I-70 Junction to Montecello, Utah
0.0 Junction of U.S. Highway 163 with Interstate 70 at Crescent Junction. Turn south onto U.S. Highway 60 toward Moab (fig. 6.1). Low hills to the southwest and southeast are in Mancos Shale, but on the skyline to the south are Jurassic rocks exposed on the upthrown block of the Moab Fault. At ten o'clock folded Jurassic rocks form both flanks of the Salt Valley Anticline (fig. 6.2).
Figure 6.2. Southeastward along Salt Valley Anticline to the La Sal Mountains, in the distance, from south of Crescent Junction at approximately Mile 1.1. Rocks from the Jurassic Entrada Formation up through the Morrison Formation are exposed along the flanks of the structure.
1.1 Approximate axis of Salt Valley Anticline crosses highway. Tertiary intrusions core the La Sal Mountains which rise to approximately 12,000 feet at ten o'clock. Salt Valley Anticline is one of a series of salt intrusion structures developed along the flank of the Paradox Basin. Several of these have graben faults along their crests. Salt Valley Anticline has Cretaceous Mancos Shale (fig. 6.3) dropped down as a "keystone" between flanks of older Jurassic Entrada, Morrison, and lower Cretaceous Burro Canyon Formations. At nine o'clock the Uncompahgre Uplift forms the faint hills on the skyline. The Henry Mountains, at three o'clock, are also cored by Tertiary intrusions and are the locality where Gilbert visualized laccolithic type intrusions.
4.1 Dakota Sandstone exposed in bluffs cast of the road and the spur line of the D&RGW Railroad. The highway is on Mancos Shale above Dakota Sandstone cuestas. Older Burro Canyon beds (fig. 6.3) arc visible below the Dakota Sandstone in gullies through the cuesta.
5.4 Cross Rockhouse Creek. Morrison and Burro Canyon beds visible on the flank of Salt Valley Anticline. The road continues in Mancos Shale. A low cuesta to the southwest of the road is held up by silty equivalents to the Ferron Sandstone (fig. 6.4) which is part of a delta complex exposed near the Wasatch Plateau far to the west.
Figure 6.4. Northwestward along the gentle cuesta capped by silty beds of (he Ferron Sandstone at their easternmost extent in the Mancos Shale, from approximately Mile 9.5.
9.5 Side road to microwave relay station to west. At ten o'clock the prominent castellate erosion features in the interior of the Salt Valley Anticline, in Arches National Park, are in the Moab Tongue of the Entrada Sandstone (fig. 6.3). The overlying light-colored Curtis Sandstone and Morrison Formation form the biscuit-like dip slopes.
13.2 Entrance Road to Canyonlands Airport.
13.6 Cross spur line of railroad on overpass. Prominent butte ahead is capped with Dakota Sandstone above slope zone on Morrison and Burro Canyon Formation above Entrada Sandstone cliff.
14.9 Cross down through cuesta cap of Dakota Sandstone onto greenish and varicolored beds of the Burro Canyon Formation.
15.8 Cross concrete bridge over Courthouse Wash. Greenish beds are lower Cretaceous Burro Canyon Formation. The deep cut to the east is for diversion of the wash which experiences common summer flash floods. Maroon and greenish gray Morrison beds are exposed in badlands along either side of the road beyond the mouth of the gully.
17.9 Bright green Burro Canyon beds are faulted against cliff-forming Wingate and underlying Chinle and Moenkopi beds at three o'clock to the southwest (fig. 6.5). To the north Morrison beds are exposed on the stripped surface on the south side of Salt Valley Anticline and north flank of Courthouse Wash Syncline.
Figure 6.5. Cliff-forming Wingate Sandstone, capped by moderately well-bedded Kayenta Sandstone, on the left, is offset along the Moab Valley Fault against slope-forming Morrison and Cedar Mountain Formations on the right as seen from approximately Mile 18.0.
18.8 Road is in massive sandstone of Morrison Formation. To the southwest bright green beds of the Chinle Formation are exposed to uranium mine access road at about the base of the formation and the top of the Moenkopi beds. Top of the cliff above is in Kayenta beds above the prominent cliff of Wingate Sandstone. The trace of the Moab Valley Fault is close against the base of the escarpment where reddish Cutler and Moenkopi beds form irregular erosional features (fig. 6.6).
Figure 6.6. Prominent cliffs of Wingate Sandstone are capped by moderately well-bedded Kayenta Sandstone and occur above slopes of Chinle Formation. These exposures are on the east side of the side road which leads south into Canyonlands National Park, at approximately Mile 20.3. Moenkopi beds form the lowest part of the slope above the Cutter cliffs, which are exposed in the foreground near the bottom of the canyon wall.
20.3 Side Road to Canyonlands National Park and Dead Horse Point State Park to the south. HW-313 Road Guide. for log of this road. Morrison beds on both sides of the road are downfaulted against Permian Cutler redbeds to the south along the Moab Fault. U.S. Highway 163 crosses the trace of the Moab Fault approximately 0.7 mile ahead to the southeast.
22.4 Overlook into deep railroad cut in Cutler redbeds, The railroad was constructed to service potash mines developed along the Colorado River downstream from Moab.
24.6 Shallow bend in the highway. Morrison beds on the north are faulted down against the pink to maroon arkose of the Cutler sequence.
25.6 Begin bend on highway near the mouth of Moab Canyon. Light-colored limestone and shale in cuts to the south are in the Honaker Trail Formation, as are those directly ahead. Marine fossils occur in the shale and limestone north and east of the railroad fill by the deep double railroad cut.
At the north end of the cliff on the bend, the highway crosses the Moab Fault (fig, 6.7). Here massive Jurassic Entrada Sandstone is faulted against Pennsylvanian Permian Honaker Trail and Cutler (fig. 6.9) rocks. The crinkled maroon Dewey Bridge Member of Entrada forms the erosional break between the massive Entrada Sandstone above and the fractured lighter colored Navajo Sandstone below.
Figure 6.7.View southwestward over the Visitors Center to the narrows at the lower end of Moab Canyon, from the park above the headquarters of Arches National Park. Cliffs on the skyline are in Wingate Sandstone, above slopes of Moenkopi and Chinle beds. Pennsylvanian and Permian rocks are exposed in narrow road cuts in the mouth of the canyon and in the deep railroad cuts to the left. The Moab Fault crosses the highway at the mouth of the canyon and has dropped Navajo Sandstone, Carmel Formation, and massive Entrada Sandstone down against the upper part of the Paleozoic sequence near the prominent bend on the park road, to the right of the canyon mouth.
26.2 Junction of Side Road into Arches National Park with U.S. Highway 163. Park headquarters and Visitors Center are visible a short distance down the side road to the northwest, at the base of the cliffs of Entrada and Navajo Sandstone. See Guide Segment 6B for a log of the road into various parts of Arches National Monument.
27.2 Junction of Utah State Highway 279 with U.S. Highway 163. Utah State Highway 279 leads south along the western side of a uranium mill tailings pond and then south into the gorge of the Colorado River to a potash plant development. See HW-279 Road Guide. for a log of this route. Moab Valley, into which we've now entered, is a salt anticline that is en echelon with Salt Valley. Moab Valley also has a collapsed "keystone" of Mancos Shale and older rocks apparently produced by collapse following solution of salt at depth. Faulted Wingate and Chinle rocks are exposed north of Atlas Minerals uranium concentration plant, and on the southwest margin of Moab Valley.
28.2 Cross Courthouse Wash. Uppermost Chinle beds exposed in road cuts both east and west of the bridge show northward dip off the Moab Valley salt anticline into Courthouse Wash Syncline.
28.8 South Bridge Abutment Over Colorado River and Junction of Utah State Highway 128 with U.S. Highway 163 , the state highway which leads northward upstream along the river to Cisco and Castle Valley. Upper beds of Chinle Formation and massive cliffs of Wingate Sandstone and beehive-weathering Navajo Sandstone are visible upstream and downstream to the south near where the Colorado River exits from the valley. Paradox Formation piercement features are present east of the river gorge on both the northeast and southwest margins of the valley.
30.0 Enter Moab. Chaotic Paradox gypsiferous units are exposed along the border fault zone of the valley to the north.
31.4 Bridge over Mill Creek at the south end of Moab business district. Tan and gray Paradox piercement bodies are visible through the trees to the southwest along the southern border fault of the collapsed "keystone." Jointed Wingate and Navajo Sandstones cap the faultline escarpment. Peaks of the La Sal Mountains rise above the Jurassic and Triassic rocks to the cast.
38.0 Grand County-San Juan County Line. Rolling country nearby is in Morrison Formation dipping beneath gray Mancos Shale of the collapsed "keystone" to the east. Older Jurassic rocks form the valley walls beyond the border faults.
43.2 Begin climb out of Moab Valley across badly fractured Morrison beds which are here fault juxtaposed against Chinle and Wingate Formations. The road continues over the summit in Morrison beds.
46.4 Cane Springs State Park. The springs issue from near the base of the massive Moab Tongue of the Entrada Sandstone near a fault which has dropped Morrison and older beds on the west down against the Entrada Sandstone on the cast. The fault is particularly dramatic approximately one-half mile north of the park area where slope-forming Morrison abuts massive cliff-forming Entrada.
South of the park the highway continues in crinkly-bedded Dewey Bridge Member of the Entrada Formation on the tableland at the top of the Navajo Sandstone and below the cliffs of Entrada Sandstone.
47.6 Cross drainage. Road is in Dewey Bridge beds to the south and north, but drops onto upper Navajo near the drainage. Ledge- and slope-weathering Morrison Formation caps the Entrada cliff on the east. The road continues at about this same stratigraphic level for several miles.
51.6 Natural Gas Compressor Station on the west. Crinkly maroon Dewey Bridge Member is exposed at the base of the cliff of beehivelike outcrops of massive Entrada Sandstone. Navajo Sandstone is exposed in gullies to the west.
53.3 Junction of Utah State Highway 46 with U.S. Highway 163. The state highway leads east to La Sal and the Big Indian uranium district. Massive sandstone east of the junction is Entrada Sandstone beneath intensively prospected uranium-bearing Morrison Formation. Mt. Peale, the high southern peak in the La Sal Mountains to the northeast, is cored by a Tertiary intrusion and has an elevation of 12,721 feet.
56.6 Window Arch Turnout (fig. 6.9). The road is in Dewey Bridge beds and the arch is in Entrada Sandstone. Navajo Sandstone is exposed in the gully to the west. Abajo Mountains, held up by Tertiary igneous intrusions, are visible on the skyline to the south from near here and are part of the distinctive igneous province of this part of the Colorado Plateau. For the next seven miles the highway is constructed at approximately the level of the thin red crinkled Dewey Bridge Member, with some road cuts exposing upper Navajo Sandstone and some others the lower part of the massive Entrada Sandstone which generally forms cliffs east of the road (fig. 6. 10).
Figure 6.9. Window Arch as seen from the north at approximately Mile 56.5. The arch is in the Moab Member and the road is on the Dewey Bridge Member of the Entrada Sandstone
Figure 6.10. View northward of rounded, massive, sandstone cliffs of the Entrada Formation overlain by slope zones on the Summerville and Morrison Formation, as seen northward front approximately Mile 60.0. The road and the slope zone in the foreground is on the crinkly Dewey Bridge Member of the Entrada Formation, above massive white Navajo Sandstone which is exposed in the gullies on either side of the road.
63.9 Side Road to Canyon Rim Recreation Area-Needles Overlook. The road to the west leads to scenic overlooks on the rim of the Colorado River gorge, across from Dead Horse Point State Park. To the east massive Jurassic rocks are dipping westward off the Lisbon Valley Anticline, another salt-related fold. The Lisbon Valley oil field is developed along the cuesta to the southeast, on the west flank of the surface anticline, but in a subsurface anticline in Mississippian Redwall Limestone.
70.7 Junction of Utah State Highway 211 with U.S. Highway 163. The state highway leads west to Indian Creek State Park and the eastern part of Canyonlands National Park. For a description of the state highway route and access roads in the park see HW-211 Road Guide..
Church Rock (fig. 6.11), a small Entrada outlier to the east of the junction, gives the valley its name. Low bluffs to the cast are also in Entrada Sandstone, overlain by slope-forming Summerville and Morrison Formations.
Figure 6.11. Church Rock, an outlier of the Entrada Formation in the center of Church Rock Valley, as seen eastward from approximately Mile 71.0 near the junction of the highway that leads westward into Canyonlands National Park.
74.2 Top of the Entrada Sandstone is at valley level. Summerville Formation is exposed in poor outcrops along the highway and in vertical castellate outcrops along the western wall of the valley. The formation is only 25 to 30 feet thick here and is overlain by the more sandy, stream-deposited Morrison Formation on both sides of the valley. Small faults locally offset the distinctive formation bands (fig. 6.12).
Figure 6.12. Westward from the highway at approximately Mile 74.2 to a small fault which has offset the light-colored Entrada Sandstone. A thin deep reddish Summerville Formation overlies the massive Entrada beds and occurs below the prominently bedded Morrison Formation.
75.3 Begin dugway through relatively poor exposures of Morrison Formation. Dakota Sandstone forms the rim at the crest of the canyon walls.
77.4 Cross small drainage. Massive sandstone south of the bridge is Dakota Sandstone whose basal contact is approximately at the bridge level.
The road climbs up through the Dakota Sandstone for the next mile and rises out onto a rolling stripped surface on top of the formation at the head of the small canyon. The intrusion-cored Abajo Mountains rise above the stripped plain and are flanked by their own debris.
80.6 Entrance to Monticello airport on the west. Mancos Shale is exposed in road cuts from near here into Monticello. Some of the shale exposures are armoured with gravel swept down from the Abajo Mountains to the southwest.
84.9 Junction of U.S. Highway 666 with U.S. Highway 163 in Monticello. Follow HW-666 Road Guide. for a continuation of the guide along U.S. Highway 666 toward Cortez and Durango and follow HW-160 Road Guide. for a continuation of the route log toward Blanding, Bluff, and Monument Valley and across the Navajo Indian Reservation toward Grand Canyon National Park.
85.3 Leaving Monticello east on U.S. Highway 666. The road for several miles is constructed in the lowermost Mancos Shale across the flat uplands and in uppermost Dakota Sandstone across inscribed drainages. Much of the Great Sage Plain, through which we are now driving, is veneered with reddish brown loess, windblown dust and silt, which has helped make the area a moderately fertile farming region.
88.3 Cross Vega Wash. Excellent exposures of Dakota Sandstone can be seen both to the south and north. Lower Mancos Shale is exposed in road cuts both cast and west of the wash.
92.1 Double road cuts in Mancos Shale, with weathered reddish loess blanket on top, are typical of the next 5 miles. Juniper woods are left on some of the less favorable areas.
96.5 Junction of side road south to Eastland, U.S. Highway 666 continues in lower Mancos Shale.
101.2 Colorado-Utah State Line. To the east the highway crosses through poor exposures of Dakota Sandstone in the divide areas and good exposures in the canyons and gullies for the next several miles.
106.7 Junction Colorado State Highway 141 North to Egnar. Dakota Sandstone is exposed in gully bottoms wherever topography dips below the general base of the Mancos Shale and where red loess of Dove Creek soil has been removed by erosion.
107.5 Pass three tall concrete elevators west of Dove Creek.
107.9 Entering Dove Creek , the pinto bean capital of the world according to local billing.
108.8 Leaving Dove Creek heading southeast on U.S. Highway 666. Dakota Sandstone is exposed in gully banks and bottoms beneath the reddish loess soil.
112.2 Small strip mines in Dakota Sandstone on the north. Coal in the formation appears to be as much as 3 feet thick here and to occur in a deltaic or low barrier-island complex.
114.5 Cross Sharp Creek. Extensive exposures of Dakota Sandstone are visible along the creek and are capped, on the west side by Mancos Shale above upper Dakota and Carbonaceous shale. Similar exposures can be studied in Alkali Creek, approximately I mile ahead to the southeast.
116.7 Large elevators in Cahone. Dakota Sandstone is exposed all through town.
118.4 Dolores County-Montezuma County Line. U.S. Highway 666 continues through poor exposures of Dakota Sandstone. The Abajo Mountains to the west, La Sal Mountains to the north, and Ute Mountain to the south are all cored with late Tertiary igneous intrusions that are relatively fine grained. Apparently the intrusions were relatively cold when they were emplaced.
121.5 Pleasantview community.
125.5 Yellowjacket , a single-store farming community. Deep red Dove Creek soil blankets Dakota Sandstone. The loess soil is up to 8 or 9 feet deep in some areas, even on crests of some of the low hills. Cross-bedded white sandstone of the Dakota Formation is visible in gullies to the west.
129.7 Junction of Colorado State Highway 147 with U.S. Highway 666. State Highway 147 leads east to Dolores and the Dolores River Valley. Mancos Shale is exposed here in broad downward-bowed structure below surrounding Dakota Sandstone exposures along the highway to the southeast and northwest. Dakota Sandstone is exposed in small canyons and gullies and locally has been prospected for coal.
130.1 Double road cuts in Dakota Sandstone and Mancos Shale where highway passes beneath large irrigation flume. Mancos Shale exposed on the divides and Dakota Sandstone is exposed in the gullies from here to Cortez. Morrison Formation is exposed in some of the deep canyons some distance west of the highway. Dove Creek loess soil covers much of the uplands.
135.3 Weil-exposed coaly Dakota Sandstone in road cuts and gully exposures,
137.2 Cross-bedded Dakota Sandstone shows well on the north side of the Toad. The softer coally parts of the formation are less well exposed but are evident in areas where the formation has been prospected or mined on a local basis, particularly in the northwestern outskirts of Cortez.
138.4 Triangle Separation of U.S. Highways 160 and 666 in Western Cortez. U.S. Highway 666 continues south toward Shiprock, New Mexico and U.S. Highway 160 continues cast to the entrance to Mesa Verde National Park, Durango, and Pagosa Springs. Cortez is built on Dakota Sand stone and Mancos Shale. U.S. Highway 160 east of town is, in large part, on Mancos Shale for some distance at the foot of Mesa Verde (fig. 6.13).
Figure 6.13. View eastward along the northern escarpment of Mesa Verde from near Cortez, Colorado. Mancos Shale forms the flat land and lower gray slopes at the bast of the escarpment. Sandstone beds of the Mesa Verde Group cap the ridge and the plateau surface.
from Field Guide: Northern Colorado Plateau by J. Keith Rigby - Purchase Information
