This field trip route highlights Grand Canyon National Park’s Desert View Drive (Figure 1.1 of FIELD GUIDE TO THE GEOLOGY OF THE SOUTH RIM). Following AZ Hwy 64 along the eastern leg of the South Rim from Grand Canyon Village to Desert View, the highway offers spell-bindingly scenic vistas and access to some of the park’s more challenging hiking trails and remote backcountry. Roadside overlooks and hiking trail options combine to reveal an exceptional geologic story preserved in the canyon’s multihued rocks and its complex structural features. The tilted sedimentary rocks of the Grand Canyon Supergroup are visible from nearly every viewpoint and hiking trail, and record the rise and fall of a supercontinent, inundation and retreat of epicontinental seas, and tectonism and beveling of mountain ranges by erosion. The classic Paleozoic sedimentary rock sequence, pervasively exposed throughout the park, offers a spectacular view into sedimentation on a passive continental margin affected by marine invasions and retreats, later uplifted and deformed by regional mountain building.
To bring this geological story alive, one can make as much effort as desired or permitted by the constraints of time and physical ability. Five amazing vista overlooks at Grandview Point, Moran Point, Lipan Point, Navajo Point, and Desert View provide enough scenery and dispense with enough geologic detail to paint quite a picture; while multiple day-hiking and backpacking excursions from the rim and along the Colorado River offer exceptional detail commiserate with the excursions necessary to reach them.
0.0 (0.0) Refer to Map 1B.1. Intersection of Desert View Drive (AZ Hwy 64) and the entrance road to Yaki Point. Personal vehicles are not allowed on this road March 1st through November 1st; use the park-provided shuttle service; and please see Field Trip 1A for details. Remain on Desert View Drive heading east.
1.2 (1.2) Parking area for the Shoshone Point Trailhead on the left (north). Shoshone Point offers a wonderful opportunity to contemplate the vastness of the Grand Canyon from a seldom visited rimtop perch. Sunrises are marvelous, the geology is awesome, and its relative isolation from the throngs of tourists visiting the Grand Canyon Village area make a short hike here especially appealing.
Park in the trailhead parking area and walk up the gravel/packed earth road leading from its northeast end. The trail/road gently climbs toward the rim over an undulating surface of Kaibab Limestone carpeted by a forest of ponderosa pine. In just over a mile, you reach the point. The Park Service has constructed a picnic area complete with pavilion and modern, composting pit-toilets here and offers this location for group use during weddings, reunions, etc. Your route to the point passes through the oval parking area and picnic area on the way, but the path to the point is obvious.
Grand Canyon National Park personnel chose this location well; the scenery is gorgeous, and the solitude is refreshing. Shoshone Point, as with all points on the South (and North) Rim, is capped by the Kaibab Limestone; outcrops of which light up marvelously at sunrise (Figure 1B.1). The point heads a long ridgeline that descends somewhat northeasterly toward the inner gorge, passing Newton Butte before forking into separate ridges around the perimeter of Lonetree Canyon. The main ridge separates Cremation Canyon on the left from the western arm of Grapevine Canyon and the canyon of Boulder Creek on the right. Spectacular sunrise views of Cremation Canyon and its western headwall comprised of the stair-stepped Paleozoic Kaibab Limestone, Toroweap Formation, Coconino Sandstone, and Hermit Shale and upper Supai Group are offered here (Figure 1B.2). These formations are observed to form the same pattern, a product of differential erosion of alternating hard and soft rocks, throughout the Grand Canyon. Cremation Canyon and Grapevine Canyon lay along the northwest-southeast trend of the Cremation Fault and Grandview – Phantom Monocline. A careful examination of the middle section of Cremation Creek’s wash beyond Newton Butte will reveal an up-to-the southwest offset in Paleozoic Tonto Group and crystalline basement rocks produced by compressional reactivation of the Cremation Fault during the Late Cretaceous – Early Tertiary Laramide Orogeny; this faulting occurred in conjunction with development of the monoclinal fold. Grapevine Canyon is also cut along the down-to-the-northwest Vishnu and McKee Faults which trend northeast-southwest, forming a conjugate set with the Cremation Fault. This high-angle crisscrossing of major faults probably explains in part the large size and complexity of Grapevine Canyon.
Figure 1B.1. Sunrise dappled Kaibab Limestone at Shoshone Point.
Figure 1B.2. The western wall of upper Cremation Canyon as viewed from Shoshone Point; note the alternating cliff-slope-cliff pattern of resistant Kaibab Limestone, soft mudrocks of the Toroweap Formation, and resistant Coconino Sandstone, a product of differential erosion.
2.3 (1.1) A view to the south opens up here briefly, offering up Red Butte, an erosional remnant of Mesozoic sedimentary rock capped by basaltic lavas, as well as the more distant hills and mountains of the San Francisco Volcanic Field
2.8 (0.5) The parking area for an overlook into an unnamed western tributary of Grapevine Canyon lies on the left-hand (northeast) side of the road.
This tributary of Grapevine Creek has carved its course along the northeast-southwest trending Proterozoic Vishnu Fault (Figure 1B.3). Note the linear nature of this canyon, a product of fault-controlled erosion. Looking further afield, one can trace the Vishnu Fault across the inner gorge of the Colorado River, straight up Vishnu Canyon and past Vishnu Temple (the isolated butte capped by a remnant of light-colored Coconino Sandstone). Displacement is down to the northwest and the Vishnu Fault does bisect Paleozoic rocks, probably indicating reactivation by normal faulting related to Basin and Range extension within the past 17 million years.
Figure 1B.3. A product of fault-controlled erosion, this western tributary of Grapevine Creek has carved its course along the northeast-southwest trending Proterozoic Vishnu Fault; in the distance, the same fault can be traced across the inner gorge of the Colorado River, and straight up Vishnu Canyon past the Coconino Sandstone-capped Vishnu Temple.
3.6 (0.8) The parking area on the left (northeast) offers another opportunity to examine the complex Grapevine Canyon.
From the overlook, one can observe another unnamed western tributary to Grapevine Canyon, this one carved along the northeast-southwest trending Proterozoic McKee Fault. Displacement on this fault is again down to the northwest and the normal faulting ruptures Paleozoic rocks. Basin and Range extension has likely reactivated the fault within the past 17 million years.
5.4 (1.8) Refer to Map 1B.2. Another overlook of Grapevine Canyon can be found on the left (north) here.
This tributary of Grapevine Creek, oriented slightly northwest, lies at odds to the previous two canyons, having carved its course along a north-south trending Proterozoic fault, probably a splay of the Cremation Fault (Figure 1B.4). Displacement appears down to the northeast and it also cuts Paleozoic rocks. Not far to the northeast lies the axis of the Grandview – Phantom Monocline, a large single-limbed fold in the Paleozoic sequence overlying the Cremation Fault system; it is quite possible the fault splay occurring in this canyon is related to brittle fracturing of Paleozoic rocks as they were bent downward to the northeast across the fault when it was reactivated by compression during the Laramide Orogeny between 70 and 40 million years ago.
Figure 1B.4. A tributary of Grapevine Canyon cut along a north-south oriented splay of the Cremation Fault; down-to-the-northeast displacement suggests brittle failure of Paleozoic rocks related to the Laramide compressional folding that formed the nearby Grandview – Phantom Monocline.
5.9 (0.5) The highway crosses a fault here with apparent down-to-the-east displacement and then quickly traverses a small NW-SE trending graben as it climbs the opposing fault scarp exhibiting down-to-the west displacement just ahead. Map 1B.2 displays several distinctive topographic lineations heading south-southeast from the canyon rim near here where the surface has been broken by faults with east side down displacement. All of these normal faults cut the Paleozoic sequence and lay close to the axis of the Grandview – Phantom Monocline, suggesting brittle fracturing of the rocks in association with the Cremation Fault system and Laramide monoclinal folding.
7.6 (1.7) Refer to Map 1B.3. Junction of Desert View Drive and entrance road to the Grandview Point overlook on the left (north). Turn left onto the Grandview Point Road.
8.3 (0.7) Grandview Point overlook parking area; park and walk to the viewpoint just ahead. This overlook also provides access to the Grandview Trail (see the Grandview Trail Loop – Tr 1B.2 described in the Optional Hiking Trails section of Field Trip 1B).
By walking to several potential rim view locations in the Grandview Point area, you can stitch together an amazing 180º panoramic vista of the Grand Canyon. I would suggest starting with the northeast side of the overlook for an upcanyon view and then work your way around to the northwest side and downcanyon. To begin, by looking east, you can grab an excellent view into upper Hance Canyon and the Sinking Ship, a ridge comprised of Paleozoic rocks that have been tilted down to the northeast across the axis of the Grandview – Phantom Monocline which passes diagonally across your field of view from the northwest to the southeast. The monoclinal fold developed between 70 and 40 million years ago in response to reactivation of the underlying Proterozoic Cremation Fault by compressional tectonics associated with the Laramide Orogeny. Looking further to the northeast provides a view of Horseshoe Mesa, a horseshoe-shaped ridge of Redwall Limestone separating Hance Canyon from Cottonwood Canyon and the object of one superb day-hiking and/or backpacking destination. Also to the northeast, one catches a first glimpse of sedimentary rocks related to the Late Proterozoic Grand Canyon Supergroup. Gazing carefully into the inner gorge on the upcanyon side of Horseshoe Mesa, you can observe dark gray crystalline basement rocks overlain by eastward tilted layers of reddish Hakatai Shale and Bass Formation intruded by a dark basaltic sill. These rocks form the basal layers of the Supergroup, the entire package of which was back-tilted into an enormous graben bounded on the east side by the Butte Fault, a structural feature formed in the latest Neoproterozoic that you will see much more of as you travel toward Desert View. Finally, swinging around to the northwest offers a great view into the main tributary of upper Grapevine Canyon (Figure 1B.5); this canyon parallels the Cremation Fault system and is carved along a major splay of that fault. Reverse motion on the Cremation fault warped the overlying Paleozoic sedimentary rocks during the Laramide Orogeny, forming the Grandview – Phantom Monocline, evidence of which can be observed in the distant western wall of Grapevine Canyon (above and left of where the canyon bends to the north).
Figure 1B.5. The main tributary of Grapevine Canyon has formed along a major northwest-southeast splay of the Cremation Fault; here, you are standing on the crustal block lifted up to the southwest by reverse motion on the fault during the compressional Laramide Orogeny, the same motion having produced the Grandview – Phantom Monocline.
9.0 (0.7) Junction of the Grandview Point Road and Desert View Drive. Turn left (east) onto Desert View Drive.
11.9 (2.9) The road begins descending Buggeln Hill here; the steep descent is a product of folding of the Paleozoic sequence by the Laramide age Grandview – Phantom Monocline. The topographic expression of the monoclinal fold can be seen in Map 1B.3 heading to the southeast.
13.8 (1.9) Desert View Drive passes the trailhead for the New Hance Trail on the left (north) (see the New Hance Trail – Tr 1B.4 described in the Optional Hiking Trails section of Field Trip 1B).
14.9 (1.1) Refer to Map 1B.4. Junction of Desert View Drive and entrance road to the Moran Point overlook on the left (north). Turn left onto the Moran Point Road and drive to the overlook parking area.
Moran Point lies at the top of a ridgeline dividing the main drainage of Red Canyon on the west from a significant eastern tributary. Red Canyon has dissected its course along a zone of weakness in the rocks caused by the Hance Fault. From your rim view, you can peer into the canyon’s depths in relative comfort; the New Hance Trail being one of the toughest to hike on the South Rim. The canyon affords one of the few access routes to the Colorado River in the eastern Grand Canyon (on the New Hance Trail) and is so named for extensive exposures of the Hakatai Shale in the lower reaches of the drainage (Figure 1B.6), a rock unit of the lower Unkar Group, itself the basal portion of the Late Proterozoic Grand Canyon Supergroup. Carefully examine Red Canyon’s western wall across from your position and note that it forms part of a ridge separating Red Canyon from Mineral Canyon, stair-stepping down through Supai rocks and along a narrow rib of Redwall. Below the Redwall cliffs, lay the yellow-brown and olive-drab ledges and slopes of the Muav Limestone and then a long flat covered in the greenish-gray slopes of Bright Angel Shale leading all the way to the north end of the ridge.
Figure 1B.6. Red Canyon has formed along the northeast-southwest oriented Hance Fault; the view here is of the central portion of the canyon where red mudstones of the Hakatai Shale lay exposed in the bottom of the drainage, giving the canyon its name.
It is the exposed rocks in the wall of the canyon below the Bright Angel Shale that are the most interesting (Figure 1B.7); these are comprised of the Grand Canyon Supergroup. To the south (left), tilted layers of bright red Hakatai Shale form the sloping base of the canyon wall and these rocks are overlain by a massive cliff of similarly tilted, brown Shinumo Sandstone. From the left, and just as one would expect, the canyon wall exposes Tapeats Sandstone in a massive cliff below the sloping greenish mudstones of the Bright Angle Shale, but notice that the cliff pinches out toward the right (north) against a tall buttress of Shinumo Sandstone. Careful observation of the far-right end of the wall reveals a similar wedge of Tapeats Sandstone that pinches out southward against tilted cliffs of Shinumo Sandstone. It is the Bright Angel Shale that actually caps these Shinumo cliffs. The three lower Paleozoic rock units, the Tapeats Sandstone, Bright Angel Shale, and Muav Limestone, form the Tonto Group and were deposited successively, in sequence, as the Cambrian ocean advanced onto the western margin of the North American continent (where the Grand Canyon region stood at the time). What you are observing in the spectacular outcrop of the Red Canyon’s western wall and ridge is an ancient island of resistant bedrock (the Shinumo Sandstone) that remained above the rising sea for a time (during deposition of the Tapeats Sandstone), only to succumb to the waves eventually (during deposition of the Bright Angel Shale). The erosional contact between the tilted sedimentary rocks of the Grand Canyon Supergroup and the horizontal, undeformed Paleozoic sedimentary rocks above forms the Great Unconformity, an angular unconformity here, representing an approximate 600-million-year gap in the rock record.
Figure 1B.7. A close-up view of Red Canyon from Moran Point reveals the tilted layers of the Hakatai Shale and Shinumo Sandstone exposed in its western wall; here, the rocks of the lower Paleozoic Tonto Group cap the older Supergroup rocks, although the basal Tapeats Sandstone actually pinches out against the Shinumo cliffs which would have formed an “island” in the rising waters of the Cambrian sea that was only inundated during Bright Angel deposition.
Another spectacular view unfolds at the far western end of the Moran Point parking area. Here, your view to the west takes in the eastern face of the Sinking Ship, a crenulated ridge separating the two main branches of upper Hance Canyon. A discerning eye will quickly notice that the rocks forming this ridge are bent downward toward the northeast. This bending is direct evidence of the Grandview – Phantom Monocline, a Late Cretaceous – Early Tertiary structure formed by reactivation of the Cremation Fault during the Laramide Orogeny. Compression caused the block to the south of the fault to move upward in reverse motion relative to the northern block, resulting in the observable down-to-the-north displacement of Paleozoic rocks.
15.2 (0.3) Junction of the Moran Point road and Desert View Drive. Turn left (east) onto Desert View Drive (Hwy 64).
19.0 (3.8) Refer to Map 1B.5. Junction of Desert View Drive and entrance road to the Tusayan Ruins and History Museum on the right (south). Turn right onto the Tusayan road and drive to the ruins and museum parking area.
This archeological site preserves the Tusayan Pueblo Ruin, believed to have been occupied by Ancestral Puebloan people for no more than a few decades around 1185 A.D. By walking a relatively flat 0.1 mile trail around the village, one can access the remains of several structures, including a small and a large kiva for ceremonial activities, a unit house (a kind of early apartment building for an extended family), and grain storage areas surrounding a central plaza (Figure 1B.8). Evidence of agricultural fields lay nearby. The Park Service has made no attempt to rebuild the structures, although park archeologists have stabilized the ruin in an effort to protect it from ongoing degradation. Kiva and room blocks have been only partially excavated to allow you to experience an archeological site. The adjacent museum houses a small collection of related artifacts.
Figure 1B.8. The remains of a large kiva preserved at the Tusayan Pueblo Ruin, thought to be associated with ceremonial activities at this small Ancestral Puebloan archeological site.
19.4 (0.4) Junction of the Tusayan Ruins Road and Desert View Drive. Turn right (east) onto Desert View Drive (Hwy 64).
20.5 (1.1) The parking area for an unnamed overlook into Seventyfive Mile Canyon lies on the left-hand (northeast) side of the road.
The overlook affords a great view nearly perpendicular to the unusually aligned canyon of Seventyfive Mile Creek which carved its course along the more or less, east-west oriented Proterozoic Seventyfive Mile Fault (Figure 1B.9). The linear nature of this canyon, a product of fault-controlled erosion, lies at odds to most canyons tributary to the Colorado heading on the South Rim because the fault’s orientation crosscuts the usual trend. Displacement is up to the north and the Seventyfive Mile Fault does bisect Paleozoic rocks, probably indicating reactivation by reverse faulting related to Laramide compression about 70-40 million years ago. This viewpoint also offers your first opportunity to gaze across the broad reaches of the eastern Grand Canyon (Figure 1B.9). In the distance, the Colorado River occupies a much wider valley than previously observed; its narrow inner gorge is missing. This change in valley morphology is chiefly related to downcutting of the river through extensive exposures of soft sedimentary rocks of the Grand Canyon Supergroup (note the red slopes of Hakatai Shale near the valley floor); the Supergroup rocks are tilted eastward, preserved in an immense graben bounded on its eastern edge by the Butte Fault system formed in the Late Proterozoic. Less resistant rocks such as these allow rivers the luxury of expending some of their energy on lateral migration of the channel, hence the wide valley, rather than concentrated all of their efforts on cutting a channel downward (recall the crystalline basement rocks exposed further downriver and the relative narrowness of Granite Gorge).
Figure 1B.9. A marvelous view of Seventyfive Mile Canyon and the broad expanse of the eastern Grand Canyon beyond; the canyon of Seventyfive Mile Creek is aligned nearly east-west along an unusually oriented Late Proterozoic fault that runs sharply counter to most N-E basement fault lineaments of the region, while the eastern Grand Canyon is unusual in itself because of its wide-open morphology, a by-product of canyon carving through soft sedimentary rocks of the Grand Canyon Supergroup.
20.8 (0.3) Junction of Desert View Drive and the entrance road to the Lipan Point overlook on the left (north). Turn left onto the Lipan Point Road.
21.2 (0.4) Lipan Point overlook parking area; park and walk to the overlook just ahead. This overlook also provides access to the Tanner Trail (see the Tanner Trail – Tr 1B.5 described in the Optional Hiking Trails section of Field Trip 1B).
The overlook at Lipan Point provides eye-popping views both upriver and down. Begin at the eastern (right-hand) end of the parking area for a superb view toward the north of the eastern Grand Canyon’s broad valley and the distant Walhalla Plateau of the North Rim (Figure 1B.10). Here, the Colorado River occupies a meandering course in an unusually wide valley and is without its classic narrow inner gorge, a considerable change in morphology from the canyon further west, a feature that is primarily controlled by the expansive mudstones of the Dox Formation in this area. The Dox is a middle member of the Unkar Group, itself the basal portion of the nearly 13,000 feet of sedimentary rocks that make up the Grand Canyon Supergroup, back-tilted to the east in a very large graben produced by Late Proterozoic regional extension and formation of the Butte Fault system. Soft rocks such as the Dox Formation mudstones give rivers license to wander, expending some of their erosive power on lateral migration rather than vertical dissection, thus explaining the broad river valley in this part of the Grand Canyon.
Figure 1B.10. This superb view encompasses the vastness of the eastern Grand Canyon, its gentle morphology and the river’s meandering channel a by-product of canyon carving through soft sedimentary rocks of the Grand Canyon Supergroup; it also offers an excellent location to observe the Great Unconformity and East Kaibab Monocline.
Again, looking across the main canyon toward the north, the brick red to grayish Dox mudstones form the lower slopes on either side of the river from your position (Figure 1B.10). Careful observation of these rocks reveals their distinctive 20º tilt, down toward the east. Higher up-section within the Unkar Group, dark volcanic rocks of the Cardenas Basalt, capped by ledgy brown layers of the Nankoweap and lower Galeros Formations follow the same tilted pattern. The Middle Cambrian Tapeats Sandstone forms a distinctively thick, nearly level, brownish cliff-band overlying these tilted layers, and the contact between them creates an angular unconformity. Here that unconformity represents the Great Unconformity, a gap in the geologic record of roughly 500 million years, although the gap increases in time from west (Dox Formation) to east (Galeros Formation). Back at river level, you may have noticed that the Colorado River meanders through two broad curves within your field of view. Unkar Creek flows down from the Walhalla Plateau, and empties into the river from the north, forming a large fan-delta on the inside bend of the second curve. Migration of the meaner loop, combined with growth of this delta toward the southeast has pushed the Colorado in that direction, causing a steep cutbank to form on the outside edge of the meander (exhibited as cliffs in resistant Dox sandstones).
Now take in the broader picture presented in your view, especially examine the entire Paleozoic sequence (Figure 1B.10); one can discern that the sedimentary rock layers forming the Walhalla Plateau are quite flat, but look carefully at the same layers as they travel to the east and the entire package appears to bend downward. Following the cliff-band of Tapeats Sandstone from left to right (west to east) works especially well for this. This is not an optical illusion; in fact, this down-to-the-east bending is direct evidence of the East Kaibab Monocline, its fold axis lying above the trace of the Butte Fault. The Butte Fault system was reactivated as a reverse fault by a compressional tectonic regime associated with the 70- to 40-million-year-old Laramide Orogeny; up-to-the-west faulting produced the observed bending (Figure 1.8 of FIELD GUIDE TO THE GEOLOGY OF THE SOUTH RIM).
Near the west (left-hand) end of Lipan Point’s parking area, an amazing panoramic vista unfolds down canyon, where the wide valley formed in Dox Formation mudstones narrows to a gorge bordered by a distinctive grey-green bench as the river transitions first through the thick strata of resistant Shinumo Sandstone and then into the crystalline basement rocks of Upper Granite Gorge (Figure 1B.11). Here, the river is expending all of its energy just to carve downward through much more harder rocks. In the near ground, Seventyfive Mile Creek has cut an unusual east-west oriented canyon along the Late Proterozoic Seventyfive Mile Fault which is aligned at a high angle relative to most of the N-E basement fault lineaments exposed in the Grand Canyon. The canyon is floored by reddish mudstones of the lower Dox, surrounded by a bath-tub ring of Tapeats Sandstone cliffs. In the middle distant and further afield, one can follow the same brownish cliff-band of Tapeats Sandstone for reference. Above the Tapeats lies the gray-green bench consisting of Bright Angel Shale known as the Tonto Platform. Down canyon, the thick brown cliffs rising up to greet the Tapeats are Shinumo Sandstone, well exposed on the northern wall of the gorge below Seventyfive Mile Canyon; below them are slopes of red Hakatai Shale and a final cliff-band of Bass Formation intruded by a basaltic sill (the faint white layer near river level in the distance is metamorphosed Bass). Beyond that layer, the river enters Granite Gorge, where the Colorado has carved a narrow, tortuous path through dark Vishnu Schist and Zoroaster Plutonic Complex.
Figure 1B.11. This incredible down canyon view from Lipan Point offers a spectacular vista of the morphologic transition from wide valley formed in soft Dox Formation mudstones to narrow gorge bordered by resistant sandstones and then crystalline basement rocks; the down-to-the-east tilted sedimentary rocks of the Grand Canyon Supergroup are left behind as the river passes from Neoproterozoic graben into rocks of the Middle Proterozoic Grand Canyon Metamorphic Suite.
21.7 (0.5) Junction of the Lipan Point Road and Desert View Drive. Turn left (east) onto Desert View Drive.
22.9 Junction of Desert View Drive and entrance road to the Navajo Point overlook on the left (north).
(1.2) Turn left onto the Navajo Point Road and drive to the overlook parking area.
Navajo Point provides one of the more scenic vistas on the South Rim, but unfortunately, it is often overlooked by visitors anxious to reach nearby Desert View and all of its accoutrements. The view here is of Tanner Canyon and the open expanse of eastern Grand Canyon’s Colorado River corridor. Tanner Canyon joins the main canyon of the Colorado where a thick package of softer, less resistant sedimentary rocks of the Grand Canyon Supergroup has been exposed by erosion, which allowed the river to carve its wide valley. Tanner Canyon is aligned along the same trend as the Colorado River’s Marble Canyon and the 4000-foot-high cliffs known as the Palisades of the Desert; both canyons and cliffs offering up scenic spender galore (Figure 1B.12). And as is the case for many a canyon in the Grand Canyon region, these topographic features are fault controlled, aligned along the major NE-SW oriented Butte Fault system which provided structural weaknesses in the rocks that were later exploited by erosion.
Figure 1B.12. The unparalleled view upcanyon from Navajo Point; wide-open vistas serve up a plethora of geologic wonders created by the Butte Fault system and East Kaibab Monocline.
The presence of the Butte Fault system, the prevalence of the Grand Canyon Supergroup, the carving of aligned canyons and bounding cliffs, and the wide-open spaces of the Colorado River’s main valley, are as it turns out, all related. It is worth pausing here for a few moments to consider the geologic story so majestically portrayed in this place. The Butte Fault became active about 750 million years ago, when extensional tectonics began breaking up the supercontinent Rodinia along a rift zone west of the Grand Canyon region, generating several NW-SE trending normal faults in the crystalline basement and overlying sedimentary rocks of the ancient Supergroup (Figure 1.3 in FIELD GUIDE TO THE GEOLOGY OF THE SOUTH RIM), the Butte Fault being the most significant (Figure 1.7 in FIELD GUIDE TO THE GEOLOGY OF THE SOUTH RIM). Normal faulting wrenched apart the overlying sedimentary package, sending crustal blocks tilting downward to the east into fault-bounded grabens (Figure 1.8 in FIELD GUIDE TO THE GEOLOGY OF THE SOUTH RIM). The Chuar syncline (Figure 1.7 in FIELD GUIDE TO THE GEOLOGY OF THE SOUTH RIM) formed in rocks of upper Supergroup age (the Chuar Group and Sixtymile Formation), suggests that depositional processes continued to accumulate the last of the Supergroup rocks, while simultaneously folding them into synclines aligned along actively growing faults (Figure 1.8 in FIELD GUIDE TO THE GEOLOGY OF THE SOUTH RIM). Later erosion peneplained the entire region between roughly 740 million and 545 million years ago, only to have deposition resume in the Cambrian, beginning with accumulation of the Tapeats Sandstone (Figure 1.8 in FIELD GUIDE TO THE GEOLOGY OF THE SOUTH RIM). The contact between Supergroup rocks and the Tapeats Sandstone in the eastern Grand Canyon forms an uncompromising example of an angular unconformity, part of the region-wide Great Unconformity. Late Proterozoic sedimentary rocks of the Grand Canyon Supergroup are always found juxtaposed against normal faults and preserved as northeastward-tilted wedges in large fault-bounded depressions known as half-grabens, planed-off by erosion, and buried beneath a thick sequence of Paleozoic rocks; this pattern is well-expressed in your Navajo Point view (Figure 1.8 in FIELD GUIDE TO THE GEOLOGY OF THE SOUTH RIM).
When the Butte Fault and many of its Late Proterozoic partners were reactivated as reverse faults by Late Cretaceous through Early Tertiary (about 70 to 40 million years ago) compressional tectonics associated with the Laramide Orogeny, the thick sequence of Paleozoic sedimentary rocks that had accumulated was warped in places into monoclinal folds that parallel older basement faults and bend down to the northeast across the buried faults (Figure 1.3 and Figure 1.8 in FIELD GUIDE TO THE GEOLOGY OF THE SOUTH RIM). From Navajo Point, as you gaze upcanyon, you can observe the East Kaibab Monocline, which lies more or less over the Butte Fault, with its Paleozoic rock layers bent down along a single northeastward-dipping fold limb; the upper part of the limb forms the rocks exposed in the eastern margin of the Walhalla Plateau, and the lower part of the limb forms the rocks comprising the exceptional cliffs of the Palisades of the Desert east of Marble Canyon (Figure 1B.12). Although not visible from here, an even more recent period of deformation has begun to impact the region; beginning roughly 17 million years ago, the Butte Fault returned to its roots and is now undergoing extension once more as basement faults are being reactivated as normal faults that are chewing into the Colorado Plateau from the west, induced by Basin and Range extensional deformation (Figure 1.8 in FIELD GUIDE TO THE GEOLOGY OF THE SOUTH RIM).
From Navajo Point, it becomes obvious then, that the plainly visible Colorado River and its broad valley are a consequence of the river having cut a generally westward path across a particularly large north-south oriented Late Proterozoic graben and its preserved wedge of soft Supergroup rocks created by the Butte Fault system (Figure 1.3 and 1.7 in FIELD GUIDE TO THE GEOLOGY OF THE SOUTH RIM). In your view here, the Colorado River meanders through an unusually broad section of the Grand Canyon where erosion of the thick, mud-rich Dox Formation prevailed (Figure 1B.12). Differential erosion of this sort is often observed where rivers dissect weaker rocks and can expend more energy on lateral migration. Alternately, the resistant igneous and metamorphic basement rocks of the Colorado’s Granite Gorge formed further downriver are exposed in a narrow, steep-walled inner canyon. Rivers must use most of their energy just to carve downward through strong, resistant, crystalline rocks, and cannot afford to waste precious energy on migrating laterally across wide valleys. Marble Canyon, upriver, is also quite narrow; in this case the river is carving through the thick, dense Redwall Limestone which is also quite resistant to erosion. Tanner Canyon and Marble Canyon are aligned north-south in conjunction with the Butte Fault and the East Kaibab Monocline (Figure 1.7 in FIELD GUIDE TO THE GEOLOGY OF THE SOUTH RIM and Figure 1B.12) where erosion would have been enhanced by structurally induced weaknesses in the Paleozoic and Late Proterozoic sedimentary rock layers encountered by the Colorado River and by a regional dip of the land related to offsetting elevations between the higher Kaibab Plateau to the northwest and adjacent lower Marble Platform to the southeast. The position of the Colorado’s course relative to the Butte Fault and East Kaibab Monocline is probably not a coincidence, but it is worth noting that the sheer cliffs of the Palisades of the Desert lie along the trend of the Butte Fault and the East Kaibab Monocline, essentially at the break in slope where rock layers flattened out at the base of the fold’s eastward dipping limb.
23.0 (0.1) Junction of the Navajo Point Road and Desert View Drive. Turn left (east) onto Desert View Drive.
23.6 Junction of Desert View Drive and entrance road to the Desert View area on the left (northeast).
(0.6) Turn left onto the Desert View Road and drive to the parking area. After a leisurely stroll to the overlook and perhaps a little shopping, you have completed Field Trip 1B; return the way you came at your leisure.
Desert View provides scenery and shopping, what more could you ask for? However, before you become distracted by shiny trinkets (even by the worthy Grand Canyon Association Bookstore), make your way to the overlook just beyond the Desert View Tower. From this fine perch, you can gaze directly over the edge into Tanner Canyon, as well as upriver into Marble Canyon. Let your eyes linger on your Marble Canyon view, a careful examination of the layer cake of sedimentary rocks exposed by erosion of the Colorado River will reveal a number of geological secrets you don’t want to miss (Figure 1B.13). First, the broader view; follow the easily recognized upper layers of Kaibab Limestone, Toroweap Formation, and Coconino Sandstone from the Walhalla Plateau in the west to the Marble Platform in the east, it should quickly become evident that the rocks are offset (the rock formations are much lower to the east). A discerning eye may notice that the rock layers actually do bend downward from plateau to platform. This revelation is direct evidence of the East Kaibab Monocline, the down-to-the-east folding of Paleozoic strata over the Butte Fault (Figure 1.7 in FIELD GUIDE TO THE GEOLOGY OF THE SOUTH RIM). The folding resulted from Laramide compressional reactivation of the Butte Fault system as a reverse fault between 70 and 40 million years ago, the same mountain building event that produced the ranges of the Rocky Mountains to the northeast.
Figure 1B.13. The unparalleled view up Marble Canyon from the overlook at Desert View Watchtower provides an exceptional opportunity to examine the Butte Fault system and accompanying East Kaibab Monocline.
The Colorado River initially cuts along the trend of the Butte Fault system and the axis of the East Kaibab Monocline where it occupies Marble Canyon, and then it cuts diagonally across the tilted layers of Late Proterozoic Grand Canyon Supergroup rocks (Figure 1B.13). Paleozoic sedimentary rocks overlie Supergroup rocks along an angular unconformity comprising the Great Unconformity in the eastern Grand Canyon; notice the cliff band of brown Tapeats Sandstone lying directly on the tilted Supergroup rocks. Sedimentary rocks of the Grand Canyon Supergroup are tilted down-to-the-northeast within a huge graben bounded on the eastern side by the Butte Fault. Looking closely at the meandering Colorado and you’ll notice two large, light colored, sandy patches where the river first bends to the left and then to the right as it flows downstream. The main trace of the Butte Fault actually lies just west of Marble Canyon and is best observed in the cliff face across the river from Tanner Rapids which lies directly between these two patches of sand (Figure 1B.13). The cliff face is mainly comprised of a thick band of dark Cardenas Basalt, fractured by two splays of the Butte Fault, with the middle section dropped into a small subsidiary graben at Tanner Rapids that is inset within the much larger graben that tilted the entire package of Supergroup rocks to the east. Closer observation of the eastern fault splay bounding the Tanner Graben allows you to trace it northeast, where you can pick up the Cardenas Basalt on the eastern, up-thrown side of the fault. The graben and normal fault motion indicated here is associated with the initial development of the Butte Fault, and is a product of crustal extension in the Grand Canyon region associated with rifting of the Rodinian supercontinent during the Late Proterozoic. Continuing further northeast along the fault trace, you can see that the Paleozoic rocks on the west side of Temple Butte and Chuar Butte are bent sharply down to the east along the fault, expressing the reverse fault motion and compressional folding related to Late Cretaceous to Early Tertiary Laramide reactivation of the Butte Fault system described earlier.
If you wish to avoid the crowds around Desert View Tower, head southeast along a trail that leaves the pavement near the tower to a marvelous overlook of the Palisades of the Desert and Marble Platform (Figure 1B.14). From this location, it is quite easy to observe that the Paleozoic sedimentary rocks comprising the sheer cliff “palisades” are tilted somewhat eastward; you are looking at the downwarped side of the East Kaibab Monocline with the fold axis passing nearly beneath your feet. The Palisades of the Desert form an unusually cohesive and quite impressive 4000-foot-high cliff from Kaibab Limestone through Redwall Limestone; the “steps” created by softer, more erosive rocks are nearly missing in the rock sequence at this end of the Grand Canyon because the Toroweap Formation is comprised of resistant sandstones (rather than the usual mudstones and evaporites) and the Hermit Shale is relatively thin (it thickens westward). Recall that the Grand Canyon region lay at the western margin of the North American continent throughout this time, and both of these features are related to eastward-directed facies changes associated with marine invasions from the west. Across the small canyon further to the southeast, a flat-topped hill blanketed in junipers rests rather strangely on the Marble Platform; this odd bit of topographic relief is Cedar Mountain (Figure 1B.15). The hill resembles an old cinder cone in profile, but is actually a tiny erosional remnant of Mesozoic sedimentary rocks that once covered the region in a blanket thousands of feet thick, a thin layer of resistant Shinarump Conglomerate of the Chinle Formation capping reddish mudstones of the Moenkopi Formation, both units of Triassic age.
Figure 1B.14. The Palisades of the Desert and the Marble Platform from a rim trail overlook just southeast of the Desert View Watchtower.
Figure 1B.15. Cedar Mountain, a remnant of Triassic Moenkopi Formation capped by the Shinarump Conglomerate of the lower Chinle Formation is best observed from a rim trail overlook just southeast of the Desert View Watchtower.
Road Route Maps
Map 1B.1. Color shaded-relief map of the Phantom Ranch 7.5” Quadrangle containing segments of Field Trip 1B and Field Trip 1C.
Map 1B.2. Color shaded-relief map of the Tusayan East 7.5” Quadrangle containing segments of Field Trip 1B and Field Trip 1C.
Map 1B.3. Color shaded-relief map of the Grandview Point 7.5” Quadrangle containing a segment of Field Trip 1B.
Map 1B.4. Color shaded-relief map of the Cape Royal 7.5” Quadrangle containing a segment of Field Trip 1B.
Map 1B.5. Color shaded-relief map of the Desert View 7.5” Quadrangle containing segments of Field Trip 1B.