2013

U.S. Department of the Interior

U.S. Geological Survey

Prepared in cooperation with the Navajo Nation

Geologic Map of the Winslow 30’ × 60’ Quadrangle, 

Coconino and Navajo Counties, Northern Arizona

By George H. Billingsley, Debra Block, and Margaret Hiza Redsteer

Pamphlet to accompany

Scientific Investigations Map 3247

View looking north from the Painted Desert Overlook north of Winslow, Arizona, showing the colorful, easily eroded beds of the 

Petrified Forest Member of the Upper Triassic Chinle Formation. Buff-colored ledges above red beds in the distance are strata of the 

overlying Owl Rock Member of the Chinle Formation. Photograph by George Billingsley, 2009.
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2013

For more information on the USGS—the Federal source for science about the Earth,

its natural and living resources, natural hazards, and the environment—visit 

http://www.usgs.gov or call 1–888–ASK–USGS

For an overview of USGS information products, including maps, imagery, and publications,

visit http://www.usgs.gov/pubprod

To order this and other USGS information products, visit http://store.usgs.gov

Suggested citation:

Billingsley, G.H., Block, D., and Hiza Redsteer, M., 2013, Geologic map of the Winslow 30′ x 60′

quadrangle, Coconino and Navajo Counties, northern Arizona: U.S. Geological Survey Scientific 

Investigations Map 3247, pamphlet 25 p., 3 sheets, scale 1:50,000, available at 

http://pubs.usgs.gov/sim/3247/.

Any use of trade, product, or firm names is for descriptive purposes only and does not imply 

endorsement by the U.S. Government.

Although this report is in the public domain, permission must be secured from the individual 

copyright owners to reproduce any copyrighted material contained within this report.
iii

Contents

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

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

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

Mapping Methods..........................................................................................................................................1

Special Note ..........................................................................................................................................3

Map Scale..............................................................................................................................................3

Geologic Setting.............................................................................................................................................3

Paleozoic Rocks.............................................................................................................................................3

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

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

Chinle Formation ...................................................................................................................................5

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

Kayenta Formation................................................................................................................................6

Dakota Sandstone and Mancos Shale..............................................................................................7

Cenozoic Sedimentary and Volcanic Rocks..............................................................................................7

Bidahochi Formation ............................................................................................................................7

Volcanic Rocks of Hopi Buttes Volcanic Field .................................................................................8

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

Surficial Mapping Approach...............................................................................................................8

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

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

Acknowledgments.......................................................................................................................................10

Description of Map Units............................................................................................................................10

Surficial Deposits................................................................................................................................10

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

Sedimentary Rocks.............................................................................................................................17

References Cited..........................................................................................................................................21

Figures

Figure 1. Index map of Winslow 30’ × 60’ quadrangle, Arizona..............................................................2

Figure 2. Schematic cross section northwest to southeast across Hopi Buttes area.......................4

Tables

Table 1. Geochronologic data from Hopi Buttes Volcanic Field, Little Colorado River area ...........24

1

Introduction

This geologic map of the Winslow 30′ × 60′ quadrangle, 

Arizona, is a cooperative effort of the U.S. Geological Survey 

(USGS) and the Navajo Nation to provide regional geologic 

information for resource management officials and visitor information services of the Navajo Nation. Field work on the Navajo 

Nation was conducted with the cooperation of, and under a 

written permit from, the Navajo Nation Minerals Department. 

Any persons wishing to conduct geologic investigations on 

the Navajo Nation must first apply for, and receive, a permit 

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

Window Rock, Arizona, 86515, telephone (928) 871–6587. 

The Winslow quadrangle, which encompasses approximately 5,018 km2

 (1,960 mi2) within Coconino and Navajo 

Counties of northern Arizona, is bounded by longitude 110° 

to 111° W. and latitude 35° to 35°30′ N. South of the Navajo 

Nation, private and State lands form a checkerboard pattern 

along the south edge of the quadrangle (fig. 1). 

The geologic map of the Winslow quadrangle was prepared 

by the USGS Navajo Land Use Planning Project in cooperation 

with the Navajo Nation and funded through the USGS National 

Cooperative Geologic Mapping Program to provide connectivity to the regional geologic framework of the Grand Canyon 

area of northern Arizona. The Winslow geologic map will benefit local, state, federal, Navajo, and private land-resource managers who direct environmental and land-management programs 

such as range management, biological plant and animal studies, 

flood control, water resource investigations, and natural hazards 

associated with sand dune mobility. The geologic information 

will support future and ongoing geologic investigations and 

associated scientific studies within the Winslow quadrangle.

Geography

The Winslow quadrangle, which lies within the southern 

Colorado Plateaus geologic province (herein called the “Colorado Plateau”), is locally subdivided into six physiographic parts: 

the Little Colorado River Valley, Painted Desert, Newberry 

Mesa, Ives Mesa, Marcou Mesa, and the Hopi Buttes (fig. 1). 

Elevations range from 2,067 m (6,782 ft) at the Radio Facility 

within the Hopi Buttes (Tsezhin Bii) to about 1,428 m (4,685 ft) 

at the Little Colorado River northwest of Leupp (fig. 1). 

Settlements within the Winslow quadrangle include Winslow (the largest), Leupp, Dilkon, Indian Wells, Tolani Lake, 

Bird Springs, and Teesto (fig. 1). The town of Old Leupp (west 

edge of sheet 1) was abandoned in the 1940s due to potential 

flood problems and moved 1.5 km (1 mi) west to Sunrise, now 

called Leupp. 

State Highway 77 provides access to the east half of the 

Winslow quadrangle; State Highway 87 provides access to the 

central part; and State Highway 99 provides access to the west 

half. Navajo Highway 15 provides access from Leupp eastward across the central part of the Winslow quadrangle to Bird 

Springs, Dilkon, and Indian Wells (fig. 1). Navajo Highway 2 

provides access northward from Leupp to Tolani Lake. Unimproved dirt roads provide access to remote parts of the Navajo 

Reservation. Some roads are maintained by the Navajo Nation 

Roads Department in Window Rock, Arizona, and others are 

maintained locally by local Chapter governments (Leupp, Tolani 

Lake, Bird Springs, Dilkon, Teesto, Indian Wells, White Cone, 

and Greasewood Springs Chapters). Four-wheel-drive vehicles 

are recommended for driving on dirt roads of the Navajo Nation 

owing to mud or snow in the winter months and sandy conditions in the spring and summer months. Extra water and food is 

highly recommended for travel in this region. 

Previous Work

An early reconnaissance photogeologic map that includes 

the Winslow quadrangle was compiled by Cooley and others 

(1969 [sheet 4 of 8; scale 1:125,000]) for the Navajo and Hopi 

Indian Reservations of Arizona, New Mexico, and Utah. This 

map was not registered to a topographic base map at the time 

because a base larger than 1:250,000-scale did not exist. The 

map by Cooley and others (1969), which was used as part of 

the Flagstaff 1° × 2° quadrangle by Ulrich and others (1984), is 

adjacent to the following 1° × 2° quadrangle maps: the Marble 

Canyon quadrangle by Haynes and Hackman (1978); the 

Shiprock quadrangle by O’Sullivan and Beikman (1963); and the 

Gallup quadrangle by Hackman and Olson (1977). Two largescale geologic maps and reports within the Hopi Buttes (Tsezhin 

Bii) Volcanic Field were produced by Vazquez (1998, 1999) and 

Hooten (1999a, 1999b). The geology in these two large-scale 

maps, although too detailed to include in this map, does provide significant information and insight about the complexity 

of diatreme volcanoes of the Hopi Buttes area. The Quaternary 

geology of all previous maps has been modified and significantly 

updated to match the consistency and detail of the Cameron 

30′ × 60′ quadrangle map (Billingsley and others, 2007), which 

adjoins the northwest corner of the Winslow map. 

Mapping Methods

The geologic map of the Winslow quadrangle was produced 

by stereoscopic analysis of aerial photographs, augmented by 

extensive field checking. Primary resources include color aerial 

photographs at 1:24,000-scale, flown in 2004, 2005, and 2006, 

and also at 1:40,000-scale, flown in 2005. The geologic linework 

originally was compiled onto 1:24,000-scale paper USGS topographic maps. The 32 draft paper maps then were scanned and 

georeferenced to the corresponding 7.5′ topographic map digital 

raster graphics (DRGs) in ArcGIS. Geologic features were digitized and symbolized from the field sheets, and additional field 

checks were performed where needed.

Many of the Quaternary alluvial and eolian deposits have 

similar lithologic and geomorphic characteristics and were 

mapped almost entirely by photogeologic methods. Pliocene(?), 

Pleistocene, and Holocene surficial deposits were differentiated 

chiefly on the basis of differences in morphologic character and 

physiographic position as observed on color aerial photographs 
2

Figure 1. Index map of Winslow 30' × 60' quadrangle, Arizona, showing physiographic, cultural, and geologic locations ment
3

and in the field. Older alluvial and eolian deposits are significantly eroded, whereas younger deposits are only slightly eroded 

and are actively accumulating material. Surficial unit contacts 

that are adjacent to alluvial, eolian, and bedrock map units are 

approximate. 

Special Note 

The channel of the Little Colorado River was mapped 

by stereo-photographic methods using 2005 color digital 

orthophoto quadrangles (DOQs) and drawn on 1979 and 1986 

1:24,000-scale USGS topographic base maps. The present-day 

(2005) river channel morphology does not match that depicted 

on the 1979 and 1986 topographic base maps because of changing geomorphic conditions of the Little Colorado River.

Map Scale

Although the nominal scale of a USGS 30′ × 60′ topographic quadrangle is 1:100,000, we present the geologic map 

of the Winslow quadrangle in two panels at the 1:50,000-scale 

in order to preserve geologic features that were mapped and 

compiled at the 1:24,000-scale but are too detailed to show at 

the 1:100,000-scale. For map plotting purposes and readability, 

we present the geologic map as west (sheet 1) and east (sheet 2) 

panels, each consisting of sixteen 7.5ʹ quadrangles. The consolidation of sixteen 1:24,000-scale maps into a single panel gives 

the user a greater synthesis of the regional geology, and yet 

each panel retains the detail of the original mapping scale. In 

some areas, the details may be hard to read on plotted maps, but 

because these maps are available online, any difficulty in reading the “busy” areas of the map can be remedied by magnified 

viewing on screen. A third sheet contains a Correlation of Map 

Units, a List of Map Units, and an explanation of map symbols 

that are applicable to both map sheets. This pamphlet contains 

the complete Description of Map Units for all units on both map 

sheets. 

Geologic Setting

The Winslow quadrangle is characterized by gently dipping Paleozoic and Mesozoic strata, which dip 1° to 2° northeastward in the southwestern part of the quadrangle (sheet 1) 

and become nearly flat-lying in the northeastern part of the 

quadrangle (sheet 2). In the northeastern part (sheet 2), a shallow Cenozoic erosional basin developed about 20 m.y. ago, 

which subsequently was filled with flat-lying Miocene and 

Pliocene lacustrine sediments of the Bidahochi Formation, as 

well as associated volcanic rocks of the Hopi Buttes Volcanic 

Field. The lacustrine sediments and volcanic rocks unconformably overlie Triassic, Jurassic, and Cretaceous strata (fig. 2; see 

also, Ort and others, 1998).

Beginning about early Pliocene time, the Little Colorado 

River and its tributaries began to remove large volumes of 

Paleozoic and Mesozoic bedrock from the map area. This 

erosional development has continued through Pleistocene 

and Holocene time. Fluvial sediments accumulated episodically throughout this erosional cycle, as indicated by isolated 

Pliocene(?) and Pleistocene Little Colorado River terrace-gravel 

deposits (QTg4) on Tucker Mesa and Toltec Divide west of 

Winslow and younger terrace-gravel deposits (Qg4) along the 

margins of the Little Colorado River Valley (sheet 1). These 

gravel deposits suggest that the ancestral Little Colorado River 

and its valley has eroded and migrated northeastward toward 

its present location and largely parallels the strike of the Chinle 

Formation. Today, the Little Colorado River meanders within a 

5-km (3-mi) wide valley between Winslow and Leupp, where 

soft strata of the Chinle Formation is mostly covered by an 

unknown thickness of Holocene flood-plain deposits (Qf, Qf1, 

Qf2, Qf3). In modern times, the Little Colorado River channel has changed its position as much as a 1.5 km (1 mi) during 

flood events (Block and others, 2009), but for much of the 

year the channel is a dry river bed. Surficial alluvial and eolian 

deposits cover extensive parts of the bedrock outcrops over the 

entire Winslow quadrangle (sheets 1, 2). 

Paleozoic Rocks

In the southwest quarter of the Winslow quadrangle (sheet 

1), tributary drainages to the Little Colorado River have eroded 

small canyons that expose about 50 m (165 ft) of Paleozoic 

strata. The oldest unit exposed is in Cow Canyon (southwest 

edge of sheet 1) where approximately 11 m (35 ft) of Permian 

Coconino Sandstone crop out. Subsurface well logs indicate 

that the red sandstone at the base of the Coconino Sandstone 

(not exposed at the surface) is likely to be the northern extent 

of the Schnebly Hill Formation (Blakey, 1990) that is exposed 

in the Verde Valley southwest of the Winslow quadrangle. The 

Coconino Sandstone and the underlying Schnebly Hill Formation are important water-bearing sandstones in the subsurface 

of the southwestern part of the Winslow quadrangle (sheet 1; 

see also, Hoffmann and others, 2005). The combined thickness 

of the Coconino Sandstone and the Schnebly Hill Formation is 

about 366 to 396 m (1,200 to 1,300 ft; Hoffmann and others, 

2005). 

The Coconino Sandstone is unconformably overlain by 9 

m (30 ft) of the Permian Toroweap Formation, present in the 

subsurface in the vicinity of Leupp (sheet 1). Elsewhere, it is 

unconformably overlain by the Permian Kaibab Formation 

(Hoffman and others, 2005). The Coconino Sandstone (and the 

underlying Schnebly Hill Formation) may be equivalent to, or 

may be a northeastward facies change into, the DeChelly Sandstone (Baars, 2000), present in the subsurface northeast of the 

Winslow quadrangle. However, this correlation is speculative 

and will remain so until future drilling information can confirm 

or refute it. 

A regional unconformity known as the “Tr-1” (Pipiringos 

and O’Sullivan, 1978), which has erosional relief of less than 

2 m (6 ft), separates the Kaibab Formation from the overlying 

Triassic Moenkopi Formation. This unconformity is easily recognized by a color change from the gray-white sandy limestone 
4

Figure 2. Schematic cross section northwest to southeast across Hopi Buttes area (sheet 2), showing Tertiary erosion surface that was cut 

rocks and was subsequently filled with Miocene rocks of the Bidahochi Formation and the volcanic rocks of Hopi Buttes Volcanic Field (wid
5

of the Kaibab Formation to the light-red sandstone and siltstone 

of the Moenkopi Formation. Erosional depressions and channels 

between the Kaibab and Moenkopi Formations were subsequently filled with angular and subangular chert and sandstone 

breccia or conglomerate less than 0.5 m (2 ft) thick derived 

from Permian erosion of the Kaibab Formation. 

Mesozoic Rocks

Erosion by the Little Colorado River and its tributaries 

has exposed about 548 m (1,800 ft) of Mesozoic sedimentary 

rock strata in the Winslow quadrangle (sheets 1, 2). West to 

east across the quadrangle, the Mesozoic rocks undergo abrupt 

facies and thickness changes within each formation. The Mesozoic rocks are, in ascending order, the Moenkopi Formation 

(Middle? and Lower Triassic), the Chinle Formation (Upper 

Triassic), the Moenave Formation (Lower Jurassic), the Kayenta Formation (Lower Jurassic), the Dakota Sandstone (Upper 

Cretaceous), and the Mancos Shale (Upper Cretaceous). 

Moenkopi Formation

Overlying the Kaibab Formation is a sequence of reddish 

sandstone ledges and siltstone slopes of the Moenkopi Formation, which is exposed in the southwestern one-third of the 

Winslow quadrangle (sheet 1) but is partly covered by surficial 

deposits of the Little Colorado River between Leupp and Winslow. The Moenkopi Formation thins slightly from west to east 

across the southwest quarter of the quadrangle (south half of 

sheet 1) and averages about 67 m (220 ft) thick. The Moenkopi 

Formation is unconformably overlain by light-brown sandstone 

and conglomeratic-sandstone ledges of the Shinarump Member 

of the Chinle Formation. An unknown amount of the upper part 

of the Moenkopi Formation was removed by Triassic erosion 

prior to deposition of the overlying Chinle Formation. 

As defined by McKee (1954), the following four formal 

and informal members of the Moenkopi Formation are recognized in the Little Colorado River Valley, in ascending order: 

the Wupatki Member, the lower massive sandstone member, 

the Holbrook Member, and the Moqui Member. The Wupatki 

Member, which thins west to east and pinches out just west of 

the city of Winslow, is too thin (4.5 m [15 ft] thick) to show 

at map scale and is herein included as part of the lower massive sandstone member (^ms). The lower massive sandstone 

member unconformably overlies the Kaibab Formation in the 

Winslow area and forms a small, continuous, light-red cliff or 

ledge that gradually thins to less than 3 m (11 ft) southeastward 

across the southwestern part of the Winslow quadrangle (sheet 

1). 

The overlying Holbrook and Moqui Members, undivided 

(^mhm) make up the bulk of the Moenkopi Formation, as 

defined by McKee (1954) and Hager (1922). The lower, slopeforming Moqui Member (McKee, 1954) is exposed along 

“Moqui Wash” (known today as Tucker Flat Wash) 13 km (8 

mi) west of the city of Winslow and is 26 m (85 ft) thick. The 

Moqui Member weathers to a red slope below the cliff-forming, 

brown Holbrook Member. Sandstone beds of the Holbrook 

Member, as originally defined by Hager (1922), form an 

irregular line of bluffs north of the Little Colorado River Valley 

between Holbrook and Cameron, Arizona (south and northwest 

of the Winslow quadrangle, respectively). The Holbrook and 

Moqui Members are herein mapped as undivided because of 

their variable thicknesses, as well as the difficulty in distinguishing them from the overlying sandstone cliffs and bluffs of 

the Shinarump Member of the Chinle Formation. 

The regional uplift that terminated the deposition of 

the Moenkopi Formation caused an erosional unconformity 

between the Moenkopi Formation and the overlying Chinle 

Formation (Blakey, 1990; Riggs and Blakey, 1993). This unconformity is known as the “Tr-3” unconformity (Blakey, 1994; 

Blakey and Ranney, 2008). Depth of the drainages that eroded 

into the Moenkopi Formation averaged about 10 m (30 ft) in the 

southwestern part of the Winslow quadrangle (sheet 1). These 

eroded streams and valleys began to accumulate mud, sand, 

gravel, and conglomerate that formed the basal deposits of the 

Shinarump Member of the Chinle Formation. 

Chinle Formation

The Triassic Chinle Formation is the most colorful formation in the Winslow quadrangle (sheets 1, 2) and is subdivided 

into the following three mappable subunits, in ascending order: 

the Shinarump Member, the Petrified Forest Member, and the 

Owl Rock Member as defined by Repenning and others (1969). 

The Shinarump Member of the Chinle Formation is found 

in scattered outcrops between Leupp and Winslow that are 

largely covered by fluvial deposits of the Little Colorado River. 

The Shinarump Member, which is between 6 and 24 m (20 and 

80 ft) thick, contains numerous petrified logs and petrified-wood 

fragments in irregular sandstone and siltstone beds that are of 

variable thickness and locally pinch out or intertongue laterally 

within the unit. The contact between the Shinarump Member 

and the overlying Petrified Forest Member is gradational and 

highly variable. 

The Petrified Forest Member is the middle section of the 

Chinle Formation and forms the multicolored blue, red, and 

gray-green, soft hills of the “painted desert” badlands northeast 

of the Little Colorado River Valley. The Painted Desert Overlook, 19 km (13 mi) northeast of the city of Winslow along 

State Highway 87, provides spectacular views of these deposits. 

 Akers and others (1958) subdivided the Petrified Forest 

Member into three subunits on the basis of their slight lithologic and color differences. The boundaries between these three 

subunits are variable and gradational throughout the Winslow 

quadrangle and become indistinct in lithology and color on 

a regional scale. For this reason, they are herein collectively 

mapped as the Petrified Forest Member of the Chinle Formation. The Petrified Forest Member is between 122 and 150 m 

(400 and 500 ft) thick throughout the Winslow quadrangle 

(sheets 1, 2). 

Overlying the Petrified Forest Member is the Owl Rock 

Member of the Chinle Formation. The contact between the Owl 

Rock and the Petrified Forest Members is highly gradational in 
6

the lateral and vertical sense but is commonly marked at or near 

the base of the lowest siliceous limestone bed of the Owl Rock 

Member. The Owl Rock Member consists of a sequence of 

gray, ledge-forming, siliceous limestone beds that are interbedded with light-red and yellow-gray, slope-forming, calcareous 

siltstone. At some locations, as many as seven siliceous limestone beds that form flat-ledge outcrops are present within the 

Owl Rock Member. These beds are resistant to erosion and form 

the cap rock for Newberry Mesa, Ives Mesa, and Marcou Mesa 

northeast of the Little Colorado River (fig. 1). 

The unconformable contact between the Owl Rock 

Member and the overlying Moenave Formation is marked by 

a sharp contrast in color and lithology between the blue-gray 

mudstone of the Owl Rock Member and the orange-red sandstone of the Moenave Formation. This regional unconformity, 

which is known as the “J-O” unconformity (Pipiringos and 

O’Sullivan, 1978; Peterson and Pipiringos, 1979), separates 

Triassic rocks from their overlying Jurassic rocks. The thickness 

of the Owl Rock Member is about 67 m (220 ft), gradually thinning out southeastward across the Winslow quadrangle (sheets 

1, 2).

Moenave Formation 

The red, slope-forming siltstone and sandstone strata of the 

Jurassic Moenave Formation (Jm) unconformably overlie that 

of the Owl Rock Member of the Chinle Formation throughout 

the Winslow quadrangle (sheets 1, 2). The environmental and 

regional correlations, as well as paleogeographic reconstructions for the fluvial and eolian systems of the Moenave Formation and the Wingate Sandstone, are described by Edwards 

(1985), Clemmensen and others (1989), Nations (1990), Blakey 

and others (1992), Riggs and Blakey (1993), and Blakey and 

Ranney (2008). Regional and local trends suggest that some of 

the fluvial-dominated cycles of the upper Moenave Formation 

correlate well with the eolian-dominated cycles of the Wingate 

Sandstone northeast of the Winslow quadrangle (Blakey, 1994). 

However, the Wingate Sandstone in southern Utah and in the 

Monument Valley area of northeastern Arizona thins southward 

and may not extend this far south into Arizona (Anderson and 

others, 2000). As a result of this uncertainty, the term Wingate Sandstone is not used for the sandstone sequence above 

the Moenave Formation in the Hopi Buttes area (sheet 2), as 

mapped by Cooley and others (1969), but it is herein informally 

mapped as the upper sandstone member of the Moenave Formation (Jms) until further correlative stratigraphic studies can be 

done. 

 The Wingate Sandstone as mapped by Cooley and others 

(1969) includes a lower white and upper light-red sandstone 

that overlies the Moenave Formation in the southwestern part 

of the Hopi Buttes area. These white and light-red sandstones 

are herein informally mapped as the upper sandstone member 

of the Moenave Formation (Jms) for the following reasons: (1) 

these sandstones have gradational and intertonguing contacts 

between them and also with the underlying Moenave Formation; (2) both sandstones undergo facies changes eastward in 

which they become a light-red sandy siltstone east of Dilkon 

and Indian Wells (fig. 1), becoming indistinguishable from the 

upper part of the Moenave Formation; and (3) no unconformities are apparent within or below each sandstone unit with the 

upper part of the Moenave Formation. 

The Moenave Formation commonly weathers as a red 

slope throughout the east half of the Winslow quadrangle (sheet 

2) except where beds of the upper sandstone member (Jms) 

form weak, white-gray or light-red ledges in the southwestern 

part of the Hopi Buttes area (best exposed at Red Cheek Butte; 

fig. 1). In the southern part of the Hopi Buttes (sheet 2), some of 

the upper sandstone beds of the Moenave Formation have been 

removed by Tertiary erosion, and what remains is unconformably overlain by dark-brown and white mudstone and argillaceous sandstone that forms the lower part of the Bidahochi 

Formation (Tbl). Overall, the Moenave Formation is between 

73 and 98 m (245 and 320 ft) thick. 

Kayenta Formation

The purple-red, slope-forming siltstone and sandstone 

sequences of the Kayenta Formation (Jk) unconformably overlie the white-gray upper sandstone member of the Moenave Formation in the northern-central part of the Hopi Buttes area near 

State Highway 87 (sheet 2). Northwest of the Winslow quadrangle, the Kayenta Formation unconformably overlies red sandstones of the Moenave Formation, having an erosional relief 

of from 2 to 15 m (6 to 50 ft) (Nations, 1990). This contact is 

referred to as the “sub-Kayenta unconformity” (“J-sub-K”), as 

defined by Riggs and Blakey (1993) and Blakey (1994). 

North and west of the Winslow quadrangle, the following 

units are present, in ascending order: the Kayenta Formation, 

the Navajo Sandstone, the Entrada Sandstone, the Dakota Sandstone, and the Mancos Shale (Billingsley and others, 2007). 

Along the very north-central edge of the Winslow quadrangle, 

the Navajo Sandstone (or the Entrada Sandstone; not mapped 

separately) may be present at Round Top butte, Montezumas 

Chair, and Bad Medicine Butte west of State Highway 87, but 

the outcrop is too limited in extent and exposure to determine. 

The gray, small-scale trough-crossbedded sandstone outcrop at 

Round Top butte is likely the southern extension of the Entrada 

Sandstone (not mapped). This sandstone and the underlying 

Kayenta Formation have largely been removed by Early Cretaceous erosion, and what remains has been subsequently overlain 

by Cretaceous rocks of the Dakota Sandstone and the Mancos 

Shale west of State Highway 87 and also near Teesto at the 

north-central edge of the Winslow quadrangle (sheets 1, 2). 

Between State Highways 87 and 77, in the northern-central 

part of the Hopi Buttes, Tertiary erosion has removed most of 

the Cretaceous and Jurassic rocks down to the Moenave Formation. This erosion surface is subsequently overlain by Miocene 

rocks of the Bidahochi Formation and by the volcanic rocks of 

Hopi Buttes Volcanic Field along the north edge of the Winslow 

quadrangle (sheet 2; see also, fig. 2). 
7

Dakota Sandstone and Mancos Shale

The Cretaceous Dakota Sandstone (Kd) is present at Montezumas Chair, Round Top butte, and Bad Medicine Butte west 

of State Highway 87 in the northwestern part of the Hopi Buttes 

(fig. 1). The Dakota Sandstone consists of a lower sandstone 

member, a middle carbonaceous member, and an upper sandstone member, all having gradational contacts between them 

(O’Sullivan and others, 1972); however, all three members 

are too small to show at map scale and are herein collectively 

mapped as the Dakota Sandstone, undivided.

The lower sandstone member of the Dakota Sandstone 

occupies shallow channels of a regional Cretaceous unconformity eroded into the underlying Jurassic Kayenta Formation 

(or the Entrada Sandstone?) at Montezumas Chair and Round 

Top butte. The middle carbonaceous member of the Dakota 

Sandstone contains a thin coal bed less than 0.5 m (2 ft) thick 

that was partly mined in the late 1940s or early 1950s and is 

now marked by numerous abandoned prospects on the east and 

north sides of Round Top butte. The upper sandstone member is 

thin and lenticular with a gradational contact with the overlying 

Mancos Shale (Km). 

Most of the blue-gray, slope-forming Mancos Shale has 

been removed from the Hopi Buttes area by Tertiary erosion and 

what remains is largely covered by extensive landslide (Ql) or 

talus and rock-fall (Qtr) deposits. Neither the original thickness of the Mancos Shale nor the extent of volcanic intrusion is 

known.

Cenozoic Sedimentary and Volcanic 

Rocks

The Miocene sedimentary and volcanic rocks of the Hopi 

Buttes Volcanic Field are important because they contain critical 

landscape information about the early erosional development 

of this part of the Colorado Plateau; however, the type section 

for the Miocene and Pliocene Bidahochi Formation is outside 

of the map area, and an equivalent section does not recur within 

the Winslow quadrangle. Consequently, we have informally 

redefined the stratigraphic nomenclature for this map. 

Bidahochi Formation 

The Bidahochi Formation was originally defined by 

Repenning and Irwin (1954) and Shoemaker and others (1957, 

1962) who separated it into the following three informal members, in descending order: an upper fluvial member, a middle 

volcanic member, and a lower mudstone and argillaceous 

sandstone member (all Miocene and Pliocene). These subdivisions are based on a section referenced at White Cone Peak, a 

natural landmark about 6.5 km (4 mi) northeast of White Cone, 

Arizona, just northeast of the Winslow quadrangle. 

The upper fluvial member of the Bidahochi Formation 

(Miocene and Pliocene) is not present within the Winslow quadrangle but is present just north and northeast of the quadrangle. 

The lower mudstone and argillaceous sandstone member (Tbl) 

is present within the Hopi Buttes area of the Winslow quadrangle (sheet 2). This lower part of the Bidahochi Formation 

unconformably overlies the lower part of the Moenave Formation (Jm) in the southeast quarter of the Winslow quadrangle; 

upper strata of the Moenave Formation (Jms), in the northeast 

quarter; and the Kayenta Formation (Jk), in the Teesto area, 

along the north-central edge of the quadrangle (fig. 2). For mapping purposes, the originally defined middle volcanic member 

is herein redefined as part of the volcanic rocks of Hopi Buttes 

Volcanic Field, on the basis of field observations, recent studies, and measured sections published by Dallegge and others 

(1998a, 1998b), Ort and others (1998), Dallegge and others 

(2001), and Dallegge and others (2003; see their table 1). 

The Miocene and Pliocene age of the Bidahochi Formation is based on vertebrate fossil faunas (Morgan and White, 

2005), fossil fish (Spencer and others, 2008), paleomagnetic 

studies (Lindsey and others, 1984), and radiometric data (Dallegge and others, 2003). Vertebrate fossil collections from the 

(upper) Bidahochi Formation at White Cone Peak (northeast 

of the quadrangle) indicate a late Miocene through Pliocene 

age (Lindsay and others, 1984). Fossil teeth, which were used 

to identify rodents, moles, shrews, frogs, and rabbits (Baskin, 

1979; Lindsay and others, 1984), are most common in the 

upper member of the Bidahochi Formation above the 6.69 Ma 

volcanic-age locality near White Cone Peak (Scarborough and 

others, 1974). Fossil fish were also reported by Uyeno and 

Miller (1965) from the upper member of the Bidahochi Formation near White Cone Peak and at the “Coliseum” diatreme (fig. 

1) west of Indian Wells. Uyeno and Miller (1965) suggested a 

large, permanent aquatic habitat associated with swift flowing 

rivers at the time that the Bidahochi Formation was deposited 

in this area. The fish fossils at White Cone Peak are found in 

distal fluvial-overbank or deltaic-lacustrine deposits (Spencer 

and others, 2008). The fish fossils at the “Coliseum” are found 

within white, 1-m (3-ft) thick lacustrine sediments that are interbedded with thick volcanic tuffaceous ash and pyroclastic surge 

and air-fall deposits (Tc). At the “Coliseum,” no connection is 

apparent between the lacustrine volcanic-crater sediments (Tc) 

or other local volcanic maar-sediments to the lower or upper 

members of the Bidahochi Formation, aside from fish fossils. A 

volcanic ash bed (located outside the quadrangle about 9.5 km 

[6 mi] northeast of Indian Wells, between Wood Chop Mesa and 

“Triplets Mesa”) that lies about 75 m (246 ft) above the base of 

the lower part of the Bidahochi Formation yielded an 40Ar/39Ar 

age of 13.71±0.08 Ma (Dallegge and others, 1998a; Ort and 

others, 1998; Dallegge and others, 2001; Dallegge and others, 

2003; see also, table 1, this report).

The vertical transition between the originally defined 

lower, middle, and upper members of the Bidahochi Formation 

is not evident within the east half of the Winslow quadrangle. 

Only the lower member is present in the quadrangle below the 

volcanic rocks of Hopi Buttes Volcanic Field; for this reason, 

the lower mudstone and argillaceous sandstone Bidahochi 

Formation (Tbl) within the Winslow quadrangle is considered to 

be Miocene age only (sheet 2). North of White Cone Peak and 

along State Highway 77, the white upper fluvial member of the 

Bidahochi Formation appears to be interbedded, intertonguing, 
8

or in gradational contact with the lower mudstone and argillaceous sandstone member, and no unconformity is apparent 

between them. 

Field observations of the Bidahochi Formation by the 

authors and by Dr. Michael Ort (Northern Arizona University) 

suggest that the lower and upper members of the Bidahochi 

Formation are time correlative across the landscape but at different elevations. In other words, the mudstone and argillaceous 

deposits likely were deposited at the same time as the upper 

fluvial deposits, which were interrupted periodically by volcanic 

ash-fall deposits. Moreover, the upper fluvial deposits contain 

numerous eolian and fluvial sandstone lenses that likely were 

deposited upland and downwind of the mudstone and argillaceous playa deposits, making both previously defined upper and 

lower members of the Bidahochi Formation time equivalent. 

Volcanic Rocks of Hopi Buttes Volcanic Field

The volcanic rocks of Hopi Buttes Volcanic Field were 

described by Williams (1936) and well documented by White 

(1991). The originally defined middle volcanic member of 

the Bidahochi Formation (Repenning and Irwin, 1954; Shoemaker and others, 1957, 1962) is herein redefined for mapping 

purposes as part of the volcanic rocks of Hopi Buttes Volcanic 

Field because of the following: (1) the volcanic rocks form a 

mappable sequence of multiple related volcanic rock types, 

(2) they are time equivalent with parts of the lower member 

of the Bidahochi Formation, and (3) they are interbedded only 

within the lower part of the Bidahochi Formation at varying 

stratigraphic positions and do not appear to regionally separate 

the upper and lower members of the Bidahochi Formation as 

originally described at White Cone Peak. 

The volcanic rocks of Hopi Buttes Volcanic Field are not 

mapped in detail because of multiple intertonguing, crosscutting unconformities and overlapping stratigraphic complexities 

between several volcanic eruptional events that distributed a 

variety of volcanic rock types in different parts of the Hopi 

Buttes, as was shown by Vazquez (1998, 1999) and Hooten 

(1999a, 1999b). For mapping purposes, the volcanic rocks are 

herein subdivided into intrusive dikes, plugs, or necks (Ti); 

volcanic-crater sediment deposits (Tc); mafic monchiquite and 

basanite flows (Tm), as defined by Vazquez and Ort (2006); 

mafic tuff-and-ash deposits (Tmt); and mixed monchiquite and 

basanite flows and tuff deposits, undivided (Tmu). 

Justification for separating the volcanic rocks from the 

original middle volcanic member of the Bidahochi Formation 

is as follows: (1) the volcanic and associated volcanic-crater 

sedimentary rocks can be mapped as separate rock types; (2) 

the thin deposits of volcanic ash and tuff that separated the 

originally defined upper and lower members of the Bidahochi 

Formation at White Cone Peak are absent northeast of that landmark; (3) the volcanic deposits are interbedded within the lower 

Bidahochi Formation about 50 m (165 ft) below the top of 

White Cone Peak and at several discontinuous horizons; (4) the 

volcanic rocks either overlie or are adjacent to Triassic, Jurassic, 

and Cretaceous rocks at different locations throughout the Hopi 

Buttes; (5) the volcanic rocks are unevenly distributed, having 

variable thicknesses and numerous local unconformities; (6) the 

volcanic-crater sedimentary rocks (Tc) are interbedded with or 

overlain by other volcanic rocks that are locally disconnected 

from the Bidahochi Formation at multiple topographic horizons 

above and below Bidahochi horizons throughout the volcanic 

field; and (7) the volcanic-crater sedimentary rocks may not be 

connected to the Bidahochi Formation.

The age of the volcanic rocks of Hopi Buttes Volcanic 

Field ranges between 7.5 and 6.5 Ma (Vazquez, 1998, 1999; 

Vazquez and Ort, 2006). Vazquez (1999) obtained 40Ar/39Ar ages 

of 7.21±0.45 Ma, 6.99±0.75 Ma, 6.53±0.69 Ma, and 6.81±0.06 

Ma from different vents outside the quadrangle near Wood 

Chop Mesa in the northeastern part of the Hopi Buttes (table 

1). Thus, an average age of 7 Ma for the volcanic rocks of Hopi 

Buttes Volcanic Field in this area is not far above the 40Ar/39Ar 

13.71±0.08 Ma age (Dallegge and others, 1998a, 1998b) for the 

lower mudstone and argillaceous sandstone of the Bidahochi 

Formation at White Cone Peak and Wood Chop Mesa.

In 1964, a radiometric date of 4.2 Ma was reported by 

Evernden and others (1964) from the middle (volcanic) member 

of the Bidahochi Formation at White Cone Peak; however, it 

was determined later that the dated volcanic unit came from a 

diatreme volcano just north of White Cone Peak (Scarborough 

and others, 1974). The air-fall tuff at White Cone Peak yielded 

an age of 6.69±0.16 Ma; thus, the volcanic ages in the 2 to 4 Ma 

age range likely are incorrect because they do not fit within the 

6.5 to 7.5 Ma average age range (table 1).

At White Cone Peak, one to four tuffaceous volcanic 

deposits (0.05 to 2 m [1 to 5 ft] thick) are interbedded within 

various levels of mudstone and argillaceous sandstone of the 

lower Bidahochi Formation. The interbedded volcanic rocks are 

about 50 m (165 ft) below the upper white fluvial parts of the 

Bidahochi Formation. These interbedded tuffaceous volcanic 

rocks thin and pinch out northeast and north of White Cone 

Peak and, therefore, do not provide a consistent marker bed 

division between the lower and upper deposits of the Bidahochi 

Formation.

Quaternary Surficial Deposits

Surficial Mapping Approach

During the last several years, surficial deposits on the 

Colorado Plateau have largely been ignored because their significance to landscape and biological development was not recognized. Today we are beginning to learn the importance of these 

geologic deposits to other scientific discipline studies in biology 

and climatic change, as well as evolution of the landscape. 

Surficial sedimentary deposits that have accumulated on 

the land surface over the last several hundred thousand to a 

million years or more (that is, Quaternary and latest Tertiary 

age) are generally unconsolidated or weakly consolidated as 

thin deposits that can be several tens of meters thick. Surficial 

deposits have accumulated through the actions of running water 

or wind, or a combination of both fluvial and eolian processes. 

Steeper slopes of buttes and mesas often have landslide, talus, 
9

and rock-fall deposits. Alluvial deposits of major washes and 

floodplains are often remobilized by wind, providing a major 

source of sand for nearby or distant eolian sand-dune and 

sand-sheet deposits. Extensive eolian deposits commonly are 

stabilized by vegetation in most areas, but their transport can be 

partially reactivated during severe drought or storm conditions. 

Mapping surficial deposits across an area as large as the 

Winslow quadrangle poses unique challenges. First, natural 

exposures that reveal lithologic details below the upper surface 

of these materials are not common; hence, map units have to be 

defined and then projected laterally using criteria other than lithologic content and internal stratigraphic details. Second, in the 

time available to make the map, we could not visit more than 

a few locations where such lithologic and stratigraphic details 

are revealed. Third, although their fairly recent geologic age 

is obvious, very little age data for surficial materials is available that would allow them to be assigned confidently to the 

Holocene, Pleistocene, Tertiary, or their various subdivisions. 

Finally, a map-unit naming scheme that combines information 

about lithology, geologic age, and genesis is difficult to develop 

and communicate to map users. To accommodate these issues, 

we adopted the following strategy for classifying and mapping surficial materials and assigning them a geologic age: The 

materials are classified and named using genesis (for example, 

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

lower Holocene, middle Pleistocene), and lithology (for 

example, sand, gravel) as classifying criteria. This strategy has 

evolved from previous surficial mapping methods of the Grand 

Canyon region of northern Arizona that have slowly developed 

over the last decade (Billingsley and Workman, 2000; Billingsley and Wellmeyer, 2003; Billingsley and others, 2006a, 2006b, 

2007, 2008). 

The discontinuous aspect of surficial deposits across the 

Grand Canyon region does not lend itself to easy projection and 

correlation of deposits that may or may not be the same age. 

This strategy depends on the relative correlation and projection of map units, but it does not necessarily place these map 

units accurately within the Quaternary and latest Tertiary global 

chronology. 

Information about the surficial deposits has been 

obtained mainly by aerial-photographic interpretation; age 

determinations, which are generalized, are based mainly on 

geomorphologic criteria such as the relative position in local 

alluvial-terrace sequences, the degree of erosional dissection of 

alluvial fans, and the superposition or stabilization of sand-dune 

and sand-sheet deposits. Therefore, all age assignments for 

surficial materials are provisional, and the age of a specific unit 

in one area may not be the same as that indicated for the same 

unit in another area. Names of units that have time implications 

such as young, intermediate, old, and older are intended only to 

indicate local relative stratigraphic position, not a unit’s actual 

age uniformly throughout the map area.

Local Surficial Deposits

The Little Colorado River, which is the principal drainage 

within the Winslow quadrangle, is typically a dry river most 

of the year. The Little Colorado River flows northwest across 

the southwest quarter of the Winslow quadrangle (south half 

of sheet 1) toward the Colorado River in the Grand Canyon. 

Fluvial deposits of the Little Colorado River and its tributaries 

provide the principal supply of sand and silt that form extensive 

eolian-sand deposits that are generally transported by southwesterly winds to the northeast. 

The surface water that flows down Tucker Flat Wash, Cow 

Canyon, and numerous unnamed tributaries in the southwest 

quarter of the Winslow quadrangle (south half of sheet 1) drain 

northeast toward the Little Colorado River and into internal 

drainage basins (dry lakes in fig. 1) before reaching the river. 

These large playa lakes or ponded areas (Qps) are caused by 

overbank flood-plain sediment accumulations along the current and old natural channel levees of the Little Colorado River. 

These ponded areas can become temporary shallow lakes several feet deep during wet climatic conditions, either when the 

Little Colorado River overflows its floodplain levees or when 

significant water flows down the tributary drainages. Tucker 

Flat Wash is largely a low-gradient alluvial-plain drainage consisting of fine-grained sediment that is subject to intense dust 

storm activity during dry windy conditions. 

Eolian deposits have accumulated as thick sand dunes or 

sand sheets transported to the northeast by southwesterly winds 

during dry climatic conditions on and against the southwest 

slopes of Newberry, Ives, and Marcou Mesas northeast of the 

Little Colorado River Valley. These eolian deposits are gradually eroded by local storm water runoff and transported back 

to the Little Colorado River where they are often recycled and 

blown back to the mesas. Eventually these sediments are transported by fluvial processes into and through the Grand Canyon. 

Other surficial deposits in the Winslow quadrangle consist 

of numerous landslides (Ql) and associated talus and rock-fall 

deposits (Qtr) and older alluvial fan deposits commonly found 

around and below volcanic outcrops of the Hopi Buttes area. 

Man-made diversion dams, stock tanks, and gravel pits are 

shown on the maps to illustrate the human impact upon the 

landscape.

Structural Geology

During the Laramide orogeny, about 80 to 40 Ma, compressional stresses acting on the southern Colorado Plateau 

region produced several east-dipping monoclinal structures 

west and north of the Winslow quadrangle (Huntoon, 2003). 

One Laramide monocline present in the southwest corner of the 

Winslow quadrangle is herein named the Winslow Monocline 

(sheet 1). Strata along the Winslow Monocline dip northeastward between 6° and 15°, the steepest dips being in the lower 

hinge of the fold. The vertical relief of strata averages about 

60 m (200 ft) up-to-the-southwest. Red rocks of the Moenkopi 

Formation are being rapidly eroded off the upper limb of the 

Winslow Monocline, exposing the resistant sandy limestone of 

the Kaibab Formation. Several gentle, parallel, northeast-plunging anticlines and synclines are perpendicular to the general 

northwestern trend of the axial trace of the Winslow Monocline. 

The monocline may form an important barrier or control to local 
10

groundwater flow by directing flow within buried sedimentary 

strata to the northwest toward Blue Springs in the Little Colorado 

River Gorge northwest of the Winslow quadrangle (Billingsley 

and others, 2007). 

Paleozoic and Mesozoic strata in the west half of the Winslow quadrangle (sheet 1) exhibit a regional northeasterly dip 

of about 1° to 2° that gradually diminishes toward the northeast 

quarter of the Winslow quadrangle (north half of sheet 2). Strata 

of the Cenozoic Bidahochi Formation (sheet 2) are basically flat 

lying and have not been tectonically altered other than by localized diatreme volcanic eruptions in Miocene time. 

Cenozoic extensional faulting during late Pliocene time 

(younger than 3 Ma) has produced several small northwest-trending graben and horst structures that are similar to those northwest 

of the Winslow quadrangle (Billingsley and others, 2007). Small 

faults and folds have not been identified in the northeast quarter 

of the Winslow quadrangle, but these likely are veiled by softsediment deformation within the thick mudstone and siltstone 

strata of the Chinle Formation. Recent earth-crack and sinkhole 

development within or near graben structures has temporarily 

interrupted runoff in some tributaries to the Little Colorado River 

near Leupp (sheet 1). 

In the Kaibab Formation, circular, bowl-shaped depressions characterized by inward-dipping strata are likely to be the 

surface expressions of collapse-formed breccia pipes originating 

from the dissolution of the deeply buried Mississippian Redwall 

Limestone or another similar buried limestone deposit (Wenrich, 1989). Collapse features are not common in the Winslow 

quadrangle and may reflect the lack of limestone deposits and 

(or) limestone dissolution at depth. 

Acknowledgments

The support of the U.S. Geological Survey’s National 

Cooperative Geologic Mapping Program of Reston, Virginia, 

and the Navajo Nation is gratefully appreciated. We also 

appreciate the advice, revisions, and expertise of Michael H. Ort 

of Northern Arizona University, Flagstaff, Arizona; Jonathan 

C. Matti, U.S. Geological Survey, Tucson, Arizona; Charles 

L. Powell, II, and Taryn Lindquist, geologic map editor, 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

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

pits and trench excavations and used to build livestock tanks, drainage diversion dams, 

roads, and other man-made construction projects (not all highway road excavations are 

mapped). No distinction between cut or fill excavations is made on map. Agricultural fields 

are not shown

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

and clay, mixed with gravel, pebbles, and cobbles; poorly sorted. Pebbles and cobbles 

dominantly are angular to rounded, red, white, gray, and black chert clasts; subrounded to 

rounded red sandstone clasts; and angular to subrounded mafic monchiquite and basanite 

clasts in Hopi Buttes area. Deposits intertongue with, overlap, or are inset against adjacent 

surficial deposits (Qa1, Qa2, Qa3, Qv, Qg1, Qg2, QTdi), and they overlap or erode into 

flood-plain deposits (Qf, Qf1, Qf2, Qf3), ponded sediments (Qps), and mixed alluvium and 

eolian deposits (Qae). Stream channels subject to high-energy flows and flash-flood debris 

flows. Little or no vegetation in stream channels except for salt cedar (tamarisk), russian 

olive, and cottonwood trees along Little Colorado River and several large washes. Contacts 

with other alluvial deposits are gradational and approximate. Stream-channel deposits of 

Little Colorado River are mapped as shown on 1:24,000-scale color aerial photographs 

flown in 2005 (Block and others, 2009). Channel of Little Colorado River meanders within 

its floodplain valley between Winslow and Leupp. Downstream (northwest) of Leupp, Little 

Colorado River channel is confined within narrow bedrock strata of the Moenkopi and 

Kaibab Formations. Thickness, 2 to 9 m (6 to 30 ft)

Qf Modern flood-plain deposits (Holocene)—Gray-brown to light-red clay, silt, and fine-grained 

sand; weakly consolidated by clay and calcite cement. Deposits include some lenticular 

gravel, subangular to rounded pebbles, and cobbles; intertongue with or are overlapped by 

adjacent fluvial or eolian surficial deposits (Qs, Qv, Qa1, Qps, Qd, Qes). Forms shallow 

flats 0.5 to 1 m (2 to 3 ft) above stream-channel deposits (Qs). Subject to overbank flooding 

in lateral and vertical sense along Little Colorado River and larger tributary valleys. Supports sparse to light growths of sagebrush, grass, tumble weed, and thick growths of salt 

cedar (tamarisk) trees and other high-desert shrubs that trap and accumulate more recent 

eolian-sand deposits. Thickness, 0.05 to 2 m (2 to 6 ft) 
11

Qps Ponded sediments (Holocene)—Gray to brown clay, silt, sand, and thin gravel lenses along 

margins; weakly consolidated by clay, calcite, and gypsum cement. Locally includes small 

chert and limestone fragments or pebbles derived from nearby bedrock outcrops. Deposits 

commonly occupy man-made or natural internal drainage depressions. Desiccation cracks 

commonly form on dry hardpan surfaces that often restrict plant growth. Sandy ponded areas 

support growths of seasonal grass, especially downwind (northeast) of local parabolic dunes 

below and on Newberry, Ives, and Marcou Mesas. Thickness, 1.5 to 9 m (5 to 30 ft)

Qd Dune sand and sand-sheet deposits (Holocene)—Hopi Buttes area (sheet 2): Light-red and 

white, fine-grained quartz sand; locally derived mainly from other surficial units whose 

sediments are easily eroded by wind (Qs, Qf, Qf1, Qf2, Qf3, Qg1, Qg2, Qg3, Qa1, Qa2, 

Qa3, Qae, QTdi). Originally those sand grains were derived from erosion of nearby bedrock outcrops of the Moenave, Kayenta, and Bidahochi Formations and include fragmented 

grains of volcanic rock (Tm, Tmt, Tmu). Forms lumpy, undefined sand-dune or sand-sheet 

deposits often concealed beneath moderate growths of grass, sagebrush, and pinyon pine 

and juniper woodlands at higher elevations of volcanic mesas and buttes. Little Colorado 

River area (sheet 1): White to light-red, fine- to coarse-grained, windblown sand; composed 

primarily of quartz, chert, and some feldspar grains locally derived from other surficial 

deposits eroded by wind (Qs, Qf, Qf1, Qf2, Qf3, Qa1, Qa2, Qa3, Qg1, Qg2, Qg3, Qae). 

Contacts are approximate and subtly gradational with adjacent alluvial deposits and bedrock 

and are likely to change on yearly basis under influence of variable weather conditions such 

as strong windstorms and sheet-wash erosion associated with local severe thunderstorms. 

Locally includes topographically controlled climbing and falling sand-dune and sand-sheet 

ramp accumulations on gentle slopes or steep bedrock terrain northeast of Little Colorado 

River Valley. Contacts between young sand-dune and sand-sheet deposits (Qd, Qes) and 

old sand-dune and sand-sheet deposits (QTd, QTes) are difficult to constrain by empirical 

observation but, as mapped, show boundaries that illustrate potential differences between 

young and old sand accumulations on Ives Mesa, on Marcou Mesa, and in some areas of 

Hopi Buttes. Supports moderate growths of grass and high-desert shrubs that help stabilize 

all eolian-sand accumulations during wetter conditions. Thickness, 1 to 61 m (3 to 200 ft)

Qes Eolian sand-sheet deposits (Holocene)—Extensive sand-sheet deposits northeast and east of 

Little Colorado River Valley, especially in and along large tributary washes and over gently 

sloping terrain below Newberry, Ives, and Marcou Mesas. Forms thin sand-sheet deposits on alluvial fan slopes of various ages and on “Dilkon deposits” (QTdi) slopes in Hopi 

Buttes area. Commonly intertongues with surficial deposits (Qae, Qdp, Qdb); contacts are 

gradational in both lateral and vertical sense. Supports moderate growths of grass and small 

high-desert shrubs that help stabilize or trap accumulating deposits. Thickness, 0.3 to 4.5 m 

(1 to 15 ft)

Qdl Linear-dune deposits (Holocene)—White, gray, and light-red, fine- to medium-grained, wellsorted quartz sand accumulations that are aligned in general northeast direction. Commonly 

transitional with other eolian surficial deposits (Qd, Qes, Qdp, Qdb). Linear dunes generally are 12 to 24.5 m (40 to 80 ft) wide and less than 0.8 km (0.5 mi) long, but they can 

extend over 5 km (3 mi) or more in length on Ives and Marcou Mesas. Thickness, 2 to 9 m 

(6 to 30 ft)

Qdp Parabolic-dune deposits (Holocene)—White, gray, and light-red, fine- to coarse-grained, 

well-sorted quartz sand arranged into individual parabolic dunes; most commonly present 

as complex intertonguing parabolic-dune deposits below and on Newberry Mesa (sheet 1). 

Ponded sediments (Qps) commonly form in low internal-drainage areas within parabolicdune complexes. Contacts merge with adjacent eolian and alluvium deposits and bedrock 

outcrops. Supports sparse grassy vegetation. Thickness, 2 to 9 m (6 to 30 ft) 

Qdb Barchan-dune deposits (Holocene)—White, gray, and light-red, fine- to coarse-grained, 

unconsolidated, well-sorted quartz sand that forms isolated barchan dunes and (or) complex 

barchanoid dunes; found mainly on Newberry Mesa northeast of Tolani Lake (sheet 1) and 

along tributary drainages to Little Colorado River. Subject to changing aerial extent and 

shape on yearly basis owing to seasonal windstorms. Supports sparse grassy vegetation in 

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

Qa1 Young alluvial fan deposits (Holocene)—Southwest of Little Colorado River Valley (sheet 

1): Gray-brown silt, sand, gravel, pebbles, cobbles, and boulders; weakly consolidated by 

calcite, gypsum, and minor amounts of salt cement. Silt and sand is derived primarily from 
12

eroded outcrops of the Kaibab and Moenkopi Formations that also supply dissolved calcite, gypsum, and minor amounts of salt that precipitates as cement. Pebbles, cobbles, and 

boulders are subangular to rounded limestone, chert, and sandstone clasts locally derived 

from bedrock. Also includes small, subrounded to rounded pebbles and cobbles of basalt, 

andesite clasts, and pyroclastic fragments derived from San Francisco Volcanic Field west 

and southwest of quadrangle. Supports light to moderate growths of sagebrush, cactus, and 

grass. North and northeast of Little Colorado River Valley (sheet 2): Gray, light-brown, and 

light-red clay, silt, sand, pebbles, and cobbles of chert, limestone, and sandstone; derived 

from local Mesozoic sedimentary rocks and monchiquite, basanite, and decomposed tuff 

from local outcrops of the volcanic rocks of Hopi Buttes Volcanic Field. Commonly is 

overlapped by or intertongues with various Quaternary surficial deposits (Qs, Qps, Qf, Qd, 

Qes, Qv, Qg1, Qae). Clay, silt, and sand are derived primarily from local outcrops of the 

Chinle, Moenave, Kayenta, and Bidahochi Formations; also derived from Cretaceous rocks 

north and northeast of quadrangle that commonly supply cementing ingredients of clay, calcite, gypsum, and minor amounts of salt for all surficial alluvial deposits north and northeast 

of Little Colorado River. Subject to extensive sheet-wash erosion, wind erosion, flash-flood 

debris flows, and minor arroyo erosion. Thickness, 1 to 6 m (3 to 20 ft) 

Qg1 Young terrace-gravel deposits (Holocene)—Southwest of Little Colorado River (sheet 1): 

Light-brown, pale-red, and gray, well-sorted, interbedded clay, silt, sand, gravel, pebbles, 

cobbles, and some boulders. Includes abundant rounded and well-rounded clasts of quartzite, quartz, chert, and assorted metamorphic crystalline rocks derived from Tertiary rocks 

south, southeast, and southwest of quadrangle. Also includes well-rounded gray limestone, 

white chert, and red sandstone clasts derived from local Permian and Triassic strata south 

and southwest of Little Colorado River Valley, as well as subrounded to well-rounded clasts 

of yellow, red, gray, and brown quartzite, black chert, and multicolored petrified-wood fragments locally derived from the Shinarump Member of the Chinle Formation. Includes minor 

amounts of rounded basalt clasts originating from San Francisco Volcanic Field southwest 

of quadrangle. Supports light to moderate growths of grass, cactus, and high-desert shrubs; 

subject to flash-flood erosion and sheet-wash flooding. North and northeast of Little Colorado River (sheet 2): Gray, brown, and light-red clay, silt, sand, and chert-pebble gravel. 

Clasts include pebbles and cobbles of chert, sandstone, and limestone derived from the Owl 

Rock Member of the Chinle Formation below Newberry, Ives, and Marcou Mesa areas; 

also include numerous subangular fragments of coarse gravel, pebbles, and cobbles of black 

monchiquite, basanite, and gray tuff locally derived from Hopi Buttes area. Unit grades 

downstream into flood-plain deposits (Qf, Qf1, Qf2) in principal-tributary washes where 

gradients are low. Locally overlaps alluvial deposits (Qa1, Qf, Qv) and often is covered by 

young eolian deposits (Qd, Qes). Supports light or no vegetation, mainly grass and desert 

shrubs. Forms benches about 1 to 3.5 m (3 to 12 ft) above stream-channel (Qs) or modern 

flood-plain (Qf) deposits. Thickness, 2 to 6 m (6 to 20 ft) 

Qf1 Young flood-plain deposits (Holocene)—Gray-brown clay, silt, and fine- to coarse-grained sand; 

weakly consolidated by clay content. Forms benches 1 to 3 m (3 to 10 ft) above streamchannel (Qs) or modern flood-plain (Qf) deposits. Subject to cut-bank channel erosion in 

Little Colorado River Valley and local streams in large tributary washes. Overlapped by thin 

accumulations of young surficial deposits (Qd, Qes, Qps, Qa1). Supports thick growths 

of salt cedar (Tamarisk) trees, grass, tumble weed, camel thorn bush, and various other 

high-desert shrubs. Often subjected to overbank flooding by Little Colorado River and local 

tributary streams. Thickness, 1 to 6 m (3 to 20 ft)

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

fan deposits (Qa1); partly cemented by calcite, gypsum, and clay. Surfaces are partly eroded 

by arroyos as deep as 1 to 3 m (3 to 10 ft) and commonly covered by eolian deposits (Qd, 

Qes) north and northeast of Little Colorado River Valley. Commonly is overlapped by or 

intertongues with fluvial deposits (Qa1, Qv, Qtr, Qg1, Qg2). Includes minor amounts of 

subrounded to subangular basalt clasts of San Francisco Volcanic Field in southwestern part 

of quadrangle (sheet 1); also includes abundant subangular chert clasts north and northeast 

of Little Colorado River Valley and abundant volcanic clasts and lithic fragments in Hopi 

Buttes Volcanic Field. Supports light to moderate growths of grass, sagebrush, and cactus 

throughout. Thickness, 2 to 15 m (6 to 50 ft)
13

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

lenses of small gravel or conglomerate; weakly consolidated. Lithologically similar to young 

terrace-gravel deposits (Qg1). Silt and fine-grained sand matrix is mixed with subangular to rounded pebbles and boulders of local bedrock. Forms benches that range in height 

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

young terrace-gravel deposits (Qg1) in upper reaches of tributary washes. In large principaltributary washes, unit grades downstream into intermediate-age and old flood-plain deposits 

(Qf2, Qf3). Supports growth of grass and variety of high-desert shrubs. Subject to cut-bank 

or headward erosion by local streams. Locally intertongues with, is overlain by, or is inset 

into other surficial deposits (Qa1, Qa2, Qv, Qae, Qtr, Ql). Thickness, 2 to 7.5 m (6 to 25 

ft) 

Qf2 Intermediate-age flood-plain deposits (Holocene)—Gray-brown clay, silt, and fine-grained 

sand; weakly consolidated by clay and calcite cement. Lithologically similar to young floodplain deposits (Qf1) but forms flat benches 3 to 4.5 m (10 to 15 ft) above stream-channel 

(Qs) or modern flood-plain (Qf) deposits. Subject to cut-bank and headward erosion by local 

stream channels. Overlapped by various accumulations of thin surficial deposits (Qd, Qes, 

Qps, Qa1). Supports sparse to moderate growths of grass, tumble weed, and other highdesert shrubs in north half of quadrangle (sheets 1, 2); thick to moderately thick growths of 

grass, camel thorn bush, tumble weed, salt bush, and other desert shrubs along with scattered 

cottonwood, salt cedar (tamarisk), and willow trees in Little Colorado River Valley (sheet 1). 

Eolian-sand accumulations commonly cause temporary blockage of local runoff that forms 

ponded sediments (Qps) on flat flood-plain deposits (Qf2, Qf3) in Little Colorado River 

Valley and in wide, principal-tributary washes. Subject to overbank flooding in Little Colorado River Valley and along local washes. Thickness unknown but may exceed 30 m (100 ft) 

in some areas; visible thickness, 3 to 9 m (10 to 30 ft)

Qf3 Old flood-plain deposits (Holocene)—Gray-brown clay, silt, and fine sand; also includes thin 

lenses of stream gravel and interbedded alluvial fan gravel along margins. Lithologically 

similar to younger flood-plain deposits (Qf, Qf1, Qf2). Forms wide, flat benches, 4.5 to 

10.5 m (15 to 35 ft) above local stream-channel (Qs) and other flood-plain (Qf, Qf1, Qf2) 

deposits. Subject to cut-bank erosion and extensive headward erosion by local streams. 

Overlapped by thin accumulations of young surficial alluvium or eolian deposits (Qd, Qes, 

Qps, Qae, Qa1, Qa2). Supports sparse to moderate growths of grass and variety of small 

high-desert shrubs throughout quadrangle. Subject to local overbank flooding or channel 

erosion. Thickness unknown in Little Colorado River Valley but may exceed 14 m (45 ft) in 

some areas upstream of Leupp where bedrock is exposed (sheet 1); in other areas upstream 

of Leupp, visible thickness, 3 to 14 m (10 to 45 ft) 

Qae Mixed alluvium and eolian deposits (Holocene)—Gray, light-red, and brown clay, silt, and fineto coarse-grained sand interbedded with lenses of pebbly gravel. Deposits on Newberry and 

Ives Mesas (sheet 1) contain white, angular to subangular chert fragments locally derived 

from the Owl Rock Member of the Chinle Formation. Deposits within Hopi Buttes (sheet 2) 

contain black, white, and gray, angular to subrounded volcanic fragments locally derived 

from nearby volcanic outcrops. Unit has accumulated by both alluvial and eolian processes, 

resulting in interbedded sequence of thin-bedded, mixed clay, silt, sand, and small gravel, 

typical of young fluvial (Qa1, Qa2) and eolian (Qd, Qes) deposits. Subject to sheet-wash 

erosion during wet conditions and accumulation of eolian-sand deposits during dry conditions. Commonly overlies young fluvial and eolian surficial deposits (Qf, Qf1, Qf2, Qf3, 

Qa1, Qa2) and often is overlapped by young or fresh eolian-sand deposits (Qd, Qes). Supports light to moderate growths of grass, cactus, and small high-desert shrubs. Thickness, 1 

to 6 m (3 to 20 ft) 

Qsd Silt-dune deposits (Holocene)—Brown and gray clay, silt, and very fine sand; unsorted. Forms 

small, rounded dunes locally derived from dry-lake surfaces where ponded sediments (Qps) 

are transported by southwesterly winds in dry conditions and accumulate on and near northeastern shores of temporary lakes southwest of Little Colorado River (fig. 1; see also, sheet 

1). Supports little to no vegetation. Thickness, 2 to 6 m (6 to 20 ft)

Qg3 Old terrace-gravel deposits (Holocene)—Red and purple clay, silt, sand, and subrounded to 

rounded pebbles and cobbles. Multicolored chert clasts are locally derived from the Chinle 

Formation; subrounded black volcanic clasts are locally derived from the volcanic rocks of 

Hopi Buttes Volcanic Field. Forms isolated flat terrace deposits about 17 m (55 ft) above 
14

local stream channels and about 7.5 to 9 m (25 to 30 ft) above principal-tributary drainages 

east and southeast of Hopi Buttes. Unit grades downstream and coalesces or intertongues 

with old flood-plain deposits (Qf3) along principal drainages downstream to Little Colorado 

River Valley. Thickness, 7.5 to 24 m (25 to 80 ft)

Qv Valley-fill deposits (Holocene and Pleistocene?)—Gray and light-brown clay, silt, sand, and 

gravel lenses; weakly consolidated by gypsum, calcite, and clay cement. Includes rounded 

clasts of limestone and subrounded to angular chert; also includes subrounded to angular 

basalt clasts southwest of Little Colorado River Valley and rounded to subrounded clasts of 

Triassic sedimentary rocks and mafic volcanic rocks in Hopi Buttes area. Intertongues with 

or overlaps alluvial fan (Qa1, Qa2) and young terrace-gravel (Qg1) deposits, representing 

low-energy, low-gradient fluvial deposition. Subject to sheet-wash flooding and temporary 

ponding. Supports moderate growths of grass at lower elevations in central part of quadrangle (sheets 1, 2) and moderately thick growths of sagebrush, grass, cactus, and some juniper 

trees at higher elevations above 1,867 m (5,500 ft). Thickness, 1 to 6 m (3 to 20 ft)

Qa3 Old alluvial fan deposits (Holocene and Pleistocene)—Hopi Buttes area (sheet 2): Gray and 

light-brown silt, sand, and gravel, mixed with assorted brecciated, subangular, and subrounded pebbles and cobbles of black monchiquite and gray tuff; weakly consolidated by 

calcite and gypsum cement. Commonly overlies “Dilkon deposits” (QTdi) and is overlain by 

young eolian and mixed alluvium deposits (Qd, Qes, Qae). Includes large boulders, small 

cobbles, and pebbles of volcanic rocks derived from nearby talus and rock-fall deposits (Qtr) 

and landslide deposits (Ql). Supports moderate growths of grass, sagebrush, cactus, cliff 

rose bush and scattered pinyon pine and juniper tree woodlands. Below Newberry, Ives, and 

Marcou Mesas (south halves of sheets 1 and 2): Lithologically similar to younger alluvial 

fan (Qa1, Qa2) and older alluvial fan (QTa) deposits near and northeast of Little Colorado 

River; consists of unsorted, brown and red-purple clay, silt, sand, and angular gray chert 

pebbles and small boulder debris; weakly consolidated by clay and calcite cement. Supports 

sparse or no vegetation. Thickness, 1.5 to 7.5 m (5 to 25 ft) 

Qtr Talus and rock-fall deposits (Holocene and Pleistocene)—Brown, gray, slope-forming, 

unsorted mixture of clay, silt, sand, and small, large, and very large angular boulders; 

on steep slopes below all ledges of the Owl Rock Member of the Chinle Formation and 

volcanic mesas and buttes of Hopi Buttes area. Contacts gradational with adjacent surficial 

deposits: landslide deposits (Ql), “Dilkon deposits” (QTdi), alluvial fan deposits (Qa1, 

Qa2, Qa3), and fluvial and eolian surficial deposits (Qg1, Qg2, Qg3, Qae, Qv). Subject 

to extensive sheet-wash erosion, headward erosion, and arroyo cutting. Unit may become 

unstable in wet conditions. Only thick or extensive deposits are shown. Thickness, 2 to 11 m 

(6 to 35 ft) 

Ql Landslide deposits (Holocene and Pleistocene)—Weakly consolidated masses of unsorted, 

angular rock debris. Includes detached, stratified blocks that have rotated backward and slid 

downslope as loose, coherent masses and deformed strata. Often includes and is associated with local talus and rock-fall deposits (Qtr) adjacent to and below landslide masses. 

Older landslide deposits weather and erode to form thick gentle slopes of “Dilkon deposits” 

(QTdi). Landslide masses in Hopi Buttes area commonly include soft mudstone and argillaceous sandstone strata of the lower Bidahochi Formation (Tbl), causing some landslides 

to become unstable during wet conditions, especially where landslide masses steeply rest 

against, or overlie, soft sediments of the lower Bidahochi Formation. Thickness, 3 to 61 m 

(10 to 200 ft)

Qg4 Older terrace-gravel deposits (Pleistocene)—Gray and light-brown clay, silt, sand, gravel, 

cobbles, and boulders; weakly cemented by clay, calcite, and gypsum; poorly sorted. 

Includes abundant rounded and well-rounded clasts of quartzite, quartz, chert, and assorted 

metamorphic crystalline rocks derived from scattered Tertiary rocks south, southeast, and 

southwest of quadrangle; also includes well-rounded white chert, gray limestone, and red 

sandstone clasts locally eroded from Permian and Triassic strata south of Little Colorado 

River Valley, as well as well-rounded clasts of yellow, red, gray, and brown quartzite, black 

chert, and subrounded clasts of petrified wood locally derived from the Shinarump Member 

of the Chinle Formation. Forms terrace deposits about 17 m (55 ft) above stream-channel 

deposits (Qs) along principal tributary washes near Little Colorado River and as much 

as 25 m (80 ft) above stream-channel (Qs) and flood-plain (Qf, Qf1, Qf2, Qf3) deposits 

of Little Colorado River. Commonly covered by thin deposits of subrounded to rounded, 
15

wind-polished pebble and cobble clasts that form thin veneer of desert pavement on surface 

of deposits near Little Colorado River Valley. Unit is about 12 to 30 m (40 to 100 ft) below 

oldest terrace-gravel deposits (QTg4) of Little Colorado River at Tucker Mesa and Toltec 

Divide west of Winslow (fig. 1; see also, sheet 1). Thickness, 2 to 25 m (6 to 80 ft) 

QTd Old sand-dune deposits (Pleistocene and Pliocene?)—Tan, light-red, and light-yellow, coarseto fine-grained sand and silt; weakly consolidated. Forms isolated sand deposits on eroding 

bedrock ridges or slopes of badland topography below Marcou and Ives Mesas (fig. 1). Unit 

is extensively eroded and is assumed to represent remnants of old eolian sand-dune or sandsheet deposits. Thickness, 1 to 12 m (3 to 40 ft) 

QTes Old eolian sand-sheet and dune deposits (Pleistocene and Pliocene?)—Light-red to lightbrown, very fine- to medium-grained sand and silt. Found as isolated deposits along eroding 

edges of Ives and Marcou Mesas, as well as on “Dilkon deposits” (QTdi) and below old 

alluvial fan deposits (Qa3). Extensively eroded unit is preserved mostly under younger alluvium and eolian deposits (Qae, Qa1, Qa2, Qa3, Qd, Qes). Contains white carbonate-soil 

horizon in upper 1 m (3 ft) in most outcrops. Thickness, 1 to 3 m (3 to 10 ft)

QTa Older alluvial fan deposits (Pleistocene and Pliocene?)—Gray and light-brown clay, silt, sand, 

and gravel; poorly sorted; weakly consolidated. Includes carbonate-soil horizon (Gile and 

others, 1981; Machette, 1985) in upper 1 to 1.5 m (3 to 5 ft). Consists mainly of erosional 

outwash debris from bedrock outcrops of the Petrified Forest and Owl Rock Members of 

the Chinle Formation below Newberry, Ives, and Marcou Mesas; also contains angular 

fragments and clasts of monchiquite and basanite volcanic rocks from Hopi Buttes, mixed 

with fluvial and eolian silt and sand on Marcou Mesa. Supports moderate growths of grass 

and small desert shrubs. Thickest and most extensive deposits form southwestern extent of 

Ives Mesa. Commonly covered by thin to thick eolian-sand (Qd, Qes), mixed alluvium and 

eolian (Qae), and alluvial (Qps, Qv) deposits. Thickness, 1 to 49 m (3 to 160 ft)

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

gravel, pebbles, and cobbles; poorly sorted; weakly consolidated by calcite and clay cement. 

Pebbles and cobbles are mostly small, well-rounded, black chert; gray, light-red, and brown 

quartzite; and yellow to white quartz. Includes well-rounded, reddish-brown quartzite 

boulders as much as 30 cm (1 ft) in diameter on Tucker Mesa and Toltec Divide (sheet 1). 

Pebbles and cobbles weather out and form protective armored surface that help preserve 

underlying fine-grained silt and sand deposits. Extensively eroded and gullied; locally fills 

channels eroded into underlying sandstone strata of the Moenkopi Formation or of the 

Shinarump Member of the Chinle Formation on Toltec Divide and Tucker Mesa west and 

northwest of Winslow. Deposits are about 30 to 60 m (100 to 200 ft) above modern Little 

Colorado River drainage. Although deposits of this unit on Toltec Divide, on small isolated 

unnamed hills southwest of Toltec Divide (south of Interstate 40), and on Tucker Mesa 

(west of Toltec Divide) are mapped as being similar in age, deposits on Tucker Mesa may be 

slightly older, as they appear to be about 30 m (100 ft) higher than deposits on Toltec Divide 

(sheet 1). Deposits are likely those of ancestral Little Colorado River; current location of 

Little Colorado River suggests northeastward migration of river and its valley of as much as 

7.5 to 10.5 km (5 to 7 mi). Supports little to no vegetation. Thickness on Tucker Mesa, 6 to 

7.5 m (20 to 25 ft); thickness on Toltec Divide, 6 to 18 m (20 to 60 ft) 

QTdi “Dilkon deposits” (Pleistocene? and Pliocene?)—Unit was informally defined by Sutton (1974) 

as “Dilkon terrace” for its relatively unbroken and extensive deposits near Dilkon; however, 

we herein informally map them as “Dilkon deposits” because they form extensive and discontinuous alluvial pediment slopes, not stream terraces, within Hopi Buttes Volcanic Field 

(sheet 2). [Note that, at some lower elevations and valleys east and southeast of Hopi Buttes 

(sheet 2), especially adjacent to mesas and buttes in Bidahochi Wash, Pueblo Colorado 

Wash, and Cottonwood Wash areas, “Dilkon deposits” as mapped on higher ridges could be 

interpreted as old alluvial fan deposits (Qa3), on the basis of their limited lateral extent and 

sandier material composition; however, we chose to map them as “Dilkon deposits” because 

they are more similar to this unit’s description.] Unit is composed of mixed gray fluvial and 

eolian silt and sand that supports abundant clasts of subrounded and subangular pebbles and 

cobbles of black monchiquite, basanite, and gray volcanic tuff derived from the volcanic 

rocks of Hopi Buttes Volcanic Field. Unit, which is weakly to moderately consolidated by 

calcium cement, overlies eroded bedrock of the Moenave Formation (Jm) in southern part 

of Hopi Buttes; the upper sandstone member of the Moenave Formation (Jms) in central 
16

part; and outcrops of the Dakota Sandstone (Kd), the Mancos Shale (Km), the Bidahochi 

Formation (Tbl), and older surficial deposits (QTa, QTes) on north and east slopes of Hopi 

Buttes. Commonly overlain by young alluvial and eolian deposits (Qa1, Qa2, Qa3, Qd, 

Qes, Qae). Includes as many as 10 caliche paleosols and alluvial gravels 0.5 to 1.2 m (2 to 

4 ft) thick. Overlaps or intertongues with local landslide (Ql) and talus and rock-fall (Qtr) 

deposits below mesas and buttes; contacts are gradational and approximate between landslide deposits and talus and rock-fall deposits. Thickness, 4.5 to 25 m (15 to 80 ft) 

QTs “Shonto deposits” (Pleistocene? and Pliocene)—Unit was informally defined by Sutton (1974) 

as “Shonto terrace” because of its presence as isolated higher alluvial remnants above 

“Dilkon deposits” (QTdi) southwest of Shonto Butte (T. 23 N., R. 18 E.); however, we 

herein informally map them as “Shonto deposits.” Unit is composed primarily of benchforming, subangular to angular fragments of monchiquite, basanite, and volcanic tuff mixed 

with minor amounts of alluvial and eolian silt and sand; weakly consolidated by calcium 

cement. Includes angular monchiquite and basanite boulders as large as 40 cm (16 in) in 

diameter. Forms isolated deposits 12 to 19 m (40 to 60 ft) above “Dilkon deposits” (QTdi) 

and is capped by 0.6 to 1.8 m (2 to 6 ft) of caliche-cemented, subangular and angular volcanic rocks and gravel derived from Shonto Butte; includes monchiquite boulders. Thickness, 

8 to 18 m (20 to 60 ft)

VOLCANIC ROCKS

Volcanic rocks of Hopi Buttes (Tsezhin Bii) Volcanic Field (Miocene)—Unit was originally 

defined as the middle volcanic member of the Bidahochi Formation (Repenning and Irwin, 

1954; Shoemaker and others, 1957, 1962); however, we herein redefine them as the volcanic 

rocks of Hopi Buttes Volcanic Field because it forms a mappable sequence of volcanic rocks 

that intertongues with deposits of the lower Bidahochi Formation (Tbl) of Miocene age near 

White Cone Peak northeast of quadrangle and in northeast quarter of quadrangle (sheet 2)

Ti Intrusive dikes, plugs, or necks (Miocene)—Black, dark-gray, and brown intrusive monchiquite, basanite, and unsorted scoriaceous and palagonitic tuff; highly eroded. Includes 

clinopyroxene, pyroxenite inclusions in limburgite, and olivine phenocrysts (Lewis, 1973). 

Forms impressive towering, circular or oblique circular monoliths or buttes about 122 to 427 

m (400 to 1,400 ft) in diameter that display numerous cooling joints. Some larger intrusions 

commonly are capped by basanite or monchiquite flows or brown to gray welded-tuff beds. 

Smaller dikes and plugs of various widths (0.5 to 9 m [1 to 30 ft] or more) commonly are 

associated with larger necks and plugs that generally align along northwest-trending bedrock 

fractures and joints 

Tc Volcanic-crater sedimentary rocks (Miocene)—Commonly deposited within circular maar 

crater-vent depressions that display inward-dipping stratified pyroclastic and surge deposits 

interbedded with lacustrine sedimentary deposits. Consists of undivided epiclastic and lacustrine volcanic and fluvial sedimentary rocks of gray, light-yellow, and tan to white claystone, 

thin-bedded calcareous siltstone and sandstone, globular or bedded travertine, and gypsum 

interbedded with interbedded pyroclastic and mafic gray tuff and white ash. Bedded ash and 

tuffaceous conglomerate and sandstone deposits are moderately well sorted and commonly 

show intense soft-sediment deformation. Within “Coliseum” diatreme between Indian Wells 

and Dilkon (Na Ah Tee Canyon 7.5ʹ quadrangle; see also, fig. 1), 1-m (3-ft) thick sandy sediments contain fish fossils (Uyeno and Miller, 1965) that may suggest an environmental-sedimentary connection to the upper Bidahochi Formation north and northeast of quadrangle. 

Fossil algae and plant fragments are tentatively identified in other nearby maar volcaniccrater sediments. Thickness, 0.5 to 36+ m (1 to 120+ ft)

Tm Mafic monchiquite and basanite flows (Miocene)—Black, dark-gray, and brown porphyritic 

monchiquite and basanite. Contains olivine, clinopyroxene, and phlogopite phenocrysts. 

Thick monchiquite flows display prominent columnar cooling joints. Includes xenoliths of 

crystalline metamorphic rocks near vent areas on Wood Chop Mesa (fig. 1; sheet 2). Include 

abundant kaersutite megacrysts near top of some bedded deposits in Wood Chop Mesa area. 40Ar/39Ar age on kaersutite about 0.7 km (0.5 mi) east of Wood Chop Mesa (just east of sheet 

2) is 6.81±0.06 Ma (Vazquez, 1999). 40Ar/39Ar ages of basanite flows in Wood Chop Mesa 

area are 6.99±0.75 Ma, 6.53±0.59 Ma, and 7.21±0.45 Ma (Vasquez, 1999). Thickness, 3 to 

43+ m (6 to 140+ ft) 
17

Tmt Mafic tuff-and-ash deposits (Miocene)—Gray and white palagonitic lithic tuff and pyroclasts 

of porphyritic monchiquite or basanite fragments containing phenocrysts and glomerocrysts 

of clinopyroxene, olivine, and some phlogopite. Includes palagonitic tuffs containing welded 

ash to lapilli tuff, local bomb-rich layers, and multiple deposits of air-fall ash and surge 

deposits (Hooten and Ort, 2002). Commonly merges into or is interbedded with siltstone and 

travertine sediments of volcanic-crater sedimentary rocks (Tc) in maar depressions. Forms 

isolated deposits topographically above or below outcrops of the Bidahochi Formation 

throughout Hopi Buttes (sheet 2). Thickness, 2 to 55+ m (6 to 180+ ft) 

Tmu Mixed monchiquite and basanite flows and tuff deposits, undivided (Miocene)—Gray 

or brown monchiquite and basanite flows interbedded with mafic tuff-and-ash deposits. 

Contains abundant phenocrysts and glomerocrysts of clinopyroxene, olivine, and phlogopite. 

Includes several mixed flows and pyroclastic deposits from multiple volcanic eruptions in 

north half of Hopi Buttes area (sheet 2). Thickness, 9 to 146+ m (30 to 480+ ft) 

SEDIMENTARY ROCKS

[Consists of Cenozoic, Mesozoic, and Paleozoic sedimentary rocks (Tertiary, Cretaceous, Jurassic, Triassic, 

and Permian sedimentary rocks)]

Bidahochi Formation (Pliocene and Miocene)—Originally defined by Repenning and Irwin 

(1954) and Shoemaker and others (1957, 1962) as the following three informal members, 

in descending order: the upper fluvial member, the middle volcanic member, and the lower 

mudstone and argillaceous sandstone member (Pliocene and Miocene). However, we herein 

redefine the Bidahochi Formation to include only two of the original members, the upper 

fluvial member (present northeast of quadrangle) and the lower mudstone and argillaceous 

sandstone member; only the lower mudstone and argillaceous sandstone member (Tbl) is 

present within quadrangle (sheet 2). Lower member of the Bidahochi Formation is either 

associated with or below the Miocene volcanic rocks of Hopi Buttes (Tsezhin Bii) Volcanic 

Field; thus, it is considered to be Miocene (not Pliocene and Miocene) in age within map 

area (sheet 2) because it is stratigraphically within or below the Miocene volcanic rocks of 

Hopi Buttes. The middle volcanic member of the Bidahochi Formation is herein redefined as 

the volcanic rocks of Hopi Buttes (Tsezhin Bii) Volcanic Field 

Tbl Lower mudstone and argillaceous sandstone member (Miocene)—White, greenish-gray, 

and yellowish-gray claystone, light-red and red-brown mudstone and siltstone, gray sandstone, and thin-bedded conglomerate, all primarily of lacustrine origin; interbedded with 

thin, gray, silicic ash-tuff beds in lower part; slope forming. Unit is easily eroded below 

outcrops of volcanic rocks in Hopi Buttes area, producing weak support of overlying volcanic rocks that results in formation of landslide (Ql) or talus and rock-fall (Qtr) deposits that 

cover substantial areas of outcrop of this unit. Sanidine minerals from felsic vitric-ash bed 

in lower part at “Triplets Mesa” (informally named in Dallegge and others, 1998a) less than 

1 km east of quadrangle (sheet 2) yielded 40Ar/39Ar age of 13.71±0.08 Ma (Dallegge and 

others, 1998a, 1998b). In northwestern part of Hopi Buttes (sheet 2), unit unconformably 

overlies gray Cretaceous rocks and reddish siltstone and sandstone of the Kayenta Formation 

(Jk); in central and northeastern part, red and white strata of the upper sandstone member of 

the Moenave Formation (Jms); in southwestern and southern part, red strata of the Moenave 

Formation (Jm); and in extreme southeast quarter, gray limestone and red siltstone of upper 

part of the Chinle Formation (^co). Unit represents sedimentary deposits within Tertiary 

erosional basin present in eastern two-thirds of Hopi Buttes area (fig. 2). Thickness, 150 m 

(492 ft)

Km Mancos Shale (Upper Cretaceous)—Blue-gray to medium-gray, thinly laminated to thin-bedded, slope-forming, carbonaceous bentonitic claystone, siltstone, and mudstone, interbedded 

with light-gray, fine- to medium-grained sandstone and thin-bedded limestone. Contact with 

the underlying Dakota Sandstone (Kd) is gradational. Cretaceous strata at Bad Medicine 

Butte, Montezumas Chair, Round Top butte, as well as at unnamed buttes north of Teesto 

(fig. 1), are mostly covered by landslide (Ql) and talus and rock-fall (Qtr) deposits. Thickness, 30+ m (100+ ft)

Kd Dakota Sandstone, undivided (Upper Cretaceous)—Lower sandstone unit (not mapped 

separately): Light-orange to light-gray, silty sandstone and conglomeratic sandstone; well 

cemented; forms cliff. Fills channels eroded as much as 1 to 3 m (3 to 10 ft) deep into under-
18

lying gray sandstone beds that may be the Entrada Sandstone (not mapped) just above the 

Kayenta Formation (Jk). Lower sandstone is locally discontinuous in short lateral distance. 

Includes red and gray, well-rounded chert and quartzite pebble clasts less than 5 cm (2 in) in 

diameter within conglomeratic-sandstone lenses. Unit unconformably overlies gray-white 

sandstone beds that may overlie the Entrada Sandstone (not mapped) at Bad Medicine Butte, 

Montezumas Chair, and Round Top butte (figs. 1 and 2). Middle unit (not mapped separately): Dark-gray-brown, carbonaceous, flat-bedded mudstone, siltstone, and black coal, 

interbedded with brown, conglomeratic, crossbedded lenticular sandstone. Coal beds, which 

generally are less than 0.5 m (2 ft) thick, have been partly mined, probably in late 1940s 

and early 1950s, but now are abandoned as prospects on east and north side of Round Top 

butte and Bad Medicine Butte. Gypsum is common constituent as thin to thick stringers and 

pockets and isolated crystals. Contact with underlying lower sandstone unit is gradational, as 

is contact with the overlying Mancos Shale (Km). Thickness, 9 to 24 m (30 to 80 ft).

Unconformity between unit and underlying Triassic and Jurassic rocks has been 

established as regional angular unconformity, on the basis of deposition of unit overlying 

younger rocks north of quadrangle and older rocks south and southeast of quadrangle (fig. 

2). Although these relations do establish angularity of pre-Dakota unconformity, angularity 

is so small that it is not apparent at most outcrops within Navajo Nation (Harshbarger and 

others, 1958) 

Glen Canyon Group (Jurassic)—Overlies the Triassic Chinle Formation and includes the 

Jurassic Moenave Formation (Jm, Jms), the Wingate Sandstone in Utah and northeastern 

Arizona, the Kayenta Formation (Jk), and the Navajo Sandstone (the Wingate Sandstone 

and the Navajo Sandstone are not present in quadrangle). Contact between the Moenave and 

Chinle Formations is arbitrarily placed at lithologic, topographic, and color change between 

underlying purple and white mudstone, sandstone, and gray limestone of the Owl Rock 

Member of the Chinle Formation (^co) and overlying red to orange-red mudstone, siltstone, 

and sandstone of the Moenave Formation (Jm), which may be equivalent to the Wingate 

Sandstone. In addition, the Jurassic Entrada Sandstone may be present at Bad Medicine 

Butte, Montezumas Chair, and Round Top butte (fig. 1), pinching out just east and south of 

these buttes; further study is needed to confirm if the Entrada Sandstone is present in this 

part of quadrangle

Jk Kayenta Formation (Lower Jurassic)—Purple, lavender, and light-red, slope-forming, fluvial crossbedded mudstone, siltstone, and fine-grained silty sandstone. Includes gray-white, 

slope-forming, very fine grained, trough-crossbedded sandstone in upper part that may be 

the Entrada Sandstone, which overlies the Navajo Sandstone northwest of quadrangle; the 

Navajo Sandstone pinches out just north of quadrangle (Billingsley and others, 2007). Unit 

is mostly covered by landslide deposits (Ql), talus and rock-fall deposits (Qtr), and “Dilkon 

deposits” (QTdi). Includes minor lenticular thin-bedded ledges of medium-grained sandstone in middle and lower part. Contact with the underlying upper sandstone member of the 

Moenave Formation (Jms) is gradational and marked at topographic and lithologic change 

to cliff-forming light-red or gray-white sandstone. Thickness, 98 to 122 m (320 to 400 ft) 

Jm Moenave Formation (Lower Jurassic)—Orange-red and light-red, slope-forming, flatbedded and low-angle crossbedded, fine- to coarse-grained siltstone and silty sandstone. 

Unit generally weathers as slope, except in western part of Hopi Buttes where gray-white 

and light-red strata of the upper sandstone member (Jms) forms rounded cliffs or ledges of 

sandstone. Forms Red Rock Cliffs northwest of quadrangle (Billingsley and others, 2007). 

Upper part of unit is partly removed by Tertiary erosion in northern-central and southeastern 

part of Hopi Buttes where overlain by dark-brown or white mudstone and siltstone of the 

lower mudstone and argillaceous sandstone member of the Bidahochi Formation (Tbl). Unit 

is unconformably overlain by purple-red siltstone and sandstone of the Kayenta Formation 

(Jk) in northwestern part of Hopi Buttes (sheet 2). Contact with the underlying Owl Rock 

Member of the Chinle Formation (^co) is gradational. Thickness, 92 to 134 m (300 to 440 

ft) 

Jms Upper sandstone member (Lower Jurassic)—Consists of two subunits (not mapped 

separately), a lower gray-white sandstone subunit and an upper light-red sandstone subunit, 

that weather to rounded cliff outcrops as exposed at Red Cheek Butte (fig. 1; sheet 2). 

Lower gray-white subunit is cliff-forming, medium- to fine-grained, low-angle-crossbedded 

sandstone that gradationally overlies red and orange-red sandstone and siltstone slopes of the 
19

Moenave Formation (Jm) in southwestern and central part of Hopi Buttes (east edge of sheet 

1; west edge of sheet 2). Lower gray-white sandstone subunit, which extends northwest of 

quadrangle to Moenkopi Plateau (Billingsley and others, 2007), is disconformably overlain 

by light-red, cliff-forming, fine-grained, low-angle-crossbedded sandstone subunit as 

exposed at Red Cheek Butte (fig. 1; sheet 2). Upper light-red sandstone subunit is thickest 

near Dilkon. Both gray-white and light-red sandstone subunits undergo eastward facies 

change to red siltstone and sandstone fluvial beds in upper part of the Moenave Formation 

(Jm) in southeastern part of Hopi Buttes where it has been partly removed by Tertiary 

erosion. In southern part of Hopi Buttes (fig. 2), unit is unconformably overlain by redbrown or white mudstone and argillaceous sandstone of the lower mudstone and argillaceous 

sandstone member of the Bidahochi Formation (Tbl); in northern-central part, by graywhite mudstone and argillaceous sandstone of the lower member (Tbl) of the Bidahochi 

Formation; and in northwestern part, by purple and red-brown siltstone and sandstone of the 

Kayenta Formation (Jk). Thickness, 25 to 30 m (80 to 100 ft) 

Chinle Formation (Upper Triassic)—Consists of the Owl Rock, the Petrified Forest, and the 

Shinarump Members (Repenning and others, 1969) 

^co Owl Rock Member (Upper Triassic)—Gray-red and light-purple, slope- and ledge-forming, 

nodular limestone, interbedded with purple, light-blue, and light-red calcareous claystone, 

siltstone, and sandstone. Limestone beds are gray, cherty, lenticular, silty, irregularly bedded, 

and 0.5 to 1.5 m (1 to 5 ft) thick, and they extend laterally several kilometers, forming as 

many as seven resistant limestone ledges at Newberry Mesa and northern part of Ives Mesa 

(fig. 1). Includes upper red, slope-forming siltstone and claystone interval that gradually 

thickens from 12 m (40 ft) in northwestern part of quadrangle (sheet 1) to 43 m (240 ft) near 

east-central edge of quadrangle (sheet 2). Unit contains abundant mud pellets and silicified 

clay and concretionary chert nodules and generally maintains consistent thickness across 

quadrangle. Contact with the underlying Petrified Forest Member (^cp) is gradational and 

is arbitrarily placed at lowest limestone bed, or at nodular calcareous gray-white siltstone in 

slope below lowest limestone bed. Thickness, 80 to 92 m (260 to 300 ft)

^cp Petrified Forest Member (Upper Triassic)—Purple, blue, light-red, red-purple, and grayblue, slope-forming mudstone and siltstone, interbedded with white to yellow-white, coarsegrained, lenticular sandstone. Includes lenticular alluvial stream-channel features that exhibit 

large-scale, low-angle trough-crossbedding. Petrified logs and petrified-wood fragments 

are common in white or yellow-white sandstone beds. Blue and red claystone beds weather 

into rounded hills or slopes that have rough, puffy, popcorn-like surfaces owing to swelling 

clay. Contact with the underlying Shinarump Member (^cs) is gradational and is arbitrarily 

placed at lithologic and topographic change from claystone and siltstone slopes of unit to 

coarse-grained conglomeritic sandstone ledges of the Shinarump Member. Thickness, 107 to 

131 m (350 to 430 ft)

^cs Shinarump Member (Upper Triassic)—White, light-brown, and yellowish-pink, cliff-forming, coarse-grained sandstone and conglomeratic sandstone. Includes cliff-forming, lowangle-crossbedded sandstone, interbedded with purple, light-red, and blue, slope-forming, 

poorly sorted siltstone and mudstone in upper part (sheet 1). Lithology is highly variable but 

relatively homogeneous from regional viewpoint, consisting of about 75 percent sandstone, 

20 percent conglomerate, and 5 percent mudstone. Pebbles generally are black, brown, and 

gray, well-rounded quartzite and chert. Petrified logs and petrified-wood fragments are abundant at some localities but generally are scattered throughout unit. Unit is mostly covered by 

flood-plain deposits in Little Colorado River Valley. Forms cap-rock ledges of Tucker Mesa 

and Toltec Divide (southwestern part of sheet 1) where it overlies similar coarse-grained 

channel sandstones of the Holbrook and Moqui Members, undivided, of the Moenkopi 

Formation (^mhm). Sandstones of unit often are distinguished from underlying sandstones 

of the Moenkopi Formation by presence of scattered, well-rounded pebble clasts versus no 

pebble clasts present in the Moenkopi Formation sandstone beds. Contact with underlying 

red siltstone and sandstone of the Moenkopi Formation is unconformable. Thickness, 18 to 

24 m (60 to 80 ft) 

Moenkopi Formation (Middle? and Lower Triassic)—Red, slope-forming, fine-grained, 

thin-bedded, shaley siltstone and sandstone. Includes the following two subunits, in ascending order: the lower massive sandstone member, and the undivided Holbrook and Moqui 

Members. The lower massive sandstone member also includes the Wupatki Member of the 
20

Moenkopi Formation (McKee, 1954) because it generally is less than 4.5 m (15 ft) thick 

and pinches out in southwest quarter of quadrangle just west of Winslow (sheet 1). Overall, 

unit has unconformable contact with the underlying Kaibab Formation (Pk), representing 

regional Permian–Triassic unconformity. Thickness, 67 m (220 ft) 

^mhm Holbrook and Moqui Members, undivided (Middle? and Lower Triassic)—Reddishbrown, slope-forming, alternating sequence of claystone, siltstone, and sandstone (McKee, 

1954). Includes large- to medium-scale trough-crossbedding and abundant cusp-type ripple 

marks that testify to isolated fluvial-channel origin of the Holbrook Member; meander channels of the Holbrook Member are easy to recognize on 1:24,000-scale color aerial photographs between Winslow and Leupp. Commonly also includes sandstone and siltstone beds 

of the Moqui Member, making it an undivided map unit. Includes interbedded thin-bedded 

limestone, conglomeratic sandstone lenses, and gypsiferous siltstone and numerous gypsum 

veins in the Moqui Member. Thickness, about 25 to 37 m (80 to 120 ft) 

^mss Lower massive sandstone member (Lower Triassic)—Light-red and light-brown, cliffforming, crossbedded, fine-grained calcareous siltstone and sandstone. Unit gradually thins 

eastward to Winslow and forms isolated sandstone knobs along Interstate 40 (sheet 1). Salt 

weathering of sandstone forms weathered holes and fluted shapes in sandstone outcrops. 

Includes basal thin-bedded red siltstones of the Wupatki Member of the Moenkopi Formation (southwest edge of sheet 1). Unconformable contact with the underlying Kaibab Formation (Pk) is marked at distinct color change from red strata of the Moenkopi Formation to 

gray strata of the underlying Kaibab Formation. Thickness, about 3 to 26 m (10 to 53 ft) 

Pk Kaibab Formation (Cisuralian1)—Light-gray, cliff-forming, fine- to medium-grained, thin- to 

medium-bedded (0.3 to 2 m [1 to 6 ft]), fossiliferous, sandy, cherty limestone; weathers to 

dark gray. Characterized by gray to white, fossiliferous chert nodules and white chert lenses 

parallel to limestone bedding; chert weathers to dark gray to black. Some chert nodules 

contain concentric black and white bands. Includes breccia chert beds as much as 1 m (3 

ft) thick in upper part, near contact with the overlying Moenkopi Formation. Unit thins 

eastward to less than 8 m (25 ft) southeast of quadrangle. Thickness (Hoffmann and others, 

2005), 24 to 40 m (80 to 130 ft)

Pc Coconino Sandstone (Cisuralian)—Tan to white, cliff-forming, fine-grained, well-sorted, 

crossbedded quartz sandstone. Contains large-scale, high-angle planar-crossbedded sandstone sets that average about 11 m (35 ft) thick. Upper part may be sandstone beds of the 

Toroweap Formation. Drill holes near Leupp indicate that only 6 to 9 m (20 to 30 ft) of the 

Toroweap Formation (sandstone) is present in that area (Hoffmann and others, 2005). Sharp 

planar contact with underlying the Schnebly Hill Formation of Blakey (1990) is present in 

subsurface of southwestern part of quadrangle (sheet 1). This unit and the Schnebly Hill 

Formation are important water-bearing sandstone aquifers in subsurface of southwest quarter 

of quadrangle (south half of sheet 1) (Hoffmann and others, 2005) and perhaps also east and 

south of quadrangle. Thickness (Hoffmann and others, 2005), 366 to 396 m (1,200 to 1,300 

ft). Only top 11 m (35 ft) of unit is exposed in Cow Canyon (southwest edge of sheet 1)

1

Please note that Lower Permian is now referred to as Cisuralian.
21

Blakey, R.C., 1994, Paleogeographic and tectonic controls 

on some lower and middle Jurassic erg deposits, Colorado 

Plateau, in Caputo, M.V., Peterson, J.A., and Franczyk, K.J., 

eds., Mesozoic systems of the Rocky Mountain region, USA: 

Rocky Mountain Section, SEPM Society of Sedimentary 

Geology Meeting, Denver, Colo., Special Publication, p. 

273–298. 

Blakey, R.C., and Ranney, Wayne, 2008, Ancient landscapes of 

the Colorado Plateau: Grand Canyon, Ariz., Grand Canyon 

Association, 156 p. 

Blakey, R.C., Nation, M.J., and Tuesink, M.F., 1992, Jurassic 

fluvial-eolian recycling, Colorado Plateau—Sediment for the 

“Great Sand Pile”: Society of Economic Paleontologists and 

Mineralogists 1992 Theme Meeting, p. 14.

Block, Debra, Malmon, Daniel, and Hiza, Margaret, 2009, 

Effects of floods and climate on channel planform change of 

the Little Colorado River, Arizona [abs.]: Geological Society 

of America Abstracts with Programs, v. 41, no. 7, p. 41.

Clemmensen, L.B., Olsen, H., and Blakey, R.C., 1989, Ergmargin deposits in the Lower Jurassic Moenave Formation 

and Wingate Sandstone, southern Utah: Geological Society of 

America Bulletin, v. 101, p. 759–773.

Cooley, M.E., Harshbarger, J.W., Akers, J.P., and Hardt, W.F., 

1969, Regional hydrogeology of the Navajo and Hopi 

Indian Reservations, Arizona, New Mexico, and Utah: U.S. 

Geological Survey Professional Paper 521–A, plate 1 (sheet 2 

of 9), p. A1–A61.

Dallegge, T.A., 1999, Correlation and chronology of the 

Miocene-Pliocene Bidahochi Formation, Navajo and Hopi 

Nations, northeastern Arizona: Flagstaff, Northern Arizona 

University, unpublished M.S. thesis, 304 p. 

Dallegge, T.A., Ort, M.H., and McIntosh, W.C., 1998a, 

Correlation and chronology of the lower units of the MioPliocene Bidahochi Formation, Navajo and Hopi Nations, 

northeastern Arizona: Geological Society of America 

Abstracts with Programs, v. 30, no. 6, p. 7.

Dallegge, T.A., Ort, M.H., and McIntosh, W.C., 2003, 

Mio-Pliocene chronostratigraphy, basin morphology 

and paleodrainage relations derived from the Bidahochi 

Formation, Hopi and Navajo Nations, northeastern Arizona: 

The Mountain Geologist, v. 40, no. 3, p. 55–82.

Dallegge, T.A., Ort, M.H., McIntosh, W.C., and Perkins, 

M.E., 2001, Age and depositional basin morphology of the 

Bidahochi Formation and implications of the ancestral upper 

Colorado River, in Young, R.A., and Spamer, E.E., eds., 

Colorado River origin and evolution: Grand Canyon, Ariz., 

Grand Canyon Association, Grand Canyon Symposium 

Monograph 12, p. 47–51.

Dallegge, T.A., Ort, M.H., Vazquez, J.A., and White, D.L., 

1998b, Volcanism and sedimentation in the Miocene-Pliocene 

Hopi Buttes and Hopi Lake [abs.], in Dubendorfer, E.M., ed., 

Geologic excursions in northern and central Arizona: Field 

trip guidebook for Geological Society of America, Rocky 

Mountain Section Meeting, May, 1998, Flagstaff, Northern 

Arizona University, p. 35–58.

Damon, P.E., Shafiqullah, M., Harris, R.C., and Spencer, J.E., 

1996, Compilation of unpublished Arizona K-Ar dates from 

References Cited

Akers, J.P., Cooley, M.E., and Repenning, C.A., 1958, 

Moenkopi and Chinle Formations of Black Mesa basin and 

adjacent areas, in Anderson, R.Y., and Harshbarger, J.W., 

eds., Guidebook of the Black Mesa basin, northeastern 

Arizona: New Mexico Geological Society Guidebook, 9th 

Field Conference, Oct. 16–18, 1958, p. 88–94.

Anderson, T.C., Sprinkel, D.A., and Willis, G.C., 2000, Geology 

of Glen Canyon National Recreation Area, Utah-Arizona, in

Sprinkel, D.A., Chidsey, T.C., Jr., and Anderson, P.B., eds., 

Geology of Utah’s Parks and Monuments: Salt Lake City, 

Utah Geological Association Publication 28, Millennium 

Field Conference, p. 301–335.

Baars, D.L., 2000, Geology of Canyonlands National Park, 

Utah, in Sprinkel, D.A., Chidsey, T.C., Jr., and Anderson, 

P.B., eds., Geology of Utah’s Parks and Monuments: Salt 

Lake City, Utah Geological Association Publication 28, 

Millennium Field Conference, p. 61–83.

Baskin, J.A., 1979, Small mammals of the Hemphillian age 

White Cone local fauna, northeastern Arizona: Journal of 

Paleontology, v. 53, p. 695–708.

Billingsley, G.H., and Wellmeyer, J.L., 2003 (revised 2006), 

Geologic map of the Mount Trumbull 30' × 60' quadrangle, 

Mohave and Coconino Counties, northwestern Arizona: 

U.S. Geological Survey Geologic Investigations Series Map 

I–2766, scale 1:100,000, 36 p., available at http://pubs.usgs.

gov/imap/i2766/.

Billingsley, G.H., and Workman, J.B., 2000, Geologic map 

of the Littlefield 30' × 60' quadrangle, Mohave County, 

northwestern Arizona: U.S. Geological Survey Geologic 

Investigations Series Map I–2628, scale 1:100,000, 25 p., 

available at http://pubs.usgs.gov/imap/i2628/.

Billingsley, G.H., Block, D.L., and Dyer, H.C., 2006a, Geologic 

map of the Peach Springs 30' × 60' quadrangle, Mohave and 

Coconino Counties, northwestern Arizona: U.S. Geological 

Survey Scientific Investigations Map 2900, scale 1:100,000, 

16 p., available at http://pubs.usgs.gov/sim/2006/2900/.

Billingsley, G.H., Felger, T.J., and Priest, S.S., 2006b, Geologic 

map of the Valle 30' × 60' quadrangle, Coconino County, 

northern Arizona: U.S. Geological Survey Scientific 

Investigations Map 2895, scale 1:100,000, 22 p., available at 

http://pubs.usgs.gov/sim/2006/2895/.

Billingsley, G.H., Priest, S.S., and Felger, T.J., 2007, Geologic 

map of the Cameron 30' × 60' quadrangle, Coconino 

County, northern Arizona: U.S. Geological Survey Scientific 

Investigations Map 2977, scale 1:100,000, 33 p., available at 

http://pubs.usgs.gov/sim/2007/2977/.

Billingsley, G.H., Priest, S.S., and Felger, T.J., 2008, Geologic 

map of the Fredonia 30' × 60' quadrangle, Mohave and 

Coconino Counties, northern Arizona: U.S Geological Survey 

Scientific Investigations Map 3035, scale 1:100,000, 23 p., 

available at http://pubs.usgs.gov/sim/3035/.

Blakey, R.C., 1990, Stratigraphy and geologic history of 

Pennsylvanian and Permian rocks, Mogollon Rim region, 

central Arizona and vicinity: Geological Society of America 

Bulletin, v. 102, p. 1,189–1,217.
22

Lewis, P.H., 1973, Mica pyroxenite inclusions in limburgite, 

Hopi Buttes Volcanic Field, Arizona: Brigham Young 

University Geological Studies, v. 20, pt. 4, p. 191–225.

Lindsay, E.H., Updyke, N.D., and Johnson, N.M., 1984, 

Blancan-Hemphillian land mammal ages and Cenozoic 

mammal dispersal events: Annual Review of Earth and 

Planetary Sciences, v. 12, p. 445–488.

Machette, M.N., 1985, Calcic soils of the southwestern United 

States, in Weide, D.L., and Faber, M.L., eds., Soils and 

Quaternary geology of the southwestern United States: 

Geological Society of America Special Paper 203, p. 1–23.

McKee, E.D., 1954, Stratigraphy and history of the Moenkopi 

Formation of Triassic age: Geological Society of America 

Memoir 61, 133 p.

Morgan, G.S., and White, R.S., Jr., 2005, Miocene and Pliocene 

vertebrates from Arizona, in Hacket, A.B., and Lucas, S.G., 

eds., Vertebrate paleontology in Arizona: New Mexico 

Museum of Natural History and Science Bulletin, no. 29, p. 

115–136.

Nations, M.J., 1990, Analysis of eolian architecture and 

depositional systems in the Jurassic Wingate Sandstone, 

central Colorado Plateau: Flagstaff, Northern Arizona 

University, unpublished M.S. thesis, 222 p. 

Ort, M.H., Dallegge, T.A., Vazquez, J.A., and White, J.D.L., 

1998, Volcanism and sedimentation in the Mio-Pliocene 

Bidahochi Formation, Navajo Nation, northeastern Arizona, 

in Duebendorfer, E.M., ed., Geologic excursions in northern 

and central Arizona: Field trip guidebook for Geological 

Society of America, Rocky Mountain Section Meeting, May, 

1998, Flagstaff, Northern Arizona University, p. 35–57.

O’Sullivan, R.B., and Beikman, H.M., 1963, Geology, structure, 

and uranium deposits of the Shiprock quadrangle, New 

Mexico and Arizona: U.S Geologic Miscellaneous Geologic 

Investigations Map I–345, scale 1:250,000.

O’Sullivan, R.B., Repenning, C.A., Beaumont, E.C., and 

Page, H.G., 1972, Stratigraphy of the Cretaceous Rocks 

and the Tertiary Ojo Alamo Sandstone, Navajo and Hopi 

Indian Reservations, Arizona, New Mexico, and Utah: U.S. 

Geological Survey Professional Paper 521–E, 65 p. 

Peterson, Fred, and Pipiringos, G.N., 1979, Stratigraphic 

relations of the Navajo Sandstone to Middle Jurassic 

Formations, southern Utah and northern Arizona: U.S. 

Geological Survey Professional Paper 1035–B, 43 p. 

Pipiringos, G.N., and O’Sullivan, R.B., 1978, Principle 

unconformities in Triassic and Jurassic rocks, western 

Interior U.S.—A preliminary report: U.S. Geological Survey 

Professional Paper 1035–A, 29 p.

Priest, S.S., 2001, Appendix A—Geochron database, in Young, 

R.A., and Spamer, E.E., eds., Colorado River origin and 

evolution: Grand Canyon, Ariz., Grand Canyon Association, 

Grand Canyon Symposium Monograph, no. 12, p. 233–250.

Repenning, C.A., and Irwin, J.H., 1954, Bidahochi Formation 

of Arizona and New Mexico: American Association of 

Petroleum Geologists Bulletin, v. 38, no. 8, p. 1,821–1,826.

Repenning, C.A., Cooley, M.E., and Akers, J.P., 1969, 

Stratigraphy of the Chinle and Moenkopi Formations, Navajo 

the University of Arizona laboratory of isotope geochemistry, 

1971–1991: Arizona Geological Survey Open-File Report 

96–18, 53 p.

Edwards, D.P., 1985, Depositional controls on the Lower 

Jurassic Dinosaur Canyon Member of the Moenave 

Formation, southern Utah and northern Arizona: Flagstaff, 

Northern Arizona University, unpublished M.S. thesis, 243 p.

Evernden, J.E., Savage, D.E., Curtis, G.H., and James, G.T., 

1964, Potassium-argon dates and the Cenozoic mammalian 

chronology of North America: American Journal of Science, 

v. 262, p. 98–145.

Gile, L.H., Hawley, J.W., and Grossman, R.B., 1981, Soils and 

geomorphology in the Basin and Range area of Southern 

New Mexico—Guidebook to the Desert Project: New Mexico 

Bureau of Mines and Mineral Resources Memoir 39, 222 p., 

1 plate.

Hackman, R.J., and Olson, A.B., 1977, Geology, structure, and 

uranium deposits of the Gallup 1° × 2° quadrangle, New 

Mexico and Arizona: U.S. Geological Survey Miscellaneous 

Investigations Series Map I–981, scale 1:250,000. 

Hager, Dorsey, 1922, Oil possibilities of the Holbrook area in 

northeast Arizona: Mining and Oil Bulletin, v. 8, no. 1, p. 

23–27, 33–34; no. 2, p. 71–74, 81, 94; no. 3, p. 135–140.

Harshbarger, J.W., Repenning, C.A., and Irwin, J.H., 1958, 

Stratigraphy of the uppermost Triassic and Jurassic rocks 

of the Navajo country, in Anderson, R.Y., and Harshbarger, 

J.W., eds., Guidebook of the Black Mesa basin, northeastern 

Arizona: New Mexico Geological Society Guidebook, 9th 

Field Conference, Oct. 16–18, 1958, p. 98–114.

Haynes, D.D., and Hackman, R.J., 1978, Geology, structure, 

and uranium deposits of the Marble Canyon 1° × 2° 

quadrangle, Arizona: U.S. Geological Survey Miscellaneous 

Investigations Series Map I–1003, scale 1:250,000.

Hoffmann, J.P., Bills, D.J., Phillips, J.V., and Halford, K.J., 

2005, Geologic, hydrologic, and chemical data from the 

C aquifer near Leupp, Arizona: U.S. Geological Survey 

Scientific Investigations Report 2005–5280, 42 p., available 

at http://pubs.usgs.gov/sir/2005/5280/.

Hooten, J.A., 1999a, Phreatomagmatic diatremes of the 

western Hopi Buttes Volcanic Field, Navajo Nation, Arizona: 

Flagstaff, Northern Arizona University, unpublished M.S. 

thesis, 140 p.

Hooten, J.A., 1999b, Map of the volcanic geology of the 

Castle Butte Trading Post vicinity, Hopi Buttes (Tsezhin 

Bii), Navajo Nation, Arizona: Arizona Geological Survey 

Contributed Map CM–00–A, 1 sheet.

Hooten, J.A., and Ort, M.H., 2002, Peperite as a record of early 

stage phreatomagmatic fragmentation process—An example 

from the Hopi Buttes Volcanic Field, Navajo Nation, Arizona, 

USA: Journal of Volcanology and Geothermal Research, v. 

114, p. 95–106.

Huntoon, P.W., 2003, Post-Precambrian tectonism in the Grand 

Canyon region, in Beus, S.S., and Morales, Michael, eds., 

Geology of the Grand Canyon (2d ed.): New York, Oxford 

University Press, p. 222–259.
23

Sutton, R.L., 1974, The geology of Hopi Buttes, Arizona, in

Karlstrom, T.N.V., Swann, G.A., and Eastwood, R.C., eds., 

Geology of northern Arizona with notes on archaeology and 

paleoclimate, part II—Area studies and field guides; Hopi 

Buttes–Navajo Buttes area: Geological Society of America 

Rocky Mountain Section, Guidebook no. 27, p. 647–671.

Ulrich, G.E., Billingsley, G.H., Hereford, Richard, Wolfe, E.W., 

Nealey, L.D., and Sutton, R.L., 1984, Map showing geology, 

structure, and uranium deposits of the Flagstaff 1° × 2° 

quadrangle, Arizona: U.S. Geological Survey Miscellaneous 

Investigations Series Map I–1446, scale 1:250,000.

Uyeno, Teruya, and Miller, R.R., 1965, Middle Pliocene 

Cyprinid fishes from the Bidahochi Formation, Arizona: 

Copeia, v. 1965, no. 1, p. 28–41.

Vazquez, J.A., 1998, Maar volcanism in the Wood Chop Mesa 

area, Hopi Buttes Volcanic Field, Navajo Nation, Arizona: 

Flagstaff, Northern Arizona University, unpublished M.S. 

thesis, 210 p.

Vazquez, J.A., 1999, Map of the volcanic geology of the Wood 

Chop Mesa area, Hopi Buttes (Tsezhin Bii), Navajo Nation, 

Arizona: Arizona Geological Survey Contributed Map 

CM–99–A, scale 1:12,000, 1 sheet.

Vazquez, J.A., and Ort, M.H., 2006, Facies variation of eruption 

units produced by the passage of single pyroclastic surge 

currents, Hopi Buttes Volcanic Field, USA: Journal of 

Volcanology and Geothermal Research, v. 154, p. 222–236.

Wenrich, K.J., 1989, Mineralization of breccia pipe in northern 

Arizona: Economic Geology, v. 80, no. 6, p. 1,722–1,735.

White, J.D.L., 1991, Maar-diatreme phreatomagmatism at 

Hopi Buttes, Navajo Nation (Arizona) USA: Bulletin of 

Volcanology, v. 53, p. 239–258.

Williams, Howel, 1936, Pliocene volcanoes of the Navajo-Hopi 

country: Geological Society of America Bulletin, v. 47, p. 

111–172.

and Hopi Indian Reservations Arizona, New Mexico, and 

Utah: U.S. Geological Professional Paper 521–B, 34 p.

Reynolds, S.J., Florence, F.P., Welty, J.W., Roddy, M.S., Currier, 

D.A., Anderson, A.V., and Keith, S.B., 1986, Compilation of 

radiometric age determinations in Arizona: Arizona Bureau of 

Geology and Mineral Technology, Geological Survey Branch, 

Bulletin 197, 252 p.

Riggs, N.R., and Blakey, R.C., 1993, Early and Middle Jurassic 

paleogeography and volcanology of Arizona and adjacent 

areas, in Dunne, George, and McDougall, Kristin, eds., 

Mesozoic paleogeography of the western United States-II: 

Pacific Section, SEPM Society for Sedimentary Geology, 

Book 71, p. 347–375. 

Shoemaker, E.M., Hensley, F.S., Jr., and Hallagan, R.W., 1957, 

Diatremes on the Navajo and Hopi Reservations, Arizona, in

Geologic investigations of radioactive deposits—Semiannual 

progress report, December 1, 1956, to May 31, 1957: U.S. 

Geological Survey TEI-690, Book 2, p. 389–398 (issued by 

U.S. Atomic Energy Commission Technological Information 

Services, Oak Ridge, Tenn.).

Shoemaker, E.M., Roach, C.H., and Byers, F.M., Jr., 1962, 

Diatremes and uranium deposits in the Hopi Buttes, Arizona, 

in Petrologic studies—A volume to honor A.F. Buddington: 

Geological Society of America, p. 327–355.

Scarborough, R.B., Damon, P.E., and Schfiqullah, M., 1974, 

K-Ar age for a basalt from the volcanic member (unit 5) 

of the Bidahochi Formation [abs.]: Geological Society of 

America Abstracts with Programs, v. 6, p. 472.

Spencer, J.E., Smith, G.R., and Dowling, T.E., 2008, Middle 

to late Cenozoic geology, hydrography, and fish evolution 

in the American Southwest, in Reheis, M.C., Hershler, R., 

and Miller, D.M., eds., Late Cenozoic drainage history of 

the southwestern Great Basin and Lower Colorado River 

region—Geologic and biotic perspectives: Geological Society 

of America Special Paper 439, p. 279–299.
24

Table 1. Geochronologic data from Hopi Buttes Volcanic Field, Little Colorado River area; reprinted “as is” from Priest (2001) with permission from publi

Grand Canyon, Arizona) (written commun., August 19, 2009). 

Sample

number

Age

(Ma)

Reliability

(ka)

Sample locality

and type

General Locality Latitude Longitude Reference 

970712F 15.46 ±0.58 Bidahochi Fm, felsic ash bed Hopi Buttes; Member 1 at East 

Point Mesa

35.389 109.951 Dallegge, 1999

970719E 15.19 ±0.11 Bidahochi Fm, felsic ash bed Hopi Buttes; Member 2 at SW 

end of Wood Chop Mesa

35.424 110.041 Dallegge, 1999

970705C 14.81 to 

71.98

Bidahochi Fm, felsic ash bed Hopi Buttes; Member 5 N of 

Greasewood Trading Post

35.558 109.832 Dallegge, 1999

970705C 13.85 ±0.02 Bidahochi Fm, felsic ash bed Hopi Buttes; Member 5 N of 

Greasewood Trading Post

35.558 109.832 Dallegge, 1999

HB96-1 13.71 ±0.08 Bidahochi Fm, felsic ash bed Hopi Buttes 35.319 110.292 Dallegge and others, 19981

UAKA 73-137 13.85 ±0.20 Bidahochi Fm air-fall tuff Hopi Buttes 35.634 110.082 Reynolds and others, 1986 Vitric 

beds, (UAKtoo ol

UAKA 74-132 8.49 ±0.27 Hopi Buttes Diatreme 14 Hopi Buttes; ring dike at S edge 

of diatreme 14, elev 1823 m

35.326 110.327 Damon and Spencer (written 

commun, 2000)

Dense 

UAKA 74-131 7.84 ±0.74 Hopi Buttes Diatreme 14 Hopi Buttes; top of butte SE of 

diatreme 14, elev 1957 m

35.323 110.319 Damon and Spencer (written 

commun, 2000)

Moncslight

UAKA 76-11 7.84 ±0.185 Bidahochi basalt bomb Hopi Buttes; bomb at top of bed 

correlative w/Bidahichi Fm.

35.556 110.09 Damon and Spencer (written 

commun, 2000)

SourcS15, T

UAKA 76-12 7.82 ±0.18 Bidahochi dike Hopi Buttes; dike strikes N45E 35.561 110.093 Damon and Spencer (written 

commun, 2000)

Moncsequewhich a flow 4.8 km 

980118B 7.71 ±0.06 Phlogopite, mafic tuff Hopi Buttes; Member 5 at Flat 

Tire Mesa

35.546 110.152 Dallegge, 1999

UAKA 74-146 7.35 ±0.17 Bobcat Butte diatreme Hopi Buttes, spatter of Bobcat 

Butte diatreme

35.473 110.406 Damon and Spencer (written 

commun, 2000)

Vesicbiotit

7.21 ±0.45 Lava groundmass Hopi Buttes; Martinez maar Vasquez, 1998

UAKA 76-10 7.01 ±0.16 Na-Ah-Tee 2 basalt Hopi Buttes; near top of hill w/

microwave tower (Na-Ah-Tee 2), elev 2065 m

35.471 110.188 Damon and Spencer (written 

commun, 2000)

Monc

UAKA 76-20 7 ±0.24 Hopi Buttes diatreme Hopi buttes; diatreme centered 

in S20, 6 mi SW of White Cone Trading Post

35.549 110.156 Damon and Spencer (written 

commun, 2000)

Moncritic obetwerocks

6.99 ±0.75 Lava groundmass Hopi Buttes; Haskie maar Vasquez, 1998

UAKA 73-133 6.86 ±0.16 Bidahochi Fm basalt Hopi Buttes; S end of Roberts 

Mesa

35.629 110.099 Reynolds and others, 1986 Basal

Bidah

6.81 ±0.06 Amphibole megacryst Hopi Buttes; Churro maar Vasquez, 1998

UAKA 74-134 6.81 ±0.4 Petrified Forest maar Petrified Forest 35.076 109.802 Damon and others, 1996 Proba

moncmaar 

1 Note that this reference (Dallegge and others, 1998) from original volume (Priest, 2001) has become “Dallegge and others, 1998a” in this report.
25

Table 1. Geochronologic data from Hopi Buttes Volcanic Field, Little Colorado River area; reprinted “as is” from Priest (2001) with permission from publis

Grand Canyon, Arizona) (written commun., August 19, 2009).—Continued

Sample

number

Age

(Ma)

Reliability

(ka)

Sample locality

and type

General Locality Latitude Longitude Reference 

UAKA 73-133 6.86 ±0.16 trachybasalt Hopi Buttes; 3.5 km NW of 

White Cone Trading Post

Reynolds and others, 1986

UAKA 74-145 6.62 ±0.14 Bobcat Butte diatreme Hopi Buttes; Bobcat Butte 35.472 110.404 Damon and Spencer (written 

comun, 2000)

Basalinclud

UAKA 76-8 6.6 ±0.15 Flat Mesa basalt Hopi Buttes; lava flow capping 

Flat Mesa ~1 m above base of flow, elev 1951 m

35.463 110.245 Damon and Spencer (written 

comun, 2000)

Moncgraine

UAKA 76-7 6.56 ±0.17 Gray Mesa basalt Hopi Buttes; near margin of 

flow capping Tesihim Butte, 1 m above base, elev 1914 m

35.475 110.113 Damon and Spencer (written 

comun, 2000)

MoncBasal bedde

UAKA 76-9 6.55 ±0.14 Tesihim Butte basalt Hopi Buttes; near margin of 

flow capping Tesihim Butte, 1 m above base, elev 1914

35.543 110.099 Damon and Spencer (written 

comun, 2000)

Moncritic.

6.53 ±0.59 Lava groundmass Hopi Buttes; Haskie maar Vasquez, 1998

UAKA 85-88 6.26 ±0.29 Woodruff Butte basalt Holbrook area; monchiquite 

basalt on top of Woodruff Butte

34.799 110.041 Damon and others, 1996

UAKA 76-6 5.98 ±0.13 Deshgish Butte basalt Hopi Buttes; top of Deshgish 

Butte, elev ~1946 m

35.52 110.068 Damon and Spencer (written 

comun, 2000)

Dense sure rcaps t

HB1 5.7 ±1.10 Hopi Buttes diatreme Hopi Buttes; Hoskietsko Butte 35.378 110.058 Reynolds and others, 1986 Gabb

tremetreme 

UAKA 74-133a 4.41 ±0.18 White Cone basalt Hopi Buttes; near top of first 

diatreme N of White Cone Peak, N edge, elev 2022 m

35.596 110.042 Damon and Spencer (written 

comun, 2000)

Basal

UAKA 74-147a 4.23 ±0.59 Hokietsko Butte basalt Hopi Buttes; dike at NW edge 

of Hokietsko Butte at elev 1743 m

35.377 110.059 Damon and Spencer (written 

comun, 2000)

Basalthis b

KA-1027 4.2 Bidahochi Fm trachybasalt Hopi Buttes; White Cone Peak 35.579 110.056 Reynolds and others, 1986 Trach

memb

HB2 2.17 ±0.20 Hopi buttes diatreme Hopi Buttes; Coliseum diatreme 35.383 110.137 Reynolds and others, 1986 Grano

averabefore 

UAKA 72-62 0.529 ±0.079 Tappan Springs basalt San Francisco Volcanic Field 35.887 111.455 Reynolds and others, 1986 Flow 

NE trpies c