Geologic map of the Tuba City 30'x 60'quadrangle, Coconino

2012

U.S. Department of the Interior

U.S. Geological Survey

Prepared in cooperation with the National Park Service, the U.S. Forest Service, the Navajo Nation, and

the Hopi Tribe

Geologic Map of the Tuba City 30’ x 60’ Quadrangle, Coconino

County, Northern Arizona

By George H. Billingsley, Philip W. Stoffer, and Susan S. Priest

Pamphlet to accompany

Scientific Investigations Map 3227

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Contents

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

Geography .............................................................................................................................................1

Previous Work ...............................................................................................................................................1

Mapping Methods .........................................................................................................................................2

Geologic Setting ............................................................................................................................................2

Precambrian Rocks ......................................................................................................................................3

Paleoproterozoic ..................................................................................................................................3

Mesoproterozoic ..................................................................................................................................3

Neoproterozoic .....................................................................................................................................3

Paleozoic Rocks ............................................................................................................................................4

Cambrian ...............................................................................................................................................4

Devonian ................................................................................................................................................4

Mississippian ........................................................................................................................................4

Pennsylvanian ......................................................................................................................................4

Permian ..................................................................................................................................................4

Mesozoic Rocks ............................................................................................................................................5

Moenkopi Formation ............................................................................................................................5

Chinle Formation ..................................................................................................................................6

Moenave Formation .............................................................................................................................6

Kayenta Formation ...............................................................................................................................7

Kayenta Formation-Navajo Sandstone Transition Zone ................................................................7

Navajo Sandstone ................................................................................................................................7

Carmel Formation .................................................................................................................................7

Entrada Sandstone-Cow Springs Sandstone ..................................................................................7

Dakota Sandstone ................................................................................................................................8

Mancos Shale .......................................................................................................................................8

Cenozoic Volcanic Rocks ............................................................................................................................8

Pliocene-Pleistocene Gravel Deposits ............................................................................................8

Quaternary Surficial Deposits .....................................................................................................................8

Surficial Mapping Technique .............................................................................................................8

Local Surficial Deposits ......................................................................................................................9

Structural Geology ........................................................................................................................................9

Acknowledgments ......................................................................................................................................11

Description of Map Units ...........................................................................................................................11

Surficial Deposits ...............................................................................................................................11

Volcanic Rocks ...................................................................................................................................16

Sedimentary Rocks ............................................................................................................................16

Neoproterozoic Rocks ......................................................................................................................24

Mesoproterozoic Rocks ....................................................................................................................26

Paleoproterozoic Rocks ....................................................................................................................27

References Cited .........................................................................................................................................27

Conversion Factors

Inch/Pound to SI

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

mile, nautical (nmi)

1.852 kilometer (km)

yard (yd)

0.9144 meter (m)

Area

acre 4,047 square meter (m

)

acre 0.4047 hectare (ha)

acre 0.4047 square hectometer (hm

)

acre 0.004047 square kilometer (km

)

square foot (ft

) 929.0 square centimeter (cm

)

square inch (in

) 0.09290 square meter (m

)

square foot (ft

) 6.452 square centimeter (cm

)

section (640 acres or 1 square mile) 259.0 square hectometer (hm

)

square mile (mi

) 259.0 hectare (ha)

square mile (mi

) 2.590 square kilometer (km

)

Introduction

This geologic map is a cooperative effort of the U.S.

Geological Survey (USGS) in collaboration with the National

Park Service, the U.S. Forest Service, the Navajo Nation, and

the Hopi Tribe to provide regional geologic information for

resource management ofcials and for visitor information

services of the National Park Service, the U.S. Forest Service,

the Navajo Nation, and the Hopi Tribe. Funding for the map

was provided by the U.S. Geological Survey National Geologic

Mapping Program, Reston, Virginia.

Field work on the Navajo Nation lands was conducted

under a permit from the Navajo Nation Minerals Department.

Anyone wishing to conduct geologic investigations on the

Navajo Nation lands must rst apply for, and receive, a permit

from the Navajo Nation Minerals Department, P.O. Box 1910,

Window Rock, Arizona 86515, (928) 871-6587. Permission to

conduct eld work on portions of the Hopi Moenkopi District

at the south-central edge of the map was granted by the Depart-

ment of Natural Resources of the Hopi Tribe. Any person wish-

ing to conduct geological investigations within Hopi lands must

obtain permission from the Department of Natural Resources,

The Hopi Tribe, P.O. Box 123, Kykotsmovi, Arizona 86039,

(928) 734-3601.

The Tuba City 30' x 60' quadrangle encompasses approxi-

mately 5,018 km

(1,920 mi

) within Coconino County,

northern Arizona, and is bounded by lat 36° to 36°30' N., long

111° to 112° W. The map area is within the southern Colorado

Plateaus geologic province (herein Colorado Plateau). The map

area encompasses the southwest portion of the Navajo Nation,

part of the Hopi lands, and eastern Grand Canyon National

Park, where new geologic mapping is needed for geologic con-

nectivity to the regional geologic framework. The Tuba City

30′ x 60′ quadrangle will benet local, federal, state, Navajo,

and Hopi resource managers who direct environmental and land

management programs such as range management, biological

studies, ood control, water resource investigations, and natural

hazard assessments associated with sand dune mobility. Our

geologic information will support ongoing and future geologic

investigations and associated studies within the region.

The west half of the Tuba City quadrangle was mapped

primarily by George Billingsley and the east half was mapped

primarily by Phil Stoffer. Mapping was compiled at 1:24,000-

scale using a combination of aerial photography, digital ortho-

photos, and eld checking. The mapped area is presented as two

1:50,000-scale views, west half (sheet 1) and east half (sheet 2),

with related information on a third sheet (sheet 3). This pam-

phlet contains a description of map units applicable to the entire

Tuba City quadrangle.

Geography

The Tuba City quadrangle is locally subdivided into eight

physiographic areas: the Grand Canyon (which includes the

Little Colorado River Gorge and Marble Canyon), Walhalla

Plateau, Kaibab Plateau, the southern part of House Rock

Valley (west of Marble Canyon), Coconino Plateau, Moenkopi

Plateau, Kaibito Plateau, and Marble Plateau (east of Marble

Canyon) as dened by Billingsley and others, 1997 (g. 1,

sheet 3). Shinumo Altar, Blue Moon Bench, Limestone Ridge,

Bodaway Mesa, Yon Dot Mountains, Red Point Hills, and the

Painted Desert are collectively referred to as part of the Marble

Plateau. Landmark features of the Kaibito Plateau east of the

Echo Cliffs include Preston Mesa, Middle Mesa, a portion of

White Mesa, Tuba Butte, and Wildcat Peak. The Moenkopi

Plateau in the southeast corner of the map area includes Coal

Mine Mesa. Coal Mine Canyon erodes into Coal Mine Mesa

and is a tributary to Moenkopi Wash. Elevation ranges from

about 2,480 ft (756 m) at the Colorado River in Grand Canyon,

southwest corner of map, to about 8,860 ft (2,700 m) on the

Kaibab Plateau, north rim of Grand Canyon near Point Imperial,

west-central edge of map.

Settlements within the Tuba City quadrangle area include

Tuba City, Moenkopi, Moenave, The Gap, and Cedar Ridge.

Not shown are the small communities of Coal Mine Canyon

about 1 mi (1.6 km) south of the southeast corner of the map

and Tonalea about 1.6 km (1 mi) northeast of the northeast

corner of the map.

U.S. Highway 160 and State Highway 264 provide access

to the eastern half of the map area, U.S. Highway 89 to the cen-

tral part, and State Highway 64 to the Grand Canyon and south-

west corner. Roads and trails within the Kaibab National Forest

are maintained by the National Forest Service, and roads in the

Grand Canyon National Game Preserve of House Rock Valley

area are maintained by the National Forest Service and the

Grand Canyon Trust. Roads on Walhalla Plateau are maintained

by Grand Canyon National Park. Unimproved dirt roads provide

access to remote parts of the Navajo Nation Reservation. Some

are maintained by the Navajo Nation Roads Department in

Window Rock, Arizona, and others are maintained locally by

chapter governments (Cameron, Coalmine Canyon, Tuba City,

Bodaway/Gap, Kaibito, and Tonalea Chapters). Four-wheel

drive vehicles are recommended for winter driving on dirt roads

of the Navajo Nation areas north and west of Tuba City due

to mud and snow. Four-wheel drive is also recommended for

all unmaintained dirt roads north and east of Tuba City due to

sandy conditions. Extra water and food is highly recommended

for travel in this region.

The Kaibab National Forest and Grand Canyon National

Park manage lands in the western third of the quadrangle. The

Navajo Nation and local Navajo chapter governments manage

lands in the eastern two-thirds of the area. The Hopi Tribe and

Moenkopi Village manage the Hopi Moenkopi District in the

south-central map area.

Previous Work

An early reconnaissance photogeologic map that includes

the eastern two-thirds of the Tuba City quadrangle was com-

piled by Cooley and others (1969, map 1 of 9) for the Navajo

and Hopi Reservations of Arizona, New Mexico, and Utah.

These maps were not registered to a base because a topographic

base larger than 1:250,000-scale did not exist. Wilson and

others (1969) compiled an early reconnaissance geologic map

of Coconino County and the State of Arizona (1:500,000-scale)

using the work of Cooley and others (1969). A geologic map

of the Marble Canyon 1° x 2° quadrangle (1:250,000-scale)

covers the Tuba City quadrangle (Haynes and Hackman, 1978).

Huntoon and others (1996) produced a geologic map of the

eastern part of Grand Canyon National Park and vicinity, and

Timmons and others (2007) most recently produced a geologic

map of the Butte Fault/East Kaibab Monocline area in eastern

Grand Canyon. The Precambrian bedrock geology of Timmons

and others (2007) in Grand Canyon is reproduced on this map.

The Quaternary geology of all previous maps has been modied

and signicantly updated to match adjoining 30′ x 60′ quad-

rangle maps, which include Valle (Billingsley and others, 2006),

Cameron (Billingsley and others, 2007), and Fredonia (Billing-

sley and others, 2008). The Grand Canyon 30' x 60' quadrangle

(Billingsley, 2000) adjoins the west edge of the Tuba City

quadrangle and reects the bedrock geology of Huntoon and

others (1996), but the Quaternary geology was not mapped in

detail on that map.

Mapping Methods

Geologic mapping of the Tuba City quadrangle was pro-

duced by stereoscopic analysis of aerial photographs augmented

by digital orthophotos and extensive eld checking. Primary

resources include 1:54,000-scale black and white aerial photo-

graphs from 1958 and 1968 and 1:24,000-scale and 1:40,000-

scale color aerial photographs from 2005. Geologic features

were compiled onto 1:24,000-scale topographic maps. Geologic

map units were extensively eld checked to verify bedrock and

surcial units and descriptions. Mapping of the eastern half of

the quadrangle was enhanced by using 1:40,000-scale digital

color orthophotos. The orthophoto mapping is not quite aligned

with the 1:24,000-scale base in some areas.

Many of the Quaternary alluvial and eolian deposits have

similar lithology and geomorphic characteristics and were

mapped almost entirely by photogeologic methods. Pliocene,

Pleistocene, and Holocene surcial deposits are differentiated

chiey on the basis of morphologic character and physiographic

position. Older alluvial and eolian deposits generally exhibit

extensive erosion whereas younger deposits are actively accu-

mulating material and are slightly eroded. Eolian deposits are

stabilized by vegetation in most areas but are partially reacti-

vated during severe drought or storm conditions.

In the eastern half of the quadrangle, small eolian and bed-

rock outcrops were not individually mapped. Instead, they were

lumped into a dominant classication. All surcial contacts

adjacent to alluvial, eolian, and bedrock map units are approxi-

mate.

Surcial deposits within the Grand Canyon area were not

investigated in the eld and are largely photo interpretations

based on previous eld reconnaissance mapping (Huntoon and

others, 1996). For a detailed description of surcial deposits and

Precambrian rocks within the Grand Canyon area, see Timmons

and others (2007).

Mapping was compiled by hand on 1:24,000-scale paper

topographic maps. The base maps were then scanned and

brought into ArcMap for georeferencing. Geologic features

were digitized, symbolized, and cross-checked against the origi-

nal eld sheets in an ArcGIS personal geodatabase. Thirty-two

detailed 1:24,000-scale maps were compiled to produce this

publication. This map is the eighth in a series of digital 30′ x 60′

geologic maps of the Grand Canyon region.

Geologic Setting

The Tuba City quadrangle is characterized by nearly at-

lying to gently dipping sequences of Paleozoic and Mesozoic

strata that overly tilted Precambrian strata or metasedimentary

and igneous rocks that are exposed at the bottom of Grand

Canyon. The Paleozoic rock sequences from Cambrian to

Permian age are exposed in the walls of Grand Canyon, Marble

Canyon, and Little Colorado River Gorge, herein collectively

referred to as the Grand Canyon. Mesozoic sedimentary rocks

are exposed in the eastern half of the quadrangle where resis-

tant sandstone units form cliffs, escarpments, mesas, and local

plateaus. A few Miocene volcanic dikes intrude Mesozoic rocks

southwest, northwest, and northeast of Tuba City, and Pleisto-

cene volcanic rocks representing the northernmost extent of the

San Francisco Volcanic Field are present at the south-central

edge of the quadrangle (Ulrich and Bailey, 1987; Billingsley

and others, 2007). Quaternary deposits mantle much of the

Mesozoic rocks in the eastern half of the quadrangle and are

sparsely scattered in the western half. A brief discussion of the

surcial deposits is presented later in the text.

Principal folds are the north-south-trending, east-dipping

Echo Cliffs Monocline and the East Kaibab Monocline. The

East Kaibab Monocline elevates the Kaibab, Walhalla, and

Coconino Plateaus and parts of Grand Canyon. Grand Canyon

erosion has exposed the Butte Fault beneath the east Kaibab

Monocline, providing a window into the structural complexity

of monoclines in this part of the Colorado Plateau. Rocks of

Permian and Triassic age form the surface bedrock of Marble

Plateau and House Rock Valley between the East Kaibab and

Echo Cliffs Monoclines (g. 1, sheet 3).

The Echo Cliffs Monocline forms a structural boundary

between the Marble Plateau to the west and the Kaibito and

Moenkopi Plateaus to the east. Jurassic rocks of the Kaibito and

Moenkopi Plateaus are largely mantled by extensive eolian sand

deposits. A small part of the northeast-dipping Red Lake Mono-

cline is present in the northeast corner of the quadrangle.

A broad and gentle elongated anticline, the Limestone

Ridge Anticline, forms the crest of Marble Plateau. Here,

Paleozoic and Mesozoic strata generally dip less than 1° to 2°

in all directions from a central high area along Limestone Ridge

north of Bodaway Mesa and east of Cedar Ridge and The Gap

(g. 1, sheet 3). The Limestone Ridge Anticline plunges gently

southeast toward the Painted Desert at the south edge of the

quadrangle and northward toward Lees Ferry, Arizona, at the

north-central edge of the quadrangle. The Tuba City Syncline is

a very broad northwest-southeast-oriented synclinal downwarp

that parallels the Echo Cliffs Monocline north of Tuba City.

The Preston Mesa Anticline is a small fold present on Kaibito

Plateau north of Tuba City (g. 1, sheet 3; Cooley and others,

1969; Haynes and Hackman, 1978).

Precambrian Rocks

At the bottom of Grand Canyon in the western third of the

quadrangle, the Colorado River has exposed the oldest rocks of

late Precambrian age. Proterozoic rocks of the Grand Canyon

form three main packages that record distinct depositional and

tectonic episodes in the Paleoproterozoic, Mesoproterozoic, and

Neoproterozoic. These rocks, from oldest to youngest, include

the Granite Gorge Metamorphic Suite and Zoroaster Complex

(Paleoproterozoic), the Unkar Group (Mesoproterozoic), and

the Chuar Group (Neoproterozoic).

Paleoproterozoic

The Paleoproterozoic rocks form the basement rocks

for the map area and underlie all younger rocks in the region.

These metamorphic and igneous rocks are commonly called

the Granite Gorge Metamorphic Suite and Zoroaster Complex

(Ilg and others, 1996: Karlstrom and others, 2003). Within the

quadrangle, these rocks span ages between 1,680 and 1,750±2

Ma (Hawkins and others, 1996); however, some of the oldest

rocks are dated at 1,842 Ma southwest of the quadrangle (Ilg

and others, 1996). These lithologic units represent a complexly

deformed package of metasedimentary and metavolcanic rocks

intruded by numerous granitic dikes and plutons. These rocks

record the assembly and stabilization of a juvenile continental

crust in the southwest during a southward (present coordinates)

growth of the Laurentian continent by the accretion of volcanic

arc terrains (Hoffman, 1988; Karlstrom and Bowring, 1988). Fol-

lowing continental assembly, the Paleoproterozoic rocks stabi-

lized and remained at middle crustal depths from 1.65 to 1.45 Ga

as suggested by the 1.375 Ga age of granite near Quartermaster

Canyon in western Grand Canyon (Karlstrom and others, 2003).

Mesoproterozoic

The 1.4 Ga thermal/tectonic events are hypothesized

to have been regionally important in driving the uplift and

exhumation of middle crustal rocks prior to the deposition of

the Mesoproterozoic sediments of the Grand Canyon Super-

group. The beveling of the basement metamorphic and igneous

rocks prior to deposition of the Grand Canyon Supergroup is

recognized as the Greatest Angular Unconformity (Powell,

1875) marked between basement Paleoproterozoic rocks and

the overlying Mesoproterozoic rocks of the Unkar Group. The

Great Unconformity separates all Precambrian rocks from the

overlying Paleozoic rocks in the Grand Canyon region.

The 1,250 to 1,100 Ma Unkar Group is approximately

6,900 ft (2,100 m) thick and is divided into ve formations, in

ascending order: the Bass Formation, Hakatai Shale, Shinumo

Sandstone, Dox Formation, and Cardenas Basalt as dened

by Timmons and others (2007). These ve formations reect

nomenclature usage published by Timmons and others (2007)

and do not reect the USGS style as dened by Elston (1979)

and Hendricks and Stevenson (2003). The succession contains

both uvial and shallow-marine deposits with one main discon-

formity below the Shinumo Sandstone. In general, the rocks of

the Unkar Group dip northeast (10°–30°) toward normal faults

and the normal faults dip 60° southwest (Sears, 1973).

The combined sedimentologic and deformational history

of the Unkar Group highlights an important period of geologic

history in the U.S. Southwest. Plate tectonic forces at the plate

margin (currently west Texas) created massive alpine-scale

mountain ranges along the eastern margin of Laurentia (Gren-

ville orogeny). The far eld forces related to that collision mani-

fested as deformational features and depositional systems in

Grand Canyon (Timmons and others, 2007). Rocks of the lower

Unkar Group are involved in northeast-striking monoclines that

record northwest-directed crustal shortening (see Red Canyon

on map; Timmons and others, 2005, 2007). These monoclines

are intimately related to deposition of the lower Unkar Group.

The lower Unkar Group and its associated deformation are

buried by the upper Unkar Group that records dominantly

northeast-directed extension along northwest-striking faults

(Timmons and others, 2005).

Neoproterozoic

Deformation of the Unkar Group continued into Nan-

koweap Formation time as indicated by an unconformity

within that formation and an angular unconformity between the

Nankoweap and overlying Chuar Group rocks. Rocks of the

Chuar Group include, in ascending order, the Galeros Forma-

tion and the Kwagunt Formation that are in turn subdivided into

four and three members, respectively (Karlstrom and others,

2000). Deposition of the mudstone-dominated Chuar Group

began approximately 300 m.y. after the eruption of the Cardenas

Basalt and marks a new depositional and deformational episode

in the Grand Canyon and adjacent areas. By 800 to 742 Ma,

deposition of approximately 5,250 ft (1,600 m) of the Chuar

Group of sediments had ended, and deposition of the overlying

Sixtymile Formation occurred soon after.

Rocks of the Chuar Group record an important episode of

sedimentation and deformation related to the incipient rifting

of Laurentia in the Neoproterozoic. Faulting and folding of the

Chuar Group and the Sixtymile Mile Formation record east-

west extensions along north-striking normal faults (Dehler and

others, 2001). The timing of deformation and the marine depo-

sitional setting are consistent with an early phase of continental

rifting and basin formation as rifting begins along the present

day western cordillera.

The Precambrian bedrock presented in this map is that

of Timmons and others (2007). Surcial deposits in the Pre-

cambrian area have been slightly modied from Timmons and

others (2007) to better match and correlate with adjacent 30′

x 60′ maps of the Grand Canyon area (Billingsley and others,

2006, 2007, 2008).

Paleozoic Rocks

The erosion of Grand Canyon by the Colorado River

has exposed about 3,300 ft (1,006 m) of Paleozoic strata.

These Paleozoic rocks are likely present in the subsurface

of Coconino, Marble, Kaibito, and Moenkopi Plateaus with

variable facies and thickness changes and an overall gradual

thinning of most units toward the east. Paleozoic rocks from

oldest to youngest are the Tapeats Sandstone (Lower(?) to

Middle Cambrian), the Bright Angel Shale (Middle Cam-

brian), the Muav Limestone (Middle Cambrian), the Temple

Butte Formation (Middle and Upper Devonian), the Redwall

Limestone (Lower, Middle, and Upper Mississippian), the

Surprise Canyon Formation (Upper Mississippian), the lower

part of the Supai Group, undivided (Lower, Middle, and Upper

Pennsylvanian and Upper Mississippian), and the Esplanade

Sandstone, the Hermit Formation, the Coconino Sandstone,

the Toroweap Formation, and the Kaibab Formation (Permian,

Cisuralian).

Cambrian

Based on exposures in Grand Canyon and in the Verde

Valley 40 mi (65 km) south of the map area, the Tapeats Sand-

stone and Bright Angel Shale gradually thin south and east of

the map area and gradually thicken west and north. Both units

locally pinch out on elevated Precambrian monadnocks west of

the map area and likely do the same under the plateaus sur-

rounding the Grand Canyon. The Muav Limestone gradually

thins east and southeast and thickens west and north of the map

area and may locally pinch out onto Precambrian rocks as it

does just west of the map area in eastern Grand Canyon (Hunt-

oon and others, 1996; Billingsley, 2000).

Devonian

The Temple Butte Formation includes a purple-red dolo-

mite, siltstone, and conglomerate that ll channels as deep as

120 ft (35 m) in the Marble Canyon area. The unit is locally

discontinuous between channels in Marble Canyon and likely

east of the Marble Canyon area. The Temple Butte Formation is

a continuous unit in the southwest quarter of the map area and

gradually thickens to the south and west.

Mississippian

The Redwall Limestone gradually thins eastward and

thickens westward as seen in Grand Canyon exposures and

unconformably overlies either the Temple Butte Formation or

the Muav Limestone where the Temple Butte is locally missing.

The Redwall Limestone forms a thick 500 to 550 ft (152 to 168

m) reddish-gray cliff in eastern Grand Canyon. The overlying

Surprise Canyon Formation is a discontinuous unit that locally

lls shallow channels or caves eroded into the top part of the

Redwall Limestone.

Pennsylvanian

The lower Supai Group, undivided, unconformably over-

lies the Redwall Limestone or the Surprise Canyon Formation

(where present) and gradually thins eastward in the subsurface

of the map area. The lower Supai Group maintains a general

thickness of about 800 ft (244 m) north of the map area and

gradually thickens westward.

Permian

The Esplanade Sandstone is the upper part of the Supai

Group and forms a prominent sandstone cliff that gradually

thins east and south and thickens north of the map area. The

Hermit Formation unconformably overlies the Esplanade Sand-

stone where channels have eroded into the Esplanade as deep as

30 ft (9 m).

The Hermit Formation thins eastward to less than 20 ft

(6 m) in the Little Colorado River Gorge and likely pinches

out before reaching the Tuba City area. The Hermit Formation

thickens north and west of the Grand Canyon in the subsurface

of the map area. A sharp planar erosional contact separates the

Hermit Formation from the overlying Coconino Sandstone.

The Coconino Sandstone forms a shear buff-white cliff in

the Grand Canyon and is about 600 ft (183 m) thick throughout

the southwest half of the map area and thins to the north and

west of the quadrangle. The basal part of the Coconino Sand-

stone includes a red sandstone in the Little Colorado Gorge that

is likely the northern extent of the Schnebly Hill Formation

exposed in the Verde Valley south of the quadrangle as dened

by Blakey (1990; Ronald C. Blakey, oral commun., 2005).

The Coconino Sandstone (not the Schnebly Hill Formation)

is actually a tongue of the Seligman Member of the Toroweap

Formation in the western and northern part of Grand Canyon

(Fisher, 1961; Schleh, 1966; Rawson and Turner, 1974; Bill-

ingsley and others, 2000; Billingsley and Wellmeyer, 2003) but

is a well-established unit in Grand Canyon nomenclature that

forms a distinct mappable unit throughout the Grand Canyon

region. The Coconino Sandstone and Schnebly Hill Formation

gradually thicken south and southeast of the map area. Both the

Schnebly Hill Formation and the Coconino Sandstone form an

important groundwater bearing unit known as the “C” aquifer.

The Toroweap Formation overlies the Coconino Sandstone

and undergoes a substantial west-to-east facies change in the

Grand Canyon and in the subsurface of the map area. All three

members of the Toroweap Formation, as dened by Sorauf and

Billingsley (1991), are recognized in the south and west edges

of the map as, in ascending order, the Seligman, Brady Canyon,

and Woods Ranch Members. All three members become

indistinguishable along the eastern rim of Grand Canyon,

Marble Canyon, and the Little Colorado River Gorge owing to

a facies change into cliff-forming sandstone and are mapped

there as the Toroweap Formation, undivided. The west-to-east

Toroweap facies change roughly parallels the Colorado River.

The Toroweap Formation gradually thins east, north, and south

of the Grand Canyon area and thickens west.

The Kaibab Formation forms the rim of the Grand

Canyon and the surface bedrock for much of the Coconino,

Walhalla, and Kaibab Plateaus, House Rock Valley, and the

western half of Marble Plateau where not covered by remnants

of the Moenkopi Formation or surcial deposits. The Kaibab

Formation is divided into, in ascending order, the Fossil

Mountain and Harrisburg Members as dened by Sorauf

and Billingsley (1991). A gradational and arbitrary bound-

ary separates the ledge- and cliff-forming Fossil Mountain

Member from the overlying slope- and ledge-forming Harris-

burg Member of the Kaibab Formation in the walls of Grand

Canyon and its tributaries. The Fossil Mountain Member

contains brachiopod, sponge, and trilobite fossils and abundant

chert beds, lenses, and nodules. The Harrisburg Member is pri-

marily a sandy limestone or calcareous sandstone that locally

contains a few mollusk fossils. The Harrisburg Member of

the Kaibab Formation forms a ledge-and-slope prole above

the cliff-forming Fossil Mountain Member. The Harrisburg

Formation is often weathered or stained dark gray or black by

manganese oxide. The Fossil Mountain and Harrisburg Mem-

bers undergo a west-to-east facies change within the map area,

making it increasingly difcult to distinguish one member

from the other east of the Grand Canyon. The Kaibab Forma-

tion gradually thins east of the map area and thickens toward

the northwest and west.

Mesozoic Rocks

An unconformity with general relief of less than 10 ft (3

m) separates the Permian Kaibab Formation from the overlying

Triassic Moenkopi Formation. This unconformity is commonly

recognized by a color change from the grayish-white sandy

limestone beds of the Kaibab Formation to the light-red, thin-

bedded siltstone and sandstone beds of the Moenkopi Forma-

tion. Erosional depressions and channels form the lenticular

basal part of the Moenkopi Formation. Channels are lled with

angular and subangular chert and sandstone conglomerate or

breccia deposits derived from the Kaibab Formation.

Erosion has exposed about 2,300 ft (700 m) of Mesozoic

strata in the eastern half of the map area and removed most of

these rocks from the western half. In ascending order, Meso-

zoic rocks present are the Moenkopi Formation (Lower and

Middle(?) Triassic); the Chinle Formation (Upper Triassic);

the Glen Canyon Group consisting of the Moenave Formation

(Upper Triassic(?) to Lower Jurassic), the Kayenta Formation

(Lower Jurassic age from Doelling and others, 2000), rocks

of the Kayenta Formation-Navajo Sandstone transition zone

(Lower Jurassic), and the Navajo Sandstone (Lower Jurassic

age from Doelling and others, 2000); and the San Rafael Group

consisting of the Carmel Formation (Middle Jurassic) and the

Entrada Sandstone-Cow Springs Sandstone, undivided (Middle

Jurassic). Unconformably overlying the Jurassic rocks are the

Dakota Sandstone (Upper Cretaceous) and the Mancos Shale

(Upper Cretaceous age from Doelling and others, 2000). All

Mesozoic strata undergo rapid facies and thickness changes in

all directions in the Moenkopi and Kaibito Plateau areas.

Moenkopi Formation

Overlying the Kaibab Formation is a sequence of red

sandstone ledges and siltstone slopes of the Moenkopi Forma-

tion. The Moenkopi Formation forms extensive outcrops on the

southern part of the Marble Plateau east of the Little Colorado

River Gorge and north-south along the Echo Cliffs to Cedar

Ridge and as scattered outcrops on the northern part of Marble

Plateau. Prior to Cenozoic erosion, the Moenkopi Forma-

tion covered the entire map area as thick as 1,000 ft (300 m)

(Billingsley and others, 2006). Deposits gradually thin eastward

to about 350 ft (107 m) in the Moenkopi Wash and Echo Cliffs

areas (Repenning and others, 1969) and thicken northward to

about 460 ft (140 m) northwest of the map area and to less than

220 ft (67 m) at Cedar Ridge at the north-central edge of the

map area.

The Moenkopi Formation is subdivided into three mem-

bers south of the Little Colorado River as described by McKee

(1954) and Hager (1922) and mapped by Billingsley and others

(2007). In ascending order they are the Wupatki Member, the

Shnabkaib Member, and the Holbrook and Moqui Members,

undivided. The Moenkopi Formation in northwestern Arizona

and southern Utah, as mapped by Billingsley and Workman

(2000) and Billingsley and others (2008), used the subdivi-

sions of Stewart and others (1972). North of the map area, the

Moenkopi is divided into three parts, in ascending order, as the

lower members, undivided, the Shnabkaib Member, and the

upper red member as mapped by Billingsley and Priest (2010).

The Little Colorado River is a convenient geographic boundary

for separating Moenkopi Formation nomenclature south and

southeast of Cameron from nomenclature north and northwest

of Cameron. Facies changes are numerous and common in all

Moenkopi Formation map units along a southeast-northwest

direction across the map area. The Wupatki Member southeast

of Cameron is the lateral equivalent of the lower members,

undivided, northwest of Cameron. The lower massive sand-

stone is the lateral equivalent of the Shnabkaib Member and the

Holbrook and Moqui Members are the lateral equivalent of the

upper red member.

The Moenkopi Formation forms a continuous outcrop

north of the map area along the Echo Cliffs to Lees Ferry and

then west along the Vermilion Cliffs into Utah and northwest-

ern Arizona and south of the map area into the Little Colorado

River Valley. The nomenclature of both McKee (1954) and

Stewart and others (1972) used for this map is based on tracing

and correlating the stratigraphic units of each member across

northern Arizona and observing the facies changes from the

Little Colorado River Valley to the Vermilion Cliffs and west to

Fredonia.

The Wupatki Member is the approximate equivalent of

the lower red Virgin Limestone and middle red members of the

Moenkopi Formation of northwestern Arizona and is mapped

as the lower members, undivided (^mlm), in Billingsley and

Priest (2010). The Virgin Limestone Member is present at Cedar

Ridge and in the Yon Dot Mountains on Marble Plateau as a

light-gray, thin-bedded, ne-grained limestone about 6 in thick

but is too thin and discontinuous to show at map scale. It does

provide a stratigraphic marker bed between the lower red and

middle red members for correlation purposes at the northern

edge of the map area.

Mapping along the Vermilion Cliffs northwest of Marble

Plateau (Billingsley and Priest, 2010) visibly demonstrates that

the Shnabkaib Member undergoes a facies change from a thick

white siltstone, gypsiferous sandstone, and limestone sequence

to a yellowish-white, crossbedded, ledge-forming, ne- to

coarse-grained calcareous sandstone and thin limestone south-

ward along the Echo Cliffs to the Little Colorado River Gorge.

The Shnabkaib Member continues a facies change southward

to a light-red, ne-grained, cliff-forming, crossbedded uvial

sandstone southeast of the Little Colorado River Gorge and into

the Little Colorado River Valley south of the map area where

McKee (1954) describes the unit as the lower massive sandstone

member. Thus, the lower massive sandstone member and the

Shnabkaib Member are one and the same, representing a shore-

ward facies change from marine to coastal tidal at from north-

western Arizona southeast to the Little Colorado River Valley.

Southeast of the map area, the Holbrook and Moqui

Members (McKee, 1954; Hager, 1922) erode to a uniform,

mostly covered slope below the cliff-forming sandstones of

the Holbrook Member. A variable and sometimes discontinu-

ous boundary exists between the members. The Holbrook and

Moqui Members are approximately correlative to the upper red

member of the Moenkopi Formation in northwestern Arizona

and southern Utah (McKee, 1954; Repenning and others, 1969)

and the upper red member of Billingsley and Priest (2010)

and may, in part, be Middle(?) Triassic age. The Holbrook and

Moqui Member nomenclature (Billingsley and others, 2007)

is used on this map because the unit exhibits similar lithology,

topographic expression, stratigraphic position, and proximity to

the Little Colorado River Valley. The unit undergoes a rapid and

complex northward facies change in the eastern part of Marble

Plateau between the Little Colorado River Gorge and Cedar

Ridge and thins northward along the Echo Cliffs to Lees Ferry.

The Moenkopi Formation was deposited from shallow tidal

ats and uvial oodplains that drained northwest toward south-

ern Utah (Blakey and Ranney, 2008). This coastal setting was

followed by a northwest uvial drainage system that deposited

the overlying Chinle Formation. The streams and valleys began

to accumulate mud, sand, gravel, and conglomerate deposits

of the Shinarump Member of the Chinle Formation. Drainages

eroded into the Moenkopi Formation average about 30 ft (10 m)

deep and locally as much as 100 ft (30 m). This unconformity

is known as the T-3 unconformity (Blakey, 1994). The Moen-

kopi Formation is unconformably overlain by the light-brown,

cliff-forming sandstone and conglomeratic sandstone and purple

to light-red siltstone of the Shinarump Member of the Chinle

Formation.

Chinle Formation

The Chinle Formation is the most colorful unit in the map

area and is subdivided into three members seen along the Echo

Cliffs. In ascending order they are the Shinarump Member, the

Petried Forest Member, and the Owl Rock Member as dened

by Akers and others (1958) and Repenning and others (1969).

The Shinarump Member includes an informal sandstone and

siltstone member as dened by Repenning and others (1969).

The Shinarump Member is thickest in the Painted Desert along

U.S. Highway 89 where accumulations are between 180 and

200 ft (55 and 60 m) thick. Basal, tan, conglomeratic, ledge-

forming sandstone beds contain numerous petried logs and

wood fragments and lenses of well-rounded quartzite and chert

pebbles. The upper informal sandstone and siltstone sequence

is predominantly a lenticular maze of thin to thick interbedded

stream-channel and ood-plain deposits of light-brown con-

glomerate and dark-purple, gray, and dark-red lenticular cross-

bedded siltstone and sandstone. The sandstone and siltstone

member is a transitional unit between the Shinarump Member

and the Petried Forest Member. The sandstone and siltstone

member sequence is not as crossbedded or as conglomeratic as

the underlying basal Shinarump Member and gradually thins

and pinches out northward to Cedar Ridge. The thickness of the

Shinarump Member and sandstone and siltstone member, undi-

vided, is variable due to widespread local channel pinch outs

and thinning of various lenticular units. The contact between the

Shinarump and sandstone and siltstone unit and the overlying

Petried Forest Member is gradational and approximate.

The Petried Forest Member forms the multicolored blue,

red, white, and grayish-green mud hills of the Painted Desert

badlands between the Little Colorado River Gorge and Moen-

kopi Wash and northward along the Echo Cliffs Monocline and

U.S. Highway 89. Locally, the Petried Forest Member can be

subdivided into three units based on slight lithologic and color

differences according to Akers and others (1958), but these units

are herein mapped together as the Petried Forest Member of the

Chinle Formation because the gradational boundaries between

them is arbitrary. The three units are, in descending order, a red

mudstone and sandstone, a gray mudstone and sandstone, and a

blue mudstone. The Petried Forest Member generally maintains

a thickness between 300 and 400 ft (92 and 122 m).

Gradationally overlying the Petried Forest Member is the

Owl Rock Member. The Owl Rock Member consists of an inter-

bedded sequence of gray, ledge-forming, siliceous limestone and

light-red to yellowish-gray, slope-forming, calcareous siltstone

beds that form Ward Terrace in the southeast corner of the map

area (g. 1, sheet 3). The contact between the Petried Forest

and Owl Rock Members is arbitrary and generally marked about

10 to 15 ft (3 to 4.5 m) below the lowest gray limestone bed of

the Owl Rock Member. The contact of the Owl Rock Member

with the overlying Moenave Formation is unconformable and

marked by a sharp contrast in lithology and color change from

gray mudstone, siltstone, and limestone to orange-red uvial

sandstone of the Moenave. This regional unconformity is known

as the J-O unconformity (Pipiringos and O’Sullivan, 1978; Peter-

son and Pipiringos, 1979) and separates Triassic strata from the

overlying Jurassic rocks. The Owl Rock Member gradually thins

northward along the Echo Cliffs Monocline.

Moenave Formation

The type section of the Moenave Formation is near the

community of Moenave, west of Tuba City. The Moenave

Formation originally included, in ascending order, the Dinosaur

Canyon Member (Colbert and Mook, 1951) and the Springdale

Sandstone Member, originally described by Gregory (1950) as

part of the Chinle Formation and redened as the upper member

of the Moenave Formation by Harshbarger and others (1958).

More recently, the Springdale Sandstone Member was reas-

signed to the basal part of the Kayenta Formation (Beik and

others, 2007). Thus, the Dinosaur Canyon Member represents

the entire Moenave Formation within this quadrangle. The Moe-

nave Formation is a red, slope-forming unit that gradually thins

north and northeast of the map area and is removed by modern

erosion southwest of the map area.

Kayenta Formation

The Kayenta Formation unconformably overlies the Moe-

nave Formation. This unconformity is the sub-Kayenta Forma-

tion unconformity (J-sub-K) as dened by Riggs and Blakey

(1993) and Blakey (1994). Erosional relief is generally less than

6 ft (2 m) in the map area but can be as much as 50 ft (15 m)

north of the map area (Nation, 1990). The Kayenta Formation

includes, in ascending order, the Springdale Sandstone Member

and an upper slope-forming sequence of siltstone and sandstone.

The Springdale Sandstone forms an orange-red, thick-bedded

sandstone cliff overlain by the purple-red, slope-forming

siltstone and sandstone of the upper Kayenta Formation from

southwest of Tuba City and northwest along the Echo Cliffs.

The upper sequence undergoes a facies change northward to

a series of light-red sandstone ledges and small, red siltstone

slopes at Cedar Ridge.

Kayenta Formation-Navajo Sandstone Transition

Zone

The Kayenta Formation grades upward into a sequence

of interbedded red and white crossbedded sandstone ledges

and purple-red mudstone and siltstone slopes mapped as the

Kayenta-Navajo transition zone. The crossbedded sandstone

cliffs within the transition zone in the map area grade north-

ward into the Navajo Sandstone. The purple-red mudstone and

siltstone slopes grade southward into the Kayenta Formation.

Blakey (1994) subdivided the Navajo Sandstone of this region

into two parts, as suggested by Marzolf (1983). The lower part

is equivalent to and intertongues with eolian and uvial deposits

of the Kayenta-Navajo transition zone and the upper part is the

eolian cliff-forming Navajo Sandstone found above the young-

est documentable horizon of intertonguing. This subdivision of

the Navajo Sandstone is recognized by Marzolf (1983) as the

“wet lower part” and the “dry upper part.”

The Kayenta-Navajo transition zone is about 240 ft (73

m) thick in the map area and grades laterally northwestward

to become the basal part of the Navajo Sandstone near Cedar

Ridge. The succession of uvial, eolian, and lacustrine strata

become more frequent as the Kayenta Formation thins in the

zone of facies change southeast of the map area (Middleton and

Blakey, 1983; Sargent, 1984; Long, 2008). Several springs and

seeps are associated with the basal Navajo Sandstone tongues

within the Kayenta-Navajo transition zone in the Tuba City,

Moenave, and Moenkopi areas. The lowest sandstone cliff

marks the approximate contact between the Kayenta Formation

and the Kayenta-Navajo transition zone. The upper contact of

the Kayenta-Navajo transition zone is marked at the base of the

massive overlying Navajo Sandstone.

Navajo Sandstone

The Navajo Sandstone consists of red and white, cliff-

forming, eolian, crossbed sets and is the upper part of the

Navajo Sandstone as proposed by Blakey (1994). The Navajo

Sandstone includes several shallow lake horizons represented

as thin-bedded, silica-cemented sandy limestone 1 to 2 ft (0.5

to 1.2 m) thick that are highly lenticular and have limited lateral

extent. These resistant limestone beds are at various strati-

graphic levels within the Navajo Sandstone and locally form

cherty limestone ledges, ridges, or small hills on the Kaibito and

Moenkopi Plateaus. The number of limestone ledges increases

southeast of the map area. The Navajo Sandstone thins south

and east of the map area and is gradually removed by Creta-

ceous erosion southeast of the map area.

Carmel Formation

The beveled upper surface of the Navajo Sandstone is

an erosional unconformity known regionally as the J-1 and

J-2 unconformity (Pipiringos and O’Sullivan, 1978; Blakey,

1994). At Coal Mine Mesa in the southeast corner of the

quadrangle, as much as 30 ft (9 m) of erosional relief separates

the Navajo Sandstone from the overlying Jurassic Entrada

Sandstone-Cow Springs Sandstone, undivided. The erosional

channels are lled with conglomerate and sandstone that are

likely correlative to the southernmost extent of the Carmel

Formation (Jc) at Middle Mesa north of Coal Mine Mesa

(east-central edge of the quadrangle) where about 30 ft (9

m) of the Carmel Formation overlies the Navajo Sandstone.

The Carmel Formation is also present northeast of the Red

Lake Monocline in the northeast corner of the quadrangle.

The Carmel Formation has been removed from much of the

Kaibito Plateau by modern erosion.

Entrada Sandstone-Cow Springs Sandstone

Strata overlying the Navajo Sandstone in the southeast

corner of the map area consists mostly of white and interbed-

ded, red and white, crossbedded Entrada Sandstone overlain

by a yellowish, crossbedded cliff of Cow Springs Sandstone,

undivided (Je). This sandstone sequence includes thin red beds

of the Carmel Formation at the base that extend a short distance

southward into the subsurface of Coal Mine Mesa and then

pinch out. The upper part of the sandstone sequence, above the

interbedded red and white sunstone beds, is a yellowish-white,

cliff and slope of planar crossbedded sandstone that is a south-

ern extension of the Cow Springs Sandstone (Harshbarger and

others, 1958).

The lower part of the Entrada Sandstone consists of mas-

sive, white, very ne grained, cliff- and slope-forming sand-

stone that weathers steel gray and contains multiple small-scale,

low-angle trough crossbeds at Moenkopi Plateau, southeastern

quarter of the map. In the northeast quarter of the quadrangle,

a red and white, at-bedded sequence of cliff-forming sand-

stone makes up a middle red sandstone sequence of the Entrada

Sandstone. These red siltstone and sandstone beds increase to

more reddish sandstone north of the quadrangle and pinch out

south of Coal Mine Mesa on Moenkopi Plateau in the southeast

quarter of the quadrangle.

The Entrada Sandstone-Cow Springs Sandstone, undi-

vided, is unconformably overlain by the Cretaceous Dakota

Sandstone in the eastern Coal Mine Mesa area and northeast

of the quadrangle and are overlain by Tertiary gravels (Tgs) in

the western part of Moenkopi Plateau. The Jurassic-Cretaceous

unconformity is widespread east, northeast, and southeast of the

map area.

Dakota Sandstone

The Dakota Sandstone crops out at Coal Mine Mesa on

Moenkopi Plateau in the southeast corner of the map area and

on White Mesa in the northeast corner. The Dakota Sandstone is

subdivided into three informal units. In ascending order they are

the lower sandstone member, the middle carbonaceous member,

and the upper sandstone member. All are present at Coal Mine

Mesa and have gradational contacts between them (O’Sullivan

and others, 1972). All three members are too small to show at

map scale and are collectively mapped as the Dakota Sandstone

(Kd).

A coal bed, locally several feet thick, was mined from

this unit at Coal Mine Canyon for use at Tuba City in the early

1900s. The Dakota Sandstone has a gradational and arbitrary

contact with the overlying Mancos Shale.

Mancos Shale

The lower part of the Mancos Shale is present at Coal

Mine Mesa on the Moenkopi Plateau. Modern erosion has

removed most of the bluish-gray, thin-bedded, slope-forming

Mancos Shale from Coal Mine Mesa and White Mesa. Rem-

nants of the Mancos Shale are now largely covered by extensive

deposits of Pleistocene and Holocene eolian and uvial sand,

silt, and mud. At White Mesa, much of the Dakota Sandstone

and Mancos Shale deposits have been removed by Tertiary ero-

sion. What remains is partly overlain by gravels and sedimen-

tary deposits of Tertiary age.

Cenozoic Volcanic Rocks

Shadow Mountain, located about 1 km south of the south-

central edge of the map, is an isolated Pleistocene pyroclastic

cone with associated basalt ows that are chemically and

petrologically similar to rocks of the San Francisco volcanic

eld. This cone represents the northernmost extent of this

volcanic eld. Shadow Mountain has a K-Ar age of 0.649±0.23

Ma (Damon and others, 1974; Condit, 1974; Ulrich and Bailey,

1987; Wolfe and others, 1987). These deposits (Qi, Qsb, Qsp)

adjoin those of the Cameron 30′ x 60′ quadrangle (Billingsley

and others, 2007) at the south-central edge of the map area.

Older intrusive dikes (Ti) are oriented generally north-

south in Moenkopi Wash southwest of Tuba City, in Hamblin

Wash south of The Gap, at Tuba Butte northwest of Tuba City,

and at Wildcat Peak northeast of Tuba City. A new

Ar/

age from a dike at Wildcat Peak yields an age of 19.05±Ma

(Peters, 2011). This north-south dike is similar in composi-

tion and orientation to the other three dike locations mentioned

above and are all assumed to be a similar Miocene age. This age

may reect the southernmost extent of the 21 to 26 Ma volca-

nic laccolithic mountains in southern Utah, Navajo Mountain,

and the Henry Mountains. The 19 Ma age also explains why

there are no volcanic surface ows associated with these dikes,

because any ows that may have occurred have been eroded

away during Late Tertiary and Quaternary erosion along with

much of the upper bedrock that exposes these dikes today.

Pliocene-Pleistocene Gravel Deposits

The oldest gravel and sediment deposits (Tgs) cap mesas

or ridges as much as 50 ft (17 m) thick, mainly in the east-

ern part of the quadrangle. These deposits commonly form a

cap-rock deposit on Middle Mesa, on Coal Mine Mesa, and at

Crooked Ridge. The deposits rest unconformably on beveled

surfaces of the Navajo Sandstone and the Carmel Formation.

Gravel clasts within the sandstone and siltstone sediments are

composed of well-rounded pebbles and cobbles of chert, quartz-

ite, sandstone, limestone, some fossil wood fragments, and

reworked marine fossils derived mainly from Cretaceous rocks

and perhaps some Jurassic rocks east of the map area.

Younger old terrace gravel deposits (QTg5, QTg6, QTg7)

are present at three different levels above Moenkopi Wash and

below the oldest gravel and sediment deposits (Tgs) capping

Middle Mesa and Moenkopi Plateau east of Tuba City. These

deposits reect various stages of incision into the Navajo

Sandstone by an ancestral Moenkopi Wash probably within the

last few hundred thousand years. In the Grand Canyon, gravel

(QTg5) and sediment deposits of Quaternary age, but with a

different lithology, form isolated, well-consolidated terrace

deposits about 400 to 450 ft (122 to 137 m) above the Colorado

River.

Quaternary Surficial Deposits

Surficial Mapping Technique

Surcial deposits on the Colorado Plateau have largely

been ignored because their role on the landscape was not recog-

nized. Today we are learning how signicant these deposits are

on biology, soil science, and climate studies as well as on the

evolutionary development of the landscape.

Surcial sedimentary deposits have accumulated over the

last several hundred thousand years. They generally occur as

unconsolidated or weakly consolidated deposits of local extent

overlaying bedrock. They are usually a thin veneer but can be

as much as several tens of meters thick. Surcial deposits have

accumulated mainly as a result of running water (uvial or

alluvial deposits), wind (eolian deposits), or a combination of

both. Steep slopes near buttes and mesas often have landslide,

talus, and rockfall deposits. Deposits in alluvial valleys, washes,

and oodplains are often remobilized by wind forming adjacent

sand dune and sand sheet deposits.

Mapping surcial deposits across an area as large as

the Tuba City 30′ x 60′ quadrangle poses unique challenges.

Although a fairly recent age is obvious, very little data is avail-

able to condently assign the deposits to Holocene, Pleistocene,

or older. A map-unit naming scheme that combines information

about lithology and genesis was needed. To accommodate these

criteria, the materials are classied and named using genesis

(for example, alluvium, eolian, talus, landslide), geologic

age (for example, Holocene, Pleistocene), and lithology (for

example, sand, gravel). This strategy has evolved from previous

surcial mapping in the Grand Canyon region (Billingsley and

Workman, 2000; Billingsley and Wellmeyer, 2003; Billingsley

and others, 2006, 2007, 2008).

Information about surcial deposits was obtained mainly

by aerial photo interpretations. Ages are based mostly on

geomorphologic criteria, such as relative position in local

alluvial-terrace sequences, degree of alluvial fan dissection, and

superposition or stabilization of dune and sand sheet deposits.

The discontinuous aspect of surcial deposits does not lend

itself to easy correlation. Therefore, all age assignments for sur-

cial materials are provisional and the age of a specic unit in

one area may not be correlative to the same unit in another area.

Unit names with time implications, such as young, intermedi-

ate, old, and older, are intended only to indicate local relative

stratigraphic position, not age uniformity, throughout the map

area. A few eolian units common to both the Cameron and Tuba

City 30′ x 60′ quadrangles were adjusted to a younger age for

this publication and, therefore, are not the same color as on the

Cameron 30′ x 60′ quadrangle (Billingsley and others, 2007).

Local Surficial Deposits

Surcial uvial deposits are found throughout parts of

the western map area and tend to be isolated because of steep

topography and rapid modern erosion. In contrast, extensive

eolian deposits cover large areas of the Kaibito and Moen-

kopi Plateaus in the eastern part of the map, where the Navajo

Sandstone is the primary source for surcial sand sheet and sand

dune deposits. Not all sand deposits are individually shown. In

several areas, such as north and east of Tuba City, sand depos-

its are mapped as an undifferentiated unit consisting of vari-

ous dune types and small pockets of bedrock. These extensive

eolian deposits are transported northeastward across Moenkopi

and Kaibito Plateaus by southwesterly winds. In many areas,

these eolian deposits are continually recycled; storm runoff

erodes then redeposits them in enclosed ponded (Qps) depres-

sions, where wind moves them back onto and across the plateau.

Eventually, much of the eolian sand is uvially transported by

uvial processes into main drainages, such as Moenkopi Wash

and Hamblin Wash, that drain into the Little Colorado River,

through the Grand Canyon, and out of the region.

Other surcial deposits include travertine deposits that

originate from springs in the Grand Canyon and form travertine

dams in the bed of the Little Colorado River Gorge that are

too small to show at map scale. Numerous landslide (Ql) and

talus and rockfall (Qtr) deposits are below the rims of the Little

Colorado River Gorge, Marble Canyon, and Grand Canyon and

along the Echo Cliffs east of U.S. Highway 89. Diversion dams,

stock tanks, gravel pits, and a landll east of Tuba City are

mapped to show the human impact upon the landscape.

Structural Geology

Structural deformation of the Paleoproterozoic (X), Meso-

proterozoic (Y), and Neoproterozoic (Z) rocks at the bottom

of Grand Canyon are well illustrated by Timmons and others

(2007) showing the multiple extensional and folding events of

Mesoproterozoic and Neoproterozoic time that largely corre-

sponds with the deposition of Unkar and Chuar Group rocks.

Rocks of the Unkar Group were faulted and slightly tilted as

coherent blocks then were beveled by a period of erosion that

lasted nearly 300 million years. Deposition of the overlying

Chuar Group resulted in an angular unconformity between the

Unkar and Chuar Groups (Timmons and others, 2007). During

Neoproterozoic time, the Chuar Group was subjected to addi-

tional folding and, most importantly, west-down normal slip on

Butte Fault formed a deep Chuar Group depocenter; drag along

this fault produced the Chuar Syncline of Neoproterozoic age

(Timmons and others, 2007).

Large high-angle to nearly vertical normal-fault separations

in Proterozoic basement rocks set the stage for structural defor-

mation of younger Paleozoic and Mesozoic strata. Compres-

sional folding of Paleozoic and Mesozoic rocks along reactivated

Proterozoic high-angle faults began in Late Cretaceous and early

Tertiary time—a period known as the Laramide Orogeny that

peaked about 65 Ma. Numerous northeast- to east-dipping sinu-

ous monoclines in the western half of the map area are the result

of Laramide compression along Proterozoic faults. Concurrent

and subsequent erosion has removed much of the Mesozoic

strata that once covered the entire map area (Huntoon, 1990,

2003; Huntoon and others, 1996; Timmons and others, 2007).

The East Kaibab Monocline has elevated the landscape

to the west forming the topographic highlands of the Walhalla

and Kaibab Plateaus (g. 1, sheet 3). The East Kaibab Mono-

cline extends northwestward into Utah and forms the structural

boundary between the Kaibab Plateau and House Rock Valley

to the east (Billingsley and others, 2008). The monocline also

extends southeast of the map area to Gray Mountain (Billings-

ley and others, 2007). Strata along the East Kaibab Monocline

dip northeast between 20° and 80° with the steepest dip in the

lower part of the fold in Grand Canyon (Timmons and others,

2007). Vertical relief of Paleozoic strata along the East Kaibab

Monocline and Butte Fault in Grand Canyon averages about

1,000 ft (305 m) up to the west.

The Echo Cliffs Monocline, another major fold, extends

from Cedar Ridge at the north-central edge of the map south-

eastward along U.S. Highway 89 and the Echo Cliffs to about

Hidden Springs northwest of Moenave. From Hidden Springs,

the Echo Cliffs Monocline bends southwest into the Painted

Desert, where it gradually broadens and terminates just south

of the south-central edge of the map. In this area, the southwest

trend of the Echo Cliffs Monocline is structurally aligned with

the northeast trend of the Mesa Butte Fault located about 12 mi

(19 km) south of the map edge (Billingsley and others, 2007).

The Echo Cliffs Monocline continues north of the quadrangle

to Lees Ferry and then northwest into southern Utah. Permian,

Triassic, and Jurassic strata that outcrop along the Echo Cliffs

Monocline dip east 12° to 18° along the north half of the struc-

ture and southeast 3° to 4° along the south half.

Northeast-trending high-angle normal faults intersect the

Echo Cliffs Monocline just south of Cedar Ridge where strata is

folded to a near vertical position and partially faulted as much

as 100 ft (30 m). Folding along the Echo Cliffs Monocline has

elevated Marble Plateau an estimated 1,700 ft (518 m) up to the

west at Cedar Ridge in the north half of the quadrangle and less

than 500 ft (152 m) west of Moenkopi Wash in the south half of

the quadrangle. Oddly enough, the average elevation of Marble

Plateau west of the Echo Cliffs Monocline is nearly at the same

average elevation, about 6,200 ft (1,890 m), as the Moenkopi

and Kaibito Plateaus east of the monocline.

Blue Spring Monocline is a small northwest-trending fold

displaying northeast-dipping Paleozoic and Mesozoic strata in

the southwest quarter of the map area. Relief along this mono-

cline is generally less than 200 ft (60 m) and the average dip

of strata is about 5°. Several collapse structures align along

the northwest trend of the Blue Spring Monocline, suggesting

enhanced karst solutioning of the Redwall Limestone (Wenrich

and Huntoon, 1989; Wenrich and Sutphin, 1989). The Blue

Spring Monocline is one of the most important hydrological

structures within the map area because Blue Spring and several

associated springs issue from the top part of the Redwall Lime-

stone at the northwest extent of the Blue Spring Monocline at

the bottom of the Little Colorado River Gorge. Numerous north-

west-trending joints, fractures, and small faults associated with

the Blue Spring Monocline form a major hydrologic avenue for

groundwater transport from regions southeast of the map area

to Blue Spring. Blue Spring is the largest natural owing spring

in Arizona. Daily discharge is nearly 200 ft

/s (Don Bills, oral

commun., 2012).

On the eastern side of the quadrangle, a few broad north-

northwest-trending folds roughly parallel the Echo Cliffs Mono-

cline. The Tuba City Syncline extends from Coal Mine Mesa

north to and beneath Crooked Ridge and north of the map area.

The White Point Fault (Cooley and others, 1969) is not very

evident in the crossbedded Navajo Sandstone where reverse

fault drag along the fault makes it difcult to locate strata,

which may dip west as much as 22° between White Point Mesa

and Preston Mesa. The White Point Fault gradually disappears

beneath sand deposits north and south of White Point. North-

east of White Point is the Preston Mesa Anticline (Cooley and

others, 1969). This anticline trends northwest-southeast through

Preston Mesa with strata dipping less than 5°. The Red Lake

Monocline trends northwest-southeast at the northeast corner of

the quadrangle between Wildcat Peak and White Mesa. Strata

along Red Lake Monocline dip 15° to 20° east in the vicinity of

Kaibito just north of the map area.

During the Miocene, Pliocene, and Pleistocene, east-west

extension reactivated deep-seated faults along some mono-

clines, producing normal faults that reversed Cretaceous and

Tertiary offset, as well as accentuated the dip of the mono-

clines by reverse drag along the faults (Huntoon, 1990, 2003).

Extensional faulting during the late Pliocene produced many

graben structures. A time frame of less than 3 m.y. is inferred,

based on similar extensional fault evidence along the Hurricane

and Toroweap Faults west and south of the map area (Billing-

sley and Workman, 2000; Billingsley and Wellmeyer, 2003;

Billingsley and others, 2006, 2007, 2008), but this is not well

constrained. North- and northeast-trending grabens and faults

in the Little Colorado River Gorge and Marble Plateau areas

appear to be the most recent tectonic structures in the area based

on minor offset of Pleistocene and Holocene(?) alluvial deposits

and Pleistocene volcanic rocks south of the map (Billingsley

and others, 2007). Several sinkholes have developed along frac-

tures and joints associated with the faults and grabens. These

sinkholes have temporarily interrupted runoff to some small

tributaries of the Little Colorado River.

The Laramide erosional period starting about 60 Ma began

to transform the landscape to its current conguration, but

Neogene Tertiary and Quaternary erosion greatly deepened and

broadened the Grand Canyon. The meandering Little Colorado

River occupied a strike valley in soft Mesozoic rocks between

the East Kaibab Monocline and Marble Plateau and has been

superimposed as a subsequent stream into the resistant rocks of

the Kaibab Formation in the southern part of Marble Plateau,

preserving the older meander pattern. At about the same time,

an unnamed drainage from the northeast was meandering on

the Navajo Sandstone along a strike valley that parallels the

Echo Cliffs Monocline in the vicinity of The Gap. This drainage

system is responsible for at least two of the topographic gaps in

the Echo Cliffs. Well-rounded sandstone and chert pebbles and

cobbles of Jurassic and Cretaceous age suggest that the Crooked

Ridge drainage originated from the Black Mesa area east or

northeast of the quadrangle and that pebble imbrication of the

gravels in the sandy sediment indicate a southwest-owing

stream that deposited the Crooked Ridge stream sediments

toward the Echo Cliffs Monocline, then meandered southeast

along a monoclinal strike valley towards the Tuba City area.

Lag gravels scattered on the Kaibito Plateau northeast and near

Tuba City are evidence of this drainage.

The Little Colorado River and its tributaries became

integrated with the Colorado River sometime in late Miocene

or early Pliocene time after about 6 to 9 Ma (Lucchitta, 1979,

1990; Ranney, 2005). Continued headward erosion of the Little

Colorado River, caused by erosional deepening of the Colo-

rado River in Grand Canyon, has gradually extended the Little

Colorado River Gorge upstream toward Cameron and into the

eastern half of the map area. Headward erosion from the Colo-

rado River continues westward into the Kaibab and Walhalla

Plateaus and has greatly enhanced the widening process of

eastern Grand Canyon along the East Kaibab Monocline.

Circular bowl-shaped depressions in the Kaibab and Moen-

kopi Formations, characterized by inward-dipping strata, are

likely to be the surface expression of collapse-formed breccia

pipes created by dissolution of the Mississippian Redwall Lime-

stone at depth. Collapse features are indicated by a black dot on

the map and may or may not represent breccia pipes at depth.

Drilling is needed to conrm breccia pipes within collapse

structures. Exposed breccia pipes are indicated by red dots.

Large-scale collapse depressions may be the result of sev-

eral interconnecting smaller collapse features or breccia pipes,

such as the Shadow Mountain collapse on the Marble Plateau at

the south-central portion of the quadrangle (g. 1, sheet 3). The

Shadow Mountain collapse is a circular, alluvial-lled structural

basin about 0.6 mi (1 km) in diameter. The Chinle Formation

dips between 5° and 18° toward the center of the collapse. Brec-

cia pipes have the potential for uranium and other minerals at

depth, but not all breccia pipes are mineralized (Wenrich and

Sutphin, 1989; Wenrich, 1992). Only circular collapse features

that have inward-dipping strata are marked on the map as poten-

tial breccia pipes at depth.

Gypsum dissolution in the Harrisburg Member of the

Kaibab Formation has resulted in several sinkholes on the

Kaibab Plateau. The sinkholes are likely Pleistocene and

Holocene in age because they disrupt local drainages and are

commonly lled with locally derived, ne-grained sediments.

Gypsum deposits within the Kaibab and Toroweap Formations

are thickest along the west edge of the map as evidenced by the

increase in sinkholes of that area.

Acknowledgments

We appreciate the cooperation and support of the Water

Resource Division and the Geologic Division of the National

Park Service, Fort Collins, Colorado, and the Grand Canyon

Science Center, National Park Service, Grand Canyon National

Park, Arizona. We appreciate the Navajo Nation Minerals

Department and the Hopi Tribe for permission to publish

those portions of this map involving Navajo Nation and Hopi

Tribal lands. We also appreciate the advice, revisions, and

geologic information provided by Mark Timmons of New

Mexico Bureau of Mines and Mineral Resources, Socorro, New

Mexico, and Karl Karlstrom of the University of New Mexico,

Albuquerque, New Mexico. We are indebted to Dr. Charles L.

Powell, II, and Jan Zigler of the U.S. Geological Survey, Menlo

Park, California, for their technical advice and assistance in the

preparation of this map and report.

DESCRIPTION OF MAP UNITS

SURFICIAL DEPOSITS

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

based on differences in morphologic character and physiographic position on 1:24,000-scale, 1968, black

and white; 1:24,000-scale, 2005, color; and 1:40,000-scale, 2005, color aerial photographs and on field

observations of the lithology. Older alluvial and eolian deposits generally exhibit extensive erosion, have

greater topographic relief, and in some areas have developed a carbonate soil subhorizon. Younger depos-

its are actively accumulating material or are lightly eroded. On Moenkopi and Kaibito Plateaus, exten-

sive eolian sand sheet and dune deposits are stabilized by vegetation during wet conditions and become

destabilized and mobile when disturbed by livestock or human activity. These deposits are also partially

reactivated during severe drought conditions or spring wind events. Young surficial deposits are actively

accumulating material and are vulnerable to wind or water erosion. Eolian and alluvial contacts are provi-

sional and arbitrary.

Qaf Artificial fill and quarries (Holocene)—Excavated alluvium and bedrock material removed

from barrow pits and trenches to build livestock tanks, drainage diversion dams, landfills,

roads, and other construction projects (not all road and construction excavations are shown)

Qs Stream-channel deposits (Holocene)—Poorly sorted, interbedded mud, silt, sand, pebbles, and

gravel. Intertongue with or inset against young, intermediate, and old alluvial fan (Qa1,

Qa2, Qa3), young, intermediate, and old terrace-gravel (Qg1, Qg2, Qg3), and upper part

of valley alluvial (Qv) deposits; overlaps and intertongues with ood-plain (Qf) and ponded

sediment (Qps) deposits. Stream channels subject to high-energy ows and ash oods.

Little or no vegetation in stream channels, except for some salt cedar (tamarisk), Russian

olive, and cottonwood trees. Contacts with adjacent alluvial or eolian deposits are approxi-

mate. Stream-channel deposits of Moenkopi and Hamblin Washes do not necessarily reect

stream-channel deposits of today owing to low-gradient channel changes caused by yearly

uctuations in stream levels and ooding events. Thickness, 3 to 30 ft (1 to 9 m)

Qf Flood-plain deposits (Holocene)—Gray, brown, to light-red interbedded lenses of clay, mud,

silt, and sand. Include minor lenticular gravel deposits, partly consolidated by gypsum and

calcite cement. Intertongue with or overlap stream-channel (Qs), valley-ll (Qv), young

terrace-gravel (Qg1), and young alluvial fan (Qa1) deposits. Subject to stream-channel ero-

sion or overbank ooding in lateral and vertical sense. Similar to valley-ll (Qv) deposits in

small tributary drainages; subject to widespread and frequent overbank ooding along Colo-

rado River, Little Colorado River, Moenkopi Wash, and Hamblin Wash areas. Support thick

growths of sagebrush and grass, tumble weed, desert shrubs, and tamarisk trees. Subject to

temporary ponding and often mixed with ponded sediments (Qps) or mixed alluvium and

eolian (Qae) deposits in broad drainages on Moenkopi and Kaibito Plateaus. Thickness, 3 to

30 ft (1 to 9 m)

Qes Sand sheet deposits (Holocene)—White, gray, ne- to coarse-grained, windblown sand com-

posed mainly of quartz and chert grains derived primarily from the Navajo Sandstone and

Moenave Formation. Deposits form extensive cover over gently sloping terrain on Moen-

kopi and Kaibito Plateaus in eastern third of map. Also form thin sand sheets on alluvial

fan slopes below the Echo Cliffs parallel to U.S. Highway 89. Commonly intertongue with

mixed alluvial and eolian (Qae) deposits that share a gradational lateral and vertical contact.

Support moderate growths of grass and small high-desert shrubs that tend to stabilize the

deposits. Thickness, 1 to 15 ft (0.3 to 4.5 m)

Qd Dune sand and sand sheet deposits (Holocene)—Grand Canyon, Coconino Plateau, and Marble

Plateau areas: White, gray, and light-red, ne- to coarse-grained, windblown sand composed

mainly of quartz, feldspar, and chert grains derived from Proterozoic, Paleozoic, and Meso-

zoic sand and gravel deposits that accumulate in stream-channel (Qs) or valley-ll (Qv)

deposits and are transported by wind to form lumpy, undened geometric sand dunes or sand

sheet deposits on ood-plain (Qf) and young terrace-gravel (Qg1) deposits near washes in

west half of map. Support moderate growths of grass and sagebrush

Moenkopi and Kaibito Plateau areas: White, gray to light-red, ne- to coarse-grained

sand composed mainly of quartz, chert, and minor feldspar derived from nearby Triassic

and Jurassic sedimentary rocks east of U.S. Highway 89. Include topographically controlled

climbing and falling dunes, complex dunes, parabolic dunes, barchan dunes, and sand sheets

that mantle bedrock slopes north and south of Moenkopi Wash, along the Echo Cliffs, and

within drainages on Moenkopi and Kaibito Plateaus. Navajo Sandstone (Jn) is the primary

source of sand on Moenkopi and Kaibito Plateaus. Unit has arbitrary and gradational con-

tacts, in the lateral and vertical sense, with adjacent surcial deposits and bedrock outcrops.

Sand is generally transported northeast by southwesterly winds that erode local Triassic

sandstone units and older sand deposits. Unit distributes a fresh veneer of sand over bedrock

and older eolian deposits on Coal Mine Mesa. Support moderate growth of grass, Mormon

tea, and high desert shrubs. Wet conditions stabilize all eolian deposits on Moenkopi and

Kaibito Plateaus. Thickness, 3 to 200 ft (1 to 61 m)

Qdl

Linear dune deposits (Holocene)—White, gray, light-red, ne- to medium-grained, well-sorted,

unconsolidated sand accumulations that are aligned and generally trend northeast. Often

merge with dune sand and sand sheet (Qd), sand sheet (Qes), parabolic dune (Qdp), and

barchan dune (Qdb) deposits. Linear dunes are generally 40 to 80 ft (12 to 24.5 m) wide and

less than 0.5 mi (0.8 km) long but can reach over 3 mi (5 km) or more in length on Moen-

kopi and Kaibito Plateaus. Individual linear dunes are mapped where they form prominent

landscape features on Moenkopi and Kaibito Plateaus. Groups of linear dunes are mapped as

linear dune and sand sheet deposits (Qdlu). Thickness, 6 to 40 ft (2 to 12 m)

Qdp

Parabolic dune deposits (Holocene)—White, gray, light-red, ne- to coarse-grained, well-

sorted, unconsolidated quartz sand arranged most commonly in complex interconnecting

parabolic dune deposits or occasionally in individual parabolic dunes. Sandy ponded sedi-

ments (Qps) are commonly formed on upwind (southwest) side of dune complex. Bedrock

or older sand accumulation is often exposed at southwest side of parabolic dunes. Contact

merges with adjacent dune sand and sand sheet (Qd) and sand sheet (Qes) deposits, mixed

alluvial and eolian (Qae) deposits, and local Mesozoic bedrock outcrops on Moenkopi and

Kaibito Plateaus. Support little to sparse grassy vegetation. Thickness, 6 to 30 ft (2 to 9 m)

Qdb Barchan dune deposits (Holocene)—White, gray, light-red, ne- to coarse-grained, well-sorted,

unconsolidated quartz sand that forms isolated barchan dunes or a cluster of interconnecting

barchan dunes mainly northeast of Tuba city, on Kaibito Plateau. Subject to yearly change

in extent and shape due to seasonal storms and sand mobility. Support little to sparse grassy

vegetation. Thickness, 6 to 40 ft (2 to 12 m)

Qdm Mixed dune deposits (Holocene)—White, gray, light-red, ne- to coarse-grained, well-sorted,

unconsolidated quartz sand derived primarily from the Navajo Sandstone (Jn). Parabolic

and linear dunes are the dominant dune types and are often interconnected and associated

with massive sand sheet (Qes) deposits. Linear dunes often form as downwind extension of

parabolic dunes on Moenkopi and Kaibito Plateaus and parabolic dunes often attach to or are

part of linear dunes. Include quite a few Navajo Sandstone (Jn) and ponded sediment (Qps)

deposits too small to show at map scale. Often covered annually by active dune sand and

sand sheet (Qd) deposits. Thickness, 6 to 40 ft (2 to 12 m)

Qdlu Linear dune and sand sheet deposits (Holocene)—White, gray, light-red, ne- to coarse-

grained, well-sorted, unconsolidated quartz sand derived primarily from the Navajo Sand-

stone (Jn) on Moenkopi and Kaibito Plateaus. Unit is often a cluster or group of closely

spaced linear dune and sand sheet deposits. Individual linear dunes often merge and separate

as an interconnecting mass of dune forms with abundant sand sheet deposits between. Sup-

port little to sparse grassy vegetation. Thickness, 9 to 40 ft (3 to 12 m)

Qg1 Young terrace-gravel deposits (Holocene)—Light-brown, pale-red, and gray, well-sorted,

interbedded clay, silt, sand, gravel, pebbles, cobbles, and some boulders. Include well-

rounded clasts of quartzite, quartz, chert, sandstone, and limestone. Support light to moder-

ate growths of grass, cactus, and desert shrubs. Subject to ash-ood erosion and overbank

ooding. Locally overlap young alluvial fan (Qa1), ood-plain (Qf), and valley-ll (Qv)

deposits. Often covered by dune sand and sand sheet (Qd) and sand sheet (Qes) deposits

in east half of quadrangle. Support light vegetation, mainly grass, and a few desert shrubs.

Form benches about 3 to 12 ft (1 to 3.5 m) above stream-channel (Qs) or ood-plain (Qf)

deposits. Subject to frequent ash ood erosion. Thickness, 6 to 20 ft (2 to 6 m)

Qa1 Young alluvial fan deposits (Holocene)—In Grand Canyon: Reddish-gray to light-brown silt,

sand, gravel, pebbles, cobbles, and boulders; partly consolidated by calcite and gypsum

cement. All material is derived primarily from Precambrian and Paleozoic rocks and subject

to ash-ood debris ows. Pebbles, cobbles, and boulders are subangular to rounded. Little

to no vegetation cover. Thickness 10 to 30 ft (3 to 9 m)

On Marble Plateau: Gray-brown to red silt, sand, gravel, pebbles, cobbles, and boul-

ders; partly consolidated by gypsum and calcite cement. Local outcrops of the Kaibab and

Moenkopi Formations provide silt and sand and also supply calcite, gypsum, and some salt

as cementing agents for most alluvial deposits on Marble Plateau. Support light growths of

sagebrush, cactus, and grass. Thickness 3 to 20 ft (1 to 6 m)

In eastern third of map area: Gray, light-brown, and light-red, clay, silt, sand, pebbles,

and cobbles of chert, limestone, and sandstone; unconsolidated. Unit often overlapped by

stream-channel (Qs), ponded sediments (Qps), ood-plain (Qf), dune sand and sand sheet

(Qd), and sand sheet (Qes) deposits. Intertongue with upper part of valley-ll (Qv), young

terrace-gravel (Qg1), and mixed alluvium and eolian (Qae) deposits. Clay, silt, and sand are

primarily derived from local outcrops of Triassic, Jurassic, and Cretaceous rocks. Subject

to extensive sheet-wash erosion, wind erosion, ash ood debris ows, and arroyo erosion.

Thickness, 3 to 30 ft (1 to 9 m)

Qg2 Intermediate terrace-gravel deposits (Holocene)—Gray and brown silt, sand, gravel, and

lenses of pebbles or conglomerate; partly consolidated. Lithologically similar to young

terrace-gravel (Qg1) deposits. Siltstone and ne-grained sandstone matrix is mixed with

subangular to rounded pebbles and boulders derived from nearby bedrock. Form benches

about 15 to 30 ft (4.5 to 9 m) above modern streambeds and about 6 to 20 ft (2 to 6 m) above

young terrace-gravel (Qg1) deposits in upper reaches of tributary streams. Support growths

of grass and a variety of high-desert shrubs. Subject to cutbank erosion. Locally intertongue

with, overlain by, or inset into young and intermediate alluvial fan (Qa1, Qa2), valley-ll

(Qv), mixed alluvium and eolian (Qae), talus and rockfall (Qtr), and landslide (Ql) deposits.

Thickness, 6 to 25 ft (2 to 7.5 m)

Qa2 Intermediate alluvial fan deposits (Holocene)—Lithologically similar to young alluvial fan

(Qa1) deposits; partly cemented by calcite, gypsum, and clay. Surface of unit is partly

eroded by sheetwash erosion that incises as much as 3 to 10 ft (1 to 3 m). In eastern third of

quadrangle, unit is often covered by dune sand and sand sheet (Qd) and sand sheet (Qes)

deposits. Unit is commonly overlapped by young alluvial fan (Qa1) deposits and inter-

tongues or overlaps with valley-ll (Qv), talus and rockfall (Qtr), and young and inter-

mediate terrace-gravel (Qg1, Qg2) deposits. Support light to moderate growths of grass,

sagebrush, and cactus. Thickness, 6 to 50 ft (2 to 15 m)

Qps Ponded sediments (Holocene)—Gray or red-brown clay, silt, sand, and gravel; partly consoli-

dated by calcite and or gypsum cement. Locally include small lenses of angular to sub-

rounded chert and limestone fragments or pebbles in sandy matrix. Similar to ood-plain

(Qf) deposits but occupy man-made ponded areas or natural internal drainage depressions

caused by sinkhole development on plateau surfaces in western half of quadrangle. Deposits

on Moenkopi and Kaibito Plateaus are commonly formed in depressions created by tem-

porary sand dune dams or in wind deation hollows of dune sand and sand sheet (Qd) and

parabolic dune (Qdp) deposits. Desiccation cracks often develop on hardpan surfaces during

dry conditions. Thickness, 5 to 30 ft (1.5 to 9 m)

Qg3 Old terrace-gravel deposits (Holocene)—Gray and light-brown, clay, silt, sand, gravel, cobbles,

and boulders partly consolidated by clay, calcite, and gypsum cement; poorly sorted. Include

abundant rounded and well-rounded clasts of quartzite, quartz, chert, sandstone, and lime-

stone in Grand Canyon. Form terrace deposits adjacent to and as much as 400 ft (122 m)

above the Colorado River. Thickness, 25 to 80 ft (7.5 to 24 m)

Qa3 Old alluvial fan deposits (Holocene)—Gray and light-brown, unsorted silt, sand, and gravel

mixed with brecciated and subrounded pebbles and cobbles of red sandstone and gray lime-

stone and chert; partly consolidated by calcite and gypsum cement. Unit often overlain by

sand sheet (Qes) and mixed alluvium and eolian (Qae) deposits in eastern half of quad-

rangle. Include large boulders, small cobbles and pebbles of sedimentary rocks derived from

nearby talus and rockfall (Qtr) and landslide (Ql) deposits in western half of map. Support

moderate growths of grass, sagebrush, cactus, and various desert shrubs. Thickness, 5 to 25

ft (1.5 to 7.5 m)

Qae Mixed alluvium and eolian deposits (Holocene)—Gray, light-red, ne- to coarse-grained inter-

bedded sand, brown clay and silt, and lenses of pebbly or brecciated gravel. Include angular

white chert fragments locally derived from Permian strata on Kaibab and Marble Plateaus;

white, gray, brown, and red chert fragments derived from members of the Chinle Forma-

tion in Painted Desert area; and white to gray chert fragments and concretionary sandstone

pebbles derived from Navajo Sandstone on Moenkopi and Kaibito Plateaus. Deposits accu-

mulate by combinations of alluvial or eolian processes resulting in an interbedded sequence

of mixed mud, silt, sand, and gravel. Deposit subject to sheetwash erosion and arroyo cutting

during wet conditions and wind-blown sand accumulations during dry conditions. Sediments

commonly accumulate on broad sandy atlands or on gently sloping alluvial fans. Support

light to moderate growth of grass, cactus, sagebrush, and high desert shrubs. Thickness, 3 to

40 ft (1 to 12 m)

Qv Valley-ll deposits (Holocene)—Gray and light-brown silt, sand, and lenses of gravel; partly

consolidated by gypsum and calcite. Include occasional rounded clasts of limestone, sand-

stone, and subrounded to angular chert derived from nearby bedrock; include abundant

rounded chert or quartz pebbles derived from Shinarump Member of the Chinle Formation

in Painted Desert area. Intertongue or overlap young and intermediate alluvial fan (Qa1,

Qa2) deposits and young terrace-gravel (Qg1) deposits. Commonly reect low-gradient,

low-energy sediment accumulation in shallow drainages in all areas of the map area. Subject

to sheetwash ooding and temporary ponding due to grasses at lower elevations; sagebrush,

grass, cactus, and some forest trees at elevations above 6,000 ft (1,830 m); sagebrush and

temporary blockage by eolian sand accumulation on Moenkopi and Kaibito Plateaus. Thick-

ness, 3 to 30 ft (1 to 9 m)

Qt Travertine deposits (Holocene and Pleistocene(?))—Gray and tan, stained light-red, massive,

porous, cliff-forming freshwater limestone. Include angular clasts of local talus breccia or

stream gravel. Formed by rapid chemical precipitation of calcium carbonate from springwa-

ter discharge as encrustations on steep slopes or cliffs. Deposits are primarily near base of

Cambrian Muav Limestone along east side of Colorado River and north side of Little Colo-

rado River in Grand Canyon. Include numerous dams in bed of Little Colorado River too

small to show at map scale. Include minor deposits at seeps along contact between Kayenta

Formation-Navajo Sandstone transition zone (Jkn) and underlying Kayenta Formation (Jk)

in Moenkopi Wash area that are too thin to show at map scale. Thickness, 6 to 60 ft (2 to 18

Qtr Talus and rockfall deposits (Holocene and Pleistocene(?))—In Grand Canyon: Gray to yellow-

ish-red silt, sand, and gravel mixed with abundant angular limestone, sandstone, and chert

rocks and boulders derived from steep-walled areas of Proterozoic and Paleozoic strata;

partly cemented by calcite and gypsum.

Along Echo Cliffs: Red to yellow, silt and sand mixed with angular rocks and boulders

of light-red or white sandstone and red to dark-red siltstone derived from Mesozoic outcrops

along Echo Cliffs and Moenkopi wash; partly cemented by calcite. Unit often associated

with or adjacent to landslide (Ql) deposits. Unit commonly grades downslope into young,

intermediate, and old alluvial fan (Qa1, Qa2, Qa3) deposits or young and intermediate

terrace-gravel (Qg1, Qg2) deposits. Thickness, 5 to 45 ft (1.5 to 14 m)

Ql Landslide deposits (Holocene and Pleistocene)—Landslides are unconsolidated to partly

consolidated masses of angular unsorted rock debris. Include stratied blocks (slumps) that

rotated backward against parent outcrop and slid downslope as loose incoherent masses of

broken rock fragments and deformed strata; often form talus and rockfall (Qtr) deposits

adjacent to and below landslide masses. Include individual car- and house-size boulders.

Gradational and arbitrary contact with young, intermediate, and old alluvial fan (Qa1, Qa2,

Qa3) and young, intermediate, and old terrace-gravel (Qg1, Qg2, Qg3) deposits. Subject to

extensive sheetwash erosion, ash-ood debris ows, and arroyo erosion. Thickness, 10 to

200 ft (3 to 61 m)

QTg4 Older terrace-gravel deposits (Pleistocene and Pliocene(?))—Gray and light-brown silt, sand,

gravel and well-rounded at pebbles and cobbles along higher beveled terraces of Navajo

Sandstone (Jn) along Moenkopi Wash. Unit contains mud, silt, and sandy gravel derived

from Cretaceous outcrops east of map area. Form terraced benches or ridges on Navajo

Sandstone about 30 to 45 ft (9 to 14 m) above Moenkopi Wash. Unit is mainly exposed in

cliff areas and commonly covered by thin dune sand and sand sheet (Qd) deposits. Thick-

ness, 2 to 10 ft (0.5 to 3 m)

QTg5 Youngest old terrace-gavel deposits (Pleistocene and Pliocene(?))—Gray and light-brown

clay, silt, sand, and gravel, poorly sorted; cemented by calcite on higher terrace levels along

Moenkopi Wash. Contain rounded fragments of Cretaceous fossils and well-rounded at

quartzite, chert, sandstone, and limestone pebbles. Fossil fragments are derived from Creta-

ceous rocks east of the map area. Include iron-rich sandstone concretions probably derived

from underlying Navajo Sandstone (Jn). Unit is covered by dune sand and sand sheet (Qd)

deposits. Support moderate growths of grass and low desert shrubs. Thickness, 3 to 60 ft (1

to 18 m)

QTg6 Intermediate old terrace-gravel deposits (Pleistocene and Pliocene(?))—Gray and light-

brown clay, silt, sand, and gravel, poorly sorted; cemented by calcite. Contain angular to

subrounded chert, limestone, and sandstone pebbles derived from Cretaceous rocks east

of the map area. Form isolated outcrops north of Moenkopi Wash and along U.S Highway

160 east of Tuba City. Unit is mostly covered by extensive eolian sand deposits (Qd, Qes).

Thickness, 6 to 30 ft (2 to 9 m)

QTg7 Oldest old terrace-gravel deposits (Pleistocene and Pliocene(?))—Gray and light-brown clay,

silt, sand, and gravel, poorly sorted; cemented by calcite. Lithology similar to youngest and

intermediate old terrace-gravel deposits (QTg5, QTg6) at highest levels north of Moenkopi

Wash and east of Tuba City. Unit may represent part of an extensive pediment surface that

drained from Black Mesa area east of map and formed before incision of Moenkopi Wash.

Thickness, 6 to 18 ft (2 to 6 m)

Tgs Gravel and sedimentary deposits (Pliocene(?) and Miocene(?))—Gray, brown, and white

clay, sand, silt, and gravel, poorly sorted; consolidated. Unit consists mostly of ne-grained

gray silty sand that includes scattered pebbles and cobbles of well-rounded gray sandstone

and limestone derived from Jurassic and Cretaceous rocks east and northeast of the map

area. Forms extensive thin veneer on Moenkopi Plateau that overlies beveled Jurassic and

Cretaceous rocks of the Navajo Sandstone (Jn), Entrada Sandstone (Je), Dakota Sandstone

(Kd), and Mancos Shale (Km), in southeast quarter of map. Forms consolidated caprock

deposit on Middle Mesa that overlies beveled Jurassic rocks of the Carmel Formation (Jc)

and Navajo Sandstone (Jn), east edge of map. Forms partly consolidated mixed sandstone,

siltstone, mudstone, and minor pebble sediments on Crooked Ridge in northeast corner of

map. Unit at all three localities forms the highest surcial uvial deposits, have a similar

lithology, and are at approximate similar elevations that may be Pliocene (?) age based on

relevant elevations above younger uvial deposits of Moenkopi Wash. Age may be Mio-

cene(?) as suggested by Lucchitta (2011). Thickness, 6 to 100 ft (2 to 30 m)

VOLCANIC ROCKS

Shadow Mountain is an isolated pyroclastic cone with associated basalt flows and dikes at the south-

central edge of the map area. These volcanic rocks are chemically and petrologically similar to rocks of the

San Francisco volcanic field, representing the northernmost volcanic rocks of that field, and have a K-Ar

age of 0.649±0.23 Ma (Damon and others, 1974; Condit, 1974). Miocene dikes are exposed in Moenkopi

Wash, in Hamblin Wash, at Tuba Butte, and at Wildcat Peak. A recent

Ar/

Ar age from a dike at Wildcat

Peak is 19.05±0.10 Ma (Peters, 2011).

Qi Intrusive dikes of Shadow Mountain (Pleistocene)—Black olivine-labradorite basalt dikes, 1 to

3 ft (0.5 to 1 m) wide

Qsp Pyroclastic deposits of Shadow Mountain (Pleistocene)—Black and red scoria, cinder, and ash

of olivine-labradorite basaltic composition. Overlie associated basalt ows (Qsb) and the

Petried Forest and Shinarump Members (^cp, ^cs) of the Chinle Formation. Thickness, 3

to 135 ft (1 to 40 m)

Qsb Basalt ows of Shadow Mountain (Pleistocene)—Black olivine-labradorite basalt largely

covered by associated pyroclastic (Qsp) deposits. Basalts owed into small graben north of

main cone, providing evidence that the graben is older than the ow. Flow is offset by a fault

suggesting that faulting has occurred within the last 65 k.y. Thickness, 40 ft (12 m)

Ti Intrusive dikes (Miocene)—Dark-gray basalt composed of plagioclase, clinopyroxene, olivine,

and opaque oxides. Dikes occur in Moenkopi Wash southwest of Tuba City, in Hamblin

Wash south of The Gap, at Tuba Butte northwest of Tuba City, and at Wildcat Peak northeast

of Tuba City. Dikes are extensively weathered and are 2 to 6 ft (0.05 to 2 m) wide and 15 to

33 ft (5 to 10 m) in height

SEDIMENTARY ROCKS

Km Mancos Shale (Upper Cretaceous)—Bluish-gray to light-gray, thinly laminated to thin-

bedded, slope-forming, carbonaceous claystone, siltstone, and mudstone with interbedded

light-gray, fine- to medium-grained sandstone. Includes bentonitic claystone, siltstone,

and some thin-bedded limestone. Locally fossiliferous with cephalopods that are later-

ally equivalent to those in the Tropic Shale in the lower part of Mancos Shale in southern

Utah. Age as defined by Doelling and others (2000). Deposited on a shallow sea floor

that transgressed southwest from the midcontinent. Gradational and arbitrary contact with

underlying Dakota Sandstone (Kd). Deposit is mostly removed by Tertiary erosion on

Moenkopi Plateau south of Moenkopi Wash. Erosion channels as deep as 20 ft (6 m) are

filled with Tertiary gravel and sedimentary deposits (Tgs) and probably represent wide-

spread alluvial pediment and stream-channel deposition. Largely covered by sand sheet

(Qes) and dune sand and sand sheet (Qd) deposits at Coal Mine Mesa on Moenkopi Pla-

teau in southeast corner of map (sheet 2) and on White Mesa in northeast corner of map

(sheet 2). Thickness, 140 ft (43 m)

Kd Dakota Sandstone (Upper Cretaceous)—Medium- to light-gray, slope-forming, laminated to

thin-bedded mudstone, siltstone, and sandstone. Locally includes lower sandstone, middle

carbonaceous, and upper sandstone members as dened by O’Sullivan and others (1972;

northeast and southeast corners of map). Age as dened by Doelling and others (2000)

Lower sandstone member: Light-orange to light-gray silty sandstone and conglomeratic

sandstone that forms cliffs as much as 20 ft (6 m) thick seen in channels eroded into under-

lying Entrada Sandstone-Cow Springs Sandstone, undivided (Je). Unit pinches out or thins

in short lateral distance within channels. Clasts in sandstone are composed of red and gray,

well-rounded chert and quartzite typically less than 2 in (5 cm) in diameter. The regional

angular unconformity between the Dakota Sandstone and underlying Jurassic-Cretaceous

rocks is based on the Dakota Sandstone overlying younger rocks north of the map area and

overlying older rocks south and southeast of the quadrangle. Although these relations estab-

lish the angularity of the pre-Dakota Sandstone age unconformity, the dip is so small that it

is not apparent at most outcrops within the area (Harshbarger and others, 1958)

Middle carbonaceous member: Dark-grayish-brown, carbonaceous, at-bedded mud-

stone, siltstone, and coal and interbedded brown, conglomeratic, crossbedded lenticular

sandstone. Coal beds are generally less than 2 ft (0.5 m) thick at east end of Coal Mine Mesa

on Moenkopi Plateau (southeast corner of map). Coal was mined from thicker coal beds

at the rim of Coal Mine Canyon. Coal-seam res in the recent past add vibrant red color

(baked clay) in upper cliffs of Coal Mine Canyon. Gypsum is a common constituent in the

siltstones, appearing as thin veins and isolated crystals. The upper sandstone member is not

present in the map area

Unit unconformably overlies Entrada Sandstone-Cow Springs Sandstone, undivided

(Je), in eastern part of Coal Mine Mesa where lower sandstone member is not present (J-2

unconformity of Pipiringos and O’Sullivan, 1978). Mostly covered by extensive dune sand

and sand sheet (Qd) deposits. Overall thickness, 10 to 40 ft (3 to 12 m)

San Rafael Group (Middle Jurassic)—The San Rafael Group (Middle Jurassic) includes, in

ascending order, the Carmel Formation (Jc) and the Entrada Sandstone (Je) that overlies

beveled crossbeds of the Navajo Sandstone (Jn), known as the J-2 unconformity that is rec-

ognized primarily on differences in lithology and color change from white sandstone of the

Navajo to red siltstone of the Carmel. The Carmel Formation represents a shallow marine

environment within a seaway that moved southward from Canada into northern Arizona and

extended to and pinches out in the subsurface of Coal Mine Mesa. Overlying the Carmel

Formation are white and red sandstone deposits of the Entrada Sandstone-Cow Springs

Sandstone, undivided (Je), that represent a coastal beach and marine tidal at

Je Entrada Sandstone-Cow Springs Sandstone, undivided (Middle Jurassic)—White, light-

gray, and yellowish, very fine grained, trough crossbedded sandstone. Includes interbedded

(5 to 7 ft [1.5 to 2 m]) thick beds of red siltstone and sandstone representing southern extent

of reddish Entrada Sandstone units just north of quadrangle that thin rapidly southward and

pinch out near and just south of Coal Mine Mesa. Interval of uppermost red, flat-bedded

siltstone and sandstone is likely equivalent to the Summerville Formation north of map area.

Uppermost interval of yellowish-white, fine-grained, crossbedded sandstone is equivalent to

the Cow Springs Sandstone northeast and east of quadrangle area. The Summerville Forma-

tion and Cow Springs Sandstone are equivalent to lower part of Morrison Formation north

of the map area (Doelling and others, 2000) and east of the map area at Black Mesa (Cooley

and others, 1969). Unit as a whole forms a cliff where overlain by resistant conglomeratic,

coarse-grained sandstone lenses of Dakota Sandstone (Kd), or Tertiary conglomeratic gravel

and sedimentary (Tgs) deposits. Unit thins south and southeast of map area and thickens

rapidly north. Thickness, 115 to 250 ft (35 to 76 m)

Jc Carmel Formation (Middle Jurassic)—Red and light-gray, slope-forming sandstone, silt-

stone, claystone, and silty calcareous and gypsiferous sandstone at Middle Mesa (east edge

of quadrangle), along Red Lake Monocline (northeast corner of quadrangle), and as isolated

outcrops (northwest quarter of quadrangle). Unit thins southward and pinches out south and

east of the Moenkopi Plateau. Present as dark red silty sandstone interval between base of

Entrada Sandstone (Je) and top of Navajo Sandstone (Jn) at the east end of Coal Mine Mesa

and is locally absent at west end of Coal Mine Mesa. Unconformably overlies upper bev-

eled surface of Navajo Sandstone (Jn), known regionally as the J-2 unconformity; erosional

relief is generally less than 15 ft (4.5 m) but can be as much as 30 ft (9 m). Ripple marks and

abundant rounded sandy fecal pellets about 0.5 in (1 cm) diameter are found in lenticular,

light-gray sandstone beds as much as 3 ft (1 m) thick. Locally contains white and red calcite

and white barite crystals. Unit pinches out southward into subsurface of Moenkopi Plateau;

locally removed by modern erosion from most of Kaibito Plateau. Unit gradually thickens

north and northeast of quadrangle. Thickness, 0 to 30 ft (0 to 9 m)

Glen Canyon Group (Lower Jurassic)—Includes, in ascending order, Moenave Formation

(Jm), Springdale Sandstone Member of Kayenta Formation (Jks), Kayenta Formation (Jk),

the Kayenta Formation-Navajo Sandstone transition zone (Jkn), and the Navajo Sandstone

(Jn). The Moenave Formation unconformably overlies the Triassic Chinle Formation. The

unconformity between the Triassic and Jurassic is based primarily on differences in lithol-

ogy, topography, and color change. The purple and white mudstone, sandstone, and gray

limestone of the Owl Rock Member of the Chinle Formation (^co) is overlain by red mud-

stone, siltstone, and sandstone of the Moenave Formation (Jm). The basal light-red sand-

stone of the Moenave Formation may be a lateral equivalent of the Lukachukai Member of

the Wingate Formation as mapped by Cooley and others (1969) but is herein included within

the lower part of the Moenave Formation, because it is lithologically the same as the overly-

ing beds of the Moenave Formation and because the Wingate Sandstone thins southward

from Utah and does not appear to reach the map area

About 20 mi (32 km) north of the map area, the upper boundary of the Glen Canyon

Group is the J-2 unconformity between the Navajo Sandstone (Jn) and Page Sandstone

(Doelling and others, 2000). At Middle Mesa, east central edge of the map area, the J-2

unconformity is between the Navajo Sandstone and Carmel Formation (Jc), and in the

extreme southeast corner of the map area, it is between the Navajo Sandstone and the

Entrada Sandstone-Cow Springs Sandstone, undivided (Je)

Jn Navajo Sandstone (Lower Jurassic)—Red, white, and tan, cliff-forming, high-angle cross-

bedded, fine- to medium-grained, well-sorted sandstone. Includes massive horizontal or

planar bedding. Quartz grains are frosted. Crossbeds are as much as 35 ft (11 m) thick.

Includes many discontinuous thin beds of gray to light-purple siliceous limestone, dolo-

mite, or dark-red sandy siliceous mudstone that form resistant ledges and flat-topped ridges

or small mesas on surface of Moenkopi and Kaibito Plateaus. Siliceous beds were formed

in playas or ponds between sand dunes and become increasingly common on Moenkopi

Plateau. Crossbeds contain numerous small, rounded, black and reddish-black, pea-size

hematite concretions as much as 3 in (7.5 cm) in diameter. Crossbed dip direction indicates

paleowinds were generally from the north and northwest. Gradational and arbitrary contact

with underlying Kayenta Formation-Navajo Sandstone transition zone (Jkn) marked at

lowest white or red massive sandstone cliff. Unit rapidly thins east and southeast of map

area and thickens north and northwest. Unit is removed by erosion in west half of map.

Thickness, 400 to 600 ft (122 to 183 m)

Jkn Kayenta Formation-Navajo Sandstone transition zone (Lower Jurassic)—Light-red and

white, fine- to medium-grained, massive to crossbedded, cliff-forming beds of Navajo

Sandstone lithology that intertongue with purple and light-red, slope-forming mudstone,

siltstone, and sandstone beds of Kayenta Formation lithology. Forms sequence of red and

white sandstone cliffs that alternate with purple and light-red mudstone and siltstone slopes

resulting in arbitrary map contact. This zone is considered to be the lower “wet part” of the

Navajo Sandstone by Marzolf (1983, 1991) and Blakey (1994). Gradually thins northward

and becomes basal part of the Navajo Sandstone near Cedar Ridge. Individual red and

white sandstone units thin or lens out into purplish siltstones of the Kayenta Formation

south of the map area. Several springs and seeps issue from base of Navajo Sandstone

along Echo Cliffs from Cedar Ridge to Tuba City and Moenkopi. Thickness, 0 to 240 ft (0

to 73 m)

Jk Kayenta Formation (Lower Jurassic)—Includes an upper slope-forming light-purple,

siltstone and sandstone and the basal orange-brown, cliff-forming Springdale Sandstone

Member. The Springdale Sandstone 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) but has since been reassigned as the basal

part of the Kayenta Formation based on paleontological data and a prominent Jurassic

unconformity at its base (Blakey, 1994; Marzolf, 1991; Lucas and Tanner, 2006; Tanner and

Lucas, 2007; Biek and others, 2007)

Upper slope-forming unit: Purple, lavender, and light-red uvial, crossbedded, ne-

grained mudstone, siltstone, and silty sandstone that undergo a northward facies change

from mostly slope-forming siltstone, mudstone, and sandstone at Moenkopi Wash to mostly

cliff-forming red sandstone and minor siltstone along Echo Cliffs at Cedar Ridge. Age is

determined by Peterson and Pipiringoes (1979) and Biek and others (2000). Along Echo

Cliffs, often covered by landslide (Ql) and talus and rockfall (Qtr) deposits caused when ero-

sion of underlying Kayenta Formation undercuts overlying Navajo Sandstone cliffs allowing

large blocks of both Navajo Sandstone and upper Kayenta Formation to fail as landslide

masses; especially prevalent where joints and fractures nearly parallel Echo Cliffs (g. 1).

Unit is unconformable with underlying cliff-forming Springdale Sandstone Member (Jks).

Thickness, 300 to 470 ft (92 to 143 m)

Jks Springdale Sandstone Member (Lower Jurassic)—Light-red to reddish-brown and dark-

red, cliff-forming, thin- to thick-bedded sandstone. Includes low-angle trough crossbed sets

with fluvial conglomeratic sandstone lenses containing dark-red mudstone and siltstone

rip-up clasts and poorly preserved petrified and carbonized fossil plant remains north of

map area (Peterson and Pipiringos, 1979; Biek and others, 2000). Crossbeds are separated

by thin-bedded to laminated dark-red siltstone and mudstone that locally contain mudstone

pellets. Unconformable contact with underlying Moenave Formation (Jm). Light-red, fine-

grained, crossbedded sandstone filling channels eroded into top of Springdale Sandstone

may represent southern extent of Wingate Sandstone. Thickness, 100 to 140 ft (30 to 43 m)

Jm Moenave Formation (Lower Jurassic)—Includes only the Dinosaur Canyon Member as

redefined by Blakey (1994), Marzolf (1991), Lucas and Tanner (2006), Tanner and Lucas

(2007), and Biek and others (2007) in the map area. Age is after Peterson and Pipiringos

(1979) and Biek and others (2000, 2007). Forms reddish-brown slopes and ledges of thin-

bedded, flat-bedded, and crossbedded, fine- to coarse-grained fluvial siltstone and silty sand-

stone. Unconformable contact with underlying Owl Rock Member of the Chinle Formation,

known as the J-O unconformity separating Triassic rocks from overlying Jurassic rocks.

Commonly covered by landslide (Ql) or talus and rockfall (Qtr) deposits. Thickness, 80 to

140 ft (25 to 43 m)

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

the Petried Forest Member, and the Shinarump Member and the sandstone and siltstone

member, undivided (Repenning and others, 1969)

^co Owl Rock Member (Upper Triassic)—Grayish-red and light-purple, slope- and ledge-form-

ing, nodular siliceous limestone interbedded with purple, light-blue, and light-red calcareous

siltstone and sandstone. Limestone beds are gray, cherty, lenticular, silty, irregular bedded,

1 to 5 ft (0.5 to 1.5 m) thick; extend laterally for several miles and form resistant benches

or ledges along Echo Cliffs and Ward Terrace (fig. 1, sheet 3). Number of limestone beds

decreases northward from several at Ward Terrace to two at Cedar Ridge. Contains abundant

mud pellets and silicified clay and concretionary chert nodules. Gradually thins northward

along Echo Cliffs and thickens slightly southeast of map area. Unconformable contact

between Owl Rock Member of the Chinle Formation and overlying Moenave Formation

commonly marked by a distinct lithologic and color change from purple and white calcare-

ous siltstone and sandstone and gray limestone of Owl Rock to dark-red and orange-red,

coarse-grained sandstone of Moenave Formation. Gradational contact with underlying Petri-

fied Forest Member placed at lowest laterally continuous limestone bed or at nodular calcar-

eous grayish-yellow siltstone slope about 10 to 15 ft (3 to 4.5 m) below lowest prominent

limestone bed. Thickness, 100 to 200 ft (30 to 60 m)

^cp Petrified Forest Member (Upper Triassic)—Purple, blue, light-red, greenish-gray, and

grayish-blue, slope-forming mudstone and siltstone. Includes interbedded white, coarse-

grained, lenticular, channel-fill sandstone. Includes three informal units of Akers and others

(1958), in descending order: red mudstone and sandstone, gray mudstone and sandstone, and

blue mudstone. Includes large lenticular erosion channels and large-scale, low-angle trough

crossbeds. Petrified logs and wood fragments common in lower white or yellowish-white

sandstone; alternately may be within upper part of Shinarump and sandstone and siltstone

member, undivided. Gradational contact with underlying Shinarump Member and sandstone

and siltstone member, undivided, at change from slope-forming multicolored mudstones of

Petrified Forest Member to tan cliffs and purple slopes of coarse-grained sandstone of Shi-

narump Member. Weathers into rounded hills or slopes with a rough, puffy, popcorn surface

caused by swelling of clay when wet. Thickness, 400 to 500 ft (122 to 153 m)

^cs Shinarump Member and sandstone and siltstone member, undivided (Upper Triassic)—

White, light-brown, tan, and yellowish-pink, cliff-forming, coarse-grained sandstone and

conglomeratic sandstone. Includes cliff-forming, low-angle, crossbedded sandstone inter-

bedded with slope-forming, poorly sorted, purple, light-red, and blue siltstone and mud-

stone. Lithology is highly variable locally but regionally homogeneous, consisting of about

75% sandstone, 20% conglomerate, and 5% mudstone. Pebbles are generally brown, black,

or light-colored, well-rounded quartz and siliceous composition. Petrified logs and wood

fragments are generally scattered throughout unit but common at some localities. Uncon-

formable contact with underlying red siltstone and sandstone of Moenkopi Formation. Unit

is thickest in Painted Desert area; thins north along Echo Cliffs and thins south of map area.

Thickness, 60 to 200 ft (18 to 60 m)

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

Holbrook and Moqui Members, undivided, Shnabkaib Member, and Wupatki Member. The

basal Timpoweap Member of the Moenkopi Formation is present but too thin and limited in

extent to show at map scale so is included in the Wupatki Member

The Moenkopi Formation is mostly eroded in the Grand Canyon area, but remnants

form Cedar Mountain, Gold Hill, Yon Dot hills, Shinumo Altar (g. 1, sheet 3), and several

isolated outcrops on Marble and Coconino Plateaus

^mhm Holbrook and Moqui Members, undivided (Middle(?) and Lower Triassic)—Reddish-

brown and tan, slope-forming, alternating sequence of claystone, siltstone, and sandstone

(McKee, 1954). Unit is equivalent to upper red member of Stewart and others (1972) in

northwestern Arizona. Siltstone and sandstone beds include large- to medium-scale trough

crossbedding and abundant cusp-type ripple marks, interbedded thin limestone, lenses of

conglomeratic sandstone, chert nodules, and thin veins of gypsum. Gradational contact with

underlying Shnabkaib Member. Unit undergoes rapid facies change from red siltstone-sand-

stone sequence in northern part of map area to mostly tan sandstone sequence in the south.

Tan sandstone beds increase in thickness north to south across the map and become similar

to conglomeratic beds of the overlying Shinarump Member and sandstone and siltstone

member, undivided (^cs). Include numerous channel lenses that are often confused with

the Shinarump. Thus, uncertainties exist in the central part of the map where unconformi-

ties between similar sandstones are numerous and difficult to differentiate. Typically, small

pebbles within a sandstone lens or bed denotes the Shinarump Member and sandstone and

siltstone members, undivided, of the Chinle Formation. Thickness, 80 to 120 ft (25 to 37 m)

^ms Shnabkaib Member (Lower Triassic)—Yellowish-white and light-brown, cliff-forming,

crossbedded, fine-grained, calcareous siltstone and coarse-grained sandstone. Unit is equiva-

lent to lower massive sandstone member of the Moenkopi Formation as defined by McKee

(1954) south of the map area (Billingsley and others, 2007). Lowermost ledge-forming

sandstone undergoes a facies change from light-red calcareous sandstone south of map area

to yellowish-white calcareous gypsiferous sandstone and dolomite north of map area. Gra-

dational contact with underlying Wupatki Member marked at base of lowest tan or light-red

sandstone cliff. Thickness, 50 to 100 ft (15 to 30 m)

^mw Wupatki Member (Lower Triassic)—Red and red-brown, slope-forming, thin-bedded,

mudstone, siltstone, and sandstone as defined by McKee (1954). Interbedded sandstones as

thick as 1 to 3 ft (0.5 to 1 m) form resistant ledges within crumbly red-brown mudstone/silt-

stone slopes. Bedding surfaces often contain small-scale ripple marks, salt crystal casts, mud

cracks, and rain-drop impressions. Unit is equivalent to lower red member, Virgin Limestone

Member, and middle red member of Stewart and others (1972) in northwestern Arizona.

Virgin Limestone Member is present at Cedar Ridge and in Yon Dot Mountains on Marble

Plateau but is too thin to show at map scale. Virgin Limestone beds consist of yellowish-

white, thin, platy, silty limestone and siltstone about 1 to 3 ft (0.3 to 1 m) thick and about 15

to 20 ft (4.5 to 6 m) above Harrisburg Member of the Kaibab Formation (Pkh); represent

the regional Permian/Triassic unconformity. Unit includes basal Timpoweap Member of

the Moenkopi Formation. Timpoweap Member is composed of subangular to subrounded

conglomerate in calcareous sandstone matrix; small, white, angular chert pebbles and frag-

ments derived from Kaibab Formation occupy shallow depressions and channels eroded into

underlying Harrisburg Member of the Kaibab Formation in western half of map. Thickness,

30 to 85 ft (9 to 26 m)

Kaibab Formation (Cisuralian)—Includes, in descending order, the Harrisburg Member and

Fossil Mountain Member as dened by Sorauf and Billingsley (1991)

Pkh Harrisburg Member (Cisuralian)—Reddish-gray and brownish-gray, ledge- and slope-

forming, gypsiferous siltstone, calcareous sandstone, and thin-bedded sandy limestone. Top

of unit near Little Colorado River Gorge includes white, low-angle, crossbedded, calcare-

ous sandstone with mollusk fossils; elsewhere, upper part is primarily sandy, cherty lime-

stone. Forms surface of Kaibab, Coconino, and Marble Plateaus and House Rock Valley in

west half of quadrangle. Contact with underlying Fossil Mountain Member is gradational

and marked at topographic break between grayish-white, slope- and ledge-forming sandy

limestone and sandstone sequence of Harrisburg Member and underlying cliff-forming,

gray to light-brown, thick-bedded, cherty limestone and sandy limestone of Fossil Mountain

Member. Unit gradually thins west to east and undergoes shoreward facies change from

mostly cliff- and slope-forming limestone and siltstone marine sediments in west half of

quadrangle to mostly sandy marine calcareous sandstone east of Grand Canyon. Difficult to

distinguish members in subsurface of eastern half of quadrangle. Thickness, 120 to 80 ft (37

to 25 m)

Pkf Fossil Mountain Member (Cisuralian)—Light-gray, cliff-forming, fine- to medium-grained,

thin- to medium-bedded (1 to 6 ft [0.3 to 2 m]), fossiliferous, cherty (25% to 30%), sandy

limestone and dolomite. Weathers dark gray; cliff surfaces often stained by black magnesium

oxide. Includes abundant gray and white, fossiliferous chert nodules and white chert breccia

beds. Chert nodules may contain concentric black and white bands or fossil sponges. White,

cliff-forming, chert breccia beds 4 to 10 ft (1 to 3 m) thick commonly present in uppermost

part help establish contact between Harrisburg (Pkh) and Fossil Mountain (Pkf) Members.

Unit gradually thins eastward and undergoes a shoreward facies change from limestone,

dolomite, and sandy limestone to calcareous sandstone and sandy limestone similar in

texture, composition, and appearance to overlying Harrisburg Member. Unit commonly

forms cliff below slopes and ledges of Harrisburg Member along rim of Grand Canyon,

Marble Canyon, and Little Colorado River Gorge. Unconformable contact with underlying

Toroweap Formation (Pt) attributed in part to solution and erosion of gypsiferous siltstone

in Toroweap but mostly to channel erosion; average erosional relief about 10 ft (3 m). Unit

gradually thins east and southeast in subsurface of map area, becoming indistinguishable

from upper Harrisburg Member. Thickness, 230 to 180 ft (70 to 55 m)

Pt Toroweap Formation, undivided (Cisuralian)—Includes, in descending order, the Woods

Ranch, Brady Canyon, and Seligman Members, undivided, as dened by Sorauf and Bill-

ingsley (1991). All three members are present on western side of Marble Canyon and Grand

Canyon. All three members undergo a rapid shoreward (eastward) facies change from cliff

and slope units west of Colorado River to cliff units east of Colorado River. Unit gradually

thins east and southeast in subsurface of map area and thickens west (Billingsley, 2000;

Billingsley and Wellmeyer, 2003; Billingsley and others, 2007). Eastern extent is unknown

but likely extends to or pinches out at eastern margin of map. Thickness, 200 to 250 ft (60 to

76 m)

Ptw Woods Ranch Member (Cisuralian)—Grand Canyon and Marble Canyon areas: gray and

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

with gray, thin-bedded limestone. Weathers to reddish-gray slope. Bedding locally distorted

due to dissolution of gypsum and gypsiferous siltstone. Erosional undercutting of overlying

Kaibab Formation results in numerous landslides and large open cracks near canyon rims

that tend to be accentuated along pre-existing joint and fracture systems. Unit undergoes

shoreward (eastward) facies change to mostly brown, cliff-forming, calcareous sandstone

and dolomite that weathers dark brown. Contact with underlying Brady Canyon Member is

gradational and marked at lithologic and topographic break between slope-forming gypsifer-

ous siltstone and sandstone of Woods Ranch and cliff-forming limestone of Brady Canyon

in western two-thirds of Marble Canyon and Grand Canyon area; becomes indistinguishable

from underlying Seligman and Brady Canyon Members in eastern third of Marble Canyon,

southeastern Grand Canyon, and Little Colorado River Gorge and subsurface of Marble

Plateau. Thickness, 100 to 180 ft (30 to 55 m)

Ptb Brady Canyon and Seligman Members, undivided (Cisuralian)—

Brady Canyon Member: Gray to brown, cliff-forming, thin- to medium-bedded (1 to

5 ft [0.05 to 1.4 m]), ne- to coarse-grained, limestone and sandy limestone. Weathers light

gray. Contains white and gray chert nodules that make up less than 5% of unit. Gradational

contact with underlying Seligman Member marked at base of limestone cliff in western part

of quadrangle. Becomes indistinguishable from other Toroweap Members east of Marble

Canyon, Grand Canyon, and Little Colorado River Gorge. Thickness, 20 to 30 ft (6 to 9 m)

Seligman Member: Gray, light-purple, and yellowish-red, slope-forming, thin-bedded

dolomite, sandstone, gypsum, and calcareous sandstone. Forms slope or recess between

overlying Brady Canyon Member and underlying Coconino Sandstone (Pc) in Marble

Canyon and Grand Canyon. Undergoes easterly shoreward facies change similar to Brady

Canyon and Woods Ranch Members; pinches out before reaching Little Colorado River

Gorge. Sharp unconformable contact with underlying white, cliff-forming Coconino Sand-

stone. Coconino Sandstone intertongues with lower part of Seligman Member west and

north of map area (Fisher, 1961; Schleh, 1966; Rawson and Turner, 1974; Billingsley and

Wellmeyer, 2003; Billingsley and others, 2006). Undergoes gradual shoreward (eastward)

facies change along with overlying Brady Canyon and Woods Ranch Members, making

all indistinguishable from one another east of Colorado River where they are mapped as

Toroweap Formation, undivided (Pt). Thickness, 10 to 20 ft (3 to 6 m)

Pc Coconino Sandstone (Cisuralian)—Tan to white, cliff-forming, ne-grained, well-sorted, cross-

bedded quartz sandstone. Thin red sandstone beds at base of Coconino Sandstone in Little

Colorado River Gorge are likely the northern edge of the Schnebly Hill Formation as dened

by Blakey (1990) in the Verde Valley south of the quadrangle. Contains large-scale, high-

angle, planar crossbeds that average about 11 m (35 ft) thick. Locally includes amphibian

trackways and low-relief wind ripple marks on crossbed surfaces. Unconformable contact

with underlying Hermit Formation (Ph) is sharp and planar with relief generally less than 3

ft (1 m) but locally as much as 8 ft (2.5 m); marked by distinct color and topographic change

between white, cliff-forming sandstone of Coconino Sandstone and dark-red, slope-forming

siltstone of Hermit Formation. Unit is exposed only in walls of the Grand Canyon but is

present in the subsurface of eastern half of map. Unit gradually thickens east and southeast

of map area and signicantly thins to the north and west. Thickness, 200 to 600 ft (60 to 183

Ph Hermit Formation (Cisuralian)—Red, slope-forming, ne-grained, thin- to medium-bedded

siltstone and sandstone. In Little Colorado River Gorge, upper part contains red, massive,

low-angle, cross-stratied calcareous sandstone and siltstone beds that may be equivalent, in

part, to Schnebly Hill Formation in Verde Valley south of map area (Blakey, 1990). Siltstone

beds throughout unit weather dark red and crumbly and ll widespread shallow erosion

channels; form recesses between thicker sandstone beds. Contains poorly preserved plant

fossils in channel-ll deposits in lower part of unit at Grand Canyon. Red cliffs and ledges

of sandstone immediately below contact with Coconino Sandstone (Pc) are often bleached

yellowish-white color owing to groundwater seepage from Coconino Sandstone. Uncon-

formably overlies Esplanade Sandstone (Pe) with erosional relief generally less than 10 ft (3

m). Unit thins southeast of Grand Canyon to less than 40 ft (12 m) at Little Colorado River

Gorge and may extend into subsurface of eastern part of map area. Unit thickens north and

west of map area. Thickness, 40 to 360 ft (12 to 110 m)

Supai Group (Cisuralian, Pennsylvanian, and Upper Mississippian)—Includes in descending

order, the Esplanade Sandstone and Wescogame, Manakacha, and Watahomigi Formations,

undivided

Pe Esplanade Sandstone (Cisuralian)—Light-red and pinkish-gray, cliff-forming, fine- to

medium-grained, medium- to thick-bedded (3 to 10 ft [1 to 3 m]), well-sorted calcareous

sandstone. Includes interbedded dark-red, thin-bedded, crumbly, recessive and slope-forming

siltstone beds in upper and lower part. Crossbeds are small to medium scale, low- and high-

angle planar. Unconformable contact with underlying Pennsylvanian and Upper Mississippian

rocks (*Ms) marked by erosion channels as much as 30 ft (9 m) deep in Grand Canyon and

Little Colorado River Gorge area. Thickness, 350 to 400 ft (107 to 122 m)

*Ms Wescogame (Upper Pennsylvanian), Manakacha (Moscovian), and Watahomigi (Bash-

kirien and Serpukhovian) Formations, undivided—Includes, in descending order,

the Wescogame, Manakacha, and Watahomigi Formations as defined by McKee (1982).

Individual formations are difficult to identify because of similar lithology and topographic

expression; unconformable contacts are shallow, difficult-to-find erosion channels. Herein,

the three formations are shown as one map unit

Wescogame Formation: Light-red, pale-yellow, and light-gray upper slope unit and

lower cliff unit. Upper slope unit consists mainly of dark-red, ne-grained siltstone and

mudstone interbedded with light-red, coarse-grained, calcareous sandstone, dolomitic sand-

stone, siltstone, mudstone, and conglomerate. Lower cliff unit consists mainly of light-red

to gray, high-angle, large- and medium-scale, tabular-planar, crossbedded sandstone and

calcareous sandstone as much as 40 ft (12 m) thick. Unconformable contact with underly-

ing Manakacha Formation marked by erosion channels 3 to 6 ft (1 to 2 m) deep in Grand

Canyon area. Channels commonly lled with limestone/chert conglomerate west of map

area. Thickness, 130 to 150 ft (40 to 45 m)

Manakacha Formation: Light-red, white, and gray upper slopes and ledges of sand-

stone, calcareous sandstone, dark-red siltstone, and thin gray limestone. Upper slope consists

mainly of shaley siltstone and mudstone with minor interbedded, thin-bedded limestone and

sandstone. Carbonate content increases west of map area forming numerous ledge-forming,

thin and medium limestone beds at west edge of map. Upper slope is about 75 to 100 ft

(23 to 30 m) thick in Grand Canyon. Lower cliff is dominated by reddish-gray, medium- to

thick-bedded, crossbedded, calcareous sandstone and sandy limestone. Lower cliff is about

60 ft (18 m) thick. Carbonate content increases west of map area, forming numerous gray

limestone ledges (McKee, 1982). Unconformable contact between Manakacha Formation

and underlying Watahomigi Formation marked at base of lower red sandstone cliff; erosional

relief nearly at, generally less than 3 ft (1 m). Thickness, 200 ft (60 m)

Watahomigi Formation: Gray and purple, slope-forming limestone, siltstone, mud-

stone, and minor conglomerate. Minor red chert lenses and nodules in lower limestone beds.

Includes alternating gray, thin-bedded cherty limestone ledges interbedded with purplish-

gray siltstone and mudstone in upper part. Upper ledge/slope averages about 70 ft (21 m)

thick. Lower slope consists mainly of purplish-red mudstone and siltstone, interbedded

with thin-bedded, aphanitic to granular limestone with red chert veins and nodules. Fossil

conodonts in lower thin limestone beds west of map area are Late Mississippian age (Martin

and Barrick, 1999). Unit includes purple siltstone and gray limestone interbedded with red-

dish conglomeratic sandstone that lls small erosion channels cut into underlying Surprise

Canyon Formation (Ms) or into Redwall Limestone (Mr). Lower Supai Group gradually

thins eastward and gradually thickens westward in west half of map. Thickness, 100 to 120

ft (30 to 37 m)

Ms Surprise Canyon Formation (Serpukhovian)—Dark-reddish-brown, massive to thin-bedded,

poorly sorted siltstone, sandstone, thin-bedded gray limestone, dolomite, and a basal gray

and white conglomerate of subrounded chert clasts derived from Redwall Limestone in

dark-red or black sandstone matrix. Unit is locally absent throughout map area and limited

to deposits within paleovalley and karst caves eroded into top half of underlying Redwall

Limestone (Billingsley and Beus, 1999). Unit is likely present in subsurface of eastern part

of map area. Sandstone and siltstone beds contain plant and bone fossils, mud cracks, and

ripple marks. Thickness, 0 to 100 ft (0 to 30 m)

Mr Redwall Limestone, undivided (Mississippian)—Includes, in descending order, Horseshoe

Mesa, Mooney Falls, Thunder Springs, and Whitmore Wash Members, with no middle Mis-

sissippian as dened by McKee (1963) and McKee and Gutschick (1969). Members are too

small to show at map scale because of steep topography in Grand Canyon. Unit overall is

light- to dark-gray, cliff-forming, thin- to thick-bedded, ne- to coarse-grained, fossiliferous

limestone and dolomite. Includes thin-bedded gray and white chert beds, lenses, and nod-

ules. Exposed mainly as sheer cliff in Grand Canyon; gradually thins eastward in subsurface.

Is an important aquifer because of solution caverns and joint and fracture systems. Thick-

ness, 400 to 450 ft (122 to 137 m)

Horseshoe Mesa Member: Light olive-gray, ledge- and cliff-forming, thin-bedded,

ne-grained limestone. Weathers to receding ledges. Gradational and disconformable con-

tact with underlying massive-bedded limestone of Mooney Falls Member marked by thin,

platy limestone beds that form recess about 3 to 9 ft (1 to 3 m) thick near top of Mooney

Falls Member cliff. Fossils locally common. Includes distinctive ripple-laminated lime-

stone, oolitic limestone, and some chert lenses. Unit locally absent in Paleozoic section

where removed by Late Mississippian paleovalley erosion. Thickness, 50 to 100 ft (15 to

30 m)

Mooney Falls Member: Light-gray, cliff-forming, ne- to coarse-grained, thick-bedded

to very thick bedded (4 to 20 ft [1 to 6 m]), fossiliferous limestone. Limestone weathers dark

gray; chert beds weather black. Upper part includes dark-gray dolomite beds, oolitic lime-

stone, and chert beds. Karst caves in upper part contain red sandstone and siltstone depos-

its of Surprise Canyon Formation (Ms) in Marble Canyon. Disconformable contact with

underlying Thunder Springs Member is distinguished by lithology; massive-bedded, gray

limestone of the Mooney Falls Member overlies thin-bedded, dark-gray to brown dolomite

and white chert beds of Thunder Springs Member. Thickness, 300 ft (75 m)

Thunder Springs Member: Roughly half of member is gray, cliff-forming, fossilifer-

ous, thin-bedded limestone and half is brownish-gray, cliff-forming, thin-bedded (1 to 5 in

[2 to 12 cm]), nely crystalline dolomite and ne- to coarse-grained limestone interbedded

with thin beds of white chert. Locally includes large-scale crossbedding and irregular gently

folded beds. Nautiloid fossils are common in upper 10 ft (3 m) of unit. The disconformable

planar contact with the underlying Whitmore Wash Member is distinguished by a distinct

lack of chert in Whitmore Wash Member. Thickness, 100 ft (30 m)

Whitmore Wash Member: Yellowish-gray and brownish-gray, cliff-forming, thick-

bedded, ne-grained dolomite. Weathers dark gray. Unconformable contact with underly-

ing Temple Butte Formation (Dtb) or Muav Limestone (_m) marked by low-relief erosion

channels about 5 to 10 ft (2 to 3 m) deep. Contact generally recognized where major cliff of

light-gray Redwall Limestone overlies stair-step ledges of dark-gray Devonian Temple Butte

Formation in Grand Canyon, Little Colorado River Gorge, and Marble Canyon; locally over-

lies channel lled with reddish-purple mudstone and dark-gray contorted limestone beds of

Temple Butte Formation within Marble Canyon. Otherwise unit most commonly overlies at

ledges of light-gray to greenish-gray, thin-bedded limestone of Cambrian Muav Limestone

in Marble Canyon area. Thickness, 80 to 100 ft (25 to 30 m)

Dtb Temple Butte Formation (Upper and Middle Devonian)—Purple, reddish-purple, dark-gray,

and light-gray, ledge-forming dolomite, sandy dolomite, sandstone, mudstone, and lime-

stone, as dened by Beus (2003). Purple and light-gray, ne- to coarse-grained, thin- to

medium-bedded, ripple-laminated ledges of mudstone, sandstone, dolomite, and conglom-

erate-ll channels eroded into the underlying Cambrian Muav Limestone; channels are as

much as 40 to 120 ft (12 to 37 m) deep in Marble Canyon. Carbonate ledges weather to dark

gray. Unconformity at base represents major stratigraphic break spanning about 100 m.y. in

the Grand Canyon that includes part of Late Cambrian, all of Ordovician and Silurian, and

most of Early and Middle Devonian. Unit thins east and north of the map area, thickens west

and south, and is likely intermittent or discontinuous in the subsurface of the northeastern

two-thirds of the map. Thickness, 0 to 120 ft (0 to 37 m)

Tonto Group (Middle and Lower(?) Cambrian)—Includes, in descending order, the Muav

Limestone, Bright Angel Shale, and Tapeats Sandstone as dened by Noble (1922) and

modied by McKee and Resser (1945). The age and depositional history of Cambrian rocks

in Grand Canyon are explained by Rose (2003). Tonto Group overlies tilted strata of the

Grand Canyon Supergroup of Mesoproterozoic age (1.4 to 1.1 Ma). Grand Canyon Super-

group rocks may be present only in the western part of the map. Otherwise, Tonto Group

overlies igneous and metamorphic rocks of Paleoproterozoic age (1.7 to 1.6 Ma). This hiatus

is known regionally as the Great Unconformity

_m Muav Limestone (Middle Cambrian)—Dark-gray to light-greenish-gray, brown, and orange-

red, cliff-forming, fine- to medium-grained, thin- to thick-bedded, mottled, fossiliferous,

silty limestone, limestone, dolomite, and calcareous mudstone. Includes unnamed siltstone

and shale beds of green and purplish-red, micaceous siltstone, mudstone, and thin beds of

brown sandstone. Contact with underlying Bright Angel Shale is gradational and lithology

dependent; marked at base of lowest prominent limestone cliff. Unit gradually thins west to

east, thinning to an unknown thickness in subsurface of eastern two-thirds of quadrangle.

Thickness, 320 to 380 ft (97 to 115 m)

_ba Bright Angel Shale (Middle Cambrian)—Green and purple-red, slope-forming siltstone,

shale, and red-brown to brown sandstone. Includes abundant green and purple-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

underlying Tapeats Sandstone is gradational and marked at top of transition from dominantly

green siltstone slopes to dominantly brown sandstone ledges above Tapeats Sandstone cliff.

Unit generally maintains a uniform thickness across western part of map area based on expo-

sures in Grand Canyon; gradually thins eastward in subsurface. Thickness, 200 to 300 ft (60

to 90 m)

_t Tapeats Sandstone (Middle and Lower(?) Cambrian)—Brown and red-brown, cliff-form-

ing, coarse-grained sandstone and conglomerate. Unconformable contact with the underly-

ing Proterozoic surface is called the Great Unconformity. Tapeats Sandstone fills lowland

areas between Proterozoic highlands and is locally absent on Proterozoic highlands. Variable

thickness, 0 to 300 ft (0 to 91 m)

NEOPROTEROZOIC ROCKS

Neoproterozoic igneous and sedimentary rocks, as mapped by Timmons and others (2007), are

exposed in the Grand Canyon and are likely present in the subsurface in the eastern part of the quadrangle.

Zs Sixtymile Formation, undivided (Neoproterozoic)—Informally divided into, in descending

order, the lower, middle, and upper members (Elston, 1979). Lower member is composed of

slumped blocks of dolomite surrounded by black shale exposed mainly in Sixtymile Canyon

in eastern Grand Canyon. Middle member is thick sequence of white to red, laminated and

thinly bedded siltstone, locally disrupted by intraformational brecciation and folding. Upper

member contains intraformational breccias and red fluvial sandstones derived from the

middle siltstone member. Unit unconformably overlain by Tapeats Sandstone. Thickness,

196 ft (60 m)

Chuar Group (Neoproterozoic)—Includes, in descending order, the Kwagunt Formation and

Galeros Formation as dened by Ford and Dehler (2003), modied by Timmons and others

(2007). A correlation by long-distance lithologic comparison, micropaleontologic assem-

blages, paleomagnetism, and very limited isotopic dating suggests the Nankoweap Forma-

tion, Chuar Group, and Sixtymile Formation were deposited within the 1,000 to 700 m.y.

period. The Cambrian Tonto Group overlies these tilted strata in the subsurface west and east

of Grand Canyon in the Tuba City quadrangle (sheet 1); this hiatus is known regionally as

the Great Unconformity

Kwagunt Formation (Neoproterozoic)—Includes, in descending order, the Walcott, Awatubi,

and Carbon Butte Members as mapped by Timmons and others (2007)

Zkw Walcott Member (Neoproterozoic)—Black to gray mudstone, gray dolomitic sandstone

(12 to 31 ft [4 to 9.5 m] thick), brecciated dolomite and sandstone. A thin tephra deposit

yielded a U-Pb zircon age of 742±6 Ma, providing an upper age limit for the Chuar Group

(Karlstrom and others, 2000). Thickness, 838 ft (255 m)

Zka Awatubi Member (Neoproterozoic)—Red, green, blue, and light-brown mudstone, silt-

stone, and sandstone. A basal tan to light-brown stromatolite carbonate bed contains fossil

biohermal dome features. Thin-bedded sandstone and siltstone contain ripple foreset beds

and mud-crack casts. Near top of member, organic shale preserves the macroalgal fossil,

Chuaria circularis, first described by Ford and Breed (1973). Thickness, 823 to 1,128 ft (252

to 344 m)

Zkcb Carbon Butte Member (Neoproterozoic)—Interbedded sandstone and siltstone. Basal

sandstone is brown, medium- to fine-grained, thick sandstone, forming a distinctive marker

bed approximately 252 ft (76 m) thick, and includes abundant soft-sediment deformation

features, interference ripple marks, and mud-crack casts (Ford and Breed, 1973). Above

basal sandstone unit are thin, interbedded, multicolored, mudstone, siltstone, and sandstone.

Thickness, 112 to 223 ft (34 to 68 m)

Galeros Formation (Neoproterozoic)—Includes, in descending order, the Duppa, Carbon

Canyon, Jupiter, and Tanner Members as mapped by Timmons and others (2007)

Zgd Duppa Member (Neoproterozoic)—Fine-grained siliciclastic unit dominated by shale and

interbedded thin-bedded siltstone. Includes interbedded calcareous siltstone beds about 3 ft

(1 m) thick. Variable thickness, 571 to 2,050 ft (174 to 625 m)

Zgcc Carbon Canyon Member (Neoproterozoic)—Fine-grained, interbedded siliciclastic mud-

stone, siltstone, and sandstone. Includes several thin dolomite and sandstone marker beds,

3 to 6 ft (1 to 2 m) thick. Sandstone beds contain symmetric and interference ripple marks,

low-angle crossbeds, and mud-crack casts. Stromatolite fossils become more common

toward top of unit. Thickness, 1,546 ft (471 m)

Zgj Jupiter Member (Neoproterozoic)—Fine-grained, interbedded siliciclastic mudstone,

siltstone, sandstone, and dolomite. Dolomite and some sandstone beds form several marker

beds throughout unit. Base of unit is stromatolitic dolomite, 40 ft (912 m) thick. Interbedded

sandstone beds contain symmetric ripple marks, mud-crack casts, and raindrop impressions.

Thickness, 868 to 1,516 ft (264 to 462 m)

Zgt Tanner Member (Neoproterozoic)—Very fine grained siliciclastic siltstone, sandstone,

and thin dolomite. Include dark-brown dolomite at base of unit that unconformably overlies

sandstone beds of the Nankoweap Formation. Thickness, 20 to 80 ft (6 to 24 m)

YZn Nankoweap Formation, undivided (Neoproterozoic to latest Mesoproterozoic)—Unconfor-

mity-bounded Nankoweap Formation separates rocks of the Neoproterozoic Chuar Group

and Late Mesoproterozoic Unkar Group. Includes an upper and lower member, undivided

(Gebel, 1978). Upper member is composed of siltstone and thick-bedded, ne-grained, red

sandstone at base and more massive 3-ft-thick (1-m-thick) sandstone bed toward top of sec-

tion, capped by white, ne-grained quartz sandstone. Unit contains trough crossbeds, ripple

marks, mud cracks, soft-sediment deformation, and rare salt casts. Lower member is domi-

nated by hematite-cemented quartzite sandstone and siltstone with lenses of lithic sandstone

derived from underlying Cardenas Basalt. Thickness, 330 ft (100 m)

MESOPROTEROZOIC ROCKS

Mesoproterozoic igneous and sedimentary rocks, as mapped by Timmons and others (2007), are

exposed in the Grand Canyon and are likely present in the subsurface in the eastern part of the quadrangle.

Unkar Group (Mesoproterozoic)—Includes, in descending order, Cardenas Basalt and the Dox

Formation as defined by Hendricks and Stevenson (2003) and modified by Timmons and

others (2007). Unkar Group rocks have been correlated to mafic intrusions of similar age

and type in the southwestern United States (Howard, 1991). Cambrian Tonto Group overlies

these tilted strata in the subsurface west and east of eastern Grand Canyon

Yc Cardenas Basalt (Mesoproterozoic)—Includes informal members, in descending order: the

lapillite, fan-jointed, and bottle-green members (Lucchitta and Hendricks, 1983). Lapillite

member is composed of scoriaceous fragments of volcanic bombs and ash matrix interbed-

ded in massive basalt flows a few meters to several tens of meters thick (Lucchitta and

Hendricks, 1983). Includes diabase intrusions that intrude both the Unkar Group and crystal-

line basement rocks as dikes and sills from a few tens of meters to 981 ft (300 m); dikes

are thinner and locally utilize fault planes; similar in texture, mineralogy, and chemistry to

Cardenas Basalt, suggesting a shared and common source. Thickness, 163 to 294 ft (50 to 90

m). Fan-jointed member is composed of porphyritic and vesicular basaltic andesite, approxi-

mately 163 ft (50 m) thick (Hendricks and Lucchitta, 1974). The bottle-green member con-

sists of thin, discontinuous sequences of interbedded basalt flows and sandstone beds, highly

altered, and contains secondary chlorite, epidote, talc, and zeolites; approximately 294 ft (90

m) thick

Dox Formation (Mesoproterozoic)—Includes, in descending order, the Ochoa Point, Coman-

che Point, Solomon Temple, and Escalante Creek Members as mapped by Timmons and

others (2007) and described by Hendricks and Stevenson (2003). Contacts between members

of Dox Formation are gradational and based mainly on topographic expression, depositional

environments, and color change

Ydo Ochoa Point Member (Mesoproterozoic)—Red slope- and cliff-forming micaceous mud-

stone that grades upward into red quartz sandstone and silty sandstone. Includes salt-crystal

casts in mudstone and asymmetrical ripple marks and small-scale crossbeds in sandstone.

Thickness, 250 to 300 ft (976 to 91 m)

Ydc Comanche Point Member (Mesoproterozoic)—Light-red, pale-green to white, slope-

forming, mudstone and siltstone and minor thin-bedded sandstone. Includes mud cracks,

ripple marks, salt casts, wavy to irregular bedding, and stromatolitic dolomite beds within or

adjacent to white siltstone beds. Thickness, 508 ft (155 m)

Yds Solomon Temple Member (Mesoproterozoic)—Cyclical sequence of red mudstone,

siltstone, and quartz sandstone. Includes thin beds of argillaceous dolomite or calcareous

siltstone. Mud cracks and ripple marks are common. Thickness, 920 ft (280 m)

Yde Escalante Creek Member (Mesoproterozoic)—Light-brown to greenish-brown sandstone,

calcareous sandstone, and arkosic sandstone. Includes an upper dark-brown to green shale

and mudstone. Thickness, 1,278 ft (390 m)

Ys Shinumo Sandstone, undivided (Mesoproterozoic)—Includes ve informal members, in

descending order: the Seventy Five Mile Rapid, Cottonwood Camp, Papago Creek, Ribbon

Falls, and Surprise Valley Members, undivided (Timmons and others, 2007). Consists of red,

brown, purple and white, cliff-forming, ne- to coarse-grained, well-sorted quartz arenite

and subarkose sandstone with siliceous cement. Upper massive sandstone shows dramatic

contorted bedding. Unconformable contact with underlying Hakatai Shale truncates cross-

beds and alluvial channel deposits. Thickness, 1,132 ft (345 m)

Yh Hakatai Shale, undivided (Mesoproterozoic)—Includes three informal members, in descending

order: the Stone Creek, Cheops Pyramid, and Hance Rapids members based on lithology of

Beus and others (1974) and Reed (1976). The Cheops and Hance Rapids members are red to

bright-red, slope-forming, highly fractured, argillaceous mudstones and shale. Upper Hance

Rapids member is purple and red, cliff-forming, medium-grained sandstone. Unit contains

mud cracks, ripple marks, and tabular-planar crossbed structures. Gradational contact with

underlying Bass Formation. Thickness, 448 to 981 ft (137 to 300 m)

Yb Bass Formation (Mesoproterozoic)—Gray and reddish-gray dolomite interbedded with arkose

and sandy dolomite and siltstone interbedded with intraformational breccias and conglomer-

ates throughout sequence. Interbedded with dolomite and mudstone beds. Beds of white,

very ne grained tephra deposits with a U-Pb zircon age of 1254±2 Ma (Timmons and

others, 2007) toward base of section. The basal Hotauta Conglomerate Member (Noble,

1922) consists of rounded, gravel-sized clasts of chert, granite, quartz, plagioclase crystals,

and micropegmatites in quartz sand matrix (Dalton, 1972). Contains biscuit-form and bio-

hermal stromatolite beds (Nitecki, 1971). Unconformable contact with underlying Paleopro-

terozoic granites and schists. Thickness, 196 to 327 ft (60 to 100 m)

PALEOPROTEROZOIC ROCKS

Paleoproterozoic intrusive igneous and metasedimentary rocks, as mapped by Timmons and others

(2007), are exposed in Grand Canyon and are likely present in the deep subsurface of the eastern part of the

quadrangle.

Xg Granite (Paleoproterozoic)—Unfolded to weakly foliated, medium- to fine-grained muscovite-

biotite, granitic pegmatite and aplite dikes, sills, and small plutons. U-Pb zircon ages range

from 1,685 to 1,680±1 Ma (Hawkins and others, 1996)

Xgd Granodiorite-gabbro-diorite and granodiorite complexes (Paleoproterozoic)—Weakly to

well-foliated, medium- to coarse-grained quartz-plagioclase and diorite-hornblende-bearing

granitoids of probable volcanic arc origin (1.74 to 1.71 Ga)

Xv Vishnu Schist of Granite Gorge Metamorphic Suite (Paleoproterozoic)—Quartz-mica schist,

pelitic schist, and meta-arenites of probable volcanic arc basin origin. Locally contains

graded bedding and turbidite layering. Strongly foliated with multiple generations of folds

and foliations (Ilg and others, 1996)

Xr Rama Schist and Gneiss of Granite Gorge Metamorphic Suite (Paleoproterozoic)—Quartz-

ofeldspathic schist and gneiss of probable felsic to intermediate metavolcanic origin;

strongly foliated; yields a U-Pb zircon age of 1,741±1 Ma (Hawkins and others, 1996)

Xbr Brahma Schist of Granite Gorge Metamorphic Suite (Paleoproterozoic)—Amphibolites,

biotite-hornblende schist and biotite schist of probable mac volcanic origin. Local metafel-

site interbeds contain phenocrysts of quartz and feldspar; beds yield a U-Pb zircon age of

1,750±2 Ma (Hawkins and others, 1996)

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