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.