Chapter II: Introduction (1)

Like the early Spanish explorers who first saw Palo Duro Canyon, today’s visitor is likely to view the impressive canyon with surprise and awe. This great depression—it is more than 2 miles wide and as much as 800 feet deep within park boundaries—contains a fascinating assortment of multicolored geologic formations and erosion-produced rock sculptures of many shapes, colors, and size. The geographic setting of the canyon further heightens its impact on the visitor, for it is surrounded by the level, virtually treeless plains of the Texas Panhandle. (_See_ upper background area in fig. 1, frontispiece).

It is not surprising that this scenic area has been set aside as a State park, for Palo Duro Canyon has long been of interest to man. First, as the hunting grounds of prehistoric Indians who stalked the now-extinct Ice Age mammoths and bison that roamed the valley floor. Later, the canyon was frequented by the Comanches, Apaches, Kiowas, and other Indians of historic time. These tribes, like those before them, found both food and refuge within the canyon. However, it was not until 1876 that Palo Duro Canyon was inhabited by the white man. It was during this year that pioneer cattleman Charles Goodnight herded some 1,600 head of cattle into the canyon and established a camp there (p. 6).

Today’s visitor to Palo Duro Canyon can re-live some of the fascinating history of this interesting area. One can still see a replica of Colonel Goodnight’s primitive dugout, follow the faint trace of the Comanche Trail, or perhaps find the fossil bones of prehistoric creatures that lived hundreds of thousands—even millions—of years ago. But most visitors to Texas’ most colorful canyon are not attracted by its interesting history. They come instead to enjoy the scenery and recreational opportunities that are present. These are readily accessible, for a carefully engineered, hard-surface road leads from the rim of the canyon to the canyon floor. There are campgrounds, picnic areas, concessions, and even an outdoor theatre (fig. 23). The location of these facilities and some of the canyon’s more interesting geologic features are shown on the generalized place map of the canyon (fig. 2).

This publication does not attempt to describe the scenic beauty of Palo Duro Canyon, for this must be seen to be appreciated. Rather, it discusses the geologic setting and origin of the canyon, the methods by which some of the more interesting geologic features were formed, and briefly reviews the history of the area. Hopefully, it will enable the visitor to understand better the meaning behind the canyon scenery, thereby enhancing his visit.

ACKNOWLEDGMENTS

Many people have assisted in the preparation of _The Geologic Story of Palo Duro Canyon_, and their help is gratefully acknowledged: Professor Jack T. Hughes, Dr. Frank W. Daugherty, Dr. Robert C. Burton, Meade Humphries, and Jim Hughes of the West Texas State University Geology Department provided much information about the area and assisted in the field; help was also provided by Mr. Pete Cowart, Mr. Earl Burtz, Mr. Jerry Tschauner, Mr. Bob Watson, Mr. King, and other park personnel; Mr. C. Boone McClure, of the Panhandle-Plains Historical Museum, furnished some of the photographs; Mr. J. Dan Scurlock, Mr. Bill Collins, and Mr. Harold Allums, of the Texas Parks and Wildlife Department, made available certain maps and statistical data; Mrs. Ples Harper of Canyon assisted in assembling information and photographs for the Pioneer Amphitheatre; and the aerial photograph of Palo Duro Canyon was taken by Mr. W. A. Hester and made available through the courtesy of Mr. Charles A. Wolflin of Amarillo.

Drs. Peter T. Flawn, Peter U. Rodda, and Ross A. Maxwell of the Bureau of Economic Geology read much of the manuscript and offered many helpful suggestions, and Mr. A. Richard Smith provided special information on caves in the Palo Duro area. Special thanks are due to Miss Josephine Casey who edited the manuscript and to Mr. J. W. Macon, cartographer, who assumed responsibility for preparing the maps. Thanks are due also to my wife, Jennie, who critically read the manuscript and took a number of the photographs. Finally, I would like to thank Dr. J. Daniel Powell of The University of Texas at Arlington for invaluable assistance in the field and his enthusiastic co-operation throughout the project.

PARK HISTORY

Palo Duro Canyon’s long and colorful past has created considerable interest among historians, archeologists, and geologists. Historians have traced the written history of man and his effect on the Palo Duro area, but archeologists have delved much further into the past. They have sought out and studied the more enduring records of the canyon’s early inhabitants—their tools, utensils, and weapons. The geologist, however, is interested in history that far antedates even the most primitive human inhabitant of the canyon. The earth scientist has probed the geologic record of the Palo Duro area, using rocks, minerals, and fossils as clues to the geologic history and development of the canyon.

Palo Duro Canyon is unique among Texas’ State parks because of its many contributions to history, archeology, and geology. Here the written record, the artifacts of prehistoric man, and the geologic formations overlap and complement each other in many respects. Although this guidebook is primarily concerned with the geologic history of the canyon, a brief review of its human history is also included.

ANCIENT MAN IN PALO DURO CANYON

Archeological studies indicate that the earliest known inhabitants of Palo Duro Canyon lived in the canyon from about 10,000 to 5,000 B.C. These early men apparently hunted the bison and now-extinct elephant-like mammoths that roamed the Palo Duro area during the Ice Age of Pleistocene time (_see_ geologic time scale, fig. 6). Their stone weapons and other artifacts have been found in and around the canyon. It is assumed that these primitive people—like those who came later—were attracted by the streams and springs that are found in the canyon and by game that came there to feed. There is also evidence that the Indians took advantage of certain of the canyon’s geologic features. They fashioned tools, weapons, and utensils from the rocks exposed in the canyon and used certain of the shallow caves and rock shelters as their homes.

INDIANS OF THE PLAINS

Various tribes of Plains Indians of historic times also used Palo Duro Canyon as a camping ground. The presence of these Indians is known from many campsites and burials. In addition, flint chips and stone artifacts, potsherds, ornaments of shell and bone, grinding slabs, stone mortars (fig. 15), and a few pictographs (fig. 3) have provided considerable information about the culture of these people. Among the tribes believed to have frequented the canyon at various times are the Apaches, Cheyennes, Arapahos, Kiowas, and Comanches. However, it is the Comanches who are most closely associated with the Palo Duro area, for the canyon is located near the center of their last homeland. Indeed it was here that the Comanches were finally defeated and driven from this part of the Plains. The battlefield where Colonel Ranald Mackenzie’s troops fought the Comanches is located near the southeast corner of the park (_see_ fig. 7). This skirmish, which took place in 1874, is believed to have been the last major Indian battle in Texas.

Although most of the canyon’s archeological sites have been picked over and many of the artifacts removed, important finds are still occasionally reported. Park visitors who make discoveries of this type are urged to report them to a park ranger in order that they might be called to the attention of the proper authorities.

ADVENT OF THE WHITE MAN

Although the history of Palo Duro Canyon is rich in Indian lore, it was the coming of the white man that heralded the development of the area. Today it is generally believed that Francisco Vasquez de Coronado was the first white man to view the canyon. Coronado and his men are thought to have camped here during the winter of 1541, as they crossed the High Plains in search of the fabled Seven Cities of Cibola.

Later, during the 17th and 18th centuries, the canyon was a favorite resting place of the buffalo hunters and Indian traders who frequented the Plains. The canyon was also popular during the first half of the 19th century, for it was then that it was occupied by the Comanches and served as a trade center for the Spaniards and Indians who came from New Mexico. These traders, called _comancheros_, bartered for loot taken by the Comanches on their raids of early settlements and wagon trains that passed through the Panhandle-Plains region.

This same era marked the beginning of American interest in the Palo Duro country. During this period the area was visited by several expeditions including those of Long and Pike and the Texas-Santa Fe Expedition of 1841. However, the canyon was not fully explored or mapped until 1852. This important survey was carried out by a party which was under the supervision of Captain R. B. Marcy.

But it was not until 1876 that the first white man established permanent residence in Palo Duro Canyon. In 1876—just two years after McKenzie’s rout of the Comanches—Colonel Charles Goodnight herded more than 1,600 head of cattle into the canyon. Here he laid out his first permanent ranch and lived in a primitive earthen dugout. Not only was Goodnight’s Palo Duro Ranch the first in the canyon, it is also thought to have been the first commercial cattle ranch in the Texas Panhandle. In later years Colonel Goodnight formed a partnership with John Adair of Ireland, and together they developed the famous JA Ranch—a vast spread of some 600,000 acres. Today’s visitor to Palo Duro Canyon can visit a partially restored dugout similar to that occupied by the canyon’s early settlers (fig. 30).

From the late 1800s until about 1930, the Palo Duro country remained the domain of the Panhandle-Plains cattleman. It was, nonetheless, a favorite picnic and camping spot of the residents of nearby towns and cities. In 1933 the recreational potential of the canyon was finally recognized and land for the Palo Duro Canyon State Park was purchased by the State of Texas with money obtained through a public revenue bond issue. Today, most of the park revenue received through gate admissions, concession receipts, and mineral leases goes into a fund that pays off the remaining balance of the revenue bonds. During the initial phase of the park’s development, most of the improvements in the area were made by members of the Civilian Conservation Corps who worked under the supervision of the National Park Service.

Currently, Palo Duro Canyon State Park is visited by approximately 300,000 visitors each year and is one of the State’s more popular recreational and scenic areas.

REGIONAL SETTING

Palo Duro Canyon State Park is located in the Panhandle of Texas (fig. 5) approximately 13 miles east of Canyon on State Highway 217 (_see_ fig. 7). It is about 12 miles south and 8 miles east of Amarillo via Ranch Road 1541 which intersects State Highway 217. The park includes more than 15,000 acres of Palo Duro Canyon, a complexly dissected area which spreads into Randall, Armstrong, and Briscoe counties.

More specifically, the Palo Duro area is situated on the Llano Estacado or High Plains area which comprises approximately 20,000 square miles of Texas and New Mexico (_see_ fig. 5). Generally speaking, the Llano Estacado is a high isolated plateau or broad mesa, rising above the surrounding rolling plains in a nearly flat, island-like mass. On the west, southwest, and south, the Llano Estacado is bounded by the valley of the Pecos River, while its eastern escarpment is drained by the headwaters of the Red, Brazos, and Colorado Rivers.

The rim of Palo Duro Canyon is formed by the Eastern Caprock Escarpment. Caprock is the term used to describe a massive layer of calcareous rock which supports the High Plains surface (_see_ p. 26). Because it is more resistant to forces of erosion than the softer, underlying more or less horizontal strata, the caprock forms an abrupt, precipitous escarpment at the edge of the High Plains. With the exception of the resistant caprock, however, the surficial deposits on the High Plains are for the most part unconsolidated sediments.

The Llano Estacado is essentially devoid of native trees and is characterized by a sparse, but uniform, covering of grasses. The surface rocks are of Tertiary and Quaternary age (_see_ geologic time scale, fig. 6) and have a general easterly to southeasterly slope of about 9½ feet per mile. In the vicinity of Palo Duro Canyon, rocks of Late Cenozoic age are directly underlain by Permian and Triassic formations. These Permian and Triassic rocks, which are discussed elsewhere in this publication, are not normally exposed except in deeply eroded areas such as the canyon.

_Showing:_
Q & T Pleistocene and Pliocene undifferentiated
Trdo Dockum Group (Triassic)
P Permian undifferentiated

THE GEOLOGIC STORY

THE CANYON’S ROCKS AND MINERALS

Palo Duro visitors—regardless of age—seem to have an innate curiosity about the canyon’s rocks. This is not surprising, for most of the features of the park landscape are composed of or have been sculptured from solid rock. In short, much of the natural beauty of Palo Duro Canyon has been derived from the character of its exposed rock formations and the effect of geologic agents upon them.

Because rocks are the raw materials of geology and the stuff from which landscapes are formed, it will be helpful for the visitor to know something about the general characteristics of rocks and their role in the development of the landscape. Rock is everywhere around us and is one of the most common objects in the world, yet few people can actually define a rock. So, at the outset it should be stated that _a rock is a naturally formed aggregate of minerals_, and _a mineral is a naturally occurring substance which has a fairly definite chemical composition, distinctive physical properties, characteristic internal structure, and which commonly occurs in definite shapes called crystals_. Although not an exact scientific or legal definition of a mineral, the above explanation is satisfactory for the purposes of this publication.

Although most visitors show considerable interest in the canyon’s rocks and minerals, few of them know the story behind the rocks. They do not know how the rocks were formed, of what they are composed, how they change, and how they differ. More important, they fail to realize the historical significance of the rocks and how they can be used to interpret events that occurred in the canyon many millions of years ago. Thus, before one studies the geologic story of Palo Duro Canyon, it is helpful to know something about the various kinds of rocks. There are three major classes of rocks in the earth’s crust: _igneous_, _sedimentary_, and _metamorphic rocks_.

_Igneous rocks_ solidified from an original molten state. Common examples of igneous rocks include granite, basalt, and volcanic ash. Although no igneous rocks are found in Palo Duro Canyon, they are widely exposed in parts of West and Central Texas.

_Metamorphic rocks_ were originally igneous or sedimentary in origin. However, these rocks have undergone such great physical and chemical change that they have been transformed into a different kind of rock. Thus, metamorphic changes alter limestone to marble or sandstone to quartzite. No metamorphic rocks crop out in the canyon, but, like the igneous rocks, they are common in some parts of the State.

All of the geologic formations exposed in Palo Duro Canyon are composed of _sedimentary rocks_. These are rocks that have been formed by the compaction and cementation of rock and mineral fragments called _sediments_, or by the precipitation of material from solution. Sandstone, conglomerate, shale, and caliche (_see_ p. 26) are examples of sedimentary rocks that are exposed in the canyon.

Sedimentary rocks are typically _stratified_, that is, they occur in layers or beds called _strata_. In addition, sedimentary rocks—especially those of marine origin—commonly contain _fossils_. These fossils are traces or evidence of prehistoric plants and animals that have been preserved in the rocks, and they may provide clues as to the age of rocks and the manner in which they were formed. Fossil remains have been found at a number of places in the park and these are discussed later.

UNRAVELING EARTH HISTORY

In order to understand better the geologic history and development of the canyon, one should also have some knowledge of the basic principles of earth history and should be familiar with the geologic time scale (fig. 6).

GEOLOGIC TIME SCALE
ERA
PERIOD
EPOCH
SUCCESSION OF LIFE
CENOZOIC “RECENT LIFE”
QUATERNARY 0-1 MILLION YEARS
Recent
Pleistocene
TERTIARY 62 MILLION YEARS
Pliocene
Miocene
Oligocene
Eocene
Paleocene
MESOZOIC “MIDDLE LIFE”
CRETACEOUS 72 MILLION YEARS
JURASSIC 46 MILLION YEARS
TRIASSIC 49 MILLION YEARS
PALEOZOIC “ANCIENT LIFE”
PERMIAN 50 MILLION YEARS
CARBONIFEROUS
PENNSYLVANIAN 30 MILLION YEARS
MISSISSIPPIAN 35 MILLION YEARS
DEVONIAN 60 MILLION YEARS
SILURIAN 20 MILLION YEARS
ORDOVICIAN 75 MILLION YEARS
CAMBRIAN 100 MILLION YEARS
PRECAMBRIAN ERAS
PROTEROZOIC ERA
ARCHEOZOIC ERA
APPROXIMATE AGE OF THE EARTH MORE THAN 4 BILLION 550 MILLION YEARS

The geologist has learned that the earth’s physical features have not always been as they are today. It is known, for example, that mountains now occupy the sites of ancient seas. Coal is now being mined where swamps existed many millions of years ago. Furthermore, the earth’s plants and animals have also been subject to great change. The trend of this organic change is, in general, toward more complex and advanced forms of life. However, some forms have remained virtually unaltered while others have become extinct at different points in geologic time.

In order to interpret earth history, the earth scientist gathers evidence of the great changes in climate, geography, and life that took place in the geologic past. He does this by studying the rock formations, the structural relationships of these formations, and the landforms of the area. The record of ancient events is pieced together by studying the stony layers of the earth as one might study a giant history book. Indeed, the sedimentary rocks are the rocky “pages” of earth history, for in them we find the tracks and trails, and bones and stones, which reveal the intriguing story of life long ago.

Much of the basic information which the geologist uses to reconstruct the geologic history of a region comes from his examination and interpretation of _bedrock outcrops_. _Bedrock_ is the solid unweathered rock which underlies loose earth material such as soil, sand, and gravel. An _outcrop_, or _exposure_, is a place where bedrock is exposed at the surface.

The first chapter of earth history begins with the most ancient rocks known. Because they were formed early in geologic time, these rocks are normally found deeply buried beneath younger rocks which have been deposited on top of them. It is for this reason that earth history is read from the bottom up, for the earliest formed rock layers correspond to the opening chapter in our earthen history book. The later chapters are found in the upper younger rocks which are located nearer the surface. Thus, in “reading” the geologic history of Palo Duro Canyon we start with the oldest “chapter” which is recorded in the Quartermaster Formation (p. 17) of Permian age, for these are the oldest rocks exposed in the canyon.

But deciphering earth history is not as simple as it might appear. In many areas the rock layers are not always found in the sequence in which they were originally deposited. In places, great structural disturbances have caused some of the rocky “pages” to become shuffled and out of place; others may be missing completely. Many rocks have been destroyed by weathering and erosion or greatly altered by metamorphism. As a result, the story recorded in these particular rocks is lost forever. These missing “pages” make the ancient story even more difficult to interpret so the geologist must then depend on other evidence that will permit him to “fill in the blanks.”

The record revealed in the rocks indicates that our planet is at least 4½ billion years old and that life has been present for more than 3 billion years. During this vast span of time the earth and its inhabitants have undergone many changes.

THE GEOLOGIC COLUMN AND GEOLOGIC TIME SCALE

The _geologic column_ refers to the total succession of rocks, from the oldest to the most recent, that are found in the entire earth or in a given area. For example, the geologic column of Texas includes all rock divisions known to be present in the State. By the same token, the geologic column of Palo Duro Canyon consists of the geologic formations exposed there. Thus, by referring to the geologic column previously determined for a specific area, the geologist can determine what type of rock he might expect to find in that particular region.

The _geologic time scale_ (fig. 6) is composed of named intervals of geologic time during which were deposited the rocks of the geologic column. These time intervals bear the same names that are used to distinguish the various units of the geologic column. For example, one can speak of Permian _time_ (referring to the geologic time scale) or of Permian _rocks_ (referring to rock units of Permian age in the geologic column).

Both the geologic column and the geologic time scale are based upon the _principle of superposition_. This basic geologic concept states that unless a series of sedimentary rock has been overturned, a given rock layer is older than the strata above it, and younger than all of the layers below it. Thus, the field relationship of the rocks plus the type of fossils (if present) give the geologist some indication of the _relative_ age of the rocks. Relative age does not imply age in years; rather, it fixes age in relation to other events that are recorded in the rocks.

Within recent years, however, it has become possible to assign ages in years to certain rock units. This is accomplished by a system of rock dating based on very precise measurements of amounts of radioactive elements (such as uranium). When present in the rocks, radioactive minerals change or decay at a known rate so that they are natural “clocks.” This method of dating has made it possible to devise a time scale in years which gives some idea of the tremendous amount of time that has passed since the oldest known rocks were formed. It has also been used to verify the previously determined relative ages of the various rock units.

The largest unit of geologic time is an _era_, and each era is divided into smaller time units called _periods_. A period of geologic time is divided into _epochs_, which, in turn, may be subdivided into still smaller units. The geologic time scale might be roughly compared to the calendar in which the year is divided into months, months into weeks, and weeks into days. Unlike years, however, geologic time units are arbitrary and of unequal duration, and the geologist cannot be positive about the exact length of time involved in each unit. The time scale does, however, provide a standard by which he can discuss the age of fossils and their surrounding rocks. By referring to the time scale it may be possible, for instance, to state that a certain event occurred during the Paleozoic Era in the same sense that one might say that something happened during the American Revolution.

There are five eras of geologic time, and each has been given a name that is descriptive of the degree of life development that characterizes that era. Hence, Paleozoic means “ancient-life” and the era was so named because of the relatively simple and ancient stage of life development.

The eras, a guide to their pronunciation, and the literal translation of each name is shown below.

Cenozoic (SEE-no-zo-ic)—“recent-life”
Mesozoic (MES-o-zo-ic)—“middle-life”
Paleozoic (PAY-lee-o-zo-ic)—“ancient-life”
Proterozoic (PRO-ter-o-zo-ic)—“earlier-life”
Archeozoic (AR-kee-o-zo-ic)—“beginning-life”

Archeozoic and Proterozoic rocks are commonly grouped together and referred to as Precambrian in age. In most places Precambrian rocks have been greatly contorted and metamorphosed, and the record of this portion of earth history is most difficult to interpret. Precambrian time represents that portion of geologic time from the beginning of earth history until the deposition of the earliest fossiliferous Cambrian strata. Precambrian time probably represents as much as 85 percent of all geologic time.

The _oldest_ era is at the _bottom_ of the time scale because this part of geologic time transpired first and was then followed by the successively younger eras which are placed above it. This is, of course, the order in which the various portions of geologic time occurred and during which the corresponding rocks were formed.

As mentioned above, each of the eras has been divided into periods, and most of these periods derive their names from the regions in which the rocks of each were first studied. For example, the Pennsylvanian rocks of North America were first studied in the State of Pennsylvania.

EXPLANATION
Q & T Pleistocene and Pliocene undifferentiated
Rdo Dockum Group
P Permian undifferentiated

The Paleozoic Era has been divided into seven periods of geologic time. With the oldest at the bottom of the list, these periods and the source of their names are:

Permian (PUR-me-un)—from the Province of Perm in Russia
Pennsylvanian (pen-sil-VAIN-yun)—from the State of Pennsylvania
Mississippian (miss-i-SIP-i-un)—from the Upper Mississippi Valley
Devonian (de-VO-ni-un)—from Devonshire, England
Silurian (si-LOO-ri-un)—for the Silures, an ancient tribe of Britain
Ordovician (or-doe-VISH-un)—for the Ordovices, an ancient tribe of
Britain
Cambrian (KAM-bri-un)—from the Latin word _Cambria_, meaning Wales

The Carboniferous Period in Europe includes the Mississippian and Pennsylvanian Periods of North America. Although this classification is no longer used in the United States, the term Carboniferous is found in many of the earlier geological publications and on many of the earlier geologic maps.

The periods of the Mesozoic Era and the source of their names are:

Cretaceous (cre-TAY-shus)—from the Latin word _creta_, meaning
chalky
Jurassic (joo-RAS-ik)—from the Jura Mountains of Europe
Triassic (try-ASS-ik)—from the Latin word _triad_, meaning three

The Cenozoic periods derived their names from an old outdated system of classification which divided all of the earth’s rocks into four groups. The two divisions listed below are the only names of this system which are still in use:

Quaternary (kwah-TUR-nuh-ri)
Tertiary (TUR-shi-ri)

Although the units named above are the major divisions of geologic time and of the geologic column, the geologist generally works with smaller units of the column called _geologic formations_. A geologic formation is a unit of rock that is recognized by certain physical and chemical characteristics. A formation is generally given a double name which indicates both where it is exposed and the type of rock that makes up the bulk of the formation. For example, the Beaumont Clay is a formation consisting of clay deposits that are found in and around Beaumont, Texas. For convenience in study, two or more successive and adjoining formations may be placed together in a group. Thus, the Tecovas and Trujillo Formations have been placed in the Dockum Group. Likewise, a formation may be subdivided into smaller units such as members, which may also be given geographic or lithologic (rock type) names.

GEOLOGIC FORMATIONS EXPOSED IN PALO DURO CANYON

As noted above, all of the rocks which crop out in Palo Duro Canyon are sedimentary in origin. They represent four different geological periods: the Permian, Triassic, Tertiary, and Quaternary (fig. 12).

Although these rock formations differ considerably in composition and age, they do not tell the whole geologic story of the area. Long spans of geologic time are not represented by rock units because the region was undergoing erosion or no sediments were being deposited during certain portions of geologic time. Rocks that had formed during one geologic period were removed by erosion during a later period. Thus, segments of the geologic record were destroyed or never recorded. For this reason, much of the geologic history of the Palo Duro area is unrecorded and must be inferred from fragmentary evidence borrowed and pieced together from adjacent areas. Even so, an interesting story can be assembled from the rocks that remain in the canyon today.

In general, the following descriptions of the formations exposed in Palo Duro Canyon State Park follow the procedure that most geologists use in presenting the results of their geologic investigations. The more distinctive characteristics of the rock units are described in order that they may be more easily recognized, and the ways in which the rocks were formed are also considered. With this background it is then possible to review the geologic history recorded in the bedrock of the canyon. A simplified geologic map is presented in figure 7; this shows the distribution of the major rock types in the canyon. The reader will find it helpful to refer to this map when reading the descriptions of the various formations.

Quartermaster Formation.—

The oldest formation exposed in the canyon is the Quartermaster Formation of Permian age (_see_ fig. 6) which is named from exposures along the banks of Quartermaster Creek in Roger Mills County, Oklahoma. One of the more colorful formations in the park, the Quartermaster is composed primarily of brick-red to vermilion shales which are interbedded with lenses of gray shales, clays, mudstones, and sandstones. Averaging about 60 feet thick where exposed in the park, the Quartermaster forms the floor and lower walls of the canyon.

The rocks of this formation are easily examined at many places throughout the canyon and in them can be seen a number of interesting geologic phenomena. Probably the most noticeable of these features are the shining white veins of _gypsum_ that lace the face of the red shale outcrops (fig. 8). A soft, transparent to translucent mineral that can be scratched by a fingernail, gypsum is hydrous calcium sulfate (CaSO₄·2H₂O). Three varieties of gypsum are found in the canyon: (1) _satin spar_, a fibrous variety with a silky sheen; (2) _selenite_, a colorless, transparent variety which commonly occurs in sheet-like masses; and (3) a fine-grained massive variety called _alabaster_. Satin spar is the most common variety of gypsum present and it commonly occurs in thin bands interbedded with the mudstones and sandstones. It is much more noticeable in the shales, however, for it is typically seen in narrow veins which criss-cross the surface of the outcrop and intersect the bedding planes at various angles. Although normally white, some of the satin spar has a soft pink or bluish hue due to the presence of impurities in the mineral.

The presence of gypsum in the Quartermaster red beds is of special significance to the geologist, for it provides valuable information about the geologic history of the Palo Duro area. It is known, for example, that when a landlocked body of sea water in an arid climate becomes separated from the ocean, one of the most common salts to precipitate is hydrous calcium sulfate, or gypsum. Gypsum may also be precipitated when a lake without an outlet evaporates in an arid climate. Geologic evidence suggests that the sediments which gave rise to the rocks of the Quartermaster Formation were deposited in a landlocked arm of the sea during the latter part of the Permian Period. As evaporation continued and the sea water was reduced to approximately one-third of its original volume, gypsum was precipitated. There must have been periodic influxes of silt- and mud-bearing waters entering the ancient Permian sea, for layers of shale and mudstone are interbedded with the gypsum.

It is believed that much of the satin spar and selenite gypsum was originally _anhydrite_ (CaSO₄). Unlike gypsum, anhydrite does not contain water, but it can be changed to gypsum in the presence of moisture. There are two lines of evidence that indicate an anhydrite origin for the Quartermaster gypsum. First, microscopic examination of gypsum samples reveals the presence of residual anhydrite crystals embedded in the gypsum. Second, many of the gypsum beds have been squeezed into rather gentle _folds_. These consist of small _anticlines_, upfolds or arches, and _synclines_, downfolds or troughs (fig. 9). It has been suggested that this folding took place as the anhydrite underwent _hydration_, or took on water. As hydration occurred and the anhydrite was converted to gypsum, the gypsum expanded, thereby exerting both lateral and vertical pressure on the beds around it. This produced the crumpled, wave-like folding so characteristic of certain of the gypsum beds. However, there is not complete agreement that the folding in the gypsum is due to the hydration of anhydrite. Certain geologists attribute this deformation to slumping caused by solution cavities, for gypsum is relatively easily dissolved in water. As the gypsum was dissolved and carried away in solution, the removal of the supporting layers of gypsum permitted slumping and consequent deformation in the overlying shales and mudstones. Although some geologists believe that the folds were caused by expansion due to the hydration of anhydrite and others support deformation related to the removal of soluble gypsum, there is general agreement that the folding is local and not related to regional or widespread deformation.

Not all of the red Quartermaster shales are uniformly colored. Some of them contain gray-green, circular spots called _reduction halos_ (fig. 10). These spots, which in places give the red shales a distinctive polka-dot appearance, have been produced as the result of chemical change of certain minerals within the shale.

As noted earlier, sediments are usually laid down in horizontal layers. However, in certain environments, sediments may be deposited in such a way that the layers are inclined at angle to horizontal (fig. 11). This structure, called _cross-bedding_ or _cross-stratification_, is found in certain sandstones and other coarse-grained or fragmental sedimentary rocks. Cross-bedding typically consists of rather distinct inclined layers separated by _bedding planes_ (the surface of demarcation between two individual rock layers). Bedding of this type commonly occurs in sedimentary rocks formed in rivers, deltas, and along the margins of lakes or oceans. The cross-bedding in the Quartermaster and certain of the Triassic formations is believed to have been developed under similar conditions. Although cross-bedding is also common in certain rocks of _eolian_ origin (deposited by wind) none of the cross-bedding in the canyon’s rocks is due to the action of wind.

In addition, some of the Quartermaster strata have _ripple marks_ on their surfaces. These features are common in certain sedimentary rocks and were formed when the surface of a bed of sediment was agitated by waves or currents. The size, shape, and cross section of the ripple marks can be used to tell whether the marks were produced by waves or currents. The ripple marks in the Quartermaster appear to have been formed by the action of waves on a shallow sea floor.

A number of interesting geologic features in the canyon have been formed in part in the Quartermaster Formation. These include the multi-hued Spanish Skirts (fig. 26), the Devil’s Slide (fig. 35), Capitol Peak (fig. 32), and Catarina Cave (fig. 27). The latter is a rather unusual cave in that it has developed in a large mass of landslide debris divided by projecting bedrock of the Spanish Skirts. The cave has been formed by _suffosian_, a process whereby water enters the landslide debris on the upper slopes and follows buried channels in the landslide removing rock debris as it passes through. The flood water exits at the base of the landslide by means of Catarina Cave. The plan of the cave closely resembles the drainage patterns of surface gullies.

Tecovas Formation.—

Rocks of the Triassic System (fig. 6) are well represented in Palo Duro Canyon and consist of the _Tecovas_ and _Trujillo_ Formations. These formations are part of the Dockum Group of Late Triassic age.

Having a total thickness of about 200 feet, the Tecovas (which is named from exposures found on Tecovas Creek in Potter County, Texas) consists largely of multicolored shales. Also present are thin layers of soft sandstone, which are disseminated throughout the shales, and a more prominent bed of white sandstone, which marks the middle of the formation. The Tecovas shales overlie the Quartermaster Formation, and the lower zone of lavender, gray, and white shales forms a relatively smooth slope that is easily distinguished from the steeper slopes of gullied red-and-white-banded shales beneath them (fig. 12).

But the contact zone between the Tecovas and Quartermaster shales involves more than a mere change in color. Here is one of the missing “chapters” in the geologic history of the canyon, for part of the Late Permian record and all of the record of Early and Middle Triassic time are missing from the geologic column. Such gaps in the column are represented by _unconformities_ in the rocks. Here the unconformity is an ancient erosional surface between the Tecovas Formation of Late Triassic age and the Late Permian Quartermaster Formation, and there are many millions of years of earth history represented in this missing “chapter” in the geologic story of Palo Duro Canyon. During this vast span of time, thousands of feet of sediments were probably deposited, converted into rock, and then later removed by erosion.

Near the middle of the Tecovas Formation there is a bed of white, crumbly (friable) sandstone. Averaging about 15 feet in thickness, this sandstone contains many _joints_ (small crack-like fractures) along which no appreciable movement has taken place (fig. 8). There are two distinct sets of these joints which intersect each other at right angles. The distinctive joint patterns, the color, and the friability of this sandstone clearly differentiate it from the harder, darker, and more coarse-grained sandstones of the overlying Trujillo Formation (p. 22).

The upper part of the Tecovas consists of a layer of orange shale which overlies the middle sandstone unit and is in contact with the lower part of the Trujillo Formation.

The fossils which have been found in the Tecovas Formation suggest that these rocks were derived from sediments deposited in swamps and streams. Unlike the _marine_ deposits of the Quartermaster, the rocks of the Tecovas were formed from _continental_ deposits laid down on the land. Fossils found in the canyon include the bones and teeth of the extinct semi-aquatic reptiles known as _phytosaurs_ (fig. 13) and bone and skull fragments of a primitive amphibian called _Buettneria_ (fig. 14). _Coprolites_ (the fossilized excrement of animals), pieces of petrified wood, and the teeth and bones of lungfish have also been reported from the Tecovas.

A number of minerals including _hematite_, an iron mineral, and _psilomelane_, a barium-magnesium oxide, occur in the Tecovas. Hematite is an ore of iron and psilomelane a manganese ore, though neither of these is present in commercial quantities in the canyon.

The Tecovas also contains a number of _concretions_ which range from a fraction of an inch to as much as 6 inches in diameter. These spherical masses are generally harder than the fine-grained shaly sands in which they are found and were thus left behind when the surrounding rock was eroded away. Some of these concretions are marked by cracks or veins filled with the mineral _calcite_. Concretions bearing this type of structure are called _septaria_, or _septarian concretions_.

_Geodes_ are also found in the Tecovas Formation. These are rounded concretionary rocks with a hollow interior that is frequently lined with mineral crystals. Well-formed crystals of clear calcite have been found in many of the geodes from the Tecovas.

Among park landmarks that are characterized by the multi-hued Tecovas strata are the middle portion of Triassic Peak (fig. 25), the upper part of the Spanish Skirts (fig. 26), Capitol Peak (fig. 32), and the Devil’s Slide (fig. 35).

Trujillo Formation.—

Named from rock exposures on Trujillo Creek in Oldham County, Texas, the Trujillo is easy to distinguish from the underlying Tecovas Formation. The contact is quite distinct and lies between the top of the orange Tecovas shale and the base of the massive-bedded, cliff-forming Trujillo sandstone (fig. 25). Although generally fine grained and thickly bedded, there are local concentrations of pebble-sized rock fragments in the Trujillo. The weathered surface of the lower sandstone is stained red or dark brown by iron oxides. However, a fresh, unweathered surface is typically gray or greenish gray in color, and careful examination of the unweathered rock reveals the presence of tiny flakes of mica.

The basal Trujillo sandstone is one of the most conspicuous rock units in the canyon and forms many of the prominent benches and mesas so typical of the Palo Duro landscape. In places the sandstone is cross-bedded (p. 20) and contains channel deposits of coarse sand which suggest that the sediments from which it was derived were deposited in ancient stream beds.

Red, maroon, and gray shales overlie the basal sandstone member of the Trujillo, and these shales are overlain by cross-bedded, coarse-grained sandstone. Another interval of varicolored shales separates the middle sandstone bed from the upper sandstone member. The middle sandstone unit is a conspicuous ledge- or cliff-forming rock and is medium to coarse grained and commonly cross-bedded. In most localities, the upper sandstone is overlain by a section of red and green shales which mark the uppermost limits of the Trujillo Formation. In places, however, this shale section has been removed by erosion and rocks of Tertiary age directly overlie the sandstone.

Although fossils are not common, the remains of _Buettneria_ (fig. 14), leaf imprints, pieces of mineralized wood, and the scattered teeth and bone fragments of reptiles and amphibians have been found. Phytosaur remains, especially teeth, have also been collected from the Trujillo sandstones.

The Indians who formerly inhabited the Palo Duro area (p. 3) put the rocks of the canyon to a number of uses. This appears to be especially true of the rather coarse-grained Trujillo sandstones, which were commonly used for constructing primitive rock shelters. The abrasive surface of the sandstone was especially well suited for grinding grain, and mortar holes have been found in a number of places. One of these (fig. 15) can be seen along the tracks of the Sad Monkey Railroad (p. 35) near the foot of Triassic Peak. The Indians also used the clays of the Quartermaster, Tecovas, and Trujillo Formations to make pottery, and iron and copper minerals such as hematite and malachite were used to make red and green pigments for decoration and war paint.

The Trujillo shales and sandstones can be seen in a number of Palo Duro’s more spectacular geological oddities. These erosional remnants are best developed where blocks of erosion-resistant sandstone protect underlying pedestals of softer shale (fig. 15). This type of differential weathering (p. 31) has produced a number of interesting and unusually shaped pedestal rocks or “hoodoos” (figs. 16 and 20). The most spectacular erosional remnant—and one that has come to be the “trademark” of Palo Duro Canyon—is the Lighthouse (fig. 31). The great jumble of boulders called the Rock Garden (fig. 34) is also composed largely of massive blocks of dislodged Trujillo sandstone. These boulders accumulated on the canyon floor as a result of landslides. In addition, the rock profile known as Santana’s Face (fig. 28) is a naturally sculptured profile in the Trujillo sandstone that forms the cap of Timber Mesa.

Ogallala Formation.—

The Ogallala Formation is named from exposures around Ogallala in Keith County, Nebraska. There is a major unconformity between the Trujillo Formation of the Triassic and the overlying Ogallala Formation of Pliocene (Late Tertiary) age. Missing here is the geologic evidence for what may have been some of the more exciting chapters in the canyon’s history. There is no record, for example, of the Jurassic and Cretaceous Periods which together encompass almost 120 million years of earth history. Also missing is any evidence of what transpired during more than 90 percent of the Tertiary Period, for no rocks of Paleocene, Eocene, Oligocene, or Miocene age are exposed in the canyon. Together these four epochs comprise approximately 47 million years of earth history. It is impossible, of course, to determine how many geologic formations may have been formed and later eroded during the 167 million years represented by this unconformity. However, our knowledge of present-day deposition and erosion suggests that the missing geologic record undoubtedly represents many thousands of feet of rock.

The lower portion of the Ogallala Formation is composed of a reddish-brown, fine- to medium-grained sandstone that contrasts sharply with the underlying red and green shales that are exposed in the top of the Trujillo Formation. Much of this sandy rock is characterized by pebbles consisting of a variety of igneous, sedimentary, and metamorphic rocks. Because it consists of rock and mineral fragments of varied composition and size, this kind of sedimentary rock is called a _conglomerate_. The type of rock fragments found in basal Ogallala conglomerates suggests that they were transported to the Panhandle-Plains area by streams flowing southeastward from the Rocky Mountains. As these streams deposited their loads, they left behind a wide spread blanket of sand, gravel, and mud which formed an extensive alluvial plain that extended from western Nebraska to northwest Texas. Although it is less than 100 feet thick in Palo Duro Canyon, in places this great mantle of _fluvial_ (stream-deposited) sediments is as much as 900 feet thick.

Most of the Ogallala Formation consists of a mixture of diverse rock types such as conglomerate, sandstone, siltstone, clay and marl. But the upper part of the formation is characterized by thick _caliche_ deposits. A dull, earthy calcite deposit, caliche typically forms in areas of scant rainfall. It is believed to originate when ground moisture, containing dissolved calcium bicarbonate, moves to the surface where the moisture steadily evaporates leaving a calcium carbonate crust on or near the surface (fig. 17).

Caliche, which derives its name from the Latin _calix_, meaning “lime,” may be firm and compact or loose and powdery. It is also commonly found mixed with other materials such as clay, sand, or gravel. Caliche commonly occurs in the Trans-Pecos, southwestern Gulf Coastal Plain, and the High Plains area of Texas (_see_ fig. 5, p. 8). In the latter area it typically makes up the “caprock.” Caliche is commonly quarried in these parts of Texas where it is used as road material and as an aggregate.

Good exposures of Ogallala caliche can be seen on the surface around the overlook at Coronado Lodge on the northwest rim of the canyon (fig. 17). Ogallala strata also crop out along the upper reaches of Park Road 5 as it starts to descend into the canyon. But probably the most spectacular exposures of the Ogallala are exposed in the precipitous face of the Fortress Cliff (fig. 33) which forms part of the eastern rim of the canyon.

Also located within the Ogallala Formation is a very important _aquifer_—a porous, water-bearing rock formation. This fine-to coarse-grained sandstone is very porous and permeable and is the most important single water-producing formation in the Panhandle-Plains area.

Opal and chert are locally abundant in the Ogallala conglomerates. The opal, which is found in small cavities in the conglomerate is not of the gem variety but it does _fluoresce_. Minerals that exhibit _fluorescence_ emit visible colors when exposed to ultraviolet light. For this reason, the Ogallala opal is sought after by rock and mineral collectors. The chert, a flint-like variety of quartz, occurs as nodules in the conglomerate and in a well-developed layer near the base of the formation. Both of these _siliceous_ (silica-bearing) rocks were apparently prized by the Indians, who used them to fashion knives, scrapers, projectile points, and other artifacts. The Indians also learned that flat slabs of caliche were ideal for lining fireplaces and to construct primitive rock shelters.

A number of Pliocene vertebrates have been found in the Palo Duro area. Known as the “Age of Mammals,” the Tertiary Period was characterized by mammals as diverse as were the reptiles of the Mesozoic Era. Among these unusual creatures were such now-extinct species as the saber-tooth cat and the elephant-like shovel-jawed mastodon (fig. 18). The remains of these as well as bones of giraffe-like camels, pony-sized horses, and sloths have been found in the vicinity of the canyon. The grassy plains of Pliocene time were also inhabited by large tortoises which reached lengths of up to 3 feet (fig. 19). Dioramas showing how these animals might have looked, as well as their actual remains, are on display in the Hall of Pre-History in the lower floor of the Panhandle-Plains Historical Museum in Canyon, 13 miles west of the park (p. 35).

Rocks of the Pleistocene.—

The youngest rocks in Palo Duro Canyon State Park were formed during the Pleistocene Epoch of the Quaternary Period of the Cenozoic Era (_see_ geologic time scale, p. 11). Pleistocene rocks are rather widespread in much of the Panhandle-Plains area and they are mostly composed of sediments which were deposited in stream valleys, in lakes or ponds, or by the wind. Most of the Pleistocene strata in the park area consist of loose deposits of silt and sand which were deposited by wind action. Known locally as “blow sand,” this reddish-brown, silty sand overlies the Ogallala caliche at most points along the canyon’s rim.

HOW THE CANYON WAS CARVED

The visitor seeing Palo Duro Canyon for the first time may find it difficult to believe that this yawning chasm began as a simple gully. But to the _geomorphologist_—the geologist who studies the origin and development of landscapes—Palo Duro Canyon is but a gully magnified many times over. This is evident because the shape of the canyon, the nature of its tributaries, and the character of its walls indicate that it has been deepened and lengthened by the downcutting of a stream and widened by other geologic processes.

THE GEOLOGIC WORK OF RUNNING WATER

Palo Duro Canyon is a classic example of a land-form that has been created by the geologic work of _running water_. Undoubtedly the most important single agent of erosion, running water probably does more to wear away the land than all the other geologic agents combined. This is not surprising considering the fact that the earth’s annual precipitation (such as rain and snow) equals about four billion tons of water. Although the amount of precipitation varies greatly from place to place, the average annual precipitation on land is about 40 inches of water. Of this, roughly 25 percent runs off from the land to form streams.

When one drives through the park and fords the normally gently flowing waters of the Prairie Dog Town Fork of the Red River he may well wonder if this unimposing stream actually is the geologic agent that is responsible for this deep gorge. But the visitor who happens to be present during a severe rainstorm will soon be convinced, for during heavy rains this gentle stream becomes a raging torrent. As the river increases in size it also becomes a more effective land-shaping tool, for the larger and swifter the stream, the more rock material it can carry. Thus, when flowing at peak capacity, this branch of the Red River becomes a moving ribbon of sandpaper whose load of sand, silt, and gravel has cut and scoured the canyon walls and floor for hundreds of thousands of years. How long has it taken the river to carve this remarkable chasm? Although there is no way of knowing for sure, geologic evidence indicates that the canyon has formed during the last one million years—a relatively short time, geologically speaking.

The work of the river is made still more effective by water and sediment which it receives from its tributaries; this added water substantially increases the volume and velocity of the river. Although many of the tributary streams are dry throughout much of the year, they carry large quantities of water during heavy rains. Moreover, because most of these streams flow over rock surfaces which are not protected by thick soil or vegetation, their waters are quickly transported to the master stream. Thus, the volume and velocity of the Prairie Dog Town Fork of the Red River make it possible—especially during flood periods—for the river to carry a large load of rock particles which effectively erodes the stream channel. Where does this rock debris come from? Most of it is eroded from the sides and bottom of the river’s channel.

The river carries its load in a number of ways. Material such as salt and other soluble matter is transported in a dissolved state or in _solution_. Still more, for example, silt and fine sand, is carried in _suspension_. These sediments are suspended between the surface of the water and the bottom of the stream channel. Those particles that will not dissolve in water and are too heavy to be carried in suspension, constitute the _bottom load_ of the stream. These larger sediments, such as gravel, cobbles, and boulders, roll, bounce, or slide along the stream bed.

As flash floods course through Palo Duro Canyon, the river uses its load to erode further the rocks over which it passes. Each moving rock fragment literally becomes a cutting tool for _abrasion_ as the loose rock particles slowly wear away the banks and bed of the stream. Eventually the abraded rock fragments become smooth and rounded and the stream channel is gradually worn down to a lower level; it is also widened.