Summary of Geologic History

THECANYON KING, a 93-foot 150-passenger stern-wheeler which hauls passengers some 30 miles below Potash and returns. Trips run during the spring and early summer, when water depth permits. Photograph by Henry Lansford, Boulder, Colo. (Fig. 69)

POTASH MINE OF TEXAS GULF, INC. at Potash, as viewed from a boat. High cliffs on right are Wingate Sandstone capped by Kayenta Formation and underlain by slopes of Chinle and Moenkopi Formations. (Fig. 70)

EVAPORATION PONDS, used to separate potash from common salt, viewed from jeep trail. Black borders are parts of plastic membranes covering bottoms of ponds. Crest of Cane Creek anticline and La Sal Mountains in right background. (Fig. 71)

Across the river east from Potash is Jackson Hole, a large rincon. Since abandonment, which shortened the river by about 3½ miles, the river has cut its channel nearly 200 feet deeper. It is comparable in size to the large rincon along Green River below Bowknot Bend (p. 90) but probably is somewhat younger. Both rincons may be as old as late Tertiary (fig. 80). Just below Potash we cross the axis of the huge Cane Creek anticline (fig. 31) and also leave Grand County to enter San Juan County. A mile east of this point, high on the canyon wall, is the School Section 13 uranium mine, which has yielded considerable ore and is expected to resume production sometime during 1973. It can be seen from the river or the trail, and some of the tailings are visible on the left flank of the anticline infigure 13.

Voyagers who cross the axis of the Cane Creek anticline may observe on the right-hand (west) bank a protruding oil-well casing, some drill bits, and several shacks—all that remain of the Frank Shafer No. 1 oil test started during the winter of 1924-25 and completed by the Midwest Exploration Co. (Baker, 1933, p. 81). As described by Maxine Newell (U.S. Natl. Park Service, written commun., 1970),

The well blew in in December 1925, caught fire, and spewed burning oil 300 feet into the air. * * * The local Times-Independent newspaper called it “Mother Nature’s Christmas Gift to Grand County.” The gusher burned down the rig, a barge of equipment, and it took three months to get it under control. Then it didn’t produce.

Various 1925 and 1926 issues of the Moab Times-Independent reported that despite many efforts to plug the well, it continued to flow from 1,000 to several thousand barrels of oil per day for 6 months or more, all of which floated down the river. The last blowout occurred in 1937, after which the well was plugged with an additional 180 tons of cement.

Mrs. Newell added,

The stories told of the early-day exploration are endless and delightful. Equipment and supplies were barged down the Colorado River by the old Moab Garage Company; in winter months materials were carried by team and sled over the river ice. They would take a couple of rig timbers and pile a lot of lumber on them (they could take 10,000 feet), then we’d give them a start with a crowbar and the mules would trot all the way downhill to the well. When they’d get there they had a little trouble stopping sometimes; they would turn into the bank, unload, then put the double trees on one mule, ride the other, and head back for a new load of rig lumber.

The evaporation ponds shown in figures31and71are in Shafer Basin, a synclinal basin separating the Cane Creek anticline and Shafer dome. We cross the axis of Shafer Basin about 2 miles below the county line.

Further downstream is Shafer dome, a closed anticlinal bulge just beyond the W-shaped bend in the river as shown infigure 29. Parts of the dome also show up in the lower right offigure 13and the lower left offigure 15. From almost anywhere in the Goose Neck, the sharp bend of the river shown infigure 15, we get an excellent view of Dead Horse Point some 2,000 feet above.

Robert R. Norman (oral commun. Feb. 27, 1973) described to me a small petrified forest—which he said resembles a log jam—in the eastern part of the Shafer dome, at mileage 39 (Baars and Molenaar, 1971, p. 65), just north of this point about half way between the river and the jeep trail below Dead Horse Point. He estimated that there probably are 20 to 30 logs, some of which are as large as 18 inches in diameter and more than 20 feet long, and also described a stump about 3 feet in diameter. They occur in red beds at about the middle of the Rico Formation, hence could be either Pennsylvanian or Permian in age (figs.9,80). The original wood has been replaced by silica (SiO₂) and stained a dark reddish brown, as shown infigure 72.

Mr. Norman and his brother also discovered many teeth of a primitive sharklike fish in the Rico Formation at the same general locality as the petrified wood and also in the Rico on the Cane Creek anticline. I submitted two of the teeth to Dr. David H. Dunkle, curator of the Cleveland Museum of Natural History, who reported them to be “one tooth of the cochliodont ‘shark’Deltodus, and one tooth of the petalodont ‘shark’Petalodus” (written commun., May 22, 1973).

About 4 miles below the Goose Neck, we enter Canyonlands National Park and remain in the park almost to the north end of Lake Powell.

About 6½ miles into the park, at the north end of a bend much like the Goose Neck, is the mouth of Lathrop Canyon, where many boaters stop for lunch and where a side road connects with the White Rim Trail (fig. 1).

Six and one half miles below Lathrop Canyon is the mouth of Rustler Canyon, which is joined near its mouth by Indian Creek—the creek followed by the highway leading to The Needles from U.S. 163. Within an airline distance of only 3 miles, the lower reach of Indian Creek, an intermittent stream, flows past four small rincons, three of which (fig. 73) are within an airline distance of only 0.8 mile. The stream has cut its new channel into the red sandstones and shales of the Cutler Formation only 15 to 20 feet deeper than the abandoned ones in the two rincons at the left infigure 73and only about 25 feet deeper than the one on the right. These figures suggest, at least to me, that these cutoffs probably occurred sometime during the Holocene Epoch, or age of man—that is, probably within the last 10,000 years (fig. 80). A detailed study of these rincons might change this estimate, particularly if, say, buried driftwood or other carbonaceous material could be found for an age determination by the radiocarbon method.

PETRIFIED LOG, near middle of Rico Formation, about 1 mile southeast of Dead Horse Point. Log is estimated to be about 18 inches in diameter. Photograph by Robert R. Norman. (Fig. 72)

RELATIVELY RECENT RINCONS ALONG INDIAN CREEK, about 3½ miles above mouth and about 2 miles east of Canyonlands National Park. Above, stereoscopic pair of aerial photographs by U.S. Geological Survey; below, sketch showing drainage changes. The stereoscopic pair can be viewed without optical aids by those accustomed to this procedure, or by use of a simple double-lens stereoscope. (Fig. 73)

Figure 73, diagram

THE LOOP, of Colorado River, about 5 miles northeast of the confluence. Lower canyon walls are unnamed upper member of Hermosa Formation overlain by slopes of the Rico Formation. Jointed sandy ledges at top become sandier to south, where they comprise the Cedar Mesa Sandstone. Aerial photograph by U.S. Geological Survey. (Fig. 74)

About 5 miles below the mouth of Rustler Canyon and Indian Creek, and also about 5 miles above the confluence, is The Loop—an even sharper and more symmetrical figure eight than Bowknot Bend of the Green River (fig. 62). An aerial view of The Loop (fig. 74) shows that the channels on the south loop are only about 500 feet apart and that those on the north loop are only about 1,700 feet apart. At the narrowest places, both saddles are considerably eroded—the southern one is only about 150 feet above the river, but the northern one is still about 350 feet above. Erosion of both saddles has been hastened by the facts that the axis of the Meander anticline (seep. 108) passes through each saddle and that an interesting reverse fault (fig. 75) passes through the lower and thinner southern saddle. The differences between reverse and normal faults are shown by comparing figures56and76. It seems inevitable that some day the small saddle will be cut through by the Colorado River, and a new rincon will result. Eventually, the other loop also probably will be abandoned. As one of my colleagues remarked, how wonderful it would seem, to be present at the proper moment to witness such an event, particularly if one had a time-lapse movie camera to record it for posterity!

REVERSE FAULT in southern saddle of The Loop, looking northwest from boat in river. Apparent angle of dip is 12° below horizontal. Rocks at left, above fault plane, have been shoved about 10 feet past and over those on right. Curving of dark bed near middle of fault plane is called “drag.” (Seefig. 76.) Rocks are unnamed upper member of Hermosa Formation. (Fig. 75)

CUTAWAY VIEW OF REVERSE FAULT, resulting from horizontal compression, which caused a shortening of earth’s crust. Note “drag” of beds on each side of fault plane. Low-angle reverse faults, also called thrust faults, may have displacements ranging from a few feet to many miles. From Hansen (1969, p. 116). (Fig. 76)

About a mile and a half below the south saddle of The Loop we meet the mouth of Salt Creek, which drains a large part of the Needles district.Figure 77was taken in Salt Creek canyon about 2 airline miles above the mouth looking southeast toward Six-Shooter Peaks and Shay Mountain, northernmost of the Abajo Mountains, on the horizon.

A mile and a half above the confluence is The Slide, a jumbled mass of angular blocks of rock that fell from the northwest canyon wall and originally probably extended all the way to the southeast bank of the river. As shown infigure 78, it still extends nearly across the river, leaving only a narrow deep chute along the southeast bank. Just after the photograph was taken, we hit rough fast water in the chute, with waves about 2 feet high. At higher stages of the river, progressively more of The Slide is covered by water, and there is less tendency for waves to form. The date of this landslide is not known, but it is shown on a map by Herron (1917, pl. 22A) made prior to 1917 and may well have occurred during prehistoric times.

Soon we reach the confluence of the Green and Colorado Rivers (figs.59,60). This important junction of two mighty rivers was noted by all previous voyagers, but their impressions of it differed considerably. Powell (1875, p. 56) remarked:

These streams unite in solemn depths, more than one thousand two hundred feet below the general surface of the country. The walls of the lower end of Stillwater Cañon are very beautifully curved [seefig. 67], as the river sweeps in its meandering course. The lower end of the cañon through which the Grand comes down, is also regular, but much more direct, and we look up this stream, and out into the country beyond, and obtain glimpses of snow clad peaks, the summits of a group of mountains known as the Sierra La Sal [La Sal Mountains]. Down the Colorado, the cañon walls are much broken.

Dellenbaugh (1902, p. 277) gave a fuller description but concluded: “In every way the Junction is a desolate place”—an appraisal with which I disagree. The most colorful account I have read is that of Captain Francis Marion Bishop, a member of Powell’s 1871 expedition, who recorded in his journal for September 15, 1871 (1947, p. 202):

Well, we are at last, after many days of toil and labor, here at the confluence of the two great arteries of this great mountain desert. No more shall our frail boats dash through thy turbid waters, Old Green, and no more shall we press on to see the dark flood from the peaks and parks of Colorado. Grand and Green here sink to thy rest, and from thy grave theColorado de Grandeshall flow on forever, and on thy bosom henceforth will we battle with rock and wave. One can hardly tell which is the largest of the two rivers. Neither seems to flow into the other, but there seems to be a blending of both, and from their union rolls the Colorado River.

SALT CREEK CANYON, looking southeast from point on rim 2 miles above mouth. Lower ledges are limestones in unnamed upper member of Hermosa Formation; slope and upper cliff are Rico Formation capped by remnants of Cedar Mesa Sandstone. Horizon shows Six-Shooter Peaks in center and Shay Mountain, northernmost of Abajo Mountains, at right. Photograph by E. N. Hinrichs. (Fig. 77)

THE SLIDE, which partly blocks the Colorado River about 1½ miles above the confluence. View downstream. (Fig. 78).

Cataract Canyon heads at the confluence, but the rapids do not appear until we leave Spanish Bottom some 3½ miles below. Between The Loop and Spanish Bottom, the Colorado River follows closely the axis of an anticline. Along this reach the rock strata dip downward away from the river, as shown infigure 61. This fold was noted by Powell and some of his men, and Bishop (1947, p. 203) reported in his journal for September 16, 1871:

He [Steward] is at a loss how to account for the folded appearance of the strata here. But doubtless will find some explanation. Says the dip recedes from the river cañon, and thinks it is a fissure. Maj. [Powell] thinks it is owing to an upheaval, and that the beds next to the river have broken up from the mass, etc., etc.

Forty-four years later Harrison (1927) named this structure the Meander anticline and concluded that the weight of the rocks on each side of the river had squeezed underlying beds of salt in the Paradox Member of the Hermosa Formation and caused them to move upward along the river, where the confining strata had been removed by erosion. Harrison’s theory was accepted by Baker (1933) and most later workers in the area. Thus we have what may be termed an erosional anticline, whose axis, or crest, follows the river. Erosional anticlines also occur elsewhere, as along the Eagle and Roaring Fork valleys of central Colorado. Mutschler and Hite (1969) suggested that this zone of weakness in Canyonlands overlies and follows a break in the hard Precambrian (fig. 80) rocks that underlie the area at great depth. At any rate, Powell was on the right track even though he was totally unaware of the underlying salt or the deep-seated fault.

Smooth water continues from the confluence to Spanish Bottom, where the Old Spanish Trail comes down to the river from the west and continues up Lower Red Lake Canyon to the east. As mentioned earlier, this is about the south end of the Meander anticline, and an intruded chunk of the Paradox Member, mostly gypsum, occupies part of the mouth of Lower Red Lake Canyon, as shown infigure 79.

The remaining 10 miles or so of Cataract Canyon within Canyonlands National Park contains many rapids and should be traversed only under the leadership of experienced river guides. If and when Lake Powell reaches its maximum level, it will extend to within about a mile of the park, but at present (1973) it heads near the mouth of Gypsum Canyon, about 5 miles below the park.

GYPSUM PLUG of Paradox Member, intruded along south end of Meander anticline at mouth of Lower Red Lake Canyon. Common salt has been removed by solution, leaving residue of gypsum and some shale. Photograph by Donald L. Baars. (Fig. 79)

Petroglyph

GEOLOGIC TIME SPIRAL, showing the sequence, names, and ages of the geologic eras, periods, and epochs, and the evolution of plant and animal life on land and in the sea. The primitive animals that evolved in the sea during the vast Precambrian Era left few traces in the rocks because they had not developed hard parts such as shells, but hard shells or skeletal parts became abundant during and after the Paleozoic Era. (Fig. 80)

The Age of the EarthThe Earth is very old—four and a half billion years or more according to recent estimates. Most of the evidence for an ancient Earth is contained in the rocks that form the Earth’s crust. The rock layers themselves—like pages in a long and complicated History—record the surface-shaping events of the past, and buried within them are traces of life—the plants and animals that evolved from organic structures that existed perhaps three billion years ago.Also contained in rocks once molten are radioactive elements whose isotopes provide earth scientists with an atomic clock. Within these rocks, “parent” isotopes decay at a predictable rate to form “daughter” isotopes. By determining the relative amounts of parent and daughter isotopes, the age of these rocks can be calculated.Thus the results of studies of rock layers (stratigraphy), and of the progressive development of life (paleontology), coupled with the ages of certain rocks as measured by atomic clocks (geochronology), attest to a very old Earth!

The Age of the Earth

The Earth is very old—four and a half billion years or more according to recent estimates. Most of the evidence for an ancient Earth is contained in the rocks that form the Earth’s crust. The rock layers themselves—like pages in a long and complicated History—record the surface-shaping events of the past, and buried within them are traces of life—the plants and animals that evolved from organic structures that existed perhaps three billion years ago.

Also contained in rocks once molten are radioactive elements whose isotopes provide earth scientists with an atomic clock. Within these rocks, “parent” isotopes decay at a predictable rate to form “daughter” isotopes. By determining the relative amounts of parent and daughter isotopes, the age of these rocks can be calculated.

Thus the results of studies of rock layers (stratigraphy), and of the progressive development of life (paleontology), coupled with the ages of certain rocks as measured by atomic clocks (geochronology), attest to a very old Earth!

Having finished our geologic ramble through Canyonlands National Park, let us see how this pile of eroded rocks fit into the bigger scheme of things—the geologic age and events of the earth as a whole, as depicted infigure 80. As shown infigure 9, the rock strata still preserved in the park range in age from Pennsylvanian to Jurassic, or from about 300 to 175 million years ago, a span of about 125 million years. This seems an incredibly long time, until you note that the earth is some 4.5 billion years old and that our rock pile is but one twenty-fifth, or 4 percent, of the age of the earth as a whole. Thus, infigure 80the rocks exposed in the park occupy only about the left-hand third of the top whorl of the spiral.

But this is not the whole story. As indicated earlier, about 10,000 feet of younger Mesozoic and Tertiary rocks that once covered the area have been carried away by erosion, and if we include these, the span is increased to about 250 million years, or nearly a full whorl of the spiral.

Deep tests for oil and gas tell us that much older rocks underlie the area, and we have seen that some of these rocks played a part in shaping the park we see today—note the breaks in the deep-seated Precambrian rocks and the salt in the Paradox Member. In addition to the Precambrian igneous and metamorphic rocks, there are about 2,000 feet of Paleozoic sedimentary rocks older than the Pennsylvanian Paradox Member. Most of these sedimentary rocks were laid down in ancient seas during Cambrian, Ordovician, Devonian, Mississippian, and Pennsylvanian times (fig. 80). There are some gaps in the rock record caused by temporary emergence of the land above sea level and erosion of the land surface before the land again subsided below sea level so that deposition could resume. Silurian rocks are absent altogether, presumably because here the Silurian Period was dominated by erosion rather than deposition.

While Pennsylvanian and Permian sediments were being deposited in and southwest of the park, a large area to the northeast—called by geologists the Uncompahgre highland, because it occupied the same general area as the present Uncompahgre Plateau—rose slowly above sea level. Whatever Paleozoic rocks there were on this rising land, plus part of the underlying Precambrian rocks, were eroded and carried by streams into deep basins to the northeast and southwest. Thus, while mostly marine or nearshore deposits were being laid down in and near the park, thousands of feet of red beds were being laid down by streams in an area between the park and the Uncompahgre Plateau. During part of Middle Pennsylvanian time a large area including the park and known as the Paradox Basin was alternately connected to or cut off from the sea, so the water evaporated during cutoff periods and was replenished during periods when connection with the sea resumed. In this huge evaporation basin were deposited the layers of salt and gypsum plus some potash salts and shale that now make up the Paradox Member.

The old Uncompahgre highland continued to shed debris into the bordering basins until Triassic time, when it began to acquire a veneer of red sandstone and siltstone of the Chinle Formation (Lohman, 1965). The area remained above sea level during the Triassic Period and most if not all the Jurassic Period, although the Jurassic Carmel Formation was laid down in a sea that lay just to the west.

Late in the Cretaceous Period a large part of central and southeastern United States, including the eastern half of Utah, sank beneath the sea, as shown infigure 81, and received thousands of feet of mud, silt, and some sand that later compacted into the Mancos Shale. This formation and all the younger and some older strata have long since been eroded from the park area but are present in adjacent areas, such as the lower slopes of the Book Cliffs north of Green River, Crescent Junction, and Cisco (fig. 7).

The land rose above the sea at about the close of the Cretaceous and has remained above ever since, although inland basins and lakes received sediment during parts of the Tertiary Period. Compressive forces in the earth’s crust produced some gentle folding of the strata at the close of the Cretaceous, but more pronounced folding and some faulting occurred during the Eocene Epoch, when most of the Rocky Mountains took form. During the Miocene Epoch molten igneous rock welled up into the strata to form the cores of the nearby La Sal, Abajo, andHenry Mountains (fig. 7). Additional uplift and some folding occurred in the Pliocene and Pleistocene Epochs.

LATE CRETACEOUS SEA, which covered parts of central and southeastern United States. (Fig. 81)

Much of the course of the Colorado River was established in the Miocene Epoch, with some additional adjustments in the late Pliocene and early Pleistocene Epochs (Hunt, 1969, p. 67). Erosion during much of the Tertiary Period and all of the Quaternary Period, combined with some sagging and breaking of the crust brought on by solution and lateral squeezing of salt beds beneath The Needles, The Grabens, and the Meander anticline, produced the landscape as we now see it.

The Precambrian rocks beneath the area are about 1.5 billion years old, so an enormous span of time is represented by the rocks and events in and beneath Canyonlands National Park.

If we consider the geologic formations that make up the Colorado Plateau—including national parks (N.P.), national monuments (N.M.) (excluding small historical or archeological ones), Monument Valley, San Rafael Swell, and Glen Canyon National Recreation Area—certain formations or groups of formations play starring roles in some parks or monuments, some play supporting roles, and in a few places the entire cast of rocks gets about equal billing. Let us compare them and see how and where they fit into the geologic time spiral (fig. 80).

Dinosaur N. M., with exposed rocks ranging in age from Precambrian to Cretaceous, represents the greatest time span (nearly 2 billion years) but has one unit—the Jurassic Morrison Formation—in the starring role, for this unit contains the manydinosaur fossils that give the monument its name and fame; several older units have supporting roles. Grand Canyon N. P. and N. M. are next, with rocks from Precambrian through Permian (excluding the Quaternary lava flows in the N. M.), but here there is truly a team effort, for the entire cast gets about equal billing. Canyonlands N. P. stands third in size of cast, with rocks ranging from Pennsylvanian to Jurassic, but we would have to give top billing to the Permian Cedar Mesa Sandstone Member of the Cutler Formation, from which The Needles, The Grabens, and most of the arches were sculptured; the Triassic Wingate Sandstone and Kayenta Formation get second billing for their roles in forming and preserving Island in the Sky and other high mesas.

Now let us consider those with only one or few players in the cast, beginning at the bottom of the time spiral. Black Canyon of the Gunnison N. M., cut entirely in rocks of early Precambrian age (except for only a veneer of much younger rocks), obviously has but one star in its cast. Colorado N. M. contains rocks ranging from Precambrian to Cretaceous—equal to Dinosaur in this respect—but it is unique in that all the rocks of the long Paleozoic Era and some others are missing from the cast; of those that remain, the Triassic Wingate and Kayenta are the stars, with strong support from the Jurassic Entrada Sandstone.

All the bridges in Natural Bridges N. M. were carved from the Permian Cedar Mesa Sandstone, also the star in Canyonlands N. P. In Canyon de Chelly (pronounced “dee shay”) N. M. and Monument Valley (neither N. P. nor N. M., as it is owned and administered by the Navajo Tribe), the de Chelly Sandstone Member of the Cutler Formation—a Permian member younger than the Cedar Mesa—plays the starring role.

Wupatki N. M., near Flagstaff, Ariz., stars the Triassic Moenkopi Formation. Petrified Forest N. P. (which now includes part of the Painted Desert) also has but one star—the Triassic Chinle Formation, with its many petrified logs and stumps of ancient trees. The Triassic-Jurassic Glen Canyon Group (fig. 9), which includes the Triassic Wingate Sandstone and Kayenta Formation and the Triassic-Jurassic Navajo Sandstone, receives top billing in recently enlarged Capitol Reef N. P., but the Triassic Moenkopi and Chinle Formations enjoy supporting roles.

The Triassic-Jurassic Navajo Sandstone, erosional remnants of which are found on the high mesas of Canyonlands N. P., is the undisputed star of Zion N. P., Rainbow Bridge N. M., and Glen Canyon National Recreation Area, despite the fact that the latter is the type locality of the entire Glen Canyon Group (fig. 9).The Navajo also forms the impressive reef at the eastern edge of the beautiful San Rafael Swell (a dome, or closed anticline,fig. 7), now crossed by Highway I-70 between Green River and Fremont Junction, Utah.

As we journey upward in the time spiral (fig. 80), we come to the Jurassic Entrada Sandstone, which stars in Arches N. P., with help from the underlying Navajo Sandstone and a supporting cast of both older and younger rocks. The Entrada also forms the grotesque erosional forms called “hoodoos and goblins” in Goblin Valley State Park, north of Hanksville, Utah.

Moving ever upward in the spiral, we come to the Cretaceous—the age of the starring Mesaverde Group, whose caves in Mesa Verde N. P. now house beautifully preserved ruins once occupied by the Anasazi, the same ancient people who once dwelt in Canyonlands N. P.

This brings us up to the Tertiary Period, during the early part of which the pink limestones and shales of the Paleocene and Eocene Wasatch Formation were laid down in inland basins. Beautifully sculptured cliffs, pinnacles, and caves of the Wasatch star in Bryce Canyon N. P. and nearby Cedar Breaks N. M. This concludes our climb up the time spiral, except for Quaternary volcanoes and some older volcanic features at Sunset Crater N. M., near Flagstaff, Ariz.

Thus, one way or another, many geologic units that formed during the last couple of billion years have performed on the stage of the Colorado Plateau and, hamlike, still lurk in the wings eagerly awaiting your applause to recall them to the footlights. Don’t let them down—visit and enjoy the national parks and monuments of the Plateau, for they probably are the greatest collection of scenic wonderlands in the world.

Dinosaur

Many reports covering various aspects of the area have been cited in the text by author and year, and these plus a few additional ones are listed below under “Selected References.” A few of general or special interest should be mentioned, however.

Between 1926 and 1931 virtually the entire area now included in the park was mapped geologically in three classic reports—two by Baker (1933, 1946) and one by McKnight (1940). These men and their field assistants mapped the area by use of the plane table and telescopic alidade without benefit of modern topographic maps or aerial photographs, except for topographic maps of narrow stretches along the Green and Colorado Rivers made under the direction of Herron (1917). Only small sections could be reached by automobile, so nearly all the area was traversed using horses or by hiking.

During the uranium boom of the early and middle 1950’s, the U.S. Geological Survey remapped the topography of most of the area at a scale of 1:24,000 and also remapped the geology of much of the area at this same scale. The southern part of the Needles district was mapped by Lewis and Campbell (1965). The geologic mapping west of the Green and Colorado Rivers was done by F. A. McKeown, P. P. Orkild, C. C. Hawley, and others; that east of the Colorado River and a little between the two rivers was done by E. N. Hinrichs and others. Only four of the geologic maps have been published (Hinrichs and others, 1967, 1968, 1971a, b), but all this work and the older reports were used by Williams (1964) in compiling the 1:250,000-scale geologic map of the Moab quadrangle, by Williams and Hackman (1971) in compiling a similar map of the Salina quadrangle, and by Haynes, Vogel, and Wyant (1972) in compiling a similar map of the Cortez quadrangle. These three maps show the geology of the entire park.

The 1970 issue of the Naturalist in which the cited papers by Jennings, Newell, and Stokes appear also contains other papers on Canyonlands National Park, including one on the plants.

Several early reports on the Green and Colorado Rivers and their potential utilization contain a wealth of information and many fine photographs—two reports on the Colorado River by La Rue (1916, 1925), one on the Green River by Wooley (1930), and one on the upper Colorado River (above the confluence) by Follansbee (1929).

For those who wish to learn more about the science of geology, I suggest the textbook by Gilluly, Waters, and Woodford (1968).

My deep appreciation goes to Bates Wilson, former superintendent of Canyonlands National Park, and to Joe Carithers, former assistant superintendent, for their splendid cooperation in supplying data and information and for making available four-wheel-drive vehicles. I also wish to thank Chuck Budge, former chief ranger; Dave May, assistant chief ranger; Joe Miller, former maintenance engineer; Bob Kerr, new superintendent; Maxine Newell, park historian and member of the staff at Arches National Park; Jerry Banta, park ranger at Arches; and Dave Minor, district ranger for the Needles district, for their many favors.

I am grateful to several colleagues and friends for the loan of photographs, for geologic help and data, and for reviewing this report. I am also deeply grateful to my wife Ruth for accompanying me on all the field work and for her help and encouragement.

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