2008

U.S. Department of the Interior

U.S. Geological Survey

Prepared in cooperation with the National Park Service, U.S. Forest Service, and Bureau of 

Land Management

Geologic Map of the Fredonia 30 ́ x 60 ́ Quadrangle,

Mohave and Coconino Counties, Northern Arizona

By George H. Billingsley, Susan S. Priest, and Tracey J. Felger

Pamphlet to accompany

Scientific Investigations Map 3035

View looking south into Kanab Canyon from Gunsight Point, showing lower Permian strata from Esplanade 

Sandstone to Kaibab Formation at the rim. Photograph by George H. Billingsley.

1

Introduction

This geologic map is the result of a cooperative effort of 

the U.S. Geological Survey, the National Park Service, the U.S. 

Forest Service, and the Bureau of Land Management (BLM) 

and the Kaibab-Paiute Tribe to provide a regional geologic 

database for resource management officials of all government and agencies, city municipalities, private enterprises, and 

individuals of this part of the Arizona Strip. The Arizona Strip 

is part of northwestern Arizona north of the Colorado River 

and bounded by the States of Nevada and Utah. Field work 

on the Kaibab-Paiute Indian Reservation was conducted from 

2002 to 2005 with permission from the Kaibab-Paiute Tribal 

Government of that administration and permission was granted 

to publish a geologic map of 4 quadrangles online (Billingsley 

and others, 2004). The Kaibab-Paiute Tribal government of 

2006 to 2008 requested that all geologic information within 

the Kaibab-Paiute Indian Reservation not be published as 

part of the Fredonia 30 ́ x 60 ́ quadrangle (this publication). 

For further information, contact the Kaibab-Paiute Tribal government at HC 65 Box 2, Fredonia, Arizona, 86022, telephone 

# (928) 643-7245. Visitors to the Kaibab-Paiute Indian Reservation are required to obtain a permit and permission for access 

from the Tribal Offices at the junction of State Highway 389 

and the paved road leading to Pipe Spring National Monument.

The Fredonia 30 ́ x 60 ́ quadrangle encompasses approximately 5,018 km2 (1,960 mi2) within Mohave and Coconino 

Counties, northern Arizona and is bounded by longitude 112° to 

113° W., and latitude 36°30 ́ to 37° N. The map area lies within 

the southern Colorado Plateaus geologic province (herein Colorado Plateau). The map area is locally subdivided into seven 

physiographic parts: the Grand Canyon (Kanab Canyon and its 

tributaries), Kanab Plateau, Uinkaret Plateau, Kaibab Plateau, 

Paria Plateau, House Rock Valley, and Moccasin Mountains 

as defined by Billingsley and others, 1997, (fig. 1). Elevations 

range from 2,737 m (8,980 ft) just west of State Highway 67 on 

the Kaibab Plateau, southeast corner of the map area to about 

927 m (3,040 ft) in Kanab Canyon, south-central edge of the 

map area.

Figure 1. Index map of the Fredonia 30 ́ x 60 ́ quadrangle, Arizona showing the physiographic, cultural, 

and geologic locations mentioned in the text.
2

The Vermilion Cliffs are a prominent, 457-m (1,500-ft) 

high feature in the northern part of the map area that mark the 

southern, western, and eastern edges of the Moccasin Mountains, and the western edge of the Paria Plateau. The north edge 

of the map area is the Utah/Arizona State line. Settlements 

within the Fredonia 30 ́ x 60 ́ quadrangle include Colorado City, 

Fredonia, Moccasin, Kaibab, and Jacob Lake, Arizona (fig. 

1). U.S. Highway 89A provides access to the northeast quarter of the map area, State Highway 389 provides access to the 

northwest quarter of the map area, a short paved road from State 

Highway 389 leads to Pipe Spring National Monument and the 

towns of Kaibab and Moccasin, Arizona, and State Highway 67 

(a one-way in and one-way out access road) provides access to 

the North Rim of the eastern Grand Canyon about 32 km (20 

mi) south of the southeast quarter of the map area.

The Bureau of Land Management Arizona Strip Field 

Office in St. George, Utah, manages BLM lands in the western, 

central, and northeastern part of the Fredonia quadrangle that 

are accessible by several unimproved dirt roads. Gravel roads in 

this part of the map area are maintained by the BLM but travel 

on some of these roads requires a 4-wheel-drive vehicle. Access 

to the Vermilion Cliffs National Monument (BLM) in the northeast corner of the map area is by a gravel road in House Rock 

Valley that leads north from U.S. Highway 89A; back country 

hiking or use permits are required from the BLM offices in 

Fredonia, Arizona, or St. George, Utah. Part of the Cottonwood 

Point Wilderness area (BLM) is within the northwest corner of 

the map area just east of Colorado City, Arizona.

U.S. Forest Service graveled roads provide access to 

the Kaibab National Forest and the Grand Canyon National 

Game Preserve in the southeastern quarter of the Fredonia 

quadrangle, but access is often restricted or the areas closed 

during winter months because of heavy snow accumulations 

from October through April, including closure of State Highway 67 to the North Rim of Grand Canyon. Access to the 

Kanab Canyon Wilderness Area and canyon tributaries is by 

foot trails; back country hiking permits are required and are 

obtained from the Kaibab National Forest Visitors Center at 

Jacob Lake, Arizona. Back country hiking permits, obtained 

from Grand Canyon National Park at Grand Canyon, Arizona, 

are required for foot travel into Grand Canyon National Park 

at the south-central edge of the map in Kanab Canyon area. 

Extra water and food is highly recommended for travel into 

the remote areas of the Arizona Strip (this map area). There 

are several small parcels of private and State land scattered 

throughout the map area, mainly near the settlements of Colorado City and Fredonia, Arizona.

The Fredonia quadrangle is one of the few remaining areas 

near the Grand Canyon where new geologic mapping is needed 

for geologic connectivity of the regional geologic framework. 

This map provides an updated regional geologic database for 

use by federal, state, and private land resource managers who 

direct environmental and land management programs such as 

range management, biological studies, flood control, and water 

resource investigations. The geologic information will support 

future and ongoing local geologic investigations and associated 

scientific studies of all disciplines within the Fredonia quadrangle and the Grand Canyon area.

Kanab Creek, which flows south toward the Colorado 

River in Grand Canyon, is the principal drainage in the western 

two-thirds of the map area. House Rock Valley Wash drainage, 

which flows southeastward toward Marble Canyon of the Grand 

Canyon about 21 km (13 mi) east of House Rock Valley, drains 

the eastern third of the map area. Elevations below about 1,525 

m (5,000 ft) generally support a sparse growth of sagebrush, 

cactus, grass, and various high-desert shrubs. Elevations above 

about 1,525 m (5,000 ft) commonly support moderate to thick 

growths of sagebrush and grass in alluvial valleys, while woodlands of pinion pine, juniper, and oak trees thrive on hilly terrain 

between 1,525 to 2,135 m (5,000 to 7,000 ft), and forests of 

ponderosa pine and douglas fir thrive at elevations above 2,235 

m (7,000 ft) on the Kaibab Plateau. Salt cedar (tamarisk) and 

Russian olive trees grow along the banks of Kanab Creek and its 

tributary washes.

Previous Studies

Hemphill (1956), Marshall (1956 a–e), Marshall and 

Phillmore (1956), McQueen (1956; 1957), Minard (1957), 

Morris (1956; 1957), Pillmore (1956), Pomeroy (1957), and 

Wells (1958; 1959; 1960) made the earliest photogeologic maps 

of the area for the U.S. Atomic Energy Commission. Those 

maps were later compiled onto a geologic map of Coconino 

County, Arizona, by Wilson and others (1960) and onto a state 

geologic map of Arizona by Wilson and others (1969). More 

recent geologic maps within the Fredonia 30 ́ x 60 ́ quadrangle 

include Billingsley and others (1983), Bush (1983), Billingsley 

(1992), Billingsley and others (2001), Billingsley and others 

(2004), Billingsley and Hampton (2001), and Billingsley and 

Wellmeyer (2001). Geologic maps of adjacent areas include the 

Grand Canyon 30 ́ x 60 ́ quadrangle that borders the south edge 

(Billingsley, 2000), the Littlefield 30 ́ x 60 ́ quadrangle that 

borders the west edge (Billingsley and Workman, 2000), and the 

Kanab 30 ́ x 60 ́ quadrangle that borders the north edge (Sable 

and Hereford, 2004).

Mapping Methods

The geology was mapped using 1:24,000-scale 2005 color 

aerial photographs courtesy of the Bureau of Land Management, Arizona Strip Office in St. George, Utah, and 1:24,000-

scale 1994 color aerial photographs courtesy of the U.S. Forest 

Service, North Kaibab Ranger District in Williams, Arizona. 

The map units and geologic structures were field checked to 

insure accuracy and consistency of map unit descriptions. 

Many of the Quaternary alluvial deposits have similar lithology 

but have different geomorphic characteristics and are mapped 

almost entirely by aerial photography. Relative ages of surficial 

fluvial and eolian deposits are approximate and are determined 

by stratigraphic position and the amount of erosional degradation.

Susan S. Priest and Tracey J. Felger (U.S. Geological 

Survey), Flagstaff Science Center, compiled the map in digital 

format using Arc/Map techniques. Twenty-six detailed 1:24,000 

scale USGS quadrangles and parts of five other 1:24,000-scale 
3

quadrangles (Moccasin, Pipe Valley, Pipe Spring, Clear Water 

Spring, and Fredonia; fig. 2, map sheet) initially compiled to 

produce this map can be seen as view maps in the USGS web 

site address. This map is the 7th of a series of digital geologic 

maps of the Grand Canyon region.

Geologic Setting

The Fredonia map area is north of the eastern Grand 

Canyon and within the southern part of the Colorado Plateau 

physiographic province (Billingsley and others, 1997). The area 

is characterized by nearly horizontal Paleozoic and Mesozoic 

sedimentary strata that have an average regional dip of about 1° 

to 2° north-northeast in the western two-thirds of the map area; 

the strata are gently warped by minor anticlinal and synclinal 

folds and are offset by normal faults. The Kaibab Anticline 

(sometimes referred to as the Kaibab Uplift or Kaibab Arch) 

is a broad, large scale, north trending, north plunging anticline 

in the eastern third of the map area; the anticline axial trace is 

approximately located in the northeast quarter of the map area 

(see cross-section A–A ́). The Kaibab Anticline elevates the 

Paleozoic strata as much as 610 m (2,000 ft) higher than the surrounding plateaus west and east of the structure and forms the 

Kaibab Plateau, a sub plateau of the Colorado Plateau. The eastern flank of the Kaibab Anticline is marked by the East Kaibab 

Monocline that is divided into an upper and lower segment in 

the southeast corner of the map area. The western flank of the 

Kaibab Anticline is marked by the Muav and North Road Faults 

that offset Paleozoic strata down-to-the-west. The Big Springs 

Fault angles southeastward into the Kaibab Plateau towards the 

north rim of Grand Canyon at the south edge of the map area. 

Mesozoic strata that once covered the Kaibab Anticline have 

been removed by Cenozoic erosion. The East Kaibab and Moccasin Monoclines are the principal folds in the map area and all 

have east-dipping strata and a general north-south axial trend. 

The Moccasin Monocline is not shown on the map because it 

lies within the Kaibab-Paiute Indian Reservation. A small part 

of the Moccasin Monocline is shown within the private town of 

Moccasin, Arizona.

The Sevier, Toroweap, Big Springs, Muav, and North Road 

Faults are the principal faults within the map area and have a 

general north-south strike and offset Paleozoic and Mesozoic 

strata down-to-the-west. There are several small normal faults 

and minor folds throughout the map area that commonly parallel the northeast and northwest trending bedrock joints and 

fractures.

The sedimentary section within the map area consists 

of about 793 m (2,600 ft) of Paleozoic strata and about 1,035 

m (3,400 ft) of Mesozoic strata including some minor Tertiary stream-channel (Ts) deposits. Quaternary deposits are 

widely distributed and consist primarily of fluvial alluvium 

and eolian sand deposits. The fluvial and eolian deposits are 

often intertongued and are mapped as mixed alluvium and 

eolian deposits. Talus, rock fall, and landslide deposits are also 

mapped as well as most man made quarries, small open pit 

mines, drainage diversion dams, large ditches, and stock tanks, 

but agricultural fields and several minor road cut excavations 

are not mapped. Map contacts between all Quaternary surficial 

deposits are approximate and are shown as a solid line where 

deposits intertongue and exhibit a gradational facies changes 

in both the lateral and vertical sense. The surficial units are 

important to local resource managers for helping to base 

management decisions regarding rangeland conditions, flood 

control problems, biological studies, soil erosion, and construction and development projects. The surficial deposits are commonly Pleistocene? or Holocene age (less than 2 m.y.) based on 

K-Ar dates of volcanic rocks associated with similar surficial 

deposits mapped in the southwest corner of the map area and 

adjacent parts of the Uinkaret Volcanic Field (Billingsley and 

Workman, 2000; Billingsley and others 2001; Billingsley and 

Priest, 2003).

Paleozoic and Mesozoic Sedimentary Rocks

The Paleozoic and Mesozoic stratigraphic units exposed 

within the map area include, in order of oldest to youngest 

(bottom to top): Redwall Limestone (Mississippian), Supai 

Group (Upper Mississippian, Pennsylvanian, and Lower Permian), Hermit Formation (Lower Permian), Coconino Sandstone 

(Lower Permian), Toroweap Formation (Lower Permian), 

Kaibab Formation (Lower Permian), Moenkopi Formation 

(Lower and Middle(?) Triassic), Chinle Formation (Upper Triassic), Moenave Formation (Lower Jurassic), Kayenta Formation (Lower Jurassic), and Navajo Sandstone (Lower Jurassic). 

The Surprise Canyon Formation (Billingsley and Beus, 1999) is 

not exposed in the map area but may be present in the subsurface of the map area as a reddish sediment accumulation in 

local paleovalleys and karst caves eroded into the top part of the 

Redwall Limestone. The Surprise Canyon Formation, the most 

fossiliferous rock strata in Grand Canyon, contains numerous 

shallow water marine fossils and land-based plant fossils. Ages 

of the Mesozoic strata have been revised on the basis of new 

data from these strata in southern Utah (Biek and others, 2007).

Gray limestone cliffs of the Redwall Limestone (Mississippian) form narrow canyon walls within the lower part of Kanab 

Creek and Jumpup Canyon at the south-central edge of the map 

area and are the oldest exposed rock unit of the map. Devonian 

and Cambrian rock strata shown on cross-sections A–A ́ and 

B–B ́ are based on exposures south of the map area in the Grand 

Canyon. The Surprise Canyon Formation (Upper Mississippian) is likely present in the subsurface of the map area, and it 

would be a reddish marine stratum that fills erosional valleys, 

channels, and karst features within the upper part of the Redwall 

Limestone. The lower part of the Supai Group (Upper Mississippian, Pennsylvanian, to lower Permian) forms the red slopes 

and cliffs above the Redwall Limestone in lower Kanab Creek 

and its tributaries; a light-red cliff of the Esplanade Sandstone 

(Lower Permian) caps the lower part of the Supai Group. The 

Esplanade Sandstone forms a sandstone bench or platform in 

the lower reaches of Kanab Creek at about 1,250 m (4,100 

ft) elevation which forms the Sanup Plateau in the western 

Grand Canyon area about 48 km (30 mi) west of the map area. 

Above the Esplanade Sandstone bench is a 250-m (825-ft) thick 

dark-red siltstone and sandstone slope of the Hermit Forma-
4

tion (Lower Permian) that is commonly covered by talus and 

rockslide deposits. A 45-m (150-ft) thick, light-brown to white 

cliff of the Coconino Sandstone (Lower Permian) overlies the 

red Hermit Formation in the south half of the map area. Because 

the Coconino Sandstone pinches out from the south into the 

central part of the map area, the gray strata of the Toroweap 

Formation (Lower Permian) unconformably overlies the red 

Hermit Formation. The Coconino Sandstone pinch out is visible 

in the upper reaches of Kanab Creek and north of Warm Springs 

Canyon of the Kaibab Plateau, but most of the pinch-out is in 

the subsurface of the northern quarter of the map area.

Gray cherty limestone and reddish-gray to white siltstone 

and gypsum beds of the Toroweap Formation (Lower Permian) overlie the Coconino Sandstone where the Coconino is 

present, otherwise the Toroweap strata unconformably overlies the Hermit Formation. The gray limestone, siltstone, and 

gypsum beds of the Kaibab Formation (Lower Permian) form 

much of the bedrock surface in the southern three-quarters of 

the map area and the gray rim rock cliffs of Kanab Creek and 

its tributaries of the Grand Canyon. The reddish siltstone and 

gray gypsum beds within the Harrisburg Member of the Kaibab 

Formation thin eastward into the Kaibab Plateau area, whereas 

the gray sandy and cherty limestone beds within the Harrisburg 

thicken eastward. The limestone beds are often confused with 

or mapped as part of the upper Fossil Mountain Member of the 

Kaibab Formation where lower siltstone and gypsum beds are 

absent.

A regional unconformity separates the Permian Kaibab 

Formation from the overlying Triassic Moenkopi Formation. 

The unconformity is often difficult to distinguish in most areas 

due to the lack of erosional relief and similarity of lithology and 

color of both units. The unconformity is marked by wide, shallow, stream-channel valleys eroded into the Kaibab Formation. 

The deeper channels are identified by deposits of conglomerate 

composed of well rounded small boulders, cobbles, and pebbles 

of chert and limestone that are derived from erosion of the 

underlying Kaibab Formation that forms the basal Timpoweap 

Member of the Moenkopi Formation.

The term Rock Canyon Conglomerate was proposed 

and abandoned by Gregory (1948, 1952), used by Nielsen 

and Johnson (1979), and Nielsen (1986, 1991). But the term 

Timpoweap Member of the Moenkopi Formation is used in this 

report as used by Stewart and others (1972); Billingsley and 

Workman (2000); and Sable and Hereford (2004). The conglomerate forms the lower part of the Timpoweap Member of 

the Moenkopi Formation, however, where the conglomerate is 

not present, a yellowish fine-grained limestone and sandstone 

is commonly present within the shallow paleovalleys and in 

many places is interbedded with conglomerate. The limestone 

beds form the upper part of the Timpoweap Member and 

become very widespread from west to east across the northern 

part of the map area within shallow paleovalleys eroded into 

the Kaibab Formation (Billingsley and Workman, 2000; Sable 

and Hereford, 2004). The limestone beds of the Timpoweap 

Member have similar characteristics to the limestone beds of 

the underlying Harrisburg Member of the Kaibab Formation 

making it difficult in many areas to distinguish them, mainly 

where the erosional unconformity has low relief; especially 

along the northern edge of the map area. For this reason, the 

Timpoweap Member, as mapped by Sable and Hereford (2004) 

on the north Kaibab Plateau in Utah (northeast edge of map 

area) cannot be distinguished with certainty from upper limestone beds of the Harrisburg Member of the Kaibab Formation; 

thus, strata contacts of that area will not match adjoining strata 

of the Kanab quadrangle in Utah. The lack of chert nodules 

and the presence of small chert pebble clasts within limestone 

beds of the Timpoweap generally help to distinguish between 

limestone beds of the Timpoweap Member of the Moenkopi 

Formation from those of the Harrisburg Member of the Kaibab 

Formation, but not consistently.

In the north-central part of the map near Fredonia and 

Pipe Spring National Monument, Arizona, the surface bedrock 

is composed of red siltstone and sandstone, gray gypsum, and 

gray-white dolomite of the Moenkopi Formation (Lower and 

Middle(?) Triassic). At Colorado City, Moccasin, and Kaibab, 

Arizona, and along the east side of House Rock Valley, the surface bedrock is mostly white sandstone and multi-colored blue 

and red siltstone, mudstone, and claystone of the Chinle Formation (Upper Triassic). Above the Chinle Formation, reddishbrown claystone, siltstone, and sandstone beds of the Moenave 

and Kayenta Formations form the lower cliffs and slopes of the 

Vermilion Cliffs between Colorado City and Fredonia, Arizona, 

and on the east side of House Rock Valley in the northeast 

corner of the map area. Above the red slopes of the Kayenta 

Formation, light-red and white, large-scale cross-bedded sandstone cliffs of the Navajo Sandstone (Jurassic) form the upper 

and main part of the Vermilion Cliffs. The Navajo Sandstone 

is the surface bedrock of the highlands of Moccasin Mountains 

east of Colorado City in the northwest part of the map area and 

the Paria Plateau in the northeast corner of the map area.

The surficial deposits are generally 1 to 18 m (3 to 60 ft) 

thick and are mostly alluvial deposits, such as alluvial fans, 

alluvial terraces, and mixed alluvium and eolian deposits. 

Eolian deposits are mainly confined to the Paria Plateau area 

and are mainly derived from outcrops of the Navajo Sandstone. 

Most of the eolian deposits are stabilized by grassy vegetation 

during wet climatic conditions but become locally active during 

prolonged dry conditions.

The basalt flows and pyroclastic cones in the southwest 

corner of the map area are part of the eastern extension of the 

Uinkaret Volcanic Field. The main body of the Uinkaret Volcanic Field is west of the map area (Billingsley and Workman, 

2000; Billingsley and others, 2001).

Structural Geology

Monoclines, such as the Moccasin and East Kaibab Monoclines, developed in response to the Laramide orogeny of Late 

Cretaceous through Eocene time along pre-existing Proterozoic 

fault zones (Huntoon, 2003). Extensional stresses from Miocene 

to the present time have resulted in down-to-the-west normal 

faulting along these Precambrian basement faults effectively 

reversing part of the Laramide offset of strata by displacing 

monoclinal strata down-to-the-west. Most of the normal fault 

displacements within the map area probably occurred during 
5

Pliocene and Pleistocene time and continue today as observed 

along parts of the Toroweap Fault in the southwest corner of 

the map, the Muav, Big Springs, and North Road Faults in the 

east-central part of the map, and the Hurricane Fault about 

23 km (14 mi) west of the map area (Jackson, 1990; Stenner 

and others, 1999; Billingsley and Workman, 2000; Fenton and 

others, 2001; Billingsley and Wellmeyer, 2003; Amoroso and 

others, 2004; Raucci, 2004).

Toroweap and Sevier Faults

The Sevier and Toroweap Faults, the principle structural 

features in the western half of the map area, form the boundary 

between the Uinkaret Plateau west of the faults and the Kanab 

Plateau east of the faults (Billingsley and others, 1997). The 

Toroweap Fault, southwest corner of the map, has a northeast 

strike for about 13 km (8 mi), then turns and extends northwest 

for about 6.5 km (4 mi) and dies out. At the bend in the fault 

strike, the Toroweap Fault connects to the Sevier Fault (see 

cross-section A–A ́). The Sevier Fault continues on a northeast 

strike for about 8 km (5 mi) and bends to a general north-south 

strike that eventually passes through Pipe Spring National 

Monument in the northwest part of the map area. Overall, the 

Toroweap and Sevier Faults join northeast of Heaton Knolls 

in the southwest part of map area and are both aligned on a 

common fault system.

Displacement of strata along the Toroweap Fault is generally about 73 m (240 ft) down-to-the-west in the southwest 

corner of the map and gradually decreases northeastward. A 

Pleistocene basalt, which came from Heaton Knolls volcano 

southeast of and near the fault, flowed over the Toroweap Fault. 

The basalt flow was partly offset by the Toroweap Fault downto-the-west about 12 to 18 m (40 to 60 ft) indicating young 

tectonic activity along this part of the Toroweap Fault. Displacement of strata along the Sevier Fault gradually increases from 

14 m (45 ft) down-to-the-northwest at its junction with the 

Toroweap Fault to as much as 396 m (1,300 ft) at Pipe Spring 

National Monument and about 366 m (1,200 ft) at the Arizona/

Utah State line.

Moccasin Monocline and West Segment of the 

Sevier Fault

Just north of Pipe Spring National Monument, a short 

northwestern segment of the Sevier Fault and associated Moccasin Monocline splits off the main segment of the Sevier Fault 

(Billingsley and others, 2004; Sabol, 2005). Northeast of Pipe 

Spring National Monument, the Sevier Fault continues north to 

the Vermilion Cliffs where the fault parallels the east-facing part 

of the Vermilion Cliffs for about 5 km (3 mi) to Sandy Canyon 

Wash (not shown on this map) and northward into Utah just east 

of Coral Pink Sand Dunes State Park about 5 km (3 mi) north of 

the map area. A gentle east-dipping unnamed monocline is present along the Sevier Fault in Utah north of the map area.

It can be argued that the Moccasin Monocline fold is really 

an inclined anticline and syncline pair. But the term Moccasin 

Monocline is used here as in Billingsley and others (2004) and 

Sabol (2005). West dipping strata as much as 46 degrees is visible on the east side of the Sevier Fault in Pipe Valley drainage 

southwest of Pipe Spring National Monument and may reflect 

fault drag along the Sevier Fault in that area.

West Kaibab Fault Zone

The West Kaibab Fault Zone was originally defined 

by Powell (1875, p. 182–190). Dutton (1882, p. 183–186) 

described three fault lines which comprised the West Kaibab 

Fault Zone. Noble (1914) made a detailed study of the southern end of one of the West Kaibab Faults that enters the Grand 

Canyon. Strahler (1948) named the individual faults of the 

West Kaibab Fault Zone: Muav Canyon Fault (Muav Fault 

by Huntoon and others, 1996; Billingsley, 2000), Big Springs 

Fault, North Road Fault, and LeFevre Graben (spelled Le Fevre 

on 1988 USGS 7.5’ quadrangle). The term West Kaibab Fault 

Zone is not used for this map because of the confusion of intersecting faults.

In the east-central part of the map area, the Muav and the 

North Road Faults form a topographic and structural boundary between the Kaibab and Kanab Plateaus. The Muav Fault, 

as mapped here, extends southward into the Grand Canyon 

(Huntoon and others, 1996; Billingsley, 2000) and extends 

northeastward to the vicinity of U.S. Highway 89A northwest 

of Jacob Lake, Arizona. Although Strahler (1948) used the 

name Big Springs Fault from its junction with the Muav Fault 

in Warm Springs Canyon north to U.S. Highway 89A, the name 

Muav Fault is used here because it forms a continuous fault line 

strike northeastward to U.S. Highway 89A and the North Road 

Fault. Big Springs Fault forms a junction with the Muav Fault 

at Warm Springs Canyon and angles off southeastward into the 

Kaibab Plateau to the north rim of Grand Canyon. At the south 

edge of the map area, the Muav Fault offsets Paleozoic strata 

down-to-the-west as much as 122 m (400 ft) and is associated 

with east-dipping strata of the Crazy Jug Monocline in the 

Grand Canyon just south of the map area (Huntoon and others, 

1996; Billingsley, 2000).

Paleozoic and Mesozoic strata dip gently west of the 

Kaibab Anticline, but the structural trend of the Muav Fault 

north of U.S. Highway 89A most likely trends northeast in 

the subsurface for about 5 km (3 mi) to the North Road Fault, 

described by Strahler (1948), and continues to the Arizona/Utah 

State line. The North Road Fault offsets Paleozoic and Mesozoic strata down-to-the-west as much as 70 to 80 m (230 to 260 

ft). The North Road Fault also forms the east side of Le Fevre 

Graben; the west-bounding fault of Le Fevre Graben is herein 

named Le Fevre Ridge Fault.

The Big Springs Fault and Monocline splay south from the 

Muav Fault near the mouth of Warm Springs Canyon west of 

Jacob Lake, Arizona. The Big Springs Fault offsets strata about 

160 m (525 ft) down-to-the-west near Warm Springs Canyon 

and extends south and southeastward into the Kaibab Plateau 

and north rim of the Grand Canyon as offset of strata diminishes (Huntoon and others, 1996; Billingsley, 2000). Paleozoic 

strata along the Big Springs Monocline west of Big Springs 

Fault has an easterly dip between 8o and 2o and less than 2o dip 
6

east on east side of the fault. Several minor grabens are present 

throughout the length of the Kaibab Anticline with Le Fevre and 

Summit Valley Grabens being the largest north of Jacob Lake, 

Arizona. Many smaller normal faults are shown at map scale 

with no estimated offsets to help show the structural fabric of 

the map area. Several smaller faults are not shown at 1:100,000 

map scale but are present and are shown on the 1:24,000-scale 

maps that accompany the digital map database.

East Kaibab Monocline

The East Kaibab Monocline is a prominent structure that 

forms the eastern limb of the Kaibab Anticline. Powell (1875, 

p. 182–190) first described the East Kaibab fold; Babenroth and 

Strahler (1945) renamed the fold the East Kaibab Monocline. 

The basal part of the East Kaibab Monocline north of Trail 

Canyon and the lower segment of the East Kaibab Monocline 

south of Trail Canyon marks the structural boundary between 

the Kaibab Plateau (anticline) and House Rock Valley. The 

East Kaibab Monocline is the largest and most pronounced 

monocline in the map area and splits into an upper and a lower 

segment (Billingsley and Wellmeyer, 2001; Billingsley and 

others, 2001; Billingsley and Hampton, 2001). The intermediate 

bench land between the two monocline segments is called Little 

Mountain and is part of the Kaibab Plateau. The Upper and 

Lower East Kaibab Monoclines merge northward to become the 

East Kaibab Monocline about 6.5 km (4 mi) north of U.S. Highway 89A at Trail Canyon. At Trail Canyon, the Trail Canyon 

Fault seems to offset the East Kaibab Monocline as a strike-slip 

fault, but this is interpreted as a strike-slip separation caused 

by normal fault slip. Trail Canyon Fault bends to an east-west 

strike south of U.S. Highway 89 A and forms a graben that dies 

out about 1.5 km (1 mi) east of Jacob Lake, Arizona.

House Rock Valley is at the base of the East Kaibab Monocline and Lower East Kaibab Monocline and is about 1.5 to 3 

km (1 to 2 mi) wide in the northeast quarter of the map area and 

widens southward in the vicinity of U.S. Highway 89A. House 

Rock Valley is flanked on the east by red cliffs of Mesozoic 

strata of the Vermilion Cliffs. The Navajo Sandstone forms the 

bedrock rim of the Vermilion Cliffs, which also marks the western edge of the Paria Plateau. Part of House Rock Valley, the 

Vermilion Cliffs, and the Paria Plateau are within the new BLM 

administered Vermilion Cliffs National Monument.

Bedrock Joints and Fractures

Bedrock joints and fractures are prominent surface features 

visible in the sandstone and limestone bedrock units throughout the map area, such as the Esplanade Sandstone (Permian), Kaibab Formation (Permian), Shinarump Conglomerate 

Member of the Chinle Formation (Triassic) and the Navajo 

Sandstone (Jurassic). These rocks units are well-cemented, 

cliff-forming strata where regional stress patterns are reflected 

as joints and fractures that are visible on bedrock outcrops. The 

joint and fracture patterns reflect old and young regional stress 

patterns from compressional or extensional tectonic events of 

different ages from Proterozoic through Cenozoic time for the 

Colorado Plateau. Bedrock joints and fractures are vertically 

continuous through all hard and soft Paleozoic and Mesozoic 

rock strata exposed in the map area. Several joint and fracture 

symbols shown on the Paria Plateau and Moccasin Mountains 

areas of the map are located in eolian sand sheet and sand dunes 

but are also visible in small outcrops of the Navajo Sandstone 

and as lineations of vegetation in thin sand cover.

There are four different joint and fracture systems in 

the map area: north-south, northeast-southwest, northwestsoutheast, and east-west oriented. At least two and sometimes 

three joint and fracture sets are present in different parts of the 

map, but typically only two sets are prominent, those oriented 

northeast-southwest and northwest-southeast. The northwestsoutheast and northeast-southwest orientated joint and fracture 

systems seem to be the youngest in the map area because many 

of the joints and fractures are visible as semi-open cracks, 

particularly in the Esplanade Sandstone and Navajo Sandstone. 

The cracks are also visible as surficial expressions in eolian 

sand deposits in the Moccasin Mountains above the Vermilion 

Cliffs and depicted as linear vegetation growths where the joints 

and fractures are filled with eolian sand deposits allowing local 

vegetation to established deep rootholds. On aerial photographs, 

the linear vegetation patterns are visible in sand sheet and dune 

deposits.

However, northwest of the map area at Zion National 

Park, the north-northwest oriented joint and fracture zone is 

documented by Rodgers (2002) as the youngest in the region. 

Rodgers concluded that the north-northwest oriented joint (fracture) zones and subsequent isolated joints indicate a pervasive 

extensional feature that is characteristic of west-southwest 

tectonic extension of the central Basin and Range Province that 

has affected the western Colorado Plateau Province since midMiocene time.

Collapse Structures and Sinkholes

Circular bowl-shaped areas with inward-dipping strata 

are collapse structures that may have developed because of 

collapse-formed breccia pipes caused by the dissolution of 

limestone within the deeply buried Mississippian Redwall 

Limestone (Wenrich and Huntoon, 1989; Wenrich and Sutphin, 

1989). A black dot on the map marks such collapse structures 

and a red dot marks visible breccia in breccia pipes in Kanab 

Creek of Grand Canyon. Collapse features in the Kaibab Formation and younger strata, however, cannot be distinguished with 

certainty from shallow collapse structures that are caused by the 

dissolution of gypsum in the Kaibab or Toroweap Formations. 

Drilling is required to confirm that breccia pipes are present 

at depth in the subsurface of the collapse structure. The deepseated breccia pipes contain potential economic high-grade ore 

deposits of copper and uranium minerals (Wenrich, 1985) and 

some of the breccia pipes in the map area have been mined for 

uranium and the location is marked on the map with a mine 

symbol. The primary metal is uranium along with Ag, Pb, Zn, 

Cu, Co, and Ni (Wenrich and Huntoon, 1989).

Karst sinkholes are the result of gypsum dissolution within 

the Woods Ranch Member of the Toroweap Formation and 
7

Harrisburg Member of the Kaibab Formation and are common 

in the map area. Sinkhole depressions are most common at 

higher elevations of the Kaibab Plateau and may reflect a higher 

precipitation rate than at lower elevations of the Uinkaret and 

Kanab Plateaus. The largest and deepest karst sinkholes are on 

the Kaibab Plateau and are likely the result of dissolution of 

gypsiferous strata in the Woods Ranch Member of the Toroweap 

Formation because the sinkholes are more than 12 to 30 m (40 

to 100 ft) deep, are steep sided or cliff walled, and nearly extend 

through the Kaibab Formation. The shallower karst sinkhole 

depressions throughout the map are most likely the result of 

dissolution of gypsiferous strata in the Harrisburg Member of 

the Kaibab Formation because these sinkholes are usually only 

a few meters deep and do not have steep-sided or shear rock 

walls. Most of the shallower sinkholes are associated with the 

Harrisburg Member of the Kaibab Formation in the western half 

of the map area because the gypsiferous sediments within the 

Harrisburg Member are thickest in that part of the map.

Acknowledgments

We appreciate the assistance of Becky Hammond, a geologist and field manager of the Arizona Strip, Bureau of Land 

Management, Arizona Strip Field Office, St. George, Utah; 

Connie Slusser of the Bureau of Land Management, National 

Science and Technology Center, Denver, Colorado who assisted 

in providing the 1976 infrared aerial photos and the 2002 color 

aerial photograph coverage for this study. Joann Isbrecht of the 

Southwest Geographic Science Information Team at the U.S. 

Geological Survey, Flagstaff, Arizona, graciously provided 

Landsat 1999 satellite imagery for this map area. The advice 

and suggestions of Phillip Stoffer of the U.S. Geological Survey, 

Menlo Park, California, Paul Umhoefer, Northern Arizona 

University, Flagstaff, Arizona, and Charles L. Powell, II, U.S. 

Geological Survey, Menlo Park, California, the edits by Theresa 

Iki of the U.S. Geological Survey, Menlo Park, California are 

greatly appreciated. 

DESCRIPTION OF MAP UNITS

[Some unit exposures on the printed map are too small to distinguish the color for unit identification. These 

units are labeled where possible, and unlabeled units are attributed in the geodatabase.]

SURFICIAL DEPOSITS

Holocene, Pleistocene, and Pliocene(?) surficial deposits are differentiated from one another chiefly on 

the basis of difference in morphologic character and physiographic position observed on 1976 and 2002 

aerial photographs and by field observations. Older alluvial and eolian deposits generally exhibit extensive 

erosion and surface soil development, whereas younger deposits are actively accumulating material or are 

lightly eroded. Salt and gypsum are common constituents in all alluvial deposits derived from the Kaibab, 

Moenkopi, and Chinle Formations in the map area. Contacts with adjacent surficial deposits and bedrock 

deposits are gradational and locations are approximate.

Qaf Artificial fill and quarries (Holocene)—Alluvium and bedrock material removed from quarries 

and trench excavations used to build stock tanks, drainage diversion dams, roads, or other 

manmade construction projects; not all modern highways cuts are shown. Include uranium 

and copper mine excavations. No map distinctions between cut or fill excavations. Agricultural fields are not shown

Qs Stream-channel deposits (Holocene)—White to light-red interbedded silt, sand, gravel, and 

pebbles; unconsolidated and poorly sorted. Pebbles and some cobbles are mostly sandstone 

above the stratigraphic position of the Shinarump Member of the Chinle Formation; below 

the Chinle, clasts are dominated by black, well-rounded pebbles of quartzite or chert derived 

from the Shinarump Member of the Chinle Formation. Intertongue with or inset against 

young alluvial fan (Qay), young terrace-gravel (Qgy), and upper part of valley alluvial (Qv) 

deposits, overlaps flood-plain (Qf) and ponded sediment (Qps) deposits. Stream channels 

subject to intermittent high-energy flash floods that produce local sediment accumulation on 

flood-plain (Qf), young terrace-gravel (Qgy), and young alluvial fan (Qay) deposits. Little 

or no vegetation in stream channels except for occasional tamarisk trees, willow trees, and 

grass. About 1 to 4 m (3 to 12 ft) thick

Qt Travertine deposits (Holocene)—Gray and tan, massive, porous, cliff-forming fresh water 

limestone. Include angular clasts of local talus breccia or gravel. Formed by rapid chemical precipitation of calcium carbonate of spring water. Form encrustations on steep slopes 

or cliffs below active and non-active spring outlets. Thickest deposits are at Slide Spring in 

Slide Canyon, an eastern tributary to Snake Gulch in upper Kanab Canyon. Thickness, 2 

to18 m (6 to 60 ft)
8

Qf Flood-plain deposits (Holocene)—Light-red or gray silt, fine- to coarse-grained sand, and gravel 

lenses; partly consolidated by gypsum or calcite cement. Gravel locally contains yellow, red, 

black, and white subrounded to subangular chert and quartz, well-rounded red sandstone, 

and gray-blue rounded limestone fragments and pebbles 0.5 to 1 cm (0.25 to 0.75 in) in 

diameter. Gradational lateral and vertical contact between stream-channel (Qs), flood-plain 

(Qf), and young alluvial fan (Qay) deposits. Support thick growths of tamarisk trees and 

other water-dependent plants where stream bedrock is very shallow, usually less than 3 m 

(10 ft) below floodplain surface. Dense growths of tamarisk help trap and accumulate sediment that develops flood-plain deposits within and along drainages. Deposits are generally 1 

to 2 m (3 to 6 ft) above stream-channel (Qs) deposits and often grade laterally into streamchannel deposits. About 1 to 6 m (3 to 20 ft) thick

Qps Ponded sediments (Holocene)—Light-red to white clay, mud, silt, and fine-grained sand. 

Locally include small angular to subrounded fragments of bedrock clasts from nearby 

outcrops. Deposits are common sediment in sinkhole depressions. Sediment accumulates in 

temporary ponded areas on young terrace-gravel (Qgy) deposits due to sand dune accumulations or overbank sand and mud that form levee deposits preventing sediments from eroding 

back into local drainages for an extended amount of time. Include ponded deposits consisting of sand and silt on Moccasin Mountains and Paria Plateau where widespread sand sheet 

and sand dunes form temporary dune blockage across local drainages, or as blowout depressions formed within sand dunes. Youngest deposits accumulate in lowland areas where artificial diversion dams, stock tanks, or roads block drainages. Desiccation cracks often form 

on dry hardpan surfaces. Clay and fine silt content of sediment largely restricts plant growth 

except in sandy areas above Vermilion Cliffs. About 0.5 to 2 m (1 to 6 ft) thick

Qd Dune sand and sand sheet deposits (Holocene)—On Moccasin Mountains and Paria Plateau 

above Vermilion Cliffs; consists of light-red to white silt and fine- to coarse-grained eolian 

sand derived from the Navajo Sandstone (Jn). Only most extensive and thickest deposits 

are shown. Gradational contacts between young mixed alluvium and eolian (Qae) deposits 

based on geomorphologic interpretation on aerial photos. Below Vermilion Cliffs, deposits 

accumulate along local stream drainages and on gentle slopes of young alluvial fan (Qay) 

deposits. Deposit often leads to fine-grained climbing dunes or falling dunes of dune sand 

and sand sheet (Qd) accumulations on steep topography along base of Vermilion Cliffs on 

west side of Paria Plateau. In Pipe Valley south of State Highway 389 and in House Rock 

Valley along U.S. Highway 89A, white to light-brown and light-red, fine- to coarse-grained 

quartz sand partly stabilized by grass and small high-desert shrubs during wet conditions. 

Support moderate growths of grass, black brush, and other small high-desert shrubs above 

Vermilion Cliffs; mostly grass below Vermilion Cliffs. Unit partly stabilized by grassy vegetation or crypto-organic soil growths in local stream drainage areas below Vermilion Cliffs. 

About 1 to 2 m (0.5 to 6 ft) thick near and below Vermilion Cliffs; about 3 to 11m (9 to 35 

ft) thick on Moccasin Mountains and Paria Plateau

Qae Young mixed alluvium and eolian deposits (Holocene)—Composed of gray, light-red, and 

white silt and fine- to coarse-grained, eolian and fluvial sand lenses; includes interbedded 

reddish-brown and gray silt and clay. Include a few coarse-grained gravel lenses composed 

primarily of angular chert fragments and red to white sub-rounded sandstone pebbles on 

Moccasin Mountains and Paria Plateau. Below Vermilion Cliffs in House Rock Valley and 

south and west of Yellowstone Mesa, includes multicolored and black, well-rounded chert 

pebbles derived from Shinarump Member of the Chinle Formation. Commonly occupies 

upper slopes of young alluvial fan (Qay) deposits. Below Vermilion Cliffs west of Colorado 

City, unit mostly composed of white and light-red sand and red silt that intertongues with 

young alluvial fan (Qay) deposits. Unit often overlapped by dune sand and sand sheet (Qd) 

deposits. Support thick to moderate growths of grass, cactus, and sagebrush; thick sagebrush, cliff rose bush, and pinion pine, oak, and juniper trees above Vermilion Cliffs. About 

1.5 to 18 m (5 to 60 ft) thick

Qc Colluvial deposits (Holocene)—Gray to light-brown, poorly sorted, fine- to coarse-grained, 

slope-forming mixed silt, sand, gravel, and small, well-rounded pebbles. Include angular 

fragment clasts of petrified wood, sub-rounded sandstone, and small well-rounded black, 

red, yellow, and brown quartz and chert pebbles derived from Shinarump Member of the 

Chinle Formation; partly consolidated. Form pediment slopes below Yellowstone Mesa and 

southwest of Colorado City, west quarter of map area. Small well-rounded pebbles form a 
9

partial desert pavement cover on some surfaces. Unit intertongues with young alluvial fan 

(Qay) deposits and is partly eroded by arroyos as much as 3 m (10 ft) deep. Surfaces are 

moderately vegetated and stabilized by grasses and small pebble desert pavement. About 3 

to 12 m (10 to 40 ft) thick

Qv Valley-fill deposits (Holocene)—Gray to light-red, slope-forming, unsorted mixture of mud, silt, 

sand, gravel, small pebbles, and cobbles. Partly consolidated by calcite and gypsum cement. 

Include sandstone, limestone, and chert clasts in sandy matrix locally derived from nearby 

Paleozoic and Mesozoic sedimentary rock outcrops in northwestern third of map area. On 

Kaibab Plateau; composed mostly of gray silt, sand, and numerous white to yellow chert 

fragments. Similar to stream-channel (Qs) deposits but occupies low-gradient drainages 

that deposit mostly fine-grained sand or silt in flat drainage floors, especially in Nail Canyon 

and Snake Gulch west of Jacob Lake, Arizona. Similar to or interbedded with flood-plain 

(Qf) deposits in Pipe Valley area. Subject to extensive sheet wash erosion, deposition, flash 

flood debris flows, temporary ponding of floods, sheet wash and arroyo erosion. Commonly 

interbedded with stream-channel (Qs), dune sand and sand sheet (Qd), and ponded sediment 

(Qps) deposits. About 1 to 6 m (3 to 20 ft) thick 

Qtr Talus and rock fall deposits (Holocene)—Along Vermilion Cliffs; consists of red to yellow 

silt and sand mixed with angular rocks and boulders of light-red sandstone and dark-red 

siltstone; partly cemented by calcite. Form talus debris slopes in steep-walled canyons and 

on lower slopes of Vermilion Cliffs; often associated with and adjacent to or below landslide 

(Ql) deposits. Include some boulders of Navajo Sandstone or Shinarump Member of the 

Chinle Formation larger than 3 m (10 ft) near landslide (Ql) deposits near base of Vermilion 

Cliffs. In Kanab Creek drainages; consists of gray to yellow silt, sand, gravel mixed with 

small to large angular rocks and boulders of gray limestone, white chert, and white to tan 

sandstone derived from the Kaibab and Toroweap Formations and Coconino Sandstone; 

partly cemented by calcite and gypsum. Form talus debris cover on red slopes of Hermit Formation; associated with and below landslide (Ql) deposits. Unit often grades down slope into 

young or old alluvial fan (Qay, Qao) deposits or young or old terrace-gravel (Qgy, Qgo) 

deposits. About 1.5 to 14 m (5 to 45 ft) thick

Qgy Young terrace-gravel deposits (Holocene and Pleistocene(?))—Below Vermilion Cliffs; consists of red, white, and gray interbedded fine- to coarse-grained sand and thinly laminated 

silt; partly consolidated by clay and calcite cement. Include interbedded thin beds of gray 

or red mud and clay and interbedded lenses of gravel composed of gray subangular chert 

fragments. Unit cut by modern erosion as much as 9 m (30 ft) deep in Kanab Creek near 

Fredonia, and other drainages eroded into the Vermilion Cliffs.

On Kanab Plateau, Uinkaret Plateau, and Kanab Canyon areas; consists of gray and 

light-brown, fine- to coarse-grained silt, sand, and gravel; partly consolidated by gypsum and 

calcite cement. Include gray-blue subrounded limestone and light-red sandstone clasts, in 

matrix of mostly white angular and subangular chert gravel. Deposits commonly intertongue 

with or overlapped by young alluvial fan (Qay) and mixed alluvium and eolian (Qae) 

deposits and inset against old terrace-gravel (Qgo) deposits. Subject to flash flood erosion 

or overbank accumulations of flood-plain (Qf) sediments in upper Kanab Creek drainage 

and its northeastern tributaries in Muggins Flat, north-central part of map area. Terraces are 

generally 1.2 to 9 m (4 to 30 ft) above local streambeds and as much as 18 m (60 ft) above 

stream channel in upper reaches of Kanab Creek and some of its tributaries. Unit often cut 

by arroyo erosion as much as 6 m (20 ft) in south-central part of map and as much as 18 m 

(60 ft) above stream channels in upper reaches of Kanab Creek and some of its tributaries. 

Moderately vegetated by sagebrush, grass, cactus, tamarisk trees, willow trees, juniper and 

pinion pine trees at elevations above 1,525 m (5,000 ft); mostly vegetated by grass, thick 

growths of cactus, sagebrush, desert shrubs, and some cottonwood trees in lower reaches of 

Kanab Creek. About 1 to 18 m (3 to 60 ft) thick or more

Qay Young alluvial fan deposits (Holocene and Pleistocene(?))—Vermilion Cliffs area; consists of 

light-red and brown silt and fine- to coarse-grained sand and gravel; partly consolidated by 

calcite and clay. Include subangular red and white chert fragments and small red and white 

sandstone and gray limestone clasts generally less than 5 cm (2 in) in diameter derived 

locally from nearby Vermilion Cliff outcrops. Include large boulders of the Shinarump 

Member of the Chinle Formation as much as 2 m (6 ft) in diameter below Yellowstone 

Mesa area. Clay content greatest below or in outcrops of Petrified Forest Member of the 
10

Chinle Formation. Include numerous black, brown, yellow, red, and gray, very well rounded 

quartzites and chert pebbles 1.5 to 5 cm (0.5 to 2 in) in diameter and occasional rounded, 

gray-white petrified wood fragments down slope of Vermilion Cliffs areas. Locally covered 

by thin eolian dune sand and sand sheet (Qd) deposits, young mixed alluvium, and eolian 

(Qae) deposits at distal ends of alluvial fan deposits.

On Kanab Plateau, Uinkaret Plateau, and in Kanab Creek drainages; gray, light-red, 

and light-brown silt, sand, and white cherty gravel, partly consolidated by gypsum and 

calcite. Include lobes of flash flood debris flows of unsorted angular boulders in sandy 

matrix that often form temporary dams that block principal drainages, primarily in Kanab 

Creek, Nail Canyon, and Snake Gulch, central part of map area. Surfaces are generally gullied as much as 3 m (10 ft) or partly covered by desert pavement of small gravel or pebbles 

in northwest quarter of map area; partly consolidated by calcite, clay, and gypsum cement 

below stratigraphic level of the Chinle Formation; mostly unconsolidated above Chinle 

below Vermilion Cliffs. Commonly overlapped by or intertongue with stream channel (Qs) 

deposits in upper Kanab Creek drainages and Muggins Flat area. Intertongue with landslide 

(Ql) and talus and rock fall (Qtr) deposits at upper reaches of alluvial fans below Vermilion 

Cliffs where unit is heavily dissected by erosion. Subject to extensive sheet wash erosion or 

sediment accumulation during heavy storms. Support moderate growths of grass, sagebrush, 

cactus, juniper, pinion pine, and various small high-desert shrubs. About 2 to 18 m (6 to 60 

ft) thick

Ql Landslide deposits (Holocene and Pleistocene)—Vermilion Cliffs area; consists of unconsolidated masses of unsorted rock debris that include detached blocks of Mesozoic strata that 

have rotated backward and slid down slope against parent cliff as loose incoherent masses of 

broken rock and deformed strata, often surrounded by talus and rock fall (Qtr) deposits. Parallel to the Vermilion Cliffs, landslide masses are as large as 3 km (2 mi) in length. Out from 

the Vermilion Cliffs, landslide masses are 0.8 km (0.5 mi) in width and have slid down slope 

153 to 213 m (500 to 700 ft) or more. Unit often partly covered by eolian dune sand and 

sand sheet (Qd) deposits. Individual landslides may become unstable during wet conditions 

and creep down slope where unit is underlain by claystone or siltstone bedrock of Kayenta 

Formation or Petrified Forest Member of the Chinle Formation.

Kanab Creek and tributary canyon drainages; consists of partly consolidated masses of 

unsorted rock debris that include detached blocks of Permian strata that have either fallen or 

slide down soft gypsiferous slopes of the Woods Ranch Member of the Toroweap Formation. 

Support sparse growth of sagebrush, cactus, grass, juniper trees, and pinion trees. About 8 to 

60 m (25 to 200 ft) thick

Qgo Old terrace-gravel deposits (Pleistocene)—Gray, light-brown to light-red clay, silt, sand; partly 

consolidated by calcite and gypsum cement in tributaries of Kanab Creek drainages. Locally 

contain lenses of small rounded to subrounded pebble gravel and conglomerate composed of 

white and red sandstone, blue-gray limestone, abundant subrounded or angular white chert, 

and scattered, well rounded, multicolored quartzite pebbles in fine- to coarse-grained gravel 

matrix. Down slope of Vermilion Cliffs, include well rounded quartz, chert, or quartzite 

pebbles of various sizes derived from Shinarump Member of the Chinle Formation. In eastern tributary drainages of Kanab Creek and Muggins Flat west of Kaibab Plateau, include 

occasional well-rounded pebbles and small cobbles of brown, purple, and gray quartzite 

clasts derived from old gravel and sedimentary (Ts) deposits. Unit forms terraces about 9 to 

37 m (30 to 120 ft) above stream channel (Qs) deposits along Kanab Creek and its tributaries and often covered by thin eolian dune sand and sand sheet deposits or lag gravel deposits 

too thin to show at map scale. Support sparse growth of sagebrush, black brush, cactus, and 

grass. About 2 to 6 m (6 to 20 ft) thick

Qao Old alluvial fan deposits (Pleistocene and Pliocene(?))—Red, gray, and brown poorly sorted 

mixture of mud, silt, sand, and gravel derived from the Kaibab Formation on the west side 

of Kaibab Plateau, and angular to subrounded fragments of chert, limestone, and sandstone derived from the Hermit Formation, Coconino Sandstone, Toroweap Formation, and 

Kaibab Formation on east side of Kaibab Plateau. Partly consolidated by calcite and gypsum 

cement. Include scattered, well rounded, brown, black, gray, and purple quartzite pebbles 

and cobbles derived from old stream-channel (Ts) deposits. Stony surface where not covered 

by dune sand and sand sheet (Qd) deposits along base of Vermilion Cliffs; surface often 

exhibits desert pavement composed mainly of black, well rounded pebbles in northwest 
11

quarter of map area. Unit is extensively eroded and contributes material to young alluvial fan 

(Qay) deposits. Oldest deposits form elevated and isolated alluvial fan slopes that overlie 

bedrock strata of the Moenkopi Formation or Kaibab Formation. Unit is about 9 to 37 m (30 

to 120 ft) above young alluvial fan (Qay) deposits in north-central part of map area. Surface 

is consolidated by calcite and gypsum cement forming a rocky calcrete soil zone 0.5 to 1.2 

m (2 to 4 ft) thick; extensively gullied and eroded near fan edges. Cobbles and boulders on 

fan surface are encased in calcite rinds and caliche detritus material common. Intertongue 

with talus and rock fall (Qtr) and landslide (Ql) deposits. Support pinion pine, juniper, and 

oak woodlands with grass, cactus, and sagebrush. Adjacent to or overlapped by young alluvial fan (Qay) and dune sand and sand sheet (Qd) deposits. About 1.5 to 15 (5 to 50 ft) thick

QTg Terrace-gravel deposits (Pleistocene and Pliocene(?))—Gray and light-brown, mud, silt, sand, 

gravel, and cobbles; poorly sorted and partly consolidated by calcite, gypsum, and clay 

cement. Pebbles and boulders are rounded clasts of gray limestone and white chert derived 

from local outcrops of Kaibab Formation (Pkh and Pkf), scattered brown and purple-brown 

quartzite cobbles reworked from old stream-channel (Ts) deposits, and multicolored, mostly 

black well rounded pebbles from Shinarump Member (^cs) of the Chinle Formation. 

Form isolated deposits in upper Kanab Creek and in some tributaries as much as 92 m (300 

ft) above modern drainages, particularly in upper Jumpup Canyon. Deposits are partially 

preserved in abandoned cutoff meander loops or in isolated abandoned point bars in upper 

Kanab Creek canyon. In Jumpup Canyon, a tributary to Kanab Creek, unit fills 170 m (560 

ft) deep ancestral Jumpup Canyon drainage that had previously eroded through Kaibab and 

Toroweap Formations, Coconino Sandstone, and into upper part of Hermit Formation. About 

5 to 8 m (15 to 25 ft) thick; about 170 m (560 ft) thick in Jumpup Canyon

VOLCANIC ROCKS

Heaton Knolls Basalt (Pleistocene)—Herein formally defined as the Heaton Knolls Basalt 

named for Heaton Knolls, the type area that forms a series of linear Pleistocene volcanic 

cinder cones on U.S. Geological Survey 7.5’ Heaton Knolls quadrangle (sec. 3, T. 36 N., 

R. 6 W., and sec. 34, T. 37 N., R. 6 W.), Kanab Plateau, Mohave County, Arizona (fig. 1). 

Heaton Knolls and associated Findlay Knolls volcanoes represent the northeastern extent of 

the Uinkaret Volcanic Field (Billingsley and others, 2001)

Qhkp Pyroclastic deposits (Pleistocene)—Light-red, grayish-black, and brown olivine basalt fragments of mixed cinder, scoria, volcanic bombs, and volcanic ribbons. Forms 91 m (300 ft) 

high Heaton Knolls and Findlay Knolls pyroclastic cones that overlies associated basalt 

flows (Qhkb) that are aligned in north-northwest trend for 2.5 km (1.5 mi) reflecting the 

north-northwest trend of bedrock joints and fractures in southwest corner of map area. 

Unit also partly overlies Harrisburg Member of the Kaibab Formation on northeast flank of 

Heaton Knolls. About 91 m (300 ft) thick

Qhkb Basalt flows—Dark-gray, finely crystalline, alkali olivine basalt. Include fine-grained groundmass of plagioclase, olivine, augite, and glass of which olivine is most common constituent. 

Basalt overlies strata of Harrisburg Member of the Kaibab Formation (Pkh) that straddle 

Toroweap Fault and is overlain by associated pyroclastic (Qhkp) deposits. Lavas flowed 

out in radial pattern from several eruptive centers along north-northwest fissures southeast 

of Toroweap Fault and part of basalt flowed northwestward over the Toroweap Fault scarp. 

Offset of Paleozoic strata along this segment of the Toroweap Fault before eruption of 

Heaton Knolls was offset about 49 m (160 ft) down-to-the-northwest and subsequent offset 

of the Heaton Knolls Basalt is about 12 m (40 ft) down-to-the-northwest for total offset of 

about 60 m (200 ft) near Heaton Knolls. About 2 to 73 m (6 to 240 ft) thick

Qgrb Basalt of Graham Ranch (Pleistocene)—Informally named for Graham Ranch in upper 

Toroweap Valley, the type area (sec. 3, T. 35 N., R. 7 W.), Uinkaret Volcanic Field, Uinkaret 

Plateau, Mohave County, Arizona (Billingsley and others, 2001). Incorrectly named the Sage 

Basalt by Billingsley and Workman (2000) and Billingsley (2000) before it was known that 

the name Sage Basalt was already in use. Includes four unnamed pyroclastic cones and associated basalt flows in upper reaches of Toroweap Valley just southwest of map area. Darkgray finely crystalline to glassy alkali olivine basalt; vuggy with calcite fillings. Includes 

altered olivine in glassy groundmass with abundant olivine phenocrysts 0.25 to 1 mm in 

diameter. K-Ar age, 0.63±0.24 Ma, obtained by Jackson (1990) from basalt of Graham 

Ranch about 3 km (2 mi) south of southwest corner of map area. Lavas emerged from fis-
12

sures in bedrock in Harrisburg Member of the Kaibab Formation and coalesced into radial 

patterns from each fissure. Much of the basalt flowed north and west into upper reaches of 

Toroweap Valley and into southwest corner of map area. The basalt and one associated pyroclastic cone is offset by the Toroweap Fault about 26 m (85 ft) down-to-the-west; underlying 

Kaibab Formation is offset about 67 m (220 ft) down-to-the-west for total offset of 93 m 

(305 ft) just southwest of map area (Billingsley and others, 2001; Billingsley and Wellmeyer, 

2003). Basalt in southwest corner of map area is offset by Toroweap Fault about 26 m (85 ft) 

down-to-the-west; underlying Kaibab Formation is offset about 74 m (240 ft) down-to-thewest for a total offset of about 99 m (325 ft). About 3 to 60 m (10 to 200 ft) thick

SEDIMENTARY ROCKS

Ts Old stream-channel deposits (Pliocene and Miocene(?))—Red, gray, and light-brown, poorly 

sorted, partly consolidated, matrix-supported pebbles and boulders of well-rounded red, 

brown, gray, and purple quartzite or chert up to 48 cm (20 in) in diameter. Matrix consists 

of red, brown, and gray, partly consolidated, coarsely textured arkosic fluvial sandstone 

and siltstone. Form isolated sediments in early Tertiary paleodrainage of ancestral Kanab 

Creek system that eroded into the Moenkopi and Kaibab Formations on the Kanab Plateau. 

Only three deposits are preserved. Two deposits form small reddish hills; Cedar Knoll 

(sec. 4, T. 39 N., R. 1 W.) and Little Cedar Knoll (secs. 13 and 24, T. 39 N. R. 2 W.) about 

17.5 km (11 mi) southeast of Fredonia, Arizona, near Forest Service Highway 212 at about 

1,707 m (5,600 ft) elevation. Deposits are about 304 m (1,000 ft) above present level of 

Kanab Creek 13 km (8 mi) west of Cedar Knoll and Little Cedar Knoll. Unit is currently 

being mined for road gravel at Little Cedar Knoll. A third deposits fills a paleovalley channel eroded 3 to 5 m (10 to 15 ft) deep into Harrisburg Member of the Kaibab Formation 

between Jumpup and Sowats Canyons 3 km (2 mi) northeast of The Gooseneck (sec. 29, 

T. 37 N., R. 2 W.) at elevation 1,828 m (6,000 ft), south-central part of map area. Distance 

between Little Cedar Knoll south to The Gooseneck locality is about 22 km (14 mi); elevation drops about 183 m (600 ft) suggesting a southward paleogradient of about 13 m/km 

(43 ft/mi). Quartzite pebbles, cobbles, and boulders commonly form surface pavement or 

lag gravel in vicinity of Cedar Knoll, Little Cedar Knoll, and near The Gooseneck area. 

Quartzite pebbles and cobbles from Cedar Knoll and Little Cedar Knoll are commonly 

reworked into young, and old alluvial fan (Qay, Qao) deposits toward Kanab Creek and 

into young and old terrace-gravel (Qgy, Qgo) deposits. Quartzite pebbles and cobbles 

form minor patches of desert pavement or lag gravel surfaces down slope of Cedar Knoll 

and Little Cedar Knoll on bedrock surfaces. Quartzite gravels are present in old terracegravel (Qgo) deposits on southeast side of Muggins Flat area indicating that quartz gravels 

were derived from other outcrops in southern Utah. A minor quartzite lag gravel deposit is 

present near U.S. Highway 89A about 8 km (6 mi) northwest of Jacob Lake, Arizona, and 

does not represent a sedimentary deposit, but is indicated on the map to illustrate highest 

elevation 2,300 m (7,545 ft) for this type of lag gravel on Kaibab Plateau. Isolated remnants of quartzite lag gravels are scattered on several ridges on east side of Kaibab Plateau 

near 2,300 m (7,545 ft) elevation in the vicinity of U.S. Highway 89A, but are too thin and 

widely scattered to show on map. Thickest deposits are at Cedar Knoll, about 14 m (45 ft) 

thick and at Little Cedar Knoll, about 20 m (65 ft) thick

Jn Navajo Sandstone (Lower Jurassic)—White, light-red, and yellowish-gray, cliff-forming, 

medium crossbedded to thickly crossbedded, well-sorted, fine- to coarse-grained eolian 

quartz sandstone; lower part is interbedded with dark-red, flat-bedded, coarse-grained sandstone and siltstone of Kayenta Formation. Age determination is by Peterson and Pipiringos 

(1979) and Biek and others (2000). Lower part is commonly red; upper part is commonly 

white but can be either all red or all white. Includes lenses of interbedded dark purple-gray, 

thin-bedded, calcareous sandstone or siliceous limestone formed by freshwater deposits 

within and between sand dunes. High-angle, crossbedded sandstone sets are interbedded 

with low-angle, crossbedded sandstone sets and thin flat-bedded sandstone sets. Unit commonly covered by thin to thick eolian dune sand and sand sheet (Qd) deposits or young 

mixed alluvium and eolian (Qae) deposits. Unit is highly fractured by near vertical northeast-, northwest-, and north-oriented bedrock joints and fractures.

Paria Plateau area; unit is highly fractured by near vertical joints and fractures and a 

few high angle normal faults with northwest strike. Gradational and intertonguing contact 
13

with underlying sandstone facies of Kayenta Formation along Vermilion Cliffs, northeast 

quarter of map area. Unit supports moderate growths of pinion and juniper trees, cliff-rose 

bush, sagebrush, and various high-mountain shrubs. Incomplete section in map area due to 

modern erosion of top part of unit. Thickens north of map to as much as 610 m (2,000 ft). 

About 457 m (1,500 ft) thick in Moccasin Mountains area; about 330 m (1,080 ft) thick in 

Paria Plateau area

Jk Kayenta Formation (Lower Jurassic)—Includes an upper slope-forming siltstone, and a basal 

cliff of the Springdale Sandstone Member. The Springdale Sandstone Member was originally described as the upper member of the underlying Moenave Formation (Averitt and 

others, 1955; Stewart and others, 1972; Sargent and Philpott, 1987; Billingsley and others, 

2004) and has been reassigned to the basal part of the Kayenta Formation on the basis of 

paleontological data and a prominent Jurassic unconformity at the base of the Springdale 

(Blakey, 1994; Marzolf, 1994; Lucas and Tanner, 2006; Tanner and Lucas, 2007; Biek and 

others, 2007). Upper slope-forming unit is dark-red and light reddish-brown, calcareous 

mudstone, siltstone, and cliff-forming sandstone that undergo a facies change eastward from 

mostly slope-forming siltstone and mudstone at Moccasin Mountains to a mostly cliffforming sandstone at Paria Plateau, northeast corner of map area. Age of unit determined 

by Peterson and Pipiringoes (1979) and Biek and others (2000). Along Vermilion Cliffs, 

unit often covered by landslide debris (Ql) and talus and rock fall (Qtr) deposits caused by 

erosion of soft sediments of Kayenta Formation that undercuts resistant overlying cliff of 

Navajo Sandstone allowing large sections of both Navajo Sandstone and upper Kayenta Formation to fail as landslide masses, especially where the bedrock joints and fractures parallel 

Vermilion Cliffs. Kayenta Formation is deposited in river floodplains, river channels, playas, 

and shallow lake environments (Blakey, 1994; Peterson, 1994). Unconformable contact with 

underlying Moenave Formation (Jm). Thickness increases from 143 m (470 ft) at Ed Lamb 

Point westward to nearly 183 m (600 ft) in Potter Canyon southwest of Moccasin Mountains 

and thickness of intertonguing Lamb Point Tongue of Navajo Sandstone decreases in northwest quarter of map area. About 143 to 183 m (470 to 600 ft) thick

Jks Springdale Sandstone Member (Lower Jurassic)—Light-red to reddish-brown, cliff-forming, thin- to thick-bedded sandstone and conglomeratic lenses. Includes low-angle trough 

crossbedded sets of fluvial sandstone that contain dark-red mudstone and siltstone rip-up 

clasts and poorly preserved petrified and carbonized fossil plant remains within crossbedded sets (Peterson and Pipiringos, 1979; Biek and others, 2000). Crossbeds are separated 

by thin-bedded to laminated dark-red siltstone and mudstone beds that locally contain mudstone pellets (Wilson, 1967). Unconformable contact with underlying Dinosaur Canyon 

Member of the Moenave Formation. Unit deposited by northeast to southwest flowing 

streams based on crossbedding studies by Wilson (1967). Thickens north and east of map 

area to about 60 m (200 ft) in Utah. Forms light-red sandstone cliffs that weather dark red 

on east side of House Rock Valley, northeast quarter of map area. Thickness ranges from 

about 37 to 60 m (120 to 200 ft)

Jm Moenave Formation (Lower Jurassic)—Includes, in descending order, the Dinosaur Canyon 

Member and Whitmore Point Member, undivided as redefined by Blakey, 1994; Marzolf, 

1994; Lucas and Tanner, 2006; Tanner and Lucas, 2007; Biek and others, 2007. Originally 

defined as the upper Member of the Moenave Formation by Averitt and others (1955), Stewart and others (1972), and Sargent and Philpott (1987). Age determination after Peterson and 

Pipiringos (1979) and Biek and others (2000)

Dinosaur Canyon Member (Lower Jurassic)—Reddish-brown, slope- and ledge-forming, 

thin-bedded, very fine-grained sandstone and silty sandstone. Gradational contact with 

underlying Whitmore Point Member of the Moenave Formation west of Fredonia area, 

marked by distinct color contrast between blue-green, green, and yellow mudstone and 

siltstone of Whitmore Point Member to reddish-brown siltstone and sandstone of Dinosaur 

Canyon Member; unconformable contact with Owl Rock Member of the Chinle Formation 

in House Rock Valley area where Whitmore Point Member is missing. Unit commonly covered by landslide (Ql) and talus and rock fall (Qtr) deposits. Thickness ranges from about 37 

to 60 m (120 to 200 ft)

Whitmore Point Member (Lower Jurassic)—Type section is near Potter Canyon at southwest point of Moccasin Mountains (elev. 2,013 m [6,603 ft]) at Radio Towers). Named for 

Whitmore Point by Wilson (1967) 5.6 km (3.5 mi) west of Pipe Spring National Monument, 
14

but the name Whitmore Point is not on 1988 USGS 7.5’ Moccasin quadrangle. Composed of 

reddish-brown sandstone and siltstone interbedded with reddish-purple to greenish-gray and 

blue mudstone and claystone, and thin gray dolomitic limestone. Limestone contains small 

reddish-brown chert nodules and poorly preserved fossil algal structures and fish scales and 

bones near Zion National Park north of map area (Biek and others, 2000; 2007). Unconformable contact with underlying Chinle Formation in west half of map area; unit thins eastward 

to less than 12 m (40 ft) at Vermilion Cliffs on east side of House Rock Valley, northeast 

quarter of map area. Thickness ranges from about 12 to 24 m (40 to 80 ft)

Chinle Formation (Upper Triassic)—Includes, in descending order, the Owl Rock Member, 

Petrified Forest Member, and Shinarump Member as used by Stewart and others, 1972; 

Sargent and Philpott, 1987; Biek and others, 2000; 2007. Owl Rock is mapped as part of 

Petrified Forest Member (^cp) below Vermilion Cliffs west of Fredonia, Arizona, because 

it is too thin to show, but is mapped separately near Colorado City, Arizona, and in House 

Rock Valley area

^co Owl Rock Member (Upper Triassic)—Light-red and blueish-white coarse-grained sandstone, 

gray, fine-grained sandstone and siltstone interbedded with thin-bedded, 12 cm to 0.5 m (5 in 

to 2 ft) thick grayish-white siliceous limestone beds. Limestone contains red and white chert 

nodules and lenses. Gradational contact with underlying Petrified Forest Member. About 9 

to 18 m (30 to 60 ft) thick

^cp Petrified Forest Member (Upper Triassic)—Gray, light-purple, blue, to light-red, slopeforming claystone, siltstone, and white, coarse-grained sandstone. Mudstone weathers to 

frothy popcorn surface. Includes petrified wood and calcite nodules. Unit is mostly covered 

by eolian sand sheet (Qes), dune sand and sand sheet (Qd), and young mixed alluvium and 

eolian (Qae) deposits, and young, intermediate, and old alluvial fan (Qay and Qao) deposits. Contact with underlying Shinarump Member is gradational in vertical and lateral extent 

because of intertonguing and phases changes. Thickness ranges from about 183 to 213 m 

(600 to 700 ft)

^cs Shinarump Member (Upper Triassic)—White to yellowish-brown, cliff-forming, thin- to 

thick-bedded, coarse-grained, low-angle crossbedded sandstone, gravel, and conglomeratic 

sandstone. Includes numerous small channel lenses and pockets of small pebble conglomerate composed of well rounded to subrounded, multicolored quartz, quartzite, and black 

chert pebbles in gravely sandstone matrix. Black chert pebbles are dominant clasts. Pebbles 

average about 2.4 to 4.8 cm (1 to 2 in) in diameter and include some well-rounded quartzite 

cobbles as large as 24 cm (10 in) in diameter and numerous angular petrified wood fragments and segments of petrified logs. Black pebbles eroded from Yellowstone Mesa area 

form desert pavement of lag gravel on all alluvial fan and colluvial surfaces down slope of 

mesa, southwest quarter of map area. Unit is source area for well rounded, multicolored 

quartz, quartzite, and chert pebbles in all surficial units below outcrops of the Shinarump 

Member of the Chinle Formation. Weathered sand from the Shinarump Member provides 

source for local eolian sand sheet (Qes) and dune sand and sand sheet (Qd) deposits that are 

transported by southwesterly winds up and over Petrified Forest Member. Unit fills broad 

channels that are as much as 9 m (30 ft) deep and 0.8 to 1.5 km (0.5 to 1 mi) wide eroded 

into underlying upper red member of Moenkopi Formation (^mu). Thickness ranges from 

about 6 to 38 m (20 to 125 ft)

Moenkopi Formation (Middle(?) and Lower Triassic)—Includes, in descending order, upper 

red member, Shnabkaib Member, middle red member, Virgin Limestone Member, lower red 

member and Timpoweap Member, as used by Stewart and others (1972). Boundary between 

Middle(?) and Lower Triassic lies within the upper red member (Morales, 1987). Formation 

as a whole gradually thickens northwesterly across map area. (Timpoweap Member is partly 

redefined because of west to east facies change within map area)

^m Moenkopi Formation, undivided (Middle(?) and Lower Triassic)—Light-red and dark-red, 

slope-forming siltstone and sandstone and minor gray gypsum. Exposed as isolated outcrops 

in House Rock Valley along lower limb of East Kaibab Monocline and on Little Mountain of 

the Kaibab Plateau between the west and east segments of the East Kaibab Monocline. Units 

are likely equivalent to the lower red and middle red members, minus the Virgin Limestone 

Member of the Moenkopi Formation. Units are often capped by older alluvial sediments 

except along State Highway 89A near House Rock Valley. Thickness, about 6 to 14 m (20 to 

45 ft
15

^mu Upper red member (Middle(?) and Lower Triassic)—Light-red and dark-red, slope- and 

ledge-forming sequence of siltstone, sandstone, and conglomerate interbedded with minor 

gray gypsum. Includes small dark-red and brown resistant sandstone cliffs in upper part that 

exhibits minor unconformity at bottom of lowest dark-red sandstone cliff (middle part of 

unit, not shown on map) that may represent boundary between Early and Middle Triassic 

age (Moralas, 1987; Billingsley and Workman, 2000). Gradational contact with underlying 

Shnabkaib Member approximately placed at top of highest thick white siltstone and dolomite bed of Shnabkaib Member. About 49 m (160 ft) thick

^ms Shnabkaib Member (Lower Triassic)—Interbedded and intertonguing, white to light-gray, 

laminated to thinly bedded, slope-forming, aphanitic dolomite and light-gray, calcareous 

siltstone and silty gypsum. Includes some light-red, thin-bedded mudstone, siltstone, and 

sandstone in lower and upper part. Gradational contact with underlying middle red member; 

map contact placed at lowest thick white or light-gray calcareous siltstone and dolomite bed 

of the Shnabkaib Member. Unit thickness is variable within map area because of approximate upper and lower contacts; unit thickens northwestward and thins eastward and southeastward. Thickness ranges from about 27 to 114 m (90 to 375 ft)

^mm Middle red member (Lower Triassic)—Reddish-brown, thin-bedded to laminated, slopeforming gypsiferous siltstone and sandstone, white and gray gypsum, minor white platy 

dolomite, green siltstone, and gray-green to red gypsiferous mudstone. Includes abundant 

thin veinlets and stringers of gypsum deposited in fractures and cracks throughout unit. 

Includes minor beds of white laminated dolomite, green siltstone, and gray-green to red 

gypsiferous mudstone. Mud cracks and ripple marks common throughout. Gradational contact with underlying Virgin Limestone Member at top of highest light-gray limestone bed of 

Virgin Limestone Member in Fredonia and Muggins Flat, north-central part of map; gradational lower contact with lower red member in House Rock Valley marked by color contrast 

between dark-red lower red member and light-red middle red member, northeast quarter of 

map area. Unit gradually thickens northeasterly across map area. Thickness ranges from 

about 55 to 92 m (180 to 300 ft)

^mv Virgin Limestone Member (Lower Triassic)—Includes two light-gray, thin-bedded to laminated, ledge-forming limestone beds [ 0.3 to 1 m (1 to 3 ft)] thick, separated by pale-yellow, 

light-red, and blue-gray, thin-bedded slope-forming gypsiferous siltstone that makes up 

bulk of unit. Lower limestone bed contains star-shaped crinoid plates and poorly preserved 

Composita brachiopods in upper part 14.5 km (9 mi) east of map area. Lower limestone bed 

thickens and thins due to channel fill cut as much as 1.3 m (4 ft) deep into underlying darkred siltstone and sandstone of lower red member of the Moenkopi Formation south of Fredonia, Arizona, near Kanab Creek. Upper limestone bed contains abundant fossil algae and 

pinches out a few kilometers east of Fredonia, Arizona; whereas lower limestone bed thins 

eastward to western edge of Kaibab Plateau and is not present in House Rock Valley east of 

Kaibab Plateau. Unit as a whole thickens west and north, thins south and east of Fredonia, 

Arizona. Forms small mesas near Kanab Creek and thin white ledges in Muggins Flat area, 

north-central part of map. Thickness ranges from 0 to 25 m (0 to 80 ft)

^ml Lower red member (Lower Triassic)—Dark-red, slope-forming, thin-bedded, fine-grained, 

gypsiferous, sandy siltstone, sandstone, and pale-yellow to gray laminated silty gypsum. 

Ledge-forming light red sandstone beds become more numerous in upper reaches of Kanab 

Creek and Fredonia areas. Gypsum, siltstone, and sandstone in lower part are derived from 

erosion of Harrisburg Member of the Kaibab Formation. Includes prominent ledge-forming, 

red-gray to light purple-red, coarse-grained to conglomeratic, thin-bedded, low-angle crossbedded calcareous sandstone marker bed, 2 to 4 m (6 to 13 ft) thick in lower part that forms 

resistant sandstone surface of Kanab Plateau west of Kanab Creek and south of Pipe Spring 

National Monument area. Marker bed includes raindrop impressions and rare carbonaceous 

plant fossils in Short Creek 5 km (3 mi) west of map area (Billingsley and Workman 2000; 

Billingsley and others, 2002). Interbedded or gradational contact with underlying limestone, 

sandstone, or conglomerate of the Timpoweap Member, otherwise unconformable contact 

with Harrisburg Member of the Kaibab Formation. Locally fills paleovalleys eroded into 

Harrisburg Member of the Kaibab Formation or pinches out onto paleohills of the Kaibab in 

southwest quarter of map area. Thickness ranges from about 36 to 76 m (120 to 250 ft)

^mt Timpoweap Member (Lower Triassic)—Includes an upper and lower part: Upper part 

consists of gray to yellow-gray, cliff-forming, fine-grained, thick-bedded sandy limestone 
16

as much as 3 m (10 ft) thick. Locally includes gray, interbedded, coarse-grained, low-angle 

crossbedded calcareous sandstone containing small, rounded chert pebbles. Gradationally 

overlies conglomerate or thin-bedded sandy yellowish limestone of lower part except where 

unit unconformably overlies Harrisburg Member of the Kaibab Formation. Unit is difficult to 

distinguish from Harrisburg Member of the Kaibab Formation at north edge and is mapped 

as Harrisburg Member of the Kaibab Formation in that area, whereas adjoining geologic 

map of Kaibab Plateau in Utah is mapped, in part, as Timpoweap Member of the Moenkopi 

Formation (Sable and Hereford, 2004).

Lower part consists mainly of cliff- and slope-forming, gray, dark-gray, white and 

reddish-brown chert conglomerate in gray gravel sandstone matrix. Includes yellow, reddishbrown, interbedded, calcareous, thin-bedded, cross-stratified, sandstone, siltstone, gray 

gypsiferous siltstone, and yellow to gray, thin-bedded sandy limestone. Conglomerate clasts 

are subangular to rounded pebbles and cobbles of limestone and chert derived from erosion 

of nearby and underlying Kaibab Formation. Conglomerate is pebble-supported in most 

outcrops with pebbles compressed into one another; where matrix-supported, matrix is gray 

limestone and coarse-grained cherty sandstone. Conglomerate clasts are as much as 30 cm 

(12 in) in diameter. Imbrication of pebbles in conglomerate indicates northeasterly flow 

of depositing streams. Unconformable contact with underlying Harrisburg Member of the 

Kaibab Formation in paleovalleys. Rock Canyon Conglomerate was proposed and abandoned by Gregory (1948, 1952), used by Nielsen and Johnson (1979), and Nielsen (1986, 

1991). Timpoweap Member of the Moenkopi Formation is used in this report as used by 

Stewart and others (1972) and Sable and Hereford (2004). Unit gradually thins west to east 

across map area and is largely confined to shallow wide paleovalleys in upper reaches of 

Kanab Creek and Muggins Flat area. Thickness ranges from 0 to 30 m (0 to 100 ft)

Kaibab Formation (Lower Permian)— Includes, in descending order, Harrisburg and Fossil 

Mountain Members as defined by Sorauf and Billingsley (1991)

Pkh Harrisburg Member (Lower Permian)—Includes an upper, middle, and lower part in the 

western two-thirds of map area; due to facies changes, all three parts merge into one sandy 

limestone lithology eastward. In western two-thirds of map area, upper part consists of 

slope-forming, red and gray, interbedded gypsiferous siltstone, sandstone, gray gypsum, 

and thin-bedded gray limestone. Uppermost pale-yellow or light-gray, fossiliferous (mollusks and algae) sandy limestone, 1 to 2 m (2 to 6 ft) thick weathers yellowish-gray, brown, 

and reddish-gray; forms resistant caprock of Harrisburg Member in south-central half of 

map area around Kanab Creek drainages. Gradational contact with middle part. Unit is very 

similar in content, color, and weathering characteristics as limestone of the Timpoweap 

Member of the Moenkopi Formation. Some Timpoweap Member limestone beds contain 

small well-rounded chert or quartzite pebbles, whereas Harrisburg Member upper limestone 

beds contain scattered angular white chert fragments.

Middle part consists of two cliff-forming limestone beds that together gradually 

increases in thickness eastward across map area from 6 m (20 ft) to as much as 14 m (46 

ft). Upper limestone bed is gray, thin-bedded, irregularly bedded cherty limestone that 

weathers dark brown or black. Lower limestone bed is light-gray, light-brown, and white, 

thick-bedded, sandy limestone separated from upper cherty limestone by about 3 m (10 ft) 

of thin-bedded gypsiferous sandstone and siltstone that thins eastward and northeastward to 

less than 1 m (3 ft). Both limestone beds and intervening gypsiferous sandstone and siltstone 

beds increase and decrease in thickness at expense of each other. Both limestone beds merge 

to form ledges and cliffs in small tributary canyons of the northern Kaibab Plateau and is difficult to distinguish from cherty limestone cliffs and ledges of the Fossil Mountain Member 

of the Kaibab Formation. Erosional unconformity separates middle part of Harrisburg 

Member from lower part where the lower sandy limestone bed fills erosion channels that are 

as much as 4 m (14 ft) deep in west half of map area and are less than 1 m (3 ft) deep in east 

half.

Lower part is slope-forming, light-red, fine- to medium-grained gypsiferous siltstone 

and sandstone interbedded with gray, medium-grained, thin-bedded limestone and gray to 

white, massive-bedded gypsum. West of Kaibab Plateau, lower part maintains uniform thickness of about 40 m (130 ft) and thins eastward and southeastward across Kaibab Plateau. 

Dissolution of gypsum in lower part has locally distorted limestone beds of middle part 

causing them to slump or bend into local tributary drainages of Kanab Creek area in west 
17

half of map area. Gradational contact between slope-forming Harrisburg Member and underlying cliff-forming Fossil Mountain Member of the Kaibab Formation is marked at top of 

upper cherty limestone bed of Fossil Mountain Member. Harrisburg Member gradually thins 

eastward across map area and undergoes an eastward facies change to mostly white and gray 

sandy limestone and calcareous sandstone. Thickness ranges from about 30 to 52 m (100 to 

170 ft)

Pkf Fossil Mountain Member (Lower Permian)—Light-gray, fine- to medium-grained, thin-bedded, fossiliferous, cliff-forming, sandy, cherty limestone. Unit characterized by thin bedded, 

white chert beds and chert nodules in cliff-forming sandy limestone. Weathered chert bands 

are stained black or dark gray. Unconformable contact with underlying Woods Ranch 

Member of the Toroweap Formation is caused by combination of dissolution of gypsum in 

the Woods Ranch Member and channel erosion with relief as much as 2 to 4.5 m (6 to 15 ft). 

Thickness ranges from about 61 to 80 m (200 to 265 ft)

Toroweap Formation (Lower Permian)—Includes, in descending order, Woods Ranch Member, 

Brady Canyon Member, and Seligman Members, undivided as defined by Sorauf and 

Billingsley (1991)

Ptw Woods Ranch Member (Lower Permian)—Gray, slope-forming gypsiferous siltstone and 

pale-red silty sandstone interbedded with white, laminated gypsum. Beds are locally distorted because of dissolution of gypsum in upper part. At higher elevations of the Kaibab 

Plateau, dissolution of gypsum produces large sinkholes into overlying Kaibab Formation. 

Gradational contact with underlying Brady Canyon Member marked at top of limestone cliff 

of Brady Canyon unit. Variable thickness due to dissolution of gypsum beds, about 49 to 81 

m (160 to 265 ft)

Ptb Brady Canyon and Seligman Members, undivided (Lower Permian)—Units are mapped 

as one because the Seligman Member is too thin to show at map scale in most areas. Brady 

Canyon Member; gray, cliff-forming, medium-bedded, fine- to coarse-grained, fetid, fossiliferous limestone; weathers dark gray. Includes thin-bedded dolomite in upper and lower 

parts. Limestone beds average about 0.3 to 1m (1 to 3 ft) thick and contain chert lenses and 

nodules. Limestone beds undergo eastward facies change from limestone to sandy limestone 

to calcareous sandstone and become less fossiliferous. Unit is about 55 m (180 ft) thick 

in Kanab Creek area, thins eastward and northward to about 40 m (130 ft) in House Rock 

Valley. Gradational contact between cliff-forming Brady Canyon and slope-forming Seligman Members.

Seligman Member; gray to purple-red, slope-forming, thin-bedded dolomite and limestone beds interbedded with reddish gypsiferous siltstone and sandstone and gray gypsum. 

Unconformable contact with underlying Coconino Sandstone in southern two-thirds of map 

area and with underlying Hermit Formation in northern third; mostly flat plannar contact in 

most areas; erosional relief less than 1 m (3 ft). Contact mostly covered by talus and alluvial 

deposits in Kanab Creek drainage area. Seligman Member thins eastward from about 22 m 

(70 ft) in Kanab Creek area to less than 6 m (20 ft) on east side of Kaibab Plateau. Brady 

Canyon and Seligman Members combined gradually thin eastward across map area from 

about 67 to 40 m (220 to 130 ft) thick

Pc Coconino Sandstone (Lower Permian)—Light-brown, yellow-red, and tan, cliff-forming, 

fine-grained, well-sorted, cross-stratified quartz sandstone. Contains large scale, high-angle, 

planar crossbedded sandstone sets that average about 6 m (20 ft) thick or less. Lower 1.5 

m (5 ft) is thin-bedded, partly calcareous, flat-bedded sandstone of Seligman Member of 

the Toroweap Formation that forms a sharp planar unconformable contact with underlying 

Hermit Formation with relief generally less than 1 m (3 ft). Unit gradually thickens from 

northwest to southeast in southeastern two-thirds of map area; unit pinches out in northwest 

and north-central part of map where Toroweap Formation (Ptb) overlies the Hermit Formation. Thickness ranges from about 0 to 52 m (0 to 170 ft)

Ph Hermit Formation (Lower Permian)—Red, slope-forming, fine-grained, thin-bedded, siltstone and sandstone. Upper part contains red, massive, low-angle crossbedded calcareous 

sandstone interbedded with siltstone where sandstone beds gradually thin or pinch out from 

north to south across map area. Dark-red crumbly siltstone beds fill shallow erosion channels 

and form recesses between thick, light-red sandstone beds in upper part; lower part contains more siltstone. Unit locally contains poorly preserved plant fossils within channel-fill 

siltstone deposits in lower part. Sandstone bleaches to yellowish-white in upper 1 to 3.5 m (3 
18

to 12 ft) of contact with overlying Coconino Sandstone or Toroweap Formation. Base of unit 

unconformably overlies Esplanade Sandstone (Pe) with erosion channels generally less than 

3 m (10 ft) deep. Just south of map area, some erosion channels are as much as 40 m (130 

ft) wide and 9 m (30 ft) deep (Billingsley, 2000). Unit thins southward and southeastward of 

map area and thickens westward and northward. In southwest quarter of map area, lower 18 

m (60 ft) of unit is equivalent to upper slope unit of Esplanade Sandstone of McKee (1982), 

(Billingsley, 2000), but is included as part of Hermit Formation in this map area because 

upper Esplanade Sandstone units thin northward and pinch out along and in south edge of 

map area making this upper slope unit of the Esplanade Sandstone indistinguishable from 

the Hermit Formation slope. Hermit Formation gradually thins eastward and southward, 

thickens westward and northward across subsurface of map area. Approximate map contact between the Hermit Formation and Esplanade Sandstone at lowest red siltstone bed of 

Hermit Formation on surface of light-red, thick bedded sandstone of Esplanade Sandstone. 

Thickness ranges from about 150 to 340 m (500 to 800 ft)

Supai Group (Lower Permian, Upper, Middle, and Lower Pennsylvanian, and Upper 

Mississippian)—Includes, in descending order, Esplanade Sandstone (Lower Permian); and 

Wescogame Formation (Upper Pennsylvanian), Manakacha Formation (Middle Pennsylvanian), and Watahomigi Formation (Lower Pennsylvanian and Upper Mississippian), undivided, as defined by McKee (1975; 1982). Upper Mississippian and Lower Pennsylvanian 

age for Watahomigi Formation is defined by Martin and Barrick (1999)

Pe Esplanade Sandstone (Lower Permian)—Light-red, white, and pinkish-gray, cliff-forming, 

fine- to medium-grained, medium- to thick-bedded [1 to 3 m (3 to 10 ft)], well sorted calcareous sandstone. Includes interbedded dark-red, thin-bedded, crumbly recesses of slopeforming siltstone between sandstone beds in upper and lower part. Crossbeds are small- to 

medium-scale, planar low-angle and high-angle sets 3 to 12 m (10 to 40 ft) thick. Unconformable contact with underlying Wescogame Formation is marked by erosion channels as 

deep as 15 m (50 ft) filled with calcareous sandstone and limestone conglomerate; average 

channel depth about 11 m (35 ft) in lower reaches of Kanab Creek area. About 122 to 137 m 

(400 to 450 ft) thick

*Ms Wescogame Formation (Upper Pennsylvanian), Manakacha Formation (Middle Pennsylvanian), and Watahomigi Formation (Lower Pennsylvanian and Upper Mississippian), 

undivided—As defined by McKee (1982). Watahomigi Formation is Upper Mississippian 

and Lower Pennsylvanian age as defined by Martin and Barrick (1999).

Wescogame Formation is light-red, pale-yellow, and light-gray upper slope and lower 

cliff unit composed of fine- to coarse-grained gray sandstone, dolomitic sandstone, siltstone, 

mudstone, and conglomerate. Upper slope is composed mostly of light-red, fine-grained 

siltstone, mudstone, and interbedded light-red sandstone. Lower cliff is composed mainly of 

light-red to gray, high-angle, large- and medium-scale, tabular-planar, crossbedded sandstone sets as much as 12 m (40 ft) thick. Includes interbedded dark-red, thin-bedded siltstone 

in upper part. Unconformable contact with underlying Manakacha Formation marked by 

erosion channels as deep as 9 m (30 ft). Erosional channels commonly filled with limestone/

chert pebble conglomerate. About 40 m (130 ft) thick.

Manakacha Formation consists of light-red, white, and gray upper slope and lower 

cliff of sandstone, calcareous sandstone, dark-red siltstone, and gray limestone. Upper slope 

is composed mainly of shaly siltstone and mudstone with minor amounts of interbedded, 

thin-bedded limestone and sandstone. Carbonate content in upper slope increases westward 

to form numerous ledge-forming, thin- and medium-bedded sandy limestone beds west of 

map area. Upper slope is about 18 m (60 ft) thick. Lower cliff unit is predominantly a crossbedded, calcareous sandstone, dolomite, and sandy limestone, about 30 m (100 ft) thick. 

Unconformable erosional contact between Manakacha and underlying Watahomigi Formations marked at base of lower sandstone cliff of Manakacha Formation. Erosional relief is 

generally less than 1 m (3 ft), and contact is mostly a wavy unconformable surface. About 

55 m (180 ft) thick.

Watahomigi Formation consists of gray and purplish-red, slope-forming limestone, 

siltstone, mudstone, and conglomerate. Forms an upper ledge and slope unit and lower cliff 

unit. Upper ledge and slope unit is sequence of alternating gray, thin-bedded cherty limestone ledges and purplish-gray siltstone and mudstone slopes; limestone beds contain Early 

Pennsylvanian conodont fossils (Martin and Barrick, 1999); red chert lenses and nodules 
19

are common in limestone beds. Includes limestone chert pebble conglomerate at base; upper 

ledge and slope unit locally contains Pennsylvanian fossils and averages about 21 m (70 

ft) thick. Lower cliff unit consists of a basal, purplish-red mudstone and siltstone overlain 

by thin-bedded aphanitic to granular limestone cliff with red chert nodules and chert veins. 

About 30 to 40 m (100 to 130 ft) thick

Mr Redwall Limestone (Upper and Lower Mississippian)—Includes, in descending order, the 

Horseshoe Mesa, Mooney Falls, Thunder Springs, and Whitmore Wash Members as defined 

by McKee (1963), and McKee and Gutschick (1969).

Horseshoe Mesa Member consists of light olive-gray, ledge- and cliff-forming, thinbedded, fine-grained limestone. Weathers to receding ledges. Gradational and disconformable contact with underlying massive-bedded limestone of Mooney Falls Member marked 

by thin-bedded, platy limestone beds that form 1 to 3 m (3 to 10 ft) thick recess at base 

of member near top of Redwall Limestone cliff. Fossils are not common except locally. 

Includes distinctive ripple laminated limestone beds and oolitic limestone and some chert. 

Thickness ranges from about 14 to 30 m (50 to 100 ft).

Mooney Falls Member consists of light-gray, cliff-forming, fine- to coarse-grained, 

thick-bedded to very thick bedded (1.5 to 6 m [4 to 20 ft]) fossiliferous limestone. Includes 

dark-gray dolomite beds in lower part; oolitic limestone and chert beds are restricted to the 

upper part. Contains large-scale, tabular and planar, low-angle cross-stratified limestone beds 

in upper third of unit. Limestone weathers dark gray, chert beds weather black. Disconformable contact with underlying Thunder Springs Member distinguished mainly by lithology; 

massive bedded gray limestone of Mooney Falls Member overlies thin-bedded dark-gray to 

brown dolomite and chert beds of Thunder Springs Member. About 122 m (400 ft) thick.

Thunder Springs Member consists of about 50 percent white, cliff-forming, fossiliferous, thin-bedded, alternating bands of white chert, and about 50 percent brownish-gray, 

thin-bedded (2.4 to 12 cm [1 to 5 in]), finely crystalline dolomite and fine- to coarse-grained 

limestone. Weathers into distinctive prominent band of black and light-brown bands on cliff 

face. Disconformable planar contact with underlying Whitmore Wash Member distinguished 

by distinct lack of chert in Whitmore Wash Member. About 30 to 46 m (100 to 150 ft) thick.

Whitmore Wash Member consists of yellowish-gray and brownish-gray, cliff-forming, 

thick-bedded, fine-grained dolomite that is partly exposed within map area in lower reach 

of Kanab Creek. Weathers dark gray. West and north of map area, unit is mostly limestone. 

Unconformable contact with underlying Temple Butte Formation marked by erosional 

channels of low relief, about 1.5 to 3 m (5 to 10 ft) deep just south of map area (Billingsley, 

2000). About 24.5 m (80 ft) thick

UNITS SHOWN ONLY IN CROSS SECTION

[Based on exposures in Grand Canyon (Billingsley, 2000; Billingsley and Workman, 2000; Billingsley and 

Wellmeyer, 2003)]

Dtb Temple Butte Formation (Upper and Middle Devonian)—Purple, reddish-purple, dark-gray, 

and light-gray, ledge-forming dolomite, sandy dolomite, sandstone, mudstone, and limestone 

as defined by Beus (2003). The unconformity at base of Temple Butte Formation represents 

a major stratigraphic break in Paleozoic rock record in Grand Canyon that includes part of 

the Late Cambrian, all of the Ordovician and Silurian, and most of the Early and Middle 

Devonian, representing about 100 m.y. Dark-gray Devonian strata are distinguished from 

underlying light-gray Cambrian rocks by color contrast. Unit thickens westward, thins 

southward. Thickness ranges from about 24 to 106 m (80 to 350 ft)

Tonto Group (Middle and Lower(?) Cambrian)—Includes, in descending order, Muav Limestone, Bright Angel Shale, and Tapeats Sandstone as defined by Noble (1922), modified 

by McKee and Resser (1945); recognized on the basis of distinct lithology. All limestone 

and dolomite in the Cambrian sequence belong to the Muav Limestone; shale and siltstone 

belong to the Bright Angel Shale; and sandstone and conglomerate belong to the Tapeats 

Sandstone. The Tonto Group strata unconformably overlie Statherian Paleoproterozoic 

(1.7 to 1.6 billion years) igneous and metamorphic rocks; this hiatus is known as the Great 

Unconformity. See Rose (2003) for a revised age and depositional history of Cambrian rocks 

in the Grand Canyon

_m Muav Limestone (Middle Cambrian)—Dark-gray, light-gray, brown, and orange-red, cliffforming limestone, dolomite, and calcareous mudstone. Contact with underlying Bright 
20

Angel Shale is gradational and lithology dependent and marked at base of lowest prominent 

cliff-forming limestone. Muav Limestone generally thins from west to east in subsurface of 

map area. Intertonguing and facies change relations between Muav Limestone and Bright 

Angel Shale produce variable thickness trends. Thickness ranges from about 24 to 213 m 

(80 to 700 ft)

_ba Bright Angel Shale (Middle Cambrian)—Green and purple-red, slope-forming siltstone, shale, 

and reddish-brown to brown sandstone. Includes the ledge-forming reddish-brown sandstone 

member of McKee and Resser (1945). Consists of green and purplish-red, fine-grained, 

micaceous, ripple-laminated, fossiliferous shale and siltstone; dark-green, medium- to 

coarse-grained, thin-bedded, glauconitic sandstone; and interbedded purplish-red and brown, 

thin-bedded, fine- to coarse-grained, ripple laminated sandstone. Contact with Tapeats Sandstone is approximately marked at top of vertical transition zone from predominantly green 

shale and siltstone to predominantly brown sandstone above Tapeats Sandstone cliff. About 

60 to 90 m (200 to 300 ft) thick

_t Tapeats Sandstone (Middle and Lower(?) Cambrian)—Brown and reddish-brown, cliff-forming, coarse-grained sandstone and conglomerate. Unconformable contact with underlying 

Statherian Paleoproterozoic surface forms the Great Unconformity. Tapeats Sandstone fills 

lowland areas and thins across or pinches out against Proterozoic highlands. Variable thickness from 0 to 60 m (0 to 200 ft)

PROTEROZOIC CRYSTALLINE ROCKS

The intrusive and metamorphic rocks are as defined by Ilg and others (1996), Hawkins and others (1996), 

and Karlstrom and others (2003). There is at least a 50 percent chance that younger Proterozoic sedimentary rocks of the Grand Canyon Supergroup exposed in the eastern Grand Canyon area (Huntoon and 

others, 1996) may be present in the eastern subsurface of this map area.

Xu Crystalline rocks, undivided (Statherian, Paleoproterozoic)—Undivided intrusive and metamorphic rocks. Includes granite plutons, stocks, and pegmatite and aplite dikes, gabbro-diorite, and granodiorite rocks, garnet schist, hornblende-biotite schist, orthoamphibole-bearing 

schist and gneiss, and probable felsic metavolcanic rocks

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