 790? 170a 

14, well!_ ____ · ___________ 4,600 4, 100 500 ------------ ------------ ------------ ------------ 2 ________________ 4,602 4,052 550 4, 102 4,052 50 500'fa 3 ________________ 4,650 4,063 587 4,250 4,063 187? 400?a 4 ________________ 4, 650 3,953 697 4,330 3,953 377 320a 5 ______ _____ _____ 4,656 4,016 640 4,351 4,029 322 305a 

4,018 4,016 2 11 

15, well!_ _______________ 4, 700 4, 134 566 4,405 4, 155 250 295a 

21b 2 ________________ 4, 664 4,059 605 4,274 4,059 215 390a 

3---------------- 4, 700 4,200 500 4, 366 4,200 166 334a 4 _____ ___________ 4,689 4, 169 520 4,349 4, 169 180 340a 

5---------------· 4,699 4,389 310 ------------ ------------ ------------ 310 6 ________________ 4, 700 4,109 591 4,440 4, 109 331 260a 

21, well L _______________ 4, 750 4,347 403 4,480 4,347 133 270a 2 ________________ 4, 750 4,337 413 4,476 4,337 139 274a 3 ________________ 4, 700 4,300 400 4,440 4,300 140 260a 4 ________________ 4,775 4,348 427 4,568 4,348 220 207a 5 ________________ 4,775 4,368 407 4,563 4,385 178 212a 

17b 6 ________________ 4, 750 4,350 400 4,500 4,350 150 250a 

22, well!_ _______________ 4, 735 4, 134 601 4,459? (?) (?) 276?a 

(?b) 2 ________________ 4, 737 4, 136 601 4,537 4,242 295 200a 

4,232 4, 136 96 10 
78 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

TABLE 12.-Summary of well-log data in Chino-Lonesome Valley, Arizona-Continued 

Well Basalt Thickness, in feet 

of overlying (a)d intervening, an Section and well Altitu~e (feet above sea level) Altitude (feet above sea level) underlying (b), 

Depth (feet) Thickness (feet) sedimentary 

I I 

deposits Top Bottom Top Bottom 

IT. 16 N., R. 2 W.-Continued 

Sec. 22, well3 ________________ 4, 725 4, 125 600 4,458 4,230 228 267a 

4, 210 4, 125 85 20 4 ________________ 4, 700 4,270 430 4,500? 4,270 230? 200?a 5 ________________ 4, 750 4,550 200 ------------ ------------ ------------ 200 6 ________________ 4, 725 4,025 700 4,450 4, 102 348 275a 

77b 7 ________________ 4, 725 4, 177 548 4,442 4, 177 265 283a 23, well!_ _______________ 4, 703 4,403 300 ------------ ------------ ------------ 300 2 ________________ 4, 650 4, 132 518 4,361 4, 132 229? 289a 3 _____ ___________ 4,650 4,315 335 4,450 4,315? 135? 200?a 26, well!_ _______________ 4, 750 4,300 450 4,560 4,300? 260? 190?a 

27, well!_ _______________ 4,763 4,345 418 4,449 4,345? 104? 314a 2 ____ _________ ___ 4, 764 4, 311 453 4,528 4,404 124 236a 

4,368 4,345 23 36 

34b 3 ________________ 4, 725 4,525 200 4,530? ------------ 5? 195?a 4 ________ ________ 4,800 4, 610 190 4,618 4,610 8 182a 5 ________________ 4,820 4, 153 667 4,663 4,346 329 145a 

4, 161br? ------------ ------------ ------------ ------------ 185?b 

28, well L _______________ 4,850 4,600 250? 4, 650 4, 600 50 200a 2 ________________ 4,820 4,420 400 4,640 4,420 220 180a 

33, well!_ _______________ 4,850 4,530 320 4,590 4, 530 60 260a 

34, well!_ ____ ___________ 4, 799 4,529 270 4, 729 4,529 200 70a 2 ________________ 4,829 4,590 239 ------------ ------------ ------------ ----------- 35, well L ______________ _ 4, 778 4,543 235 4,548 4,543 5 230?a 2 ________________ 4,800 4,258 542 4,650 4,258? 392? 150a 

T. 15 N., R. 2 W. 

Sec. 17, well!_ ______________ _ 5,057 

5, 150 

4,627 

4, 772 

430 19, well!_ ______________ _ 378 ----- 5~ o7o?- ----- 4~ 9oo?- -------i 7o?- -------so;--

21, well L ______________ _ 

23, well!_ ______________ _ 25, well!_ ______________ _ 

2 _______________ _ 

26, well L ______________ _ 30, well L ______________ _ 2 ___ ____________ _ 

32, well!_ ______________ _ 36, well L ______________ _ 

Sec. 1, well L _________ , ______ 10, well10 _______________ 

14, well!_ _______________ 2 ________________ 

3---------------- 21, well!_ _______________ 

2 ________________ 

3 ________________ 

4 ________________ 

22, well L _______________ 

2 ________________ 23, well!_ _______________ 

5,069 

5,076 

5,010 

5,014 

5,025 

5, 185 

5, 199 

5,300 

5,050 

5,025 

5,220 

5, 196 

5,200 

5,200 

5,350 

5,565 

5, 525 

5,550 

5,340 

5,453 

5, 197 

4, 709 

4,498 

4, 171 

4, 213br? 

4,202 

4, 663 

5,035 

5,019 

5, 168 

4, 680 

128b 

578 360 ------------ ------------ ------------ ------578?--

839 ----- 4~ 36o-- ----- 4~ 2i3-- -------i47-- 65oa _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 42b or br? 

812 

362 

150 

180 

132 

370 

4,364 4,222 142 650a 

20b 

362 

150 

150?a 

============ ============ ============ ------37o __ _ 

T. 14 N., R. 2 W. 

4,854 

4,326 

4,973 

4,920 

4, 187 

5,060 

5,230br 

5,261 

5,250 

5, 295br? 

5,230 

4,764 

4,603 

4, 718 

171 

894 

223 

280 

1,013 

290 

304 

275 

·320 

576 

850 

479 

----- 4~ 62o?- -----( 5so-- -------- 4o?-

5,200 5, 190 10 

5,465? 5,413? 52? 

5,380 5,360 20 

5,340 5,290 50? 

5,265 5, 140 125? 

------------ ------------ ------------ ------------ ------------ ------------

171 

600?a 

254b 

223 

280 

1,003b 

120 

100a 

152b 

230? 

170a 

130b 

25? 

376?b 

850 

479 
CENOZOIC ROCKS 

TABLE 12.-Summary of well-log data in Chino-Lonesome Valley, Arizona-Continued 

Section and well 

Sec. 26, well!_ ______________ _ 2 _______________ _ 

27, well!_ ______________ _ 

28, well L ______________ _ 33, well L ______________ _ 

2 _______________ _ 

3---------------- 34, well L ______________ _ 2 _______________ _ 3 _______________ _ 4 _______________ _ 

Sec. 4, well L __ · ____________ -I 

Sec. 5, well!_ ______________ _ 

7, well L ______________ _ 8, well L ______________ _ 14, well!_ ______________ _ 17, well!_ ______________ _ 18, well 1_ ______________ _ 

20, well!_ ______________ _ 22, well!_ ______________ _ 23, well!_ ______________ _ 34, well L ______________ _ 

Sec. 5, well!_ ______________ _ 6, well L ___ ~ __________ _ 24, well L ______________ _ 31, well!_ ______________ _ 2 _______________ _ 

Sec. 2, well!_ ______________ _ 6, well L ______________ _ 

Sec. 26,8 well L---------------1 L ______________ _ 

1 Basalt penetrated at top of well. 2 Basalt penetrated at bottom of well. 

Well Basalt 

Altitude (feet above sea level) Altitude (feet above sea level) 

I 

Depth (feet) Thickness (feet) 

I Top Bottom Top Bottom 

T. 14 N., R. 2 W.-Continued 

5,200 

5,214 

5,273 

5,377 

5,350 

5,350 

5,400 

5,350 

5,350 

5,425 

5,400 

4, 690 

5,065 

5,067br 

4,860 

5,029br 

5, 125 

5, 137 

4, 980br? 

5,282br 

4,878 

5,085 

5, 169 

5,040 

510 

149 

413 

252 

213 

370 

118 

472 

265 

256 

360 

T. 13 N., R. 2 W. 

5,300 

5,340 

5,400 

5,288 

5,330 

5,040 

12 

10 

360 

5, 350 1 5, 050 300 ·I------------I------------1------------I 

4, 717 

4,750 

4,725 

4,830 

4,770 

4,764 

4,775 

4,804 

4,840 

4,810 

4,820 

4,820 

4,914 

5,000 

4,783 

4,950 

5,045 

5, 3251 5,060 

4,567 

3,665 

4,415 

4,560 

4,258 

4,459 

4,365 

4,444 

4,447 

4,508 

4,520 

4,555 

4,596 

4,585 

4,283 

4,600 

4,702 

T. 16 N., R. 1 W. 

150 

1,085? 

310 

270 

512 

305 

410 

360 

393 

302 

T. 15 N., R. 1 W. 

300 

265 

318 

415 

500 

T. 14 N., R. 1 W. 

350 

343 

4, 705br? 

5, 175 

4,660 

T. 15 N ., R. 1 E. 

150 

400 

4,577? 

4,429 

4,567 

4,415 

10? 

14 

1

------------1------------1------------1 

------------ ------------ ------------

79 

Thickness, in feet 

of overlying (a), intervening, and 

underlying (b), sedimentary deposits 

510 

147 

243 

252 

50 a 151b 

lOa 

350b 

118 

? 

265 

300 

140?a 

296a 

270? 

512? 

305 

410 

393 

302? 

300 

265 

415 

350 

340 

150 

400 
80 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

TABLE 12.-Summary of well-log data in Chino-Lonesome Valley, Arizona-Continued 

Well Basalt Thickness, in feet 

of overlying (a), 

intervening, and 

Section and well Altitude (feet above sea level) Altitude (feet above sea level) underlying (b), 

Depth (feet) 

I 

Thickness (feet) sedimentary deposits 

Top I Bottom Top Bottom 

T. 14 N., R. 1 E; 

Sec. 11, well L ______________ _ 16, well L ______________ _ 

28, well L ______________ _ 2 _______________ _ 

4,875 

4,817 

4,675 

4,725 

4,525 

4,217 

3,845 

4,325 

350 

600 

830 

400 

350 

600 

830 

400 

T. 13 N., R. 1 E. 

Sec. 2, well 1_ ______________ _ 

11, well L ______________ _ 

4,550 

4,540 

3, 911 

3,690 

3,795br 

probably Pliocene or Pleistocene, but in many places 

such evidence is lacking or inconclusive. 

In 1946 K. K. Kendall of the Water Resources Division of the U.S. Geological Survey found fragmentary antelope and llamalike camel bones in the basin deposits north of Prescott. C. L. Gazin of the National 

Museum stated: "The llama-like camel * * * may represent a small species of Pliauchenia, * * *" possibly 

of Pliocene age (written commun. to C. A. Anderson, 

1947). These bones were found along the Williamson Valley road (near 1,313,500 N., 326,000 E.), in a 

road cut on the west side of Route 89 (near 1,301,200 N ., 

344,200 E.), about a mile south of Willow Creek (near 

1,302,900 N., 340,500 E.), and in the NW% sec. 23, T. 

14 N., R. 2 W., probably due east of the preceding location. During the present investigation, an unidentifiable bone fragment was found south-southwest of 

Glassford Hill (near 1,297,500 N., 355,000 E.). All 

these bones came from about the same stratigraphic horizon-below the middle basalt flows (fig. 24A) in 

orange-colored tuff or in the immediately underlying 

gravel. 

The Williamson Valley road area is the most promising locality for fossils and contains fairly abundant 

bone fragments. J. F. Lance (oral commun., 1956) 

found an antelope leg bone that he thought is not 

younger than middle Pliocene and may well be the same 

age as a vertebrate fauna 20 miles south of Prescott. 

These fossils (Reed, 1950; Bryant, 1951) were discovered along Milk Creek (fig. 1) in the Mount Union 

quadrangle ; they are early Pliocene in age according 

to Lance. The bones occur in sedimentary rocks that" 

resemble the rocks north of Prescott except for having 

been tilted slightly. The similarity is increased by identical white rhyolite tuff beds in both. 

639 

850 

3,964 3,934 30 586a 

23b 

745 

Specimens of fossiliferous fresh-water limestone 

northeast of the basin were studied by E. B. Leopold 

(1955 and 1957), by D. vV. Taylor, R. W. Brown, and 

R. Rezak (1955), and by K. E. Lohman (1957) of the 

U.S. Geological Survey. The limestone is reported to 

be moderately organic-the organic material is in an 

amorphous or macerated condition. Fossils include a 

medium-sized gastropod-probably a Lymnaea-fragments of dicot wood, rootlets, corroded conifer grainsprobably Juniperus-fungal hyphae, filamentous green 

algae, spores, an undetermined Silicoflagellate-like or 

Heliodiscoaster-like form, diatoms,· corroded sponge 

spicules, concretionary laminated algal deposits around 

pebbles-similar to water biscuits of modern freshwater lakes'-and crisscrossing tubes of undetermined 

origin, possibly stem molds or worm burrows. None 

of the material is diagnostic as to age, but it does indicate a subaqueous shallow dominantly fresh-water 

environment. 

According to Lohman, the diatoms consist of freshwater and brackish- or saline-water forms (table 13). 

The largest number of species 'are fresh-water forms, 

whereas the largest number of individuals are brackish- or saline-water forms. The identification of 

Hyalodisc?M radiat?M and its variety articus, the most 

abundant diatom, is uncertain. The badly leached or 

corroded condition of all specimens of both, in contrast 

to good preservation of delicate structures of most other 

diatoms, suggests reworking of an older deposit or 

transportation :from a different habitat. Hyalodiscus 

cf. H. radiatus var. artica was originally described from 

Franz-Josef ~and associated with marine and some 

brackish- and fresh-water species; this association suggests a tidal estuary. The diatoms have known geologic 

ranges of Miocene or Pliocene to Recent, except for 
CENOZOIC ROCKS 81 

Navicula bituminosa, which has been found previously 

only in late Tertiary (Miocene or Pliocene) beds in 

Hungary. Two forms, Gomphonema bohemicum and 

Hyalodiscus cf. H. radiatus var. artica, live today only 

in cold water. The others, except the extinct Navicula 

bituminosa, are temperate-water species. Because of 

the foregoing associations, Lohman suggested that the 

limestone was deposited in a shallow somewhat saline 

lake fed by streams of temperate water and by streams 

originating in higher, colder country (such as the Colorado Plateau and its volcanic peaks) . 

TABLE 13.-Diatoms from fossiliferous limestone of late Tffftiary ( ? ) age. Limestone underlines basalt a.nd over. lies 

andesitic gravel, 5 miles northeast of the village of Chino 

Valley (1,386,200 N., 353,600 E.) 

[Report by Kenneth E. Lohman, August 30, 1957. Occurrence: A, 

abundant; C, common; F, fairly common; and R, rare.] 

Oymbella ehrenbergii Kiitzing (F) 

parva (Wm. Smith) Cleve (F) 

Fragilaria cf. F. pinnata Ehrenberg (R) 

Gomphonema angustatum (Kiitzing) Rabenhorst (F) 

bohemicum Reichelt and Fricke (F) 

intricatum Kiitzing (F) 

lanceolatum Ehrenberg ( R) 

Hyalodiscus cf. H. radiatus (O'Meara) Grunow (0) 

cf. H. radiatus var. arctica Grunow (A) 

sp. (F) 

Navicula bituminosa Pantocsek (F) 

lucidula Grunow (R) 

Nitzschia cornmutata Grunow (A) 

cf. N. commutata Grunow (F) 

palea (Kiitzing) Wm. Smith (R) 

Pinnularia gibba var. parva (Ehrenberg) Grunow (F) 

interrupta Wm. Smith (R) 

microstauron var. biundulata Muller (F) 

microstauron var. brebissonii (KiUzing) Hustedt (R) 

Some of the white rhyolite tuff above the vertebrate 

fossil locality east of Williamson Valley road contains 

abundant pollen; pollen studies of this material are now 

being made at the Geochronology Laboratories of the 

University of Arizona (Jane Gray, written oommun., 

1959). 

The Colorado Plateau northeast of the PrescottPaulden area is covered by volcanic rocks that, according to Robinson ( 1913, p. 38) , were erupted in three 

stages: ( 1) widespread eruption of basalt from small 

cones, (2) eruption of lava of andesitic to rhyolitic 

composition from isolated large cones and a large num:-

ber of small ones, and (3) eruption of basalt from 

many small cones. The last period of eruption continued until Recent times; it was widespread, but not 

as widespread as the basalt eruptions of the first stage. 

Although not based on stratigraphic and fossil evidence, 

Robinson's assumption (1913, p. 91-92) that the first 

stage of eruption occurred in the late Pliocene has been 

widely quoted. Gravels beneath the plateau basalts 

were deposited as a result of uplift to the south that 

probably occurred in late Miocene or early Pliocene, 

according to Longwell (1946, p. 832). 

Although fossils are lacking, the Hickey Formation 

of the Jerome area and Clarkdale quadrangle is considered to be Pliocene ( ? ) , and the younger formations, 

Pliocene(?) to Pleistocene(?) (Anderson and Creasey, 

1958, p. 58, 61; Lehner, 1958, p. 554, 561-562, 565-566). 

STRATIGRAPHIC RELATIONS AND CORRELATIONS 

The upper Tertiary ( ? ) rocks rest on Precambrian 

rocks in the southern half of the area (pl. 1) and on 

successively younger rocks to the northeast across the 

northern half of the area (pl. 2, sec. L-L'). This 

is illustrated in part by the map showing the approximate present thickness of Paleozoic and Cenozoic rocks 

(fig. 31), as northeast of Chino-Lonesome basin the 

thickness is due largely to Paleozoic rocks. The surface on which the upper Tertiary (?) rocks were deposited had considerable relief. The rocks are overla.in by Quaternary pediment gravel and Recent gravel 

and alluvium. 

Attempts to correlate the upper Tertiary ( ? ) rocks in 

the Prescott-Paulden area with the Hickey and ferkinsville Formations to the east have so far proved futile. The volcanic and sedimentary rocks in the PrescottPaulden area are obviously westward continuations of 

rocks mapped as Hickey and Perkinsville to the east, 

but the criteria used to distinguish the two formations 

do not apply in the Prescott-Paulden area. 

The distribution and possible relations of the upper 

Tertiary(?) formations in the Prescott-Paulden-Jerome.:.Clarkdale ·area are shown on plate 4. As shown 

on this plate, the Hickey Formation consists of upper 

Tertiary(?) basalt and sedimentary rocks in the southwestern part of the Jerome area and of older (prea,ndesite) basalt and gravel, andesite, and younger (postandesite) basalt in the southwestern part of the Clarkdale quadrangle. (See Anderson and Creasey, 1958, p. 

56-59, pl. 1, also p. 78-83, figs. 5, 6; Lehner, 1958, p. 

549-556, pl. 45, also p. 568-576, for descriptions of the 

Hickey Formation and its distribution, as mapped by 

them, in these areas ; the volcanic rocks of the Hickey 

Formation according to them consist largely of basalt.) 

On plate 4 the name Perkinsville Formation (Lehner, 

1958, p. 563-566, pl. 45, also p. 556-563) has been applied to the upper Tertiary(?) rocks in the northeast 

corner of the Paulden quadrangle. 

In the Jerome-Clarkdale area the Hickey Formation 

was distinguished from the younger formations on the 

basis of relation to deformation and erosion. The 

Verde Formation is e-ast of the Black Hills and east of 

the Verde fault; the older Quaternary gravel~alled 

older Quaternary gravels in the text but braced as 

Pliocene ( ? ) to Pleistocene on the map explanation and 

correlated with the Verde Formation by Anderson and 
82 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

Creasey ( 1958, p. 61, pl. 1) -are west of the Black Hills 

and west of Coyote fault; the Perkinsville Formation is 

north of the Black Hills. The Hickey Formation 

forms a thick sequence of basalt flows on top of the 

Black Hills, downfaulted flows east and west of the two 

bounding faults, and downwarped flows north and 

south of the Black Hills. The flows are under lain 

locally by gravel that is limited to northward-draining 

channels, except in the southern part of the Jerome area 

where sedimentary material is more abundant and generally predominates over basalt. East of the Verde 

fault the Verde Formation unconformably overlies the 

Hickey Formation. Except where downfaulted or 

downwarped, the Hickey Formation is confined to 

topographic highs, where it occurs as erosion remnants. 

Erosion, initiated by post-Hickey deformation, resulted 

in about 1,300 feet of relief and in the present southward drainage, according to Lehner ( 1958, p. 555). 

The younger formations are more closely related to present topography. They accumulated mainly in topographic lows. 

The stratigraphic relations within the upper Tertiary ( ? ) rocks in the Prescott-Paulden area are not 

clearly understood. The sequence, as worked out in the 

central part of the Paulden quadrangle, consists of 

gravel and a little basalt-referred to here as older 

gravel and older basalt---overlain by andesite that in 

turn is overlain by basalt and gravel. During reconnaissance in much of Yavapai County, andesite (or 

dacite) was observed in many places above gravel and 

below basalt. To conclude that all the andesite (or 

dacite) is contemporaneous and is important as a stratigraphic marker is tempting, but such conclusions have 

not been proved. The andesite may be older than, an 

early facies of, or younger than basalt of the Hickey 

Formation, or it may be of several ages. The presence 

of basaltic-looking rocks related to andesite and of andesitic-looking rocks related to basalt have complicated 

the picture. The upper Tertiary (?) rocks all appear to 

have been deposited after the last major deformation in 

the area. 

The older basalt, which is quantitatively unimportant 

and may possibly be an early basaltic facies of andesite, 

occ~rs in four areas: ( 1) west of the Pinnacle ( 1,400,000 

N., 353,000 E.), (2) on the eastern edge of the area, 2,000 

and 3,000 feet northeast of St. Mathews Mountain, ( 3) 

1,000 and 2,000 feet southeast of Stewart Ranch ( 1,407,-

500 N., 354,500 E.), and (4) in the headwaters of Bull 

Basin Canyon ( 1,396,000 N., 372,500 E.). It consists · 

of flows, except at the first locality, where it includes a 

cinder cone (pl. 2) . _ 

The older gravel extends from northeast of ChinoLonesome basin newrly to Hell Canyon. Included with 

the older gravel are the gravels along the western margin of the area, which are probably older than andesite 

and which extend for about 4 miles north of the latitude 

of the village of Chiiw Valley; a small patch of gravels 

in the northeast corner of the area (1,453,000 N., 397,000 

E.) is also included. The gravel beneath basalt along 

Hell Canyon, some of which is too thin to show on plate 

4, and that beneath basalt north and south of the Verde 

River near the eastern edge of the area may also be part 

of the older gravel. Fragments of Precambrian volcanic and intrusive rocks are characteristic of the older 

gravels. These Precambrian fragments must have been 

derived from rocks south or southwest of Chino-Lonesome basin, probably prior to the formation of the basin. 

The small patch of gravel in the northeast corner is probably older gravel because it contains Mazatzal Quartzite 

pebbles that must have come from rocks south of the 

Verde River lowland. The pebbles of Mazatzal Quartzite and some of the Precambrian fragments along Hell 

Canyon and the Verde River may have been derived 

from older gravels. 

The older gravel is intruded by andesite plugs and 

overlain by andesite flows, breccias, mud flows, and 

gravels composed largely of andesite fragments. The 

contact between older gravel and overlying andesitic 

gravel, tuff, and ml'ld flow is well exposed on the sides 

of the .gulches west (fig. 21), east, and south of the Pinnacle (1,400,000 N., 353,000 E.) and appears to be conformable and gradational. At only one place was a possible disconformity observed. 

Most of the basalt northeast of the basin rests on andesite or on older gravel that generally contains andesite 

fragments at the top. In places these ahdesitic gravels 

are only a few inches thick. Most, if not all, of the thin 

andesitic gravels are related to the andesitic period of 

volcanism and not to a period of erosion following eruption of andesite; they are lateral extensions of andesitic 

gravel and mud flows that underlie andesite breccia and 

massive andesite (fig. 21). Erosion prior to eruption 

of the basalt, however, may have removed overlying 

andesite breccia, massive andesite, and much of the 

andesitic gravel. 

The Hickey Formation (as mapped by Lehner) in the 

southwest _corner of the Clarkdale quadrangle consists 

of the same sequence: older gravel and a little basalt, 

andesite, and post-andesite basalt (pl. 4). Lehner 

(1958, p. 553) recognized andesite in the area but included it with and considered it a facies of the basalt of 

the Hickey formation. 

Basalt and overlying gravel in the northeast corner 

of the Paulden quadrangle are part of the Perkinsville 

Formation. The basalt flowed from the Colorado 

Plateau rim southward into the Verde River lowland. 
CENOZOIC ROCKS 83 

Basalt of the Perkinsville Formation has been arbitrarily distinguished (pl. 4) from the basalt south of 

Hell Canyon and the Verde River. As the base·of some 

of this basalt slopes northward toward the Verde River 

lowland, the basalt may have been erupted after formation of the lowland and at nearly the same time as the 

Perkinsville basalt. On the other hand, the base of 

some of this basalt and of some of what is shown as 

Perkinsville basalt along Hell Canyon upstream from 

King Spring (west of 376,500 E.) has the same attitude 

as the underlying Paleozoic rocks (pl. 4, sec . .A-.A.'); it 

may have been downwarped into the lowland. Nearly 

all the basalt in the Paulden quadrangle, including Perkinsville basalt just north of the area (near 384,000 E.), 

overlies andesite; andesite, therefore, cannot be used as 

evidence for distinguishing basalts of different ages, except for the small amounts of basalt beneath andesite. 

Gravel and interbedded fresh-water limestone beneath 

the lowest basalt (Perkinsville) in the northwest corner 

of the Clarkdale quadrangle is continuous with the 

gravel and limestone beneath basalt immediately to the 

west. Lehner mapped them as Perkinsville; I found 

it impossible to distinguish the gravel from the older 

gravel to the southwest. It is lithologically similar and 

contains Paleozoic and a few Precambrian fragments, 

whereas gravel of the Perkinsville in most places, according to Lehner ( 1958, p. 563-564), is composed 

largely of basalt derived from older basalts. The limestone along Hell Canyon southeast of Drake is between 

underlying gravel and overlying basalt. Limestone 

south of Granite Creek (1,386,200 N., 353,600 E.) underlies basalt and overlies older gravel, which contains 

andesite fragments at the top. The limestone north of 

Granite Creek (1,390,500 N., 358,000 E.) probably occupies the same position, but it may underlie the 

andesite. 

The sequence as far as known in the southern part 

of the basin consists of sedimentary material and a few 

interbedded basalt flows. North and northeast of Prescott, the sedimentary material is overlain by three basalt 

flows or flow series that are separated by as much as 100 

feet of gravel and rhyolitic tuffaceous rocks. Figure 14 

(southwest corner) shows lower, middle, and upper 

basalt flows and the gravel and tuff beneath these flows. 

The middle and upper flows rest on relatively gently 

northward-dipping surfaces (fig. 24). The middle basalt flows rest on Precambrian rocks in places and on 

increasingly thicker basin deposits to the north. 

In the exposed part of the basin, fanglomerate and 

coarse fluviatile deposits grade into and interfinger with 

the finer grained lacustrine deposits of the interior of 

the basin. Rhyolite tuff deposits east and west of 

Glassford Hill suggest correlation of the underlying 

deposits. The tuff on the west side is above gravel and 

below the middle basalt flows. The tuff east of Glassford (near 1,299,500 N., 384,700 E.) is above gravel that 

to the west underlies the upper basalt flows. 

Where exposed in the central part of the basin, the 

fine-grained lacustrine deposits are similar to those exposed to the southeast. East of Granite Creek (pl. 1, 

1,345,000 N., 360,000 E.) these deposits are overlain by 

basalt that is probably about contemporaneous with 

the basalt north of Prescott and with basalt to the 

east (pl. 1, northeast corner). The eroded edges of thin 

nearly horizontal flows in the northeast corner suggest 

that these flows spread out westward on a relatively level 

surface (pl. 1, sec . .A-.A.') after the basin was largely 

filled. At one place (1,354,600 N., 394,000 E.) a tuff bed 

beneath basalt contains large white rhyolite pumice 

lapilli; the tuff is identical lithologically with tuff that 

underlies the upper basalt flows on the south side of 

Glassford Hill. The contemporaneity of the rhyolite 

tuffs, however, has not been proved. 

Basalt at the headwaters of the Verde River (Sullivan Lake, pl. 2) also appears to rest on basin deposits. 

The continuity of the basin and its deposits northwest 

and southeast of Sullivan Lake, however, cannot be 

proved because of absence of subsurface data. Certainly 

the basin is much narrower south of Sullivan Lake than 

elsewhere, if the small exposures of Paleozoic rocks east 

and west of Del Rio Ranch represent the margins of the 

basin; the Paleozoic rocks could be xenoliths in andesite. 

Basalt near Sullivan Lake is part of the basalt northeast of the basin, which to the east is underlain by older 

gravel that contains andesite fragments at the top. 

The relationships of the upper Tertiary( n rocks of 

the basin to older gravel and to andesite are uncertain. 

The andesite plug south of Glassford Hill and the flow 

on the northeast side of the Dells Granite, however, are 

considered contemporaneous and are interpreted as 

probably older than the upper basalt flows of Glassford 

Hill. 

The deposits in Chino-Lonesome basin appear to be 

the result of continuous and contemporaneous deposition in a single basin, but this cannot be proved or disproved because of the extensive cover of Quaternary 

pediment gravel and alluvium. This cover masks possible structural discordances or erosional unconformities within various parts of the basin. 

The sedimentary rocks mapped as part of the Hickey 

Formation in the southwestern part of the Jerome area 

are unquestionably the same as the sedimentary rocks 

in the southeastern part of the Prescott quadrangle and 

probably the same as those in the basin as a whole. 

The sedimentary record for the most part indicates 

drainage into the basin-the coarser material is near the 
84 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

EXPLANATION 

Base of the middle basalt flows (shaded); 

solid line where underlain by orange tuff 

(lined pattern) (outcrop width greatly 

exaggerated) 

u 

D Fault 

Dashed where approximately located; 

queried where doubiful; U, upthrown 

side; D, downthrown side 

Structure contour 

Drawn on base of the middle 

basalt flows 

.5300 

Altitude of base of the middle(?) basalt 

flows in down-faulted block 

1,300,000N 

w 

0 

8 

6 

"' "' 

0 

0 

0 

6 

"' "' 1,310,000 

EXPLANATION 

Base of the upper basalt flows (shaded); 

underlain by tuff and gravel 

Structure contour 

Drawn on base of the upper 

basalt flows 

Outline of base of basalt of Glassford Hill • 5850 

Altitude of basalt-granite contact 

•.!!2..Q9 

Altitude of basalt-alluvium contact, base 

concealed 

•....5..5.QQ 

Altitude of contact of basalt with underlying cinder cone 

0 0 0 0 0 0 0 0 0 

6 6 6 "<t L[) 1.0 

"' "' "' 

0 0 0 0 8 0 0 

6 0 "<t L[) 

"' "' 

/--~~_Q 

( - ~ / -....._" 

\ 5500 \ 1,310,000 

1,300,000 

0 1 MILE 

FIGURE 24.-Structure contour of the base of basalt flows of late Tertiary(?) age north of Prescott. Upper map: base of the middle 

basal't flows, showing outcrops of underlying orange tuff ; lower map : base of the upper basalt flows. 
CENOZOIC ROCKS 85 

margins-but other drainage directions east of the 

Prescott area may mean that the sediments do not all 

belong to the same period. In Tex Canyon (pl. 4, 

1,304,000 N., 435,000 E.) the gravel is composed chiefly 

of Paleozoic rocks, which must have come from the 

north, possibly when drainage was southwestward into 

Chino-Lonesome basin. On the other hand, along the 

eastern margin of Lonesome Valley (roughly between 

1,295,000 N. and 1,300,000 N. and between 410,000 E. and 

420,000 E.) and farther east, the gravel contains fragments of alaskite that must have come £Tom the southwest, possibly after the basin had been filled sufficiently 

for them to be carried across. A northward drainage, 

possibly before formation of the basin, is indicated by 

gravel beneath basalt on Kendall Peak (pl. 4, 1,330,000 

N., 430,000 E.); this gravel is composed solely of Precambrian fragments, although Paleozoic rocks lie a 

short distance to the north. In the Jerome-Clarkdale 

area north of Kendall Peak, gravel beneath basalt of 

the Hickey Formation filled northward -draining channels (Anderson and Creasey, 1958, p. 57, 58). Lehner 

(1958, p. 5'54) considered it to be possibly correlative 

with scattered remnants of once extensive gravel deposits beneath basalt on the Colorado Plateau (Koons, 

1948 ; Price, 1950) ; if so, this gravel may be consider· 

ably older than the gravel in the southern part of 

Chino-Lonesome Valley. 

It is tempting to correlate the thick sequence of 

volcanic rocks in the Chino artesian basin (pl. 1, sees. 

A-A', F-F'/ pl. 2, sees. H-H', J-J'; table 12) with the 

thick sequence of basalt of the Hickey Formation on top 

of the Black Hills. If it is downfaulted Hickey, then 

the overlying basin deposits may have accumulated after 

post-Hickey faulting. The basalt mapped as Hickey 

west of Coyote fault apparently is the same as the basalt 

in the east-central part of the area (pl. 4, sec. B-B'), 

which is tentatively correlated with the basalt that overlies sedimentary rocks of the basin to the west and southwest (pl. 1, sec. A-A'). If basalts of two ages are present, they have not been distinguished. 

The many similarities between Chino-Lonesome basin 

and Verde basin and their deposits suggest a correlation. Arching of the Black Hills and major movement 

on the two bounding faults undoubtedly occurred at the 

same time and may have resulted in simultaneous formation of the two basins. Both basins were filled with 

fanglomerate and finer fluviatile and lacustrine deposits 

interbedded with basalt flows. The basin deposits have 

since been cut by pediments, and the pediments themselves have been dissected during a more recent cycle of 

erosion. The Verde Formation contains Silicoflagellateor Heliodiscoster-like forms (E. B. Leopold, written 

commun., 1958) similar to those in fresh-water limestone in the Paulden quadrangle (seep. 80, this report), 

but it contains an abundance of limestone an~ a paucity 

of rhyolite tuff compared with the deposits in ChinoLonesome basin. Paleozoic limestones surround much 

of the Verde basin but are a:bsent around much of ChinoLonesome basin; this difference may account for the 

difference in carbonate content in the two basins. 

Although rhyolite tuff had not been previously reported 

from the Verde Formation, some was recovered from 

three drill holes (A. R. Still, oral commun., 1956) . 

The occurence of rhyolite tuff in the Hickey Formation (Lehner, 1958, p. 553-554; Anderson and Creasey, 

1958, p. 56) also suggests a correlation of the Hickey 

with the deposits in Chino-Lonesome basin. On the 

one hand, contemporaneity of rhyolite tuffs has not been 

proved, and on the other hand, the rhyolite tuff in the 

Hickey is located in places where its inclusion in the 

Hickey might be questioned (pl. 4, 1,376,000 N., 407,500 

E. and 1,305,000 N., 436,800 E.). 

No definite conclusions as to stratigraphic relations 

and correlations of the upper Tertiary ( ~) rocks have 

been made as a result of the present study. The foregoing discussion is an attempt to point out some of the 

difficulties in correlating these rocks with formations to 

the east. Some of the problems will undoubtedly be 

solved by more fossil finds, by determinations of the 

potassium-argon age of biotite in volcanic rocks, and by 

other methods of study now being developed. The situation may be more complex than is suggested by the two 

formations now recognized to the east. 

QUATERNARY DEPOSITS 

The Quaternary deposits include Pleistocene pediment and younger terrace gravels and Recent gravel and 

alluvium. In Chino Valley, both east and west of Granite Creek, and in many other places, pediment and 

terrace gravels and the Recent material grade imperceptibly into one another. The Recent material has been 

mapped separately only along larger gulches and 

washes. 

PLEISTOCENE GRAVELS 

DISTRIBUTION 

Pediment gravels at one time covered much of the 

Prescott-Paulden area. The largest remnant (figs. 28, 

29) lies east of Glassford Hill ; smaller patches remain, 

mainly around the margins of the basin. Gravels cap 

flat-topped hills-remnants of the main pediment-that 

form a row on each side of Granite Creek from the 

Granite Dells northward to the north side of Chino 

Valley. In the relatively fla.t country southwest and 

east of Drake (northern part of pl. 2), pediment or 

terrace gravels are difficult to differentiate from gravels 

of late Tertiary ( ~) age. Younger terrace gravels are 
86 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

widely distributed along most of the gulches that cross 

the upper. Tertiary ( ~) sedimentary rocks, especially 

along Lynx Creek and the Agua Fria River valleys 

(pl. 1). 

THIOKNEBS AND STRATIGRAPHIC RELATIONS 

The Pleistocene gravels are veneers on pediment and 

terrace surfaces. They are generally 0-25 feet thick but 

locally are as much as 50 feet thick. 

The pediment gravels are a;bout conformable to the 

nearly horizontal upper Tertiary(~) rocks but in a few 

places overlie them with an angular unconformity of 

2°-3°. The pediment gravels overlap the upper Tertiary ( ~) rocks onto the Precambrian and Paleozoic rocks 

in a few places on the north and northeast sides of the 

basin and, locally, in the southern part-for example, 

north of Green Gulch and west of Lynx Creek (pl. 1, 

between 1,285,000 N. and 1,291,000 N.; near 380,500-

381,000 E.; and near 1,292,000 N., 361,000 E.). They are 

overlain by Recent gravel and alluvium only near hills, 

such as Glassford Hill. 

The younger terrace gravels overlie the upper Tertiary ( ~) deposits but at altitudes lower than the pediment 

gravels in any one area. They are locally overlain by 

Recent gravel and alluvial and colluvial material. 

LITHOLOGY 

The Pleistocene gravels are a heterogeneous mixture 

of boulders, cobbles, pebbles, and finer grained material 

derived from Precambrian, Paleozoic, and upper Tertiary(~) rocks. Cobbles and boulders of alaskite and 

gabbro as much as 8 feet long are not uncommon in the 

southern part of the area, where other Precambrian 

rock fragments are pebble to cobble sized. Away from 

the southern margin of the area, few fragments are larger than cobbles, and on the terraces few are larger than 

pebbles and sma.ll cobbles. Sorting is characteristically poor, but some material is sorted. The color ranges 

from dusky red and grayish brown through lighter 

shades of brown and gray. Most pediment gravels are 

dark red or brown, but some pediment gravels and 

many terrace gravels are lighter colored. On aerial 

photographs the pediment gravels on the hills that parallel Granite Creek and on the large pediment remnant 

east of Glassford Hill resemble, in their dark color, 

basalt-capped hills. The dark color is due to iron oxide 

coating on quartz and other grains of the matrix. These 

dwrk pediment gravels contrast markedly with the underlying light-colored silt, clay, and marl of the upper 

Tertiary ( ~) deposits. Other dark-colored gravels are 

aprons of basalt or andesite wround many volcanic 

hills-for example the apron on the northeast side of 

Glassford Hill (fig. 14) . Some of these aprons are ped!-

ment gravels, but many are more recent deposits. 

In the southern part of the area most of the gravels 

are composed of Precambrian rocks that were derived 

from the south or west or from reworking of the upper 

Tertiary(~) rocks. Along the eastern margin (pl. 1) 

the gravels contain Precambrian and Paleozoic rocks 

that were derived from the east. In the northern part 

of the area (pl. 2) the gravels are composed of Paleozoic 

and less abundant Precambrian rocks or of upper Tertiary ( ~) volcanic rocks. Near basalt or andesite masses, 

volcanic fragments are very abundant but generally become scarce away from the volcanic rock outcrops. The 

gravels contain fragments of Mazatzal Quartzite near 

outcrops of this formation and for some distance to the 

northeast of these outcrops, where they have in part 

been derived from upper Tertiary ( ~) gravels that contained fragments of the quartzite. 

In the southern part the terrace gravels are subangular to subrounded. Lack of rounding is due in part 

to the strongly foliated or jointed character of the Precambrian rocks. Angular cobbles and boulders in gravels near the southern margin of the basin probably represent upper Teritary ( ~) material that accumulated 

on steep alluvial fans and that was let down during 

erosion of the fanglomerate without being moved far. 

The large boulders of alaskite and gabbro on flat pediment surfaces several miles from higher Precambrian 

hills probably attained their present positions in this 

way, although they could have been carried there during flash floods. 

RECENT ALL UVIU:M 

DISTRffiUTION 

The distribution of the larger areas of Recent alluvium is shown on plates 1 and 2. In addition narrow 

ribbons occur along most of the smaller gulches and 

washes, especially where they cross the upper Tertiary ( ~) or some areas mapped as Pleistocene gravels. 

Finer grained alluvium covers the flats bordering drainage lines; coarser material is in the stream beds, and 

both coarse and fine colluvial material covers slopes between pediment or terrace surfaces and the valley bottom. Andesitic and basaltic alluvium surrounds hills 

of upper Tertiary ( ~) volcanic rocks, effectively conceals underlying rocks, and merges with pediment and 

younger gravels. 

THICKNESS AND S.TRATIGRAPHIC RELATIONS 

The thickness of the alluvium varies, and its maximum thickness is unknown. Presumably the deposits 

are thin, as most streams are degrading, but where there 

is an abrupt decrease in gradient, small alluvial fans are 

being built up. This is especially true east of Glassford 

Hill, where small gullies descend abruptly from the 
STRUCTURE 87 

pediment surface to the alluvial flat along the Agua Fria 

River and its tributaries. Where gullies dissect the al~ 

!uvial flats, 5 to 10 or, locally, 20 feet of fine-grained alluvium is exposed. The alluvium is separated from the 

underlying upper Tertiary ( ~) lacustrine deposits by a 

few inches to a few feet of reddish-brown gravel. Along 

Coyote Wash (pl. 1, 1,317,000 N., 391,500 E.) a gully 

25 feet deep in the lacustrine deposits has exposed an 

older gravel-lined channel that is filled with fine-grained 

alluvium (fig. 25). River gravels where placered along 

Lynx Creek, are as much as 25 feet thick. 

FIGURE 25.-Recent alluvium in channel cut in fine-grained sedimentary 

rocks of late Tertiary ( ?) age and exposed in a recent gully along 

Coyote Wash (pl. 1, 1,317,000 N., 391,500 E.). To the left, the 

channel extends nearly to the bottom of the gully. Rounded cobbles 

line the bottom of the channel, but much of the overlying material 

is fine-grained alluvium-largely clay. Note the light-colored wellbedded character of the older deposits, which oonsist of sand, silt, 

clay, and marl ; some marly layers are nearly white. 

LITHOLOGY 

The fine-grained alluvium 'is gray or yellowish brown 

to brownish black. The darker color is characteristic of 

alluvium derived from upper Tertiary ( ~) basalt or from 

some of the mafic Precambrian rocks. Light yellowishbrown colors are common along the Agua Fria River 

and its tributaries, where the alluvium has been derived 

from fine-grained sedimentary rocks of late Tertiary ( ~) 

age. Much of the alluvium is composed of clay, silt, and 

fine sand, and locally it contains abundant plant material. Coarser material forms thin layers or fills 

channels. 

The coarser material, which is concentrated along 

drainage channels, is composed of sand, pebbles, cobbles, some silt and clay, and scattered boulders several 

feet in diameter. Many fragments are subrounded. 

Sorting and stratification are generally absent. Coarse 

colluvial gravels cover some slopes below pediments and 

may largely conceal underlying fine-grained sedimentary rocks of late Tertiary ( n age (fig. 28). 

AGE 

The pediment gravels were laid down after the upper 

Tertiary ( ~) rocks were deposited and the upper part 

removed by erosion. They were probably deposited 

after the last faults that cut the younger of the upper 

Tertiary ( ~) rocks, although a fault scarp probably of 

Recent age can be traced on aerial photographs along 

the north side of Big Chino Wash for more than 20 

miles from the northwestern part of the area (pl. 2, 

1,437,200 N., 330,000 E.). On the basis of the amount of 

dissection that the pediments have undergone, of the 

amount of downcutting through Precambrian rocks below the pediment surface, and of the presence of mammoth teeth in younger terrace deposits, the pediment 

gravels are considered Pleistocene in age. 

The terrace gravels are younger than the pediment 

gravels, and some of the lowest ones may be of very 

recent age. A mammoth tooth, found by G. H. Hazen, 

Water Resources Division, U.S. Geological Survey, in 

terrace gravels 50-100 feet above Granite Creek (pl. 1, 

near 1,301,200 N., 344,200 E.) was identifi3d by C. L. 

Gazin of the National Museum as M ammuthus sp.; it 

indicates ·a Pleistocene or possibly a late Pleistocene 

age. A mammoth tooth ( ~) was found in clay in the 

southeastern part of the area (pl.1, 1,309,400 N., 399,300 

E.) during the present investigation. A Pleistocene 

horse (genus Equus) was reported by Hay (1927, p. 55) 

from Lynx Creek (location not given) probably from 

alluvium deposited during erosion of the upper Tertiary ( ~) rocks. 

Some alluvium is Recent in age. Small nonpetrified 

mammal bones, associated with the remains of bugs, 

twigs, droppings, and carbonized wood fragments, occur 

in silt and clay in the bottom of valleys tributary to the 

west side of the Agua Fria River (southeast part of 

pl. 1) and in coarser gravel underlying the alluvium 

5-10 feet below the top of the gullies. 

STRUCTURE 

The major structural features in the Prescott-Paulden 

area are tight folds, shear zones, and strike faults produced by major deformation in Precambrian time; 

normal faults, sharp monoclines, and gentle folds were 

produced by less severe disturbances during the period 

since the close of the Paleozoic Era. 

STRUCTURE OF OLDER PRECAMBRIAN ROCKS· 

Precambrian deformation in the Prescott-Paulden 

area may have been the result of one period of orogeny 
88 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

which included intrusion of igneous rocks, preceded and 

followed by deformation. It produced isoclinal folds, 

foliation parallel to bedding, and strike faults in many 

of the Alder Group rocks and foliation and shear planes 

in intrusive rocks (S-tectonites). In the Mazatzal 

Quartzite, deformation produced open folds (B-tectonites) and no foliation. 

The structure of the Precambrian rocks of Arizona 

has been summarized by Anderson (1951) and by Anderson and Creasey ( 1958, p. 45 and 62) . They stated 

that the degree and type of metamorphism of the older 

Precambrian rocks varies from place to place and ranges 

from thermal metamorphism related to granitic intrusions to mild or intense dynamic metamorphism but 

that the structures are similar in a broad way. The folds 

trend north, northwest, and northeast and indicate an 

east-west compression that may have occurred during 

a single period of orogeny. 

Until the recent proof of a pre-Alder granitic intrusion (see footnote 7, p. 49), only one major orogeny 

in Arizona during the Precambrian had been proved; 

it separated older Precambrian rocks from younger 

Precambrian rocks in northwestern and southeastern 

Arizona. In central Arizona, where younger Precambrian rocks are absent, it separated older Precambrian 

rocks from Paleozoic rocks. Wilson ( 1939) called it the 

Mazatzal revolution, because it involved the Mazatzal 

Quartzite. He stated that no pre-Mazatzal deformation or granite has been recognized, although a minor 

unconformity separated the quartzite from older rocks. 

Hinds (1936, p. 100), on the other hand, suggested two 

periods of orogeny and accompanying granitic intrusion : one prior to and the other after the accumulation 

of the Mazatzal Quartzite. 

It is unlikely that only one period of major orogeny 

occurred in the tremendous length of time represented 

by the Precambrian, but little evidence for more than 

one has been found. In the Paulden quadrangle the 

abundance and size of the quartz pebbles in the conglomeratic facies of the Mazatzal Quartzite, the very 

low grade of metamorphism of the quartzite, and the 

absence of granitic rocks or quartz veins intruding the 

quartzite suggest that the Mazatzal was deposited after 

the major deformation and granitic intrusions in this 

area. Because the quartzite is in fault contact with 

the Alder Group, the difference in degree and type of 

deformation and metamorphism does not prove a preMazatzal orogeny. 

STRUCTURE OF THE ALDER GROUP 

Alder Group rocks occur in small windows in younger 

rocks or are so isolated by intrusive rocks or separated 

by faults or zones of intense shear that stratigraphic relations are uncertain. Consequently, the broad structural pattern has not been unraveled, although structural continuity apparently exists within individual 

"blocks." 

Northeast-trending structures occur in the discordant 

Chaparral fault zone, a zone characterized by distributive shear and bounded by Spud and Chaparral faults 

(pl. 1, southeast corner). Elsewhere, Precambrian deformation produced generally north-trending steeply 

dipping structures: (1) isoclinal folds, strike faults, 

and foliation parallel to bedding in the Alder Group 

and (2) foliation and shear planes in intrusive rocks. 

Most postintrusion structures are about parallel to pre~ 

intrusion ones. The probable large displacement on 

the Chaparral fault zone makes any correlation of the 

stratigraphic units and of the structure on the two sides 

of the zone highly questionable. For this reason, the 

structures within and west of the shear zone are discussed separately. 

Deformation, which may have been part of a single 

orogeny, probably preceded and followed intrusion of 

igneous rocks. Xenoliths of foliated volcanic rocks in 

unfoliated Government Canyon Granodiorite prove 

that some structures are preintrusive. The preintrusion structures in the Alder Group are isoclinal folds 

and foliation that, except in the noses of folds, are about 

parallel to bedding. _ Postintrusion structures are foliation, distributive shear, and strike-faults. The northtrending structures may have been produced during successive surges, and the northeast-trending structures in 

the Chaparral zone may have formed slightly later. 

West of the Chaparral zone postintrusion structures in 

intrusive rocks are parallel to structures in the volcanic 

rocks that are presumed to antedate the intrusive rocks. 

Northeast-trending foliation and shear planes in volcanic and intrusive rocks in the Chaparral zone are discordant to the north-trending structures both east and 

west of the shear zone. A few minor zones of northeast-trending shear cut north-trending structures in 

volcanic rocks east and west of this zone; none were observed cutting north-trending structures in intrusive 

rocks outside the zone. The relation of north- to northeast-trending postintrusion structures, therefore, is uncertain. 

STRUCTURE EAST OF THE CHAPARRAL ZONE 

The Alder Group east of the Chaparral zone includes 

the Spud Mountain Volcanics in the southeastern corner 

(pl. 1), the Indian Hills Volcanics in the east-central 

part (pls. 1, 2); and probably the unnamed tuffaceous 

rocks of the Alder( n Group farther north (pl. 2). 

The Spud Mountain and Indian Hills Volcanics are 

part of a large structural block in the western part of 
STRUC'I'URE 89 

the Jerome area (Anderson and Creasey, 1958, p. 71-

74). The unnamed tuffaceous rocks of the Alder(~) 

Group are separated from these volcanics by intrusive 

rocks. 

Spud Mountain Volcanic8.-The Spud Mountain 

Volcanics were isoclinally folded prior to the formation 

of the northeast-trending Chaparral zone. Near Spud 

Mountain the strike of bedding and early foliation 

ranges from N. 20° E. to N. 45° W., but the general 

strike is about north. On Spud Mountain the strike 

swings from north toN. 45° W., and close to the Spud 

fault it swings back to the northeast. As bedding and 

foliation both make the swing, they were probably 

folded by drag on the major fault zone. Narrow zones 

of foliation, zones of breccia, or single planes of shear 

that strike N. 45° E. toN. 65° E. n~ar Spud Mountain 

are clearly at an angle to early foliation. The structure near Spud Mountain is probably an anticline'; a 

syncline may lie to the east (pl. 1, sec. E-E') ; both 

probably plunge gently southward. No evidence of the 

direction that tops of beds face was found near Spud 

Mountain, but Anderson and Creasey ( 1958, p. 72) 

found sufficient evidence nearby to propose this interpretation of the structure. 

Indian Hill8 Volcanic8 and wnnamed tuffcweows rock8 

of the Alder(.~). Group.-In the east-central part of the 

Prescott-Paulden area, lithologic units trend north and 

northwest, as do sparse bedding in the volcanics and 

foliation in volcanic and intrusive rocks. Dips are 

vertical to steeply east or west. .Small drag folds in 

the tuff unit of the Indian Hills Volcanics plunge north 

25°-35°, but drag folds in the unnamed tuffaceous rocks 

plunge south 45°-60°. Although foliation and drag 

folds in the volcanics are for the most part parallel to 

foliation and mineral streaking in the adjacent intrusive rock~, the drag folds and some foliation are considered preintrusion because foliation and drag folds in 

the unnamed tuffaceous rocks in upper King Canyon 

(1,389,500 N., 382,400 E.) are cut at a slight angle by an 

alaskite dike. 

STRUCTURE WEST OF THE CHAPARRAL ZONE 

Green Gulch V olcanic8.-Lithologic units and structures in the Green Gulch Volcanics trend north ward except next to the Chaparral fa.ult. Here gabbro (mostly 

south of the map area) and the volcanics have been 

dragged into the fault, and northeast foliation cuts the 

earlier structures in the volcanics. West of the fault, 

bedding and foliation are steep and, with few exceptions, 

dip west. Scattered determinations of the directions in 

which tops of beds face suggest that, except for minor 

reversals, the beds face west. Sparse b lineation, formed 

by intersection of foliation and bedding, plunges north 

10°-25°, parallel to the plunge of minor drag folds. The 

a lineation was observed in a few places. Steeply northplunging crenulations in foliation and bedding are probably related to later cross fractures. Based on the few 

determinations, the formation (at least east of 386,000 

E.) is interpreted as the east limb of a north-plunging 

tightly folded syncline. Lineation in the western outcrops of the formation (near and east of 380,000 E.) 

plunges south or southwest 40°-75°. Some of it is 

streaking on a plane of shear that is postintrusion in 

age; it is parallel to sparse lineation in associated intrusive rocks. Lenticular and dikelike masses of alaskite, aplite, and gabbro, many too small to show on the 

geologic map, trend northward, parallel to the structural and lithologic trends in the tuffaceous rocks. Some 

of these intrusive rocks have a north-trending foliation. 

Tewa8 Gulch F 01'11Uttion.-The largest structural unit 

within the Prescott-Paulden area is the Texas Gulch 

Formation in the south-central part. The formation is 

bounded on the east by intrusive rocks and apparently 

separated on the west by a sheer zone from the unnamed basaltic flows of the Alder ( ~) Group. Data 

suggest a south-plunging syncline, within which are 

numerous smaller isoclinal or near isoclinal folds. 

Reasons for assuming a major syncline are as follows: 

( 1) Lineation, believed to be the b direction of the 

structural coordinate system and related to deformation 

that produced the folds, plunges southward; (2) the 

outcrop of the formation progressively widens to the 

south ; ( 3) tops of beds on the east generally face west 

(fig. 4); and ( 4) unmapped beds of gray staurolite(?) 

schist and conglomerate and float of jasper-magnetite 

are present on the west (near 1,285,400 N., 353,000 E.). 

.Jasper-magnetite and some of the conglomerate are 

identical to the eastern beds of jasper-magnetite and 

conglomerate; the schist may represent metamorphosed 

gray slate such as is associated with the eastern beds of 

conglomerate. 

Lineation consists of plunge of minor drag folds, 

intersection of cleavage and bedding, and elongation of 

pebbles. The pattern of drag folds, graded bedding, 

channeling, and cleavage bedding relations give consistent information on the direction in which tops of 

beds face, especially in the southern part of and immediately west of the unit containing jasper-magnetite 

beds. North of 1,285,000 N. the pattern of drag folds 

indicates numerous reversals of dip. Identical beds of 

conglomerate on both sides of the unit containing jaspermagnetite beds complicate the picture of a south-plunging syncline. The conglomerate bed west of this unit 

has been repeated by folding. Along the southern border of the area (near 1,274,000 N., 358,000 E.), rhyolite 

crystal tuff caps small hills, and its contact with the 

underlying andesitic rocks plunges south as do minor 
90 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

folds in the tuff. Foliation, lineation, and boudinage 

structure in a few lenticular and dikelike masses of intrusive rocks, too small to map, indicate postintrusion 

deformation. 

Because outcrops of the Texas Gulch Formation along 

Granite Creek south of the Verde River (pl. 2) are 

too small, its structure or relations to the formation in 

the southern part of the area cannot be determined. 

Beds in the western outcrops strike east and dip south, 

whereas foliation trends north. In the eastern outcrops, 

drag folds plung-e 50°~70° S. Intense north-northeast 

foliation parallels the fault that brought the formation 

in contact with the Mazatzal Quartzite; but the Mazatzal is not foliated. 

Unna'J1Wd volcarnic r()cks of the Alder(.~) Group.-

The unnamed basaltic flows near 350,000 E. in the southern part of the area (pl. 1) are separated from the Texas 

Gulch Formation by a shear zone. All the other masses 

of unnamed volcanic rocks in the southern part of the 

area are separated from one another by intrustive rocks. 

Foliation and zones of distributive shear in igneous 

rocks that intrude the volcanic rocks are about parallel 

to foliation in the volcanics. 

.Between the largest mass of gabbro on the west and 

alaskite porphyry on the east, deformation of volcanic 

and intrusive rocks was erratic. The unnamed basaltic 

flows and much of the alaskite are nonfoliated, except 

along the east and west margins and along ]}arrow zones 

within them. Distributive shear was more intensive in 

and adjacent to the unnamed tuffaceous rocks, especially 

in the northwestern part, where deformation resulted 

in mechanical mixing of the rocks and in the formation 

of narrow dikelike masses of alaskite augen gneiss and, 

locally, of mylonite. Except in one area near 1,291,000 

N., 376,000 E., where trends are north-northwest, bedding, lithologic units, and foliation in volcanic and intrusive rocks trend northward and are vertical or dip 

65° or more west. A few small north-plunging drag 

folds in tuff may be related to earlier deformation. Most 

lineation is postintrusion, it .plunges south 35°-60° and 

consists of mineral streaking and intersection of two 

cleavages or of bedding and foliation. 

In the unnamed tuffaceous rocks along 364,000 E., 

bedding and foliation strike northward and dip steeply west or are vertical. The pattern of a few northplunging drag folds indicate east-facing beds. North 

of 1,292,000 N., steeply south-plunging lineation of postintrusion origin parallels lineation in the Prescott 

Granodiorite to the west. East and west contacts with 

intrusive rocks are largely narrow zones of shear. 

Bedding, flow-banding, and foliation in the unnamed 

basaltic flows near 350,000 E. trend northward and are 

vertical or dip more than 80° west. The direction that 

tops of beds face was determined in only one place 

where graded bedding in a tuffaceous bed indicated 

that the bed faces east. Breccia fragments have been 

stretched in some beds, but considerable areas of the 

rock are massive. Deformation may have been preintrusion, as most of the gabbro is massive. 

The northern part of the westernmost mass of unnamed volcanic rocks trends northward, except at its 

northern end, where its trend is northeast at an angle 

to foliation in the volcanics. The northeast trend is 

probably due to a fault or shear zone. A pronounced 

lineation plunges gently south in places; and elsewhere 

a faint lineation plunges steeply north or south; the 

structural significance of the lineation is unknown. In 

the southern part of the volcanic rocks, foliation and 

bedding trend nort{heast ; the trend becomes more easterly to the south. Less intense postintrusion deformation in the area may account for the more easterly 

strikes. Lit-par-lit injection of granodiorite along 

straight and contorted beds and inclusions of schistose 

and folded volcanics in the granodiorite prove deformation occurred prior to intrusion of the granodiorite. 

The unnamed basaltic flows north of the large outcrop of Mazatzal Quartzite (pl. 2) are mostly massive 

but are locally cut by a very faint foliation. The volcanics are probably separated . ftbm the quartzite by a 

fault. 

STRUCTURE IN THE CHAP ABRAL ZONE--THE. CHAP ARBAL VOLCANICS 

AND CHAPARRAL AND SPUD FAULTS 

Rocks of the Chaparral Volcanics 3/re separated from 

other formations by faults, and their stratigraphic position in the Alder Group is not known. The volcanics and associated intrusive rocks probably occupy a 

wide fault zone that is characterized by distributive 

shear. The bounding faults, foliation, and lithologic 

units trend northeast at an angle to the earlier northward trends in adjacent rocks. Deformation within 

the zone was so intense that some alaskite was reduced 

to augen gneiss or to a dense mylonite. Most contacts 

are mechanical, and volcanic and intrusive rocks grade 

into one another owing to mechanical mixing. 

The volcanic rocks were probably folded during an 

earlier period of deformation that produced northtrending structures in adjacent rocks. This early period 

is suggested by a faint north-trending foliation in the 

northwest part of the volcanics, and by contorted bedding and bedding at an angle to the northeast foliation 

locally found in tuff that lies between alaskite and the 

Prescott Granodiorite. 

Northeast-trending foliation is the dominant structural feature within the zone. It dips 65° W. to 80° 

E., the dips to the west predominating. Lineation in 
STRUCTURE 91 

both volcanic and intrusive rocks is related to the deformation that produced the northeast structure. It 

plunges southward 10°-35° and consists largely of Inineral streaking, but some of it consists of the plunge of 

minor drag folds. A few north-plunging axes of folds 

in crenulated foliation are due to later cleavage. In 

the eastern andesitic tuff, a gentle north-plunging pencil structure was formed by the intersection of northeast foliation and later cleavage. 

The Chaparral and Spud faults (pl. 1, sees. B-B', 

E-E') bound the Chaparral zone. This zone strikes 

about N. 30° E. within the map area, but to the southwest the trend is about N. 50° E. In detail within the 

map area, the Chaparral fault trends about N. 25° E. 

and the Spud fault trends about N. 35° E. The faults 

may dip steeply west if their dips are parallel to the 

dip of foliation in volcanic and intrusive rocks within 

the zone. The northwest side of the zone moved northeastward relative to the southeast side, and in detail 

similar drag is found along all the narrow zones of late 

foliation within and adjacent to the Chaparral zone. 

Displacement may be as much as several miles. 

To the northeast the fault zone is buried and does 

not reappear near Indian Hills (Mingus Mountain 

quadrangle, 1,324,000 N., 410,000 E.) along its strike 

extension. A fault zope of this magnitude would be 

unlikely to die out in this short distance; unless offset 

by a fault, its strike must continue to change _to a more 

northerly and then a northwesterly direction These 

changes would bring the fault zone west of the low 

hills in the east-central part of the area, where the 

structures trending north-north west in the volcanic and 

intrusive rocks may be related to the zone. 

STRUCTURE OF THE MAZATZAL QUARTZITE 

Precambian deformation of the Mazatzal Quartzite 

(pl. 2) produced open folds and local zones of small 

tight folds and small-scale thrusts but no foliation. 

As the formation is separated from Alder Group rocks 

by faults (1,402,300 N., 346,700 E.; and 1,393,300 N., 

353,500 E.), its stratigraphic position and the relation 

of its structure to that of the Alder Group are unknown. 

The major structures in the Mazatzal Quartzite (fig. 

5; pl. 2, sec. G-G') are two northeast-trending anticlines 

that plunge gently southward. The anticlines are separated by a fault. The fault is not exposed, but its 

trend and approximate location are determined by 

structural discontinuity of the rocks on the two sides 

of the fault and by the close proximity of discordant 

outcrops of the upper argillite. The fault presumably 

continues northwest and separates the Mazatzal from 

the unnamed basaltic flows of the Alder ( ? ) Group 

(1,393,300 N., 353,5-00 E.). 

A conspicuous feature of the western anticline is that 

1

ms-447 0-----00----rT 

it plunges to the north on the south end of the exposure 

and that its eastern limb in this area swings abruptly 

to the southeast and has nearly vertical dips. Similarly, 

the western limb swings a way from the axis toward 

the southwest. These features suggest that the original 

structure, formed by northwest-southeast compression, 

was later deformed by forces acting at right angles to 

the earlier forces. Wilson ( 1939, p. 1156) explained 

the steeply upturned structure as caused presumably 

by a northwest-trending fault to the south whose trace 

is concealed by alluvium. 

The eastern limb of both anticlines is somewhat 

steeper than the western limb. Dips of the western 

limbs average about 20° in the eastern anticline and 

30° in the western anticline, except in the northwestern 

exposures, where dips average about 55°. 

East of the crest of the western anticline, a small 

thrust fault (Wilson, 1939, pl. 3, fig. 1, p. 1156) cuts 

the quartzite along Granite Creek ( 1,386,600 N., 355,-

000 E.; indicated by symbol, fig. 5). Slickensides and 

some breccia formed, and small drag folds lie above 

the plane of the thrust to the east (1,386,000 N., 355,-

300 E.) and beneath the plane of the thrust to the west 

(1,386,700 N., 354,700 E.); displacement is probably 

minor. 

Along the nort~-trending part of Granite Creek 

(1,389,600 N., 351,300 E. to 1,391,200 N., 351,000 E.) 

and for several hundred feet to the east, the rocks are 

shattered (the area is indicated by joint symbol on 

fig. 5). Slickensides formed on small thrust faults 

that parallel, or nearly parallel, bedding planes; breccia 

occurs along steeply dipping joints. Except in one 

place the beds dip consistently about 30° W. and can 

be traced across brecciated joints. This shattered area 

may be the place where Wilson (1939, p. 1155) believed 

that his measured section was ended by a fault. It is 

doubtful, however, that major displacement occurred; 

the upper argillite a short distance to the west has not 

been displaced, and the beds exposed to the south in 

the west-flowing part of Granite Creek are not affected. 

The shattering is too irregular in pattern to have been 

caused by a fault; it may be due to intrusion of an underlying andesite plug of late Tertiary ( ? ) age or to 

collapse following withdrawal of andesitic magma. 

Steep reversals of dip occur at several places-in 

the extreme southeastern part, in the southwestern part 

(near 1,387,000 N., 348,000 E.), and on the east side of 

Granite Creek at the north end of the shattered zone. 

Some of these may be due to intrusion of andesite. The 

one east of Granite Creek is a tight east-trending fold 

about 200 feet wide. Along the south edge of the fold, 

beds are vertical and are marked by slickensides, by 

breccia, and by gouge containing ellipsoidal "pebbles" 
92 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

of quartzite. The east-trending fold does not continue 

to the west side of the creek. 

The Mazatzal Quartzite formed topographic highs 

during several periods since the Precambrian; during 

Cambrian and Devonian times, when both the Tapeats 

Sandstone and Martin Limestone cut out against it, and 

during Late Tertiary ( ~) times, as proved by the presence of pebbles of the quartzite in gravels near Hell 

Canyon and beneath basalt in the extreme northeast 

corner of the quadrangle. Much of the quartzite today 

stands above the surrounding younger formations. 

Whether it has remained as a monadnock, been exhumed at various times, or been successively uplifted is 

not known. In places it now stands at least 150 feet 

above outcrops of the Redwall Limestone. As pebbles 

of the Mazatzal have not been observed in adjacent Redwall Limestone and as the Red wall does not obviously 

cut out against the Mazatzal, it seems likely that the 

area underlain by the quartzite was relatively uplifted 

in post-Paleozoic times. This conclusion is supported 

by the steep dips of the upper Martin where it abuts 

against the Mazatzal south of Granite Creek; these dips 

may be due partly to compaction and initial dip. 

STRUCTURE IN THE INTRUSIVE ROCKS 

Most of the structures in the intrusive rocks in the 

area have been mentioned in the discussion of the structure of the Alder Group. Brief srinnnaries and additional data are given here. 

Many of the intrusive rocks have been foliated, in 

places intensely so; lithologic trends and structures are 

about concordant to north-trending structures in the 

volcanic rocks, to northeast-trending structures in the 

southwestern part, or to the discordant northeast-trending structl.~res in the Chaparral zone. Many intrusive 

masses form narrow lenticular sill-like or tonguelike 

masses within the volcanic rocks. Small lenses or 

tongues of gabbro are about as abundant as basaltic 

flows for about 1,000 feet west of the tongue of gabbro 

that partially splits the volcanic rocks near 350,000 E. 

in the southern part of the area. Discordant-appearing 

contacts-for example, north and south of the gabbro 

near 1,289,000 N., 374,000 E.-may be more apparent 

than real, as narrow prongs of volcanic rocks extend 

into the gabbro and vice versa owing to ipjection or to 

later distributive shear. 

Where the intrusive roeks are relatively undeformed, 

intrusive breeeias are widely preserved and indieate 

magrnatie stoping. Good examples can be seen in alaskite porphyry along Charcoal Gulch and along Green 

Gulch near its junction with Charcoal Gulch in the 

southeastern part, in the Government Canyon Granodiorite in the southwestern part, and in the Prescott Granodiorite in the east-central part (pl. 1). 

Aerial photographs reveal a north-trending lineation 

in the largest mass of alaskite porphyry and, to a lesser 

extent, in the largest body of alaskite. This lineation is 

not particularly evident on the ground; it is probably 

eaused by a greater density of vegetation along faults, 

joints, or shears because of more abundant soil and 

water where the rocks are broken. A few north-trending zones of sheared or foliated alaskite separating massive alaskite support this conclusion. 

Most gabbro bodies, particularly along their east and 

west margins, are foliated, and the foliation parallels 

their northward trends. The two largest masses, however, also have a northeast- to east-trending planar 

structure, which may be partly caused by crystal settling. Faint foliation, joints, shear zones, and quartz 

veins parallel to the layering suggest that some of the 

layering is due to postintrusion deformation and metamorphism. Some postinstrusion structures may be tension and thrust fractures related to deformation that 

produced the north-trending distributive shear. 

Gabbro, Prescott Granodiorite, and alaskite masses 

within the Chaparral zone were probably dragged into 

the shear zone and rotated to their present position, although preexisting northeast-trending structures could 

have guided the intrusions. 

Post-Precambrian faults cut the older Precambrian 

rocks, but where Paleozoic or younger rocks are absent, 

they are difficult to recognize. Gouge along fault or 

shear zones is interpreted as indieative of post-Precambrian movement, as gouge apparently was not produced 

during or before the deformation that formed the Chaparral zone. Gouge, breccia, and shears, some along lineaments that shows up on aerial photographs, were observed between the Government Canyon Granodiorite 

and the second largest mass of gabbro (north end), in 

the Prescott Granodiorite in Miller Valley (near 1,292,-

600 N., 333,000 E.) and about half a mile north (near 

1,303,000 N., 324,500 E.) and half a mile west (west of 

quadrangle) of Forbing Park, and in the Dells Granite 

near the junction of Routes 89 and 89A. These zones 

cut some quartz and tourmaline veins; they also parallel 

north-northeast joints in the Prescott Granodiorite and 

Dells Granite (fig. 14). The joints may have formed 

at the same time as the gouge-filled shears, or recurrent 

movement may have occurred along them. Parallelism 

of the north-northeast and ·west-northwest joints in 

Paleozoic rocks to the north to the major joints in the 

Dells Granite suggest a common age, but the parallelism 

may be fortuitous; the joints may be related to cooling 

and crystallization of the granite. The steeply dipping 

major system of joints-those trending north-northeast 

and "·est-northwest-in the Dells Granite is illustrated 

on figure 26, which also shows aN. 25° W. nearly ver-
D 

· 0-1 percent 

~ L_d 

1-2 percent 

STRUCTURE 

EXPLANATION 

2-3 

-

percent 3-4 percent 4-6 percent 

ID 

6-8 percent 8-10 percent 10-12 

-

percent 12-14 

-

percent 

FIGURE 26.-Contour diagram of 274 joints in the Dells Granite; the poles are plotted on the lower hemisphere. 

93 
94 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

tical set and a few gently dipping (0°-50°) joints that 

strike about parallel to the major system. The gently 

dipping joints may be more abundant than appears, because little attention was paid to them· in the field. 

STRUCTURE OF PALEOZOIC AND CENOZOIC ROCKS 

Major post-Paleozoic structural features are shown on 

the structure contour map of the Paulden, Clarkdale, 

and Mingus Mountain quadrangles (pl. 5) . Structures 

in the Prescott quadrangle are not shown, because Paleozoic rocks have been eroded from all but the extreme 

northeast corner. Structures in the Clarkdale and 

Mingus Mountain quadrangles are included to illustrate 

the regional setting. The contour of the base of the 

Red wall Limestone eliminates the effect of the topographic high of Mazatzal Quartzite (pl. 2) that resulted in nondeposition of the Tapeats Sandstone and 

most of the Martin Limestone. Within the area underlain by the Mazatzal, some irregularities may be due 

to ·forcible intrusion of andesite (notably near 1,400,-

000 N., 356,500 E.) or to subsidence due to withdrawal 

of andesitic magma. 

Although the Paulden quadrangle lies largely south 

of the Mogollon Rim, the present boundary of the Colorado Plateau, and most of the younger Paleozoic rocks 

have been stripped from it, structurally this area belongs to the Plateau province; the rocks are generally 

flat lying, having a gentle north to northeast dip 13 interrupted by shallow folds, sharp monoclines, and 

faults. 

The general north to northeast regional dip of the 

Paleozoic rocks of north-central Arizona is interrupted 

in the Paulden quadrangle (pl. 5). Interruption of the 

regional dip by west-facing Bull Basin monocline resulted in a northwest-plunging anticline that meets 

southwest-plunging Black Mesa anticline near the center of the quadrangle. Black Mesa anticline is bounded 

on the northeast by Limestone Canyon monocline and 

on the southwest 'by Big Chino fault or monocline. 

From Black Mesa anticline the rocks dip gently eastward across the northern part of the quadrangle. The 

rocks are also deformed along other monoclines and 

disrupted by faults. Structural relief along the eastern 

margin is about 3,250 feet; along the northern edge, 

2,750 feet; along the southeastern anticline, 1,500 feet; 

and along Bla.ck Mesa anticline, 1,000 feet. Structural 

relief along the southwest side of this anticline is at 

least 1,400 feet; and south ot' here along the western 

margin of the quadrangle, 1,500 feet. 

For purposes of description the headings "Older 

structure" and "Younger structure" are used. Only 

13 The absence of dip and strike symbols on the map (pl. 2) generally 

indicates that dips are less than 10°. 

those structures that clearly deform the rocks of late 

Tertiary ( ~) age are called younger structures. 

OLDER STRUCTURE 

MONOCLINES 

AlthouglrSmaller in size, monoclines in the Paulden · 

quadrangle exhibit many of the features characteristic 

of the monoclines of the Colorado Plateau. Many of 

the terms used by Kelly ( 1955) in his discussion of 

monoclines are used in this report ; some types of monoclines are illustrated in figure 27. 

Simple monoclines 

With regional dip 

Opposed to regional 

dip 

___ /Anticlinal bend 

~Synclinal bend 

/Broad anticlinal bend 

""'\sharp synclinal bend 

With no,mal faults ~ ~ 

Broad (Kaibab) type 

Horst type 

After Kelley, (1955, figure 2) 

FIGURE 27.-Variations of monoclines in cross sections. 

Monoclines are characterized by great ratio of length 

to wic\th; the length may be measured in miles, the 

width in a few hundred feet. Most of the monoclines 

in the area are exposed for less than ·2 miles. The 

longest one is more than '6 miles long; one has been 

traced for more than 17 miles, largely northwest of 

the quadrangle. Most of the monoclines are tight and 

where poorly exposed may be confused with drag along 

a fault. Sharpness of flexure, especially of synclinal 

bend, is characteristic; a bed may . change from nearly 
STRUCTURE 95 

horizontal to vertical within a few inches. Anticlinal 

bends are generally broader. The monoclines are 

straight, curved, or branching and include double monoclines-broad (Kaibab) or horst types (fig. 27). Most 

of them trend northwest or north; a few small ones 

trend northeast to east ; they face northeast, south west, 

or south. Many are associated with faults. They cannot be traced across Precambrian rocks, and small ones 

are difficult to trace in massive rocks such as the Redwall Limestone. The Verde monocline is a horst type of 

structure; Black Mesa anticline might he described as 

a broad (Kaibab) type of structure. 

Limestone Canyon morvooline.-Limestone Canyon 

monocline (pl. 2, sees. B-B', C-C', H-H'; pl. 5) lies on 

what appears to be the northeast side of Black Mesa 

within the Paulden quadrangle, although to the northwest it actually runs approximately through the middle 

of the mesa. The monocline faces northeast and has 

been traced from about half a mile southeast of Lower 

Limestone Tank (1,452,700 N., 337,300 E.) for more 

than 17 miles to the northwest. At its northwest end 

(north of the center of Piccacho Butte quadrangle, 

fig. 1), it is buried by basalt of late Tertiary ( ~) age. 

At its southeast end it is buried by gravel and apparently dies out. Throughout its exposed length the zone 

of deformation is less than 1,000 feet wide. Martin, 

Redwall, and Supai beds are exposed along the structure. Dips range from about 30° to vertical; the strata 

northeast of the monocline are about horizontal or dip 

gently eastward; those southwest of it are nearly horizontal except south of the southeast end of the monocline,-where dips are gently southeast. Structural relief 

across the monocline is between 300 and 500 feet near 

and northwest of the quadrangle boundary and decreases to the southeast. The exact amount of structural 

relief was not estimated, as a known stratigraphic horizon is not exposed in the synclinal bend. 

Big Chino monocline or fault.-A major structure, 

Big Chino monocline or fault, forms the boundary between Black Mesa and the northwestern part of ChinoLonesome basin; it extends from north of Paulden for 

at least 26 miles to the northwest. For more than 4 

miles northwest of Route 89, the Martin and Redwall 

strata dip southwest 10°-40°. Many small northwesttrending faults (pl. 2, sec. C-C'), most having the 

northeast side downdropped, however, displace the 

beds. Northwest of the quadrangle the exposed Paleozoic beds are about horizontal; southwest of here they 

are buried by upper Tertiary ( ~) rocks. Conclusive 

proof of major displacement was obtained from a wildcat oil well (No. 1, sec. 20, T. 18 N., R. 2 E.; 1,430,800 

N., 326,200 E.) that penetrated the Tapeats-Martin 

contact about 1,400 feet below the estimated altitude of 

this contact about 2 miles northeast of the well. 

Whether this structural relief is due largely to faulting 

or to warping is unknown. 

Verde monocline.-The Verde monocline (pl. 2, sees. 

J-J' and JI;J-M' to T-T') is a complex branching horsttype (fig. 27) structure that extends from the east edge 

of the Paulden quadrangle (near 1,403,000 N.) for about 

4 miles to the west-northwest. It becomes a fault in the 

Clarkdale quadrangle, where it is exposed for about 

1 mile. 

The monocline forming the south side of the horsttype structure faces south and is opposed to the regional 

dip; that on the north side faces l).Orth in the direction 

of the regional dip. Structural relief is at least 300 

feet on the south-facing monocline and is probably less 

on the north-facing one. Southeast of the Verde River, 

the south-facing monocline forms a narrow hogback in 

which the average dip of the beds is 30°-50°. The anticlinal bend involving Precambrian quartz diorite, Tapeats Sandstone, and basal Martin Limestone is well exposed half a mile southeast of the Verde River; the 

quartz diorite-Tapeats contact in places is almost vertical. The synclinal bend, involving Redwall and 

Supai beds, is well exposed about 1~ miles southeast 

of the Verde River. Near the Verde River (1,410,500 

N., 388,000 E.) the monocline splits into two branches, 

one trending slightly south of west, the other continuing 

northwest for about· 2,000 feet, then swinging more 

nearly due west. Here the contact between quartz diorite and Tapeats is vertical or slightly overturned. 

Paleozoic rocks on the anticlinal bend have been removed by erosion. The synclinal bend, involving beds 

in the B unit of the Martin, is well exposed on the north 

side of the Verde River (1,411,500 N., 386,500 E.), 

where the beds make an abrupt turn from nearly horizontal to vertical. 

The north-facing monocline on the north side of the 

horst-type structure lies only 200-300 feet northeast of 

the south-facing monocline near the east edge of the 

quadrangle; but some 3,000 feet from the quadrangle 

boundary, it swings northwest until it is about 2,000 

feet from the south-facing monocline, where it resumes 

its west-northwest trend for about 1 mile. Here it is 

offset to the north a few hundred feet by a north-trending fault. West of here displacement is largely along 

a fault, which dies out abruptly. 

A north-facing monocline branches off the south-facing monocline a short distance north west of the Verde 

River (1,412,000 N., 386,000 E.) and extends northwest 

for about 3,000 feet, where it horsetails out into at least 

five north-trending faults or faulted monoclines. Cumulative vertical separation . on the branches is close to 

500 feet. 
96 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

Bull Basin rnonocline.-The west-facing Bull Basin 

monocline (pl. 2 sees. A-A', E-E', J-J', K-K'; pl. 5) 

on the west side of the southeastern anticline lies near 

and largely west of Bull Basin Canyon and trends 

north-northwest and then north from 1,390,000 N., 

379,000 E. for about 4 miles. Faults mark its trend 

over some of this distance. South of about 1,400,000 

N. the monocline appears to branch, the west branch 

trending nearly south. Total structural relief is 600-

700 feet. The monoclines and faults may continue to 

the southeast for at least another 4 miles (pl. 5); the 

southernmost outcrop of the contact between the Martin 

and Red wall Limestones ( 1,372,600 N., 378,000 E.) is 

about 800 feet below the contact's altitude about 2 miles 

to the east, and only one fault, which has a stratigraphic 

throw of about 250 feet, was found (1,372,000 N., 

387,500 E.). South of the Verde River, the monocline 

is buried by gravel, beneath which it is offset about half 

a mile to the southeast by a nortlnYest-trending fault; 

it reappears near Hubbel Ranch (1,418,000 N., 373,700 

E.), "·here it has been mapped as a fault ; poorly exposed, steeply dipping beds, however, suggest a monocline (pl. 2, sec. D-D'). Structural relief here is about 

700 feet. 

Other monoclinal structures.-Other monoclinal 

structures occur in the area : 

1. A south-facing arcuate monocline is north of St. 

Mathews Mountain. A younger fault has downdropped the Tapeats on the north giving the 

effect of anomalous (reverse) drag (pl. 2, sec. 

L-L'). 

2. A south-facing monocline (pl. 2, sec. A-A') trends 

east-northeast from 1,377,000 N., 387,000 E., and 

is exposed for a little more than 1 mile. Structural relief appears to be about 500 feet and to 

decrease to the east, where the monocline may 

pass into a fault. 

3. A northwest-facing monocline trends northeast from 

1,414,500 N., 365,700 E., for about 4,000 feet and 

dies out abruptly to the southwest; structural 

relief at the northeast end is about 300 feet and 

appears to be due entirely to a fault. 

4. A southeast-facing monocline trends northeast from 

1,400,000 N., 344,800 E., for about 4,000 feet. 

East-dipping beds exposed to the south-southwest suggest that it has a length of at least 

11-h miles. At the southwest end of the main 

exposures, the structure is narrow; at the northeast, it becomes broader. 

FAULTS 

Vertical to high-angle faults trend northwest to north 

and northeast to east. Most of them are shown as 

vertical in structure sections, as the amount and direction of dip on fault planes was determined only locally. 

Few are exposed for more than 2 miles. Some die out; 

others pass into monoclines. Stratigraphic throw 

ranges from less than 100 feet to at least 750 feet; some 

of the larger displacements· represent vertical separation 

across several faults or across faults and monoclines. 

The amount of displacement on minor faults in the 

Paleozoic rocks can be determined only where the contact between formations or a thin unit within a formation is cut. In the massive Redwall Limestone, fa"ults 

are difficult to trace. One low-angle thrust was ob--

served; it displaced unit 1 of the Red wall Limestone 

and had an apparent dip slip of about 8 feet, as exposed in a cut near 1,425,600 N., 344,000 E. 

Faults with vertical displacements of 250-700 feet 

are exposed for short distances in the northeast ·corner 

of the area (pl. 2). Most trend eastward, although a 

:few trend northward. The north side of most easttrending faults is downthrown; the accumulated vertical 

separation (pl. 2, sec. L-L') is about 1,200 feet. An 

eastward-trending fault (pl. 5), probably part of this 

group, is exposed for a short distance in Bear Canyon 

about a mile east of the Paulden quadrangle (Lehner, 

1958, p. 570; pl. 45) ; it has a stratigraphic throw of 

about 600 feet, the north side being downthrown. 

The major north-trending fault in the northeast corner of the area (near 1,450,000 N., 398,200 E .) has a 

vertical separation of at least 700 feet, the east side 

being downthrown (pl. 2b, sec. L-L'). Farther west a 

buried fault trending north-northeast is indicated on 

plates 2 and 5. Its trace is suggested by topographic 

expression and by slight displacement of basalt and 

gravel in Hell Canyon. Just north of the quadrangle· 

boundary (near 385,000 E.), the fault brought the Supai 

Formation on the west up into contact with the Coconino 

Sandstone on the east. Four miles farther north the 

vertical separation of the contact between the Coconino 

Sandstone and Kaibab Limestone is an estimated 400-

500 feet, and this movement was largely pre-Perkinsville in age. 

Several faults in the southeastern part of the Paulden quadrangle are westward extensions of faults in 

the Clarkdale quadrangle (Lehner, 1958, pl. 45). The 

southernmost one trends northeast from 1,380,000 N., 

395,000 E. The north side is downthrown, and the vertical separation is about 300 feet (pl. 2, sec. L-L'). 

East of the quadrangle boundary the fault curves north 

then north-northwest and re-enters the quadrangle near 

1,393,500 N., where the west side is downthrown. A 

fault trending east-northeast having the south side 

downthrown about 300 feet extends for about 11h miles 

:from 1,386,500 N., 392,500 E. (pl. 2, sec. L-L') and 
STRUCTURE 97 

continues for llh miles into the Clarkdale quadrangle, 

where it is buried by gravel. It offsets slightly the 

fault just described, whereas most of the east-trending 

faults in the Paulden area are offset by north-trending 

faults. 

Near the northeast side of Chino Valley, east of Granite Creek, northwest-trending displacements have resulted in a total vertical separation estimated at about 

800 feet (pl. 2, sec. G-G'). A fault, in which the 

west side is downthrown about 250 feet, is indicated 

by a small outcrop of Tapeats Sandstone (near 1,372,000 

N., 387,500 E.) and by a sliver of probable Tapeats a 

mile to the northwest. Another fault or monocline 

about 2 miles to the west is indicated by the altitude of 

the contact between the Martin and Red wall Limestones, 

as mentioned in the discussion of Bull Basin monocline (p. 96). 

A fault near the headwaters of King Canyon (1,387,-

900 N., 385,000 E.) trends eastward. The north side is 

upthrown; the stratigraphic separation is about 150 

feet near where the fault swings to the northeast and 

decreases west and northeast of here. The Tapeats 

Sandstone on the south side is steeply upturned. 

The northwest-trending fault that probably offsets 

Bull Basin monocline south of the Verde River is exposed for about half a mile. Near the Verde River 

(1,416,000 N., 368,000 E.) the stratigraphic throw is 

about 400 feet, the east side being downthrown. The 

fault is buried by gravel and basalt (near 1,415,000 N., 

370,000 E.). About 1,300 feet northwest of the Verde 

River, the fault meets a northeast-trending- fault or 

monocline; the fault was not recognized to the northwest. 

West of Bull Basin monocline the top of the Redwall 

Limestone is about 150 feet lower than the base of this 

same limestone 1,500 feet to the southwest (near 1,-

395,000 N., 370,000 E.) ; the structural relief, therefore, 

is about 400 feet (pl. 2, sees. J-J' and K-K'). Although buried, this structure probably trends northwest 

(from near 1,391,500 N., 374,000 E.), but whether the 

displacement is due to a fault or a monocline is unknown. The 20° NE. dip of the Redwall south of the 

structure suggests a flexure. The structure marks the 

probable northeast side of the topographic high of 

Mazatzal Quartzite. 

The irregular southwestern margin of Chino-Lonesom~ basin suggests an erosional valley, but the rather 

straight trends of parts of the eastern and northeastern 

boundary suggest structural displacement, as does the 

depth of wells in basin fill close to Precambrian or 

Paleozoic bedrock outcrops (figs. ·20, 22, 23) . Except 

for Coyote fault in the western part of the Mingus 

Mountain quadrangle and the structure on the southwest side of Black Mesa (see "Monoclines") structures 

that may have partly outlined the basin have been completely obscured by basin fill, by subsequent pedimentation, and by wearing back of fault scarps by erosion 

during and after deposition of the upper Tertiary (?) 

rocks. 

Faults may in part outline the Dells Granite (pl. 1). 

The fault on the southwest side is suggested by the 

known minimum depth of the basin a short distance 

south west of granite outcrops (pl. 1, sec. F -F') . The 

one on the southeast side is suggested by the change, beneath basalt, from intensely foliated north-trending 

rocks to massive granite on \vhat may be an extension of 

the fault that separates gabbro from Government Canyon Granodiorite to the southwest; it may have localized the Glassford cinder cone. 

In the southern part of the area, a few high-angle 

north- and northeast-trending faults offset lithologic 

units of Precambrian . rocks and have horizontal displacements of 100-1,000 feet. The faults are intruded 

by Tertiary ( ? ) andesite dikes. 

JOINTS 

In many places the Paleozoic rocks are well jointed, 

especially in the Martin Limestone and to a lesser extent the Tapeats Sandstone. In general these joints 

strike N. 30° E. and N. 60° W. Their origin is unknown, but the two directions are about the same as 

those of the major joints in the Dells Granite and as 

those of some faults. In the northeastern part of the 

Clarkdale quadrangle, Lehner ( 1958, p. 542, .571) reported well-defined joints especially in the Coconino 

Sandstone, that trend N. 50° ,V. and N. 45° E. and are 

about parallel to nearby high-angle faults. 

YOUNGER STRUCTURE 

STRUCTURE FORMED BY INTRUSION OF ANDESITE PLUGS 

Some steep dips in Paleozoic rocks are interpreted as 

due to forceful intrusion of andesite plugs, but the possibility of deformation associated with a fault or a 

monocline at an earlier time cannot be eliminated. The 

best example of structure probably formed by intrusion 

of andesite is found about three-fourth mile east of the 

Pinnacle (pl. 2, near 1,400,400 N., 356,500 E.). The 

Paleozoic rocks east of the plug dip steeply ( 65 °) east; 

those soutlnvest of the plug dip steeply southwest (pl. 

2, sec. F-F'). A short distance west of the plug the 

unnamed basaltic flows of the Alder(?) Group are 

about 100 feet above the Redwall Limestone on the 

southwest side of the plug, an occurrence suggesting 

that the basaltic rocks were uplifte~ by an underlying 

plug. 

Small outcrops of Tapeats Sandstone and Martin 
98 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

Limestone at the north end of the large area of andesite 

west of Route 89 (pl. 2) may have been dragged up by 

the andesite. If not, and if the Paleozoic-Precambrian 

basement is close to the surface here, then Chino-Lonesome basin is relatively narrow at this place (figs. 22, 

23) or is separated into two parts. 

FAULTS 

Faults having displacements as much as 2,800 feet 

cut Hickey basalt in the Jerome area (pl. 5), but no 

:faults of this magnitude were observed cutting the 

upper Tertiary( n rocks in the Prescott-Paulden area. 

Four faults c.ut these rocks in the area between Prescott 

and the Granite Dells and Glassford Hill (pl. 1). Orange tuff underlies the basalt on both sides of the northeast-trending fault southwest of the Granite Dells (fig. 

24A) and the basalt south of fault near Prescott. If 

the orange tuff in each place represents the bed beneath 

the middle basalt flows, then vertical displacement may 

have been about 200 feet in the first locality and 300-400 

feet in the second. 

In the southern part of the Paulden quadrangle, a 

few faults cut basalt and have displacements of not 

more than 100 fe~t. Actual displacement is hard to 

prove because of the difficulty in tracing faults through 

basalt. In a few places where apparently faulted, the 

basalt flowed against fault scarps, or slight movement 

along an older fault disrupted the basalt. 

Faults trending north-northeast cut basalt and older 

rocks about 1,500 feet above the junction of Rattlesnake 

Wash with Hell Canyon and in two places along Hell 

Canyon-one just east and one about half a mile west 

of King Spring. Vertical displacement of the base of 

the basalt is 50-100 feet. Post-basalt movement on the 

westernmost structure probably was largely in the form 

of a flexure; fine sand beneath basalt on the south side 

of the canyon dips steeply (35°) east and the basalt is 

downwarped. One basalt flow overlies a thin bed of 

fresh-water limestone above sand .and gravel west of 

the flexure; four flows overlie the limestone east of it. 

Three flows lie west of the fault east of King Spring, 

and at least four flows are east of it. 

A low fault scarp cuts upper Tertiary(?) gravel 

along the northeast side of Big Chino Wash (southwest 

side of Black Mesa), largely northwest of the Paulden 

quadrangle. It shows up well on aerial photographs 

for a distance of about 26 miles. Its course is somewhat 

sinuous, and it locally branches; in places a grabenlike 

depression was probably carved out by a stream that 

temporarily followed the fault. The scarp probably 

formed during renewed movement along an older structure-Big Chino monocline or fault. 

AGE OF ·THE STRUCTURES 

Structural disturbances are known to have occurred 

intermittently since the close of the Paleozoic Era, but 

the sedimentary record in this area yields little information as to when they occurred. Price (1949) reported a conspicuous disconformity between the Kaibab 

(Permian) and the Moenkopi (Early Triassic) . McKee ( 1951, p. 494) stated that the first major uplift in 

central Arizona after the Precambrian probably occurred in the Late Triassic. Monoclines on the Colorado Plateau are Late Cretaceous to early Tertiary in 

age (Babenroth and Strahler, 1945, p. 148-149; Kelley, 

1955, p. 797). Remnants of once extensive gravel deposits beneath basalts on the Plateau and in north- and 

northeast-trending channels beneath basalt south of the 

Plateau margin indicate uplift to the south probably 

in the late Miocene or early Pliocene (McKee, 1951, p. 

498). East of the Prescott-Paulden area, Anderson and 

Creasey (1958, p. 78-83) and Lehner (1958, p. 568-579) 

recognized two major periods of deformation. One affected only Paleozoic and older rooks; the other, the 

stronger, followed accumulation of the Hickey formation but continued in milder form during and after 

accumulation of the Verde and Perkinsville Formations. 

It is characterized chiefly by normal faults trending 

north and north-northwest. 

None of the major structures in the Paulden quadrangle are clearly younger than the upper Tertiary ( ? ) 

rocks, and because of uncertainties as to the relations of 

the basalt to Hickey and Perkinsville basalts, the relations of these structures to post-Hickey deformation are 

uncertain. The terms "older and younger structures" 

do not imply deformation in pre- or post-Hickey times. 

MONOOLINES 

The possibility of a Late Cretaceous-early Eocene age 

for monoclines in the Paulden quadrangle is appealing 

because of the similarity of the monoclines to those on 

the Colorado Plateau that are of this age. However, 

a monocline in the southeastern part of the Clarkdale 

quadrangle has tilted Pliocene ( ? ) basalt of the Hickey 

Formation (Lehner, 1958, p. 579); the Verde fault of 

post-Hickey age passes northward abruptly into a monocline (Anderson and Creasey, 1958, p. 80). The youngest beds involved in monoclines in the Paulden quadrangle are those of the Supai Formation, hut younger 

Permian beds, since removed by erosion, undoubtedly 

also were folded. The monoclines were probably formed 

after the Paleozoic rocks were regionally tilted to the 

northeast (pl. 5), and they are older than at least some 

of the north- and northwest-trending faults. No in-

. volvement of any upper Tertiary ( ? ) rocks in the monoclinal structures was observed; some monoclines are 

buried by upper Tertiary ( ? ) rocks. 
PHYSIOGRAPHY 99 

Bull Basin monocline is older than the gravel east 

of it. This gravel was probably deposited in a valley 

carved into the uplifted side of the block. Limestone 

Canyon monocline is older than the gravel northeast 

of the monocline, as is indicated by the presence in the 

gravel of pebbles of Martin Limestone derived from the 

uplifted block to the southwest. Limestone Canyon 

monocline northwest of the quadrangle and the fault 

extension of the Verde monocline east of the quadrangle 

are buried by basalt, but these basalts may both be -

Perkinsville in age. The monocline north of St. 

Mathews Mountain is older than basalt that buries it at 

the east edge of the quadrangle. To the east this basalt 

is called Hickey by Lehner (1958). Bull Basin and 

Verde monoclines are older than the Verde River; the 

intervening uplifted area (pl. 2, sec. D-D'; pl. 5) was 

worn down before the river took its present course. 

FAULTS 

Lehner (1958, pl. 45) mapped many faults in the 

Clarkdale quadrangle that cut basalt of the Hickey 

Formation (pl. 4). Most of the faults are east of 

Coyote fault. Of those that extend into the Paulden 

quadrangle, none clearly displaces the upper Tertiary ( ? ) basalt more than a minor amount, although 

displacement of Paleozoic rocks may be 300 feet or 

more. The fault that curves northward east of the area 

and reenters it near 1,3'93,500 N. does not obviously 

disturb the older gravel. The northwest-trending fault 

that offsets Bull Basin monocline south of the Verde 

River does not disturb the older gravel or the overlying 

(post-andesite) basalt that conceals the probable trend 

of the fault. 

The faults that cut Precambrian rocks in the southern 

part of the area (pl. 1) are probably younger than the 

Precambrian, but older than the upper Tertiary(?) 

rocks; the faults are intruded by andesite dikes that also 

probably have the same age limits. The principal movement on the faults, however, may have taken place at 

a much earlier period than the intrusion of the dikes. 

Quartz veins and zones of mild silification, presumably 

of Precambrian age, occupy or parallel some of the 

faults; the first movement, therefore, may have been in 

the Precambrian. 

In the southwestern part of the area, movement on 

some faults occurring after basalt deposition may have 

been as much as 400 feet, if the orange tuff bed on which 

the displacement was measured is everywhere correlative. Only small faults cut the basalt (Perkinsville?) 

in the northeast part of the area. 

Recurrent movement probably occurred along the 

structure on the southwest side of Black Mesa (largely 

northwest of the area) ; the most recent movement forming the low fault scarp in upper Tertiary ( ? ) gravel. 

CONCLUSIONS 

The structural low in which the Verde River flows 

eastward from Chino-Lonesome basin may have formed 

at the same time that deformation arched the Black 

Hills, faulted and downwarped basalt of the Hickey 

Formation north of the Black Hills, and produced the 

major movement on Coyote and Verde faults. However, the underlying structure does not appear to have 

controlled the course of the Verde River to any extent 

(pl. 5) , except where the Verde leaves the basin and 

for a short distance south of its junction with Hell Canyon. The structure was probably buried by upper Tertiary (?) rocks when the river's course was determined. 

The covering rocks would be considered Perkinsville 

were it not for the fact that they include older gravel 

that probably antedates the formation of Chino-Lonesome basin. 

Until the relation of the upper Tertiary(?) rocks to 

the Hickey and Perkinsville Formations in the type 

areas is known, the age of the major deformation cannot 

be determined. If basalt in the southeastern part of 

the Paulden quadrangle is Hickey, then most of the 

structure there is pre-Hickey in age; if these rocks or 

some of them, however, are Perkinsville in age, then 

some of the structure may also be post-Hickey in age. 

Similarly, some or all of the rocks mapped as Hickey 

west of Coyote fault in the Jerome-Clarkdale area may 

be Perkinsville in age and may have accumulated after 

Chino-Lonesome basin was formed. 

PHYSIOGRAPHY 

GENERAL FEATURES 

The major physiographic feature of the PrescottPaulden area is the broad Chino-Lonesome Valley, 

which extends from a short distance southeast of the 

area for 60 miles to the northwest (figs. 1, 30). The 

southwestern boundary of the valley is quite irregular 

and consists of a series of mountain ranges, of which 

only the northern part of the Bradshaw Mountains extends into the area. The southeastern part of the valley 

is bounded on the east by the uplifted Black Hills block 

(Mingus Mountain quadrangle) ; the northwestern part 

is bounded by the uplifted Black Mesa block (mostly 

northwest of the area). Between these two blocks is a 

low relatively flat but locally dissected area that extends northeastward to the south western boundary of 

the Colorado Plateau (the Mogollon Rim). 

Chino-Lonesome Valley is an erosional and structural basin filled with upper Tertiary (?) rocks. Exterior drainage commenced when the basin was filled 

sufficiently for water to spill over a low point into the 

Verde River drainage. This point is located near the 
100 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

center of the northeastern boundary (near 1,406,000 N., 

337,000 E.), not at one end, as in normal valleys. 

The existence of temporary base levels allowed formation of gravel-strewn pediments and terraces. Drainage 

in the southern half of the valley was northward until 

the Lonesome Valley portion was captured by head ward 

erosion of the Agua Fria River. Rapid dissection of 

the pediment followed the stream capture. The Verde 

River (fig. 2) and its tributaries northeast of the basin 

have cut steep-walled canyons in the generally horizontal Paleozoic and Cenozoic rocks. The surface forms are 

largely erosional, except for some formed by alluviation 

along valley bottoms. 

MOUNTAINS 

The mountains and hills are of several types, each 

type depending primarily on the rocks and structure 

involved but locally on the erosional history of the area. 

In the southern part, erosion of schistose rocks having 

nearly vertical structures produced long sharp ridges 

separated by north-trending gulches. Higher ridges 

and peaks reflect a greater resistance to erosion. In the 

soutlnvestern part of the area, some subdued, rounded 

hills, generally composed of massive granite, represent 

a \veathered erosion surface that was buried during late 

Tertiary (?) time and later exhumed. 

The topographic form of the isolated Dells Granite 

is controlled by nearly vertical joints (fig. 14). Square 

to rectangular hills, locally having precipitous sides, 

rise 50-200 feet above the valleys. The major valleys 

in the granite trend approximately N. 25° E. and N. 70° 

'\V., parallel to the major joints. The valleys are 200-

1,000 feet apart and as much as half a mile long. 

In the south western part of the area ( pL 1), flattopped mesas and buttes are part of a maturely dissected 

lava plateau or plain. Flat-topped hills in Chino-Lonesome Valley are remnants of once extensive pediments 

(figs. 28, 29). Northeast of the basin, flat-topped 

hills are capped by nearly horizontal Paleozoic rocks 

or basalt flo,vs of late Tertiary ( ? ) age. 

Hogbacks were formed by erosion of steep monoclines. 

Flatiron-shaped slopes (dissected dip slopes) are fairly 

common in folded Mazatzal Quartzite. 

Glassford Hill (fig. 14) ·in the southwestern part of 

the area is a cinder cone ; the cone was partly buried 

by nearly horizontal basalt flows that were eroded to 

form a roughly circular hill. St. Mathews Mountain in 

the east-central part (pl. 2) is a dissected cone of andesitic flow, breccia, and intrusive-plug material and was 

also partly buried by basalt. Dissected andesitic plugs 

or domes form isolated hills (fig. 19) on the north side 

of the Chino-Lonesome Valley east of Granite Creek. 

Erosion of andesite that is cut by steeply dipping joints 

and flow planes produced sharp peaks such as the Pinnacle (pl. 2, 1,400,000 N., 353,000 E.). · Erosion of andesitic gravel and breccia produced rounded hills covered 

with andesitic rubble. 

PEDIMENTS 

A broad pediment, strewn with sand and gravel, covered much of Chino-Lonesome Valley. The pediment 

sloped from the margins toward the center and then 

along the axis of the valley to the Verde River. It probably formed at the time that a temporary base level 

occurred along the river; much of it was subsequently 

destroyed by erosion. Lower pediments or terraces 

formed during shorter periods when temporary base levels had occurred along Granite Creek and the Verde 

and Agua Fria Rivers. 

FIGURE 28.-Pediment east of Glassford Hill. The view is to the southwest from th~ east edge of the area (pl. 1, 1,310,000 N., 398,000 E.)· 

The eroded edge of the pediment is across the Yaeger-Agua Fria alluvial fiat. The Bradshaw Mountains are in tbe background, and 

Glassford Hill is on the extreme right. Coarse gravel in foreground is largely colluvial material from pediment gravel to the east. 

It conceals fine-grained sedimentary rocks of late Tertiary ( ?) age such as are shown in figure 2'5. 
Area of map 

PHYSIOGRAPHY 

112°30' 112° 15' 

EXPLANATION 

.. 

Younger alluvial surfaces 

Pediment 

-

surfaces 

Volcanic and sedimentary rocks 

of late Tertiary(?) age 

Precambrian and Paleozoic rocks 

101 

1 0 1 2 4 MILES 

l_____L___L_L__j _ ____L______J 

FIGURE 2'9.-Distribution of pediment remnants in 'Chino-LonesQme Valley, Ariz. 
102 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

The pediment is cut largely on basin fill, but in a 

few places it can be traced onto Precambrian and Paleozoic rocks around the margin. It is easy to recognize 

where its gravels are underlain by fine-grained lacustrine deposits, but it is difficult to recognize where cut 

on fanglomerate or on basalt if the pediment gravels 

are composed largely of basalt fragments. 

The major pediment remnant is east of Glassford Hill 

(figs. 28, 29). Smaller remnants occur on both sides of 

Granite Creek and around the margins of the basin. The 

east side of the pediment remnant east of Granite Creek 

slopes imperceptibly into lower terraces and into alluvium of the valley floor. In other places, where erosion 

has been rapid, the pediment remnants end abruptly. 

DRAINAGE 

CHINO-LONESOME VALLEY 

One of the interesting physiographic features of the 

area is the drainage pattern in Chino-Lonesome Valley ; 

the pattern records the history of drainage changes (fig. 

30). Unlike a normal valley, which has an outlet at one 

end, the major outlet, the Verde River, of the 60-mile 

long valley is near the center of the northeast side. 

Northwest and west of the headwaters (Sullivan Lake), 

of the Verde River, drainage is southeastward (Big 

Chino Wash) and eastward (Williamson Valley Wash). 

South of Sullivan Lake drainage was entirely to the 

north and northwest until its southern part was captured by headward erosion of the south-flowing Agua 

Fria River because of its steeper gradient. Route 89A 

follows the inconspicuous present divide between northand south-flowing drainage for most of its distance 

across the valley. Water falling north of the highway 

(pl. 1, near the Gila and Salt River meridian; fig. 1) 

travels, via Granite Creek and the Verde and Salt 

Rivers, almost twice as far to the Gila River near 

Phoenix, as does water falling south of the highway, 

which reaches the same point in the Gila River via the 

Agua Fria River. 

The capture resulted in deep dissection of the pediment. The existence of temporary hase levels along 

the Agua Fria and its tributaries, especially along Lynx 

Creek, resulted in the formation of lower pediments 

or terraces and may account for some of the slight alluviation that occurred along the river and its tributaries. 

Recent rapid erosion due to lowering of base level or to 

climatic changes has cut gullies 5-25 feet deep into 

alluvium and basin deposits (fig. 25). 

The northward drainage of the valley consists of 

three parts. About 40 percent of the area is drained 

by Granite Creek and its tributaries. The remainder 

is almost equally divided between the washes east and 

west of Granite Creek, which were formerly the principal northward drainage lines. After capture of its 

headwaters by the Agua Fria River, the wash east of 

the creek could no longer remain a major drainage line; 

some stagnation and alluviation has occurred along it. 

The wash west of Granite Creek at one time drained all 

the area west of Granite Creek (west of the dotted line 

that extends northward from the Granite Dells, fig. 30) 

and possibly the area southwest of the Granite Dells. 

This drainage was captured by headward erosion of 

tributaries on the west side of Granite Creek, two north 

of and one south of the airport. 

Granite Creek is a superimposed stream. It was let 

down onto resistant Dells Granite and Mazatzal Quartzite from overlying upper Tertiary ( ? ) rocks or from 

a pediment cut on the upper Tertiary(?) or Precambrian rocks. Had its course been a short distance to the 

west, the creek would now be on softer basin deposits. 

At the time the course was determined, however, the 

softer rocks may have been concealed by resistant volcanic rocks. From the Dells Granite to the Mazatzal 

Quartzite, a distance of about 12 miles, the Granite 

Creek drainage was confined to a strip 1-21h miles 

wide (fig. 30, east of the dotted line) that is bounded 

by flat-topped hills, which are pediment remnants. 

The creek bottom within this strip is a quarter to more 

than half a mile wide. The wide valley flat probably 

formed because the creek had a very low gradient caused 

by the temporary base level formed by the resistant 

Precambrian rocks. The creek could widen its valley 

upstream from the resistant rocks but could do little 

downcutting. The reason why the creek was originally 

confined to this narrow strip is obscure. Granite Creek 

now drains a large mountainous area that received more 

rainfall than do the areas drained by the washes to the 

east and west since their headwaters were captured. 

Granite Creek enters the Verde River about 100 feet 

lower than does the wash to the west. This lower base 

level may explain why the creek captured the headwaters of the drainage system to the west. This wash 

may now be cutting back more rapidly because it is on 

softer material and also because of permanent stream 

flow below Del Rio Springs, which taps the Chino-Artesian basin. 

NORTHEAST OF CHINO-LONESOME VALLEY 

The area northeast of Chino-Lonesome Valley as far 

as the Verde River is quite deeply dissected, but north 

of the river it is largely a flat land. The low relief 

appears to be due mainly to smoothing out of irregularities by basalt ·that flowed south from the Colorado 

Plateau. It could, however, be an extension of the 

pediment in Chino Valley. The lowland extends northward from the north -central part of the area and forms 

a break in the escarpment of the plateau (fig. 1). The 
112°45' 

D 

Cenozoic rocks 

Precambrian and Paleozoic basement rocks 

Contact west of long 112° 80' and north of lat 85°00' 

taken from reconnaissance mapping 1955-56 

Drainage divide 

Upper Granite Creek drainage basin 

Agua Fria drainage basin 

PHYSIOGRAPHY 

112°30' 

0 

Base and drainage compiled from U.S. Geological 

Survey 15-minute topographic quadrangles, 

Paulden and Prescott; U.S. Army Map Service 2o 

maps, Williams and Prescott; and Soil Conservation Service aerial photographs 

4 MILES 

FIGURE 30.---Drainage pattern in Lonesome, Chino, and Williamson Valleys, Prescott-Paulden area, Arizona. 

103. 

35°00' 

34°30' 
104 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

southwest-faeing Black Mesa escarpment, mostly west 

of the area, appears to be an offset part of the Mogollon 

Rim. The Verde River and its tributaries have cut 

steep-walled gorges as much as 300 feet deep into the 

relatively flat basalt and gravel plane and into the underlying Paleozoic and Precambrian rocks. Structure 

in the Paleozoic rocks apparently had little control on 

the course of these streams, except that the Verde River 

leaves Chino-Lonesome Valley near a structural low. 

The faults and monoclines were probably buried by 

upper Tertiary ( ~) rocks or by pediment gravels at the 

time that the stream courses were determined. 

ECONOMIC GEOLOGY 

ORE DEPOSITS 

HISTORY 

Mining in the Jerome-Prescott area prior to the exploration of Arizona and New Mexico by the Spaniards 

was carried on by Indians. The presence of hammers 

and other stone implements in ancient workings at the 

site of the Silver Belt mine, a short distance southwest 

of the Iron King mine, indicates mining in the Prescott 

area during prehistoric time (Galbraith, 1947, p. 42). 

The first recorded discovery of an economic deposit was 

made in 1863, when Joe Walker and a party of prospectors found gold in Hassayampa River and Lynx 

Creek in the Prescott region (Hamilton, 1883, p. 47). 

The Lynx Creek placers have contributed a considerable 

part of the placer gold of the state and county. A. 

little placer mining has ·been done on other creeks in 

the area. Lode mining during historic time close to 

the Prescott area commenced with the rediscovery of 

the ore deposits at the site of the Silver Belt mine in 

1870 (Lindgren, 1926, p. 128). Rich silver ore was 

mined at this mine until1880. 

The Iron King lead -zinc mine (southeast corner of 

pl. 1) is the only important lode deposit discovered 

within the Prescott-Paulden area. It has been the leading mine in the Prescott-Jerome area since the closing 

of the United Verde mine at Jerome in 1953. Mining 

was begun at the site of the present Iron King mine 

probably about 1880. Production was sporadic and 

minor until 1937, when the . present operation was 

started. 

Except for the Mazatzal Quartzite, the Precambrian 

rocks in the Prescott and Paulden quadrangles are riddled with prospect pits, tunnels, and shallow shafts, 

largely dug on quartz veins. A small amount of ore, 

mostly gold, has been produced from some of them. 

Many of these veins were prospected during the early 

days of mining, but prospecting and small-scale development work have continued intermittently since then. 

MINERALOGY 

Brief descriptions of the minerals directly related to 

the ore deposits are given in this section. The list includes hypogene ore and gangue minerals-formed by 

ascending ore-forming solutions-and supergene ore 

minerals-formed by descending waters-but not the 

common rock-forming minerals. Some hypogene and 

supergene ore minerals are of no economic importance. 

The data on mineralogy have been obtained from brief 

examination of material on dumps of small prospects 

and from the following sources : Anderson and Creasey 

(1958, p. 91-95), Galbraith (1947), Wilson and others 

( 1934), and Lindgren ( 1926, p. ·24-31). 

HYPOGENE MINERALS 

ORE MINERALS 

A'rsenopyrite (FeAsS) .-Small crystals of arsenopyrite are scattered throughout the massive sulfide ore 

body at the Iron King mine. It was also noted in 

specimens on some of the dumps of small prospects (near 

1;27 4,600 N., 390,500 E. and 1,282, 700 N., 393,800 E.). 

0 halcopyrite ( CuFeS2 ) .-Small quantities of chalcopyrite occur in many of the fissure vein deposits and in 

the copper vein a short distance west of the Iron King 

mine. 

Galena (PbS) .-Galena, as scattered medium to large 

crystals, is common in many of the fissure veins in the 

area. In the Iron King massive sulfide ore it is an 

important . constituent, where it occurs as very fine to 

microscopic grains. It is ·present in , the< Gold Coin 

group (1,293,600 N., 368,300 E.) and was noted in small 

prospects in the following areas: 1,287,200 N., 371,500 

E.; 1,274,600 N., 390,500 E.; 1,282,700 N., 393,800 E.; 

and along 393,300 E., behveen 1,282,100 N. and 1,283,400 

N. Near the east edge of the Paulden quadrangle south 

of the Verde River (1,422,400 N., 396,000 E.), cubes of 

galena, more than 1 inch square, occur in calcite veins 

in the Mississippian Redwall Limestone. Galena was 

also reported by Lindgren (1926, p. 102) in a quartz 

vein (the "Peters silver mine") in the southeastern 

part of the Paulden quadrangle, probably in sec. 7, T. 

16N.,R.1E. 

Gold (Au) .-Gold is economically important in the 

Iron King mine, in many of the small quartz veins in 

the area, and in the placer deposits along Lynx Creek. 

The gold at the Iron King mine is free-milling and occurs in galena, sphalerite, and pyrite, as indicated by 

metallurgical tests and assays. Chiefly because it is most 

abundant, pyrite carries most of the gold. Visible ,gold 

has been reported from some of the quartz veins, notably the Gold Coin group (1,293,600 N., 368,300 E.), the 

White Horse prospect (1,285,500 N., 370,500 E.), a 

prospect near 1,274,000 N., 369,200 E., and in Precam-
ECONOMIC GEOLOGY 105 

brian rocks north and south of the boundary between 

the Prescott and Paulden quadrangles. Placer gravels 

along Lynx Creek near Walker (about 3 miles south 

of the Prescott quadrangle) have yielded nuggets of 

about 5 ounces, 'vhereas the golq. from lower Lynx Creek 

ranges from finely divided material to nuggets of about 

three-tenths of an ounce (Wilson, 1952, p. 43). 

Hematite (Fe2 0 3 ) .-Specular hematite is widespread 

as veinlets in Precambrian rocks. Hematite is an a bundant constituent in some of the beds of jasper-magnetite 

in the Texas Gulch Formation. It is concentrated along 

cross laminae and bedding planes in some of the Mazatzal Quartzite. 

111 agnetite (Fea04) .-Although of no economic importance at present, magnetite is a major constituent in 

the narrow beds of jasper-magnetite in the Texas Gulch 

Formation and in some of the quartz-magnetite veins 

in Alder Group rocks, especially in the unnamed tuffaceous rocks. Magnetite-rich zones occur in gabbro, especially in and east of the largest mass (near 1,289,000 

N., 371,600 E.; 1,288,700 N., 374,000 E.; and 1,290,500 

N., 37 4,500 E.) and in some of the western part of the 

westernmost mass. Magnetite in the gabbro is associated with ilmenite. Magnetite is also present in black 

sands in an area locally called the Nugget Patch 

( 1,290,000 N ., 370,000 E.) and in gulches that drain 

areas of gabbro and late Tertiary,( ? ) basalt. 

Molybdenite (MoS2) .-Scattered flakes of molybdenite were observed in large quartz veins in the extreme 

southwestern corner of the Prescott quadrangle. Molybdenite also occurs in Copper Basin (Kirkland-Iron 

SpringB quadrangles) about 7 miles west-southwest of 

the city of Prescott. 

Platinum (Pt) .-Platinum has been reported from 

the black sands near Prescott (Galbraith, 1947, p. 10). 

Pyrite (FeS2 ) ·-:-Pyrite is the principal ore mineral in 

most of the fissure veins in the area and is a major constituent in the massive sulfide deposit at the Iron King 

mine. Scattered pyrite crystals are widespread wherever there has been even minor hydrothermal alteration. 

It is sparsely disseminated as tiny cubes in some areas 

of alaskite, Prescott Granodiorite, and Alder Group 

rocks. Pyrite is recovered in the concentrator at the 

Iron King mine largely for its gold content but partly 

because of the demand for its use as a smelter flux. 

Scheelite (Ca W04) .-Scheelite occurs in quartz veins 

in the Gold Coin group (1,293,600 N., 368,300 E.) and 

has been reported from quartz veins in the Prescott 

Granodiorite south of Prescott. 

Serpentine minerals (antigorite and chrysotile, 

H4MgaSi20 9 ) .-Serpentine minerals, of no economic importance, occur in some gabbro, especially in the north-

. ern part of the western mass. 

Sphalerite (ZnS) .-Sphalerite, as minute grains 

forming streaks and aggregates in the pyritic massive 

sulfide and as grains interstitial to the pyrite, is the 

most abundant ore mineral in the Iron King mine. 

Many of the fissure veins in the area contain scattered 

crystals of sphalerite. It was noted at the New Strike 

prospect ( 1,276,200 N ., 357,200 E.) and at a small prospect at the southern edge of the Prescott quadrangle 

(near 384,700 E.); it was also reported by Lindgren 

(1926, p. 102) in a quartz vein (the "Peters silver 

mine") in the southeastern part of the Paulden quadrangle. 

Stibnite (Sb2S3 ) .-Stibnite has_ been reported from 

the Malley Hill mine (Galbraith, 1947, p. 22) on Lynx 

Creek (the exact location is unknown; it may be south 

of the map area). 

Tennantite [ ( Cu, Fe) 12As4Sla].-Silver-bearing tennantite in the Iron King mine adds to the silver content 

of the ore. 

GANGUE MINERALS 

Barite (BaS04) .-Barite is reported (Lindgren, 

1926, p. 25) in the Silver Belt vein, southwest of the 

Iron King mine. 

Carbonate minerals.-Several varieties of carbonate 

minerals occur in the ore deposits. Ankerite 

[CaC03 • (Mg, Fe, Mn) C03 ] is the principal carbonate 

mineral at the Iron King mine. Calcite (CaCOa) is 

found' in many of the fissure veins 1n .the area, as are 

ankerite and dolomite [ (Ca, Mg) COa]. Brown carbonate, possibly siderite (FeC03 ), was noted in a few 

of the fissure veins. 

Chlorite (complex silicate of Fe, Mg, Al20a) .-Alteration zones associated with some of the fissure vein 

deposits contain chlorite. 

Piedmontite (manganese-bearing epidote) .-Although of no economic importance and probably not 

related to any ore-hearing solutions, piedmontite is described here because it is a relatively rare mineral and 

is widely distributed in the southwestern part of the 

Prescott quadrangle. It forms small veinlets and disseminated grains in the southwestern part of the westernmost mass of gabbro, in the Government Canyon 

Granodiorite, and in Prescott 'Granodiorite northnorthwest of Prescott. It is pink, but as seen under 

the microscope, the oolor is not evenly distributed; 

it grades on the edges into a yellow mineral having 

yellow absorption but the same indices of refraction. 

The indices of refraction of the piedmontite are: a, 

1.738; {3, 1.753; y, 1.773 and X, yellow; Y, purple; and 

Z, purple (as determined by Marie L. Lindburg of the 

U.S. Geological Survey in 1949). 

Quartz (Si02) .-Quartz is the principal gangue mineral in most of the ore deposits of the Prescott quad-
106 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

rangle and is the most abundant one in the fissure veins 

of both quadrangles. At the Iron King mine it occurs 

as rather pure masses associated with the massive sulfide or is interstitial to the sulfide grains. It is the main 

constituent in the quartz-magnetite veins in some Precambrian volcanic rocks. Quartz has been mined for 

flux from a quartz vein ( 1,284,000 N ., 398,000 E.) about 

2 miles north of the Iron King mine. Considerable 

amounts are in the large quartz veins on the hill in the 

extreme southwestern corner of the Prescott quadrangle 

and in a large quartz vein in quartz diorite along the 

Verde River (1,413,500 N., 382,300 E.). 

S(3ri.cite [HzKAla(Si04)a].-Sericite is a fine-grained 

variety of muscovite that is widespread in the alteration 

zone associated with the Iron King massive sulfide ore 

bodies and occurs in many of the narrow alteration 

zones associated with the fissure veins. 

Tourmaline (complex silicate of B, AI, Fe, Mg) .-

Black tourmaline occurs in some of the fissure veins. 

Tourmaline-quartz and tourmaline veins are abundant 

in the Dells Granite and the westernmost mass of Prescott Granodiorite, where much of the tourmaline occurs 

as fine hair-like needles. Some of it forms dikelike 

or podlike masses as much as 5 feet wide. Tourmaline 

veins may be younger than some of the quartz veins. 

SUPERGENE ORE MINERALS 

Anglesite (PbS04) and cerussite (PbC03 ) .-Angelsite and cerussite occur in the oxidized parts of the Iron 

King mine and may be present at the surface of some 

of the fissure veins that carry galena. 

0 erargyrite ( AgCl) .-Cerargyrite has been reported 

from the Silver Belt mine, southwest of the Iron King 

mine, where it was found associated with cerussite in 

ancient workings (1Galbraith, 1947, p. 42). 

Chalcocite ( CuzS) .-Small quantities of chalcocite 

are found in many of the fissure veins that contain primary chalcopyrite. It was noted specifically in a prospect near 1,27 4,000 N ., 369,200 E. 

Ohrysocolla (CuSi03 ·2Hz0) .-Films of chrysocolla 

are common at the surface of the fissure veins that carry 

chalcopyrite and at the United States mine ( 1,423,900 

N., 39·9,300 E.). 

Limonite (hydrated iron oxide).-Limonite gossan 

developed at the surface over the Iron King massive 

sulfide deposit and in minor amounts over most of the 

fissure deposits. Some limonite (gossan) was mined at 

the Iron King mine for its precious metal content in 

the early days of mining. 

Mal a chit e [CuCoa ·Cu(OH) 2 ] and azurite 

[2CuCOa·Cu(OH)2].-The green and blue copper carbonates malachite and azurite occur as scattered films 

at the surface of many of the fissure veins, in Tapeats 

Sandstone, and in calcite veins and disseminations in 

the Supai Formation at and south of the United States 

mine. 

M ang(Jffl,ese oxides.-Minor amounts of manganese oxides are associated with many of the fissure veins. 

Vanadinite [PbCl· Pb4 (V04) 3 ] .-Vanadinite occurs 

as yellow to yellowish-green and light-brown needles 

and crusts in galena-bearing calcite veins in Redwall 

Limestone south of the United States mine (1,422,400 

N., 396,000 E.). 

Wulfenite (PbMo04.)-Wulfenite occurs with vanadinite as thin orange wedges south of the United States 

mine. 

GENERAL CHARACTERISTICS 

The ores deposits of the Prescott-Paulden area consist 

of Precambrian massive sulfide deposits, Precambrian 

and possi~ly younger fissure veins, a few noneconomic 

post-Paloozoic fissure veins and disseminated deposits, 

and Quaternary gold placer deposits. Practically all 

the base metal production and much of the precious 

metal production has come from the Iron King lead-zinc 

mine in the southeastern corner, the only known massive 

sulfide deposit within the area. Fissure veins have been 

mined largely for their precious metal content, principally gold; production from them has been small, but 

the amount is unknown. Placer deposits have probably 

supplied less than one-sixth of the gold produced in 

the area. 

As most ore deposits in north -central Arizona are 

Precambrian in age, a know ledge of the thickness of the 

overlying Paleozoic and Cenozoic rocks is important 

in exploring for ore deposits in Precambrian rocks. For 

this reason a map (fig. 31) showing the approximate 

thickness of Paleozoic and Cenozoic rocks in the Paulden quadrangle has been compiled. The approximate 

minimum thickness of Cenozoic rocks in Chino-Lonesome basin is shown on figure 23. 

The configuration of the Precambrian surface is illustrated in the structure contour map of the Paulden, 

Clarkdale, and Mingus Mountain quadrangles (pl. 5). 

As the contours are drawn on the base of the Redwall 

Limestone, the Precambrian surface is about 500 feet 

below the altitudes shown on plate 5, except in an area 

of about 23 square miles that is probably underlain 

by the Mazatzal Quartzite. Within this area the Precambrian surface may be as little as 19 feet below the 

base of the Redwall. The area that is underlain by the 

Mazatzal is economically unimportant, as no ore . deposits occur in exposed portions of the Mazatzal and 

the quartzite has not been intruded by granitic rocks 

or by quartz veins. 

MASSIVE SULFIDE DEPOSITS 

Deposits composed of granular aggregates of sulfide 

:minerals and little or no gangue minerals are referred to 
ECONOMIC GEOLOGY 107 

as massive sulfide deposits. The Iron King mine at 

Humboldt, the only massive sulfide deposit in the Prescott-Paulden area, and the United Verde and United 

Verde Extension mines at Jerome are examples of this 

type of deposit. Pyrite is the dominant mineral, but 

variable amounts of other sulfides, especially chalcopyrite, sphalerite, and galena are present. Where appreciable amounts of these minerals (other than pyrite) occur, the ore is generally banded. Most massive sulfide 

deposits exhibit sharp contacts with host rock, but locally they grade into disseminated deposits. Silification 

and sericitization of the host rocks are common. 

Minable ore shoots are formed where the pyrite-rich 

facies was fractured and base or precious metals were 

added. This type of deposit was formed probably by 

hydrothermal mineralizing solutions that replaced 

schistose rocks. 

FISSURE-VEIN DEPOSITS 

The fissure veins were formed principally by fissure 

filling, but replacement of the wall rock occurred along 

some of them. They occupy shear zones, some of which 

are parallel to the foliation in the enclosing rocks. 

Lindgren (1926, p. 37-48) described two types of 

fissure-vein deposits in the Jerome and Bradshaw Mountains quadrangles: gold-quartz veins of undoubted Precambrian age and gold and silver veins that he considered younger than the gold-quartz veins and possibly 

late Mesozoic or early Tertiary in age. The goldquartz veins are widely distributed throughout the Precambrian rocks of these two quadrangles; the younger 

veins are confined apparently to the southern part and 

south of the Prescott quadrangle. 

The gold-quartz veins are massive or have a crude 

banding. The quartz, which is glassy to milky, occurs 

as pods or lenses in shear zones, which strike parallel 

or at an angle to the foliation in the country rock. Few 

of the veins can be traced for as much as 1,000 ·feet. 

Calcite, ankerite, or siderite ~ay be present. Tourmaline occurs in many of them. The sulfides, which are 

not abundant, consist of pyrite, chalcopyrite, sphalerite, 

and galena. Gold, some of it in visible particles, is present in many of the veins. Scheelite has been noted in 

some of them. In the eastern part of the Prescott and 

Paulden quadrangles, north and south of the boundary 

between them, unmineralized Paleozoic rocks overlie 

Precambrian rocks that contain quartz veins, an occurrence suggesting that the mineralization is Precambrian 

in age. Locally, as in the headwaters of King Canyon 

(1,385,400 N., 385,100 E.) , copper carbonate occurs in 

the Tapeats Sandstone. The copper was probably dissolved out of quartz veins in adjacent alaskite and redeposited in the sandstone by ground water. Quartz, 

'7158-44'7 0----.'65------8 

quartz-tourmaline, and tourmaline veins are abundant 

in the Dells Granite and in the southwestern mass of 

Prescott Granodiorite, but gold and sulfide minerals 

are generally absent from or very sparsely distributed 

in these veins; few of these veins have been prospected. 

Most younger fissure veins are straight and narrow 

and have well-defined walls. The quartz gangue is 

milky and has a drusy structure. Carbonate accompanies quartz in many of the veins, which also have minor 

and variable amounts of arsenopyrite, sphalerite, chalcopyrite, galena, and some tetrahedrite and tennantite. 

Gold and some native silver occur in the oxidized zone; 

gold is not visible in the primary ore. According to 

Lindgren ( 1926, p. 42) many of the veins are associated 

with rhyolite porphyry dikes, which are younger than 

the regional metamorphism and deformation that involved the Precambrian rocks. Other veins, according 

to Lindgren, are apparently related to stocks of quartz 

diorite or granodiorite that he considered possibly postPrecambrian in age. One of these stocks has been 

proved to be Precambrian in age (see p. 96, 35, 50). 

POST-PALEOZOIC MINERALIZATION 

Most of the ore deposits in Yavapai County are Precambrian in age or are probably Precambrian, as are 

the quartz-bearing intrusive rocks from which mineralizing solutions were probably derived. A few are considered Late Cretaceous to early Tertiary in age, partly 

because of similarities to the porphyry copper deposits 

of this age. In the Copper Basin copper-molybdenum 

deposits (W. P. Johnston 14 ; Johnston and Lowell, 

1961) about 7 miles west-southwest of Prescott (Iron 

Springs and Kirkland quadrangles, fig . .1), pyrite, chalcopyrite, bornite, and molybdenum occur in breccia 

pipes in the Copper Basin stock (predominantly quartz 

monzonitic). Surrounding the central copper-molybdenum zone are zinc-lead-silver deposits in which galena 

occurs as cubes as much as 2 inches on a side. The 

Bagdad porphyry copper deposit (about 40 miles west 

of Prescott) is likewise considered to be Late Cretaceous 

or early Tertiary in age (Anderson, Scholz, and Strobell, 1955, p. 79-80) . Lack of overlying Paleozoic rocks 

in these areas makes a positive age assignment 

impossible. 

In the eastern part of the Paulden quadrangle, the 

Supai Formation of Pennsylvanian and Permian age 

has been mineralized, a fact thus proving the existence 

of mineralizing solutions of post-Paleozoic age. Near 

the Verde River from a short distance east to about 

eight-tenths of a mile west of the quadrangle boundary, 

much of the fine-grained red Supai sandstone has been 

14 Johnston, W. P., 1955, Geology and ore deposits of the Copper 

Basin mining district, Yavapai County, Arizona: Utah Univ. Ph. D. 

thesis, p. 96-98. 
108 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

330,000 

4 

750 ____ ___ 

r I I ~~~ 

3 

\ 

\ 

\ 

\ 

EXPLANATION 

0 

Area of outcrop of Precambrian rocks 

?-

Isopach 

4 

Solid isopachs are_drawn on exposed contacts: ()-foot isopach is the contact between 

Precambrian and Paleozoic or Cenozoic rocks; 50()-foot isopach is the contact 

between the Martin and Red wall Limestones, except in the area of the Mazatzal 

Quartzite; and 750-foot isopach is the contact between the Redwall and Supai 

Formations. Dashed isopachs are approximately located; queried isopachs are doubiful 

Fault or monocline 

Shown only where different unit thicknesses are brought into contact or where 

thickness lines are offset 

390,000 

4 MILES 

THICKNESS OF PALEOZOIC AND 

CENOZOIC ROCKS, IN FEET 

D 0-250 [2] 1500-1750 

0 250-500 0 1750-2000 

0 500-750 0 2000..:2250 

0 750-1000 G 2250-2500 

0 1000-1250 0 2500-3200 

0 1250-1500 

FIGURE 31.-Thickness of Paleozoic and Cenozoic rocks, Paulden quadrangle, Arizona. 
ECONOMIC GEOLOGY 109 

bleached white, the silty layers remaining red. At the 

prospect called the United States mine north of the 

river (1,423,900 N., 399,300 E.) and in some of the Supai 

beds south of the river, hydrous copper carbonate and 

silicate minerals are disseminated in bleached sandstone 

or are associated with coarse calcite veinlets in sandstone. Material on dumps from small prospect pits in 

the Redwall Limestone south of the river (1,422,400 N., 

396,000 E.) consists of coarse calcite, cubes of galena 

more than an inch on a side, and a little wulfenite and 

vanadinite. The area has been explored by shallow 

pits in the Redwall and by several shafts of unknown 

depth in the Supai (United States mine), but the deposits are probably too small and low grade to be of 

value. The date of the workings is unknown; it may 

be later than 1922, as the area is not mentioned by 

Lindgren ( 1926). 

PLACER GOLD DEPOSITS 

Placer gold deposits occur in Quaternary gravels 

along the present streams and locally as a mantle on 

pediment surfaces. These gravels rest on Precambrian 

bedrock or on the upper Tertiary (?) deposits. The 

placer gravel is well rounded except near the headwaters 

of the streams. Small nuggets have been recovered 

from the upper reaches, but most of the gold downstream from the Precambrian bedrock is finer grained. 

The gold has been derived from gold-quartz veins. 

- DESCRIPTION'S ' OF IND'IVIUUAL DEPOSITS 

IRON KING MINE 

The Iron King ore deposit was studied by Creasey ; 

for a detailed account of the deposit, the reader is referred to the report on the Jerome area (Anderson and 

Creasey, 1958, p. 155-169), from which the present brief 

summary has been taken. (See also Creasey, 1950, 1952; 

Mills, 1941, 1947.) 

The Iron King lead-zinc mine is in the southeastern 

corner of the Prescott quadrangle and in the northern 

part of the Big Bug mining district. It is the leading 

mine in the district and the only mine in operation 

since 1953. The mineralized outcrop extends for only 

about 300 feet into the quadrangle, although the deposit is being mined for some distance to the north 

beneath the Cenozoic cover. Since 1936 production 

from this mine has come largely from north of the 

quadrangle boundary, although earlier production was 

largely from south of the boundary. 

Production from the Iron King mine from 1906 to 

January 1, 1952, included about 21,486 ounces of gold, 

6,624,101 ounces of silver, 72,573,620 pounds of lead, 

209,199,140 pounds of zinc, and 6,345,740 pounds of 

copper from approximately 1,640,060 tons of ore (Anderson and Creasey, 1958, p. 155). Production from 

1952 through 1956 included about 97,397 ounces of gold, 

3,280,850 ounces of silver, 46,790,978 pounds of lead, 

117,014,330 pounds of zinc, and 2,206,888 pounds of 

copper from approximately 1,043,152 tons of ore (U.S. 

Bureau of Mines, 1953-58). The mine has been developed by seven shafts; only two of these are used and 

both are north of the mineralized outcrop. Some of 

the older shafts are caved. Levels are at 100-foot intervals, except below the 1,200-foot level, where intervals 

are greater; the 2,100-foot level was under development 

in 1958. Drifts are driven along the veins, and raises 

extend above them. 

The deposit was localized in a sheared and deformed 

zone in the andesitic tuff unit of the Spud Mountain 

Volcanics and is about parallel to the regional foliation. 

Intense cataclastic deformation occurred along this zone. 

The rocks were then hydrothermally altered, and early 

vein minerals were introduced. These vein minerals 

were granulated, and a still later period of deformation 

produced a fracture cleavage on the earlier deformation. 

During the early period of mineralization or hydrothermal alteration following the early period of deformation, quartz, pyrite, and ankerite were concentrated . 

in well-defined veins in en echelon shears along the east 

or footwall side of the sheared zone. Disseminations 

and narrow veinlets of these minerals and of sericite 

were deposited west of the veins. The veins and the 

sporadically mineralized zones to the west were then 

intensely sheared, especially the northern parts, and in 

these new openings sphalerite, arsenopyrite, galena, 

tennantite, sparse chalcopyrite, sericite, and probably 

pyrite, ankerite, and quartz were deposited. 

Except where it occurs in veinlets, the quartz of the 

early phase of mineralization or hydrothermal alteration 

cannot be distinguished from the quartz originally present in the metamorphic rocks. Pyrite and ankerite form 

veinlets and disseminated crystals and grains. Pyrite 

is associated with other alteration minerals. Ankerite 

is associated with pyrite and quartz; it also veins the 

late-stage sulfide minerals. 

The twelve sulfide veins that lie along the footwall 

(east) side of the alteration zone are well defined, and 

most of the production of the mine has come from them. 

They crop out in an area that is about 2,500 feet long 

by 100 feet wide. The other sulfide veins in the alteration zone west of the footwall crop out erratically and 

are mostly nonproductive. 

Fracturing and. shearing controlled the size and shape 

of the alteration zone and the widths, lengths, and special relations of the veins. The veins appear to be 

slightly discordant to the structure of the alteration 

zone. 
110 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

Each of the twelve en echelon veins extends in a horizontal plane farther north than the adjacent vein to the 

east. In a vertical plane, each vein extends to a higher 

altitude than its eastern neighbor. The veins strike 

about N. 22° E., dip 71° W., and plunge northward 

between 55° and 60°. They range in width from 1 to 14 

feet and are hundreds of feet long. The contact between 

massive sulfide and wallrock is abrupt. 

Fine-grained massive sulfides and massive quartz 

make up the vein material. The color of the massive 

sulfides ranges from pale yellow to nearly black, depending on the ratio of pyrite to sphalerite and carbonate. 

Quartz is gray, white, and greenish gray. Differences in 

the relative amounts of pyrite, sphalerite, or gangue produce a fine banding in most of the ore; banding is indistinct or absent in nonproductive parts of the veins. 

Pyrite, arsenopyrite, sphalerite, chalcopyrite, galena, 

and tennantite comprise the sulfide minerals, of which 

pyrite is dominant. Ankerite, quartz, sericite, and a 

little residual chlorite constitute the nonsulfide minerals; of these minerals quartz and ankerite are dominant; either one may be more abundant except in the 

northern ends of the veins, where quartz is almost the 

only nonsulfide mineral. 

Deposition of ore-forming minerals (chiefly sphalerite) in fractures or microscopic shear planes in early 

vein filling and variation in relative .rates of deposition 

of the vein minerals probably caused the banding in 

this deposit. Mineral zoning is characteristic of the 

deposit and is generally similar in each vein. The 

northern end of each vein consists mostly of massive 

quartz, south of which the vein is massive sulfide---

largely sphalerite and galena-the content increasing 

to a maximum and then decreasing gradually to the 

south as the pyrite content increases. 

Postmineralization structures include faults, joints, 

and probably fracture cleavage. Larger faults that offset veins are reverse strike faults and are nearly parallel 

to the veins. 

FISSURE VEINS IN THE SOUTHERN PART OF THE PRESCOTT 

QUADRANGLE • 

Although mineralized fissure vein deposits are widespread in the Precambrian rocks along the southern 

part of the Prescott quadrangle, none appears to be of 

any economic importance, and production from them 

has been very small. They have been prospected intermittently since the early days of mining, and shafts 

100 or more feet deep have been sunk along some of 

them. The veins are in the northern margins of the 

Big Bug, Walker, and Groom Greek districts and in 

the Prescott and Lynx Creek districts. Because of the 

similarity of the deposits and the indefinite boundaries 

of the districts, they are not discussed by district. 

The Silver Belt-McCabe vein is about 1,500 feet northwest of the Iron King deposit. It was traced by 

Creasey (Anderson and Creasey, 1958, p. 169) for about 

14,000 feet; only about 1,200 feet of the vein is within 

the Prescott quadrangle. The Kit Carson vein lies 

about 1,300 feet northwest of the Silver Belt-McCabe 

vein and was traced by Creasey (Anderson and Creasey, 

1958, p. 17 4) for about 4,000 feet, only about 500 feet 

being exposed within the map area. Both veins are 

buried to the north beneath the upper Tertiary (?) 

gravels. The strike of the northern sectors of these 

veins is about N. 30° E., about parallel to the Iron 

King zone. The Silver Belt-McCabe vein dips 70°-

800 NW., but the Kit Carson vein dips steeply southeast. The veins may intersect at depth. Several prospect pits and shallow shafts were dug in the part of 

th~ veins within the map area. Gold and silver ore 

"·as produced from three mines on the Silver BeltMcCabe vein, south of the Prescott quadrangle, in the 

early days of mining in the district. 

The shear zones containing the veins consist of fissile 

rock containing abundant chlorite. The wall rock, Spud 

Mountain breccia, is foliated but not fissile, because actinolitic hornblende rather than a micaceous mineral is 

present. Fissile somewhat bleached areas, generally 

only a few feet wide, make up the veins, but some 

bleached zones on the Silver Belt-McCable vein south of 

the map area are 15 feet wide. The ore shoots are 

lenses or pods, most of which are narrower than the 

part of the vein in which they occur. 

The drusy character of these veins, in contrast to the 

massive character of the Iron King deposits, and some 

of the quartz veins in the area suggest that these deposits formed at moderate depths and after the major 

Precambrian deformation. The shear zones in which 

the vein material occurs, on the other hand, are mica.-

ceous; they parallel the structure produced by Precambrian deformation in the area, so that a Precambrian 

age for their formation is probable. 

On the west side of the Spud Mountain about 3,000 

feet northwest of the Kit Carson vein, shear zones occur in breccia of the Spud Mountain Volcanics adjacent 

to the Spud fault and in gabbro and granodiorite within 

the fault. They strike N. 20°-45° E. and dip steeply 

east or west. Several veins have been prospected. 

Quartz, carbonate (at least some of which is probably 

ankerite), pyrite, arsenopyrite, galena, and chalcopyrite 

were noted on some of the dumps along these shear 

zones. Many of the quartz pods and lenses in portions of the shear zones contain minor amounts of pyrite 

and copper carbonates. 

East-trending steeply northward-dipping shear zones 

and quartz veins in granodiorite and gabbro north and 
ECONOMIC GEOLOGY 111 

south of the old State Route 69 (near 1,295,500 N., 

370,000 E.) have been prospected, some of them by shafts 

100 or more feet deep. The highly sheared zones are 

generally 1-4 feet wide, but locally pods of quartz are 

as much as 10 feet wide. Chlorite or sericite has been 

formed along some of the shear zones. Large areas of 

the granodiorite to the northeast show minor silicification, sericitization, and some chloritization. Minute 

pyrite· crystals are rather widely disseminated, and 

quartz, quartz-tourmaline, and tourmaline veins are 

abundant. Both massive and drusy quartz veins occur 

in the area. Pyrite and chalcopyrite were noted in 

specimens from the drusy quartz. Carbonate, fine tourmaline needles as individual crystals and as masses, 

pyrite, and locally chalcopyrite and malachite occur in 

the massive quartz veins. During development work 

on the Gold Coin group (1,293,600 N., 368,300 E.) in 

1950, scheelite was found together with chalcopyrite and 

minor amounts of galena; gold in pockets was reported. 

Two tons of gold ore were shipped in 1950; 110 tons, in 

1946; 1 carload, in 1939; and 2 carloads, in 1935 (U.S. 

Bureau of Mines. 1935-58). 

The New Strike prospect (1,276,200 N., 357,200 E.) is 

located on a strong shear zone that strikes about N. 12° 

W. and dips about 80° W. about parallel to the foliation 

in the rhyolitic tuff host rock, Texas Gulch Formation. 

The prospect has been explored by an adit and several 

shallow shafts and pits for a distance of about 1,500 

feet. According to the U.S. Bureau of Mines (1935-

58), 1,171 tons of zinc-lead ore was shipped in 1942, 

1943, 1946, and 1949. The prospect was reopened 

briefly in the fall of 1952. The rocks in the shear zone 

havebeen silicified and sericitized and contain quartz, 

sericite, carbonate, chlorite, and epidote. Pyrite and 

sphalerite were noted on the dump. 

The Bullwhacker prospect (1,291,000 N., 352,000 E.) 

in what has been called the Prescott district occurs in 

unnamed 'basaltic flows of the Alder ( ~) Group that 

have been intruded by gabbro. According to Blake 

(1898, as quoted in Wilson and others, 1934, p. 28), the 

mine "sometimes called the Bowlder claim * * * is 

notable for bearing coarse gold of high grade in a small 

quartz vein. The vein varies in thickness from a few 

inches to a foot * * *. There is apparently one ore 

'shoot' or chimney pitching northward. The claim has 

been worked to a depth of 132 feet by a shaft, and most 

of the pay ore [has been] extracted ( 1886) to that 

depth." The shaft was caved at the time of Lindgren's 

visit (1926, p. 108). Additional prospecting has been 

done since then, as several shafts in the vicinity were 

observed that are not mentioned in either of the reports. 

According to Lindgren the "vein of massive quartz is 

several feet wide and trends N. 18° E., probably with 

the schist * * *. The massive milky-white quartz contains a little pyrite in crystals and stringers." Calcite 

is associated with quartz in some of the specimens on 

the dump, and a little malachite coats fractures. 

About seven-tenths of a mile east-northeast of the 

Bullwhacker prospect, several shallow shafts and pits 

have been dug in a quartz vein that trends about N. 25° 

W. and dips about 80° E. In places the quartz vein is 

as much as 5 feet wide. Copper stains are abundant on 

the quartz specimens on the dumps. 

The Whitehorse prospect (near 1,285,500 N., 370,500 

E.) is dug in quartz veins in gabbro that is cut by many 

pegmatite, aplite, and granodiorite dikes. The exact 

vein from which some of the high-grade gold ore was 

produced about 1900 (Mr. G. S. Fitzmaurice of Prescott, oral oommun., 1955), is not known as several adits 

and pits have been dug in quartz veins in the area. The 

gold is reported to have been in visible flakes. Specimens on some of the dumps contain pyrite and a little 

chalcopyrite. The quartz is vuggy and the vugs contain 

quartz crystals, a botryoidal manganese mineral, and 

fibrous malachite. 

About 2,000 feet northeast of the Whitehorse prospect, an east-trending shear zone, which dips about 65° 

N., contains a milky vuggy quartz vein. Limonitic 

stains after sulfide are aJbundant. Galena and pyrite 

are in fractures, and crystals of pyrite, one-eighth inch 

in size, are imbedded in the quartz. Near the quartz 

vein, epidote veins are rubundant in the gabbro. Their 

relation to the quartz veins and to mineralizing solutions is not known, but epidote is not abundant in the 

adjacent areas. 

FISSURE VEINS IN MINERAL POINT DISTRICT AND ADJACENT 

AREAS 

Some prospecting has been done on quartz veins in 

Precambrian rocks in the Mineral Point district (eastcentral part of the Prescott-Paulden area) and along 

the Verde River in the eastern part of the Paulden 

quadrangle. 

Lindgren (1926, p. 102) mentioned Ford's copper 

prospect and "Peter's silver mine" in the Mineral Point 

district (probably near sec. 7, T. 16 N., R. 1 E.). He 

stated that shafts were sunk in copper-stained schist at 

Ford's prospect and that at Peter's mine a 2-foot vein 

of quartz in sheared red granite ( alaskite) contained a 

little pyrite, galena, sphalerite, and black streaks of 

felty tourmaline. The Old Hopkins mine (pl. 1, 

1,345,700 N., 394,500 E.) produced some gold, according 

to G. S. Fitzmaurice (oral commun., 1953) of Prescott. 

Production of gold, silver, and copper fro~ the Mineral Point district from 1932--57 is given in table 14. 
112 GEOLOGY OF THE PRESCOTT AND PAUL.DEN QUADRANGLES, ARIZONA 

TABLE 14.-Value of gold, silver, and copper recovered from the 

Mineral Point district, 1932--57 

[Minerals Yearbooks, U.S. Bur. Mines, 1932-57] 

1932-34_____________ 0 

1935 ________________ 1 $3,238 

1936________________ 9,462 

1937________________ 0 

1938________________ 5,217 

1939________________ 2,753 

1940 _______________ _ 

1941--~------------- 1942-45 ____________ _ 

1946 _______________ _ 

1947-57 ____________ _ 

$7,844 

70 

0 

35 

0 

TotaL________ 28, 619 

1 According to Minerals Yearbook, the 1935 production from the district was entirely from lode mines, but according to Wilson (1952, 

p. 57), $3,194 of placer gold was produced in 1935. 

Most quartz veins in the Mineral Point district are 6 

inches to 4 feet wide and occur in shear zones. They 

strike from north-northwest to northeast, except for a 

few that strike eastward. The dips are steep. The 

quartz is massive and glassy or milky. Pyrite occurs 

in small cubes, and minor amounts of copper staining 

(malachite, azurite, and chrysocolla) indicate the presence of primary copper minerals, probably chalcopyrite. 

LYNX CREEK PLACER DISTRICT 

Gold placer deposits occur over a distance of more 

than 16 miles along Lynx Creek and some of its tributary gulches from near Walker (fig. 1), about 3 miles 

south of the Prescott quadrangle, to its junction with 

the Agua Fria River, just east of the rna p area. 

HISTORY OF OPERATIONS .AND PRODUCTION 

Operation of the Lynx Creek placers can be briefly 

summarized as follows: ( 1) early (prior to 1885) smallscale operations, and ( 2) later large-scale operations, 

mostly unsuccessful, and intermittent small-scale operations, especially during economic depressions. 

The placers were discovered in 1863 by a party of 

California miners headed by Captain Joe Walker, and 

more than 200 men were soon working them, according 

to State Historian Hall (Wilson, 1952, p. 39). Active 

work with hand rockers, pans, and small sluices continued for several years before the richest gravels were 

exhausted. Of the 100 men reported to be working 

these placers prior to 1885, some recovered about $20.00 

a day, according to Gilmore (Wilson, 1952, p. 39), and 

one man is reported to have recovered $3,600 in 11 days 

from the lower reaches of the creek, according to 

Shananfelt (Wilson, 1952, p. 39-41). 

· Much money has been spent in efforts to work the 

placers on a large scale; these operations have been confined to the area near the highway bridge over Lynx 

Creek (1,292,500 N., 362,700 E.) and near the Fitzmaurice property along the east-trending portion of the 

creek (sec. 22, T. 14 N., R. 1 W., through sec. 19, T. 14 

N., R. 1 E.; 366,700 E., to 387,700 E.). These operations are summarized below, mostly from data given by 

Wilson (1952, p. 41-42). 

In the late 1880's, an Englishman, B. T. Barlow-Massick, built a small dam rubove the highway bridge across 

the creek and installed a 30-inch pipe from the dam for 

about 2 miles down the creek for use in hydraulic mining of the gravels. The dam was soon destroyed by a 

flood. 

From 1892 to 1895 a steam shovel was in operation 

on a gravel flat a·bout half a mile below the bridge. 

About 1900, the Speck Co. tried out an old dredge a 

short distance below the bridge, but the roughness of 

the bedrock prevented success. Later, Mr. F. G. Fitzmaurice of Prescott, 'vho owned placer claims on lower 

Lynx Creek for many years, operated the Speck Co. 

dredge for a short time, but after recovering about 

$800 worth of gold, the dredge fell apart. A large 

expensive patented gold-saving machine was tried out 

nearby at about this time but, also, without success. 

In 1927, the Lynx Creek Mining Co. attempted largescale operations with a movable plant consisting of an 

excavator, a stacker, screens, and sluices. A large yardage of material was treated. In 1932, a California-type 

dredge was installed on the Fitzmaurice property below 

the lower dam (sec. 22) . The dredge was operated 

from March to July 1933 by the Ca1ari Dredging Co. 

In one 60-day period, 60,000 cubic yards of gravel, yielding approximately 32 cents per cubic yard, was treated. 

The operation is described in some detail by Wilson 

( 1952, p. 41-42). 

Upper Lynx Creek from the area called Bigelow Flat 

(1,279,000 N., 359,700 E.) to half a mile below the highway bridge was leased by a Mr. Barnes, according to 

F. G. Fitzmaurice (oral commun., 1953) and operated 

by doodle bug during 1940-41. Doodle bug is a term 

used in placer operations for unconventional methods of 

getting the gravel to a conventional gold-saving machine. It is used where lack of water or other factors 

make conventional dredging operations impractical. It 

may consist of dragline, power shovel, or other improvised equipment. 

Other dredging operations are summarized by Wilson 

(1952, p. 42) as follows: 

Arizona Dredging and Power Co. : Latter part of 1933. 

Lynx Creek Placer Mine Co., 1934-40: Treated 556,115 

cubic yards of gravel in 1938 and 542,815 cubic 

yards in 1939 with large floating washing plant and 

two draglines; was largest producer of placer gold 

in Arizona (mostly on Fitzmaurice property). 

Phoenix Lynx Creek Placers Co. : 1934. 

Rock Castle Placer Mines Co. : Last quarter of 1939 ; 

handled about 12,000 cubic yards of bench gravel 

(above the Lynx Creek Placer mine dredge) by 
ECONOMIC GEOLOGY 113 

means of a dry-land dredge equipped with four 

bow !-amalgamators. 

Placer King Mines, Inc. : In September 1940 took over 

property and equipment of Lynx Creek Placer Mine 

Co. 

Big Bug Dredging Co. : 1941. 

Minona Mining Co.: 1948--49, on Fitzmaurice property. 

Other dredges at several properties: 1940-42. 

Parker and Raymond: 1952--53, dragline dredge. 

Intermittent small-scale placer operations have been 

carried on for many years. According to A. S. Konselman (Wilson, 1952, p. 42), the average earnings during the spring and summer of 1933 amounted to 50 cents 

per day per man; at this time approximately 30 men 

were recovering gold by rocking and sluicing largely in 

dry side gulches on upper Lynx Creek. According to 

F. G. Fitzmaurice (oral commun., 1953) as many as 

500-600 men worked the placers during 1933-34. One 

160-acre plot is reported to have had 100 men working 

on it. 

Total production from Lynx Creek was probably 

about $2 million. Records of early-day yield are not 

available, and much of the recovery by individuals has 

not been recorded or the records were not accurately 

kept. The principal producing periods were prior to 

1885 and 1933--42. It is not possible to make sense out 

of the various estimates and records of production from 

the district, nor to be certain how much of the production has come from the portion of the district that lies 

within the Prescott quadrangle. Most of the production, however, probably came from within the Prescott 

quadrangle, as all the large-scale operations have been 

from this part of the district. Production from 1914 

to 1957 is given in table 15. The district has accounted 

for about 20 percent of the placer gold produced 1n 

the State and about 34 percent of that produced 1n 

Yavapai County. 

GEOLOGY AND OCCURRENCE OF THE GOLD 

The geology along Lynx Creek is shown on plate 1. 

A stock of granodiorite considered by Lindgren ( 1926, 

p. 21-22) as possibly post-Precambrian hut by Wilson 

(1937, fig. 5, p. 34) as Precambrian in age is south of 

the map area near Walker. Wilson's map also shows 

schist and undifferentiated diorite and granite in this 

area. Within the Prescott quadrangle, the northtrending part of Lynx Creek is cut on Prescott Granodiorite, gabbro, unnamed tuffa·ceous rocks of the 

Alder ( ? ) Group, fine-grained granite, coarse-grained 

granite, and rocks of the Texas Gulch Formation. The 

east-trending part of the creek east of coordinate line 

370,000 E. is cut on upper Tertiary ( ? ) rocks that consist of well-cemented coarse gravel close to Precambrian 

bedrock but grade eastward into fine-sand, silt, clay, 

TABLE 15.-Value ot gold and silver production of the Ly'YUJJ 

Creek placers, 1914-57. 

[Mineral Resources of the United States, U.S. Geol. Survey, 1914-23, 

and U.S. Bur. Mines, 1924-31 ; and Minerals Yearbooks, U.S. Bur. 

Mines, 193,2-57. Data for the years 1914-31 taken from Wilson, 

Hl37 facing p.. 116.] 

1914 _____________ $3,733 1936 _____________ $144,328 1915 _____________ 4,587 1937-38 __________ 73,981 1916 _____________ 1,372 1939 _____________ 92,324 1917 _____________ 2,424 1940 _____________ 71,257 1918 _____________ 1,647 1941 _____________ 153,650 1919 _____________ 1,225 1942 _____________ 3,055 1920 _____________ 0 1943 _____________ 280 

1921 _____________ 1,104 1944 _____________ 0 

1922 _____________ 1,225 1945 _____________ 0 

1923 _____________ 2,356 1946 _____________ 1,859 1924 _____________ 765 1947 _____________ 0 

1925 _____________ 314 1948 _____________ 1,969 1926 _____________ 445 1949 _____________ 12,822 1927 _____________ 0 1950 _____________ 70 

1928 _____________ 0 1951 _____________ 105 

1929 _____________ 2,764 195-2 _____________ 0 

1930 _____________ 2,378 1953 _____________ 1,896 1931 _____________ 1,034 1954------------- 0 

1932 _____________ 4,563 1955 _____________ 35 

1933 _____________ 26,672 1956 _____________ 0 

1934 _____________ 126,681 1957 _____________ 0 

1935 _____________ 100,905 

TotaL _____ 1 843,825 

1 Total may include values of some placer gold from the part of the 

district that lies south of the Prescott quadrangle. 

and limy beds. The Precambrian formations and foliation within them trend northward; dips are steep to 

vertical. Gold is found in gravels along the entire 

length of Lynx Creek. It was probably derived from 

gold -quartz veins in the Walker district. Where the 

creek bed is cut on Precambrian rocks, a distance of 

about 8 miles, placers occur as thin benches or bars a 

few yards in width. Where the creek bed is cut on 

upper Tertiary(?) deposits, placer gravels attain a 

maximum width of about 1,000 feet and a thickness, 

according to Wilson ( 1937, p. 35) , of 8-24 feet. Wilson 

stated that some gold was said to be present throughout this thickness, but the richest material is at the bottom of the gravels and in a 4-foot streak about 2 feet 

higher. Gold occurs along some small dry side gulches 

tributary to upper Lynx Creek. 

Lindgren (1926, p. 109) stated that the average value 

of the placers was reported at 18 cents per cubic yard. 

H.e reported: "At Walker the placers yielded nuggets 

worth as much as $80, about $16 an ounce. Lower 

Lynx Creek produced a finer grained gold of higher 

value, worth about $18 an ounce. Such an enrichment 

in the value of the gold is common and indicates a solution of the silver by the waters." According to Wilson 

( 1952, p. 43), the "gold of lower Lynx Creek ranges 

from finely divided material up to $6 to $8 nuggets, and 
114 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

is associated with considerahle hematitic and magnetitic 

blruck sand." During the operations lof the Calari 

Dredging Co. in 1933, 85-90 percent of he gold in the 

gravels was extracted. "It ranged in ize from flour 

up to fragments 0.1 inches in diameter * *" (Wilson, 1952, p. 42). 

OTHER PLACER DEPOSITS 

Placer gold occurs along the upper bra ches and main 

course of Granite Creek, mostly south f the Prescott 

quadrangle, although gold has been reco ered nearly as 

far north as the Granite Dells. Some gold has been 

reported in washes and in pediment and errace gravels 

along Granite Creek north of the Gra:p-ite Dells and 

near Del Rio, about 20 miles north of rescott (Lindgren, 1926, p. 54) . The Granite Cree · placers were 

discovered in the 1860's and worked to a considerable 

extent during the 1880's. The New En land Gulch, a 

tributary, was reported to have been ve rich; one oldtime placer miner recovered a:bout $20,00 worth of gold 

prior to 1922 (Wilson and Tenney, 1932, p. 37) . Some 

small nuggets were found when excava ing for buildings in Prescott, according to Mr. H. R. ood (Wilson, 

1952, p. 56). Granite Creek pla·cer pr duction from 

1931 to 1957 is given in table 16. 

TABLE 16.-Recorded production of placer g Zd from Granite 

Creek, 1931-51 

[Mineral Resources of the United States and Miner ls Yearbooks, U.S. 

Bur. Mines, 1931-57] 

1931 ________________ _ 

19.32 ________________ _ 

1933 ________________ _ 

1934 ________________ _ 

1935----------------- 1936 ________________ _ 

1937-38 _____________ _ 

$390 

623 

414 

144 

84 

1941 ________________ _ 

1942-43 _____ 1 _______ _ 

1944--------t -------- 1945-46 _____ T _______ _ 1947 ________ T _______ _ 

10 1948-57 -----r -------

$245 

0 

70 

0 

35 

0 

1939 ________________ _ 0 

385 

560 

TotaL__________ 1 3, 020 

1940------------~----

1 Wilson (1952, p. 57) listed Granite Creek placer production 1931-49 

as $1,983. 

An area locally called The Nugget Patch (1,290,000 

N., 370,000), between the headwaters of Clipper Wash 

and a wash that enters Lynx Creek below the Lower 

Dam, is reported to contain gold in black sands, probably derived from the underlying quartz veins in 

gabbro. A little development work was done in 1948 

by Mr. D. P. Lawson, hut the operations were hampered 

by lack of water. 

NONMETALLIC DEPOSITS 

BUILDING STONE 

Precambrian, Paleozoic, and upper Tertiary ( ~) rocks 

are used as building stone and in road construction. 

The Prescott Granodiorite near Prescott is the most 

widely used of the Precambrian rocks, principally for 

foundations and trim in homes and larger buildingsfor example, the trim on Yavapai County Court House 

(1916) in downtown Prescott. The granodiorite is fine 

to medium grained and takes a good polish; the large 

poikilitic microcline crystals, as much as an inch across, 

give a pleasing effect when the light is reflected from 

their cleavage planes. Mazatzal Quartzite and some 

interbedded conglomerate are used in and near the village of Chino Valley for foundations and home 

construction. 

Upper Tertiary ( ~) rocks used in home construction 

include some of the tuffaceous sedimentary rocks, especially the orange-colored tuff used for trim and other 

construction when sufficiently indurated. A gray rhyolite tuff bed north of Prescott was used in constructing 

the Armory in Prescott and a few fireplaces. The tuff 

(described on p. 73) crops out beneath basalt near the 

tops of two hills south of Willow Creek: ( 1) On the 

east side of the hill near 1,306,700 N., 332,200 E., and 

( 2) on the north end of the hill near 1,305,000 N ., 331,800 

E., where it has been quarried. Attempts have been 

made to quarry the Glassford cinder cone for cinder 

blocks, but apparently the large bombs and blocks of 

basalt make the material undesirable. 

Sandstone is quarried in the extreme northeastern 

corner of the Paulden quardangle (sees. 26, 27, 34, and 

35, T. 19 N., R. 1 E.). Many more quarries are north 

and east of the quadrangle. The Coconino Sandstone 

and some of the sandstone beds near the top of the 

Supai Formation are strongly crossbedded on a large 

scale, and much of the rock splits readily along crossbeds into thin slabs and sheets. Sandstone that splits 

into pieces not more than 2 inches thick and as much as 

4--6 feet square (minimum of 18 inches on a side) is 

sold as flagstone for exterior use, chiefly in steps, sidewalks, and patios. Sandstone that is more than 2 inches 

thick is cut into strips 2-4 inches thick and about 3lj2 

inches wide for use as exterior decoration or veneers on 

buildings. Very large pieces are cut into building 

blocks. A more detailed account of this resource is 

given by Lehner (1958, p. 587-588). 

LIMESTONE 

Limestone is widespread in the Paulden quadrangle, 

but only parts of units 1, 2, and 4 of the Redwall are 

pure enough to be suitable for use as raw material for 

cement and lime. Limestone was being quarried in 

1928 (Tenney, 1928, p. 109) at Cedar Glade (Drake) 

in the north-central part of the quadrangle. The broken 

limestone was trammed to the kiln, where it was burned 

and shipped as lime. The Drake operation was one of 
ECONOMIC GEOLOGY 115 

the three principal producers in Yavapai County for a 

long period prior to 1928 (Wilson and Roseveare, 1949, 

p. 25) . Open pits and remnants of kilns are ( 1) along 

Limestone Canyon (NWl4SEl4 soo. 34, T. 19 N., R. 2 

W.), (2) about three-fourths mile southwest of Drake, 

and (3) about 1% miles north-northeast of Paulden. 

In 1956, the limestone near Drake was drilled, but the 

project was dropped, in part because of lack of sufficient 

water and good clay in the area. 

WATER RESOURCES OF THE PRESCOTT AREA 

A study of the water resources of the Prescott area 

was made in 1945 and 1946 by personnel of the Ground 

Water Branch of the U.S. Geological Survey. The 

study was made under a cooperative agreement at the 

request of the Honorable James Whetstine, at that time 

Mayor of Prescott, and an informal report on the preliminary results of the study was submitted to the city 

in September 1945. 

Geologic and hydrologic fieldwork was carried on by 

K. K. Kendall.and H. M. Babcock of the GroundWater 

Branch with assistance and cooperation by Mayor 

Whetstine and by Mr. Charles Shaw, at that time Water 

Superintendent for Prescott. The information pre- _. 

sented in this section is condensed from the preliminary 

results of K. K. Kendall and H. M. Babcock. Record 

of wells and springs in the Prescott area, collected during the investigation, is shown in table 17. The location of these wells and of other wells in Chino-Lonesome 

Valley is shown on plate 3. 

HISTORY OF USE OF GROUND AND SURFACE WATER 

Prescott was founded in 1864, and since then the problem of an adequate water supply has been an ever-present concern. Until 1884 the inhabitants of the city 

depended entirely on shallow wells for their water supply. At that time a dam was constructed on Miller 

Creek to impound the surface flow, and water was 

pumped from the storage reservoir to a tank a:bove the 

city. As this supply was inadequate and the water of 

poor quality, a large portion of the water supply continued to he dbtained from wells. In 1891, an infiltration gallery, a permeable structure equivalent to a horizontal well, was constructed in the channel of Granite 

Creek. As the city continued to grow, the supply from 

this gallery became inadequate, and in 1899 another gallery was constructed nearby. The demand for water 

soon outgrew the supplies available from the infiltration galleries, and in 1901 a pipeline was constructed to 

Del Rio Springs (near Puro, 1,391,000 N., 342,200 E., 

pl. 2), about 19 miles north of Prescott. An adequate 

supply was available from this source, but the cost of 

pumping a distance of 19 miles and lifting the water 

about 1,000 feet was considered excessive. 

In an attempt to obtain a cheaper water supply, a 

dam (Goldwater Lake) was built in 1923 on Bannon 

Creek aJbout 3 miles south of Prescott ( 1,273,500 N ., 

337,300 E.). Later, another dam was built a short distance upstream, and several small dams were constructed 

on nearby streams. Water was piped from these 

smaller dams to the reservoirs on Bannon Creek. Upon 

completion of these storage reservoirs, the pipeline to 

Del Rio was abandoned and later removed. 

In 1945 Prescott was dependent primarily on this 

system of surface storage reservoirs for its water supply. Some additional water was obtained from the 

infiltration galleries on Granite Creek and from a privately owned well about 4 miles north of the city-No. 

1, sec. 14, T. 14 N., R. 2 W. These sources were inadequate, and a period of severe drought complicated the 

situation. 

As the investigation by the U.S. Geological Survey in 

1945 and 1946 did not indicate an adequate water supply close to Prescott, in 194 7 the city drilled two wells 

(Nos. 6 and 7, sec. 22, T. 16 N., R. 2 W.) that tapped 

the Chino artesian basin. The wells were located approximately 5 miles south of Del Rio Springs, thereby 

reducing the piping costs by an estimated $140,000. 

The first well was completed in October 1947 and yielded 

more than 1,000 gpm (gallons per minute) during a 

pumping test of several hours. The second well, a quarter of a mile to the north, was completed in December 

of the same year. The yield here was about 1,850 gpm, 

which equaled the capacity of the testing equipment. 

Water from these wells was piped to Prescott in May 

1948, ·and the wells are now the principal source of 

supply. Surface water from Goldwater Lake is still 

used, and much of the water that supplies Miller Valley 

comes from wells tapping a small artesian basin in the 

area. 

Water for domestic use outside the city of Prescott 

is dbtained principally from wells. Water for irrigation near the village of Chino Valley is obtained from 

deep wells that tap the Chino artesian basin and is supplemented hy water brought along an irrigation ditch 

to Chino Valley from 'artificial Watson Lake in the 

Granite Dells. Water from springs along Del Rio 

Creek, at and south of Puro (1,391,000 N., 342,200 E.) 

and from nearby wells, for many years supplied water 

to Grand Canyon Village and still supplies Ashfork 

and Seligman on the Santa Fe Railroad. Water for 

stock on the range is obtained from "tanks"-basins 

formed mostly by earthen dams across gullies where 

runoff is impounded. This supply is supplemented by 

)Vater pumped from shallow or deep wells. 
116 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

TABLE 17.-Record of wells and springs in the Prescott area 

[All wells are drilled unless otherwise noted in the remarks column. Well and spring records were collected by H. M. Babcock and K. K. Kendall of the U.S. Geol. Survey and by John Gibbs (1945-46). Pump and power: Cf, centrifugal; J, jet; C, cylinder; T, turbine; B, bucket; G, gasoline; E, electric; H, hand; W, windmill; and 

N, none. Use of water: D, domestic; S, stock; I, irrigation; P, public supply; and N, none. Measuring point was generally top of casing, top of pump base, top of water- pipe clamp, or top of well curb] · 

Well Water 

level 

(depth Date of Pump 

Section and well Owner Driller Altitude below measure- and 

(feet Depth Diam- meas- ment power 

above (feet) eter uring sea (inches) point 

level) in feet) 

T.l3N.R.,2W. 

Sec. 2, wellL ____ J. Roberts __ ---------- ---------------- -------- --------- 30 60 22.3 6/ 5/46 Cf, G 

3, wellL ____ E. H. Smith __________ White _________________ --------- 107 1102.0 J, E 

2----- Boyd Tenny ______ ____ ---- -------------------- --------- 25 60 -------- ---------- c, w 

4, well2 _____ G. E. Jones ___ ___ _____ --- --------------------- --------- 16 72 -------- ---------- C, E 

5, wellL ___ _ H. Cory ____ __________ Bob Kuhne __ ___ ______ --------- 360 8 1100.0 T, E 

2 _____ M. E. Claw ___________ 

-B'oi>-KUhile== = === ===== --------- 20 60 8.6 6/17/46 J, E 

9, wellL ____ A. F. Bumpas ________ --------- 130 6 J, E 

12, wellL ____ H . B. Warbass ________ ------------------------ --------- 22 60 I 15.0 B, H 

T. 14 N ., R. 2 W. 

Sec.10, well L_ __ _ San Dreta .. __________ __ White & Kuhne____ __ 5, 219.9 894.0 84.7 7/1/46 N 

14,wellL ___ _ E. Weston ____________ E. Weston ____________ 5,196.2 223.0 10 148.0 9/ /46 T, E 

3 _____ ----_do __ --------------- ___ __ do __ -------_______ 5, 200. 0 1, 013.0 14 150.0 N 

16, well L__ __ Johnson ____ ----------_ ----------------------- _ 5, 206.8 120. o 6 28.2 8/10/46 Cf, E 

2 _______ __ _ do ________________ ------------------------- 5,209.1 130. 0 17.3 7/ 1/46 c,w 

c,w 

c,w 

3 _____ Ralph Murphy _______ ------------------------ 5;227.5 30. 0 

4 _____ W. H . Handcock ______ ------------------------ _________________ _ 60 22. 4 ___ _do_--

60 -------- ----------

18, well L ____ Roy Haines ___________ ------------------------ ___ ______ 30.0 60 10.5 6/13/46 C,H 2 _____ U.S. Forest Service ___ ------------------------ ___________________________________________ _ N 

3 __ __ , D . W. Fuller __________ ------------------------_________ 60.0 

4 _____ B. A. Logan __________ --------------------------------- 100.0 

19, well!_ ____ L. C. Holmes _________ Fred Green ___________ ---------

2 _____ B. A. Logan_---------- ------------------------ --------- 3_____ L. W. Keeley--------- ------------------------ ________ _ 20, well L ____ Roy C. Saline_----------------------------------------

21, well L____ Dan SideL___________ Bob Kuhne___________ 5, 350.0 

2 _____ J. C. Brown ___________ Fred Green ___________ 5,565.0 

97.0 

100.0 

48.0 

12. 0 

290.0 

304.0 

5 __________ do __ -------------- ------------------------ 5, 518.8 62.0 

22, well 2_____ E. Weston __ ---------- E. Weston __ ---------- 5, 452.6 --------- 3 __________ do __________________ ___ do ________________ ------------------

23, well L ____ City of Prescott _______ J. Pulleum ____________ 5, 196.7 479.0 2 __________ do _____________________ do ________________ 5,199.4 44.0 

3 _____ ------------------------· ------------------------ --------- 61.0 

24, well L ____ W. R. Storm __________ ------------------------ 5, 250.7 91.0 

26, well 2-----1 City of Prescott_______ J. Pulleum____________ 5, 214.0 149.0 

3----- \ U.S. Veterans Adm ___ ------------------------ 5, 215.8 25.0 

4_____ City of Prescott_ ______ ------------------------ --------- 9. 0 

See footnotes at end of table. 

Cf, G 

C,W 

6 11. 9 6/13/46 

6 -------- ----------

6 -------- ---------- J, E 

6 -------- ---------- C,E 60 -------- ---6ii3/46- C,E 

60 6.4 Cf, E 

6 -------- ---------- C,W 

6 170.0 7/18/46 J, G 

48 49.2 7/ 5/46 N 

4 212.0 8/12/46 N 

36 13.5 7/ 5/46 N 

6 155.0 1946 N 60 1. 45 12/ 1/46 N 

60 26.8 7/ 9/46 C,H 

48 83.2 8/ 8/46 c,w 

8 5.8 11/ 7/45 N 

72 

30 1.7 

3. 7 11/ 9/45 N 8/22/45 N 

Use of water 

D 

D, I 

D 

D, I 

D 

I 

D 

D 

Temperature Remarks 

(oF) 

56 Dug well; reported water from coarse gravel. 63 Reported water from 

caliche. 

Dug well; reported water from caliche. 

61 Dug well; reported water from fractured 

quartz 15-16 ft.2 

63 Reported water from 

weathered granite.3 

59 Dug well. 

64 Reported water from 

weathered granite. Reported discharge, 

6 gpm from alluvial 

fill. 

N Reported discharge, 60 gpm with 70-foot 

drawdown when 

used. 

D, S, P, I __________ Reported water from 

N 

D 

s 

D, I 

D, S 

D 

D, S 

D, S, I 

S, I 

D, S 

D 

D 

D, S 

D 

D 

N 

N 

N 

N 

N 

D, S 

D, S 

N 

N 

N 

coarse gravel at 215 

ft. Reported discharge, 250' gpm. 

Reported well can be 

bailed nearly dry. 

65 Dug to 60ft; drilled 

6Q-120 ft. 

65 Reported water from 

hard rock 128-130 ft. 

57 Dugwell. 61 Do.2 

59 Do.2 

64 

60 

Spring, measured flow 

2 gpm 7/10/46. 

63 Reported 25-ft drawdown after pump- ing 5 hours.2 

60 

61 Dug well. 

57 Dug well; reported water from decomposed granite.2 

(2). 

65 Reported discharge, 5 

gpm.2 

Dug well. 

Dug well. 

City test well 3.2 Dug to 34 ft. Test 

welll. 

59 Dug well. 

62 Dug well; reported water from weathered granite.2 

Measured discharge 

about 3 gpm, with 

14-ft drawdown, 

July 1946. Test 

well 2. Originally pumped at 40 gpm; 

later, it produced less than 3 gpm.2 

Dug well. 
ECONOMIC GEOLOGY 117 

TABLE 17.-Record of wells and springs in the Prescott area-Continued 

Well Water 

level 

(depth Date of Pump TemperSection and well Owner Driller Altitude I below measure- and Use of ature Remarks 

(feet Depth Diam- meas- ment power water (° F) 

1 

above (feet) eter uring sea 

I 

(inches) point 

level) in feet) 

T. 14 N., R. 2 W-Conth,tued 

Sec. 27, well 1_ ____ U.S. Veterans Adm ___ ------------------------ 5, 272.5 41a. 0 8 I 26,0 N N Reported discharge, 5 

gpm.2 2 _____ 

-Y:iiv-apaicolilii:Y-E!o-s~- -B"ob-Kuilile=========== -5;376:6- 16.0 60 6. 0 6/20/46 C,W s 64 Dug well. 

28, well L ____ 252.0 6 I 46.0 6/12/46 T,E D, I 6a Measured discharge, 10 

pi tal. gpm, with 56-ft 

drawdown, July 

1946. Water reported to stand near surface 

in winter. After 

pumping all summer 

• (about 6 months) water is down more than 100ft. 2 _____ Black_-------------- __ ------------------------ -5;4oi:i- 85.0 6 -------- ---------- c,w D 62 a _____ Yavapai County ______ ------------------------ 40.0 120 11. a 7/17/46 T,E I 57 Dug well; reported 

Hospital. pumps dry in 5 

hours. 

4 _____ _____ do _________________ ------------------------ 5, 401.7 180.0 12 2.8 6/12/46 J, E Reported discharge, 

10 gpm. 5 _____ _____ do _________________ H . MaxwelL __________ 5,a79. 0 72 21.6 7/17/46 C,E Dug well, reported 

discharge, a gpm. 

6----- Stephenson ___________ ------------------------ --------- 22.0 60 I 11. 0 E D 61 Dug well. 7 _____ J. F. Scott _________ ___ ------------------------ --------- 180.0 6 115.0 J, E D, I 60 (2), 

29, well l_ ____ C. J. Walworth -------- ------------------------ --------- 16.0 60 7. a 6/lata6 Cf, E D 59 Dugwell.2 

2 __ ___ _____ do _________________ ------------------------ --------- 19. 1 60 14.1 ___ do _____ Cf, E D 64 Do. a _____ C. A. Holz ------------ ------------------------ --------- 20.0 60 10. 1 ___ do _____ Cf, E D 59 Dug well; reported 

pumped dry in 5 

hours. 4 _____ _____ do __ _______________ ------------------------ --------- 18.0 60 16.0 ___ do _____ C,H I 58 Dug well. 5 _____ J.D. Garrett_ _________ ------------------------ --------- 11.0 60 6. 0 ___ do _____ Cf, E D 57 Do. 

6----- D. Haymore __________ ------------------------ --------- 65.0 6 16a. 0 Cf, E D, S 59 Reported well can be 

pumped dry in a days. 

7 _____ v. R~muz _____________ Bob Kuhne ___________ 5, a89. 6 168.0 6 I 18.0 Cf, E D 60 Reported discharge, 

10 gpm. 8 _____ G. D. Owens __________ ------------------------ -5;377:i- 55.0 48 14. 0 C,E D Dug well. 2 

9 _____ L. WelL _______ _______ ------------------------ 256.0 8 17.8 8/ 8/46 C,E D 59 Reported discharge, 

40 gpm. 10 _____ L. R. Templin ________ ------------------------ --------- 16.0 60 I 11.0 Cf, E D, S 65 Dug well, reported water from decomposed granite.z 

ao, well L_ ·-- H. A. McDowelL _____ ------------------------ -----·--- 16.0 60 10.0 6/14/46 C,E D, s Dug well. 

31, well!_ ____ Docherty __ ----------- ------------------------ ---·----- a9. 0 72 I 4. 0 J, E D, I 60 Dug well; estimated 

discharge, 15 gpm. a2, well 1_ ____ H. Fee ________________ 

-B"<>l>-Kuhue=~~=~~==~== --------- 44. 0 60 27. 0 6/18/46 J, E D 60 Dug well. 2 _____ F. W. Steed ___________ --------- 41.0 6 112.0 Cf, E D 61 Well is dug 20 feet 

and drilled 21 feet. aa, well4 _____ D. Miller ______________ 0. Cook _______________ --------- 115.0 I 20.0 C,E D 64 Reported water from 

alluvial fill and decomposed granite. 5 _____ V. B. Balcom _________ ------------------------ --------- 140.0 I 25.0 E ----- D, I 64 

6 _____ A. B. Romero _________ ------------------------ --------- 15.0 60 18.0 J, E D 61 Dug well.2 

7---"- J. J. Pruitt__ __________ ------------------------ --------- 8a. 0 8 I 50. 0 C,E D, I 59 Dug to aa feet; reported 

discharge, 5 gpm.2 8 _____ Deshane __ ------------ ------------------------ --------- 20.0 60 -------- ---------- J.E D, I 59 Dug we11.2 9 _____ H. Allan _____________ ------------------------ --------- --·------- 60 I 10.0 Cf, E I 60 Dug well; reported 

struck alkali water at 85ft. 10 _____ A. Rivas ______________ ------------------------ --------- ao. 0 48 I 20.0 N N 55 Dug well.z 

ll _____ J. E. Benagas ______ ___ ------------------------ --------- 17. 0 48 10.0 6/19/46 B,H D 59 Do. 12 _____ D. Hyslip ____ _____ __ __ ------------------------ --------- 41.0 60 -------- ---------- C,E D Dug well: reported 1-ft 

drawdown after 

pumping 4 gpm for 4 hours. la _____ E. L. Lee _____________ ------------------------ --------- 2a. 0 60 -------- ---------- C,H D 56 Dug well. 14 _____ E. Leva _______________ ------------------------ --------- 12.0 48 9. 0 6/18/46 N N 60 Do. 15 _____ A. N. Garcia __________ ------------------------ --------- 45.0 48 17.0 6/19/46 N N 55 Do. 

a4, well L ____ City of Prescott_ ______ Bob Kuhne ___________ --------- 472.0 -------- ---------- N N 67 Artesian well; flows 7 gpm; reported drawdown, 68 ft when 

pumping 52 gpm.2 2 _____ _____ do _________________ Fred Green ___________ --------- 265.0 19.0 7/12/46 N N Measured discharge, 10 gpm, 6/12/46. a _____ KYC Radio Station ___ ------------------------ --------- 256.0 159.0 C,E D Reported discharge 10 gpm. 6 _____ M. F. Tallent_ ___ _____ ------------------------ --------- 12.0 48 19, 0 C,H D 58 Dug well. 

7----- T. W. Mayfield _______ ------------------------ --------- 18. 0 60 110.0 Cf, G D, I Dug well; reported discharge 6 gpm. 

a5, well l_ ____ Vandenberg ___________ ------------------------ --------- 8. 0 60 I 4. 0 c,w D, S, I 60 Dug well; reported 

drawdown, 1 ft after 

pumping 12 gpm for 

8 hours.z 

See footnotes at end of table. 
118 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZO~A 

TABLE 11.-Record of wells and springs in the Prescott area--Continued 

Well Water 

level 

(depth Date of Pump TemperSection and well Own!lr Driller Altitude below measure- and Use of ature Remarks 

(feet Depth Diam- me as- ment power water (oF) 

above (feet) eter uring sea (inches) point 

level) in feet) 

T. 14 N ., R. 3 W. 

Sec. 13, well 1 ___ U.S. Forest Service ___ ------------------------ ___ ___ _______________ _____________ -------------------- S ___ _____ __ Spring; estimated flow 

1gpm. 24, well L .. Tom Iglehart. ________ ------------------------ __ ______ _ 51 60 45. 0 6/14/46 Of, E D ---------- Dug well; reported water from weathered granite. 

T. 15 N ., R. 2 W. 

Sec. 17, well L--- R. E. Perkins _________ ------------------------ 5, 057.0 

23, well L.-- _____ do_________________ White_________________ 5, 076.0 

25, well L ___ City of Prescott_ ______ E. Weston ____________ 5, 010.0 

2 _________ do _________________ ChurchilL ____________ 5,014.0 

30, well L___ Webb _________________ ------------------------ 5, 185.0 

2____ C. Brown _____________ ------------------------ 5, 198.9 

32, well L___ Webb _________________ J. Pulleum ____________ ---------

1 Water level reported. 2 See table 18 for water analysis. 

430 

578 

839 

812 

150 

180 

132 

Perennial flow in streams is limited to the Verde 

River and two of its tributaries. Granite Creek has a 

permanent flow of water below a spring ( 1,401,500 N., 

346,000 E.) where the creek crosses a fault about 0.8 

mile south of the Verde River. Del Rio Creek issues 

from springs that tap the Chino artesian basin, and 

flows north to the headwaters of the Verde River. Hell 

Canyon, a tributary of the Verde River, has a permanent flow for a few hundred feet below King Spring 

(1,435,600 N., 376,900 E.) where it crosses a fault, but 

water soon disappears into the upper Tertiary( n 

gravel. A few springs are found in the southern part 

of the area, especially along and west of Lynx Creek. 

Generally water flows down intermittent streams and 

smaller gulches and gullies in winter for short periods 

owing to runoff of rain and melting snow and in summer for a few hours following rains, which may be of 

torrential proportions. Major gulches that cross Precambrian rocks in the southern part of the area may 

have sustained flow for four or five months in the winter 

and for shorter periods in the summer. Once the water 

reaches the alluvium of the valleys, however, it disappears within a short distance. 

GROUND•W ATER RESOURCES 

Only the sedimentary and associated volcanic rocks 

of late Tertiary ( ~) age in the Prescott area contain 

sufficient water for large-scale production. Therefore, 

most of the investigation was concerned with these materials. The water-bearing properties of the upper Ter8 329.9 6/ 5/46 C,W 

8 391.0 ___ do _____ c,w 

8 1384.0 T,G 

14 332.9 6/ 5/46 N 

6 1100.0 C,G 

6 1100.0 C,G 

10 Dry N 

t s 

D,S 

D 

N 

s 

I, S 

N 

63 

68 

62 

Reported drawdown, 

200 ft, pumping 200 

gpm. 

Reported discharge, 10 

gpm. 

Reported discharge, 21 

gpm. 

Not completed as of 

October 1946. 

tiary ( ~) deposits are discussed in detail; those of the 

Precambrian rocks are discussed only briefly. (See pl. 

1 for distrrbution of the rocks discussed.) 

OCCURRENCE OF GROUND WATER 

PRECAMBRIAN ROCKS 

The Precambrian schist is not porous and cannot be 

considered a good aquifer. Shallow wells, however, 

may obtain small supplies of ground water from faults, 

open joints, and planes of foliation in the weathered 

zones of the schist. 

Limited supplies of water can be obtained from shallow wells in the granitic rocks, especially along joints, 

faults, and weathered zones and locally along the contact zones between granitic rocks and schist. The 

amount of water that can be withdrawn from wells in 

the granitic rocks is generally not more than 1 or 2 

gpm. In several mines, however, water flows from 

large fractures in such quantities as to hinder mining 

operations. 

UPPER TERTIARY(t) ROCKS 

For ease in discussing the water-bearing properties 

of the upper Tertiary ( ~) rocks, the three basalt flows 

in the Prescott area are called the lower, middle, and 

upper basalt flows. Distribution of the middle and 

upper basalt flows is· shown in figure 24. The basalt 

flows are separated by fanglomerate and tuffaceous 

rocks. Orange ·tuff underlines the middle basalt flows. 

The lower basalt flows in the Prescott area are a 

possible source of domestic ground-water supplies 
ECONOMIC GEOLOGY 119 

where the rock is brecciated, but large supplies cannot 

be developed. Small supplies of ground water might 

be obtained from the middle basalt flows in areas where 

joint zones occur below the water table. The upper 

basalt flows on the ridge south of Willow Creek ( 1,305,-

500 N., 336,500 E.) and east of Granite Creek are above 

the water table and therefore are not an aquifer. Intrusive bodies of basalt and andesite are probably not 

important aquifers as they are so small. Small supplies might be obtained from joint zones in these rocks. 

The sedimentary deposits above the middle basalt 

flows on the east-trending ridge south of Willow Creek 

and on the east end of Granite Creek and the fanglomerates south of Prescott are above the water table and 

therefore are not aquifers. The fanglomerate part of 

the beds below the orange tuff is generally not a good 

aquifer. However, sufficient water for domestic and 

stock purposes can be obtained from it in areas where 

it lies below the water table. Smne of the white pumice 

tuffs and coarse lapilli tuffs northwest of Prescott, 

mostly below the orange tuff, are porous and would 

probably be good aquifers if they were below the water 

table. However, they are not extensive. Most of the 

remaining tuffaceous materials in this area are tightly 

cemented and would yield very little water to wells. 

The sedimentary deposits and associated volcanic 

rocks that underlie the lower and, locally, the middle 

basalt flows and that compose the valley fill are better 

aquifers in the Prescott area than are the overlying deposits. However, most of the fanglomerate is poorly 

sorted and composed of boulders in a matrix of clay, silt, 

sand, pebbles, and cobbles. Ground water occurs principally in the small voids or interstices in these materials. Although many alluvial fans in other regions contain good aquifers, most of the fanglomerate that composes the valley fill in this area is tightly cemented and 

poorly sorted, so that it is relatively impermeable and 

does not yield water readily to wells. Most of the wells 

in the valley fill yield small quantities of water, and the 

drawdowns are large. Weill, sec. 28, T. 14 N., R. 2 W. 

(pl. 3; table 17), which is 252 feet deep, produced about 

10 gpm with a 56-foot drawdown. Well 2, sec. 26, T. 

14 N., R. 2 W., which is 149 feet deep, produced 3 gpm 

with a 14-foot drawdown. Weill, sec.lO, T. 14 N., R. 2 

W., which is 894 feet deep, produced 60 gpm with a 

70-foot drawdown. 

Well 1, sec. 14, T. 14 N., R. 2 W., which is 223 feet 

deep, differs from the other wells in the area. The discharge of this well is about 250 gpm. The water is reported to be derived from about 8 feet of coarse river 

gravel and cobbles near the bottom of the well. A 

complete log of this well is not available, but from a 

description of the water-bearing materials penetrated, 

it is apparent that the water is coming from a buried 

river channel. The course of this buried channel is 

probably northwest, parallel to the southwest side of 

Granite Dells and then curved northward between the 

Dells and Granite Mountain into Chino Valley. Well 

3, sec. 14, T. 14 N., R. 2 W., which is located a few 

hundred feet east of Well 1, sec. 14, T. 14 N., R 2 W., 

was drilled to a depth of 1,013 feet and produced very 

little water; it may have been drilled to one side of the 

channel. 

QUATERNARY DEPOSITS 

The recent alluvium, located along creeks and washes, 

is generally less than 30 feet thick. It is composed of 

unsorted poorly bedded clay, silt, sand, pebbles, and 

cobbles. Although it is permeable and yields water to 

wells quite readily, it is too thin to be a source of large 

quantities of water. An infiltration gallery intercepts 

most of the underflow in the Recent sand and gravel 

of Granite Creek. 

MOVEMENT OF GROUND WATER 

The water that enters the valley fill percola.tes downward to the water taJble and thence moves through the 

valley fill in a general north ward direction toward 

Chino Valley and ·Del Rio Springs. The ground water 

is discharged from artesian wells in Chino Valley and 

from the springs. ' 

In Miller Valley ground water moves southeast, in 

the general direction of the course of Miller Creek. 

Most of the underflow of Miller Valley is probably 

forced to the surface at the narrow constriction above 

the confluence of Miller Creek with Granite Creek, although some of it may flow northeastward between the 

two prongs of granodiorite ( 1,297,000 N ., 333,000 E.). 

The underflow from Granite Crook mov~ northeastward towards the narrows north of the Veterans Hospital at Whipple, at which point most of it is intercepted 

by the infiltration gallery. Below the gallery the movement of ground water is to the north, west of ·Granite 

Dells. 

SOURCE OF GROUND WATER 

The principal sources of ground water in the Prescott 

area are ( 1) seepage losses from surface flow of washes 

and (2) direct infiltration from rainfall and melting 

snow. Much more recharge is contributed by seepage 

losses than by direct infiltration from precipitation. 

Most of the washes lose water rapidly by downward 

percolation through the coarse alluvium and fanglomerate at the edges of the mountains. The larger washes, 

such as Granite and Willow Creeks, have more sustained flow than the many small washes ·of the area, 

affording an opportunity for recharge thro~ghout the 

length of their courses across the valley fill south of 
.. 

120 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

Granite Dells. Recharge also occurs by infiltration 

from surface reservoirs in which the waters of these two 

creeks are impounded. 

WATER-BEARING PROPERTIES OF VALLEY FILL 

The valley fill comprises a heterogeneous mixture of 

gravel, sand, and clay intercalated with volcanic rocks. 

Mechanical analyses of drill cuttings from well 1, sec. 

23, T. 14 N., R. 2 W., are typical of these materials. In 

27 out of 37 samples analyzed from a depth of 18-479 

feet, 30-60 percent of the sample passed through a 100-

mesh screen. In seven samples it was less than ~0 percent, and in the remaining three, it ranged from 65 to 90 

percent. In 18 of the 37 samples, less than ~0 percent of 

the sample was retained on a 28-mesh screen. In only 

five did 50-58 pe.rcent of the sample remain on the 28-

mesh screen. In the other sam·ples it wa.s 30-50 percent. 

This preponderance of fine-grained material indicates 

a low permeability. 

The rate of flow (transmissibility) of water through 

the valley fill is very low, as is shown by the large drawdown required to cause the water to flow into the wells 

drilled in this material. To determine the rate of flow, 

pumping tests were made on well1, sec. 28, T. 14 N., R. 

2 W., in Miller Valley and on well 2, sec. 26, T. 14 N., 

R. 2 W., below the highway bridge over Granite Creek. 

The drawdown in the wells during the tests and the 

rates of recovery of the water levels after pumping 

ceased were measured. From these data, the average 

coefficient of transmissibility (rate of flow) of the aquifer was computed by the Theis recovery formula (Wenzel, 1942, p. 126) as follows: 

T= 264q log1o·!:._ 8 . t'' 

in which "'T= coefficient of transmissibility; q=discharge of the pumped well, in gallons per minute; s= 

the residual drawdown, in feet; t=the time since pumping began, in any unit; and t'=the time since pumping 

stopped, expressed in the same unit as t. The coefficient of transmissibility has been defined by Theis 

( 1935, p. 520) as the number of gallons of water that 

will move in 1 day through a vertical strip of the aquifer 1 foot wide at a hydraulic gradient of unity. 

The pumping test on well1, sec. 28, T. 14 N., R. 2 W., 

was made on July 18 and 19, 1946; a turbine pump was 

used. An ·average discharge of rubout 10 gpm was maintained for 25 hours. The coefficient of transmissibility 

was computed to be about 440 gpd per sq ft. The test 

on well2, sec. 26, T. 14 N., R. 2 W., was made on July 9, 

1946; a centrifugal pump was used. An average discharge of a:bout 3 gpm was maintained for 6 hours. The 

coefficient of transmissibility was computed to be 70 gpd 

per sq ft. 

The materials composing much of the valley fill also 

are probably poor aquifers because they are similar to 

those penetrated by the two test wells. 

QUALITY OF WATER 

COLLECTION AND ANALYSES OF SAMPLES 

The chemical character of waters of the Prescott area 

has been determined on the basis of analyses of 29· 

samples of ground and surface water. The samples 

were collected and analyzed by the U.S. Geological S-q.rvey during 1946 and 1947. These analyses (table 18) 

show the quantities of mineral matter dissolved in the 

waters in terms of parts by weight of dissolved solids 

per million parts of water. On the basis of the analyses, the waters in the area may be evaluated for various 

uses to the extent that such uses are affected by dissolved mineral matter. The analyses do not, however, 

show the sanitary condition of the waters. The significance of the various constituents and properties reported in waters is discussed in annual reports of the 

U.S. Geological Survey entitled, "Quality of surface 

waters of the United States." 

CHEMICAL CHARACTER OF THE WATER 

Waters of the Prescott area are, in general, moderately mineralized; very few of those sampled contained enough mineral matter to impart an objectionable 

taste. Most 'of ·t.hem contain less t-ha-n 300 , p.pm (parts 

per million) of hardness, and some contain less than 

100 ppm. A few contain as much as 400 or 500 ppm. 

Only one of the water samples tested for fluoride 

contained more than 1.5 ppm, and it was only slightly 

above 1.6 ppm, the allowable amount set by the U.S. 

Public Health Service (1946). 

SURFACE WATER 

In past years the main portion of the public water 

supply was obtained from Goldwater Lake, a reservoir 

south of Prescott on Bannon Creek, a tributary of 

Granite Creek. The quality of water from this source 

is indicated on table 18. These samples were collected 

in 1947 at a time when a long-continued drought had 

depleted the supply. The samples, therefore, probably 

contain a higher than normal concentration of dissolved 

matter. The water contained a moderate amount of 

dissolved matter, mainly calcium and bicarbonate. 

Many more samples, taken at different time.s with different quantities of inflmy, would be needed before any 

conclusion could be drawn as to the average quality of 

water in this reservoir. 

Very little information is available regarding the 

quality of surface waters from other sources in and 

near Prescott. Analyses of samples taken from low flow 

of the Hassayampa River approximately 8 miles south 
ECONOMIC GEOLOGY 121 

TABLE 18.-Analyses of water from wells, springs, and surface watets in the Prescott area 

[Inpartspermillion, except specific conductance. Analyses by the U.S. Geol. Survey, except well2, sec. 26, T . 14 N., R 2 W., which was analyzed by the University of Ari- zona. Samples collected by H. B. Babcock and K. K. Kendall of the Geol. Survey] 

Specific Sodium Total Date of Depth conduc- Calcium Magne- and po- Blear- Sulfate Chlor- Fluor- Nitrate Borate Dis- hard- Location and well collec- (feet) tance (Ca) sium tassium bonate (S04) ide ide (N03) (B03) solved ness as tion (KX105 (Mg) (Na,K) (HC03) (Cl) (F) solids CaC03 at 25°C) 

Wells 

T . 13 N., R . 2 W.: 

Section 4, well2 ________________ 6/17/46 16 74.8 84 23 40 5, well L-------------·· - 6/19/46 360 64.2 82 18 26 9, wellL __________ _____ 6/17/46 130 59. 8 62 30 61 T. 14 N., R. 2 W.: Section 16, well4 ________________ 6/12/46 --------- 87. 6 109 26 18 18, well L _______________ 6/13/46 30 41.5 44 17 22 19, well L _______________ ___ do _____ 97 71.4 86 32 26 20, well L--------- ----- ___ do _____ 12 54. 3 53 21 38 21, well L ______________ _ 6/12/46 290 46. 6 58 15 22 2 ________________ ___ do _____ 304 49.0 60 18 24 23, well L ___________ ___ _ 5/26/46 479 42. 3 10 3. 4 85 24, well L __________ _____ 7/ 8/46 91 51.0 74 9.5 13 26, well2 _______________ _ 6/12/46 148 -------- - 82 15 17 27, well L _______________ 6/24/46 413 48. 7 --------- --------- --------- 28, well7 _______________ _ 6/18/46 180 35.7 42 9.4 18 29, well L _______ ______ __ 6/13/46 16 42.6 43 11 12 5 _______________ _ ___ do _____ 11 22.5 23 6.8 13 g ____ ____________ 6/14/46 55 169 171 64 16 10 ______ __ ________ ___ do _____ 16 18.8 20 5. 7 9. 9 30, well L _______________ ___ do ____ _ 16 94.2 102 30 7.1 33, well6 ________________ 6/20/46 15 117 142 42 36 

1---------------- 6/18/46 85 54.6 62 14 29 g ________________ 6/20/46 20 79. 1 80 29 36 10 _____________ ___ 6/18/46 30 63. 8 67 20 22 34, well L _______________ 6/14/46 472 44. 7 ----- .--- --------- --------- 35, well L ______________ _ 6/21/46 8 80.7 64 65 24 

319 39 43 0. 6 311 11 47 1.0 440 27 14 .6 

268 50 87 .4 224 22 10 .6 401 32 27 .6 276 43 17 1.0 245 16 24 .6 270 11 29 . 4 213 9.3 25 1.6 160 20 16 .6 255 34 44 --------- 257 --------- 31 --------- 163 10 19 . 6 104 28 23 .4 80 26 9 .2 274 72 295 .4 54 25 8 . 2 159 66 93 .2 215 179 123 . 5 176 31 34 . 8 164 45 62 .2 140 85 40 .4 206 --------- 21 --------- 450 50 33 .6 

32 --------- . 8 --------- 1.2 ---------

28 0.2 6. 7 .2 . 5 . 1 5.0 .1 1.0 . 1 2. 0 .1 .3 --------- 93 --------- --------- --------- --------- --------- 13 --------- 37 .1 9. 9 . 2 9. 7 .2 16 . 1 78 .1 84 --------- 59 --------- 157 --------- 46 --------- --------- --------- 14 ---------

419 

339 

412 

450 

233 

402 

314 

257 

277 

240 

305 

537 

---------

192 

206 

127 

763 

111 

455 

712 

316 

490 

349 

--------- 472 

3 

27 

04 

8 27 8 

37 

18 9 0 

6 

8 

34 

21 

2 

22 

3 

22 

06 

4 

9 

4 

26 6 

------14 15 

8 

4 

2 

6 

0 

4 

8 

7 

2 

8 

9 

69 

7 

37 

52 

21 

31 

24 

--------42 

Surface Water 

Del Rio Spring, T. 17 N., R. 2 W ., sec. 34. _ _ _ _ _ _ _ __ _ _ _ _ ____ __ _ _ __ _ __ _ 8/19/46 

Goldwater Reservoir, T . 13 N ., R. 2 w_______________________________ 10/18/47 

Lower Hassayampa River, T. 12 N ., R. 2 W., sec. 11_____________ ______ 9/30/46 

Upper Hassayampa River, T. 12 N ., R. 2 W., sec. 111 _______ , ___ __________ do _____________ _ 

56.1 

34. 1 

75.4 

112 

1 This sample contained 209 parts of free H2S04, and a pH of 3.6. 

41 

40 

25 

14 

of Prescott are given in table 18. At this point the 

river water passes over mine tailings, and the acidity 

and the high sulfate content are the result of contamination from this source. Too few analyses of the 

waters of the Hassayampa River are available to determine the average quality of the water. 

GROUND WATER 

Granitic rocks.-Water from shallow wells in the 

western part of the city of Prescott and from wells 

southwest and northwest of the city comes from the 

weathered zone of the granitic rocks or from the disintegrated granitic material overlying the bedrock. 

This water is rather low in dissolved solids, chiefly calcium and bicarbonate. The concentration generally 

ranges from about 100 to 300 ppm, but some water 

contains as much as 500 ppm. Most of the \Yells are 

shallow, and local contamination may increase the 

amount of dissolved solids normally present in water 

from the granitic rocks. Samples from several of the 

wells contained excessively high concentrations of nitrate. Considerable amounts of chloride and sulfate 

occur in the more highly mineralized waters. 

47 

14 

278 

162 

55 

32 

43 

400 

1,250 1 

31 0. 8 

.3 

1.3 

.2 

315 

211 

. 2 --------- ·-------- .---------

11 --------- --------- --------- ---------

206 

158 

435-· 

840 

Volcanic rocks.-Several wells in the area obtain 

water from tuffs or from basaltic or other volcanic 

rocks. These wells are located mostly in the eastern 

part of Prescott. Water from these rocks is rather uniform in composition, containing between 300 and 500 

ppm of dissolved solids, which typically consist of about 

equal amounts of calcium, magnesium, and sodium; bicarbonate is the principal anion. The silica content 

of these samples \vas not determined. However, ground 

waters in similar rocks elsewhere in Arizona contain 

considerable amounts of silica. 

Fanglomerate.-Water from fanglomerate, the principal aquifer in the Prescott area, contains 150-500 ppm 

of dissolved solids, mainly calcium and bicarbonate. 

Small amounts of both sulfate and chloride are generally present. The sulfate content of water from the 

fanglomerate is characteristically lower than the chloride content, whereas the sulfate content of nearly all 

water from other formations in the area exceeds the 

chloride content. This relationship has been of some 

value in correlating the ground waters of the area with 

aquifers from which they were derived. Incomplete 
122 GEOLOGY OF THE PRE.SCOTT AND PAULDEN QUADRANGLES, ARIZONA 

data indicate that at least some of the waters from the 

fanglomerate are high in silica. 

Recent allwviwm.-A few wells in the Prescott area 

obtain water from Recent alluvium along stream channels. Samples of this water contained about 500-1,000 

ppm of dissolved matter, chiefly calcium, magnesium, 

and bicarbonate. Relatively large amounts of sulfate 

and chloride occur in the more highly mineralized waters from the alluvium. 

CONCLUSIONS 

The only area near Prescott favorable for groundwater development, apparently, is in the valley fill between Prescott and Granite Dells. The adequacy of 

this source is in doubt. A study of the avaliable well 

records and well logs and of the geology of the area 

indicates that the fanglomerate will not transmit water 

rapidly, except along buried stream channels, as is 

shown by well 1, sec. 14, T. 14 N., R. 2 W., which produced 250 gpm from a buried stream channel. 

The ground water in the area is generally of good 

chemical quality, although most of it is much harder 

than the surface water. Fluoride content in the ground 

water is generally below the deleterious level. 

The Chino artesian flow comes from "porous basalt" 

and has proved to be an adequate supply for the city. 

Supplementary water is obtained from the Goldwater 

reservoirs. Private wells also supply water for many 

residences outside the city limits, especially those in 

Miller Valley, whose wells tap a small artesian basin. 

The water in this basin comes from fanglomerate that 

underlies basalt. 

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124 GEOLOGY OF THE PRESCOTT AND PAULDEN QUADRANGLES, ARIZONA 

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A Page 

Accessibility---------------------------------- 4 Acknowledgments____________________________ 3 

Age determination,/ Government Canyon 

Granodiorite.----------------____ 50 Yarber Wash mass_____________________ ___ 50 

Agua Fria River, capture of tributary to Verde 

River __ -------------------------- 102 

Alaskite and related rocks, distribut.ion, 

alaskite __ ------------------------ 41 distribution, alaskite porphyry______ _____ 41 

quartz monzonite._----------------- 40 

general character, alaskite and alaski~ 

porphyry--------------___________ 42 

quartz monzonite_---------------- 42 

relations to other rocks, alaskite_ _ _ _ __ ___ 44 

alaskite prophyry _ ------------------- 44 

aplite __ ------------------------------ 44 

quartz monzonite_------------------- 42 Alaskite porphyry __________________________ __ 42,44 

Alder Group_-----------------------------___ 7, 88 

Alder(?) Group, unnamed tuffaceous rocks 

structure. __________ -------------~ 89 Alder Series. See Alder Group. 

Alkali ratio of argillite, Mazatzal Quartzite.__ 27 

Alteration zones ___ --------------------------_ 48 

Analyses, argillite, Mazatzal Quartzite________ 26 

quartzose intrusives and gabbro__________ 30 

water quality __ -----------------------___ 121 

Anderson, C. A., cited________________________ 88 

Anderson, C. A., and Creasey, S. C., cited.__ 7, 

11, 14, 33, 35, 48, 59, 81, 82, 85, 89, 98, 109, 

110. 

!~~=~:: ~;;~i;;:~~ ~~~~~~~~~~~~~~~~~~~~~~~~- ~~· 70, ~~ structure formed by intrusion ____________ 71 97 

Andesite dikes, age___________________________ '65 

Tertiary(?).--------------------------____ 65 

Andesitic breccia, Spud Mountain Volcanics__ 15 

Andesrtic flows and tuffs, Texas Gulch Forma- tion _____________________________ _ 13 

Andesitic gravels.-------------------- 70 

Andesitic tuff, Chaparral Volcanics ___ ~~~~~~~~ 17 

Spud Mountain Volcanics 16 

Anglesite ___ --------------------~ ~~~~~~ ~~ ~ ~~~~ 106 

Argillite. See Mazatzal Quartzite. 

Arsenopyrite.-------------------------------- 104 

B 

Bagdad porphyry copper deposit_ __ __ ____ ___ _ 

Barite ______ --------------- _____ ___ __________ _ 

Barlow, I. H., analyst_ ______________________ _ 

Basalt ____________________________ -------- ___ _ 

Basalt, older _________________________________ _ 

younger_---------------------·--- ________ _ 

Basaltic andesite 

Basaltic flow unit,-G;;;~-G-~l~hv~i~~~i~--~~~ 

Basic inclusions 

Berthoud, S. M.~-;~~~;;t~~~~~~~~~~~~~~~~~~~~~ 

Big Bug Creek mass, Prescott Granodiorite __ 

Big Bug mining district.---------------------

Big Chino monocline or fault_ _______ __ ______ _ 

Big Chino Wash ____________________________ _ _ 

Biotite andesite _____ _ -------------- ______ ___ _ 

Black Mesa anticline ________________________ _ 

107 

105 

27 

66 

82 

82 

71 

17 

70 

26 

35 

109 

95 

102 

71 

94 

INDEX 

[Italic page numbers indicate major references} 

Page 

Blackmon, P. D., analyst__________ __________ 26 

Botts, S.D., analyst_________________________ 26 

Brannock, W. W., analyst __ ------------------ 30 

Bright Angel Shale___________________________ 53 

Building stone________________________________ 114 

Bull Basin monocline _______________________ __ 94,96 

Bullwacker prospect__________________________ 111 

c 

Carbonate minerals _____ ---------------------- 105 

Catlinite. See Argillite. 

Cenozoic rocks._---------------------------__ 65 

Cerargyrite _________ ---------------------- ____ 106 

Cerussite_____________________________________ 106 

Chalcocite____________________________________ 106 

Chalcopyrite __ -------------------____________ 104 Chaparral fault _______________ __ __________ _ 16, 89,91 

Chaparral mass, Prescott Granodiorite_______ 35 

Chaparral Volcanics, andesitic tuff___________ 17 

distribution_---------------------------__ 16 

internal structure __ ---------------------- 17 

lithology ______ --------------_____________ 17 

rhyolitic tuff __ -----------__ ______ ____ ____ 17 

stratigraphic relations.------------------- 16 

structure __ ---------------------__________ 90 

Chaparral zone __________________ ---------- 89, 90,91 

Chemical character of water_-----------__ ____ 120 

Chino artesian basin ________________________ 115,122 

Chlorite ________ ----------------------------__ 105 

Chrysocolla. _ -------------- ______ ------------ 106 

~~~:~ec_o_~~~~ ~~~~~~~~~~~ ~~~~~~~~~~~~~~:~:~:~: 67, ~ Coconino Sandstone, age_____________ ____ ____ 64 

correlation________________________________ 64 

distribution ________ --------------________ 64 

lithology_________________________________ 64 

stratigraphic relations____________________ 64 

thickness.____________________________ __ __ 64 

use as building stone_____________________ 114 

Conclusions. _____________________ -.------_____ 122 

Conclusions, relations of structures to upper 

Tertiary('?) rocks_____________ ____ 99 

Copper Basin deposits.- --------------------- 107 

Creasey, S. C., cited_------------------------ 109 

D 

Dacite(?), Texas Gulch Formation___________ 12 

Dells Granite, distribution___________________ 44 

general character __ ----------------------- 45 

late-stage products of crystallization_____ _ 46 

relations to other rocks___________________ 47 

Del Rio Springs______________________________ 115 

Description of individual ore deposits___ ______ 109 

Diabase dikes._---------------------------___ 29 

Dikes. ___ ------------------------------------ 70 Drainage _____________________________________ 6, 102 

Drainage, Chino-Lonesome Valley . ____ __ ___ . 102 

northeast of Chino-Lonesome Valley_____ 102 

Drainage direction in late Tertiary(?) time. __ 83, 85 

Drainage pattern in Lonesome, Chino, and 

Williamson Valleys_______________ 103 

E 

Economic geology____________________________ 104 

Elmore, P. L. D., analyst____________________ 26 

F Page 

Fanglomerate ••• ----------------------------- 71 Fanglomerate, ground water in_______________ 121 

Faults ________________ ------------------ ______ 96, 98 

Faults, age___________________________________ 99 

Fissure-vein deposits. ____ ----------------____ 106 

Fissure veins, Big Bug district.______________ 110 

Groom Creek district____________________ _ 110 

Mineral Point district and adjacent area.. 111 

Prescott district •. ------------------------ 110 

southern part of Prescott quadrangle.____ 110 

Walker district.__________________________ 110 

west side of Spud Mountain______________ 110 

Fresh-water limestone------------------------ 67 

G 

Gabbro _____________________________ --------__ 29 

Gabbro, relation to other rocks_______________ 33 

Gabbro and related rocks, general character__ 31 

iron-rich gabbro.------------------------- 33 

Galena.------------------------------------__ 104 

Garnet-epidote-quartz alteration zone_________ 20 

Gazin, C. L., quoted_________________________ 80 

Glassford Hill area, cinder cones______________ 68 

Gold. __ ---------_-----------------------_____ 104 Gold Coin group____________________ ___ ______ 111 

Gold deposits, placer_____________________ ____ 10.9 

Goldwater Lake on Bannon Creek___________ 115 

Government Canyon Granodiorite, age_______ 35 

distribution._---------------------------- 34 

genP.ral character. ____________ ------------ :l4 

relation to other rocks__________________ __ :l!i 

Granite, coarse-grained, distribution__________ 44 

coarse-grained, general character._________ 44 

relations to other rocks_______________ 44 

fine-grained, distribution__ _______________ 47 

general character •.. ------------------ 47 

nilations to other rocks_______________ 47 

Granite Creek, drainage history_-----------.. 10~ 

infiltration galleries----------------------- 115 

Granitic rocks, ground water in._------------ 121 

GraveL_------------------------------------- 71 

Gravel, older. __ ---- ____ ----------------______ 82 

younger .• --------------------------______ 82 

Green Gulch Volcanics, basaltic flow unit.... 17 

breccia beds •. ---------------------------- 18 

distribution._._------------------------__ 17 

internal structure------------------------- 17 

lithology_-------------------------------- 17 

pillows. _______ ------------------------___ 17 

stratigraphic relations____________________ 17 

structure .• ____ ----------------------_____ 89 

thickness .. __ -----------------.___________ 17 

tuffaceous unit..------------ __ -------____ 18 

Ground water, chemical quality______________ 121 

fanglomerate.---------------------------- 121 granitic rocks __ ___________________________ 121 

movement________________________________ 119 

occurrence ..... -----------------____ ______ 118 

source.-------------_--------------_______ 119 

volcanic rocks. __________ ----------- ___ ___ 121 

Ground-water resources.--------------------- 118 

Gutschick, R. C., cited_______________________ 60 

H 

Hathaway, J. C., analyst ... ------------------ 26 

Hematite _______________ --------------------__ 105 

125 
126 

Page 

Hickey Formatian, Jerome and Clarkdale 

area_----------------------------- 81 

History of use of ground and surface waters___ 115 

Hornblende andesite.------------------------ 70 

Howell, D. H., cited __ ----------------------- 27 

Hubbel Ranch_______________________________ 59 

Huddle, J. W., and Dobrovolny, E., cited ____ 59,64 

Hughes, P. W ., cited _______________________ __ 61,63 

Humidity, average, in Prescott area .. _------- 6 

Hypogene minerals, gangue minerals_________ 105 

ore minerals------------------------------ 104 

Igneous intrusions, in Alder Group___________ 10 

Indian Hills Volcanics, andesitic :flows________ 15 

basaltic :flows----------------------------- 15 

distribution_-,---------------------------- 14 

internal structure_________________________ 14 

lithology_-------------------------------- 14 

rhyolite :flows_____________________________ 14 

stratigraphic relations____________________ 14 

structure._------------------------------- 89 thickness ____ ---_------___________________ 14 

tuffaceous sedimentary rocks_------------ 15 

Indian ruins---------------------------------- 4 

In.filtration galleries, Granite Creek___________ 115 

Intrusive rocks.------------------------------ 28 Intrusive rocks, age___________________________ 49 

conclusions as to age---------------------- 49 

conclusions as to relations________________ 49 

older than Alder Group__________________ 49 

other_-_ ---_---------- ___ --- ____ ---------- 47 

Iron Formation. See Texas Gulch Formation 

jasper-magnetite beds. 

Iron King mine ____ -------------------------- 109 

J 

Jaffe, H. W., age determination by___________ 50 

Jasper-magnetite beds, Texas Gulch Formation __ ---------------------------- 12 

Jerome Formation. See Martin Limestone. 

Joints, Dells Granite._----------------------- 97 

K 

Kaolinite, in argillite------------------------- 27 

Kit Carson vein______________________________ 110 

L 

Lacustrine deposits, fine-grained ______________ 72, 73 

Lake Watson_________ ________________________ 115 

Late-stage products of crystallization_-------- 46 

Laudermilk, Jerry, cited______________________ 25 

Lehner, R. E., cited ____________________ 60, 64, 81, 96 

Limestone ____ - __ -- __ --_---_---- _____ ------___ 114 

Limestone, fresh-water __ --------------------- 73 

Limestone Canyon monocline_--------------- 94 

Limonite _______ -----_------__________________ 106 

Lindburg, M. L., analyst_____________________ 105 

Lindgren, Waldemar, cited _____________ 107,111,113 

Location of area __ ---------------------------- 4 

Longwell, C. R., cited________________________ 63 

Lynx Creek mass, Prescott Granodiorite_____ 35 

Lynx Creek placer district____________________ 112 

M 

McKee, E. D., cited _______________________ 52, 65,98 

McNair, A. H., cited ______________________ 53, 59,63 

Magnetite ________________ : ___________________ 105 

Malachite____________________________________ 106 

Malapais (malpais), defined__________________ 68 

Manganese oxide.---------------------------- 106 

INDEX 

Martin Limestone, age __ --------------------- correlation _______________________________ _ 

distribution ___ ------------------------- __ 

lithology, A unit_ ___ ---------------------

B unit_ ___ ----------------------------

C unit_ ____ ---- ___ --------------------

D unit __ -----------------------------

stratigraphic relations __ ------------------

thickness ____ -----------------------------

Massive sulfide depositS----------------------

Mauv Limestone----------------------------- Mazatzal Quartzite, age _____________________ _ 

alkali ratio __ -----------------------------

Page 

59 

59 

57 

57 

58 

58 

59 

57 

57 

106 

53 

27 

27 

anticlines ___________ ------ ___ --------_____ 91 

argillite _______ --- __ ---------------------__ 25 

chemical analyses------------------------- 26 

correlation _______________ ---- ___ ----_---__ 27 

distribution ___ --------------------------- 20, 21 

internal structure------------------------- 20 

lithology_-------------------------------- 20 

measured section, Del Rio area___________ 22 

mineralogy------------------------------- 26 

quartzite and conglomerate.-------------- 24 

stratigraphic relations __ ------------------ 20 

structure __ ------------------------------- 91 

thickness _________ ------------------------ 20 

use as a building stone____________________ 114 

Mazatzal Revolution_________________________ 88 

Measured section, Mazatzal Quartzite, Del 

Rio area__________________________ 22 

Mineralization, age--------------------------- 106 

Mineral Point mass, Prescott Granodiorite___ 35 

Mo~nkopi Formation_________________________ 64 

Molybdenite._-----------------_------------- 105 

Monoclinal structures, other------------------ 96 

Monoclines, age______________________________ 98 

Montmorillonite, in argillite__________________ 27 

Mountains __ --------------------_------------ 100 

Mud :flows_---------------------------------- 70,72 

N 

New Strike prospect-------------------------- 111 

Nonmetallic deposits.------------------------ 114 

Nygaard, E. A., analyst---------------------- 26 

0 

Ore deposits---------------------------------- 104 

p 

Paleozoic and Cenozoic rocks, structures______ 98 

Paleozoic rocks, general features______________ 50 

thickness in north-Oifutral Arizona________ 51 

Paleozoic sedimentary rocks------------------ 50 

Paleozoic sedimentary rocks, measurzd sections.---------------------------- 51 

Pediment gravels. See Pleistocene gravels. 

Pediments _____________________ -- __ -- ___ ------ 100 

Perkinsville Formation, Clarkdale area_______ 81 

Phyrophyllite, in argillite_------------------- 27 

Physical features_____________________________ 4 

Physiography_________ __ ______________ _______ 99 

Piedmontite ________ ------ _______ --------- ____ 105 

Pillow lavas __________________ ---------------- 17,19 

Pipestone. See Argillite. 

Placer deposits, other________ _________________ 114 

Platinum ___________ -------------------_______ 105 

Pleistocene gravels. ___ ----------------------- 85 

Population and industry_____________________ 4 

Post-Paleozoic mineralization_________________ 107 

Post-Precambrian structures_________________ 92 

Precambrian orogeny_________________________ 87 

Precambrian rocks, older_____________________ 7 

younger _____________ ---_-----------------

Precambrian structures ______________________ _ 

Precipitation __ ---________ --------___________ _ 

Precipitation, average, in Prescott area ______ _ 

Prescott Granodiorite, distribution ___________ _ 

general character __ --------------------- relations to other rocks __________________ _ 

use as building stone ____________________ _ 

Prescott mass, Prescott Granodiorite ________ _ 

Previous work ______________ --------- __ --~- __ _ 

Price, W. E., Jr., cited _______________________ _ 

Pyrite ________ --- __ ----_--___________________ _ 

Q 

Page 

92 

6 

6 

35 

37 

37 

114 

35 

3 

64 

105 

Quartz ____ --------------------_______________ 105 

Quartz diorite, Jerome area. See Yarber Wash 

mass, Prescott Granodiorite. 

Quartz diorite, relations to other rocks________ 33 

Quartz diorite. See Gabbro. 

Quartz-magnetite veins_______________________ 48 

Quartz monzonite. See Alaskite. 

Quartz porphyrY----------------------------- 47 

Quartz veins---------------------------------- 48 

Quartzose intrusive rocks, chemical analyses__ 30 

gabbro, chemical analyses________________ 30 

normative composition_______________ 31 

variation diagrams___________________ 32 

modal analyses_________________________ 29 

normative composition___________________ 31 

variation diagrams_______________________ 32 

Quaternary deposits-------------------------- 85 

Quaternary deposits, age_____________________ 87 

ground water in-------------------------- 119 

Quaternary gravels, Jerome area __ ------------ 81 

R 

Recent alluvium_____________________________ 86 

Recent alluvium, age_________________________ 87 

fossils ___________ ----------------__________ 87 

ground water in__________________________ 121 

Record of wells and springs, Prescott area.___ 116 

Redwall Limestone, age______________________ 61 

correlation._______________________________ 61 

distribution __ ---------------------------- 60 

lithology, unit L------------------------- 60 

unit 2. __ ----------------------------- 60 

unit 3. __ --------------------------- __ 61 

unit 4-------------------------------- · 61 

mineralization in.------------------------ 109 

stratigraphic relations____________________ 60 

thickness.-------------------------------- 60 

Relations of buried volcanic rocks in Chino 

artesian basin to Hickey Formation._---------------------------- 85 

Rhyolite crystal tuff, Texas Gulch Formation_ 14 

Rhyolite dikes-------------------------------- 48 

Rhyolite :flow or massive tuff, Texas Gulch 

Formation. ______ ------ __ -------__ 14 

Rhyolitic :flows, Indian Hills Volcanics.------ 14 

Rhyolitic tuff ___ ----------------------------- 67 

Rhyolitic tuff, Chaparral Volcanics___________ 17 

Rose, H. J., Jr., analyst__-------------------- 26,30 

s 

Salida Gulch mass, Prescott Granodiorite____ 35 

Scheelite ______ ------------------------------- 105 

Sedimentary rocks---------------------------- 66 

Sericite ______ ------ __ ----_---_---_---_-- __ -_-_ 106 

Serpentine minerals __ ------------------------ 105 

Silicified breccia zones------------------------ 48 

Silicified zones-------------------------------- 48 

Silver Belt-McCabe vein_____________________ 110 

Similarities of deposits in Chino-Lonesome 

basin to Verde Formation________ 85 
Page 

Sphalerite._---------------------------------- 105 

Spud fault--------------------------------- 16, 89,91 

Spud Mountain Volcanics, andesitic breccia__ 15 

andesitic tuff.---------------------------- 16 

distribution __ ---------------------------- 15 

internal structure------------------------- 15 

lithology ____ ----------------------------- 15 

stratigraphic relations __ .----------------- 15 

structure ___ -.---------------------------- 89 

thickness_-------------------------------- 15 

Starkey, H. C., analyst_____________________ __ 26 

Stibnite. ____________ ------------------------- 105 

Stoyanow, A. A., cited_______________________ 59 

Stratigraphy, Alder Group___________________ 10 

Stream capture, Agua Fria River_____________ 102 

Structure, Alder Group_______________________ 87 

east of the Chaparral zone________________ 88 

in the chaparral zone--------------------- 90 

older Precambrian rocks__________________ 87 

west of Chaparral zone___________________ 89 

Structures, age .•• ---------------------------- 98 

faults------------------------------------- 96,98 

formed by intrusion of upper Tertiary(?) andesite plugs ___________________ _ 71,97 

in intrusive rocks------------------------- 9t 

in Paleozoic and Cenozoic rocks ________ _ • 94 

monoclines._----------------------------- 94, 98 

older __ ._-- ___ ---------------------------- 94 

younger_--------------------------------- 97 

Sullivan Lake, headwaters of Verde River____ 102 

Supai Formation, age ___________________ ·______ 63 

correlation ______ -------------------------- 63 

distribution._---------------------------- 61 

lithology, lower member__________________ 62 

middle member______________________ 63 

upper member________________________ 63 

mineralization ______________________ ------ 107 

relations to Callvill'e and Naco limestones_ 63 

stratigraphic relations____________________ 61 

thickness.- _____ --- _________________ ---___ 61 

Supergene ore minerals.---------------------- 106 

Superposition, Granite Creek_________________ 102 

Surface water, chemical quality--------------- 120 

T 

Tapeats Sandstone, age_______________________ 53 

conglomerate in upper part_ ___________ 52, 53, 56 

correlation _____ ---- ___________ ---_------__ 53 

disconformity below the Martin Limestone_---- _________ ---- _____ ---___ 56 

distribution __ ---------------------------- 51 

INDEX 

Tapeats Sandstone, age-Continued 

distribution of central Arizona ___________ _ 

limestone and sandstone pebbles _________ _ 

lithology, lower unit _____________________ _ 

upper unit _____ --_------_---- ________ _ 

stratigraphic relations __ ------------------

thickness.--------------------------------

thickness in central Arizona _____________ _ 

Temperature, average, in Prescott area ______ _ 

Tennantite-----------------------------------

Tertiary andesite ___ -------------------------- Tertiary(?) andesite dikes ___________________ _ 

Tertiary basalt flows __ --------------------- __ 

Texas Gulch Formation, andesite flows and tuffs _____________________________ _ 

conglomerate. ______ ------------ ____ ---_-- correlation _______________________________ _ 

dacite(?)----------------------------------

distribution __ ----------------------------

internal structure ________ ----------------- jasper-magnetite beds ____________________ _ 

lithology ___ ------------------------------

rocks of undetermined origin_------------ rhyolite crystal tuff ______________________ _ 

rhyolite flow or massive tuff _____________ _ 

rhyolitic tuff ___________ ------------------

slate _____ ---------------------------------

stratigraphic relations __ ------------------ structure. _____ --- _______________________ _ 

thickness_----_--- ___ --------------_------ undifferentiated _________________________ _ 

The Pinnacle, cinder cones west oL _________ _ 

Topographic highs formed by Mazatzal Quartzite since the Precambrian _____ ___ _ 

Tourmaline. __ ------------------------------- Tourmaline veins ____________________________ _ 

Tuffaceous rocks, rhyolitic ____ ---------------- unnamed Volcanics, Alder(?) Group _____ _ use as building stone ____________________ _ 

Tuffaceous unit, Green Gulch Volcanics _____ _ 

Tuffs _________ -----_--------------------------

u 

Unconformity, at base of Cenozoic rocks ___ __ _ 

at base of Paleozoic rocks-----------------

Unnamed volcanic rocks of the Alder(?) 

group, basaltic flows _____________ _ 

distribution ___ --------------------- _____ _ 

garnet-epidote-quartz alteration ____ ------

internal structure ___________ --------------

lithology ________ ------------------- _____ _ 

Page 

54 

56 

52 

52 

52 

52 

54 

6 

105 

66 

65 

66 

13 

12 

11 

12 

11 

11 

12 

11 

12 

14 

14 

12 

12 

11 

89 

11 

11 

68 

92 

106 

48 

73 

19 

114 

18 

70 

64 

50 

19 

18 

20 

19 

19 

127 

Page 

Unnamed volcanic rocks of the Alder(?) 

group, basaltic flows-·Con. 

pillows_-------------------------_________ 19 

stratigraphic relations. __ ----------------- 18 

structure •• ------------------------------- 89,90 thickness ___ --- ________ ------_____________ 18 

tuffaceous rocks._------------------------ 19 

Upper Tertiary(?) rocks, age_________________ 75 

correlations ____________ ----_______________ 81 

distribution_ •• --------------------------- 66 fossils ___________________ ---_---___________ so 

ground water_____________________________ 118 

lithology •• _------------------------------ 67 

relations to Hickey and Perkinsville Formations .• ------------------------ 82 

sequence, central Paulden quardangle____ 82 

southern part of basin____________________ 83 

stratigraphic relations _____________ .______ 81 

thickness _______ ------------------------______ 74 

v 

Valley fill, water-bearing properties___________ 120 

Vanadnite ___ ---- _ _ _ _ _ _ _ __ _ _ _ ___ _ _ _ _ _ __ _ _ _ _ _ _ _ 106 

Vegetation._-----.---------------------------- 7 

Veins _______ --------- _____ ----------------____ 48 

Verde fault----------------------------------- 81 

Verde Formation, Jerome and Clarkdale areas. 81 

Verde monocline _____ ------------------------ 95 

Verde River---------------------------------- 102 

Verde River, relation to monoclines__________ 99 

Volcanic rocks, ground water_________________ 121 

"\V 

Water, for domestic use and irrigation________ 115 

Water-bearing properties of valley filL_______ 120 

Water resources, Prescott area________________ 115 

White, K. E., analyst________________________ 26 

Whitehorse prospect-.------------------------ 111 

Williamson Valley Wash . -------------------- 102 

Wilson, E. D., cited _______________ 28, 88, 91,112,114 

Wilson, E. D., and others, cited-------------- 111 

Wulfenite .• ---------------------------------- 106 

y 

Yarber Wash mass, Prescott Granodiorite---- 35 

Yavapai Schist .. See Yavapai Series. 

Yavapai Series ••• ---------------------------- . 

U.S. GOVERNMENT PRINTING OFFICE: 1965 Q-758-447