Prepared in cooperation with the Water Resources Division of the National Park Service

Geologic Map of the Valle 30‘ x 60‘ Quadrangle, Coconino County, Northern Arizona

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

Pamphlet to accompany Scientific Investigations Map 2895

View looking downstream into Cataract Canyon showing the Lower Permian strata of the Coconino Plateau (photograph by G.H. Billingsley, 2003).

2006

U.S. Department of the Interior U.S. Geological Survey INTRODUCTION the Coconino Plateau along State Highway 64 northeast corner of the map area, to about 4,200 ft (1,280 m) at the The geologic map of the Valle 30´ x 60´ quadrangle is bottom of Cataract Canyon. the result of a cooperative effort between the U.S. Geolog- Settlements within the map area include Tusayan ical Survey and the National Park Service to provide geo- and Valle, Arizona (fig. 1). State Highway 64 and U.S. logic information for regional resource management and Highway 180 provide access to the Tusayan and Valle visitor information services for Grand Canyon National areas. Indian Route 18 is a paved highway in the north- Park, Arizona. The map area encompasses approximately west corner of the map area that is maintained by the 1,960 mi2 within Coconino County, northern Arizona and Hualapai and Havasupai Indian Tribes and leads from is bounded by long 112° to 113° W. and lat 35°30´ to 36° State Route 66 about 7 mi (11 km) east of Peach Springs, N. and lies within the southern Colorado Plateaus geo- Arizona to Hualapai Hilltop, a parking lot just north of logic province (herein Colorado Plateau). The map area the map area at the rim of Cataract Canyon where visi- is locally subdivided into four physiographic parts; (1) tors begin an 8 mi (13 km) hike into Havasupai, Arizona. the Grand Canyon (Cataract Canyon and extreme north- Other remote parts of the map are accessed by two dirt east corner of the map area), (2) the Coconino Plateau, roads, which are maintained by Coconino County, and (3) the Mount Floyd Volcanic Field, and (4) the San Fran- by several unmaintained local ranch roads. Weather con- cisco Volcanic Field as defined by Billingsley and others, ditions restrict travel within the area and visitors must 1997 (fig.1 ). Elevations range from 7,460 ft (2,274 m) on obtain permission to access a few local ranch lands in the

113°00' 112°00' 36°00' S up t HAVASUPAI ai Tusayan FaultGRAND CANYON M Faul n INDIAN e a NATIONAL PARK o n li y n Co Coconino n c a e S c RESERVATION o o s b San n k onin 64 c a o Tu r in l n i M 18 n G e o dstone Far e r Wash

m Vishnu R id Da Cataract Canyon of ge Wash Ant HUALAPAI Box K Ranch Angel icl m Grand Canyon ine t INDIAN l Was u l a KAIBAB RESERVATION F ge Anita

h e Sandstone h An NATIONAL Hazen Hole c in Station n cl a ght FOREST Tank o i e Fault D R n

Dik ra o Br ght Wash w M i Cata e Br Redlands Ranch onoclin Red Butte Tan H s M Red o COCO d r r ac s

s Fault n e ai a k a W s l t Howard h

Dr d aw up Rodger e Hill

Faul S t NINO R Re Farm d Willaha Hor Rose Well Camp 180 se Anticline Da h m s Dr Vishnu aw 64 er Wa Long SAN FRANCISCO Point Tin House Mill Dam VOLCANIC FIELD C Ranch m a Sp t ring Black Markham ara Syncline c Val Red t le Valle Tank Dam y Lake Markha Camp Fault Zone W a sh Duff P 180 Au MOUNT FLOYD Brown Tank LAT

brey S SAN FRANCISCO Rhodes VOLCANIC FIELD u Horse p EA VOLCANIC FIELD Tule a 64 Canyon i Four Lake U

Lake M C Hills o a n n Clif o y c o Bishop li n f n s Lake e 35°30' 0 5 10 15 20 MILES

0 5 10 15 20 25 30 KILOMETERS Volcanic rocks Main dirt road Intermittent stream

Federal land boundary Monocline Anticline

Lake or stock tank Syncline Fault—Bar and ball on downthrown side Figure 1. Index map of the Valle 30' x 60' quadrangle showing some locations and geologic and structural features mentioned in the text.

 south-central edge of the map area. Extra water and food entirely using photogeologic methods. Relative ages of are highly recommended when traveling in this remote alluvial deposits with similar lithologies were determined region. Access into Cataract Canyon is restricted to horse on the basis of stratigraphic position and the amount of or foot travel and visitors must obtain permission from erosional degradation. Several map units and structures the Havasupai Tribe to hike within the Havasupai Indian were investigated in the field to insure accuracy of place- Reservation (fig. 1). ment. Map contacts between alluvial and eolian units are In the central part of the map area, most of the land approximate. is privately owned and managed by the Babbitt Ranches Tracey Felger and Susan S. Priest, Flagstaff Science Inc. in conjunction with the Nature Conservancy and the Center, U.S. Geological Survey, used ARC/MAP tech- Navajo Tribe. In the southern half of the map, land alter- niques to compile the map in digital format. This is the nates between privately owned land and State land form- 4th map in a series of new digital 1:100,000-scale geo- ing a checkerboard pattern. The National Park Service logic maps for the Grand Canyon region. manages land in Grand Canyon National Park (extreme northeast edge of map area), the U.S. Forest Service Geologic setting manages lands in the Kaibab National Forest, the Huala- pai Tribe manages lands in the northwest quarter of the The map area is characterized by nearly flat lying map area, and the Havasupai Tribe manages lands within to gently dipping Paleozoic, Mesozoic, and Cenozoic Cataract Canyon and adjacent parts of the Coconino Pla- strata. Miocene, Pliocene, and Pleistocene volcanic rocks teau (fig. 1). form a protective caprock over most of the Mesozoic and Cenozoic rocks along the south and east margins of PREVIOUS WORK the map area. The southwest limb or part of the Kaibab Upwarp or anticline elevates the northeast part of the map Wilson and others (1969) compiled an early recon- area where Paleozoic and Mesozoic strata have a regional naissance photogeologic map of this area as part of a southwest dip averaging about 2 degrees toward the broad geologic map of Coconino County and which was later Cataract Syncline in the vicinity of Cataract Canyon and compiled at 1:500,000 scale for the State of Arizona Valle, Arizona. The regional dip in the southwest half of map. A new 1:1,000,000-scale geologic map of Arizona the map area is about 1 to 2 degrees northeast towards the was recompiled by Reynolds (1988) using the same geo- Cataract Syncline. The Cataract Syncline axis is approxi- logic data. Wenrich and others (1997) and Billingsley mate and closely follows the northwest trend of Cataract and others (2000b) mapped the northeastern part of the Canyon (Huntoon, 2003). Hualapai Indian Reservation, which encompassed the northwest corner of this map. Wolfe and others (1987) mapped the San Francisco Volcanic Field in the south- PALEOZOIC AND MESOZOIC east corner of this map and Huntoon and others (1996) SEDIMENTARY ROCKS mapped a portion of the northeast corner of the map area. Nearly 1,500 ft (460 m) of Lower Permian strata are The Quaternary geology of Wenrich and others (1997), exposed in the walls of Cataract Canyon. The Paleozoic Billingsley and others, (2000b), and Wolfe and others strata in the map area are, oldest to youngest, the Espla- (1987) has been modified and updated (see index to geo- nade Sandstone, the Hermit Formation, the Coconino logic mapping on geologic map). Sandstone, the Toroweap Formation, the Kaibab Forma- Geologic maps of adjacent areas include (1) the tion. Grand Canyon 30´ x 60´ quadrangle, which borders the north edge of this map (Billingsley, 2000), (2) the Mount ESPLANADE SANDSTONE Trumbull 30´ x 60´ quadrangle adjacent to the northwest corner of this map (Billingsley and Wellmeyer, 2003), The Esplanade Sandstone is incompletely exposed and (3) the Coconino Point and Grandview Point quad- at the bottom of Cataract Canyon but based on exposures rangles adjacent to the northeast corner of this map (Bill- in Grand Canyon just north of the map and in the Verde ingsley and others, 1985). Huntoon (1999) produced a Valley southeast of the map, the Esplanade Sandstone local structural geologic map of the Cataract Basin area. maintains a relatively uniform thickness of about 400 to 450 ft (123 to 137 m) thick throughout the subsurface of the Coconino Plateau. Regionally, the Esplanade Sand- MAPPING METHODS stone gradually thins to the east, south, and southwest but The geology was mapped first by photogeologic thickens slightly to the north and northwest. The Espla- methods using 1974 black and white 1:24,000-scale stereo nade represents a coastal and near coastal deltaic, eolian aerial photographs and later by extensive field checking. sand dune, and nearshore fluvial environments. The high- Many of the Quaternary units have similar lithology and lands that may have supplied most of the sediment were geomorphic characteristics and were mapped almost generally south and east of the map area, while shallow

 seas were present to the west and northeast. An erosional the map area. The Seligman Member is an accumulation unconformity separates the Esplanade Sandstone from of nearshore beach sandstone and shallow marine lime- the overlying Hermit Formation; channels eroded into the stone deposits that are about 55 ft (17 m) thick in the Esplanade are as much as 130 ft (40 m) deep in Cataract northwest corner of the map, and gradually thins south- Canyon just north of the map area (Billingsley, 2000). eastward to less than 30 ft (9 m) thick. Onshore winds supplied abundant sand from the beaches inland to the HERMIT FORMATION east and southeast to form coastal and inland sand dunes The Hermit Formation is a fluvial deposit of fine- comprising the Coconino Sandstone. The Coconino grained sand and silt that filled channels eroded into the Sandstone forms a tongue within the Seligman Member Esplanade Sandstone and eventually covered the entire of the Toroweap Formation (Fisher, 1961; Schleh, 1966; Esplanade. Based on exposures surrounding the map area, Rawson and Turner, 1974; and Billingsley and others, the Hermit Formation in the subsurface is about 260 ft 2000a) in the western Grand Canyon area but overlies (80 m) thick in the east part of the map, thickens to about the Hermit Formation in the central and eastern part of 850 ft (260 m) in the northwest part, and thins to less than the map area. The Coconino Sandstone forms a mappable 80 ft (25 m) thick near the southwest and south edge of unit about 200 ft (60 m) thick in the Cataract Canyon the map. The clastic sediments of the Hermit Formation area, thickens to more than 400 ft (122 m) in the subsur- accumulated as lowland deltaic deposits from meander- face in the southeast corner of the map and is about 500 ing fluvial streams and overbank floodplain deposits. A ft (153 m) thick in the northeast part of the map, based on few low-amplitude eolian sand dunes intertongue with exposures southeast and northeast of the map area (Bill- the fluvial deposits. ingsley, 2000; Billingsley and others, 2000b). The Brady Canyon Member of the Toroweap For- COCONINO SANDSTONE mation consists of thin beds to moderately thick beds of limestone deposited in a shallow sea that covered much The Coconino Sandstone, a crossbedded eolian of the Coconino Sandstone on the Coconino Plateau and sandstone, generally thickens from west to east across the Grand Canyon area. The Brady Canyon Member thins map area. The Coconino is about 160 ft (50 m) thick in from 250 ft (76 m) along the west edge of the map to the northwest corner of the map, about 250 to 280 ft (76 about 40 ft (12 m) along the east edge. The Brady Canyon to 85 m) thick at the southeast edge, and thickens to about thins eastward across the Coconino Plateau almost pro- 500 ft (153 m) or more near the east edge of the map area. portionally to the thickening of the underlying Coconino The base of the Coconino Sandstone intertongues within Sandstone. the Seligman Member of the Toroweap Formation along Evaporite deposits of gypsum, gypsiferous siltstone, the west edge of the map and overlies the Hermit Forma- and gypsiferous sandstone of the Woods Ranch Member tion in the central and eastern portions of the map area of the Toroweap Formation overlie the Brady Canyon (see discussion in Toroweap Formation section below). Member. The Woods Ranch Member represents a north- The Coconino Sandstone is buff-white along the north westward regressive phase of the Late Permian Toroweap edge of the map area and light red to brown in the south- sea. Sediments of the Woods Ranch Member accumulated west corner of the map. Fossil amphibian footprints and to about 65 ft (20 m) thick in the southeast half of the wind ripple marks are commonly found within the cross- map area and about 200 ft (60 m) thick in the northwest bedded sets. half grading into thin deposits of calcareous sandstone and gypsiferous sandstone in the northeast and south- TOROWEAP FORMATION west corners of the map area. The configuration of the Shallow seas west and north of Grand Canyon began marine deposits of the Woods Ranch Member reflects the to gradually transgress across the Hermit Formation and overall northwest-southeast axis of a marine embayment deposited beach and coastal sand dune deposits above the between the Kaibab Plateau and Aubrey Cliffs suggesting disconformity. The transgressive phase of the Toroweap that the Kaibab Plateau and Aubrey Cliffs areas may have Formation, represented by the sandstone and limestone been slightly elevated during or before deposition of the deposits of the Seligman and Brady Canyon Members of Woods Ranch Member. Massive gypsum beds, as much the Toroweap Formation, was followed by a regressive as 30 ft (9 m) thick, accumulated within the central part phase that deposited the siltstones and gypsum beds of of the map area conforming to the general configuration the Woods Ranch Member of the Toroweap Formation. of the present Cataract Syncline. After withdrawal of the These three members of the Toroweap Formation are sea, dissolution and erosion of the Woods Ranch Member undivided on the map because they are too thin to show sediments produced an eroded surface with 30 to 100 ft at map scale but are shown on the Littlefield (Billingsley (9 to 30 m) of relief that was subsequently buried by the and Workman, 2000) and the Mount Trumbull (Billing- Kaibab Formation (Billingsley, 2000; Billingsley and sley and Wellmeyer, 2003) geologic maps northwest of Wellmeyer, 2003).

 KAIBAB FORMATION rately northwest of the map area (Billingsley and Work- man, 2000; Billingsley and Wellmeyer, 2003). The Kaibab Formation forms the surface bedrock of much of the Coconino Plateau map within and sur- The Toroweap and Kaibab Formations as they relate to rounding the map area. These deposits are partly covered regional structure by younger Mesozoic or Cenozoic strata and Tertiary to Early Permian seas encroached and withdrew twice Pleistocene volcanic rocks in the southwest and southeast from northwestern Arizona, Nevada, and Utah; the cycles part of the map. The Kaibab Formation has two mappa- deposited the Toroweap and Kaibab Formations, respec- ble members, the Harrisburg Member (Pkh) (upper part) tively. The Brady Canyon Member of the Toroweap For- and the Fossil Mountain Member (Pkf) (lower part). mation and the Fossil Mountain Member of the Kaibab The Fossil Mountain Member is a cliff-forming cherty Formation represent the shallow marine transgressions. limestone about 350 ft (107 m) thick along the west edge The Woods Ranch Member of the Toroweap Formation of the map and thins to 300 ft (92 m) where it forms a and the Harrisburg Member of the Kaibab Formation limestone cliff at the rim of Cataract Canyon, and thins represent the marine regressions. All members of each to about 230 ft (70 m) at the east edge of the map area. formation undergo a facies change from shallow marine The Fossil Mountain Member represents a transgression conditions west of the Kaibab Anticline to nearshore and of the Early Permian sea that encroached from northwest tidal flat coastal marine conditions east and southeast of to southeast over eroded deposits of the Toroweap For- the Kaibab Anticline. The facies change is nearly parallel mation of the Coconino Plateau. A gradational bound- to the axis of the Kaibab Anticline suggesting that minor ary separates the cliff-forming Fossil Mountain Member uplift along this structure may have influenced both the from the overlying slope-forming Harrisburg Member of Toroweap and Kaibab Formations facies change during the Kaibab Formation. Early Permian time. Deposits of the Harrisburg Member of the Kaibab Formation form much of the surface bedrock within the MOENKOPI AND CHINLE FORMATIONS map area. Recessive slope-forming beds of the Harrisburg The Triassic Moenkopi Formation is comprised of Member overlie cliff-forming beds of the Fossil Mountain a sequence of red sandstone ledges and sandy siltstone Member throughout most of the map area. The Harrisburg slopes. Overlying the Moenkopi Formation at Red Butte Member consists of evaporite and tidal-flat deposits left by is a white conglomeratic sandstone cliff of the Shina- the regressive phase of the Kaibab-age sea as it retreated rump Member of the Chinle Formation. The Moenkopi west and northwest. The configuration of the regressive Formation is partly preserved under Quaternary and phase of the Kaibab-age sea embayment, which is par- Tertiary volcanic rocks along the east and south edges allel to the Cataract Syncline, is remarkably similar in of the map, but was mostly eroded during the Cenozoic aerial extent to the regressive phase of the Woods Ranch from the central and northwest half of the map area. The Member of the Toroweap Formation sea embayment. The Moenkopi Formation once covered all of the Coconino main difference is that the Harrisburg Member sediments Plateau area and ranged in thickness from about 1,000 ft extended farther southeast to at least Flagstaff, Arizona (305 m), as preserved at Red Butte along the north edge (Sorauf and Billingsley, 1991). Erosion and dissolution of of the map, to about 800 ft (244 m) along the south and gray gypsum and light-red gypsiferous siltstone and sand- southeast edge. stone deposits of the Harrisburg Member have resulted About 80 ft (25 m) of the Triassic Shinarump in the development of several internally drained karstic Member of the Chinle Formation is preserved beneath depressions on the Coconino Plateau, especially near Cat- a 165 ft-thick (50 m) caprock of Tertiary (9 Ma) olivine aract Canyon (Huntoon, 2000). basalt at Red Butte, which is a prominent landmark on Region-scale erosion followed the withdrawal of the the Coconino Plateau that owes its existence to the basalt Kaibab-age sea; stream channels eroded as much as 60 caprock. Remnants of the Chinle Formation preserved at ft (18 m) deep into the Harrisburg Member. The stream Mount Logan 25 mi (40 km) northwest of the map area channels were subsequently filled with fluvial conglom- and at Cedar Ranch Mesa 10 mi (16 km) southeast of the erate and sandstone deposits derived from erosion of the map area, reveal that at least the lower part of the Chinle Harrisburg Member deposits. The channel-fill deposits Formation may have covered the entire map area before comprise the basal Timpoweap Member of the Moenkopi Cenozoic erosion. Formation (not shown at map scale) at scattered loca- tions throughout the map area, particularly near Redlands CENOZOIC ROCKS Ranch and Red Butte. Because many of the members of the Moenkopi Formation are not conclusively identified Laramide erosion uncovered progressively older within the map area, individual members are not mapped rocks to the south and west of the map area, including separately on this map; they are, however, mapped sepa- Precambrian basement rocks along the southwestern edge

 of the Colorado Plateau region. North-flowing paleoval- most of the cinder cone deposits being less than 1 Ma. ley and tributary drainages eroded into the Moenkopi and A 2-Ma basalt flow forms Howard Mesa at the southeast Kaibab Formations of the Coconino Plateau and were edge of the map. The oldest basalt flow, about 9 Ma, is at subsequently filled with late Paleocene and early Eocene Red Butte (Wolfe and others, 1987). fluvial conglomerate, sandstone, gravel, and silt depos- The volcanic rocks in the Mount Floyd Volca- its interbedded with local freshwater limestone deposits nic Field have not been studied in detail and this map (Young and Hartman, 1984; Young, 2001). These Ter- is the first attempt to map these rocks. Further study of tiary sediments (Ts) accumulated to an unknown thick- these rocks is required to better understand the timing ness on the Coconino Plateau before the erosion of Grand of volcanic eruption events and rock types in relation to Canyon. Remnants of these sedimentary rocks are pre- landscape development. McKee and McKee (1972) con- served beneath the Tertiary (6.5 Ma) volcanic rocks of ducted the first dating of these rocks and obtained K-Ar the Mount Floyd Volcanic Field in the southwest quarter ages of 7.03±0.4 and 14.4±0.5 Ma from a basalt flow at of the map area. Erosion of these Tertiary sediments left Long Point southwest of Tin House Ranch. However, behind a significant accumulation of scattered quartzite there is only one basalt flow at Long Point. An40 Ar/39Ar lag gravel deposits on the Coconino Plateau surfaces, age of 6.76±0.13 Ma was obtained for this project from especially near and around Rose Well Camp, Black Tank a basalt sample near Duff Brown Tank (sec. 26, T. 26 N., Camp, and upper Cataract Canyon (fig. 1). R. 3 W.) just south of Long Point and an 40Ar/39Ar age of Clasts from these lag gravels are extremely durable 6.38±0.04 was obtained from an obsidian flow that over- and some have been transported down Cataract Canyon lies the basalt flow southwest of Black Tank Camp (sec. into the Colorado River and beyond. Clasts from these 18, T. 26 N., R. 4 W.; Peters, 2002). These two ages con- gravels are well-rounded pebbles, cobbles and boulders of form to the 7.03±0.4 Ma obtained by McKee and McKee Precambrian quartzite, granite, metamorphic crystalline (1972). rocks, and Cretaceous volcanic rocks derived from south Weathering of the volcanic rocks of the Mount Floyd and southwest of the map area near Prescott, Bagdad, and Volcanic Field area produces a fine-grained decomposed Kingman, Arizona (Young, 2001). The Tertiary sediments volcanic soil deposit over extensive surficial basalt flows. here are very similar to Tertiary sediments of the Clarion This fine-grained material washed into lowland streams Formation in southern Utah, but there is no evidence that and valleys or into natural ponded basins and is the source these deposits once extended across the Grand Canyon for a distinctive variety of silt dune (Qsd) deposits. The into Utah. However, similar stratigraphy and fossils silt dunes have formed downwind on the northeast side of between the Tertiary deposits north and south of Grand dry valleys and local lakebeds. Canyon strongly suggest the deposits were continuous Other surficial deposits in the map area are- com and were deposited within a Laramide basin across the prised of landslide and associated talus deposits around Grand Canyon and have since been removed by Grand and below the volcanic outcrops of the Mount Floyd Canyon erosion (Young, 1985, 1999, 2001; Billingsley Volcanic Field and at Red Butte. Quaternary fluvial and others, 1999, 2000b; Huntoon, 2003). and eolian deposits cover much of the map area as thin The Tertiary sediments at the northern end of Long alluvial fan, terrace-gravel, sand dune, sand sheet, and Point have a slightly different composition than other mixed fluvial and eolian deposits. The alluvial deposits Tertiary sediments preserved beneath the Mount Floyd are largely unconsolidated and are the source for exten- Volcanic Field south and southeast of Long Point. At sive, thin eolian sand dune and sand sheet deposits that Long Point, the sediments contain several rhyolitic vol- cover much of the west and central part of the Coconino canic clasts and petrified wood fragments that may have Plateau. These eolian deposits are stabilized by grassy been transported down paleovalleys from the west. Some vegetation during normal and wet years but during the of the boulders within the gravelly sediments are as much recent drought (2000–2003), extensive sand dune and as 15 inches (36 cm) in diameter. The rhyolite volcanic sand sheet deposits have become mobilized, especially clasts are common in similar sediments at Thornton west of Cataract Canyon. Lookout 4 mi (6.5 km) west of the map area. STRUCTURAL GEOLOGY VOLCANIC ROCKS High-angle fault separation to nearly vertical normal- The Quaternary and Tertiary basalt flows of the San fault separation of Paleozoic and Mesozoic strata and Francisco Volcanic Field formed a protective caprock monoclines of variable dip annotations are the charac- over the Moenkopi Formation and Harrisburg Member of teristic structures in the map area. The tectonic structures the Kaibab Formation along the east and southeast part of deformed the Paleozoic and younger rocks. There are the map area. K/Ar ages from the San Francisco Volcanic two primary classes of tectonic structures: (1) compres- Field rocks are generally Pleistocene and Pliocene with sional folds in the form of broad warping of the crust

 and localized monoclines, and (2) extensional high-angle extensional tectonism in the Basin and Range Province normal faults. to the west. The result was normal faulting throughout The regional warping that caused the Kaibab Anti- the map area during Miocene(?) to Holocene (Hunt- cline northeast of the map area, Cataract Syncline through oon, 2003). Late Tertiary faulting commenced along the the center, and the Hualapai uplift to the west and south- Laramide monoclines where reactivated Precambrian west occurred during the Laramide orogeny dating from faults caused down faulting along the monoclines oppo- late Eocene to Late Cretaceous time (Naeser and others, site in offset to Laramide folding. As extension contin- 1989). This period of northeast-southwest compression ued, faulting spread to areas between the monoclines. also coincided with uplift of the Colorado Plateau. Ero- The Supai Monocline did not experience sufficient exten- sion, rather than deposition, has been the dominant pro- sion to down fault to the east; however, rifting of the area cess since the onset of Laramide uplift. west of the monocline was extreme for the region. Laramide northeast-southwest compression reac- Between the east-dipping Vishnu Monocline and tivated deeply buried favorably oriented faults in the west-dipping Supai Monocline south of Howard Hill, Precambrian basement (Huntoon, 2003). Reverse dis- a 2-mi-wide (3-km-wide) structural horst has a topo- placements along the generally north and northwest graphic relief of about 500 ft (153 m). This horst is about trending Precambrian faults produced localized mono- 8 to 10 mi (13 to 16 km) long and gradually diminishes clines—sharp step-like folds—in the Paleozoic and at its south end near Cataract Canyon. The horst structure Mesozoic overburden as it folded above the faults. The in the subsurface would likely form a barrier for north- Supai Monocline is the principle monocline that devel- west flowing ground water in all aquifers for most of its oped in the Cataract Basin area but is considered a minor length, but ground-water flows are likely to concentrate monocline owing to the small offset across it. Surface and pass through this structure along the northwest-ori- strata of the Kaibab Formation dip west an average of 8° entated joints and faults (cross section C–C´) termed the and as much as 20° in some areas. The Supai Monocline Markham Dam Fault Zone by Huntoon (2003). is unusual in that the east side is displaced up, opposite The Markham Dam Fault Zone in the center of Cata- to most of the monoclines in the western Colorado Pla- ract Basin is one of the most extensive and most active teau. Its profile indicates that the fault in the Precambrian of all extensional fault zones on the southern Colorado basement was reactivated as an east-dipping instead of Plateau (fig. 1). Huntoon (2003) states that this fault west-dipping fault. zone is broken by northwest-trending faults and grabens There are several fold structures within the map that are intersected by a few northeast-trending grabens. area that are likely to influence surface and ground water There are minor separations of Holocene(?) and Pleis- circulation. Red Horse Anticline and Syncline south of tocene alluvial deposits and numerous sinkholes that Red Butte are east-west oriented folds that are largely have developed along joints associated with the faults. In responsible for the development and control of Red addition, a cluster of northwest-trending faults, most that Horse Wash. The Red Horse Syncline has accumulated are down-to-the-west, also occur in the vicinity of Rose a general thickness of alluvium up to about 140 ft (43 m) Well Camp, 10 mi (16 km) west of the Markham Dam thick over the Moenkopi Formation that has the potential Fault Zone. The fluvial sediments in Farm Dam Draw to contain perched shallow water accumulations. This and Sandstone Wash are likely to contain local perched structure likely controls ground water flows to parallel shallow water within the alluvial deposits. The youthful- the structure from east to west along its length. ness of both the Markham Dam and Rose Well faulting is North of Red Butte, the east-west trending Skin- partly expressed by closed basin sediment accumulation ner Ridge Anticline and Syncline, a structure similar to along the downthrown side of some of the faults. Many the Red Horse Anticline and Syncline, is likely respon- of the closed topographic basins on the Coconino Plateau sible for the early development of the east-west trending in this region are also the result of minor faults and frac- Coconino Wash because Coconino Wash parallels these tures and the resulting dissolution of gypsum migrating structures for several miles. down the fractures and faults in the Toroweap and Kaibab The south limbs of the Red Horse and Skinner Ridge Formations. Low intensity earthquakes reflect continued Anticlines have a low dip that closely reflects the regional faulting in this region. dip of the Kaibab Anticline. If the stratum were tilted Extension associated with normal faults accounts back to a horizontal position, both folds would reflect for much of the late Tertiary subsidence in the center of that of a monocline. However, it is not certain if these the Cataract Syncline. Open earth cracks and sinkholes, folds occurred before uplift of the Kaibab Anticline, which capture significant volumes of surface runoff, which would make them a monocline, or as they are now, have developed along normal faults in the Kaibab For- the surface expression of an anticline and syncline. mation. The extent of topographically closed subsidence East-west extensional stresses supplanted Laramide depressions on the downthrown sides of normal faults is compression in mid-Tertiary time, coinciding with major revealed by the fact that of the 3,020 sq mi surface area

 of the Cataract Basin, 209 sq mi drains internally (Melis In the southwest quarter of the map area, other inter- and others, 1996). nal drainage basins developed in volcanic rocks and formed intermittent lakes such as Tule Lake, Red Lake, HOWARD HILL DOME Bishop Lake, and Horse Lake. These enclosed depres- Howard Hill is a stratigraphic dome about 1 mi in sions result from minor tectonism as the primary process diameter, as expressed in strata of the Harrisburg Member followed by some probable dissolution of the Tertiary of the Kaibab Formation, which rises about 200 ft (60 limestone under the volcanic rocks of the Mount Floyd m) above the surrounding plateau surface. Howard Hill Volcanic Field. Dome is herein named for Howard Hill (sec 22, T. 28 REDLANDS RANCH BASIN N., R. 1 E.) in Coconino County, 2 mi (3 km) north of Willaha, Arizona, a railroad siding of the Grand Canyon The Redlands Ranch Fault and the Supai Monocline railway. Strata around the base of the dome dip between are about 3 mi apart in the central part of the map area. 7° and 10°. A high-angle normal ring fault offsets strata Redlands Ranch is situated in a basin between these two down around the outside of the dome as much as 70 ft structures and is the lowest structural part of the Coconino (22 m). The ring fault does not completely circumvent Plateau. Remnants of the Moenkopi Formation are pre- the dome but is present on the north, east, and south side served at Redlands Ranch due, in part, to a large half- where the stratigraphic dip is the greatest. A few minor mile diameter collapse structure within the basin where normal faults strike northeast across the dome with less the Moenkopi Formation has downdropped an additional than 5 ft (1.5 m) of offset. 200 ft (60 m) into the collapse. The static water level at The dome is probably a basaltic laccolith, as shown Redlands Ranch should be higher in the Paleozoic sec- on cross section A–A´, although it hasn’t been drilled. tion than at any other part of the Coconino Plateau. The interpretation is justified because a few laccoliths of similar size are present in the San Francisco Volcanic COLLAPSE STRUCTURES Field southeast of the map area and the ring fault is simi- Inward-dipping strata characterize circular bowl- lar to ring faults in several small laccoliths in the Henry shaped depressions in the Kaibab and Moenkopi For- Mountains in southeast Utah (Hunt and others, 1953). mations. Breccia pipes underlie many such surface The intrusion at Howard Dome probably dates from the depressions. Breccia pipes are collapse structures caused 9 Ma activity that produced the lava cap at Red Butte, 10 primarily by dissolution of the deeply buried Mississip- mi (16 km) east of Howard Hill. pian Redwall Limestone. The dissolution of gypsum in the Woods Ranch Member of the Toroweap Formation INTERNAL DRAINAGES within these collapse structures enhances their surface Several areas west of Cataract Canyon have inter- bowl-shaped expression (Wenrich and Huntoon, 1989). nal surface drainage, such as at Hazen Hole Tank (fig. Drilling is required to confirm that the breccia pipes do 1). The primary cause of the internal drainage is exten- originate in the Redwall Limestone rather than from dis- sional faulting and development of structural depressions solution of gypsum in the Toroweap and Kaibab Forma- along grabens. The secondary cause of internal drainage tions. Large-scale collapse depressions ½ to 1 mi (0.8 to is the dissolution of gypsum in the Toroweap and Kaibab 1.6 km) in diameter that are likely breccia pipes at depth Formations. The gypsum is transported down numerous are at Redlands Ranch, Box K Ranch, in Coconino Wash joints and small faults forming surficial sinkhole depres- east of Cataract Canyon, and in Farm Dam Draw west of sions on the Coconino Plateau. The aerial distribution Tin House Ranch. There are 100 collapse structures plot- of sinkholes shown on the map generally delineates the ted on the Valle quadrangle. The surface expression of a extent of the Permian embayment during the regressive collapse structure on the Coconino Plateau is a large cir- phase of the Toroweap and Kaibab-age seas discussed cular patch of alluvium about a third of a mile in diameter earlier. The modern gypsum karst developed in the Har- supporting a moderate growth of sagebrush and grass in a risburg Member of the Kaibab Formation, indicated by subtle depression surrounded by ponderosa pine, pinion sinkholes on the map, is among the best developed on the pine and juniper forest. southern Colorado Plateau owing to the presence of thick Five collapse structures were drilled by Energy Fuels deposits of gypsum. The northwestward extension of the Nuclear Inc. in the Red Butte area confirming each struc- Permian depocenter is also indicated by the distribution ture is a breccia pipe at depth (Wenrich, 1992). One of of sinkholes in the Harrisburg Member on the Littlefield these drilled breccia pipes contains a significant uranium 30´ x 60´ quadrangle northwest of this map area (Billing- ore deposit. High-grade ore deposits have been mined sley and Workman, 2000). The internal drainage depres- from breccia pipes elsewhere near the Grand Canyon sions are likely excellent fracture zones for ground water area. The primary metal is uranium along with Ag, Pb, recharge to the lower aquifers. Zn, Cu, Co, and Ni (Wenrich and Huntoon, 1989). Sev-

 eral suspect features identified by Wenrich (1992) are not Qf Flood-plain deposits (Holocene)—Gray, plotted on the Valle 30´ x 60´ map because they cannot be brown, and light-red clay, silt, sand, and verified in the field. Only collapse features with inward some lenticular gravel; partly consolidated dipping strata are shown. by gypsum and calcite cement. Intertongue Minor folds, sinkholes, enclosed surface drainage or overlap young terrace-gravel (Qgy), basins, and other surface irregularities on the Coconino valley-fill (Qv), and young alluvial fan Plateau are largely due to the dissolution of gypsum and (Qay) deposits. Subject to lateral stream- gypsiferous siltstone within the Harrisburg Member of channel erosion or overbank flooding. Sim- the Kaibab Formation and to some extent, the dissolu- ilar to valley-fill deposits but form broad, tion of gypsum within the Woods Ranch Member of the flat, valley floors subject to widespread Toroweap Formation. The sinkholes are likely Holocene frequent overbank flooding. In broad flood- and Pleistocene age because they disrupt local surface plains, minor arroyo development may drainages and are commonly filled with ponded fine- occur near downstream drainage outlets. grained sediments. The deposits of gypsum in the Kaibab Support thick growths of grass, cliffrose and Toroweap Formations are thickest along a northwest- bush, and sagebrush that help to trap and southeast axial trend in the vicinity of Cataract Canyon accumulate fine-grained sediment. Subject of the ancient embayment of the Kaibab and Toroweap to temporary ponding in broad drainage Formation-age sea, as discussed earlier. As a result, many floodplains. Thickness, 6 to 20 ft (1.8 to 6 of the largest depressions occur near and west of Cataract m) Canyon. Qd Dune sand and sand sheet deposits (Holo- cene)—White to gray, fine- to coarse- ACKNOWLEDgMENTS grained, wind-blown sand. Composed of quartz and chert sand of the Harrisburg The cooperation and support of Water resource Divi- Member of the Kaibab Formation that sion of the National Park Service, Fort Collins, Colorado accumulates from young terrace-gravel and Grand Canyon National Park, Arizona are gratefully (Qgy) or valley-fill Qv ( ) sources. Form appreciated. We also appreciate the advice, revisions, and shallow sand dune or thick sand sheet information of Paul Umhoefer, Northern Arizona Uni- deposits. Commonly occur as lumpy, unde- versity, Flagstaff, Arizona; Peter W. Huntoon, Boulder fined sand dune shapes or thick to thin sand City, Nevada; Charles L. Powell II, and Theresa Iki, of sheet deposits on floodplain (Qf) and young the U.S. Geological Survey, Menlo Park, Calif., for their terrace-gravel (Qgy) deposits along Sand- technical advice and assistance in the preparation of this stone Wash, Rodgers Draw, and Farm Dam map and report. Draw in west-central part of map area, and minor deposits along Coconino Wash and Red Horse Wash in northeast part of map DESCRIPTION OF MAP UNITS area. Include climbing and falling dunes or SURFICIAL DEPOSITS thick sand accumulations on gentle slopes of bedrock outcrops adjacent to large drain- Holocene, Pleistocene, and Pliocene(?) surficial deposits are ages. Sand locally transported northeast differentiated from one another chiefly on the basis of differ- by southwesterly winds, especially along ences in morphologic character and physiographic position Sandstone Wash and Farm Dam Draw observed on 1974 black and white aerial photographs and where stream channels are wide and sandy. from field observations. Older alluvial and eolian deposits Include sand dune or sand levees along generally exhibit extensive erosion and have greater topo- southwest edge of extensive sand sheet graphic relief, whereas younger deposits are either actively (Qss) deposits and along southwest edge of accumulating material or are lightly eroded extensive young mixed alluvium and eolian Qaf Artificial fill and quarries (Holocene)—Allu- (Qae) deposits where topography flattens vium and bedrock material excavated from to prairie-like conditions. Sand dune and bar-pits and trenches to build livestock sand sheet deposits are mostly hidden or tanks, drainage diversion dams, roads, and covered by forest growths in the forested other construction projects. Include copper lands near Tusayan, Arizona, Coconino mine excavations and mine dumps south- Wash, and Red Butte areas. Deposits largely west of Tusayan and west of State Highway absent in southeast third of map area due to 64. Does not include all highway road cuts volcanic rock outcrops. Support moderate and roadbed fill growth of grass in southwest part of map

 area and sagebrush, pinion pine, juniper, of valley-fill (Qv) and young terrace-gravel and ponderosa pine woodlands in northeast (Qgy) deposits. Surfaces are partly eroded map area. Thickness, 3 to 20 ft (1 to 6 m) and cut by small arroyo erosion. Surface has Qgy Young terrace-gravel deposits (Holocene)— thin sandy calcrete soil mixed with large Light-brown, pale-red, and gray, poorly cobbles and boulders of basalt near Mount sorted fluvial mud, silt, sand, gravel, peb- Floyd Volcanic Field. Subject to extensive bles, cobbles, and boulders. Composed sheet-wash erosion and flash flood debris mainly of subangular to well-rounded Paleo- flows. Support moderate growth of high zoic sandstone, limestone, and chert clasts desert shrubs, sagebrush, cactus, and grass. of local origin. Include well-rounded clasts Thickness, 3 to 25 ft (1 to 7.5 m) of quartzite, quartz, assorted metamorphic Qps Ponded sediments (Holocene and Pleisto- crystalline rocks, and well-rounded volca- cene(?))—Gray to brown clay, silt, sand, nic rocks derived from Tertiary sediments and lenses of gravel. Locally include small (Ts), southwest and southeast part of map chert and limestone fragments or pebbles. area. Interbedded silt, sand, gravel, and peb- Similar to floodplain Qf ( ) deposits but bles to boulders are partly consolidated by occupy natural internal drainage depres- gypsum and calcite cement. Locally over- sions and man-made stock tank areas. Inter- lap young alluvial fan (Qay) and valley-fill nal drainage sinkhole ponded sediments are (Qv) deposits. Little to moderate vegeta- common in northwest quarter of map area. tion in terrace-gravel deposits; primarily Accumulate in several small areas within grass and sagebrush. Contact with adjacent sand dune and sand sheet deposits near alluvial and eolian deposits is approximate. Farm Dam Draw, many too small to show Subject to flash flood and sheet wash ero- at map scale. Desiccation cracks common sion. Form fluvial terrace benches about 3 on dry playa-like hardpan surfaces restrict to 40 ft (1 to 12 m) above stream drainages. plant growth. Lake beds in the Mount Floyd Deposit intertongues with landslide (Ql) and Volcanic Field area are dry most of the time talus and rock fall (Qtr) deposits in Cata- and are source areas of silt for silt dune ract Canyon. Unit fills erosion channels cut (Qsd) deposits. Support little or no veg- into bedrock and young alluvial fan (Qay) etation or minor growths of seasonal grass. deposits. Support moderate growth of local Thickness, 5 to 35 ft (1.5 to 11 m) shrubs, sagebrush, and grass. Thickness, 3 Qss Sand sheet deposits (Holocene and Pleis- to 40 ft (1 to 12 m) tocene(?))—White, brown, and gray, Qay Young alluvial fan deposits (Holocene)— fine- to coarse-grained wind-blown sand. Gray-brown silt, sand, gravel, and some Composed primarily of quartz and feld- boulders. Clasts are subangular to rounded spar grains derived from erosion of Tertiary limestone, chert, and sandstone locally sediments (Ts) in southwest half of map derived from Mesozoic and Paleozoic out- area. Composed of quartz grains and small crops of the Moenkopi and Kaibab Forma- chert fragments derived from Harrisburg tions. Include medium- to coarse-grained Member of the Kaibab Formation in central sand and gravel to well-rounded pebbles of part of map area. Form extensive deposits quartzite and quartz derived from Tertiary over gently sloping terrain of flat prairie- sediments (Ts); basalt, andesite, rhyolite, land topography downwind (northeast) of and obsidian clasts and fragments from the sand dune deposits in southwest and central Mount Floyd Volcanic Field in southwest part of map area. Intertongue with young part of map area and rounded to subrounded mixed alluvium and eolian (Qae) deposits clasts and fragments of basalt from the San and old mixed alluvium and eolian (QTae) Francisco Volcanic Field in southeast part deposits. Arbitrary and gradational lateral of map area. Include subrounded to angu- and vertical contact between sand sheet lar basalt clasts from Red Butte in northeast (Qss) and sand sheet and dune (Qd) depos- quarter of map area. Partly consolidated by its based on morphologic interpretation of silt, gypsum, and calcite. Overlapped by aerial photographs. Only most extensive ponded sediments (Qps), floodplain (Qf), deposits shown. Support moderate growth sand sheet and dune (Qd), and sand sheet of grass and small high-desert shrubs. (Qss) deposits. Intertongue with upper part Thickness, 1 to 10 ft (0.3 to 3 m)

 Qsc Eolian and fluvial silt deposits (Holocene and face has thin upper calcrete soil that forms Pleistocene(?))—Brown to medium-gray flat rocky and sandy surface near Mount clay, silt, and fine-grained sand composed of Floyd Volcanic Field outcrops. Include decomposed and weathered volcanic rock. numerous basalt clasts from Mount Floyd Similar to eolian silt dune (Qsd) deposits Volcanic Field in southwest quarter of map except they are thinner, widespread, and area. Commonly overlapped by or inter- restricted to the Mount Floyd Volcanic tongue with talus and rock fall (Qtr), land- Field area. Silt and clay matter is primarily slide (Ql), and young alluvial fan (Qay) derived from weathered volcanic rock that deposits. Support moderate growth of grass, has accumulated as fine-grained silt and sagebrush, cactus, cliffrose bush, and some sand in young terrace-gravel (Qgy), valley- scattered pinyon and juniper trees. Thick- fill Qv( ), ponded sediments (Qps), and silt ness, 5 to 25 ft (1.5 to 7.5 m) dune (Qsd) deposits transported down- Qtr Talus and rock fall deposits (Holocene and wind (northeasterly) onto nearby slopes of Pleistocene)—Brown, gray, slope-form- basaltic and andesitic pyroclastic depos- ing, unsorted mixture of mud, silt, sand, its. Gradational and arbitrary contact with pebbles, cobbles, and very large broken adjacent alluvial or eolian deposits. Include boulders. Form talus debris slopes in Cata- unsorted fragments of small pebbles and ract Canyon and below volcanic outcrops cobbles derived from local basalt, rhyolite, of the Mount Floyd Volcanic Field and Red or obsidian, and pyroclastic deposits. Partly Butte. Include individual car- and house- consolidated by calcite and clay cement. size basalt boulders at Red Butte and Long Form extensive thin deposits downwind of Point areas. Clasts are mostly angular to young alluvial fan (Qay) deposits. Form subangular. Gradational and arbitrary con- thin veneer over most volcanic rocks in the tact with landslide (Ql), young alluvial Mount Floyd Volcanic Field area where fan (Qay), floodplain (Qf), young terrace- only thickest and most extensive depos- gravel (Qgy), and valley-fill (Qv) deposits. its are shown. Support moderate to thick Subject to extensive sheet-wash erosion, growth of grass, sagebrush, some cactus, flash-flood debris flows, and arroyo erosion. and scattered pinion/juniper woodlands. Only thick or extensive deposits shown. Thickness, 1 to 25 ft (0.3 to 7.5 m) Thickness, 1 to 25 ft (0.3 to 7.5 m) Qae Young mixed alluvium and eolian deposits Ql Landslide deposits (Holocene and Pleisto- (Holocene and Pleistocene(?))—Gray, cene)—Unconsolidated to partly con- light-red and brown clay, silt, and fine- to solidated masses of unsorted rock debris. coarse-grained sand interbedded with lenses Include detached blocks that have rotated of coarse-grained gravel. Include white backward and slid downslope as loose inco- angular chert fragments. Formed by wind- herent masses of broken rock and deformed and water-transported sediment by fluvial or strata. Include talus debris, rock glaciers, eolian processes resulting in an interbedded and rock-fall debris on lower slopes, adja- accumulation of alluvial and eolian depos- cent to, and below landslide masses. Some its. Deposit subject to sheet wash erosion in landslide blocks may become unstable in wet conditions, eolian sand accumulation in very wet conditions. Only large landslide dry conditions. Commonly occupy broad blocks are shown. Many small landslide flatland or gently sloping topography down- masses commonly found below cliffs of wind (northeast) of tributary drainages and volcanic rock of the Mount Floyd Volcanic valleys in northwest two-thirds of map area. Field, Red Butte, and around edges of the Often overlapped by sand sheet (Qss) or San Francisco Volcanic Field. Thickness, sand sheet and dune (Qd) deposits. Support 10 to 200 ft (3 to 60 m) thick to moderate growth of grass, cactus, Qsd Silt dune deposits (Holocene and Pleisto- and local high desert shrubs. Thickness, 1 to cene)—Brown and medium-gray clay, silt, 6 ft (0.3 to 1.8 m) and fine-grained sand composed of decom- Qao Old alluvial fan deposits (Holocene and Pleis- posed and weathered volcanic rock. Include tocene)—Lithologically similar to young subrounded to angular fragments of pebbles alluvial fan (Qay) deposits; partly consoli- and cobbles of local basalt rocks about 4 to dated by calcite and gypsum cement. Sur- 6 inches (9.6 to 14.5 cm) in diameter and as

10 much as 1 ft (0.3 m) in diameter. The basal- outcrops or small mesas about 30 ft (9 m) tic rocks are randomly scattered within and above young terrace-gravel (Qgy) depos- on silt dunes. High winds during wet condi- its and about 120 ft (37 m) above modern tions may have blown basalt rocks across drainage of Cataract Canyon near Redlands flat slick muddy lake surfaces and up onto Ranch. Deposits near Redlands Ranch were slick muddy dune surfaces. Source for silt once part of thicker and more widespread dunes is locally derived from dry lake sur- deposits along Cataract Canyon, now faces of ponded sediments (Qps), such as largely removed by modern erosion. Thick- Red Lake, Tule Lake, Bishop Lake, Horse ness, 10 to 20 ft (3 to 6 m) Lake, and several unnamed dry lakes and ponds in the Mount Floyd Volcanic Field VOLCANIC ROCKS and transported by southwesterly winds to Volcanic rocks of the San Francisco Volcanic accumulate on northeast shores of lakes and Field (Pleistocene, Pliocene, and Mio- ponds. Support little to no vegetation due to cene)—Volcanic rocks of the San Fran- heavy silt and clay content. Thickness, 6 to cisco Volcanic Field are defined, in part, by 80 ft (1.8 to 25 m) Wolfe and others (1987) Qv Valley-fill deposits (Holocene and Pleisto- QTi Intrusive dike or plug (Pleistocene and cene)—Gray and light-brown silt, sand, Pliocene; Matuyama age)—Dark-gray and lenses of gravel; partly consolidated aphyric basalt and microporphyritic olivine by gypsum and calcite cement. Include basalt. Includes welded pyroclastic frag- occasional rounded clasts of limestone, ments. Source for pyroclastic cones (QTp) subrounded to angular chert, and sub- and basalt flows QTb ( ). Specific dikes or rounded to angular basalt. Intertongue or plugs are 5 to 15 ft (1.5 to 4.5 m) wide overlap young alluvial fan (Qay) deposits QTp Pyroclastic deposits (Pleistocene and Plio- and young terrace-gravel (Qgy) depos- cene; Matuyama age)—Dark-gray to red its. Sediment accumulation is the result of cinders, agglutinated spatter, bomb and low-energy and low-gradient stream flows. ribbon fragments; yellow-brown to red- Subject to sheet-wash flooding and tempo- brown where weathered. Cones rounded, rary ponding where vegetation is thickest. somewhat subdued, little dissected although Support moderate growth of grass in lower superficially gullied. Thickness, 200 to 400 elevations in central area of map, and heavy ft (60 to 122 m) sagebrush, grass, cactus, and some juniper QTb Basalt flows (Pleistocene and Pliocene; trees at higher elevations, generally above Matuyama age)—Dark-gray, yellow- 6,000 ft (1,830 m). Thickness, 3 to 12 ft (1 brown to brown, aphyric and slightly por- to 3.7 m) phyritic basalt and microporphyritic olivine QTae Old mixed alluvium and eolian deposits basalt; surfaces mostly smooth, relatively (Pleistocene and Pliocene(?))—Lithologi- flat, undissected. Includes thin, interbedded cally similar to young mixed alluvium and pyroclastic deposits near pyroclastic cone eolian (Qae) deposits, but often capped by areas. Thickest near flow margins in some thin poorly developed calcrete soil; forms areas. Thickness, 30 to 200 ft (9 to 60 m) thicker deposits than young mixed alluvium QTai Basalt and andesite dikes and necks (Pleis- and eolian (Qae) deposits. Include small tocene and Pliocene; Matuyama age)— cobbles and boulders. Form flat mesa-like Dark-gray intersertal to subophitic basalt benches about 30 to 120 ft (9 to 37 m) with abundant phenocrysts of clinopyrox- above modern drainage erosion in central ene, plagioclase, and sparse olivine and part of map area. Unit is overlain in part by hornblende. Source for Quaternary/Tertiary sand sheet and dune (Qd) and sand sheet basaltic and andesite flows and pyroclastic (Qss) deposits in central and west half of deposits. Dikes and necks are 1 to 4 ft (0.5 map area. Thickness, 10 to 20 ft (3 to 6 m) to 1.3 m) wide QTg Old terrace-gravel deposits (Pleistocene QTap Basalt and andesite pyroclastic deposits and Pliocene(?))—Lithologically similar (Pleistocene and Pliocene; Matuyama to young terrace-gravel (Qgy) deposits age)—Dark-gray intersertal to subophitic but dominated by well-rounded quartzite pyroclastic deposits. Weathers light yellow- pebble and cobble clasts. Form isolated brown. Contain abundant phenocrysts of

11 clinopyroxene and plagioclase in glassy includes plagioclase-phyric, aphyric, and groundmass. Form small pyroclastic cones slightly porphyritic basalt. Smooth surfaced, and isolated pyroclastic deposits. Thick- partly dissected. Composed of plagioclase, ness, 20 to 200 ft (6 to 60 m) clinopyroxene, olivine, and opaque oxides. QTab Basalt and andesite flows (Pleistocene and Thickness less than 90 ft (28 m) Pliocene; Matuyama age)—Dark-gray Trb Basalt flow of Red Butte (Miocene)—Dark- intersertal to subophitic basalt, with or gray olivine basalt. Weathers brown; mas- without glass; partly blocky, hummocky, sive flow. K/Ar age, 8.92±0.23 Ma (Wolfe locally gullied. Weathers yellow-brown to and others, 1987), 9.73±0.91 Ma and brown. Contains abundant phenocrysts of 8.78±0.22 Ma (Reynolds and others, 1986). clinopyroxene and plagioclase, subordi- Forms basalt caprock over thin soil deposit nate phenocrysts of orthopyroxene, sparse 3 to 5 ft (1 to 1.5 m) thick that was baked to phenocrysts of olivine and hornblende and a bright red; also partly overlies Shinarump scattered rounded quartz grains with clino- Member of the Chinle Formation where soil pyroxene reaction rims. Groundmass is is not present. Source of basalt is not pres- mostly fine grained or glassy and contain ent in the immediate vicinity of Red Butte plagioclase microlites, opaque oxide, and and is assumed to be a dike under the basalt small crystals of clinopyroxene. Thickness, flow or is covered by surrounding landslide 80 to 300 ft (25 to 92 m) (Ql) deposits. Thickness, 165 ft (50 m) Thma Andesite flows of Howard Mesa (Plio- Volcanic rocks of the Mount Floyd Volcanic cene)—Dark-gray to gray-black andesite; Field (upper Miocene)—Volcanic rocks in includes two lobes extending into map area the southwest part of the map area repre- from the south. Contains scattered pheno- sent the northern part of the Mount Floyd crysts of plagioclase and quartz 1/8 inch in Volcanic Field and have not been studied diameter. Plagioclase is intensely corroded; in detail. Paleomagnetic ages have not been quartz is less abundant, is corroded and has determined. Hand specimens have been pyroxene reaction rims. Groundmass is identified in the field during the course of hyalocrystalline consisting of glass, plagio- this mapping project and are assigned tem- clase microlites, hornblende prisms altered porary rock unit descriptions that are sub- to opaque oxide, and other opaque grains. ject to change pending future investigations. K/Ar age, 2.06±0.18 Ma, polarity reversed A suggested general 40Ar/39Ar age for the (Wolfe and others, 1987). Thickness, 200 ft northern part of the Mount Floyd Volcanic (60 m) or more Field is 6.76±0.13 Ma and 6.38±0.04 Ma Tyi Young intrusive rocks (Pliocene; Gauss or (Peters, 2002) Gilbert age)—Dark-gray basalt and mixed Tri Rhyolite, rhyodacite, and obsidian dikes, pyroclastic dikes and necks. Composed of necks, and vent areas (upper Miocene)— plagioclase, clinopyroxene, olivine, and Red, gray, and black rhyolite and rhyo- opaque oxides. Intrusives from 4 to 20 ft dacite. Rhyolite exhibits convoluted and (1.2 to 6 m) wide twisted thin platy flow patterns; weathered Typ Young pyroclastic deposits (Pliocene; outcrops resemble roof shingles. Map con- Gauss or Gilbert age)—Dark-gray to red tacts are approximate because erosion has cinder and spatter fragments; weather yel- not fully exposed extent of these intrusive lowish-brown, brown, or reddish-brown. features. Vent area is source for extensive Composed of clinopyroxene and olivine rhyolite, rhyodacite, and obsidian flows that phenocrysts, plagioclase, opaque oxides, overlie older basalt flows east of Red Lake. and glass. Mass wasting has diminished Include dikes and flows of black, gray, and slope angles of pyroclastic cones; flanks red obsidian within vent areas are gullied to extensively eroded. Cones are Tr Rhyolite, rhyodacite, and obsidian flows elongated and aligned along a northwest (upper Miocene)—Light gray, dark red, trend in the Four Hills area indicating the and grayish-black. Obsidian flows are influence of bedrock fractures and bedrock mostly black obsidian but often contain joints on vent position and orientation. black and gray-banded obsidian or red to Thickness, 30 to 200 ft (9.2 to 60 m) red and black obsidian east of Red Lake and Tyb Young basalt flows (Pliocene; Gauss or Gil- southwest of Black Tank Camp (sec. 18, T. bert age)—Medium- to dark-gray basalt; 26 N., R. 4 W.). 40Ar/39Ar age, 6.38±0.04

12 Ma (Peters, 2002). Flows overlie one or snail fossils (Young and Hartman, 1984; more olivine basalt flows Tba( ). Thickness, Young, 2001). Thickest limestone beds are 30 to 200 ft (9.2 to 60 m) near Black Tank Camp (sec. 3, T. 26 N., R 4 Ti Basalt and andesite dikes, plugs, and necks W.) and at Duff Brown Tank (sec. 28, T. 26 (upper Miocene)—Dark-gray, finely crys- N., R. 3 W.). Conglomerate beds are thick- talline alkali-olivine basalt. Contains augite est at the base of sedimentary rocks and and olivine phenocrysts in glassy ground- are partly consolidated thin units within mass. Intrusive units align in north or north- the sedimentary sequence. Conglomerate west trend, which parallel local prominent clasts consist primarily of quartzite, chert, north and northwest strike of near-vertical and minor granite or metamorphic crystal- fractures, joints, and faults in bedrock strata line rocks derived from sources south of of the Coconino Plateau area. Dikes are 2 to map area as far away as Prescott and King- 30 ft (0.6 to 9.2 m) wide; necks are as much man, Arizona. Clasts are well rounded and as 100 ft (30 m) in diameter. Includes hypo- weather out of the general slope deposit and thetical laccolithic intrusion beneath Howard form extensive lag gravel deposits within Hill as shown on cross section A–A´ several miles of outcrop. Several outlying Tp Pyroclastic deposits (upper Miocene)—Red hills are covered by lag gravel conglom- and reddish-gray cinders, scoria, ash, and erate derived from the erosion of Tertiary glassy fragments of basalt, partly unconsol- sedimentary rocks north of the Mount idated. Form pyroclastic cones that overlie Floyd Volcanic Field. Extensive conglom- associated basalt and andesite flows (Tba). erate and sandstone deposits form rounded Cones are extensively eroded and gullied. hills or ridges in the Rose Well Camp vicin- Thickness, 20 to 400 ft (6 to 122 m) ity. Rocks of the Mount Floyd Volcanic Tba Basalt and andesite flows (upper Mio- Field form a protective caprock over these cene)—Dark- to light-gray, finely crystal- Tertiary sedimentary rocks throughout the line alkali-olivine basalt. Most of the basalt southwest quarter of the map area. Thick- came from elongated fissure dikes (Ti) and ness, 60 to 180 ft (18 to 55 m) vent areas beneath pyroclastic cone deposits ^cs Shinarump Member of the Chinle Formation (Tp). Basalt flowed onto flat, partly eroded (Upper Triassic)—White, coarse-grained, Tertiary sedimentary rocks of freshwater cliff-forming, low-angle crossbedded sand- limestone, sandstone, and siltstone (Ts). stone and pebble conglomerate. Unit is Several basalt flows merge or coalesce into overlain by thin soil that is baked brick red one large flow suggesting an eruptive phase by overlying basalt flow at Red Butte. Sand- of a similar time; 40Ar/39Ar age, 6.76±0.13 stone and conglomerate is partly baked red Ma (Peters, 2002) at Duff Brown Tank (sec. by basalt flow where basalt is in direct con- 28, T. 26 N., R. 3 W.). Thickness, 25 to 300 tact. Disconformable contact with underly- ft (7.5 to 92 m) ing red siltstone and sandstone beds of the Moenkopi Formation. Unit is likely part SEDIMENTARY ROCKS of a paleovalley filled with fluvial deposits Cenozoic, Mesozoic, and Paleozoic sedimentary rock. that make up the Shinarump Member of the Tertiary rocks include siltstone, sandstone, and freshwa- Chinle Formation. Thickness, 85 ft (26 m) ter limestone (Ts) deposits beneath the volcanic rocks of ^m Moenkopi Formation (Upper(?) and Lower the Mount Floyd Volcanic Field and areas west of Rose Triassic)—Red, slope-forming, fine- Well Camp, southwest third of map area. The Tertiary grained, thin-bedded shaley siltstone and age sedimentary rocks are not formally named. sandstone. Includes a white, cliff-forming, Ts Sedimentary rocks (lower Eocene and upper coarse-grained, low-angle crossbedded Paleocene)—Light-red, gray, and white sandstone in lower quarter of unit that may interbedded siltstone, sandstone, arkosic be equivalent to the Moki Member of the gravel, lenticular conglomerate, and gray, Moenkopi Formation east of the map area, or thin-bedded [1 to 3 ft (0.5 to 1 m)] freshwa- the Shnabkaib Member of the Moenkopi For- ter limestone. Limestone beds contain long mation north of the map area. Unit is mostly vertical tubular structures generally ½ inch eroded from map area except for outcrops (0.12 cm) in diameter and 2 ft (1.3 m) in beneath volcanic rocks in southeast quarter, length and early Eocene to late Paleocene isolated outcrops in southwest part of map

13 in the vicinity of Valle, Arizona, and at Red cracks represent a shallow marine tidal Butte. A complete section of the Moenkopi flat subject to extensive dry conditions Formation is present only at Red Butte. The during the late part of Kaibab Formation basal Timpoweap Member of the Moenkopi deposition. Lower part is yellowish-gray Formation (unit not mapped) is a conglom- to pale-red gypsiferous siltstone and cal- eratic limestone or calcareous sandstone careous sandstone; gray thin-bedded sandy with small chert-conglomerate pebbles that limestone; and gray to white, thick-bedded occupy shallow Triassic channels eroded gypsum in the vicinity of Cataract Canyon into underlying Harrisburg Member of the and northwest half of map area. Dissolution Kaibab Formation in eastern quarter of the weathering of gypsum beds within lower map area (mapped as Moenkopi Formation part has resulted in warping and bending ^m). Channels that are too small to show at of limestone beds in middle part into or map scale are exposed along Spring Valley near local drainages on the Coconino Pla- Wash and on private ranch lands just east of teau. Gypsum dissolution within the Har- State Highway 64 and are as much as 50 ft risburg Member of the Kaibab Formation (15 m) deep. Other channel exposures are is also responsible for the development of east of Red Butte, along Red Horse Wash on several large-scale sinkhole depressions U.S. Forest Service lands southeast of Red and internal drainage basins such as Hazen Butte, along State Highway 64 southwest Hole Tank, northwest half of map area. of Red Butte just north of Red Horse Wash, Dissolution of gypsum beds in underly- and southwest of Redlands Ranch. Unit ing Toroweap Formation may be partly is distinguished from underlying red silt- responsible for several internal drainage stone and sandstone beds of the Harrisburg basin depressions in northwest half of map Member of the Kaibab Formation (Pkh) by area, especially in the vicinity of collapse its darker red color and thin-bedded, platy, structures. Contact with underlying Fossil coarse-grained sandstone beds as opposed Mountain Member of the Kaibab Forma- to massive-bedded, pale-red, undulating, tion is gradational and arbitrarily marked at siltstone and sandstone beds of the Har- top of thick, white, cherty limestone zone risburg Member of the Kaibab Formation. near top of limestone cliff in canyon profile. Forms unconformable contact with under- Thickness, 120 ft (37 m) in northeast quar- lying Harrisburg Member of the Kaibab ter of map thickening to about 260 ft (80 m) Formation representing the regional Perm- in west half of map ian/Triassic boundary. Thickness, 1,000 ft Pkf Fossil Mountain Member—Light-gray, (305 m) cliff-forming, fine- to medium-grained, Kaibab Formation (Lower Permian)— thin- to thick-bedded [1 to 6 ft (0.3 to 1.8 Includes, in descending order, Harrisburg m)], fossiliferous, sandy, cherty limestone. and Fossil Mountain Members as defined Weathers dark gray. Unit characterized by by Sorauf and Billingsley (1991) gray to white fossiliferous chert nodules Pkh Harrisburg Member—Reddish-gray and and white chert lenses parallel to limestone brownish-gray, slope-forming gypsum, bedding; chert weathers dark gray to black. siltstone, sandstone, and thin-bedded lime- Some chert nodules contain concentric stone. Includes yellowish-gray fossiliferous black and white bands. Includes brecciated sandy limestone at top of unit that is eroded chert beds 4 to 10 ft (1.2 to 3 m) thick in from much of the map area. A gray, thin- upper part near contact of overlying Har- bedded, fossiliferous cherty limestone and risburg Member of the Kaibab Formation. sandy limestone in middle part of unit form Chert makes up about 20 percent of unit much of the surface bedrock in the central and becomes sandier in northeast quar- map area. Calcareous sandstone beds west ter of map area. Generally forms cliff at of and near Cataract Canyon have large- rim of Grand Canyon (Cataract Canyon) scale dessication cracks up to 2 ft (0.6 m) overlain by thin cover of gray to red silt- wide filled with reworked calcareous sand- stone and sandy limestone beds of Har- stone that form resistant polygon patterns risburg Member. Unconformable contact averaging about 14 ft (4.3 m) in diameter; with underlying Woods Ranch Member of the patterns on aerial photos resemble the the Toroweap Formation (Pt) attributed to surface of a golf-ball. These dessication solution erosion and channel erosion; aver-

14 age channel relief about 10 ft (3 m). Some of crossbedded sandstone equivalent to channels have eroded as much as 150 ft (46 the Coconino Sandstone, which is mapped m) into Woods Ranch Member just north separately. Includes yellowish-gray to red, of map area at National and Mohawk Can- thin-bedded sandstone below Coconino yons (Billingsley, 2000). Erosion channels Sandstone tongue in the western Grand are filled with sandy cherty limestone typi- Canyon area; these beds thin eastward cal of the Fossil Mountain Member strata, across the map area allowing the Coconino which provides an extra thickness of the Sandstone to unconformably overlie the Fossil Mountain section. Thickness, 230 ft Hermit Formation in the central and east- (70 m) in east half of the map, thickening to ern Grand Canyon areas. Forms slope or about 300 ft (92 m) in west half recess between cliff-forming Brady Canyon Pt Toroweap Formation, undivided (Lower Member and cliff-forming Coconino Sand- Permian)—Includes, in descending order, stone (Pc) in west half of map area, and Woods Ranch, Brady Canyon, and Selig- slight recess at base of Coconino Sandstone man Members, undivided, as defined by at contact of red sandstone and siltstone of Sorauf and Billingsley (1991). the Hermit Formation. Coconino Sandstone Woods Ranch Member is gray and light- intertongues within lower part of Selig- red, slope-forming gypsiferous siltstone man Member (Fisher, 1961; Schleh, 1966; and silty sandstone, interbedded with white Rawson and Turner, 1974; and Billingsley laminated gypsum beds and thin-bedded and others, 2000a). Thickness, 30 ft (9.2 m) gray limestone. Gypsum beds are as much in east half of map, increasing to 55 ft (17 as 10 ft (3 m) thick. Unit as a whole weath- m) in west half ers reddish gray. Bedding locally distorted Pc Coconino Sandstone (Lower Permian)—Tan due to dissolution of gypsum. Contact to white or pale-red, cliff-forming, fine- with underlying Brady Canyon Member is grained, well-sorted, crossbedded quartz gradational and arbitrarily marked at top sandstone. Contains large-scale, high- of cliff-forming limestone beds of Brady angle, planar crossbedded sandstone sets Canyon. Unit commonly thins to less than that average about 35 ft (11 m) thick. 20 ft (6 m) thick in vicinity of large collapse Locally includes small and large fossil structures due to dissolution of gypsum. footprints and low-relief wind ripple marks Variable thickness owing to dissolution of on crossbedded planar sandstone surfaces. gypsum and channel erosion in upper part; The lower and upper [5 to 20 ft (1.5 to 6 m)] average thickness, 65 ft (20 m) in north- intertongues with thin-bedded, partly calcar- central part of map, thickens to 200 ft (60 eous, flat-bedded sandstone beds of Selig- m) in west half of map, thins to less than 50 man Member of the Toroweap Formation ft (15 m) in southeast quarter of map. in western Grand Canyon area (Billingsley Brady Canyon Member is gray, cliff-form- and others, 2000a; Billingsley, 2000; Bill- ing, thin- to medium-bedded [1 to 5 ft (0.5 ingsley and others, 2001; Billingsley and to 1.5 m)], fine- to coarse-grained, fetid, Wellmeyer, 2003). Coconino Sandstone is fossiliferous limestone. Weathers dark gray. mapped separately from Toroweap Forma- Includes thin-bedded dolomite in upper and tion because it forms a mappable unit and lower part. Contains white and gray chert is an established unit of the Grand Canyon nodules that make up less than 8 percent nomenclature. Unconformable contact with of unit. Contact with underlying Seligman underlying Hermit Formation (Ph) in the Member is gradational and arbitrarily placed central and eastern Grand Canyon area as at base of cliff-forming limestone of Brady a sharp planar contact with erosional relief Canyon. Thickness, 40 ft (12 m) in northeast less than 3 ft (1 m) but locally as much as 8 half of map area, increasing to about 130 ft ft (2.5 m). Thickness of Coconino increases (40 m) at northwest edge of map as exposed from 150 (46 m) to over 500 ft (153 m), west in Grand Canyon (Billingsley, 2000; Bill- to east in subsurface of map area according ingsley and Wellmeyer, 2003). to exposures in Grand Canyon north of map Seligman Member is gray, light-purple, area and several miles south of map area yellowish-red, slope-forming, thin-bedded Ph Hermit Formation (Lower Permian)—Red, dolomite, limestone, sandstone, gypsum, slope-forming, fine-grained, thin-bedded and calcareous sandstone. Includes a unit siltstone and sandstone. Upper part contains

15 red, massive, low-angle crossbedded calcar- and high-angle sets. Unconformable con- eous sandstone and siltstone beds. Dark-red tact with underlying Wescogame Forma- crumbly siltstone beds fill shallow erosion tion marked by erosion channels as much channels. Siltstone beds form recesses as 50 ft (15 m) deep filled with calcareous between thicker light-red sandstone beds. sandstone and limestone conglomerate; Unit locally contains poorly preserved plant average channel depth about 35 ft (11 m) in fossils within channel fill deposits in lower Cataract Canyon, north of map area. Ero- part of formation. Sandstone beds thicken sion of Cataract Canyon has not extended and thin laterally either as channel fill or completely through Esplanade Sandstone. low-angle crossbedded sand dune or stream Total thickness in Cataract Canyon north of channel accumulations. Sandstone bleaches map area is 400 to 450 ft (122 to 137 m); to yellowish-white at upper contact with Billingsley, 2000). Incomplete exposure in Coconino Sandstone (Pc). Unconform- map area; thickness, 120 ft (37 m) ably overlies Esplanade Sandstone (Pe) with erosion channels generally less than UNITS SHOWN ONLY IN CROSS SECTION 10 ft (3 m) in depth. Some channels are as [Based on exposures in Grand Canyon ½ to 20 mi north of the much as 130 ft (40 m) and commonly 30 map area (Billingsley, 2000), northwest of map area (Billings- ft (9.2 m) deep in lower Cataract Canyon ley and Wellmeyer, 2003), and west of map area (Billingsley area just north of map area (Billingsley, and others, 2000b] 2000). Otherwise, erosional relief is gener- *Ms Wescogame (Upper Pennsylvanian), ally less than 10 ft (3 m) between channel Manakacha (Middle Pennsylvanian), areas. Unit thins south and east of Cataract and Watahomigi Formations (Lower Canyon to less than 260 ft (80 m) in south- Pennsylvanian and Upper Mississip- east part of map based on thinning of unit in pian), undivided—Wescogame Forma- Grand Canyon (Billingsley, 2000); thickens tion is light-red, pale-yellow, and light-gray west and north of Cataract Canyon to 850 upper slope unit and lower cliff unit. Upper ft (260 m); Billingsley and others, 2000b; slope consists mainly of dark-red, fine- Billingsley and Wellmeyer, 2003) grained siltstone and mudstone interbedded Supai Group (Lower Permian, Upper, Middle, with light-red, coarse-grained calcareous and Lower Pennsylvanian, and Upper sandstone and dolomitic sandstone and Mississippian)—Only the Esplanade Sand- conglomerate. Lower cliff consists mainly stone of the Supai Group is exposed in map of light-red to gray, high-angle, large- and area. Units beneath the Esplanade Sand- medium-scale, tabular-planar crossbedded stone are exposed in Grand Canyon north sandstone and calcareous sandstone sets as of the map area. The Supai Group includes, much as 40 ft (12 m) thick. Includes inter- in descending order, Esplanade Sandstone bedded dark-red, thin-bedded siltstone in (Lower Permian), Wescogame Formation upper part of cliff. Unconformable contact (Upper Pennsylvanian), Manakacha For- with underlying Manakacha Formation mation (Middle Pennsylvanian), and Wata- marked by unconformity of erosion chan- homigi Formation (Lower Pennsylvanian nels as much as 80 ft (25 m) deep in west- and Upper Mississippian) as defined by ern part of map area and less than 30 ft (9 McKee (1975, 1982). Age of Watahomigi m) deep in eastern part of map area. Chan- Formation is defined by Martin and Barrick nels commonly filled with limestone/chert (1999). Divided into Esplanade Sandstone conglomerate. The Wescogame Formation (Pe); and Wescogame, Manakacha, and thickens slightly from west to east, averag- Watahomigi Formations, undivided (*Ms) ing about 130 ft (40 m) thick in west part of Pe Esplanade Sandstone (Lower Permian)— map area to about 150 ft 46 m) in east part. Light-red and pinkish-gray, cliff-forming, Manakacha Formation is light-red, white, fine- to medium-grained, medium- to thick- and gray upper slope and lower cliff of bedded [3 to 10 ft (1 to 3 m)], well sorted sandstone, calcareous sandstone, dark- calcareous sandstone. Includes interbedded red siltstone, and gray limestone. Upper dark-red, thin-bedded, crumbly recesses of slope consists mainly of shaley siltstone slope-forming siltstone between sandstone and mudstone with minor interbedded, beds in upper and lower part. Crossbeds are thin-bedded limestone and calcareous small- to medium-scale, planar low-angle sandstone. Carbonate content of upper

16 slope increases westerly to form numerous to dark-red mudstone of Surprise Canyon ledge-forming, thin- and medium-bedded Formation. Unit averages about 100 ft (30 limestones. Upper slope is about 100 ft (30 m) thick along east edge of map area thick- m) thick in east half of map area, decreas- ening to 200 ft (60 m) along west edge ing to less than 60 ft (18 m) thick in west Ms Surprise Canyon Formation (Upper Missis- half. Lower cliff is dominated by grayish- sippian)—Dark reddish-brown siltstone red, medium- to thick-bedded, crossbed- and sandstone, gray limestone and dolo- ded calcareous sandstone, dolomite, and mite, and grayish-white chert conglomerate sandy limestone. Lower cliff is about 60 in dark-red or black sandstone matrix. For- ft (18 m) thick in east part of map area, mation locally absent throughout map area thickening to about 100 ft (30 m) in west and present only in paleovalleys and karst part. Carbonate content increases westward caves eroded into top half of the Redwall across map area forming numerous gray Limestone (Mr). Consists of an upper slope, limestone ledges. Unconformable contact a middle cliff, and lower slope in west half between the Manakacha and underlying of map area; forms slope in east half of map Watahomigi Formations marked at base of area. lower sandstone cliff of Manakacha Forma- Upper slope consists of reddish-brown, tion; erosional relief is generally less than 3 thin-bedded siltstone, calcareous sand- (1 m) ft as a wavy unconformable surface. stone, and reddish-gray, thin-bedded sandy Overall thickness, 200 ft (60 m) throughout limestone. Contains numerous ripple marks map area. and marine fossils. Thickness ranges from Watahomigi Formation is gray and pur- about 50 to 75 ft (15 to 23 m). Middle cliff plish-red, slope-forming limestone, silt- consists of a reddish-gray, thin-bedded, stone, mudstone, and conglomerate. Forms coarse-grained silty and sandy limestone an upper ledge/slope and a lower slope. containing numerous marine fossils. Aver- Upper ledge/slope consists of alternat- age thickness about 50 ft in (15 m) west ing gray, thin-bedded cherty limestone third of map area, thins and pinches out in ledges interbedded with purplish-gray east two-thirds of map area based on expo- siltstone and mudstone. Limestone beds sures in Grand Canyon north of map area contain Early Pennsylvanian conodont fos- (Billingsley, 2000). Lower slope consists of sils (Martin and Barrick, 1999); red chert dark reddish-brown to black, iron-stained, lenses and nodules are common in lime- thin-bedded, coarse- to medium-grained stone beds. Includes limestone chert-pebble siltstone, sandstone, limestone, and con- conglomerate at base, locally containing glomerate. Sandstone and siltstone beds Early Pennsylvanian fossils. Upper ledge contain numerous plant fossils and bone and slope averages about 70 ft (22 m) thick fossils, mudcracks, and ripplemarks. Sand- throughout map area. Lower slope consists stone is coarse grained and thin bedded of purplish-red mudstone and siltstone with some low-angle, crossbedded sets. interbedded with thin-bedded, aphanitic Conglomerate beds consist of white and to granular limestone in upper part with gray chert clasts supported in dark-red to red chert veins and nodules. Conodonts in black, coarse-grained chert sandstone or lower thin limestone beds are Late Missis- gravel matrix, all derived from erosion of sippian (Martin and Barrick, 1999). Unit the Redwall Limestone. Thickness of lower includes purple siltstone and gray lime- slope, about 3 to 60 ft (1 to 18 m), averages stone interbedded with conglomerate that about 25 ft (7.5 m). In east half of map area, fills small erosion channels cut into either the Surprise Canyon Formation consists the Surprise Canyon Formation (Ms) or mainly of dark reddish-brown, slope-form- Redwall Limestone (Mr). Purple shale and ing, massive to thin-bedded, poorly sorted mudstone of lower slope unconformably siltstone and sandstone containing plant overlies gray Redwall Limestone in major- fossils. ity of map area and unconformably overlies The Surprise Canyon Formation is the the Surprise Canyon Formation where pres- most fossiliferous rock unit in the Grand ent. Contact with the Surprise Canyon For- Canyon. Overall, thickness averages about mation is often based on color change from 145 ft (44 m) in west half of map area, thin- purple mudstone of Watahomigi Formation ning to less than 50 ft (15 m) in east half

17 Mr Redwall Limestone, undivided (Upper half of map area. Fossil content increases and Lower Mississippian)—Includes, from east to west across map area. Discon- in descending order, Horseshoe Mesa, formable planar contact with underlying Mooney Falls, Thunder Springs, and Whit- Whitmore Wash Member is distinguished more Wash Members, as defined by McKee by distinct lack of chert in the Whitmore (1963) and McKee and Gutschick (1969). Wash. Member is about 100 ft (30 m) thick Horseshoe Mesa Member is light- in south half of map area, increasing to olive-gray, ledge- and cliff-forming, thin- about 150 ft (46 m) thick in north half. bedded, fine-grained limestone. Weathers Whitmore Wash Member is yellow- to form receding ledges. Gradational and ish-gray and brownish-gray, cliff-forming, disconformable contact with underlying thick-bedded, fine-grained dolomite. Unit massive-bedded limestone of Mooney Falls is mostly limestone in western and northern Member marked by thin-bedded platy lime- part of map area. Unconformable contact stone beds of Horseshoe Mesa Member that with underlying Temple Butte Formation form recess about 3 to 9 ft (1 to 3 m) thick (Dtb) marked by erosion channels of low near top of Mooney Falls cliff. Fossils are relief about 5 to 20 ft (1.5 to 6 m) in depth. locally common. Includes distinctive ripple- Contact generally recognized where major laminated limestone and oolitic limestone cliff of the Redwall Limestone overlies stair- beds and some chert lenses. Member thick- step ledges of the Temple Butte Formation in ens slightly from east to west across map Grand Canyon. Uniform thickness through- area; locally absent where removed by Late out map area, about 80 ft (25 m) Mississippian paleovalley erosion. Thick- Dtb Temple Butte Formation (Upper and Middle ness, 50 to 100 ft (15 to 30 m). Devonian)—Purple, reddish-purple, dark- Mooney Falls Member is light-gray, cliff- gray, and light-gray, ledge-forming dolo- forming, fine- to coarse-grained, thick- mite, sandy dolomite, sandstone, mudstone, bedded to very thick bedded [4 to 20 ft (1.2 and limestone, as defined by Beus (2003). to 6 m)] fossiliferous limestone. Limestone Purple, reddish-purple, and light-gray, fine- weathers dark gray; chert beds weather to coarse-grained, thin- to medium-bedded, black. Includes dark-gray dolomite beds in ripple-laminated ledges of mudstone, sand- lower part in western quarter of map area; stone, dolomite, and conglomerate fill chan- oolitic limestone and chert beds restricted nels eroded into the underlying Cambrian to upper part throughout map area. Contains strata; channels are as much as 100 ft (30 large-scale, tabular and planar, low-angle m) deep in east half of map area, and about cross-stratified limestone beds in upper 40 ft (12 m) deep in west half of map area. third of unit in western half of map area. Disconformable contact with underlying Channel deposits are overlain by dark-gray Thunder Springs Member distinguished by to olive-gray, medium- to thick-bedded lithology; massive-bedded, gray limestone dolomite, sandy dolomite, limestone, and of the Mooney Falls overlies thin-bedded, sandstone. Unit weathers to dark-gray dark-gray to brown dolomite and white sequence of ledges. Unconformity at base chert beds of the Thunder Springs Member. represents major stratigraphic break in the Unit thickens from about 250 ft (76 m) in Paleozoic rock record in Grand Canyon, southeast quarter of map to about 400 ft spanning part of the Late Cambrian, all of (122 m) in northwest quarter. the Ordovician and Silurian, and most of Thunder Springs Member; about half Early and Middle Devonian time, about of member is gray, cliff-forming, fossilifer- 100 million years. Dark-gray Devonian ous, thin-bedded limestone and about half is rocks are distinguished from underlying brownish-gray, cliff-forming, thin-bedded light-gray Cambrian rocks by color con- [1 to 5 in (2.4 to 12 cm)], finely crystal- trast. Unit thickens from about 50 ft (15 m) line dolomite and fine- to coarse-grained in east half of map area to as much as 275 ft limestone interbedded with white chert (84 m) in west half of map area, excluding beds. Limestone common in north half of extra channel fill thickness map area; dolomite is common in south Tonto Group (Middle and Lower(?) Cam- half. Locally includes large-scale crossbed- brian)—Includes in descending order, ding and irregularly folded beds in north Muav Limestone, Bright Angel Shale, and

18 Tapeats Sandstone as defined by Noble relations between the Muav Limestone and (1922) and modified by McKee and Resser Bright Angel Shale produce variable thick- (1945). These Cambrian units are recog- ness trends. Overall, the Muav Limestone nized on basis of distinct rock types: lime- thickens from about 359 ft (107 m) in east stone and dolomite lithologies belong to part of map area to about 600 ft (183 m) in the Muav Limestone; shale and siltstone west part lithologies belong to the Bright Angel _ba Bright Angel Shale (Middle and Lower(?) Shale; and sandstone and conglomerate Cambrian)—Green and purple-red, slope- lithologies belong to the Tapeats Sandstone forming siltstone and shale, and interbeds (Rose, 2003). Tonto Group may overlie of reddish-brown to brown sandstone of tilted strata of Grand Canyon Supergroup Tapeats Sandstone lithology. Includes of Middle Late Proterozoic (1.4 to 1.1 bil- ledge-forming red-brown sandstone lion years) age in east part of map area and member of McKee and Resser (1945). igneous and metamorphic rocks of Early Consists of green and purplish-red, fine- Proterozoic (1.7 to 1.6 billion years) age grained, micaceous, ripple-laminated, fos- in central and west part of map area; this siliferous siltstone and shale; dark-green, hiatus is known regionally as the Great medium- to coarse-grained, thin-bedded, Unconformity glauconitic sandstone; and interbedded _m Muav Limestone (Middle Cambrian)— purplish-red and brown, thin-bedded, Dark-gray, light-gray, brown, and orange- fine- to coarse-grained, ripple-laminated red, cliff-forming limestone, dolomite, sandstone. Includes gray, thin-bedded, fine- and calcareous mudstone. Includes, in grained, micaceous silty dolomite in upper descending order, unclassified dolomites, part in western quarter of map area. Inter- Havasu, Gateway Canyon, Kanab Canyon, tonguing and facies change relations with Peach Springs, Spencer Canyon, and Ram- the underlying Tapeats Sandstone produce part Cave Members of McKee and Resser variable thickness trends. Contact with (1945). These members consist of fine- to Tapeats Sandstone is arbitrarily marked medium-grained, thin- to thick-bedded, at lithologic vertical and lateral transition mottled, fossiliferous, silty limestone, lime- from predominantly green siltstone and stone, and dolomite. Three unnamed slope- shale to predominantly brown sandstone forming siltstone and shale units of Bright above Tapeats Sandstone cliff. About 350 Angel Shale (_ba) lithology are positioned ft (107 m) thick in east quarter of map area, between cliff-forming members of Muav thickening to about 500 ft 153 m) in north- Limestone. These unnamed siltstone and western quarter, thinning to about 150 ft shale units are green and purplish-red, (46 m) in southwest quarter micaceous siltstone, mudstone, and shale, _t Tapeats Sandstone (Middle and Lower(?) and thin brown sandstone. Contact with the Cambrian)—Brown and reddish-brown, underlying Bright Angel Shale is grada- cliff-forming sandstone and conglomerate. tional and lithology dependent. Contact is Includes an upper slope-forming transition arbitrarily marked at base of lowest promi- zone of nearly equal distribution of brown nent limestone of Rampart Cave Member sandstone of Tapeats Sandstone lithology of the Muav Limestone in west quarter and green siltstone and shale of Bright of map area, and at base of limestone of Angel Shale lithology, and a lower sand- Peach Springs-Kanab Canyon Members stone and conglomeratic sandstone. Lower of the Muav Limestone in east three-quar- cliff consists mainly of medium- to coarse- ters of map area. All members of the Muav grained, thin-bedded, low-angle planar and Limestone thicken from east to west across trough crossbedded sandstone and con- map area and thin south to the south edge glomeratic sandstone; sandstone beds are 6 of map area. However, the Peach Springs, to 24 in (14 to 58 cm) thick. Unconformable Spencer Canyon, and Rampart Cave Mem- contact with underlying Early Proterozoic bers change to purplish-red and green silt- rocks that form the Great Unconformity. stone/shale facies of the Bright Angel Shale The Tapeats Sandstone fills lowland areas in east quarter of map area where they are and thins across or pinches out against Pro- included as part of the Bright Angel Shale terozoic highlands. Variable thickness, 0 to map unit. Intertonguing and facies change 400 ft (0 to 122 m)

19 Xu Crystalline rocks, undivided (Early Protero- Billingsley, G.H., Wenrich, K.J., Huntoon, P.W., and zoic)—Includes various types of igneous Young, R.A., 1999, Breccia-pipe and geologic map and metamorphic granite, and crystalline of the southwestern part of the Hualapai Indian schist and gneiss. Thickness unknown Reservation and vicinity, Arizona: U.S. Geological Survey Geologic Investigations Map I–2554, scale 1:48,000, 50 p. REFERENCES Billingsley, G.H., and Workman, J.B., 2000, Geologic map of the Littlefield 30´ x 60´ quadrangle, Mohave Beus, S.S., 2003, Temple Butte Formation, in Beus, S.S., County, northwestern Arizona: U.S. Geological and Morales, Michael, eds., Grand Canyon geology: Survey Geologic Investigations Series I–2628, scale New York, Oxford University Press, p. 107–114. 1:100,000, 25 p. [http://geopubs.wr.usgs.gov/i-map/ Billingsley, G.H., 2000, Geologic map of the Grand i2628/]. Canyon 30´ x 60´ quadrangle, Coconino and Mohave Fisher, W.L., 1961, Upper Paleozoic and lower Meso- Counties, northwestern Arizona: U.S. Geologi- zoic stratigraphy of Parashant and Andrus Canyons, cal Survey Geologic Investigations Series I–2688, Mohave County, northwestern Arizona: Lawrence, scale 1:100,000, 25 p. [http://pubs.usgs.gov/imap/i- Kans., University of Kansas, Ph.D. dissertation, 345 2688/]. p. Billingsley, G.H., Barnes, C.W., and Ulrich, G.E., 1985, Hunt, C.B., Averitt, Paul, and Miller, R.L., 1953, Geol- Geologic map of the Coconino Point and Grandview ogy and geography of the Henry Mountains region, Point quadrangles, Coconino County, Arizona: U.S. Utah: U.S. Geological Survey Professional Paper Geological Survey Miscellaneous Investigations 228, 234 p. Series Map I–1644, scale 1:62,500. Huntoon, P.W., 1999, Hydrologic features (structural geo- Billingsley, G.H., Hamblin, K.W., Wellmeyer, J.L., and logic map of the Cataract extensional basin, Arizona), Dudash, Stephanie, 2001, Geologic map of part of the in Errol Montgomery and Associates, Supplemen- Uinkaret Volcanic Field, Mohave County, northwest- tal assessment of hydrologic conditions and poten- ern Arizona: U.S. Geological Survey Miscellaneous tial effects of proposed groundwater withdrawal, Field Studies Map MF–2368, scale 1:31,680, 25 p. Coconino Plateau groundwater sub-basin, Coconino [http://geopubs.wr.usgs.gov/map-mf/mf2368/]. County, Arizona: Supplement to final Environmen- Billingsley, G.H., Harr, Michelle, and Wellmeyer, J.L., tal Impact Statement for Tusayan growth, Kaibab 2000a, Geologic map of the upper Parashant Canyon National Forest, U.S. Department of Agriculture, and vicinity, northwestern Arizona: U.S. Geological Forest Service, Southwest Region, 85 p. Survey Miscellaneous Field Studies Map MF–2343, Huntoon, P.W., 2000, Variability of karstic permeability scale 1:31,680, 27 p. [http://geopubs.wr.usgs.gov/ between unconfined and confined aquifers, Grand map-mf/mf2343/]. Canyon region, Arizona: Environmental and Engi- Billingsley, G.H., and Huntoon, P.W., 1983, Geologic neering Geoscience, v. 6, no. 2, p. 155–170. map of the Vulcan’s Throne and vicinity, western Huntoon, P.W., 2003, Post-Precambrian tectonism in the Grand Canyon, Arizona: Grand Canyon Natural Grand Canyon region, chap. 14 of Beus, S.S., and History Association, Grand Canyon, Ariz., scale Morales, Michael, eds., Grand Canyon geology (2d 1:48,000. ed.): New York, Oxford University Press, p. 222– Billingsley, G.H., Spamer, E.E., and Menkes, Dove, 1997, 259. Quest for the pillar of gold, the mines and miners Huntoon, P.W., Billingsley, G.H., Sears, J.W., Ilg, B.R., of the Grand Canyon: Grand Canyon Association Karlstrom, K.E., Williams, M.L., and Hawkins, Monograph no. 10, Grand Canyon, Ariz., 112 p. David, 1996, Geologic map of the eastern part of Billingsley, G.H., and Wellmeyer, J.L., 2003, Geologic the Grand Canyon National Park, Arizona: Grand map of the Mount Trumbull 30´ x 60´ quadrangle, Canyon Ariz., Grand Canyon Association and Flag- Mohave and Coconino Counties, Arizona: U.S. staff, Ariz., Museum of Northern Arizona, scale Geological Survey Geologic Investigations Series 1:62,500. I–2766, scale 1:100,000, 36 p. [http://pubs.usgs.gov/ Martin, Harriet, and Barrick, J.E., 1999, Conodont bio- imap/i2766/]. stratigraphy of the Surprise Canyon Formation, Billingsley, G.H., Wenrich, K.J., and Huntoon, P.W., chap. F of Billingsley, G.H., and Beus, S.S., eds., 2000b, Breccia-pipe and geologic map of the south- Geology of the Surprise Canyon Formation of the eastern part of the Hualapai Indian Reservation and Grand Canyon, Arizona: Flagstaff, Ariz., Museum vicinity, Arizona: U.S. Geological Survey Geologic of Northern Arizona Press, Museum of Northern Investigations Series I–2643, scale 1:48,000, 2 Arizona Bulletin no. 61, p. 97–116. sheets, 18 p. McKee, E.D., 1963, Nomenclature for lithologic sub-

20 divisions of the Mississippian Redwall Limestone, Richard, M.S., Reynolds, S.J., Spencer, J.E., Pearthree, Arizona: U.S. Geological Survey Professional Paper P.A., compliers, 2000, Geologic map of Arizona: 475–C, p. C21–C22. Arizona Geological Survey Map, M–35, Tucson, McKee, E.D., 1975, The Supai Group—subdivision Arizona, scale 1:1,000,000. and nomenclature: U.S. Geological Survey Bulletin Rose, E.C., 2003, Depositional environment and history 1395–J, p. J1–J11. of the Cambrian Tonto Group, Grand Canyon, Ari- McKee, E.D., 1982, The Supai Group of Grand Canyon: zona: Flagstaff, Arizona, Northern Arizona Univer- U.S. Geological Survey Professional Paper 1173, sity, Masters Thesis, 349 p. 504 p. Schleh, E.E., 1966, Stratigraphic section of Toroweap and McKee, E.D., and Gutschick, R.C., 1969, History of the Kaibab Formations in Parashant Canyon, Arizona: Redwall Limestone of northern Arizona: Geological Arizona Geological Society Digest, v. 8, p. 57–64. Society of America Memoir, v. 114, 726 p. Sorauf, J.E., and Billingsley, G.H., 1991, Members of the McKee, E.D., and McKee, E.H., 1972, Pliocene uplift of Toroweap and Kaibab Formations, Lower Permian, the Grand Canyon region—time of drainage adjust- northern Arizona and southwestern Utah: Mountain ment: Geological Society of America Bulletin 83, p. Geologist, v. 28, no. 1, p. 9–24. 1923–1932. Wenrich, K.J., 1992, Breccia pipes in the Red Butte area McKee, E.D., and Resser, C.E., 1945, Cambrian history of Kaibab National Forest, Arizona: U.S. Geological of the Grand Canyon region: Carnegie Institution of Survey Open-File Report 92–219, 13 p. Washington Publication 563, 232 p. Wenrich, K.J., Billingsley, G.H., and Huntoon, P.W., McNair, A.H., 1951, Paleozoic stratigraphy of part of 1997, Breccia-pipe and geologic map of the north- northwestern Arizona: American Association of eastern part of the Hualapai Indian Reservation and Petroleum Geologists Bulletin 35, p. 503–541. vicinity, Arizona: U.S. Geological Survey Miscella- Melis, W.S., Phillips, W.M., Webb, R.H., and Bills, D.J., neous Investigations Series I–2440, scale 1:48,000, 1996, When the blue-green waters turn red; histori- 19 p. cal flooding in Havasu Creek, Arizona: U.S. Geolog- Wenrich, K.J., and Huntoon, P.W., 1989, Breccia pipes ical Survey Water Resources Investigations Report and associated mineralization in the Grand Canyon 96–4059, 136 p. region, northern Arizona, in Elston, D.P., Billings- Naeser, C.W., Duddy, I.R., Elston, D.P., Dumitru, T.A., ley, G.H., and Young, R.A., eds., Geology of Grand and Green, P.F., 1989, Fission-track dating—Ages Canyon, northern Arizona with Colorado River for Cambrian strata, and Laramide and post-Middle guides, Lees Ferry to Pierce Ferry, Arizona: Ameri- Eocene cooling events from the Grand Canyon, Ari- can Geophysical Union, Washington, D.C., 28th zona, in Elston, D.P., Billingsley, G.H., and Young, International Geological Congress Field Trip Guide- R.A., eds., Geology of Grand Canyon, northern book T115/T315, p. 212–218. Arizona (with Colorado River Guides): American Wenrich, K.J., and Sutphin, H.B., 1988, Recognition of Geophysical Union, 28th International Geological breccia pipes in northern Arizona: Arizona Bureau Congress, Guidebook T115/315, p. 139–144. of Geology and Mineral Technology Field Notes, v. Noble, L.F., 1922, A section of the Paleozoic formations 18, no. 1, p. 1–5. of the Grand Canyon at the Bass Trail: U.S. Geologi- Wenrich, K.J., Van Gosen, B.S., Balcer, R.A., Scott, J.H., cal Survey Professional Paper 131–B, p. 23–73. Mascarenas, J.F., Bedinger, G.M., and Burmaster, Peters, Lisa, 2002, 40Ar/39Ar geochronology results Betsi, 1988, A mineralized breccia pipe in Mohawk from the Mount Floyd Volcanic Field, Arizona: New Canyon, Arizona—lithologic and geophysical logs: Mexico Geochronology Research Laboratory Inter- U.S. Geological Survey Bulletin 1683–A, Breccia nal Report, no. NMGRL-IR-281, 7 p. pipes in northern Arizona, 66 p. Rawson, R.R., and Turner, C.E., 1974, The Toroweap Wilson, E.D., Moore, R.T., and Cooper, J.R., 1969, Geo- Formation; a new look, in Karlstrom, T.N.V., Swann, logical map of the State of Arizona: Arizona Bureau G.A., and Eastwood, R.L., eds., Geology of north- of Mines and the U.S. Geological Survey, University ern Arizona with notes on archaeology and paleocli- of Arizona, scale 1:500,000. mate, Part 1, Regional Studies: Geological Society Wolfe, E.W., Ulrich, G.E., and Newhall, C.G., 1987, of America Rocky Mountain Section Meeting, Flag- Geologic map of the northwest part of the San Fran- staff, Ariz., p. 155–190. cisco Volcanic Field, north-central Arizona: U.S. Reynolds, S.J., Florence, F.P., Welty, J.W., Roddy, M.S., Geological Survey Miscellaneous Field Studies Map Currier, D.A., Anderson, A.V., and Keith, S.B., 1986, MF–1957, scale 1:50,000, 2 sheets. Compilation of radiometric age determinations in Young, R.A., 1985, Geomorphic evolution of the Colo- Arizona: Arizona Bureau of Mines and Geological rado Plateau margin in west-central Arizona—A Mineral Technologies, 197, 258 p. tectonic model to distinguish between the causes

21 of rapid asymmetrical scarp retreat and scarp dis- 1:48,000, 50 p. section, in Hack, J.T., and Morisawa, Marie, eds., Young, R.A., 2001, Geomorphic, structural, and strati- Tectonic geomorphology, Binghamton Symposium graphic evidence for Laramide uplift of the south- in Geomorphology, International Series 15: London, western Colorado Plateau margin in northwestern Allen and Urwin, p. 261–278. Arizona, in Erskine, M.C., ed., Faulds, J.E., Bartley, Young, R.A., 1987, Landscape development during the J.M., and Rowley, P.D., co-eds., The geologic transi- Tertiary, in Colorado Plateau, in Graf, W.L., ed., tion, high plateaus to great basin; a symposium and Geomorphic systems of North America: Geological field guide, The Mackin Volume: Utah Geologi- Society of America Centennial, v. 2, p. 265–276. cal Association Publication 30 and Pacific Section Young, R.A., 1999, Nomenclature and ages of Late Cre- American Association of Petroleum Geologist Pub- taceous(?)—Tertiary strata in the Hualapai Plateau lication GB 78, p. 227–237. region, northwest Arizona, in Billingsley, G.H., Young, R.A., and Hartman, J.H., 1984, Early Eocene Wenrich, K.J., Huntoon, P.W., and Young, R.A., fluviolacustrine sediments near Grand Canyon, Ari- Breccia-pipe and geologic map of the southwestern zona; evidence for Laramide drainage across north- part of the Hualapai Indian Reservation and vicin- ern Arizona into southern Utah: Geological Society ity, Arizona: U.S. Geological Survey Miscellaneous of America Abstracts with Programs, v.16, no. 6, p. Investigations Series Map I–2554, 2 sheets, scale 703.

22