Geology of the 

Clarkdale Quadrangle 

Arizona

GEOLOGICAL SURVEY BULLETIN 1021-N

A CONTRIBUTION TO GENERAL GEOLOGY

GEOLOGY OF THE CLARKDALE QUADRANGLE, ARIZONA

By ROBERT E. LEHNER

ABSTRACT

The 15-minute Clarkdale quadrangle is in north-central Arizona, in Yavapai 

and Coconino Counties. It was mapped in 1952 and 1953 to determine the 

stratigraphic and structural setting, and the depth of sedimentary cover in the 

area north of the Precambrian massive sulflde copper deposits at Jerome, Ariz.

The quadrangle includes three major topographic divisions. Part of the 

Colorado Plateau projects into the northern limits of the quadrangle and is 

bounded by an abrupt cliff referred to as the Mogollon Rim. Part of the Black 

Hills (Woodchute Mountain) extends into the south edge of the quadrangle. In 

the area between, low cuestalike hills are traversed by the Verde River, which 

follows a meandering course through the quadrangle from the west-central 

boundary to the southeast corner.

The stratigraphy includes Precambrian rocks which crop out in small areas 

chiefly in the vicinity of Jerome and in the southwest corner of the? quadrangle. 

They are overlain unconformably by a thin unit the Tapeats sandstone (?) 

(Cambrian). Upon the Tapeats (?) rests the Martin limestone (Upper Devonian) 

with seemingly conformity, which in turn is overlain unconformably by the 

Red wall limestone (lower Mississippian). The Red wall is overlain unconformably by the Supai formation (Pennsylvanian and Permian), here subdivided 

into three members. Above the Supai in normal stratigraphic succession are 

the Coconino, Toroweap, and Kaibab formations (Permian); the only unconformity occurs between the Toroweap and Kaibab. Mesozoic rocks are not 

present in the quadrangle.

Lava, gravel, carbonate lakebeds, and alluvium overlie considerable areas 

of the Paleozoic rocks. The lava and associated gravel beds are separated-by 

structural and physiographic features into two ages: Pliocene (?) (Hickey formation) and Pliocene (?) to Pleistocene (?) (Perkinsville and Verde formations).

The structural features of the quadrangle, disregarding the Precambrian, 

belong to two general periods; an early period (late Triassic, Cretaceous, or early 

Tertiary age) which predates the Hickey formation (Pliocene ?), and a late 

period (late Tertiary or Quaternary) which postdates the Hickey. An uplift 

of the region to the southwest occurred in the early deformation and thereby 

tilted the Paleozoic strata producing a regional dip to the northeast of about 8°. 

Some normal faulting accompanied this early deformation. Erosion then beveled 

the tilted strata so that the oldest rocks are exposed in the southern and southwestern part of the quadrangle. The youngest rocks crop out to the northeast. 

During the Pliocene (?), the early lava flows of the Hickey formation were ex511
512 CONTRIBUTIONS TO GENERAL GEOLOGY

truded throughout most of the area. After this extrusion, the late and strongest 

deformation occurred; it consisted principally of normal faults accompanied by 

slight rotation of the individual fault blocks and uplift of the Colorado Plateau. 

Also, local monoclinal folding took place. It was at this time that the Black 

Hills were blocked out by marginal northward- and northwestwardftrending 

faults. This late faulting also caused the reversal of the drainage which previously had been to the north.

The Verde formation, which comprises lava, lakebeds, and gravel, accumulated 

ifl'.a-basin on the east side of the Black Hills. At the same time lava and, gr,avel of 

the Perkinsville formation accumulated north and northwest of the Black Hills.

Pediment gravel of Quaternary age is present in the southeastern and eastern 

parts of the quadrangle. Recent river terraces and riverwash are present in parts 

of the valley of the Verde River. . .

The well-known copper, deposits of the Jerome district have been the chief 

mineral resource in the quadrangle, but the deposits are mined out. The only 

commodity commercially exploited now is building stone which is quarried from 

the upper member of the Supai and from the Coconino sandstone in the northern 

part of the quadrangle. : .

INTRODUCTION

. The study of the Clarkdale quadrangle was made by the U. S. 

'Geological Survey to obtain the regional setting of the.important 

copper mines at Jerome, to obtain more data about the structure north 

of Jerome, and to gather information on the thickness of the Paleozoic 

cover over the Precambrian rocks which are host rocks for the ore 

deposits at Jerome. In May 1951, about 12 square miles of the Clarkdale quadrangle centering around the mines at Jerome were mapped 

as part of the study of the Jerome area (Anderson and Oeasey, 

1957).

PREVIOUS WORK

: Much of the previous work in the area has been concerned with the 

local geology of the ore deposits centering around Jerome. Because

this report is confined largely to the regional geology, only references 

related to regional problems are considered.

Early work in the area was of a stratigraphic nature, and Ransome

(1916) wrote a brief description of the stratigraphic section around

Jerome with notes on the stratigraphy between Jerome and Payson. 

Reber (1922) after years of experience and observations in the district wrote an excellent description of the geology and ore deposits 

of ;the Jerome area.

During part of his reconnaissance mapping for the Arizona Bureau

of Mines, Jenkins (1923) was the first to study and map the Verde 

.formation in the valley of the Verde River and to report a detailed 

account of these deposits.

The first published map of the area accompanied Lindgren's report 

(1926) on the Jerome and Bradshaw Mountains quadrangles. The
GEOLOGY OF THE CLARKDALE QUADRANGLE, ARIZ. 513

map was very generalized and the report was primarily concerned 

with the mines and prospects and did not treat the regional geology 

in detail.

Stoyanow (1936) studied the Devonian strata in the Jerome area 

as a part of a regional correlation study of the Paleozoic formations 

in Arizona. A similar study was made on the Redwall limestone in 

the Jerome area by Gutschick (1943).

Mahard (1949) made a comprehensive study of the late Cenozoic 

chronology of the upper valley of the Verde River, which included 

primarily the geologic history of the valley.

Aerial mapping in Sycamore Canyon just north of the Clarkdale 

 quadrangle by Price (1950a) revealed evidence of a northward-flowing drainage before the early basaltic eruptions on the plateau. Price 

(1950b) also mapped the Kaibab limestone and the Moenkopi formation (Price, 1949) which proved to be one of the southernmost occurrences of the Moenkopi in Arizona.

The most recently published work which concerns the area, in part, 

is that of McNair (1951), who extended his previous Paleozoic 

stratigraphic studies in northwestern Arizona into the Jerome area. 

He believed that the basal sandstone of Paleozoic age is Devonian 

and related to the Martin limestone rather than the Tapeats sandstone 

of Cambrian age.

ACKNOWLEDGMENTS

The writer is grateful to Nick Perkins and his sons for their cordial 

cooperation in allowing the use of their cabin during the course of the 

mapping in the remote northeast quarter of the quadrangle and for 

their useful information on trails and general accessibility of much 

of that little frequented area. Stratigraphic information was contributed by E. D. McKee, of the University of Arizona.

The writer was assisted by H. C. Rainey from June to October 1952 

and from October 1952 to February 1953 by D. D. Dickey, who also 

aided the writer in measuring sections and compiling the illustrations.

GEOGRAPHY

LOCATION, CULTURE, AND ACCESSIBILITY

The Clarkdale quadrangle lies mostly in Yavapai County, central 

Arizona, but includes an area in Coconino County along the north 

boundary. It is bounded by parallels 34°45' and 35° and meridians 

112° and 112°15/ and covers about 245 square miles (fig. 70).

The principal towns in the quadrangle are Jerome and Clarkdale. 

Jerome is on the steep east slope of Woodchute Mountain near the 

center of the south boundary of the quadrangle where the United
514

Figure 70. Index map of area.

Verde and United Verde Extension mines are located, The economy

of Jerome depended upon mining, but today the mines are closed. The

population of the town decreased steadily after the United Verde

Extension mine closed in 1938, and rapidly after the United Verde 

mine closed in February 1953. At present (1953), Only a few families

remain, and the town already has acquired the title of "the largest 

ghost town in the West." Clarkdale, whicn is 4 miles east-northeast 

of Jerome in the valley of the Verde River, is owned and controlled 

by the Phelps Dodge Corp. The town grew around the smelter and
GEOLOGY OP THE CLARKDALE QUADRANGLE, ARIZ. 515

concentrator for the United Verde mine, and when the smelter was 

closed in June 1951 the population of Clarkdale decreased. The concentrator, however, remained active until February 1953 for milling 

copper-zinc ore.

Sparsely inhabited areas are present in the quadrangle. These 

areas include the small settlement called Centerville, 1 mile south of 

Clarkdale, which grew as a result of the smelter activity at Clarkdale. Another small settlement is Tapco which is associated with the 

generator plant of the Arizona Power Co. and is about 1 mile north 

of Clarkdale. Perkinsville comprises the small group of houses clustered along a branch of the Atchison, Topeka, and Santa Fe Railway 

on the north side of the Verde River in the west-central part of the 

quadrangle. The economy of this sparsely populated community depends upon ranching, farming, and railroad maintenance work.

Many Indian ruins are present within the quadrangle and the largest of these has been preserved and made into a national monument 

the Tuzigoot National Monument about 1% miles east of Clarkdale. 

The museum located at the ruins contains several pieces of copper ore 

which were probably used by the Indians for pigments to color their 

garments and bodies. Other ruins in the quadrangle include a cave 

and pueblo site at Perkinsville; many pueblos and a few caves in the 

Sycamore Basin country in the northeastern part of the quadrangle; 

and a small cliff-dwelling in the east wall of Sycamore Canyon, about 

2 or 3 miles above its mouth.

A branch line of the Atchison, Topeka, and Santa Fe Railway 

connects Clarkdale with Drake which is west of the area mapped 

(fig. 70). From Clarkdale the railroad follows the Verde River across 

most of the quadrangle. Clarkdale is connected to Jerome by the 

Tunnel and Smelter Railroad which formerly carried ore from the 

mine to the smelter. Since the mine closed this railroad has not 

operated.

Jerome is on U. S. Highway 89A, which connects Flagstaff and 

Prescott (fig. 70). This highway is the only paved road in the area. 

An improved dirt road connects Jerome, Perkinsville, and Williams, 

which is to the north on U. S. Highway 66. An improved dirt road 

connects U. S. Highway 89 near the town of Chino' Valley with 

Perkinsville, and a graded road about 5 miles north of Perkinsville 

connects the Perkinsville-Williams road with U. S. Highway 89 to 

the west near Drake.

In this report, a 10,000 foot grid based on the Arizona (Central) 

rectangular coordinate system is used for some localities within the 

quadrangle. This grid is shown on plate 45.

420029 58
516 CONTRIBUTIONS TO GENERAL GEOLOGY 

PHYSICAL FEATURES

The Clarkdale quadrangle includes a representative part of the 

"mountain region" which extends northwest-southeast through central 

Arizona and a representative part of the "plateau region" which extends over the northern and northeastern parts of the State, as defined by Ransome (1904, p. 14-15).

The "mountain region" in the area mapped is limited to the southcentral part of the quadrangle where Woodchute Mountain is a part 

of a short south-southeastward-trending range known as the Black 

Hills. The Black Hills are characteristic of the mountain region 

where short and generally parallel ranges are separated in part by 

intermontane valleys filled with deposits to unknown depths. Flanking the Black Hills on the east is the valley of the Verde River and 

on the west are Lonesome and Chino Valleys.

Woodchute and Mingus Mountains just south of the quadrangle 

are the highest mountains in the Black Hills, and both are capped with 

lava and are mesalike. The summits are relatively flat, and steep to 

vertical cliffs surround their margins.

Northward from the base of Woodchute Mountain, an expanse of 

relatively low hills extends about 6 or 7 miles to where the meandering Verde River has cut a deep gorge into the rocks.

The great erosion scarp that marks the south margin of the Colorado 

Plateau is 5-8 miles beyond the river. It is almost 1,800 feet high, and 

is often referred to as the Mogollon Rim. This rim is serrate in outline as a result of youthful streams cutting steep-walled canyons back 

into the tableland, and at places severing parts of the plateau from 

the main mass to form outlying mesas such as Black Mountain in the 

east-central part of the quadrangle. The surface of the plateau extends northward and IS relatively flat, forming an even skyline, except 

locally where volcanic mountains such as San Franoiaco and Bill 

Williams Mountains interrupt this regularity,

The maximum relief of 4,516 feet in the area is from the summit

of Woodchute Mountain, which has an altitude of 7,834 feet, to the 

bottom of the Verde River in the southeast corner of the quadrangle, 

which has an altitude of 3,318 feet. The summit of Casnor Mountain 

which is in the northeastern part of the quadrangle is 6,500 feet above 

sea level and is the highest part of the plateau in the quadrangle. The 

surface of the relatively low but dissected area between the plateau 

and Woodchute Mountain, slopes toward the Verde River, and has a

relief of about 500 feet; tho altitude ranges from 4,500 and 5,000 feet. 

The Verde River is the only large perennial stream in the quadrangle, The river enters the west-central part of the quadrangle, 

flows in a meandering easterly and southerly direction, and exits at 

the southeast corner of the quadrangle. Sycamore Creek, which is
GEOLOGY OF THE CLARKDALE QUADRANGLE, ARIZ. 517

the major tributary of the Verde River, is perennial in the lower 

4 miles of its course; the flow is sustained chiefly by Summers spring.

CLIMATE AND VEGETATION

The climate of the area -is arid "to semi'arid. Weather dataware 

available for Jerome, which is at an altitude of 5,250 feet, and for 

Clemenceau, which is iii the Galley of the Verde River 0.7 mile south 

of the quadrangle boundary at an altitude of 3,460 feet.

The average annual temperature of Jerome is 60°F; the average 

daily minimum temperature is 48.9°F; and the average daily maximum temperature is Yl.2°. The summer and winter temperatures of 

Jerome are lower than those at Clarkdale or Clemenceau because of 

the difference in altitude. The higher altitudes of the summit areas 

of Woodchute Mountain and the plateau result in cool summers and 

cold winters in those places.

Average temperature, in degrees Fahrenheit

City

Clemenceau ________________

Jerome.. _________________ .

Length of 

record, 

in years

16

39

January

44.3

42.3

July

84.0

78.8

Maximum

110

105

Minimum

9

7

The precipitation averages reveal two seasons of precipitation during the year one in the summer, the other in the winter. The summer rains begin in late June or early July and last through August. 

August usually is the wettest month of the year, and June normally is 

the driest. The summer rains are local sliowers or thunderstorms, 

which form quickly and result in sudden downpours that cause torrential .steamflows.. Along the Mogollon Rim, the prevailing westerly and 

southwesterly winds of the desert regions cool as they rise and cause 

considerable precipitation. In this area precipitation is high compared with that of the State as a whole.

Average precipitation, in inches

City

Clemenceau..

Length 

of 

record, 

in 

years

16 

39

. Monthly

Jan.

0.95 

1.86

Feb.

1.12 

2.11

Mar.

0.66 

1.70

Apr.

0.72 

.98

May

0.27 

.51

June

0.24 

.36

July

1.38 

2.79

Aug.

1.80 

2.93

Sept.

1.70 

1.42

Oct.

0.61 

1.13

Nov.

0.77 

1.33

Dec.

1.07 

1.67

An-' 

nual

11.29 

18.79

During the winter February is the wettest month. Snowfall is 

normal above the 5,000 foot altitude and much snow accumulates on 

the summit area of Woodchute Mountain and on the plateau. At the
518 CONTRIBUTIONS TO GENERAL GEOLOGY

6,000-foot altitude it frequently attains depths of %-2 feet; at the 

7,000-foot altitude, 1^-3 feet. Little snow falls at Jerome, and practically none in the valley of the Verde River.

Vegetation in the Clarkdale quadrangle shows effects of the wide 

range in altitude and the resulting climatic conditions. This vegetation (Humphrey, 1950; Little, 1950) is typical of the Upper Sonoran 

zone and may be grouped into four types: pine forest, pinyon-juniper 

woodland, chaparral, and grassland. The zones or belts of these 

principal types of vegetation are not sharply limited but blend into one 

another, and the precipitation, altitude, type of soil, and many other 

factors regulate the distribution of the vegetation types.

The pine forest is restricted to the higher altitudes, commonly above 

6,000 feet. The ponderosa pine (Pinus ponderosa) , also called western 

yellow pine, is the most abundant tree of this forest and occurs on the 

summits of the Black Hills and on the plateau to the north. Within 

the pine forest, near its lower limits, are small but compact thickets 

of Gambel oak (Quercus gambeli) and New Mexico locust (Robinia 

neomexicana). Some maple trees are also found in the canyons of 

Woodchute Mountain along the lower fringes of the pine forest.

The pinyon-juniper woodland type of vegetation covers more of 

the quadrangle than does any other. It extends from the foothills of 

Woodchute Mountain northward across the Verde River to the base 

of the plateau. The piny on pines (Pinus edulis] are scarce, but three 

varieties of juniper trees are abundant. They are Utah juniper 

(Jimiperus utahensis) , oneseed juniper (Jwmperm monosperma) , and 

alligator juniper (Juniperus pachyphloea) . Of these, the Utah juniper is the most abundant and is restricted to an altitude below 7,000 

feet on the Colorado Plateau. The alligator juniper is generally found 

in the chaparral zone on the high north slopes of Woodchute Mountain.

Chaparral is a brush-type vegetation, thick in some places and open 

in others; it grows best on the north slopes and foothills of Woodchute 

Mountain and on the steep rocky slopes and ridges of the plateau 

escarpment in the northern part of the quadrangle. Shrubs of this

belt are ef many species, but the shrub live oak (Quercw twrbmtta) is

most common. Other abundant shrubs are manzanita (Arctostaphylos 

pwngens] and catclaw (Acacia greggi). Locally abundant are mountainmahogany (Cercocarpus sp.), apacheplume (Fallugia paradoxa), 

and cliffrose (OowaniastansburiaTia).

The grassland in the quadrangle is limited to the valley of the

Verde Eiver although many grasses are interspersed among the stands

Of junipefj Which have encroached upon former grasslands as in the 

northwestern part of the quadrangle. The predominant grasses of this

vegetation type are blue grama, black grama, hairy grama, and sideoats grama.
GEOLOGY OF THE CLARKDALE QUADRANGLE, ARIZ. 519

Several species of cactus, predominantly cholla and pricklypear 

(Opwntia sp.), are widely scattered among all the vegetation types 

except the ponderosa pine. Century plant or mescal (Agave parryi) is 

abundant at the lower altitudes of the chaparral on the east and north 

sides of Woodchute Mountain.

Along Sycamore Creek and the Verde Kiver large willow, cottonwood, sycamore, and some walnut trees are abundant because of the 

moist soil.

GENERAL GEOLOGY

The rock formations of the Clarkdale quadrangle, whose distribution and structure are shown on plates 45 and 46, represent the Proterozoic, Paleozoic, and Cenozoic eras. Rocks belonging to the Mesozoic 

era are absent. The formations are shown schematically on plate 47.

OLDER PRECAMBHIAN BOCKS

The Precambrian rocks in Arizona are divided into two major systems, older Precambrian and younger Precambrian (Butler and Wilson, 1938, p. 11; Anderson, 1951, p. 1333). Only the older Precambrian rocks are present in the area of this investigation.

The Precambrian rocks in the Clarkdale quadrangle were not 

studied in detail by the writer. The subdivisions and names (pi. 45) 

are those used by Anderson and Creasey (1957) in their report on the 

Jerome area except for the Spud Mountain volcanics in the southwest 

corner of the quadrangle, which were identified in the field by 

Anderson.

The Precambrian rocks comprise metamorphosed volcanic and intrusive formations. The volcanic rocks are subdivided into the Spud 

Mountain volcanics, the Deception rhyolite, and the Grapevine Gulch 

formation; the intrusive rocks are gabbro and quartz porphyry. Although all the Precambrian rocks have been altered by regional 

metamorphism, and, around the ore deposits at Jerome by hydrothermal alteration, Anderson and Creasey were able to determine their 

original nature and to map each separately. The Deception rhyolite 

is a fine-grained compact rock that is commonly porphyritic and contains phenocrysts of quartz and feldspar. The Grapevine Gulch formation consists of fine- to medium-grained tuffaceous sedimentary 

rocks. The Spud Mountain volcanics comprise andesitic breccias and 

tuffacepus rocks; the breccias are characterized by large equant saussuritized crystals.

The quartz porphyry consists of relict phenocrysts of quartz in a 

matrix now altered to quartz and sericite. The gabbro is a dark 

granular rock containing hornblende and saussuritized plagioclase. 

The quartz porphyry is older than the gabbro, and both intrude the 

volcanic formations.
520 CONTRIBUTIONS TO GENERAL GEOLOGY

The reader is referred to the report on the Jerome area by Anderson 

and- Creasey (19.5.7). for-the-detailed geology of the Precambrian rocks.

 ,. TJ3TCONFORMITY AT THE BASE OF THE PALEOZOIC BOCKS

The base of the Paleozoic rock sequence is separated from the older 

Precambrian basement complex by a conspicuous unconformity. The 

horizontal to mildly diping Paleozoic cover rests upon a surface of 

acutely deformed. Precambrian rocks which were intruded by igneous 

bodies.

The erosional surface on the older Precambrian rocks in the quadrangle appears to be one of very low relief, although not much is 

known about it because of the few exposures. The basal sandstone of 

Paleozoic age which rests on this surface is locally absent because 

of minor topographic highs that rise as much as~ 50 feet above 

the general level. Elsewhere in the Mingus Mountain area scattered 

hills of the older Precambrian rocks are as much as 400 feet above the 

normal surface.

PALEOZOIC SEDIMENTARY BOCKS

Except in the southwest corner, the Clarkdale quadrangle contains 

rocks of Paleozoic age, and in most parts, they are exposed. In the 

southeast and northwest corners of the quadrangle these rocks are 

partly concealed by Cenozoic deposits. The total thickness of the 

Paleozoic rock sequence is about 3,350 feet, and the ages of the rocks 

range from Cambrian (?) to Permian. The Paleozoic rocks dip, in 

general, about 8°-10° NE. in much of the quadrangle, but they are 

horizontal in the Colorado Plateau in the northeast corner of the 

quadrangle, Recent erosion has beveled the inclined strata, SO that 

the older formations crop out in the southwestern part of the quadrangle, with successively younger formations cropping out to the 

northeast.

In the southern part of tliG quadrangle, the Paleozoic rocks crop out 

around the margins of Woodchute Mountain, and in the northern 

part, they are conspicuously displayed in the precipitous cliffs of the 

Mogollon Rim, Which marks the south edge of the Colorado Plateau. 

In the middle part of the quadrangle they CFOp Ollt in a series of northwestward-trending ridges, locally accentuated by faults of similar

strike.

TAPEA.TS SANI>STONE(?> 

DISTRIBUTION

The Tapeats sandstone (?) has the smallest areal distribution of any 

of the Paleozoic formations in the Clarkdale quadrangle, and the 

combined outcrops cover less than 1 square mile. There are five small
GEOLOGY OF THE CLARKDALE QUADRANGLE, ARIZ. 521

.areas where the Tapeats (?) is exposed as inliers in younger Paleozoic 

and Tertiary rocks.

Most of the Tapeats sandstone(?) outcrops are in the southwest 

corner of the quadrangle. This is due to the regional northeast tilt, 

which results in successively younger rocks cropping out to the northeast. Probably the best exposed section of Tapeats (?) in the quadrangle is in Munds Draw (coordinates N. 1,374,000; E. 402,000).

On the east side of Woodchute Mountain above the dump of the 

United Verde mine at Jerome, the Tapeats (?) crops out between the 

Haynes fault and other faults of that area. Another exposure of 

Tapeats (?) is about 1% miles northeast of the pit at Jerome. Here 

it crops out in a continuous exposure for nearly 3,000 feet in the 

opencuts of the Verde Tunnel and Smelter Railroad, which formerly 

connected the smelter at Clarkdale with the United Verde mino 

(coordinates N. 1,368,000; E. 444,000).

The two other occurrences of Tapeats (?) are in the Verde River 

canyon between Perkinsville and the Packard Ranch (coordinates 

.N. 1,410,000; E. 427,000 and N. 1,406,000; E. 450,000).

THICKNESS AND STRATIGRAPHIC RELATIONSHIP

The thickness of the Tapeats sandstone (?) in the quadrangle ranges 

from a few inches to about 60 feet. The greatest thickness is in Munds 

Draw where the formation is 60 feet, although about 1 mile to the 

south it is only 25 feet. The Tapeats (?) exposed on the east side of 

Woodchute Mountain near Jerome averages 50 feet in thickness. 

Near Packard Ranch in the Verde River canyon it is 40-60 feet, 

whereas west of Mormon Pocket in the Verde River canyon (coordinates N. 1,410,000; E. 427,000), it has a maximum thickness of about 

15 feet. Nearby it wedges out and the overlying Devonian limestone 

rests directly on Precambrian rocks.

The range in thickness of the Tapeats (?) largely results from the 

uneven Precambrian surface upon which it was deposited. Because 

of the few exposures of the basal contact of this sandstone in the 

quadrangle, the relief of the underlying Precambrian surface is not 

well known, but in the Mingus Mountain quadrangle to the south, 

Anderson and Creasey state that Precambrian topographic highs rise 

into the overlying Martin limestone in many widely distributed areas.

The Martin limestone of Devonian age overlies the Tapeats sandstone^) and the contact between them appears to be gradational. 

The contact has been arbitrarily placed at the base of the first massive 

limestone bed which overlies yellow to green limy siltstone and marl.

Krieger (oral communication, 1953), who mapped the Paulden 

 quadrangle (adjacent on the west), stated that she has found a possible 

stratigraphic break between the Tapeats (?) and the overlying Martin 

limestone of Devonian age.
522 CONTRIBUTIONS TO GENERAL GEOLOGY

LITHOLOGY

The lithology of the Tapeats sandstone(?) in the Clarkdale quadrangle shows no significant deviation in the widely separated outcrops. 

In nearly every exposure a basal crossbedded sandstone forms a ledge 

that averages 50 feet in thickness. Above this sandstone is a sequence 

of weaker rocks, 10-15 feet thick, that consists of calcareous shaly 

siltstone and mudstone. Where the basal sandstone unit locally is 

cut out against topographic highs on the old Precambrian surface, 

the upper shaly unit rests directly upon the Precambrian rocks.

The lower unit of the Tapeats (?) is composed of medium- to coarsegrained sandstone including lenses of granules and pebbles; the 

pebbles are as much as one-half inch in diameter. The unit displays 

well-defined cross lamination in beds which range from a few inches 

to about 15 feet in thickness. However, not all beds show cross lamination. Lenses of granules and pebbles formed as shallow, cut-and-fill 

channels are relatively common. Individual laminae are well defined 

but adjoining strata commonly have marked contrast. The contrasts 

between individual laminae give an overall heterogeneous appearance 

to the unit. The sand is bonded with a siliceous-ferruginous cement 

which differs in abundance from place to place. Where the iron content is low and silica high the rocks are very hard and relatively light 

in color. Inversely, where the iron content is high and silica low, the 

rocks are somewhat friable and are relatively dark. Most commonly, 

however, the rocks are very ferruginous, which makes the unit appear 

a dusky red to dark reddish brown; the predominant color is reddish 

brown. The sand grains, granules, and pebbles in the Tapeats (?) 

consist chiefly of jasper, quartz, and chert, with subordinate amounts 

of f eldspathic and unidentified dark minerals.

The upper unit of the Tapeats sandstone (?) consists of shaly siltstone and mudstone. This unit is very thin bedded and weathers to a

slope, in contrast to the ledge-forming unit below. It ranges in thickneSS from 10 to 15 feet. Dark-reddish-brown slightly fissile mudstone

in beds 5 feet thick, rest directly on the basal sandstone unit. Structureless siltstone, in beds 2-3 inches thick, is intercalated among them. 

The lower reddish-brown beds grade upward into lighter rocks that 

range from shades of yellowish gray and pale olive to dusky yellow.

The lighter beds are slightly calcareous structureless mudstone and

Siltstone and are separated by fissile shale partings 1-6 inches thick;

these shale partings are light green and dark red. The bedding appears tO be irregular but individual beds cannot be traced readily because this unit is poorly exposed. Some thin sandstone beds are at the

top of the TapeatS ( ?) in a few places but are not everywhere present 

where the Tapeats (?) is exposed throughout the quadrangle. Some 

siltstone beds in the upper unit of the Tapeats sandstone (?) are very 

micaceous.
GEOLOGY OF THE CLARKDALE QUADRANGLE, ARIZ. 523 

AGE AND CORRELATION

The basal sandstone of Paleozoic age in the Clarkdale quadrangle 

appears to be gradational upward into the Martin limestone of Devonian age, as it does in the Mingus Mountain quadrangle, but it also 

appears to be the stratigraphic equivalent of the Tapeats sandstone of 

Cambrian age in the Grand Canyon.

The strongest evidence in support of a Devonian age for the 

Tapeats (?) is the gradation into, conformity with, the overlying 

Martin limestone. However, this may be more apparent than real in 

the light of Krieger's recent investigations (oral communication, 1953) 

where she has found a possible break above the Tapeats(?) in the 

Paulden quadrangle, which adjoins the Clarkdale quadrangle on the 

west. The area of Tapeats (?) which Krieger mapped is only a few 

miles from the Tapeats sandstone at Simmons (fig. 70). McNair 

(1951) traced the Tapeats from the Grand Canyon south and eastward 

to Simmons. McKee (written communication, 1953) has found many 

Cambrian trilobites in the shales overlying the Tapeats at Juniper 

Mountain (Camp Wood quadrangle) and stated that from there to the 

Clarkdale quadrangle, exposures are fairly continuous along the north 

side of Chino Valley. Less significant reasons for considering the 

basal sandstone of the Paleozoic as Tapeats sandstone of Cambrian 

age are based partly on its stratigraphic position and partly on lithologic similarity to known Tapeats.

No new evidence on the age of the Tapeats (?) was found in the 

Clarkdale quadrangle; this report, therefore, follows Anderson and 

Creasey (1957) who, because of the lack of a positive age and because 

the term Tapeats had been previously used, preferred to continue using 

Tapeats, but appended a query to express uncertainty.

MARTIN LIMESTONE

DISTRIBUTION

The Martin limestone is limited chiefly to that part of the quadrangle which is south of the Verde River. The most extensive exposures are along the southwest boundary of the quadrangle where the 

Redwall limestone of Mississippian age has been eroded from the footwall blocks adjacent to large normal faults. In the vicinity of Jerome 

the Martin limestone crops out beneath younger rocks that compose 

Woodchute Mountain, and extends southward in a peripheral band 

around Mingus Mountain to the south. Outcrops of this limestone 

also are abundant along the footwall of the Verde fault and subsidiary 

faults where erosion has exposed them. Northward, between Woodchute Mountain and the Verde River, the Martin limestone is exposed 

along many of the fault scarps. . It is well exposed in the canyons of

 420029 58 3
524 , ; CONTRIBUTIONS TO GENERAL GEOLOGY

the Verde "River and Sycamore Creek, and in a small area in S O B 

Canyon (coords. N. 1,395,000; E. 447,400). The only exposure of the 

Martin north of the Verde Kiver is in Sycamore Canyon.

THICKNESS AND STRATIGRAPHIC RELATIONSHIP

The thickness of the Martin limestone, which was measured in four 

widely separated localities, averages about 455 feet. It is 465 feet 

thick in the Mingus Mountain quadrangle, 2% miles south of Coyote 

tank (coordinates N. 1,365,700; E. 407,500), and in Haynes Gulch (coordinates N. 1,368,000; E. 433,000); just north of Jerome, it is 441 feet 

thick. A section in the Verde Eiver canyon (coordinates N. 1,409,500; 

E. 427,500), west of Mormon Pocket, revealed 444 feet of Martin, and 

at the Packard Ranch area in the Verde River canyon (coordinates N. 

1,407,000; E. 449,400) it is 480 feet the thickest section in the Clarkdale quadrangle.

Where there are local topographic highs on the old Precambrian 

surface, the Martin limestone rests directly on Precambrian rocks. 

Elsewhere, the Martin limestone rests on the Tapeats sandstone (?). 

Because the contact between the Martin and the underlying Tapeats 

sandstone(?) appears to be gradational, the contact has been placed 

arbitrarily at the base of the lowest massive limestone bed, which locally has some sandstone lenses in its basal part. The contact between the 

Martin and the overlying Red wall limestone is unconformable. The 

cut surface on the Martin limestone shows very little relief over short 

distances, and has a relief that averages 10-15 feet, with a maximum of 

35 feet as observed over wide distances.

LITHOLOGY

Though Martin limestone is the formal designation, this formation 

consists of limestone, dolomitic limestone, dolomite, some limy siltstone 

and sandstone, and copious amounts of disseminated argillaceous and 

arenaceous impurities among the carbonate rocks. The formation as 

a whole is progressively darker from bottom to top as the result of an 

increase in impurities. The formation is uniformly bedded and forms 

steplike slopes. These characteristics help to easily distinguish it from 

the overlying Redwall limestone, which is more massive and lighter.

The Martin limestone has comparatively few fossils, and the lower 

part of the formation seems to be barren. The beds generally are 

fossiliferous towards the top of the formation, and a few are very 

fossiliferous, containing abundant gastropods, brachiopods, and corals. 

No fossils were collected and no paleontologic data were gathered while

mapping the quadrangle.

In the Jerome area the Martin limestone can be subdivided into four 

parts which may be classified as members in detailed mapping. They
GEOLOGY OF THE CLARKDALE QUADRANGLE, ARIZ. 525

do not correspond to the subdivisions of Huddle and Dobrovolny 

(1945; 1952, p. 73), who arbitrarily divided the Martin farther east 

into three members. The units chosen were used chiefly for structural 

control in this study. Although they are not differentiated on plate 45, 

they are described individually and are designated from bottom to top 

as units A> B, C, and D.

Unit A. Unit A includes a nonpersistent basal sandstone and a thinbedded dark-gray dolomitic limestone, which ranges from 20 to 50 feet 

in thickness. The basal sandstone, of local occurrence in the Clarkdale 

quadrangle, has a uniform texture containing well-rounded and frosted 

grains. In places it contains limonitic spots, which give it a "freckled" 

appearance. It is lenticular and seldom more than l1/^ feet thick. 

This sandstone may be reworked Tapeats sandstone (?). The overlying ledge-forming dolomitic unit is very persistent and has uniform 

lithologic characteristics which make it an excellent marker bed. 

Stoyanow (1936, p. 497) has noted this unit at Jerome and says that it 

can be recognized at the headwaters of the East Verde River near 

Pine and Pay son. It is also present near Simmons, about 20 miles 

to the west, and probably extends northward from there.

The dolomitic limestone ranges from light brownish gray to brownish gray, and contains minor areas of yellowish gray and pale red, 

visible upon close inspection. The colors appear to be locally affected 

by the coarseness of grains and by the percentage of the argillaceous 

impurities. Acid tests indicate that the rock is more dolomitic where 

it is coarse grained and more calcitic where it is fine grained. The 

fine-grained areas which are lighter in color occur interstitially in 

larger areas of coarse-grained material. The grain size as a whole 

ranges from fine to coarse, but medium to coarse sizes are predominant. 

Possibly much of the coarseness is due to recrystallization.

Beds range from 14 inch to 3 feet in thickness, and the thinner beds 

alternate with the more massive ones. Weathering of the faces of the 

thicker beds has etched out textures and structures of these rocks so 

that it is not uncommon to see crossbedding, channeling, and fragments of limestone in relief on the surfaces. These features indicate 

that, although the carbonate materials are of subaqueous origin, they 

were mechanically transported and deposited.

The massive beds which commonly are more dolomitic and coarser 

grained than the thin ones show many ovoid to circular accretionary 

masses of white calcite. Chert occurs as nodules and lenses in the 

upper few feet of the unit.

Unit B. Overlying the brownish-gray lower unit is a sequence of 

uniformly thin-bedded aphanitic light-colored slightly dolomitic limestone beds which are designated as unit B. This unit generally is 

homogeneous in appearance, and probably is the most prominent of
526 CONTRIBUTIONS TO GENERAL GEOLOGY

the section because it is light and is limited at top and bottom by 

darker units. Because of its thin bedding, this unit commonly forms 

a slope. It ranges in thickness from 80 to 110 feet but averages about 

85 feet.

Unit B is characteristically light gray to white on the weathered 

surfaces and pinkish gray on the unweathered surfaces. Locally, 

one or two beds near the bottom of the unit may be dark gray. The 

thickness of individual beds ranges from a few inches to several 

feet, and probably averages about 8 inches. The limestone beds are 

separated by shaly interbeds or partings as much as 3 inches thick. 

On slopes the shaly mudstone is not conspicuous and may go undetected, whereas in cliffs or steep walls, the shale interbeds are more 

distinct. The shale is dark gray and appears as a dark band between 

the lighter beds, which emphasizes the uniform bedding of the unit. 

A good example of this may be seen about 1 mile north of Jerome 

on the Jerome-Perkinsville road. The limestone is very aphanitic 

and in most places does not show stratification on unweathered surfaces. Disseminated sand grains stand out in relief on the weathered 

surfaces of some beds and locally on unweathered surfaces. Chert 

is fairly abundant as nodules, lenses, and thin layers parallel to the 

bedding; it is in shades of light yellow to dark gray or black, and is 

present in the limestone and the shale interbeds.

Within 6-10 feet of the top of the unit is a persistent sandstone 

bed that ranges from 1 to 3 feet in thickness. In some places, it is 

so well cemented with silica that it is more nearly an orthoquartzite 

than a sandstone. Chert is moderately common along this bed or 

zone. Some limestone grains are admixed with quartz sand grains 

in a few localities. The sandstone weathers from a light rusty brown 

to a darker brownish red, hence, the local name "Red Marker" has 

been applied. This horizon marker has been used extensively in the 

vicinity of Jerome for determining offsets on faults of minor 

displacement.

Unit O. Unit C overlies unit B with a distinct and abrupt lithoiogic 

change. In contrast to the underlying unit #, w^t 0 is much darker 

and coarser grained, has fewer shale partings, is thicker bedded, and 

forms receding ledges. The thickness of this unit ranges from 65 

to 80 feet but averages about 70 feet. Unit G is characteristically a 

sequence of mottled dolomitic limestone beds.. The mottling, produced by a difference in grain size, is similar to that in the lower unit. 

The fine-grained areas are pale red to grayish orange pink, and the 

medium-grained areas are yellowish gray to light olive gray. The 

mottling appears to result from partial recrystallization. The size 

and shape of the recrystallized areas is variable, but on any given 

surface it is generally measured in inches. The beds range from less
'GEOLOGY OF THE CLARKDALE QUADRANGLE, ARIZ. 527

than an inch to about 4 feet in thickness. Stratification is not evident within most beds. Very few thin partings of shale are present. 

Vugs of coarsely crystalline calcite are abundant.

Unit D. In contrast to all the other units of the Martin limestone, 

each of which is uniform in character, unit D shows the greatest 

variation in lithology, color, and texture. This unit includes all the 

rock types of other units, in alternating sequence. Such diverse 

lithology produces alternating dark and light beds which gives the 

unit a heterogeneous appearance. The unit ranges from 260 to 270 

feet in thickness and consists chiefly of dolomitic limestone and limestone, with lesser amounts of interbedded calcareous shaly siltstone 

and sandstone. The limestone is less dolomitic and more argillaceous 

and arenaceous towards the top, except in the uppermost 50 feet.

For the most part, the lower fourth of unit D consists of interbedded light-gray aphanitic dolomitic limestone similar to the limestone of unit B, light-olive-gray to dark-gray medium- to coarsegrained dolomitic limestone and (or) dolomite, and medium- to lightgray thin-bedded finely laminated dolomitic limestone. Chert layers 

and lenses are abundant in the thin-bedded zones. The bedding ranges 

from a few inches to several feet in thickness and is uniform and 

regular.

Above the lower fourth of the unit, the section becomes more argillaceous so that shaly mudstone and platy siltstone become prominent 

lithologic types. Because much mud apparently was introduced, 

the dolomitic limestone beds are contaminated with argillaceous impurities that cause a purple to red mottling. In many places, interbeds of purple or lavender calcareous shaly mudstone separate these 

impure dolomitic beds.

A little less than half way up the unit, beds that total about 40 feet 

in thickness consist of alternating thin-bedded impure slabby dolomitic limestone and purple calcareous shale. This part of the unit 

forms a slope and includes most of the argillaceous impurities.

Argillaceous materials are also present, but in lesser amounts, 

scattered throughout the overlying beds, except in the top 50 feet of 

the unit. These uppermost beds consist of grayish-orange-pink 

medium-grained dolomitic limestone that is uniformly bedded and 

crops out in steplike ledges.

A few distinctive beds in unit D merit individual attention as they 

constitute key or marker beds. In the Jerome area, two beds are 

lithologically unique in the section. These are light-olive-gray 

medium- to coarse-grained dolomitic limestone beds that contain many 

inclusions of fine-grained moderate red sandstone in irregularly 

shaped masses which range from less than an inch to about 9 inches 

in diameter. Each of these beds is 2 feet thick. They occur 40 and 

50 feet respectively above the base of the unit. Also a 7-foot mas-
528 CONTRIBUTIONS TO GENERAL GEOLOGY

sive yellowish-gray fine-grained dolomitic limestone, bearing an 

abundance of solitary- and colonial-type corals, occurs 150 feet above 

the base of the upper unit. This bed may be f ossilif erous only locally, 

because in other areas the fossils could not be located. A prominent 

feature in the Verde River canyon near the mouth of Sycamore Canyon, is a 3-foot ledge of sandstone, 175 feet above the base of the 

upper unit.

AGE AND CORRELATION

In Arizona, Devonian strata have been referred to as the Temple 

Butte limestone, a name proposed by Walcott (1890, p. 50) but used 

only in the Grand Canyon area in the northern part of the State; 

the Martin limestone, a name that Ransome (1904, p. 33) assigned to 

the Devonian rocks at Bisbee, but which has been used mostly in the 

central and southeastern part of the State; and the Jerome formation, 

a name used by Stoyanow (1926, p. 316-317) for the Devonian rocks in 

north-central Arizona.

Huddle and Dobrovolny (1945) demonstrated that the Martin limestone of the Globe-Miami area probably is continuous with the Devonian strata of the Pine-Payson area and stated that "there seems 

to be no reason for recognizing the Jerome formation of Stoyanow." 

For this reason Anderson and Creasey (1957) decided to use the name 

Martin for the Devonian rocks in the Jerome area also. This report 

follows that usage.

Ransome (1916, p. 161) took a random f aunal sample from a fossiliferous bed in the upper part of the Martin limestone at Jerome. The 

fauna, examined by Kindle, was assigned to Late Devonian age.

Stoyanow (1936, p. 495-500) studied the Devonian section at Jerome 

and listed fossils and their locations in the section which proved Late 

Devonian in age.

McNair (1951, p. 516) compared the Martin limestone of the Jerome 

area with the Devonian strata of the Grand Canyon, and reported that 

the purple soft, crumbly, silty beds, which are more abundant in the

Martin limestone toward the north, are also a conspicuous rock type 

of the Temple Butte limestone.

The upper part of the Martin limestone of central Arizona is of 

Late Devonian age, but the lower and middle parts may be Middle 

Devonian, according to Huddle and Dobrovolny (1902, p. 6T, 80), who 

stated that their fossil collection indicates that the Martin may contain 

equivalents of some of the f aunal zones of the Devils Gate formation of 

Merriam in central Nevada.

REDWAXJL. LIMESTONE

DISTRIBUTION

The Redwall limestone occurs sporadically throughout the south 

half of the Clarkdale quadrangle, except in the southeast corner where
GEOLOGY OF THE CLARKDALE QUADRANGLE, ARIZ. 529

it is entirely hidden by younger rocks. It occurs extensively along 

the west margin of the quadrangle as far north as the Verde River, 

and in the vicinity of Jerome it forms a peripheral band that crops 

out on the steep slopes around Woodchute and Mingus Mountains 

to the south. Also, east of the Verde fault, the Redwall has been 

exposed by subsidiary faulting and large patches of the formation 

crop out north of Woodchute Mountain where erosion has stripped 

the overlying Supai formation from uplifted fault blocks. The Redwall occurs along scarps of the north-northwestward-trending faults 

which branch from the Verde vault in the vicinity of the Jerome area. 

A small and isolated occurrence of it may be seen in S O B Canyon. 

Almost a continuous exposure occurs along the entire course of the 

Verde River from where it enters the quadrangle on the west to where 

Syca'more Creek joins it.

The only exposures of the Redwall limestone north of the Verde 

River are in Sycamore Canyon, along the scarp of the Railroad fault 

on the west side of Packard Mesa, and along the scarps of the Verde 

and Orchard faults east and northeast of Perkinsville. The best exposures are in Sycamore Canyon, the Verde River canyon, and in the 

vicinity of Jerome.

THICKNESS AND STRATIGRAPHIC RELATIONSHIP

The Redwall limestone ranges in thickness from 235 to 285 feet 

within the quadrangle, but probably averages about 250 feet. The 

greatest thickness in any of the five sections measured is in Haynes 

Gulch in the vicinity of Jerome, where the section is 285 feet thick. 

The thinnest section, 235 feet, is in S O B Canyon. The Redwall is 

255 feet (incomplete section) in Little Coyote Canyon on the west 

side of Woodchute Mountain about 2 miles south of the quadrangle 

border; 252 feet in the Verde River canyon (coords. N. 1,412,000; E. 

423,000); and 241 feet in Sycamore Canyon (coords. N. 1,413,400; E. 

454,000). These data show that the Redwall limestone is progressively 

thinner from Jerome towards the northeast.

The Redwall limestone unconformably overlies the Martin limestone of Late Devonian age, and is unconformably overlain by the 

Supai formation. The exact position of the contact between the Martin 

and the Redwall is not everywhere discernible because the lowest unit 

of the Redwall contains reworked sediments from the Martin and 

therefore resembles the Martin. The zone of reworked material is as 

much as 35 feet thick in places but at other places it is absent, owing 

to the relief on the Devonian surface. The contact is gently undulating and from a distance the two formations appear conformable. 

The base of a massive bluish-gray oolitic limestone member, which 

directly overlies the reworked residual material above the Martin
530 CONTRIBUTIONS TO GENERAL GEOLOGY

limestone, was used for mapping the contact between the Redwall and 

the Martin.

The contact between the Redwall limestone and the overlying Supai 

formation is easily determined. It can readily be observed on the east 

and north sides of Woodchute Mountain along the road from Jerome 

to Perkinsville. The Redwall generally is a massive limestone that 

forms conspicuous cliffs. The top of this limestone commonly forms 

a bench from which the soft red shale and siltstone of the basal Supai 

formation have been eroded. The contact is irregular; the local relief 

is as much as 15-30 feet in a lateral distance of 100 feet, and fragments 

of limestone and chert fill the hollows.

LITHOLOGY

The Redwall limestone, which is generally a cliff-forming unit, 

consists chiefly of light-gray to white aphanitic to coarsely crystalline 

thin- to thick-bedded limestone. It has an overall massive appearance, 

which is due partly to the homogeneity of the beds but chiefly to planes 

of separation between many of the beds which are so inconspicuous 

when viewed from a distance, that the formation appears to be a single 

stratum. The limestone generally is f ossilif erous throughout, though 

locally beds are barren. The limestone characteristically contains 

solution channels and caverns, many of which have collapsed or have 

been filled. Where they have collapsed, large blocks of limestone 

conglomerate that fill them are cemented with a bright red, claylike 

sediment, which probably is a residue from solution of the limestone. 

The channel-filling consists chiefly of chert released by solution from 

limestone matrix. The caverns are both vertical and horizontal in 

attitude; the horizontal ones extend along the strike of the bedding. 

Many of these occur along the Chino Yalley-Perkinsville road where 

the road meanders through Wildcat Draw just outside of the west 

border of the quadrangle.

Woodell (Stoyanow, 1936,p. 514),Gutschick (1943), and Gutschick 

and Easton (1953) have studied the Mississippian strata in the Jerome 

area in detail. Woodell divided the limestone into six faunal zones 

and listed the species of fossils present in each. Gutschick (1943, p. 

2-5), who Studied the Redwall limestone from the Pine-Payson area 

northwestward along the margin of the Colorado Plateau to near 

Seligman, Ariz., divided the formation into four members. The four 

members as designated by Gutschick are as follows, from the base 

upward: (I) A white crystalline oolitic limestone member; (II) a 

fine-grained cherty pOIOUS limestone member; (III) a massive coarsely 

crystalline limestone member; and (IV) a gray, micro-oolitic aphanitic 

limestone member. The units used in describing the Redwall in the 

text of this report correspond to the members of Gutschick, but the 

contact between units 3 and 4 was located in a different place. In this
GEOLOGY OF THE CLARKDALE QUADRANGLE, ARIZ. 531

report it is placed at the base of the bluish-gray micro-oolitic limestone near the top of the formation, whereas Gutschick and Easton 

(1953, p. 4) placed it about 25 feet below where they believed that they 

recognized a disconformity. No disconformity could be found at this 

horizon by the writer.

Although the four members of Gutschick were recognized during 

the present study, they were not mapped separately except in a few 

local areas where detailed information was desired for interpreting 

the structure. For this reason they are not shown on plate 45. In 

order to describe the Redwall limestone as adequately as possible, each 

of the four units is described separately.

Unit L Unit 1 of the Eedwall consists of a lower thin-bedded 

clastic unit that constitutes reworked deposits of the Martin limestone, 

and an upper unit that constitutes bluish-gray oolitic thick-bedded 

limestone. The lower unit consists chiefly of limestone, arenaceous 

limestone, and calcareous sandstone materials which resemble many 

of the Upper Devonian lithologies. This unit wedges out against 

topographic highs that remain on the upper surface of the Martin 

limestone. As much as 35 feet of these beds has been measured in 

some places. The beds are very light gray and lavender to pink; the 

pink results from impurities. Most of the beds in the lower part of 

the unit are thin, but higher up they are moderately thick (severa.1 

feet). Locally a thin zone of sandstone, partly conglomeratic, is 

present at the base. The thin beds normally weather to slopes.

The upper part of unit 1 consists of massive beds of aphanitic oolitic 

limestone, which range from 25 to 55 feet in thickness, and is characteristically bluish gray and cliff forming. The rock generally is a 

mass of conspicuous oolites, which stand out in relief on weathered 

surfaces.

Gutschick and Easton (1953, p. 3), stated that an unconformity 

which cuts out the oolitic limestone to the north and northwest, is at the 

top of their member I. They believed that because of this unconformity the oolitic limestone is not recognized in the Grand Canyon area. 

Huddle and Dobrovolny (1952, p. 87), however, traced this unit 

laterally into a rubble breccia that consisted of large limestone and 

chert blocks in a matrix of red sandy mudstone. This relationship 

conforms with observations made by the writer in the Clarkdale quadrangle, and indicates that the oolitic blue limestone unit is conformable 

with the overlying member, but that laterally parts of it that were 

especially susceptible to solution formed in caves that later collapsed 

to form thick irregular breccia zones.

Unit 2. Unit 2, which ranges from 55 to 80 feet in thickness, is a 

light gray to cream fine-grained cherty limestone. The abundance of 

chert in this unit is characteristic. The chert, which is white to yel420029 58 ft
532 CONTRIBUTIONS TO GENERAL GEOLOGY

low and weathers to a rusty brown, occurs as nodules, lenses, and layers 

within the beds and along the bedding planes of the limestone. Fossils 

are commonly preserved in the many chert nodules. Where this unit 

is exposed to weathering, large blocks of chert are scattered about on 

the surface. The limestone occurs as beds 2-5 feet thick, and is fine 

to medium grained. It is fossiliferous though not abundantly so. 

This unit appears to have been especially susceptible to the formation 

cf caverns. These caverns have collapsed or been refilled with limestone and chert breccia.

Unit 3. Unit 2 is overlain conformably by unit 3. Unit 3 is a yellowish- to light-gray homogeneous coarsely crystalline crinoidal limestone, which probably averages 100 feet in thickness. It is thick 

bedded and the most fossiliferous unit of the formation. The weathered surface of the limestone is rough as a result of its coarse crystallinity and the abundance of small crinoidal discs that it contains. 

Unit 3 differs from unit 2 in grain size, color, and absence of chert.

Unit 4' Unit 4 consists of a bluish-gray aphanitic to oolitic cliffforming limestone that is present nearly everywhere in the Clarkdale 

quadrangle except where it has been removed by pre-Supai erosion. 

It averages about 40 feet in thickness, and resembles the oolitic phase 

of unit 1, except that it is more aphanitic, lighter, and has smaller 

oolites that can be recognized only with the lens. This unit, because 

of its color and its cliff-forming tendencies, forms a nearly continuous 

band at the top of the formation, visible for several miles or more.

AGE AND CORRELATION

In Arizona, rocks of early Mississippian age have been called the 

Kedwall limestone in the northern part of the State and the Escabrosa 

limestone in the southeastern part of the State. The Redwall, as 

originally defined by Gilbert (1875, p. 162, 177-186), included rocks 

both older and younger than Mississippian. Later, Noble (1922, p.

26, 54), who made detailed studies in the Grand Canyon area, restricted the name to strata of Mississippian age. The Escabrosa limestone was a name proposed by Ransome (1904, p. 42-44), for the 

Strata Of Mississippian age in the Bisbee area of southern Arizona, and 

this term has been widely used in the southeastern part of the State. 

In central Arizona, Huddle and Dobrovolny (1952, p. 86) have shown 

that the two formations probably are continuous and form a single 

inappable unit. In their report dealing with the Mississippian limestone of central Arizona, they use the name Redwall limestone.

The Mississippian strata in the Jerome area have long been referred 

to as the Redwall limestone. Ransome (1916, p. 162) reported that 

the faunas show close affinities with the lower Burlington (lower 

Osage group). Stoyanow (1936, p. 505) stated that the Escabrosa 

and the ."Redwall limestone formations are not exactly taxonomic
GEOLOGY OF THE CLARKDALE QUADRANGLE, ARIZ. 533

equivalents but overlap each other; he believed that the Redwall began 

somewhat later than the Escabrosa. He further stated (Stoyanow, 

1936, p. 514) that species collected by Woodell in the Redwall limestone of the Jerome area indicate that the faunas range from late 

Kinderhook into Keokuk and Burlington times.

Gutschick (written communication, 1955) assigned his member I 

to Kinderhook age and placed the break between Kinderhook and 

Osage between his member I and II. He correlated his member II 

with the top of the Alamogordo and the base of the Nunn members 

of Laudon and Bowsher of the Lake Valley limestone in New Mexico. 

His member III is Osage in age and correlated with the Burlington 

limestone of the Mississippi Valley. Gutschick tentatively placed 

his member IV in the uppermost part of the Osage (Keokuk affinity) 

but felt that this did not necessarily preclude a Meramec assignment.

SUPAI FORMATION

DISTRIBUTION

The Supai formation has greater areal distribution in the quadrangle than any other formation, and presents a vast expanse of red 

rocks that extend from the north side of Woodchute Mountain northward and northeastward in many places to the limits of the quadrangle. 

Elsewhere, the Supai is present for the most part, as inliers or outliers except for the southeastern part of the quadrangle where it is 

covered by the younger Verde formation. The Supai formation has 

a general northeasterly dip except in the northeastern part of the 

quadrangle where it flattens as it approaches the Mogollon Rim. Erosion has beveled these dipping beds so that they thin to the south 

and are largely absent on Mingus Mountain south of the quadrangle.

THICKNESS AND STRATIGRAPHIC RELATIONSHIP

The Supai formation ranges from 1,550 to 1,665 feet in thickness 

within the Clarkdale area. The latter figure was determined by 

McKee (oral communication, 1953) from a section in Sycamore Canyon. McKee believes that the basal 332 feet of the section is equivalent 

to the Naco formation of Pennsylvanian age, but this part is included 

in the Supai in this report. The 1,550 feet of Supai was measured 

in a composite section from the Verde River in the vicinity of Mormon 

Pocket north to Henderson Flat at the base of the Mogollon Rim. 

Most of the Supai, particularly the lower and upper parts, forms 

cliffs, which confine examination to the few accessible canyon walls 

or slopes.

Hughes (1949, p. 33; 1952) measured a maximum of 1,155 feet of 

Supai at Black Mesa about 10 miles south of Ashf ork. In the vicinity 

of Fossil Creek, Huddle and Dobrovolny (1945) measured 2,200 feet 

of Supai; this excluded the basal 470 feet which they assigned to the
534 CONTRIBUTIONS TO GENERAL GEOLOGY

Naco formation of Pennsylvania!! age. McNair, (1951, p. 530) measured a section of the Supai in Chino Valley near the south edge of 

Picacho Butte; it totaled 1,052 feet.

The Supai formation rests unconformably on the Redwall limestone. The unconformity is marked by an erosion surface on the 

Redwall limestone which shows a relief of about 15 to 30 feet in 

the area. Upon this surface rests a basal limestone conglomerate 

and (or) chert breccia of the Supai which is held together by a matrix 

of red mud. The contact is conspicuous because of the striking difference in lithology and color between the two formations.

Overlying the Supai formation in the Clarkdale quadrangle is the 

Coconino sandstone, whereas in the Grand Canyon area the Hermit 

shale separates the Supai from the Coconino. The contact between 

the Supai and the Coconino is intertonguing. The contact has been 

assigned primarily on the basis of differences in the type of crossbedding shown by each formation. Crossbedding in the upper part 

of the Supai formation consists of thick coextensive sandstone beds 

that contain one or more sets of torrential-type cross laminae, the 

beveled surfaces of which are covered by horizontal beds of very thinly 

laminated siltstone and fine-grained sandstone. In contrast, the 

Coconino sandstone is considered to be an eolian deposit, and displays 

giant, wedge-shaped, crossbeds throughout its vertical range.

McKee (oral communication, 1953), in his regional studies has 

recognized the problem of drawing a boundary between the Supai and 

the Coconino and has arbitrarily placed the upper limits of the Supai 

at the top of the uppermost flat-bedded siltstone or sandstone, and 

this procedure is followed through this report.

LITHOLOGY

The Supai formation, which is a red-bed deposit, consists of both

detrital and chemical rocks. The detrital rocks, which are the most

abundant, occur chiefly as sandstone, siltstone, and shaly mudstone, 

whereas the chemically deposited rocks, which consist of limestone

and chart, and are most abundant near the base, constitute a very

minor part of the formation. Such a diversity of sedimentary rocks

indicates that the formation must have accumulated in a complex

environment.

The Supai formation has been divided into members in order to

interpret structure more precisely. The subdivision of the formation

into members is based on the divisions of Huddle and Dobrovolny

(1945) Which, include lower ? middle, and upper members. McKee 

(oral communication, 1953), recognized these same subdivisions in

Oak Creek Canyon and elsewhere, These members are distinctly

different in lithology, color, and topographic expression.
GEOLOGY OF THE CLARKDALE QUADRANGLE, ARIZ. 535

Lower member. The lower member of the Supai formation ranges 

from 580 to 625 feet in thickness and consists chiefly of sandstone and 

siltstone and minor amounts of shaly mudstone; it contains a few 

limestone beds, and some chert breccia and (or) limestone conglomerate. In the lower part of the member the beds are thinner.

Shaly mudstone is commonplace, so that the unit forms a gentle 

slope at the base but is increasingly steep toward the top, as the amount 

of shaly mudstone decreases. Some beds crop out prominently, other 

beds are concealed; the result is a stairlike slope typical of nearly 

flatlying beds of different composition. The lower member of the 

Supai is the only one exposed south of the Verde River. Prominent 

outcrops of this member north of the river make up the top of Packard 

Mesa, form the clifflike walls of the inner gorge of Sycamore Canyon 

from its mouth almost to the northeast corner of the quadrangle, and 

crop out in large areas northeast and northwest of Perkinsville, in 

places where overlying Tertiary or Quaternary gravel has been eroded 

away.

Many beds of the lower member of the Supai are lenticular. The 

sandstone beds commonly are laminated or cross laminated. They are 

generally fine grained and in places grade into siltstone. Conglomerate deposits are lenticular and contain medium-gray limestone and 

pale-red siltstone pebbles, which are-as much as an inch in diameter. 

The few limestone beds in the lower part of the member are light bluish gray to light brownish gray aphanitic to coarsely crystalline, and 

form conspicuous ledges 1-6 feet thick. The siltstone is pale to dark 

reddish brown and thin to thick bedded. Many beds are cross laminated. The thin beds are more friable and are a deeper red than the 

thick beds.

At the base of the lower member is a conglomerate and (or) breccia 

zone locally as much as 15 feet thick, which rests unconformably on 

the Eedwall limestone. The conglomerate consists of pebbles and 

boulders of limestone, which are loosely cemented with a purplishred and greenHo gray silty shale. Many spherical to ovoid chert concretions which range from several inches to several feet in diameter, 

and which show concentric banding of many colors, weather out from 

this zone. Some chert fragments are present in the conglomerate, but 

they are rare in comparison with limestone gravel. The conglomerate occurs in pockets, and was undoubtedly derived from the Redwall limestone with little transportation. In other places a breccia 

consists entirely of chert and is dark reddish brown and poorly 

sorted. It has an even upper surface. The chert fragments range 

from a fraction of an inch to as much as an inch in diameter. The 

conglomerate is common in the vicinity of Jerome and Woodchute 

Mountain. Elsewhere, in the area west of Antelope Hills, the breccia 

is more common.
536 CONTRIBUTIONS TO GENERAL GEOLOGY

Approximately the basal third of the lower member of the Supai, 

overlying the basal breccia or conglomerate beds, is composed chiefly 

of siltstone, but contains some shaly mudstone. Intercalated within 

this part of the member are beds of limestone conglomerate, limestone, 

and sandstone. This part of the member forms a moderate slope.

The upper half to two-thirds of the basal member is comprised 

chiefly of sandstone, but contains thin intercalated siltstone and some 

limestone beds. The bedding is thicker and more massive toward the 

top of the member so that in most places this part forms a very steep 

slope or, more commonly, a cliff. The upper 70-90 feet is a conspicuous sandstone unit, which is pale red to pink, very fine grained, thick 

bedded, with cross laminae in the beds, partly calcareous, and cliff 

forming. Its surfaces weather pale reddish brown to light brown. 

This massive cliff-forming sandstone contrasts sharply to the overlying, slope-forming sequence of siltstone and conglomerate of the 

middle member.

Middle member. The middle member which ranges from 250 to 300 

feet in thickness, is present only north of the Verde Eiver; erosion 

has stripped it from the area south of the river. The middle member 

topographically forms broad flat areas with a few gently rolling and 

rounded hills such as occur north of the Mormon Pocket area and 

northwest of Black Mountain in the Cow and Henderson Flats. It 

forms a moderate slope above the inner walls of Sycamore Canyon 

west of Black Mountain where erosion is especially active. The middle 

member also crops out north and south of the Drake road where it 

leaves the west side of the quadrangle north of coordinate N. 1,440,000; 

within a mile radius circumscribing the intersection of coordinates 

N. 1,430,000 and E. 420,000; and north along the course of Sycamore 

Canyon to where it leaves the northeast corner of the quadrangle.

The principal rock in this member is siltstone, but it is intercalated 

with conglomerate, sandstone, and some limestone. The siltstone 

ranges in color from reddish brown to grayish red. Throughout the 

member, zones of thin layers alternate with beds that are from 6 

inches to 3 feet thick. Massive siltstone beds are relatively resistant to 

weathering and form weak rounded ledges. Some of the slitstone

beds are calcareous and contain nodules; they have been traced laterally 

into gray limestone.

Few of the conglomerate beds are thicker than 3 feet, although one 

bed at the top of the member is nearly 10 feet in places. Probably 

25 percent of the middle member consists Of conglomerate beds; the 

so-called "intraformational conglomerates" of the Supai. The conglomerate beds are very lenticular and many grade both laterally 

and upward into siltstone. The gravel constituents of the conglomerate include pale-brown to pale-red siltstone (some of which is lami-
GEOLOGY OF THE CLARKDALE QUADRANGLE, ARIZ. 537

nated), and light-brownish-gray to medium-gray limestone. The pebbles range from % to 5 inches in diameter, but more commonly are 

an inch or less; they are well rounded. The matrix is usually a palered to reddish-brown siltstone.

The sandstone is limited to perhaps three or four beds that are 

thick in comparison with the other rocks of this member. The sandstone is light brown to pale reddish brown, fine grained, and generally 

forms resistant, rounded ledges. Some beds are calcareous and show 

prominent cross lamination. They commonly range from 5 to 10 feet 

in thickness.

Limestone is the least common rock type in the middle member. 

Only a few beds are present in most sections. Locally a dark-pinkishgray aphanitic sandy cross-laminated limestone occurs at the base of 

the member. This limestone weathers into a pitted surface and is 

lighter on the weathered than on the unweathered surfaces. It wedges 

laterally and commonly is l-l1/^ feet thick, though in a few places it 

is almost 5 feet thick.

The contact between the middle and upper members is placed at the 

base of the lowest reddish-orange to light-brown friable large scale 

cross-laminated sandstone. The sandstone weathers into slabs several 

inches thick and is typical of the sandstone throughout the upper member. Inasmuch as the upper member is predominantly a sequence of 

medium- to coarse-grained sandstone, its basal contact is prominent.

Upper member. The upper member of the Supai formation ranges 

from 650 to 750 feet in thickness, and is present only north of the 

Verde River. This member forms a wide peripheral band around 

Black and Casner Mountains, and comprises nearly half the rocks 

that make up the precipitous Mogollon Rim, which projects into the 

northern part of the quadrangle and extends along Sycamore Canyon 

where it has been cut into the Colorado Plateau. In the northwest 

quarter of the quadrangle most of the upper member of the Supai is 

covered by lava and gravel so that inliers of this member occur in 

many of the drainage systems which traverse the beds of lava and 

gravel.

The contact between the middle and upper members is characterized 

by a sharp break in topography and lithology. In contrast to the 

slope-forming, dominantly siltstone sequence of the middle member, 

the upper member is a sequence of sandstone and a few interbedded 

siltstone beds that form cliffs, buttresses, and pinnacles.

This member contains about eight times as much sandstone as siltstone. The sandstone has a distinct outcrop and color which is not 

readily confused with lith'ologic characteristics in other members; it 

is dominantly reddish orange though some is light brown to moderate 

reddish brown. Most of the sandstone is cross laminated on a large
538 CONTRIBUTIONS TO GENERAL GEOLOGY

scale, and, the rock weathers into slabs and plates. The sandstone 

beds generally are very friable and form a sandy soil. Some are calcareous and most are medium to coarse grained. The bedding is 

massive; some beds measure more than 150 feet in thickness, and, 

commonly, include a few partings or lenses of flat-bedded siltstone. 

Irregular folding due to penecontemporaneous deformation is conspicuous in the upper member at Sand Flat (coordinates N. 1,446, 500; 

E. 421,200), but was not seen anywhere else.

Intercalated in the upper member are beds of pale-reddish-brown 

siltstone which range from a few feet to almost 30 feet in thickness, 

and probably averages 6-8 feet. The siltstone beds show irregular 

wavy laminae. Cross laminae, in most places, are absent, and the 

horizontal bedding of the siltstone beds is usually very noticeable 

where they separate strongly cross-laminated sandstone. The siltstone 

weathers into rounded ledges.

The contact between the upper member of the Supai and the 

Coconino sandstone is difficult to determine in places. Because there 

are no siltstone beds in the Coconino of other areas, and because at 

close range the crossbedding in the upper member of the Supai resembles that of the Coconino, the contact is arbitrarily placed at the 

top of the uppermost flat or horizontally bedded red siltstone. However, in many places talus blocks of the Coconino sandstone conceal 

parts of the upper Supai so that locally it is difficult to locate the 

uppermost siltstone. The Coconino sandstone is typically buff to 

cream, but locally may have the same reddish color as the Supai. However, the color boundary commonly is in close coincidence with the 

top of the uppermost flat-lying bed of the Supai. The Supai has 

horizontal-bedding planes, throughout, whereas the Coconino has 

huge, sweeping planes that separate individual wedges or sets of crossbedding. The structures of the eolian Coconino sandstone are on such 

a large scale that they have very shallow angles and are almost horizontal in places. The low angles of these parting planes add difficulty 

in placing the contact on the basis of the highest horizontal-bedding 

plane. From a distance, a greater length of the contact can be observed, 

and the boundary at once becomes evident.

AGE AND CORRELATION

The Supai formation, as originally denned by Darton (1910, 

p. 25-27) in the eastern Grand Canyon region of northern Arizona, 

included about 800 feet of red sandstone and shale underlying the

Coconino sandstone and overlying the Kedwall limestone. As defined

by Darton the Redwall limestone included rocks of both Mississippian 

and Pennsylvanian or Permian age, but Noble (1922, p. 59-62) redefined the Supai formation, assigning to it about 250 feet of red shale,
GEOLOGY OF THE CLARKDALE QUADRANGLE, ARIZ. 539

purple and gray limestone with chert and red calcareous sandstone 

formerly included in the Kedwall. Noble also redefined about 300 feet 

of red shaly siltstone and fine-grained sandstone from the top of the 

Supai and assigned to it the name Hermit shale. When redefining 

the Supai formation, Noble (1922, p. 62) regarded the entire Supai 

as probably Pennsylvanian in age.

The Supai 'formation, as 'now classified, is Permian and Pennsylvanian. Work by Huddle and Dobrovolny (1945) has resulted in an 

attempt to define the age of the Supai formation more closely. They 

stated that the formation transgresses time lines and probably ranges 

in age from Des Moines (Pennsylvanian) through Leonard (Permian). In addition, they reported that the lower member probably 

ranges from Des Moines through Wolf camp, and inter fingers with 

the underlying Naco formation (Pennsylvanian). Also, they correlated the middle member of the Supai with the Abo formation of 

New Mexico and assigned it to Leonard age and possibly in part to 

Wolf camp age. They assigned the upper member entirely to Leonard 

age and equated it with the Yeso formation of New Mexico.

In recent years there has been a tendency among geologists to separate beds of Pennsylvanian age from the Supai formation. In the 

Clarkdale quadrangle, however, the lack of an unconformity, the apparent absence of fossils, and the similarity of lithology in the Pennsylvanian and the Permian beds make this separation impractical.

Kansome (1904, p. 44-54) introduced the term Naco for limestone of Pennsylvanian age overlying the Escabrosa limestone of early 

Mississippian age in the Bisbee quadrangle. Later, the limits of the 

Naco were extended northwestward from Bisbee to the Globe-Miami 

area of Arizona.

Huddle and Dobrovolny (1945) further extended the limits northward into the Pine-Pay son area of central Arizona, which is about 

50 miles southeast of Jerome. Here, they differentiated strata of 

Pennsylvanian age from the Supai formation and referred them to the 

Naco formation. The Naco-Supai contact was placed above a sequence 

of gray limestone and shale beds and below a sequence of beds consisting of sandstone, shale, and some limestone. They regarded the 

Naco as of Pennsylvanian age, ranging from Lampasas to Virgil.

Jackson 1 and Winters (whose stratigraphic work in the Fort 

Apache area of Arizona has not been published but is quoted by 

Jackson) removed the Pennsylvanian beds from the Supai and assigned them to the Naco. The similarity between the Permian and

1 Jackson, R. L., 1951, 'The stratigraphy of the Supai formation along the Mogollon 

River, central Arizona : Unpublished thesis in files of the University of Arizona.

420029 5£
540 CONTRIBUTIONS TO GENERAL GEOLOGY

Pennsylvanian rocks forced these workers to select for the contact an 

arbitrary plane above the highest bed containing a marine Pennsylvanian fauna.

Winters 2 regarded the Pennsylvanian-Permian boundary proposed 

by Huddle and Dobrovolny (1945) as an arbitrary one which forms 

an unnatural break in a continuous rock sequence that has similar 

lithology and faunal assemblages; therefore, he assigned 410 feet to 

the proposed boundary. Winters' Naco formation has an uppermost 

bed of gray ripple-marked fossiliferous thin-bedded limestone, which 

is overlain by gray reddish-brown claystone that grades upward into 

noncalcareous siltstone and sandstone. From f usilinids present in the 

limestone, Winters established a Virgil age for the upper Naco.

West of Fort Apache, where Winters had worked, Jackson 3 found 

fossils of Des Moines age at Fossil Creek, in the Pine-Payson area, in 

the highest f ossiliferous unit of the Naco. Jackson stated that the distribution of the lithologic assemblages between the Fossil Creek and 

the Fort Apache areas clearly indicate a regression of the Pennsylvanian sea toward the south and southeast as sedimentation exceeded 

subsidence. He suggested also in his stratigraphic work, the name 

Packard Kanch member for a subdivision of the Supai (lower half 

of lower member in this report) which he could trace to the east. He 

stated that his Packard Ranch member becomes more calcareous eastward and intertongues with the Naco, and is evident, therefore, that 

the basal part of the Supai is of Pennsylvanian age in that area.

Gilluly, Cooper, and Williams (1954) have subsequently assigned 

the name Naco to a group, subdivided into several formations.

COCONINO SANDSTONE

DISTRIBUTION

The Coconino sandstone which is believed to be an eolian deposit, 

underlies much of the plateau of northern Arizona. Its occurrence 

in the northern part of the Clarkdale quadrangle marks its southernmost limits in this area. Within the quadrangle, the Coconino crops 

out almost continuously around the upper margin of Black Mountain. 

Pre-Tertiary erosion has removed a considerable part of the formation 

around the south and west margins of the mountain, so that in many 

places only thin remnants are left.

The Coconino standstone is a prominent feature along the Mogollon 

Rim where it forms the highest cliff in the upper wall. In the northwestern part of the Clarkdale quadrangle, much of it is covered by lava 

and gravel, and the largest surface exposures in the quadrangle are in 

the Sand Flat area.

* Jackson, op. clt. 

8 Idem.
GEOLOGY OF THE CLARKDALE QUADRANGLE, ARIZ. 541 

THICKNESS AND STRATIGRAPHIC RELATIONSHIP

The Coconino sandstone ranges from 500 to 650 feet in thickness in 

the quadrangle. According to McKee (1934, p. 82) at Pine, Ariz., 

(about 55 miles southeast of the quadrangle) the Coconino is 1,000 feet 

thick, which is the thickest section known. McNair (1951, p. 533-534) 

measured a section of the Coconino at Aubrey Cliffs (about 65 miles 

northeast of the quadrangle) which totaled 405 feet. Noble (1922, p. 

67) reported a thickness of 30 feet of Coconino sandstone near the 

upper end of Kanab Canyon of the Grand Canyon area. Farther 

north near the Arizona-Utah border, the Coconino disappears. The 

thickness of the Coconino sandstone therefore increases southward 

from the north boundary of the State.

The Coconino sandstone conformably overlies the Supai formation, 

and passes laterally into its upper part through intertonguing. 

Within the quadrangle, exposures favorable for the study of the contact between the Supai and the Coconino sandstone are few because in 

most places this contact is on the side of inaccessible cliffs. The contact is discussed on page 538.

The contact between the Coconino sandstone and the overlying ToroAveap formation is sharp. The crossbedded upper levels of the Coconino sandstone are beveled to a smooth plane, and this is overlain by a 

thin, horizontal layer of fine grayish-orange to light-brown sandstone, 

which forms the base of the Toroweap formation. Horizontal beds of 

the Toroweap are in marked contrast to the large scale crossbeds of the 

Coconino. Basal beds of the Toroweap form a narrow band atop the 

Coconino that can be seen for miles along the Mogollon Rim.

From work in western Arizona, Longwell (1928, p. 39) was uncertain whether the Coconino-Toroweap contact was an unconformity 

or a surface separating rocks of different origin. McKee (1938, p. 15), 

however, believed that the two formations are conformable over a 

wide area and that the Toroweap represents a change in conditions 

of sedimentation. McKee noted particularly the lack of relief, basal 

conglomerate, and other evidence which might indicate an interval of 

erosion preceding deposition of the Toroweap. He argued that "extensive truncation of sloping laminae in the Coconino to a perfectly 

flat surface can be accounted for only by a beveling of sediments while 

still unconsolidated."

LITHOLOGY

The Coconino sandstone is a massive very pale-orange to grayishorange fine-grained conspicuously crossbedded quartz sandstone. The 

most outstanding and characteristic features of this homogeneous formation are its uniform massiveness, large-scale crossbedding, and 

uniform fineness of grain size.
542 CONTRIBUTIONS TO GENERAL GEOLOGY

Almost all the sand grains in the Coconino are of quartz but they 

include very minor amounts of clay and iron oxides, and scattered 

traces of feldspar and heavy minerals. The grains generally are well 

cemented by silica. In places the sandstone is almost as resistant as 

quartzite; elsewhere, it is moderately firm to friable. The grains are 

uniformly small (0.125-0.25 millimeter) and are rounded to subangular. Most of the grains are pitted and frosted; some grains are 

stained with iron oxide but a few are clear.

Iron oxides and claylike impurities form thin threadlike lines between laminae as observed on surfaces broken oblique to the planes 

of laminae. These impurities are red to lavender and are as much as 

several inches thick at the base of the large wedge-shaped crossbeds. 

Some brown to purplish-brown diffusion bands are cut at an angle 

across the lamination planes. The smooth surface of these slabs have 

an attractive color banding.

The entire formation consists of sweeping crossbeds as much as 

50 feet long, which are truncated and then overlain by other crossbeds, so that the beds form irregular wedges. Each wedge consists 

of thin, inclined laminae which form subparallel concave curves that 

flatten downward and become tangential to a plane of truncation at 

their lower ends. The wedges differ considerably in thickness, and 

the cross-laminae dip at angles of 15°-30°. The dip of a majority of 

the foreset beds in the Clarkdale quadrangle is to the south, and this 

prevailing direction is responsible for the shape of the erosional pinnacles and peaks between Henderson and Cow Flats. Here the peaks 

have asymmetrical profiles and the slopes are more gentle on the 

south than on the north. This erosional pattern apparently is caused 

by the sandstone on the south sides weathering along dip slopes of 

the crossbeds, Avhereas that on the north sides breaks along- vertical 

joints to form cliffs.

The Coconino sandstone typically weathers into slabs and blocks 

and readily splits into individual thin beds with smooth even surfaces along the bedding planes. Strong northeastward- and northwestward-trending joints in the northeast corner of the quadrangle 

have also been a factor in causing the sandstone to weather into

blocks. Ripple marks occur locally on the surfaces of slabs.

AGE AND CORRELATION

Darton (1910, p. 21, 27) proposed the name Coconino for the exposures Of the sandstone in the walls of the Grand Canyon. The 

Hermit shale below the Coconino in the Grand Canyon region has 

been determined by White (1929) as late early Permian in age from 

its flora, and, according to McKee (1938, p. 217), the Kaibab limestone above the Coconino is definitely of middle Permian (Leonard)
GEOLOGY OF THE CLARKDALE QUADRANGLE, ARIZ. 543

age. The Coconino, therefore, must also be of Permian age. Footprints, especially Laoporus, correlate with Lyons sandstone of Colorado, and others (McKee, written communication, 1955).

TOROWEAP FORMATION

DISTRIBUTION

The Toroweap formation was defined by McKee (1938, p. 12) 

from his extensive studies in northwestern Arizona. He subdivided 

the Kaibab limestone originally described by Darton (1910, p. 

28) into the Toroweap formation and the Kaibab limestone (restricted). This division was based on unconformable relationship 

between the two formations, on characteristic faunas of each formation, and on distinctive lithology of each formation.

In the Clarkdale quadrangle the Toroweap formation occurs only 

in the northern part, and it extends no more than 2% miles south of 

the north boundary. The Clarkdale quadrangle is about the southern 

limit of the formation in this part of Arizona. The Toroweap forms 

a narrow band immediately above the Coconino sandstone and below 

the Kaibab limestone in the summit areas of Casner Mountain and 

the Mogollon Eim. North of Sand Flat and east of the PerkinsvilleWilliams road the formation crops out from beneath the lava about 

iy2 miles east of Sand Flat and forms a part of the Mogollon Rim.

THICKNESS AND STRATIGRAPHIC RELATIONSHIP

The thickness of the Toroweap formation in the Clarkdale quadrangle ranges from 150 to 165 feet as measured at three localities 

within a distance of 9% miles. The thickness of the Toroweap measured by McKee (1938, p. 187-188) in Aubrey Cliffs, which is northwest of Seligman, Ariz., is 299 feet thick. It is 361 feet thick (McNair, 

1951, p. 535) at South Hurricane Cliffs in the Grand Canyon region. 

The Toroweap becomes thicker from the quadrangle toward the 

northwest corner of the State.

The Toroweap formation conformably overlies the Coconino sandstone with a sharp contact. The conspicuous crossbedding of the 

Coconino is beveled on top and covered by horizontal bedding of the 

Toroweap.

The Kaibab limestone overlies the Toroweap formation and the contact between these formations is easily recognized. The upper part of 

the Toroweap consists of soft mudstone and siltstone beds which 

readily break down into slopes, whereas the Kaibab limestone is a 

cliff-forming unit. The contact is placed immediately below the uppermost yellow massive sandstone at the base of the Kaibab limestone. 

This sandstone grades upward into the overlying limestone, and is 

believed to be reworked Toroweap. The upper contact of the Toro-
544 CONTRIBUTIONS TO GENERAL GEOLOGY

weap is a gently undulating surface. In most places the contact, 

where exposed, is on the face of a cliff, so cannot be studied in detail. 

Talus from the overlying Kaibab limestone commonly conceals it. 

McKee (1938, p. 28-35) cited many places in other parts of the 

region where there is evidence of an unconformity between these 

two formations.

LITHOLOGY

The Toroweap formation, defined by McKee (1938, p. 12, 17), 

includes those beds of sandstone, limestone, and gypsum unconformably beneath the Kaibab limestone and conformably above the Coeonino sandstone. At the type locality in Toroweap Valley in the 

Grand Canyon area, McKee (1938, p. 13,17-28) divided the formation 

into three members: upper red member (a) that represents a time of 

receding sea, middle limestone member (/?) that represents a time of 

a sustained sea, and lower member (7) that represents a time of 

advancing sea. He reported that eastward these members lose their 

identity through interfmgering of units where the formation consists 

of sandstone only. For this reason, he divided the formation laterally 

into western and eastern phases and designated the intermediate area, 

where sedimentary types are mixed, as the transitional phase of deposition.

In the Clarkdale quadrangle the lithology of the Toroweap indicates 

that it is a part of the transitional phase where possibly the members 

of the western phase are partly formed and intertongue with sandstone of the eastern phase. Here the formation can be subdivided 

lithologically into three main units, which consist from bottom to top 

of red to buff sandstone, calcareous sandstone and arenaceous limestone, and alternating red and buff sandstone, siltstone, and some 

shale including a few white fine-grained pure sandstone beds intercalated. These units may be the easternmost, recognizable equivalents 

of McKee's three units.

The basal rock unit is a grayish-orange medium-grained argillaceous 

sandstone, which grades upward into a grayish-orange-pink to lightgray fine-grained calcareous sandstone in the eastern part of the 

quadrangle. The uppermost 2 feet of this unit is a white coarsegrained clean sandstone. Bedding is massive, and the unit commonly 

forms a cliff. Westward this unit of sandstone grades laterally into 

pale-reddish-brown and grayish-orange very fine grained calcareous 

sandstone which is in beds 1-10 inches thick. This unit is progressively 

calcareous and thicker from east to west. It ranges in thickness from 

9 feet in the eastern part to 15 feet in the western part of the Clarkdale 

quadrangle. Probably this unit is laterally equivalent to the lower 

red member (y) of McKee's western phase of deposition of the Toroweap formation.
GEOLOGY OF THE CLARKDALE QUADRANGLE, ARIZ. 545

In the Clarkdale quadrangle, the most prominent unit of the Toroweap formation is the middle unit. The eastern part of this unit is 

very calcareous sandstone which grades laterally to the west into a 

very sandy limestone. The unit increases in thickness westward from 

15 to about 80 feet, but averages about 50 feet throughout the area. 

It forms a massive cliff and because of its yellowish-gray color, which 

is in contrast to the darker units above and below, it appears at a 

distance as a narrow ribbon visible for many miles along the upper 

part of the Mongollon Rim, above the precipitous Coconino Cliffs.

East of the quadrangle the middle unit of the Toroweap loses its 

identity in a sequence of sandstone beds that constitute the eastern 

phase. The basal few feet of this unit is composed of siltstone which 

contains a light-greenish-gray and grayish-orange-pink mottling. 

The unit as a whole characteristically weathers into cavities, several 

inches in diameter, that appear to have been formed by the weathering 

out of fossils; however, these cavities are the result of differential 

weathering, for no fossils were seen in the Toroweap formation in 

this locality. This unit probably grades laterally into the middle or 

limestone member (/?) of McKee's threefold division of his western 

phase.

Above the arenaceous limestone-calcareous sandstone (middle) unit 

is a sequence of alternating grayish-orange to buff and pale-reddishbrown sandstone and siltstone and some shaly mudstone. This upper 

unit averages about 90 feet in thickness, and is a typical redbed series. 

Most of the rocks in this sequence are very friable, soft, and break 

down easily into slopes. The unit is progressively more thin bedded, 

more calcareous, and includes more redbeds westward from the Clarkdale quadrangle. In the eastern part of the quadrangle, in contrast, 

redbeds are absent and the section consists of light noncalcareous 

sandstone only. A few light-gray to white and a few variegated reddish-brown clean sandstone beds are intercalated in this sequence. 

The upper unit probably is equivalent to the upper red member (a) 

of McKee's western phase of deposition.

AGE AND CORRELATION

McKee (1938, p. 217) reported that the marine fauna of the Toroweap formation is not yet well enough known for critical analysis. 

Because the overlying Kaibab limestone (as redefined by McKee) has 

been definitely established as being of middle Permian (Leonard) age, 

and because the upper part of the Supai formation and the Coconino 

sandstone are definitely Permian, the Toroweap formation must be of 

Permian age.
546 CONTRIBUTIONS TO GENERAL GEOLOGY

KAIBAB LIMESTONE

DISTRIBUTION

Darton (1910, p. 28) changed the name Aubrey limestone of Gilbert 

(1875, p. 177) to Kaibab limestone, because the term Aubrey had been 

adopted by the U. S. Geological Survey for the group of which this 

limestone forms a part. From detailed work in the Grand Canyon 

area, Noble (1914, p. 70) divided the Kaibab limestone into members 

because large parts of it are not limestone, but sandstone, red beds, and 

gypsum. Following the work of Noble, other workers, especially 

McKee, have studied the Kaibab limestone in great detail. In 1938, 

McKee published the results of his study; he reported that the Kaibab, 

as originally defined, contained the deposits of two, rather than one, 

advances and retreats of the sea. He therefore divided the Kaibab into 

two formations the Kaibab limestone and the Toroweap formation. . 

This classification and terminology is used in this report.

The Kaibab limestone is restricted to the northern part of the Clarkdale quadrangle where it occupies summit areas as a narrow white 

peripheral band near the top of Casner Mountain and along the 

Mogollon Rim. In many places, overlying basalt conceals the Kaibab, 

but the basalt has been eroded from large areas of the flat plateau surface, north of Henderson Flat, and in these places the Kaibab is 

exposed. Even at a distance the Kaibab can easily be differentiated 

from the underlying Toroweap, and, like the Toroweap, it can be 

traced for many miles along the Mogollon Rim.

THICKNESS AND STKATIGRAPHIC RELATIONSHIP

A complete section of the Kaibab limestone does not exist in the 

Clarkdale quadrangle. The limestone is thickest where it is protected 

from present erosion by overlying basalt, but even in these places, a 

considerable part of it had been removed before extrusion of the basalt. The maximum thickness of the Kaibab limestone in the quadrangle is about 250 feet. About 2 miles north of the quadrangle and 

on the west side of Sycamore Canyon, McKee (1938, p. 186-187) 

measured a, complete section of Kaibab that totaled 360 feet.

The Kaibab limestone unconformably overlies the Toro^oap. The 

contact between the two formations is gently undulating in the darkdale quadrangle, and although this does not prove an unconf ormable 

relationship, the detailed work of McKee (1938, p. 28-35) in northern 

Arizona, establishes the unconformity. In the Clarkdale quadrangle, 

(he contact is in most places inaccessible, for it is concealed by talus 

from the Kaibab. This contact is considered to be at the base of a 

yellow fine-grained sandstone which grades upward into limestone of 

the Kaibab. The sandstone appears to be reworked sediment from 

the Toroweap formation.
GEOLOGY OF THE : CLARKDALE QUADRANGLE, ARIZ. 547

. The Kaibab limestone is in places exposed at the surface but elsewhere is covered by basalt of probable Tertiary or later age. A conspicuous unconformity exists between the Kaibab and the overlying 

basalt.

LITHOLOGY

The Kaibab is a heterogeneous mixture of rock types, only part of 

which are limestone. It consists of beds of sandy limestone and sandstone that alternate with layers of chert. Although the Kaibab was 

not studied in great detail in this investigation, its lithology and general character suggest that in the Clarkdale quadrangle it is characteristic of facies 2 of the beta member as described by McKee (1938, 

p. 45,46-47).

The Kaibab as a whole is relatively thin bedded and commonly forms 

a cliff or a steep slope composed of small cliffs and ledges. Most of the 

bedding planes are distinct and some are abundantly fossiliferous, 

especially containing large brachiopods of the genus Dictyoclostm. 

Chert is increasingly abundant upwards in the section and, on the 

surface of the plateau, in places where the Kaibab has been exposed to 

erosion, fragments of chert weathered from the formation blanket the 

surface.

At the base of the Kaibab is a grayish-orange fine-grained calcareous 

sandstone, 6-18 feet thick, which grades upward into a very paleorange to pale-yellowish-orange sandy limestone. The sandstone contains very fine wavy laminations, but generally has a massive appearance. This sandstone seems definitely to consist of sediments of Toroweap age reworked by the transgressing Kaibab sea. The sandstone in 

many places contains horizontal lavender streaks which represent argillaceous impurities. It weathers as a cliff wall but is slightly recessed with respect to the overlying limestone. Kocks of the Toroweap 

below the basal sandstone of the Kaibab are much softer, and thus 

form slopes.

The limestone beds of the Kaibab range from 1 to 8 feet in thickness, 

are moderate to very sandy, and are very pale orange to pale yellowish 

orange and light gray. The bedding is fairly regular. The lightgray limestone is generally less sandy than the pale-yellowish-orange 

limestone. Scattered calcite crystals (1-4 millimeters) are characteristic. Sand grains are fine and uniform in size, are subrounded to 

subangular, and are predominantly of quartz.

The sandstone beds are conspicuous in the sequence about 150-200 

feet above the base of the Kaibab. They are yellowish gray to nearly 

white, calcareous, fine grained and somewhat friable. The sand grains 

are subroundeol to subangular. Crossbedding is present .but not prominent. The bedding of the sandstone is more massive than that of

420029 58 6 . - ' \ ', , '. :
548 CONTRIBUTIONS TO GENERAL GEOLOGY

the limestone, and ranges in thickness from several feet to as much as 

15 feet.

Only a few thin beds of chert are present in the lower part of the 

3£aibab. The chert is more abundant towards the top, and particularly 

so, about 230 feet up. Much of the chert occurs as large balls almost 

8 inches in diameter. The resistance of chert to weathering results 

in its accumulation as chips and blocks concentrated on the surface of 

the Kaibab. The chert is dull yellowish gray to nearly white and 

shows relict textures of sand grains. The weathered surfaces of the 

chert are grayish orange or dark brown.

AGE AND CORRELATION

The Kaibab limestone is Permian in age. McKee (1938, p. 217) 

reported that he had established a middle Permian (Leonard) age by 

the brachiopod fauna of the formation. He correlated the Kaibab 

with the upper part of the Leonard formation of Texas and believed 

it to be equivalent to the San Andres formation of New Mexico, the 

Chiricahua of Stoyanow in southern Arizona, and probably the 

Phosphoria formation, in part of Utah, Idaho, and Wyoming.

UNCONFORMITY AT THE BASE OF THE TERTIABY ROCKS

Based upon the proximity of Lower Triassic rocks of the Moenkopi 

formation 4 (Price, 1949) in Sycamore Canyon to the north of the 

Clarkdale quadrangle, it is evident that during the interval between 

Triassic and late Tertiary, the area was uplifted and tilted to the 

northeast. If Jurassic or Cretaceous sediments were ever deposited 

in this region, erosion, since then, has erased all evidence. Erosion

removed about 2,100-2,300 feet of Paleozoic rocks from the Woodchute

Mountain area, and 3,200-3,600 feet from the Mingus Mountain quadrangle, farther south (Anderson and Creasey, 1957). An unknown

thickness of Precambrian rocks probably have been eroded. A surface 

marked by considerable relief was formed by erosion of these rocks, 

Tertiary basalt and gravel of the Hickey formation accumulated on

this erosion surface.

CENOZOIC BOCKS

Lacustrian deposits and thick accumulations of other sediments,

which consist mostly of coarse materials but contain some fine sediments, were deposited in many valleys and in basins of central Arizona

as a result of uplift and crustal disturbances during late Miocene or 

early Pliocene time. Furthermore, interbedded lava flows indicate

that volcanism was widespread in this region. Tne thickness of the 

deposit is variable, aid for most areas is unlmown, In some localities

4 Price, W. E., Jr., 1948, Rim rocks of Sycamore Canyon, Arizona: Unpublished thesis 

in files of the University of Arizona. . , : 
GEOLOGY, .OF TE^E CLARKDALE QUADRANGLE, ARIZ. 549

data from wells give a minimum figure, which exceeds several thousands of feet. The deposits are nearly barren of fossils, and only 

locally have they been dated precisely through discovery of vertebrate 

remains. In most places, their age must be considered tentative.

Within the Clarkdale quadrangle Cenozoic rocks consist of the 

Hickey formation of probable Pliocene age; the Verde and Perkinsville formations, which are tentatively correlated with each other, 

and which are younger than the Hickey; Quaternary gravel; and 

Recent river terrace and riverwash deposits. The Hickey formation 

is separated from the Perkinsville and Verde formations by structural, 

physiographic, and, in part, lithologic evidence.

HICKEY FORMATION

DISTRIBUTION

The Hickey formation was named by Anderson and Creasey (1957) 

from exposures of lava flows and gravel on Hickey Mountain, which 

is just south of Woodchute Mountain. According to Anderson and 

Creasey some of the lava and gravel in Lonesome Valley on the west 

side of Hickey and Mingus Mountains also are part of the Hickey 

formation. The physical continuity between rocks of the Hickey 

formation in Lonesome Valley and those on the summit of Mingus 

Mountain is broken by the marginal fault along Mingus Mountain. 

From the summit area of this mountain, the Hickey formation extends 

northward into the Clarkdale quadrangle.

The Hickey formation in the Clarkdale quadrangle is, to a large 

extent, confined to the high topographic features. Areas which structurally have been lowered and isolated from the larger masses are exceptions. The sedimentary rocks of the Hickey formation in the 

Clarkdale quadrangle appear to be stream deposits, confined to northward- and northeastward- trending relict channels beneath the volcanic 

flows. Judging from the pattern of outcrops (pi. 45), two major 

channels seem to be represented : one trends northeastward from the 

southwest corner of the quadrangle, and the other trends northward 

from Jerome; they join near the headwaters of S 0 B Canyon, and 

extend from there in a northeasterly direction, and pass through the 

west side of Black Mountain. Other minor channels tributary to the 

major ones are present in many places at the base of the volcanic flows 

of the Hickey formation.

The volcanic rocks of the Hickey formation cover the top of Woodchute Mountain and extend southward as a capping on Mingus Mountain. On the north side of Woodchute Mountain, they occur on the 

tops of ridges which radiate out from the mountain. Large patches 

of the volcanic rocks occur northward from Jerome in the hangingwall block of the Verde fault. Much of the Hickey probably extends
550 CONTRIBUTIONS TO GENERAL GEOLOGY

eastward from the Jerome area for some distance, probably as faulted 

segments, under the younger Verde formation. In the central part 

of the quadrangle the Hickey blankets the Antelope Hills, and occurs 

as isolated remnants on both sides of the Verde River in the vicinity 

of Mormon Pocket. Black and Casner Mountains are also capped 

with Hickey formation. Atop the plateau it forms outliers and parts 

of a broad, volcanic sheet that extends far to the north over the plateau 

surface.

THICKNESS AND STRATIGRAPHIC RELATIONSHIP

Regionally, the Hickey formation is variable in proportion of volcanic to sedimentary rocks. Flows coalesce and interfinger with each 

other and with thick deposits of detrital material which accumulated 

in valleys and basins. In the Clarkdale quadrangle, the Hickey formation consists of much more volcanic than sedimentary rocks.

The thickness of the Hickey formation is extremely variable, owing 

to the fact that it accumulated on a highly irregular surface. The 

quadrangle has no complete sections because erosion has removed different amounts from the top of the formation.

The most conspicuous exposure of the Hickey formation occurs on 

Woodchute Mountain. Here, about 1,400 feet of volcanic flows occur 

plus about 50 feet of gravel in minor channels at the base of the flows. 

In the Antelope Hills in the central part of the quadrangle, the volcanic rocks of the Hickey formation range in thickness from 100 to

300 feet. The thickness of the volcanic rocks of the Hickey formation on Black Mountain ranges from almost 50 feet on the northeast 

side to more than 500 feet on the southwest side. On Casner Mountain and on the part of the plateau which projects into the northern 

part of the quadrangle these volcanic rocks are as much as 250 feet 

thick and are even thicker to the north away from the plateau edge.

Tka cKarmels containing tne sedimentary rocks of the Hickey formation range from a few feet to more than several hundred feet in

depth. The maximum, tliiclmess or the sedimentary rOCKS OT thft

Hickey formation within the Clarkdale quadrangle is on the west side

of Black Mountain along Sycamore Canyon.

Deformation and erosion followed accumulation of the Hickey 

formation so the younger Verde and Perkinsville formations overlie 

it unconformably. In the southwest corner of the Clarkdale quadrangle Quarternary gravel beds, which extend southwestward into 

Lonesome Valley, mask the Hickey formation. This gravel may represent tke means by wnion the extensive pediment surface was carved

in the valley,

LITHOLOGY

Sedimentary rocks. The sedimentary deposits of the Hickey 

formation in the Clarkdale quadrangle are believed to be relics of 

former stream deposits beneath the volcanic rocks and they consist of
GEOLOGY OF THE CLARKDALE QUADRANGLE, ARIZ. 551

materials that are variable both in composition and in grain size. 

Also, the thickness of these deposits within the quadrangle ranges from 

a few inches to about 200 feet. The gravel grades from fine to coarse 

and includes some silt and sandy beds and lenses. The degree of sorting and the formation of bedding differ greatly. The sandy bedsare well sorted and many are intercalated as lenses within beds that 

contain large boulders. These rest in a matrix of unsorted cobbles, 

pebbles, and silt. There are also local, well-bedded gravel beds 

throughout the formation. Most beds contain some angular to subrounded boulders 2-4 feet in diameter, although the average diameter 

of the gravel probably is 2-8 inches.

The degree of consolidation of the gravel in the Hickey formation 

is variable, and in many places the gravel beds are so weakly bound 

together that they do not withstand weathering. Elsewhere the gravel 

is well lithified with lime cement and clay matrix.

Gravel of the Hickey formation includes lithologic representatives 

of the Paleozoic formations within the quadrangle; a small amount of 

basaltic material derived from the penecontemporaneous Tertiary 

volcanic rocks of the Hickey formation; and Precambrian rocks that 

consist of quartz diorite porphyry, Deception rhyolite, breccia of the 

Spud Mountain volcanics, foliated rocks that include hornblende schist, 

alaskite, aplite, quartz porphyry, and rocks that resemble those of the 

Grapevine Gulch formation and gabbro. Basaltic gravel of Tertiary age forms a minor percentage of the total deposits. Inasmuch 

as the channels that contain these gravel deposits are below all the 

lava flows in the quadrangle, the presence of lava among the gravel 

indicates that some volcanism was active in the region to the south 

and east of the quadrangle before the major outpouring of lava during 

Hickey time. Probably the source of the gravel was to the southwest 

of the Clarkdale quadrangle, although more information on the Precambrian rocks of central Arizona is necessary before a more positive 

statement can be made. Many of the gravel deposits of Precambrian rock types appear to have been derived from sources of restricted 

occurrence. Anderson (oral communication, 1953) stated that foliates 

such as the hornblende schist are common in the Prescott quadrangle where the grade of metamorphism is higher than in the Mingus 

Mountain quadrangle. Furthermore, he reported that there is no 

alaskite and very little aplite in the Mingus Mountain quadrangle, 

whereas Krieger 5 has mapped these rocks in the southeastern corner 

of the Prescott quadrangle. The breccia of the Spud Mountain volcanics has been mapped by Anderson and Creasey (1957) along the 

west margin of the Black Hills in the Mingus Mountain quadrangle,

5 Krleger, M. H., A study of the geology of the Prescott quadrangle, Arlz., unpublished 

report.
552 CONTRIBUTIONS TO GENERAL GEOLOGY

and Kreigor has mapped large areas of the breccia in the Prescott 

quadrangle.

Volcanic rocks. The volcanic rocks of the Hickey formation consist almost entirely of basalt flows, but contain small amounts of 

detrital accumulation of basalt, andesite flows, and thin beds of pumiceous tuff.

The individual flows range in thickness from about 20 to almost 

60 feet, but probably average 40-50 feet. They are massive although 

in places somewhat vesicular and some have scoriaceous tops. 

Brecciated zones consist of angular fragments and blocks of both 

scoriaceous and massive material. Columnar jointing is common and 

is most frequently observed on steep slopes or cliffs where talus does 

not obscure the tiers of the flows.

The basalt of the Hickey formation is typically medium gray to 

grayish black on fresh surfaces but weathers brown on exposed surfaces. Megascopically it is mostly porphyritic with an aphanitic 

groundmass. A majority of the phenocrysts are glassy olivine, or 

iddingsite pseudomorphs after olivine, but augite and feldspar 

crystals have been recognized in hand specimens. Under the microscope the basalts appear completely holocrystalline. The textural 

varieties range from intergranular, where interstitial augite occurs 

in an aggregate of grains and not in large crystals, to subophitic, 

where the plagioclase and olivine crystals are separated by interstitial pyroxene and scattered iron ores. Intergranular textures are 

the most common.

The mineralogy of the basalts consists of a typical olivine basalt 

assemblage. Minerals present are olivine, plagioclase, pyroxene, 

magnetite, and some calcite. The olivine crystals are euhedral and 

are porphyritic or glomerophorphyritic; olivine also is present in the 

groundmass. Some olivine phenocrysts show rims, as well as whole 

crystals, which are altered to iddingsite, and still others are serpentinized The interstitial Olivine in the groundmass is less altered than

the phenocrystic olivine. Plagioclase feldspar OCCUFS RS phenOCrjStS 

but more commonly is confined to the groundmass. The plagioclase 

is between Ane0 and An70. The pyroxene is a greenish-gray augite 

with a weak purplish tint. The plagioclase and pyroxene appear to

have two distinct associations within the groundmaSS; in SOHie TOcks 

the plagiOClaSe feWSpar IS Ul euhedral prisms in a matrix of olivine

and pyroxene, whereas in otKer rocks interstitial pkgioCkSG SGpftflltCS

euhedral pyroxene prisms. Magnetite OCCUFS either as dust particles

throughout the rock, or as scattered grains of coarse size. The rock is

a light gray where the magnetite is in large grains, and grayish black

where the magnetite is disseminated as fine dust. Calcite in the basalt 

is assumed to be secondary. :
GEOLOGY OF THE CLARKDALE QUADRANGLE, ARIZ. 553

Basalt in dikes, which are present at the base of the Mogollon 

escarpment just north of Henderson Flat and on top of Packard Mesa 

above the Verde Kiver, is similar in mineralogic structure and assemblage to that in the flows. Some of the dikes also have calcite amygdules. Many dikes that are too small to map, are present along the 

Jerome-Perkinsville road in the. vicinity of Woodchute Mountain.

In areas where there is little topographic relief, the basalt decomposes at the surface and forms a thin layer of brown powdery soil. 

The residual soil contains abundant angular fragments and boulders 

with rounded edges which were derived from the lava.

Included in the volcanic rock series are local biotite- and hornblende-bearing lava flows, which probably are andesites but which are 

too small to differentiate on plate 45. Localities in which these rocks 

were noted are on top of the hill at First View Pass on the JeromePerkinsville road (coordinates E. 432,500; N. 1,374,500), at the base 

of the volcanic rocks of the Hickey formation southwest corner of 

the quadrangle (coordinates E. 406,500; N. 1,371,000) and in the hill 

which projects into the west boundary of the quadrangle (coordinates 

N. 1,371,000). Similar rocks may occur elsewhere among the volcanic 

rocks of the Hickey formation. In the Prescott quadrangle, to the 

southwest, Krieger 6 separated biotite and hornblende andesites from 

the upper Tertiary (?) rocks; large areas of andesite occur in the 

Paulden quadrangle.

The tuffaceous and basaltic sedimentary rocks of the Hickey formation are composed of pyroclastic materials and of materials derived 

from the basalt flows, which accumulated in local depressions during 

lulls of volcanism. The rocks are pale red, grayish red, and light 

brownish gray and are well sorted and bedded. The detritus is nearly 

all basalt; it ranges from microscopic particles to pieces the size of 

hickory nuts, all of which are subangular to subrounded. Locally 

the sedimentary rocks contain vitric and crystal fragments. Opaline 

material commonly fills the interstices surrounding large particles. A 

good exposure of these sedimentary rocks is in the roadcut leading 

to the summit of Black Mountain on the east side. Thin wedges of 

rocks also are present between flow-layers on Woodchute Mountain. 

They have been described by Anderson and Creasey (1957) and occur 

along Highway 89A where it crosses the summit of Mingus Mountain.

A single deposit of tuffaceous sedimentary rocks, that contains 

largely pumice, quartz grains, and a few scattered crystal grains of 

olivine, pyroxene, and unidentifiable minerals, is present in the southwest corner of the quadrangle (coordinates N. 1,376,000; E. 407,500). 

This deposit is in beds %-l inch thick. They are white and gray in

 Krieger, M. H., op. clt. . ... . ,. .
554 CONTRIBUTIONS TO GENERAL GEOLOGY

alternating bands which are reminiscent of varved sediments. Most 

of the light beds generally are coarse grained and are composed almost 

wholly of pumice fragments, but they contain some quartz grains and 

scattered dark minerals; all grains are rounded to subrounded, Comparable pumice-bearing, tuffaceous sediments were recognized by 

Anderson and Creasey (1957) in one small area in the Mingus Mountain quadrangle and Krieger (written communication, 1955) has 

found similar beds associated with andesite in the Pauldren quadrangle. Widespread occurrences of rhyolitic tuff are common near 

Prescott and farther south.

AGE AND CORRELATION

The age of the Hickey formation is unknown because no diagnostic 

fossils have been discovered in it. Kreiger 7 and Anderson and Creasey 

(1957) had assigned the Hickey to the Pliocene (?), but this age determination is based largely on inference which can be summarized as 

follows: (1) Much of the satisfactory dating of the Cenozoic basin 

deposits in central Arizona, which are similar to the Hickey formation, has been made to the Pliocene epoch (Gidley, 1922 and 1926; 

Knechtel, 1936, p. 86-87); (2) fragmentary antelope and llamalike 

camel bones found in late Tertiary (?) rocks near Prescott do not preclude the possibility of a Pliocene age (Anderson and Creasey, 1957); 

(3) the complexity of geologic events subsequent to deposition of the 

Hickey formation does not favor a Pleistocene age for the Hickey; 

and (4) general similarity to gravel of early Pliocene age, 20 miles

south of Prescott near Milk Creek in the Walnut Grove basin (Anderson and Creasey, 1957).

The possibility exists that gravel at the base of the Hickey is significantly older than gravel deposits such as those in Lonesome Valley

which are higher in the section. The youngest formation older than 

the Hickey known in the vicinity of the Clarkdale quadrangle is 

the Moenkopi formation Of Triassic age. Any gravel that accumulated between Moenkopi and the beginning of Hickey time might be 

included in the basal gravel of the Hickey formation, for there is

no criterion by which they could be separated. Price (1950a, p. 505-

507), Who Studied these gravel deposits about a mile north of the

ciarkdau aJ-ea in Sycamore Canyon, believed that they are probably 

Miocene to Pliocene in age.

Robinson (1913) recognized three general periods of volcanic activity of the San Franciscan field in the Flagstaff-Williams area of the 

plateau first period, basalt flows; second period, andesite and rhyolite 

flows; and third period, basalt flows. In the Clarkdale quadrangle,

two periods of volcanism are recognized older basalt flows

7 Krieger, M. H., op. clt.
GEOLOGY OF THE CLARKDALE QUADRANGLE, ARIZ. 555;

and younger basalt flows (Perkinsville and Verde). It is possible that 

the volcanic rocks of the Hickey represent Kobinson's first-period basalt flows, and that the younger volcanic facies of the Perkinsville and 

Verde represent his third-period basalt flows. Robinson (1913, p. 88) 

stated that some of the basalt of the third period flowed off the edge of 

the plateau and reached the lower Country to the south, which is precisely the relationship of the volcanic flows of the Perkinsville and 

Verde formations. Robinson (p. 91-92) placed the first-period basalt 

in late Pliocene. He arrived at this age determination by correlating a 

supposed peneplain, upon which the older basalt rests, with a similar 

feature in the physiographic cycles of southern Nevada in the Basin 

and Range province. However, significant data obtained by Koons 

(1945) on the prelava surface of erosion, indicates that early concepts 

of a buried peneplain are not supported by the facts. Robinson's age 

designation, therefore, seems inconclusive.

Lake deposits of the Bidahochi formation in the Hopi Butte Country 

east-northeast of Flagstaff are of middle or late Pliocene age 

(Williams, 1936; Hack, 1942). Stratigraphically, this formation has 

been shown to be older than the oldest lava of the San Franciscan field 

by Childs (1948, p. 378) who traced a pediment which truncates the 

Bidahochi formation from the Hopi Buttes to northeast of Flagstaff, 

where Robinson's first-period basalt is above the pediment. He therefore suggests a very late Pliocene or early Pleistocene age for the oldest 

basalt.

In the Clarkdale quadrangle evidence shows that erosion produced 

about 1,300 feet of relief after the accumulation of the Hickey but 

before the accumulation of the Perkinsville and Verde formations. 

This erosion, introduced by regional uplift, resulted in southward 

drainage, which generally has persisted to the present, and this pattern 

was well established before the accumulation of the lava of the Perkinsville and Verde formations. This sequence of physiographic events in 

relation to the general periods of basalt flows in the quadrangle, conform to the sequence described by Robinson (1913, p. 92-95) for the 

Flagstaff region, Koons (1945, p. 179-189), for the western Grand 

Canyon region, and to those of Maxson (1950, p. 14) from work in the 

Grand Canyon. Koons correlated the stages of eruption in the Uinkaret volcanic field with the stages postulated by Colton (1937) in the San 

Franciscan field, and he stated that the oldest flows antedate cutting of 

the Grand Canyon.

From his studies on the age of the Colorado River, Longwell (1946, 

p. 832) suggested that the plateau was uplifted in late Miocene or early 

Pliocene time. This age is tentatively based on the fact that the 

Muddy Creek formation is the youngest formation through which the
556 " CONTRIBUTIONS TO GENERAL GEOLOGY

ri,ver cuts. The Muddy Creek formation is believed to be as old as 

Miocene. . - , \

The local Cenozoic volcanic history of the Clarkdale quadrangle 

may be correlated with the general history of the Colorado Plateau, 

which is based on relationship of the lava to topography. Although 

the chronology of the volcanic history is clear in each aresi, attempts 

to date these events in terms of absolute geologic time is difficult.

The earliest series of plateau lava flows and those of Woodchute and 

Mingus Mountains are probably contemporaneous, but this cannot be 

proved. Undoubtedly, lava from different centers coalesced with 

other lava that erupted within the same general period. The location 

of these areas of coalescence is unknown because of the similarity of the 

extrusive material from the different centers. Woodchute and Mingus 

Mountains are composed of a very thick sequence of lava flows and a 

few interbedded sedimentary deposits, therefore, they probably are 

close to a locus of extrusion.

Basaltic dikes north of Henderson Flat are considered to be feeders 

for the volcanic flows in the Hickey formation for the following 

reasons: These dikes are not spatially associated with the young 

basalt of the Perkinsville and Verde formations which, for the most 

part, flowed south into the quadrangle from the plateau. With the 

exception of Black Mesa southwest of Perkinsville, no centers of eruption of the young lava flows are recognized within the Clarkdale quadrangle. In contrast, dikes spatially associated with the volcanic flows 

of the Hickey formation are common throughout the quadrangle. The 

spatial relationship of dike to flow is particularly close on the Sycamore

Canyon side of Casner Mountain.

INTERMEDIATE BASALT

Basalt flows intermediate in age between those of the Hickey and 

those of the Perkinsville and Verde occur west of Black Mountain 

along both sides of Sycamore Canyon. On the west side of the canyon

they occur at the intersection of coordinates N. 1,420,000; E. 453,000

and N. 1, 424,000; E. 456,000. Also north of here two very small

exposures are present. On the east side of the canyon the only expo occurs at the intersection of coordinates N, 1,418,000; F.

456,500. uri^o i«.tw«1Q<i; &t« i=,^e^it ^c^ores ITV thickness from 50 to 150 feet and 

COnSistS Of Several flOWS, The lowermost flow rests on a smootn sunaop

of the Supai formation which is inclined slightly SOUthW9,rd. IflO

northernmost isolated patch of basalt On the W6St Side Of Sycamore

CanVOfl IS ft P1US' ^w g^^®* ls associated with these lava flows.

Both megascopically and microscopically the intermediate basalt,

which is typical olivine basalt, is similar to other basalt flows in the
GEOLOGY OF THE CLABKDALE QUADRANGLE, ABIZ. 557

quadrangle. It is holocrystalline throughout, with an intergranular 

texture. As seen in thin section, the phenocrysts consist of olivine, 

plagioclase, and augite, separated by interstitial olivine, plagioclase, 

and aggregate augite. The plagioclase is calcic labradorite; the olivine 

is partly altered to iddingsite. A high percentage of magnetite grains, 

distributed throughout the groundmass, also occur in the basalt.

The lava of the Hickey formation is older than the intermediate 

basalt, which was first recognized because of its relationship to topography. The base of the basalt flows is 500 feet lower than the base 

of the lava of the Hickey which indicates the amount of erosion which 

must have taken place here between the two periods of extrusion. 

There is no gravel beneath the intermediate basalt. Gravel beneath 

the lava of the Hickey on Black Mountain are in channels which are 

at a higher altitude than the topographic surface upon which the 

intermediate basalt rests. If the surface upon which the intermediate 

basalt now rests was present at the time of deposition of the Hickey, 

then there should be gravel beneath the intermediate lava owing to 

its relationship to topography at that time.

The volcanic rocks of the Perkinsville and Verde are younger than 

the intermediate basalt, which was extruded before the canyon-cutting 

phase of Sycamore Canyon. This is indicated by the presence of 

basalt on both sides of the canyon. The volcanic rocks of the Perkinsville and Verde, on the contrary, were extruded after the area had 

become incised, because these flows occur near the bottom of the present 

canyon. It is unlikely that the intermediate basalt is equivalent to 

the Verde or Perkinsville and extruded from separate vents on the two 

sides of the canyon; there is no evidence of a vent on the southeast 

side.

The intermediate basalt represents a local phase of volcanism most 

closely related in time to the latest general time of volcanism (Perkinsville and Verde) rather than to the older time (Hickey). Only a 

tentative age can be assigned to the intermediate basalt, and Pliocene 

(?) to Pleistocene (?) age is favored.

VERDE FORMATION

DISTRIBUTION

Jenkins (1923) was the first to map, study, and describe the lakebeds 

in the drainage basin of the Verde River. He assigned to these beds 

the name Verde formation. The lakebeds are confined to this basin on 

the west by the Black Hills; on the east and north by the deeply 

dissected Mogollon Rim; and on the south by hills of volcanic rocks. 

The Verde formation is a thick sequence of limy lacustrian deposits, 

the areal extent of which covers mote than 300 square miles, including 

a maximum width of'15 miles and a length of 40 miles. The northwest
558 : CONTRIBUTIONS' ,TO GENEEALI GEOLOGY ,1 : > ."f 0

limits of this formation occur in the southeast quarter of the Clarkdale 

quadrangle.

, Marginal to, and intertonguing with the fine-grained lakebed facies 

of the Verde formation is a gravel facies. This facies extends westward from Clarkdale almost to Jerome, but northward it diminishes 

in width toward the SOB Canyon area where it forms a narrow band 

of gravel cropping out from beneath the fine-grained carbonate facies. 

Isolated patches of gravel occur near the junction of the Verde River 

and Sycamore Creek. A few patches of the gravel are present on the 

south slopes of Black Mountain and in the upper part of Sycamore 

Canyon.

The volcanic rocks of the Verde formation consist of basalt flows 

interbedded with the gravel and fine-grained carbonate rocks. Basalt 

flowed down Sycamore Canyon and then followed the course of the 

Verde Eiver canyon. Remnants of this flow are exposed intermittently 

along the inner walls of Sycamore Canyon. The largest continuous 

segment of the flow is exposed from the confluence of Sycamore 

Canyon and the Verde River canyon, south along the Verde River to 

a point about 3 miles north of Clarkdale, where it is concealed by 

younger lakebeds of the Verde formation.

THICKNESS AND STRATIGRAFHZC RELATIONSHIP

The total thickness of the Verde formation is not known because a 

complete section is not exposed. Jenkins (1923, p. 71) reported that 

the log data from a well above the smelter at Clarkdale, together with 

the thickness of additional beds exposed nearby at the surface, indicate 

a total thickness of 1,400 feet or more for this area. Also, with information from a well 2 miles south of Camp Verde at the south end 

of the drainage basin of the Verde River, plus the surface exposure, 

he obtained a total minimum thickness of 2,000 feet. Mahard (1949,

p. 104) measured an incomplete but detailed section along the west 

bank of the Verde River, 1 mile north of the smelter, which totaled 

733 feet. He also measured a section 1,040 feet thick 2 miles north of

where U. S. Highway 89A crosses the Verde River. These figures of

Manard must be increased by an unknown thickness lying below the

present river level if a complete thickness is to be calculated. Within

the Clarkdale quadrangle, a little more than 1,000 feet of the Verde

formation is exposed.

Following deposition of the Hickey formation, a prolonged period

of erosion ensued, and this was followed by faulting and uplift relative to the areas to the west and north of the quadrangle. Accumulation of the Verde formation followed shortly thereafter, and it is in 

unconformable relationship with all the older formations with which 

it comes into contact. The gravel and lava of the Perkinsville forma-
GEOLOGY OP.THE CLARKDALE QUADRANGLE, ARIZ. 559

tion accumulated at about the same time as the Verde and they are 

tentatively correlated with it. Quaternary gravel beds have subsequently formed as pediment veneers, terraces, and river wash on the 

Verde formation.

South from the junction of Sycamore Canyon and Verde River 

canyon, two flows are exposed along the walls of the river gorge. 

The lower lava has been interpreted by Mahard (1949) to have flowed 

down SOB Canyon, and the upper lava from Sycamore Canyon. 

Observations by the writer, however, indicate that both flowed from 

Sycamore Canyon. The older flow is a single layer of basalt; its 

base is at an altitude of 4,000 feet in Sycamore Canyon but descends 

below the present Verde River bed opposite SOB Canyon a drop 

in altitude of about 550 feet. In the mouth of Sycamore Canyon, 

this older flow is about 50 feet higher than the younger, showing that 

Sycamore Creek cut down its floor about 50 feet between the time of 

the first and second lava flows. Downcutting during this interval 

may have removed all vestige of the early flow up Sycamore Canyon. 

The lava in S O B Canyon is almost accordant with the underlying 

Supai formation that dips about 15° E; this gives the erroneous impression that the lava flowed down SOB Canyon. Actually it is part 

of the Hickey formation which was deformed during the period of 

structural adjustment which preceded deposition of the lavas of the 

Verde formation. This structure is a southern extension of a monocline which is prominent about iy2 miles to the north. It has been 

referred to by Mahard (1949, p. 122) and Jenkins (1923, p. 70) as the 

"Railroad Bend Structure" (see page 578). The lava in S O B 

canyon is a continuation of one of the flows of Hickey age partly covered by the Verde formation to the southwest.

Outside the limits of the Clarkdale quadrangle, other occurrences 

of lava has been reported interbedded with the lakebeds. Mahard 

(1949, p. 108-118) reported two thin lava flows interbedded with the 

lakebeds at a point 8 miles north of Camp Verde where the Montezuma Castle highway follows the valley of Dry Beaver Creek. He 

stated that 100 feet of lakebeds separate the lower and upper flows, 

which are 23 and 34 feet thick, respectively, and that they can be 

traced northward to House Mountain. Jenkins (1923, p. 69) wrote 

that the old Verde lake was formed through the damming of the Verde 

River by surface lava flows. About 6-8 miles south of Camp Verde, 

lava and lakebeds are interbedded in about equal amounts.

LITHOLOGY

Most of the Verde formation consists of fine-grained carbonate 

rocks including limestone, calcareous sandstone, limy siltstone, and 

marl. Marginal, to, and intertonguing with these carbonate rocks 

that are interpreted as lake deposits, are gravel beds accumulated as
560

fans along steep hills that probably surrounded the basin. Interbedded with these two types of rock in parts of the basin are basalt 

flows which are considered a part of the Verde formation. These 

three rock types are described separately below.

Fine-grained carbonate fades. The fine-grained carbonate rocks of 

the Verde formation consist of limestone, calcareous sandstone, and 

calcareous clay which are lenticular, and variable in proportion from 

place to place. Mahard (1949, p. 104-105) concluded from studies 

of two sections, which he measured 5 miles apart, that none of the detailed units recognized in either section could be correlated. He also 

noted that the uppermost beds in both sections are largely composed 

of limestone. He stated 

the Verde formation is not composed of beds which were uniformly spread over 

wide areas but instead is built up of thin lenses of material of varying composition, the lenses overlapping and inter fingering with one another.

Limestone is the most conspicuous lithologic type in the Verde 

formation, probably because of its normal light color and its resistance to erosion. Most of the beds are characteristically white, though 

some are light gray or pink. The rock is very hard, impure, aphanitic, and vuggy. Jenkins (1923, p. 77) suggested that the hardness 

probably has resulted from reprecipitation. The beds, which range 

from 1 to 10 feet in thickness, weather into shelves or ledges, and 

some cap hills. Most of the limestone beds are argillaceous, and contain many rounded grains of quartz. Small tubelike structures, about 

the diameter of a pencil, and several inches long, are present in many 

of the beds; these tubes closely resemble plant stems.

Sandstone, siltstone, and marl alternate with limestone beds. These 

rocks are most abundant near the margins of the formation and in 

the lower parts of exposures. Most of them are pinkish gray to 

grayish orange. A majority of the sandstone beds are fine grained 

and calcareous, and most of the grains are rounded quartz. The 

siltstone and marl are likewise calcareous. These lithologic types 

are not as resistant to weathering as limestone. They are friable, 

and Weather into Slopes, to form colluvial material.

Saline deposits are reported about 20 miles south of the Clarkdale 

quadrangle in the Verde formation in the vicinity of Camp Verde by 

Jenkins (1923, p. 73-75). He stfttfid 

here must have been the deepest portion of the old lake in which the strata 

Were formed fOr here its sediments are thickest, and here deposits of salts 

(sodium suitote, principally) are found in Quantities, S&OWing that at times 

Where tllC Iftke evaporated down to brine tne only remaining portion Of thG 

body of water was at this placG.

GrOfOel faCtG8. The gravel deposits are gray and consist of coarse to

fine gravel, sand, and silt. Sand and gravel botk are very lenticular, 

and many small channels of gravel are cut throughout the sand layers.
GEOLOGY OF THE CLARKDALE QUADRANGLE, ARIZ. 561

The lithology of the gravel differs from place to place and reflects the 

types of bedrock surrounding the basin of accumulation. The gravel 

consists of abundant Precambrian rock fragments below Jerome, 

whereas largely rocks of Paleozoic and Tertiary ages are commonly 

found on the south slopes of Black Mountain. The gravel in Sycamore Canyon, beneath and above the intracanyon basalt flow, is comprised mostly of rock types from the Mogollon Rim. The gravel is 

progressively much finer towards the area of fine-grained carbonate 

deposits. These beds appear to have been deposited primarily as fans, 

which extended into the old Verde lake, periodically interrupting accumulation of fine-grained lake deposits. The result is an interfingering of gravel and lake deposits.

Gravel of the Verde formation weathers into a loose, incoherent 

surface accumulation on the tops and sides of hills, and well-preserved 

exposures are few. The best exposures of these deposits are along 

U. S. Highway 89A between Jerome and Cottonwood, where roadcuts 

reveal the details of bedding and plainly show the interfingering 

relationship between gravel and lakebeds.

Volcanic rocks. Lava of the Verde formation is basaltic rock similar to that which occurs in other formations of the Clarkdale quadrangle. The flows are holocrystalline olivine basalt, showing intergranular texture. Interstitial pyroxene crystals occur as aggregates. 

Probably a little more secondary interstitial calcite is found in these 

rocks than in other basalts. Columnar jointing is typical but there 

is no evidence of pillow structure in the flows, indicating that the old 

Verde lake may have been dry at the time of extrusion.

AGE AND CORRELATION

No diagnostic fossils have been found in the Verde formation. 

Jenkins (1923, p. 76-77) found a few poorly preserved gastropods, 

similar in appearance to some fresh-water types, which he collected 

south of Black Mountain (coordinates N. 1,404,000; E. 468,500). 

From a collection of mollusks made by Mahard (1949, p. 119) from 

the summit of a lakebed mesa, 1 mile north of the Clarkdale smelter 

on the west side of the Verde River, the following genera were identified : Sphaeriucm sp., Lymnaea sp., Physa sp., Gyrawlus sp., Pupilla ? 

sp. Mahard stated that species of these genera indicate an environment of submerged plants in a body of water not more than 10 feet 

deep. This may account for many tubelike structures, in some of the 

limestone, which appear to be plant stems.

Jenkins (1923, p. 77) suggested that the Verde formation is late 

Tertiary or very early Pleistocene in age, because he considered the 

lava, with which the Verde formation is associated, to be of late Tertiary age. Mahard (1949, p. 126) similarly postulated a late Plio-
562 CONTRIBUTIONS TO GENERAL GEOLOGY

cene or Pleistocene age for the Verde formation. This is based on 

Robinson's (1913) conclusions that all igneous activity associated with 

the San Francisco Mountain area falls within these time limits. 

However, as previously stated, (page 555) Robinson's dating of the 

earliest lava was based on invalid evidence.

The lava, which is interbedded with the lakebeds of the Verde formation and which represents the youngest period of volcanism recognized in the area, may be correlative with Robinson's third-period 

basalt flows. Robinson (1913, p. 93-95) placed these lava flows in the 

Quaternary period (Pleistocene) because of the relationship of the 

lava to topography and the lack of appreciable erosion. He noted 

that the third-period flows followed youthful drainage courses (as 

shown by the lava in Sycamore Canyon) and flowed off the plateau 

edge, which shows little subsequent recession.

From studies of the glaciation of San Francisco Mountain, Sharp 

(1942) found evidence of Wisconsin glaciation which spread outwash 

later covered by third-period basalt flows of Robinson. This, of 

course, dates the basalt at base of the San Francisco Mountains, but it 

does not show that the Perkinsville and Verde lava flows are correlative with Robinson's third-period basalt flows. Maxson (1950, 

p. 14) favored a Pleistocene age for young lava that has flowed down 

tributary canyons to the Grand Canyon and cascaded down the walls 

of the Grand Canyon. However, it is not intended here to conclude 

that all lava flows which have flowed over canyon walls or on canyon 

floors are Pleistocene, but to indicate that they may be of the same 

general period of extrusion in this region.

The Verde formation accumulated after the major movement of 

the Verde fault which elevated and blocked out the Black Hills on 

the east, of which Woodchute Mountain is a part. The block faulting 

of the Black Hills may have started in late Tertiary time. The geologic history following the accumulation of the Verde formation includes the formation of three pediment levels (Anderson and Creasey, 

1957) on the Verde formation, and the dissection of lakebeds of the

Verde by erosion SO that the present relief is now more than 1,000 feet 

in the area.

A tentative age assignment from late Tertiary (proTooMy Pliocene) 

to Pleistocene is inferred.

Even though a precise age cannot be determined for the Verde 

formation, the relative age in relation to other formations within 

the quadrangle seems clear. The Verde IS doubtless younger than 

the Hickey, and is correlated with the Perkinsville. This correlation 

is based on the belief that structural control was the cause of accumulation in both formations, and in relation to the present erosion 

cycle. Both the Verde and the Perkinsville accumulated after fault-
GEOLOGY OF THE CLARKDALE QUADRANGLE, ARIZ. 563

ing of the Hickey, and uplift of the Black Hills mountain block. 

Volcanism during accumulation is a feature common to both formations. The lava flows of the Perkinsville which spread south over 

the rim of the plateau into the northern part of the Clarkdale quadrangle, are interpreted as contemporaneous with those intercalated 

in the Verde.

PERKINSVIIJLE FORMATION

DISTRIBUTION

The Perkinsville formation is named from the excellent exposures 

of gravel and intercalated lava flows on the north side of the Verde 

Eiver near Perkinsville. This formation, for the most part, crops 

out in the northwest quarter of the Clarkdale quadrangle, although 

a broad but short belt extends southward along the western part to 

the foothills on the northwest side of Woodchute Mountain. The 

formation extends far to the west of the quadrangle in a sheetlike 

deposit, consisting of gravel intercalated with lava; it also extends 

northward in old surface depressions on the plateau.

A period of erosion followed deposition of the Hickey formation. 

Subsequent to this erosion, there was strong tectonic activity, which 

consisted chiefly of normal faulting, but also of mild tilting of the 

strata. The topography of structural troughs where the Perkinsville 

accumulated largely controlled the distribution of the formation.

THICKNESS AND STRATIGRAPHIC RELATIONSHIP

The-thickness of the Perkinsville formation is variable, owing to 

the mode of accumulation. The thickest part within the Clarkdale 

quadrangle is between Black Mesa and the Orchard fault (coordinates 

N. 1,401,400; E. 411,750) where a drill hole cut through 200 feet of 

gravel before reaching the sandstone surface of the Supai below. 

The relief on formation outcrops in this vicinity is about 300 feet, 

indicating total thickness of about 500 feet. Exposures elsewhere 

In the quadrangle indicate thicknesses of 300 feet or more which 

seem to be normal.

The Perkinsville unconformably overlies all older formations in 

the Clarkdale quadrangle. The only younger deposits are overlying 

Quaternary terrace gravel beds along the Verde Eiver at Perkinsville and perhaps vestiges of pediment gravel which could not be 

differentiated. Biverwash also is present but is not shown on the 

geologic map of the area.

IITHOLOGY

Sedimentary rocks. The sedimentary rocks of the Perkinsville 

formation consist primarily of coarse to fine gravel, but sand, silt, 

and some limestone are also present. The gravel beds were derived
564 CONTRIBUTIONS TO GENERAL GEOLOGY

chiefly from two source areas. Those north of the Verde River are 

from the rim sector of the plateau farther north. They consist of 

almost 60 percent basalt; but also contain sandstone from the Coconino, several rock types from the Supai formation, and limestone 

from the Kaibab, and chert. The Toroweap, which is friable for the 

most part, probably contributed materially to the matrix of the gravel. 

Gravel south of the Verde River was derived chiefly from the Woodchute Mountain block and the hills west of the southwestern part of 

the Clarkdale quadrangle, and was spread northward to the Verde 

River area. Basalt constitutes almost 60 percent of these gravel beds. 

They also contain rock types representative of all the Paleozoic and 

Tertiary formations in the southern part of the quadrangle. Cobbles 

and boulders of Precambrian rocks are abundant, in contrast to a 

lack of these types north of the Verde River. Most Precambrian 

rock types appear to have been derived from gravel deposits of the 

Hickey formation, rather than directly from Precambrian bedrock.

The gravel of the Perkinsville formation is increasingly coarse 

toward source areas; sand and silt deposits are abundant near the 

Verde River. Good exposures of sand and silt occur along the railroad east of the highway bridge near Perkinsville, and gravel beds 

are well exposed for several miles up Munds Draw south of the 

Verde River and in the northward-trending canyon on the north 

side of the river at Perkinsville. The gravel is fairly well bedded, 

rounded, and evenly sorted. Bedding is less evident to the north 

and to the south, away from the Verde River, for the gravel weathers 

into loose, unconsolidated accumulations on the tops and slopes of 

hills, masking the character and detail of depositional structures.

West and northwest of Black Mesa, along the west boundary of 

the Clarkdale quadrangle but south of the Verde River is a white 

limestone bed about 4r-Q feet thick, which is interbedded with gravel. 

This limestone is thicker and more prominent west of the quadrangle 

limits than near Black Mesa. The limestone is more resistant to 

weathering than the gravel beds and therefore forms a weak ledge 

which interrupts the gentle sloping profile of the gravel hills. Fragments of detrital sediment are scattered throughout most of the 

limestone. The limestone breaks into heavy very irregular angular 

chunks.

Volcanic rocks. The volcanic rocks of the Perkinsville formation 

except those on Black Mesa and two isolated exposures that form a 

thin band between gravel beds just south of the mesa came from 

north of the Clarkdale quadrangle. These flows were all extruded 

probably in the vicinity of Bill Williams Mountain which is 13 miles 

north of the Clarkdale quadrangle, and flowed south along topographic 

depressions and drainage courses to spill over the plateau rim. One
GEOLOGY OF THE CLARKDALE QUADRANGLE, ARIZ. 565

point of entry into the Clarkdale area is where the Kailroad fault 

splits into several branches, and forms a notch in the rim of the 

plateau. The other point of entry was in the northwest corner of the 

quadrangle where there appears to have been an erosional recess 

that funneled and guided the flows. The lava flowed over irregular 

topography in that part of the quadrangle, but farther south it flowed 

over an even surface of gravel. Here the lava flows fanned out and 

spread with a uniform thickness of about 50 feet.

The lava of the Perkinsville formation is normal olivine basalts 

except for one flow which is andesite. The lava flows generally 

have a fresher appearance than do the Hickey and intermediate 

basalt in the quadrangle. They have relatively uniform texture, but 

differ in porosity. The tops of some flows are scoriaceous and amygdaloidal; the amygdules are composed chiefly of calcite. Lower parts 

of the lava flows are massive and dense. Nearly everywhere the 

basalt flows are grayish black to dark gray on fresh fracture. They 

weather into irregular, lumpy surfaces, and detached blocks form 

rounded surfaces. The residue forms a fine brown to gray soil.

The basalt flows of the Perkinsville formation are generally holocrystalline and porphyritic. Phenocrysts are chiefly olivine and show 

a glomeroporphyritic texture. The olivine crystals are changed, in 

part, to iddingsite. In a few places where they are scarce, they may 

have been altered to magnetite. A few phenocrysts of augite and 

plagioclase feldspar are present. The basalt shows, for the most 

part, a distinct intergranular texture where interstitial augite occurs 

as an aggregate of grains and not in large crystals. Some of the 

augite is slightly purple indicating a titanif erous variety. The plagioclase is calcic labradorite. The groundmass is composed of small 

feldspar laths (labradorite) containing augite, olivine, and magnetite 

grains.

Only one small occurrence of andesite has been noted. It is 1^4 

miles north of the junction of the Drake and Perkinsville-Williams 

roads. The rock is light gray containing prominent, black, hornblende needles that are in strong contrast to the background. The 

rock is an olivine-hornblende andesite with a pilotaxitic texture 

one in which the groundmass occurs as a felt of microlites. The 

hornblende is oxyhornblende, which has an extinction angle that 

reaches a maximum of 5°; part of the hornblende is replaced by 

magnetite. The olivine is microporphyritic, and some hypersthene 

is present. The microlite crystals of plagioclase feldspar are too 

small to be determined, but they are assumed to be composed of 

calcic andesine. .

AGE AND CORRELATION

No fossils have been found in the Perkinsville formation, therefore, 

its precise age is not known. Tentatively, the Perkinsville is believed
566 CONTRIBUTIONS TO GENERAL GEOLOGY

to be Pliocene (?) to Pleistocene (?) in age, and is correlated with 

the Verde. The reasons for this age assignment have been discussed 

in connection with the Verde formation which is believed to have 

accumulated contemporaneously.

QUATERNARY GRAVEL

DISTRIBUTION

Quaternary gravel covers a small part of the area within the Clarkdale quadrangle, and is confined to three widely separated localities. 

One of these is in the southwest corner where a large sheet of Quaternary gravel forms the floor of Chino Valley. Another gravel locality 

is in the valley of the Verde Kiver. Here the gravel extends from a 

locality west of Clarkdale, through Clarkdale, and southeastward into 

the Mingus Mountain quadrangle, where it is very extensive. The 

third area in which the gravel occurs is on the southeast side of Black 

Mountain along the east border of the quadrangle. Here, also, the 

gravel is part of a thin, alluvial veneer that extends eastward from the 

quadrangle.

THICKNESS AND STRATIGRAPHIC RELATIONSHIP

The Quaternary gravel in all three localities described above occurs 

as an alluvial veneer on flat, but gently sloping, pediment surfaces. 

The gravel ranges in thickness from a few inches to as much as 30 feet, 

but commonly is less than 5 feet. The pediment surfaces are trenched 

by channels which increase in depth toward the Verde KijVer. The best 

exposures of these gravel beds are in some of the channels that U. S. 

Highway 89 A crosses between Clarkdale and Cotton wood. At these 

localities exposures of the carved surface of the Verde formation 

beneath the gravel show the remnant of a pediment.

The gravel unconformably overlies all older formations with which 

they come into contact. In turn, the gravel deposits along the Verde 

Kiver have cut terraces and are covered by riverwash of Kecent age, 

which has collected in the drainage systems that dissect them.

LITHOLOGY

The Quaternary deposits consist of fine to coarse gravel that is 

subrounded, but poorly sorted and occurs in a matrix of fine-grained 

sediment. The gravel beds are not consolidated, except locally where 

Cemented by caliche. Most of the beds contain rock types of Precambrian and Paleozoic ages and also Tertiary basalt. Only the gravel 

Southeast of Black Mountain is barren of Precambrian rock types. 

The Quaternary gravel in the southeastern part of the quadrangle has 

a high percentage of Precambrian fragments; whereas gravel in the 

southwest corner of the quadrangle has a high percentage of Paleozoic 

fragments. The gravel beds are dark reddish brown where composed
GEOLOGY OF THE CLARKDALE QUADRANGLE, ARIZ. 567

of a high percentage of Precambrian fragments, but are gray where 

they consist chiefly of Paleozoic fragments.

RECENT ALLUVIAL, RIVER TERRACES AND RIVERWASH

The terrace sediments were deposited by the Verde River upon its 

flood plain at a time when the river had attained a temporary base 

level and was broadening its valley by lateral planation. Subsequent 

rejuvenation of the river has resulted in cutting downward, sideward, 

headward, and removing the earlier sediments except for segments, 

now terraces, along the flanks of the valley.

Alluvial terraces and riverwash occur mostly in and along the channel of the Verde River from a point about 3 miles north of Clarkdale, 

south to where the r^ver leaves the quadrangle. In the Packard 

Ranch area where the Verde River and Sycamore Creek join, terrace 

deposits and riverwash are present, but the terrace deposits are so 

small that they were included with the riverwash in mapping. Along 

the Verde River at Perkinsville, the riverwash and the terrace deposits 

are differentiated.

The alluvial river terraces are 5-10 feet high and border the wide 

wash of the Verde River bed. The deposits consist of a wide succession, and mixture, of unconsolidated clay, silt, sand, and gravel; 

finely stratified. Most of the sediment was derived from rocks of 

Paleozoic age, and, locally, much of the silt was derived from heterogeneous poorly sorted lakebeds of the Verde formation.

The thickness of the riverwash has not been determined, however, 

the deposits are not believed to be very thick. The riverwash contrasts 

strongly to the terrace deposits in that the wash is generally much 

coarser; it consists of fine to coarse gravel, which is poorly sorted. 

During floods large boulders are carried downstream, and as the floods 

ebb, finer sediment is deposited and fills in and around the boulders.

STBUCTUEE 

GENERAL FEATURES

The structural features of the Clarkdale quadrangle are here limited 

to the deformation recorded by the Paleozoic and Cenozoic rocks; 

not enough Precambrian rocks are exposed in the quadrangle to warrant a discussion of Precambrian structural features. In the adjoining 

Mingus Mountain quadrangle Precambrian features have been described in the comprehensive report by Anderson and Creasey (1957).

Although the physiographic boundary between the Colorado Plateaus province and the Basin and Range province is along the Mogollon 

Rim in this region (Fenneman, 1931), the area included in the Clarkdale quadrangle closely resembles a southern block of the Colorado 

Plateaus province in which erosion has cut deeper (to Precambrian
568 CONTRIBUTIONS TO GENERAL GEOLOGY

rocks in Prescott area) than farther north, but where major uplift is 

essentially vertical along normal faults. The structural types in the 

quadrangle differ little if any from those farther north in the main 

plateau. Therefore, the Prescott-Jerome-Clarkdale area may be 

thought of as blocks raised higher than the more northerly plateau 

blocks, and stripped of much, and all in some areas, of Paleozoic and 

Mesozoic formations. These views concur with and are outlined in 

more detail by McKee (1951, p. 486).

DEFORMATION OP PALEOZOIC AND CENOZOIC BOCKS

No evidence of any erogenic disturbances in the Clarkdale quadrangle occurs from the close of Precambrian through the time in which 

the Kaibab limestone of Permian age was deposited. Statewide, as 

far as known, the local pre-Devonian disturbance southeast of the 

Pine-Payson area (McKee, 1951, p. 488) is the only occurrence during 

Paleozoic time. Minor epeirogenic disturbances are reflected by 

changes in lithologic character and unconformable relationship between the different Paleozoic formations. Similarly, the interval 

which separates the Kaibab (middle Permian) from the Moenkopi 

(Early and Middle (?) Triassic), recognized by Price (1949) a mile or 

so north of the quadrangle, is marked by a conspicuous unconformity 

that indicates epeirogenic disturbance only.

A general early period of deformation in the Clarkdale quadrangle 

is postulated to have taken place between the time when the Moenkopi 

was deposited and that when the Hickey formation accumulated. The 

sedimentary rocks in the quadrangle do not indicate whether there was 

more than one episode of disturbance, and if so, when such occurrence 

might have taken place during this broad interval of time (post-Lower 

Triassic-Pliocene ?).

However, McKee (1951, p. 494) stated 

the first extensive uplift in Arizona after the pre-Cambrian probably came 

during the Upper Triassic epoch. At that time the region south of the Colorado 

Plateau apparently was uplifted for the Shinarump of Late Triassic age was 

deposited as a broad sheet of gravel over much of northeastern Arizona and adjoining areas.

McKee (1951, p. 495-496) further cited evidence for Cretaceous 

uplift in southeastern, southern, and southwestern Arizona where 

many gravel and conglomerate beds were deposited during this epoch.

A second major period of deformation in the area, after the accumulation of the Hickey formation, but before the deposition of the 

Verde and Perkinsville formations also is postulated. This deformation Was the strongest subsequent to Precambrian time. Strata were 

elevated, tilted, and faulted, and locally, faults pass into monoclinal 

folds.
GEOLOGY OF THE CLARKDALE QUADRANGLE, ARIZ. 569

Included with this late period of deformation are minor faults which 

displace the Verde and Perkinsville formations. These faults represent recurrent movement along previous fault planes.

EAHLY PERIOD OF DEFORMATION

Deformation that affected the rocks of Paleozoic age only, in the 

Clarkdale quadrangle, resulted in gently tilting these rocks to the 

northeast and in displacement by faults. Uplift and tilting of the 

strata are indicated by the sedimentary rocks of the Hickey formation. These are stream gravel beds, left as relics of a former northeastward-trending drainage system. They rest on Precambrian in the 

southeast corner of the quadrangle and on upper Paleozoic rocks in the 

northeast corner. The gravel contains fragments of Precambrian and 

early Paleozoic rocks so could only have come from the southwest. 

Similar gravel has been reported in the area north of the Clarkdale 

quadrangle by Price (1950a) and in Oak Creek canyon by Hears 

(McKee, 1951, p. 498). Further evidence of pre-Hickey uplift and 

tilting lies in the fact that the volcanic rocks of the Hickey formation 

overlap successively older rocks from northeast to southwest. The 

Paleozoic rocks in this area also once extended from the present plateau 

area to the south and west, as pointed out by McKee (1951, p. 486). 

To what degree the strata were tilted can only be estimated because 

later deformation has further changed the structure. Probably the 

dip was a few degrees.

Faults, which displace Paleozoic rocks, but not the Hickey formation of late Tertiary age, are present in the foothills on the east and 

north sides of Woodchute Mountain. One such fault, which has a 

vertical displacement of about 150 feet, occurs at the intersection of coordinates N. 1,378,000 and E. 430,000. Another minor fault is present 

at the intersection of coordinates N. 1,375,000 and E. 439,000. Other 

small faults are also present in these areas. Movement on the Bessie 

fault (1 mile east of Jerome), which is related to the pre-Hickey 

period of deformation, was recognized by Anderson and Creasey 

(1957) in the Mingus Mountain quadrangle, but has not been recognized in the Clarkdale quadrangle.

The Coyote fault in the southwest corner of the Clarkdale quadrangle, which is the major marginal fault on the west side of Woodchute and Mingus Mountains, gives evidence of at least two movements. The first is related to the pre-Hickey; the second is related 

to the post-Hickey.

Before the accumulation of the Hickey formation the west block 

along the Coyote fault was uplifted relative to the east block so that 

the Martin limestone of Devonian age was brought into juxtaposition 

with the Eedwall limestone of Mississippian age. The evidence of 

this is shown by the lava flows of the Hickey formation that rest on
570 . CONTRIBUTIONS TO GENERAL GEOLOGY

the Martin west of the fault and on the Kedwall east of the fault. 

The vertical displacement for this movement near the south boundary 

of the quadrangle is about 500 feet. Southward in the Mingus Mountain quadrangle, the initial movement on the fault had a minimum 

vertical displacement of 800 feet, as determined by Anderson and 

Creasey (1957).

The second movement along the fault was reverse to the first; the 

west block moved down relative to the east block. The Hickey formation is displaced about 250 feet vertically at the south boundary of 

the quadrangle, and the displacement decreases to a few feet just north 

of where section Z>-Z>' crosses the fault as shown on plate 45.

In the northeast quarter of the Clarkdale quadrangle the age of five 

faults can be determined with respect to the Hickey formation. Four 

of these are older than the Hickey and one is younger. The faults 

which are older than the Hickey formation and therefore belong in 

the early period of deformation include both northeastward- and 

northwestward-trending structures. Some faults in this area occur 

where the Tertiary rocks are not present, so that no clear-cut evidence 

exists to determine whether they are older or younger than the 

Tertiary rocks.

Faults, in the central part of the quadrangle near Mormon Pocket 

and 2 miles north of Perkinsville, may or may not belong to the early 

structural period because the age cannot be determined with respect to 

the Hickey formation. However, east of where the Perkinsville-Williams road leaves the north edge of the quadrangle, and north of Sand 

Flat, the northwestward-trending faults are dominant, and some do 

not displace the Hickey formation. Here, they fan out and form a 

series of step faults, where the downthrow is on the same side of the 

several subparallel faults.

In the northwest quarter of the quadrangle a northwestward-trending fault is concealed beneath the volcanic rocks of the Perkinsville

formation except for a short segment exposed in Bear Canyon. The 

stratigraphic throw on this fault in Bear Canyon is about 600 feet 

with the south side upthrown. In cross section A-A1 (pi. 46) the fault 

shows a vertical displacement of 550 feet. Similarly, a cross section 

drawn from the most southerly outcrop of the Coconino about 1,000 

feet west of the Railroad fault southwesterly into section 27 indicates 

that a fault displaces the Paleozoic rocks about 500 feet. This fault

presumably occurred in the early period of deformation because the

upthrown block was eroded level with the downthrown block before

the accumulation of the Perkinsville. The formation accumulated

soon after the late period of intense deformation so that in most places 

the formation accumulated in structural troughs and against fault 

scarps (Orchard fault).
GEOLOGY OF THE CLARKDALE QUADRANGLE, ARIZ. 571

Many faults in the northern part of the quadrangle strike N. 50° W. 

and N. 45° E., and where the dips could be measured are essentially 

vertical. The displacement ranges from 50 to 150 feet, but most commonly are about 50 feet. Well-defined joint systems, common to the 

northeastern part of the quadrangle, are similar in strike to the faults 

and are also essentially vertical. Price 8 who mapped an area of 

Sycamore Canyon about 8 miles long north of the Clarkdale quadrangle, noted that all the faults in that area also had a northeasterly 

or northwesterly trend. He stated that the northwestward-trending 

faults are most prominent, and dip at high angles between 70°-90°. 

He mentioned also that the northwesterly faults tended to produce 

grabens and were definitely older than the basalt on the plateau.

The time of the early period of deformation can only be inferred. 

McKee (1951, p. 494) stated that the first uplift, for which there is 

evidence in Arizona after the Paleozoic era, came during the Triassic 

period when the region south of the Colorado Plateau was uplifted 

to form the source for the Shinarump conglomerate of Late Triassic 

age which was deposited as a broad sheet of gravel throughout much 

of the northeastern part of the State. However, the sedimentary 

evidence, particularly in southern, southwestern, and western Arizona 

(McKee, 1951, p. 495-496), shows that, there, deformation was regional 

during Cretaceous time. Evidence cited by Babenroth and Strahler 

(1945, p. 149) indicates that the East Kaibab monocline and associated faulting in the Grand Canyon area clearly formed during Late 

Cretaceous to early Tertiary time (Laramide time). The early period 

of deformation in the Clarkdale quadrangle may have occurred at 

this time.

LATE PERIOD OF DEFORMATION

The strongest deformation in the area since the close of the Precambrian era occurred in the late period of deformation and the 

structural features are characterized chiefly by northward to slightly 

northwestward-trending normal faults. In general the only recognizable folds are very minor and gentle monoclines. However, locally 

they may be strong, where the strata did not yield to faults, at least 

above the basement rocks.

The late period of deformation resulted in block faulting and uplift. 

One block, however, relative to adjacent blocks, became the horst block 

of Woodchute and Mingus Mountains. On the north side of Woodchute Mountain, transverse faults occur between the marginal 

longitudinal faults.

Structural features occurring in this period of deformation produced the major topographic features and the present drainage system. 

This deformation also produced the basins in which the Perkinsville

8 Price, W. E., Jr., op. cit.
572 CONTRIBUTIONS TO GENERAL GEOLOGY

and Verde formations accumulated but other factors also influenced 

the accumulation of these formations.

The late period of deformation probably took place in late Tertiary 

time, and is a part of the deformation that produced the Basin and 

Range province. The deformation occurred after the accumulation 

of the Hickey formation (Pliocene?) and before the deposition of 

the Perkinsville and Verde formations (Pliocene or Pleistocene).

FAULTS

Verde fault. The Verde fault extends north-northwestward from 

Jerome, with a sinuous trace, to about a mile north of Perkinsville, 

where it ends against a transverse fault. Southward from Jerome, it 

extends southeastward along the east margin of the Black Hills, of 

which Mingus Mountain is a part. The Verde fault has the greatest 

vertical displacement of any fault in the Clarkdale quadrangle.

The dip of this fault plane differs along the strike and generally 

becomes steeper toward the north. South of Jerome, the fault has a 

dip as low as 45° E. At Jerome, the dip is about 60° E., and, about 

1 mile north, the dip is 55° E. To the north, the dip of the fault plane 

becomes steeper, and 2% miles north of Jerome, the dip is as much as 

80° E.

Just north of where coordinate N. 1,380,000 intersects the Verde 

fault, a pod-shaped block is wedged along the fault plane. South of 

this block, the Verde fault characteristically and persistently dips to 

the east, but north of it, the Verde fault dips to the west. In the 

vicinity of this pod-shaped block is a point of minimum vertical displacement along the Verde fault, which had a scissorslike movement; 

the fault both north and south of the block is the normal type. An 

alternate interpretation is that two different faults intersect, Either 

interpretation is possible, but as there is no break in the trend of the 

faulting, the Verde fault is regarded as a single structure throughout. 

The northern segment dips 60°-80° W., but most commonly Y5°-80° 

W. Small blocks (horses) of mappable size are wedged along the 

fault plane and are common of this segment.

About 21/3 miles north of the south boundary of the Clarkdale quadrangle the Verde fault splits into two branches, although it is possible 

that the split may be due to the intersection of two different faults. 

The west branch is essentially vertical where it parts from the Verde 

fault. To the northwest, along the trace of this branch, the dip of

the fault plane is 75°-80° W. This branch dies out about 4 miles 

northwest from where it parts from the Verde fault.

The stratigraphic throw on the Verde fault differs greatly along its 

length. In the vicinity of Jerome, it is about 1,500 feet; about 1% 

miles north of Jerome it is only 450 feet. Part of the difference is due
GEOLOGY OP THE CLARKDALE QUADRANGLE, ARIZ. 573

to the transverse Haynes fault which joins the Verde fault just north 

of Jerome. The Haynes fault is a northward dipping normal fault 

having a stratigraphic throw of about 750 feet, which accounts for 

much of the northward decrease in the throw on the Verde fault. The 

remainder (300 feet) must take place between Jerome and a point 1% 

miles to the north. Where coordinate N. 1,378,000 intersects the main 

branch of the Verde fault, the throw is only 150 feet. The western 

branch of the Verde fault, 2% miles north of Jerome, has a vertical 

displacement of 50-75 feet (west side down), whereas the main eastern 

branch has a vertical displacement of about 100 feet (east side down). 

This is near the hinge point of the Verde fault. North of the junction 

of the two branches in the vicinity of Bakers Pass tank, the throw on 

the Verde fault is more than 400 feet (west side down); it is about 

445 feet where the Verde River crosses the fault at coordinate N. 1,410,- 

000. Where the fault ends against a transverse fault, the vertical 

displacement is more than 400 feet.

South of the Verde River, an eastward-trending fault, which is 

younger than the Verde fault, but which formed during the same 

period of deformation, displaced the Verde fault a little more than 

100 feet laterally.

Movement also occurred on the Verde fault during the Precambrian; it has been discussed at length by Anderson and Creasey (1957) 

who stated that the maximum vertical displacement of the Precambrian movement is about 1,000 feet; the maximum total net slip, which 

includes Precambrian and later displacement, is about 3,300 feet; its 

approximate bearing and plunge are N. 85° E. and 50° E.; and the 

rake is about 66° S. These calculations are based on the assumption 

that the intersection of a small mass of Deception rhyolite defines a 

point on the Verde fault that can be recognized on both the hanging 

wall and the footwall of the Verde fault.

Reverse drag on the hanging wall of the Verde fault north of Jerome 

indicates movement during the early period of deformation. However, this is local and may be due in part to adjustment of the fault 

block during, or following, the main faulting.

Anderson and Creasey (1957) reported recurrent movement along 

the Verde fault during or after the accumulation of the Verde formation. Where the recurrent movement was recognized, the Verde fault 

plane dips 35°-45° E., and .6-12 inches of crushed gravel lies against 

a slickensided wall of Precambrian rocks. It was not possible to determine the vertical displacement because of no reference planes for 

measuring it, and because deposition and faulting may have occurred 

simultaneously.

. Fault compleso north of Hopewell. The most complexly faulted 

area in the Clarkdale quadrangle is east of the Verde fault and north
574 CONTRIBUTIONS TO GENERAL GEOLOGY

of Hopewell, where many closely spaced faults have disturbed the 

strata. Because of the mapping scale, many faults in this area are 

not shown on plate 45. All are normal faults and are parallel, to 

subparallel except a few which have sinuous traces. Most of them 

dip east, but a few dip west. Generally those that dip east have the 

greatest stratigraphic throw.

The net stratigraphic throw across this faulted area, is difficult to 

determine precisely, but the general approximation was calculated at 

several places. In each of three evenly spaced sections, drawn perpendicular to the general strike of the faults, the sum of the stratigraphic throws of the westward-dipping, normal faults was subtracted 

from the sum of the eastward-dipping faults to determine the net 

displacement. One cross section, drawn N. 65° E. through the intersection of coordinates N. 1,372,300 and E. 440,000, showed a net throw 

of about 650 feet with east side down. Another section north of the 

first and trending N. 75° E. through the intersection of coordinates 

N. 1,379,100 and E. 440,000, revealed a net throw of about 235 feet 

with the east side down. The third section, still farther north, in 

the vicinity of Bakers Pass, drawn N. 70° E. through the intersection 

of coordinates N. 1,385,500 and E. 440,000, indicated a net throw of 

about 250 feet with the west side down. The fact that to the south, 

the sum of the throws on the eastward-dipping faults is greater than 

the westward-dipping faults, and that to the north near Bakers Pass 

the reverse is true, seems significant when compared with the movement on the Verde fault in this area. Nearby is the place where the 

Verde fault plane changes in dip from east, through the vertical, to 

west. The net stratigraphic throws of the fault complex north of 

Hopewell indicate a hinge-type movement like that on the Verde 

fault down on the west, north of the hinge, and down on the east, 

south of the hinge.

Bessie fault and other small faults. A few faults in the Clarkdale

quadrangle displace the Verde formation. Largest of these is the 

Bessie fault, which is exposed in the quadrangle for 1 mile. To the 

nortk, it fceeomes obscured by the gravel fades Of the Verde formation, and to the south, it is exposed in the Mingus Mountain quadrangle for a short distance before it dies out. The Bessie fault in

the Mingus Mountain quadrangle (Anderson and Creasey, 1957)

seems to have had three periods of movement, but in the Clarkdale 

quadrangle Only tWO periods can be ascertained. During the first 

period the Redwall limestone was moved down on the east into juxtaposition with the Precambrian rocks. This displacement was about 

550 feet. The second movement was during or after the accumulation of the gravel facies of the Verde formation and displaced these 

gravels about 50 feet. The Bessie fault is essentially vertical where
GEOLOGY OF THE CLARKDALE QUADRANGLE, ARIZ. 575

U. S. Highway 89A crosses and northward it flattens until at a point 

one-half mile north of the highway it dips 55° E.

The Bessie fault and other small faults which displace the Verde 

formation are present in the vicinity of Hopewell. East of and 

parallel to the Bessie fault, and east of Jerome in Deception Gulch, 

post-Verde faulting is well exposed in the roadcut of U. S. Highway 89A.

Coyote fault. The Woodchute-Mingus Mountain block in thie 

southwest corner of the quadrangle is bounded on the west by the 

Coyote fault, which also had two periods of movement. The earlier 

movement occurred before the accumulation of the Hickey formation; the lava of this formation rests on Precambrian rocks west 

of the fault because the Paleozoic rocks had been eroded after the 

west block was uplifted during the early deformation. (See page 

569). Later movement on the Coyote fault occurred after the accumulation of the Hickey formation, and is contemporaneous with 

the major movement on the Verde fault. Displacement on these two 

faults resulted in the elevation of the Woodchute-Mingus Mountain 

block.

The Coyote fault which shows post-Hickey movement has a strike 

length of about 1 mile in the Clarkdale quadrangle. The north end 

of this fault is approximately where cross section D-D' (pi. 1) intersects the trace of the fault. North of this point the Hickey formation 

is not dislocated. Southward, the Coyote fault extends into the 

Mingus Mountain quadrangle where it is referred to by Anderson and 

Creasey (1957) as a fault zone; although it is poorly exposed as much 

as 15 miles south of the Clarkdale quadrangle, segments are recognized. The lava, which overlaps the fault, north of cross section 

D-D', doubtless is the same lava cut by the fault along the south 

boundary of the quadrangle. The vertical displacement of the Coyote 

fault can be determined from the base of the lava on both sides of the 

fault. It ranges from a knife edge where cross section D-D' intersects the fault to nearly 250 feet at the south boundary of the Clarkdale quadrangle. In the Mingus Mountain quadrangle, Anderson 

and Creasey stated that the maximum vertical displacement is about 

1,200 feet.

Orchard fault. The Orchard fault, which is several miles east of 

the Coyote fault, extends northward along coordinate E. 420,000 from 

the west flank of Woodchute Mountain to a point about 2 miles north 

of the Verde River, where it is concealed by the Perkinsville formation. It is a normal fault and dips to the west. The fault is well 

exposed, except where the gravel of the Perkinsville formation was 

deposited against and overlapped the fault scarp, and, even in these 

localities where erosion locally has removed the gravel, traces of the 

fault are revealed.
576 CONTRIBUTIONS TO GENERAL GEOLOGY

On the west flank of Woodchute Mountain, the dip of the fault 

plane ranges from 85° W. to vertical. Here, the vertical displacement is about 250 feet. From the point where the Haynes fault 

offsets the Orchard fault, northward to Perkinsville, the dip of the 

fault decreases to 70°-80° W. The vertical displacement is difficult 

to determine along the fault between these two points because the 

gravel of the Perkinsville formation conceals the Paleozoic rocks in 

the downthrown block. Therefore, only the approximate vertical 

displacement can be given; it is about 600 feet where coordinate N. 

1,400,000 intersects the fault. Just north of Perkinsville, the fault 

plane dips 60°-65° W., the lowest recorded along its trace. In this 

area, the minimum vertical displacement is probably about 250 feet, 

although it could be as much as 550 feet.

Like the Verde formation, the Perkinsville is in fault contact with 

the Paleozoic rocks in places where recurrent movements occurred 

along preexisting faults (Orchard fault). The precise displacement 

cannot be determined, but it is believed that the movement was not 

much more than 50 feet. The evidence for this minor adjustment 

includes the outcrop pattern, and faceted and minutely striated pebbles of the gravel along the fault plane. These zones of faceted 

pebbles are no more than an inch or so wide.

The Orchard fault is offset more than 500 feet laterally by the 

transverse Haynes fault, and also by a small one about % mile to the 

south. However, some faults parallel and subparallel to the Haynes 

fault are cut by the Orchard.

Haynes fault. The Haynes fault extends from the Verde fault 

at Jerome, northwestward across the north slope of Woodchute Mountain for about 4% miles, seemingly where it dies out. It is a normal 

transverse fault that dips about 70°-80° N. The relative displacement of the Haynes fault is unique, because the other transverse 

faults between the Verde and Orchard faults are downthrown on the 

south.

In the vicinity of Jerome the Haynes fault becomes compound, 

and the stratigraphic throw of this compound zone is about 750 feet. 

About 1 mile west along the fault the stratigraphic throw is about 100 

feet less. Farther to the west, but east of the Orchard fault, only 

the vertical displacement, about 500 feet, can be measured by using 

the base of the Hickey formation. This may not be significant because the base of this formation is irregular in this area. West of the

Orchard fault, the approximate vertical displacement of the base of

the Hickey formation is 150 feet.

As the vertical displacement decreases to the west along the Haynes 

fault, it is possible that there was rotation along a hinge west of the 

Orchard fault and that west of this hypothetical hinge, the Haynes 

continues as a southward-dipping fault. A fault with the south
GEOLOGY OF THE CLARKDALE QUADRANGLE, ARIZ. 577

side downthrown on the projection of the Haynes was not connected 

with the Haynes fault on the map because such connection could not 

be found in the field and because the relative movement of each is 

reversed.

Railroad fault. The Eailroad fault extends from the Verde River, 

northwestward along the west side of Packard Mesa, to the boundary 

of the Clarkdale quadrangle and beyond. At the southwest corner of 

the Packard Mesa the fault bifurcates. One branch swings eastward 

to an almost due east course and passes near the juncture of Sycamore 

Creek and the Verde River and extends beneath the Verde formation. 

The other branch continues southward across the Verde River as 

far as S 0 B Canyon, where it seemingly dies out. Of these two 

branches, the one to the east has the greater stratigraphic throw.

On the west side of Packard Mesa in the vicinity of coordinate 

N. 1,426,000, the Railroad fault bifurcates, and still farther north 

between Henderson Flat and the quadrangle boundary, the fault has 

at least four prominent branches. Only the easternmost branch is 

exposed along its full strike length, and details of the western 

branches are concealed by the Perkinsville formation.

The Railroad fault is a normal type with the west side downthrown. 

About 214 miles north of the Verde River the fault plane dips 75° W. 

From here to the north it was not possible to measure the dip because of 

poor exposures, but the relationship of the trace of the fault to the 

topography indicates steep or vertical dips to the west. At the southwest corner of Packard Mesa near coordinate N. 1,410,000 the fault 

dips 80° W. South of this point, the branch which swings to the 

east becomes slightly steeper on the curve and dips 85° SW. The 

other branch, which continues to the south, remains at a constant dip 

of80°W.

The stratigraphic throw on the Railroad and subordinate faults 

is variable; where coordinate N. 1,410,000 intersects the fault, it is 

about 800 feet. South of this point, where the branch veers to the 

east it is 600 feet. On the branch that continues to the south it is about 

150 feet. To the north where coordinate N". 1,426,000 intersects the 

fault, a branch trends westward. The throw on the east branch is 

about 250 feet, and on the west branch it is about 500 feet. The 

total throw on both branches is essentially the same as it is to the 

south, where there was a single plane of movement. Northwest of 

Henderson Flat, where cross section A-A' (pi. 45) intersects the 

fault zone, the fault has four branches, three of which are downthrown on the west, and the westernmost branch is downthrown on 

the east. The net stratigraphic throw across this group of faults is 

the west side down about 450 feet. This figure was obtained by subtracting the stratigraphic throw of the westernmost upthrown block 

from the total throw of the downthrown blocks of the three eastern
578 . CONTRIBUTIONS TO GENERAL GEOLOGY

branches. The data show that the Kailroad fault decreased in throw 

about 350 feet to the north as it approached the Colorado Plateau.

Other faults. Other faults of the late deformation that merit consideration are for the most part along the west margin of the quadrangle.

The many faults between Black Mesa and coordinate N. 1,380,000 

are all the normal type. These faults trend about the same as the 

others in the quadrangle. Only three have continuity along the 

strike and have a stratigraphic throw of 150 feet or greater. One 

trends east-northeastward along the Chino-Perkinsville road, south 

of coordinate N. 1,390,000. This fault is downthrown on the south 

and has a stratigraphich throw of about 300 feet. It displaces another 

moderately large fault that trends northwestward near the quadrangle boundary. The latter fault splits into two branches where it 

curves sharply to the west. The blocks form a steplike arrangement 

across these branches and are successively downthrown to the northwest. The only other large fault in this area is the eastward-trending 

fault at the south end of Black Mesa, which dips 80° S. and has a stratigraphic throw of about 400 feet. This fault is probably the extension 

of the eastward-trending fault, south of the Verde Kiver in the central 

part of the quadrangle, but this interpretation cannot be proved, 

because of cover by the Perkinsville formation.

FOLDS

A few folds in the Clarkdale quadrangle consist of local steepening 

of the dip and indicate drag in areas of strong faulting. Minor 

undulations or gentle warps are present in places. Nearly everywhere, except in the vicinity of the plateau, the pre-Perkinsville and 

pre-Verde strata have a homoclinal dip to the northeast, and probably 

average between 6° and 10°. These strata were tilted, in part, during 

the early period of deformation; but most of the tilting resulted from 

the late period of deformation, as shown by the fact that the Hickey

formation dips to the northeast also. Furthermore, restoration of 

fault blocks to their position in pre-Hickey time will not produce 

an acceptable reconstruction of the geologic conditions that existed 

at the time of deposition of this formation. Some warping and 

tilting must have taken place during the late period of deformation. 

The most pronounced fold in the quadrangle is a monocline, which 

is along the Verde River, about 1 mile south of its junction with 

Sycamore Creek (coordinates N. 1,400,000; E. 453,000). Here, the 

beds of the Supai formation strike about N. 10° E. and dip as much 

as 60° E. The lava which flowed down Sycamore Canyon rests against 

the flank of this fold. Overlapping both the lava and the Supai 

formation are lakebeds of the Verde formation with a normal depositional contact. As a result of sagging and compaction during or
GEOLOGY OF THE CLARKDALE QUADRANGLE, ARIZ. 579

shortly after their deposition on the steep hill slope of the Supai 

formation, the lakebeds dip about 15° E. away from the steeply inclined beds of the Supai. Jenkins (1923, p. 70) reported this structure 

in his report on the lakebeds which he named the Verde formation 

and concluded that the lava and the lakebeds were faulted against the 

Supai. Later Mahard (1949, p. 122) visited this locality and reported 

that the lakebeds and lava flows of the Verde are not in fault relationship with the Supai formation. The Verde formation doubtless rests 

on the Supai with a normal depositional contact.

This monocline extends to the south beneath the Verde formation 

and is exposed again in S 0 B Canyon where lava of the Hickey 

formation, which rests on the Supai, is also involved in the flexure. 

The lava of the Hickey dips steeply to the east there. Mahard (1949) 

believed that these lava deposits were part of a post-Hickey flow which 

flowed down SOB Canyon before the deposition of the Verde formation. However, the lava flows were tilted by folding (pre-Verde 

flexure) and are not initial flow attitudes.

PHYSIOGRAPHY

Most of the present topographic features have resulted from the 

latest period of deformation, and subsequent erosion has carved the 

faulted and tilted bedrock to form the present surface. The dominant 

physiographic features in the quadrangle include Woodchute Mountain, which is the northern part of a fault block; the Colorado Plateau, 

which is bounded on the south by a precipitous cliff (Mogollon Rim), 

that overlooks the lowland to the south; eroded fault scarps and small 

cuestalike ridges between Woodchute Mountain and the plateau; and 

pediments on the flanks of Woodchute and Black Mountains.

The drainage of the quadrangle is external. Although the drainage 

of the main part of the plateau north of the quadrangle is northward, 

many youthful streams have eroded deep through its margin (Mogollon Rim) and drain south in the quadrangle.

WoodcJiute Mountain. Woodchute Mountain along the south-central part of the quadrangle is the north end of a short mountain range 

called the Black Hills an elongated fault block about 20 miles long 

and 6 to 12 miles wide. The Black Hills are bound on the west by the 

Coyote fault and on the east by the Verde fault.

The eastern profile of Woodchute Mountain is broken by a pronounced escarpment caused by the Verde fault. It separates the higher 

and much steeper cliffs of Woodchute Mountain from the lower long, 

smooth, rounded fingerlike ridges that extend out to form the foothills. The fault scarp is thoroughly dissected so that the only topographic expression of its position is an abrupt change in slope. At 

present the valley of the Verde River is being exhumed so that most
580 . CONTRIBUTIONS TO GENERAL GEOLOGY

of the long, uniformly sloping foothills are composed of coarse gravel 

of the Verde formation.

Woodchute Mountain is steep and dissected on the north and west. 

The north side has long irregularly trending and sloping spurs 

separated by youthful canyons, the courses of which are influenced 

by the structure.

The summit of Woodchute Mountain is relatively flat and mesalike. 

It is controlled largely by the flat attitude of the lava flows that cap it. 

Woodchute Mountain is at an altitude of 7,834 feet which is about the 

same altitude as Mingus Mountain to the south.

The valley of the Verde Biver bounds Woodchute Mountain on the 

east and the relief between the two is about 4,500 feet. Lonesome 

Valley bounds the mountain on the west, and the relief between the 

center of the valley and the top of the mountain is about 3,000 feet.

Colorado Plateau. The dominant physiographic feature in the 

northern part of the quadrangle is the south edge of the Colorado 

Plateau. Here, the Mogollon Rim, the precipitous cliff that marks the 

south edge of the plateau, rises abruptly from the valley of the Verde 

River. Many steep-sided, narrow canyons of which Lonesome Pocket 

and Sycamore Canyon are examples have been carved into the plateau 

and along its borders. Dissection has resulted in isolating some areas 

from the main plateau mass to form flat-topped buttes and mesas. 

Black Mountain is an example.

The plateau is more than 6,400 feet in altitude and has a relief of 

about 1,800 feet. The resistant sandstone of the upper member of the 

Supai formation and the monolithic Coconino sandstone comprise 

two-thirds of the height of the escarpment. The other third is cliffforming units of Kaibab limestone and basalt flows. About 150 feet 

of the Toroweap formation forms a slope.

Area between Woodchute Mountain and Colorado Plateau. The 

surface of the area between the Colorado Plateau and Woodchute 

Mountain, although dissected, is gently inclined toward the Verde 

River on each side. The altitude of this surface ranges from about 

5,000 at the base of the higher land masses to about 4,300 feet near 

the Verde River. Many eroded fault scarps interrupt this area of 

low relief and add a general cuestalike appearance to the topography. 

Also, resistant units in the Supai formation, and differential weathering between the base of the Supai and the underlying Redvrall limeStone, add to this cuestalike appearance.

In the area of the Perkinsville formation, lava and gravel have 

covered earlier irregular topography and reduced the relief to a 

relatively even surface. Gravel fanned out towards the Verde River 

from the Woodchute Mountain block and from the plateau scarp, 

during its formation, and filled in structural troughs and depressions.
GEOLOGY OF THE CLARKDALE QUADRANGLE, ARIZ. 581

The lava flowed over the Mogollon Rim into the valley of the Verde 

River, covering lower gravel,, and these lava flows in turn were covered by more gravel.

Pediments. Pediments, which form relatively smooth slopes, are 

limited to the bases of certain parts of Woodchute and Black Mountains. In the valley of the Verde River a low level pediment surface 

was carved on the Verde formation in the vicinity of Clarkdale and 

south beyond the Clarkdale quadrangle boundary. Part of a pediment surface which was cut on both the Verde and the Supai formations extends from the southeast side of Black Mountain beyond the 

limits of this quadrangle. The pediment surfaces dip only a few 

degrees and are mantled with a veneer of gravel. Planed bedrock 

surfaces below the gravel veneer are clearly exposed in the valley of 

the Verde River. The pediments have been trenched subsequent to 

their formation by a dendritic arrangement of gulches and arroyos 

and the flat-topped interstream remnants are covered with a veneer of 

red gravel which ranges in thickness from a few inches to perhaps 30 

feet. The depth of dissection increases progressively toward the 

master streams.

In the southwest corner of the Clarkdale quadrangle on the west 

side of Woodchute Mountain is part of the vast surficial deposit of 

gravel which extends far to the west in Lonesome Valley and forms 

a veneer on a pediment surface.

Drainage. The drainage of the Clarkdale quadrangle is dendritic. 

The master through-flowing stream is the Verde River which enters 

the west-central part of the quadrangle and follows a meandering 

course southeastward. The chief tributary of the Verde River in the 

quadrangle is Sycamore Creek. All the drainage lines in the quadrangle extend to the Verde River, except for some in the southwest 

corner of the quadrangle that reach the Verde River by a circuitous 

route through Granite Creek in the Prescott and Paulden quadrangles.

The Verde River is perennial and locally braided. Sycamore Creek 

is perennial below Summers Spring, 4 miles above its mouth. All 

other streams in the quadrangle are ephemeral, and flow only when 

water is supplied by local storms. At such times the flow rarely 

lasts for more than a few hours at any one locality.

GEOLOGIC HISTORY

The geologic history of the Clarkdale quadrangle is moderately clear 

from the present back to the time when a prolonged interval of erosion 

had reduced to flatness the surface of the Precambrian rocks. Upon 

the surface which was cut across the structural planes of the Precambrian rocks, sediments apparently accumulated from nearby Pre-
582 CONTRIBUTIONS TO GENERAL GEOLOGY

cambrian hills during early Paleozoic time and filled in the lower parts 

of the surface. These sediments, which are poorly sorted and .variable 

in composition, indicate a mixture of detrital fragments which had 

little transportation. They probably represent, to a large extent, 

regolith reworked by the wave action of an advancing sea of Cambrian (?) age which spread over the area from the north and 

northwest.

If it is assumed that the basal Paleozoic rocks are the Tapeats sandstone of Cambrian age, then this area of deposition represents the 

southeast margin of the shelf that bordered the Cordilleran geosyncline. The seas which at the beginning of Cambrian time covered only 

the extreme western part of Arizona, transgressed southeastward as 

the basin was depressed. The transgression of the sea seemingly extended farthest south into the Jerome area during deposition of the 

Tapeats sandstone (?) as shown in the eastern part of the Grand 

Canyon. Whether the Bright Angel shale and the Mauv limestone of 

Cambrian age were ever deposited in the Jerome area is not known, 

although both are present about 47 miles west-northwest of Jerome 

near Walnut Creek Ranger Station in the Camp Wood quadrangle. 

After regression of the Cambrian sea, the Jerome area was a site 

either of erosion or of nondeposition, because there is no record of 

Ordovician nor Silurian deposits in central Arizona. Although the 

relationship between the Tapeats sandstone (?) and the overlying 

Martin limestone of Devonian age appears to be gradational in the 

Clarkdale quadrangle, Krieger 9 has found a possible unconformity 

between the Tapeats(?) and the Martin limestone, which suggests, 

perhaps, the hiatus or unrepresented interval of time.

The Martin limestone was deposited in a Late Devonian sea which, in 

a general way, followed the trend of the Cambrian(?) transgression 

from the northwest. The first deposition of the Martin must have 

been in waters agitated by currents, because the basal unit is a clastic, 

crossbedded limestone. The Devonian sea deposited this basal unit 

concordantly on the Cambrian(?) sandstone. Although the bulk of 

the Martin is dolomitic limestone, the abundance and distribution of 

sand and clay impurities clearly indicate that a SOUTC6 of terriginous 

material was present throughout the accumulation of the formation. 

Local beds of limy sandstone accumulated where, for a time, detrital 

impurities predominated. Coral reefs in the upper part of the Martin 

indicate that locally, at least, the sea was relatively shallow.

When the area was later inundated by the early Mississippian sea, 

which encroached from the north and northwest, the uppermost strata 

of the Martin were reworked and redistributed to form thin, wavy, 

conglomeratic beds of sand. As the sea advanced, the bluish-gray

1 Krieger, M. H., op. cit.
GEOLOGY OF THE CLARKDALE QUADRANGLE, ARIZ. 583

oolitic limestone of the lower member of the Redwall limestone was 

deposited in it. As deposition continued beds of light-gray crinoidal 

limestone were laid down. After deposition of the crinoidal limestone, 

more calcareous oolites were laid down. Toward the close of early 

Mississippian time, the sea withdrew from the area toward the geosyncline to the northwest. Erosion of Redwall limestone surface followed 

retreat of the sea, and an irregular surface with a relief of 30 feet or 

so was carved.

The Clarkdale area, in what probably was late Pennsylvanian time, 

seemingly was a mud flat, marginal to a marine basin, the waters of 

which had transgressed from the northwest to connect with marine 

waters from the southeast. In the low areas, on the eroded surface of 

the Redwall, limestone conglomerate and chert breccia collected. A 

few thin beds of limestone in the lower part of the redbeds of the 

Supai formation may represent extended tongues of deposits formed in 

these seas.

Permian deposition was a continuation of the Pennsylvanian, as 

shown by the redbeds of the Supai which accumulated to a great 

thickness. These sediments, perhaps in part, represent a mud flat 

environment marginal to a marine basin, and in part, deltaic deposits 

brought in by a drainage system from the north. The upper part 

of the Supai interfingers with the overlying Coconino sandstone. 

Because there is a vertical alternation between these two formations, 

it is assumed that sedimentation was continuous throughout much 

of the area, during the changes from environments of deposition of 

Supai time to those of the Coconino time.

Deposition of the sand of the Coconino began at the close of Supai 

sedimentation when the red silts and sands were covered by eolian 

sand transported into the area from the north. The sand was deposited as large dunes, and the area became a desert, which stretched 

far to the north and probably to the south. Thus, the climatic changes 

from the time of deposition of the Supai to that of the Coconino was 

perhaps one of gradual change toward aridity.

An encroachment from the northwest of the sea, in which sediments 

were deposited during Toroweap time, caused the termination of 

Coconino deposition. This is indicated by the remarkably level contact, where the uppermost beds of the Coconino were beveled and the 

sands reworked while still unconsolidated, for there is no surface 

of relief at the top of the Coconino sandstone. The lithology of the 

Toroweap indicates a shallow oscillating sea. The arid to semiarid 

climate represented by the Coconino persisted throughout Toroweap 

time. The average grain size of the sediments in the Clarkdale 

quadrangle is fine, and it is assumed that the surrounding topography 

was flat and featureless. The Toroweap sea regressed to the northwest
584 CONTRIBUTIONS TO GENERAL GEOLOGY

after the Toroweap had been deposited. During the hiatus that followed channels were eroded locally but no great time elapsed as indicated by the minor amount of erosion accomplished and by faunal 

evidence from the Toroweap and the overlying Kaibab limestone.

Following this brief erosion period, the Kaibab sea spread into the 

Clarkdale quadrangle and deposited the Kaibab limestone. In the 

quadrangle, these sediments, in general, consist of alternate layers that 

range from sandy limestone to limy sandstone, but westward they 

grade into beds of limestone, and eastward into pure sandstone of the 

shore facies.

From the end of Kaibab deposition in middle Permian time, when 

the sea withdrew toward the west, there is no evidence of sedimentary 

deposition in the Clarkdale quadrangle until Late Tertiary time. 

However, the presence of Lower Triassic rocks to the north allows 

reasonable inference to be made concerning the gap in the geologic 

history of the area. The Moenkopi formation of Early Triassic age 

rests unconformably on the Kaibab limestone in Sycamore Canyon, 

about 2 or 3 miles northeast of the quadrangle. The time represented 

by the unconformity was sufficiently long to allow the consolidation of 

sediments deposited during Kaibab time which are represented in the 

Triassic conglomerate beds and, as indicated by fossils, was equal 

to the duration between middle Permian (Guadalupian) and early 

part of Early Triassic (pre-Meekoceras). The Moenkopi is a continental red bed deposit in the Sycamore Canyon area, which was 

formed on a vast flood plain covered with streams, lake basins, and 

playas. According to McKee (1938) the Moenkopi occupies a low, 

flat area that bordered an Early Triassic seaway on the northwest. 

Because there is an average thickness of 250 feet of these sediments in 

Sycamore Canyon, the top being erosional, they most likely once 

extended farther south and covered the Clarkdale quadrangle. It is 

probable that the Shinarump conglomerate and Chinle formation of 

Triassic age extended throughout the Clarkdale area too.

If the clastic sediments of the Shinarump conglomerate and Chinle 

formation were ever deposited over the Clarkdale quadrangle, it is

then iiecesaary to postulate that'a region somewhere to tile SOllth and

southwest was uplifted (Late Triassic uplift) before or during that 

time of deposition to provide the source material. 

Assuming that the Shinarump and Chinle were deposited in the

area, it can be inferred that an uplift perhaps in Cretaceous or early 

Tertiary time then followed, because the strata were tilted, faulted,

and eroded before deposition of the Hickey (Pliocene !). McKee

(1951, p. 495^96) has pointed out the evidence for uplift during 

Cretaceous time and Babenroth and Strahler (1945) have shown that 

the Kaibab monoclinal flexure occurred during early Tertiary time.
GEOLOGY OF THE CLARKDALE QUADRANGLE, ARIZ. 585

There is no evidence in the quadrangle that can be used for dating 

the. crustal disturbances which occurred between the Moenkopi and 

Hickey times of deposition. The disturbance could be Late Triassic, 

Early Cretaceous, or early Tertiary, or.a combination of these times.

Gently dipping sedimentary rocks were truncated by erosion so 

that the oldest Paleozoic rocks were exposed to the southwest and 

progressively younger strata exposed to the northeast. Upon this 

surface the drainage during Pliocene(?) time cut deep channels 

leading northward. The stream gravel which accumulated in these 

channels forms part of the Hickey formation, and reflects a source 

in the direction of Prescott. Some of these gravel beds were carried 

in their channels far northward in the area that is now the Colorado 

Plateau. At the same time volcanism in the form of widespread eruptions of basalt and, locally, of andesite, occurred mostly from local 

vents or fissures. The basalt, in the Hickey formation, overlapped 

successively younger rocks ranging in age from Precambrian in the 

southwestern part of the Clarkdale quadrangle, to Permian in the 

northeastern part of the quadrangle. An extremely thick sequence 

of flows on Woodchute Mountain indicates that it was a site of extrusion, probably fissure eruptions. Vents of Bill Williams Mountain 

at Williams, Ariz., of the San Francisco Mountain at Flagstaff, and 

others, likewise contributed lava flows that accumulated in the plateau 

part of the Clarkdale quadrangle.

After the accumulation ofHhe Hickey formation the area of the 

Clarkdale quadrangle was subjected to a period of strong deformation 

which tilted and block-faulted the rocks. These structural features 

are referred to as the late period of deformation in the quadrangle 

and occurred probably during late Tertiary time. During this crustal 

disturbance, the Woodchute-Mingus Mountain block was elevated 

along boundary faults; most of the normal faults which extend north 

and northwest across the area were formed; and the plateau was uplifted relative to the Basin and Range province to the south and 

southwest. It was from this time of deformation that the present 

southward flowing drainage originated.

This late period of deformation in the Clarkdale area initiated a 

vigorous cycle of erosion. Much of the Hickey formation was eroded, 

and the escarpment of the plateau was carved. While erosion was cutting away the land, a brief and localized spurt of volcanism took 

place. Basalt, intermediate in age between Hickey and Perkinsville 

or Verde rock, was extruded on the west side of Black Mountain. 

This basalt rests on the middle and upper members of the Supai 

formation, whereas basalt flows of the Hickey formation rest on 

Coconino sandstone. This difference in age is a means of determining 

the amount of erosion that took place between the Hickey time of
586 CONTRIBUTIONS TO GENERAL GEOLOGY

eruptions and that-of the intermediate basalt. Furthermore, the 

intermediate basalt is present on both sides of the present Sycamore 

Canyon, which indicates that the floor of Sycamore Canyon was not 

appreciably lower than the base of the lava at the time that they 

were extruded.

As erosion progressed during what probably was Pliocene or Pleistocene time, gravel deposits of the Verde formation started to accumulate 

along the east side of the horst block of the Woodchute and Mingus 

Mountains, and at the same time gravel of the Perkinsville formation 

was accumulating between Woodchute Mountain and the plateau to 

the north. While this deposition was taking place, Sycamore Creek 

was actively cutting its canyon. During this episode, volcanic activity 

was renewed. Lava flowed across and dammed the south end of the 

valley of the Verde River. This barrier impounded a lake in which 

the lakebeds of the Verde were deposited. Lava also flowed off the 

plateau in the northern part of the Clarkdale quadrangle and spread 

as a thin sheet over the lower gravel of the Perkinsville, and some 

lava flowed down Sycamore Canyon. Gravel continued to accumulate 

along the east side of the horst block of the Woodchute and Mingus 

Mountains, and interfingered with the lakebeds; whereas between 

Woodchute Mountain and the plateau, the gravel of the Perkinsville 

continued to accumulate.

After the deposition of the Verde and Perkinsville formations, the 

lava barrier at the south end of the valley of the Verde River presumably was breached, lowering the base level of the drainage. This 

rejuvenated the streams and caused the meanders of the Verde River to 

be incised and superposed upon the underlying structure. Accelerated 

stream erosion, also caused deposits of the Verde formation in Sycamore Canyon to be removed.

Some time after, or during the accumulation of the Perkinsville and 

Verde formations, there was a minor recurrent movement along some

of the faults which displaced strata of these formations.

Changes in base level have resulted in the formation of pediment

surfaces at different levels in the valley of the Verde Kiver, and terraces have been formed along the Verde Kiver. Although the drainage which traverses the Clarkdale area contains wash material, there

is no extensive deposition at the present time.

MINERAJL RESOURCES 

The mineral resources of the Clarkdale quadrangle include copper

and some associated gold and silver, building stone, and limestone,

Although all these, except the limestone, have been produced commercially, the only product of considerable value has been the copper.
GEOLOGY OF THE CLARKDALE QUADRANGLE, ARIZ. 587

The copper deposits are all in the southern part of the quadrangle 

and center around Jerome; they are chiefly of two types: massive sulfide 

replacement bodies of Precambrian age, and Tertiary lava and gravel 

which have been impregnated with supergene chrysocolla. The 

massive sulfide deposits consist of an aggregate of sulfide minerals, 

such as pyrite, chalcopyrite, sphalerite, and galena; gangue minerals 

are scarce or absent. The ore deposits of the Jerome area have been 

studied recently in great detail by Anderson and Creasey (1957).

The Red wall, which is a relatively pure limestone, has been exploited 

as a source of lime in a few places. It was quarried from small pits, 

and presumably used as a flux. Locally some limestone has been 

quarried for road aggregate and railroad ballast.

Sandstone is the only resource that is being actively exploited at 

present in the quadrangle. Many small quarry sites dot the landscape in the northern part of the quadrangle, near the Mogollon Rim 

where the sandstone of the upper member of the Supai and the Coconino crops out. Probably the greatest quarrying activity in the 

quadrangle is near Sand Flat east of the Perkinsville-Williams road 

in Coconino County, where the Coconino sandstone is quarried. Red 

sandstone of the upper member of the Supai is quarried between 

Black Hills tank and Rafael tank, north of coordinate N. 1, 430,000 

and east of Perkinsville-Williams road. A number of quarries are in 

the northwest corner of the quadrangle, near where coordinate E. 

410,000 intersects the Yavapai-Coconino County line. Here an inlier 

of Coconino sandstone and Supai formation crops out, and both formations are quarried.

The sandstone beds of the upper member of the Supai and of the 

Coconino are strongly crossbedded on a large scale and split readily 

along the crossbedding planes, so that large flat, smooth sheets and 

slabs of sandstone can be obtained with little effort. These beds 

range in thickness from 1 to 8 inches or more and have uniform texture. Sand grains range from medium to fine grained. Different 

types of cement or bond of the grains produces a number of colors. 

Although the Coconino sandstone is buff, in general, it locally ranges 

between grayish orange and grayish yellow because of slight differences in the proportion of its iron oxide and (or) siliceous bond. 

Likewise, the generally reddish orange of the Supai has a cement of 

calcium carbonate and a matrix of clay, which differs in proportion, 

so that in some places the rocks are pale red, and in others are lavender 

or moderate red.

Most of the quarry sites are located where individual crossbeds are 

thin and easy to split, because thin flagstone commands a higher 

market price than thick blocks. In quarrying, an operator may have 

to cut through a thick bed to find thin-bedded rock, but, generally
588 CONTRIBUTIONS TO - GENERAL GEOLOGY

he selects a site where the rock is chiefly thin bedded, usually in 1- to 

3-inch beds. Subordinate to the thin bedded and easy splitting qualities of the rock, the location of the quarry is next governed by the 

color of the rock. The most popular colors are red, lavender, and 

yellow. Buff to grayish-orange rock is very commonplace and not 

in great demand.

The sandstone quarries are open pits, of which many are worked 

into a hillside. The overburden or waste is cleared away by hand, or, 

in a few places, by bulldozers. Some drilling and blasting are done: 

a row of holes is drilled 6-8 feet back from the face, and blasting 

charges are put in the holes; but this method is wasteful. For lifting 

or splitting the beds, wedges usually are driven into notches.

The stone is quarried chiefly for flagstone which may be as much as 

2 inches thick with a minimum of 18 inches on a side. Most of the 

flagstone is in slabs about 4-6 feet square. Stone that is more than 

2 inches thick is quarried for building purposes. At the quarries the 

stone is neither cut nor prepared in any way for the market. It is 

sold in the dimension that it was quarried, the size only determining 

whether it is flagstone or "cutting stone." Flagstone is used chiefly 

for exterior steps, sidewalks, and platforms. The large-dimension 

stones are cut by stone dealers into strips 2-4 inches thick and about 

31/2 inches wide, for use as exterior decoration or veneers by the building industry, and the very large pieces are cut into building blocks.

The production of stone in the Clarkdale quadrangle is estimated 

at 50-100 tons per month, but at times operations halt during the 

winter. Individual producers commonly quarry out a truckload and 

sell it at Drake, Ariz., where there is a cutting machine and loading 

dock. The stone is shipped from there to the West Coast. At the 

quarry, flagstone sells at $12 per ton, and cutting stone at about $6-$8 

per ton. The largest producing.quarries are.northwest of the darkdale quadrangle from where the sandstone is shipped to Ashfork.

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GEOLOGY OF THE CLARKDALE QUADRANGLE, ARIZ. 589

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590 CONTRIBUTIONS TO GENERAL GEOLOGY

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White, David, 1929, The flora of the Hermit shale: Carnegie Inst. Washington

Pub. 405. 

Williams, Howel, 1936, Pliocene volcanos of the Navajo-Hopi

Soc. America Bull,, v. 47, p. 111-172.
INDEX

Page

Accessibility... 513-515

Acknowledgments._____________.. 513 

Alluvial river terraces__.________.. 567

Basalt, Intermediate, age._________... 557

Intermediate, distribution..._______ 566

geologic history___..______... 585

lithology..- . 556-557

thickness.-._..___.. .. 556 

Bessie fault................................. 574-575

Bibliography..... ...... . . 588r590

Cenozolc rocks, general___________ 548-549 

Climate....................................... 517

Goconlno sandstone, age...___ . 542-543 

correlation._._____________.. 542-543 

distribution............................... 540

geologic history.. ... 583 

llthology............................._ 541-642

stratlgraphlc relationship____... . 641 

thickness.....-..-...............-.. ... . 541

Colorado Plateau....-.-.......- ........-.. 580

Copper deposits........ . .: 587

Coyote fault..__.______1______ 676 

Culture.....___._____________ 613-515

Deception rhyollte.._____________ 519 

Deformation, early period.......______ 669-571

late period..... __._____... 571-579

Drainage....... ... 581

Fault, Bessie.................... ...___ 574-575

complex north of Hopewell_____... 573-574 

Coyote...._..______________ 576

Haynes.............__............_. 676-577

Orchard......__..................... 575-576

Railroad....________________ 577-578

unnamed_________________ 578 

Verde............_..............._.. 572-573

Folds... ..................................... 578-579

Qabbro....................................... 519

Geologic history........____.______ 581-586

Grapevine Gulch formation._________ 519 

Gravel. See Quaternary gravel.

Haynes fault......___________._ 576-577

Hlckey formation, age___________ 654-556 

correlation._,._____________ 554-556 

distribution......____________ 549-550

geologic history.._____________ 585 

lithology, sedimentary rocks______ 550-552 

volcanic rocks____________ 552-554 

stratigraphic relationship___.. __ . 660 

thickness.__.______________ 550

rage 

Intrusive rocks .__ . 519

Jenkins, 0. P., quoted __ _ ... 560

Kaibab limestone, age, . M& 

correlation______... _ 648 

distribution............... ....... 64ft

geologic history. 684 

lithology--. . 647-64*

stratigraphic relationship.. _ .... 646-547

'thickness............. _......... 646

Limestone quarries_________ ...... 587

Location of area_______..._ . 513-515

Mahard, R. H., quoted....... 680

Martin limestone, age.. ______ ...... 528

correlation..______ _ ... 528 

distribution............................ 523-524

geologic history_ . 582

lithology, general____ . . 524-526

unit^4................................ 525

unit B ...................... 525-526

unit C1.............................. 526-627

unit D.............................. 527-528

stratigraphic relationship. .. 524

thickness__________._ ... 624

McKee, E. D., quoted_-__ _ 668

Mineral resources....__.._ 586-588

Moenkopi formation_._______ ___- 584

Orchard fault. _. -. 575-575 

Ore deposits._________ .. ... 687

Paleozoic rocks, general.. .. 620

Pediments. ..__ _ 681

Perkinsville formation, age_ __ .. 665-666

correlation....___..._ 665-566

distribution.., . 663

geologic history.._ _ 686

lithology, sedimentary rocks..__.__ 563-564

volcanic rocks.. ___ _ 564-565

stratigraphic relationship. ... 563

thickness_._.___.____.___ 663

Physical features._______..__....... 515-517

Physiography, area between Woodchute

Mountain and Colorado Plateau... 580-681

Colorado Plateau..__.____..___ 580

pediments_.______ . _. 581

Woodchute Mountain.____.____ 679-680

Precambrianrocks...____ __ .. 519-520

Precipitation... _.... 617-518

Previous work.________..__ _ 612-613

Quartz porphyry_______.__ __ 519

591
592 INDEX

Quaternary gravel, distribution.. ------- 566

lithology..-- _._ 566-567

stratigraphic relationship. __ -....--.... 566

thickness..-..-.---.--__. __ ...._ 566

Railroad fault.... ............. ...... 577-578

Redwall limestone, age. ______.___ 532-533 

correlation-________________ 532-533 

distribution..._..._______.-.._ 528-529 

geologic history________ .. 583 

lithology. general_______... .... 530-531

unit 1...-.-.-.-._._____...... 531

unit 2..-.... 531-532

unit 3--.. .. 532

unit 4-...-. .. 532

stratigraphic relationship.... . 529-530

thickness__.._...__._.. 529-530 

Riverwash....__________ . 567

Sandstone quarries. _____________ 587-588 

Spud Mountain volcanics. - _________ 519 

Supai formation, age...._____ . 538-540

correlation ._______________ 538-540 

distribution......_____.____..__ 533

geologic history _____________ _ 583

lithology, general_____________ 534

lower member. _ ___.. ____ 535-536

middle member....________ 536-537

upper member_._________ 537-538 

stratigraphic relationship__ __.. 533-534 

thickness............................... 533-534

Page 

Tapeats sandstone, age._....._...____ 523

correlation________________ 523 

distribution.... . .- . 520-521

geologic history..______.__.____ 582 

lithology.-...-........... 522

stratigraphic relationship_________ 521

thickness__________________ 521

Temperature.._______________ 517

Terraces..___________________ 567

Toroweap formation, age... -... 545

correlation.__________________ 545

distribution....____.. .---.-._ 543

geologic history...._... .. ,. 583-584

lithology.... .......... ...... 544-545

stratigraphic relationship . 543-544 

thickness...................-...... . 543-544

Unconformities._______________ 519,548

Vegetation.---.. ......... ...... 518-519

Verde fault ......__....-.--.---._ 572-573

Verde formation, age...__................ 561-563

correlation.... ....................... 561-563

distribution-.---........_....-...--.. 557-558

geologic history.______________ 586

lithology, fine-grained-carbonate facies__ 560

general.-...-..___.-.-.-..-.._ 559-560

gravel fades.._____. ..._._.. 560-561

volcanic rocks..____..-.-____ 561

' stratigraphic relationship________ 558-559

thickness........___..__.......... 558-559

Woodchute Mountain.___________ 579-580

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