Stratigraphy of the De Chelly sandstone of Arizona and Utah
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Authors Peirce, H. Wesley (Howard Wesley)
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STRATIGRAPHY OF THE DE CKELLY SANDSTONE
OF ARIZONA AND UTAH
/*• - - Hoc Wesley Peirce
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
THE UNIVERSITY OF ARIZONA
1962 THE UNIVERSITY OF ARIZONA
GRADUATE COLLEGE
I hereby recommend that this dissertation prepared under my
direction by H, Wesley Peirce entitled ^Stratigraphy of the De Chelly
Sandstone of Arizona and Utah” be accepted as fulfilling the dissertation
requirement of the degree of Doctor of Philosophy,
After inspection of the dissertation, the following members of
the Final Examination Committee concur in its approval and recommend
its acceptance:*
/kIa Qizm. ,______//A/ / v / / / * / £ ^ / / > 7 ™ ^ /V . 1%
"lAy • c'^W -JuR _$V v l ! / (a / ^ 2 —
*This approval and acceptance is contingent on the candidate's adequate performance and defense of this dissertation at the final oral examina tion* The inclusion of this sheet bound into the library copy of the dis sertation is evidence of satisfactory performance at the final examina tion. STATEMENT BY AUTHOR
This thesis has been submitted in partial fulfillment of require ments for an advanced degree at The University of Arizona and is de posited 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 acknowledgment 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 interests of scholar ship. In all other instances, however, permission must be obtained from the author.
SIGNED:
I STRATIGRAPHY OF THE DEC KELLY SANDSTONE OF ARIZONA AND UTAH
by
H. Wesley Peirce
ABSTRACT
The Permian De Chelly Sandstone of Gregory can be subdivided, on the basis of contrasting depositional environments, into five members no one of which is coextensive with the De Chelly Sandstone as a whole.
The distribution of these members reflects instability in part of the area formerly occupied by the earlier Paleozoic Defiance Positive ele ment. The various members.of the De Chelly are believed to correlate with: (1) the uppermost evaporitic and dark detrital sediments of the
Supai Formation found in the subsurface to the south of the Defiance
Plateau, (2) the Coconino Sandstone of the Grand Canyon region, and (3) the San Andres Formation of the Zuni area in New Mexico. Emphasis is placed on: (1) the distribution and nature of sedimentary structural types such as cross stratification, stratification, channels, and ripple marks, and (2) modification of sandstone characteristics by secondary solution and cementation processes. TABLE OF CONTENTS......
...... » .... ., . Page
INTRODUCTION ...... 1
General Statement,...... 1 . Purpose ...... 1 Description of Areas...... 2
Defiance Plateau ...... 2 Monument V alley ...... 5
Methods of Study ...... 6 Acknowledgments ...... 6
HISTORICAL SKETCH ...... 9
General Statement ...... 9 Previous Workers and Nomenclature ...... 9
STRATIGRAPHY ...... 16
Definition of the De Chelly Sandstone...... 16 Contacts ...... 27
Upper Contact...... 27
Defiance Plateau ...... 27 Monument Valley ...••...... 32
Lower.Contact ...... 32
Defiance Area ...... 32 Monument V a lle y ...... 34
Age...... 40 Sedimentary Structures ...... 43
General Statement ...... 43
v Page
Stratification ..V...... 44 : : Cross .Stratification...... 51
! White House Member . •...... 51 Black Creek Member ...... 67 'a--' - Hunters JPouxt.A4ember ...... 78
Texture ...... 86 '' ' ' V Grain S iz e ...... 86 Grain Roundness, Shape, and Surface Character istics ...... 96
Composition ...... 99
General Statement...... 99
Depositional Components...... 101 Post-Depositional Components...... 106
Cementation ...... 114
General Statement...... 114 Carbonates ...... 115 Quartz ...... 120 Stylolites ...... 129
Regional Correlation ...... 132 Paleogeography...... 143
Conditions of Deposition ...... 144
Hunters Point Member ...... 144 Oak Springs Member...... 146 White House,Member...... 147 Black Creek Member...... 148 Fort Defiance Member ...... 149
SUMMARY...... 151
APPENDIX A— DEFINITIONS OF SOME STRATIFICATION TERMS ...... 157 vi Page
APPENDIX B— CRITERIA FOR CLASSIFICATION OF CROSS STRATIFICATION ...... 158
APPENDIX C— DESCRIPTION OF MEASURED SECTIONS .... 160
REFERENCES CITED...... 204
LIST OF FIGURES
Figure Page
1. Index map showing location of Defiance Plateau and Monument Valley areas ...... 3
2. Percentage distribution of types of stratification in • the De Chelly Sandstone of the Defiance Plateau area...... 45
3. Percentage distribution of types of stratification in the De Chelly Sandstone of the Defiance Plateau area ...... 46
4. Relative numbers and average .thicknesses of units with contrasting types of stratification found in the White House and Black.Creek Members of the . Defiance Plateau ...... 49
5. Relative numbers and average thicknesses of units with contrasting types of stratification found in the Hunters Point Member of the Defiance Plateau ...... 50
6. Direction of dip of cross strata ...... 69
7 . ; Dip angles of cross s tr a ta ...... 70
8. Histograms showing average grain-size distribution in the De Chelly Sandstone ...... 89
9. Histograms showing average grain-size distribution in the De Chelly Sandstone ...... 90
vii Figure Page
10. Histograms showing average grain-size distribution in the Be Chelly Sandstone ...... 91
11. Classification of the Be Chelly Sandstone based upon composition...... 100
12. Correlation chart—Befiance Plateau to Zuni Moun tains. Comparing Baars, Read, and this paper...... 134
13. Correlation of prominent Permian sandstones of northeastern Arizona with White House and Black Creek Members of the Be Chelly Sandstone ...... 138
14. Correlation chart of upper part of exposed Permian section, east side Befiance Plateau, southern por tion, with subsurface to south...... 142
LIST OF PLATES
Plate Page
1. Locations of measured sections of Be Chelly Sandstone and areas of outcropping Permian sandstones ...... in pocket
2. Summation of Permian nomenclature ...... in pocket
3. Graphic sections of Be Chelly Sandstone— Monument Valley and Defiance P lateau...... in pocket
4. Be Chelly Sandstone exposures ...... 4
5. Members of Be Chelly Sandstone-—western flank of the Befiance Plateau in type area. Canyon de Chelly ...... 19
6. Members of the Be Chelly Sandstone, Bonito Canyon— east flank of the Defiance P la te a u ...... 20
7. Fort Defiance Member of the De Chelly Sandstone, Bonito Canyon ...... 21
v iii P late Page
22, Arcuate structures in the White House Member of the De Chelly Sandstone...... 61
23. Inclined erosion surfaces in the White House Member - of the De Chelly Sandstone ...... 62
24* Cross stratification and animal tracks in White House ; Member of the De Chelly Sandstone ...... 65
25. Cross stratification and ripple marks in White House Member of the De Chelly Sandstone ...... 66
26. Animal tracks and ripple marks in White House - Member of the De Chelly Sandstone...... 68
27. . Exposures of Black Creek Member of the De Chelly Sandstone...... 72
28. Horizontally stratified unit in Black Creek Member, > « ,, : southern end of Defiance Plateau northeast of Houck ...... ;...... 74
29. Hunters Point Member, northern Defiance Plateau ...... 79
30. Stratification in the Hunters Point Member a ...... 80
31. Variable nature of cross stratification in Hunters Point Member ...... 81
32. Channel in Hunters Point Member ...... 82
33. Channel and ripple marks in Hunters Point Member .... 83
34. Ripple marks and cross stratification in Hunters Point Member ...... 84
35. Feldspars in the De Chelly Sandstone ...... 102
36. Chert and mica in the De Chelly Sandstone...... 104
37. Sericite-like "clots" in the De Chelly Sandstone ...... 108
38. Sericite-like material in the Coconino Sandstone 110 x Plate Page
39o Ferruginous material in the De Chelly Sandstone ...... 112
40. Sketches of some petrographic aspects—De Chelly . Sandstone...... 117
41. Sketches of some petrographic aspects—Coconino and De Chelly Sandstones...... 118
• • * - ' < > at ~ < ; , • • >■ i , - • . • 42. Evidence of pre-Shinarump Conglomerate induration of De Chelly Sandstone...... 123
43. Upper contact of White House Member of De Chelly Sandstone, Monument Valley a r e a ...... 125
44. Photomicrographs of some secondary effects in the De Chelly Sandstone ...... 127
45. Photomicrographs of some secondary effects in the De Chelly Sandstone ...... 128
46. Photomicrographs of some secondary effects in , De Chelly and Coconino Sandstones ...... 130 * •
LIST OF TABLES
Table Page
1. Measured thicknesses of the De Chelly Sandstone and its component p a r ts...... 17
2. Some textural data for the De Chelly Sandstone ...... 92
3. Percentage of silt-clay and carbonate (solubles) in 81 samples of the De Chelly Sandstone, Defiance r Plateau ...... 116
3d INTRODUCTION
General Statement
This study of the De Chelly Sandstone is largely a consequence of work done under a program of mineral resources investigations con ducted by personnel of the University of Arizona Geology Department and sponsored by the U.S. Bureau of Indian Affairs. Field and labora tory work associated with the resources study were conducted during the period between June of 1952 and May of 1954. Subsequently, inter mittent laboratory investigations have been conducted to the present time.
Purpose
It is the principal purpose of this paper to present a more de tailed description of the units composing what has been called the De
Chelly Sandstone than has heretofore been presented, and to consider the application of the descriptive data to an interpretation of their geo logical history. It is hoped that not only will a better understanding of this stratigraphic interval evolve, but that these data will aid in defining
some of the problems encountered in attempting regional correlations
with other prominent Permian sandstone units. 2
Description of Areas
The De Chelly crops out in northeastern Arizona and southeast
ern Utah. Outcrops of this sandstone are restricted to two disconnected
structurally high regions: (1) the Defiance Plateau in northeastern
Arizona and (2) Monument Valley in northeastern Arizona and southeast
ern Utah (fig. 1).
Defiance Plateau
The Defiance Plateau parallels the Arizona-New Mexico State boundary. It is a conspicuous physiographic feature in Apache County, northeastern Arizona. The plateau, almost four times as long as it is
wide, includes an area of approximately 1, 500 square miles. It rep
resents the eroded, flat-topped portion of a north-plunging anticline that
is asymmetrical to the east. The anticline occupies, at least in part, a position coincident with the Defiance Positive area that limited deposition
of some of the Paleozoic formations that are found in the subsurface a
few miles away.
The more spectacular and scenic exposures of the De Chelly
are in vertical-walled east- to northeast-trending canyons and cliffs
carved into the flanks of the Defiance anticlinal structure (pi. 4, fig. 1).
These include, on the east, the canyon of Black Creek, and tributaries
thereto, the cliffs north of Oak Springs, Hunterts Point and Bonito 3 Aneth
T A H
Defiance
Kingman Flagstaff
PHOENIX Globe
ucson
EXPLANATION | | Defiance Plateau
Bisbee Monument Volley
IOO Miles
Figure 1 Index map showing location of Defiance Plateau and Monument Valley areas PLATE 4
DE CKELLY SANDSTONE EXPOSURES
Figure 1. —Cliff-making White House Member of De Cbelly Sand
stone in Canyon de Cbelly on western flank of Defiance
Plateau.
Figure 2. —Cliff-making White House Member of De Cbelly Sand
stone in western Monument Valley area. 4 5
Canyon and, on the west, Nazlini Canyon and Canyon de Chelly with its tributaries. Locations of measured sections and partial exposures are shown on plate 1 (in pocket).
Much of the gently rolling central part of the Defiance Plateau is developed on or near the upper portion of the De Chelly.
The southeasternmost outcrop of the sandstone is about 5 miles north of Houck. From this point the sandstone is exposed northward in discontinuous outcrop until it is covered by younger formations north of
Lukachukai Trading Post. The southwesternmost outcrop is located about a mile east of Klagetoh. The sandstone is exposed discontinuously northward to a few m iles east of Many Farms.
Monument Valley :
Monument Valley straddles the Arizona-Utah State boundary
(fig. X). The portion in Utah is in San Juan County and that in Arizona is in Navajo and Apache Counties. The valley area, as considered in this paper, includes more than 750 square m iles and is bounded on the north by the San Juan River, on the east and south by Comb Ridge mono cline, and on the west by a series of mesas. The De Chelly forms por tions of the famous monuments, buttes, and mesas in Monument Valley.
Many of these contain complete exposures, but their vertical walls dis courage detailed measurement and description (pL 4, fig. 2). However, folds bring the sandstone into accessible position in a few localities. 6
■ Methods of Study ' ' r
r ' ; G \ . • I '/.'G ' !.• t .:, : ...i- ;V V- V ; Field data were gathered by measurement and description of complete and partial stratigraphic sections of the De Chelly Sandstone, as well as by examination of local exposures. Investigation was not limited entirely to the Defiance Plateau and Monument Valley. In order to learn more about related Permian stratigraphy, stratigraphic sections were examined in the Grand Canyon and Mogollon Rim regions of Arizona and the Zuni Mountain area of New Mexico.
Laboratory study of samples collected from measured sections included mechanical analyses, heavy “miner al studies, and the establish ment of mass as well as individual grain characters by petrographic methods. Thin-section study proved an invaluable aid to establishing characteristics of the De Chelly and other sandstones.
Considerable time was given to the examination of well cuttings in the hope of being able to partially fill gaps in information caused by the erratic distribution of outcrop sections of the De Chelly and other possibly related sandstones.
' Acknowledgments
The writer is indebted to the Indian Service for making this study possible. Transportation and other aids were provided during parts of the fieldwork. 7
E. D. McKee, director of the Indian Service Geology Project during the summers of 1952 and 1953, suggested the study of the De
Chelly Sandstone.
Dr. George Kiersch, director of the project since the end of the summer of 1953, guided the writing of preliminary reports for the
Indian Service.
Dr. Evans B. Mayo, professor of geology at the University of
Arizona, supervised the writing of this report.
Dr. John W. Harshbarger, formerly head of the U. S. Geological
Survey Ground Water Branch office in Arizona, and members of his staff, kindly provided data obtained from their work on the Navajo Indian
Reservation. Dr. Fred L. Peirce, my brother and fellow geology stu dent at the University, now with the Humble Oil C o., assisted in the field during the summer of 1953 and part of the summer of 1954, On a few occasions assistance was given by the late Boyd Moore. BoycPs great enthusiasm for the out of doors will long be remembered.
L. F. Brady of the Museum of Northern Arizona and Dr. John
F. Lance of the University accompanied me in the field for a few days during the summer of 1957. For their time and enlightening observa tions gained from many years of dealing with Arizona geology, I am grateful.
I owe much to my fellow geology students, as well as to the director and staff of the Arizona Bureau of Mines, especially Robert T. 8 OrHaire who drafted most of the illustrations in this report HISTORICAL SKETCH
General Statement; . ; - r
Several workers have considered certain aspects of the De ' . - '■ • ■ '• . ' - v-1/ j- . ; ; : • ■ • : . \;r ; ; CheUy Sandstone, including regional and local stratigraphic correla-
tions, nomenclature, and data regarding contacts, thicknesses, compo
sition, texture, and sedimentary structure.
The most frequently visited exposures of the De CheUy have
been those in Bonito Canyon near Fort Defiance on the east and Canyon
de Chelly on the west side of the.Defiance Plateau. Much has been
written about the De Chelly that was based only upon a visit to either
one or both of these localities.
Following is a review of workers who have published important
data based upon actual field contact with the De CheUy. Plate 2 (in
pocket) is a chart summarizing Permian nomenclatural development.
Previous Workers and Nomenclature
Although the cliff-forming sandstones so conspicuous in Monu
ment Valley and Canyon de.Chelly were noted by early workers, it re
mained for Gregory (1917) to recognize them as being of possible
Permian age. He appUed the term De CheUy Sandstone to this sequence
9 10 of massive, cliff-forming, cross-stratified, "red" sandstones that are overlain unconformably by the Trias sic Shinarump Conglomerate and underlain conformably by the red beds of the Permian(?) Moenkopi For mation (Supai of today). Gregory extended this name, De Chelly, to designate all of the cliff-forming sandstones in the Defiance Plateau and
Monument Valley that are overlain by Triassic formations and underlain by red beds. He did not describe or designate a type section; consequent ly Canyon de Chelly should be considered a type area of the De Chelly
Sandstone. McKee (1934) published the first, and to this writing, the only formally measured and described section of De Chelly Sandstone in the type area.
Miser (1925) traversed a strip along the San Juan River in southern Utah, studying the stratigraphy along the way. Miser thought that he recognized the De Chelly Sandstone.of Gregory, but instead of considering it Permian as Gregory did he relegated it to member status within the Triassic Moenkopi Formation.
Miser considered a lower sandstone, separated from the De
Chelly Sandstone by several hundred feet of Triassic "Moenkopi" red beds, to be the Permian Coconino Sandstone (Cedar Mesa Sandstone of today).
Darton (1925) visited the Defiance Plateau while conducting re
connaissance mapping for a new State geologic map of Arizona. . Darton
redefined the Permian(?) Moenkopi Formation of Gregory and designated 11 it Permian Supai Formation. Furthermore, he considered the overlying sandstones to be Coconino and made the following statement: "The sand stone (Coconino) is uplifted and exposed over a considerable area extend ing from near Winslow to Holbrook and in the Defiance uplift in the cen tral and northern part of Apache County where there cannot be the slight est doubt as to its identity."
As a result of this strong belief, Gregory1^ De Chelly of the
Defiance area was designated Coconino on the 1924 issue of the geologic map of Arizona. In extending this nomenclature northward into Monu ment Valley, Darton, in a manner similar to Miser, failed to properly identify the unit that Gregory had assigned to the De Chelly Sandstone.
Darton, as a consequence, identified a strati graphically lower unit as
Coconino Sandstone (Cedar Mesa Sandstone), and assigned Gregory's
De Chelly unit to a part of the Triassic Moenkopi Formation, as did
Miser. , vv . ... ' , ■ r-- r: . ;
Baker and Reeside (1929) attempted to correlate the Permian of southern Utah (including Monument Valley), northern Arizona (in cluding the Grand Canyon and Defiance regions), northwestern New
Mexico, and southwestern Colorado. It was necessary for these men to try to reconcile the differences in stratigraphic nomenclature that had arisen as a consequence of conflicting opinions of several previous workers. As a first step they concluded that attempts to use Grand
Canyon stratigraphic nomenclature in Monument Valley and the Defiance 12
Plateau were not satisfactory. They extended the Permian Cutler For mation of southwestern Colorado into Monument Valley and subdivided it into five members and designated them, from older to younger,
Halgaito Tongue, Cedar Mesa Sandstone, Organ Rock Tongue, De Chelly
Sandstone, and Hoskinnini Tongue. The term "Cutler: Formation" was also extended to the Defiance Plateau where it was subdivided into two major components—the De Chelly and an underlying unnamed sequence of red beds,: A local red-bed unit overlying the De Chelly at Bonito Can yon was also included in the Cutler Formation. Their correlation charts suggest that the Permian red beds underlying the De Chelly Sandstone at
Bonito.Canyon represent extensions of the Organ Rock Tongue as defined in Monument Valley to the north. ; - ^ ^ .
Baker and Reeside thought that the De Chelly Sandstone, as observed in Monument Valley and the Defiance Plateau, could be easterly extensions: of the Coconino Sandstone as known in the Grand Canyon and
Holbrook regions to the west. :
McKee (1934) visited Canyon de Chelly, Nazlini Canyon, and the Kin-Li-Chee area (east of Ganado) on the west flank and the Bonito
Canyon section on the east flank of the Defiance Plateau. McKee pre ferred to call the red beds underlying the De Chelly Sandstone the Supai
Formation, because of resemblances to the Grand Canyon Supai Forma tion. An effect of this was to raise the De Chelly Sandstone back to formational status. 13
McKee provided the first measured section of the De Chelly
Sandstone at its type area in Canyon de Chelly. As a result of this work he subdivided the sandstone into three members, designated upper, middle, and lower. Criteria for distinguishment were based on nature of stratification, lithology, and erosional behavior; He also applied this three-fold subdivision to the section at Bonito. Canyon and recog nized the overlying red beds of Baker and Reeside but did not classify them other than as Permian red beds.
At this time McKee was gathering data for a paper about the
Coconino Sandstone of the Grand Canyon region, so was visiting the
Defiance Plateau to see if a relationship could be found between the De
Chelly and Coconino Sandstones. McKee states that the sandstones ex posed in the Kin-Li-Chee area are "true" Coconino, and that this sand
stone forms the upper portion of the De Chelly as seen in the walls of both Nazlini Canyon to the north and Bonito Canyon to the east near
Fort Defiance. McKee, however, did not define or recognize a contact between a Coconino and a De Chelly Sandstone. He thought that the re
lationship between the two was gradational, both laterally and vertically.
Baker (1936) provided more detail as to the nature of the De
Chelly in the Monument Valley area, as well as relations to bounding
formations. However, he continued the stratigraphic nomenclature
presented by Baker and Reeside (1929).
R e a d (1951) reported on the Permian stratigraphy of the east 14 flank of the Defiance Plateau. . Considering the text, diagrams, and pictures in this reference there is inconsistency in the application of
Permian nomenclature, an inconsistency that must derive from the con fusion of existing terms.
However, it is my understanding that Read thought that the cliff-making sandstones exposed in the cliffs at the head of Black Creek
Canyon, underlain by his Yeso Formation, were equivalent to the Glorieta
Sandstone of the Zuni Mountain area in New Mexico, the Coconino Sand stone of the Mogollon region in central Arizona, and the upper member of the De Chelly Sandstone.as defined elsewhere on the Defiance Plateau by McKee. v
Northward from Black Creek at Oak Springs Cliffs, Read rec ognized that a lower sandstone tctok the place of red beds but still re mained separated from the upper sandstone by a "transition" zone of red beds. Read subdivided the latter section into a De Chelly Sandstone composed of three members: (1) an upper sandstone, (2) central transi tion unit, and (3) a lower sandstone underlain by red beds of the Supai
Formation. % : / , ' .
Regarding one phase of depositions! history Read states the following: “The great tangentially cross-bedded sandstones of the
Meseat Blanca, Glorieta, Coconino, and DeChelly types are interpreted as migrating beach and bar deposits, some of which are transgressive and others regressive." 15
Balk (1954) studied the geology of the Fort Defiance quadrangle.
The principal Permian rock outcrop sections in this quadrangle are in
Buell Park and in Bonito Canyon, the most widely referred to De Chelly
section on the Defiance. Plateau, and possibly the most confused. Balk
recognized a sequence of red beds that he chose to call lower Cutler
Formation that changes vertically to sandstones he referred to as upper
Cutler Formation, Overlying the upper Cutler sandstones Balk rec
ognized a De Chelly Sandstone. In his text Balk separated the Cutler
Formation and the De Chelly, thus indicating that he did not consider
the De Chelly to be a member of the Cutler Formation. However, he
stated that the De Chelly Sandstone is now considered to be a member
of the Cutler Formation and quoted Baker and Reesiders (1929) work.
He did not mention the subdivisions of the Bonito Canyon section made
by McKee and Read. Balk*s lower and upper Cutler Formations are
McKeeEs Supai Formation and lower De Chelly Sandstone Member, re- . - .. \ " ' 1: ^-.V v •’ v ■. ■ - ;» - / : ■ ' t ••• • ' *< 1' spectively.
Most recently Baars (1962) and Read and Wanek (1961) have
expressed views concerning nomenclature of Permian formations on
the Colorado Plateau. These works are not included in the nomenclature
chart, but are discussed in a later section of this report. STRATIGRAPHY
Definition of the De Chelly Sandstone .
: : ■ i 1 i The Permian De Chelly Sandstone attains a maximum outcrop thickness of slightly over 800 feet at Canyon de Chelly, thins to a pinch- out near the San Juan River in Utah, and thins to approximately 250 feet at the southern end of the Defiance Plateau (table 1)6 Indications are ; ; ' • ' . ; that the sandstone thickens into part of the Black Mesa basin west of
Canyon de Chelly„ < ■ 1
As considered here, the De Chelly Sandstone is a composite
set of strata (see Glossary, Appendix A), However, it tends to become
a coset of cross strata both in western Monument Valley and on the
west flank of the Defiance Plateau. It becomes a composite set of strata
in eastern Monument Valley and on the eastern and southern portions of
the Defiance region. This differ mice in the distribution of sedimentary
structural types within the De Chelly Sandstone reflects differences in
the depositional environments of its component parts. Differences in
color, grain-size distribution, feldspar content^ and cementation seem
to be coincident with gross differences in distribution of sedimentary ■ . : : ' ■ . . ; . ; - : : structural types. Using these criteria it is possible to subdivide the
■ ....16 -...... -- ...... - ' ;; MEASURED SECTIONS ■■ MEMBERS
W hite " B lack F t. Oak H u n ters T o ta l - House « C reek ' D e fia n c e : b r i n g s P o in t T h ic k n e ss ... Canyon DeChelly 570 0 0 . U5 202 817
N aslini Canyon 502 : 0 0 16? ?
Bonito Canyon < 200 • 105 1 0 6 - ' 0 227 638
Hunters Point ... 0 217 0 50 : 238 505
Oak Springs C liffs U5 125 0 128 17L 1*72
Black Creek . 0 :/ 133P 0 0 - 0 ' Pine Springe : 0 225 0 0 i° 1 225
Comb Ridge 529 0 0 / ; o 0 ; 529
O lje to 2Ul 0 0 ; :0 :o 21*1
Piute Farms _■ 30 0 0 ; . 0 • 0 30
P - Partial
TABLE I - MEASURED THICKNESSES OF THE DECHELLY SANDSTONE AND ITS COMPONENT PARTS 18
De Chelly Sandstone into from one to five members depending upon lo cality. Geographic names have been assigned to these members and are intended only as informal field terms found useful in discussing the
De Chelly Sandstone and its component parts.
The De Chelly Sandstone is overlain unconformably by Triassic formations. It is underlain by the darker, slope-forming silty sand stones of the Permian Supai Formation in the Defiance area and by the darker, slope-forming micaceous siltstones of the Permian Organ Rock
Tongue of the Cutler Formation in Monument Valley. The latter contact varies from one of disconformity to one of seeming gradation.
In the type area, Canyon de Chelly, the three-fold division of
McKee has been followed although his lower, middle, and upper members have been designated Hunters Point, Oak Springs, and "White House
Members, respectively (pi. 5).
Although two of these three members are recognized at Bonito
Canyon near Fort Defiance, it is thought that the White House Member forms only the lower part of McKee's and Read1 s upper member and of
Balk's "De Chelly" Sandstone at this locality. To the remaining sand stone overlying the White House Member and constituting a part that
McKee likened to Coconino Sandstone, the term "Black Creek Member" has been given (pi. 6). The overlying red beds, thought to be Permian in age, are referred to as the Fort Defiance Member (pi. 7).
The lowest or Hunters Point Member unites as one the sandstones PLATE 5
MEMBERS OF DE CHELLY SANDSTONE—WESTERN FLANK OF THE DEFIANCE PLATEAU IN TYPE AREA, CANYON DE CHELLY
Figure 1. —Hunters Point Member (McKee's lower member) of
the De Chelly Sandstone forms lower slope and is under
lain by darker Supai Formation. Dark band just below
alcove is Oak Springs Member (McKee's middle mem
ber). White House Member (McKee's upper member)
forms upper cliff and is overlain by the Shinarump
Conglomerate.
Figure 2. —Closeup of the water-deposited Oak Springs Member
(McKee1 s middle member) in Canyon de Chelly. 19 PLATE 6
MEMBERS OF THE DE CHELLY SANDSTONE, BONITO CANYON— EAST FLANK OF THE DEFIANCE PLATEAU
Figure 1.—Hunters Point Member (lower member of McKee)
forms lower slope underlain by darker Supai Forma
tion. Note dark bands in lighter colored sandstone.
Oak Springs Member not well defined. White House
Member forms upper cliff but represents only partial
thickness of the upper sandstones (see below).
Figure 2. - - Ledge-making sandstones in lower half belong to
Black Creek Member that overlies the White House
Member. The slope above Black Creek Member
sandstones is the position of the Fort Defiance Mem
ber (see following plate). 20
\ PLATE 7
FORT DEFIANCE MEMBER OF THE DE CHELLY SANDSTONE, BONITO CANYON
Figure L —Ledge-forming silty sandstones with interbedded,
darker siltstones.
Figure 2»—Ledge-forming silty sandstones with interbedded,
darker siltstones
22 that McKee and Read, working in different locations, each refer to as lower member of the De Chelly Sandstone. This unit forms the prom inent cliff overlying red beds of the Supai Formation at Hunters Point
(pi. 8).
The Oak Springs Member unites the middle member of McKee and the transition of Read. The member, consisting of horizontally stratified dark-colored sandstones and micaceous silty sandstones, rep resents a transgression of Supai type lithology over the Hunters Point
Member. It coalesces with the Supai Formation southward between the
Oak Springs and Black Creek sections. The member shows its best development at Oak Springs Cliffs (pi. 9),
At Canyon de CheUy the Oak Springs Member is overlain by large-scale cross-stratified sandstones that form the widely photographed sheer cliffs. These sandstones are referred to as the White House
Member because the White House Trail in Canyon de CheUy National
Monument provides the only convenient access for studying a near com plete section of this member. White House itself is a ruin situated in a natural alcove in this sandstone.
It is the White House Member, the only De Chelly Sandstone component recognized in Monument Valley, that makes up the sheer cliff waUs of the famous buttes and monuments for which the valley is named.
The Black Creek Member, which overUes the White House PLATE 8
HUNTERS POINT MEMBER OF THE DE CHELLY SANDSTONE, EAST FLANK OF THE DEFIANCE PLATEAU
Figure I . —Type section of Hunters Point Member (lower mem
ber of Read) at Hunters Point, Note limestone unit at
top of slope of Supai Formation.
Figure 2,—Hunters Point Member (lower member of Read) over-
lying slope-making darker units of Supai Formation.
The limestone of figure 1 above is in similar position
here but is obscured by trees. Lower cliff at Oak
Springs Cliffs section. 23 PLATE 9
OAK SPRINGS MEMBER, EAST FLANK OF THE DEFIANCE PLATEAU
Figure 1,—Type section of Oak Springs Member (transition of
Read). Slope maker is lower part of Oak Springs Mem
ber overlying Hunters Point Member. Oak Springs
Cliffs.
Figure 2 .—Oak Springs Member at Hunters Point,
25
Member in parts of the Defiance Plateau, is characterized by being a composite set of strata in which horizontally stratified sandstone units are in amounts approximately equal to cross-stratified sandstones, and arranged in alternating sequence. The sandstones tend to be very light colored and silicified. These characteristics obtain, so far as is known, wherever the Moenkopi Formation is the overlying unit with the excep tion of the Bonito Canyon section where the Moenkopi is not recognized.
In Black Creek Canyon the De Chelly Sandstone is constituted entirely of this member (pi, 10).
The red-bed unit that overlies the Black Creek Member and underlies the Shinarump Conglomerate at Bonito Canyon is not well understood. It has been considered Permian largely because it does not have a typical Moenkopi aspect and because an unconformity has not been recognized at its base. This unit has been observed to the south just north of the Window Rock-Ganado Highway but outcrops are such that the basal contact is not exposed. This unit is here referred to as the Fort Defiance Member of the De Chelly Sandstone. Information about it is limited, yet it is a part of the local stratigraphy.
As herein defined, the De Chelly Sandstone is composed of five lithostratigraphic units which have been given informal member status. Because of the restrictions imposed by the capricious occur rence of outcrops of sections of the De Chelly Sandstone, it has not been possible to determine, with precision, lateral relationships and PLATE 10
BLACK CREEK MEMBER
Figure L —Black Creek Member near Pine Springs, southern
Defiance Plateau. Note division of section into units
that contrast in weathering habit, and color shade.
The slabby, light-colored sandstones are cross
stratified whereas the darker, more massive-weather
ing units are characterized by horizontal stratification.
This is a composite set of strata.
Figure 2 .—Black Creek Member in type area at head of Black
Creek Canyon resting on darker units of Supai For
mation. Here a limestone resembling those previous
ly shown occurs 180 feet below base of Black Creek
Member (Read's "Yeso" Limestone). 26 a
m
if!; 27 continuity between the members herein informally defined,
. Contacts
Upper Contact
Defiance Plateau
The De Chelly Sandstone on the Defiance Plateau is overlain by the Moenkopi Formation to the south and the Shinarump Conglomerate
Member of the Chinle Formation to the north, both of Triassic age.
The Moenkopi Formation overlies the Black Creek Member of the De Chelly Sandstone at Hunters Point and at all visited areas to the south along the east flank of the Defiance Plateau# The Moenkopi
Formation is not known to continue north of the Ganado-Window Rock
Highway. Sections measured north of this highway, on the Defiance
Plateau, are overlain by the Shinarump Conglomerate (pi. 11).
The contact of the Black Creek Member with the Moenkopi For mation is sharp. The contact appears to be planar with very little con spicuous irregularity or relief. Color, grain size, and sedimentary structures are the contrasting features that manifest a sharp contact.
The dark Moenkopi siltstones contrast markedly with very light colored underlying sandstones.
As in many contacts there is little to suggest the magnitude of the hiatus that separates these formations. That considerable time is PLATE 11
UPPER CONTACT OF THE DE CKELLY SANDSTONE
Figure 1. —Slope above cliff is composed of Triassic Moenkopi
Formation. Cliff is Black Creek Member of the De
Chelly Sandstone, Shinarump Conglomerate overlies
Moenkopi Formation on the small hill. Near Pine
Springs, southern Defiance Plateau.
Figure 2. —Irregular, channeled contact between Triassic
Shinarump Conglomerate and De Chelly Sandstone at
Buell Park, east flank of Defiance Plateau. 28 29 represented is suggested by projection of age assignments made else where. Seemingly the sandstones remained close to existing base level subsequent to deposition. Possible evidence of some erosion and re deposition is indicated by an exposure just east of Klagetoh. Dark
Moenkopi siltstones overlie perfectly preserved ripple marks developed on the upper surface of a light-colored horizontally stratified sandstone unit that is 8 feet thick. This could be a basal Moenkopi sandstone de rived from the erosion and redeposition of underlying De Cbelly Sand stone. However, evidence is lacking that would suggest that Permian sediments were removed in quantity prior to the deposition of the
Moenkopi Formation.
North of the Ganado-Window Rock Highway the De Chelly Sand stone is overlain by the Shinarump Conglomerate. The contact is ir regular, the sandstones having been channeled into prior to deposition of the Shinarump. At places a definite contact is difficult to locate, particularly when the Shinarump lacks pebbles and is cross stratified on a medium scale. Frequently the lowest pebble zone does not repre sent the. base of the Shinarump.
Deep channels (pL 42) cutting the White House Member of the
De Chelly Sandstone testify to removal of some of the section. However, it is difficult to evaluate the extent to which, regionally, the De Chelly
Sandstone was removed during this erosion period. Pertinent to this question is whether or not the Moenkopi Formation is absent because 30 of erosion or nondeposition. The absence of the Moenkopi Formation over much of the northern part of the Defiance area suggests that minor uplift was effected either before or after the deposition of the formation.
In either case it is logical to infer that Permian sediments in this area were partially removed by erosion,
A problem is presented by the fact that the Shinarump is not everywhere in contact with lithologically identical material. At the mouth of Bonito Canyon near Fort Defiance, the Shinarump is.in contact with the Fort Defiance Member of the De Chelly Sandstone, Here the
Shinarump is not in contact with identical units on the two walls of Bonito
Canyon. To the west at Nazlini Canyon and Canyon de Chelly, the Shina
rump overlies typical large-scale cross-stratified sandstones of the
White House Member (pi. 12, fig. 1), Exposures are so limited that
tracing of units laterally is impossible for any distance. That different
members underlie the Shinarump Conglomerate suggests that the younger
member (Fort Defiance) may have at one time been more extensive,
particularly toward the, west. If the latter is the case, then it is prob
able that some of the sandstones to the west were also removed by
erosion.
The maximum amount of erosion of the De Chelly Sandstone
took place in the northern part of the Defiance area where the Moenkopi
Formation is absent. Nevertheless, the northern sections are thicker
than sections to the south, indicating that southward thinning is due PLATE 12
UPPER CONTACT OF THE DE CKELLY SANDSTONE
Figure 1, —Sandstones of the Shinarump Conglomerate, with
sporadic pebbles only, overlying the White House
Member with irregular erosional contact* A contact
of this nature might be difficult to recognize when
penetrated by a drill hole unless the sand types were
understood weU enough to differentiate them* Nazlini
Canyon, west side Defiance Plateau,
Figure 2. —Triassic Hoskinnini Member of the Moenkopi For
mation overlying White House Member of De Chelly
Sandstone, western Monument Valley. Note apparent
planar contact. Organ Rock Member of Cutler For
mation at base of cliff* De Chelly here considered a
coset of cross strata, 31 32 largely to factors other than late Permian or early Triassic removal at the top of the De Chelly Sandstone.
Monument Valley
In the Monument Valley area the White House. Member of the
De Chelly is overlain by the Hoskinnini Member of the Triassic Moenkopi
Formation (Gray, 1961). The Moenkopi units are dark and generally flat bedded, so that they contrast with the underlying lighter colored, large-scale cross-stratified sandstones of the White House Member.
From a distance the contact appears perfectly planar (pi. 12, fig. 2).
In detail it contains irregularities of low relief (see plate 43 in section on cementation). Frequently, minor hills are undercut so as to create an overhang of sandstone. These features suggest that the sandstones may have been partially indurated prior to the erosion that produced these surface characteristics.
Lower Contact
Defiance area
In the Defiance area the De Chelly Sandstone is underlain by the Permian Supai Formation. From Pine Springs to and including the
Black Creek section the Black Creek Member is in contact with the darker silty sandstones of the Supai Formation, whereas northward the 33
Hunters Point Member overlies the Supai. Even though different mem bers overlie the Supai, the contact appears very similar as far south as
Hunters Point, The slope-forming, dark-colored, horizontally strati fied, silty sandstones of the Supai Formation contrast with the cliff making, lighter colored, cleaner sandstones that constitute the mem bers of the Be Chelly. A zone less than 20 feet thick appears to con stitute the vertical change to Be Chelly (pis. 8 and 10, fig. 2).
As mentioned previously, the Hunters Point Member changes laterally to Supai red beds between Oak Springs Cliffs and Black Creek.
This relationship indicates that there cannot be much time represented, relatively speaking, in the contact zone between Hunters Point Member and the Supai Formation, Similarity of contact aspect between the Black
Creek and Hunters Point Members with the Supai Formation suggests that, as in the latter case, there is no significant hiatus between the Black
Creek Member and the Supai Formation either.
These contact relationships indicate that these two members of the Be Chelly Sandstone in the southern part of the Befiance Plateau were deposited in environments laterally adjacent to the then existing depositional environment of the Supai Formation,
The lower contact at the northern sections, including Bonito
Canyon on the east and Canyon de Chelly on the west, presents a some what different aspect than that to the south. These northern sections do not have lower contacts that are closely defined. At Bonito Canyon the 34 lower member, as presented in this paper, contains red beds inter- bedded with cross-stratified sandstones (pL 6, fig. 1). If the dark hor izontally bedded silty sandstones are thought of as being Supai tongues then the choice of contact is arbitrary. A similar situation obtains at sections in the Canyon de Chelly area, although there are fewer "tongues" of Supai lithology. Thus, the zone of arbitration is thinner.
In summary, the De Chelly Sandstone in the Defiance area is bounded by an erosional unconformity at the top and by a gradational or transitional zone at the bottom regardless of which member is in con tact with the Supai Formation.
Monument Valley
The White House Member of the De Chelly Sandstone in the
Monument Valley area is underlain by the dark micaceous siltstones and mudstones of the Organ Bock Tongue of the Cutler Formation. The contact between these two units is not identical over the whole of the visited outcrop area. Variations were noted in a north-south as well as an east-west direction. The variation is in the nature of the basal portion of the De Chelly and not so much in the Organ Rock itself.
As noted by previous workers, the De Chelly thins northward and does not cross the San Juan River in the area of Piute Farms.
Plate 13, figure 1, is a view of the lower contact south of Piute Farms where the sandstone is about 30 feet thick. The contact is distinctly PLATE 13
LOWER CONTACT OF DE CHELLY SANDSTONE WITH ORGAN ROCK TONGUE OF THE CUTLER FORMATION, WESTERN MONUMENT VALLEY, UTAH
Figure 1. —Sharp contact of White House Member of De Chelly
Sandstone with Organ Rock Tongue, Fracture and
bedding control position of bleaching in Organ Rock
Tongue, Similar features in the Grand Canyon area
have been described as "sand-filling cracks” in darker
unit,
Figure 2 .—Two sharp contacts: lowermost is considered to be
De Chelly Sandstone-Organ Rock Tongue contact. The
massive unit is thought to represent loess-like material
deposited in front of advancing sand dunes.
36 sharp. Near Holliday Mesa, a short distance north of Oljeto, Utah, the
De Chelly Sandstone is about 300 feet thick. Plate 13, figure 2, shows two clear contacts above and below a structureless siltstone that does not have the characteristics of either the Organ Rock or the De Chelly.
The unit is considered to be an accumulation of loess-like material that represents the initial phase of aeolian deposition in this area over which windblown sand advanced and deposited. As a result of this interpreta tion, the structureless unit is placed in the De Chelly, and the contact is described as sharp and disconformable.
At the inner hogback of Comb Ridge in the eastern portion of
Monument Valley, the De Chelly is about 500 feet thick. Here there is a distinct contact between sandstones and darker, finer grained, thinner bedded sediments (pi. 14). However, the basal sandstones differ from those observed to the west in that the western deposits are cross strati fied on a much larger scale and are interpreted as having been deposited
subaerially. Although smaller scale cross stratification in itself does not prove aqueous deposition, it increases the possibility for it,
The lower contact seems to represent a disconformity of un
determined magnitude. This is more strongly suggested to the west
and north than it is to the east where the De Chelly attains maximum
known outcrop thickness in Monument Valley.
As pointed out elsewhere, the cross stratification trends in
dicate that the depositing currents, thought to be wind, were flowing in PLATE 14
LOWER CONTACT OF DE CHELLY SANDSTONE WITH ORGAN ROCK TONGUE OF THE CUTLER FORMATION, EASTERN MONUMENT VALLEY, UTAH
Figure 1,—Contact is similar to type seen in southern Defiance
. Plateau. A zone of well-defined thin-bedded silty sand
stone units underlies the more massive appearing White
House Member of the De Chelly Sandstone. South of
Goulding$s Trading Post, Utah.
38 a southerly direction at the time the sandstones were deposited. Much of the sand deposited to the south of the Monument Valley area must have passed over the then existing surface developed on the Organ Rock sediments. There is always the consideration that the sand may have been brought to the area by aqueous action and reworked by wind action.
It is possible that the sandstones cross stratified on a small scale at the base of the De Chelly to the east might represent remnants of formerly more extensive aqueous deposits of sand.
It is axiomatic that disconformities become more prominent near the margins of basins of deposition where more time may.be rep resented in contacts than by actual deposits. It seem s possible to con sider that the zone of northward-thinned De Chelly Sandstone approxi mates the original margin or depositions! limit of White House Member sandstones. The sharp contact in this zone might be the type developed by the encroachment of sediments toward a basin margin. In this case the deposits are visualized as ’'backing out” of the basin in an upwind direction. This necessitates that the deposits in the thinned zone be among the later and not the earlier deposits. It seems clear that in the
Monument Valley area the De Chelly thins toward the direction of source.
The Coconino Sandstone of the Grand Canyon region also has a sharper contact at its base in the thinned areas to the north. Plate 15, figure 1, is a view of a lower contact of the Coconino with the Hermit
Shale as seen along the Kaibab Trail. At this locality the Coconino is PLATE 15
UPPER AND LOWER CONTACTS OF COCONINO SANDSTONE, KADBAB TRAIL, GRAND CANYON
Figure 1. —Sharp contact of Coconino Sandstone with underlying
Hermit Shale,
Figure 2, —Sharp contact of Coconino Sandstone with overlying
sandstone of the Toroweap Formation, Note trunca
tion of cross strata. 39 40
approximately 300 feet thick. Farther to the southeast, in the walls of
Oak Creek Canyon, the Coconino overlies the Supai Formation. As
pointed out by McKee (1938) a sharp contact cannot be drawn, as the
two contrasting lithologies alternate vertically to produce a transition
zone. The Coconino here is about 650 feet thick, at least double the
thickness observed at the Kaibab Trail section at Grand Canyon, In a
similar manner Coconino Sandstone thins northward toward the source
as determined by cross-stratification trends. The northward thinning
seems to be accompanied by an increasingly sharp lower contact which
also suggests encroachment upon a basin margin that exercised some
control on the deposition of the Coconino Sandstone,
These features, coupled with seeming similarities in environ
ments of deposition, give reason to consider that the Coconino and the
. White House Member of the De Chelly, in Monument Valley, are anal
ogous.: ■ . . , %: .
Age
The De Chelly Sandstone, except for a few undatable vertebrate
tracks, is not known to be fossiliferous. Thus, it is not yet possible to
assign an age based upon internal evidence. Age assignments are made
by evaluating relationships with overlying and underlying formations and
by projecting regional stratigraphic relationships as they are thought to
be. 41
Stratigraphic projections are necessary because not only is
Monument Valley separated from the Defiance area by 40 m iles of younger rocks, but each in turn is separated from other localities con taining Permian sequences, i. e ., the Mogollon, Grand Canyon, Zuni
Mountain, and southwestern Colorado areas. Gross correlations are possible but attempts at refinement become hazardous (see pL, 1, in pocket). , .
. As far as is known, one fossil locality has been reported from the strata that constitute the bounding formations of the De Chelly Sand stone. Gregory (1917, p. 31) quotes White as stating that plants found in the red beds (Supai) below the De Chelly in the Bonito Canyon area were identified as "Walchia, " characteristic of Permian.
According to Cooley (1957, p. 23), it is the Holbrook Member of the Moenkopi Formation that overlies the De Chelly in the southern part of the Defiance region. Paleontological study of the Moenkopi For mation elsewhere indicates it to be Early to Middle(?) Trlassie in age
(McKee, 1954). '
In the Mogollon, Grand Canyon, and Zuni areas Permian sand
stones that many workers have considered to be equivalent to the De
Chelly Sandstone are overlain by marine formations. The Kaibab that
overlies the Coconino in the Grand Canyon and Mogollon regions is con
sidered by McKee (1938, p. 171) to be Leonardian in age. Because the
upper portion of the Supai Formation, which underlies the Coconino, is 42 also considered of Leonardian age, the Coconino must be considered as
Leonardian in age. . ■
The San Andres Formation as represented in the Zuni Mountains of New Mexico contains an upper marine limestone.and a lower, sand stone referred to as the Glorieta Sandstone.. Read (1951), as previously stated, considered the Black Creek Member of this report as seen at
Black Creek.Canyon to be a Glorieta-Coconino type sandstone. A log of samples taken by the U. S. Geological Survey from a water well at St.
Michaels, Arizona, between Hunters Point and Fort Defiance, indicates the presence of 18 feet of limestone below the Shinarump and above the
De Chelly (Black Creek Member) (Peirce, 1958). Samples on file at the
Arizona Bureau of Mines from this hole do contain a rather pure light- gray limestone at this horizon. It is difficult to understand why indica tions of this limestone have not been noted in outcrops of this horizon less than a mile to the west. This limestone can best be considered an extension of the San Andres the age of which, in the Zuni Mountain area, apparently is subject to debate. Elsewhere the limestones of the San
Andres Formation have been dated as Leonardian, Guadalupian, and parts of both (Permian Subcommittee, 1960). It is possible that the
limestones.of the San Andres. Formation in west-central New Mexico
are somewhat younger than the youngest Kaibab in the Mogollon re
gion. It is, therefore, possible that -some of the De Chelly Sandstone,
especially the Black Creek Member, is younger than the Coconino 43
Sandstone of the Mogollon region. A distinction has been made between the White House and Black Creek Members of the De Chelly Sandstone.
Where both of these members are present the White House type is over- lain by the Black Creek type. Although lateral relationships between these units are not understood, it is possible that the White House Mem ber and Coconino Sandstone may form an equivalent pair, whereas the
Black Creek Member and Glorieta Sandstone may form another nearly equivalent pair. This view, then, will not allow a simple correlation of the Glorieta with the Coconino, although they are probably in juxtaposition.
The De Chelly Sandstone, as a whole, is probably to be con sidered Leonard!an in age with the recognition that all parts may not be at the same position within the. Leonardian.
Sedimentary Structures
General Statement
Sedimentary structures recognized in the De Chelly Sandstone vary in scale from the overall stratification habit of the formation to small-scale features observed in individual strata.
The various members of the De Chelly Sandstone are defined largely on the basis of contrasting sedimentary structure. These dif ferences indicate that the De Chelly Sandstone is composed of detrital 44 sediments deposited in changing environments.
Cross stratification, horizontal stratification, the interplay between these two types, ripple marks, and channels constitute the sedimentary structures of importance. Of these, cross stratification is the most pronounced and well known because it is so prominently displayed in the walls of Canyon de Chelly and in Monument Valley, two areas that have received and continue to receive much photographic publicity.
Stratification
Terminology to be used in describing stratification and cross stratification has not been standardized. Constructive suggestions on this subject, which aid detailed description and comprehension of stratifi cation, were published by McKee and Weir (1953). This system, with modifications, is used in this paper. For definitions and criteria for classification of cross stratification, please see appendices A and B.
The De Chelly Sandstone, as previously pointed out, is a com posite set of strata (see Appendix A). The nature and proportions of stratification types seem to vary throughout the De Chelly in a systematic manner.
Figures 2 and 3 are designed to show the percentages of stratification types in parts of this sandstone as determined from data collected from measured sections. Only the prominent sandstones FIGURE 2
PERCENTAGE DISTRIBUTION OF TYPES OF STRATIFICATION IN THE DE CHELLY SANDSTONE OF THE DEFIANCE PLATEAU AREA
Ao CANYON DE CHELLY - Combined Hunters Point and White
House Members.
B. BONITO CANYON - Combined Hunters Point, White House,
and Black Creek Members.
C. HUNTERS POINT - Combined Hunters Point and Black Creek
-Members.
D. OAK SPRINGS CLIFFS - Combined Hunters Point, White
House, and Black Creek Members.
E. PINE SPRINGS - De Chelly Sandstone, Black Creek Member.
F. BLACK CREEK - De Chelly Sandstone, Black Creek Member.
G. HUNTERS POINT - Black Creek Member.
H. BONITO CANYON - Black Creek Member.
L BONITO CANYON - White House Member. 45
lOO-i 1 0 0 -1
Cross-bedded,small scale
Flat-bedded Indefinite FIGURE 3
PERCENTAGE DISTRIBUTION OF TYPES OF STRATIFICATION IN THE DE C KELLY SANDSTONE OF THE DEFIANCE PLATEAU AREA
Jo CANYON DE CKELLY - White House Member.
K. NAZLINI CANYON - White House Member.
L. OAK SPRINGS CLIFFS - Combined White House and Black
Creek Members.
M. BONITO CANYON - Combined White House and Black Creek
Members.
N. CANYON DE CHELLY - Hunters Point Member.
O. BONITO CANYON » Hunters Point Member.
P. HUNTERS POINT - Hunters Point Member.
Q. OAK SPRINGS CLIFFS - Hunters Point Member. 46
lOO-i
7 0 -
lOOi IOO-i
70 -
100-|
8 0 -
Y//A Cross-bedded Y~/L/A Large - medium scale Cross^bedded,small scale
Flat-bedded 1 Indefinite 47 composing the Hunters Point, White House, and Black Creek Members are considered.
Figures 2A, B, C, and D show the overall combined percent ages of stratification types found in the sandstone members present at each of the localities represented. Although the percentage of sand stones cross stratified on a large to medium scale is dominant in each of these sections, it should be noted that figure 2A, representing Canyon de.Chelly on the west side of the Defiance Plateau, demonstrates that over 90 percent of the combined Hunters Point and White House Mem bers is composed of such sandstones. Figures 2B, C, and D, repre senting Bonito Canyon, Hunters Point, and Oak Springs Cliffs on the east side of the Defiance Plateau, demonstrate a relative decrease in the percentage of sandstones cross stratified on a large to medium scale present in each of these sections.
The remaining examples show stratification type percentages by members and certain combinations of members, so as to reveal better the nature of overall change in the De Cbelly Sandstone. These examples show that the proportion of sandstones cross stratified on a large to medium scale to sandstones that are horizontally stratified in the Black Creek Member (figs. 2E, F, G, and H) is considerably less than the proportion of such sandstones in the White House Member (figs.
21 and 3J,.K). The Black Creek Member, known to occur only in sec tions in the eastern and southern parts of the Defiance Plateau, shows !,•
48 a decrease in percentage of cross-stratified sandstones in the De Chelly toward the east and south. Another important example of this decrease is shown by the stratification habit of the Hunters Point Member (figs.
3N, O, P, and Q). This member, too, shows a considerable decrease in the percentage of sandstones cross stratified on a large to medium scale from west to east and south. 'W
Whereas figures 2 and 3 show overall percentages of stratifica tion types, figures 4 and 5 show the number and average thicknesses of units that represent the stratification types.
Figures 4A and B clearly show the similarity in stratification iit : habit of the White House Member as represented at Canyon de Chelly and Nazlini Canyon on the west side of the Defiance Plateau. These figures indicate also that the units in greatest number and average 4 thickness are those that are cross stratified on a large to medium scale.
Figures 4C, D, E, F, and G clearly indicate a contrasting stratification habit for the prominent sandstones above the Oak Springs Member in the
east and southern parts of the Defiance Plateau. The nearly equal num
bers of horizontally and cross-stratified units are a reflection of the
fact that these types alternate vertically.
Figure 5A demonstrates that the Hunters Point Member at
Canyon de Chelly tends to be a coset of cross strata. Figures 5B, C,
and D, representing this member on the east side of the Defiance
Plateau, indicate a trend to the south in which the large- to medium- FIGURE 4
RELATIVE NUMBERS AND AVERAGE THICKNESSES OF UNITS WITH CONTRASTING TYPES OF STRATIFICATION FOUND IN THE WHITE HOUSE AND BLACK CREEK MEMBERS ON THE DEFIANCE PLATEAU
A0 CANYON DE CHELLY - White House Member, northwestern
Defiance Plateau,
B„ NAZLINI CANYON - White House Member, northwestern
Defiance Plateau,
C, BONITO CANYON - White House and Black Creek Members,
east-central Defiance Plateau,
D, HUNTERS POINT - Black Creek Member, southeastern
Defiance Plateau,
E, OAK SPRINGS CLIFFS - White House and Black Creek Mem
bers, southeastern Defiance Plateau.
F, BLACK CREEK - Black Creek Member, southeast Defiance
Plateau.
Go PINE SPRINGS - Black Creek Member, southern Defiance
Plateau 49
h 20-
5 12-
10 12 14 16 18 20 . 22 24 26 28 NUMBER OF UNITS
X= LARGE-MEDIUM SCALE CROSS-STRATIFIED UNITS F= FLAT BEDDED UNITS FIGURE 5
RELATIVE NUMBERS AND AVERAGE THICKNESSES OF UNITS WITH CONTRASTING TYPES OF STRATIFICATION FOUND IN THE HUNTERS POINT MEMBER ON THE DEFIANCE PLATEAU
A. CANYON DE CKELLY - Hunters Point Member.
B. BONITO CANYON - Hunters Point Member.
C. HUNTERS POINT - Hunters Point Member.
D. OAK SPRINGS CLIFFS - Hunters Point Member. 50
e 60-
x 40-
< 30-
2 . 3 NUMBER OF UNITS
X= LARGE-MEDIUM SCALE CROSS-STRATIFIED UNITS F= FLAT BEDDED UNITS S= SMALL SCALE CROSS-STRATIFIED UNITS 51 scale cross-stratified units decrease in average thickness to the point where they have the same average thickness as the flat-bedded and small- to very small-scale cross-stratified units. Plate 16 also con trasts these stratification characteristics.
Cross Stratification
White House Member
The White House Member contains cross stratification of two aspects, and these are illustrated in plates 17 and 18. As far as known to the author, these contrasting types of set arrangements have not been adequately defined in geologic literature. It is thought that they are so basic, having been recognized in many of the well-known cross-strati fied sandstones on the Colorado Plateau, that a simple terminology should be developed that can be applied to them. On plate 17 appears a sequence of cross-stratified units separated vertically by nearly hori zontal surfaces, whereas plate 18 shows sequences of cross strata not readily subdivided, vertically, into such distinct units.
According to the system of McKee and Weir (1953), the types of cross stratification represented are planar and trough in which the set shapes are tabular and lenticular, respectively. However, plate 19 illustrates a complicating factor. Smaller scale oblique erosion surfaces limit the lateral extent of otherwise tabular sets. In the zone of the PLATE 16
CONTRASTS IN STRATIFICATION ASPECTS— HUNTERS POINT MEMBER, EAST FLANK DEFIANCE PLATEAU
Figure 1.—Hunters Point Member near Bonito Canyon illustrat
ing scale of cross stratification and thick units.
Figure 2. —Hunters Point Member at Oak Springs Cliffs. Weather
ing out of units is reflection of thinner bedding, smaUer
scale of cross stratification, and more horizontally
stratified units than in section represented by figure 1. 52
■- x i * *4 4 U» PLATE 17
CROSS STRATIFICATION IN THE WHITE HOUSE MEMBER OF THE DE C KELLY SANDSTONE
Figure 1.—Cross-stratified units defined by horizontal planes
of separation. Apparent dip directions are remark
ably similar. Looking at north waU of Canyon de
CheHy.
Figure 2,—Similar to above as exposed on cliff. Dark planes
represent thin, silty sandstone units that overlie sur
faces of truncation. In this picture each cross-
stratified unit is composed of a single set of cross
strata. 53
i PLATE 18
CROSS STRATIFICATION IN THE WHITE HOUSE MEMBER OF THE DE CKELLY SANDSTONE
Figure 1. —A vertical coset of cross strata in which horizontal
features are developed poorly. Near Hoskinnini Mesa,
western Monument Valley,
Figure 2 ,—Upper portion of White House Member showing con
trasting nature of shapes of sets of cross strata in
small area. Left side contains series of near planar
truncation surfaces. Right side contains only gently
curved surfaces of erosion that appear to cut the
previously existent planar surfaces. Eastern Monu
ment Valley near Comb Ridge.
PLATE 19
CROSS STRATIFICATION IN THE WHITE HOUSE MEMBER OF THE DE CHELLY SANDSTONE
Figure 1 .—Oblique surface of erosion in left center of photo
graph* This surface truncates the lower set of cross
strata but constitutes a depositional surface in respect
to the overlying set. The oblique surface is confined
between two larger scale horizontal surfaces* The
higher surface appears to be traceable across the
smooth cliff face to the right. Canyon de CheUy look
ing northeast. White House ruin in lower center of
cliff.
Figure 2.—Similar to above, oblique truncation or depositional
surface in center, pinchout of darker thin unit overlying
a horizontal surface (below center right at edge of ex
posure). Canyon de CheUy looking northeast. 55 56 oblique surface the sets are no longer tabular but wedge to lenticular in shape, depending upon whether the truncating surface is planar or con cave upward. This demonstrates that the unit first described as a tabular set of cross strata is, in fact, a coset of cross strata in which the sets are laterally distributed and confined between two nearly hori zontal surfaces. For this type of cross-stratified unit the term "lateral coset of cross strata" is proposed.
In the case represented by plate 18, figure 1, the only hori zontal features may be the upper and lower contacts of the formation.
To describe this arrangement of sets the term "vertical coset of cross strata” is proposed.
Where the lateral coset-type of cross stratification is developed the horizontal surfaces are surfaces of erosion that are thought to be closely associated with the manner of deposition of the underlying cross strata which they truncate. Frequently, these nearly flat surfaces are overlain by thin units of silty sandstone or sandy siltstone that are flat bedded and irregularly laminated. These deposits appear to be closely associated with the overlying cross strata with which they appear to merge (pis. 20 and 21, figs. 2 and 2). The erosion surfaces are the larger scale features, the flat-bedded deposits occupying restricted areas on these surfaces. This is suggested by the higher frequency of occurrence of erosion surfaces without overlying flat-bedded materials, and the fact that flat-bedded units frequently pinch out while the PLATE 20
HORIZONTAL TRUNCATION SURFACES IN WHITE HOUSE MEMBER OF DE CHELLY SANDSTONE
Figure 1«-»A sharp surface that truncates cross strata and is
overlain by similar cross strata. Thin-bedded unit N , absent. Actual dip direction of cross strata is simi
lar. Kin-Li-Chee area looking north.
Figure 2 .—Horizontal truncation of cross strata with thin unit
of silty sandstone overlying truncating surface. Over-
lying cross strata seem to merge with the thin unit.
Soft-rock deformation over notebook. Kin-Li-Chee
area near position of figure 1, looking south. 57 PLATE 21
HORIZONTAL TRUNCATION SURFACES AND OVERLYING THIN-BEDDED UNITS IN CROSS-STRATIFIED WHITE HOUSE MEMBER OF DE CHELLY SANDSTONE
Figure 1.—Near Sawmill on east flank of the Defiance Plateau.
Figure 2. —Exposure at Oak Springs Cliffs. This is character
istic White House Member that is overlain here by
Black Creek Member and underlain by Oak Springs
Member. Thirty miles south of location of figure 1. > 58 59 underlying truncation surface persists (pi. 19, fig. 2). Because of local pinching, out of flat-bedded deposits, they are viewed as being wholly contained within the White House Member and not tongues of some other laterally equivalent lithology. Although a particular flat-bedded unit might be local in occurrence, such beds are distributed within the White
House Member wherever it has been examined on the Defiance Plateau.
Plate 21 illustrates that these features are present on the eastern flank of the Defiance Plateau near Sawmill and also 30 miles to the south at
Oak Springs Cliffs. They are also present in the White House Member at Bonito Canyon. They are known to occur over a north-south distance of 60 m iles and an east-west distance of 25 m iles.
The actual extent of lateral development of the nearly flat trun cation surfaces is not precisely known because of physical limitations of tracing as well as outcrop conditions.. Even though one can see for con siderable distances in Canyon de Chelly, these structures stand out clearly only on weathered exposures and continuity is broken by rela tively fresh, smooth sections on cliff faces (pL> 19, fig. 1). However, it is doubtful that the average surface will extend for more than half a mile and perhaps considerably less.
Because of the difficulty of observing in plan the cross stratifi cation in the Canyon de. Chelly area, it is instructive to look at another locality that contains similar phenomena but in which cross stratifica tion can be studied in more detail. 60
Near Kin-Li-Chee, about 6 m iles east of Ganado, several washes have been cut into the upper portions of the De Chelly Sandstone.
Though limited vertically, these washes expose many of the features seen at. Canyon de Chelly, including cross stratification of the lateral coset type, near horizontal truncation surfaces, and silty beds that overlie portions of the truncation surfaces (pi. 20). Sets of cross- stratified sandstone are exposed in three dimensions.
Individual sets of cross strata belonging to the lateral coset- type of set distribution may be arcuate in plan view. In some struc tures strike of cross strata changes as much as 170° (pi. 22). . As sociated with these structures are reptilian tracks and wide-crested, low-amplitude ripple marks that are oriented up and down the dip of cross strata. These tracks and ripple marks were developed subaerial- ly and, therefore, the sandstones in which these features are developed were deposited by wind activity. Some of the arcuate or dunal struc tures were deposited either on thin flat-bedded silty units or on an under lying nearly horizontal erosion surface without intervening flat-bedded deposits (pi. 20). Oblique surfaces of erosion laterally separate in dividual sets (pi. 23, fig. 1). Locally, a vertical coset of cross strata may occur in which inclined planar and concave erosion surfaces are developed with exclusion of internal horizontal structures. In this case, vertically distributed lenticular and wedge-shaped sets characterize the unit and the unit will be bounded by horizontal surfaces (pi. 23, fig. 2). PLATE 22
ARCUATE STRUCTURES IN THE WHITE HOUSE MEMBER OF THE DE CKELLY SANDSTONE
Figure 1«—Person sitting on axis of an arcuate structure that is
flatly truncated above. Flaggy weathering of cross
strata. Near Kin-Li-Chee. Looking south.
Figure 2. —A larger arcuate structure with axis of curvature
pointing to right of picture. Strike of cross strata
change 170°. Near Kin-Li-Chee. Looking south.
PLATE 23
INCLINED EROSION SURFACES IN THE WHITE HOUSE MEMBER OF THE DE CHELLY SANDSTONE
Figure 1.—A lateral coset of cross strata with inclined contact
between two adjacent arcuate structures. Although the
dip directions are opposite the axes of the two arcuate
structures are parallel indicating similarity in direc
tion of flow of depositing current* Note change in angle
of dip near base of older structure. Kin-Li-Chee area.
Looking east.
Figure 2 .—A vertical coset of cross strata with inclined erosion
surfaces dominant. Horizontal truncating surfaces near
base of exposure. Kin-Li-Chee area. Looking south. 62
<■
v 63
It is thought that the flat-bedded silty units were deposited in shallow, standing water with but minor current action, and that deposi tion was controlled in part by gentle concavities on erosion surfaces.
That water was involved is suggested by the fact that these comparative ly thin units are irregularly and discontinuously laminated. This struc ture is revealed by alternating laminae of silt and sand with sand tend ing to concentrate in very small lenses. Frequently, coarse to very coarse sand grains are concentrated in these units. That currents in volved were of small magnitude is suggested by the high silt content with attendant coarse sand grains, bedding structures, lack of recog nizable cross stratification, and the absence of observed channeling in the underlying sandstones coupled with the lack of reworked zones at the contact between silty beds and underlying cross-stratified sandstones.
The fact that some of the silty units pinch out is suggestive of rather local restricted deposition.
The nearly flat surfaces of erosion are thought to have been produced by subaerial processes closely related to the manner of depo sition of the cross-stratified sands. That wind action produced these surfaces is strongly indicated by the fact that surfaces were cut upon sandstones almost certainly wind deposited and overlain by similarly deposited sandstones without intervening silty or other units that would suggest that subaqueous activity had been operative. Local ponding, whether for reasons of high water table or surface accumulation. 64 provided traps for windblown materials including mica minerals. Coarse to very coarse sand grains might well have existed on erosion surfaces as a lag concentrate and subsequently incorporated into the flat-bedded deposits and sorted into small lenses by minor current action.
It is believed that the sandstones of the White House Member in
Canyon de Chelly are continuous with those exposed in the Kin-Li-Chee area, and that they represent a similar environment of deposition. This conclusion is based upon the similarity of sedimentary structures in each of these areas. Such features as wind ripples and animal tracks were not observed in Canyon de Chelly, largely because outcrops expos ing the surfaces of foreset structures are not plentiful.
Nazlini Canyon, located between Canyon de Chelly and Kin-Li-
Chee, contains typical White House Member sandstones. The lateral coset-type of cross stratification is prominent and wind ripple marks and tracks are present (pi. 24).
Whereas the lateral coset-type of cross-stratification develop ment is weU illustrated, by the White House Member in the Defiance region, the vertical coset-type of set distribution is well developed in
White House Member sandstones found in the Monument Valley area (pi.
18). That most of these sandstones are also wind deposits is beyond reasonable doubt. Animal tracks and wind ripples on foreset strata along with the nature of the cross stratification associated with these features would seem to make any other conclusion unlikely (pis. 25 and PLATE 24
CROSS STRATIFICATION AND ANIMAL TRACKS IN WHITE HOUSE MEMBER OF THE DE C KELLY SANDSTONE
Figure 1.—White House Member sandstones showing character
istic horizontal surfaces in otherwise cross-stratified
sandstones. Apparent westerly dip directions similar
in successive lateral coset-type units, Nazlini Canyon,
north wall.
Figure 2, —Animal tracks taken from a foreset structure in one
set of a lateral coset-type unit, Nazlini Canyon. 65 PLATE 25
CROSS STRATIFICATION AND RIPPLE MARKS IN WHITE HOUSE MEMBER OF THE DE CKELLY SANDSTONE
Figure 1, —Large-scale cross stratification of vertical coset
type with a characteristic wedge-shaped set in center.
Wind ripple marks on cross strata of the central wedge
with axes aligned up and down dip. Western Monument
VaUey area.
Figure 2 .—Wind ripple marks oriented up and down dip of cross
strata. Two different layers contain ripple marks.
Western Monument Valley area. 66 67
26).
A comprehensive statistical analysis of cross stratification in this member was not made, but a number of data were collected in the course of fieldwork and are summarized in figures 6 and 7, Figure 6 shows the nature of the angle of dip of cross strata and indicates that a dip angle of 24° is most common. Figure 7 is a compilation of readings made on the direction of dip of cross strata. These show that this di rection ranges from near north to southeast, but that the grouping is confined largely to a direction between N. 40° W. and S. 30° E., a range of 170°. Such a range seem s quite logical when it is remembered that the dip direction of a single arcuate foreset structure may vary this much or more. The central point between these extremes would be S.
55° W. and should approximate the average direction of current flow— in this case, wind.
Reiche (1938) and Read (1961) each conducted statistical studies of this member. Both agree that the average direction of dip is toward the southwest in the Defiance area. Readts data for Monument Valley are the more complete, and indicate that the average direction of dip is west of south in eastern Monument Valley and slightly east of south in western Monument Valley.
Black Creek Member
As previously pointed out, the Black Creek Member is a PLATE 26
ANIMAL TRACKS AND RIPPLE MARKS IN WHITE HOUSE MEMBER OF THE DE CHELLY SANDSTONE
Figure 1»—Track trail going up dip of cross strata. Western
Monument Valley.
Figure 2 .—Wind ripples oriented up and down dip. Near Comb
Ridge, eastern Monument VaUey. 68
) FIGURE 6
DIRECTION OF DIP OF CROSS STRATA
Frequency of dip direction of cross strata, White House Member west side of Defiance Plateau. Solid line is summation of 172 readings. Dashed line represents 30 readings taken near
Klagetoh. NUMBER OF READINGS 1 1 2 2 3 3 4 45 40 35 30 25 20 15 10 5 NORTHWEST " QUADRANT- 0 5 0 5 0 5 0 5 W 85 80 75 70 65 60 55 50 5 0 5 0 5 0 5 045 0 5 0 5 0 5 0 S 5 10 15 20 25 30 35 40 4 5 50 55 60 65 70 75 80 85 OT WS QUADRANTSOUTHWEST 1 1 2 8 3 36 30 8$ 20 15 10 5 5 0 15N 10 5 S 5 10 15 20 25 30 35 40 45 50 55 60 K 70 75 80 W 95 SO 75 70 65 60 55 ^0 45 40 35 iO 25 20 15 lb 5 SOUTHEAST 5 30 25 g FIGURE 7
DIP ANGLES OF CROSS STRATA
Frequency of dip angles of cross strata in White House Member, west side of Defiance Plateau, Solid line is summation of 172 readings. Dashed line represents 30 readings taken near
Klagetoh, 70
z 20-
DEGREES OF DIP 71 composite set of strata. It is composed of horizontally stratified and cross-stratified units in alternating succession. Whereas the flat-bedded units in the White House Member are relatively thin and constitute a low percentage of the member, the horizontally stratified units in the Black
Creek Member are frequently as thick or thicker than the cross-strati fied units with which they are interbedded. This mixed sedimentary structural aspect is present in all of the sections measured on the east ern and southern portions of the Defiance Plateau, and is an important basis for subdividing the ’’upper" De Chelly Sandstone of McKee and
Read into two members (pi. 10, fig. 1 and pi. 27).
Information concerning sedimentary structures in the Black
Creek Member is not as complete as it is for the White House Member.
In part this can be attributed to the nature of exposures. The member is exposed largely in canyons and erosional features cut into the steeply dipping east flank of the Defiance anticline where vegetation is abundant, outcrops are frequently discolored, and tracing of beds is difficult (pi.
23, fig. 1). Exposures that allow examination of cross strata in plan view or examination of surfaces of cross strata for such features as tracks and ripple marks are not abundant.
Most of the cross-stratified units in the Black Creek Member
are of the lateral coset type that were not observed to be noticeably dif
ferent than those noted in the White House Member. Angle of dip of
cross strata as well as direction of dip appear very similar. A unit of PLATE 27
EXPOSURES OF BLACK CREEK MEMBER OF THE DE CHELLY SANDSTONE
Figure 1,—A single set of cross-stratified sandstone underlain
and overlain by horizontally stratified sandstones.
Looking east, note southerly direction of dip of cross
strata. Near top of Black Creek Member, Hunters
Point area.
Figure 2 .—Smooth-weathering dark units are horizontally strati
tied, whereas the irregular lighter colored units are
cross stratified. About 6 m iles northeast of Houck,
Arizona. Looking northeasterly.
73 the vertical coset type occurs at the tops of both the Pine Springs and
Oak Springs Cliffs sections.
That the Black Creek Member consists of sandstone deposited in contrasting environments is beyond question. Perhaps the most obvious contrast is the different energy levels suggested by the sedi mentary structural types. These contrasts suggest that cycles of trans gression and regression are involved and that two basic environments existed adjacent to one another. It is thought that the horizontally stratified units are aqueous deposits, whereas the majority of the cross- stratified units are wind or dune deposits. Slight shifts in environmental controls caused transgression and regression of the aqueous environ ment, which in turn controlled the distribution of wind or dune deposits.
The nature of the aqueous environment of deposition was one in which conspicuous cross stratification could not develop, perhaps rela tively persistent quiet waters (pL> 28).
It is probable that water-deposited material was derived both
by reworking of dune deposits as well as from windborne material trapped by the aqueous medium. A noticeable increase in content of silty mate
rial in water-deposited units to the south accompanied by thinning of
cross-stratified units suggests that a more permanent water body ex
isted in that direction. However, these trends might be in response to
local and not regional conditions.
The lack of recognized fossils in the water-laid deposits PLATE 28
HORIZONTALLY STRATIFIED UNIT IN BLACK CREEK MEMBER, SOUTHERN END OF DEFIANCE PLATEAU NORTHEAST OF HOUCK 74
)
I 75 restricts recognition of the nature of the aqueous medium, whether con tinental, brackish, or marine. With present understanding, it is neces sary to consider three possibilities: (1) the influence of San Andres-
Kaibab time marine conditions, (2) the influence of Supai time brackish- water conditions, and (3) conditions between these times.
The Permian San Andres Formation, consisting of an upper marine limestone and a lower:sandstone (Glorieta) is exposed in the
Zuni Mountains of New Mexico 40 m iles east of the Defiance area.
Limestones thought to be continuous with the San Andres Formation occur in the subsurface to the south of the Defiance Plateau near St. Johns,
Arizona. 5 v
. Although limestone occupying the same relative position as the
San Andres limestone has not been observed in outcrop anywhere on the
Defiance Plateau, a limestone underlying Shinarump Conglomerate and overlying the Black Creek Member sandstones was penetrated during the drilling of a water well at St. Michaels, Arizona (Peirce, 1958).
This locality is only a mile or so from the east flank of the Defiance anticline. In the Zuni Mountain area sandstones are frequently inter- bedded with limestones, indicating that deposition of sandstone and lime stone probably occurred adjacent to one another and became interbedded by transgression and regression of the respective environments. The position of a limestone immediately above sandstones of the Black Creek
Member at St. Michaels suggests a possible.relationship between parts 76 of the Black Creek Member and marine phenomena. The horizontally stratified sandstones may represent near-shore accumulations in a shal low marine environment. ■ « -
As pointed out previously, the Hunters Point Member changes to red beds, the Oak Springs "red-bed" member coalescing with the
Supai Formation to the south of Oak Springs Cliffs. One wonders, then, if the horizontally stratified sandstones of the Black;Creek Member
could represent phases of the Supai Formation that were possibly de posited under brackish-water conditions. Although cross-stratified units of the Black Creek Member, when last observed in outcrop, ap pear to be thinning to the south, it is not known whether they pinch out
entirely. Holes drilled for oil, gas, and water south of the Defiance
Plateau all seem to have good sandstones in the stratigraphic position
of the Black Creek Member. However, unless cores are recovered,
the nature of the sedimentary structures is impossible to determine,
and many of these sandstones may not be cross stratified* Precedent
for such an occurrence. can be seen south of Show Low, Arizona, along
Forestdale Creek. The light-colored sandstones that occur between the
red beds of the Supai Formation and beds of the Kaibab Formation are
not noticeably cross stratified and appear almost identical to some of
the horizontally stratified sandstones that occur in the.Black Creek
Member in the eastern and southern Defiance area.
The third possibility, considering the Black Creek Member to 77 be a self-contained unit not compounded from the intermingling of White
House Member and San Andres or White House.Member and Supai For mations, does not seem likely. The contrast in sedimentary structures is persistent for at least 30 miles along the east flank of the Defiance, and therefore should be considered of regional and not just local sig nificance, Because the only known Permian marine formations are .. % - .: / . ■: . . . • ' those associated with San Andres-Kaibab- and Supai Formations, any self-contained aqueous environment must have been land locked and in itially fresh water, . It is doubtful that such a seemingly ephemeral con dition could persist long enough to effect the transgressive-regressive relationships that are suggested by the inter bedding of sedimentary structural types in the Black.Creek Member,
Although considerably more information is needed before posi tive statements are justified, it is thought that the Black Creek Member is correlative with a part of the San Andres Formation, but it is not known precisely how to make the correlation. The Black Creek Mem ber and the Glorieta may form a direct connection in the subsurface, but it is possible that these sands rise in time toward the Defiance area
such that some of the Black Creek Member may be equivalent to some
of the limestones of the.San Andres Formation. Considerably more at
tention must be given to studying sedimentary structures in both the
Black Creek Member and Glorieta sandstones in order to be able to
begin to comprehend their origins. 78
Hunters Point Member
Outcrops of the Hunters.Point Member are restricted to lower parts of isolated canyons. On the west flank of the Defiance Plateau it is exposed only in parts of Canyon de Chelly and tributary canyons. On the east flank it is exposed at Buel Park, Bonito Canyon, Hunters Point, and at Oak Springs Cliffs. Because of facies change, it is absent in all observed exposures along Black Creek Canyon. It has not been rec« ognized in .Monument Valley. .
In its most northern exposures. Canyon de CheUy on the west and Bonito Canyon on the east flank of the Defiance Plateau, the Hunters
Point Member tends to be a massive-weathering, complicated coset of cross strata of the vertical coset type (pi. 29). To the south the unit becomes a composite set because it is made up equally of both hori zontally stratified and cross-stratified sandstones (pi. 30).
Cross stratification developed in this member is exceedingly variable in scale, type and shape (pi. 31, etseq.). These variations accompanied by interbedded, horizontally stratified sandstones and silty sandstones reflect varying environments of deposition. The nature of the cross stratification, internal channeling (pi. 32 and pi. 33, fig. 1), / and water-formed ripple marks (pL 33, fig. 2 and pi. 34, fig. 1) strong ly indicate that much of this member was deposited in an aqueous envi ronment. Many of the sandstones are thought to be of fluviatile origin. PLATE 29
HUNTERS POINT MEMBER, NORTHERN DEFIANCE PLATEAU
Figure 16—Intricate coset of cross strata that forms a rounded
slope. Upper cliffs are composed of White House Mem
ber sandstones. Canyon de.Chelly, looking north.
Figure 2 .—Similar to above except that cross stratification
obscured by surface staining. Slabby or flaggy weather
ing White House Member above. Bonito Canyon,. look
ing east. 79 PLATE 30
STRATIFICATION IN THE HUNTERS POINT MEMBER
Figure 1,—Thin-bedded, horizontally stratified sandstone, top
unit of member at Oak Springs Cliffs* Southern
Defiance Plateau in background. Looking south.
Figure 2. —Low-angle medium-scale cross strata with lenticular
to wedge-shaped sets overlain by thin-bedded sand
stones. Hunters Point. Man in this picture is the late
Boyd Moore. Looking north.
PLATE 31
VARIABLE NATURE OF CROSS STRATIFICATION IN HUNTERS POINT MEMBER
Figure 1«—Medium-scale cross strata with tangential basal
contact. Overlain and underlain by horizontally strati
fied sandstones. Hunters Point section. Looking
north.
Figure 2. —Very small to small-scale cross stratification,
Hunters Point section. Looking north. 81 PLATE 32
CHANNEL IN HUNTERS POINT MEMBER
Figure 1.—Edge of channel, Buell Park, east side of Defiance
Plateau, Looking south.
Figure 2. —Base of channel illustrated in figure 1, Looking
south. 82 PLATE 33
CHANNEL AND RIPPLE MARKS IN HUNTERS POINT MEMBER
Figure 1.—Channel fiUed with sand and truncated by horizontal
ly stratified sands. Hunters Point Member in back
ground. Oak Springs Cliffs. Looking northwest,
Figure 2. —Water ripple marks, Oak Springs Cliffs, ) 83
) s
/
:
) PLATE 34
RIPPLE MARKS AND CROSS STRATIFICATION IN HUNTERS POINT MEMBER
Figure 1.—Oscillation ripples(?) and faintly developed ripple
laminae. Bonito Canyon, east side of Defiance
Plateau. Looking east.
Figure 2 .—Same as figure 1. Showing cross-stratified unit
underlying rippled sandstone. Small-scale cross
stratification is of the trough type with lenticular to
wedge-shaped sets. Looking east. 84 85
The disappearance of the member between the Oak Springs
Cliffs and Black Creek sections, 3 miles apart, is thought to reflect a facies change controlled by the existence of two adjacent, contrasting
depositional environments. Such a change could exist between a river
and associated flood-plain deposits or between a deltaic environment
where higher energy continental phases come into direct contact with
lower energy phases associated with basin waters of an adjacent envi
ronment. An important point here is the fact that the boundary between
the two environments persisted throughout Hunters Point time within a
lateral distance of less than 3 miles.
It is thought that these relationships can be best explained by
considering the red bed or Supai phase to have existed lateral to, or to
have been a part of, a delta that advanced, locally, from a direction
west of north. Such a concept is not incompatible with the southeast
erly flow direction postulated by Read (1961), as a result of his studies
of cross-strata dip directions of sandstones in this member in the
Defiance area.
The river or fluvlatile system thus postulated might well have
contributed significant quantities of materials in solution to Supai basin
waters, which, upon evaporation, produced at least some of the evaporite
deposits that exist a short distance to the south and southwest at an ap-*
proximately similar stratigraphic position.
Very little, if any, subsurface information is available for 86 this sandstone unit; consequently, the only information is that afforded by outcrops, if this member is penetrated by drilling its recognition,
may hinge on whether or not the overlying Oak Springs Member can be
recognized. . If not, the sandstones are likely to be lumped with the
upper sandstones. : .
. Because of a general lack of data, the overall shape of the
Hunters Point Member.is not known. One dimension, that afforded by
exposures, is at least 40 miles in a north-south direction. Because of
its development at Canyon de Chelly, its northernmost outcrop exposure,
it continues an unknown distance northward in the subsurface but does
not reappear in Monument Valley. It probably grades laterally into red
beds of the Cutler or Supai Formations. Available trends suggest that
the long axis of this sandstone body is oriented west of north, such that
it cuts obliquely across the north-south elongated Defiance anticline.
This sandstone represents an unexplored, relatively porous
and permeable zone that may occur in the subsurface in parts of both
the Black Mesa and San Juan basins. Stratigraphic and (or) structural
traps for fluids might very well be present within it.
Texture
Grain Size
While measuring and describing exposures of the De Chelly 87
Sandstone, a first-sized sample was taken of each unit described.
Many of these samples were subsequently subjected to mechanical anal
yses using standard procedures (Krumbein and Pettijohn, 1938). In all
cases a series of screens were used consisting of U. S. standard sieve
mesh numbers 35, 45, 60, 80, 120, 170, and 230. Using the Wentworth
grade scale for sands (see table below) this screen series divides each
sand size class into two parts, thus giving more points with which to
construct histograms and cumulative curves.
Sieve Mesh Opening in Phi Wentworth Size No. Millimeters Class
18 1.00 0.0
25 0.71 0.5 Coarse Sand
35 1/2 1.0
45 .35 1.5 Medium Sand o 60 .M
1/4 1
80 .177 2.5 Fine Sand
120 1/8 3.0
170 .088 3.5 Very F^ne Sand
230 1/16 4.0
'-230 -1/16 Silt and Clay
The data obtained from mechanical analyses were used to
construct cumulative curves which provided data for the determination 88 of such statistical parameters as median diameter, Trask*s sorting coefficient, and skewness. However, for ease of viewing, a series of histograms were developed to help summarize the mechanical analysis data. Histograms are presented in figures 8, 9, and 10 that tend to show grain?size distribution in smaller and larger parts of the De
Chelly Sandstone. Each histogram is an average of the individual analyses made on each sample taken from the part represented. Be cause there are 27 histograms, some of the statistical highlights shown therewith are summarized in table 2.
Gregory (1917, p. 33) states: "The Dechelly sandstone is fine grained throughout and remarkably uniform in texture. It consists es sentially of grains of two sizes— spherical grains of quartz, averaging about 0.19 millimeter in diameter and making up the bulk of the rock and less well-rounded grains 0.5 to 0.6 millimeter in diameter."
McKee (1934, p. 224) concurred with and reiterated Gregory's observations but added that " ... the larger-sized grains of the De Chelly sandstone have diameters which are considerably greater than those of the sand grains found throughout the northern part of the Coconino for mation, but the smaller ones average only slightly larger than those of the Coconino." McKee was concerned largely with exposures on the western flank of the,Defiance Plateau, whereas Gregory observed many exposures throughout the Defiance and Monument Valley areas.
Figure 8A is a histogram calculated by averaging the individual FIGURE 8
HISTOGRAMS SHOWING AVERAGE GRAIN-SIZE DISTRIBUTION IN THE DE CKELLY SANDSTONE
Histograms showing average grain- size distribution in the De Chelly Sandstone and its parts as determined from the summa tion of analyses made of samples taken from the parts repre sented, Median diameter, sorting coefficient, and number of samples are also indicated. Solid part shows percentage re tents on each screen, whereas the other grouping is by Went worth grade divisions.
A. DE CHELLY SANDSTONE - all samples.
B. HUNTERS POINT MEMBER - all samples.
C. WHITE HOUSE AND BLACK CREEK MEMBERS COMBINED - all samples.
D. CANYON DE CHELLY - Hunters Point and White House Members combined.
E. BONITO CANYON - Hunters Point, White House, and Black Creek Members combined.
F. HUNTERS POINT - Hunters Point and Black Creek Members combined.
G. OAK SPRINGS CLIFFS - Hunters Point, Oak Springs, White House, and Black Creek Members combined.
H. WHITE HOUSE AND BLACK CREEK MEMBERS - Large- and medium-scale cross-stratified sandstones.
L WHITE HOUSE AND BLACK CREEK MEMBERS - Hori zontally stratified units. 89 SAMPLES"125 SAMPLES«84 S0*L25 SO*124 m :.l64mm, m *.170 mm.
SAMPLES*19 50 = 1.22 m - .174 firm
l00l SAMPLES 3 31 I00i l00l SAMPLES : 15 SO: |.I9 S0= |.36 m :.I56 m: .14 I
•s FIGURE 9
HISTOGRAMS SHOWING AVERAGE GRAIN-SIZE DISTRIBUTION IN THE DE CHELLY SANDSTONE
Histograms showing average grain-size distribution in parts of the De Chelly Sandstone as determined from the summation of analyses made of samples taken from the part represented* Median diameter, sorting coefficient, and number of samples are also indicated. Solid part shows percentage retents on each screen, whereas the other grouping is by Wentworth grade divi sions.
A. HUNTERS POINT MEMBER - large- to medium-scale cross- stratified sandstones.
B. HUNTERS POINT MEMBER - Horizontally stratified sand stones.
C. HUNTERS POINT MEMBER - Small-scale cross-stratified sandstones.
D. HUNTERS POINT MEMBER - Bonito Canyon.
E. HUNTERS POINT MEMBER - Hunters Point.
F. BONITO CANYON - White House and Black Creek Members combined.
G. HUNTERS POINT - Black Creek Member.
H. NAZLINI CANYON - White House Member.
L PINE SPRINGS - Black Creek Member. 90 SAMPLES"II SAMPLES "9 SAMPLES"# SO "1.25 SO"124 SO«L28 m =,171 m*.l42 m*.l33
@,9 I 2 2J5 3 IS 4 B
SAMPLES * 10 SAMPLES < 18 SO » U7 SO * 1.32 m $.167 m $.186
0 -5 I 0 .5 I 1.5 2 2.5 3 3.5 4
100 SAMPLES*9 SAMPLES"# 90- SO 5 1.28 SO* 1.20 m ’.IS) m$.l 57 80- 70- 60- % 50- 40- 30-
2 0 - 10 0 0 FIGURE 10
HISTOGRAMS SHOWING AVERAGE GRAIN-SIZE DISTRIBUTION IN THE DE CHELLY SANDSTONE
Histograms showing average grain-size distribution in parts of the De Chelly Sandstone as determined from a summation of analyses made of samples taken from the part represented. Median diameter, sorting coefficient, and number of samples are also indicated. Solid part shows percentage retents on each screen, whereas the other grouping is by Wentworth grade divi sions.
A. BLACK CREEK CANYON - Black Creek Member.
B. CANYON DE CHELLY - Large- to medium-scale cross- stratified sandstones in White House Member.
C. MONUMENT VALLEY, WESTERN - Large-scale cross- stratified sandstones from White House Member.
D. MONUMENT VALLEY, EASTERN - Comb Ridge area, large-scale cross-stratified sandstones from White House Member.
E. WHITE HOUSE MEMBER - Horizontally stratified sand stones.
F. BLACK CREEK MEMBER.
G. OAK SPRINGS CLIFFS - Upper sandstone.
H. K3N-LI-CHEE, WEST SIDE DEFIANCE PLATEAU - One arcuate set large-scale cross strata, White House Member.
L . OAK SPRINGS CLIFFS - Hunters Point Member. 100- SAMPLES*6 100- SAMPLES*5 SAMPLES>4 ao« S0*L22 90- SO % 1.26 SO s 1.17 m=.l8l m*.l30 m = .187 eo- 60 7 0- 70- 60- 60- 50- 50 40- 40- 30- 30- 1 20- 20- 10- I 0- IJL 0 5 15 2 25 5 15 4 A B
100- SAMPLES =3 SAMPLES «6 SAMPLES=10 90- SO * U4 S O *1.66(4) SO = 1,26 m =.149 m *.120 (5) m 2.1 35 8 0- 70- 60- ■ 50- 40- 30- 20-
10- 0- 0 .5 I 1.5 2 25 .5 I 15 2 25 3 3J54
lOO-i SAMPLES * 7 100 SAMPLES*6 100- SAMPLES=I9 90- SO * 1.19 90- SO = 1.25 90- SO* 1.19 m *,149 m * J76 m2j59 80- 80- 60- 70- 70- 70- 60- 60- 60- 50- 50- 50- 40- 40- 36- 30- 2 0 - p 20 - 10- Ti 10- 0 5 I 15 2 25 3 35 4 0 .5 i/LmIJ52 2.53 3 5 4 0 5 I 15 2 25 3 35 4 S i l t C oarse S o rtin g M edian F ig . C lay Sand In d ex mm.
DeCbelly Sandstone (all samples)------IT 1.2S .161* 8 O.S Upper sandstone---- - — ------ItC 1.21; .170 7 0 .7 Large scale X-stratified sandstones ------Uh 1.21 .170 S 0.1* Horizontally stratified sandstones------l a 1.3 6 .11*1 13 0 .6 White House Member------6E 1.66 .120 21* 1 .0 Black Creek Member------6F 1.2 6 .13S 9 - Bonito Canyon------— - - - - 5f 1.32 .186 9 2 .0 Hunters Point------5Q 1.28 .181 s Oak Springs Cl i f f s------— ------60 1.19 .11*9 s Black Creek Canyon ------6A 1.22 .181 6 Pine Springs ------— — S i 1.2 0 .1S7 8 Nazlini Canyon ------Sh 1.11* .177 U - Canyon DeC belly (X-stratified sandstones) - - - 6B 1.28 .130 10 U.o W. Monument Valley (X-stratified sandstones)- - 6C 1.17 .187 2 T r. B. Monument Valley ( ” n )— 6D 1.12* .31*9 1* T r. Kin-Li-Chee (X-stratified, one set) - — - — 6h 1.25 .176 11 T r.
Lower sandstone (Hunters Point Member)------UB 1.29 .ISO 12 T r. Large scale X-stratified sandstones ------SA 1.2S .171 7 T r. Horizontally stratified sandstones ------SB 1.21* .11*2 12 T r. Small scale X-stratified sandstones ------SC 1.28 .133 H* T r. Bonito Canyon ------SD i.S o .126 21* T r. Hunters Point - - — ------SB 1.17 .167 6 T r. Oak Springs Cliffs ------61 1.19 .159 S T r.
Upper and lower sandstones combined Canyon DeChelly ------liD _ 21 T r. Bonito Canyon ------liE 1 .3 6 .166 12 T r. Hunters Point ------ItF 1.2 2 .171* S T r . Oak Springs C l i f f s ------LO 1.19 .1S6 S T r.
TABLE 2 - SOME TEXTURAL DATA FOR THE DECHELLY SANDSTONE ______("Fig." refers to histogram.)______93 analyses of 125 samples taken from the De Chelly Sandstone. This fig ure suggests that the De Chelly is composed principally of fine sand with a modal size between 0.125 and 0.177 millimeters. The sandstone has a sorting coefficient of 1.25 and a median diameter of 0.164 milli meters. Coarse sand grains, volumewise, are relatively insignificant in the De Chelly, although they are quite eye catching when present* It is thought that the presence or absence of coarse sand grains is not a valid criterion for judging whether or not a particular sandstone is De
Chelly. McKee*s qualitative suggestion that the De Chelly Sandstone contains coarser sand grains than does northern Coconino Sandstone has not been confirmed. In making mechanical analyses of randomly collected Coconino samples from eastern and central Grand Canyon as well as Oak Creek Canyon south of Flagstaff, Arizona, significant quantities of grains larger than 0.5 mm were isolated. Two samples contained 8.7 and 4.8 percent of coarse grains and these were "north ern" Coconino samples. It would seem unwise to consider coarse grains in the De Chelly a unique and distinctive feature of value in considering regional correlations until more complete data are available for evalua tion.
The remarkable uniformity of grain size within the De Chelly
Sandstone, as mentioned by Gregory, is demonstrated by considering the data that represent different parts of the De Chelly. Of the 25 median diameters listed in table 2, only one, that shown for horizontally 94
stratified sandstones in the White House Member, falls outside of the
fine sand category between 0.125 and 0.25 mm, and this by only 0.05
mm. This is not to say that siltstone and coarse-grained sandstone do li not exist in the De Chelly, because they do. However, they are in such
A a proportionately small quantity as to have little influence on the average
median grain size.
Overall, the sandstones that are cross stratified on a large to
medium scale constitute the greatest percentage of the De Chelly. These
average 0.170 mm in median diameter, slightly coarser than for the
formation as a whole. Horizontally stratified sandstones found in the •A Black Creek Member constitute the type next in importance. Figure
10F indicates that these have a median diameter of 0.135 mm, or less
than the average for the sandstone as a whole.
Horizontally stratified sandstones in the White House Member
have already been shown to have average thicknesses much less than .
the horizontally stratified sandstones in the Black Creek Member. The
former (fig. 10E) also contrast in being darker colored, having a wider
range in grain size with more coarse grains as well as a higher silt-
clay content than the latter.
Data gathered indicate a somewhat coarser median diameter
for the upper sandstones in sections along the east flank of the Defiance
Plateau. These belong largely to the Black Creek Member. Sandstones
of the Black Creek Member tend to be more conspicuously silicified, a i;< 95 phenomenon that results in grain enlargement. It is very probable that the. greater median diameter indicated is, at least in part, a response to secondary silicificaticm.
The Hunters Point Member consists of sandstones both hori zontally stratified and cross stratified on various scales from very small to large. At Hunters Point and Oak Springs.Cliffs this unit is well developed and consists of well-sorted clean sand with a median diameter close to 0.160 mm. However, this same member at Bonito
Canyon and at Canyon de Chelly is not as well sorted, largely because of increasing silt-clay content in the form of silty sandstone units, especially at Bonito Canyon. The larger scale cross-stratified sand stones of the Hunters Point Member (fig. 9A) have an average grain size similar to those of the large-scale cross-stratified sandstones of the White House and Black Creek Members (fig. 8H).
In summary, the De Chelly is a well-sorted fine-grained sand stone that displays considerable overall uniformity. Horizontally strati fied sandstones of the White House and Black Creek Members have con trasting textural characteristics that suggest possible differences in modes of deposition.
In some localities, especially along the southeastern flank of the Defiance Plateau, the Hunters Point Member is a sandstone unit that has textural characteristics not greatly different from those found in the upper sandstones. 96
It is important to recognize that secondary processes can and do affect primary grain size and formational texture. It is difficult to make meaningful textural comparisons between imaffected sandstones and those that have been subjected to a.secondary process such as silicification.
Grain Roundness, Shape, and Surface Characteristics
Quantitative studies were not made of roundness and shape of sand grains in the De Chelly Sandstone. Many of the samples provided by mechanical separations have been examined qualitatively for general characterization of these features.
Roundness is related to the relative angularity of a sand grain, whereas shape is related to the relative lengths of the three axes of solids that describe width, thickness, and height. Such geometrical terms as oblate, tabular, disc, equant, bladed, and prolate can be used to describe basic shapes. Any of these basic shapes can vary a great deal in roundness and still retain the basic shape. . It is much easier to produce roundness than it is to change.one basic shape.to another; there fore, shape is controlled largely by particle form as determined in source rocks.. Roundness, on the other hand, can reflect history be tween particle release from a source rock and final deposition.
Secondary processes, whether constructional or destructional, that occur after sand deposition modify primary roundness and shape 97 characteristics. - Silicification or secondary enlargement of quartz grains, when well developed, masks primary characteristics. In such cases primary grain aspects can be observed best in thin section. Thin sections, however, afford only a two-dimensional study; therefore, shape determination is restricted.
Sand grains in the De Chelly Sandstone were deposited as rounded to well-rounded grains, with the exception of micas and certain heavy minerals, such as zircon and tourmaline. Micas are very dif ficult to round because of elastic properties. Zircons and tourmalines occur both as near euhedral prismatic crystals and as perfectly rounded forms, suggesting that more than one source existed. Well-rounded feldspars, quartz grains, chert, and quartzite fragments indicate that sand grains were in a mature state of abrasion at the time of deposition.
Grain shapes are variable and reflect control of mineral cleav age and possibly source-rock characteristics. .
Quartz grains tend to be irregularly equant in shape with tendencies to be either slightly prolate or oblate, hi a few instances, both rod and flat-disc shapes were noted. Quartzite grains are almost
always nearly spherical. Muscovite and biotite are always disc shaped
owing to perfect basal cleavage. Feldspars, too, are frequently disc
shaped for the same reason, although spherical to prolate shapes were
also noted.
Quartz-grain shapes in the De Chelly Sandstone indicate that 98 the ultimate, source rocks for these grains contained roughly equi- dimensional quartz.
Grain-surface phenomena in the De Chelly Sandstone are of different scales that require both binocular and petrographic micro scope examination. . : f V
De Chelly Sandstone grains that are not covered by secondary quartz overgrowths have surfaces that are markedly cratered, gullied, grooved, or furrowed. These features provide a surface topography on parts of many grains that is smooth, not jagged or angular.
The sand grains exhibit a variability in surface luster. Some appear dull or "frosted” while others are relatively clear and polished.
Feldspars, although opaque, are well polished with smooth surfaces.
Heavy minerals have well-polished bright surfaces. Quartz grains ap pear as "frosted" as well as well-polished grains. Petrographic ex
amination of "frosted” grains demonstrated without exception that the phenomenon was caused by the light scattering effect of myriads of
minute quartz crystals, or. incipient silicification.
The genesis of the various grain-surface features in the De
Chelly Sandstone is known, at least in part, to have been caused by
secondary post-depositions! processes. Certainly "frosting" caused
by silicification is. of this nature. . In the chapter on cementation it is
pointed out that partial solution of some quartz grains has definitely
taken place. The nature of this solution is such as to produce smooth 99 craters, grooves, or furrows on grain surfaces. It is impossible to demonstrate that all such surface features on sand grains of the De
Chelly Sandstone are caused by post-depositional solution, but it is important to raise a question as to what extent grain roundness, shape, and surface characteristics have been modified by post-depositional destructional and constructional processes.
Composition
General Statement
Compositional estimates were made by grain counts in thin sections as well as by loose grain counts under a binocular microscope. : ; Samples were taken largely from the White House, Black Creek, and
Hunters Point Members. A classification method of Folk (1961) is shown in figure 11, indicating that feldspar content ranges from 2 to ' approximately 20 percent, rock fragment and mica content ranges from
2 to 4 percent, with the remainder quartz. These data, according to
FolkEs method, indicate that the De Chelly Sandstone is composed of orthoquartzites and subarkoses. The White House and Hunters Point
Members are subarkoses and the Black Creek Member is an ortho- quartzite. ! 100
Quartz
Feldspar Metaquartzite Mica Q- Qrthoquortzite SA= Suborkose FSG= Feldspathic subgraywacke SG= Subgraywacke A= Arkose G= Graywacke
Figure 11-Classification of the De Chelly sandstone based upon composition. 101
Depositional components
Together, quartz and feldspar account for between 96 and 98 percent of the primary constituents of the De Chelly Sandstone, Many feldspars are altered and soft, so that it is possible that more feldspar was present at the time of deposition. Indeed, it is entirely possible that the orthoquartzites have been generated, in part, by post-deposi- tional destruction of feldspars in what were once subarkoses.
Microcline and plagioclase appear to dominate the feldspar group. This may well be caused by the comparative difficulty of iden tifying orthocla.se in thin section. On the other hand, the feldspars, as a group, are rather easily distinguished from quartz when viewed under binocular microscope; however, they are difficult to classify specifical ly by this method.
Feldspars show a wide range of states of alteration varying from water clear, glassy, fresh forms to cloudy, soft, altered grains with skeletons of less-altered material. The feldspars are found in the same grain-size ranges as quartz, although feldspar percentage relative to quartz increases in,sizes under the maximum grain size in any given sample (pi. 35).
Quartz is the dominant constituent in the De Chelly Sandstone ranging from about 86 to 96 percent of the primary grain content. There
is considerable variation in extinction of individual grains ranging from PLATE 35
FELDSPARS IN THE DEC KELLY SANDSTONE
Figure 1. —Microcline (center) in a sample taken from the Hunters
Point Member at Oak Springs Cliffs. Note size of grain
compared to quartz grains.
Figure 2. —Plagioclase (center) grain in a sample taken from
the White House Member in Canyon de Chelly.
103 straight to extremely undulose; however, the vast majority show some development of undulatory extinction. It is quite clear that, with the exception of uncommon metaquartzite fragments, each quartz grain is a single crystallographic unit and not a composite of two or more dis tinct units.
There are two types of inclusions in quartz—rutile needles and dusty streaks and (or) microlites that very often appear to be zircon, tourmaline, or mica. Many grains do not have conspicuous inclusions.
It is to be noted that feldspars frequently contain microlites similar to those seen in quartz.
Taken together, quartz and feldspar characteristics suggest that these grains were derived from crystalline source rocks, probably largely granitic in nature.
Recognizable rock fragments constitute less than 2 percent of the primary grain content and these are restricted to the most durable
siliceous types, chert (pi. 36, fig. 1) and metaquartzite. These grains
are usually very well rounded and equant in shape. Though in small quantity, these siliceous rock fragments are found throughout the De
Chelly Sandstone.
Mica, although restricted in quantity in the well-sorted sand
stones, is also widespread in occurrence. It tends to concentrate in
the thin, flat-bedded, water-deposited silty sandstones that occur in
the.White House, Fort Defiance, and Oak Springs Members (pi. 36, PLATE 36
CHERT AND MICA IN THE DE CHELLY SANDSTONE
Figure 1.—Large chert grain in sample taken from White House
Member of the De Chelly Sandstone. Near Comb Ridge
in eastern Monument Valley, Arizona.
Figure 2. —Mica (center) in dark silty sandstone sample taken
from Oak Springs Member of the De Chelly Sandstone,
Canyon de Chelly. Note chip-like angular quartz grains, 104 105 fig. 2).
It is not unusual to find that mica, both biotite and muscovite, constitute the coarsest particles in many of the White House Member sandstones in the Defiance and Monument Valley areas. In such cases there may be but 5 or 10 flakes on the screen above the coarsest quartz grains. Muscovite predominates over biotite. Many of the large micas tend to form books that have not been torn completely apart, either naturally or by the disaggregation process preceding mechanical anal ysis. Mica grains are up to 2 mm in largest dimension in otherwise fine-grained sandstones.
Primary clay minerals have not been recognized in the well- sorted sandstones of the De Chelly, although they probably occur in the finer grained silty sandstones found in each member.
. Heavy minerals constitute the remaining class of detrital con stituents that has been recognized. As a group they form much less than 1 percent of the rock. Representatives are dominated by the most durable of heavy minerals, tourmaline and zircon. In the darker sand stones of the White House Member, metallic iron oxides frequently make up over half of the heavy suite. These are invariably only weakly mag netic and many are now hematite. Partial alteration to a .white por- cellanic substance suggests that ilmenite is present and is altering to leucoxene. In the orthoquartzites, metallic iron oxides are rare. This is partially suggested by the prevailing very light colors seen in the 106
orthoquartzites of the Black Creek Member. However, opaque heavies
are present as what appear to be leucoxene grains.
Zircon occurs as colorless and pink grains that vary from
rounded prismatic to spherical. Elongate zircons frequently exhibit
two-dimensional euhedralism, while others are rod-like but very well
rounded on the sides and ends.
Tourmaline habit is similar to zircon, except that a greater proportion of tourmaline is anhedral, elliptical to circular.
Post-depositional components
Substances formed or emplaced after deposition of detrital com
ponents are limited to available open spaces. The bulk of the sandstones
are believed to have been deposited initially with a minimum of matrix
material, thus providing ingress and egress of circulating fluids as well
as potential storage space for newly formed components, which include
quartz, carbonates, clay and micaceous minerals, and iron compounds.
Some of these are considered in more detail in the section on cementa
tion; ;
"Clays" in the De Chelly Sandstone have been mentioned in the
literature. Gregory (1917, p. 33) mentions that "light-colored specks
of kaolin are present in the hand specimen and in places give the rock
an appearance of a mixture of salt and cayenne pepper."
McKee (1934, p. 224) states: "The sand grains of the DeChelly 107 sandstone are rounded in shape and composed of white quartz, red quartz, and kaolin The white quartz and the kaolin are found through out the formation both in Canyon DeChelly and in canyons where it occurs to the south. Since kaolin is of a negligible amount in the true Coconino sandstone, its presence or absence in a sand sample makes an excel lent criterion of relationship."
Neither Gregory or McKee indicate that "kaolin'*- was identified by use of standard techniques used in identification of clay minerals. It is true that clots of a white pulverulent substance are quite conspicuous against the darker background of sand grains coated with ferruginous material such as characterizes the White House Member. In most cases these conspicuous concentrations take the shape of a void space
(pi. 37). These are not to be considered as kaolin "sand" as suggested by McKee. Highly clouded and altered feldspars in the sandstone produce a similar looking material when crushed. However, the fact that the white clots take the shape of the. container is strong evidence that the material was either mechanically redistributed after formation or formed where it is by chemical processes. In any event, the clots are
considered to have been emplaced after deposition of the sandstones.
In regard to McKeets statement that "kaolin" is negligible in the true
Coconino sandstone I have seen this phenomenon well developed in
Coconino sandstone over a wide region. The Coconino is much lighter
in color than the White House Member of the De Chelly Sandstone; PLATE 37
SERICITE-LIKE "CLOTS" IN THE DE CHELLY SANDSTONE
Figure 1.—Sericite-like concentration in sample of the .White
House Member taken from near Kin-Li-Chee, Arizona,
This material was probably formed and (or) emplaced
after deposition of the sandstone.
Figure 2 ,—Similar to above. Sample from Hunters Point Mem
ber collected at Oak Springs Cliffs, east flank of the
Defiance Plateau,
109 consequently the white clots are not nearly so conspicuous* However, binocular-microscope study reveals that they are as characteristic of the Coconino Sandstone as they are of the De Chelly Sandstone. The value of "kaolin" as a "criterion of relationship" is to be questioned in this instance.
Balk (1954, p. 148) suggests that illite was detected in De
Chelly Sandstone by differential thermal analysis. Jerry Harbour, a
University of Arizona graduate student, kindly ran a differential thermal analysis curve on some of the white, clot-forming material. He con cluded that the material tested was not kaolin. Thin-section study demonstrates conclusively the formation of birefringent micaceous or sericite-like material along solution zones in the White House Member in the Monument Valley and Defiance areas. Similar material is present in similar solution zones in the Coconino Sandstone (pi. 38). These data merely indicate that minerals of secondary origin, other than quartz, do occur and that much of the "kaolin" of Gregory and McKee is of secondary or post-depositional origin.
Folk (1961, p. 91) makes this observation:
In some cases pore space in permeable sandstones is fiUed with vermicular hexagonal stacks of water-clear kaolin, encrusting fringes of chlorite, or montmorillonite, or large flaky sericite crystals, all probably precipitated from solu tion just as salt in a beaker in one of the many manifestations of diagenesis.
It is suggested, then, that the majority of the conspicuous white. PLATE 38
SERICITE-LIKE MATERIAL IN THE COCONINO SANDSTONE
Figure 1.—Development of sericite-like material along a zone
in which solution of quartz grains has taken place.
Note development of quartz overgrowths.
I l l earthy clots found throughout much of the De Chelly Sandstone originated in response to secondary processes not yet well understood*
Iron compounds are most prominent in the darker sandstones.
Gregory (1917, p. 33) states that ”... the prevailing light-red to red- yellow hue of the strata is maintained chiefly by the ferritic pigment which with calcite, constitutes the cement."
McKee (1934, p. 225) states "the cement in the DeChelly is both iron and lime. ” Both authors mention "red” quartz grains.
A discussion of iron compounds is intimately associated with the general subject of color and "red beds. ” It is the intention here not to restate what has previously been written about red beds, but instead to relate observations made of the De Chelly Sandstone.
Binocular and thin-section studies of the darker sandstone in the De Chelly show that "ferritic" material does not constitute a cement in the sense that it fills void spaces and binds grains together. The
"red" quartz grains of the De Chelly appear red because of more or
less ferritic material that tends to occupy minute irregularities found
on surfaces of most quartz grains (pL 39). Only a small percentage of
the surface area of a quartz grain needs to contain ferritic material in
order to give it a reddish color when viewed megascopically.
It is difficult to determine when quartz grains acquired these
surface-coloring agents. In cases where quartz overlays are present
in the darker sandstones of the White House Member, overgrowths PLATE 39
FERRUGINOUS MATERIAL IN THE DE CHELLY SANDSTONE
Figure 1.—Ferruginous material surrounding surfaces of quartz
grains in sample of darker colored White House Member
collected in Canyon de CheUy,
Figure 2. —Lighter colored sample of Black Creek Member show
ing faint ferruginous rims. Collected at Oak Springs
Cliffs. Sample contains well-developed quartz over-r
growths but they are difficult to distinguish in plain
light 112 113 frequently cover ferritic-coloring matter. In other cases the dominant coloring ferritic material covers quartz overgrowths. In the section on cementation evidence is given that suggests that quartz cementation may have occurred early in the post-depositional history of the De Chelly
Sandstone. If this is true, then the acquisition of some ferritic surface matter may have been early. Many modern sand dunes contain a hue of color not unlike that seen in much of the White House Member sand- < stones. Sand grains of modern dunes are colored by pigments that occupy protected positions on grain surfaces. Thus it seems possible that the "red” quartz grains of the De Chelly Sandstone were “red” at the time of deposition. It is interesting to note that fresh water-clear grains of feldspar are not red or otherwise colored by pigment which suggests, that quartz very possibly has an affinity for certain ferritic compounds that feldspar does not have. : v/. 1 :
It is important to differentiate different episodes of ferritic accumulations in sediments. If paleomagnetic studies measure certain magnetic properties of these ferritic-coloring agents, then timing would seem to be important. It is quite clear that the De Chelly Sandstone . has acquired ferritic material in stages, some of which may have been previous to the time of deposition or at least before quartz overgrowths and some definitely later than overgrowth development. Thin sections show that both stages may be well developed or either one alone may be dominant. 114
Cementation
General Statement
Two phenomena tend to bind sand grains together: (1) inter stitial or matrix material deposited with sand grains, and (2) post- depositional introduced materials and effects. Durability of a sand stone is related to the nature and extent of development of binding media.
Any pore-space modification must necessarily affect permeabil ity-porosity characteristics, which in turn affect the ability of a sand- stone to hold or transfer fluids. The De Chelly Sandstone is an im portant aquifer on the Navajo Indian Reservation. Because helium gas is produced from strata believed to be correlative with part of the De
Chelly Sandstone^ permeability of the De Chelly Sandstone may very well influence currently unknown positions of additional helium reserves.
Durability in part influences the extent to which a stone can be used, either as construction stone or flagging.
Gregory (1917) writes that the De Chelly Sandstone is cemented by "ferritic” pigment and calcite. McKee (1934), in contrasting the De
Chelly and Coconino Sandstones, states that the De Chelly Sandstone cement is composed of iron and calcareous materials and the Coconino
Sandstone is characterized by a siliceous (quartz) cement. r
Carbonates
; " : ' : : : , " ; : Although previous workers have emphasized the calcareous nature of the De Chelly Sandstone, the carbonate content as a whole is low. Table 3 shows the carbonate cohtmt of 81 samples taken from four : . ; ; ; . : : , .. : ; :i . different stratigraphic sections in the Defiance area. Of the 81 samples.
35 contain less than 1 percent, and 63 less than 5 percent carbonate. : i i i : : : ' ' : i .... Of the 43 samples taken from large-scale cross-stratified sandstone units, 25 contain less than 1 percent, and 38 less than 5 per i j cent carbonate. The three samples containing 15 to 20 percent carbonate ! are from flat-bedded units.
In all except a few cases, carbonate is not present in sufficient amounts to yield, by itself, a well-cemented rock. Thin-section study
suggests that most of the carbonate is secondary. Evidence includes i fracture fillings and relationships to other secondary features such as quartz overgrowths and iron oxide. Quartz is invariably euhedral f
against calcite (pi. 41, fig. E). Some prominent iron rims are younger
than quartz additions (pL 40, fig. A), and older than calcite (pi. 41,
fig. D). As has been pointed out many times by other workers, euhedral
quartz against calcite may be a replacement feature, thus indicating
that calcite is older than quartz. In this case, however, the absence of
calcite inclusions in quartz, together with relations to iron oxide sug
gest that calcite was introduced after secondary quartz rims were % Carbonate % S ilt and Clay
m DeChelly Stratification te House Member F l a t Hunter1a Point Member -
Bonito Canron Combined Black Creek and Cross-Strat White House Members : Indefinite: F l a t Hunter1 e Point Member Cross-Strat
Hunter1 a Point Black Creek Member I n d e f i n i t e
H unter's Point Member
F l a t
TABLE 3 - PERCENTAGE OF SILT-CU T AND CARBONATE (SOUJBUS) IN 81 SAMPI2S OF THE DEC BELLI SANDSTONE, DEFIANCE PLATEAU H* PLATE 40
SKETCHES OF SOME PETROGRAPHIC ASPECTS— DE CHELLY SANDSTONE i i S
Figure A. Solution (C) and quartz addition (B). Ferruginous rim (dots) interpreted as boundary of original grain. Second stage of ferruginous accumulation coats the secondary quartz.
Figure B. Quartz additions (A*B*) showing development of crystal faces. Exterior contact types are quartz cement against quartz cement and quartz cement against another detrital grain.
Figure C. Interlocking of quartz. Without ferruginous rim s as a reference it is difficult to judge whether the process has been constructive (filling of space by secondary quartz) or destructive (solution of grains at contacts) or possibly a combination of both phe nomena.
Figure D. Construction process dominant.
Figure E. Destruction process dominant. Solution zones con tain ferruginous, argillaceous, and sericitic mate rial.
Figure F. Quartz grains "floating" in carbonate (B), Detached fragments in grain (A) are of similar optical orienta tion and ferruginous rim(?) is in calcite. Irregular nature of other quartz grains is believed to result from both corrosion and a third-dimensional over lap. 117 PLATE 41
SKETCHES OF SOME PETROGRAPHIC ASPECTS— COCONINO AND DE CHELLY SANDSTONES
Figure A. De Chelly Sandstone—Construction and destruction. Grain (A) subjected to both processes. Two stages ferruginous accumulation (dots and dashes). Is boundary between grains (C) and (B) original to either grain? Ferruginous rim (D) not protected by silica addition so actual stage ferruginous material not de termined.
Figure B. Coconino Sandstone, Ashfork, Ariz. —Construction and destruction. Solution zone contains sericitic, argillaceous material. Late stage ferruginous ac cumulation not present,
Figure C. Coconino Sandstone, Ashfork— Construction phe nomena dominant in field.
Figure D. De Chelly Sandstone, lower member, Bonito Canyon— Destruction grain (A) with ferruginous, sericitic, argillaceous material along solution zone (B). Car bonate (C) in pore space believed to be later than solution activity.
Figure E. De Chelly Sandstone, upper member, Bonito Canyon- Silica additions earlier than carbonate (A). Some cor rosion of quartz by carbonate-bearing solutions seems possible. Carbonate-filling fracture outside of field is evidence suggesting carbonate late.
Figure F. De Chelly Sandstone, upper member, Kin Li Chee— Destruction by solution activity along a stylolite zone. Ferruginous, sericitic, and argillaceous materials distributed along solution zone. Grains A, B, C, D, E, and F are remnants of separate detrital grains. 118 CD f o i > * * • .
. f.)
E F 119 formed.
As Indicated in table 3, the flat-bedded sediments tend to have a higher carbonate content than do the cross-stratified sandstones. In
a few samples, particularly from the Pine.Springs section on the south
ern part of the Defiance Plateau, the phenomenon known as "luster- mottling" can be observed. Thin-section study of such examples shows I that there is unequal concentration of carbonate. The "floating" quartz
grain problem is manifested in areas of high carbonate concentration.
In each such area, carbonate is all in optical continuity. The carbonate
encloses corroded quartz grains that do not often touch one another, at
least in two dimensions (pi. 40, fig. F). An interesting and perhaps
significant question here concerns the age of the carbonate. Is it re
lated to the general environment of deposition of the detrital grains, or
is it of secondary origin? The flat-bedded sandstones, frequently silty,
in which carbonate of this type occurs are probably subaqueous deposits,
thus introducing the possibility of contemporaneous or near contempo
raneous deposition of carbonate and detrital constituents. If this is the
case, then the possibility exists that at some place laterally distant,
calcareous sandstones might grade to limestones. However, it is not
possible to test this possibility by outcrop tracing.
Although there are numerous ramifications to this problem, it
is thought that the carbonate is secondary and that it is not directly
related to the environment of deposition of the sandstone. The reason 120 for this opinion is that, other than the corrosion effects, which could still have been produced in the environment of deposition, infrequent secondary units of quartz cement appear to be earlier than the carbonate which surrounds them because of the lack of carbonate inclusions in secondary quartz. It is suggested that replacement of quartz by car bonate is largely responsible, for the production of these "floating" grains. In such strata carbonate very effectively reduces pore space to a minimum. It is suggested that if this phenomenon is widespread in any given unit, then it might serve as a permeability block for either upward, downward, or laterally moving fluids.
Quartz
Although not recognized or emphasized by previous workers, quartz cement, developed in varying degrees, is the most important single cementing agent in the De Chelly Sandstone. It shows its best development, as a rule, in the very light colored sandstones that form the Black Creek Member, as well as the light-colored sandstones that make up parts of the Hunters Point Member. The darker White House
Member shows considerable variation in the extent of development of quartz cement, being poorly developed at Canyon de Chelly but well
developed in many of the sand units at Nazlini Canyon and in western
Monument Valley. -
Quartz cementation is of considerable interest because the 121 prevailing light-colored Coconino Sandstone of the Grand Canyon and
Mogollon slope provinces is characterized by quartz cement, The ob served development, whether in outcrop or drill-hole sample, of quartz cement throughout the vertical and areal extent of the Coconino Sand stone suggests a striking uniformity of conditions of cementation. How ever, such uniformity of development is characteristic of only a part of the De Chelly Sandstone. Whether or not the differences in cementation of these sandstones is a legitimate criterion to be used in correlation would seem to depend upon an evaluation or understanding of the factors that control the position and degree of development of secondary quartz.
If it can be demonstrated that characteristics present at the time of deposition exert a basic control on the development of quartz as a ce ment, then the presence or absence of well-developed secondary quartz could become a valid criterion of relationship.
Quartz cement is present in the De Chelly Sandstone as en largements on detrital quartz grains with which they are in optical con tinuity. It constitutes the dominant cement in the majority of sandstones that are well indurated, and small amounts of quartz cement occur in almost all sandstone units. ' ' .
The development of quartz overgrowths is a chemical phe nomenon in which solution, transportation and migration, and deposi tion of silica are influenced by internal physical factors related to void
space and permeability. Externally applied forces that may influence 122 quartz growth relate to stress and temperature effects. Major questions
concerning quartz overgrowth include: (1) source of silica, (2) distance
of migration, (3) causes of precipitation, (4) time of deposition, and (5) possible related or associated phenomena. Unequivocal answers to
these questions are impossible at this time; however, an attempt will be made to describe phenomena observed in the Be Chelly Sandstone
that may significantly bear on some of these questions.
Thin-section study of samples of the Be Chelly Sandstone in
dicate that quartz is the earliest of the cementing media. Waldschmidt
(1941) concludes that quartz is the earliest cement in several sandstones
of the Rocky Mountain region. An approach to the consideration of timing
of cementation can be made through interpretation of features observed
along the upper contact of the Be Chelly Sandstone in various parts of
the Monument Valley area and at Canyon de Chelly on the west flank of
the Defiance Plateau. At all of these localities which were visited, the
upper contact is erosional. Plate 42, figure 1, shows rounded blocks
of the Be Chelly Sandstone incorporated into the Trlassie Shinarump
Conglomerate. Furthermore, the Be Chelly Sandstone was undercut
along one side of the channel (pi. 42, fig. 2). That such an overhang
was maintained, and the De Chelly Sandstone boulders could form, is
strong evidence that the sandstone had acquired a cement before the
cutting of the channel at this locality. In the Monument Valley area
such emphatic evidence was not observed. However, minor details PLATE 42
EVIDENCE OF PRE-SHINARUMP CONGLOMERATE INDURATION OF DE CHELLY SANDSTONE
Figure 1,—Boulders of White House Member sandstone in channel
filled with Shinarump Conglomerate. Note stratification
in sandstone boulders. White House Trail, Canyon de
Chelly National Monument.
Figure 2 .—Contact of Shinarump Conglomerate with White House
Member. Cross stratification dips into channel. This
contact actually overhangs, but this feature does not
show in photograph. Same locality as above.
124
(pi. 43) along the upper contact suggest that some induration had de veloped before the deposition of the overlying unit.
That some cementation had taken place in the De Chelly Sand stone prior to the deposition of the overlying units is demonstrated.
Perhaps it would be unwise to conclude, because quartz is the earliest cement recognized, that this very early cement was quartz. However, such a conclusion is a strong possibility. Because there is no known regional evidence for widespread removal of Permian deposits younger than De Chelly Sandstone, it is suggested that early cementation was effected relatively near the surface, if not when De Chelly sediments were actually at the surface.
Perhaps the most fundamental and most controversial question regarding cementation of a sandstone by quartz is the source of the silica—is it or is it not indigenous to the sandstone in which it is found?
Several writers have suggested that quartz cement can be and often is derived by the phenomenon known as "pressure solution" at points of detrital quartz grain contact. Waldschmidt (1941) thought that much of the quartz cementing sandstones that he studied was indigenous.
However, Pettijohn (1949) objects to Waldschmidt^s interpretation of thin sections and seems to suggest that the silica was probably intro
duced from outside sources.
What is the nature of the evidence such that two workers come
to contrasting conclusions? Basically, Waldschmidt*s evidence for an PLATE 43
UPPER CONTACT OF WHITE HOUSE MEMBER OF DE CHELLY SANDSTONE, MONUMENT VALLEY AREA
Figure 1. —Hoskinnini Member of the Trlassie Moenkopi Forma
tion in irregular erosional contact with underlying cross-
stratified De Chelly Sandstone,
Figure 2 ,—Hoskinnini Member of the Triassic Moenkopi Forma
tion in irregular erosional contact with underlying cross-
stratified De Chelly Sandstone. 125
~ X .. N
2iX>^ "
. 126 indigenous origin is the conclusion that detrital grains, as seen in thin section, have become intimately interlocked, a feature that requires some solution of quartz grains. If dissolving of quartz is demonstrated, then reprecipitation of quartz in pore spaces is a distinct possibility.
Pettijohn, on the other hand, thinks that the observed interlocking is the result of the mutual interference of the secondary overgrowths and not interlocking of detrital quartz grains. He concludes that there is more quartz cement than can be explained by the limited development of valid detrital grain penetration. Pettijohn^s conclusion, then, is that the majority of quartz that forms overgrowths must have been in troduced from the outside#
The critical point seems to be the recognition of what is and what is not detrital quartz. Plates 40 and 41 are sketches of phenomena observed in thin sections of samples from the Coconino and De Chelly
Sandstones. These sketches emphasize that quartz is involved in both constructional (cementation) and destructional (solution) processes.
Either cementation or solution may dominate a given field or they may be of approximately equal importance (see also pis. 44 and 45). These sketches emphasize the variety of internal contact types that may be encountered, as well as the frequent difficulty of recognizing original grain boundaries. In the De Chelly Sandstone a tendency is noted that contacts between overgrowths are often boundaries between two crystals.
There seems to be little tendency for the overgrowths to become PLATE 44
PHOTOMICROGRAPHS OF SOME SECONDARY EFFECTS IN THE DE CHELLY SANDSTONE
Figure 1.—Development of quartz overgrowths in optical con
tinuity with detrital quartz grain nuclei!. Construc- ' tion process. Note regular nature of the contact be
tween two adjoining secondary overgrowths. From
Hunters Point Member of the De Chelly Sandstone.
Figure 2. —Solution of detrital quartz grains. Destruction
process. Some suggestion of a jigsaw-puzzle effect,
but the pieces of the ’’puzzle” are apparently not in
direct contact. From White House Member of the
De Chelly Sandstone near Kin-Li-Chee. (lOOx) 127 PLATE 45
PHOTOMICROGRAPHS OF SOME SECONDARY EFFECTS IN THE DE CHELLY SANDSTONE
Figure 1. —Development of quartz overgrowths. Construction
phase dominates the field. Hunters Point Member of
the De Chelly Sandstone. (40x)
Figure 2. —Lack of overgrowth development. Irregularity of
grain surfaces and shapes caused by post-depositional
solution. Destructive phase dominates the field.
White House Member of the De Chelly Sandstone,
Canyon de Chelly. (40x)
129 mutually interlocked in a complicated manner. It is suggested that
complicated boundaries are most likely to exist between two detrital quartz grains (pi. 44) as a result of solution.
Stylolites
As far as known, stylolites have not been previously reported in either the De Chelly or Coconino Sandstones. In the course of routine thin-section studies, examples of microstylolite development were ob
served in both the.Coconino and De Chelly Sandstones (pi. 46). Un fortunately, it has been impossible to make an exhaustive study of this phenomenon so as to find out just how widespread stylolites are in either
of these two sandstones.
Heald (1955 and 1959) has collected many examples of stylolite
development in sandstones of diverse ages and locations, and has well
summarized the possible significance and implications of this feature.
The direct, immediate importance to the subject of cementation in the
De Chelly Sandstone is that the recognition of the fact that detrital quartz
can and is dissolved along stylolite seams lends credence to the pos
sibility of indigenous quartz cement.
The microstylolite seams observed in the De Chelly Sandstone
have amplitudes measurable in fractions of a millimeter. In outcrop
these seams are manifested parallel to cross lamination by a zone
darker in color than the enclosing sandstone and no thicker than an PLATE 46
PHOTOMICROGRAPHS OF SOME SECONDARY EFFECTS IN DE CHELLY AND COCONINO SANDSTONES
Figure 1. —Solution zone in center of picture. Destructive phase*
Constructive phase not developed. White House Mem
ber of the De Chelly Sandstone near Kin-Li-Chee.
(10x)
Figure 2. —Coconino Sandstone near Ashfork, Arizona, showing
both destruction and construction in same field. Note
birefringent sericite-like material that has collected
in the solution zone. This is interpreted to be post-
depositionaUy formed and not an insoluble residue. *
130
u \
131 individual lamination. Lamination is manifested by changes in grain size from lamina to lamina; stylolites may occur in the zone between two adjacent laminae containing coarser and finer detrital grains. Such an orientation as has been described above immediately suggests that permeability is important to a consideration of stylolite genesis.
It seems to be customary to say that stylolites are caused or formed through “pressure solution." Heald (1955, p0 104) states that he uses "pressure solution" to describe the process by which stylolites are formed because of previous usage in this context in the literature.
It appears as though there is much room for discussion of the absolute role that pressure of any type plays in the formation of those stylolites whose orientation is closely controlled by basic stratification. There are so many variables and aspects to consider beyond that of pressure that it does not seem wise to arbitrarily make "pressure solution" the main mechanism for the formation of such stylolites. Such a procedure r elegates other factor s to lesser roles without a hearing.
Heald (1959) attempts to demonstrate that clay partings pro moted "pressure solution" in some of the sandstones that he studied.
Most writers on the subject report that argillaceous material is usually found intimately associated with stylolite seams. Such material 1ms usually been viewed as being an insoluble residue and not a primary accumulation at the time of initial deposition of the sediment (pi. 46, fig. 2). 132
Microstylolites observed in the De CheUy Sandstone are viewed as zones of relatively Intense chemical action in which some ferruginous- argillaceous and micaceous materials have either formed or been posi tioned after the initiation of solution of detrital quartz grains. This
conclusion stems from observations illustrated in plate 41, figure F, and plate 46, figure 2. Such relationships suggest the possibility that argillaceous and micaceous materials are secondary in origin and not repositioned primary constituents. .
Regional Correlation
Exposures of Permian sedimentary rock sequences on the
Colorado Plateau are limited to structurally high areas where erosion has removed younger sedimentary rocks. The scattered occurrences
of these exposures coupled with differences in stratigraphic-lithologic
details create basic questions of correlation (pi. 1, in pocket).
Various authors have recorded their ideas concerning Permian
correlations between Grand Canyon, Monument Valley, Mogollon Rim,
Defiance Plateau, and the Zuni Mountains of central western New
Mexico.
Baars (1962) and Read (1961) have provided the most recent
works that treat regional Permian correlations between the Defiance
Plateau, Monument Valley, Zuni Mountains, Grand Canyon, and
Mogollon regions. These men do not agree as to the position of the De 133
Chelly Sandstone in the regional stratigraphic framework.
Although Baars desires to simplify or unify the seeming con fusion of Permian nomenclature, his attempts to do so have left the De
Chelly in a state of chaos. He adds; confusion for those who have some knowledge of previous work on the De Chelly.by his failure, to relate his - ' '. ideas and nomenclatural changes to previously published subdivisions of the De Chelly Sandstone. U ‘
On the east flank of the.Defiance Plateau Baars (fig. 12) re stricts the name De Chelly to Read’s lower member of the De Chelly
Sandstone and the Hunters Point Member of the De Chelly Sandstone of this paper. He refers Read’s San Ysidro Member of the Yeso Forma tion (formerly called "transition” by Read) and the Oak Springs Member of this paper to the Yeso Formation. However, he considers that the
Yeso is not present in Canyon de Chelly, but-that its stratigraphic posi tion would be above the .White House Member. Read, oh the other hand, recognizes the strong probability that the central red bed (Oak Springs
Member of this report) in the Canyon de,Chelly section* is actually con tinuous with the Yeso extension of Baars, • and, therefore, that the White
House Member of the De Chelly Sandstone (this paper) or Read’s upper member of the De Chelly Sandstone is younger than Baars’ Yeso exten
sion (fig. 12). That this is at least partly true is demonstrated by re
lationships at the. Oak Springs section where unequivocal White House
Member sandstones overlie the thickest known "Yeso" section on the DEFIANCE PLA1FEAU - ARIZONA NEW MEXICO CANYON DE CHELLY OAK SPRINGS BONITA CANYON HUNTERS POINT ZUNI MTNS. BAAR'S 1962 CLIFFS SAN ANDRES / SAN ANDRES GLORIETA GLORIETA _ DE CHELLY GLORIETA \j YESO YESO YESO DE CHELLY DE CHELLY DE CHELLY
UPPER DE CHELLY UPPER DE CHELLY SAN ANDRES UPPER DE CHELLY UPPER DE CHELLY \ % m z SAN YSIDRO SAN YSIDRO GLORIETA NOT NAMED . . • X A o LOWER DE CHELLY LOWER DE CHELLY LOWER DE CHELLY LOWER DE CHELLY SAN YSIDRO rn (A ; ' • -r m ; ' MESETA " ' BLANCA. - ■ • % l : • » ‘ /• .
FT. DEFIANCE o O 2 v m z . BLACK CREEK om BLACK CREEK m SAN ANDRES BLACK CREEK ; ■ v. H WHITE HOUSE X \ 5 o 9 s X m m f m m r WHITE HOUSE r r WHITE HOUSE GLORIETA Q OAK SPRINGS OAK SPRINGS OAK SPRINGS < (0 5 % HUNTERS POINT U) to (/) SAN YSIDRO HUNTERS POINT (/) HUNTER'S POINT t o HUNTERS POINT m x - MESETA BLANCA
FIGURE 12-CORRELATION CHART - DEFIANCE PLATEAU TO ZUNI MOUNTAINS. COMPARING BAAR'S, READ, AND THIS PAPER. 134 / 135
Defiance Plateau, Baars, not recognizing this relationship, considers all of the sandstones above the "Yeso" on the east flank to be an exten
sion of the Glorieta Sandstone of the Zuni Mountain region, and, there fore, that the Glorieta Sandstone is separated from his De Cbelly Sand
stone by the Yeso Formation. However, it has been shown (this paper) that the Black Creek Member (Baars* Glorieta Sandstone) directly over lies sandstones of the White House Member at Oak Springs Cliffs and at
Bonito Canyon. Read merely refers the sandstones above the "Yeso" to the upper De Chelly and considers them laterally equivalent to the
Glorieta Sandstone of the Zuni region. . Read has not recognized that his upper member contains two distinct sandstone phases.
Baars considers the "De Chelly" (Hunters Point of this paper) to be equivalent to the Meseta Blanca Member of the Yeso Formation.
The Hunters Point Member of the De Chelly Sandstone forms only a part of Baars1 undivided De Chelly Sandstone at Canyon de Chelly but
constitutes all of his De Chelly on the east flank.of the Defiance Plateau.
Read, on the other hand, does not believe that the Meseta Blanca
Member of the Yeso Formation extends to the Defiance area, and that if
it did its correlative would occupy a stratigraphic position below Baars6
De Chelly or the Hunters Point Member of the De Chelly Sandstone of
this paper. This interpretation is based upon: (1) the relative positions
of the lower De Chelly above and the Meseta Blanca below limestone
units present in the Defiance and Zuni areas thought to occupy similar 136
stratigraphic positions, and (2) the rapid pinchout or facies change of the lower or Hunters Point Member between Oak Springs and Black
Creek Canyon.
These factors, not considered by Baars, suggest that a direct
correlation of any part of the De Chelly Sandstone with the Meseta Blanca
of New Mexico is, at best, highly speculative.
Baars1 consideration that all of the De Chelly Sandstone is older
than the Yeso extension is a fundamental misinterpretation of consider
able magnitude, because the error is perpetuated throughout Arizona
and leads to highly questionable correlations.
Read and the present author are in close agreement. The only
objection to Readts correlations is the straight-line equivalence sug
gested between Glorieta Sandstone and all of the sandstones of the De
Chelly above"Yeso" red beds. This author allows equivalence to be
drawn only with the Black Creek Member of the De Chelly Sandstone.
Baars does not recognize a Coconino Sandstone in the Defiance
or Monument Valley areas. Considering the Glorieta and Coconino
Sandstones equivalents he concludes that the De Chelly Sandstone is
also older than the Coconino Sandstone, the latter overlying the De
Chelly Sandstone directly in the subsurface of north-central Arizona
but separated from it by "Yeso" in the Mogollon Rim and Oak Creek
Canyon areas. Here again the White House Member of the De Chelly
Sandstone overlies, not underlies, "Yeso" red beds. As a consequence 137 of this relationship the White House Member sandstones and the Coconino
Sandstone of the Mogollon Rim area are brought into a closer relation ship than Baars suggests. From available data it is possible to consider that a Coconino Sandstone directly overlies a De Chelly Sandstone in the ’ . * subsurface of north-central Arizona as Baars suggests. However, if this is true, then it is strongly suggested that Baars8 north-central
Arizona De Chelly Sandstone is not continuous with his Oak Creek
Canyon and Mogollon Rim be Chelly Sandstone. It is suggested that the latter "De Chelly*' interval is considerably lower, stratigraphically, than the north-central De Chelly interval.
A final, unequivocal statement as to the absolute relationship between the Coconino-De Chelly Sandstones is not yet possible because they cannot be traced into one another. However, as a result of the work done for this report, it is thought that the nature of the problem has been clarified. Available data suggest that the White House Mem ber and the Coconino Sandstone are either: (1) continuous, one into the other, or (2) the Coconino directly overlies, at least locally, the White
House Member of the De Chelly Sandstone but with unknown lateral re lationship (fig. 13).
That the apparent relationship between the two is close is in dicated by the willingness of some to call the De Chelly Sandstone in
Monument Valley Coconino Sandstone. Seemingly, all that remains to be done to prove that such continuity exists is to be able to see into the •WHITE OF
SANDSTONE
1. Grand Canyon 2. Sinclair Tribal No.I 3. Monument Volley 4. Canyon De Ch'elly 5. Oak Springs Cliffs 6 Zuni Mountains 7. Magadan Rim
Figure|3-Correlotion of prominent Permian sandstones of northeastern Arizona with White House and Block Creek members of the De Chelly Sandstone. 138 139 subsurface so as to trace these sandstones into one another. Doubts as to exact relationship are based upon the fact that the outcropping sand stones are not overlain by similar lithologic or formational entities nor are the detailed relationships established between the underlying units.
Experience with Permian stratigraphy indicates that sandstone bodies can and do pinch out or change facies over short lateral distances; con sequently, subsurface extensions based upon a minimum of information could prove to be faulty.
The problem of the relationship between these sandstones in volves the interpretation of the significance of basic data concerning their textural, compositional, sedimentary structural, and cementational characteristics. Because reliance for critical data must be placed upon future drilling, a most difficult consideration relates to the recognition of primary and secondary sandstone characteristics or the extent to which primary features have been modified by post-depositional events.
It seems reasonable to conclude that post-depositional history can modify texture and composition. The quantitative aspects of such changes are
subject to study.
It seems possible, then, to encounter a sandstone sequence in
a drill hole the upper half of which is characterized by being light
colored and well silicified (secondary quartz enlargement) and a lower
half that is darker colored and not well silicified. Are they to be in terpreted as two different sandstones or a single sandstone in which the 140 upper half has been modified by post-depositional processes ? This is precisely the situation in the Sinclair Tribal No, 1 hole shown on figure
11. On a strict lithologic basis the two contrasting zones appear to : have the characteristics of the Coconino and De Chelly Sandstones and therefore are shown this way on figure 13. Until the apparent relation ship in this hole is explained it seems necessary to consider that there is a De Chelly Sandstone in western Monument Valley and a Coconino
Sandstone in the Grand Canyon region and that the two overlap in the subsurface at least in the vicinity of this hole. The relationship shown between the Coconino Sandstone of the Mogollon region and the De Chelly
Sandstone of Canyon de. Chelly is influenced by the above, interpretation, together with the fact that this author does not recognize a De Chelly
Sandstone in the Mogollon region nor a clear-cut Coconino Sandstone in the Defiance region.
It is possible.to speculate, on the relationship between the
Coconino and Glorieta.Sandstones on the basis of their possible relation ships to the De Chelly Sandstone.
It has been suggested, in the subsurface to the west of the
Defiance Plateau, that a.Coconino-like sandstone overlies a White House like sandstone of the De Chelly. Relationships on the east side of the
Defiance.Plateau show that the Black Creek Member definitely overlies the White House Member of the De Chelly. These relationships make it possible to consider that the Coconino Sandstone and Black Creek 141
Member occupy similar stratigraphic positions even though there is not a direct connection between the two except, possibly, by way of the sub surface south and west of the southern end of the Defiance. Plateau (figs.
13 and 14), Here the terms Black Creek Member of the De Chelly Sand stone, Glorieta.Sandstone, and Coconino Sandstone merge and seem- ingly occupy an identical stratigraphic position. Unless the sandstones in the subsurface south of the Defiance Plateau contain hitherto unrec ognized subdivisions they will have to remain undifferentiated and no menclature will necessarily be arbitrary. -
Baars correlates the Coconino and Glorieta but considers the
Coconino to be eolian and the Glorieta to be a near-shore marine de posit. It would seem as though the Glorieta Sandstone could be at least partially younger than the Coconino and may actually transgress Coconino in east-central Arizona. It may be that the sandstones assigned to the lower Kaibab Formation of this region represent Glorieta equivalents overlying Coconino Sandstone,
Many details of correlation seem to depend upon determination of the depositional environments of the sandstone units in question. If these formations are to be assigned their proper roles and positions in geological history, it seems highly desirable to learn to recognize eolian, mixed eolian and marine, and marine sandstones. EAST SIDE DEFIANCE PLATEAU
S A N A N D R E S l — BLACK CREEK MEMBER K A I B A B L S WHITE HOUSE GLORIETA-I -----COCONINO SS
HUNTER'S POINT
1 Ook Springs Cliffs 2 Black Creek 3 Pine Springs 4 Water well near Houck 5 Argo State No.2
Figure 14-Correlation chart of upper part of exposed Permian section, east side Defiance
Plateau, southern portion, with subsurface to south. 142 143
Paleogeography
By utilizing regional stratigraphic relationships and the more local relationships within the De Chelly Sandstone, it is possible to re construct a general paleogeographic framework within which the De
Chelly was deposited.
During Permian time the well-known ancestral Uncompahgre highland, a dominant northwesterly trending positive element, extended from east-central Utah southeastward through Colorado and into New
Mexico. The ancestral Defiance positive area, apparently positive throughout much of the Paleozoic era, was covered, as far as is now known, by Permian red beds. However, parts of the Defiance area re- mained sufficiently unstable to affect later Permian sedimentation.
At the beginning of the Permian, as represented in Arizona,
seas that had been present during Pennsylvanian time were retreating
or had retreated from the area that is now the Colorado Plateau, leav ing behind a broad plain with low relief and not far above base level.
Locally, as in the Defiance area, outcrops of granitic and metamorphic
rocks formed topographic highs that acted as barriers to the spreading
out of older Permian deposits. Such evidence as: (1) dominance of
marine Permian in southern Arizona, (2) the presence of marine car
bonates within Permian red beds in the Mogollon slope region, and (3)
the presence of thick evaporites in the Holbrook-St. Johns area, suggests 144 that during Permian time sea margins were not far removed from what is now the southern Colorado Plateau region. Much of the sediment found in.Permian rocks of southeastern Utah, northeastern Arizona, and northwestern New Mexico is thought to have been derived ultimate ly from the crystalline rocks that make up the Uncompahgre positive feature. The Permian bordering the southwest-facing Uncompahgre front is considered a fanglomerate. Further to the southwest the
Permian sequence is differentiated into formations that represent largely detrital sediments deposited in.relatively persistent environ ments that shifted with time.
Each of the five members into which the outcropping De Chelly
Sandstone is divided is conceived to reflect a different or contrasting depositional environment and each, then, is of some significance in at tempting a paleogeographic reconstruction.
Conditions of Deposition
Hunters Point Member
The sandstones of the Hunters Point Member are known to exist only in the Defiance area. They are not present in outcropping closures in Monument Valley to the north and they are not known in sections south
of Oak Springs Cliffs. Read and Wanek (1961) have demonstrated that
the prevailing direction of dip of cross strata in this member is to the 145
southeast, suggesting a current flow in this direction. It is thought that the sandstones were deposited in a relatively high-energy fluvial en vironment that contrasted markedly with the environment in which the
dense limestone was deposited that occurs near, the base of the member
at both the Oak Springs and Hunters Point sections. This limestone is thought to represent an evaporitic phase correlative with some part of the gypsum - halite deposits found in the Supai Formation a few m iles to the south (fig. 12). . ; :
It seems highly probable that the fluvial sands of the Hunters
Point Member were deposited in close proximity to restricted, brackish
or sea water basins to the south in which evaporites and red beds were
accumulating in varying proportions. The sudden loss of the member
between the Oak Springs and Black Creek sections indicates a relative
persistence of the position of some feature that restricted the continuing
lateral development of the fluvial environment to the south. This re
lationship is one that might be explained by a fluvial deposit and an
adjacent flood-plain environment. However, rather than consider it as
a river and associated flood plain, it seems more reasonable to think of
the sands as accumulating in an aggrading delta building to the south
east and that the rapid change reflects the energy change found at right
angles or a flank position to main current trends.
The Hunters Point Member probably extends into the Black
Mesa basin to the west of the Defiance Plateau. As viewed here, it may 146 form a rather narrow belt of sandstone trending in a northwesterly di rection.
In considering a general immediate source area for these sands, it is thought that they were derived from the erosion of previous ly existing Permian deposits. It seems possible to consider that the erosional unconformity evidenced in the Grand Canyon region between the Hermit Shale and the sandstones of the Supai Formation may well represent an erosional period that supplied sandstones that were trans ported to the southeast, at least in part, to be redeposited nearer to base level in an area where more persistent Permian deposition is known to have taken place (McKee, 1951).
Oak Springs Member ' :
The micaceous siltstones and silty sandstones of the Oak Springs
Member reflect a northward transgression of a relatively lower energy environment over the Hunters Point Member. The youngest components of the Hunters Point Member are probably to the north and would be correlative with parts of the Oak Springs Member to the south. The
Oak Springs Member, thickens to the south toward the saline basins.
Red beds of this member have a distinct salty taste, although discrete halite particles have not been observed. 147
White House Member c > ■' -'-v
Wind-transported sands and silts of the White House.Member may have been accumulating in northeastern Arizona during parts of
Hunters Point and Oak Springs time, although direct evidence has not been observed with which to support such an interpretation. One won ders, however, why the.White House.Member thins on the east flank of the Defiance, Eolian deposition in this area might have been restricted by a persisting aqueous environment flanking the southwestward expan sion and movement of windblown sand, Reiche (1938) and Read (1961) each agree that the persistent dip direction of cross stratification in the White House Member is to the southwest in the Defiance area and south to southwest in the Monument Valley area. Sand was picked up ' ■ . . ■ - , 1 . . ... 1 '• V: ■ . - : ‘ r ' from previously deposited unconsolidated materials of the Cutler For mation in Colorado, Utah, and New Mexico and transported in suspen sion and as migrating dune fields during a period of aridity.
Although the northern and southern lim its of the White House
Member are known in the Monument Valley and southern Defiance areas, the northeasterly and southwesterly extents are not known for certain.
If one considers the Coconino Sandstone to be a continuance of the White
House Member, then it can be said that the Coconino Sandstone thins toward the southeastern part of the Defiance Plateau, This author, however, prefers not to make unequivocal correlations at this time for 148 there is evidence that at least two distinct and perhaps three sandstone
entities exist in near juxtaposition in east-central Arizona. The axis
of maximum deposition of the White House Member trends in a north
east-southwest direction from the Four Corners area into the Black
Mesa basin.
Black Creek Member
The Black Creek Member is recognized only on the eastern and
southern portions of the Defiance Plateau for an outcrop distance of
about 30 m iles. As previously pointed out, the sedimentary structural
characteristics of this member contrast with those of the White House
Member. Whereas the White House Member represents dominantly
eolian deposition, the Black Creek Member contains at least 50 percent
sandstones that were deposited in some type of aqueous environment,
These testify to changing environmental conditions regardless of whether
the specific environments are completely understood. Because of the
overlying limestone in the subsurface at St. Michaels, it seems prob
able that some of the sands of the Black Creek Member may represent
near-shore marine deposits. If this is the case then the eastern and
southern flanks of the Defiance Plateau marked the position, in Black
Creek time, of an oscillating shoreline that represents a zone of pos
sible intertonguing of continental and marine sandstones. The large-
scale cross-stratified sandstone units in the Black Creek Member may 4
149 be eolian in origin but conclusive proof for this has not been founds
They might also be near-shore marine structures, but this has not been proved either.
Fort Defiance Member
The Fort Defiance Member was deposited in an aqueous en vironment and is known to occur only over a 6-mile stretch on the east ern flank of the Defiance Plateau.
Its sediments were deposited in a relatively low-energy environ ment such as might exist in a lagoon, tidal flat, or protected embayment of some sort. Its relations to other stratigraphic units are not clear, although it would seem to occupy a stratigraphic position similar to that of the limestone above the Black Creek Member in the subsurface at St,
Michaels.; It may represent, then, a near-shore restricted marine depositional phase.
The contrasts in distribution, lithology, and sedimentary struc ture of the various components of the De Cbelly Sandstone reflect chang ing depositional environments. It is suggested that these changes were influenced by a mildly unstable zone in part coincident with the older
Defiance positive area. It would appear as though this paleogeographie influence is further evidenced by the encroachment of Permian marine deposits from the east and south, whereas to the west such deposits are many miles away. One wonders if this asymmetry in distribution bears 150 any relation to the asymmetry of the Laramide structure that we now call the Defiance anticline.
z.- : SUMMARY
The Permian De Chelly Sandstone, of probable. Leonardian age, can be subdivided into five members, none of which is coextensive with the De Chelly Sandstone as a whole. : Criteria ior distinguishing them are based largely upon sedimentary structural characteristics and lithol ogy. At no place are all five members known to occur together.
On a geographic basis, outcropping De Chelly Sandstone can be divided into four general areas with contrasting stratigraphic habit:
(1) Monument Valley, (2) north portion of the west flank of the Defiance
Plateau, (3) central portion of the east flank of the Defiance Plateau, and (4) the southern Defiance Plateau.
In Monument Valley the De Chelly Sandstone is represented by the White House Member, a sandstone deposited largely as sand dunes that migrated to the south and southwest, coalesced, built up vertically, and accumulated in such a manner as to place the youngest deposits up wind. Pinchout near the.San Juan River in Utah is due largely to non
deposition. Increase in silt content and occasional pebbles on erosion •
surfaces in the Comb Ridge area, are present because of two factors: ;
(1) proximity to source, and (2) minimum reworking.
In the north portion of the west flank of the Defiance Plateau,
151 152 represented by Canyon de Chelly, the White House .Member is underlain by the Oak Springs Member, a dark, micaceous, silty sandstone 45 feet thick, which, in turn, is underlain by the Hunters Point Member. The sandstones of this member, not present in Monument Valley to the north or the southernmost part of the Defiance Plateau, are believed to have been deposited largely in an aggrading fluviatile environment flanking a lower energy environment to the south. . Cross-stratification trends indicate persistent southeast-flowing currents suggesting that this sand stone body is probably elongated in a northwest-southeast direction, and therefore may extend into Black Mesa basin.
The overlying Oak Springs Member thickens southward toward the site of Supai evaporite accumulations. A change in depositional en vironment, perhaps influenced by instability of a part of the Defiance area, allowed sediments of this member to transgress the cross- I stratified sandstones of the Hunters Point Member. Salt-crystal molds and a saline taste suggest brackish-water deposition.
The central portion of the east Hank of the Defiance Plateau is represented by Bonito Canyon, Hunters Point, and Oak Springs. At each of these localities the Hunters Point Member is present/ the White
House Member is thin and is overlain by the Black Creek Member. The
Fort Defiance Member, overlying Black Creek Member sandstones, is present only at Bonito Canyon.
The thinning of the White House Member across the Defiance 153
Plateau is thought to reflect the presence of a persistent moist zone that restricted deposition of eolian sandstones. The Black Creek Member is thought to be composed of a mixture of wind- and water-deposited sands, such that it might be considered a transition unit between dom inantly eolian and dominantly marine or aqueous deposits.
The Fort Defiance Member, known only locally in the Bonito
Canyon area and a few miles to the south, is a red-bed type unit con sisting of alternating siltstones and silty sandstones. It may represent a tidal flat or some sort of restricted near marine environment that is transgressive over the Black.Creek Member, portions of which may be marine or near marine in origin. Indeed, some of the sands, of the
Black Creek Member, the Fort Defiance Member, and the limestone that occurs in the subsurface in the St. Michaels area may all repre sent facies of a San Andres environment that transgressed onto a slight ly positive Defiance region from the east.
In the southern Defiance Plateau region only the Black Creek
Member is present. The Hunters Point Member is absent because of lateral change southward into Supai red beds with resulting coalescence of the Oak. Springs Member with the Supai. Her e, too, a per sistent moist zone restricted development of the White House Member. The
Fort Defiance Member is absent presumably because of nondeposition.
The Black CreekMember curls around the southern end of the Defiance
Plateau so that it or correlatives of it are present in the subsurface to 154 the exclusion of all other members of the De Cbelly Sandstone. In the
structural low south of the Defiance, published stratigraphic charts in
dicate that sandstones correlative with the Black Creek Member are
overlain by limestones. Specific data as to sedimentary structural de
tails are not known for these subsurface sands. They may be totally
marine in origin so that possible continental phases pinched out some
where to the north in the subsurface. The position of these sands with
respect to the overlying marine limestones suggests that the Black Creek
Member may correlate approximately with the Glorieta Sandstone of
New Mexico.
It seems quite well demonstrated that the changing aspect of
the De Chelly Sandstone records an instability in part of the Defiance
region. It is of interest that the marine limestones of the San Andres
Formation approach a position marked by the"steeply dipping east flank
of the present Defiance anticline. On the other hand, marine units as
signed to the Kaibab Formation to the west of the Defiance are many
miles from the axis of the anticline. This asymmetry in the distribu
tion of these Permian marine units might possibly be related to the
asymmetry of the modern Defiance anticline.
. Relationship of the De Chelly Sandstone to the Coconino Sand
stone is speculative. Several lines of evidence suggest that the White
House Member is analogous, if not a direct correlative: (1) both units
approach a zero thickness line along the southern border of Utah, (2) 155 both are eolian deposits, (3) both units rest with sharp basal contact on red beds in the northern parts.of their respective outcrop areas, and
(4) the prevailing dip direction of cross stratification is southerly in both units. Lithologically, the White House Member tends to be darker in color, somewhat more coarse grained, certainly less well indurated or cemented, higher in silt-clay content, and is more feldspathic. These latter criteria are related to properties that may be either inherited at the time of deposition or subsequently;modified by post-depositional or secondary processes. Factors related to sources of detrital materials can affect composition, grain size, and color. It is thought that both the White House,Member of the De Chelly Sandstone and the Coconino
Sandstone had similar ultimate sources in Precambrian crystalline rocks, but that immediate source was from previously deposited
Permian sediments in Utah, Colorado, and New Mexico. The White
House source was in closer proximity to the fanglomeratic material shed from the Uncompahgre highland, whereas the Coconino source was from already differentiated Permian sediments much farther removed from the Precambrian positive area. This author does not subscribe to the theory that the Coconino Sandstone was derived by reworking of
Toroweap and (or) Kaibab Formation beach sand.
The Coconino Sandstone is characterized by the development of quartz overgrowths on detrital grains. This secondary cementation process may well have altered such properties as color, grain size, 156 and composition to such a point that an orthoquartzite might have been produced from a subarkose such as the White House Member of the De
Chelly Sandstone. Although it cannot be finally proved at this time, it seem s likely that the Coconino Sandstone and the White House Member of the De Chelly Sandstone are continuous in the subsurface in northern
Arizona. A more confused picture in east-central Arizona requires that constructive correlations in this area must await more detailed stratigraphic work in the Mogollon Rim region than has been done to date, APPENDIX A
DEFINITIONS OF SOME STRATIFICATION TERMS
(From McKee and Weir, 1953)
STRATIFICATION - The state of being stratified, or layered, the layers being oriented parallel to the original dip of the formation.
CROSS STRATIFICATION - The state of being cross stratified or cross layered, the cross layers being oriented at an angle to the original dip of the formation.
STRATUM ~ The basic unit, or layer, of sedimentation that is oriented parallel to the original dip of the formation.
CROSS-STRATUM - The basic unit, or cross layer, of sedimentation that is oriented at an angle to the original dip of the formation.
SET OF STRATA - The most basic group unit containing conformable strata of similar lithologic aspect.
SET OF CROSS STRATA - Most basic group unit of cross strata having a similar orientation and separated from other sets by surfaces of erosion or nbndeposition, either vertically, laterally, or both.
SUBSET OF CROSS STRATA - A minor set within a larger, more prominent set,
COSET OF STRATA - A sedimentary unit made up of two or more sets of strata.
COSET OF CROSS STRATA - A sedimentary unit made up of two or more sets of cross strata.
COMPOSITE SET - A larger sedimentary unit compounded from smaller stratified and cross-stratified units.
157 APPENDIX B
CRITERIA FOR CLASSIFICATION OF CROSS STRATIFICATION
(After McKee and Weir, 1953, with modifications)
Types of cross stratification: based upon nature of lower bounding sur face of a set of cross strata*
1* Simple cross stratification - Nonerosional
2. Planar cross stratification - Planar surface of erosion
3, Trough cross stratification - Curved surface of erosion
Descriptive terms applied to characteristics of a set of cross strata*
A. Shape
1* Lenticular - set bounded by converging surfaces at least one of which is curved*
2, Tabular - set bounded by nearly parallel planar surfaces of erosion*
3. Wedge - set bounded by planar converging surfaces of ero sion,
B. Scale - based upon lengths of foreset strata (modified for this paper)
1. Very small scale - less than 1 foot
2. Small scale - 1 to 5 feet
3. Medium scale - 5 to 25 feet
4. Moderately large scale - 25 to 50 feet
5. Large scale - 50 to 100 feet
158 159
6» Very large scale - over 100 feet
C. Dip of cross strata
1. High angle - greater than 20°
2. Low angle - less than 20°
D. Arching of cross strata ;
1. Straight ’ ;
2. Concave -X' XX f' X :-X "
3. Convex 7
Types of cosets: refers to nature of arrangement of sets of cross strata within a basic sedimentary unit, (This paper.)
lo Vertical coset of cross strata - A sedimentary unit made up of more than two sets of cross strata arranged in vertical sequence sepa- . rated by inclined surfaces (pi. 23, fig. 2).
2. Lateral coset of cross strata - A sedimentary unit made up of more than one set of cross strata arranged laterally and bounded by near- , ly horizontal surfaces (pi. 19). ;
xx x : < : APPENDIX C
DESCRIPTION OF MEASURED SECTIONS
; v : SECTION A
. South of, Piute Farms, Utah.
Section measured on east side of Monitor Butte about 5 m iles south of Piute Farms and a mile west of the road between Oljeto, Utah, and Piute Farms.
Overlying unit: Triassic Moeniopi Formation Dip of formations: Near horizontal Nature of exposure:- Steep slope - Nature.of contact: Sharp, erosional ;
De Chelly Sandstone: . : ■ . White House Member:
Unit Thickness No, Description . in feet
1 Sandstone: moderate-orange pink, fine-grained, 30 cross-stratified on a large scale, southerly dip to foresets, silicified, sharp contact with unit below.
Total thickness of White House Member, 30 feet,
Cutler Formation: Organ Rock Tongue: ' " ‘ / Siltstone: brown, calcareous, horizontally strati fied, knobby weathering, forms steep slope. . Vertical fractures and bedding control position of very light- color ed leached or bleached zones. It is thought that such phenomena have been misinterpreted, in the past, as being sand-filled shrinkage cracks.
160 161
SECTION B
Oljeto
Complete section measured north of Oljeto, Utah, near Holliday Mesa to east of road from Oljeto to Piute Farms.
Overlying unit: Tf lassie Moenkopi Formation Dip of formation: Negligible Nature of exposure: Steep slope Nature of contact: Sharp and irregular, disconformable
De Chelly Sandstone: White House Member:
Unit ' Thickness No. Description in feet
5 Sandstone: grayish-orange, medium to very fine 156.0 grained, cross stratified on large scale, com plicated vertical coset, portions calcareous, upper portion siliceous cement (quartz overgrowth), oc casional patches of coarse grains, forms steep slope.
4 Sandstone: pale-reddish-brown, fine to very fine 36.0 grained, some mica, structures inconspicuous, slightly calcareous, some secondary silica, forms rounded slope.
3 Sandstone: pale-reddish-brown, fine to very fine 32.0 grained, some mica, cross stratified on large scale, foresets cross unit, one set of a lateral co set, foreset dip 23° S. 15° E ., calcareous with quartz overgrowths, firm to slightly friable, forms rounded cliff.
2 . Sandstone: reddish-brown, very fine grained, silty, 10.0 cross stratified, one set of a lateral coset, slightly calcareous, compact, part of cliff.
1 Siltstone: reddish-brown, structureless, near base 7.0 of cliff.
Total thickness of White House Member, 241.0 feet. 162
Contact with underlying Organ Rock Tongue of Cutler Formation is sharp.
Cutler Formation: Organ Rock Tongue:
Unit Thickness No. . Description in feet
Siltstone:: reddish-brown, micaceous, very tough, knobby weathering. 163
SECTION C
Comb Ridge
Complete section measured on west side of road from Mexican Hat, Utah, to Monument No. 2 uranium mine where this road crosses the De Chelly Sandstone near Comb Ridge. Near Arizona-Utah State line.
Overlying unit: Trlassie Moenkopi Formation Dip of formation: 10° to the southeast Nature of exposure: Dissected hogback Nature of contact: Sharp, disconformable .
De Chelly Sandstone: White House Member: . .
Unit Thickness No. Description in feet
13 Sandstone: pale-reddish-brown, fine-grained, 148.0 coarse grains collect near bottoms of some of the foreset strata, cross stratified, a complicated , vertical coset of cross strata with prevailing south erly dip, small to large scale, friable but with sparkling quartz overgrowths, forms rounded slope.
12 Siltstone: reddish-brown, very fine sandy, base of 7.0 rounded slope, truncates unit below,
11 Sandstone: pale-reddish-brown, fine-grained, cross - 55.0 stratified, very large scale, unit one set of a lateral coset, friable, minor quartz overgrowth, forms rounded cliff. !.
10 Sandstone: pale-reddish-brown, very fine grained, 93.0 silty, cross-stratified on medium to large scale, a complicated Vertical coset, some calcareous ce ment, friable, platy weathering, forms slope.
9 Sandstone: pale-reddish-brown, very fine grained, 28.0 silty, cross-stratified on large scale, a lateral co set, certain foreset units darker and more silty, silty units contain numerous holes, calcareous, forms rounded slope. 164
Unit Thickness No, Description in feet
8 Sandstone: pale-reddish-brown, very fine grained, 80,0 silty, similar to unit No. 9.
7 'Sandstone: reddish-brown, very fine grained, silty, 10.0 cross-stratified on a small scale, calcareous, part of slope. .
6 Sandstone: reddish-brown, very fine grained, silty, 80.0 cross-stratified on small to large scale, a com plicated vertical coset, friable, calcareous, weathers to slope.
5 - Sandstone: reddish-brown, very fine grained, silty, 10. 0 appears massive, may be cross-stratified on a small scale, soft and friable, forms rounded slope.
4' Sandstone: as above, some muscovite, appears to 3.0 be flat bedded, calcareous, forms rounded ledge.
3 Sandstone: reddish-brown, very fine grained, silty, 8.0 cross-stratified on small to medium scale, cal careous, forms rounded ledge.
2 Sandstone: reddish-brown, very fine grained, some 2.0 muscovite, silty, appears flat bedded, some cal careous cement, flaky weathering.
1 Sandstone: reddish-brown, as above, cross-strati- 5.0 tied on a small scale.
Total thickness of White House Member, 529.0 feet.
Contact with underlying Organ Rock Tongue of Cutler Formation is sharp.
Cutler Formation: Organ Rock Tongue:
Siltstone: brown, micaceous, horizontally stratified, knobby weathering, very tough, forms rounded ledge. 165
PARTIAL SECTION D
■ Segi Canyon !
Partial section measured where road to Nokai Mesa crosses De Chelly outcrop. • v v , V
Overlying unit: Triassic. Moenkopi Formation ! Dip of formation: 24° southeast x : . : Nature of exposure: Walls of small canyon • Nature of contact: Sharp and irregular
De Chelly Sandstone: . , ^ C White House Member: ;
Unit Thickness No. Description ; in feet
Sandstone: moderate-orange-pink, fine-grained, 174.0 : cross-stratified on a large to very large scale, an intricate vertical coset, tracks and wind-ripple K : - marks well developed on some foreset surfaces, not calcareous, some quartz overgrowth, rare coarse mica, tends to be friable. r c . ;
Bottom of creek limits exposure.
"' i.: ■ 166
SECTION 1
Canyon de Chelly
Section completed by piecing together measurements made at two localities. Most of the White House Member of the De Chelly Sandstone was measured along the White House Ruin Trail. The Oak Springs and Hunters Point Members, as well as the basal portion of the White House Member, were meas ured on the south wall of Canyon de Chelly just east of the junction with Monument Canyon.
Overlying unit: Triassic Shinarump Conglomerate Dip of formations: Few degrees to west Nature of exposure: Cliff
De Chelly Sandstone: White House Member:
Contact: Near top of White House Trail a pre-Shinarump channel has cut at least 80 feet into the De Chelly Sandstone. The conglomerate contains rounded blocks of De Chelly up to 2 feet in length.
Unit Thickness No. Description in feet
47 Sandstone: pale-reddish-brown, fine-grained, 70 cross-stratified (very large scale), one set of a lateral coset dipping 23° S. 40° W ., friable quartz cement, forms cliff, tangential to unit below.
46 Sandstone: similar to unit above, one set of a lateral 9 coset, tangential to unit below.
45 Sandstone: similar to units above, one set of lateral 14 coset; tangential to unit below.
44 Sandstone and siltstone: alternating irregular 6 horizontal laminae of dark-reddish-brown siltstone and pale-reddish-brown, very fine sandstone, with some medium sand, firm, not calcareous, forms frequent indentations in normal cliff exposure. De posited on surface of erosion which flatly truncates unit below. 167
Unit Thickness No. Description in feet
43 Sandstone: moderate-reddish-orange, fine-grained, 27 cross-stratified (large scale), one set of a lateral coset dipping 28° S. 35° W., friable quartz cement. tangential to unit below.
42 Sandstone: similar to unit above. 27
41 Sandstone: similar to unit above. One set of a 26 lateral coset dipping 26° S. 63° W., calcareous material less than 1.0 percent.
40 Sandstone: similar to unit above. Laminations in 36 foreset beds conspicuous.
39 Siltstone: moderate-reddish-brown, very fine 0.5 sandy, firm, horizontally stratified, irregular and discontinuous laminations or lenses, firm, forms indentation in normal cliff exposure, deposited on surface of erosion that flatly truncates unit below.
38 Sandstone: similar to unit 40 above. This set of 50 cross strata thins laterally due to deposition on an inclined erosion surface that is gently concave up ward. This set and the laterally adjacent set have a common erosion surface at the top that is over- lain by unit No. 39. Similarly, the two sets are tangential to a common surface below. This is a good example of the lateral coset type of set distribu tion.
37 Sandstone: similar to units above. 16
36 Sandstone: pale-reddish-brown, very fine grained, 7 silty, some calcareous cement, horizontally ir regular lamination. Deposited on surface of erosion that truncates unit below. 168
Unit Thickness No. Description in feet
35 Sandstone: moderate-reddish-orange, fine-grained 10 with some medium to coarse sand distributed along laminations, cross-stratified (medium scale), one set of a lateral coset with foresets dipping 27° S. 50° W., quartz cement, friable, tangential to unit below. i;:,- - % . -
34 Siltstone: t similar to unit 39 above. Truncates 0.5 unit below. ,
33 Sandstone: similar to unit 35 above. Tangential to 6 unit below. Foresets dip 23° S. 409 W. :
32 Sandstone and siltstone: pale-reddish-brown, 0.5 horizontal irregular laminations or lenses, poorly sorted with sand grains, up to 2 mm scattered throughout coarser lenses, slightly calcareous (0.6 percent), some quartz cement. Forms indenta tion in normal cliff exposure, truncates unit below.
31 Sandstone: pale-reddish-brown, fine-grained, cross- 41 stratified (small to moderately large scale), com plicated vertical coset type in part, sets wedge shaped, sets dip to southwest, set measured dips 24° S. 10" W., inclined erosion surfaces dip in same general direction as foresets, some quartz cement, minor calcareous (0.8 percent) content, set tangential to unit below.
30 Sandstone: similar to above, one set where measured. 4
29 Siltstone:: fine sandy, similar to unit No. 32 above 1 without coarse sand grains. Truncates unit below.
28 Sandstone: similar to unit No. 31 above, one set of 14 cross strata where measured. Tangential to unit below.
27 Sandstone: similar to unit No. 28 above, one set of 15 cross strata dipping 24° S. 25° W. 169
Unit Thickness No. Description . . ; in feet
26 Sandstone: similar to unit above, cross stratifica- 20 . tion very complicated, some foresets containing medium and coarse sand grains wedge out downward in short distance. In plan the foresets wedge out and overlap one another. In some cases the larger fore sets seem to contain smaller scale cross stratifica tion internally. Prominent dip 23° S. 40° W. Tan gential to unit below^
25 Sandstone: pale-reddish-brown, fine-grained, few 7 medium grains, cross stratification (medium scale), unit one set dipping 24° S. 40° W., tangential to unit below. . . .
24 Sandstone: similar to unit No. 25 above, coarse- 4 grained laminae conspicuous, tangential to unit be low. ' '
23 Sandstone: pale-reddish-brown, very fine grained, 6 silty, horizontal irregular laminations or lenses with scattered grains to 2 mm. Very similar to unit No. 32. Low acid soluble content (0.7 percent). Truncates unit below.
22 Sandstone: pale-reddish-brown, very fine to coarse- 12 grained with adjacent laminae contrasting markedly in grain sizes. Foresets compound from series of discontinuous lenses or laminations. Foresets cross unit. ' ■ ■
21 Sandstone: similar to unit No. 22. Lenses or dis- 8 continuous laminations overlap in section and plan (partial) views giving a patchy appearance. Some quartz cement on smaller grains, low calcareous con tent (0.7 percent).
Bottom of White House Trail.
Thickness of this portion of White House Member, 437.5 feet. 170
Remainder of the White House Member as well as all of the Oak Springs and Hunters Point Members were measured on south wall of Canyon de Chelly east of the intersection of Monument Canyon with Canyon de Chelly. Correlation within the .White House.Member between areas is not exactly known. However, it is estimated that an overlap of close to 50 feet exists in this description. v
Unit Thickness No. Description in feet
20 Sandstone: moderate-orange-red, very fine 12 grained with scattering of coarser sand grains, cross stratification (small to medium scale), unit a coset containing lenticular to wedge-shaped sets, prominent northerly dip direction, some quartzitic cement; forms cliff, tangential to unit below.
- ' . - - - 19 Siltstone: paler? eddish-brown, very fine sandy 3 with few scattered grains to 1.0 mm, firm, horizontally bedded with irregularly discontinuous laminations, forms cliff where measured, truncates unit below. ;
18 Sandstone: grayish-red, very fine grained with 9 coarser grained laminae, some acid reaction, cross- stratified (medium scale), forms rounded cliff.
17 Sandstone: pale-reddish-brown, very fine grained 43 with scattered larger rounded grains, friable quartzitic cement, cross-stratified (medium to moderately large scale), unit a coset with wedge to lenticular-shaped sets, forms cliff, tangential to unit below.
16 Sandstone: grayish-red, fme-grained, friable 27 quartzitic cement, cross-stratified (moderately large scale) in which foresets cross unit, forms steep slope, tangential to unit below.
15 Siltstone: pale-brown, very fine sandy, scattered 5 larger grains to 1 mm, horizontal irregular dis continuous laminations, forms rolling slope, truncates unit below. 171
Unit . •" 'V : Thickness No. Description in feet
14 Sandstone:; pale-reddish-brown, fine-grained with 7 coarser grained laminae, some quartzitic cement, slight acid reaction, cross-stratified (medium scale), one set, part of rolling slope, tangential to unit below.
13 Siltstone: similar to unit No. 15 above. 2
12 Sandstone: pale-reddish-brown, fine-grained with 3 some coarser grained laminae, occasional grain to 2 mm, cross-stratified (medium scale), one set, tangential to unit below.
11 Sandstone: pale-reddish-brown, very fine grained 28 with coarser grains present, some quartzitic ce-) ment. Unit composed of five sets of cross strata in vertical sequence. The lower two sets are bounded by three horizontal irregularly bedded siltstones. The lowermost siltstone 0.5 foot thick truncates the unit below. . Cross strata dip to northwest at about 21°. Part of a steep slope.
10 Sandstone: similar to above. Unit is a vertical co- 43 set with lenticular to:wedge-shaped sets. Forms rolling steep slope, .tangential to unit below.
Base of White House Member. :: : ; .r: \ V . / v«;. .• . - ' ■ v •: • Thickness of portion of "White House Member ? measured at this locality, 182.0 feet.
Total thickness measured of White House Member, .619. 5 feet.
Total actual thickness of White House Member after subtracting estimated overlap of 50 feet in measurement, 570.0 feet. . . 172
Oak Springs Member:
Unit Thickness No. Description • ^ in feet
9 Siltstone: dark-reddish-brown, micaceous, very 45 fine sandy, calcareous (5.4 percent), firm, hor izontal irregular, discontinuous laminations, in dented at upper contact that causes undercutting of sandstone above, contains light-colored leached spots. " ::; - - ' ■ . ■- •"
Hunters Point Member: -
8 Sandstone: moderate-reddish-brown, very fine 8 grained, silty, firm calcareous cement (8.2 per cent), cross-stratified (very small to small scale), forms rounded slope. :
7 Siltstone: pale-reddish-brown, very fine sandy, 5 some mica, scattered coarser grains, noncalr car ecus, horizontal irregular and discontinuous bedding, weathers to slope. J
7A Sandstone: pale-reddish-brown, fine-grained 7 micaceous, silty, calcareous (15 percent), not cross stratified, massive appearing; forms slope.
6 Sandstone: pale-reddish-brown with lighter colored 150 zones. This is a complicated zone, difficult to break down into subsidiary units. Coset cross strati fied in a complicated manner on a very small to medium scale. Certain zones are silty and other zones contain pockets of coarse, rounded grains to 2 mm, generally calcareous; forms irregular rounded slope.
5 Siltstone: pale-reddish-brown, very fine sandy, 2 calcareous (15.3 percent), horizontal irregular bedding, .forms slope.
4 Sandstone: pale-reddish-brown, fine to very fine '15 grained, silty, quartzitic cement, not calcareous, cross-stratified (small and medium scale), vertical coset, rolling slope. 173
Unit Thickness No. Description in feet
3 Siltstone: dark-reddish-brown, very fine sandy, 10 some mica, calcareous, horizontal irregular bedding.
2 Sandstone: pale-reddish-brown to grayish-orange- 5 pink, fine to very fine grained, scattered coarser grains, silty, calcareous (3.7 percent), cross- stratified (small scale), trough-type sets.
Thickness of Hunters Point Member, 202.0 feet.
Total thickness df De Chelly Sandstone, 817.0 feet. ■ ■ ' . • : . . r:;, >• ; „ •; ( 7 \ ' . , ; Base of Hunters Point Member: begin continuous darker units of Supai Formation type.
1 Siltstone: pale-reddish-brown, very fine sandy, 50 , mica present, calcareous (4.5 percent), hori (exposed) zontal irregular bedding; forms continuing slope to canyon bottom. 174
SECTION 2
Nazlini Canyon
(Partial)
Partial section measured on north wall of Nazlini Canyon in steep, irregular recess cut into the canyon walL The section is located upstream away from the influence of the sharp flexure that, at this point, forms the west limb of the Defiance anticline.
Overlying unit: Triassic Shinarump Conglomerate Member of the Chinle Formation. Dip of formations: Nearly flat where measured. Nature of exposure: Cliff, access up irregular recess. Upper contact: Erosional contact with the Shinarump, with slight undulation, not readily located because of scarcity of conglomerate pebbles.
De Chelly Sandstone: White House Member:
Unit • N Thickness No. Description in feet
26 Sandstone: grayish-red, fine-grained, cross- 17 stratified on a moderately large scale, a lateral coset with wedge to lenticular-shaped sets.
25 Sandstone: grayish-orange-pink, pale-red, and 11 grayish-red laminae, fine- to medium-grained, contrasting grain size from laminae to laminae, cross stratification similar to unit No. 26.
24 Sandstone: grayish-orange-pink, fine-grained, 2 cross-stratified, some quartz cement, friable.
23A Sandstone: pale-reddish-brown, silty, horizontal- 4 ly bedded, truncates unit below.
23 Sandstone: grayish-orange-pink, medium- to fine- 8 grained, cross-stratified on medium scale, unit one set that pinches out 100 yards to east, well-developed quartz cement, tangential to unit below. Description in feet
Sandstone: moderate-orange-pink, fine-grained, 30 cross-stratified on large scale, foresets cross unit, dip 20° S. 40° W., quartz cement, firm.
Sandstone: moderate-orange-pink, fine to very fine 30 grained, cross-stratified on a moderately large scale, a complicated vertical coset, quartz cement, firm.
Sandstone:, moderate-red, fine-grained, horizontally 5 stratified, quartz cement, truncates unit below.
Sandstone: moderate-reddish-orange, fine-grained, 30 cross-stratified on large scale, foresets cross unit, lateral coset, abundant reptile tracks on foreset structures, quartz cement, firm.
Sandstone: similar to unit No. 19 above. Tracks not 31 observed. One set prominent cross stratification, dips 20° S. 5° W.
Sandstone: similar to unit above. Foresets dip 19° 41 S. 20° W.
Sandstone: moderate-reddish-orange, fine-grained, 6 cross-stratified on medium scale, foresets cross unit and dip 14° N. 80° E., quartz cement, firm, well- laminated.
Sandstone: similar to units 17, 18, and 19. Foresets 27 cross units and dip 23° S. 10° W. where measured.
Sandstone: moderate-reddish-brown, fine sand, ap- 18 pears horizontally laminated.
Sandstone: moderate-orance-pink, fine-grained, 11 cross-stratified on medium scale, a lateral coset, quartz cement, forms rounded cliff.
Sandstone: moderate-reddish-brown, fine-grained, 23 cross-stratified on medium scale, a vertical coset. Lithology similar to unit No. 15 above. 176
Unit Thickness No. Description in feet
12 Sandstone: moderate-reddish-orange, fine-grained, 35 cross-stratified on a large scale, foresets dip 20° S. 30° W. , quartz cement.
11 Sandstone: moderate-reddish-orange, fine-grained, 35 cross-stratified on large scale, some quartz cement,
10A Sandstone: similar to unit No. 11 except this is 3 horizontally stratified.
10 Sandstone: moderate-reddish-orange, dark-reddish- 36 brown circular iron oxide concentrations, fine grained, cross-stratified on large scale, a lateral coset, some quartz cement,
9 Sandstone: pale-reddish-brown, fine-grained, com- 23 posed of two sets of cross strata separated vertical ly by a horizontal surface of erosion, each set is a lateral coset, sets are 11 and 12 feet thick. : '
8 Sandstone: pale-reddish-brown, fine-grained, struc- 13 ture similar to.unit No. 9 above, calcareous and siliceous cement.
7A Sandstone: pale-reddish-brown, fine-grained, silty, 3 horizontal irregular laminations, calcareous, . truncates unit below. '
7 Sandstone: moderate-reddish-orange, fine-grained, 3 unit one set cross strata, calcareous and siliceous cement. \ 6 Sandstone: moderate-reddish-brown, fine-grained, 6 scattered coarser grains, horizontal irregular lamina tions, truncates unit below.
5 Sandstone: moderate-reddish-orange, fine-grained, 18 cross-stratified on a moderately large scale, a lateral coset, where measured foresets dip 24° S. 5 W., siliceous cement with some calcareous material. Description
4 Sandstone: moderate-reddish-orange, fine-grained, similar to unit No. 5 above,. one set cross strata dipping 24? S. 30° W. This set can be traced lateral ly at least a quarter of a mile without apparent change in dip direction.
3 Sandstone: similar to unit No. 4 above with similar lateral continuity.
Total thickness of White House Member, 502 feet.
Oak Springs Member(?):
2 Sandstone: pale-reddish-brown, very fine grained, some mica, silty, horizontal irregular lamination.
Hunters Point Member(?):
1 Sandstone: moderate-reddish-orange, fine-grained, two sets of cross strata separated vertically by a horizontal erosion surface, some calcareous and siliceous cement.
Base of cliff exposure.
Total thickness measured of De Chelly Sandstone, 529 feet. 178
SECTION 3
Bonito Canyon
A complete section measured in four parts. The Hunters Point Member was measured up the west-facing scarp just east of Quartzite Canyon 1.9 miles from the beginning of the road into Bonito Canyon from Fort Defiance. The White House, Black Creek, and Fort Defiance Members were measured by com bining exposures on both the north and south walls of Bonito Canyon.
Overlying unit: Triassic Shinarump Conglomerate Member of the Chinle Formation. Dip of formations: From near horizontal to 10° to 15 to the southeast. Nature of exposures: Cliff, steep slopes. Upper contact: Erosional unconformity; the upper contact was placed at the base of a conglomerate.
De Chelly Sandstone: Fort Defiance Member:
South wall of Bonito Canyon at Fort Defiance end.
Unit Thickness No. Description in feet
44 Sandstone: light-brown, fine-grained, cross- 4 stratified on medium scale, unit one set where measured, well-developed quartz cement, hard, tangential to unit below.
43 Sandstone: dark-reddish-brown, very fine to 10 medium-grained, silty, cross-stratified on small to medium scale. / North wall of Bonito Canyon at Fort Defiance end. Here Shinarump Conglomerate overlies unit No. 42.
42 Sandstone: moderate-reddish-brown, fine-grained, 14 massive appearing, quartz cement, firm, appears to grade from unit below. 179
Unit Thickness No. Description in feet
41 Sandstone: pale-reddish-brown, fine-grained, 8 small-scale cross stratification most conspicuous scour-and-fill type, quartz cement present, firm to friable, appears to grade from unit below.
40 Sandstone and siltstone: interbedded. 68.6
Sandstone: pale-r eddish-brown, fine- 9 grained, massive appearing, some quartz cement, firm to friable.
Sandstone: similar to unit above, upper 6 4 feet cross stratified on very small scale, minute hematitic concentrations create speckled appearance.
Sandstone and siltstone, interbedded: Sand- 46 stone - pale-reddish-brown, calcareous, some quartz cement, in ledges 2 to 7 feet thick, thicker sands show very small-scale cross stratification. Siltstone - dark-red- dish-brown, very fine sandy, micaceous, horizontal irregular laminations, calcareous, in beds 1 to 4 feet thick.
Sandstone: pale-reddish-brown, similar 2 to above,
Siltstone: dark-reddish-brown, fine- 5 sandy, micaceous, calcareous, weathers shaly.
Sandstone: pale-reddish-brown, very 0.6 fine grained, silty, horizontally laminated.
39 Sandstone: very pale orange, very fine grained, cross-stratified on a very small scale, apparent ly a reworked zone, slightly calcareous, some quartz cement.
Thickness of Fort Defiance Member, 106.0 feet. 180
.. Black Creek Member:
Unit Thickness No. Description in feet
38 Sandstone: moderate-orange-pink, fine-grained, 11 cross-stratified on medium scale, adjoining sets - f dip in opposite directions, well-developed quartz cement, some calcareous content, hard.
37A Sandstone: pale-reddish-brown, fine-grained, 1 some silt, horizontal stratification, calcareous cement (14.5 percent), weathers to indentation.
37 Sandstone: pale-reddish-brown, fine-grained, 4 horizontally stratified, some acid reaction and quartz cement, firm to friable, weathers to •: :Slope. -■ :. : '■ • : '■
36 Sandstone: pale-reddish-brown, fine-grained, top . 14 2 feet cross-stratified on small scale, lower 12 feet sedimentary structures not noticed, apparently mas sive.
35 Sandstone: grayish-orange, fine- to medium- 18 grained, cross- stratified on small to large scale, details not obtainable, some calcareous material (3.2 percent), some quartz cement, firm. ;
34A Siltstone: dark-reddish-brown, flat-bedded; forms 1 indentation, pinches out laterally.
34 Sandstone: moderate-orange-pink, fine- to medium- 8 grained, sedimentary structures not clear although appears horizontally stratified, well-developed quartz cement, some calcareous material (1.8 percent), firm, forms ledge. , ' . - ' . . I • ■ 33 Sandstone: very pale orange, fine- to medium- 8 grained, cross-stratified on medium scale, • moderate development of quartz cement, firm, forms ledge. 181
Unit Thickness No. Description in feet
32 Sandstone: similar to above, fine-grained, some 9 carbonate (2.1 percent), structure in doubt, appears massive, firm, forms ledge.
31 Sandstone: similar to above, upper 3 feet small-scale 11 cross stratified, lower 8 feet, cross stratification on a medium scale.
30 Sandstone: similar to above, fine-grained, structure 20 in doubt, massive appearing.
Thickness of Black Creek Member, 105.0 feet.
Contact with White House Member below: Change from mixed cross-stratified and horizontally stratified, lighter colored, silicified sandstones to sandstones that are mostly cross stratified, somewhat darker in color, and less well indurated.
White House Member:
29 Sandstone: moderate-reddish-orange, fine-grained, 35 a complicated coset of cross strata, quartz, and cal careous (4.* 3 percent) cement, firm, cliff.
28 Sandstone: moderate-orange-pink, fine to very fine 15 grained, structure in doubt, appears massive, some quartz cement, calcareous (4.7 percent), firm, truncates unit below.
27 Sandstone: moderate-orange-pink to pale-reddish- 13 brown, fine to very fine grained, cross-stratified on medium scale, some quartz cement, calcareous (5.0 percent).
26 Sandstone: moderate-orange-pink, fine-grained, 8 occasional medium to coarse grains along laminae, cross-stratified on medium scale, top 1 foot small- scale cross stratification, remaining foresets cross unit, moderate quartz cement, not calcareous, firm, cliff. 182
Unit Thickness NOe Description in feet
25 Sandstone: moderate-orange-pink, fine to very 11 fine grained, cross-stratified on medium scale, foresets cross unit, foresets dip 25° S. 55° E. where measured, well-developed quartz cement, firm.
24A Sandstone: moderate-orange-pink, fine-grained, 0.4 some silt, horizontal stratification, truncates unit below. ;
24 Sandstone: similar to unit No.: 25 above. 24
23 Sandstone: pale-reddish-brown, very fine grained, 14 some silt, massive appearing, some calcareous cement (2.8 percent), central 2 feet coarse to fine grained, very calcareous (10.7 percent).
22 Sandstone: moderate-reddish-brown, coarse- to 30 fine-grained, contrasting distribution within adjacent laminae, cross-stratified on large scale, a coset, southerly dip to foresets, wind ripple marks on some of the foreset surfaces, some quartz cement, some calcareous cement (4.5 percent), firm, irregular cliff.
21 Sandstone: pale-reddish-brown, fine-grained, silty, 2 horizontal irregular stratification, some acid re action, firm, truncates unit below.
20 Sandstone: pale-reddish-brown, fine-grained, cross- 7 stratified on medium scale, foresets cross unit, slight quartz cement, firm. •
19 Sandstone: moderate-reddish-orange; and sandstone, 40 silty, moderate-reddish-brown, interbedded.
Sandstone: fine-grained, cross-stratified on 19 large scaled foresets cross unit, one set of a lateral coset. •
I 183
Unit Thickness No. Description in feet
Sandstone: fine to very fine grained, silty, 1 horizontal irregular stratification, cal- _ ■: ; car eons cement (3.4 percent), truncates unit below.
Sandstone: fine-grained, cross-stratified 6 on medium scale, foresets cross unit, quartz and calcareous cement (8.2 per- % • ; cent), tangential to unit below. ;
Sandstone: silty, similar to silty sand- 1 stone above. i
Sandstone: similar to cross-stratified ; 12 sandstone above.
Sandstone: silty, similar to others above. 1 Laterally discontinuous, ^ '
Thickness of White House Member, 200.0 feet.
Contact: Sharp indicated by change to m assive slope-forming ; sandstones. Contrasts with flaggy weathering sandstones above.
Hunters Point Member:
18 Sandstone: pale-reddish-brown, coarse to very 76 fine grained, silty in part, cross-stratified in a complex manner forming a vertical coset not readily subdivided into units, scale of development varies from small to large. Contains flat, curving, and in clined planar surfaces of erosion, set shapes vary from lenticular to wedge-like, some quartz cement, calcareous (3.8 percent), forms steep rounded slope.
17 Sandstone: pale-reddish-brown, medium to very 15 fine grained, silty, horizontal irregular stratifica tion, stratification manifested by changes in grain size, calcareous, forms rounded slope. 184
Unit Thickness No, Description in feet
16 Sandstone: moderate-reddish-brown, medium- 14 grained, upper 11 feet cross stratified on medium scale, one set where measured, lower 3 feet contains small-scale cross stratification, some quartz cement, calcareous (9.8 percent).
15 Sandstone: dark-reddish-brown, very fine grained, 45 silty, some mica, horizontal irregular stratification, calcareous, massive rounded cliff.
14 Sandstone: pale-red, coarse to very fine grained, 18 silty, upper 1.5 feet cross stratified on very small scale, reworked zone, lower 3 feet cross stratified on small scale, central zone cross stratified on med ium scale, coarse grains as stringers along certain foreset beds, calcareous (14 percent).
13 Siltstone: pale-reddish-brown, fine sandy, micaceous 16 laminae, horizontal irregulat stratification, cal careous, bleached zones along fractures.
12 Sandstone: pale-red, very fine grained, silty, cross- 33 stratified on large scale, foresets dip to east and south, calcareous (2.4 piercent), top zone small-scale cross stratification, reworked.
11 Sandstone: pale-reddish-brown, fine to very fine 10 grained, silty, small-scale cross stratification, scour-and-fill type, calcareous (8.2 percent), friable, forms rounded cliff.
Thickness of Hunters Point Member, 227.0 feet.
Total thickness of De Cbelly Sandstone, 638.0 feet.
Contact: Supai Formation, arbitrary.
10 Siltstone: pale-reddish-brown, very fine sandy, 11 micaceous, horizontal irregular stratification, calcareous, knobby weathering cliff. 185
Unit T ^ ' Thickness No. Description in feet
9 Sandstone: pale-reddish-brown, very fine grains 9 to 2 mm. near base, cross-stratified on small scale, scour-and-fill type, calcareous (6.0 percent). Top zone structureless, reworked. •
8 Siltstone: similar to unit No. 10 above. 13
7 Sandstone: pale-reddish-brown, fine-grained, 6 silty, horizontally stratified, calcareous (5.4 per cent).
6 Siltstone: pale-reddish-brown, very fine sandy, 5 micaceous; horizontally stratified, calcareous, forms shaly weathering slope. :
5 Sandstone: moderate-orange-pink, fine-grained, 9 silty, small-scale cross stratification, scour-and- fill type, calcareous (3.2 percent), rolling slope.
4 Sandstone: pale-reddish-brown, very fine grained, 6 silty, very small-scale cross stratification, cal careous (8.1 percent).
3 Siltstone: moderate-reddish-brown, very fine grained, 8 horizontal irregular stratification, calcareous, shaly weathering, massive where fresh in gully exposures.
2 Sandstone: pale-red, fine sand, silty, some coarse 4 sand scattered, structure not seen, calcareous, forms ledge.
1 Siltstone: similar to unit No. 3, lowest exposure. 8
Measured thickness of Supai Formation, 79.0 feet. 186
SECTION 4
Hunters. Point
Section located about 7 miles south of St, Michaels School on west side of road. Hunters Point is a well-known topographic feature carved into the steeply dipping east flank of the Defiance anticlinal structure. The complete section of the De CheUy Sandstone is not present in the cliff exposure. The upper por tion is obtained by piecing together outcrops in gullies and smaU canyons north ot the main cliff exposure; The upper contact with the Moenkopi Formation is exposed near the foot of the second canyon north of Hunters Point.
Overlying unit: Triassic Moenkopi Formation Dip of formations: Lower member near horizontal where measured; upper member 5° to 30° easterly. Nature of exposure: Cliff, gully, and small canyon walls.
De CheUy Sandstone: ' Black Creek Member:
Contact with Moenkopi Formation flat and sharp.
Unit Thickness No. Description in feet
34 Sandstone: yellowish-gray, fine-grained, cross- 50 stratified on small, medium, and large scale, (approx.) large scale near base with sets wedge- to lenticu lar-shaped, weU-developed quartz cement, ir regular, incomplete exposure.
33 Sandstone: similar to unit No. 34 above, apparent 47 ly horizontally stratified.
32 Sandstone: similar to unit No. 34 above, cross- 20 stratified on a moderately large scale, a coset with lenticular sets.
31 Sandstone: similar to units above, silica less well 8 developed, apparently horizontally stratified.
30 Sandstone: appears to be continuation of unit No. 9 31 above. 187
Unit Thickness No. Description in feet
29 Sandstone: grayish-orange, otherwise similar to 8 units 30 and 34 above.
28 Sandstone: similar to units 32 and 34 above, fine- 30 grained, cross-stratified on a moderately large scale, sets lenticular- to wedge-shaped.
27 Sandstone: pale-reddish-brown, silty, calcareous, 1 horizontal irregular laminations, truncates unit be low.
26 Sandstone: pale-reddish-brown, fine to very fine 15 grained sand, some quartz and calcareous cement, cross-laminated on a medium scale, foresets cross unit, lateral coset type, forms rounded cliff. :
Indefinite break in exposures.
25 Sandstone: moderate-orange-pink, fine-grained, 12 friable quartz cement, slightly calcareous, cross- ; stratified on a medium scale, a coset,
24 Sandstone: moderate-orange-pink, fine-grained, 17 some quartz cement, firm to friable, horizontal ir regular lamination.
23 Sandstone: similar to unit No. 24 above, cross- 8 stratified on a medium scale, a coset.
22 Sandstone: upper 3 feet moderate-reddish-orange, 8 fine-grained, some silt, minor quartz cement, horizontally stratified, lower 5 feet moderate- reddish-brown, fine-grained, silty, horizontally stratified. ,
21 Sandstone: moderate-reddish-orange, fine-grained, 6 moderate quartz cement, cross-stratified on medium scale, foresets cross unit. 188
Unit Thickness No* Description in feet
20 Sandstone: upper 6 feet similar to lower 5 feet of 8 unit No. 22 except that unit No. 20 contains scattered grains to l/2 mm. Lower 2 feet sandstone, banded grayish-orange-pink and moderate-reddish-orange, fine-grained, silty, cross-stratified on a small scale.
Thickness of Black Creek Member, 217.0 feet.
Oak Springs Member:
19 Sandstone: pale-reddish-brown, very fine grained, 8 silty, calcareous, similar to lower 5 feet of unit No. 22. : . ' . : - / 18 Sandstone: moderate-orange-pink, fine-grained, silty, 5 some quartz and calcareous cement, horizontally strati fied.
17 Sandstone: moderate-reddish-orange, very fine grained, 10 some quartz cement, carbonate (4.5 percent), horizont ally stratified.
16 Siltstone: moderate-reddish-brown, very fine, sandy, 12 some calcareous material, horizontal irregular mi caceous laminae. . / . :
15 Sandstone: pale-red, very fine grained, calcareous, 3 horizontally(?) stratified. :: t v • ;
14 Sandstone: pale-reddish-brown, very fine grained, 12 silty, calcareous (20 percent), horizontally strati fied.
Thickness of Oak Springs Member, 50.0 feet.
Hunters Point Member:
13 Sandstone: moderate-orange-pink, fine-grained, 30 quartz, cement, upper 14 feet cross-stratified on medium scale, lower 16 feet apparently horizontally stratified. 189
Unit . ' i Thickness No. Description in feet
12 Sandstone: moderate-orange-pink, fine-grained, 62 cross-stratified on moderately large scale, a vertical coset, some quartz cement, some cal careous material (3.6 percent).
11 Sandstone: included in unit No. 12.
10 Sandstone: pale-reddish-brown and moderate- 49 orange-pink,. fine- grained, appar entity horizontally stratified, slump structure, darker portion some acid reaction. ;
9 Sandstone:: almost whiter fine-grained, cross-strati- 10 fied on medium scale, quartz cement. : ,
8 Sandstone: motjerale-orange-pink, fine-grained, - 17 ; cross stratified on a small scale, quartz cement.
7 Sandstone: pale-reddish-brown, fine to very fine 21 grained, apparently horizontally stratified, some quartz cement.
6 Sandstone: pale-reddish-brown, fine-grained, 15 scattered coarser grained laminae, cross-strati fied on small to moderately large scale, complicated coset, some quartz cement, no acid reaction.
5 Sandstone: upper 26 feet pale-reddish-brown, fine- 38 grained, cross-stratified on small scale. Central 2 feet sandstone, silty, containing scattered coarse sand grains; lower 10 feet sandstone, moderate- reddish-orange, fine-grained, cross-stratified on medium scale.
4 Sandstone: pale-reddish-brown, fine to very fine 26 grained, some silt, massive appearing, very cal careous (16 percent).
Thickness of Hunters Point Member, 238.0 feet.
Total thickness of De Chelly Sandstone, 505.0 feet, 190
Sediments of the Supai Formation:
Unit r Thickness No. Description in feet
3 Siltstone: dark-reddish-brown, very fine grained, 7 sandy, micaceous, horizontal irregular and dis- continuous laminations, calcareous, weathers shaly to rounded massive ledge. , . C : k
2 Siltstone: moderate-reddish-brown, very fine sandy 5 with occasional coarse grain, micaceous, calcareous, massive, knobby or spheroidal weathering, locally bleached near calcite veinlets.: . - x- : \
1 Limestone: light-olive-gray, thin-bedded, beds slight- 6 ly undulating, chert stringers parallel bedding.
Dark detrital sediments below form slope. Cubic-shaped salt- crystal molds present. 191
SECTION 5
Oak Springs. Cliffs
A near complete section measured up the cliffs approximately 3 miles west of the Lupton-St. Michaels road between Black Creek Canyon and Hunters Point. The northern portion of these cliffs contains the Hunters Point Member of the De Cbelly Sandstone and the southern portion the White House and Black:Creek Mem bers of this sandstone. Oak Springs is located just south of this cliff series.
Overlying unit: Triassic Moenkopi Formation . Dip of formations:. From near horizontal to a few degrees southwest. Nature of exposure: Cliff
De Chelly Sandstone: •. Black Creek Member: :
Contact: Recent erosion surface. Moenkopi crops out a few hundred yards west of the cliff edge.
Unit Thickness No. . Description C in feet
Estimated thickness of sandstone between top of 30+ cliff exposure and Moenkopi. “
27 Sandstone: very light colored, fine to very fine 40 grained, cross-stratified on a medium scale, unit is a vertical coset with wedge- to lenticular-shaped sets, well-developed quartz cement, hard, cliff top.
26A Sandstone: very light to pale-reddish-brown, fine- 21 grained, cross-stratified but details not known, moderate- to well-developed quartz cement, cliff.
26 Sandstone: pale-reddish-brown, fine-grained, hor- 6 izontally stratified, slight quartz, some calcareous cement, firm, cliff.
\ 192
Unit Thickness No. Description in feet r;i" - 25A Sandstone: ‘moderate-reddish-orange, fine-grained, 14 cross-stratified on moderately large scale, fore sets cross unit, a lateral coset, some quartz cement, firm, cliff. r :
Sandstone: pale-reddish-brown, fine-grained, hori zontal irregular stratification, small amount of quartz cement, friable, rounded cliff. 1 1 Thickness of Black Creek Member, 125.0 feet.
White House Member: •
1 Sandstone: moderate-reddish-orange, fine-grained, cross-stratified on moderately large scale, foresets cross unit, lateral coset, foresets dip 27° S. 37° W., ' some quartz cement, firm to friable, cliff.
$ Sandstone: dark-reddish-brown, very fine grained, silty, micaceous, horizontal irregular stratification.
Units 22, 23, and 24 constitute typical Canyon de Chelly arrangement and lithology. '
l Sandstone: pale-reddish-brown, fine-grained, cross- stratified, large to medium scale, unit is a complicated vertical coset, larger foresets dip 29° S. 4° E.
? Thickness of White House Member, 45.0 feet.
Oak Springs Member:
1 Sandstone: pale-reddish-brown, moderate-reddish- 128 brown, moderate-reddish-orange, pale-red, fine grained, silty, horizontal bedding, calcareous, saliniferous, in ledges 1 to 5 feet thick, forms slope. 193
Hunters Point Member:
Unit Thickness No. Description / ^ . in feet
20 Sandstone: moderate-reddish-orange, fine-grained, 13 lower 3 feet cross-stratified on a medium scale, upper 10 feet horizontally stratified, probably a re worked zone below Supai tongue, some calcareous material, firm, cliff.
19 Sandstone: pale-reddish-brown (weathered), fine 11 grained, horizontally stratified, some quartz cement,
18 Sandstone: moderate-orange-pink, fine-grained, 13 lower 3 feet cross-stratified on a medium scale, upper 10 feet massive, calcareous, some quartz cement, firm, ledge. : ,
17 Sandstone: moderate-orange-pink and moderate-red- 12 dish-brown, fine-grained, some silt in darker zones, small-scale cross stratification in part, remainder horizontally stratified, darker zones calcareous, water-ripple marks well developed,
16 Sandstone: moderate-orange-pink, fine-grained, 6 compounded from several thin units all of which con tain small-scale stratification, calcareous, firm to friable.
15 Sandstone: moderate-reddish-brown, fine to very fine 4 grained, some silt, cross stratified on medium scale.
14 Sandstone: moderate-reddish-brown, fine to very fine 27 grained, some silt, mica, series of one to two feet ledges apparently flatly stratified, calcareous, some undercutting caused by platy weathering, forms slope.
13 Sandstone: moderate-orange-pink, fine-grained, mas- 11 sive appearing, well-developed quartz cement, top cliff exposure, indented above,
12 Sandstone:, similar to above, very small, small, and 8 medium-scale cross stratified from bottom to top, slightly undulating contact with unit above. 194
Unit Thickness No. Description in feet
11 Sandstone: similar to above, calcareous, some 12 quartz cement, cross-stratified on a small scale.
10 Sandstone: moderate-reddish-brown, fine to very 2 "fine grained, silty, horizontally stratified, cal careous.
9 Sandstone: similar to unit No. 11 above. 8
8 Sandstone: moderate-orange-pink, fine-grained, 10 cross-stratified on a medium scale, foresets cross unit and dip 14° S. 50° E.
7 Sandstone: moderate-orange-pink, fine to very fine 2 grained, horizontal stratification, slightly calcareous.
6 Sandstone: moderate-orange-pink and pale-reddish- 17 brown, colors in alternating laminae, finer grained is darker, fine-grained, cross-stratified on moder ately large scale, foresets cross unit and dip 14° 8. and 73° E.
5 Sandstone: moderate-reddish-orange and moderate- 18 orange-pink, fine-grained, darker unit is channeled into and filled with lighter colored, slightly coarser sand, channels are about 6 feet deep and the filling sands are cross-stratified on a medium scale. The channel deposits are overlain by horizontally strati fied sand. Channel zone bottom is marked by an un dulating light-colored leached zone in the darker underlying sand. This phenomenon can be seen for considerable distance.
Thickness of Hunters Point Member, 174.0 feet.
Total thickness of the Be Chelly Sandstone, 472.0 feet. 195
Supai Formation:
Unit Thickness No. Description in feet
4 Sandstone: pale-reddish-brown, very fine grained, 11 silty, cross-stratified on small scale, calcareous, contains lighter colored leached spots that are not as calcareous as darker mass, firm, indented at upper and lower contacts, thin, knobby mud zone at upper contact,
3 Sandstone: similar to unit No. 4. 8
2 Sandstone: pale-reddish-brown, similar to units 3 14 and 4 above except this is slope exposure just under bottom of cliff zone of exposure.
1 Limestone: light-olive-gray, dense, thin-bedded, 8 chert stringers parallel bedding, beds slightly un- dulatory.
Slope-forming "red bed" sequence of Supai type continues below limestone. 196
SECTION 6 c
Black Creek Canyon '
(Partial)
This partial section measured and described on the north wall at the head of Black Creek Canyon where the canyon cuts through the steeply dipping Defiance monocline. Section meas ured where beds have flattened out.
Overlying unit: Triassic Moenkopi Formation to north and south Dip of formations: Flat v Nature of exposure: Cliff ; Nature of upper surface: Recent erosion surface v
De Chelly Sandstone: , . : ; ^. Black Creek Member:
Unit . ; . ^ Thickness No. Description . ' in feet
11 Sandstone: grayish-orange, fine-grained, quartz- 4 itic cement, horizontal irregular bedding, cliff, (partial) truncates unit below.
10 Sandstone: grayish-orange, fine-grained, cross- 9.0 stratified on medium scale, lateral coset type, well- developed quartz overgrowths, firm, forms cliff.
9 Sandstone: grayish-orange, fine-grained, quartzitic 10 cement, horizontal irregular bedding, cliff, truncates unit below.
8 Sandstone: fine-grained, quartzitic cement, cross- 8 stratified (medium scale), lateral coset type, one set dips 25° S. 50° W., an adjacent set dips 25° just south of east, cliff.
7 Sandstone: fine-grained, quartzitic cement, horizontal 4 irregular bedding, cliff, truncates unit below.
6 Sandstone: very pale orange, fine-grained, quartzitic 7 cement, cross-stratified (medium scale), lateral coset type, set measured dips 24° S. 70° W., cliff. 197
Unit •: 0: ■ Thickness No. Description in feet
5 Sandstone and siltstone: interbedded, horizontal 37 bedding, cliff. : y •; ;; :
4 Sandstone: moderate-reddish-orange, fine-grained, 3 quartzitic cement, cross-stratified (small and medium scale), dips to west and southeast,: cliff, irregular - con tact with unit below. / • ; • : : v - :
3 Sandstone: moderate-reddish-orange, fine-grained, 3 silty, horizontal bedding, cliff, truncates unit below.
2 Sandstone: moderate-reddish-orange, fine-grained, 48 quartzitic cement, cross-stratified (large scale), lateral coset type, set measured dips 25° S. 20° W., cliff.
: Thickness partial section of Black Creek Member, 133.0 fe e t
"Red beds" of Supai type: \
1 Sandstone: fine-grained, silty, calcareous, horizontal 20 irregular bedding, weathers to series of rounded ledges, contains light-colored bleached spots, calcite veinlets, cliff.
One-hundred and seventy feet of "red beds" composed of silty sandstone, calcareous, to top of 8 feet of thin-bedded, light weathering, dense, dark-gray limestone. • , 198
SECTION 7 -
Pine Springs
Complete section measured on walls of tributary to Black Creek Canyon approximately 3 miles east of Pine Springs Trading Post.
Overlying unit: Trlassie Moenkopi Formation composed of typical dark-brown to red ripple-marked and mud-cracked siltstone and mudstone. Dip of formations:/ Flat Nature of exposure: Cliff Nature of contact: Shape and even
De Chelly Sandstone: : Black Creek Member:
Unit Thickness No. Description i in feet
17 Sandstone: grayish-orange, fine-grained, cross- 20 stratified (medium scale), vertical coset containing lenticular- to wedge-shaped sets, firm quartz ce ment, forms ledge, truncates unit below.
16 Sandstone: similar to unit above, slightly coarser 24 grained, cross laminae (medium scale) longer than above, sets lenticular in shape, forms ledge, trun cates unit below. ; :
15 Sandstone: very pale orange, very fine grained, 13 central 4 feet cross-stratified on medium scale, upper 5 feet and lower 4 feet appear to be. horizontal ly but irregularly stratified, firm quartz cement, forms ledge. .
14 Sandstone: upper portion moderate-reddish-orange, 20 fine-grained, some quartz cement and slightly cal careous (1.25 percent), lower portion pale-red, silty, fine-grained (finer than upper portion), some quartz cement and calcareous (7.2 percent), horizontally but irregularly stratified, forms ledge. / 199
Unit Thickness No. Description in feet
13 Sandstone: grayish-orange, fine-grained, cross- 10 stratified (medium scale), lateral coset, sets wedge-shaped and tangential to unit below, firm quartz cement, forms ledge.
12 Sandstone:, pale-red, very fine grained, silty, very 19 calcareous (13.1 percent), forms irregular-weather ing cliff.
11 Sandstone: moderate-reddish-orange and moderate- 26 orange-pink, fine-grained, cross-stratified (medium scale), vertical coset, sets lenticular-shaped, firm quartz cement, darker portions moderately calcareous • ($. 8 percent), forms ledge.
10 Sandstone: pale-reddish-brown, very fine grained, 10 silty, moderately calcareous (4.3 percent), firm, structureless cliff, truncates unit below.'
9 Sandstone: moderate-orange-pink, fine-grained, 23 cross-stratified (medium to moderately large scale), dips 22° S. 45° W. where measured, sets lenticular- to wedge-shaped, well-developed quartz cement, moderately calcareous (3.6 percent), forms cliff.
8 . Sandstone: pale-reddish-brown, very fine grained, 9 silty, calcareous (6.0 percent), friable, horizontal irregular stratification, forms cliff, truncates unit below.
7 Sandstone: moderate-reddish-orange, fine-grained, 30 cross-stratified on a moderately large as well as small scale locally, sets lenticular, some quartz ce ment, moderately calcareous (4. 6 percent), friable, forms steep slope.
6 Sandstone: pale-reddish-brown, very fine grained, 8 silty, very calcareous (11 percent), firm, horizontal ly irregularly stratified, forms cliff. 200
Unit ' Thickness No. Description in feet
5 Sandstone: moderate-reddish-orange, fine-grained, 5 some silt, cross-stratified on medium scale, sets lenticular in shape, moderately calcareous, some quartz cement, forms cliff.
4 Sandstone: moderate-reddish-orange, fine-grained, 8 some silt, possibly very small-scale cross stratifi cation, calcareous (2.2 percent), forms ledge.
Total thickness of Black Creek Member, 225.0 feet.
Lower contact of the De Chelly Sandstone with Supai Formation.
3 Siltstone: pale-reddish-brown, very fine sandy, hor- 3 izontal irregular stratification, very calcareous (19.6 percent), knobby weathering.
2A Siltstone: grayish-red, very fine sandy, micaceous, 3 horizontal irregular stratification, moderately cal careous (4.0 percent), forms rounded ledge with in dentations at contacts,
2 Limestone: dusky yellow, siliceous, irregular platy. 0.5
1 Sandstone: upper 1 foot very light colored, fine- 8 grained, silty, very calcareous (17.6 percent), (exposed) lower 8 feet to base of entire exposed section moderate-reddish-orange, very fine grained, silty, horizontal irregular stratification, slight quartz cement, calcareous (2.4 percent), friable, forms slope to base of exposure at canyon bottom. 201
SECTION 8
Water Well
Water well 3-1/2 miles west of Lupton and half a mile north of U. S. Highway 66. Samples on file at Arizona Bureau of Mines*
Overlying unit: Triassic Moenkopi Formation
De Chelly Sandstone: Black Creek Member:
; Thickness in feet
Sandstone: grayish-orange to pale-reddish-brown, 210 fine-grained, quartz overgrowths well developed in some places, rounding conspicuous in others, calcareous, certain zones appear slightly darker ’ with increased silt content; apparently these slight differences reflect inter bedded units similar to what is observed at Pine Springs Section No, 7*
Supai Formation:
Sandstone: light-brown, silty, micaceous, cal- 50 car eons, secondary quartz overgrowth not well developed.
Gypsum: white, crystalline, 10
Siltstone and gypsum: interbedded. 20
Dolomite: dark-gray, granular, petroliferous odor, 20 202
SECTION 9
Argo State No. 1
T. 15 N., R. 29 E. , sec. 22, Apache County. Basic information from sample log on file at Arizona Bureau of Mines; - : ■./. ■’ -V San Andres and (or) Kaibab Limestones:
Thickness in feet
Limestone: brown to gray, very sandy in lower 186 portion, occasional sandstone bed.
Glorieta(?), Coconino(?), or Black Creek Member of the De Chelly Sandstone:
Sandstone. . 212
Supai Formation:
Sandstone and "shale": interbedded. 80
Anhydrite. 18 \
203
SECTION 10
Carter Oil Co. Santa Fe-Bonito No. 2 Well
T. 11 N ., R. 19 W., McKinley County, New Mexico. Data from U. S. Geological Survey Oil and Gas Investigations Preliminary Chart No. 10.
San Andres Limestone:
Thickness in feet
Limestone: details not known. 90
Glorieta Sandstone or Black Creek Member (?) of the De Chelly Sandstone:
Sandstone: details not known. 250
Supai or Yeso Formation:
Sandstone: dark, silty. ■ - ’ '' . 50
Gypsum: details not known. 20
, "Shale": dark-red. 100
Limestone: details not known. 20 REFERENCES CITED
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1839-1879. Plate I
f f ? f / Piute / f 6 £ \ Farms ZZ7
UTAHJ Son Juan Count UTAH ; f COLORADO ARIZONA Comb Ridge ARIZONA n e w exico Glen Cayon V M " Dam vMarble Canyon ) Bridge
Badger Shiprock Canyon Kayenta
VIMUIUH | Tribal No.I * EXPLANATION
Lukochukai #i Measured Section S Number T.R ■ Partial Section Examined HOPI Outcrop Area of Permian x- v Sandstones Conyon De Chinle %/Chelly Pg Glorieta Sandstone INDIAN Pdc De Ghelly Sandstone Pc Coconino Sandstone • RESERVATION — 36 i ^ tation -0 - Well Site Cameron Nazlini Kearns t Canyon / Bonito I / Canyon,1 - ~ nIfKin 1 LiL-1 u eA _C h ee 0 5 10 15 20 1__i----1 Canada
‘■/St.MichdeT'V^y I iL^Hunter's Point Klagetoh Pdc N- -Oak Springs allup N Block f o o t' FT i Cr. X V Wingote
.Water Well Houck Carter Oil Co. Santa Fe Bonita No.2 Flagstaff NAVAJO INDIAN RESERVATION Chambers
Winslow — 35
Sedona Holbrook
Argo State No.2
St.Johns Snowflake
MAP—LOCATIONS OF MEASURED SECTIONS OF DE CHELLY SANDSTONE ft AREAS OF OUTCROPPING PERMIAN SANDSTONES ft??/ SUMMATION OF PERMIAN NOMENCLATURE Z&7 P late 2 MONUMENT VALLEY DEFIANCE PLATEAU EAST FLANK GENERAL WESTERN SOUTHEASTER^ GENERAL WEST FLANK HUNTERS POINT OAK SPRINGS CLIFFS BLACK CREEK PINE SPRINGS f NAZLINI CANYON BONITO CANYON READ READ READ MISER DARTON BAKER AN D RBESIDE GREGORY DARTON MCKEE BAKER AND RBESIDE MCKEE GREGORY DARTON BAKER AND RBESIDE MCKEE BALK THIS PAPER THIS PAPER THIS PAPER GREGORY THIS PAPER THIS PAPER THIS PAPER 1951 THIS PAPER 1951 1951 THIS PAPER 1917 1923 1925 1929 11917 1925 1934 1929 1934 1917 1925 1929 1934 1954 \ SHINARUMP SHINARUMP SHINARUMP SHINARUMP RECENT EROSION RECENT EROSION SHINARUMP SHINARUMP SHINARUMP SHINARUMP SHINARUMP MOENKOPI SHINARUMP SHINARUMP SHINARUMP shiLa r u m p SHINARUMP SHINARUMP SHINARUMP SHIN ARUM P SHINARUMP SHINARUMP SURFACE SURFACE MOENKOPI MOENKOPI HOSKINNINI MOENKOPI MOENKOPI TRIASSIC MOENKOPI MEMBER
HOSKINNINI FORT DEFIANCE > M COCONINO RED BEDS RED BEDS RED BEDS MEMBER BLACK CREEK BLACK CREEK J z TONGUE MEMBER MEMBER J o DE CHELLY SANDSTONE W H DE CHELLY WHITE HOUSE UPPER WHITE HOUSE W H WHITE HOUSE BLACK CREEK UPPER UPPER GLORIETA BLACK CREEK BLACK CREEK DE CHELLY DE CHELLY SANDSTONE X M COCONINO(?) X CQ DE CHELLY SANDSTONE MEMBER MEMBER MEMBER MEMBER DE CHELLY MEMBER MEMBER MEMBER OR COCONINO MEMBER MEMBER SANDSTONE SANDSTONE MEMBER u 0 UPPER MIXTURE WITH WHITE HOUSE WHITE HOUSE SANDSTONE w < § SANDSTONE WHITE HOUSE DE DE CHELLY MOENKOPI MEMBER co UPPER MEMBER MEMBER MEMBER SANDSTONE Q OT DE CHELLY Q OT DE CHELLY COCONINO CO MEMBER DE CHELLY COCONINO 5 SANDSTONE SANDSTONE SANDSTONE SANDSTONE S DE CHELLY MOENKOPI SANDSTONE MIDDLE OAK SPRINGS OAK SPRINGS OAK SPRINGS ORGAN ROCK ORGAN ROCK MIDDLE OAK SPRINGS 5 TRANSITION 5 TRANSITION MOENKOPI RED BEDS TONGUE TONGUE MEMBER MEMBER MEMBER MEMBER MEMBER MEMBER 2 UPPER CUTLER d [ELLY SANDSTONE d X X 1 NOT EXPOSED X FORMATION S u LOWER HUNTERS POINT LOWER u HUNTERS POINT u LOWER HUNTERS POINT % LOWER HUNTERS POINT NOT EXPOSED kJ w SUPAI OR KAIBAB (WELL DATA) w MEMBER MEMBER MEMBER a MEMBER MEMBER MEMBER MEMBER E-* Q DE CHELLY SANDSTONE DE DE CHELLY MEMBER SANDSTONE Q YESO TYPE SUPAI SUPAI PERMIAN COCONINO LIMESTONE CEDAR MESA CEDAR MESA C DE CHELLY SANDSTONE NOT EXPOSED 5 Q SANDSTONE SANDSTONE U RED BEDS CUTLER CUTLER FORMATION COCONINO CUTLER FORMATION RED BEDS I SANDSTONE f RED BEDS SANDSTONE LOWER CUTLER g SUPAI SUPAI SUPAI SUPAI SUPAI ? MOENKOPI SUPAI SUPAI SUPAI SUPAI MOENKOPI SUPAI RED BEDS SUPAI FORMATION H D HALGAITO O HALGAITO SUPAI(?) SUPAI TONGUE TONGUE ______L 53 > a r c 2 H cn m TRIASSIC ■MONUMENT VALLEY- OLJETO B GRAPHIC OF DE SECTIONS CHELLY SANDSTON DEFIANCE E—MONUMENT 8 VALLEY e C E L AYNCANYON CANYON DeCHELLY A Y NNZIIBONITO NAZLINI CANYON 1 3 2 ------DEFIANCE PLATEAU------HUNTERS POINT 4 R A S C u TRIASSIC A SRNSBLACK SPRINGS OAK CLIFFS GREEK 6 PLATEAU s i l t s t o n e , g y p s i f e r o u s Gypsum and SPRINGS PINE
7 WATER WELL 8 ARGO STATE OIL TEST 9 Miles / m " / .7 a z (f&A. lt 3 Plate