GrOLOGY L BRARt] 

C;EP 3 1 «'5

The Supai Group 

Subdivision and Nomenclature

GEOLOGICAL SURVEY BULLETIN 1395-J

The Supai Group 

Subdivision and Nomenclature

By EDWIN D. McKEE

CONTRIBUTIONS TO STRATIGRAPHY

GEOLOGICAL SURVEY BULLETIN 1395-J

The Supai Formation of the Grand Canyon 

region is raised in rank to Supai Group and 

divided into four formations that range in 

age from Early Pennsylvanian to 

Early Permian

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1975
UNITED STATES DEPARTMENT OF THE INTERIOR 

ROGERS C. B. MORTON, Secretary

GEOLOGICAL SURVEY 

V. E. McKelvey, Director

Library of Congress Cataloging in Publication Data

McKee, Edwin Dinwiddie, 1906-

The Supai Group Subdivision and nomenclature.

(Contributions to stratigraphy)

(Geological Survey Bulletin 1395-J)

Bibliography: p.

Supt.ofDocs.no.: 119.3:1395-1

1. Geology, Stratigraphic-Permian. 2. Geology, Stratigraphic-Pennsylvanian. 3. Geology,

Stratigraphic Nomenclature Arizona Grand Canyon region. 

I. Title. II. Series. III. Series: United States Geological Survey Bulletin 139S-J 

QE75.B9 No. 1395-J [QE674] 557.3'08s [551.7'52'0979132] 75-619022

For sale by the Superintendent of Documents, U. S. Government Printing Office

Washington, D. C. 20402 

Stock Number 024-001-02656-2
CONTENTS

Page

Abstract........................................................................................................................... Jl

Introduction: field terminology and new nomenclature............................................... 1

Watahomigi Formation.................................................................................................. 2

Manakacha Formation.................................................................................................... 4

Wescogame Formation ................................................................................................... 4

Esplanade Sandstone...................................................................................................... 5

Correlation with previous subdivisions......................................................................... 5

Type section of Supai Group in Havasu Canyon......................................................... 6

References cited............................................................................................................... 11

ILLUSTRATION

Page

FIGURE 1. Index map of Havasu Canyon, northern Arizona......................................... J3

CONVERSION OF MEASUREMENTS TO METRIC 

EQUIVALENTS

1 inch - - - 2.540 centimetres 

1 foot........ . . ............... ....... 0.3048 metre

1 mile- - - - - 1.609 kilometres

in

CONTRIBUTIONS TO STRATIGRAPHY

THE SUPAI GROUP SUBDIVISION AND 

NOMENCLATURE

By EDWIN D. McKEE

ABSTRACT

The Supai Formation of the Grand Canyon region is raised in rank to Supai Group and 

divided into four formations. Widespread surfaces of erosion and thin conglomerate beds 

separate these formations which range in age from Early Pennsylvanian to Early Permian. 

From oldest to youngest, they are named the Watahomigi, Manakacha, and Wescogame 

Formations and the Esplanade Sandstone. The type sections of these formations are in 

Havasu Canyon in the vicinity of Supai village.

INTRODUCTION: FIELD TERMINOLOGY AND NEW 

NOMENCLATURE

Probably the first geologist to carefully consider subdivision of the 

Supai Formation into logical, readily recognizable units was F. E. 

Matthes of the U.S. Geological Survey. In making a topographic map of 

the Bright Angel quadrangle in 1902-3, he noticed that the red beds of this 

formation, together with the overlying Hermit Shale, characteristically 

eroded into three prominent cliffs, interspersed among four welldeveloped slopes. The discrimination of these topographic units was 

called to my attention by Matthes in the 1930's in connection with my 

studies of the Supai Formation. A "field classification" that proved useful 

in recording data at that time and in all subsequent work resulted.

Subdivision of the Supai on the basis of topographic expression, used 

during the present field investigation, recognized the following units:

Upper cliff unit, locally includes a receding ledge unit (Esplanade 

cliff)

Upper slope unit (divided by conglomerate into two parts)

Middle cliff unit

Middle slope unit

Lower cliff unit

Lower slope unit

These units can be traced throughout the Grand Canyon, and they 

differ remarkably little from one end to the other, although, in general,

Jl
J2 CONTRIBUTIONS TO STRATIGRAPHY

the cliff units are more massive and prominent toward the west, and the 

slope units are less conspicuous in that direction. In many western 

sections the middle slope unit is so weakly developed that the lower and 

middle cliff units seem to merge together. Furthermore, in the extreme 

western Grand Canyon, limestone beds in the middle of the lower slope 

unit are so massive and cliff forming that this unit locally is divisible into 

three subunits.

Although subdivisions of the Supai as originally delineated were based 

entirely on topography (and indirectly on the types of rock represented), 

certain key beds, faunal zones, and marker surfaces came to be recognized, 

and they lent much support to correlations from place to place. Most 

important of the key beds are widespread conglomerates that occur at 

three horizons (in addition to the basal conglomerate on the Redwall 

Limestone surface) and are recognized throughout most of the region. 

These conglomerates, lowest to highest, occur (1) about two-thirds the 

distance up the lower slope unit, (2) near the base of the middle cliff unit, 

and (3) about the middle of the upper slope unit.

The key bed conglomerates are distinctive lithologically.Theupper two 

conglomerates are associated with marked surfaces of erosion, having 

relief as much as 45 feet in channels; thus, they seem to represent regional 

unconformities. In some parts of the region, marine faunas above and 

below these conglomerates show that hiatuses of appreciable magnitude 

are represented by them. The uppermost conglomerate was recognized in 

25 of 31 sections that I measured, the middle one was recognized in 19 of 27 

sections, and the lower one in 14 of 25 sections.

Partly on the basis of widespread erosion surfaces and diagnostic conglomerates associated with them and partly on the basis of topographic 

expression that facilitates mapping, the Supai strata of the Grand Canyon 

are here divided into four formations which together are classed as the 

Supai Group. Thus, the Supai Formation of Darton (1910) is here raised 

in rank to Supai Group and divided into four formations, as follows 

(oldest to youngest): Watahomigi, Manakacha, and Wescogame 

Formations and Esplanade Sandstone.

WATAHOMIGI FORMATION

The Watahomigi Formation is named from Watahomigi Point on the 

west side of Havasu Canyon about 1% miles northwest of Supai village and 

directly above the type section of this formation (fig. 1). The spelling is as 

given on the U.S. Geological Survey topographic map, Supai, Ariz. 1962. 

This name is a common family name among the Havasupai Indians, but 

the official Havasupai Membership Roll, 1972, and most or all of the 

Indians of this name use the spelling "Watahomigie."
THE SUPAI GROUP SUBDIVISION AND NOMENCLATURE

36° 15' ->

FIGURE 1. Havasu Canyon, northern Arizona, showing Supai village and points on 

canyon walls from which the Watahomigi, Manakacha, and Wescogame Formations 

derive their names and the erosional bench (shaded) for which the Esplanade Sandstone is named. Location of type sections: MWE, Manakacha, Wescogame, 

and Esplanade; W, Watahomigi.
J4 CONTRIBUTIONS TO STRATIGRAPHY

The formation consists largely of limestone and mudstone in about 

equal proportions and, in most areas, forms a ledgy slope, which retreats 

from the rim of the massive Redwall Limestone. Commonly, one 

conglomerate occurs at or near its base, and another occurs locally about 

two-thirds the distance up. The middle third of the formation is 

composed mostly of limestone and forms a massive cliff in some sections, 

dividing the formation into three parts. The lower two parts are believed 

on f aunal evidence to be of Morrowan age; the upper part, above the conglomerate, is considered to be Atokan in age. The Watahomigi rests unconformably on the Redwall Limestone and is conformably overlain by 

the Manakacha Formation.

MANAKACHA FORMATION

The Manakacha Formation is named from Manakacha Point on the 

east side of Havasu Canyon, directly above Supai village. This spelling is 

according to U.S. Geological Survey usage on topographic map of Supai 

quadrangle, Arizona; the official Havasupai Membership Roll, 1972, uses 

the spelling "Manakaja" for the Indian family of that name. The type 

section of the formation is along the Apache trail, which begins in the 

village and winds up the canyonside toward the point. The Manakacha 

consists of the lowest massive cliff in the Supai Group and also the small 

bench or slope above it (lower cliff unit and middle slope unit). It consists 

of crossbedded limy sandstone or sandy limestone with minor amounts of 

mudstone. It rests conformably on the Watahomigi Formation, the 

boundary in most places being indicated by a change from slope below to 

cliff above and by the presence of the lowermost sandstones of the 

Manakacha. The upper boundary of the formation is an unconformity 

marked by a surface of erosion and by a basal conglomerate of the 

Wescogame Formation. The age of the Manakacha cliff unit is Atokan, on 

the basis of diagnostic fusulinids ranging throughout the Grand Canyon. 

The upper part (slope unit) is either Atokan or Des Moinesian in age; 

fossils thus far found in it are not unequivocal evidence of either.

WESCOGAME FORMATION

The Wescogame Formation is named from Wescogame Point on the 

west side of Havasu Canyon, about 3 miles southwest of Supai village and 

directly above Hualapai Canyon, down which the present main 

(Hualapai) horse trail to the village passes. A good section of the 

formation is exposed along this trail, but the type section is on the Apache % 

trail farther north. The Wescogame is composed dominantly of massive 

crossbedded sandstone or sandy limestone which forms a prominent cliff, 

but it includes about half the slope (upper slope unit) above. This upper 

slope is not represented at the type section but is present nearly everywhere else in Grand Canyon. Mudstone is present but not pro-
THE SUPAI GROUP SUBDIVISION AND NOMENCLATURE J5

portionately abundant in the formation. The Wescogame Formation is 

probably of Virgilian age, as indicated by fusulinids and corals. It rests 

unconformably on the Manakacha Formation and is unconformably 

beneath strata of Wolfcampian age in the Esplanade Sandstone.

ESPLANADE SANDSTONE

The geologic unit Esplanade was called by White (1929) the Esplanade 

Sandstone Member of the Supai Formation; in the present report the 

Esplanade is raised to formation rank. It is the uppermost formation of 

the Supai Group.

The geographic term "Esplanade" comes from the Esplanade platform that is a prominent bench in the walls of the Grand Canyon; it is 

especially wide and conspicuous in the western part. The term 

"Esplanade" was introduced to the Grand Canyon by C. E. Dutton (1882, 

p. 87, 121) in referring to this bench, which is carved in the uppermost 

sandstone beds of the Supai, in his description of the Toroweap area. Subsequent references to the Esplanade platform were made by Davis (1901), 

Robinson (1911, p. 90), Noble (1914, p. 18, 21, 73; 1922, p. 61), Darton 

(1925, p. 79), and others. Eventually, the name was applied to the sandstone th^t forms the bench: "for convenience of reference, the group of 

hard sandstones which supports and forms this shelf is termed the 

'Esplanade Sandstone' [Member of Supai Formation]" (White, 1929, p. 

11) and the "upper 270 feet of the Supai, hard, dark-red sandstones * * * are 

known locally as the Esplanade sandstone" (Stoyanow, 1936, p. 525).

The formation consists primarily of very fine grained cross-stratified 

sandstone that forms massive cliffs. It includes small amounts of silts tone 

and mudstone that weather into slopes, benches, or recesses and, in 

western Grand Canyon, contains some extensive beds of gypsum. Near 

Grand Wash Cliffs in the extreme western part of the Grand Canyon, it 

apparently interfingers with the Pakoon Limestone of McNair (1951) 

under Shivwits Plateau. The type section selected for this formation is 

along the Apache trail, where it passes from the inner Canyon of Havasu 

to the broad Esplanade platform bench occupied by the Hermit Shale.

The Esplanade Sandstone is of Wolfcampian age. It is underlain 

unconformably by the Wescogame Formation of Late Pennsylvanian age. 

The boundary is marked by a well-developed surface of erosion with some 

channels more than 40 feet deep and by a persistent limestone-pebble 

conglomerate. The Esplanade is overlain by the Hermit Shale of 

Leonardian age and separated from it in many places by a greatly 

channeled surface of erosion.

CORRELATION WITH PREVIOUS SUBDIVISIONS

Subsequent to the topographic work of Matthes, but independent of his 

observations, L. F. Noble (1922, p. 61) suggested an informal classi-
J6 CONTRIBUTIONS TO STRATIGRAPHY

fication of the Supai in which he recognized subdivisions A, B, and C, 

from top to bottom. His subdivision C is described as the basal slope 

beginning with "a plane of unconformity by erosion" on top of the Redwall and consisting of sandstone, shale, and limestone in about equal 

amounts. It seems to be equivalent to the Watahomigi Formation.

Noble's subdivision B is described as crossbedded sandstone below the 

middle and underlying a thick massive cliff and ledgy slope. Apparently, 

it is composed of both the Manakacha and Wescogame Foramtions of 

present usage, together with the overlying "upper slope unit"; it included 

rocks of Atokan, Virgilian, and Wolfcampian age. Although he was 

aware of the widespread conglomerate and erosion surface at the base of 

the Esplanade Sandstone, he (Noble, 1922, p. 61) placed the upper 

boundary higher at the base of the Esplanade cliff.

Noble's subdivision A is nearly equal to the Esplanade Sandstone of 

present usage but did not include the basal slope. It is described as 

containing "sandstone and some sandy shale."

Past and present terminologies are summarized and compared in the 

table giving classifications of Supai strata.

Summary of past and present classifications of Supai strata

Subdivisions of Noble 

(1922, p. 61)

Informal field terms 

for rock units

New formal terminology 

of Supai Group

Age

Esplanade cliff

Esplanade Sandstone

Upper slope

Wolfcampian 

 Erosion 

Middle cliff

Wescogame Formation

Middle slope

Manakacha Formation

Lower cliff

Lower slope Watahomigi Formation

Virgilian

 Erosion - 

Atokan(?)

Atokan

 Erosion - 

Morrowan 

 Erosion ~

TYPE SECTION OF SUPAI GROUP IN HAVASU CANYON

[Near Supai Village, Coconino County, Ariz. Watahomigi Formation measured on westsideof canyon at Navajo Falls; 

upper part of Supai Group measured along Apache trail, northeast of village]

Hermit Shale: Feet 

Siltstone, moderate-reddish-orange, thin-bedded, ledge-forming; and 

grayish-red structureless slope-forming mudstone; together form 

ledge-slope member .................................................. 170.0
THE SUPAI GROUP SUBDIVISION AND NOMENCLATURE J?

Unconformity. Erosion surface with relief of 44 feet. Consists of isolated plateaus of resistant sandstone that rise above generally flat surface 

of formation.

Feet

Supai Group Esplanade Sandstone: 

Esplanade cliff unit:

Sandstone, massive; forms residual hill or mesa; rises above general surface at % mile north. Estimated.............................................. 40.0

Sandstone, moderate-orange-pink, very fine grained, thick-bedded, 

massive; forms receding round ledges at top of main cliff................ 77.0

Sandstone, moderate-orange-pink, fine-grained (24 percent) to very 

fine grained (57 percent), slightly calcareous, very thick bedded 

(10-20 ft), massive; locally weathers to pinkish gray; forms massive 

cliff...................................................................................................... 63.0

Sandstone, moderate-reddish-orange, very fine grained, friable; contains medium-scale wedge planar cross-stratification (planes 1-10 

ft long)...........................................................................-................... 27.5

Sandstone, moderate-reddish-orange, very fine grained, thin- to thickbedded (1-4 ft), flat-bedded; less resistant than underlying unit; 

upper part contains several 2- to 3-ft beds of pale-red calcareous 

sandstone; forms cliff or receding ledges ........................................... 38.5

Sandstone and limestone. Uppermost sandstone is pale reddish brown, 

fine to very fine grained, calcareous, friable; intermediate sandstone 

is moderate reddish orange, very fine grained, calcareous, silly; basal 

limestone is pale red, silty, clastic; grains etched out on surface. 

The three units form cliffs separated by prominent parting planes; 

all contain medium-to large-scale cross-stratification; contain local 

festoon structures; weather with black varnish.................................. 45.0

Sandstone, pale-reddish-brown, very fine grained, calcareous (26 percent), silty (19 percent), flat-bedded; forms recess between major 

cliffs..................................................................................................... 9.0

Sandstone, moderate-reddish-orange, very fine grained (75 percent of 

grains), calcareous; contains subangular to subrounded grains; 

massive, structureless; contains parting zone of flat-bedded siltstone 

that separates unit into two parts; forms base of Esplanade cliff...... 24.5

Total Esplanade cliff unit............................................................... 324.5

Esplanade slope unit:

Sandstone, moderate-reddish-orange, very fine grained (rounded to 

subrounded), calcareous, thin-bedded (2-3 ft), structureless; contains 

several pale-red calcareous siltstone partings; forms recess below 

massive cliff......................................................................................... 13.0

Sandstone, moderate-reddish-orange, very fine grained, silty; very thinto thin-bedded (1-4 in.); contains irregular to festoon-type structures; forms weak ledge ...................................................................... 1.0

Conglomerate, pale-red, irregularly bedded; fills channels in underlying unit; forms resistant ledge. Matrix: pale-red fine sand. Gravel: 

diameter of most pebbles M-l in.; maximum diameter 3 in.; pebbles 

subrounded to rounded; poorly sorted; composed of olive-gray, lightgray, and pale-red limestone and siltstone......................................... 1-2.5

Sandstone, moderate-reddish-orange, very fine grained; some finegrained; silty, very thin- to thin-bedded (1-4 in.); contains irregular 

to festoon-type structure; forms slope with weak ledges................... 16.0
J8 CONTRIBUTIONS TO STRATIGRAPHY

Supai Group Esplanade Sandstone Continued Feet 

Esplanade slope unit Continued

Limestone, light-brownish-gray, aphanitic to very fine grained; surface markings suggest algae; contains thin, locally developed bands 

of chert; forms two thin beds (6 in. and 20 in.) separated by gray 

siltstone (20 in. thick) and capped by 8-in.-thick bed of concretionary limestone....................................................................................... 4.5

Sandstone, grayish-orange-pink, very fine grained, very thin bedded

(!4-2 in.), flat-bedded; forms receding ledges...................................... 17.5

Limestone, pale-red, concretionary, very hard; includes grayish-red 

silt; forms rounded ledge or slope...................................................... 5.0

Sandstone, pale-reddish-brown, very fine grained, silty; iron-coated; 

grains brittle; structureless; forms slope............................................. 2.5

Sandstone, pale-red, very fine grained, silty, structureless, crumbly;

forms slope.......................................................................................... 2.0

Sandstone, grayish-pink, very fine grained (angular), silty, thinbedded (1-2 ft); weathers to rounded ledge........................................ 5.0

Sandstone, grayish-orange-pink, very fine grained, calcareous, friable;

forms slope.......................................................................................... 4.5

Sandstone, like overlying unit but fills channel................................... 42.0

Conglomerate, pale-red to light-gray; forms thin bed at bottom of 

erosion channel. Matrix: pale-red to light-gray silt. Gravel: general 

diameter range 0.5-2 in.; maximum diameter 3 in.; mostly subrounded, few rounded, some well rounded; composed of light-gray 

limestone and reddish-brown and purplish-gray siltstone................ 5.5

Total Esplanade slope unit with basal channel sandstone and 

conglomerate................................................................................ 121.0

Total Esplanade slope unit excluding two basal channel units ... 73.5 

Total Esplanade Sandstone............................................................. 445.5

Unconformity. Channel, here 47.5 ft deep and 144 ft wide, cut into massive 

and crossbedded sandstones; filled with overlying two units.

Supai Group Wescogame Formation:

Upper slope unit: Not recognized at this locality, 

Middle cliff unit:

Sandstone; pinkish gray with small rusty-brown spots at base, grading 

upward to pale red; fine to very fine grained; calcareous; uhin bedded 

(2-4 ft) at base and at 50 ft above base; elsewhere very thick bedded 

(10-15ft); thinner beds contain flat laminae, thicker beds contain 

large-scale planar cross-stratification (up to 50 ft long); contains 

two dark-reddish-brown lenses of flat-bedded siltstone at 55 ft and 

82.5 ft above base; weathers with dark-brown varnish; forms massive 

cliff...................................................................................................... 138.5

Mudstone, light-brown, noncalcareous, thin-bedded (0.5-2 ft) flatbedded; contains abundant Rivularites; forms recess at base of cliff 8.5 

Sandstone, moderate-reddish-orange, very fine grained, calcareous, 

shaly to structureless; forms slope with weak ledges; fills upper 

part of large channel in older Pennsylvanian rocks.......................... 30.5

Sandstone, moderate-reddish orange; fine-grained to very fine grained, 

calcareous, flat-bedded; includes mud pellets and scattered pebbles 

near base; forms slope; fills channel bottoms.................................... 22.2

Total middle cliff unit with basal channel sandstones.................. 199.5
THE SUPAI GROUP SUBDIVISION AND NOMENCLATURE J9

Supai Group Wescogame Formation Continued Feet 

) Middle cliff unit Continued

Total middle cliff unit excluding basal channel sandstones......... 147.0

Total Wescogame Formation.......................................................... 199.5

Unconformity. Wide channels with rounded bottoms, cut to depths as much 

as 80 ft in cross-stratified sandstones of older Pennsylvanian age 

(here 52.5 ft deep); exposed at this horizon at many places in vicinity.

Supai Group Manakacha Formation: 

Middle slope unit:

Sandstone, moderate-reddish-orange, fine-grained to very fine grained; 

cross-stratified on large scale (up to 40 ft long); includes grayishred muddy noncalcareous very fine grained sandstone near base; 

unit forms slope.................................................................................. 73.5

Total middle slope unit, pre-erosion.............................................. 73.5

Lower cliff unit:

Limestone, grayish-orange-pink, very fine grained (subrounded), silty, 

(insoluble 33 percent); cross-stratified on small to medium scale; 

weathers with black varnished surface; forms massive resistant cliff 

with rounded edges............................................................................. 22.0

Sandstone, pale-red-purple, very fine grained, limy; strongly crossstratified (tabular planar, sets 2-3 ft thick); contains some limestone 

lenses; forms cliff or receding ledge................................................... 20.5

Sandstone and siltstone. Sandstone, pale-red purple, very fine grained; 

locally massive and thick bedded with limestone lenses; grades 

downward into pale-reddish-brown calcareous shaly to thin-bedded 

siltstone; interval forms receding ledges- 59.5

Limestone, grayish-red; includes much very fine sand (insoluble 40 

percent); crossbedded (tabluar planar); sets medium thick (1-3 ft); 

contains jasper near top; forms receding ledges................................ 16.5

Limestone, medium-light-gray; includes scattered very fine grained 

to fine-grained sand; cross-stratified- (medium scale); contains abundant chert and jasper; weathers to rough black surface; forms prominent massive cliff ............................................................................ 13.0

Limestone; light brownish gray with pale-red blotches; thick-bedded 

(4-15 ft); contains jasper layers and veins near base; cross-stratified 

(medium- scale); forms cliff......................................................:......... 39.5

Siltstone, dark-reddish-brown, calcareous (22 percent), crumbly; rests 

on irregularly channeled surface of bright-red mudstone................. 2.0-10.0

Total lower cliff unit.............!........................................................ 181.0

Total Manakacha Formation.......................................................... 254.5

Erosion surface. Structureless reddish-brown siltstone surface is channeled to 

depths of 1-2 ft at irregular intervals and locally removed entirely 

by erosion. 

Supai Group Watahomigi Formation:

Lower slope unit: 

~~ " Concealed slope...................................................................................... 5.5

Sandstone, pale-reddish-brown, very fine grained, noncalcareous, 

structureless; forms conspicuous marker bed; weathers into rounded 

ledge overlying weak cliff................................................................... 4.0

Siltstone, grayish-red, muddy, very limy, wavy- to flat-bedded, laminated ('/£-& in.); contains thin jasper lenses at top; forms weak cliff.. 27.5
J10 CONTRIBUTIONS TO STRATIGRAPHY

Supai Group Watahomigi Formation Continued Feet 

Lower slope unit Continued

Mudstone, pale-red, silty, calcareous, wavy- to flat-bedded, laminated 

('/S-1/* in.); forms steep slope................................................................. 16.5

Concealed slope; probably grayish-red mudstone................................. 22.0

Conglomerate and limestone, medium-dark-gray, concretionary; contains some jasper and lenses of intraformational limestone pebbles; 

forms rounded ledge or steep slope; marks base of Atokan strata .... 8.5

Limestone, very light gray, magnesian, very silty; contains abundant 

elongate concretions and lenses of gray chert; forms ledge at top 

of series................................................................................................ 9.5

Siltstone, dark-gray, friable; forms bench.............................................. 2.0

Limestone, very light gray, silty, fine-grained, thick-bedded (2-6 ft); 

contains thin jasper layers and crosscutting veins throughout; forms 

series of ledges separated by thin (0.5-1 ft) mudstone beds............... 14.5

Limestone, light-brownish-gray, dolomitic; interbedded with black 

mudstone containing network of calcite veins; weathers to concretionary spheres; forms slope............................................................... 2.5

Limestone, medium-gray, fine-grained; contains abundant jasper 

layers and secondary calcite fillings along fractures; weathers to 

rough surface; forms ledge ................................................................. 6.0

Limestone, light-brownish-gray, silty; weathers brown; forms weak 

ledge with straight face....................................................................... 2.5

Limestone, grayish-red, irregularly bedded; interbedded with brown 

mudstone; forms slope........................................................................ 2.0

Conglomerate and limestone, medium-light-gray, silty; contains local 

jasper lenses and lenses of dark intraformational limestone pebbles 

(max. 0.5 in.) at top of unit; forms series of resistant ledges ............ 5.5

Mudstone, pale-red-purple, slightly calcareous, crumbly; forms slope. 5.0

Limestone, medium-light-gray, fine-grained; contains thin irregular 

jasper layers; consists of a single very thick bed; forms resistant 

cliff...................................................................................................... 6.5

Concealed talus slope............................................................................. 33.0

Siltstone, pale-red, shaly; largely concealed; forms slope..................... 11.0

Conglomerate, pale-red, very thick bedded; forms resistant ledge. 

Matrix: pale-red very fine grained to fine-grained sandstone. Gravel: 

mostly M-% in. in diameter; angular to subangular; composed of 

dark-reddish-brown, moderate-orange-pink, and very dark red chert 

and flint.............................................................................................. 2.5

Concealed slope.................................................................. ...... ....... 8.0

Siltstone, pale-red, shaly, fissile; laminated limestone beds (0.25-0.5

in.) scattered throughout interval; forms slope.................................. 6.0

Conglomerate, dark-reddish-brown, thin-bedded to shaly; unit forms 

ledge. Matrix: pale-red very fine grained sandstone and siltstone. 

Gravel: abundant '/6-M in. in diameter pebbles, with a maximum 

diameter of '/£ in.; composed of very light gray, pale-red, and darkgray chert; abundant brachiopods (Composita sp.) at top of unit.... 3.0

Conglomerate, pale-red, massive; unit forms ledge. 

Matrix: pale-red mudstone. Gravel: mostly 3-6 in. in diameter, with 

maximum diameter of 8 in.; irregularly shaped with random orientation; composed of light-olive-gray and dark-reddish-brown chert.... 3.0

Limestone, yellowish-gray, aphanitic, thick-bedded (2-4 ft); weathers 

to very pitted surface; forms ledge...................................................... 5.5
THE SUPAI GROUP SUBDIVISION AND NOMENCLATURE Jl 1

Supai Group Watahomigi Formation Continued peet 

Lower slope unit Continued '

Conglomerate, dark-reddish-brown; contains much iron oxide; fills 

channel. Matrix: dark-reddish-brown mudstone. Gravel: mostly 

H-l in. in diameter, maximum diameter 4 in.; mostly angular; composed of chert...................................................................................... 3.0

Total lower slope unit.................................................................... 215.0

Total Watahomigi Formation........................................................ 215.0

Total Supai Group (excluding channel sandstones)..................... 1,014.5

Unconformity. Channeled surface with 5 ft relief in 100 ft horizontal distance. 

Redwall Limestone:

Horseshoe Mesa Member:

Limestone, yellowish-gray, aphanitic, thin-bedded (1-2 ft); forms 

receding ledges.

REFERENCES CITED

Darton, N. H., 1910, A reconnaissance of parts of northwestern New Mexico and northern

Arizona: U.S. Geol. Survey Bull. 435, 88 p.

____1925, A resume of Arizona geology: Arizona Bur. Mines Bull. 119, 298 p. 

Davis, W. M., 1901, An excursion to the Grand Canyon of the Colorado: Harvard College,

Museum Comp. Zoology, Bull. 38, Geol. Ser. 5, p. 107-201. 

Dutton, C. E., 1882, Tertiary history of the Grand Canyon district: U.S. Geol. Survey

Mon. 2, 264 p., Atlas. 

McNair, A. H., 1951, Paleozoic stratigraphy of part of northwestern Arizona:

Am. Assoc. Petroleum Geologists Bull., v. 35, no. 3, p. 503-541. 

Noble, L. F., 1914, The Shinumo quadrangle, Grand Canyon district, Arizona: U.S.

Geol. Survey Bull. 549, 100 p. 

 1922, A section of the Paleozoic formations of the Grand Canyon at the Bass

trail: U.S. Geol. Survey Prof. Paper 131-B, p. 23-73 [1923]. 

Robinson, H. H., 1911, The single cycle development of the Grand Canyon of the

Colorado: Science, v. 34, no. 864, p. 89-91. 

Stoyanow, A. A., 1936, Correlation of Arizona Paleozoic formations: Geol. Soc. America

Bull, v. 47, no. 4, p. 459-540. 

White, David, 1929, Flora of the Hermit Shale, Grand Canyon, Arizona: Carnegie Inst.

Washington Pub. 405, 221 p.

<rU.S. GOVERNMENT PRINTING OFFICE: 1975-677-311/53
Onon Memorial Library or Ueoiofly 

180 Orton Hall, 155 S. Oval Mail 

The Ohio State University 

Columbus, W 43210