Prepared in cooperation with the Navajo Nation Minerals Department

Geologic Map of the Eastern Quarter of the Flagstaff 30′

x 60′ Quadrangle, Coconino County, Northern Arizona

Pamphlet to accompany

Scientific Investigations Map 3279

2013

U.S. Department of the Interior

U.S Geological Survey
ii

CONTENTS

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

Previous Work...................................................................................................................................................................................2

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

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

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

Mesozoic Rocks................................................................................................................................................................................4

Moenkopi Formation .....................................................................................................................................................................4

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

Cenozoic Rocks................................................................................................................................................................................6

San Francisco Volcanic Field .......................................................................................................................................................6

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

Structural Geology ............................................................................................................................................................................8

Acknowledgments.............................................................................................................................................................................9

Description Of Map Units................................................................................................................................................................10

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

Volcanic Rocks ...........................................................................................................................................................................17

Sedimentary Rocks.....................................................................................................................................................................19

References Cited ............................................................................................................................................................................22
Geologic Map of the Eastern Quarter of the Flagstaff 30′

x 60′ Quadrangle, Coconino County, Northern Arizona

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

Introduction

This geologic map is the product of a cooperative effort between the U.S. Geological Survey

(USGS) and the Navajo Nation. It provides geologic information for resource management officials 

of the U.S. Forest Service, the Arizona Game and Fish Department, and the Navajo Nation

Reservation (herein the Navajo Nation). Funding for the map was provided by the USGS geologic 

mapping program, Reston, Virginia. Field work on the Navajo Nation was conducted under a 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 eastern quarter of the Flagstaff 30′ x 60′ quadrangle includes eight USGS 1:24,000-scale 

quadrangles in Coconino County, northern Arizona (fig. 1, map sheet): Anderson Canyon, Babbitt 

Wash, Canyon Diablo, Grand Falls, Grand Falls SE, Grand Falls SW, Grand Falls NE, and Meteor 

Crater. The map is bounded by lat 35° to 35°30′ N. and long 111° to 111°15′ W. and is on the 

southern part of the Colorado Plateaus geologic province (herein Colorado Plateau). Elevations range 

from 4,320 ft (1,317 m) at the Little Colorado River in the northwest corner of the map area to about 

6,832 ft (2,082 m) at the southwest corner of the map.

 Interstate 40 (I-40) provides access across the south-central part of the mapped area where

north and south access roads lead from I-40 at the Buffalo Ranch Road Exit 225, Two Guns Exit 230, 

and Meteor Crater Road Exit 233 (formerly Rimmy Jim’s Exit) that provides access south to Meteor 

Crater (fig. 2, map sheet) by a 6-mi-long (9.5-km-long) paved road (fig. 1, map sheet). Navajo Route 

15 is a paved road in the northern part of the map area that provides limited access to the Navajo 

Nation, including a 9-mi-long (14.5-km-long) dirt road that leads north toward Grand Falls at the 

Little Colorado River (fig. 3, map sheet). The Little Colorado River crossing upstream of Grand Falls 

is not bridged and is impassable when the river is flowing.

Leupp, Arizona (originally Sunrise, Arizona), is the only community within the eastern 

quarter of the Flagstaff quadrangle (east-central edge). Larger communities, such as Winslow, 

Arizona, is 26 mi (41.5 km) east of the map on I-40, and Flagstaff, Arizona, is 27 mi (37 km) west of

the map on I-40.

There are two prominent natural landmarks within the map: Meteor Crater (fig. 2, map sheet), 

a 600-ft-deep (183-m-deep) meteorite impact crater near the southeast corner of the map (Shoemaker 

and Kieffer, 1974; Kargel, 1998), and Grand Falls (fig. 3, map sheet), a 200-ft-high (60-m-high)

waterfall (commonly dry) on the Little Colorado River in the northwest part of the map. Land 

management within the southern third of the map is a checkerboard square-mile pattern of private and 
2

State land; most of the private land belongs to the Hopi Tribe. The Buffalo Ranch is 1 mi south of the 

south-central edge of the map and is managed by the Arizona Game and Fish Department. Land in 

the northern two-thirds of the map is part of the Leupp Chapter of the Navajo Nation (fig. 1, map 

sheet). Coconino National Forest manages lands west, south, and southwest of the map margins.

This geologic map provides an updated geologic framework for the eastern quarter of the 

Flagstaff 30′ x 60′ quadrangle and is adjacent to two other recent geologic maps, the Cameron and 

Winslow 30′ x 60′ quadrangles (Billingsley and others, 2007, 2013).

Previous Work

An early reconnaissance photogeologic map (1:500,000 scale) of this area was compiled by 

Wilson and others (1969) as part of a geologic map of the State of Arizona. The state map was later 

recompiled at 1:1,000,000 scale by Richard and others (2000). An excellent photogeologic map of the 

Navajo Nation area was produced by Cooley and others (1969), but this product was not registered to 

a topographic base. Other maps that encompass the eastern quarter of the Flagstaff quadrangle 

include a regional geologic map of the Flagstaff 1° x 2° quadrangle by Ulrich and others (1984) and a 

geologic map of the eastern San Francisco Volcanic Field by Moore and Wolfe (1976, 1987). A 

geologic map of the Cameron 30′ x 60′ quadrangle (Billingsley and others, 2007) adjoins the northern 

edge of this map; a geologic map of the Winslow 30′ x 60′ quadrangle (Billingsley and others, 2013) 

adjoins the eastern edge; and a geologic map of the Sedona 30′ x 60′ quadrangle (Weir and others, 

1989) adjoins the southern edge. A geologic map of Meteor Crater was prepared by Shoemaker and 

Kieffer (1974) and the reader is referred to this publication for details of the geology in Meteor 

Crater. The surficial geologic map units of this map have been modified and updated to match 

surficial data of the adjacent Cameron and Winslow 30′ x 60′ quadrangles.

Mapping Methods

The geology was mapped using color 1:40,000-scale aerial photographs flown in 2005,

followed by extensive field checking. Many of the Quaternary alluvial and eolian deposits have 

similar lithology and geomorphic characteristics and were mapped almost entirely by photogeologic 

methods. Lithology, stratigraphic position, and the amount of erosional degradation were used to 

determine relative age correlations of alluvial deposits. Geologic map units and structural features 

were field checked to ensure accuracy of location and description. Debra Block (U.S. Geological 

Survey) used ArcGIS to compile the digital database.

Geologic Setting

The map area is characterized by nearly flat lying to gently northeast dipping Paleozoic and 

Mesozoic rock strata that are partly covered by younger volcanic rocks along the western margin of 

the map area and by alluvium and eolian surficial deposits elsewhere, especially northeast of the 

Little Colorado River. The Pliocene and Pleistocene volcanic rocks of the San Francisco Volcanic 

Field form a protective caprock cover over soft Triassic strata of the Moenkopi Formation in the 

northwest quarter of the map. Remnants of a Miocene basalt flow forms a caprock over Triassic strata 

of the Chinle and Moenkopi Formations in the southwest corner of the map.

The Triassic strata in the Little Colorado River valley are mostly covered by Pleistocene and 

Holocene fluvial sand and gravel and eolian dune and sand-sheet deposits. The eolian deposits are 

commonly derived from the abundant fluvial sand along the Little Colorado River and tributaries that 

is transported northeasterly by seasonal southwesterly winds.
3

The Little Colorado River was likely established as a tributary to the Colorado River in Grand 

Canyon about 6 million years ago (Ranney, 2005). The Little Colorado River in the northern part of 

the map lies within a strike valley that parallels the retreating gently northeast dipping Triassic strata 

of the Moenkopi and Chinle Formations. In some places, the river has eroded into the underlying 

resistant Permian strata of the Kaibab Formation. After the river or its tributaries encounter the

Kaibab Formation, they become entrenched and trapped as canyon drainages into the Kaibab 

Formation. The Little Colorado River has eroded into the Kaibab Formation in the northwest quarter 

of the map and across the north-plunging Tolchico Anticline about 2 mi (3 km) upstream of Grand 

Falls. Several tributary drainages south and southwest of the Little Colorado River that meandered 

around on softer Triassic strata have been superimposed into the Kaibab Formation that preserved the 

meander patterns as small narrow meandering canyons (Padre Canyon, Anderson Canyon, Canyon 

Diablo, and others [fig. 1, map sheet]).

The Tertiary and Quaternary volcanic rocks of the San Francisco Volcanic Field are Miocene, 

Pliocene, and mostly Pleistocene age (Moore and others, 1974; Moore and Wolfe, 1976, 1987). The 

volcanic rocks range in composition from olivine-phyric basalt to calc-alkaline andesite and their

relative age relations are based on magnetic polarity, isotopic composition, field relations, and a few 

K-Ar ages by Paul E. Damon and Edwin H. McKee (Ulrich and Bailey, 1987; Duffield and others,

2006; Damon and others, 1974). Basalt lava that reached the Little Colorado River and created Grand 

Falls is about 20 ka (19.6±1.2 ka; Duffield and others, 2006).

Paleozoic Rocks

Neogene erosion of the highlands in the southwest two-thirds of the map area has exposed 

150 to 250 ft (46 to 76 m) of the Kaibab Formation in Padre Canyon, Canyon Diablo, and Anderson 

Canyon. The Permian rocks are, in ascending order, the Toroweap Formation (includes the upper part 

of the Coconino Sandstone) and the Kaibab Formation. Limited exposures of the upper Coconino 

Sandstone are exposed in the walls of Meteor Crater (Shoemaker and Kieffer, 1974) and are included 

as part of the Toroweap Formation for this map. The Kaibab Formation and the upper part of the 

Toroweap Formation are exposed in the canyon of the Little Colorado River below Grand Falls

(northwest corner of map) and in the walls of Meteor Crater. The Coconino Sandstone is not mapped 

herein because of the highly disrupted nature of the exposures in Meteor Crater and is included as 

part of the Toroweap Formation (for map details of Meteor Crater, see Shoemaker and Kieffer, 

1974). The Kaibab Formation forms the surface bedrock for most of the southwestern two-thirds of 

the map except where covered by volcanic rocks, the Moenkopi Formation, or eolian and fluvial 

surficial deposits.

Beneath the Toroweap Formation, the Coconino Sandstone forms a white or yellowish-white 

crossbedded sandstone southeast of Winslow, Arizona, and is about 600 ft (183 m) thick in the 

subsurface of the map on the basis of well data (Bills and others, 2005). Subsurface well logs suggest 

that the basal part of the Coconino Sandstone is a fine-grained red sandstone that is likely the 

northern extent of the Permian Schnebly Hill Formation of the Verde Valley as defined by Blakey 

(1990) or the red De Chelly Sandstone exposed in the Defiance Plateau northeast of this map,

because this map area lies approximately midway between the Defiance Plateau and the Verde River 

Valley (Blakey, 1996; Stanesco, 1991; Cooley and others, 1969).

The Coconino Sandstone and the basal Schnebly Hill Formation (or De Chelly Sandstone)

form the local groundwater aquifer of this area known as the “C aquifer." The Coconino Sandstone 

gradually thins north, east, and west in the subsurface of the map and thickens to the south. The 

Schnebly Hill Formation thins north and west and gradually thickens south and southwest of the map 
4

and likely intertongues with the De Chelly Sandstone northeast of the map area (Blakey, 1996; 

Stanesco, 1991).

The upper part of the Toroweap Formation is exposed in the canyon of the Little Colorado 

River downstream of Grand Falls and forms a gray-brown cliff of calcareous sandstone. Similar but 

poor exposures of the Toroweap Formation are exposed in the walls of Meteor Crater. On the basis of

local well-log records near Leupp, Arizona, (Bills and others, 2005) and exposures at the Little 

Colorado and Meteor Crater, the Toroweap Formation is about 30 to 50 ft (9 to 15 m) thick and thins 

eastward and thickens westward in the subsurface.

 The Kaibab Formation is divided into the Harrisburg Member (upper part) and the Fossil 

Mountain Member (lower part) as defined by Sorauf and Billingsley (1991). The gradational 

boundary between the lower gray, cliff-forming, cherty, sandy limestone of the Fossil Mountain 

Member and the upper gray and reddish-yellow sandy limestone of the Harrisburg Member is 

difficult to distinguish in most places; therefore, these Kaibab members are collectively mapped as 

the Kaibab Formation.

Mesozoic Rocks

The erosion of the Little Colorado River and its tributaries exposed about 280 ft (85 m) of 

Triassic strata in the northeast third of the map. The Triassic rocks are, in ascending order, the 

Moenkopi Formation and the Chinle Formation.

A regional unconformity separates the Permian Kaibab Formation from the overlying Triassic 

Moenkopi Formation with an erosional relief typically less than 10 ft (3 m) across the north-central 

portion of the map. The unconformity is easily recognized by a color contrast between the gray-white 

Kaibab Formation and the red Moenkopi Formation. Shallow erosional depressions and channels 

eroded into the upper Kaibab Formation are filled with sandy detrital sediment that contains angular 

and subangular fragments of chert that are locally derived from the Kaibab Formation and form the 

basal part of the Moenkopi Formation in most areas.

Moenkopi Formation

Overlying the Kaibab Formation is a sequence of light-red sandstone ledges and dark-red 

siltstone slopes of the Moenkopi Formation. The Moenkopi Formation is preserved as isolated 

outcrops beneath Quaternary volcanic rocks along the northwest margins of the map and is 

extensively exposed diagonally across the northeastern part of the map area. The Moenkopi 

Formation, as much as 220 ft (67 m), once covered the entire area (McKee, 1954). An unknown 

amount of the upper Moenkopi Formation was removed by Triassic erosion prior to deposition of the 

overlying Chinle Formation.

The Moenkopi Formation is subdivided into three map units as defined by McKee (1954). In 

ascending order, they are the Wupatki Member, the lower massive sandstone member, and the

undivided Moqui and Holbrook Sandstone Members.

The dark-red Wupatki Member of the Moenkopi Formation unconformably overlies the 

Kaibab Formation and thins diagonally southeastward from 75 ft (23 m) to 15 ft (4.5 m) thick and is 

locally absent in the southwest quarter of the map. The Wupatki Member gradually pinches out 8 mi 

(13 km) east of the map where the lower massive sandstone member of the Moenkopi Formation 

unconformably overlies the Kaibab Formation. A lithologic and gradational contact separates the 

slope-forming Wupatki Member from the overlying cliff-forming lower massive sandstone member 

in most areas.
5

The light-red, cliff-forming, lower massive sandstone member generally thins diagonally from 

northwest to southeast from about 40 ft (12 m) to less then 10 ft (3 m) thick. The lower massive 

sandstone member changes facies northwest of the map and correlates with the Shnabkaib Member of 

the Moenkopi Formation in northwestern Arizona (Billingsley and others, 2007).

The slope-forming Moqui Member is defined by McKee (1954) from exposures along Moqui 

Draw (Tucker Flat Wash today) 8 mi (13 km) west of Winslow near the eastern edge of the map and 

is 85 ft (26 m) thick and a lighter shade of reddish-brown then the underlying Wupatki or overlying 

Holbrook Member. The sandstone beds of the Holbrook Member of the Moenkopi Formation were 

originally defined by Hager (1922) and form an irregular line of bluffs along the Little Colorado 

River between Holbrook and Cameron, Arizona. The Holbrook and Moqui Members are mapped 

together as an undivided unit, because intertonguing and facies changes in some areas of the map 

make them difficult to separate. In general, the Moqui Member forms a uniform, mostly covered 

slope below the cliff-forming Holbrook Member. The sandstone beds of the Holbrook Member 

unconformably overlie the Moqui Member and commonly form interconnected, inverted riverchannel-ridge topography across the northeastern part of the map from Leupp to Winslow, Arizona.

The Moqui and Holbrook Members are unconformably overlain by the Chinle Formation.

A regional uplift terminated the deposition of the marine tidal flats and river floodplain

deposits that formed the Moenkopi Formation as that environment retreated northwestward into Utah,

followed by a development of a new northwest-flowing drainage system (Blakey and Ranney, 2008).

Drainages that eroded into the Moenkopi Formation averaged about 30 ft (10 m) deep and locally as 

much as 150 ft (46 m) deep. This unconformity is known as the Tr-3 unconformity (Blakey, 1994).

The eroded stream valleys began accumulating mud, sand, and gravel that formed the overlying basal

deposits of the Shinarump Member of the Chinle Formation.

Chinle Formation

The Chinle Formation is subdivided into three mappable units along the Little Colorado River 

valley in the northeast quarter of the map. In ascending order they are the Shinarump Member, the 

Petrified Forest Member, and the Owl Rock Member as defined by Repenning and others (1969).

The Shinarump Member includes an upper sandstone and siltstone member defined by 

Repenning and others (1969) in the Cameron area northwest of the map. It is predominantly a 

lenticular maze of thin to thick, interbedded, stream-channel and flood-plain deposits of light-brown, 

purple, gray, and red siltstone and sandstone that forms a transitional unit between the Shinarump 

Member and the overlying Petrified Forest Member of the Chinle Formation. Locally, this sandstone 

and siltstone member forms a minor and discontinuous, thin, upper part of the Shinarump Member 

and is herein mapped as the Shinarump Member.

The conglomeratic sandstone beds of the Shinarump Member contain numerous petrified log 

and wood fragments. Its thickness is variable owing to widespread channel erosion into the 

underlying Moenkopi Formation and is absent on local highland areas between channel valleys. The 

Shinarump Member is generally about 30 to 60 ft (9 to 18 m) thick along the Little Colorado River

area northeast of Grand Falls. The contact between the Shinarump Member and the overlying 

Petrified Forest Member is gradational and highly variable, which reflects a lithologic and thickness 

change from ledges and slopes of brown and purple sandstone of the Shinarump Member to slopeforming, multicolored mudstone and siltstone of the Petrified Forest Member.

The Petrified Forest Member of the Chinle Formation forms the multicolored blue, red, and 

gray-green soft hills of the Painted Desert badlands along and northeast of the Little Colorado River.

The Petrified Forest Member generally maintains a thickness between 400 and 500 ft (122 and 153 

m) and was likely that thick in the southwestern half of the map before being removed by Cenozoic 
6

erosion. Much of the Shinarump Member and Petrified Forest Member are covered by fluvial 

deposits of the Little Colorado River floodplain, and sand from these fluvial deposits is transported 

northeastward by southwesterly winds that blanket most of the Petrified Forest and Shinarump 

Members. The Owl Rock Member of the Chinle Formation gradationally overlies the Petrified Forest 

Member and consists of about 270 ft (82 m) of gray, interbedded, ledge-forming, siliceous limestone 

and light-red calcareous siltstone that form the highland outcrops in the northeast corner of the map.

Cenozoic Rocks

San Francisco Volcanic Field

The oldest volcanic rocks of the San Francisco Volcanic Field within the map area are 

remnants of a Miocene basalt flow (Tb), on top of an unnamed butte in the southwest corner of the 

map, that came from Anderson Mesa about 4 mi (6.5 km) southwest of the map. This basalt flowed 

northeast down a stream channel eroded into the Shinarump Member of the Chinle Formation about 6 

Ma (Damon and others, 1974) and now forms a protective caprock on soft Triassic sediments, 

creating an inverted drainage topography.

The Pleistocene basalt flows in the northwest quarter of the map came from several volcanoes 

west of the map that erupted about 800,000 to 19,000 years ago (K-Ar age, 0.786±0.14 Ma, 

0.84±0.13 Ma, and 0.87±0.14 Ma; Damon and others, 1974). The age of the youngest basalt flow that 

helped form Grand Falls is 19.6±1.2 ka as determined by four techniques: optical-luminescence, He 

surface exposure, 40Ar/39Ar, and a Magnetic secular-variation match (Esser, 2003; Duffield and 

others, 2006).

The older basalt flows of Woodhouse age (about 0.8 to 3.0 Ma; Damon and others, 1974) as 

described by Ulrich and Bailey (1987) and Moore and Wolfe (1976) flowed northeast toward the 

Little Colorado River but stopped about 2 mi (3 km) south of today’s river and formed a basalt 

caprock over strata of the Moenkopi Formation. These older basalt flows (Qbw) are collectively and 

informally called the basalt flows of Woodhouse Mesa (Wolfe and others, 1987). Woodhouse Mesa 

is located in Wupatki National Monument a few miles northwest of the map area. Younger volcanic 

eruptions just west of the map are the source of various basalt flows (Qbm1, Qbm2, Qbm, Qbr, 

Qb) shown on the northwest part of the map.

 Pleistocene volcanic eruptions to the west built up prominent pyroclastic cones and produced 

several associated basalt flows that traveled northeastward down drainages towards the Little 

Colorado River. The basalt flows filled and blocked some drainages, allowing ponded sediments to 

accumulate behind the basalt dams and also deflect the local streams around the flow margins and

into nearby lowland areas or other drainages. Two or more basalt flows reached the Little Colorado 

River at Grand Falls and one or more flows reached a now-abandoned reach of the Little Colorado 

River about 7 mi (11 km) upstream of Grand Falls on the east side of Tolchico Anticline.

The basalt flows that reached the Colorado River at Grand Falls flowed into and filled a 215-

ft-deep (65-m-deep) canyon of the Little Colorado River as it spread out northeastward from the 

canyon for a short distance, effectively forming a basalt dam of the river. This basalt also flowed

down the river for approximately 21 mi (33.5 km) and about 10 mi (16 km) upstream of the basalt 

dam (Hanson and others, 2008). Upstream of the basalt dam, the Little Colorado River drainage filled 

with sediment that allowed the river to flow north around the basalt flow and over the north rim of the 

canyon forming today’s 200-ft-high (60-m-high) Grand Falls (fig. 3, map sheet). This basalt flow

likely came from a crater called "The Sproul" on the west side of Merriam Crater about 8 mi (13 km) 
7

southwest of Grand Falls (Hanson, 2009) and is mapped as The Sproul basalt flow of Merriam Crater 

(Qbm1).

A similar age basalt flow came from two vents on the east side of Merriam Crater that appears 

to have erupted simultaneously and is mapped as the east vent basalt flow of Merriam Crater 

(Qbm2). This flow traveled northeast toward the Little Colorado and appears to have stopped about a 

mile south of Grand Falls. Prior to The Sproul and east vent flows, a basalt flow from Merriam Crater 

(Qbm) flowed northeast toward the Little Colorado River and may have reached the river first, but 

younger subsequent flows from The Sproul and east vent of the Merriam Crater system appears to 

have overflowed the Merriam Crater flow (Qbm) at Grand Falls.

Approximately 7 mi (11 km) upstream of Grand Falls, the Little Colorado River was 

superimposed across the north-plunging Tolchico Anticline and eroded a 240-ft-deep (74-m-deep) 

canyon into the Kaibab Formation, herein referred to as “Tolchico canyon” for location purposes (fig. 

4, map sheet). One or two basalt flows reached the Little Colorado River at the northeast flank of 

Tolchico Anticline and formed a basalt dam across the river. This basalt flow (Qb) came down a 

tributary drainage from the vicinity of South Sheba Crater or Merrill Crater, just west of the map 

edge. These young flows have an extensive and thicker eolian cinder cover than the basalt flows at 

Grand Falls, suggesting a possible older age for the basalt flow and dam at Tolchico Canyon. The 

40Ar/39Ar age of this flow and dam is 175 Ka (Esser, 2003; Hanson and others, 2008).

The basalt dam of the Little Colorado River at Tolchico canyon produced a large shallow lake 

and floodplain upstream of the dam that deposited fine-grained silt and sand into and along the Little 

Colorado River where it parallels a northwest-oriented strike valley eroded into soft sediments of the 

Chinle Formation. Eventually, the Little Colorado River filled the lake, overflowed the north end of 

Tolchico Anticline, and flowed back to the original canyon about 2 mi (3 km) downstream of the 

basalt dam, subsequently eroding a more recent canyon through the Moenkopi and upper Kaibab 

Formations. Based on older and higher river-gravel deposits preserved above the Little Colorado 

River valley upstream and downstream of Grand Falls and Tolchico canyon, the basalt dam at 

Tolchico canyon is Pleistocene age.

The prevailing southwesterly winds during and since the pyroclastic eruptions southwest and 

west of the map have distributed thin to thick black cinder deposits over much of the bedrock surface 

within the northern map area. Only the thickest or most widespread deposits are shown as eolian

cinder sand-sheet (Qsc), unconsolidated cinder-dune (Qdc1), consolidated cinder-dune (Qdc2), or 

mixed alluvium and eolian (Qae) deposits.

Black cinder deposits accumulated as falling dune deposits within a sharp meander bend of 

Padre Canyon (fig. 5, map sheet) that formed a cinder dune dam across the canyon about 2 mi (3 km) 

upstream of its junction with Canyon Diablo (west-central part of map; fig. 5, map sheet). The small 

lake that developed in Padre Canyon behind the cinder dune dam allowed ponded water to seep 

through open fractures in the Kaibab Formation through a narrow neck of the meander loop just 

upstream of the cinder dam. The open cracks and fractures quickly eroded a narrow slot canyon 

through the meander-loop neck. The cinder-dune-clogged meander loop was abandoned in favor of 

the narrow open-slot canyon. The cinder dune (Qdc2) accumulated to 180 ft (55 m) thick in the 260-

ft-deep (80-m-deep) canyon where it is preserved today as a consolidated cinder dune.

Black eolian cinder deposits also filled the abandoned 2-mi (3-km) section of Tolchico 

canyon of the Little Colorado River downstream of the basalt dam (fig. 4, map sheet). The black 

eolian cinders were accumulated by southwesterly winds and transported over the south rim of the 

canyon to form deposits as much as 200 ft (60 m) thick in Tolchico canyon. These black consolidated 

cinder dunes (Qdc2) are well preserved in Tolchico canyon and in Padre Canyon (figs. 4, 5, map 

sheet).
8

Surficial Deposits

A variety of fluvial stream and alluvial fan deposits of various ages and configurations are 

scattered throughout the map area. The Little Colorado River is the principal stream in the map and 

extensive ponded and flood-plain deposits have accumulated within its valley. The Little Colorado 

River channel and its flood plains have undergone extensive geomorphic reconfiguration as 

demonstrated by historic photographic records just upstream of this map in a report by Block and 

Redsteer (2011).

Terrace deposits of the older Little Colorado River are present at four stratigraphic levels 

above three younger floodplain deposits on both sides of the river in the northern quarter of the map. 

These river terraces (Qg4, Qg5, Qg6, Qg7) provide a glimpse into the Pleistocene development of 

the Little Colorado River and its valley. All older terrace deposits fill flat channel floors of the Little 

Colorado River, perhaps because of the overwhelming sediment load of the river. Both the channel 

floors and adjacent valley appear to have filled with thick river sediment, causing the river to 

meander broadly within its valley; subsequent erosion lowered the river to a new position, 

establishing a new river channel in bedrock, which then filled again with sediment. This cut-and-fill 

process appears to have repeated itself at least four times, possibly reflecting Pleistocene climate 

changes.

The alluvial deposits associated with the Little Colorado River and nearby tributaries provide 

an abundant supply of silt and sand that is subject to transportation by southwesterly winds that 

develop extensive eolian sand-sheet and dune (Qd, Qes, Qdl, Qdb) deposits northeast of the Little 

Colorado River. The eolian deposits are intermittently eroded by local fluvial erosion and sand and 

silt is transported back to the Little Colorado River where the eolian transport process repeats itself 

(Billingsley, 1987). Eventually, the sand is transported down the Little Colorado River to the 

Colorado River and through Grand Canyon. Eolian and fluvial activity commonly interact to form 

deposits from both processes, mixed alluvium and eolian (Qae) deposits, throughout the map area. 

Black volcanic cinders transported by southwesterly winds form extensive eolian cinder sand-sheets 

(Qsc) and local eolian cinder-dune (Qdc1, Qdc2) deposits.

Other surficial units include landslide (Ql) and talus and rockfall (Qtr) deposits in canyons of 

the Little Colorado River and tributary canyon drainages and extensively in the vicinity of the 

unnamed butte in the southwest corner of the map. Meteor Crater impact debris is generally localized 

to the vicinity of Meteor Crater. Several grabens and sinkholes have accumulated ponded sediments 

(Qps) as small intermittent lake deposits. These small lakes were likely an important intermittent 

water source for the prehistoric and historic inhabitants of the area. Manmade diversion dams, stock 

tanks, gravel pits, and quarries (Qaf) are mapped to illustrate the human impacts on the landscape.

Not all road and pipeline construction excavations or deposits are shown.

Structural Geology

Paleozoic and Mesozoic strata within the map area have an average regional dip of about 1°

NE., except in the northeastern quarter of the map where strata dips as much as 4° NE.. The 

landscape is gently folded by low-amplitude, alternating, northeast-plunging anticlines and synclines 

that are oriented north to south across the east-central part of the map. West of the gentle northeastplunging series of anticlines and synclines is a north-south-oriented, north-plunging anticline called 

Tolchico Anticline (Ulrich and others, 1984), which is the principal fold within the map area (fig. 1, 

map sheet). An unnamed northeast-dipping monocline is present in the southwest corner of the map 

with strata that dip between 4° and 7° NE.
9

Compressional folding of Paleozoic and Mesozoic rocks began in Late Cretaceous and early 

Tertiary time (about 65 Ma). The Laramide erosional period began removing Mesozoic strata that 

once covered the entire map area (Huntoon, 2003). Today’s landscape took shape during late Tertiary 

and Pleistocene time when the Little Colorado River drainage system developed. The Little Colorado 

River and its tributaries became firmly established and integrated with the Colorado River in the 

Grand Canyon about 5 to 6 Ma sometime during the late Miocene or early Pliocene (Lucchitta, 1990; 

Ranney, 2005).

The northeast dipping monocline in the southwest corner of the map likely overlies a deepseated reverse fault that displaced strata up-to-the-west during Late Cretaceous and early Tertiary 

time (Huntoon, 2003). During the Pliocene and Pleistocene time, northeast-southwest extension has

reactivated the deep-seated fault, and some of the normal fault separations have reversed some of the 

Cretaceous and early Tertiary fold offset, as well as accentuating the dip of the monocline by reverse 

drag along the faults. Late Cenozoic extensional faulting produced many northwest-trending grabens 

beginning in late Pliocene time (less than 2.59 Ma) on the basis of similar extensional faulting 

evidence along the Hurricane and Toroweap Faults in the Grand Canyon region northwest of the map 

area (Billingsley and Workman, 2000; Billingsley and Wellmeyer, 2003; Billingsley and others, 

2007).

The grabens and faults in the map area appear to be active on the basis of small separations of 

Pleistocene and Holocene alluvial deposits along faults and associated large open bedrock fissures 

(fig. 6, map sheet). A few sinkholes or open cracks that have developed along the fractures and joints 

associated with grabens and runoff in several minor drainages has been interrupted by recent bedrock 

open-crack fissures and sinkhole development along fractures. A small sinkhole has recently 

developed along a fracture fault in Big Anderson Tank, southwest quarter of map that now drains the 

reservoir of water.

The open bedrock fissures that align along regional joints and fractures may reflect a more 

recent tensional stress of the landscape (fig. 6, map sheet). Bedrock crack fissures as much as 500 ft 

(152 m) deep have been explored northwest of the map at Wupatki National Monument (Peter 

Huntoon, oral commun., 2005). The northeasterly folds and associated joint and fractures and 

northwesterly joint and fracture sets have controlled the shape of Meteor Crater, which is somewhat 

square in outline (fig. 2, map sheet); the diagonals of this squarish area coincide with the trend of the 

two main sets of joints (Shoemaker and Kieffer, 1974).

Acknowledgments

The cooperation and support of the Navajo Nation Minerals Department and the Leupp 

Chapter of the Navajo Nation were very helpful in permitting the mapping of this part of the Navajo 

lands. We also appreciate advice, revisions, and suggestions from Wendell Duffield of Northern 

Arizona University, Flagstaff, Arizona; Lee Amoroso of the U.S, Geological Survey, Flagstaff, 

Arizona; and Charles L. Powell, II, and Jan Zigler of the U.S. Geological Survey, Menlo Park, 

California.
10

DESCRIPTION OF MAP UNITS

SURFICIAL DEPOSITS

Surficial deposits are differentiated from one another chiefly on the basis of differences in 

morphologic character and physiographic position as observed on color 1:24,000-scale aerial 

photographs flown in 2005 and from field observations. Older alluvial and eolian deposits generally 

exhibit extensive erosion and have greater topographic relief, whereas younger deposits are either 

actively accumulating material or are moderately eroded. All surficial deposits have an approximate 

map contact (not dashed) with adjacent surficial deposits and bedrock outcrops.

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

excavated from borrow-pits and trenches to build livestock tanks, drainage 

diversion dams, roads, pipelines, and other man-made construction 

projects. Not all pipeline and highway/road excavations and landfills are 

mapped

Qs Stream-channel deposits (Holocene)—White to light-red and gray, poorly sorted 

interbedded silt, clay, sand, gravel, pebbles, cobbles, and small boulders. 

Most of the gravel, cobbles, and boulders are subrounded to round. Deposit 

intertongues with, overlaps, or is inset against other adjacent fluvial 

surficial deposits (Qa1, Qa2, Qv, Qg1, Qg2, Qf, Qf1, Qf2, Qf3, Qps, 

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 and desert shrubs along 

channel margins of Little Colorado River and larger tributaries such as 

Padre Canyon, Canyon Diablo, and Anderson Canyon. Unit often 

intertongues with other alluvial or eolian deposits, and contacts are 

gradational and approximate in the lateral and vertical sense. Streamchannel of Little Colorado River is mapped as shown on color 1:24,000-

scale aerial photographs flown in 2005. The river channel is subject to 

yearly change caused by flood events (Block and Redsteer, 2011). 

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

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

sand, and some lenticular coarse gravel; partly consolidated by clay, 

gypsum, and calcite cement. Intertongue with or overlap other alluvial 

deposits (Qs, Qv, Qg1, Qa1). Inset into numerous fluvial or eolian 

surficial deposits along Little Colorado River and main tributary drainages. 

Similar to and often adjacent to valley-fill (Qv) deposits in shallow 

drainage valleys on plateau surface in southwestern half of map where 

broad, flat valleys are subject to widespread and frequent flooding. Support 

thick growth of sagebrush, grass, and small high-desert shrubs that help 

trap and accumulate fine-grained sediment on floodplains. Subject to 

temporary ponding and often mixed with ponded sediments (Qps) in small 

graben valleys. Thickness, 3 to 30 ft (1 to 9 m)

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

includes lenses of intertonguing gravel composed locally of small isolated 

fragments or pebbles of chert, limestone, and sandstone; partly 
11

consolidated by clay, calcite, and (or) gypsum cement. Often adjacent to or 

on flood-plain (Qf, Qf1, Qf2, Qf3) deposits along Little Colorado River. 

Occupies manmade internal drainage depressions or natural depressions 

formed within extensive dune-sand or sand-sheet (Qd) areas. Desiccation 

cracks often develop in dry conditions on hardpan surfaces and clay 

content often restricts plant growth. Thickness, 5 to 40 ft (1.5 to 12 m)

Qd Dune-sand and sand-sheet deposits (Holocene)—White to gray to light-red, 

fine- to coarse-grained sand composed mainly of quartz, chert, minor 

feldspar grains and minor amounts of basaltic cinder fragments. Form

small complex parabolic dunes, barchan dunes, and dome dunes mixed 

within extensive sand sheet deposits. Primary deposits are northeast of 

Little Colorado River and locally within tributary drainages northeast of 

Little Colorado River. Support moderate growth of grass, sagebrush, and 

various small desert shrubs. Thickness, 3 to 60 ft (1 to 18 m)

Qes Young eolian sand-sheet deposits (Holocene)—White to gray, fine- to coarsegrained, windblown sand composed of quartz, chert, and minor feldspar 

grains, derived from Little Colorado River stream-channel (Qs) deposits 

northeast and east of Little Colorado River over gently sloping terrain.

Include abundant basaltic cinder fragments southwest of Little Colorado 

River. Often intertongue with mixed alluvium and eolian (Qae) deposits.

Support moderate growth of grass and small high-desert shrubs. Thickness, 

1 to 15 ft (0.3 to 4.5 m)

Qdl Linear dune deposits (Holocene)—White, gray, and light-red, fine- to mediumgrained, well-sorted, quartz sand dunes that are aligned in general northeast 

direction; unconsolidated. Only two linear dunes are shown in northeast 

corner of map area, but they are common northeast of the map. Numerous 

thin, low-amplitude, and discontinuous linear dunes are too thin to show at 

map scale within large areas mapped as dune-sand and sand-sheet (Qd) 

deposits. Thickness, 6 to 20 ft (2 to 6 m)

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

medium-grained, well-sorted, unconsolidated quartz sand arranged into 

individual parabolic dunes but most commonly present as complex 

intertonguing parabolic dunes associated with extensive young eolian sandsheet (Qes) deposits just northeast of Little Colorado River. Small ponded 

sediments (Qps) commonly form in low internal-drainage areas within 

parabolic-dune complexes. Supports sparse grassy vegetation. Thickness, 6 

to 20 ft (2 to 6 m)

Qdb Barchan dune and sand-sheet deposits (Holocene)—White, gray, light-red, fineto coarse-grained, well-sorted quartz sand and basaltic cinder fragments 

that form isolated barchan dunes northeast of Grand Falls and Little 

Colorado River. Subject to new distribution changes on yearly basis due to 

seasonal wind storms. Support little or no vegetation. Thickness, 3 to 8 ft 

(1 to 2.4 m)

Qsc Eolian cinder sand-sheet deposits (Holocene)—Black, gray, and some red, fineto coarse-grained fragments of angular to subangular, glassy, basaltic 

cinder and scoria. Similar to unconsolidated cinder-dune (Qdc1) deposits 
12

but forms thin patchy or widespread wind-blown deposits over bedrock of 

Moenkopi Formation or Kaibab Formation in west-central part of map; 

forms discontinuous and thinner deposits in east-central part of map. 

Cinder fragments become smaller and more rounded farther downwind 

(northeast) across northern half of map area becoming mixed with quartz 

sand grains. Volcanic cinders are commonly present with mixed alluvium 

and eolian (Qae) deposits. Thickness, 1 to 5 ft (0.3 to 1.5 m)

Qdc1 Unconsolidated cinder-dune deposits (Holocene)—Black and gray fine- to 

coarse-grained angular to subangular fragments of glassy basaltic cinder 

and scoria. Material is partially derived from several volcanic vent 

eruptions just west and southwest of map, such as Merrill Crater and South 

Sheba Craters about 1 to 4 mi (1.5 to 6.5 km) west of map. May include 

vesicular air-fall cinder ash deposits from other volcanic vents as far west 

as Sunset Crater, 12 mi (19 km) west of map area about 1,000 years ago 

(Hooten and others, 2001), where cinders were transported by 

southwesterly or westerly winds into map area. Deposits accumulate 

against or downslope of local topographic obstructions such as rough basalt 

flow surfaces, steep-walled drainages, and small fault-scarp ledges. 

Thickness, 3 to 10 ft (1 to 9 m) or more

Qdc2 Consolidated cinder-dune deposits (Holocene)—Black and gray, fine- to coarsegrained, angular to subangular fragments of glassy basaltic cinder ash. Unit 

is tightly compacted, well consolidated, and lightly cemented by silica and 

some calcite. Source of cinder ash is unknown but is wind-transported from 

several potential volcanic cone centers west and southwest of map. 

Deposits have been transported by southwesterly winds across surface of 

Kaibab Formation and accumulated as falling dune deposits in Tolchico 

canyon of the Little Colorado River (fig. 4, map sheet) and in Padre 

Canyon (fig. 5, map sheet). Thickness, 5 to 240 ft (1.5 to 73 m)

Qa1 Young alluvial fan deposits (Holocene)—Gray, light-brown, and light-red mud, 

silt, and sand mixed with black cinders. Include cobbles and pebbles of 

chert, limestone, and sandstone locally derived from the Kaibab, 

Moenkopi, and Chinle Formations. Partly consolidated by gypsum and 

calcite cement. Intertongues or overlaps with various Quaternary surficial 

deposits (Qs, Qps, Qf1, Qf2, Qf3, Qes, Qd, Qv, Qg1, Qae). Surface 

subject to extensive sheet-wash erosion, flash-flood debris flows, and small 

arroyo erosion. Support light to moderate growth of sagebrush, camel thorn 

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

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

well-sorted, interbedded mud, silt, sand, black cinder sand, pebbles, 

cobbles, and some boulders; partly consolidated by matrix of mud and sand 

cemented by calcium carbonate and gypsum. Include subangular to wellrounded Paleozoic and Mesozoic sandstone, limestone, and chert clasts of 

local origin. Include some well-rounded clasts of quartzite, quartz, and 

assorted metamorphic crystalline rocks reworked from Tertiary 

conglomerates south of map area. Includes well-rounded volcanic clasts 

derived from San Francisco Volcanic Field in southwest part of map.

Subject to flash-flood and sheet-wash erosion. Support little vegetation, 
13

mainly grass. Forms terraced benches about 3 to 12 ft (1 to 3.6 m) above 

stream-channel (Qs) deposits within narrow canyons in southwest twothirds of map. Thickness, 3 to 12 ft (1 to 3.6 m)

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

coarse-grained sand; weakly consolidated by clay content. Forms benches 

3 to 10 ft above stream-channel (Qs) or modern flood-plain (Qf) deposits. 

Subject to cut-bank channel erosion along Little Colorado River and by 

local streams in flatland areas in southwestern two-thirds of map. 

Overlapped by thin accumulations of young surficial deposits 

(Qd, Qes, Qps, Qa1). Supports thick growths of salt cedar (tamarisk) 

trees, grass, tumbleweed, camel thorn bush, and various other high-desert 

shrubs. Often subjected to overbank flooding or channel erosion by Little 

Colorado River and local tributary streams. Thickness, 3 to 12 ft (1 to 3.5 

m)

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

young alluvial fan (Qa1) deposits; partly cemented by calcite and gypsum; 

surfaces are more gravelly and often cut by arroyos as much as 10 ft (3 m) 

deep southwest of Little Colorado River. Surfaces are often covered by 

sand-sheet deposits too thin to show at map scale northeast of Little 

Colorado River. Unit commonly overlapped by young alluvial fan (Qa1) 

deposits near Little Colorado River and intertongues or overlap’s valley-fill 

(Qv), talus and rock fall (Qtr), and young and intermediate terrace-gravel 

(Qg1, Qg2) deposits southwest of Little Colorado River. Include abundant 

subrounded to subangular basalt clasts in southwest quarter of map area 

and abundant subangular chert clasts northeast of Little Colorado River. 

Support moderate growth of grass, sagebrush, and cactus southwest of 

Little Colorado River and little to no vegetation except grass northeast of 

Little Colorado River. Thickness, 6 to 50 ft (2 to 15 m)

Qg2 Intermediate-age terrace-gravel deposits (Holocene)—Southwest of Little 

Colorado River: Gray and brown silt, sand, and gravel, mixed with black 

cinders; unconsolidated. Lithologically similar to young terrace-gravel 

(Qg1) deposits. Composed mainly of gray and brown siltstone and finegrained sandstone matrix mixed with subangular to rounded pebbles and 

boulders of local Permian limestone and Triassic sandstone. Include wellrounded basalt clasts derived from the San Francisco Volcanic Field.

Locally intertongue with or inset into young and intermediate alluvial fan 

(Qa1, Qa2) deposits. Form terrace benches about 15 to 30 ft (4.5 to 9 m) 

above modern streambeds and about 5 to 20 ft (1.5 to 6 m) above young 

terrace-gravel (Qg1) deposits. Support minor growth of high-desert shrubs 

and grass. Northeast and east of Little Colorado River: Form isolated 

deposits of gray and red silt, sand, and multi-colored, angular chert gravel.

Form terrace benches 10 to 50 ft (3 to 15 m) above modern Little Colorado 

River. Thickness, 6 to 100 ft (2 to 30 m)

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 flood-plain (Qf1) deposits but forms flat 

benches 10 to 15 ft (3 to 4.5 m) above stream-channel (Qs) of modern 
14

flood-plain (Qf) deposits along Little Colorado River. Subject to cut-bank 

and headward erosion by local stream channels. Overlapped by various 

accumulations of thin surficial (Qd, Qes, Qps, Qa1) deposits. Supports 

sparse to moderately thick growths of grass, camel thorn bush, tumble 

weed, salt bush, and other high-desert shrubs, as well as scattered 

cottonwood, salt cedar (tamarisk), and willow trees along Little Colorado 

River. Eolian-sand accumulations commonly cause temporary blockage of 

local runoff that forms ponded sediments (Qps) on flat flood-plain deposits 

(Qf2, Qf3). Subject to overbank flooding or local tributary channel 

erosion. Thickness unknown by may exceed 100 ft (30 m) in some areas; 

visible thickness, 10 to 30 ft (3 to 9 m)

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

sand, pebbles, cobbles, and boulders derived from local Permian and 

Triassic bedrock mixed with basalt clasts and cinders in abandoned 

channels eroded into the Kaibab Formation downstream of Grand Falls. 

Include abundant rounded and well-rounded clasts of quartzite and assorted 

metamorphic crystalline rocks derived from reworking of scattered Tertiary 

sediments south, southeast, and southwest of map; partly consolidated by 

calcite and gypsum cement. Lithologically similar to younger terracegravel (Qg1, Qg2) deposits but with less gravel and more silt and sand 

content. Forms terraces about 25 to 80 ft (7.5 to 25 m) above Little 

Colorado River and about 12 to 40 ft (3.7 to 12 m) above northeasterly 

tributary drainages to Little Colorado River in northwest corner of map. 

Unit commonly covered by thin deposits of wind-polished pebble and 

cobble clasts forming a thin veneer of desert pavement on surface upstream 

of Grand Falls. Thickness, 12 to 90 ft (3.7 to 28 m)

Qf3 Old flood-plain deposits (Holocene)—Gray-brown clay, silt, and fine-grained 

sand; includes thin lenses of stream channel gravel and interbedded alluvial 

fan gravel along margins of unit. Lithologically similar to younger floodplain (Qf, Qf1, Qf2) deposits. Forms wide, flat benches, 15 to 35 ft (4.5 to 

10.5 m) above stream-channel (Qs) and other flood-plain deposits of Little 

Colorado River area. Subject to cut-bank erosion and extensive headward 

erosion by local streams. Overlapped by thin surficial alluvial or eolian 

(Qd, Qes, Qdp, Qps, Qae, Qa1) deposits. Supports sparse to moderate 

growths of grass and a variety of small high-desert shrubs. Subject to local 

flooding where thin accumulations of ponded sediments (Qps) overlie old 

flood-plain (Qf3) deposits. Thickness unknown but may exceed 60 to 80 ft 

(18 to 48 m) in some areas; visible thickness, 10 to 45 ft (3 to 14 m)

Qae Mixed alluvium and eolian deposits (Holocene)—Gray, light-red, and brown 

clay, silt, fine- to coarse-grained sand, and black cinder ash interbedded 

with lenses or beds of gravel. Include white angular chert fragments locally 

derived from the Kaibab Formation southwest of Little Colorado River, 

and white, gray, brown, and red chert fragments derived from the Chinle 

Formation northeast and east of Little Colorado River. Deposits

accumulated by combination of alluvial and eolian processes resulting in 

an interbedded sequence of mixed mud, silt, sand, cinder, and gravel. Unit 

subject to sheet-wash erosion during wet conditions and often covered by 
15

windblown sand and cinder accumulations in dry conditions. Commonly 

occupies broad, gently sloping, flatland topography. Support light to 

moderate growths of grass, cactus, and high-desert low shrubs. Thickness, 

2 to 20 ft (0.6 to 6 m)

Qa3 Old alluvial fan deposits (Holocene and Pleistocene(?))—Gray and light-brown, 

silt, sand, and gravel. Lithologically similar to young and intermediate 

alluvial fan (Qa1, Qa2) deposits with minor cinder deposits. Unit is 

extensively eroded by arroyos or local headward erosion of nearby 

drainages in northeast quarter of map; partly consolidated by clay and 

calcite cement. Surface has thin calcrete soil development on larger 

deposits. Supports moderate growth of grass, sagebrush, cactus, and low 

desert shrubs. Thickness, 5 to 35 ft (1.5 to 11 m)

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

sand, black cinders, and gray lenses of gravel; partly consolidated by 

gypsum and calcite cement west and southwest of Little Colorado River.

Include minor rounded clasts of limestone and sandstone, subrounded to 

angular chert, and basalt gravel southwest of Little Colorado River. Include 

abundant reworked sediment and fragments from Meteor Crater impact 

debris (Qmc) near Meteor Crater. Intertongues with or overlapped by 

Holocene alluvial fan (Qa1, Qa2) deposits and Holocene terrace-gravel 

(Qg1, Qg2) deposits. Commonly reflects low-energy and low-gradient 

shallow valley drainages. Subject to sheet-wash flooding and temporary 

ponding owing to thick growths of sagebrush, grass, and cactus. Thickness, 

3 to 20 ft (1 to 6 m)

Qtr Talus and rock-fall deposits (Holocene and Pleistocene)—Brown, gray, slopeforming, unsorted mixture of mud, silt, sand, pebbles, cobbles, and small to 

large angular boulders. Form talus debris slopes in steep-walled canyon of 

Little Colorado River, Canyon Diablo, and below Tertiary basalt flows of 

unnamed butte in southwest corner of map. Include individual car- and 

house-size boulders. Clasts are angular, unsorted, and partly cemented by 

calcium carbonate. Gradational contact with other Holocene surficial 

(Ql, Qa1, Qa2, Qg1, Qg2, Qv) deposits. Subject to extensive sheet-wash 

erosion, flash-flood debris flows, and arroyo erosion. Only thick or 

extensive deposits shown. Thickness, 3 to 35 ft (1 to 11 m)

Ql Landslide deposits (Holocene and Pleistocene)—Unconsolidated to partly 

consolidated masses of unsorted breccia rock debris. Include blocks of 

strata that have detached from parent source, rotated backward and slid 

down slope as loose masses of brecciated deformed strata. Deposits are 

common below unnamed butte in southwest corner of map. Locally 

includes talus and rockfall debris adjacent to and below landslide masses. 

Some landslide blocks may become unstable with minor movement in wet 

conditions. Small landslide masses in tributary canyon drainages, such as 

Canyon Diablo, have caused temporary blockage of drainage. Thickness of 

landslides, 10 to 120 ft (3 to 36 m)

Qmc Meteor Crater impact debris (Pleistocene)—Gray, light-red, unsorted, angular 

fragments of meteor impact debris derived from Meteor Crater (fig. 2, map 

sheet) approximately 50,000 years ago (Kargel, 1998). Includes unsorted, 
16

angular, sand and small breccia debris with some blocks as large as 100 ft 

(30 m) across (Shoemaker and Kieffer, 1974). Impact debris includes 

highly mixed fragments of Coconino Sandstone, Toroweap Formation, 

Kaibab Formation, and Moenkopi Formation. Mixed breccia along walls of 

crater slumps back toward center of crater (not mapped). Thickness, 3 to 50 

ft (1 to 15 m) 

Qg4 Older terrace-gravel deposits (Pleistocene)—Gray and light-brown, poorly 

sorted clay, silt, sand, gravel, pebbles, cobbles, and boulders; weakly 

cemented by clay and calcite. Include rounded and well-rounded quartzite 

and assorted metamorphic crystalline clasts derived from reworking of 

Tertiary gravel sediments south and southeast of map area. Also include 

well-rounded white chert, gray limestone, and red sandstone clasts derived 

from the Kaibab and Moenkopi Formations and subrounded to rounded 

basalt clast from San Francisco Volcanic Field. Form terrace deposits in 

abandoned Little Colorado River channels eroded into Kaibab Formation 

downstream of Grand Falls and in abandoned tributary channels southeast 

of Grand Falls that form inverted topography outcrops where not covered 

by basalt flows. Thickness, 6 to 80 ft (2 to 25 m)

Qg5 Young Little Colorado River deposits (Pleistocene)—Gray and light-brown, 

poorly sorted silt, sand, gravel, pebbles, cobbles, and boulders; 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. Include well-rounded, reddish-brown quartzite 

cobbles. Pebbles and cobbles weather out as lag gravel that forms armored 

surface that helps preserve underlying fine-grained silt and sand deposits. 

Extensively eroded and gullied; fills Little Colorado River channel eroded 

into lower strata of Moenkopi Formation and upper strata of Kaibab 

Formation downstream (west) of Grand Falls about 200 to 250 ft (60 to 76 

m) above modern Little Colorado River canyon. Unit partly covered by 

eolian cinder (Qsc, Qdc1) deposits. Thickness, 20 to 80 ft (6 to 24 m)

Qg6 Intermediate-age Little Colorado River deposits (Pleistocene)—Gray to lightbrown, poorly sorted, weakly consolidated sand and arkosic gravel with 

gray, white, red, brown, and black quartzite and chert pebbles, cobbles, and 

small boulders (0.5 in to 1 ft [1.5 to 30 cm] in diameter). Largest boulders 

are mostly subrounded clasts derived from the Kaibab Formation in 

deposits southwest and west of Grand Falls. Lag gravel forms gray 

armored cover on red hills of Moenkopi Formation southwest and west of 

Grand Falls that are about 280 to 300 ft (85 to 92 m) above modern Little 

Colorado River canyon. Deposits have similar protective lag gravel on 

ridge northeast of Grand Falls about 140 ft (43 m) above Little Colorado 

River floodplain; unit is about 100 ft (30 m) below nearby highest Little 

Colorado River deposits (Qg7) northeast of Grand Falls. Unit forms 

inverted topography of Little Colorado channel about 2 mi (3 km) northeast 

of Grand Falls. Thickness, 75 ft (23 m)

Qg7 Old Little Colorado River deposits (Pleistocene)—Light-red, gray, and brown 

interbedded siltstone, sandstone, arkosic gravel, and lenticular 

conglomerate similar to intermediate-age Little Colorado River (Qg6) 
17

deposits. Unit fills Little Colorado River channel eroded into upper 

Moenkopi Formation. Pebbles and cobbles composed mostly of wellrounded, brown, yellow-white, red-brown, gray and black quartzite and 

chert, and minor clasts of granite and metamorphic rocks derived from 

older Tertiary gravel deposits southeast of the map area; include abundant 

gray, subrounded limestone clasts derived from Kaibab Formation and red 

sandstone clasts derived from Moenkopi Formation. Unit forms highest 

Little Colorado River gravel deposits in map area that are likely 

Pleistocene age based on similar deposits northwest of map within the 

Cameron 30′ x 60′ quadrangle (Billingsley and others, 2007). Thickness, 3 

to 25 ft (1 to 7.6 m) or more

VOLCANIC ROCKS

Volcanic rocks of the San Francisco Volcanic Field (Pleistocene)—Modified 

from Moore and Wolfe (1976). For a complete history of magnetic polarity 

age determinations, analytical data, and classification of basalt types in this 

map area, see Ulrich and Bailey (1987)

Qbm1 The Sproul basalt flow of Merriam Crater (Pleistocene)—Herein 

informally named from a small volcanic crater called "The Sproul" on the 

west side of Merriam Crater, 2 mi (3.2 km) west of map edge (T. 23 N., R. 

10 E., sec. 36, USGS 7.5′ Merriam Crater quadrangle, 1969). Dark-gray 

alkali olivine basalt. Contains scattered phenocrysts of olivine, 

clinopyroxene, and rare plagioclase in groundmass of similar minerals and

opaque oxides. Basalt flow originates from The Sproul, a black basalt vent 

on west side of Merriam Crater 4 mi (6.5 km) southwest of mapped flow at 

northwest edge of map. This flow traveled northeast to Grand Falls and 

appears to merge with or overflow the basalt flow of Merriam Crater 

(Qbm) about 1 mi (1.6 km) south of Grand Falls. This flow or the basalt 

flow from Merriam Crater (Qbm), or both (?), formed a basalt dam across 

the Little Colorado River canyon resulting in the development of Grand 

Falls (fig. 3, map sheet). Basalt flow also traveled down Little Colorado 

River canyon approximately 21 mi (33.5 km) downstream of Grand Falls.

Age of the basalt dam at Grand Falls is 19.6±1.2 ka (Esser, 2003; Duffield 

and others, 2006).

A similar age basalt flow (Qbm2) from two vents on the east side 

of Merriam Crater merged and traveled northeast along and over the basalt 

flow of Merriam Crater (Qbm). Both The Sproul and the two east vent 

basalt flows appear to have erupted simultaneously shortly after 

development of the larger Merriam Crater pyroclastic cone. Thickness, 6 to 

130 ft (2 to 40 m)

Qbm2 East vent basalt flow of Merriam Crater (Pleistocene)—Herein informally 

named from two unnamed vents on the east side of Merriam Crater, 2 mi 

(3.2 km) west of map edge (T. 23 N, R. 10 E, sec. 36, USGS 7.5′ Merriam 

Crater quadrangle, 1969). Dark-gray and black porphyritic and aphyric, 

clinopyroxene-olivine and alkali-olivine basalt. Two flows came from two 

vents that appear to have erupted simultaneously on the east side of 

Merriam Crater (east vent) that traveled northeast and merged into one 
18

flow onto the basalt flow of Merriam Crater (Qbm) and appears to have 

stopped 1 mi (1.6 km) south of Grand Falls. Basalt flow of Merriam Crater 

(Qbm) is locally covered by thicker deposits of alluvium and eolian cinder 

deposits, suggesting that it is older than The Sproul or east vent flow.

Thickness, 3 to 65 ft (1 to 20 m)

Qbm Basalt flow of Merriam Crater (Pleistocene)—Herein informally named 

from Merriam Crater, 2 mi (3.2 km) west of map edge (T. 23 N., R. 10 E., 

sec. 36, USGS 7.5′ Merriam Crater quadrangle, 1969). Dark-gray to black 

olivine basalt. Basalt flow is overlain by approximately 1,000 ft (300 m) of 

red pyroclastic deposits that formed Merriam Crater cinder cone 2 mi (3 

km) west of northwest map edge. Basalt flowed northeast toward Little

Colorado River and appears to have stopped 1 mi (1.6 km) south of Grand 

Falls but may have reached the Little Colorado River and either merges 

with or is covered by The Sproul basalt flow of Merriam Crater (Qbm1). 

Flow surface near Merriam Crater is mostly covered by mixed alluvium 

and eolian cinder (Qae, Qsc, Qdc1) deposits. Thickness, 15 to 30 ft (4.5 

to 9 m)

Qbr Basalt flow of Roden Crater (Pleistocene)—Herein informally named from 

Roden Crater, 0.5 mi (0.8 km) west of map edge (T. 24 N., R. 11 E., sec.

31, USGS 7.5′ Roden Crater quadrangle, 1969). Dark-gray to black olivine 

basalt. Contains phenocrysts of olivine, clinopyroxene, and some 

plagioclase in groundmass of the same minerals plus opaque oxides. Roden 

Crater is a 500-ft-high (153-m-high) red pyroclastic cone that formed over 

the associated basalt flow from Roden Crater vent. The basalt flowed over 

1.5 mi (2.5 km) from Roden Crater northeastward over sandstone strata of 

the Moenkopi Formation. Flow appears to have stopped near and slightly 

below intermediate-age Little Colorado River deposits (Qg6) southwest of 

Little Colorado River canyon, downstream of Grand Falls. Thickness, 100 

ft (30 m)

Qp Pyroclastic deposits, undivided (Pleistocene)—Red or black, massivebedded, air-fall cinder, volcanic bomb, and splatter deposits that overlie 

basalt flows from associated eruptive vent area. Unit is matrix free, except 

for locally reworked zone in upper 3 ft (1 m) or more of unit. Contains 

xenoliths of red, white, or gray limestone and sandstone and white chert 

fragments. Unit overlies locally associated basalt flows along west edge of 

map and is partly overlapped by basalt flows (Qb) at one location along 

east edge of map. Unit does not include eolian cinder sand-sheet (Qsc) or 

cinder-dune (Qdc1, Qdc2) deposits, but may intertongue with eruptive air 

fall eolian deposits. Thickness, 10 to 15 ft (3 to 5 m)

Qb Quaternary basalt flows, undivided (Pleistocene)—Dark-gray to black 

plagioclase-phyric basalt with abundant 1- to 3-cm plagioclase laths in 

groundmass of olivine, clinopyroxene, plagioclase, and magnetite. Includes 

basalt flows from Merrill Crater, South Sheba Crater, and an unnamed 

crater (elevation 5,397) just west of map edge. K-Ar age of various flows 

west of map are 0.22±0.05 Ma, 0.46±0.05 Ma, 0.66±0.11 Ma, 0.74±0.08 

Ma, and 0.77±0.04 Ma (Ulrich and Bailey, 1987). Basalt flows appear to 

merge or overlap, which makes identifying the source eruptive vent(s)
19

difficult. One or more of these basalt flows reached the Little Colorado 

River and formed the basalt dam on the east side of Tolchico Anticline 

(175 Ka, 40Ar/39Ar; Esser, 2003). Thickness, 15 to 250 ft (4.5 to 76 m)

Qbw Basalt flow of Woodhouse age (Pleistocene)—Informally named by Ulrich 

and Bailey, 1987). Dark-gray, plagioclase-phyric and porphyritic basalt of 

similar composition to pyroclastic (Qp) deposits. Weathers yellow or 

brown. Surfaces are subdued and slightly eroded and gullied. K-Ar age of 

various flows outside of map area, 0.83±0.04 Ma, 1.04±0.04 Ma, 

1.20±0.05 Ma, and 1.38±1.01 Ma (Ulrich and Bailey, 1987; Wolfe and 

others, 1987). Flows generally followed older drainages and now represent 

inverted topography above present drainages. Thickness, 15 to 160 ft (4.5 

to 48 m)

Tb Tertiary Basalt flow (Miocene)—Dark-gray to black plagioclase-phyric 

basalt; surface weathers smooth and is locally dissected. Contains scattered 

to abundant tabular plagioclase phenocrysts as large as 1 cm in diameter

and includes abundant olivine microphenocrysts in feldspathic groundmass 

with granular to ophitic intergrowth of brown pyroxene and plagioclase. KAr age, 2.43±0.32 Ma (Ulrich and Bailey, 1987). Forms basalt caprock in 

drainage eroded into the Shinarump Member of the Chinle Formation that 

flowed northeastward from basalt flows of Anderson Mesa southwest of 

map. Basalt flow now forms inverted valley ridge on unnamed butte in 

southwest corner of map. Thickness 20 to 30 ft (6 to 9 m)

SEDIMENTARY ROCKS

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 

that are gray, cherty, lenticular, silty, irregularly bedded, and 1 to 5 ft (0.5 

to 1.5 m) thick extend laterally several miles northwest and southeast of 

map area. Unit thickens northwest and southeast of map to as much as 300 

ft (92 m); approximately 30 to 50 ft (9 to 15 m) has been removed by 

modern erosion at Newberry Mesa, northeast corner of map. Consists of as 

many as 6 to 7 resistant limestone ledges in northeast corner of map. Unit 

contains abundant mud pellets and silicified clay and concretionary chert 

nodules. Contact with underlying Petrified Forest Member (^cp) is 

gradational and arbitrarily marked at lowest limestone bed or at nodular 

calcareous gray-white siltstone in slope below lowest limestone bed. 

Thickness, 130 (40 m)

^cp Petrified Forest Member (Upper Triassic)—Purple, blue, light-red, redpurple, and gray-blue, slope-forming mudstone, siltstone, and interbedded 

white, coarse-grained lenticular sandstone. Includes large-scale erosion 

channel structures and large-scale low-angle trough crossbedding. Petrified 

logs and wood fragments are common in white or yellow-white sandstone 

beds in lower part that may be within upper part of underlying Shinarump 

Member (^cs). Contact with Shinarump Member marked at lithologic and 
20

topographic change from sloping multicolored mudstone of Petrified Forest 

Member to coarse-grained, white sandstone slopes and ledges of 

Shinarump Member. Weathers into rounded hills or slopes with rough, 

puffy, popcorn surface owing to swelling of clay content when wet; mostly 

covered by young surficial alluvium and eolian deposits in valley drainages 

and by older alluvial and eolian deposits on some ridges. Thickness, 400 to 

450 ft (122 to 137 m)

^cs Shinarump Member (Upper Triassic)—White and light-brown, ledge- and 

slope-forming, coarse-grained sandstone and conglomeratic sandstone.

Includes low-angle crossbedded white sandstone interbedded with purple, 

light-red, and blue poorly sorted siltstone and mudstone in upper part that 

may be lower part of Petrified Forest Member (^cp). Gradational contact 

with overlying Petrified Forest Member. Lithology is highly variable in 

lateral and vertical distribution but relatively homogeneous from a regional 

viewpoint; unit consists of about 75 percent sandstone, 20 percent 

conglomerate, and 5 percent mudstone (Repenning and others, 1969).

Pebbles are generally black, brown, and light-red, well-rounded quartzite 

and a black chert composition. Multicolored petrified logs and wood 

fragments are generally scattered throughout unit. Unit is locally absent 

northeast of Little Colorado River at some locations; commonly covered by 

surficial eolian deposits. Unconformably overlies red siltstone and 

sandstone of upper Moenkopi Formation (^mhm). Thickness, 0 to 40 ft (0 

to 12 m)

Moenkopi Formation (Middle(?) and Lower Triassic)—Consists of, in 

descending order, the Holbrook Sandstone and Moqui Members, 

undivided, the lower massive sandstone member, and the Wupatki Member 

as defined by McKee (1954). Overall thickness before Cenozoic erosion, 

220 ft (67 m)

^mhm Holbrook and Moqui Members, undivided (Middle(?) and Lower 

Triassic)—Reddish-brown, slope-forming, alternating sequence of 

claystone, siltstone, and sandstone (Hagar, 1922; McKee, 1954). Includes

large- to medium-scale trough crossbedding and abundant cusp-type ripple 

marks that testify to fluvial origin. Includes isolated or scattered meander 

channels of red-brown elongated resistant sandstone ridges of Holbrook 

Member that overlie red sandstone and siltstone beds of slope-forming 

Moqui Member; collectively mapped as undivided. Fossil casts of reptile 

tracks are often preserved on bottom surfaces of sandstone beds. Include 

interbedded, thin-bedded limestone, conglomeratic sandstone lenses, 

gypsiferous siltstone, and numerous gypsum veins in Moqui Member.

Thickness, 80 to 120 ft (25 to 37 m)

^mss Lower massive sandstone member (Lower Triassic)—Light-red and lightbrown, cliff-forming, crossbedded, fine-grained calcareous siltstone and 

sandstone. Forms prominent isolated ledges or sandstone knobs 10 to 20 ft 

(9 to 4.5 m) thick in northeast quarter of map between Meteor Crater and 

Grand Falls. Salt weathering of sandstone forms pitted and fluted 

weathered surface in well-exposed outcrops. Unit correlates to the 

Shnabkaib Member of the Moenkopi Formation in northwestern Arizona
21

(Billingsley and others, 2007). Minor erosional contact with underlying 

Wupatki Member (^mw) marked at base sandstone cliff. Unconformably 

overlies the Kaibab Formation, where underlying Wupatki Member is 

absent or too thin to show at map scale. This contact forms the regional 

Permian-Triassic boundary. Thickness, 10 to 20 ft (9 to 4.5 m)

^mw Wupatki Member (Lower Triassic)—Red and red-brown, slope-forming, 

thin-bedded siltstone and sandstone and interbedded crumbly red-brown 

mudstone. Thin, flat sandstone beds (1 to 2 ft [0.4 to 0.6 m]) form resistant 

ledges within slopes in northwest quarter of map. Bedding surfaces often 

contain small-scale ripple marks or rain-drop impressions. Unit gradually 

thins east and southeast across map. Unconformably overlies Kaibab 

Formation and forms the regional Permian-Triassic boundary; the contact 

is generally of low relief, less than 5 ft (1.5 m). Thickness, 20 to 35 ft (6 to 

10 m)

Pk Kaibab Formation (Cisuralian)—Includes, in descending order, Harrisburg and 

Fossil Mountain Members as defined by Sorauf and Billingsley (1991).

Members are difficult to separate because of similar lithology owing to 

facies changes of both units that collectively form a gray to light-brown, 

cliff-forming, calcareous sandstone and sandy limestone. Please note that 

Lower Permian is now referred to as Cirsuralian

Harrisburg Member: Red-gray to brownish-gray, slope-forming 

gypsum, siltstone, sandstone, and thin-bedded limestone. Includes 

yellowish-gray fossiliferous sandy limestone at top of unit that is largely 

removed by modern erosion from parts of map area. Forms surface bedrock 

throughout map area. Contact with underlying Fossil Mountain Member is 

gradational and placed at topographic break between reddish-gray, slopeand ledge-forming sandy limestone and sandstone sequence of Harrisburg 

Member and underlying gray to light-brown, cliff-forming cherty limestone 

of Fossil Mountain Member. Unit gradually thins from west to east and 

undergoes a shoreward (eastward) facies change from limestone and sandy 

limestone to calcareous sandstone and sandstone. Thickness, 80 to 120 ft 

(25 to 37 m).

Fossil Mountain Member: Light-gray, cliff-forming, fine- to 

medium-grained, thin- to medium-bedded (1 to 6 ft [0.3 to 2 m]), 

fossiliferous, cherty, sandy limestone and minor dolomite. Weathers dark 

gray or brown, often stained by black manganese oxide. Unit characterized 

by gray to white fossiliferous chert nodules and thin chert breccia beds.

Chert breccia beds are less than 3 ft (1 m) thick and commonly mark 

uppermost part of Fossil Mountain Member. Unit gradually thins from 

west to east and undergoes a shoreward (eastward) facies change from 

sandy limestone to calcareous sandstone, similar in texture, composition, 

and appearance to overlying Harrisburg Member. Typically forms cliff or 

series of ledges in lower half of tributary canyons to Little Colorado River 

and Little Colorado River canyon below Grand Falls and at Tolchico 

canyon and Meteor Crater. Unconformable contact with underlying 

Toroweap Formation attributed mostly to shallow channel erosion into 

similar color sandstone of the Toroweap Formation in Meteor Crater and 
22

below Grand Falls; average erosional relief, about 10 ft (3 m). Thickness, 

180 ft (55 m)

Pt Toroweap Formation, undivided (Cirsuralian)—White, low-angle, cliffforming, crossbedded sandstone in Meteor Crater and downstream of 

Grand Falls. Unit may be present in bottoms of some tributary canyons 

such as Canyon Diablo, Padre Canyon, and others but is too thin to show or 

is difficult to distinguish from overlying Kaibab Formation. Unit gradually 

thins southeast in the subsurface of the map area where drill holes near 

Leupp, Arizona, indicate that only 20 to 30 ft (6 to 9 m) of Toroweap 

Formation is present (Bills and others, 2005) and about the same amount is 

present in Meteor Crater (Shoemaker and Kieffer, 1974). In the subsurface, 

the Toroweap Formation has a sharp unconformable contact with 

underlying Coconino Sandstone based on exposures northwest of map area 

near Cameron, Arizona (Billingsley and others, 2007). Thickness northwest 

to southeast, 30 to 20 ft (9 to 6 m)

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