5/28/13 Utah Geology: Geologic Road Guides Utah Geology: Making Utah's geology more accessible. View south-east over St. George, Utah Road Guide Quick Select. Selection Map HW-160, 163 & 191 Tuba City to Kayenta, Bluff & Montecello, Utah (through Monument Valley) 0.0 Junction of U.S. Highways 160 and 89 , HW-160 Road Guide. follows U.S. Highway 160 east toward Tuba city and Kayenta. U.S. Highway 89 leads south toward the entrance to Grand Canyon National Park and Flagstaff. For a route description along U.S. Highway 89 northward from here see HW-89A Road Guide.. The road junction is in the Petrified Forest Member of the Chinle Formation. The member is composed of interbedded stream channel sandstone and varicolored shale and mudstone. This member erodes moderately easily and forms the strike valley to the north and south. From here the route of this guide leads upsection into younger and younger beds of the Chinle Formation. 0.7 Cross Hamblin Wash and rise from the Petrified Forest Member into the pinkish banded Owl Rock Member of the Chinle Formation. The upper member forms pronounced laminated pinkish gray and green badlands, distinctly unlike the rounded Painted Desert-type massive badlands of the underlying member. 1.6 Road rises up through the upper part of the Chinle Formation, a typical wavy to hummocky road. Highway construction is easy across the slope-forming parts of the formation, but holding the road after construction is difficult because the soft volcanic ash-bearing shales heave under load or after wetting and drying. Ashy gray marls and pinkish mudstones show well in badlands along the road (fig. 10. 1). To the north the monocline along the Echo Cliffs separates the Marble Platform on the west from the Kaibito Plateau on the east. Hamblin Wash has eroded along the outcrop of the Chinle and Moenkopi Formations between the more resistant Kaibab Limestone below and the cliff-forming Moenave and Navajo Sandstones above. www.utahgeology.com/roadguides.php?hw=hw163 1/19 5/28/13 Utah Geology: Geologic Road Guides Figure 10.1.View northward to exposures of the Owl Rock Member of the Chinle Formation along the Echo Cliffs Monocline, where Route 10 crosses the main part of the fold. 4.8 Side road north to Moenave. Approximately 500 yards north of the highway, along the Moenave Road, three-toed dinosaur foot prints (fig. 10.2) are preserved in one of the resistant sandstone beds of the upper part of the Chinle Formation, The tracks are in a barren area immediately west of the road. Local women may have exhibits of juniper seed and glass beadwork for sale at the site. ,br /> Moenave is the community to the north near the tall poplar trees and spring areas along the Moenave Sandstone escarpment. Figure 10.2.Three-toed dinosaur footprints in the upper part of the Chinle Formation north of the route on the Moenave road. 6.4 U.S. Highway 160 climbs through double road cuts in the almost Moenkopi looking upper part of the Chinle Formation in the candy-striped gypsiferous upper www.utahgeology.com/roadguides.php?hw=hw163 2/19 5/28/13 Utah Geology: Geologic Road Guides part of the section. Moenave beds hold up the escarpment to the north (fig. 10.3). 9.6 The highway now swings northward up off the floodplain of Moenkopi Wash through road cuts of Moenave Formation. These resistant sandstone beds form the plateau surface beneath the south end of Tuba City. Figure 10.3.View northward to uppermost Chinle beds and lower Moenave beds along the walls of Moenkopi Wash southwest of Tuba City at approximately Mile 8. 10.4 Junction of Access Road North to Tuba City and South to Moenkopi with U.S. Highway 160. 11.7 Small reservoir east of Tuba City. Cross-bedded Kayenta Sandstone rests on top of the resistant Moenave Sandstone near the road. The road east of Tuba City is in poor exposures of Wingate-Kayenta-Navajo Sandstone blanketed by loose drifting sand. Castle Butte to the north and Middle Mesa to the northeast show Navajo Sandstone capped by Carmel Formation. 16.4 Now abandoned uranium processing plant and associated housing. Rounded Navajo Sandstone begins to show in exposures in Moenkopi Wash to the south. Brownish beds in the immediate vicinity are probably basal Carmel Formation. 25.6 Rest area at the western base of Middle Mesa (fig. 10.4). Navajo Sandstone forms the lower, light tan, rounded bluffs and are capped by flat-bedded reddish Carmel Formation which is overlain by remnants of Entrada Sandstone at the top of the mesa. 25.6 Figure 10.4. View eastward from near the rest area at the western base of Middle Mesa at Mile 25.6. Navajo Sandstone is exposed beyond the buildings, below well-bedded Carmel and Entrada Formations. 33.3 Side Road to Tonalea School. A short distance beyond the junction the road dips down into a wash which exposes upper Navajo Sandstone, crinkly reddish Carmel Formation, and reddish brown to grayish green Entrada Formation. Red Lake Trading Post is on the western bluff of the wash south of the highway. Reddish beds of the Entrada Formation have a mottled to marbled weathered surface. Red Lake is in the valley to the south. www.utahgeology.com/roadguides.php?hw=hw163 3/19 5/28/13 Utah Geology: Geologic Road Guides 34.8 Elephant's Feet Rest Area. The "feet" are erosional remnants of light gray cross-bedded Entrada Sandstone (fig. 10.5). The "toes" are in the underlying reddish part of the formation. To the east Morrison Formation and Dakota Sandstone are exposed along the western end of Black Mesa. Figure 10.5. The Elephants Feet at Mile 34.8. These interesting erosional remnants are in Entrada Sandstone. 39.7 Junction of side road to Navajo National Monument, Inscription House and Navajo Mountain. U.S. Highway 160 swings parallel to the electric railroad right of-way. The railroad hauls coal from Black Mesa to the Navajo Power Plant near Page, Arizona. 43.2 Cow Springs Trading Post. The prominent white sandstone to the south of the trading post is the Cow Springs Sandstone (fig. 10.6) and is above the reddish part of the Entrada Formation and below the Morrison Formation. Prominent gray shale slopes near the top of the mesa expose Mancos Shale capped by the coal- bearing Cretaceous Mesa Verde Group. Figure 10.6. Cowspring Sandstone is the massive light gray unit at the base of the escarpment on the north side of Black Mesa. These exposures are southeast of www.utahgeology.com/roadguides.php?hw=hw163 4/19 5/28/13 Utah Geology: Geologic Road Guides Cowspring Trading Post, south from approximately Mile 44.0. 47.8 Coconino County-Navajo County Boundary. The Cow Springs Sandstone forms the relatively prominent light gray ledges to the south beneath Morrison beds. Morrison Formation forms the lower half of the Black Mesa escarpment and Mancos Shale and Mesa Verde beds the upper half. From high points along the road Navajo Mountain is visible toward the north. Navajo Mountain is cored by a laccolith, like intrusions in the Henry Mountains, La Sal Mountains, and Ute Mountain, but Navajo Mountain is still roofed with uparched Navajo Sandstone. 51.4 Junction of Arizona State Highway 98 with U.S. Highway 160. Arizona Highway 98 leads northwestward toward Page. To the south the front of Black Mesa still exposes Morrison beds as the gray and pinkish units near the base, with Mesa Verde Sandstone forming the mesa cap. U.S. Highway 160 continues on through Klethla Valley which is carved on nonresistant Carmel and Entrada beds. 63.6 Storage Silos and Tipple at the End of the Railroad. Coal is transported from the mines on the mesa to the southeast to the loading area by a belt system which is bridged over the highway (fig. 10.7). Coal in the strip mines area is up to 36 feet thick and as much as 100 feet of overburden is being removed in the mining operations (fig. 10.8). 64.4 Road Junction to Navajo National Monument Toward the North. A side road also leads south from here approximately 15 miles into the Peabody Coal Mine area on top of Black Mesa. Morrison and overlying Cretaceous rocks are exposed along the access road in the mesa front (fig. 10.7). Figure 10.7.Eastward along the escarpment of Black Mesa from near Mile 64.4, past the belt delivery system for Peabody Coal Company's operation. the belt delivers coal to storage and loading facilities at the end of the Navajo project railroad. East of the junction there is a double series of cliffs on the escarpment. Lower ones are held up by Morrison Formation above the light gray Cow Springs Sandstone and the upper one is held up by sandstone of the Mesa Verde Group, above the gray Mancos Shale slope. www.utahgeology.com/roadguides.php?hw=hw163 5/19 5/28/13 Utah Geology: Geologic Road Guides Figure 10.8.Peabody Coal Company Mine in Cretaceous Mesa Verde rocks on Black Mesa south of the route. Approximately 100 feet of overburden is being stripped from left and heaped in chat piles on the right to gain access to underlying coal that is up to 36 feet thick. 66.2 Rest Area. Massive very light gray Cow Spring Sandstone is "posed at the base of the mesa scarp and is overlain by reddish shale and light cliff-forming sandstone of the Morrison Formation.