Geological Survey Bulletin 1327 The Geologic Story of Canyonlands National Park

We have discussed two of the three major topographic divisions of the park—the high mesas and the benchlands—and there remains to consider the third division—the canyons of the mighty Green and Colorado Rivers and some of their tributaries. After we discuss a few features common to both rivers, we will take up the details of each river.

A glance at the map (fig. 1) shows that above the confluence both rivers are very crooked and contain many loops, or meanders, the most striking of which are Bowknot Bend of the Green River (fig. 62), several miles north of the park, and The Loop of the Colorado River (fig. 74). In contrast, the main stem of the Colorado River below the confluence is considerably straighter. Not apparent on the map are the facts that the crooked rivers above the confluence have very gentle grades and are free from rapids or falls, whereas a few miles south of the confluence the main stem plunges into Cataract Canyon—the steepest and wildest reach of the river, containing 64 rapids. These differences are partly explicable on the basis of the geologic structure and character of the rocks through which the rivers have cut. Above the confluence, the soft strata dip gently northward, so in flowing generally southward the two rivers are cutting "against the grain," which tends to impede their flow and thus reduce their grades. Below the confluence, the hard limestones of the Hermosa Formation lie relatively flat for several miles and then begin to dip gently southward, thus allowing the river to cut "with the grain" and therefore drop more rapidly.

The quiet, smooth waters above the confluence permit power boating between the towns of Green River, Utah, and Moab during part of the year, whereas the rapids below Spanish Bottom, 3-1/2 miles below the confluence, restrict river travel to float trips using sturdy boats or rafts.

Above the confluence, a so-called Friendship Cruise is run each year during the Memorial Day weekend. Participants tow their own power boats on trailers to the town of Green River, and after the boats are launched, facilities are available at nominal cost for transporting cars and boat trailers to Moab to await the arrival of the boats. Although some high-powered speedboats are reported to have made the run down the Green River to the confluence then up the Colorado River to Moab in a few hours, the trip for most boats requires 2 to 7 days.

Trips by power boats, including jet boats, can be arranged from either Green River or Moab. Some passengers from Moab return by jeep from Lathrop Canyon via the White Rim Trail, and some from Green River return on land via the Horsethief Trail. Many prefer the quieter float trip down to the confluence, with return to either town by a prescheduled power boat, and some more adventurous souls float through the rapids of Cataract Canyon all the way to Lake Powell.

In the spring of 1972, a 93-foot 150-passenger stern-wheeler (fig. 69) began passenger service on the Colorado River from just above Potash to the foot of Dead Horse Point and return (Lansford, 1972).

Entrenched and cutoff meanders

Meanders such as those above the confluence generally are formed by streams flowing in soft alluvium consisting of clay, silt, and sand, such as along the Mississippi River below Cairo, Ill. But there is no soft alluvium along the Colorado and Green Rivers, so how did these meanders form? They probably attained their serpentine shape while cutting in softer, younger material, which long ago was removed by erosion, and then continued to cut their crooked channels down, until they created the deep rock-walled canyons in which they now flow as "entrenched" meanders.

Meandering streams tend to shorten their lengths from time to time by cutting through narrow walls between adjacent loops, leaving abandoned horseshoe-shaped channels or lakes. In most of the United States these are known as oxbows or cutoff meanders, but in the desert Southwest they are commonly called by the Spanish term "rincon." Cutoffs are common along soft alluvial channels such as the lower Mississippi River valley but are rare along channels whose meanders are entrenched into hard rock. Thus, there have been many natural (and several manmade) cutoffs along the lower Mississippi during historic times, but the most recent ones along the Green and upper Colorado Rivers probably occurred a million or so years ago, during the Pleistocene Epoch (figs. 65, 80).

Mark Twain served several years as an expert riverboat pilot on the Mississippi River during which several cutoffs took place. Chapter 27 of his "Life on the Mississippi" contains sage references to both natural and artificial cutoffs and concludes with a few good-natured jibes at geologists in particular and scientists in general:

Therefore the Mississippi between Cairo and New Orleans was twelve hundred and fifteen miles long one hundred and seventy six years ago. It was eleven hundred and eighty after the cutoff of 1722. It was one thousand and forty after the American Bend cut-off. It has lost sixty-seven miles since. Consequently, its length is only nine hundred and seventy-three miles at present.

Now, if I wanted to be one of those ponderous scientific people, and "let on" to prove what had occurred in the remote past by what had occurred in a given time in the recent past, or what will occur in the far future by what has occurred in late years, what an opportunity is here! Geology never had such a chance, nor such exact data to argue from! Nor "development of species," either! Glacial epochs are great things, but they are vague—vague. Please observe:

In the space of one hundred and seventy-six years the Lower Mississippi has shortened itself two hundred and forty two miles. That is an average of a trifle over one mile and a third per year. Therefore, any calm person, who is not blind or idiotic, can see that in the Old Oölitic Silurian Period, just a million years ago next November, the Lower Mississippi River was upward of one million three hundred thousand miles long, and stuck out over the Gulf of Mexico like a fishing rod. And by the same token any person can see that seven hundred and forty-two years from now the Lower Mississippi will be only a mile and three-quarters long, and Cairo and New Orleans will have joined their streets together, and be plodding comfortably along under a single mayor and a mutual board of alderman. There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact.

Green River

Much more has been written about the Green River and the main stem of the Colorado than about the Colorado above the confluence (the former Grand River), because all but one of the early float trips began on the Green. The first reports concerning Powell's memorable voyages of 1869 and 1871 were his articles published in Scribners Monthly during 1874 and 1875 followed by his formal 1875 report "Exploration of the Colorado River of the West and Its Tributaries." As pointed out by Porter (1969, p. 21), however, Powell's narrative

is written as if everything chronicled therein occurred during the first trip. Events which actually occurred in 1871 and 1872 are reported as happening in 1869. There is no mention of the personnel of the 1871-72 party, nor is there an indication that there even was a second trip. The engravings illustrating the report were made from photographs taken by Beaman and Hillers between 1871 and 1874, but this fact is not noted.

For these reasons, Porter's account contains Powell's diary of the first (1869) trip and many of the missing photographs, plus his own beautiful color prints. Much more complete and accurate accounts of the 1871 voyage than those of Powell, including many of the photographs taken by Beaman and Hillers, were given by Dellenbaugh (1902, 1962), who was a member of Powell's 1871 expedition.

Numerous river trips were undertaken in the years following Powell's pioneering expeditions. The ill-fated Brown-Stanton voyage of 1889-90 included starts on both the Grand and the Green Rivers. (See section on "Colorado River.") More successful were Nathan Galloway and William Richmond, trappers who left Henrys Fork, Wyo., late in 1896 and reached Needles, Calif., on February 10, 1897 (Kolb, 1927, p. 338). Trappers Charles S. Russell, E. R. Monette, and Bert Loper left Green River, Utah, in three steel boats on September 20, 1907; Russell and Monette reached Needles in one boat in February 1908, but Loper was drowned. Dellenbaugh's 1902 book was carried by the Kolb brothers as a guide for their 1911 trip down the river (Kolb, 1927). In addition to making superb still photographs, the Kolb brothers took the first moving pictures in the canyons, and these are still being shown in the Kolb Studio on the South Rim of the Grand Canyon. Julius F. Stone and party traversed the canyons in 1909, and his account (1932) also contains excellent photographs. E. C. LaRue, of the U.S. Geological Survey, and assistants made two trips down the Green and Colorado Rivers in 1914 and 1915 and additional trips from 1921 through 1924. Their comprehensive hydrographic findings and studies, plus excellent photographs, are given in two reports (La Rue, 1916, 1925). The 1916 report also contains (p. 16-22) a good condensed account of earlier explorations and voyages from 1531 through 1911, taken in part from Dellenbaugh (1902).

As noted earlier, a modern river runners' guide by Mutschler (1969), which logs the Green and Colorado Rivers from Green River, Utah, to Lake Powell, is now available. River mileages in this log were taken from detailed topographic maps of both rivers prepared under the direction of Herron (1917). We will visit only a few notable features of the canyons; the mile-by-mile details for the Green River can be obtained from Mutschler (1969), and those for the Colorado River, from Baars and Molenaar (1971, p. 61-99). Several other references are given below, and additional ones are given by Rabbitt (1969, p. 20-21).

All travelers down the Green River embarking from Green River, Utah, or above, were impressed with Bowknot Bend (fig. 62), so named by Powell and his men (1875, p. 54) near the beginning of Labyrinth Canyon, which they also named for its deeply entrenched meanders. The upper photograph in figure 62 was taken by Beaman on September 10, 1871, looking eastward from the west end of the narrow saddle separating the upper and lower reaches of the river; the lower photograph was taken from the same point on August 19, 1968, by Hal G. Stephens nearly 97 years later. Although there are changes in the vegetation, as described in the caption, there are virtually no visible changes in the bedrock. Nevertheless, the distant future will likely see a breakthrough, whereby Green River will shorten itself by about 7 miles (Herron, 1917, pl. 15C). It is interesting to note that the vertical cliffs of Wingate Sandstone in and west of Bowknot Bend are only a few hundred feet above the river, whereas because of the gentle northward dip of the beds and the gentle southward grade of the rivers, the Wingate cliffs are more than 2,000 feet above the two rivers at Grand View Point and Junction Butte, at the southern tip of Island in the Sky.

BOWKNOT BEND, of Green River, looking east from west end of narrow intervening saddle. Upper photograph was taken by E. O. Beaman on September 10, 1871, during second voyage of Major John Wesley Powell and his party. Lower photograph was taken from same camera station on August 19, 1968, by Hal G. Stephens, U.S. Geological Survey, on expedition led by E. M. Shoemaker to recover camera stations of the 1871 voyage and rephotograph the scenes to record changes during the nearly 100 year interval. Note that almost no changes occurred in the bedrock, or even in the loose rocks, but that considerable change occurred in the vegetation along the river. Although salt cedar (tamarisk) had been introduced into this country from the Mediterranean area long before 1871, it had not yet spread to this area, but the bare islands shown in the earlier photograph are covered by salt cedar in the 1968 photograph. (Fig. 62)

At the mouth of Horseshoe Canyon, about 3 miles below Bowknot Bend, we pass a large rincon where the Green River shortened its course by about 3 miles. Some idea of the rincon's antiquity is gained from the facts that the river is now some 350 feet lower than at cutoff time, whereas Bowknot Bend (fig. 62) has shown no visible deepening in 97 years. This rincon was not noted by Powell or other early voyagers, seemingly because they did not happen to climb the banks at this point, but it is quite noticeable on modern topographic maps and on aerial photographs. This rincon and Jackson Hole along the Colorado River may be as old as late Tertiary (fig. 80).

At a point reported to be 350 yards above the mouth of Hell Roaring Canyon, which enters from the east about 3-1/2 miles below the rincon, an early day trapper named Julien left his mark. Stone (1932, p. 69, pl. 39A) seems to have been the first river runner to find (from a description given him by a Mr. Wheeler at Green River), record, and photograph the inscription shown in figure 63. Mutschler (1969, p. 31) indicated that this inscription is carved on a massive Moenkopi sandstone bed about 40 feet above the canyon floor. A similar inscription by Julien was found in Cataract Canyon, 31 miles below the confluence, but it is now covered by Lake Powell (Mutschler, 1969, p. 65).

INSCRIPTION BY JULIEN, near mouth of Hell Roaring Canyon, thought to have been carved by Dennis Julien, an early day trapper. Photograph by K. Sawyer, August 1914, member of expedition led by E. C. La Rue (1916). (Fig. 63)

Some boaters are met by car and taken out to Moab or Green River via the Horsethief Trail (fig. 1), just north of the park. The road along the river here continues south for 6-1/2 miles to the mouths of Taylor and Upheaval Canyons, where it becomes the White Rim Trail.

Coming down the Green River, we enter Canyonlands National Park where the Grand-San Juan county line meets the Emery-Wayne county line (fig. 1), about 2-1/4 miles north of Taylor and Upheaval Canyons. The National Park Service had three successful test wells put down in Taylor Canyon, and water under artesian pressure was found in the White Rim Sandstone at depths of 373 to 482 feet. When funds become available, they hope to complete one or more of these wells and pump the water up to Island in the Sky, where two dry holes were drilled earlier.

About 512 miles below Upheaval Canyon is an interesting ruin on a hill in the middle of a large nearly closed loop of the river enclosing Fort Bottom. This was noted by Dellenbaugh (1902) during Powell's 1871 trip and was described in more detail by Mutschler (1969, p. 33-34):

The ruin consists of two, two-story, interconnected, crudely circular towers, and a third separate, completely collapsed tower, built on the summit of the bluff with a commanding view downriver and of Fort Bottom. Other collapsed structures are present on the summit, and a slab-lined cist is present beneath the Moss Back ledge west of the towers. The ruin was built of dry laid masonry and most of the mud plaster on the inside has been washed away, leaving the structure in danger of imminent collapse. Please do not climb the walls!

Fort Bottom also contains a cabin believed to have been used by Butch Cassidy and the Wild Bunch (Baker, 1971, p. 198).

At about the mouth of Millard Canyon, we leave Labyrinth Canyon and enter Stillwater Canyon, aptly named by members of the 1869 Powell voyage (Dellenbaugh, 1902, p. 276). The beginning of Stillwater Canyon is marked by vertical walls of the White Rim Sandstone. From here Powell's men observed a butte to the southwest thought to resemble a fallen cross and named it "Butte of the Cross." Farther downstream they realized they had been looking at two buttes, a small one in front of a larger one, so the feature was renamed "Buttes of the Cross." An aerial view of Buttes of the Cross is shown in figure 64.

BUTTES OF THE CROSS, looking southwest from the air. Millard Canyon enters Green River in foreground, North Point is in right middle ground, Orange Cliffs are in background, and Henry Mountains form right skyline. White Rim Sandstone forms White Rim near mouth of Millard Canyon and near Anderson Bottom at left middle. (See fig. 65.) Buttes are Wingate Sandstone capped by Kayenta Formation; slopes down to prominent ledge are Chinle Formation, Moss Back Member forming the ledge; steep and gentle slopes between ledge and White Rim are Moenkopi Formation. Photograph by National Park Service. (Fig. 64)

About 2 miles below the mouth of Millard Canyon, at Anderson Bottom, we reach one of the most interesting features on the river—the most recent rincon of a major river in the park, if not in the entire canyon country. Although some rincons are more recent, they are along minor tributaries such as Indian Creek (fig. 73). The cutoff at Anderson Bottom probably took place during the Pleistocene Epoch, whereas most of the others along the main rivers probably occurred during the Tertiary Period (fig. 80). An aerial view of the Anderson Bottom rincon is shown in figure 65, and a sketch of the drainage change is shown in figure 66. This feature was noted and correctly interpreted by Powell and his men, who applied the name Bonita Bend to the sharp new course the river took after the cutoff.

ANDERSON BOTTOM RINCON, aerial view looking southeast. Jointed White Rim Sandstone forms the clifflike canyon walls and the mesa in middle of Anderson Bottom. Green River is now about 60 feet lower than former channel at right. Photograph by National Park Service. (Fig. 65)

DRAINAGE CHANGES AT ANDERSON BOTTOM RINCON. River shortened itself about 2 miles by this cutoff. (Fig. 66)

Continuing through Stillwater Canyon, we pass Turks Head (figs. 23, 24) and head for the confluence of the Green River with the Colorado River. Figure 67 shows the canyon just west of the confluence. The lowest and largest cliff above the river is the upper member of the Hermosa Formation, overlain by the slopes and thin ledges of the Rico Formation. The massive sandstone at the top of the canyon wall is the Cedar Mesa. Junction Butte and Grand View Point are on the right skyline.

STILLWATER CANYON, of Green River, viewed from a point on the south rim about 1 mile above (west of) confluence with the Colorado River. Upper photograph was taken by E. O. Beaman on September 16, 1871, during second Powell voyage. Lower photograph was taken from same camera station on August 23, 1968, by Hal G. Stephens, U.S. Geological Survey. (See caption for figure 62.) Note that there are no noticeable changes in rocks or bushes away from the river but that sand bars in the early photograph are covered with salt cedar (tamarisk) in the later photograph, as described for figure 62. (Fig. 67)

We have already viewed the confluence and Cataract Canyon from the land and from the air (figs. 59-61); soon we will see them from the Colorado River.

Colorado River

As indicated earlier, all but one of the early river voyages began on the Green River. The Grand (Colorado) River above the confluence was neglected for some 18 years after Powell's second voyage, until, in 1889, Frank M. Brown organized a company for construction of the proposed Denver, Colorado Canyon, and Pacific Railway. This railroad was to carry coal from mines in Colorado over a "water-level" line through the canyons of the Colorado River to the Gulf of California some 1,200 miles away; from there the coal would presumably be shipped to ports as far north as San Francisco (Dellenbaugh, 1902, p. 343-369). On March 26, 1889, Brown, president, F. C. Kendrick, chief engineer, and T. P. Rigney, assistant engineer, drove the first stake for a survey of the new line at Grand Junction, Colo., then Brown left for the East to obtain financing, and the other two plus some hired hands took off down the Grand River. After reaching the confluence they towed the boat up the Green River, thus becoming the first to make this trip upstream. They nearly ran out of food, but thanks to the hospitality of some cattlemen, they replenished their stock and after about 9 days reached the railroad at Green River, Utah. 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 on May 25, 1889. Against the advice of Major Powell and A. H. Thompson, Powell's topographer on the 1871 trip, 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 was temporarily halted. However, the indefatigable Stanton contracted for new boats built of oak and, with a reorganized party of 12, left the mouth of the Fremont (Dirty Devil) River on November 25. After many further mishaps, the party finally reached the Gulf of California on April 26, 1890. Needless to say the proposed railway was not built.

Although the Colorado River enters Canyonlands National Park about 33 river miles below Moab, most boaters or floaters begin their voyage either at Moab or near Potash, and most travelers of the White Rim Trail begin at Moab, so we will start our trip at Moab. No logs or river runners' guides are available as yet for the reach from Moab to Potash, but below Potash some details of the geology have been described by Baars in Baars and Molenaar (1971, p. 59-87).

As noted at the beginning of this chapter, above the confluence both the Green and Colorado Rivers are very crooked, have very low grades, and are free from rapids. As with the Green, the soft rocks along the Colorado have a generally low northward dip that partly explains the river's gentle grade and its southward flow through increasingly lower and older strata. Unlike the Green, however, the gentle dips of the strata in the canyons of the Colorado are interrupted by several gentle anticlinal (fig. 14) and synclinal (fig. 26) folds and by at least one fault. The most important of these geologic structures and other features will be noted as we journey down the river.

The first 14 miles from Moab Valley to Potash can be made either by river or by paved Utah Highway 279. This highway leaves U.S. Highway 163 near the uranium ore-reduction plant several miles northwest of Moab, leaves Moab Valley through The Portal (fig. 68), and follows the west bank of the river. A paved secondary road from Moab follows the east bank of the river through The Portal and through Kings Bottom, where it crosses the Kings Bottom syncline, to the mouth of Kane Springs Canyon, then becomes a gravel road that ascends this canyon southward to and beyond Hurrah Pass (fig. 30). High above this road north of Kings Bottom are petroglyphs and a few cliff dwellings in the vertical cliffs of Wingate Sandstone. A ranch "house" at Kings Bottom has been excavated entirely into the Wingate cliff. Convenient turnouts have been provided at several places along Highway 279 for viewing petroglyphs or other points of interest. Small viewing tubes welded to vertical steel posts having signs help visitors locate and see the features described.

THE PORTAL, in south wall of Moab Valley, through which the Colorado River, Utah Highway 279 (on right), and a paved secondary road (on left) leave the valley to enter the canyons in and above Canyonlands National Park. Rounded remnants on top are Navajo Sandstone; cliffs are Kayenta Formation and Wingate Sandstone; red slopes are Chinle and Moenkope Formations, and perhaps a little of the Cutler Formation at the base. Light-colored patches at base of slope behind trees on left are contorted intrusions of Paradox Member of Hermosa Formation. (Fig. 68)

The Kings Bottom syncline (fig. 30) southwest of Moab Valley brings the Navajo Sandstone down to and slightly below water level, whereas at The Portal (fig. 68) the Navajo caps the southwest wall of Moab Valley. Several anticlines at or near the river from Potash to and beyond the confluence (fig. 1) bring up strata as old as the Rico or the unnamed upper member of the Hermosa. Between these extremes, much of the river's course lies in strata of the Cutler Formation.

About 7 miles below The Portal, Highway 279 is joined on the right by a branch line of the Denver and Rio Grand Western Railroad completed in 1962 to haul potash 36 miles from the mine at Potash north to the main line at Crescent Junction. The railroad emerges from a tunnel at the head of Bootlegger Canyon. Two natural arches near the mouth of the tunnel—Pinto and Little Rainbow Bridge—can be reached by trail. About 3 miles farther down the Colorado is a temporary dock from which jet boats and the Canyon King, a 93-foot 150-passenger stern-wheeler, take off for points downriver during the spring and early summer, when water depth permits. The Canyon King (fig. 69), a small replica of a Mississippi River stern-wheeler, carries passengers about 30 miles downriver to the foot of Dead Horse Point and returns (Lansford, 1972).

THE CANYON 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)

About 12 miles below The Portal we reach Potash—the potash mine (fig. 70) of Texas Gulf, Inc. (See fig. 31 and its associated text for description of operation.) Travelers down the jeep trail below Potash pass the evaporation ponds (fig. 71) used to separate the potash from common salt.

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 3-1/2 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 in figure 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 figures 31 and 71 are 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 in figure 29. Parts of the dome also show up in the lower right of figure 13 and the lower left of figure 15. From almost anywhere in the Goose Neck, the sharp bend of the river shown in figure 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 in figure 72.

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)

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 6-1/2 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 in figure 73 and 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.

RELATIVELY RECENT RINCONS ALONG INDIAN CREEK, about 3-1/2 miles above mouth and about 2 miles east of Canyonlands National Park. Above, steroscopic pair of aerial photographs by U.S. Geological Survey; below, sketch showing drainage changes. The steroscopic pair can be viewed without optical aids by those accustomed to this procedure, or by use of a simple double-lens stereoscope. (Fig. 73)

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 (see p. 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 figures 56 and 76. 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!

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)

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." (See fig. 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 77 was 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.

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)

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 in figure 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.

THE SLIDE, which partly blocks the Colorado River about 1-1/2 miles above the confluence. View downstream. (Fig. 78)

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 [see fig. 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 canon 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 the Colorado de Grande shall 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.

Cataract Canyon heads at the confluence, but the rapids do not appear until we leave Spanish Bottom some 3-1/2 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 in figure 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 in figure 79.

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)

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.