Chapter I: Front Matter (1)

_The Geologic Story of_
COLORADO
NATIONAL MONUMENT

By S. W. Lohman

GEOLOGICAL SURVEY BULLETIN 1508

UNITED STATES DEPARTMENT OF THE INTERIOR
JAMES G. WATT, _Secretary_

GEOLOGICAL SURVEY
Doyle G. Frederick, _Acting Director_

Library of Congress Cataloging in Publication Data
Lohman, Stanley William, 1907-
The geologic story of Colorado National Monument.
(Geological Survey Bulletin 1508)
Bibliography: p. 131
Includes index.
1. Geology—Colorado National Monument.
2. Colorado National Monument.
I. Title. II. Series: United States Geological Survey Bulletin 1508
QE75.B9 no. 1508 [QE92.C6] 557.3s [557.88′17]
80-607952

For sale by the Superintendent of Documents, U.S. Government Printing
Office
Washington, D.C. 20402

Contents

Page
Preface XI
History of the Monument 1
Early history of the region 5
Prehistoric people 5
Late arrivals 10
Early settlement 10
The Brown-Stanton river expedition 11
Kodel’s gold mine 12
Recent cave dweller 13
Artesian wells 14
Geographic setting 16
The geologic story begins 17
Ancient rocks and events 24
A great gap in the rock record 26
The age of reptiles 27
Early landscape 28
Ancient sand dunes 29
The rains came 32
Another gap in the rock record 35
The sea to the west 39
Deposits and events east of the sea 39
Dinosaurs roam the Monument 47
Dinosaurs on the move 53
Yet another gap in the rock record 54
Peat bogs 55
The sea covers the Plateau 56
The sea’s final retreat 56
End of the dinosaurs 60
The age of mammals 61
Early deposits and events 63
Lake Uinta 63
The mountains rise again 64
Nearby lava flows 71
Ancestral Colorado River 72
Piracy on the high plateaus 72
The age of man 76
The ice age 77
Capture of East Creek 78
Canyon cutting 78
A look into the future 83
How to see the Monument 85
Trips through and around the Monument 88
From Grand Junction through the Redlands to the West Entrance
of the Monument 88
From Fruita to the West Entrance of the Monument 96
Through the Monument from West to East Entrances 97
From the East Entrance to Grand Junction 118
Through Glade Park from the northwest arm of Ute Canyon to
Columbus Canyon 119
From Glade Park to Grand Junction via the Little Park Road 121
Résumé of geologic history and relation to other National Parks
and Monuments in the Colorado Plateau 125
Acknowledgments 130
References 131
Additional reading 133
Index 135

Figures

Page

Frontispiece. Balanced Rock II
Figure
1. John Otto 2
2. John Otto’s Monument 4
3. Map of Colorado National Monument 6
4. Petroglyphs 9
5. Cave 14
6. Independence Monument 19
7. Rock Column of Colorado National Monument 20
8. Geologic Map 22
9. Block diagrams of early Proterozoic events 25
10. Petrified sand dunes 30
11. The Coke Ovens 31
12. Red Canyon 33
13. Thin-bedded Kayenta Formation 34
14. Kayenta Formation 36
15. Gap in the rock record 37
16. Entrada Sandstone 41
17. Moab Member of Entrada Sandstone 42
18. Mottled salmon-and-white Slick Rock Member 43
19. White Entrada Sandstone 44
20. Summerville Formation 46
21. Morrison Formation 48
22. Excavating type specimen of _Brachiosaurus altithorax_ Riggs 51
23. Skeletons of typical dinosaurs of Morrison Formation 52
24. Burro Canyon Formation and Dakota Sandstone 54
25. Mount Garfield 57
26. Photo index map 58
27. Common types of rock folds 62
28. Common types of faults 65
29. Ladder Creek monocline and Redlands fault 66
30. Lizard Canyon monocline 67
31. Kodels Canyon fault 68
32. Kodels Canyon fault 69
33. Geologic structures at Fruita entrance to Colorado National
Monument 70
34. Probable drainage patterns and land forms near the Monument at
four successive stages of development 74
35. Fallen Rock 81
36. Unaweep Canyon 82
37. Redlands fault 89
38. Closeup of updragged Wingate Sandstone along Redlands fault 90
39. Bronze plaque and monument marking the discovery of
_Brachiosaurus altithorax_ Riggs 91
40. Reverse part of Redlands fault 92
41. Northwest end of Redlands fault 93
42. Looking west into Monument Canyon 94
43. Looking west from divide on Broadway 2 miles east of West
Entrance to Monument 95
44. New fill on Rim Rock Drive between two tunnels on west side of
Fruita Canyon 98
45. Fruita Canyon 100
46. Campsites at north end of campground 101
47. Picnic area and parking lot 102
48. Window Rock 103
49. Pipe Organ 104
50. Visitor Center and the Saddlehorn 106
51. Independence Monument 107
52. Ute Canyon 110
53. Cold Shivers Point 112
54. Top of old Serpents Trail 113
55. Looking northeast from old Serpents Trail 114
56. South portal of tunnel through Wingate Sandstone 115
57. Devils Kitchen 117
58. Glade Park fault viewed from the ground 122
59. Glade Park fault viewed from the air 123
60. Ladder Creek monocline and Redlands fault 124
61. Geologic time spiral 126

Preface

From 1946 until about 1956 I carried out fieldwork intermittently on the geology and artesian water supply of the Grand Junction area, Colorado, the results of which have been published.[1] The area mapped geologically contains about 332 square miles in the west-central part of Mesa County and includes all of Colorado National Monument. During the fieldwork several successive custodians or superintendents and several park naturalists urged that upon completion of my professional paper I prepare a brief account of the geology of the Monument in terms understandable by laymen, and which could be sold at the Visitor Center. This I was happy to do and there resulted “The geologic story of Colorado National Monument,”[2] published by the Colorado and Black Canyon Natural History Association in cooperation with the National Park Service. This report contained colored sketches by John R. Stacy and a colored cover, but the photographs and many of the drawings were reproduced in black and white.

Later, after I had prepared popular style reports containing mostly color photographs on Canyonlands[3] and Arches[4] National Parks, officials of Colorado National Monument and I discussed the possibility of preparing a revised and enlarged edition of my 1965 report containing mainly color photographs, inasmuch as the supply of the black and white edition was nearing exhaustion, and later became out of print. At the meeting in the Monument on June 8, 1976, attended by Robert (Bob) E. Benton, Superintendent, A. J. (Jerry) Banta, Supervising Park Ranger, Margaret Short, Park Naturalist and Secretary of the Natural History Association, and me, it was agreed that: (1) A revised and enlarged edition containing mostly color photographs should be prepared for publication as a bulletin of the U.S. Geological Survey, and (2) that the Colorado and Black Canyon Natural History Association gave its permission for use of any or all of the copyrighted material in the first edition. The present report resulted.

The cover is a duotone of a 9- × 12-cm infrared photograph of Independence Monument taken by me. (See also fig. 6.) Most of the color photographs were taken by me on 4- × 5-inch or 9- × 12-cm tripod mounted cameras using lenses of several focal lengths, but I took some with 35-mm cameras. Some of the color photographs and all the black and white ones were taken by those credited in the captions, to whom grateful acknowledgment is made. The points from which most of the photographs were taken are shown in figure 26.

History of the Monument

The story of how Colorado National Monument came into being is as colorful as the canyons and cliffs themselves. The fantastic canyon country had a magical attraction for John Otto[5] (fig. 1) who, in 1906, camped near the northeastern mouth of Monument Canyon and began building trails into the canyons and onto the mesas—the high tablelands that separate the deep canyons. He did this back-breaking work simply because he wanted to and so that others could share the beauty of this wild country.

In 1907 Otto got the Grand Junction Chamber of Commerce to petition Secretary of the Interior James A. Garfield to set aside the area as a National Monument. Otto’s dream came true on May 24, 1911, when President William Howard Taft signed the proclamation creating the Monument. On June 14, Otto climbed to the top of Independence Monument (fig. 6) where he placed the Stars and Stripes to celebrate Flag Day. For several years thereafter Otto placed the flag atop Independence Monument on July 4th to celebrate Independence Day.

Until about 1921 the only routes into the Monument proper were John Otto’s trails, but in that year the ranchers of Glade Park joined with Otto in building the steep, twisting Serpents Trail from No Thoroughfare Canyon to the mesa above—a much shorter route to Grand Junction. It had 54 switchbacks and climbed about 1,500 feet in 2½ miles. The Serpents Trail was included in the Monument in 1933 and was used until 1950 when an easier route was built up the west side of No Thoroughfare Canyon and through a tunnel to the top of the mesa (figs. 3, 56). The Serpents Trail has been preserved as an interesting foot trail (fig. 55), which can be hiked downhill in an hour or so. A parking area near the foot of the trail allows one member of a group to drive ahead to await the others.

In 1924 John Otto got the idea that the Monument should include a herd of big game, so he talked the Colorado Game and Fish Department into shipping six young elk, and he got the local Elks Lodge to pay the transportation costs. The elk were turned loose in Monument Canyon, but they found the sparse vegetation and scant water supply ill suited to their needs, so after a few years they found a way out over the rim and migrated about 20 miles south of the Monument to lush high country where they joined with native elk and multiplied to become the ancestors of the present fine herd on Piñon Mesa (shown in fig. 34_D_). Occasionally a few return to the Monument and may be seen mainly in Ute Canyon. Native mule deer are frequently seen in and near the Monument.

Far from being discouraged, Otto then hatched the idea to start a buffalo[6] herd to be purchased by donations of buffalo nickels from school children and by contributions from the Odd Fellows and others. He finally raised enough money to get the patient Game and Fish Department to send him two cows and one bull. Unfortunately the bull died, so Otto talked the National Park Service into shipping him a bull from Yellowstone National Park. This time success crowned his efforts, and the small herd eventually multiplied to as many as 45 animals, but generally the herd has been kept at about 20-25 head ever since. You may spot some of them when you gaze down into Monument or Ute Canyons or when you drive past the northeastern boundary. Rarely, you may spot one in Red Canyon.

At the northeast corner of Fourth Street and Ute Avenue in Grand Junction is a most unusual object, which illustrates yet another peculiarity of John Otto—fantastic father of Colorado National Monument (fig. 2). Its history is best told by quoting from Al Look,[7] though its purpose still remains a mystery.

One day a horse drawn dray backed up to a vacant lot on Grand
Junction’s Main Street [corner 6th] and unloaded a granite cube four
feet square, carved on two sides. It weighed more than a ton and Otto
supervised the setting.

One side [now facing west and not visible in fig. 2] showed a three
foot circle containing a swastika with a five pointed star in each
quarter. Above the emblem was carved “Rock of Ages” and below read
“Cross of Ages.” The second side [now facing south, and shown in fig.
2] was beyond normal comprehension. Two large W’s on either side of a
small swastika were over the letters or initials P.P., then four chain
links with the letters T, H, L, J. inscribed, followed by the initials
I.E. Below on the left was “1918,” over “Year 1”. On the right was
“Old Count” and under it “New Count.” Between them stands the word
‘MARCH.’ Below this are abbreviations for the seven days of the week
with the figure 1 under MON ending with a 6 under SAT. The bottom line
[most of which is barely visible in the photograph] contained the
figure 7 in a circle, a carpenter’s square, a small rectangle,
probably representing a level, a plumb bob, a carpenter’s compass and
a circle showing the western hemisphere. That is all. It made sense to
John Otto because from somewhere he gathered considerable money to
have this monument carved by the local gravestone merchant. It stood
for several years to mystify pedestrians, and was finally moved beside
the Redlands road to the [east entrance of] Colorado Monument where it
is now hidden by weeds.[8]

It was still there in the 50’s when my family and I were startled to find it. We were afraid it might be lost forever so are glad it finally found a safe resting place on a concrete slab at the museum. I shall greatly appreciate hearing from any reader who can decipher this enigma.

Otto’s rock is at the southwest corner of The Historical Museum and Institute of Western Colorado. The main attraction inside is a life-size skeleton of _Allosaurus_ (fig. 23), whose bones are exact plastic replicas of real ones at the museum of Brigham Young University, at Provo, Utah. The painstaking casting of the “bones” and assembly of the self-supporting skeleton was done by Al T. Look, son of author Al Look listed under “References.” The museum also houses other items of interest from the Grand Junction area.

Construction of the scenic Rim Rock Drive through the Monument was begun by the National Park Service about 1931 using workers from the Civilian Conservation Corps, and the drive eventually was completed to join roads from Fruita and Grand Junction. The route from Fruita includes a winding road up Fruita Canyon and through two tunnels to the mesa (figs. 3, 44, 45).

A modern Visitor Center, new housing facilities for park personnel, additions to the campgrounds, the Devils Kitchen Picnic Area near the East Entrance, several self-guiding nature trails, and additional overlooks and roadside exhibits were completed in 1964 as part of the Mission 66 program of the National Park Service.

The Monument originally included 13,749 acres, but boundary changes in 1933 and 1939 increased the total to 17,660 acres, and the inclusion of all of No Thoroughfare Canyon and other boundary adjustments in 1978 increased the size to about 20,457 acres, or about 32 square miles (see map, fig. 3).

Early History of the Region

Prehistoric People

John Otto, early explorers, and even the Ute Indians who once hunted in the area were by no means the first people to view the Monument, in fact they were “Johnnies-come-lately.” Considerable evidence indicates that prehistoric people inhabited the area thousands of years ago.

Many years ago Al Look, of Grand Junction, discovered and excavated two caves in the part of No Thoroughfare Canyon formerly outside the Monument. He found stone projectile points, knives, awls, milling stones, parts of a sandal and coiled basket, reed matting, corn, corncobs, acorns, and animal bones, but no pottery—indicating that the people had not progressed beyond basket making. Similar artifacts were found in several other nearby places on the Uncompahgre Plateau. Archaeologists have named this old culture the Uncompahgre Complex, and date it back to a few thousand years before the time of Christ.[9] It should be pointed out that it is unlawful to remove artifacts, fossils, rocks, or minerals from a National Park or Monument.

In the summer of 1963 an archaeological survey of Colorado National Monument was carried out, under the terms of an agreement between the National Park Service and the University of Colorado, by Stroh and Ewing and their field assistants.[10] A total of 75 aboriginal sites were found of which 71 were within the Monument boundaries of that date, and 4 were closely adjacent. These comprised 41 open campsites, 24 rock shelters, 2 small caves, and 8 chipping stations. Artifacts recovered included 62 projectile points, 21 metates (grinding stones), 40 manos (hand stones), 111 whole or fragments of blades or scrapers, 6 choppers, several fragments of baskets, potsherds (bits of broken pottery) at two sites, 2 wood awls, several strands of yucca fibers, 3 corncobs, 6 kernels of corn, several bone fragments, storage cists at five sites, and petroglyphs at three locations.

Stroh and Ewing concluded that the majority of the sites appear to have been the campsites of a hunting and gathering people, and they speculated that there may have been aboriginal activity in the area from as long as several thousand years ago to relatively recent times.

The largest of the petroglyphs,[11] or rock drawings, are on a fallen slab of Wingate Sandstone in No Thoroughfare Canyon, and are shown in figure 4. Archaeologist John Crouch (footnote 10), who kindly reexamined these petroglyphs in February 1980, told me that most of the figures appear to be Shoshonian (Ute), but that some may be of the Fremont culture[12] or even older.

Late Arrivals

Early Settlement[13]

Prior to 1881 the Monument area was inhabited only by Ute Indians, but it was visited from time to time by a few fur trappers, explorers, and geologists. In 1776 an expedition led by Fathers Dominguez and Escalante passed northward across Grand Mesa, the high plateau just east of the area, which is pointed out in many of the photographs. A trading post was built by Joseph Roubidoux about 1838 just above the present site of Grand Junction. In 1853 Captain John W. Gunnison, seeking a new route for a transcontinental railroad, led an exploring party down what is now the Gunnison River Valley, past the confluence with the Grand River (now called the Colorado, p. 16), and on down the valley. Geologists and topographers of the Hayden Survey found only Ute Indians in the area in 1875 and 1876, and their field season of 1875 was abruptly cut short because of skirmishes with hostile Utes. After the Meeker (Colorado) Massacre of 1879, believed by many to have been caused mainly by the ignorance and shortsightedness of Meeker himself, treaties were signed forcing the Utes out of western Colorado onto reservations in eastern Utah, and the last of the Utes was reportedly out of the area by September 1881. The Grand Valley was immediately opened to settlement, and the first ranch was staked out on September 7, 1881. Nineteen days later George A. Crawford founded Grand Junction as a townsite and formed the Grand Junction Town Company the next month. The success of the new town was assured on November 21, 1882, when the narrow-gage line of the Denver and Rio Grande Railroad (now Denver and Rio Grande Western Railroad) reached it via the Gunnison River valley. The town of Fruita was founded by William E. Pabor in 1883 and incorporated the following year.

The Brown-Stanton River Expedition[14]

Of the many early expeditions down the Colorado River, only one went past what is now Colorado National Monument—the ill-fated Brown-Stanton expedition. After the pioneering expeditions of 1869 and 1871 down the Green and Colorado Rivers by Major John Wesley Powell and his men, the many ensuing river expeditions started in Utah or Wyoming; but the first phase of the Brown-Stanton expedition started in Colorado—at Grand Junction. In 1889 Frank M. Brown organized a company for the construction of the proposed Denver, Colorado Canyon, and Pacific Railway, which was to carry coal from mines in Colorado over a “water-level” line through the mighty canyons of the Colorado River to the Gulf of California some 1,200 miles away, from which coal would be shipped to various ports in California. On March 26, 1889, president Brown, chief engineer F. C. Kendricks, and assistant engineer T. P. Rigney drove the first stake at Grand Junction for a survey of the new line. Then Brown left for the East to obtain financing, and the other two men plus some hired hands took off in a boat down the Grand River. After reaching the confluence, they towed the boat up the Green River to the town of Green River, Utah, thus becoming the first to make this trip upstream, albeit on foot and dragging their boats. Brown, who had returned from the East, his newly appointed chief engineer Robert Brewster Stanton, and 14 others in six ill-designed boats of cedar rather than oak, left Green River, Utah, on May 25, 1889. Against the advice of Major Powell and others, they carried no life preservers. After many mishaps, Brown and two others were drowned near the head of Marble Canyon, and the ill-fated expedition temporarily ground to a halt. However, the indefatigable Stanton had new boats built of oak, and with a reorganized party of 12 left the mouth of the Dirty Devil River on November 25. After many additional mishaps the party finally reached the Gulf of California on April 26, 1890. In spite of Stanton’s heroic efforts, the railroad was never built, and the Grand Canyon was spared the huffing and puffing of locomotives.

Kodel’s Gold Mine[15]

As shown in figures 3, 8, and 26, the first major canyon west of the West Entrance of the monument is called Kodels Canyon (pronounced \‘kōd^ǝls\). It was named after an early-day stonemason turned prospector, a hermit, who came to the Fruita area before 1900 and prospected for gold until at least 1930 in the canyon that now bears his name. He seemingly built a cabin or house near the mouth of the canyon, spent most of the rest of his life in a vain quest for gold in the canyon, barricaded his house against would-be intruders, and took potshots at anyone approaching his home for fear they were after his “gold.” Some thought him only half crazy, but when he took repeated shots at an Indian named Henry Kadig, he was adjudged wholly insane and sent to the mental hospital at Pueblo, Colorado, for several years. When he got out he sold the grazing rights in his canyon to the late Irving Beard of Fruita, and seemingly was not heard from again. According to various estimates, Kodel dug an adit between 18 and 150 feet into the dark Proterozoic rock in the side of the canyon (shown in fig. 3), then sunk a shaft somewhere between 30 and 50 feet deep. He was always “on the verge of a big strike,” but there is no record of any actual production.

Later, a prospector from the midwest spent several summers digging in Devils Canyon, the next major canyon to the west, but he was equally unsuccessful. The unsuccessful attempts of Kodel and others is not surprising, for the two canyons are some 100 miles north of the Colorado mineral belt—a band extending roughly from Boulder to the western part of the San Juan Mountains, in which ore-bearing Upper Cretaceous or lower Tertiary rocks were intruded into all overlying rocks of whatever age.

Recent Cave Dweller

About 3 miles west of the Glade Park Store and Post Office are three large caves in a cliff of the Wingate Sandstone on the north wall of a canyon containing a tributary of Clark’s Wash. The middle cave, which formerly contained a small one-room framehouse and other improvements, was occupied for about 40 years prior to 1958 by Mrs. Laura Hazel Miller (fig. 5). A large cave just to the west (left) was used for storage, and another large cave just to the east formerly was fenced to shelter domestic animals. Mrs. Miller lived alone most of this time but had a dog for companionship the last few years she lived in the cave. When my wife and I visited her in the mid-fifties we had a very pleasant conversation with this very intelligent woman and could hardly believe she was 87 years old. She could not understand why anyone could live in crowded cities as she much preferred the peace and quiet of her cave. Once a week she walked the 6 miles round trip to and from the Glade Park Store and Post Office, bought what few necessities she needed, and telephoned her daughter in Grand Junction. Maybe she had something the rest of us have missed! She became sick in her nineties and moved to Grand Junction to live with her daughter. After she died, the property was sold, and I have since observed that vandals had burned her one room house and had destroyed most of the other improvements.

Artesian Wells

It may surprise you to learn that several sandstone formations supply water to artesian wells northeast of the Monument in The Redlands, Orchard Mesa, and the southwestern side of the Grand Valley, most of which are 500 to more than 1,000 feet deep. When first drilled and for some years later these wells flowed at the land surface, but eventually after too many wells had been drilled too close together, each well reduced the output of neighboring wells until most wells ceased to flow naturally. This made it necessary for most well owners to install pumps, which further aggravated the problem by reducing the artesian head (the height to which the water rises above the formation from which it issues). This created a situation not unlike too many children sucking on straws in the same ice cream soda, and led to a detailed investigation by the U.S. Geological Survey and the Colorado Water Conservation Board,[16] outgrowths of which were the present report and its predecessors.

The water system of the Ute Conservancy District was virtually completed by late 1964 and began to supply water to rural residents of Grand Valley between the towns of Palisade and Mack through a vast network of pipelines. The water is obtained from surface sources on the north flank of Grand Mesa east of the valley and is brought to the valley via a pipeline down the valley of Plateau Creek. Use of the new water has reduced the draft on many of the artesian wells. The reduced draft has locally arrested the decline in the artesian head or has actually allowed some recovery in head.

In order of their importance and productivity the water-bearing sandstones are the Entrada, the Wingate, and local sandstone lenses in the lower part (Salt Wash Member) of the Morrison Formation (fig. 7). In a few places small flows or yields are obtained from wells that tap the Dakota Sandstone and underlying Burro Canyon Formation, but inasmuch as the Dakota contains some marine sandstones from which all the salt seemingly has not yet been flushed out, the water from most of these wells is brackish or salty.

As we will see on the trip “From Grand Junction through The Redlands to the West Entrance of the Monument,” pages 88-95, in and near the Monument these sandstones look bone dry, so how can they supply water to artesian wells? They are indeed dry in all the cliff exposures, but as will be noted later when the bending and breaking of the rocks are discussed (p. 64-71), erosion has exposed the upturned sandstones so that they may take in water from the many small streams that drain the Monument and adjacent areas for short periods after summer thundershowers or during spring thaws. The water moves slowly down the dipping sandstones and becomes trapped under pressure beneath overlying beds of siltstone or mudstone—materials that are nearly impervious.

Geographic Setting

Geologists and geographers have divided the United States into many provinces, each of which has distinctive geologic and topographic characteristics that set it apart from the others. Colorado National Monument is in the northeastern part of the Canyon Lands section of the Colorado Plateau Province—a province that contains 15 national parks and monuments, about 3 times as many as any other province. This province, hereinafter referred to simply as the Colorado Plateau, or the Plateau, covers some 150,000 square miles and extends from Rifle, Colo., at the northeast to a little beyond Flagstaff, Ariz., at the southwest, and from Cedar City, Utah, at the west nearly to Albuquerque, N. Mex., at the southeast. This scenic province consists of high plateaus generally ranging in altitude from 4,500 feet to more than 7,000 feet, which are deeply and intricately dissected by literally thousands of canyons.

Colorado National Monument is drained entirely by the Colorado River, which flows to the northwest in the wide Grand Valley just a few miles from the northeastern border (fig. 3). The small streams that drain the Monument contain water only after summer thundershowers or after rapid snowmelt.

Why is the large valley of the Colorado River called the Grand Valley? The Colorado River northeast from its confluence with the Green River in the middle of Canyonlands National Park[17] formerly was called the Grand River, and the Green and Grand joined at the confluence to form the Colorado River. The Grand River was renamed Colorado River by act of the Colorado State Legislature approved March 24, 1921, and approved by act of Congress July 25, 1921. But the old term still remains in names such as Grand County, Colo., the headwaters region; Grand Valley, a town 16 miles west of Rifle, Colo.; Grand Valley between Palisade and Mack, Colo.; Grand Mesa, an extensive plateau which towers more than a mile above the Grand and Gunnison River Valleys; Grand Junction, Colo., a city appropriately situated at the confluence of the Grand and Gunnison Rivers; and Grand County, Utah, which the river traverses after entering Utah.

The Geologic Story Begins

Colorado National Monument is a land of brightly colored cliff-walled canyons and towering monoliths—a majestic sample of mysterious canyonlands that stretch hundreds of miles to the west and south. Now a desert region more than a mile above the sea, it was not always so. More than a billion years ago the site of the Monument was deep beneath the sea. Later, lofty mountains were pushed up only to be obliterated eventually by the slow but relentless forces of erosion. Millions of years later the earth shook to the stride of 10-ton dinosaurs—then the sea returned again and sharks swam over the region looking for food.

These are but a few samples of the interesting—even exciting—events in the long geologic history of the Monument. Many pages, indeed several whole chapters, of its history are missing and must be inferred from nearby regions where the story is more complete. Thus, the cliffs and canyons you are looking at did not get that way overnight. An understanding of the geologic processes and events that led to the scenic features of today should help you toward a clearer picture and greater appreciation of nature’s handiworks (fig. 6).

Geologists recognize rocks of three distinctly different modes of origin—sedimentary, igneous, and metamorphic, and there are many variations of each type. The sedimentary rocks of the Monument are composed of clay, silt, sand, and gravel carried and deposited by moving water; silt and fine sand transported by wind; and some limestone, composed mainly of the mineral calcium carbonate, which was precipitated from water solutions in freshwater lakes. In areas not far to the northeast and southwest are many sedimentary rocks of marine origin, that is, materials that were deposited in the ocean or shallow inland seas, but in the Monument marine sedimentary rocks occur only in parts of the Dakota Sandstone; however, the overlying marine Mancos Shale underlies the adjacent Grand Valley and forms the lower slopes of the Book Cliffs across the valley (fig. 25).

Igneous rocks were solidified from liquid molten rock intruded upward into any preexisting rocks along cracks, joints, and faults. Molten rock that reaches the land surface and forms volcanos or lava flows is called extrusive igneous rock. Joints are cracks or breaks in rocks along which no movement has taken place. Faults are cracks or joints along which one side has moved relative to the other. Different types of faults are shown in figure 28. Metamorphic rocks were formed from either of the other types by great heat and pressure at extreme depths in the Earth’s crust. Metamorphic rocks and some intrusive igneous rocks make up the hard, dark rock that floors all the deep canyons in and near the Monument. The nearest extrusive igneous rocks are the thick, dark lava flows that cap towering Grand Mesa to the east and Battlement Mesa to the northeast.

AGE (millions of years)
GEOLOGIC AGE
NAME OF ROCK FORMATION
KIND OF ROCK AND HOW IT IS SCULPTURED BY EROSION
THICKNESS (feet)
NAMED FOR OCCURRENCE AT OR NEAR
80
Late Cretaceous
Mancos Shale
Gray and black shale, and thin beds of sandstone and limestone.
Contains sea shells. Eroded from Monument, but underlies
Grand Valley and forms lower part of Book Cliffs.
3,800
Mancos, Colo.
Dakota Sandstone
Coaly shale, sandstone, conglomerate, and lignite coal. Contains
plant remains. Forms benches and slopes. Caps highest hill
in Monument.
150
Dakota, Nebr.
115
Early Cretaceous
Burro Canyon Formation
Green siltstone and shale, and sandstone and conglomerate. Forms
benches and slopes. Crops out on highest hill in Monument.
60
Burro Canyon San Miguel Co., Colo.
EROSIONAL UNCONFORMITY
150
Late Jurassic
Morrison Formation
Brightly colored siltstone and mudstone, and sandstone and
limestone. Contains dinosaur bones and fresh-water shells.
Forms slopes and badlands. Lower third with sandstone
lenses is Salt Wash Member, upper two thirds is Brushy
Basin Member.
600
Morrison, Colo.
170
Middle Jurassic
Summerville Formation
Brightly colored siltstone and mudstone, and thin sandstones.
Forms slopes.
54
Summerville Point San Rafael Swell, Utah
Entrada Sandstone
White and salmon-red sandstone. Upper level-bedded Moab Member
forms stair steps, lower mostly cross-bedded Slick Rock
Member forms cliffs.
150
Entrada Point Moab, Utah Slick Rock, Colo.
195
Jurassic and Triassic(?) (missing)
EROSIONAL UNCONFORMITY
210
Late Triassic(?)
Kayenta Formation
Red and purple siltstone and shale, and sandstone and
conglomerate. Forms bench between two cliffs and mesas
between canyons.
45-80
Kayenta, Ariz.
Late Triassic
Wingate Sandstone
Buff and light red sandstone. Cross-bedded and level-bedded.
Forms highest cliffs and most of named rock features in
Monument.
350
Fort Wingate, New Mex.
Chinle Formation
Red siltstone and shale, and some limestone conglomerate. Forms
steep slopes at foot of cliffs.
80-100
Chinle Valley N.E. Ariz.
GREAT UNCONFORMITY
240-1000
Triassic, Paleozoic, Younger Proterozoic (missing)
Unnamed
Schist, gneiss, granite, and pegmatite dikes. Floors main
canyons and forms high bluff above The Redlands.
Unknown
1500
Older Proterozoic

After the materials of the sedimentary rocks were deposited and covered by younger layers, they generally became saturated or partly saturated with ground water containing small amounts of dissolved minerals. Some of these minerals precipitated from solution and cemented the loose particles into rocks of varying hardness. Thus, most of the sandstones are partly cemented with the mineral calcite, composed of calcium carbonate (CaCO₃), but some are cemented also with silica (SiO₂) or hematite (Fe₂O₃).

Look almost anywhere in the Monument and you will see that the rocks are piled up in layers of different color, thickness, and hardness—much like a vast layer cake. In most of the Monument, these layers are flat or slope gently down to the northeast, but along the northeastern boundary they are sharply bent or broken as though the cake had been carelessly placed over the edge of a table and had sagged.

Let us consider these layers one by one, beginning with the oldest at the bottom, for each is a partial record of events long past. Layers of rock that can be easily recognized and distinguished from other layers are called formations and are named after a place where they are well exposed. For the name to be accepted for general usage it must be the first published description in a technical report of a particular sequence of rock layers. The places after which the formations of the Monument were named are given in the rock column (fig. 7), and the outcrops of the formations are shown on the geologic map (fig. 8). In the pages that follow, the geologic events that shaped the Monument we see today are discussed in chronological order, beginning with the oldest rocks that floor the deep canyons.

EXPLANATION
QUATERNARY
Qal—ALLUVIUM
Qls—LANDSLIDE DEPOSITS
CRETACEOUS
Km—MANCOS SHALE
Kdb—DAKOTA SANDSTONE AND BURRO CANYON FORMATION, UNDIVIDED
JURASSIC
Jms—MORRISON AND SUMMERVILLE FORMATIONS, UNDIVIDED
Je—ENTRADA SANDSTONE
TRIASSIC
TRk—KAYENTA FORMATION
TRwc—WINGATE SANDSTONE AND CHINLE FORMATION, UNDIVIDED
PROTEROZOIC
PL—SCHIST, GNEISS, GRANITE, AND PEGMATITE
CONTACT FAULT—Dashed where approximately located; dotted where
concealed. U, upthrown side; D, downthrown side
ANTICLINE
SYNCLINE
CENTRAL AXIS OF SYMMETRICAL MONOCLINE—Showing direction of plunge
UPPER BEND OF MONOCLINE—Showing direction of plunge
STRIKE AND DIP OF BEDS
ABANDONED MINE
Geology simplified from Lohman, 1965a
_(Showing location of—)_
DEVILS CANYON MONOCLINE
KODELS CANYON FAULT
LIZARD CANYON MONOCLINE
FRUITA CANYON MONOCLINE
LADDER CREEK FAULT

Ancient Rocks and Events

The dark rocks that floor all the large canyons of the Monument (fig. 6) and form the high bluffs along the northeastern boundary (figs. 37, 38, 40, 41) are of early Proterozoic[18] age—among the oldest known rocks of the Earth. Most were once sand and mud that spread out on the bottom of the sea and later hardened into sedimentary rocks (fig. 9-1). After thousands of feet of such rocks had accumulated, they were squeezed, bent, and lifted up by slow but mighty movements of the Earth’s crust to form high mountains perhaps like the Rockies. Heat and pressure that developed at great depth in the roots of these mountains changed the sediments into metamorphic rocks known as schist (finely banded) and gneiss (coarsely banded) (fig. 9-2). The rocks are about 1½ billion years old (fig. 7).

Later in Proterozoic time, about a billion years ago, molten material from below was forced upward along cracks or faults and cooled slowly to form thin seams or dikes and irregular bodies of granite (fig. 9-3). Dikes are called pegmatite when they contain large crystals of pink feldspar, white or clear quartz, black tourmaline, and large flakes of white mica. Small pegmatite dikes that pass through the older schist and gneiss may be seen along roadcuts in Fruita and No Thoroughfare Canyons.

A Great Gap in the Rock Record

If you look down into any of the large canyons in the Monument, you will notice a brick-red formation, the Chinle, which forms steep slopes at the foot of the high cliffs and lies upon the dark Proterozoic rocks along nearly straight lines of contact. Such a straight-line contact is particularly well shown about midway up the high bluffs along the northeastern boundary of the Monument (fig. 37). If the red layer and all overlying rocks were stripped away, these straight lines would be the exposed edges of a remarkably smooth, nearly flat erosion surface on the top of the dark Proterozoic rocks, as shown in the last diagram of figure 9. A vast amount of time passed between the carving of this surface and the deposition of the red Chinle, and no record of the events during this time is preserved in the Monument.

During the latter part of the Proterozoic Eon and parts of the long Paleozoic Era that followed, the dark rocks were submerged beneath the sea several times and received sediments now found in areas to the northeast and southwest. Beginning in the Pennsylvanian Period some 330 million years ago (fig. 61), a large upfold of the rocks, or anticline (fig. 27), known to geologists as the Uncompahgre Highland, rose high above sea level, probably reaching its highest level in Late Pennsylvanian or Permian time. This old highland formed an imposing chain of mountains in about the position of the present Uncompahgre Plateau.

After the old rocks were pushed up into these high mountains what became of them? From the moment the mountains began to rise, their rocks were buffeted by wind, pounded by rain, pried open by frost, scoured by debris-laden streams and, perhaps by glaciers, and the loosened rock particles were dissolved or carried to the sea. Most rocks are brittle enough to crack when bent by Earth forces. Such cracks, called joints, are easy targets for erosion. The freezing of water in joints tends to pry the rocks apart. The breakup of the rocks was hastened by the chemical attack on rock minerals by water charged with oxygen and carbon dioxide. When land plants became established in later geologic eras, soil acids formed from decaying vegetation also assisted materially in breaking up the rocks.

These same erosion processes are going on today, but their effects are scarcely noticeable from year to year except in soft earth after storms or floods. During eons of time, however, the mountains were again worn down to a nearly level plain. Missing between the red Chinle and the dark rocks are many thousands of feet of rocks, some of which once covered this surface and still occur in other regions less affected by erosion. This gap in the rock record, which represents more than a billion years, is known to geologists as a great unconformity. Missing are part of the lower Proterozoic rocks, all the upper Proterozoic rocks, all those of the Paleozoic Era, and part of those of the Triassic Period of the Mesozoic Era. (See figs. 7 and 61.)

Traces of primitive life have been found in some Proterozoic rocks in the form of lime-secreting algae and casts of worms, but no fossils of more advanced types have been found because at that time the primitive animals seemingly had not yet developed shells or skeletons. The ensuing Paleozoic Era saw the appearance and great development of shellfish, fish, amphibians, reptiles, and primitive plants. Some of the rock layers of ages missing at the Monument may be seen as near as Glenwood Springs to the northeast and Gateway to the southwest.

The Age of Reptiles

All the layers of sedimentary rocks preserved in the Monument above the dark Proterozoic ones were deposited by wind and water during the Mesozoic Era. This long era has been called the age of reptiles, for reptiles, including dinosaurs (meaning terrible lizards), were then the dominant land animals. The Mesozoic Era has been divided into three parts—the Triassic, Jurassic, and Cretaceous Periods. Rocks of each of these periods crop out in the Monument.

Early Landscape

By late Triassic time the Monument was part of a nearly flat plain cut on the dark Proterozoic rocks, but there were hills or low mountains to the northeast. Streams from these hills dropped mud, silt, sand, and some gravel on this plain and into many small lakes that occupied the gentle depressions. Later, these deposits hardened mainly into red siltstone and sandstone, but thin beds of gravel were cemented to form conglomerate, and thin beds of limestone formed in some of the shallow lakes by the precipitation of the mineral calcium carbonate. These rocks, which comprise the Chinle (pronounced Chin-lee) Formation, are only 80 to 100 feet thick in the Monument but are as much as 700 feet thick near Moab, Utah, southwest of the Uncompahgre Plateau, where the entire formation is present. There, the Chinle rests on still older Triassic and Paleozoic rocks—all absent in the Monument for the reasons noted previously. In some parts of the Plateau, sandstone or conglomerate beds in the lower part of the Chinle yield uranium ore, but these beds were not deposited in or near the Monument.

The red color of the Chinle and some of the overlying rocks is caused by minute amounts of iron oxide—the same pigment used in rouge and red barn paint. Various oxides of iron, some including water, produce not only brick red but also pink, salmon, brown, buff, yellow, and even green or bluish green. This does not imply that the rocks could be considered as sources of iron ore, for the merest trace of iron, generally only 1 to 3 percent, is enough to produce even the darkest shades of red.

Because it is soft, the Chinle is easily eroded into steep slopes at the foot of high sandstone cliffs in all canyons of the Monument and on top of the high bluffs that face The Redlands. It also forms the broad base of Independence Monument. Rim Rock Drive crosses the Chinle three times in the lower part of Fruita Canyon and twice in No Thoroughfare Canyon.

Fossil reptile bones, petrified wood, and freshwater shells come from the Chinle in parts of Arizona and Utah. Reptiles probably roamed the Monument in Chinle time, but their remains have not been located.

Ancient Sand Dunes

Still later in the Triassic Period the Monument became part of a vast desert. Winds blowing from the northwest brought great quantities of fine sand and piled them up into large dunes like those in the Sahara or in Great Sand Dunes National Monument in Colorado. But like all deserts, it was not always dry—occasional rainstorms produced many small lakes and ponds. Some of the sand was washed into these lakes or ponds and settled in level layers. This huge sandpile eventually hardened into the buff and light-red sandstone that we now know as the Wingate. The shapes of the old dunes are indicated by the steep dips of sand layers, called crossbeds, which stand out in sharp contrast to the nearly level layers formed in the lakes and ponds (fig. 10).

The spectacular scenery of Colorado National Monument owes its existence largely to the 350-foot cliffs of the Wingate Sandstone (fig. 6) and to the desert climate, which allows us to see virtually every foot of the vividly colored rocks and has made possible the creation and preservation of such a wide variety of fantastic sculptures. A wetter climate would have produced a far different and smoother landscape in which most of the rocks and land forms would have been hidden by vegetation.

Eroded remnants of the Wingate form most of the named rock features of the Monument and are shown in many of the photographs. Independence Monument—a towering slab of sandstone that resembles a bridge pier (fig. 6)—is all that is left of a high narrow wall that once connected the point east of Independence View with the high mesa north of the slab and which once separated the two entrances of Monument Canyon. In a few thousand years this remnant, too, may be gone.

Vertical cliffs and shafts of the Wingate Sandstone endure only where the top of the formation is capped by beds of the next younger rock unit—the Kayenta Formation. The Kayenta is much more resistant to erosion than the Wingate, so even a few feet of the Kayenta, such as the cap on top of Independence Monument, protect the rock beneath. Once this cap has been eroded away, the underlying Wingate weathers into rounded domes, such as the Coke Ovens.

Cold Shivers Point (fig. 53)—a toadstool shaped cap of sandstone of the Kayenta above a vertical cliff of the Wingate—is perhaps the most aptly titled feature of the Monument.

The Coke Ovens (fig. 11) and Squaw Fingers were formed partly because most of the caprock of Kayenta has been weathered away and also because the brittle rocks were cracked along an evenly spaced set of vertical joints. These joints trend northward between the two named features. More rapid weathering along these joints helped form the separate rounded domes or spires between them. Similarly, northwestward-trending vertical joints connect and helped shape Kissing Couple, Pipe Organ, and Sentinal Spire.

Many of the cliff walls of the Wingate are vertical, some even overhang, yet in some places the slopes are gentle enough to hold talus and to be climbed (fig. 12). Why is this? The answer to this question is given in a later section on “Canyon Cutting.”

Arches or shallow caves weathered out of some cliff faces of the Wingate, particularly where the underlying Chinle Formation has been partly scoured away. Although there are no large caves within the Monument, there are three in a row along the road 3 miles west of the Glade Park Post Office. One of these was inhabited until 1958 (fig. 5).

Many of the cliff faces of the Wingate are darkened or blackened by desert varnish—a natural pigment of iron and manganese oxides, silica, and clay.[19]

Dinosaurs left their footprints in the sands of the Wingate in parts of the Colorado Plateau, but no tracks or fossils have yet been found in this formation in or near the Monument.

The Rains Came

The arid climate of Wingate time was followed by a wet period, when streams from the northeast gradually covered the sand dunes with mud, sand, and some gravel. The sand and gravel of the stream channels were cemented into hard sandstone and conglomerate, and the mud of the flood plains hardened into red and purple siltstone and mudstone. The resulting Kayenta Formation makes up the bench between the two cliffs upon which the Visitor Center, campgrounds, and most of scenic Rim Rock Drive were built. Here, nature was kind, for this gently sloping bench was an ideal place to build the road from which to look down into the deep chasms. The Kayenta also caps the broad mesas between the canyons. It is about 350 feet thick in eastern Utah, only 45 to 80 feet thick in the Monument, and it is absent altogether not far east of the Monument. The reasons for the eastward thinning and ultimate disappearance of the Kayenta and some younger rocks are given in the next section.

As noted earlier, the sandstone beds and lenses of the Kayenta generally are coarser grained (some even contain small pebbles) and much harder than the underlying Wingate Sandstone—particularly the lower beds of the Kayenta, which serve as a protective capping, as shown in figure 13 and in many of the other photographs. Unlike the dominantly fine grained, well sorted, windblown sands of the Wingate, the coarser stream-laid sands of the Kayenta are angular and poorly sorted, so that small grains fill spaces between larger ones. Moreover, in addition to the calcite cement (which also holds together the sand grains in the Wingate and Entrada Sandstones), most of the sand grains and pebbles in the Kayenta are covered by interconnected “overgrowths” of silica (SiO₂), which make up about 10 percent of the rocks and serve as a nearly insoluble hard cement.[20]

The combination of the coarse and fine grains and interlocking silica “overgrowths” makes the Kayenta one of the most resistant rocks in the Colorado Plateau.

In distant views of weathered outcrops the Kayenta appears to consist mainly of thin beds or lenses of sandstone, which indeed it does, but in some fresh exposures, such as roadcuts, the highly lenticular red flood-plain deposits form striking features which may wedge out from 3 or 4 feet thick to a featheredge within horizontal distances of only a few feet (fig. 14).

The Kayenta has yielded fossil bones of dinosaurs and other reptiles in northeastern Arizona and freshwater shells in eastern Utah. As yet, however, no fossils have been reported from it in or near the Monument.

Another Gap in the Rock Record

Following the wet interval when the Kayenta Formation was deposited over wide areas of the Colorado Plateau by streams, the Plateau once again became a vast desert, and this time the dry climate persisted from the Late Triassic into the Jurassic. The howling winds piled up enormous sand dunes, layer upon layer, to a total thickness of more than 2,200 feet at Zion National Park, and as much as 500 feet remains in eastern Utah and parts of southwestern Colorado. This immense sandpile eventually was cemented by calcite into the Navajo Sandstone.

Beautifully sculptured remains of the Navajo are featured attractions at Zion, Capitol Reef, and Arches National Parks, Rainbow Bridge, Navajo, and Dinosaur National Monuments; border many miles of beautiful Lake Powell; and form the eastern flank of the San Rafael Swell. For reasons to be explained, this sandstone thins to the northeast, and is absent entirely at about the Utah-Colorado State line, some 35 miles southwest of the Monument. Thus, in the Monument, the Navajo, most of the Kayenta, and the lower part of the Entrada Sandstone are missing at another gap in the rock record, as shown in figure 15.

How is it possible that the Navajo Sandstone is more than 2,200 feet thick in Zion National Park, is several hundred feet thick in much of the Plateau in Utah and parts of southwestern Colorado, yet is absent entirely, together with a considerable thickness of younger rocks in and near Colorado National Monument? How much of the missing strata once were present in the Monument is not known, but it seems clear that at least part was present but was eroded away before the Entrada Sandstone was deposited. There is evidence[21] that following the deposition and consolidation of the Navajo Sandstone the Plateau and adjacent areas were uplifted, tilted gently westward, and eroded for a considerable period of time. Erosion naturally was most pronounced in the eastern areas, including the Monument, where the uplift was greatest. Thus, in the northeastern part of the Plateau all the Navajo and most of the Kayenta were eroded away, and erosion continued there while the lowest member of the Entrada, the Dewey Bridge Member, and the lower part of the overlying Slick Rock Member were being laid down in the Moab, Utah, area.[22] This old erosion surface is clearly visible in many places along the cliff wall on the southwest side of Rim Rock Drive between the Visitor Center and Kissing Couple.