A STUDY of the CHINLE-SHINARUMP BEDS in the LEUPP-HOLBROOK AREA, ARIZONA by Riley S

Home , Geological formation, Petrified Forest Member, Shinarump Conglomerate

A STUDY OF THE CHINLE-SHINARUMP BEDS IN THE LEUPP-HOLBROOK AREA, ARIZONA

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Authors Smith, Riley Seymour, 1908-

Publisher The University of Arizona.

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Link to Item http://hdl.handle.net/10150/298688 A STUDY OF THE CHINLE-SHINARUMP BEDS IN THE

LEUPP-HOLBROOK AREA, ARIZONA

Riley S*-1 Smith, Jr.

A Thesis Submitted to the Faculty of the

DEPARTMENT OF GEOLOGY

In Partial Fulfillment of the Requirements For the Degree of

DOCTOR OF PHILOSOPHY

In the Graduate College

UNIVERSITY OF ARIZONA

195 7 STATEMENT BY AUTHOR

This thesis has been submitted in partial fulfill ment of requirements for an advanced degree at the University of Arizona and is deposited in the University Library to be made available to borrowers under rules of the Library.

Brief quotations from this thesis are allowable without special permission, provided that accurate aclaiowl- edgement of source is made. Requests for permission for extended quotation from or reproduction of this manuscript in whole or in part may be granted by the head of the major department or the Dean of the Graduate College when in their Judgment the proposed use of the material Is in the inter ests of scholarship. In all other instances, however, per mission must be obtained from the author.

SIGNED

APPROVAL BY THESIS DIRECTOR

This thesis has been approved on the date shown below:

JOHN F. LANCE Professor of Geology CONTENTS Page

LIST OF PLATES ill

LIST OF TABLES V

LIST OF FIGURES vi

ABSTRACT vil.

INTRODUCTION 1

Purpose and Scope 2 Location and Description of Area 2 Methods Used in the Investigation 3 Field work 4 Acknowledgements 4

TOPOGRAPHY 7

Rock Exposures 8

STRATIGRAPHY", PETROGRAPHY, AND SEDIMENTATION 9

Historical Sketch of the Shlnarump and Chinle Formations in the Plateau Region 9 General Stratigraphic Relations 11 Shinarurap Conglomerate 14 Areal Extent and Thickness 14 Topographic Expression 16 Relationship to Overlying and Underlying ,r Formations 17 Moenkopi-Shinarump Contact 17 Shinarurap-Chinle Contact 18 Lithologic Aspects of the Shinarump Conglomerate 19 The Shlnarump in the Leupp-Holbrook Area.. 21 Heavy Mineral Studies 27 Primary Structures 29 Secondary Structures 29 Age of the Shinarump Conglomerate 29 Chinle Formation 30 Extent and Thickness 30

i Page

Topographic Expression 31 Relationship to Underlying and Overlying Rooks 31 Subdivisions of the Chinle Formation 32 Nomenclature Used in This Paper ., 34 The Chinle in the Leupp-Holbrook Area 34 Lower Member 38 Bentonite In the Leupp-Holbrook Area 39 Petrified Forest I-Iember 43 Owl Rock Member 45 Limestones 48 Marlstones 50 Porcellanites 51 Genesis of the Limestones and Porcellanites 54 Facies Changes in the Leupp-Holbrook Area. 57 Age Determinations 60

PALEOGEOGHAPHY AND SOURCES OF SEDIMENT 61

SUMMARY AND CONCLUSIONS 65

APPENDIX NO. 1 68

Shinarump Field and Laboratory Studies 68

APPENDIX NO. 2 89

Chinle Field and Laboratory Studies 89

PLATES... 125

BIBLIOGRAPHY. 165

11 PLATES

Plates Pag©

X. Map showing Areal Geology of the Leupp- Holbrook Area, Arizona in pocket

II. Chinle Cross-section and Correlations... in pocket

III-1. Lower member, near section 1 126 III-2. Lower member at section C 126

IV-1. Lava capped mesa southeast of Smith Butte 128 IV-2. Basalt dike at foot of Smith Butte 128 .

V-1. Shinarump outlier resting on Koenkopi... 130 V-2. Unconformity "between Shinarump and Hoenkopi 130

VI-1. South side of Smith Butte 132 VI-2. Closer view of VI-1 132

VII-1. Shinarump outlier capped by lowermost Chinle shales and silt,stones 134 VII-2. Closer view of VII-1 134

VIII-1. Low Shinarumn outcrop near Leupp 136 VIII-2. Closer view of VIII-1 136

IX-1. Shinarump outlier on eroded Koenkopi.... 138 IX-2. Sandstone lens in Shinaruiap at Holbrook. 138

X-1. Silicified log in Shinarump sands, be tween Joseph City and Holbrook 140 X-2. Cross-lamination in the Shinarump at location 2, north of "Winslow 140

XI-1. South side of Smith Butte, showing con tact of Owl Rock and '/Ungate sandstone.. 142 XI-2. Smith Butte; contact between Owl Rock and overlying Wingate 142

XII-1. Newberry Ilesa, £ mi. northeast of Leupp. 144 XII-2. Closer view of 23-D, showing poorly de fined cross-stratification 144

iii Plates Page

XIII-1. Agatized tree trunk from Lower member of the Chinle formation 146 XIII-2. Unit 16 at section C, northeast of Joseph City 146

XIV-1. Porcellanite in the Owl Rock member at Location I, 18 ml. northeast of Winslow.. 148 XIV-2. Thick porcellanite, capping mesa at Loca tion Or, east of Leupp 148

XV-1. Unit 23-D at section E 150 XV-2. Unit 23-D at section E, showing "root-like" features 150

XVI-1. Unit 21-D at section E 152 XVI-2. Unit 23-D at Smith Butte 152

• ' XVII-1. Badlands in Lower member of Chinle, 10 miles west of Joseph Cit2r 154 XVII-2. Bentonite weathering on slope in the Lovrer member at section C, 5 ml. northeast of Joseph City . 154

XVIII-1. Cross-stratification in mudstone, 10 ml. west of Joseph City 156 XVIII-2. Cross-stratification in bentonitic clays in Pet. Forest member, HE of Winslow 156

XIX-1 . Portion of section G-, unit 23-D 158 XIX-2. Section K, showing unit 23-D capping the mesa unit 21 ~D 158

XX-1. Cross-bedding in siltstone layers in the Lower member, section D, ITW of Leupp 160 XX-2. Small unconformity between two units of Lower member, HE of Joseph Citysection C 160

XJCI-1. Cliff-forming layer of the Owl Rock member, 18 mi. IIE of Winslow, section I.. 162 XXI-2. Slump structure in Owl Rock, section I... 162

XXII-1. Unit 23-D capping marlstones of Petrified Forest member, 7 ml. IT of Winslow, sec. E 164 XXII-2. Unit 23-D at section I, 18 ml. NE of Win. 164

lv TABLES

Page

Table 1. Statistical Data on Gravel-size Samples of Shlnarump conglomerate 28

Table 2. Comparisons of the Various Rock Types.... 37

Table 3. Distribution of Bentonite 41

Table 4. Llthologic Types Found in the Chinle Formation.. 59

Table 5. Gravel Analysis at Location No. 1 69

Table 6. Size Analysis of the Matrix at Location No. 1 70

Table J. Gravel Analysis at Location No, 2 74

Table 8. Size Analysis of the TThole Rock at Location No. 3 77

Table 9. Description of Gravel-sized. Constituents at Location Uo. 3 78

Table 10. Gravel Analysis at Location No. 4 82

Table 11. Size Analysis of the Matrix at Location No. 4 83

Table 12. Gravel Analysis at Location No. 5 86

Table 13. Gravel Analysis at Location No. 6 88

v FIGURES Pas©

Fig. 1. Index Map of Thesis Area 5

Fig. 2. Planar Cross-stratification and Trough Cross-stratification 24

Fig. 3. Map Showing Shinarump Cross-stratification Trends 25

Fig. 4. Histogram showing grain size of the matrix at Location Ho. 1 70

Fig. 5. Histogram showing grain sise of the Shinarump at Location No. 3 77

Fig. 6. Histogram showing grain sise of the matrix at Location Ho. 4 83

Ti ABSTRACT

The Shinarump and Chinle beds were investigated in the Leupp-Holbrook area of northeastern Arizona. Cross- stratification trends and cobble studies suggest a south eastern source for the material. A southwestern source direction is also postulated by the presence of Kaibab fossils, gray quartzite, and granite cobbles. The possibil ity exists that the granite and quartzite are from the Brad- shaw Mountains near Prescott.

Coarse clastic facies in the Lower member of the

Chinle show a decrease in quantity and grain size toward the northwest, correlating with the Shinarump findings. Another notable change is the thinning out and disappearance of some of the cliff-forming Upper Chinle units as they are traced southeastward from Leupp to Smith Butte.

The most useful feature for stratigraphic control in the area is a resistant, cliff-forming, porcellanlte bed, found at the base of the Owl Rock, the uppermost member of the Chinle.formation.

Some of the "limestones" of the Chinle formation in the area were found to be true limestones, but others are marlstones and porcellanites. The lime is believed to have

vii been precipitated by evaporation from shallow, flood plain, lake waters. The soluble salts may have been flushed out by vraters from associated streams during flood stage. The silica responsible for the highly siliceous nature of cer tain Owl Rock units is believed to have been released by the decomposition of reworked volcanic ash and its conversion

into montmorillonite. Silica carried by groundwater possib ly enriched the already siliceous rocks. The chert is secondary.

Some substantiating evidence is offered for the concept of the Shinarump as a regressive, blanket deposit, and the Chinle as transgresslve, upward building deposit.

vlli INTRODUCTION

The Colorado Plateau, which includes the Leupp-

Holbrook area, was first explored in 1540 "by Coronado and in 1776 by Escalante and other padres. The first geologist to

visit the area described in this paper was Marcou (1856) who

accompanied Lt. Whipple 011 his 1853 expedition to locate a

transcontinental railroad route. Their party skirted the

south edge of the region, following approximately the route

used today by the Sante Pe railroad. The first geologist to actually traverse the Painted Desert was Newberry (1861) who

was geologist of the expedition led by Lt. Ives in 1857.

Ives apparently was the first person to use the name "Painted

Desert".

Ilarvine and Howell, of the Wheeler survey, later made a brief reconnaissance of the geological features of the

Little Colorado Valley (Howell, 1875).

Ward (1901) made the first detailed studies of the

Painted Desert region, including the area of this report.

A few other early papers on the area under discussion have been published: Dutton (1885), Robinson (1913)» and

Gregory (191^). A notable study of the general region by

Gregory was published in 1917 as "The Geology Of The Navajo

1 2 Country". This work has been the basis for practically all

of the later, more detailed studies of the general region.

Although interpretations of the stratigraphy have been

altered, his extensive reconnaissance geology remains as a

foundation for all subsequent studies.

Darton (1925), Gamp (1930), Harrell and Eckell (1939\

Camp, et al (194-7}* Bab cock and Snyder (194-7)» Colbert (1948,

1950), McKee (1951)» Wilson (1956), and Harshbarger, et al, (in press), have made studies of the Painted Desert area

more recently.

This paper presents a detailed picture of the strati

graphy and sedimentation in the Leupp-Holbrook portion of the

Painted Desert region.

Purpose and Scone

The primary reason for the investigation is to con

tribute toward a better understanding of the sedimentary

facies and ancient environments, including sources, of the

Chinle and Shinarump formations, especially in the Leupp-

Holbrook area.

Location and Description of Area

The area of this report is near the central portion of northeastern Arizona. Portions of Coconino and Navajo counties are included. The southern boundary of the Navajo

Indian Reservation, roughly, forms a mid-line, east and west through the are-?, Index Map, Figure 1, p. 5.

The north portion of the area reaches latitude 35°

55' north and the south end is at 34° 55' north. The west ern boundary is at 111° 00' west longitude and the eastern is at 110° 10' west longitude.

This report encompasses an irregular, roughly ovate area, some 55 miles by 20 miles. The long dimension has a west-northwest trend (Plate I). Some 1100 square miles, all of which lie north of the Little Colorado River, are included in the region. Except for one Shinarump outlier, exposures south of the river were not mapped.

Methods Used In The Investigation

A Brunton pocket transit and an Abney land level were employed to measure dip and strike and to calculate the thickness of strata, respectively. Contacts between map units were sketched directly upon stereoscopic-paired, aerial photographs, then transferred to a master mosaic from which the base map (Plate I) was prepared.

Starting at Sunrise Trading Post, on the Little

Colorado River, and working eastward, columnar sections were measured at intervals.

Samples were studied under a binocular microscope and 4 a description of each was rendered on an oil-well strip log.

Colors used in descriptions are based on the color chart of the National Research Council (1948).

Tests for carbonate were made by use of dilute hydro chloric acid and where significant amounts were determined to be present, insoluble residue tests were made according to methods described by Ireland (LeRoy, 1953). Stain tests

(LeRoy, 1953) were used to distinguish limestone from dolo- mitic limestone. Clay minerals were also identified by use of stain tests (Grim, 1953). X-ray defraction studies were made of some clay samples to confirm the stain tests.

Certain friable sands and silts were screened using

U. S. Standard Selves to determine grain size and sorting.

Heavy mineral suites of sand fractions were examined and the minerals identified.

Thin-sections of selected rocks were studied.

Field Work

Field work was done during the summer and fall of

1951; the last one-half of the summer 1951; and two weeks during August, 1954. Eight months were spent in the field.

Acknowledgements

The writer wishes to thank the director, Harold FIG. I. INDEX MAP OF THESIS AREA. 6

Colten, and staff of the Museum of Northern Arizona, Flag

staff, for library, laboratory and other facilities placed

at his disposal. To John Lance of the University of Arizona

and John Harshbarger, Director of the Navajo Project for

the U. S. Geological Survey, Holbrook, are due thanks for

assistance rendered during this investigation. The author

wishes to extend his appreciation to E. D. McKee, now of the

United States Geological Survey, Denver, who suggested the

study and who gave time and advice.

Great appreciation is due my wife, Dorothy Jane

.Smith, who did the proof reading, typing and helped in re

vising the various chapters. Lastly, without the financial

assistance of A. L. Ladner, Houston, Texas, the project

would never have been completed. Fred TVagnor, of the Carter

Oil Research Laboratory of Tulsa, kindly made X-ray identifi cations of clay samples. TOPOGRAPHY

The Leupp-Holbrook region occupies a small portion of the Colorado Plateau province, which covers parts of four states: Arizona, New Mexico, Colorado and Utah. According to Fenneman (1938), the distinguishing features of the Colo rado Plateau are the approximate horizontality of its rocks; the great altitude above the sea; and the remarkable devel opment of canyons. In the Leupp-Holbrook area the land for several miles north of the Little Colorado River is a rela tively plane surface sloping gently south toward the river.

The mesas are protected by thin beds of very hard, siliceous units of the upper Chinle formation. The continuity of the mesa rims is broken repeatedly by canyon-like re-entrants where erosion has breached the protecting layers. Below the hard layers lie thick claystones, with scattered sandstones, ailtstonos and conglomerate beds. These beds erode into typical badland topography of cones, mounds and miniature canyons. Dimes develop in places where sufficient sand is accessible to the prevailing southwesterly winds. G-ulleys and dry washes dissect the badlands., (see Plate III),

Elevations range from 5500 feet above sea level a few miles north of Holbrook, to 4150 feet at Leuprj. The rim top

7 #

8 of Newberry Mesa northeast of Leupp has an approximate ele vation of 49Q0 feet. Certain lava-capped buttes north of

J Joseph Ci ,yt such as Smith Butte, rise several hundred feet above the general mesa level. In the bottom lands near the river, a few low mesa remnants of dissected Shinarump con glomerate persist,(Plate V - 1).

Drainage of the region eventually finds its way into the main Colorado River. All surface waters in the area go into the Little Colorado by way of numerous washes and chan nels. ITo perennial stream flows through the region and even the Little Colorado is frequently dry. Major drainage into the Little Colorado is by way of the Craibi, Cottonwood, and

Leroux washes, all of which become river-like torrents short ly after heavy rain storms.

Rock Exposures

In general, throughout the Colorado Plateau and in particular in the Leupp-Holbrook area, rocks are well ex posed except where burled by windblown material. Below the mesa fronts are pediment-like slopes eroded out of the Chinle claystoncs and siltstones. A thin mantle of alluvial or windblown material veneers the lower slopes toward the river but in badlands and along the mesa rims the rocks are well exposed, (Plate III -2). STRATIGRAPHY. PETROGRAPHY. AND SEDIMENTATION

HISTORICAL SKETCH OF THE SHINARUMP AND CHINLE

FORMATIONS IN THE PLATEAU REGION

Early workers recognised as Trias sic beds which now include most of the Shinarurap-Chinle strata, although not until Ward's discovery (1901) of Upper Triassic saurian fos sils in his "Leroux Member" (roughly equivalent to the Chinle formation) were the ages of these beds definitely known.

Marcou, in his book "Geology Of North America", (1858), re ferred all visible strata between the Sierra Madre (Zunl

Mountains) and the Rio Colorado Chiquito (Little Colorado) to the "Trias". Although he did not present evidence for his conclusions, apparently he was swayed by the similarity of the llthology of these rocks to that of Triassic strata in

Europe. Newberry (1C61 ) divided the strata lying; between the

Cretaceous and the Carboniferous into a "red sandstone" and a group of "variegated marls" (Chinle formation), the "marls" being considered Triassic in age. Howell (1 o7*5) likewise in cluded the "variegated marls series" of Newberry In the Tri assic along with certain overlying massive sandstones.

Powell (1876) shows a columnar section for the Uinta

Mountains area In which he has included a "Shinarump Group".

9 10

He has some 1800 feet of sediments, of which, from his der scription, the upper 800 feet of "badlands" sandstone and mudstone seemingly correspond to the "variegated marls"

(Chinle) of Newberry and the 80 feet of "conglomerate", more or less dividing his group, is equivalent to the Shinarump conglomerate of today. The lower 900 feet of Powell's group apparently corresponds to the Moenkopi formation. Although

Powell included the "Shinarump Group" in his section on the

Triassic, he apparently suspected that the beds might be Ju- assic. Powell thus included in his "Shinarump Group" the formation we know today as the Moenkopi of Early Triassic age and the Shinarump conglomerate and Chinle formations of

Late Triassic age. The Shinarump conglomerate is the only portion of Powell's group that retains the original name.

Dutton (1885) divided the beds into two parts: a

Lower Triassic, and some 1600 feet of mudstone with a sand stone "equivalent to Powell's Shinarump conglomerate" at the base. Ward (1901) re-defined the "Shinarump Group" of Pow ell, excluding the lower portion and naming it the "Moen- copie" (now I-loenkopi) formation. The "Shinarump conglomer ate" portion of Powell's group Ward placed at the base of his "Shinarump formation" which included an cOO foot thick, lower "Lithodendron" member (Ward, 1905) and an upper 800 foot portion called the "Leroux" member. These two are roughly equivalent to the Chinle formation of the present 11 time. Ward placed the "Orange-red sandstone" member of his

"Painted Desert formation" above the 'Leroux" member, the

"Orange-red" apparently being at the base of the Wingate

sandstone of Button (1G85). Ward regarded the iloenkopi as

Lower Triassic and was later proven correct, although most

early writers deemed the beds to be of Permian age. Robinson

(1913) accepted Ward's new definition of the "Shinarump" and thus the name had a confused status, being used in three or

more different ways.

Gregory, in his paper "The C-eology Of The Navajo

Country" (1917) brought order from the chaos which existed at the time. He raised the Shinarump conglomerate "member"

of Powell's original... "Shinarump Group" to the status of a formation and gave the name Chinle to the "variegated marls" of Newberry, the "Lower Trias" of Dutton and the "Lithoden- dron and Leroux members1' of Ward.

GENERAL STRATIGRAPHIC RELATIONS

Aside from a small area of the Permian Coconino sandstone exposed midway between Holbrook and Joseph City

(Babcock and Snyder, 1947) all sedimentary strata in the area of this report either are Triassic or post-I-Iesozoic in age.

The post-IIesozoic consists largely of river sands and gravels. Locally, occurrences of basaltic rocks of probable

Tertiary or Quaternary age (Harrell and Eckel, 1939) crop out 12 in the area some 10 miles north of Joseph City (see Plates IV and VI). The igneous rocks form dikes and lava flows. Smith

Butte is capped "by a basaltic lava which has protected the underlying Wingate and Chinle from erosion.

The I-Ioenkopi formation, of Early and Middle (?)

Trlassic age (McICee, 1954), unconformably overlies the Coco nino sandstone between Joseph City and Holbrook, but farther west the Kaibab limestone of Permian age comes between the two * The Kaibab, however, does not crop out In the area be tween Leupp and Holbrook. The Moenkopi formation is exten sively exposed on both sides of the Little Colorado River be tween Holbrook and Y/inslow and along the south side between

Leupp and Winslow. It no doubt underlies Shinarump and Chin le strata in the region to the north and west. The Moenkopi formation between Holbrook and Winslow has a thickness of some 200 to 400 feet (Harrell and Eckel, 1939) and consists of a series of red, red-brown, or "chocolate-brown" mudstones and sandstones. Mud cracks and ripple marks are characteris tic of some parts of this formation. Between Holbrook and

Joseph City a large road cut has exposed bedded gypsum in the

Moenkopi, indicating an arid environment of deposition for that formation, in part at least.

An extensive erosion surface was developed on the

Moenkopi before the Late Triasslc beds were deposited.

Stream channels were cut into the upper surface and filled 13 with sands and gravels of the Shinarump. In some places,

where the Shinarump is missing, the Koenkopi surface is over lain by Chinle sands and muds. In most places, however, the

Shinarump comes between the I-Ioenkopi and the Chinle which

conformably overlies the Shinarump.

Disconformably above the Chinle formation is the

Wingate sandstone, also of Late Triassic age {Harshbarger,

1954). The contact is exposed at only a few places in the

area investigated. In many places, especially between the badlands escarpment and the Little Colorado River to the

south, recent alluvial or windblown sediments cover the

eroded top of the Chinle. 14 SHINARUMP CONG-LOMERATE

Although Newberry had noted, as early as 1861, the rocks that were later called the Shinarump, Major J. W.

Powell (1873) Introduced the name. He was, however, not de fining a geological formation but rather naming an east-west escarpment in the Fredonia-Kanab area, which the Indians called "Shinarump (or Arrow) Cliffs" from the numerous petri fied logs (Arrows) present. Later, (1876), Powell used the name "Shinarump Group" in his description of a thick sequence of Triassic rocks in the north central Arizona region. Ward (1905) Included the

Moenkopi with the Shinarump. The restricted Shinarump con glomerate of current usage was defined by Gregory in 1913.

No single type section is located by Gregory although he describes several outcrops where the rocks occur.

Areal Extent And Thickness

The Shinarump conglomerate originally covered a con siderable portion of the Colorado Plateau, judging from its exposures today. Gregory (1950) states that:

/krtoiisive field work shows that the gravel lies on 0. surface of low relief unaffee tod by noticeable faults, folds, or regional upwards ar.C that it is not restricted to long trains but ::.i i" •'c: s as an al most continuous sheet nearly 100,000 s-iuarc niles in area. 2ucli remarkable persistence, so seemingly out of accord with lithologic character, seems not to have been duplicated in ancient or recent deposits. 1$ The Shinarump conglomerate is recognized westward

from the G-oodsprings Mountains of southern Nevada to Fort

Wingate, New Mexico and southwestern Colorado. It also ex

tends from near Snowflake and Flagstaff, Arizona northward

into central Utah. Some authors, notably fleaton (1950),

place the Shinarump conglomerate in northern Utah and central

Colorado. His paleogeographic map of the Upper Triassic (p.

1680) also shows the Shinarump (and Cliinle formation) in Wyom

ing, eastern New Mexico and West Texas. Validity of extend

ing these rocks so far to the east and north is questioned

by the writer. They are not correlative with the Shinarump

conglomerate but are higher in the section (McKee, 1955, per sonal communication). Most students of the Shinarump con

glomerate agree with the limits given above.

Considering its extensive distribution, the Shinarump

conglomerate is remarkably thin. In the Muddy Mountains of

Nevada its average thickness is not more than 50 feet. In

Zion Canyon national Park it ranges from 75 to 200 feet; in east central Utah from 30 to 100 feet; in the entire region of deposition as a whole, it is 50 feet or less in thickness.

A maximum recorded thickness of 350 feet is found near Monu ment Valley where an ancient channel some 250 feet in depth has been filled with Shinarump deposits. In many areas it is absent locally as a result of non-deiDosition where ancient surfaces were high topographically. 16

The Shlnarump conglomerate crops out In the Leupp-

Holbrook region only along or near the flood plain of the

Little Colorado River (Plate I). The thickness varies from

20 to 36 feet. The largest exposures in the area covered by this report are along the dip-slope of the escarpment north of United States Highway No. 66, vest from Holbrook to Joseph

City. Lesser exposures are between Jack Rabbit Trading Post and YJlnslow and others a few miles north and northeast of

WInslow. A small exposure, far from the others mentioned, is found four miles north of Sunrise Trading Post. Another very small one is approximately two miles to the northeast of the trading post (Plate I).

Topographic Expression

The Shlnarump formation, wherever present, forms prominent benches or low cliffs* Gilluly and Reeside (1927) state that:

The topographic expression of the Shlnarump is strong. It lies between two formations of relatively unreslstant material that breaks down into slopes between which the Shlnarump, though not really an extremely hard formation, has the relief of one

The tendency to form cliffs is demonstrated by the . southward facing, nearly continuous escarpment between Hol brook and Joseph City, where the cliffs are 100 to 150 feet high. 17 Relationship To Qverlylnp; And Underlying Formations

I'loenliQ-oi-ShlnaruEro Contacts -- In most parts of the

Colorado Plateau the Lloenkopi and the Shinarump have a dis-

conformable relationship. Some angularity'" has been noted by

McKee (1953) in the vicinity of the I-Ioab anticline in south

eastern Utah. In a few places the Hoenlzopi is missing and the Shinarump lies upon older formations.

Along the Little Colorado River valley, from Holbrook northwest, the Shinarump conglomerate lies upon an eroded surface of the I-Ioenkopi formation. Relief on the pre-Shina- rump surface varies from a few inches (Plate V) to several feet. Hot uncommonly where there were prominent hills on the old Moenl'opi surface, the Shinarump deposits did not cover the high places and Cliinle beds rest directly upon the

Koenkopi. In such cases, the contact between the Hoenlcopi and Chlnle is difficult to identify because of the liekness of colors and lithology. Y/here the Shinarump rents upon the

Moehkopi, the line of separation is easily observable, the grays and light browns of the Shinarump cands and gravels contrasting effectively with the reddish-brown mudstones of the Hoenliopi. The red and brown mudstonec, and siltstones of the Koenhopl formation are commonly bleached immediately be neath the contact with the Shinarump (Plato V). Bleaching also extends downward along cracks and joints. The sharp, undulatory contact and the lighter color easily establish 18 the unconformity. No definite ancient soil profile was ob served in the area examined.

Shlnarumr?-Chinle Contact. -- Because of the soft and friable nature of the lower Chinle claystones, mudstones, siltstones and sandstones observable exposures of the contact with the underlying Shinarump conglomerate are uncommon. In most places the junction between the two formations is con cealed. This is especially true in the Leupp-Holbrook area, where the top of the Shinarump, if not covered by talus, is swept clean of overlying material or else is buried by a blanket of recent windblown or fluvial debris. Clean-cut contacts are thus rare.

The Shinarump conglomerate is believed by many authors to be the introductory or basal phase of the Chinle formation. No important hiatus is recognised between it and the Chinle. Locally, diasterns may be present. In the writ er's opinion the Shinarump should continue to receive the status of a formation rather than become a member of the

Chinle as some have recently advocated. This is because:

(a) it possesses the distinctive lithology of a mappable unit, and (b) the name is so well known and so deeply en trenched in the literature that the proposed change can only lead to confusion. Why replace a short, well understood, concise terminology with the cumbersome "Shinarump member of the Chinle formation"? There is also a matter of some 19 difference In origins. The Shinarump was formed as a "re gressive sand" (I-lcKee, 1953) while the Chinle (excluding the

Shinarump) was transgressive and "built upwards" (Wilson,

1956). Bartram (1939, p. 1076) points out that a distinctive lithology is sufficient to establish the formational qualifi cation, no hiatus being necessary. In this paper the Shina rump will be referred to as a formation.

Only one exposure of the contact between the two formations was found in the area of this report. Five miles northeast of V.'inslow Is an outlier of Shinarump conglomerate with several feet of shaly Chinle siltstone ana mudstone capping it (Plate VII-l). At the contact, the Shinarump is a thin to very thin, cross-bedded, coarse sandstone. The line of junction as exposed is sharp and more or less irreg ular on a small scale. The two formations are separated by a surface of local erosion, of no more importance perhaps than the beveled planes between portions of the Shinarump it self. The overlying lowermost Chinle is a greenish-gray, slightly cross-laminated, shaly siltstone about two feet thick, above which is 17 feet of pinkish-gray claystone, the top of which is eroded.

Lltholof-lc Aspects Cf The Shinarump Conglomerate

Although the appearance of the Shinarump may vary locally, it has a unique sameness prevailing over the whole 20 extent of its exposures on the Colorado Plateau. Dutton was much impressed by the quality as he said (1885) that "the Shinarurnp conglomerate keeps its aspect unaltered wherever it spreads". Gregory (1917), after extensively observing the outcrops in widely scattered localities discerned a consider able range of differences in structure and composition, but concluded that: "The likenesses however, are much more num erous than the differences and outcrops separated by 200 miles resemble each other more closely than they resemble any parts of other Kesozoic formations." The Shinarurnp has been described repeatedly by many different writers with a considerable degree of unanimity concerning its lithologic aspects. Gregory (1917), Darton

(1925), and others picture the Shinarurnp as a white to gray, rarely brownish rock, varying from sandstone to a conglomer atic sandstone or conglomerate,(see Plates V-2, IX-2).

The Shinarurnp is everywhere lenticular, with coarse material overlapping lenses of finer material. Cut and fill structure is greatly in evidence, especially at the base where channeling is found in the ancient pro-Shinarurnp ero sion surface. The erratic fluvial cross-stratification varies fro:' short, steeply inclined laminae- to gently dipping thick cross-beds extending many tens of foe I between termina tions. Various conditions are shown on Plates VII-2, IX-2. Some outcrops are almost exclusively of sandstone; 21 many are quartzitic; others are predominantly conglomerate, composed variously of angular to rounded vein quartz, quartzite, chert and limestone gravel. A single layer of pebbles may be "plastered" along the bedding plane of a finer and more massive unit or may be intercalated parallel to the bedding in the midst of some thick unit, lending to the ver tical exposure a string of bead3 appearance. Petrified wood is present in most outcrops and varies in size from fragments a fraction of an inch in diameter to several feet in length.

Entire logs are occasionally found (Plate X-1 ). Also com mon are other materials, such as boulders of siltstone or mudstone, clay galls and, rarely, granite cobbles. Charcoal and sooty material are common at some localities.

Some observers (Mclvee 1953) have noted that the upper sones are finer grained in general and better sorted than the lover zones. This condition seems to be true also of the outcrops in the Leupp-Holbrook area.

The Shlnarump In The Leup-p-Kolbrool: Area

A series of discontinuous, lovr, sometimes cliff- forming outcrops of Shlnarump extend from Leupp southeast ward to Ilolbrool:. Detailed investigations ;;ere made at six unevenly spaced stations (Fig. 3). In addition to the gross lithologic character, cross-stratification v.ras studied in the hope that it might shed some light on the directions of 22

of ancient currents and sources of material.

Laboratory studies were made of representative samples to determine size, composition, shape, roundness, sorting and markings. In addition to mechanical analysis, the heavy minerals were investigated.

Depending upon the authority quoted and the sampling location in the Leupp-Holbrook area, the Shinarump may var

iously be called a cobble-conglomerate, a sandy-conglomer ate, a pebbly-sandstone, or even a coarse sandstone. Petti-

john (194-9) indicates that a clastic sediment having *0% or more of material larger than 4 mm in diameter could be called a gravel (conglomerate). On this basis all of the Shinarump investigated could qualify for the term. However, in 1957

Pettijohn (Fig. 11-3) displays a classification diagram after

Y/illman in which 25/j or more of material greater than 4 mm in diameter is termed gravel. The later definition will be ad hered to in this paper since any indurate? rock containing a gravel-si:;e concentration approaching 2^,' would certainly be called a conglomerate by most field geologists. Of the outcrops studied, only at '/."inslow ancl 5 ..:iles northeast of

Winslow would the rock fail to qualify — being very coarse, pebbly sandstone. In one place (".-'Inslow) the upper layer of the outcrop is so well cemented with opaline silica as to constitute an ortho-quartsite.

The thickness of the Shinarump outcrop varies from approximately 10 feet at Leupp (Location #1) where the base

is concealed and the top eroded, to approximately 40 feet at

Winslow (Location $2) where the base is exposed and the top

intact, A full section is also found at Joseph City (Loca tion #4) amounting to 25 feet and at Holbrook (Location 7)

where it is 10 feet. The average of all 7 places Investi

gated gives an observable thickness of some 20 feet.

The unweathered Shinarump varies from yellowish-gray

at Leupp, grayish-orange-pink at Winslow, to yellowish-gray at Joseph City and very pale orange at Holbrook. Weathered

colors are not consistent even in one locality but in general the same colors, increased In intensity and somewhat darker, are the rule.

Inclinations of cross-strata were studied at the several locations with somewhat anomalous results, although a general northwesterly component nay be Inferred for the ancient currents (Fig. ~).

Only two types of the three kinds of cross-stratifi cation described by I-IcKee and Weir (1953) were observed: planar and trough type (Fig. 2); sc-e Plates VII-2 and VIII-2.

Scale of cross-stratification varies from small (less than one foot between terminations) to medium (1-20 feet) and large (over 20 feet); see Plates VII-2, VIII-2 and V.

Mechanical analysis gave varying results in the grav el size material (Table 1) but the finer portions were more 24

(a) (b)

Figure No. 2. (a) Planar cross-stratification; lower bound ing surfaces of sets are planar surfaces of erosion, and (b) Trough cross-stratification; lower bounding surfaces of sets are curved surfaces of erosion.

uniform. The histograms (Fig. 4, 5> and 6) show the finer

material to be concentrated mainly in the coarse sand size

classifications. It is notable that little material, per

centage-wise, is in the very fine sand grade or smaller.

Sorting is thus, fair to good (Krumbein, 1?3C).

The average size and weight of gravel varies from

10x7^5 mm (wt. 0.75 grams) 5 miles northeast of Winslow to

28x20x14 mm (wt. 18.0 grams) at Joseph City. Rotable is the fact (see Table 1) that the gravel average else is definitely larger toward the Hclbrooli end of the line of stations.

Composition of the gravel is mostly vein quartz near

Leupp, changing to chert toward Holbrool:. Interestingly

enough, rounded granite fragments were found in the area'near OILKON INDIAN r WELLS 7/ CASTLE JVtlSE BUTTE TP "K.LEUPP

WINSLOW r JOSEPH b

HOLBROOK \

FIG.3. MAP SHOWING SHINARUMP CROSS-STRATIFICATION TRENDS. ro 0 MILES 10 C71

i 26 Holbrook. Some gray quartzite is found at various places

"but the bulk of it is northwest of Winslow. Petrified wood, carbonaceous natter, siltstone fragments, and clay galls are not uncommon as gravel material. Rounding was generally better toward the southeast.

At Leupp the gravel is subangular (0.45) whereas from Joseph

City and southeast it is subround (0.60). Little difference in sphericity was noted, although again the .average Krumbein index of sphericity was generally higher (0.74) toward Hol brook than toward Leupp (0.70).

As a measure of the maximum competency of the ancient water currents the largest cobble observed was found at Joseph City, weighing 5*390 grams while the smallest maximum sized cobble was found northeast of Winslow and weighed 3.2 grams. Currents were definitely weaker around the Winslow area it seems from the data.

Studies were made of the matrix at various places.

At all stations except 3 miles north of Winslow, the cement ing material was calcium carbonate, varying from a maximum of 3.C/J of the matrix by weight at Joseph City to 1.6$ north east of Winslow (Location #3). The main cementing agent at Vinslow (Location #2), especially in the upper layers, is opaline silica.

Angularity is notable in the sand grades, regardless of the class; most of the material ranging from angular to 27 sub-angular. Some well rounded and even "frosted" quartz

grains were observed in most fractions but were rare.

Heavy Mineral Studies

In order to investigate the heavy minerals contained

in the finer sand of the matrix, separation from the light fractions was effected by use of bromoforme liquid (specific t -gravity of 2.87). As expected, the light mineral portion was feldspar, mostly microcline, with some albitic plagioclase. The heavy mineral suite is without particular dis

tinction. Zircon and magnetite are the most common minerals, followed by tourmaline, garnet, apatite and chlorite. Titan- ite, pyroxene, hematite, enstatite, diopside and biotite are less common. The magnetite grains were well rounded without exception and, in general, so were the zircons. It is not possible to draw definite conclusions as

to type of source rock. However, from the apatite, biotite,

zircon, titanite, tourmaline, magnetite and the light miner als quarts and microcline, a possible acid igneous prove

nance may be postulated (Pettijohn, 1957). The presence of granite cobbles at two localities is additional evidence.

Gray quartzlte, similar to that exposed in the Bradshaw Mountains area near Prescott, chert cobbles, some of which contain ICaibab brachlopods, siltstone and pyroxene suggest

other source rocks. TABLE 1, STATISTICAL DATA OK GRAVSL- SIZE SAMPLES C •"-Average •"Average •-Dominant Average Average Max Location Roundness Sphericity Class and Gravel C-ravel S i.C vpe Size Weight Gra

Location Ho. 1 0.45 0.70 40% _ III 19x14x5 5.0 49x3 5miles north sub-ang. 21% =r II mm grams m west of Lcumo oo^ zz VI u% zz i,v

Location Ho. 2' 0.42 0.74 50% III 12x9x7 1.2 29x1 3 miles north sub-ang. 28% VI mm grams m of Winslow 20% - II 2% zz V

Location ITo. 3 0.32 0.71 55% — III 10x7x5 0.75 23x1 5 miles north sub-ang. 27% V mm grams m 1 east of .7inslow 18% " II

Location No. 4 0.60 0.74 50% — III 28x20x14 18.0 245x 1^ mile north sub- 28% ZZ II mm grams x87 east of Joseph round 14# zz VI City 8% zr V

Location ITo. 5 0.60 0.73 46% — III 26x20x14 14.4 1 58X 5-, miloc north sub- 3b% - II mm grams x100 west of ITolbrool; round 1 C./3 VI • Q y "V"

Location ITo. 6 "" 0.52 0.75 58% III 26x20x15 13.8 150x northwest edge sub-ang. 26% — II mm grams x120 of Ilolbrool: 11% = VI 5/frr? zz V

Roundness after Krumbeir., Sphericity after Krumbein, Shape after Payne. 28

- SIZE SAMPLES OF SHINARUMP CONLGOMERATE Average Maximum Maximum G-ravel Size Weight Composition and Color -- Percent of Weight Gravel G-ra.vel , Sample 5.0 49x^7x27 63.89 73% light orange vein quartz, 15% light grams ma grams grayish purple quartzite, 7% gray to light orange petrified wood, 5% light brown chert

1.2 29x19x16 9.9 77*$ light brown vein quartz, grams mm grams 22-h% reddish to yellowish brown chert

0.75 23x17x8 3.2 50% grayish orange chert, 20% medium grams mm grams dark gray quartzite, 30% pale yellow ish brown quartzite

18.0 245x115 5390. 34^ light olive gray chert, 30;^ dark grams x87 mm grams gray chert, ?A% pale yellowish brown chert, 0% gray red-orange chert

14.4 158x102 2140.9 86% dark to light yellowish to brownish grams x100 mm grams gray chert, 8% white to light gray to yellowish brown vein quartz, A-% grayish red to yellowish brown quartzite, 2% light r;ray --.rani to __

13.8 150x120 3030.9 70,t light to dark gray, pale to dark grams x120 mm grams yellowish brown, to pale orange chert, 28% grayish red to gray quartzite and vein quarts, 2% rale orange granite

after Payne. 29 Primary Structures

Cross-stratification has already been described. Other primary structures found are mud-cracks, rain-pits, swash-marks, ripples, worm trails and pre-consolidation slump structure. Such features as current ripple marks are common but the others are rare except in certain localities.

Secondary Structures

Jointing is universal in a consolidated rock such as the Shinarump. However, no definite trends were noted.

No proven faulting was observed although slumping produced some offset along joints.

Age Of The Shinarump Conglomerate

Some bone fragments, well water worn, have been found in the formation but do not help in dating it. Abun dant fossil wood, including some petrified tree trunks over

40 feet in length has been used by Daugherty (194-1) to assign a Late Triassic age to the formation. Its stratigraphic position conformably below the Upper Triassic Chinle supports this contention. 30

CHINLE FORMATION

A brief historical sketch of Chinle and Shinarump beds of Upper Triassic age has already been given. Gregory

(1917) names the Chinle formation from exposures near the village of Chinle, Arizona. Sediments of the formation cover a great portion of the Colorado Plateau and compose one of the most important continental Triassic exposures in the world. The report area is located along the southern portion of the Plateau.

Three things are especially noticeable when one is first introduced to the "Chinle Country": first, the color ful bands of various shades and hues of red, blue, purple, yellow, brown, gray and white of the clay and mudstones; second, the badlands topography with its cones, mounds and

"hoodoos"; and third, the profusion of petrified wood, much of it agatized, in the lower half of the formation.

The geologist notices the extreme variability of the lithology below the resistant uppermost rocks, the cross- bedding and the lensing and pinching out of the units.

Extent And Thickness

The Chinle is exposed across northern Arizona, in southeastern Nevada, across southern Utah and in northwestern

New Mexico. It is quite variable in thickness, reaching 31 more than 3000 feet In southeastern Nevada, decreasing to

300 feet to the east in the San Rafael Swell country of Utah and increasing to 1500 feet in the subsurface of the San

Juan Basin of northwestern New Mexico. At Chinle, Arizona there are 900 feet of the sediments, whereas at Joseph City a 1200 foot section was measured. TTo Chinle is known south of the Mogollon Rim In central Arizona.

Topographic Expression

The Chinle formation, comprising a varied lithology, induces a varied topography. The uppermost part of the formation is composed of more resistant rock, such as lime stone or silicified limestone (porcellanite). These hard layers form cliffs and cap extensive mesas. The softer and more friable middle Chinle is mainly claystone and shaly mudstone which erodes into the tjrpical badlands of the

Painted Desert country. The lower portion of the formation is replete with shaly mudstones, shaly siltstones, cross- bedded sandstones and even gravel beds. Such rocks form badlands with numerous ledges, benches and low mesas.

Relationship To Underlying And Overlying Rocks

The contact between the Chinle and the Shlnarump has already been discussed. Above the Chinle, in the Leupp- 32 Holbroolc area lies the Upper Triassic Wingate sandstone, although to the northwest in the Echo Cliffs region, the

Moenave formation (Harshbarger, et al, 1957) is found over lying the Chinle.

The only Chinle-Wlngate contact in the report area is found near Smith Butte, some 15 miles north of Joseph

City, Arizona. Here, several buttes are capped by Tertiary lava flows, thus protecting the softer rocks from erosion.

An excellent exposure of the contact between the Chinle and

Wingate is to be found approximately half-way up the slope on Smith Butte, where it is sharp and gently undulatory; a disconformable relationship (Plate XI ). The top Chinle layer is a hard, calcareous mud stone; the lowest Wingate is a soft, friable, silty mudstone.

Subdivisions Of The Chinle Formation

The Chinle beds or their equivalents have been repeatedly described in the literature, both before and following Gregory's 1917 paper. On the basis of lithology and field appearance he divided the formation into four mem bers. In descending order these are: Divisions A, B, C, and D. With the exception of the uppermost, all are valid

Chinle members today. In 1951 Harshbarger, et al, split off

Division A and placed it in overlying Wingate in the area of this report. Gregory's three lower divisions remain today, although more descriptive names have replaced the letter nomenclature and in some instances, further subdivision has been attempted. The following is quoted from Gregory:

Division A. the highest strata: Red, brown, pink or rarely gray calcareous shales and shaly sandstones, with a few thin beds of limestone and limestone con glomerate; form banded walls at the base of the over lying massive Wingate sandstone: intricately carved Into buttes or distributed as a patchy floor over the topmost limestone stratum of division B. Type local ities, Mesa de Ventana and Todilto Pari:.

Division 3: Gray, pinl:, and purple clierty lime stone and light to dark red shale, In alternating bands. Limestone is massive or conglomeratic, in beds 1 to 6 feet thick, 3s highly resistant, and forms the tops of mesas and local plateaus; shales are thin, calcareous, mottled, and friable. Type localities, Carson I-Iesa, Leroux Wash.

Division C: Shales and "marls", with rare calcareous sandstone, all lenticular, exceedingly friable, variegated with tones of pink, red, ash and purple; limestone conglomerate in lenses, short beds, and irregular masses is characteristic; gyp sum is common, and petrified wood almost universal; weathers into mounds, buttes, and immature mesas with typical badland expression. Type localities, Cottonwood Wash, Black Creek Valley, and Beautiful Valley and Round Rock fossil forest.

Division D: Dark-red, light-red, chocolate- colored, or rarely gray shales (70 per cent) and shaly sandstones (30 per cent); ripple marked, imbricated; brown conglomerate of lime and clay pebbles occurs in lenses; gypsum common; petrified wood in small amounts; bone fragments abundant; weathers into buttes and mesas divided by sharply cut miniature canyons, producing very rough topog raphy. Rests unconformable* (?) on the Shlnarump conglomerate. Type locality, Chinle.

In 1950 Gregory applied the name "Petrified Forest" member to Division C. Harshbarger, et al, in 1S55 substi tuted "Lower" member for Division D. In 1956 Witkind and 34 Thadden used the name "Owl Rock" member for Division B. Wilson (1956) has further subdivided the Petrified Forest member and has included the Shinarump in the Lower member. Other subdivisions of the Chinle to the east are not applicable to the Leupp-Holbrook area.

Nomenclature Used In This Paper

After extensive study of the sections in the Leupp- Holbrook area and comparison with recent subdivisions of the U. S. Geological Survey, it is not believed that new nomenclature, other than the large divisions, Owl Rock, Petrified Forest and Lower member are feasible here. Nei ther does the writer feel that Wilson's attempts ('1956) to further subdivide the Petrified Forest member serve a use ful purpose in the report area, because of the extensive intertonguing relationships.

The Chinle In The Leupp-Holbrook Area

There are extensive outcrops of the Chinle formation in the area north of the Little Colorado River, between Leupp and Holbrook. In most of these places, however, the lower Chinle has been removed by erosion. Dip is very gentle to flat, causing exposures of the Chinle to be spread out over great expanses. In general, the escarpment of the Chinle stays well north of the Little Colorado River (Plate I, in pocket:, varying from 7 miles north of Leupp to 15 miles northeast of Winslow, then closing in to a couple of miles north at Joseph City. The escarpment turns north along

Leroux Draw, some 2 miles west of Holbrook.

Upon a cursory examination, the imposing Chinle badlands and cliffs would seem to offer vertical complete ness. This is not the case however, because with one ex ception no complete sequence is present, and in some cases, little other than the well-indurated, lower siliceous layers of the Owl Rock member remain. Erosion either removed the higher portions or the lower parts v/ere covered by windblown debris, or both.

Columnar sections were measured at nine locations

(see Map, Plate I), starting from the southeastern extremity of Newberry Mesa north of Leupp and ending on Marcou Mesa,

10 miles north of Holbrook. Only one complete section, starting at the top of the Koenkopi formation and ending at the base of the Wingate formation was available, the one starting at Joseph City and extending northerly 15 miles to

Smith Butte, a mile-long mesa capped with Tertiary flow-rock (Plate VI ).

Chinle thicknesses available for measurement range from 533 feet at Section D, near Leupp; 221 feet at Section

K, 17 miles east of Leupp; to 1118 feet at Section F, running 36 north from Joseph City. In all cases, except at C and A, the sections were tied in to the key bed at the base of the

Owl Rock member (see cross-section, Plate II, in pocket).

The most useful feature for stratiGraphic control in the Leupp-Holbroc k area is a resistant, cliff-formins bed.

This unit, which is called 23-r, in reference to its position in the measured section northeast of Leupp, (Plate XII), was the only horizon which could be clearly identified con tinuously along the 40 miles of intermittent escarpment from

Newberry IIcsa, southwest to Smith Butte. The unit was miss ing because of erosion in the two easternmost sections studied.

Cross-stratification, lensing, wedge-outs and minor unconformities (Plate XX) are notable features of the lower

Chinle. In the upper Chinlo, banded fortrcss-like cliff rims may be traced for miles, wending their way back and forth in a maze of re-entrants and box canyons. Large ro tary slump structures are not uncommon (Plate >1X1).

A cursory examination cf Table II clearly indicates the decrease in coarseness of the material as one passes up ward from the Lower member into the Petrified Forest member and on into the Owl hock. Carbonate content, on the other hand, increases upward. Very little carbonate is found in the Lower member but marlstones and limestones are quite prominent in the Petrified Forest and Owl Rock members. 37 TABLE 2 — COMPARISONS OF THE VARIOUS ROCK TYPES

OWL ROCK MEMBER LITHOLOGIC THICKNESSES (in feet)

Sections Litholorj," D J G K E I F Sandstone 1 Mudstone 2 28 43 73 184 50 Claystone 23 38 12 44 Marlstone 10 42 13 31 270 Limestone 5 12 8 15 24 16 Porcellanite 22 4 2 5 6 4

'Ttttcottq PETRIFIED FOREST LIiiii'IB HJR LITHOLOGIG THICI ( in fee-

Sec tions Litholo -y D J G K E I F C Sandstone L Mudstono T( 1 22 122 253 Claystone 209 11p 100 131 121 -* o Marlstone "52 JO 51 p 25 o T Limestone L- I 5 2 Porcellanite "Jr™

LO 2R MEMBER LITHOLOGIC THICKNESS:IS (in feet)

Sections Litholofty D "Tn I F C A Conglomerate 1 1 4 Sandstone 44 72 r> 59 201 13 93 1, Siltstone 20 *~T 45 22 Mudstone 56 66 44 47 177 22 Claystone 100 25 235 180 68 Marlstone 10 6 Claystone, Including bentonite, is evenly divided between the two lower members. Bentonite Is concentrated in the

Lower member. The highly siliceous rocks are restricted largely to the Owl Rock member.

Lower Member

The Lower member was named by Harshbarger, et al, in

1955 and is Equivalent to Gregory's Division D of earlier nomenclature. This member is notable especially for its numerous bentonitic claystones, cross-bedded sandstones, siltstones, a limited number of conglomerates and a few, very thin chertlfied sandstone layers. Also of importance is the large amount of silicified wood, often as entire tree trunks (Plate XIII }, and the black, carbonized plant debris.

Some of the carbonized material has the appearance of wood which has been partly burned. Vertebrate bone debris, usu ally permineralized by silica, Is frequently observed, espe cially in the dark-gray bentonitic units. Other fossil materials observed in the member are unio-llke clams, often in such numbers as to constitute a conglomerate lens a foot or more thick and covering an area of a half acre.

Lithologically, considering the 6 sections where the

Lower member is exposed (the rocks are covered at J, G-, and

K), there Is roughly an even division between the coarse clastics and the mud3tones and claystones (see Table 2, p. 37) • 39 The topography developed and the colorations ex pressed are distinctive in the Lower member. The following are taken from the unit description: various shades of gray

-- light, medium, dark, brownish, yellowish, pinkish, blu ish; grayish purple, red purple, grayish red, pale brown and pale olive green.

The topography is Interrupted repeatedly by small flat-topped mesas, protected by thin, hard, lenticular and cross-bedded coarse clastic units, or in some cases by one- half foot jasperoid layers. The claystones and bentonites erode into the cones, "hump-backs" and narrow V-shaped valleys characteristic of badlands, (Plate XVII-1).

The sandstone lenses are rarely "clean" well sorted ones. Tlicroscope studies show that nontmorillonite clay is a common constituent of the sandstone, frequently composing

25/a of the rock. Other minerals, such as hornblende, zir con, biotite, muscovite, chlorite,, tourmaline and feldspar are found also. Cementation is commonly poor, some sand stones lacking any bond whatsoever except clay.

Bentonlte In The L o urro-Holbroo 1: Area. -- Bentonite has long been knovm to occur in the Triassic of the South west, especially in the Chinle formation. Allen (1930),

Wilson and Keller (1955)> and others have described such clays. Ross (1927) defines it as follows:

Bentonite is a rock composed essentially of a crystalline, clay-like mineral formed by the 40

devitrification and the accompanying chemical al teration of a glassy igneous material, usually a tuff or volcanic ash: and it often contains vari able proportions of accessory crystal grains that were originally phenocrysts In the volcanic glass. The characteristic clay-like mineral has a mica ceous habit and facile cleavage, high birefring ence, and a texture inherited from volcanic tuff or ash, and it is usually the mineral nontmorillonite but less often beidellite.

By common agreement a bentonite possesses certain other characteristics such as a marked ability to swell when wet, a great adsorption capacity, and a waxy luster.

Stain tests (Grim, 1953) and a number of X-ray pat terns indicate that the bulk of the clays in the Chinle are composed of the mineral montmorillonite, with lesser amounts of kaolinite, illite, and chlorite. In strongly bentonitic units (minimum Impurities and marked swelling ability when wet) montmorillonite was almost the sole clay mineral. In no case, however, was any unit entirely free from detrital quarts. Evidence seems to indicate that most of the beds have been reworked by aqueous agents, and therefore would not constitute good "time" units. Wilson (1956) believes that his "Bentonitic" unit (correlative to Unit Ho. 5 at

Location D of this paper) constitutes a time line; that is, it was formed from an ash fall in situ, without reworking.

The presence of blotlte crystals, relic glass shards and the lack of coarse detrital material would tend to substantiate the Idea. The very fine quarts sand and coarse 3ilt, found by the writer in the identical bed (Unit No. 5 at Section D) 41 is well rounded, generally. Some individual grains are almost spheres, suggesting eolian-rounded material intro duced into the ash by the wind.

Beds, which on the basis of the definition by Ross, may be called bentonites were found in all the Chinle sec tions of the report area -~ except in section K. The table below shows the distribution of bentonite in the nine sec tions examined.

TABLE 3

DISTRIBUTION OF BENTONITE (thickness in feet)

Section: D J G- K E I F C A

Petrified Forest 38 71 -- 80 50 member

Lower 39 -- 25 33 163 181 68 member

Total 39 38 71 -- 105 83 163 181 68

All of the claystones described in this paper as bentonites had the ability to swell when wet; a waxy luster;

"slickensides" parting: reacted to stain tests for montmorillonite, or had X-ray patterns to suggest the mineral. In addition, most bentonites had some relic glass structure visible, although no completely unaltered volcanic glass was observed. Minerals suggestive of pyroclastic origins, i.e., 42 euhedral blotite and hornblende were usually present. As mentioned above, detrital quartz is always present, ordi narily in such quantities and sizes as to indicate deposi tion from moving water. Bentonite colors varied from gray ish red purple to medium gray.

Attempts to determine the source of the volcanics, the parent material of the bentonitlc units, met with little success. Reworking, which is evident in most beds, makes use of thickness variation unreliable to trace down the source. Use of the size of glass shards or relics in a comparison with volcanic phenocrysts is another method that has been suggested -- the phenocrysts would be expected to fall closer to the vent of. ejection than the lighter shards.

Because of the altered nature of the shards and also the smallness of the report area it was not feasible to make such a study. Wilson (1956) suggests three possible sources which might have supplied the ash in late Triassic time:

1. Possible incorrect dating in that the volcan ics of the Excelsior formation (Nevada) might have supplied the ash. 2. Location of the source in southern Arizona or southern California. 3. A local source such as the San Francisco volcanic field.

He strongly inclines to a local source and offers

Black Knob, "located 8 miles north of Cameron" as the most likely to have furnished the vast quantities of ash neces^- sary. Yfilson is also of the opinion that the ash was 43 probably deposited over a period of months or even a few years, in explaining the great thickness of the bentonite in the western part of the Navajo Reservation. Waters and

Granger (1953) believe that the source for the volcanic ma terial is toward the south or southwest. The writer believes that the ash was deposited over a wide area, possibly by sev eral vents, making the volcanlcs quickly accessible to stream run-off and subsequent deposition, along with some quartzose detritus. Concentration by reworking would thus account for the great thickness found today, A major problem re maining on the Plateau today is the accurate determination of the locations of the ancient volcanic vents which sup plied the material.

Petrified Forest Member

The Petrified Forest member was named by Gregory

(1950) for the prominent exposures found in the Petrified

Forest National Monument of the same name. The sequence in the Leupp-Kolbrook area averages some 250 feet in thickness, composed mostly of thick-bedded, in places cross-stratified, mudstones, claystones and marlstones. Subordinate amounts of thinly cross-bedded slltstones and sandstones are present.

Colors are striking. Especially notable are shades of red, brown, purple and grayish green. Color bands fre quently traverse groups of the isolated mounds and cones, 44 which are common to badlands topography. Cross-stratifica

tion in some thiclc units may only be inferred by such colorations; see Plates XVIII and XIX-2.

Boundaries between units are seldom observed to be

sharp, even where such a condition exists, because of the

porous "alligator hide" surface developed on the slopes.

This condition is especially noticeable between bentonitic units, in some cases the "fluffed" (water expanded benton-

ite) material is found to a depth of several Inches cover

ing the firm, waxy, unweathered bed rock, (Plate XVII-2)*.

Detailed descriptions of the beds of the units of the member may be found in the Appendix. In general, there

is an increase in lime content upwards, to the extent that a few limestones are present not far beneath the contact with the Owl EocI:. The root-like features mentioned earlier are also present approximately 30 feet below the contact in the two westernmost sections. Vertebrate bone fragments and clams are sparingly found. In the report area petrified wood is less abundant than in the Lower member.

In deciding where to place the boundary between the

Petrified Forest and Lower members of the Chinle, the writer reviewed Gregory's original descriptions. In essence, the

C division (Petrified Forest member) is composed of "shales and marls, with rare calcareous sandstone". The D division

(Lower member) is described as being composed of "70 percent 45 shale and 30 percent of shaly sandstone", Including lenses of conglomerate. After detailed field and microscopic stud

ies, and guided by the above descriptions, the writer has

determined the contact between the two members to be at the

top of the extensive fine-to-coarse quartz clastic sequence

(see cross-section, Plate II). This placement is at variance

with Y/Ilson (195'5) who draws the boundary considerably lower in the section.

Owl Rock :•."ember

The Owl Rock member contains limestones, marlstones, mudstones and porcellanites. In the report area, the maxi mum thickness of 336 feet is found on the south side of Smith Dutte, (Plate VI ), the northern terminus of section

F. Table 2 shows the relative proportion of the various litholories. The siliceous limestones and porcellanites (Plate

XIV), even though rarely more than a few feet in thickness, are very hard and exceedingly resistant to i/eathering, form ing cliffs and capping extensive mesas wherever exposed.

Petti John (1937) states that:

Porcellanito is a term applied to a dense, hard rock having Ihe texture and fracture of unbiased porcelain. I'c st commonly, though not always, such rocks arc cherts with an abundance of included ma terial. Those Impure cherts are in part argilla ceous and in part calcareous The argil laceous cherts grade into siliceous shales; the 46

calcareous cherts grade into siliceous limestones. Some porcellanites are, however, silicified tuffs. Roclis consisting of a mixture of clay or silty clay and a large but variable proportion of opaline silica also are porcellaneous and have been termed porcellanite.

The hard, siliceous layers varying from one to ten feet in vertical e::tent are commonly separated by 3 to 30 feet of thick-bedded, friable marlstone or calcareous mudstone. The

calcareous and siliceous rocks will be discussed in more de tail later in the following sections.

In his original reconnaissance of the Navajo Reser vation, Gregory several times mentioned the "limestone con glomerates" of the Chinle formation. Recent work by the writer indicates that true limestones are not common to the

Leupp-Holbrook area, most of the calcareous rocks being mudstones, marlstones and porcellanites. The majority of the

"limestones'* mentioned in the literature are found in the

Owl Rock member. The base of the member is commonly drawn

just below the lowermost consistent '"limestone" unit; in this area it is 23-D. The top is the contact with the

Y7inga t e s and stone.

The Owl Rock is composed of alternating hard and soft beds, the hard beds usually cliff-forming or mesa- capping, the soft beds forming slopes. Prevailing color as a whole is a distinctive pale red purple or "violet" col or, which more or less characterises this member over much of northeastern Arizona. Upon closer inspection various other-colors are seen; greenish gray, grayish red purple and" brownish gray as well as pale red purple. The hard lay

ers are usually quite silicic in nature, thin to thick- bedded, and when dislodged from bed rock are slabby or blocky in appearance. Cross-stratification is rarely evi dent, although some of the hard "limestones", when weathered,

etch into cross-lineations (Plate XII-2) indicative of such

primary structures. The thick-bedded marlstones are usually hard when fresh but weather rapidly, becoming friable and

forming slopes. Usually the clay content is sufficiently great to allow the rock to break down readily in water.

According to the scientific definition (as opposed to commercial designations) any rock containing 50^ or more of calcium-carbonate is a limestone (Pettijohn, 1957). How ever, if the rock contains between 35-^5p carbonate and the balance is mainly clay, it is usually termed a marlstone.

Although many of the rocks in the Owl Rock member may there fore properly be called limestones (containing or more

of carbonate and well indurated), the considerable amount of

clay in some beds makes the descriptive term marl.'3tone more appropriate. In general, rocks which arc hard and cliff-

forming, which possess the required lime, and which do not break down easily in water, are termed, limestones in this

paper. Rocks which arc friable and weather into slopes and badlands, and which contain 35-65% carbonate, the balance 48 clay or fine silt, are here designated marlstones.

Most of the limestones and a few of the marlstones contain considerable amounts of silica in the form of chert nodules. These nodules show a singular disregard of bedding, being found in irregular nodular masses with random orienta tions. Rarely are they parallel to the bedding. Some cherty areas seem to grade into the surrounding rock, often encom passed by a band or zone of "cotton rock" (light gray to white tripoli-like material) said by Fowler, et al, (1935) to be the transition stage in the replacement of limestone by chert. Other chert bodies have rather sharp boundaries.

The chert, which is usually darker in color than the adjoin ing rock, ranges in size from specks to masses several inches across (Plate XIV ). Veinlets of silica and calcite are common. The evidence, including an occasional silicified snail, strongly points to an epigenetic origin for the chert.

Limestones. --As stated elsewhere, most of the limestones are found in the Owl Rock member. The following description of the lowermost unit at section C-, located 12 miles east of Leupp, is typical of many:

Unit 10 -- Limestone: light greenish gray; aphanitic texture; very hard fx^om disseminated silica; thick-bedded; blocky; forms vertical cliffs. Carbonate content = 53/'; the balance being white montmorillonite clay, medium size clear quartz silt grains and irregular masses or nodules of brownish chert, ranging in size from a fraction of an inch to several inches in diameter, Calcitc veinlets are common. Some silicified, high-spired fresh water gastropods present. Lowermost portion of unit becomes less silicic and less hard, with bedding irregular to gnarly, concretionary. Base is sharp and slightly irregular. Thickness = 8 feet.

Microscopic studies of selected limestones do not

establish their origins. Aside from a few fresh water

snails (Yen, 1951) and some fine rectangular specks of dark

gray, questionable plant debris, no fossils were observed.

Within the base of the lowermost bed In the Owl Rock member,

"root-like" features or filled "burrows" are frequently

seen (Plate XV-2 ). They have a very rough vertical orien

tation, changing directions abruptly in the most haphazard

manner. The surrounding rock Is commonly a friable, errati

cally bedded, conglomeratic appearing, gnarly limestone.

The tubes themselves vary from 1y- inches to 3-1- Inches In

diameter. Field and laboratory studies do not offer a reasonable clue to their identity. They are composed of

much harder material than the adjacent rock, weathering

"out" in bas-relief. Some tubes are filled with dark gray

ish red purple chert, others with yellowish brown, hard,

sideritlc siliceous limestone and one small Lube had a 1

Inch core of light gray, felty, acicular ealcite crystals in a clay matrix; all enclosed in a inch "shell'' of por-

cellanite. The chert fillings do not appear different from their nodular counterparts above. Others have commented on the identity of these curious features. Wilson (1956) in 50 his study of the Upper Chinle mentions that:

Numerous vertical calcareous "pipes" occur Immediately "below the Owl Rock contact in most areas. Possibly these pipes represent replace ment of roots of trees which grew In the fresh water lake environment where the Owl Rock sedi ments were deposited. The vertical pipes are re stricted to the top of the red "brown mudstone unit.

In the Leupp-Holbrook area the "root-like" forms

are mainly along the base of the Owl Rock member. However,

similar features were observed some distance below the con

tact. A search of the literature discloses no primary

structures which seem identical to those under considera

tion. Perhaps the nearest approach is shown in a photograph

by Shrock (19^5) who postulates a "fllled-root" origin for

the forms. As the 11 filled-roots" are clearly orientated

vertically and are much straighter and larger than those

discussed above, the similarity is not close. The Chlnle

features are suggestive of burrowing animals which construct

uniform tunnels when moving in search of food but expand the

workings into rooms where It is plentiful.

Marlstones. -- The marlstones grade imperceptibly

into claystones or mudstones as line content decreases, or

into limestones as it increases. The marlstones are common

to both the Owl Rock member and the underlying Petrified

Forest member. Little differences are noted except that

cross-stratification is much more prevalent in the member below and the calcareous content is not as great. Typical 51 Is unit 7-J• Marlstone: pale red purple with grayish orange pink mottling. Thick-bedded; very friable; breaks dov;n; easily weathered, forming slopes and miniature badlands. Some clam(?) fragments pres ent. Somewhat nodular appearing in places. Lime content = 39%, rest is reddish clay and fine clear quartz silt. Base is sharp and irregular. Thickness = 22 feet.

Porcellanltes. -- In many respects the most unusual rocks in the region, porcellanltes are confined to the Upper

Chinle in the Leupp-Holbrook area. Rocks fitting this de scription form all of the harder layers in the Owl Rock mem ber north of Leupp. A few porcellanltes are found in the upper portion of the Petrified Forest member. The origin of these interesting rocks is obscure. There are two rather distinctive occurrences or types found in the report area, which for convenience, are classified by color:

( 1 ) G-ray -porcellanite: This type is the most com monly observed and is exemplified by unit 23, located in section D, 7?;- miles north of Leupp. Forming the base of the

Owl Rock member, the unit crops out just beneath the top of

Newberry Mesa. Its description, taken from the Appendix, is reproduced below: (see Plate XII-2)

Porcellanite: light greenish gray, with light brownish gray irregularly ovate chert nodules and pods, otherwise aphanltlc; rock is siliceous and very hard; fractures hackly to sub-conchoidal; thin to thick-bedded.; blocky when detached; cross-bedded in part; forms vertical cliffs and caps mesas. Weathers out to grayish orange on exposed surfaces, the chert nodules becoming darker. The b0% calcite content is disseminated and also in pods and fine stringers. Insoluble material, which constitutes 60% of the rock, is mostly silicified clay and fine, clear quarts silt. Some white, loose clay in the residue reacted for montmorillonite. The base is sharp and irregular. Thiclmess = 15 feet.

Selected porcellanites were thin-sectioned and studied in order to learn more of the composition. Areas of dark grayish, almost opaque material, probably silicified clay, were observed to contain small, irregular, clear pods and velnlets showing the typical "maltese cross" of chalce dony under crossed nicols. The partially opaque material possessed some birefringence, perhaps due to the presence of montmorillonite. Other areas had aggregate polarisation, indicating a typical chert composition. Disseminated calcite was present as well as in pods and velnlets, the latter oc currences accounting for roughly 10^ of the rock. The cal cite velnlets appeared to be more recently introduced than other constituents, perhaps as a result of filling desicca tion cracks.

(2) "Purple" Forcellanite: This type is found in thin, flaggy, fairly uniform beds but higher in the Owl Rock than type (1), usually. There is some evidence at section K that it may possibly lens horizontally Into the gray type of rock. The colors of the "purple" type vary from pale red purple to light brownish gray, the latter color being found in the unit 24-a at section D. The bed has the hardness, color, aphanitic texture and sub-conchoidal fracture often 53 noted In many well-indurated rhyolitic tuffs, which it

closely resembles. The description which follows is of unit 24-a: Porcellanite: light brownish gray; weathers to light brown. Very hard; siliceous; has sub-conchoidal fracture; thin, fairly evenly bedded; forms small vertical ledge; slabby when detached. Strongly cal careous, the 40/j lime content being disseminated as well as in stringers, veinlets and pods. Clay mineral (montmorillonite?) and silica is Intimately associated with lime. Chert is not common and, where found, is in small, dark, oval areas. Base is sharp and flat. Thickness = 2 feet.

Another occurrence of '"purple" porcellanite is found as loose material on the mesa top protected by unit 6-K.

The rock contains numerous pale yellowish green dots, spots,

and larger irregular areas. The features appear to be

caused by chemical bleaching subsequent to deposition. The factor responsible for the reduction of red iron oxide to the green ferrous state must have been deposited in the sediment as it was buried, otherwise it is difficult to vis ualise outside solutions reaching the isolated spherical bleached areas without affecting the pathway. Bleaching in

"red beds" is commonly referred to contained carbonaceous or animal matter, although in this case none definitely is iden tifiable. Ilinute, black, carbonaceous-like matter found in the gray porcellanites may be responsible for the reduced

state of disseminated iron in the main body of the rock.

Oxidised, weathered surfaces turn brownish.

The mesa-capping bed 6-K ranges from very thin- 54 "bedded to thin-bedded. The underside of one slabby rock showed casts of symmetrical, parallel ripple marks. The marks were similar to those often observed 011 muddy "bottoms covered by very shallow water. The ripple index (ratio of wave length to amplitude) was found to be 7:1, or well with in the range for wave-ripple index (Tvenhofel, 1950). Prob able mud cracks were observed in the same general locality but where the unit was thicker and less uniform in lithology. Genesis Of The Limestones And Porcellanltes. -- The limestones bear the criteria of the shallow water lucustrine environment. Symmetrical ripple marks, deep mud cracks, intra-formational conglomerates and gnarly bedding clearly indicate this. Stagnant water is suggested, at least in part, by the gray green reduced state of the iron in some of the limestones, especially the lower ones in the Owl Rock member. The upper beds are more oxidised, in general.

Cross-stratification of some siliceous-lime beds, lenticu- larity and cross-laminations of thin siltstone layers, to gether with small-scale cut and fill structures point toward periodic replenishment of lake water by seasonal floods from associated streams. Incomplete evaporation of the lakes could cause the deposition of calcium carbonate ahead of other salts as suggested by King (19^7)» Twenhofel (1950). A semi-arid climate for the region as a whole would allow more or less interrnlttant replenishment and evaporation 55

of the water to proceed apace, the carbonate being precipi

tated along with intermingled, silt and clay (ash?) released

from suspension. Colloidal silica in the water nay have been flocculated by the action of contained decaying organic mat

ter1, much as postulated by Rubey (192C) for the siliceous

Mowry shale of "Wyoming. However, laboratory evidence seems

to support the opposite view -- that colloidal silica is

"protected" in solution by organic acids (Twonliofc-1, 1950). A possible modern example of the postulated ancient

lake or lakes may be found in northwestern Oklahoma, where

the Cimarron River periodically overflows a 100 square mile, flat area lying south of the stream. The Cherokee Salt

Plain, as the area is known, is receiving a slow accretion

of silt and clay, plus lime and other salts. The similarity is only partial, however, as the Chinle rocks contain no bedded halite or sulfate. In the case of the Owl Rock lime

stone the composition may have been controlled by a lack of

certain salts in the river water and by periodic flushing

out of the chlorides into the stream during flood stages,

the less soluble carbonate and silica remaining behind. The limestones grade into the marlstones on one hand and into porccllanites on the other, therefore any theory to

account for the limestones must have some bearing on the or

igin of the porcellaniteo. Clay is present in both the limestone and porcellanite, as well as in the marls. "Weathering and leaching of tuff beds and limestones (Kai- bab?) on the flanking highlands could account for unusual amounts of silica and carbonate available for transportation and deposition. This alone, however, does not seen suffi cient to account for the highly siliceous porcellanites.

Waters and Granger (1953) refer the highly siliceous rocks of the Navajo area to the devitrification of tuff, believing that silicification and devitrification occurred simultan eously; the silica filling spaces not previously filled by calcite and clay, and enclosing disseminated calcite.

The simultaneous devitrification of ash and the dep osition of silica, reinforccd by additional amounts from vadose and groundwater circulation may account for the por cellanites. Thin-sections show a considerable amount of clay, determined to be montmorillonite, mixed in a matrix of disseminated silica and calcite. The montmorillonite is significant, as Bramlette (1945) found that bentonitlc clay contains far less silica than the ash from which it was de rived. Most of the limestones, porcellanites, marlstones and sandstones do contain bentonitlc clay (montmorillonite) as interstitial material, indicating that ash was probably an original constituent of the rod-:. The randomly chert nodules in the limestone may have been formed in part by diagenesis on the shallow lake floor, then enlarged by

Intra-stratal solution and groundwater Introduced silica. 57

Silicified snails are definite evidence for replacement of calcium carbonate by silica. Although veins of chert are said to "be rare in porcellanites (PettiJohn, 1957) thin- sections of Chinle rocks do show veinlets of chalcedony cut ting areas of disseminated clay, calcite and silica.

Facies Changes In The Leupip-Holbrook Area

In general, tv;o changes in sedimentation are readily apparent from an examination of the cross-section (Plate II, and Tables 2 and 4). These are:

(1) A general increase in coarseness toward the southeast, manifested by the greater prevalence of siltstones, sandstones and conglomerates, especially in the

Lower member. At Leupp, the sllt-sand-conglomerate clastics of the Lower- member total 73 feet, expanding to 263 feet northeast of YJinslow and becoming 246 feet north of Joseph

City. The section between Joseph City and Holbrook has con siderably less of the coarser-than-mudstone clastics, but due north of Holbrook it again adds up to an impressive total.

(2) A thinning out and disappearance of some cliff- forming limestones and siliceous units of the lower Cwl Rock member toward the Holbrook end of the escarpmcnt. It may be noted on the cross-section that the lowermost bed In the Cwl

Hock member is traceable along the 40 miles of intermittent outcrops from Newberry Liesa north of Leupp to Smith Butte, 58 north of Joseph City. This unit (23-D) does, however, thin appreciably, as it is 15 feet thick at Leupp, roughly 10 feet thick north of Winslow and decreases to only 3 feet north of Joseph City. Unit 21-D is 8 feet thick at Leupp, decreases to 3 feet north of Winslow and is completely uni dentifiable within a thick extent of calcareous claystone north of Joseph City, some 40 miles southeast of Leupp.

Other lithologic changes are less distinct although real. At Leupp, unit 23-D is, in general, a very hard, sil

iceous rock with hOf? carbonate; the rest opalized clay and

silt. The rock breaks with a subconchoidal fracture and

otherwise possesses the attributes of a porcellanite, where

as at Smith Butte the same, although much thinner bed, is a true limestone containing 6hfj lime and less hard and sili

ceous. Similar changes may be noted in the ledge-forming unit 21-D, which becomes little more than a marlstone north of V/inslow, (Plate XVI-1), and is indistinguishable at Smith

Butte. Plate XVI-2 shows unit 23-D at Smith 3ulte. Compare

with unit 23-1: of Leupp (Plato XII), northeast of Leupp

(Plate XIX), north of V.'inelow (Plate XV-1), and northeast

of '/inslow (Plate XXII-2). 59 TABLE 4

LITHOLOGIC TYPES FOUND III THZ CHIIILE FORMATION

Tliickne And

Section

Location

29 27

102

221

A rr SO 261 1 OC 20

260 22'

1 118 201 350 235' 270

382

oo' oc 60 Age Determinations

Although fossil remains are scanty as compared to most marine rocks, sufficient plant and animal remains have been identified to assign a Late Triassic age to the Chinle formation. Some dissent has been raised (von Huene, 1926, and Branson, 1929) but generally the age is accepted. Gamp

(1930), Colbert (1950), and belles (1954-), who have made a study of the vertebrates found in the Chinle, are convinced that the fauna is Late Triassic in age. Dauglierty (194-1) assigned the same age to some tree and plant material. Pish remains, found in the Chinle (Camp, el al, 194-7) z-Te also said to be of Late Triassic age. Invertebrates such as Unio clams are found in great number at different levels of the Chinle but are of little value in dating. The same may be said also of the small, high-spired snails found infrequently in the upper part of the formation.

As has been stated earlier in this paper the age of the Shinarump is on somewhat less firm ground. Nevertheless, the interfingering with the Chinle in some places, the lack of a significant break between them, together with the defin ite unconformity between the 1-Ioenkopi and the Shinarump sug gest also the Late Triassic age. Daugherty, from his fossil wood studies, places the Shinarump in the Late Triassic. PALEOG-SQG-RAPHY AMD SOURCES OF SEDIMENT

McKee (1954-) pictures the Plateau country as it was j in Early Triassic (Moenkopi) time before Late Triassic depo sition began. Isopachs show a deep trough extending from

California northeastward across the southeast portion of

Nevada and into southwestern Utah. Thickness of the Moenkopi decreases southeastward from the Cordilleran geosyncline across Arizona, becoming zero before reaching Lhe Hew Mexico line. By the beginning of Late Triassic tine the situation was somewhat different. Highland had developed in an east- west trending belt along central Arizona; the "Mogollon

Highlands" of Karshbarger, et al (in press). Shinarump sed iments in the Leupp-Holbrook area evidently came from the south as shown by an increase in size of the material in that direction (Cooley, 1957), and by cross-stratification trends

(see Fig. 3, p. 25). Clastic size dintributions from Hol- brook to Loupp also show a decrease toward the north and northwest (sec Table 1). Some quartsite cobblos found in the area are similar to rocks exposed in the "ra&uhaw Mountains near Prescott, Arizona. Rounded chert cobbles containing

Kaibab (Permian)brachiopods, found in the Shinarump and in some higher beds of the Chinle assist in proving an origin

61 62 to the southwest. McKee (1937) has mentioned the occurrence in the Shinarump of both the quartzite and the Kalbab fossils.

Wilson (1956) holds for a northern source at Lee's Ferry, far to the north of the report area. The Shinarump clastics in the Four Corners area are said by Lee (1926) to be from an ancient Colorado highland.

The Shinarump was apparently deposited on a broad front, advancing northward over the report area as a regres sive blanket, filling low places and channels on the south ern margin, but farther north spreading widely as it ad vanced toward the center of the basin.

Evidence for source areas following deposition of the Shinarump is not clear in the Leupp-Holbrook area.

Coarse clastic fades decrease in total thicknesses from

Holbrook to Leupp, but incomplete vertical sequences make such data unreliable. Inclinations of cross-stratification in the lower Owl Rock member near Leupp show a current set toward the northwest, but this isolated area can hardly be considered a good indication of a northwest movement of

Chinle materials. Repenning, Cooley and Akers (in press) state that by the end of Chinle time the Mogollon Highlands had joined with the Cordilleran Geanticline (to the north).

Structurally low areas forming valleys were thus developed in Late Triassic time between the Cordil leran Geanticline and the Uncompahgre Highlands and between the Uncompahgre and. the eastern and most prominent part of the I-logcllon Highlands. Through these valleys Late Triassic streams flowed, from 63 northeastern Utah and central New Mexico into the main fluvial basin extending from the Navajo coun try westward to the sea. After the Shinarump sands and gravels had advanced inward from the surrounding highlands, thinly covering the region with a blanket-like layer, the Chinle sands, silts and shales began building upwards and outwards. (Wilson,

1956) from the structurally low areas, transported by slug gish, meandering streams on a vast flood plain. In many places, especially along the flanks of the lowering high lands, Chinle debris is found directly covering pre-Shina rump rocks where the old erosion surface was topographically high enough to escape burial by the Shinarump gravels. The

Lower member- contains considerable coarse material brought basinward as the highlands were degraded. Later periods of activity in the 1-Iogollon Highlands are reflected by occa sional sand and gravel components in the Petrified Forest member. Few fossils arc found in the upper Petrified Forest member in the Leupp-Holbrod: area and, with the advent of the Owl Rock sedimentation, a marked degree of aridity, or at least semi-aridity, seems indicated by the chemical pre cipitation of lime. Rcpcnning, et al (in press), note that the Owl Rock is restricted almost entirely to the confines of the Navajo country and that the "local distribution of the Cwl Rock member suggests the development of a structural basin in 64 this area and the presence of this "basin at a later date is

indicated "by relationships in the Wingate sandstone", Chin- le sedimentation was brought to an end by drying up of

streams and lakes as the severe aridity of Wingate time de veloped in the closing phases of the Triassic period. SUMMARY AND CONCLUSIONS

Although no hiatus divides the Shinarump from the overlying Chinle beds, there is precedent and ample justi fication for retaining the formational status of the

Shinarump c ongl orn erate.

A southern to southeastern source for Shinarump sediments deposited in the Leupp-Holbrook area is suggested by cross-stratification trends and size distributions.

Presence of ICaibab fossils embedded in waterworn chert; gray quartsite cobbles and granite pebbles raises the possi bility of a southwestern provenance, perhaps from the 3rad- shaw Mountains near Prescott. The rounded gravel material is indicative of considerable transport.

The Shinarump is believed to have been formed as a regressive blanket deposit advancing toward _the central area of a large basin formed by uplifts on the periphery. In the

Holbrook-Joseph City area, close to the source, the sedi ments are coarse gravels which filled only the stream chan nels or other low areas, failing to surmount ancient Moen- kopi hills. Raising of the Meso-Cordilleran geanticline to the west in later Triassic time provided a structural basin of

65 66 great extent, in which the Chinle sediments were deposited.

Early Chinle sands and silts were deposited by moderately sluggish streams over a wide flood plain.

Active volcanoes contributed ash which was reworked by running water. The basin was filled gradually by upward

•building and transgressive sediments, in contrast to the regressive sands and gravels of the Shinarump. Later, the

Chinle plain became the site of widely meandering, very sluggish streams and of extensive flood i^lain lakes. As a result of a general increase in aridity, the deposits show a marked increase in carbonate content toward the top of the section.

The uppermost Chinle member, the Owl Rock, is highly calcareous and siliceous, being composed of marls tone, lime stone and porcellanite. The lime is believed to have been precipitated mainly by evaporation in flood plain lakes as the climate became more arid. Incomplete evaporation or periodic flushing out of the more soluble salts is believed to be the reason why chlorides are not found.

The silica responsible for the chert and for the porcellanites may have been derived in part from the decom position and conversion of volcanic ash to montmorillonite clay. Groundwater and vadose ^;ater may have further enriched the rocks with silica.

Silicified snails, transitional zones around chert 67 nodules, and veinlets of chalcedony point toward an epigenetic origin of the chert.

Many of the "limestones" in the Leupp-Holbrook area are not true limestones, but are porcellanites or marlstones APPENDIX NO. 1

SHINARUMP FIELD AND LABORATORY STUDIES

Locat,ion No. 1

Located 5-jL- miles northwest of Leupp, The Shinarump crops out 011 a level expanse of windblown alluvium, forming a low hill composed of cross-stratified conglomerate. Both the unweathered and weathered color of the rock exposure is yellowish gray.

Thickness: -- The exposed thickness is approximately 10 feet, but as the base is conccaled the true thickness may be greater.

Contacts with underlying and overly1nr. rocks: -- The base is concealed and the top is a surface of erosion.

Gross-stratification dip and direction: -- Studies of cross-stratification inclinations (McKce, 1?40) show an average clip of 15° north, 75° vest.

Gross-stratification type and scale; -- Only medium scale (1-20 feet between terminations), trough type (McKee and Weir, 1953)> cross-stratification was observed.

Bedding: -- redding ranges from thin (2 inches to 2 feet) to thick (2 feet to 4 feet).

Lithologlc description and study: --- Approximateiy 15/j of the outcrop (composite sample) is composed of mater ial larger than 2 mm in diameter, thereby qualifying for use of the terra conglomerate (Pettijohn, 1949).

Description of the matrix: -- The matrix is firmly cemented by calcium carbonate. To disaggregate the material for mechanical analysis and to determine the percent of car bonate cement, 100 grams of the sample wore digested in di lute HC1 and washed. An analysis of the- dried insoluble portion is shown by Table 5 and the histogram (Fig. 4). Sorting is fair.

68 69

TABLE 5 -- GRAVEL ANALYSIS AT LOCATION 1

Size and Shane

Average size = 19x14x5 nun, weight 5.O grams Maximum size = 49x31x27 mm, weight -63.89 g^nis Average spheri c ity (Krunoein) = 0.70 Average roundness (Krumbein) -- 0.45 (subangular) Shapes (Payne) 40^ III = spheroidal o 7b CI a: II - oblate spheroidal Cla: VI -- prolate- spheroidal Cla: V - bladed spheroidal 4 b Cla: I ~ d 1s c - shared

Conroositlon

13% vein ajtz; colors: It. orange to It. brownish orange 153 quartsite; colors: light grayish violet petrified wood; colors: gray t: light orange 5,1 chert: colors: light brownish orange.

Composition anc Ioscrlptlon of the Itrl:: by Grade Slse:

Practically all material composing the matrix is quarts of one bind or another. Carbonate- cement amounted to 2.4b of the original sample. A detailed description of the sise groups follows:

s iso1 grains (C.9> of original sample): An "'3 -** J- % r ) estimated 1 r>"w / .l u;. <*• r • * r* " U^'JL' J. r> 1 '1 r« ngular t0 subangu- '11-u 1 lar, clea _ to :Vi ... •j liart •—1 « bany ul O 0 s!:OW f* c-f iiiite secondary c , *1 • ' 1 gome J. 1 0 0 J ^ "1 r til:art r. \:i til cryst 1 terminalI r~- 0 -anul r; C ~LII s tor c or lie 0 r* > r nted smaller g . "1 • • wbic h had no t b 0 en c. j. r:r g; ' i 1 atec . -1 -- I'O II j. ma Le IvL 20"/ ' of the :\ra nu 1c tor la is composed of V 0 o*v: _ ml brown J- ^ f. paqu0 whitc 01j ort. b'uch of -* chert sho nc; enta tions 0 «1 _L ssloii 0 other material, 1 r, ^ .j_ as if the Q i"' t ,; k_". «... * n ^ or pi as t i c C C; nditi O n at one time. "] T L" C_" _i IJ O i 1 !b -o ' J_ ' bl ^ :j I u orial - .r» .. ~ " (aT>prcxim I, '. J.. -. 0 (/ i::: c 0 .:i - :C CI I- .. - -ji'.-iri. • to gray ish, well 0 V.iicl u d o martsx Li 0 »

r n ^ -1 * 9.9 _ -bhibi (30.9b of orI nal r.amp s') : An -r> j -t* r-i O 7;—i estimated 0/j 0 J. ij--c very co a X fcj w sand gular to sub- *-* rt t • rounded, \i 1 O _' lo m ilby quart 9 "omo c ' t c*•J stained tl J. red by ir O O I'I-L do. 20 b a ppea rs to be 11 ' • ,b ^ U to pale To TABLE § 6 -- SIZE ANALYSIS OF THE MATRIX AT LOCATION 1

Retained by #10 sieve*= 8.9 grama = 2 mm+ (granules)

" #18 = 30.9 2-1 mm (very cse sand) " . " #35 " = 39.0 1-1/2 mm (coarse sand)

.. #6o = 15.8 1/2-1/4 mm (med. sand)

" " #120 " = 2.2 1/4-1/8 mm (fine sand)

" #230 = 0.4 1/8-1/16 mm (very f.sd)

" " pan " = 0.1 If _ -1/16 mm (silt)

HC1 soluble portion = 2.4 carbonate cement

Reconstructed total =99.7 grams

* U. S. sieve series

4 2 I f/s '4- % '4b '4s6 0 MM

FIG. 4. SiZE DISTRIBUTION OF MATRIX AT LOG. I 71 orange quartslte sand. Most grains are subrounded to veil rounded. A small portion of this grc.dc size Is pale yellowish "brown chert, showing impressions or indentations of earlier material.

Coarse sand (3?.0% of original sample): 95/j of the grade size is very angular, clear to slightly milky quarts grains. Conic culiedra are present, Perhaps 20% show some degree of rounding. A few rare individuals are very well rounded, some allowing a fro::, Led or- matte surface. Many of the angular, clear grains of quarts contain hematite "dust" as inclusions. Approximately 5;J of the grade size is composed of very well rounded, spherical to egg-shaped, pale orange to pale yellowish brown quartslte. A few well rounded, pale yellowish brown to white chert grains arc also present. In general, the colored greens shew a higher degree of roundness than do the clear or milky grains. Some composite grains are present.

liedlum sand ("5.^ of the original sample): CO# of this si so material is clear' quarts and Is milky quarts. Approximately Z/'l\ of the quarts is very angular. Some grains appear to have suffered, broahago. Many grains show euhed.ral quarts crystal teruinr tior.s. The rest of the clear quarts or milky quarts material is rounded to some degree, with a considerable number well rounded and, presenting a frosted surface texture. Approximately 1^ of the medium sand is orange to red quartslte, many grains showing some rounding. Red grains appeal* to be colored by a fine "dust" of hematite. rp -• 1-0 0and. (2.d: C- J;.c; origin" 1 seerpie) : Some 95% O-L- J-l J.ones V J - • r.i 0 a tor ial is clea r quarts, the :major portion '• s 1 "10 * being v cry ular• ill id fresh loohing. 'Ir-.iY " us display quartz •' eel ter•i.iina tions. r '•J this g^do siso -L." ,T> -"i • 1 :ir l,o sub a.igular, orange to 1'C-d guar t s 1. te, r* l" ..fD r 'T ' tip o VCi'et — »• ^ 11 rounded magnetite -.iu -d a few angular e tec ."•-v green hornblend c vo:.-e obs orved. -t Q L' -L ino sand (o.-v; of origini .i . • le): 90," of the sis o very n ii ^ r, clear • » th some grains snowing Lurei'; character cue to or gas include ns. ".'erne : of the very fine sand h ee -one degree of rounding. Two grains among one hundred viere well rounded and had a "frosted" texture. 72

Red or orange grains v/ere not uncommon but occurred principally in the slightly rounded group.

Silt fraction (0.1 of original sample): I-Iaterial of this size was rare and had similar composition and tex ture-to the very fine sand sir.e.

Heavy Mineral -- Light Mineral Analysis

A portion of the very fine sand wac introduced into liquid bromoform of density 2.?0. The minerals of density greater than the br*oiaofor:n caul; to the bottom and v/ere drawn off and separated from the light fraction. It wat; found that the heavy mineral suite was not large. Minerals of both the light and heavy fractions v/ere identified under the microscope but no attempt :1c to closely relate fre quency of mineral occurrence to the whole sample. Results of the study follow:

Heavy Mineral 3u.lte (in order of frequency)

(a) The most common mineral was rod to brownish, iron oxide, commonly in irregular, poorly defined grains, possibly a mixture of silica and iron oxide. (b) Magnetite, well worn and rounded grains. (c) Zircon, colorless, well rounded, to angular crystals, some doubly terminated. (d) Titanite, clear, broken and angular; symmetrical extinc tion, with high birefringence. (e) Garnet, ouhodral red crystals: little woxm.. (f) Chlorite, colorless; inde:: balsam. (g) Tourmaline, irregular and angular, reddish brown, highly pleochloric. (h) Tourmaline, irregular blue gray Lo blacl:, highly pleochloric.

Light Mineral Suite

(a) Practically all the light fraction was clear to slightly turbid, very angular quarts grains, A. few are well rounded and have "frosted'' surface textures. The few reddish grains observed were uncommon. (b) One angular cleavage fragment of microcline (-index balsam) observed. 73 Location No. 2

Several Shlnarump outliers are round 3 miles due north of Winslow. The one studied in detail Is a snail, 60 foot high mesa, capped by 40 feet of very hard quartsitic sandstone, granule to pebbly conglomerate. The resistant rock protects the soft, friable, brownish siltstcnes and mudstones of the underlying Moenkopi formation. The weathered Shlnarump, especially the massive upper portion, is colored moderate grayish red. The fresh exposures are lighter, be ing closer to a grayish orange p;'nl: in color. The beds are mostly cross-stratified.

Thickness: — The Shinarunp thickness is approximate ly 40 feet at location 2.

Contacts with underlying and overlying, rocks: — The base rests upon an ancient erosion surface of brown lioenkopi mudstone S . Til e lioenkopi is bleached light grayish green for a few inches just beneath the old eroded surface. The upper most portion of the Shlnarump is a surface of present ero sion. It is not believed that much of the upper rock lias been removed, because of the great hardness and toughness of the ortho - quart 7,1 te exposed at the top.

Cross-stratification din and direction: -- Sixty dip readings gave an average of 1C degrees inclined south 45° GG.S T.

Tyr-.e and scale of cross-stratification: -- Cross- stratification is both the planar and the trough types. Scale is medium.

13odd in, -: — Ranges from thin to thick.

Ilthologlc description and studies: -- The Shlnarump at lo cation 2 is variously a medium sandstone to a pebbly conglomerate. Post of the outcrop is so fi'rmly cemented with seer.litjary opaline silica as to constitute an ortho- quart;:.!to. tumorous grayish yellow green mu>~stone grains, ranging in s.Vl.u from a fraction of a millimeter up to sever al millimeters in diameter are found lntorcp-"r::': , throughout the outcrop. Upon weathering out, th: ni-<" j,vain:, leave pits or voids. "r-vol-slr.ed Material is not abun'ant, although iso lated pebbles and cobbles are frequently foun" annng the finer material. Gome muustone lenses or " ; • •, ranging in length from a few inches to a foot or more are found, especially in the basal portion of the outcrop. The grayish green yellow lenses may be detrital material from the lb Moenkopi mudstones, as the color and texture is similar to the "bleached" zone just below the Shinarump-'"oenkopi contact. Although little gravel material was available for roundness, shape and composition studies, search disclosed 30 pebbles v:hich could be used in making the determinations in Table 7.

TABLE 7 -- GRAVEL ANALYSIS AT LOCATION 110. 2

Size and Shape

Average size = 12.0x8.<3x6.5 mm; weight = 1.2 grams Maximum size = 28x19x16 mm: weight = 9.9 grams Average sphericity of cobbles = 0.7^ Average roundness = 0,-'-2 (subangular) Shapes (Payne): 50;' Class III - spheroidal 20;j Class VI -- prolate spheroidal 20;j Class II = oblate spheroidal 2% Claus 7 = blarled spheroidal

Combosit Ion

7S/j vein quarts; color: light brown 22% chert; colors: reddish to yellowish brown

Microscon tion of the Q,uartz1tic Sandstone

Microscopic studios were made to determine the compo sition, texture, coment and other qualities of the very hard, quartzitic sanostono caprccl:.

Texture- and coms-osltlon: -- Fully 80% of the grains are subangular to subrounded clear quart;:,. A few well rounded particles wore observed. Quartz grain- v:ere in the medium sand sis-: grade mostly (l/2 to •/•':- mm in diameter), but some Invididuals we-ro as large as 1 mm er even larger. Sub ream,1 sd yellowish orange, fine *. lv grains were common. A m dark gray subangular ov.ar-tv 1to particles were also ne Led. Light gray green, rounded mud pallets *.:ere not un common, causing cavities or voids in the otherwise dense quartzits whore the mud has been removed by weathering. The mud pellets averaged 1/4 mm in diameter with the range from 1/10 mm up to 1 mm or greater. Cement: -- Practically all bonding material apjjeared 75 to TOG silica of a v/hite, opaline variety. This sane material lined moot of the cavities or vugs. In some cavities, minute fresh-appearing quarts crystal terminations were observed. 76

Location Ho. 3

Several outliers arc found north of the Little Colorado River, approximately 5 miles northeast of Ylinslow, Arizona. A gently undulating plain covered mostly by sparse desert vegetation is broken by email hills of Shi.narx.unp and Lower Ghinlo siltstones. The color of the weathered Shinarur.p outcrop is mod erate yellowish brown and the color of the fresh rod: is yellowish rjray. The roch varies from a coarse sandstone to a granule c onrj.om era t e.

Thickness : -- The thickness could not be determined because of the covered base. The small outcrop studied has a thickness of 10 foot.

H ontacts with underlying; and overlying rocks: - - The base is concealed but the contact with the overlyin™ Chinle shaly silts tone- 1:: shari; and undulating. This is the only place in the entire report area where the Shinarunp-Chinle contact is clearly visible.

.I. '.float ion d lij and direction: -- Ho data was obtained because of insufficient workable exposures.

Oross-stratlf1catIon tyoe and, scale: -- Gross- stratification is nc.inly the trough typo, although some planar variety was observed. The scale ranges from small (0-12 inches) to modir.n ( 1-20 feet).

T-, 0 -T ,1llir;: ! -- eoddiny ran^c-s fro::: very thin (1/2 to 2 inches) to thick (2 to feet).

Lltholcr.lc description and. studies: — 1.00 crams of the whole rod: wore treated with dilute hydrochloric acid, the residue washed, dried and screened. Tlx Insoluble por tion amounted, to 97.75 crams. Results arc shown on Table 8 and. Figure 5. 77

TABLE 8 1— SIZE AMLYSIS OF THE TOOLE ROCK AT LOCATION # 3

Retained by #10 sieve* = 11.10 grams = 2mm+ (gran, and peb.)

#18 = 4.25 grams 2-1 mm (v. cse.sand)

#35 = 34.80 grama 1-1/2 mm (cse. sand)

m = 28.53 gcams 1/2-1/4 am (med.sand)

#120 = 13.22 grams 1/4-1/8 mm (fine sd.)

#230 = 2.25 grams 1/8-1/16 mm (v.f.sd.)

pan = 3.60 grams 1/16- mm (silt, trace of clay) HC1 soluble portion = 1.60 grams carbonate cement

Reconstruction of total= 99.35 grams

* U. S. sieve series

FIG. 5. SIZE DISTRIBUTION OF WHOLE ROCK AT LOC. 3 78 Description of the C-ravol-Slse Constituents

11.3 pcrcent of the insoluble material is larger than 2 mm, mostly granule and pebble else {':-C-r mm in diam eter). The rod: may be called a granule conglomerate. An analysis of the coarse material is shevm bc-lcu. Infrequent mud ^rainc or pellets './ere observed in the rod, ranging in size from less than 1 eei to over 20 mm in diameter.

TABLE 9 -- DESCRIPTION OF CrPAYbL-SIZbD CCbSTITUElTTS AT LCC.

Si so and Shs '.c

ra Average si so = 10:-:. I-'O ..L.L, v;eight -- 0.75 G ^2 Maximum si so - 2p>;: 17"'C mm weight - 3.2 grams Average sphericity• (hrimib in) ::: 0.?1 Average roundness \it w ^ r\';iso"" n} 0.32 (subangular) r Shapes (Payne): 31 Jlhrg/J V* L''~- 1 " s HI - spheroidal 27i> Class V bladed spheroidal 18Jj Class II ~ oblate spheroidal

C outdo.:it ion

4-5$ porcellanito-lihe chert: color: grayish orange 9/a chert; color: yellowish bro'sn 27% quartsite; color: pale yellowish brovn 18$ quart site; color: medium darb pray

Poserlotion of the Various Grade-sisee Crouds

_'1J L • L> 1 JLllb 0 T the cn .iro roc": is composed of silica in o no f UJ." :.other v;i ,h minor amounts of other •"7 r . !" r. f- * mineral IV • L.' • ciwV ^ J Ilea and small amounts of clay are ; -i • ' the chi ef *•—> " \""Gilo r •

Cr'.7 o an.1 V'C7 '-""Ji-vi t". Already d O r* n v1 j. od.

Vo c I'C >'j oend V'.'Z 0 rmiplc) : - 95% of the vorKJ . -1'C c Is coirs:c 1 • i rounded 3 _ i. o ; qusrts. Ono ell-r ouna e d o rang e i quarts! •1 ;' r " •. r rved. , - I. , -' v_,- - - — ns shov ,secondary enlargement v/ith crystal '"*• F- r~\ ip • r - r - C; b0 _ j , , n •*» So mo 'of th~ .o:y coarse sand grains b> .. r> i - . tors cf : ^ - 4. i ' **" V smaller grains bonded to- £,0 ui.vs . u locnO. i\ ry silic; 7 r , • '*•> .. J. r~.1 4 • . i > r.-' -I •"! 5 ... « ^ . * ' ly"' ... u V — -• i- • — -. J- * 1; . .lt- -• -1. 4 torial of this mrade is Dale o o p (m tripol J. u ic chert. 79 Some white, clay-like material is found "between the silica grains.

Coarse sand (34.8$ of original sample): -- Much the same comments apply to ;ise ; to the very coarse sand described above. In general, however, the material is more angular and there are ::.ore euhcdral quarts grains pres ent from secondary enlargements. Some very darl: gray, well rounded "quartcite" (?) Grains wore observed. A few cleavage fragments of pale orange, translucent v microcline aero !:;;:;o: ved, also some pale orange chert-like grains. As -•n the larger else group, there are many silica- ceiuented clusters cf other grains which resisted disaggrega tion.

Medium sand (28.53^ of original sample): -- Mostly clear quarts, subangular tc subroundod, with ..iany grains showing crystal tor;ilnatlcii due to secondary enlargement. Some pale orange ml croclino. A few siliceous clusters, earl: in color, wore noted.

Fine sand (13.22^ of original sample): -- Angular, clear quarts grains, many shewing secondary enlargement. Sone pale orango microcline. A few dark, siliceous clusters.

Vr-V»'f r* *• II.-. , ..T t O or rf _ r» ...-rT-r • ,,,, -I „ Comments on fine sand apply, oncopt the grains are somewhat "dirty" due to adhering clay and silt.

" I i r»" \n f." ^ v < - r«nr' r. - original sample): -- Material smaller than 1/1C mm is mostly in the silt range, with only a trace of clay. host of the grade is a ngular, clear to pale orange quart z.

Heavy Mineral Suite (in order of freq.)

(a) Zircon is most co;.:mon. Amber colored, euhedral to well rounded. Many grains contain inclusions. (b) Tourmaline-, plcochroic, black to reddish brown. Angular to prismatic grains. (c) Chlorite, colorless flakes. (d) Pyronono, colorless, showing typical 8 sided sections, (o) Magnetite, black, opaque, well worn. (f) Apatito, colerless. (g) Hematite, 2'eddish mixture of grains. 80 Llpfrt Mineral Suite

(a) 95% quarts. Subangular to rounded, clear to milky and reddish. Most quarts grains have some iron staining. (b) Hicrocline; leathered, in part, to kaolin. Llany grains are i-rell roundod. 81 Location ITo. 4

The outcrop Is a small, flat-topped mesa at the western extremity of a series of irregular, elongated Shina- rump hills or ridges stretching to the east. The weathered rod: is pale yellowish brown to dark yellowish "brown. The frc-sh rocl: is yellowish gray to very light gray. Thickness: -- At this location the Shinarump has a thickness of 23 feet and is believed to be a full section.

Contacts with underlying and overlying rocks: -- The base is exposed and rests upon an ancient eroded surface of Moenkopi mudstono. Although the upper surface of the Shina- runip is one of present day erosion, apparently little, if any, material has been removed. Cross — s 11'"-1 i i.ca t jjii ci 1o and c irec11on: -- Studies indicate an average dio of 12° north, 20° east.

Cross-stratif icatlon t.yee and scale: -- Cross- stratification is on a small to largo scale with both the planar and trough types com; ion.

Bedding: — Codding ranges from very thin (1/2 to 2 inches') to thick (2 to h feet).

Lltholc^lc description and studios: -- The rock is in general only moderately well cemented, and may be broken by striking wllh the rock hammer. It is estimated that more than 10$ of the total out crop is composed of material larger than 2 mm, thus the rock name is cong1 omerato.

Description of the matrix: -- 100 grams of the matrix was treated with dilute hydrochloric acid in order to deter mine the amount of carbonatc cement present. The Insoluble portion ".;as was hod and when dried, amounted to 96.2 grams. Calcium carbonate cement amounted to 3.S or 3.?$ of the rock sample. Faults of the screening of the residue are shown in Table 11.

Oomoosl Lion and Description of the Matrix

As In otner samples, t.. matrix is composed mainly of quartz grains. Do tailed dos cr Ip Lions of the various grade s .1 z e s folio w s:

Granule size (0.6fJ of the original material): -- 80$ of the grade is composed of clusters of finer material which 82 failed to disaggregate because of insoluble bonding material. Of the 20% which are discrete particles, all are granule size, well rounded, medium gray quart"ito. Some well rounded granules are jasper, with the bal ance well rounded, moderate red brown quartzitc. A few "books" of biotite are oresent.

coarse sand (2.42;^ of original sample): -• Mostly angular to cubrcundcd quartz grains, colorless to milky to pale yellowish brown to orange and gray. V.liite clay mineral adheres to some quartz grains. One pale yellowish brown fragment of microcllne v/as present.

TABLE 10 -- GRAVEL ANALYSIS AT LCCATIOil 4

Size and Sha-oe

Average size -- 26.7:c20.3 1 4.0 mm, weight - 18.0 grams Maximum size = 245j:115^'- V1 mm, weight = 5,390 grams Average sphericity - 73. r~ 7 _ Average roundness ~ 0.C v -ub ro unci) Shapes (Payne): 50,^ Cla ss III - spheroidal 2°'" Gl^.s s T T - oblate spheroidal - 1. nn r T r T 1 *- r< j ss - prolate spheroidal SG Tf bladed s pher0 idal

Conine s it ion

96% chert; colors are: light olive gray, dark gray, pale yellowish brown, moderate brown and grayish red b% milky cuartz

Medium sand (52.50^' of original sample): -- This si ze grade makes up the bulk of the sample and is similar in composition to the coarse sand, e;:cept that the well rounded and frosted clear quartz grains o.v-; mere common; although making up less than 3,^. A pale yellowish brown grains of potash feld spar and one book of Muscovite mica wore noted. "/.Tilte clay mineral aJimres to many of the quartz ;-.rains.

?lno ,m.o ( 10.C.J of the original !•- ) : -- Very "dirty' , w:' th while clay adhering to Iho quartz grains, most of which are -•£ the clear variety. Appro::! .atoly 40;£ of the quartz grains are very well rounded and posse ss frosted sur faces, the balance angular to subroundod. .lioth biotite and muscovite flakes were noted .as were 83

TABLE 11 - SIZE ANALYSIS OF THE MATRIX AT LOCATION 4

Retained by #10 sieve'' » 0.60 grams = 2 mm+ (gran, some peb)

" " #18 = 2.42 " = 2-1 ram (very c. sand)

" #35 " =26.12 " = 1-1/2 mm (coarse sand)

" #60 " * =52.50 " = l/2-1/4 ram (med.sand) n ,, ^ " 120 =10.00 " = 1/4-1/8 mm (fine sand)

" " #230 ss 3.15 11 = 1/8-1/16 mn (very f.B.

" " pan = 1.50 11 = 1/16- ram {silt)

HCI soluble portion = 3.80 " = carbonate cement

Reconstructed total =100.09 grams

* U. S. sieve series

i-:-1

4 2 11/2 Vir % %6 '4a O MM

FIG. 6. SIZE DISTRIBUTION OF MATRIX AT LOC. 4 84

some orange chert (?) grains.

Vcry f1 ne sand (3-15,71' of the original sample): -- Approximately 60'/. of the grade size is composed of angular to subrounded. clear quartz, "but v;ell rounded and frosted grains arc not uncommon. The "balance of the assemblage is composed of silt and clay clusters which should. lc found in the silt sizes if disaggregation had boon complete. A fov; potash feldspar, Muscovite and biotite frag ments ',:oro fouiv1 .

( 1 . 50", J of the original sample): -- Silt is the main constitv.ont of this portion with clay being a minor fraction. The silt is similar to the quartz portion of the very fine sand described above, except that less rounding is evident, V.liite clay is the other main constituent of the sample.

heavy and Liyht "Mineral Analysis

A heavy mineral suparat ion vas performed upon the very fine sand grade size. The heavy minoral suite v/as scanty. T-'inerals ichntifiof arc described below.

heavy ytnornl "i.11c "(in order of freq.)

(a) Ilagnetitc grains, irregular rounded shapes. (b) Biotite, altoring In irregular spots to iron oxide. Dark "brown color. Very common. (c) Garnet, very pale orange, angular. (d) Zircon, violet to amber color, well rounded. (e) Chlorite, greenish. (f) Anatite, clear, Inotropic, mngular. (g) Diopside (?), colorless. (h) Enstatite, colorless, slightly pleochroic, low birefring ence, with parallel extinction.

1 r T * - -::ot 1 ^ J- :Jc: j. ^ ~~* *i i "* "I* /-i

I-Iostly quartz with lesser amounts of microcline. Some twinned. plagioclase v:ith index of refraction less than balsam.

PrImary 3 true ture

Rain pits and worm trails are found on the upper, exposed flat surface of the outlier. 85 Location I!o. 5 Numerous Shinarump exposures are found in an area approximately halfway between Ilolbrool: and Joseph City, ly ing 1 mile north of United Stater: Highway 66. The roch is cross-stratified and very congloneratio. The weathered outcrop is moderate yellowish brown. The fresh roc!: is yell owish gray. lie sieving of the matrix was possible be cause of the siliceous nature of the cement. 50 cobbles which had weathered out were used in analysing: the shape, roundness, size and composition of the gravel. Petrified logs, some over 10 feet in length, were found in the upper part of the Shinarump. A study of 10,3 orientation failed to reveal information of importance. Thlchness of outcr o p: -- The outcrop is approxi mately 36 feet thich. Gontac t s with underlying and ovei'lylii", roch.s : - - The base rests upon an ancient oresion surface of brownish red Moenlcopi mudstone. The unconformity is sharp and irregular, having a relief of aryproximately 10 feet. The uppermost Shinarump is a surface of present day erosion. Little, if any, of the Shinaruinp appears to have been removed, jusging from, the proximity cf the Chinle formation. Gross-stratification dl;j and direction: -• age of 60 readings talien in the direction of the maximum inclination of beds gave a dip of 16° north 100 east. .Cross-stratification type and scale: -- Scale of the cross beds is medium (1-20 feet) and large (over 20 feet). Only the trough type cross-stratification was observed.

Llthcloglc description and studies: -- It is estimated that the exposed section is composed of over 50?/°cf gravel sise particles thereby qualifying for the term conglomerate. Description of the matrix: -- Because of the siliceous nature of the cement, it was not feasible to sieve the material. I-Iicroscopic examination showed the cement to be white opaline silica. 86

TABLE 12 -- C-RAVEL AITALYSIS AT LOCATION 5

Size and Shape

Average size = 26x20x14 mr.:, weight = 14.4 grans Maximum size = 15cx102::100 nn, weight = 2140.9 grams Average sphericity =0.73 Average roundness =0.6 (subround) Shapes (Payne): 46% Class ITI = spheroidal ytf Class IT - oblate spheroidal 12^ Class 71= prolate spheroidal • 8^ Class 7 = bladed spheroidal Co^nosltion

86^ chert; darl: to medium gray, light olive gray to moderate yellowish brown 6% quarts; light gray to white quartsite: grayish red 2% petrified wood; yellowish brown 2% granite; white (feldspar Icaoliniaed) 87 Location Ho. 6" A series of 100 foot high cliffs, capped by Shina- rump conglomerate are found along the north side of Holbrook. The particular outcrop studied is located approximately 1 mile northwest of the center of the town. The exposure is a very coarse, cross-stratified conglomerate, vrith some beds of coarse sandstone. The weathered outcrop is pale yellowish brown and the fresh rod: is voi-j, v.ale orange in color. Thichness of the outcroo: -- Thickneso is approxi mately 10 feet, which probably represents the original thickness at this location. Contacts with underlying and overlying rocks: -- The base rests upon a sharp, uiidulatory ancient erosion surface of bleached I'-ioehkopi silts tone. The uppermost portion of the 3hinaru:.:p is exposed.

Cross-stratlfIcatlen dl and direction: -- Results are rather inconclusive as readings gave too much disper sion. However, 26 inclinations (out of the 60 studied) were toward the northwest quadrant and grouped fairly close to north 50° west.

sU'-.at if icatlcn tyoc and scalo: -- All three types of cross-stratification are found; planar, simple and trough. Trough-type is the most prevalent. Scale is small to medium.

Lltholpi-rlc description and studies: -- Fully three- fourths of the Shinarmp is composed of pebble or cobble conglomerat e. 88

TABLE 13 -- GRAVEL ANALYSIS AT LOCATION 6

Size a ncl Sha" d e

Average size = 26x20x14.5 vreight = 13.3 grans Maximum size = 1 50::1 20::1 20 mm, weight = 3030.9 grams Average sphericity = 0.71 Average roundnes:; = 0. r;2 {subangular) Shapes (Payne): 5C% Class III = spheroidal 26;' Class IT - oblate spheroidal Clasi VI = prolate spheroidal f rr r*-| n n f _L Gs. o . V = bladod spheroidal

Corrroosit ion 70%, chert; gray, brovm, yello-v.-ish brovm, orange and red 26% quartzite; grayish red, light gray to dark gray 2% vein quarts; grayish red 2% granite; pale orange, much vreathered APPENDIX NO. 2

CHINLE FIELD AIID LABORATORY STUDIES

Section D

Section starts at a point 5 miles due north of Leupp, thence 3 1/2 miles north 45° east to the top of New berry Mesa; the section roughly parallels the Leupp-Oraibi highway. The roclis dip at a low angle (3/4°) north 25° east.

Erosion surface

CKIELE FORI-IATIOi: (Upper Triassic): Thickness = 533 feet OWL KOCIl M3IEER: Thickness = 37 feet Feet

25. Porcellanite ana marl in alternating layers: light greenish gray; -.-/Gathers light olive gray; very calcarcous; thin-bedded, forms steps; caps

ri n- rhJ Ci.n c • l-i n r*kj r* ^--->0O"" ^^ -1 r- y-il1 ---r "1 • ••*«*•»*••***•*•**•«••• OO£t\J

24. Porcellanite: light brownish gray: weathers to pale brown; very hard, siliceous rock; subconchoidal fracture; thick-bedded; forms verti cal ledge: high (4o£) calcium carbonate content with much clay present; base is sharp and flat. 2

23b. Shaly limestone: light greenish gray; friable; forms sloping ledges; base sharp, irregular.... 5

23. Porcellanite: light greenish gray; with green ish and reddish chert nodules and pods; rock is aphanitic, siliceous and very hard; thin to thick bedded; cross-bedded, in part; f:rms ver tical cliffs and caps mesas; blocky; a large percentage of calcite (40;}) is present, both disseminated and in pods. Insoluble residues include porcellanite, fine clear quartzose silt, and a trace of white montmorillonite clay; base is sharp and slightly irregular 15 PETRIFIED FOREST MEMBER: Thickness = 246 feet

22. Marlstone: grayish red purple; weathers to light pink and gray; slightly silty with angu lar clear quarts grains; clay and numerous rounded, calcite pellets or concretions; very thick bedded; coraent weak, forms slopes; 43.4$ carbonate; base sharp

21c. Porcellanite: light olive gray; strongly cal careous (36$); very hard; breaks with conclioi- dal fracture; blocky; forms small vertical cliffs; contains irregular chert nodules which weather brownish. A very small amount of fine white quartz silt and white clay mineral (mono- morillonite) is present, with the siliceous porcellanite after acid leaching: base share, flat

21b. Marlstone: dark pinkish gray; thin bedded; fine- white quartz silt approximately 5$; rest clay mineral and carbonate (5o$); cement weak, forms "hollow" between 21 a and 21c: base sharp, flat

21. Porcellanite: light olive gray; strongly cal careous {ZG:?~) ; very hard; breaks v.sith ccnchoi- dal fracture; blocky; forms small vertical cliffs; irregular chert nodules which weather "brownish. A very small amount ef fine white qu/ t : silt and white clay mineral ( . ...'...r.-I' ll lo.:i is present along with the siliceous porcellanite after leaching; bas-v ^harp, flat..

20. Clays ton'.: grayish red purple; small percent of silt; calcareous, cement fin:.; thick bedded, forms slopes; base transitional

19* Clay stone: pale reddish brown; very small per cent of fine silt; somewhat calcareous; thin to thickly cross-bedded (medium to large scale); firmly cemented, forms slopes and badlands; base transi t ional

18. Marlstone: light gray, silty; calcareous, firm, forms small sloping ledges; bentonitic; base transitional 91

Feet 17b. Claystone: grayish-red, with bleached spots; slightly silty; thickly cross-bedded on med ium to large scale; firmly cemented, calcar eous; forms slopes and badlands; bleached zone at top.. . . , 101

LOWER MEMBER: Thickness = 250 feet

17. I-Iudstone: pale ol::ve; silty; thickly cross- bedded on medium to large scale; firmly ce mented; calcareous; forms slopes; bentonitic clay; base gradations.! 37

16. Marlstone: pale olive; thin-bedded; alternat ing beds of harder and softer material; filled with sphc.rical calc ILic pellets 1-2 mm in diameter; very small percent of silt; firmly cemented; forms small cliffs; base sharp, flat. 10

15. Claystone: pale olive with irregular pale red purple mottling: well rounded quartz silt con tent; some frosted grains; weakly cemented; forms slopes: base gradetional 5

14. Clay3 tone: -* r."!~O i JL re d, weathei'* s to pale red- 1 r r"H 5 dish brown; a V t; - j 11 am0 unt cf rounded n quarts, silt pro id on I; ight O- bleached spots; well indurated: form c slope s and "badlands" _ 1. _ i- topography; be. z e 0. rT> , Ud U . . • . 39

13. Siltstone: pinkish gray: thinly laminated; weakly cemented; friable; forms slopes; some clay. The silt i s angu1ar to well rounded quarts; biotite and muscovite present; silici- f ied wood ; base sharp and irregular 11

12. Siltstone: pinkish gray; laminated; firmly cemented with calcium carbonate; forms ledges; base shar-o and irregular 2

11. Siltstone: light brownish gray: weathers to light pinkish gray: cross-laminated on medium scale; firmly cemented with calcium carbonate; forms irregular slopes; biotite 16 Claystone: grayish purple, weathers to pale red purple; a small amount of rounded quartz silt present: thick-bedded; v.'eakly cemented; forms slopes; "base gradational

Bentonite: grayish rod purple; mottled some; slightly silty; o ro s a -lamina t ed (medium scale); weakly cemented: forms "lopes; clay swells when wet: brcvni calcareous nodules; come biotitc; base sharp, irregular, with 6 Inch relief

Sandstone: yellowish gray, weathers to pinkish gray; composed of GO,j very fine quarts sand and 40,v white bentonitic clay matrix; massive; weak ly cemented; forms slopes: biotite common; some orthoclase; base sharp, flat , i-ludstone: yellowish gray; JO,." well rounded to quarts silt, rest white bentonitic clay, cross- laminated: v.'eakly cemented; forms irregular slopes: niuac.rous cclcite nodules: base

Sandstone: yellowish gray; medium grained, angular quarts; cross-laminated (medium scale); lov;er Z inches firmly cemented with calcium c arb o 11a te, res t weak1y c em ente d: friable; fo rm s weak ledges; one foot layer of poorly preserved Unio-like clams at top: sillcifled wood; biotite flakes; base sharp.

Bentonite: dark grayish rod, with light olive gray mottling; massive; weak calcareous cement; forms badlands, and slopes; contains a small amount of well rounded, clear quarts grains from silt sise up to 0.2 mm In diameter (Wil son's "Bentonitic" unit); bs.se gradate onal Mudstono: grayish red and light gray mottled; very thinly cross-bedded; weakly cemcnted with calcium carbonate: forms slopes; well rounded quarts silt, some frosted grains; biotite present; base gradaticnal 93

Feet 3. Sandstone: yellowish gray: conglomeratic at base (rounded chert cobbles up to 60 mm in diameter) becoming a medium sandstone towards top; thinly cross-bedded (medium scale); fri able; forms ledges. Silicified logs. Benton- itic white clay, microcline and orthoclase present 27 2. Concealed 11

1. Bentonite: slightly silty; grayish blue with bleached spots; thick-bedded; forms slopes; swells when wet; base concealed 4

Note: An unknown thickness of Chinle lies below and above this section. 94

Section J Base of section is approximately 6 1/2 miles east and 6 1/2 miles north of Leupp. Section runs approximate- • ly 1/2 mile in a no rth-nol"thv/ester ly direction. Tleds are horizontal.

Erosion surface CHIIILE FOLIATION (Upper Triassic) : Thickness = 241 feet OWL EOGi: MEMBER: Thickness = 8S feet Feet

18. Porcellanite: grayish red purple with light greenish gi'ay irregular chert masses; thin- bedded, very hard roc1,:; almost entirely silicified marl rock; slightly calcarcous in veinlets; forms mesa top; base sharp and Irregular . 2

17. Claystone: grayish red; silty and calcareous; friable: form3 slopes; thin bedded; includes 3 foot doco ancient channel filled v'ith lime stone pebble-conglomerate; base sharp and irregular 28

16. Limestone: grayish red purple; much chert in nodules; forms ledge; base sharp 1

15« Hudstone: grayish red; silty and slightly cal careous; thin bedded; forms slope: base sharp.. 2

14. Limestone: light greenish gray; thiol: bedded, very hard; forms small cliff; numerous grayish red irregular chert nodules; base sharp, flat.. 5

13. Marlstone: grayish red purple; considerable angular to rounded quarts silt; slightly bentonitic; friable: thiol: bedded; forms slopes; base sharp and slightly irregular 38

12. Porcellanite: light gray: very hard; breahs with conchoidal fracture; forms ledge: rock is 46p' lime carbonate: dark brown chei»t nodules common; base is sharp. - 2

11. Marintone: grayish red; irregular calcareous nodules and concretions; carbonate content 56^; thin-bedded, friable: forms slope or "break" be tween the harder rocks; base transitional, flat Limestone: light gray, with grayish red chert nodules; calcareous content 6q^; very hard with cub-conchoidal fracturo; thin bedded; forms cliff; base gradational Marl stone: li^ht greenish gray; friable; calcium carbonatc contcnt: forms slope or break • between ledges above and below; "/cry fine silt present; base sharp, flat Limestone: light greenish gray, with snail greenish spots; $2* calcareous; very hard with sub-concho idal fracture; thick bedded, forms cliff in conjunction with unit bO; numerous dark chert nodules: some very fine silt and white montmorillcnito clay present; base sharp«- PETRIFIED F0FLE3? ME^I-EE: Thickness - T 53 feet Marlstone: pale rod purple and grayish oranse pink not tied: 39;' calcareous; very friable; thick bedded; forms slopes. Clam (?) frag ments present; high clay content with some silt; base sharp, irregular Marlstone: light greenish gray; moderately well cemented; thin bedded; forms ledges: SOfi calcite in the form of blebs, veinlets and disseminated throughout the roc'.:; chert nodules common; upper 1 1/2 feet of the unit is very hard muds tone- with approximately 25/ carbonate; very uneven with "root-like" features having more or loss vortical orientation; deep mud- cracks (?); base sharp and irregular Marlstone: pale rod purple, very slightly silty; waxy; friable; forms slopes; gray cal careous concretions near top; bc.se gradational. . Marlstono: light greenish gray ; witl1 light gray irregular pellets or limy concretions. Firmly cemented.; forms ledges; base sharp •* 1- ~ r, « Claystone * pCt lo red, wi Li: ..'L-. lo greenish yellow bleached spots ; only the fine st of silt impur- ity; waxy , oil-ck bedd ed; firm, forms slopes and badlands; base sharp and flat 96 • Feet

3. Bentonite: grayish red, light greenish gray "bleached spots: a very small percent of fine silt present; thickly cross-beddoo on large scale; fresh roc-: has "slickensides" surface; rock firm, swllc greatly in v.rater and yields stain test for bentonite. giotite present; base gradational 38

2. Limestone conglomerate: grayish red. to light gray nettled; cross-lar.iinated on small to mpd- iuii scale; base sharp and irregular on small scale 2

1. Claystone: grayish rod, light gray bleached spots; some very fine silt present: sv:ells when wet; rock is firm; forms slopes; base concer."' cd 55

Note: An unknown thickness of Ghinle lies belov/ and above this section. 97

Section G-

Section starts at a point 12 railes east and 4 miles north of Leupp and ends l/2 mile north of starting point on top of mesa. Pocks are practically horizontal.

Erosion surface

CHIITLE FCEKATIC:: (Upper Trias sic.) : Thickness = 242 feet

OWL RCCi: Thickness - ~>8 feet Feet

12. Porcellanite: light greenish gray, extremely hare with but little lime content; thick bed ded; forms ledges and caps mesas; consider able dark grayish chcrt in irregular nodules; base shar'o and irregular 2

11. hudstone: mod ill:: rod purple: friable; calcar eous ; thick bedded; forms slopes; base sharp and irregular 28

10. Limestone: light greenish gray: very hard, siliceous rock v;ith brovnish chert nodules; carbonate content 53^; considerable fine silt and clay present. A feu cilicifled :"astropods " are present. bedding thick; breaks in blocks; forms vertical cliff: base shar} and irregular. 8

PETRIFIED ?CREST "EkEER: Thickness = 204 feet

9. Karlstone: pale rod; very irregular and nodular; carbonate content 43/**-'; thick bedded; friable; fores slopes; base gradational...... 11

8. I-Iarlstone: light greenish gray; nodular; silty; calcareous content 44^; firmly cemented; Irreg ularly bedded; forms ledges; some carbonaceous debris present; dark gray chcrt nodules; base sharp 3

7. Marls tone: pale red and light greenish gray mottled; lime content 40fJ; friable; thick bed ded; forms slopes: base gradational 30 98

Feet

6, Limestone: nodular; light greenish gray; very hard, with 63/j carbonate content; considerable silica as disseminated chalcedony and veins, and as cement in fractures filled with coarse sand and granules; bedding irregular, thick; forms cliff: base sharp and irregular..., 7

5. I-Iudstone: pale reddish brown with pale olive bleached spots: calcareous: friable; thickly cross-bedded: swells sor.ie when wot; base gradational 37

4. Marlstone conglomerate: grayish orange pink; composed of clay marl with abundant calcite granules or pebble:;; firmly c em on Led with cal cite: thinly cross-bedded: forms ledges; base is gradational > 5

3. Beiitonitc: gratis!, red: slightly calcareous; friable with wa::y ''clic lions Ides" texture; cross-bedded on large scale; forms slopes and badlands; clay swells when wet; rounded, detrital calcite pellets of granular sirve: 10 feet from top is a lens of very fine, cross-laulriated sandstone; base of unit Is gradational 71

2. Marl stone: pale red purple and yellowish gray mottled: firmly cemented; Lhin-bodded: form:; irregular shelves and caps low mesas; bedding is transected by 3 inch vein of orange chert; base gradational 2

1. Claystone: grayish red purple; somewhat silty and calcareous; friable; thickly cross-bedded; forms slopes and. badlands; base concealed 38

Note: An unknown thickness of Chinle formation lies below and above this section. 99 Section K

Located 17 miles east and 1 1/2 miles north of Leupp. Section runs 1/2 mile northeast to top of Ives Mesa The rocks are essentially horizontal.

Exposed surface

CHIIILE FCRkATTCI; (Upper Triassic): Thickness = 221 feet

OWL HOC:: I.nKBZR: Thickness - 99 feet Feet

10. Porcellanite: light greenish gray'> weathers to Grayish orange pink; very hard and tough rock: ferns mesa cap; thin to very thin-bedded; some calcite disseminated throughout the rock; num erous veinlets of chalcedony and frequent chert nodules, some displaying all transitions froiu argillaceous porcellanite to clear chalcedonic chert; base sharp 3

9. I-ludstone: pale red purple; veil cemented, in parts by chalcedony, but breaks dovn rapidly with weathering and becomes friable; forms slopes: composed mostly of coarse to fine, angular clear quartz silt; some fine sand size, little clay: carbonate content very lev,'; bedding not discornablo ; base transitional 4

8. Kudstonc: pale red purple mettled; hard; much silica cement and chalcedony vc*inlets. Lentic ular with cross-bedding barely discernable and very irregular, possibly is an intraformational II--! 1 r 3 _ •' crC ' Z 1 C ible from top; ,. * T r 1 rcont- very lo ~ 0 iy c 1 Q J. X angu- ,* lar to suor und,CCJ. s *n t til s o:.I 0 fine and very NR 4 " * n UUL.---. fine clear' U « sand 7 fe "Q± 1 rounded sand 11 R, J- rl Cs grains vero . -w1 •U # Zoi ciay XYL evid once.

n cliff; " sC Z harp nd ii'i* egula r.. ..

7. Claystone : pale red with lightly ''bleached" spots; frj able; forms slopes; lenticular and cross-bedded: non-calcareous except for numer ous small irregular nodules which are over 50^ lime; a small amount cf fine quartz silt pres ent; clay mineral swells when vet but doos not react for inontmorillonitc; base sharp 38 100 Feet

6. Porcellanite: pale red purple with "bleached" spots and irregular areas of grayish yellow green; weathers to grayish ora.nge pink; ex tremely hard siliceous roc!:; forms ledges: a very o'ns.11 percent of disseminated calcite pres ent; shallow water deposition indicated by wave ripples and by deep mud eracl.s. There seem to be two generations of chert, one rounded, detrital chert and the other authigenic, nodular chert; base is gracational 2

5. hudstone: pale red purple: somewhat calcar eous: does not break down in water; friable, thick-bedded: forms slopes: base gradational... 34

4. I'larlstone: light greenish gray; fairly hard, forms small P n ' .Oil numerous dark -jhert spots er nodules v;hich shew all transitions from marls tone t: chert; bed ding extremely irregular in places: lower 5 ft. displays numerous "root-Hire" features orien- tly vertically; upper C feet more uni- .':inute dark organic (?) debris: lime con tent considerable coarse tc fine clear quarts silt and white clay mineral, some of which is montmorillonite: base transitional.... 13

PETRIFIED FOREST IIImkjER: Thickness 122 feet

liud stone: p ale I'-ed sumle at tc grading to 3. J J light greeni ••I-, - - -1 tT -7 '• Mi Q base; friable: thi ck-bedded; carsenate c ontont 17;.^; rest coarse to fine clear quarts s lit and some white montmo ..•17 loni te clay ; pessi b le brown glass volcan ic ash shards; bs.se gV ad ational 35 f 2. Hudstone: I * '—1 i -f*u o- - •" n"!-i gray mo u tied; hard, firmly comented: very irre gularly thin bedded, top 3 feet i n very hard ledge-fo rm ing rock; very nodular with numerous if.ore O IP less vertically orient ed "root-like" fenlurQ s; shallow straiding wat er deposition goerne z U ggested. i Lime content ZZ'^y rest is ccc.rzc 0 fine, clear quarts silt, angular to cu'jr o unded, plus white montmo rillonite clay ; oas e radational... 10 101 Feet

1. Mudstone: pale reddish brovm; hi^h percent of coarse quarts silt; angular to subroiui&ed; a few well rounded clear quartz, very fine sand grains; some biotite and muscovite flakes; con siderable lino content; friable, massive, no bedding visible; forms slopes and badlands; some secondary gypsum present in thin plates; base concealed. 77

Note: An unknown but major portion of the Ghinlc formation lies below this section. 102

Section 3 Starts at a point located 14 miles north and 5 mile! east of Yfinslov and thence 2 niles northeast to the top of Ives Mesa. Beds are essentially horizontal. Exposed surface

T CKINL,11, T-* tiV T ft rn l^\it O T [L'( 1" 0 r* r* -n p, ): Thickness = 543 f

OVJL HOC ' LGI-SbR: Ihickne 000. 0 — 106 feet Feet ro > • iiudstone; pal0 rod v/i th liGht greenish gray "spots" and ir regular r- v»i*%J. ' °V ^r* ; vory hard, b10 c \vj: has appearance of rhyolite tuff'; forms nesa caos: base ska

HI nir^ i"i 1_11 1"' • --v n O n i v 23. w j.u v 0 uUii - . <_-le rod; -tJ the finest silt present; swells wh 0;: vret a nd c?oak;.; down completely

<- . fn: into discrete par tide * - O .1. 0: forms slopes; base irregular 9 ~ - ' • « • « » * • • • * 12 22. I-Iud stone con~lo::,n r* v li~ht jroonish ^ray at the top; calcareous; very hard; irregularly cross-boddcd; forms

jr.all cl iff: base sharr- and h'iV'ul.ir. • • « 21. "si : pale red; calcareous eni oe.e^lo..ier- itio. Mud cracks at top; friable: fr-r,:s slopes; thick boddod: silic ified Un-os. shar-v and irroeular...... 20. Lir.-estone-; li^ht ,^ray; silicooue ~nc! impure, Wit;.:. _ silt and s ome cl-•v% T •* \TJ R.V>' ™ ""'O •V'L - V" J*>- w~1 •>* much ch.rt ; blocky; forms 2171 £.IT. ol-L'-TlTj "Z G CI" 1 — ir: j" y an i r.tra format ional .i:~o stone c ":^lo:;:s?- ate; s ;..r horizontal lense ; of cl.o" • o * base sharp and " rremdar.

19. Hudstone• pale red: CO vis, vi ti . fino anpu2.err to quarts sil t material :n inoral. b'ealrl'* ce..i on toe": •

slopes; f" ic ii-bcdded ; b?-ao * * * « A'A'

Porcellani te: li"ht •^n*T»Ox ^ J }• thick bedded; forms C1 •= "f - carecus; s ilicified ^reat 1; reddish ir regular ch ertif i1 gastropod of unknown a ff in 103 Feet

contact; rocl: composed of siliceous chert and chalcedony; fine clear silt; and white montmorillonite clay; ripple marked at top; base sharp and irregular 6

17* Muds tone: 1 i;jht ,greenish 31* ay and pale red mottled: calcareous; friable; ferns slopes. Does not break dc\m in water. Fine to very fine, clear, ^uban^ular to v:ell rounclcd and spherical quarts silt constitutes the greater portion, rest iron-stained clay mineral: thick bedded; base irregular, Graclational 17

16. Limes Lone " conglomerate1': li^ht greenish Gray: very silty with some mor.tmorillonite clay frac tion: e:; trcmely irregularly bedded, wit J: bur- row-liko featurec haviir; a rou^Ii vortical ori entation; mud portion of the unit becomes pcr- cellanito with niv.-orou.: irregular 31-ay cherti- fied areas and nodules, most of which contain fine orjanic-libe debris; cement above and. ho le v: siliceous layer is firm to weak; major cliff for:.:3.113 unit; calcareous content cf basal portion is 3C;J; insoluble residue of chert shows "calcicasts". The outcrop lias the appear ance of a shallow water, reworked, intraformational co 113Ior.:ora t e ; base 3-radalional 12

PETRIFIED F0FE3T !IE!ZTfR: Thickness - feet

15c. I-Iudstone: reddish brown, with pale olive "bleached" spots; very sliGhtly calcareous; composed cf ar3ular to subansular, very fine sand and coarse silt, clear and iron-stained quarts 3rains, some very coarse silt sise, well rounded and spherical quarts 3'rains, probably of eolian origin. Humorous fine grained, calcar eous sand lenses; friable; forms slopes; base mradational 27

15'a. I-Iarl stone: limht 3reenish Gray and pinkish mottled. Firmly cemented, In part, by silica; 39> calcitc content; veins filled with chalce dony present, and in places rock is almost a porceilanite. Thin and very irregularly bedded; nodular, almost conrlomeratic; verte brate bone fraGments present. Forms small ledGe; base Gradational. 104 Feet

15. Mudstone: ..reddish brovn, with pale olive "bleached spots; very slightly calcareous; com posed of angular to subangular, very fine sand and coarse silt, clear and iron-stained quarts grains,.s, someCO mo very coarseCO silt size veil rounded md soherical-rO-1 r\ V' cal quaquartr.r t r. grains, ••-r« of eclian T c * n. '~ uncrous u* L---' -I— , .rccu s sand 0 : - J, 1ab 1 e: "0 slopes: base gradational•racl a tional 20

14. Hudstone: reddish bro*..n, v:ith pal live bleached spots; very slightly calcarc kj • con- 1 -1 posed of angular to subangular, very .1. ,,11^ sand and coarse silt, clear and Iron stai .Cd. '~l uartr. grains, some very coarse silt siso v 11 rounded and spherical quarts grains, probabl, • of eolian

origin. ITumerous Cine --grained, calc .TO oi*.s sand1 — A T 1 l 0 • -1 H < . t lenses; friable; Torus slopes: base gradationalt — 39

r.. • 1I ^ • U—.LUKJT •: ~| r." f0'VVJ.W v-l • 1^ V*'- 1-.-.-'-.-'^ J r.«- — 1— U -rJ ^ T; 1-1 --p-r granules and pebbles; nay be an intraformational conglomerate. Thin-bedded: forms sloping ledge; base gradational. This unit appears to be a roverbed umer- surface cf bed

ease _.s transitions.. • • • •

12. hudstone: reddish brovr. vith pale olive bleached spots; very slightly calcareous; com posed cf angular to subangular, very fin:/ sand and coarse silt, clcar and Iron-stained quarts grains, some very coarse silt sir.c veil rounded inc. senerxcai1 T> < origin. 'Tune reus fine grained, calcareous sand lenses; friable; fcrns slopes; base gradational 36

11. Sandstone: pinblsh gray; veil sorted, very fine angular to subangular, rarely rounded, clear and iron-stained an! crthoolasc quarts grains, thinly cross-laminated en a small scale; irregularly bedded and lenticular: friable; forms small ledges. This bed is probably only an extensive lens in bed If above: base share, flat "... 8

10. Bentonite: grayish purple, f;va::y", smooth tex tured, and only smallest amount cf very fine silt present; practically no lime content; svells vhen vet and reacts for montmcrillonite clay; clay has "slicbensides" parting; thicl: 105

Feet

bedded; friable; forms slopes and badlands; base concealcd 80

9. Limestone conglomerate: li^lit Grayish rod pur ple "bedded" chert and. nodular limestone con glomerate which lens out and 3rr.de one into the other horir.cntally; brown chert also fills fractures transectin3 the bedding; chert layer way bo from 1 inch to 1 foot in thickness and caps small, low mesas when present: very thin bedded J>

ri-iv_L „ -r 0f-m 4.G no : "1 1 jht Greenish r 00. pv rple; calc eous * th v fine silt pre sent in small 1 amount 3 and -n n "iq - 'o* 1 rounc c vj, '-i iv "frosted11 very * -iQ ^ and •- 1 • < 3 • •' • 'C*1 ^ s eon 0 v:hon v:et -L r-s J- 1 but do e K^> * I'-w1" Lv - L- X J. . : t . 0... e 1onite clay -1 cros u ~ b eddc O n a lar.-.e seal O • rv rms slopes „ 1 1 badlLvi. 1d fr a" *m 0r t 0 f a r. * i"~ — 3 ribbcc. inv 1 tebrate f0 3 3 • - ; salt crystal impressions at n 1 contact; base sharp and irr eGular....

LO' Ml -7*?T*n rn j "1 -| • - 2^ c 'cot m mod 0rat ely w ce:ncn.ted J coil siderable very „r* • ^ „ qua rtr sand grridi into silt with • .1. --0 n 1 n * f U cr s-bedded on a white u... — J mineral 3 - - — -• • -^0 03 ,T% r- • 'f\"> y»n ^ t~\^ p. . 0 n *) larG seal ^ ? -i- X -.1 c 1 .->.-» O « num. or ous careous J. \ r~* • n *T 1 • <-» * 1, wn n 4- mud s U one p ••••11 - ^ ^ 3 t crys ta in *02? • - i.J _/ A i. O W 4 ..^ 'fin top. Some O;11 oil I" illian at 0" * - *—* O'•* •w'l« w 3 r; r~ pres ent; b CIjaM'!•' > i.-roGU * • * • • * • • • .J _ . - I-Iarl stone: li '.J-- w u lie "'i1'-1 LJ 1"' ay tc olive g1"1 Ci y; 0 , , _ firmly coi.-iento d; th'.i'i »j edd.eC 5 X i'.l Lj led-G r- r- • 1 v/ith darl: ehor t nodi!Jos , ver•y fine c lOO-i qua• X*ts j. silt and white montm.ori lloni 0 c clay ores ent: r« J. -4. may be intrafo rmat ie nal lime Li c ne e c riGlo.mora U e 0 - j - - • in part; base - -L.-- ^ 1.. and irre 11lar... • • • « • • • • » • *

-t -• J r i Sandstone: G^- u r:. i 1ve U ; very calcareous: X J* r* f poorly sor u C< $ V 01"'J er.rso and to c carse silt with appro r 1 r- to *1 ir J.-—. * 4u e montne j." J_ llonito 1 -j-) / ^ 1 r« n clay port:on; _J _ CO 3 orm'lom oratic with J, ^ •» -T J- * mudstone p olio 1-/ i_( 0 J ^ 0 poorly c cmonted; foja:is irre - - -.J "J r-, I' 0 " C 3 ^ cro 3 -~"b cc! d oC. on medium scale; con.tain [Z i:iU c --T* -* ncl divid.od J -1 carbonired '.rood, or ml ant dC j i uri r» a n; 1 0. orable "L'j ietite and 106

Feet

rarely, unknown hard, green mineral; base gradational 33

4. Bentonite: li^ht olive Gray and li^ht brownish gray banded: firmly c oriented. but becomes friable upon v.reatherinp: cress-bedded on medium to large scale; forms slopes: come small mudstone pellet conglomerate: noncalcareous; mainly anpular to subangular, clear quart::, fine sand and silt: about 10;.v white mcntmorillonito clay and fine silt; swells when wot. riotite flahoc common:

"""i•J Li Un c—noI <- v "1 Un *, V_ — "l Ott— r« /" -I 1 <-* » Sanao uc nc : »; c-ll C — o •" 'ty c. O L.-— — ^ Liu ^ very coarse, ..1<- • i • * I c rv f. H 0* . c -1«, " c r' t, re mainder -flno to V -i. an.d: -L ^ j. ^ ly ce- n *• tV --, * r 1 "1 ~ . r» *1 -,v. o mented: ± 1 ' _L L.* L. _• t_; , m T'l'o lc pes and 1 -*1 J. - ledges; CI" OS — iJ O ^r or;. mod iu oo "! ^ i" *e ^c ^r* o "] r\- •j ™,n 1 • rr» r-> r" o ** conside Z ' i vood as lo ' and mer.t s, •n 1L:O c CO al CO m::.on ; sand "14 a ins arc mainly ii :uL r t 0 s ub an -via r to su"" iv -, i— -• ound ed , T •" 1 4 •»„ ]">n clear c uarts ) LPJ. 1 _ * 0 or ito, o t i t o, 4. . n C f".\ *"*. r • o orthocl il.d s id 0T* ' — > —• nule s are i •; -1 Q »-• o -r part " -or T of detr Ime Oil s st - •'•o—«J 1-1 • c ale arc-CL'-O j est 0 J — C 0 pproxi- r* • * ^ •* mato ly * o;„ o -•i G> 3 hite ontmo llonite clay an.d -T» -• --j r-. qu•?.r* Ju r—_ 0 _L It; ;j. 'J1. SG i 2- "* •, O -i-r ^ and irrer.ul o 28

2. I-Iud stone: praylsh red purple; very friable; t thichl u •-bedded on a lar^c scale; forr.

clonesH most clear rtuarts silt and ircn- 1 • - o r d c v ar f :-mo clay mineral and biotite; nclud ; small lenses of cross-laminated, very c lc arc- .is sands tone similar to unit belov;; b a s e o T> mud s •> •>**) r~, 1 1 V * *f" " •" i :*"» *-> •"> 2.~ * r*1 "p

• 1 * O V 1. Sandsto m X 1-V^ ; fX' — C: ble j thick bedded; forms 0"0 -r*. *-> i• sand i'un c from i. ? j. . medium Inod c.ov.t: c:. ,o Li -- ov - J. _ 50 fa in the -Tdno jii id -race; to i" r, 3 ll.t- u c ro gencus m: r* *.-i r-i 1"' Lo SUb •« • /-i i- r* rounded clcar and iron-etaInod CI L.Li, — u j c. on- siderable ar; ~~J'" " In 0"^C 1f "iin h a o 107

Feet

biotite, muQcovite, chlorite, magnetite, clay mineral and others are present. Cement is cal cium carbonate and iron o::ide; base concealed.. 11

Note: An unlinovii thiclzness of Chinle lies belovr and above this section. 108

Section I

Base of section starts 6 miles northeast of V/inslow thence 13 1/2 miles north-northeast, ending at the Dillron Castle Butte-V.Tirislcw Road junction, atop Ives Ilesa. The beds dip at a very low angle toward the north-northeast.

Ero c io n s urfac c

CHIirLi: FCRI'ATICi: (Upper Triassic) : Thickncsc = 848 feet

CT;vL ROCIC JiSMDSR: Thickness ~ 2e8 feet Feet

35. 1-Iudstone: pale red to light gray; calcareous; some silica cement and brownish chert nodules; alternately hard and soft; irregularly thin- bedded; topmost layer is hare and caps exten sive mesa: base sharp, flat 14

34. Hud stone: reddish brown with pale olive bleached spots; very coarse, angular clear- quarts silt to veil rounded, sphcrical and frosted fine sand grains. Red ela* material constitutes • l"G;b' of the rock; seme biotite; thickly cross-bedded on large scale; friable; forms slcoc s: base share; 57

33. Sandstone: light brovr.; moderately well cement ed v:ith secondary silica; laminated; forms le&gc; clear to iron-stained angular to subrounded quarts grains; siightly calcareous, het erogenous assemblage of minerals 1

T,0 * 7-j i r] r< J- R, ,r. • - ^ ^ r.f..,'' • r- ,ri J- # -f1 .-vv--, r« slopes; somewhat calcareous: breaks dov::i in hydrochloric acid; mainly fine sand and coarse silt, with clay. Other minerals are biotite, feldspar and red chert. base share 18

31. Porcellanite: light greenish pray: chalcedony and chert; calcareous content minor; gnarled to thin bedding; lenticular; very hard; forms "stops": base sharp, irregular 2

30. Clays«/ tone: alo red with pale greenish o~^r.v4 '—O bleached spots; slightly silty; non-calcareous with pellet conglomerate lens; friable: forms slopes; base sharp ana iregular 44 109

Feet

29. Limestone: light greenish gray: argillac eous and silty; very hard; thin-bedded; forms mesa caps; gnarled, irregular: seme nodular chert; base sharp and irregular

28. hudstone: pale reddish brevn; very friable; calcareous; cross-bedded; silicifled Unlos bed 4- - C foot, above the base: base sharp and irregular 33

27. Poreellanlte: light greenish gray chert; cal careous; very hard: bedding lenticular and grades irregularly laterally into nodular, 11011- pcrco1 lane0v.s limosteno; forms ledges; base

26. Iludstcne: pale red; friable; irregularly bedded, forms sl:pes: calcareous; base sharp and irregular 3

25- I-Iarl stone; grayish red purple; firmly cemented; very hard, subconchoidal fracture; thin-bedded; slabby; forms ledges; very silty v/ith angular to cuban~ular, rare17 veil reunded clear ouarts v J V grains; br.se sharp and irregular 5

2h-. Mud stone : grayish red purple; calcareous and

siliceous in oart:— Iiard:- veathors ran id.lv;c 7 forms slopes: base sharp and irregular 10

23. Limestone: light greenish gray; hard; silic eous; thin-bedded; cliff forming: irregular chert nodules and veinlets: base sharp 5

22. TIarlstone: light grayish r.'.d purple; very silty; hard: friable: forms slopes; irregular bedded; nodular; base sharp and flat 6

21. I-Iu&stone: pale reddish brevn; slightly cal careous; much very fine quarts sand and coarse silt, firmly comer.ted -.:hon fresh but upon weathering breams d.omn easily; forms slopes; "Xn <*• r> ^ V. o " ^ n x 11

20. I-Iudstone: pale red.; silty; non-- calcareous; breahs dovn vhen \:o t; friable; forms slopes; Vi n r-c r» c. --- "* /*»<"-** "t n '<-• - -T-t o ^••»«»•• • »«+• 1 10

Feet

19. Limestone •* ligilt greenish gray; very hard; silty and. r* Hiceous with irregular banded brown chert nod ulO W "U. •J thin-bedded; lenticular; blochy; forms ij.,r-i •• hr* O 11 vertical cliff or lodge: base sharp ana undulat 8

18. harls tone ; il ght grot-nich pray and oalo rod LlOttl od: qu .t J _ silty v."ith angular to subrounded clear qua rt -* j frlabio; for...s slopes; lenticular: upper sur nay have largo1 current rionlos; I CO w — «- * base wii-- .1 -» -• and * i O p v 18

17. Hudstone: ~~>al o r od: ..i o d er a t o1 y v o11 c on o nt od;

cont a ins * 1. J.h"l ar to veil rounded clear quartz 3 lit; 1 b 1otito and rod iron-stained chert and c 1— Ln"J t>— nro s olit; broahs down when v.rot; friable: , forms sic V '• c •Z ... ^ -v_4.hl. M * • • » • k • • » • « * 0 18

J- -1 . J 1 6. Lines 0 1 ; o-*-'- o* "*j ji- ^ "j *.!._• J.? very O j in part siliclfiod, becoming ontrone- ly hard In places; 1 i.:c con tout 51 ; -lit and clay naho up the bc.lr.neo; zz:?.e ". rganic" (C) debris; iforus vortical cliff; lenticular; lov,ror 2 1 /l foot in very Irregular, con.glo:.iorato- 11Ire natorial with numerous "root-1 "f" 1 1 "** . r* • > n o 1 % "1 *~i ^ U v. » kj J <—v p and i r•- _j U- • «

-^-g m ^ --g rn J x r_ _:::: iij. c ;'.iie s^ — o x es i<

t. ^ 15b. harlot jnr. congloJbiV.. U*J ; pinhlsh gray; slniil ar . -L to unit 1 1" b c 10 , o::co \J u "^i» * r' r,;1 ^ 7 13 3 •f VP ^ ^ *. i~ '\ i" T *i carbonatc conton t: bas C • • 20

-* -in n 15. Limestone : pinh --1' o-L : :.:ottlod: finely • * comentod: forms 1— ^ o -• * c arsenate content : silt cont iii v ot vOi it e no n t n o r111 o n it e r» *i J. c sharp , j. J J • • 4 *

14. 3entonlti r> (••I •* \r<-\ to no : grayish red; with vide horizonta *! j of gr""u ired -ourvie occur~ .L w . ! ") • - + n .g ^ ring frog - ^ J ve: thlchly cross-bedd ed r* on larg~. scn.lo-: clay I — —.-n.~• .--f T ..nfu. iij ) .,11..-AJ -'ir appearance w.l th "slich ensides" parting; clay

shells when vet ,J u o ^ .1 ve s poor tost foi- nont morilloni to; non orLlc'^i* oous; forr.s slopes and badlands; baso s harp, fl . t; o thin plates n r ---r.,.. of second s uprO Z • • 50 111

Feet

13. Marlstone: greenish gray, weathers to pale^ red; friable; forms slope; approximately <%0% lime content in the marl v:ith about 10;"* coarse to fine qu ul•"> V "f'L» 4-jT .Li'1 1 "f*U ,• rest white montmorillon-

ite clay: base sharp and flat •

12. Claystone: -ray ish red, with wide horizontal

bands of g purple o ccurring frequent - ly; massiv e;V thickly cross-bo ddcd on large .• r, -T S! ,~r. J- scale: cla «/ om-0--L,1 V nil!- ; wa::y .appearance with :'slic kensidos" p C„i.O *.*% **^ * •J clay swells when wet but gi ves poor te st for m ontmorillonite; non-calcar e-ous: forms slopes and badlands; bas e sharp, fla t: some thin plates of sec:ndary

LOIfZR hlm-h Thickness of this .comber at location I is "40 foe t, with unknown amount co vered be twoen beds 4 and 5.

11. Sandstone: yellowish gray with 6 foot brownish gray, cross-bedded lone of cilty mudstone near raid-port lor:; very friable; foras elopes; breaks down v.rhc:: I: bonding .:.aterxal is white montmorillonito olay ~ poorly sorted; sand is clear angular quarts, medium to fine grained and dovm into coarso silt sizes; very hotere - genous composition v;ith green biotito common; red chert, potash feldspar, chlorite and aider- it': present; inclusions of charcoal and silicified wood common; the whole unit is thickly cross-bedded on a largo scale: base is sham and slightly irregular . 180

10. Sandstone: dusky red: friable with lenticular bodies; forms slopes; very poorly sorted with a heterogenous assemblage of material ranging from clear 'angular quarts in fine sand down to silt grades; biotlte, some decomposing to red iron oxide common: clay, muscovite, ciderite, red chert and chlorite also present; cross- stratified on small to large scale; the flat lenticular cross-laminated sandstone bodies form ledges: base is sharp and irregular 55

9. Mudstone: yellowish gray; friable; thick- bedded; forms slopes; very unevenly bedded with irregular marlstone "nodules". Mas considerable lime content; 1/2 inch layer of argillaceous fine sandstone at top: base sharp and irregular

Bentonite: grayish red purple with pale olive "bleached spots; composed mostly of coarse silt and clay, seme v:ell rounded sand Material; sveils vhon v;et and reacts for ::i:ntworillonito • -f1 clay, partially i - y cementea \:hon f re sh, 'r r n weathers rapidl0 nd b ecomes f ri bio; Lhich- r> bedded; fc ms slop O 0 • Pone rap:.ionts •oresent.

Base is concealed. • • • • • • « • • » ••••«••

_r» -••lO r. *,r • r i-s. i Jlo" bIT* C u. Sandstone: yc-1lov; ish o-*- ? »_> •*, T > r- "1 r^t apart in water; fo '•rr'n'" d"o Co;.; • OZC; d Of • 1 > ... ni angular clear quar ta -* r.1.11 3 rany i. or.: medium j. J ~ r i-irl • - . • • r siso sand to vc r • 1"-' < whi C. • oi i oh.Orillon- - t~J ' 4- itc clay is the bendIn a-ont ;— I1O •-Ml o bleached "? • - 4 bi o ti te 1s prec ent "t 0 appro mat _ KJ, I t:.'" • X- n minerals are oh101'* — ° • J micro lir: 9 oit o, red !• o •" 1 £^21^ d. "V» 7 — r •-.^*1 -1* I'iO V j «...id calc te; ;;- r inated i . ^ -i on a small sealo ' f1-t • i UdS ols are

«"T 'a ,1 r- - n found as Indus onc; bci::c ch r'o 1* O ' •• •

* o"]-. 1 Mudsto nc-: pray rod ; thic _ - r. ded. Composed * r\ and rod of angular, doo.r ta ail I 1 i •on- To-** <-< •f- O "»•*• s t a ine d. no n•- s ve 11 i n;•; c 0::io 0 ioti ros-

ent; forms slopes CI '"~1 r~L badland «.-> • . Pone framments

o "j > «-i - rnr} pre s ent. 2aso L3 rroo ular• •••••••

; • "vi v.- Silty bentonite and veilowi Li- r'. " nottied, with m1 '""J — o-- purple » ty bentonite bands. Siltstoi i'"' is co::.po so d pro do mi nant ly of i. . medium to coarsr anmular, c p quar w ? 1 U 21 o ilt, with a few well i'O undo Ov_. , ^C* "" ^, r_i !' • arta > very fine • sand grains; appro ::ima tely 2 bro'.r to ' TOG1^1 — 1 - r-l ish biotite fla and boohs a.re "oresf- nt. the

oiotite breaking down Into rod iron oxide and staining the finer material in places; cement is weak; friable; forms slopes. Ease Is concealed. te: Belov; unit 5 and above unit 4 is a flat, covered area, conccalin£ the thickness between the tvo units. 113

Feet

4. Sandstone: grayish pink, firmly cemented 7• fossil wor (?) trails. Platy to paper thin splitt inp; caps irregular low mesa rs; c ros tr« j ^ laminated n t a high angle on a sma11 scal e; base i S sh rp anO irregular: top i o p surface of ero s ion • current rippl r\ 1^*10^ r>2"i l.

Siltst one: "yci1 c "o11 v:ls h brown; well sc rted; compos ed :;c n "1 T O ^ "' 1" " "*1 "1 r 11,ular to r ovaid cd clear quarts , CO -rse silt and :.i ediwm fin,'T \.j H It: n small pore nt of clay mineral; sha ~~4j ? la::: ina» tions LV\jO *.1 thin; fossils , moderat oly ".rol 1 ce- n r.ientcd • j J" ri ecendary silic' o * •? - ^r~* "J ^ ^ irre gular slo'*!o.

o "* X V~l. On vJ '»• 11'. : brownish gray; friable; J-*C 1'- ee .1 od; •P IT T slope s: composed :f very fine sa nd J-o 0 . . •• fine q mart ::: silt: consido rable ola n; •] i'-'-j 1 mainly mon j.o morillonite; much of the ol «~1 ~ ~ -L•» •nJ iron-". J. , -1 , rig, which is r c-sponsibl ^ .n r" t he col- 1 c. ~ or of the -• edimont; base is conc::a • « « 17 1. Siltstone: grayish olive ; moderat ^ "I -- '.roll cement •~.- ~fT *7 c r o s s-1am inat ed on small n n n * i L'ir~y — i on "1 »~t --n 2.?'^In"* lod~*c: — Ajjpo "i ,n U>.yi C ^ into lenses 0 I z ^ W- rtf 0 x n r p /"V"! "•" ^ ed o r c oarsc- • .i"> • • i o - t r-- * "J -}- O "1 to verJ - 11• ^ <,]_ V,<~ - - ^ 4-1 ^ O J "mostly* a'1-ul > a few well rc unci.c 5 vci"*y rino nd grains cent; appro:: V""t ^* o ly I0ri is chlo T» * ,T- v-_^ £ i"i ; ce ment for roc': i o ;; e c o nc" a ry silica in small am o aITt S i• '---.ij-c-® sharp and * rregu1 ar on s:ail sca^e

SHIlTAHUi:? CC:TGLC::iPj\T?: (upper ?riassic): Thichnesc = 10 fee^

.Rod; is yellowish gray, weather ins to yellow ish brown; conglomeritic sandstone to coarse sandstone, cemented. In part by silica; cross- stratified. cn small to medium scale; bedding very thin to thiol:; base is concealed 10 114

Scction P

Ease of section starts at a small Ghinarunp outlier 1 1/4 miles north of Joseph City. Section continues in a northerly direction to Smith 'dutte, a lava covered r.esa, some 15 miles clue north of the startinp point. Attitude of the beds is almost horizontal, a 1/2° dip tovard the north be ins the ma::imun noasurod.

WIITC-AT2 SAhDPTC:;z ("ppor Trias sic) ' Feet

Silt stcno * I* odd ish brovn, •;ith pale pro en- ish O- '"KJn * - blc- spots; thich-bedded: cross- J c tra ui*' -P •!J- d o 21 .;:oc.1 un to larpo s cale. 'fell sort od, _L u-i.- s oa ined, fine quarts silt; eoli O I"1.'', uncl od: fir;nl y cemented v; 1 tli dolomite • -n (?) and iron onido ; j- cms sheer vertical cliff over 100 1 0o t hiph basc sharp a rid in idu 1 a t i n,p, •"> r< i * rf ace of ore si on (nonconfor..:i_L 1 f" "^ «**<«•***••• 100

LJ- UA iii

?cr::.vfio:: (Upper Trlassie): Thichness = 1118

i ROC K : ihi chii ess - 33^ feet

20. Idarlstone * ^"•* L ' r ' j ^h oranpo pinh ; massive, fri- 1 able marl \ r* ,s o rod airido, very hard, thin linestone la yoi'-3 c.t 1 " rV T) f•" . , 75 feet J- 1 and 93 fo'•J u -< -•r base. Ane thor 1incstone J~* ,i. '•». , _ . i * laye"9 ... o to;/ is C o . •. i ~ cliff *ror •o > * - ~ — a.rd. a no co r.tains :iu:_:croim Chert nod •. , "• . r, , "* _ CO J- J. -. ^ base is a larpe 'oot thic-h bod of Unics (?) vhich aro silici- jy * t ed and ]-icorl y orved. P o '•' 1 "• :it 20

•U-I-J.X ndu. _i_' - i Li, 3 V.i'i .c O C f 0res ion, th c entact j. *• th 'inpa Lo sa::dstonc , ^ *" C: c shar and

4 ir+,* c ; -vf " " # 187

11 o " "t i. J- •:>al ^ • do L/Ui. - somev;•hat cal.car: pens : 11J' r« frla bio * —'or', .s slope s ; nod ium qua' * u silt pros- j. . * ij" . •~t 1 - t-.-- on Li • 1, .ron-st a ined 0 - \ tJ and -1- fl 50

18b. llarlstono: pinhish pray: friable: forms slope; silty th 3 thin, ono-foot thich, or less, hard linostone lodpes separated by tvo-feot marl layers at the uppermost part of tho vhole unit. The hard lodpes are siliceous and 115 Feet

contain nodular chert of various sises and orientations: the base is sharp and flat 96

18. Limestone: plnhioh v;ilh darl: gray chert nodules: hard, .siliceous limestone, calcium. car bonate ccntcnt 6-r%s rest silica, mainly as chert nodules, some v;l:ito clay and fine silt together vith numerous blacb cr darh brov:nlsh "organic" (?) spcchs; this bod is blochy, forms snail vor tical cliff; base sharp.. . 2

PETRIFIED FChECT I-IEhbhR: Thichness = 233 foot

17. Iludstono : • palo rod purple; massive: friable; . forms slopes and badlands; rounded, detrltal lines tone grains from gr .U1 c siso do'.;n to coarse silt siso vcry cc on; 20;; "hi to nontnor illonito clap matri:: nit majo r norticn clear, 1 .^ ^ J. r. J. 1 . angular quar Is-silt: car content i J n 1 rod: sv.'ollc v'hon \:cI; base is— concealedconcea" ed. 253

16. Sandstone: pcllov:lsh gray: friable: very irre; r» n -1 * *

Sandstone: light brovmish pray; fine to medium; angular to rounded sand ma to rial 5',j white no lit- morillonlti clay: biotite decomposing to iron o::ide; nucccvito, chlorite, microcline and detrital broyn chcrt. Poorly comentcd, friable, except for a ~ foot thich ledpc of very calcar eous marl pellet crnplomorate 20 foot from the top. Cross-bedded on small to larpe scale vith average inclination to the 17' at lC°, Ease sharr; and irropv.lar 116

Feet

14. Sandstone: pale yellowish brown; very coarse sand to silt size; angular to subrounded; white nontir.orillonite clay content approximately 10fj, "mud ball" conglomerate at top: lenticular and cross-bedded on a nediuv scale: firmly cemented with line, ferine cliff: base is sharp and irregular 8

13. Bent oni to: dar;: grayish red purple with li^lit Gray bleached spots: slightly silty, swells and reacts for racntmcrillonite; probably bentonite rewcrhed by water; slightly calcareous; base indistinct 44

12, Sandstone: light ,7,ray; 4 veryt 1 VI * ' fine grained, clear * '1 4- angular quarts. mixed w u CO silt, clay, chicrite, CC-1 cit

Very calcareous in pla,ccz 9 - e« '• r, 11 r- 1 a white arenaceous 1 imes. •- tone; 2 foot from top is a largo deposit cf UnlosT'l") •' L.1 LJ (?), silicified and poorly preserved. Seme gravel and. nodular marl- 3tone is found at the same level; base sharp..., 36

! 0 0 1 1 . 0 C-rkJ "oero id: pale brown; calca recus and arena- j 1 r» n ceouo; pocz - ' —j introduced si into the top r •fir3 r*v»ri * 0 of the sand stone of unit 10, v ' r a ^ -.W-. ^ •, j. u.lllJ nay be observed in t ho matri:: cf orang e chert. Very hard; forms ontonsive cap for low mesas; ba se radational

10, Sandstone: light sre.y, coarse grai,nod, mostly angular clear quarts, almost spherical, well rounded grains common: poorly sorted material found in all sizes down to silt grade: some very c car so sand is round ec! chcrt; rare cleav- • age fragments cf clear r.lcroclino; considerable , J' rr ^ J. n r, biotito; authigonic quar u t—' c - J i-J ^ common ? white mo ntmorillonite cl »"1 1 - ;; atri:: am.ounts to 30,1 of roch: red: is poorly c 0* ' •r"- nted: fr'iablo; for•ms rj slopes; numerous fossil lo , mainly agat 2. zed, "1 "V , -l ,. present; base sharp and I'O * * * • * • 0 J. 1 t • 9. Sandston j . 0 l"1 c d purple wi to spcchs: very poorly z or•ted and heterog, 0:10 us assemblage; angular, cle cii*1 9 coar•se sand, m:. d iU'. S and anc f'no to very if* iii.c f. r>.nci 0...,^ ^ -0r - — —• ^j ..v-—ca, ch.ort, magne- • j.. titc, ch,lor c -j approximate-i;- 3;: white clay J mineral ic 4-Ui-0 SOliC 1-1 ' «-i.long w• i t h s e c0 ndar y 117 Feet

silica cement; laterally the sandstone grades into very hard, light brown chert; forms exten sive cap for loir nesas; very thin, less than 1 foot thick; "base grades into mudstone below....

Mudstone: pinlil o ^ "iin -r wi th mudstone pellet

conglo merate at the base } coarse angular fine "i"> • sand a nd siIt: 1enticula ~ 7 c ro s s-bedded; friable; forms 39

-'pr, x j t.r •TO 1- * Benton ite: •..j -v " di ped ith yellowish Gi- ^ -i J. -r . * - i bleached spots; . X m; weathers rap • dlv •

r- . forms slope •-J J —'-i- ec.choc. c po ts react for m:ntmcr- f "p o illoni -f0 p.«-» •j !u beddod; s e ~rada t ional, 4

o - - 1 « j V P I" "*"' T 1 i r> Siltstone:i yell owish gr 6. < cous; r 0 0 P 1 a hodg go 0- mineral uj and sises: angular r\ o - i f r* ^ quart s from 1— .J 3 L so o:^ dov;n to s ilt; L 4 biotit c, muscovi C- ' i -• "i J. its; hard, cemented with a smal1 amount of s CC ondary silica; forms

"•sr ^ -1 ledges 7 e co"' cc?: ed.. 30 5. Silt stone: liyht mray; argillaceous; poorly c oriented; friable: ferns cliff; composed of c oarso sand clovm tc silt size; angular quarts Grains, some of which are woil rounded; the clay matrix is montmorillonite, forming approximately 20jS of roc!:; other minerals, bictite, crthoclase, magnetite, orange chert; unconformity at bo.se with one- foot relief 10

4. Bentonito: medium darl: gray with light gray bleached spots: waxy luster; swells when wot and reacts for p.ontmorillonite. Only very fine, well rounded silt is present. Gross-bedded on a large scale; slickensides parting: friable: forms slopes and badlands; brownish siderite con cretions common, weathering out as bumps ~n the surface; petrified tree stumps and fragments; mid port ion ccncealod; base sliarp 1 15

O A 1 4- ~ -n /- • "1 •" • * -• rr--'lipc 3. ht graV 3 '-jJ- <_> coun y very hard; cemented w'ith s i 1i c a, forms mesa c ap G and vertical cliffs. Co m"oo s e d of angular to ubangular,

"1 o-nri or"' rarely rounded, clear• quarts mat oria IlU •_;l j white clay miner a*^ Seme iron-s tain ,ri d prawns. A few fros t ed c oarse silt grains j be due to 118

Feet

either colian transport or to secondary en largement. Some flattened mud pellets paral lel to bedding; base sharp .. 5

2. I-Iud stone: grayish red; very poorly sorted material fro:.: fine angular quarts sand to coarse silt and iron-stained clay and fine silt. Abun dant detrital magnetite, hornblende, inuscovite, biotite, hematite; firmly cemcntcd with iron and secondary silica: forms ledges ; crocs- lam inc.t. ed: base concealed 8

1. Clays tone: d arl: grayish purple to grayish red, vrith small ro und ye llewish gray bleached spots; very thid:-bodded; f r i ab 1 e ; f o_rm s slopes a nd badlands; swelis wb:on wet; some fine silt, mus covit e ; b a s e conoeased 72 SHII; r-r ~~~•t- «, r-1—. ^ Upper Triassic): Thichness =

Congl omerate, c c ng1 omeratic sandstone, and r J coars A ' 1 ' r-. .j-i » yellowish gray to very light gray; weather S to ale or darh yellowish brown; very hard roc b, cap-o mesas and forms cliffs; cross -bedded C 11 OJ.1'S.11 to large scale; bedding very . thin to W J->, — ^ o1-- -« lenticular; cobbles well round 0x' 1 ,n ^ or.Yz o z o d mainly of detrital chert, maximum size 2*'C.::1 1 $:••:£7 nim; lino content is 3.8% of rod:; base —_" r* U-*O surface of erosion, undulat- 1—--o 11 r- 25 Erosional un c o nfo I'm i t y ( nonconformity)

I-IO EITICCFI FCBIIATIO": (h'arly and I-Iiddle ? Triassic)

Mud stone: darh grayish red, upper surface bleached irregularly tc light gray; cross- laminated; friable; forms slopes: base is concealed 20 119

Section C

The "base of the section is located 3 1/2 miles east and 1. 1/2 miles north of Joseph City. The section continues 3 miles north 30° east to the ton of ilarcou Mesa. Beds dro HUE at 2°.

Erosion surface

CHII'ILE FORMATION (Upper Triascic): Thickness = 382 feet

14. Conglomerate and conglomeritic sandstone: Feet light pinkish gray chert cobbles up to 100 ram in diameter, well rounded: matrix is a medium sandstone with 25;'j white nontmorillonite clay paste as bonding agent; biotite, orthoclase, chlorite and chert; rocl: is friable; forms cliff and extensive mc-sa cap; crocs-bedded on small to medium scale; much silicified wood, charcoal debris; lower 5 ft. are mainly sand stone; base sharp and undulatory; erosion surface 11

13b. Bentonite: light brownish gray; thin-bedded; friable; "dickens ides" parting: forms slope; swells when wet; base gradational 7

13. Iludstone: grayish red purple; friable; forms slopes; some -..-ell rounded, very fine quarts grains precent; bedding is very thick; base irregular and gradationa1 i 33

12. iludstone: light gray to purple gray; very silty; well cemonted with secondary silica; dees not break down in water or HC1; cross-bedded on med ium scale; contact at the base is a surface of erosion: sharp and. irregular 13

11. Iludstone: grayish rod; friable; forms ledge; considerable muscovite and biotite, angular cuartz silt, a few well rounded grains of quarts; thick bedded; base Irregular, gradational. 16

10. Claystone: grayish purple wi th bands of gray ish red purple; cross-bedded on a largo scale; slightly silty; bentonitic; friable; forms slopes; base a surface of erosion; sharp and undula t c ry 33 120 Feet

9. Bentonite: medium dark gray; 20% silt content composed of angular to subrounded, rarely -v;ell rounded quarts grains: some mica and consider able wood charcoal present. Rounded chert cob ble bears e:;terior mold of lieeholla snocies of Ka ib ab (Pe rm i an) affini•f* L> •*J- /r\rw or» ••> bo.se is sharp and flat 14

8. Bentonite: modi.urn darh gray •;ith lighter splotches; v cry yure, p ractic.->11 - no silt: breahs dovrn and ran— id "< i/v sv;ell s in \:ater, gives test for r.iont:.iorillonite; has "slichensides" parting; friable; forms slopes and badlands: considerable amount of petrified v:oo&: base is sharp and flat 13

7. Sand z tone; gray i r; ^ purpl Cj z pechlod: co mposed »~J T O T "j* 6 Of! o P ^o ubr ounCL J mranulo to silt size quar Lr v * -pil r-i rt j * •J"!_/ i"^>-» m on tmorillonit r* r» 1 o v Z O- — *~ 9 ; ,• ^ J. .« .4. ~ Km UO r.io.tr iZm ; rest is GOV ito 9 b J. , detrito.1 + chor u and. chlori to ; IIO CO ent, bended o illy v:ith ",-i T» clay : friable; f c ri:i Z JL ul ar cliff s o r ledges; cros r? bedded on U'l —. J.1 GC n 1 Q , J- ' , .• unit ai3"o.ar- ently is a v.ridc, flat-lihe lens between the ad jacent units: surface of erosion at the base; relief = 1 foot; contact sharp and irregular.... 13

6. Bentonite v-ith :rmd stone layers: medium gray lover part to grayish purple toward. top; 10f'

silt.' composed— of anrulc,?w1 to rounded clear quarts grains: rhite nontmorillcnite clay svells vlien vet; disseminated iron c::ide "dust" colors the sediment, Throe layers of grayish red nud- stone in upper part of unit. Thich bedded; fri able; ferns slopes; considerable siliclfied ".rood.; base sham and irregular...... 34

5. Mudstone: grayish red: friable: composed of very fine sand and silt and oaual narts of iron- stained clay. P'iotite, chort grains, chlorite and angular quart': compose the detritus. Cross- bedded on medium scale; 0.0 f <. fc from base is a 3 foot thich lens of " oorly indurated, .angular to rounded pea to cobble gravel, some of the chert Individuals reaching 30 o;:: in diameter.

I'.UU. io u—u bU iy O - Ct L . J.OOU thich cap of chert ified mudstone forming can to 121

Feet

low mesas. The base Is a minor surface of erosion with the relief of 1 foot 32

4. Mudstone: rcediun "ray; apprcxLnately 50$ very fine sand to coarse quarts silt, subangular to •well rounded,* cross-bedded on large scale; fresh reel: Is very firm but weathers to friable; base sharp and slightly Irregular 20

3. Chert: light brown; very hard and thin; forms caps to low mesas; weathers cut in slabs, un evenly banded 2*orisontally• base sharp and irregular 1

2, Eentonitic mudstone: yellowish gray; 15$ very fine sand and coarse silt; arenaccous material mostly angular, co.:.c silt is well rounded: large (1 mm) bocbs of biotite common: some muscovite, garnet, P.oc!: swells when wet and reacts for montnorlllcnite: very friable; thiol-: bedded; f, r 7 • J1 I<1L;o O .l,l r-•'*iV' J .J' •, "•.w' f- ^ r-^ "*vi,~i *. nv, fa* * W ^

1. Claystone: medium gray: numerous coarse silt grains, some of which arc well rounded; friable; has "slichensides" parting; forms slopes and badlands; clay dees not swell but reacts for montmorillonite: base concealed 29

SHINARUIIP CChGLChhhATh (Upper Trias sic) : Tliichness = 25 feet

Con^louerato and coarso sandstone: yellowish gray, weathers to darl: yellowish brown; well cemented with lime; forms cliffs; very thich bedded; lenticular-; cross-bedded; lower 15 ft. Is very coarse sandstone with occasional pebble or cobble: upper part conglomeratic sandstone... 25

Erosional unc c nforr.iity

HOZinCCPI FCKiATICi: (Zarly and Kiddle ? Triassic)

I-Iudstone: darl: grayish red; thinly cross- bedded; friable; upper contact zone bleached to light gray; base concealed 5 122

Section A

Base of section is located. 10 miles due north of Holbrook and runs 1 l/2 miles north 75° west to top of Marcou liesa. Beds are essentially horizontal.

SOLIAIT I-IATEEIAL (He cent) Feet

11. Sandstone: pale red, iron-stained subangular to well rounded coarse to very fine quarts sand: friable, al...;ost total lac'.: of bonding; !aa;:iiuun size grains << ram; average is in med ium sand (;:radc; nc clay. Forms top of hill: appear;; to be recent wind worked material: base sharp, irregular 11

Ero si o nal unco nf orm i t y

CHII'ILE ECEIIATICi: (Upper friasslc): Thickness = 209 feet

LOVJER I-IEIZZEP.: Thickness - 209 feet

10. Sandsteiie: pinkish rrsj, medium grained, angular to wo11 rounded quarts sand; some finer sand and coarse silt; clay, white clay content 25p; numer ous well rounded boobs of detrital biotite; some chert grains, chlorite and feldspar: very poor ly cemented: entrcmely friable, forms slopes; fossil mood common; base sharp, flat 46

9. Sandstone: yellowish ^ray, spccklcf; coarse to very fine, angular clear quarts sand; some coarse silt; a very slight a;;:ount of carbonate cement present; 3^ clay content; muscovite rare, iron o::ide clusters: cement weak: friable; very thin bedded t; thick bedded; cross-bedded; med ium scale; Icnticular, grades laterally to local conglomeratic sandstone: base is a surface of local unconformity: forms vertical cliff; contact sharp 8

c. Sandstone: li^ht brownish Gray; anpular to well rounded, very fine sand to coarse silt; clear and iron-stained quarts; no cement; bonding by the 5;J montmorillonitc clay content; magnetite and biotite rare; friable; forms slopes; 1/2 foot thick led^o of coarse lime; cemented, firm sandstone at top; base sharp 17 123

Feet

7. Bentonitic n:udstone: dark brownish gray: 3®% silt, rest clay, biotite, iron oxide, chlorite and iron-stained quarts; swells when vet; very Triable; forms elopes, alternating horizontal color bands of dark brownish gray and lighter brownish gray: base sharp and f1 cto**» 3^

6. Sandstone: pinkish gra;, > spoeklcd; very friable, no bond except white clay v;hich is 25^ of the rod:; swells when wot and reacts for bentonite; very heterogenous assemblage of minerals; brown biotite, turning to iron oxide; clear angular to rounded cuartz grains from nodiun sand to silt size range; magneti to very common, hema tite, feldspar, chlorite less common; numerous calcitc clay nodules: forms slopes and lodges; base gradational 22

5. Bentonite-: medium gray with yellowish gray cal careous modules: very fine angular to subrounded quarts s and and. s 11 J- —.1-1 ' -• ur ity: cal c ar us nod- ulcs almost f o rm c* "1-. f~* v em ent in pla ces protect- 1 •

r c "i •" 7 •-j ing the unit from J. I" nd form i resis- c : r. n »-» j, rt tant layer; numer c u W t-S. k—• O - c.0 f'ouno.; base sharp 1

4. I'udstone: pale brown, clay size material, approximately Co;J; iron stained, abundant detrital brown biotite: silt is angular to subrounded; carbonate ccment; cross-bedded on mc-dium scale; very friable; forms si:pes; base gradational.... 22

3. Siltotcne: pale brown; silt content 60/:, rest clay, biotite abundant; red color due to iron specks and staining of the clay; mica present; silt is angular to rounded clear quarts; bedding thin, fissile, forms rounded slopes: many large silicified logs and almost entire tree trunhs; base flat, shano 22

Conglomerate: overa11 colo r i s V — - ^— e orange; pebbles are medium oubaiû c.z* "bo subrounded and conpo sed mostly e•V* chert; m ^ — mm sise oboer ved wa s 50 mm in d " îl X • firmly cemented with lime; Or-1 o in T •— s and pebbles comiôse fully 75^' of the roc 1': by y:e ight: i.iatr _ni 1. s very coarse to fine sand; clear quart 2., chert of 124

Feet

various colors, books of biotite, feldspar flakes, slltstone grains, chlorite and other material plus carbonate cement; forms lecl.se; base concealed. . 4

1. Bentonitc: medium lirtht ^ray v.-ith very li£ht gray bleached areas; contains medium to very fine, clear, subrounded to veil rounded quartz sand and coarse silt. Clay sv/ellc rapidly vrhen wet and reacts for montmcrillonite; friable; forms slopes and badlands: base concealed...... 28

Note: An unhnctm thickness of the Chinle formation .. lies beloi-; and above this section. 125

Plate III-l. Badlands topography in the Lower member of the Ghinle 15 miles northeast of Winslow, near section I. The Owl Rock forms the mesa cap in the distance.

2. View of the Lower member at section G, northeast of Joseph City. Unit 14 caps the mesa. PLATE III 126 127

Plate IV-1. Vie-w southeast from Smith Butte, showing lava capped mesa (left center).

2. Basalt dike at the foot of Smith Butte. PLATE IV 128 129

Plate V-1. Shlnarump outlier resting on Iloenliopi mudstones, 1 1/2 miles north, of Joseph" City, - . showing large scale, planar type, cross- bedding.

2. Same location as above, showing unconformity between the Shlnarump and the Moenlcopi forma tion. Note medium scale, planar and trough type cross-stratification. The darK I-Ioenkopl mudstone is bleached just beneath the contact. PLATE V 130

» "V .'' . -''1 131

Plate VI-1. South side of Smith Butte. The Owl Rock member is composed of the alternating, thin, ledge-forming layers separated "by marlstones. The vertical cliff in the heavy shadow is the Wingate sandstone. Lava caps the mesa.

2. Closer view of VI-1, showing contact between the Owl Rock member of the Chinle and the cliff-forming Wingate sandstone. Lava caps the mesa. PLATE VI 132 133

Plate VII-1. Outlier of Shlnarump capped by lowermost Chinle shales and siltstones. Northeast of Winslow, Arizona.

2. Closer view of VII-1 (above), showing small scale, trough type cross- stratification. The Shlnarump is a coarse sandstone. PLATE VII 134 135

Plate VIII-1. View of low Shinarump outcrop near Leupp.

2. Closer view of VIII-1 above showing medium scale, planar type cross-strati fication. Note pebbles in the Shina rump, which is mostly a coarse sandstone at Location 1. PLATE VIII 136 137

Plate IX-1. Balanced Sliinarunp outlier resting upon eroded Moenkopi shales (dark rock at base of pedestal). Northeast of Joseph City at beginning of section C.

2. View of the Shinarump at northwest edge of Holbrook, shov:ing sandstone lens, surrounded by coarse conglomerate. PLATE IX 138 139

Plate X-1. Large, slltcified log which has weathered • out of poorly cemented Shinarump sands. Between Joseph City and Holbrook, Arizona,

2. Planar type, small scale cross-lamination in the Shinarump at Location 2, a few miles north of Winslow. The Hoenkopi forma tion underlies the firmly cemented, Shinarump sandstone. PLATE X 140 141

Plate XI-1. South side of Smith Butte, showing contact of the Owl Rock member of the Chinle and the Wingate sandstone (shaded vertical cliff in left center of photograph). The cliff in the left foreground is Wingate.

2. Smith Butte; contact between the Owl Rock member of the Ghinle formation and the overlying Wingate. The man points to the gentle unconformity. PLATE XI 142 14-3

Plate XII-1. Newberry Mesa, capped with Owl Rock porcellanites, 8 mi. northeast of Leupp at section D. The large vertical cliff near the mesa top is Unit 23-D, which forms the "base of the Owl Rock member. The thinner unit part iray down the hill is Unit 21-D of the Petrified Forest member.

2. Closer view of Unit 23-D, showing poorly defined cross-stratification. PLATE XII 145

Plat© XIII-1. Entire agatised tree trunk which has been eroded from the Lower member of the Chinle formation. Note distant view of flat-topped Smith Butte, on skyline.

2. Unit 16 at section C, northeast of Joseph City. Note cross-bedding in the poorly cemented conglomerate bed in the Lower member. A small, siliclfied tree trunlc protrudes above the massive layer. PLATE XIII 146 147

Plate XIV-1. Close view of extremely hard procellan- ite in the Ovrl Rock member at section 1, 18 miles northeast of Winslow. Note small, dark, chert nodules near center of the lower hard layer.

2. Thick porcellanite, capping mesa at section G, east of Leupp. Note chert nodules (dark). PLATE XIV 148 149

Plate XV-1. View of unit 23-D at section E, showing the Irregular bedding.

2. Vievr of unit 23-D at section E, showing "root-like" features. PLATE XV 150 151

Plate XVI-1. View showing unit 21-D at section E. The unit, several feet thick at Leupp, is very crumbly.

2. The photo of the key bed, unit 23-D, is at Smith Butte. Compare with the same bed at Leupp. PLATE XVI 152 153

Plate XVII-1. Typical badlands topography in the Lower member of the Chinle formation as found 10 miles -west of Josepih City. Note "spool" type of wind erosion in the sandstone.

2. Bentonite weathering on elope in the Lower member at section C, 5 miles northeast of Joseph City. PLATE XVII 154 155

Plate XVIII-1. Cross-stratification iri red and gray- banded mudstones, 10 miles west of Joseph City.

2. Cross«stratification shown by color differences in bentonitlc clays of the Petrified Forest member. North east of Winslow; section I. PLATE XVTII 156 157

Plate XIX-1. View of a portion of section G-, showing unit 23-D facing the cliff near top of mesa. All beds exposed below unit 23-D are in the Petrified Porest member.

2. Section X, showing unit 2^-D capping the mesa* Unit 21-D forms the bench part way dovm the slope. PLATE XIX 158 159

Plate XX-1. Large scale, low angle, cross-bedding in siltstone layers In the Lower member, seotion D, northwest of Leupp.

2. Small eroslonal unconformity between two units of the Lower member of the Ohinle at section C, northeast of Joseph Oity. Note pebbles in dark rook above the point of the pick. PLATE XX 160 161

Plate XXI-1. Gllff-forming layers of the Owl Rook member capping the banded marlstones of the Petrified Forest member. 18 miles northeast of Yflnslo-w at section I.

2. Slump structure In the Owl Roolc layers 18 miles northeast of "Wlnslow, section I. PLATE XXI 162 163

2. Unit 2^-D at section I, 18 miles northeast of Winslow. PLATE XXII 164 BIBLIOGRAPHY

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LOG.

AREAL GEOLOGY OF THE LEUPP-HOLBROOK AREA ARIZONA

EXPLANATION

WINGATE SANDSTONE "fiw

OWL ROCK MEMBER (B DIVISION) UPPER TRIASSIC CHINLE FM. LOWER CHINLE ( C 6 D DIVISIONS ) "Eel

SHINARUMP CONGLOMERATE

MEDIAL a LOWER TRIASSIC MOENKOPI FORMATION Tfm

TERTIARY VOLCANICS; EXTRUSIVE FLOW ROCKS

SCALE; ' INCH = I MILE MAY 6, 1957 RILEY S, SMITH, JR. miles

PLATE 1 MESA

"Eco

ARIZONA

o o

•fid o

WINSLOW

MAY 6, IS 57 Ti • V

/ VE 5 MESA

LOC. 3

ft« L0C.2

WINSLOW

ATCHISON SECTION A

LOG. 6

X LOC.5

i SCALE In FEET ( Wits time -1300

WIN5L0W

-1200 HOLBWOK ARIZONA

INDEX MAP -1100

- 1000 OWL ROCK MEMBER Of The CHINLE FM. - 900

o4-a I "" JNTT S3-D M& — eoo > -UNIT

PETRIFIED - 700 FOREST MEMBER -< Of The CONCEALED CHINLE FM. CONCEALED soo CONCEALED

- 500

400 LOWER UNIT 5-0 MEMBER -( (BFN CONCEALED Of The * CHINLE FM. — 300

200 >V CROSS-SECTION •iV LEUPP-HQLBROOK AREA, ARIZONA - IOCL

SHOWING CHINLE SECTIONS AND CORRELATIONS

DATUM 15 BASE OF OWL ROCK MEMBER, CHINLE FM. n, - 0 : HORIZONTAL SCALE 1 INCH* 2 Yz MILES

VERTICAL SCALE' i INCHs 100 FEET

MILES Riley S. Smith, Jr. May 13, 195? F.

y WINGATE SANDSTONE

OWL ROCK )- MEMBER Of The CHINLE FM.

)Z.JMT2JzXrs: —< -u.vir 2/-D

PETRIFIED y FOREST MEMBER Of The CHINLE FM.

sU bF :z:."iz3T]

CONCEAL Fi]

LOWER . MEMBER r Of The C. /JCE/.L hi CHINLE FM.

MIONS ilNLE FM. i SHINARUMP ,5 ~T MILES CC'ICEAlf „ MOENKOPI CONCEALED FEET FORMATION May 13, 1957

PLATE It