Moab to Shafer Dome, Utah
Potash-Shafer Dome
0.0 Junction of Utah State Highway 279 and U.S. Highway 191. Utah Highway 279 leads down the west side of the Colorado River to the mining operations at Potash. To the east can be seen the La Sal Mountains on the skyline in essentially three clusters as North Mountain, Middle Mountain, and South Mountain, beyond the Triassic cliffs of the north side of the Spanish Valley Anticline. To the south the railroad is in the Honaker Trail-Cutler sequence which is overlain by Chinle, Wingate and Kayenta Formations. Moenkopi beds are cut out here by an angular conformity between the Cutler and Chinle Formations. The railroad was put in to serve the potash mines at Potash, sixteen miles downriver to the south.
0.6 Exposures of laminated white and red beds in the upper part of the Cutler sequence on the southwest side of Moab Valley Dear Utah Highway 279, to the west. Tailing pits of Atlas Uranium Ore Reduction Plant continue to the right. Faulted Chinle and Wingate beds are exposed in the vicinity of the railroad.
1.0 Colorado River swings in close against the road. Point bar development is obvious on the eastern inside of the meander bend. Directly downstream, the Portal of the exit of the Colorado River front Moab Valley is capped by angular-weathering Wingate Sandstone, with Chinle beds forming the underlying slope. Navajo Sandstone is exposed on the skyline downstream a short distance.
2.0 The light-colored beds immediately cast of the river by the telephone poles are in the Paradox Formation. These rocks have pierced upward along the Moab Valley or Spanish Valley Fault System and are exposed several thousand feet above their normal position. No such piercement type features are visible on the western side of the river.
2.7 Base of the massive Wingate Sandstone on variegated Chinle Shales. The Wingate Sandstone is more prominently bedded here than it is in many areas, perhaps because this is its expression in the narrow canyon.
3.1 Indian ruins (probably granary structures) high on the east side of the canyon are beneath the overhanging ledge of the Kayenta Sandstone above the Wingate cliffs. Wingate Sandstone forms a massive cliff along both sides of the river and is here blanketed by desert varnish. Ahead hummocky round hills of Navajo Sandstone occur on top of the flaggy-bedded Kayenta Formation.
3.5 Alcoves and hanging gardens can be seen in the Navajo Sandstone, the formation that forms the rounded vertical cliffs on both sides of the canyon (fig. 6.29). Terraces blanketed with gravel continue downstream on both sides of the canyon at varying elevations up to 50 feet above the river.
Figure 6.29. Navajo Sandstone exposed along the gorge of the Colorado River below Moab. Gravel-capped terraces have been etched across the massive Navajo Sandstone as exposed here in the King's Bottom Syncline.
4.3 Massive Navajo Sandstone. Some erosional arch features show well in the sandstone. Fin development shows in the Navajo Sandstone on the east wall of the gorge along the strong joint system which is parallel to the Spanish Valley Fault to the north. Navajo Sandstone usually shows jointing more spectacularly than other units in the Mesozoic sequence.
4.8 Indian petroglyphs chipped in desert varnish in the Navajo Sandstone 10 to 15 feet above the road on the right. These petroglyphs are typical Fremont carvings. Fins of the Navajo Sandstone are well developed along the side of the gorge beyond Kings Bottom. The rocks are nearly flat lying here in the trough of the Kings Bottom Syncline.
5.5 Kane Springs Creek enters the Colorado River from the east. Dinosaur tracks and Indian petroglyphs are visible in Kayenta beds and blocks to the north. Complexly cross-bedded and in some cases contorted bedded and burrowed, tracked and trailed Kayenta Sandstone is exposed at river level and near the turn out. High alcoves and arches developed in the Navajo Sandstone can be seen high on the canyon wall to the east. The Kayenta Formation is expressed here in the typically ledgey slope zone which is capped with much high-level terrace gravel marking former positions of the Colorado River.
6.6 The canyon rim to the south is formed in the slabby Kayenta Sandstone. Because of the northward dip in the meander around Amasa Back, the long meander core of Kayenta Sandstone is at river level, and is alternatingly high above river level and near river level again as the channel swings back and forth from south to north then south again.
8.8 Base of the Navajo Sandstone is exposed at road level. For the next half mile Navajo Sandstone forms the outcrops in the road cuts on the north side. Some Kayenta beds are still exposed above river level on the southwest bank, with massive "beehives" of Navajo Sandstone developed high on the skyline ahead and to the south.
9.8 Bootlegger Canyon enters the canyon from the north. A road leads up the canyon to near Little Rainbow Bridge.
10.1 The river now swings approximately parallel to the branch line of the D&RGW Railroad leading from Crescent Junction south to Potash. The railroad tunnels through the long spur of the meander of the river. The railroad tunnel is approximately I mile long and opens into the head waters of Bootlegger Canyon. Kayenta rocks are exposed both east and west of the river with gravel terraces well developed to the cast on the point of Amasa Bank.
11.4 Very narrow Day Canyon leads off to the west (right). Parallel jointing is well expressed in the vertical walls of Wingate Sandstone.
12.8 Channel sandstone filling in uppermost beds of the Chinle beneath the massive shear wall of Wingate Sandstone exposed in railroad cuts to the southwest (right). To the left the massive wall of Wingate Sandstone is interrupted by a semiledge zone of wellbedded Kayenta rocks which are overlain by massive Navajo Sandstone near the top. The wall is called The Billboard.
13.0 Jug Handle Arch Visible High and to the Right in the Wingate Sandstone.
13.4 Major Tributary of Long Canyon Enters from the West. A primitive road from Big Flat and Dead Horse Point comes down Long Canyon on top of the gorge to the west- Chinle beds are exposed at the Long Canyon Junction and are also well exposed on the east side of the canyon. Beds dip sharply northward off the Kane Springs Anticline into the Kings Bottom Syncline.
14.3 Storage bins and processing plant of Potash development are directly ahead, Moenkopi rocks should appear near here but are not exposed through the thick cover.
14.5 Top of the Cutler beds is exposed at road level at the north end of the Potash railroad yards. The overlying Moenkopi Formation is thin here and forms the brownish shaly slope above the brick red units of the upper part of the Cutler sequence.
14.8 Massive red sandstones in the Rico Formation are exposed in low exposures away from the river. The high rim at the margin of Big Flat is in Wingate Sandstone on the skyline to the west.
15.3 Potash Plant to the Right. End of paved road. Return to U.S. Highway 163.
from Field Guide: Northern Colorado Plateau by J. Keith Rigby - Purchase Information
