Provo To St. George, Utah
0.0 Interchange at University Avenue South of Provo on Interstate Highway 15. The interstate highway is constructed over prodelta lake clays of Lake Bonneville or, in some areas, over younger organic marsh deposits. Provo City is currently using the area to the east of the highway for sanitary landfill and has modified the local drainage. Southeast of the intersection the road passes through marshes that border Provo Bay on Utah Lake (fig. 3.1), Water to the east is provided, in large part, by springs located near the base of the Wasatch Mountains or at the toe of the Provo River delta where porous sand was deposited over clay as the delta built southward and southwestward.
Wasatch Mountains along the east border of the valley are composed in large part of upper Paleozoic limestone but Precambrian and Cambrian rocks are exposed as the tan and very light gray lower part of the face of the front range. Dark gray outcrops in the lower part of the mountain front are fault lowered slivers of Mississippian limestone and dolomite which were dropped along the Wasatch Fault. The Wasatch Fault trace is near the base of the mountain.
1.8 Cross beneath overpass at the northern Springville interchange. Complexly folded Mississippian rocks are exposed to the east in Buckley Mountain as the light and dark gray ledges along the front. Lime kilns have been developed in these rocks and in fault slivers of the same units, to the north.
The broad embayment in the Wasatch Mountains, to the southeast, traces out a pronounced bend in the Wasatch Fault. East and southeast of Springville most rocks in the mountain are within the Oquirrh Formation, Manning Canyon Shale (fig. 3.2) forms a strike valley that separates the higher peaks of Oquirrh Formation from the older Mississippian and Cambrian rocks of the front range.
3.8 Springville Interchange Overpass. Springville, to the east, is named for the numerous springs which rim the community. Some of the springs are fault controlled and issue along fault lines where porous sand and gravel have been juxtaposed with impervious clay. Other springs in and near the city issue where the contact of porous sand and gravel on underlying clay is exposed near the front of Hobble Creek delta. Much of the town is on this delta built into Lake Bonneville from Hobble Creek Canyon, the deep notch in the Wasatch Mountains to the east.
5.4 Overpass over Union Pacific Railroad Track. Maple Mountain to the east, between Hobble Creek and Spanish Fork Canyons, has well-defined triangular facets along its western margin. These are interpreted as evidence for recurrent movement along the Wasatch Fault which occurs near the Lake Bonneville shorelines at the mountain base.
5.8 Overpass over Denver and Rio Grande Western Railroad track. The delta of Spanish Fork River is well expressed to the east as the gentle rise and flat benchlands between the alkali marshes of the lake bottom near the freeway and the mountain front. This part of the delta formed during the Provo-level stillstand of the lake.
5.9 Interchange for Access Route to U.S. Highway 89 and 50-6 in northeastern Spanish Fork. U.S. Highway 89 leads through the Wasatch Mountains and then south parallel to Interstate Highway 15. For a description of the geology along U.S. Highway 89 see HW-89 Road Guide.. U.S. Highway 50-6 leads southeastward toward Price and Grand Junction and for a description of that route see I-70 Road Guide..
The U.S. Highways 89, 50-6 access road climbs up the foreset front of Spanish Fork delta and onto the flat topset plain of the Gilbertian-type delta. Interstate 15 continues southwestward over lake bottom clays.
6.7 Interchange at the north edge of Spanish Fork. Father Escalante and his companions were the first white men to enter Utah Valley. In September 1776 they came down Spanish Fork Canyon in their search for a route between Spanish colonies in New Mexico and California and camped, three days near here with the friendly "Yuta" Indians.
Loafer Mountain, elevation 10,685 feet, is the high glaciated peak to the south. U-shaped valleys show well in the top, with cirques carved in Oquirrh Formation. Glaciers extended down to an elevation of approximately 9,000 feet.
West Mountain, to the west, is also composed in large part of Oquirrh Formation (fig. 3.2) that is part of a major thrust fault slice which apparently moved eastward 8 to 10 miles during the Sevier period of mountain building in the Cretaceous. Oquirrh rocks overrode Mississippian and older rocks that are exposed in the low hills south of the main range.
6.9 Crossover Spanish Fork River which has entrenched into its delta.
7.7 Overpass at the Benjamin interchange. Loafer Mountain to the southeast is flanked by a broad apron of pre-Lake Bonneville debris which has been dissected by young canyons. Dry Mountain, to the south, exposes metamorphic rocks along its lower western base and is capped by Mississippian rocks toward the east. The high flat uplands visible beyond between Dry Mountain arid Loafer Mountain is the northern part of the Wasatch Plateau. The plateau is made up of relatively flat-lying Cretaceous and Tertiary rocks which were deposited over folded Paleozoic and Mesozoic formations.
The low ridge in the valley approximately one mile west of interstate 15 is composed of Tertiary Salt Lake Formation and is bounded by a fault along its eastern margin. The fault is marked by a series of hot springs which extend northward for about 3 miles from the Benjamin Cemetery at the cluster of conifers on the ridge.
10.3 Payson Interchange, north edge of town. Interstate 15 continues over Lake Bonneville clays. A spit in the eastern part of town was built by Lake Bonneville where longshore currents were deflected by a hill of Tertiary volcanic rocks. Except for Dry Mountain, to the south, the other high peaks surrounding Utah Valley are held up by Oquirrh Formation, one of the thickest stratigraphic units in the state. The formation was deposited in a deep basin during Pennsylvanian and early Permian time.
14.5 Low rounded hills east of the overpass are on Precambrian gneiss and schist (fig. 3.3). Younger Precambrian and Paleozoic rocks form the ledges above. Lake Bonneville gravel and sand blanket the base of the mountains and are being quarried for construction materials. The highway now begins to climb up onto the toe of an alluvial fan built by Santaquin Creek.
Figure 3.3.View eastward from approximately Mile 14.5 near Santaquin of Precambrian (P), Cambrian (C), and Mississippian (M) rocks exposed along the western front of the Wasatch Mountains. The Wasatch Fault is near the base of the escarpment at the head of the alluvial fans.
16.6 Interchange of U.S. Highway 6 with Interstate 15. U.S. Highway 6 leads westward through the Tintic mining district toward Delta, Utah and Ely, Nevada. Godiva Mountain is the ridge on the skyline to the west and is in the center of the lead-silver producing Tintic mining district. Heyday of the district was about the turn of the century, but it has been recently reactivated by discovery of gold at depth northeast of Godiva Mountain.
17.7 Bridge over Santaquin Creek. Keigley Quarry to the north is in Cambrian, Devonian, and Mississippian limestone and dolomite and provides flux for the U.S. Steel Plant near Provo. Long Ridge is the low hills to the west and is a series of tilted fault blocks of Paleozoic and Tertiary rocks. Cretaceous and Tertiary North Horn Formation and volcanic rocks obscure Paleozoic formations in the hills west of Santaquin Canyon to the south. On the east side of Santaquin Canyon, however, Cambrian rocks arc thrust over Oquirrh rocks.
19.1 Interchange southwest of Santaquin. Rounded low hills to the east are creep and landslide accumulations of Cretaceous Tertiary North Horn Formation (fig. 3.4), Most movement must have been pre-Lake Bonneville because Bonneville-level sediments lap over the toe of the landslide debris. In the fields to the northwest the low elongate ridges are spits built out into Lake Bonneville at lower levels of the lake.
20.0 Utah County-Juab County Line at the crest of the hill. The county line is along a drainage divide at a bay bar of Lake Bonneville. The bay bar was formed at the Bonneville level of the lake and rests on a paleosol on Alpine level silt. These relationships are exposed in a railroad cut 0.3 of a mile west of the highway.
Road cuts to the south show the coarse bouldery debris of the land slides. Ahead of us to the south the reddish elongate hummocky tongue is a debris flow of North Horn material derived from exposures of the formation on the ridge to the east (fig. 3.5).
21.2 Crossing through road cuts on the toe of the debris flow tongue. Reddish clay matrix and boulders are typical. To the east Wasatch Fault at the base of the mountain front has offset all but the most recent sediments. In low morning light the scarp is particularly evident. Long Ridge makes up the western margin of the valley and is largely Paleozoic limestone but with a cap of Tertiary volcanic rocks which are related to those of the Tintic district on farther to the west.
23.5 Three cirques are present in steeply dipping Oquirrh rocks (fig. 3.6) to the southeast near the crest of Mt. Nebo (elevation 11,928 feet). Glaciers extended down to approximately 9,000 feet, but below that the V-shaped valleys were stream-eroded and unmodified by glaciation.
Figure 3.5.Tongue of landslide debris with a characteristic upper hummocky surface exposed east of the highway at Mile 21.2. The debris was derived from North Horn beds which are exposed in the ridge crest area.
28.3 Mona exit. Mt. Nebo Reservoir west of town is along Current Creek and catches water from a series of springs that issue near the head of the reservoir. Water from the reservoir is used in southern Utah Valley. Purplish volcanic rocks on Long Ridge west of the reservoir bury Paleozoic limestone and dolomite.
29.6 South end of Mona. Hummocky topography of landslide or creep deposits on the lower part of the mountains to the east is produced by Manning Canyon Shale outcrops (fig. 3.7). The same Mississippian shale forms the pass that separates Dry Mountain from Mount Nebo and forms the shoulder on Mount Nebo. Pennsylvanian Oquirrh Formation makes up the upper part of Mount Nebo and Cambrian to Mississippian rocks make up the foothills to the northwest. Recent movement along the Wasatch Fault has produced a scarp at the base of the Wasatch Mountains. The fault has offset alluvial fans approximately 60 feet here at the base of the mountains.
Figure 3.6.Mt. Nebo as seen from the northeast from approximately Mile 24.0. Three cirques are developed in the steeply dipping upper Paleozoic rocks near the crest of the mountain. Older Paleozoic rocks are exposed near the base and are cut by the Wasatch Fault whi
Figure 3.7.The south end of Mt. Nebo and a major debris slide of hummocky material from the Manning Canyon Shale as seen eastward from the south end of Mona at 19.6. Pennsylvanian Oquirrh Formation forms all the exposures above the landslide mass and is here steeply
32.3 Cross over the crest of an alluvial fan veneered with mud flow debris. Hummocky topography in the mouth of the canyon to the east is produced by broken Oquirrh rocks which were brecciated in the lower part of the overriding plate of the Nebo thrust fault. Fragmented Oquirrh rocks have been quarried for road metal along the front south of the canyons. From the quarry southward to near Nephi a younger fault scarp has displacement of up to 80 feet and marks the trace of the Wasatch Fault.
33.9 Side road west to Juab County Nephi airport. The fault scarp shows as the break in alluvial fan profile at the base of the mountain to the east and southeast.
35.6 Northern City Limits of Nephi. The Nebo thrust fault is exposed in the reddish hills at the southwest base of Mount Nebo (fig. 3.8). The fault trace crops out at valley level almost directly below the block "J" where overturned and brecciated Oquirrh Formation occurs above overturned red Ankareh Formation (fig. 3.4). Park City and Phosphoria Formations are above the thrust fault on the ridgecrest on the skyline and are above overturned Navajo Sandstone which forms the light tan outcrop belt on the north side of a moderate canyon. Arapien Shale is exposed south of the Navajo Sandstone in the lower hills north of Salt Creek Canyon. Gypsum was mined from Arapien beds near the Nephi city dump until recently. The Gunnison Plateau south of Salt Creek Canyon is not part of the overthrust fault system although gray Arapien Shale in the lower part of the hills was folded somewhat. Cliffs above the Arapien Shale are sandstone and conglomerate of the Cretaceous Indianola Formation (fig. 3.4) and were derived from erosion of the mountains produced by the Nebo thrusting and accompanying folding. Approximately equivalent and younger late Cretaceous beds bury the thrust fault toward the north and help date the thrusting as Cretaceous.
Figure 3.8.Nebo overthrust fault in Mesozoic and upper Paleozoic rocks at the southeast base of Mt. Nebo as seen northeastward from the north edge of Nephi. The fault is shown by a line and the over-thrust direction by the arrow.
38.2 Highway 132 exit at Nephi. Utah State Highway 132 leads eastward up Salt Creek Canyon and into Sanpete Valley and westward through the southern part of Long Ridge and around the north end of the Canyon Range toward Delta, Utah and Nevada.
39.7 Curve on I-15 south of Nephi. Low hills to the east are in gray Jurassic Arapien Shale. Cretaceous conglomerate and sandstone cap the high part of the Gunnison Plateau and arc part of a thick elastic wedge deposited in the Rocky Mountain Geosyncline east of the mountains produced during the Sevier orogeny. Cretaceous rocks are reported to be approximately 20,000 feet thick 10 miles to the east.
43.2 Major curve on I-15 on the crest of Levan Ridge. The ridge is produced by merging of several alluvial fans from canyons off the Gunnison Plateau to the east. To the south the rounded irregular topography of the plateau margin is a function of the ease with which the Arapien Shale erodes. Cretaceous and Tertiary rocks cap the plateau. East dip of Tertiary Green River and Flagstaff rocks on Long Ridge' shows well by gentle eastern and steep western slopes to the west.
49.2 Levan (navel spelled backwards) is just east of the Interstate. State Highway 28 leads south to Gunnison and U.S. Highway 89. Deep canyons of Chicken Creek and Pigeon Creek in the Gunnison Plateau to the east are carved in Arapien Shale. The same formation erodes to the rounded hills to the southeast of town and is overlain on the plateau crest by Cretaceous and Tertiary rocks. Beyond town U.S. Highway 91 swings westward across Juab Valley.
53.0 Major bend toward the south on the western side of Juab Valley. The highway swings parallel to the Union Pacific Railroad line. To the east we now get a long distance view of the Gunnison Plateau with soft-appearing rounded, somewhat barren to juniper-cov
57.6 Chicken Creek Reservoir to the east. Flagstaff and Green River rocks form the cuestas to the west and dip eastward beneath Oligocene volcanic rocks.
58.3 Mills Junction Road and Chicken Creek Reservoir Dam. A variety of tuffaceous Oligocene volcanic rocks are exposed beyond the south dam and bridge abutment. White and tan lacustrine Green River and Flagstaff Limestones are exposed down the gorge to the west beneath the volcanic rocks and are overlain and underlain by redbeds.
60.2 Crest of hill in double roadcuts in fossiliferous green and tan Green River Formation. Similar beds are exposed to the north and south along the highway.
63.8 Bedded conglomerate of the Cretaceous-Tertiary North Horn Formation (fig. 3.9) is exposed east of the highway. These rocks are equivalent to those that occur near the top of the Gunnison Plateau to the east and along the eastern side of the Canyon Range to the west. They are part of the coarse debris fans swept eastward from the Cretaceous-age mountains produced at the site of the present-day Canyon Range and on westward into Nevada.
65.6 Cross Sevier River. The river meanders extensively here in the southern part of Mills Valley. The low gradient of Sevier River is in part produced by deposits of the stream which accumulated as a long delta into Lake Bonneville. The valley filled with fine-grained sediments during a high stand of the lake and is now being reexcavated following the last drop in lake level, The Sevier River drains around the northern end of the Canyon Range, across Sevier Desert, past Delta, and. into Sevier Playa, and has its origin on the Paunsaugunt and Markagunt Plateaus in the southern part of the state.
68.1 Roadside rest area is developed in Sevier River sediments associated with a high level of Lake Bonneville. Rounded conglomeratic ledges on either side of the road south of the rest area are North Horn Conglomerate. The lower ledges in the eastern part of the Canyon Range are part of the same general conglomeratic section. These beds have been overridden by a thrust slice of Precambrian quartzite which is exposed as the lighter colored, well-bedded, rocks in cliffs in the upper half of the Canyon Range escarpment. The overthrust rocks are at the crest of the range from near Leamington Canyon, at the north end, southward approximately 20 miles to west of Scipio.
Oldest rocks exposed at the base of the range are the Ordovician Pogonip Group rocks which are gray to yellowish brown at the top and are overlain by the Ordovician Eureka-Swan Peak Quartzite which forms a thin, light tan cliffy bed. Somber gray Ordovician Fish Haven, Silurian Laketown, and lighter gray Devonian rocks occur immediately beneath the overthrust plate (fig. 3.10).
Figure 3.10.View westward from north of Scipio of the south edge of the Canyon Range. Distinctly bedded uppermost part of the ridge crest is held up by Precambrian rocks in an overthrust slide. Precambrian rocks here rest on Devonian beds beneath the fault. Rocks as old as lower Ordovician are exposed near the base of the escarpment toward the left.
71.1 Juab County-Millard County Line. Lower massive Cretaceous conglomerate forms cliffs below bedded over-thrust Precambrian quartzite in the Canyon Range to the west. North Horn Conglomerate and sandstone form the high country of the Valley Mountains to the southeast. Flagstaff Limestone caps the North Horn sequence along the eastern side of the range.
76.5 Junction of Utah State Highway 50 and Interstate 15 at Scipio. Directly south of town massive Cretaceous Price River Conglomerate caps the Pavant Range and rests unconformably over folded Ordovician, Silurian, and Devonian dolomite and limestone.
78.8 Beginning of major climb up into Scipio Pass through rather poorly exposed Ordovician Pogonip Group rocks.
82.0 Pass Summit. Poorly fossiliferous Ordovician limestone exposed north of the summit area as well as in roadcuts on the southwest side. The highway now drops down the western side of the Pavant Range (fig. 3.12) across alluvial fans and valley fill.
The monument commemorates the epic journey of Father Escalante and Father Dominques and eight companions who traveled through this pass in October 1776 in their search for a route between Santa Fe, New Mexico and the new Spanish port of Monterey, California. They are the first white men known to have been through here.
90.9 Junction of Utah State Highway 50 with Interstate 15 at the north edge of Holden. Utah State Highway 26 leads northwestward to Delta. Cambrian rocks are exposed on the western side of the Pavant Range and are unconformably overlain by Cretaceous Price River and North Horn beds at the range crest.
97.8 Cedar Mountain on the west is composed of eastward-dipping Tertiary volcanic rocks which are older than the volcanic rocks which have accumulated in the floor of the valley to the west.
Pavant Butte, (fig. 3.12) the prominent peak in the valley to the west, is a volcano cinder cone. It is the site of a 1930s aborted attempt to generate electricity on a commercial scale utilizing windmills.
99.6 Bridge of the Fillmore Interchange Volcanic rocks of Black Rock Desert and Fillmore volcanic field occupy much of the lower parts of the valley to the west. Horseshoe volcano to the west is a cinder cone and is being quarried for construction materials. Tabernacle volcano to the southwest is the rounded hill that rises above the black basalt flows with which it and other volcanos of the area are associated. Lavas erupted, in part, into Lake Bonneville and must have produced spectacular short-lived plumes. Other lavas predate the lake since some are reworked by lake currents, while still others are deposited on lake material and hence are younger than the lake.
Fillmore was the first capitol of Utah and the Capitol building was the first one constructed west of the Mississippi River. It housed the territorial legislature from 1855 until 1858 when the legislature adjourned to Salt Lake City.
103.1 Bridge over interstate at southern Fillmore interchange. Horseshoe volcano is to the west and Tabernacle volcano to the southwest.
107.9 Meadow and Kanosh Interchange and Junction with Utah State Highway 133. Additional volcanos are visible to the southwest.
The white mound 5 miles to the west is known as White Mountain and is made largely of wind-blown gypsum derived from evaporation of local gypsiferous springs.
112.2 Directly west from here the low, tan, rounded hills are tufa cones associated with Hatton Hot Springs. The tufa has been quarried locally for building materials.
114.1 Rest area to the west is constructed on basalt associated with Black Rock volcano to the southeast. Upper levels of Lake Bonneville have been etched into the base of the cinder cone. Other volcanos rise as pyramid-shaped peaks to the southwest.
119.3 Low ridges to the southeast of the road are steeply dipping Cambrian rocks. Those forming cockscombs closest to the road are Tintic Quartzite. The rounded hills beyond are of Cambrian limestone and shale or younger rocks, and all are included in an overthrust sheet which involves the southwestern spur of the Pavant Range.
120.3 South Kanosh exit. Cambrian rocks and young basalt dikes show immediately east and southeast of the interchange.
120.5 Major bend in the highway. Shallow terraces of highest levels of Lake Bonneville form the flat country on either side of the highway. The highway rises to the south through the Paleozoic section which is poorly exposed here in sagebrush and juniper covered hills.
123.1 Broken and overturned Ordovician Pogonip Group rocks. Some beds have been so badly broken that coherent bedding has been destroyed, particularly in some of the more easily sheared argillaceous units.
124.3 Brecciated Ordovician, Silurian, and Devonian units are overturned in a dragfold on the lower part of the thrust sheet.
125.1 Completely overturned Mississippian and Pennsylvanian rocks are "posed around the northern margin of Dog Valley. Mississippian Redwall Limestone is exposed near the road. Dog Valley has only internal drainage and must be a large sinkhole in the fragmented carbonate rocks associated with the thrust fault. Well-bedded Pennsylvanian and Permian rocks east of Dog Valley in the Pavant Range are in normal right-side-up position beneath the fault.
128.4 Tertiary volcanic flows and pyroclastic rocks exposed in road cuts on either side of a rest area in the southbound lane. Volcanic mudflow or lahar breccia and conglomerate constitute much of the ashy massive to bedded rocks.
129.3 Cove Fort Interchange with Highway 161. For a description of the geology along this route past Cove Fort and along Interstate Highway 70 and Utah State Highway 4 to the east see I-70 Road Guide.. This route connects east to U.S. Highway 89 which, in turn, connects with Interstate 70 again in the Salina, Utah area. Cove Fort was built at the request of Brigham Young out of locally quarried basalt and purplish andesite or latite. The fort was completed in 1867. It now houses a small museum.
131.4 Massive basalt is exposed on either side of the freeway. Flows have been chopped into innumerable blocks by small faults. The lava is associated with the large volcano to the south, which is about on the line between Millard County and Beaver County.
132.1 Bridge at the Junction of Interstate Highways 70 and 15. Geology along Interstate 70 east of Cove Fort is described in I-70 Road Guide..
134.9 Cross beneath bridge of Sulfurdale interchange. Between Cove Fort and here the workings at Sulfurdale can be seen periodically to the east against the base of the Tushar Mountains. Elemental sulfur is disseminated through tuffaceous rhyolitic rocks in the open pit of the inactive mine.
139.4 Cross beneath bridge at Ranch exit, The highway is constructed over old alluvial fans that are probably pre-Bonneville. Tertiary Bullion Canyon and Dry Hollow Formations are exposed in the face of the Tushar Mountains to the east. Upper ledges are in the Dry Hollow Formation.
141.3 Road cuts through tuffaceous light-colored Sevier River Formation in both the south and northbound lanes. To the south the road drops down through younger high terrace gravels.
144.4 Bridge at the Manderfield Exit. The highway is in terrace gravels and valley fill, but to the west granitic peaks of the Mineral Range rise to 9,100 feet. Granite forms the prominent serrated peaks of the skyline. Mt. Belknap (elevation 12,139) and Delano Peak (elevation 12,173) are the high points in the Tushar Range to the east and are part of a large Late Tertiary composite volcano (fig. 3.13).
Figure 3.13.View eastward of Mt. Belknap from the north edge of Beaver at approximately Mile 163. Mt. Belknap is the high point in the Tushar Range and is, in part, the remnant of an ancient stratocone volcano that makes up much of the deposits of the range.
146.3 High point on the road provides a view southward over Beaver Valley and of the prominent gravel-covered pediments or terraces that surround the valley. Terraces were apparently adjusted to a high outlet through the gap to the west at the south end of the Mineral Range.
152.9 Beaver Interchange and Junction with Utah State Highway 21. Utah State Highway 21 leads west to Millersville and Milford, around the southern end of the Mineral Range.
The Mineral Range is the site of the oldest lead-silver mining venture in the state. The Lincoln Mine, discovered in 1852, produced lead utilized for bullets by early settlers but silver in this lead made it too hard to be extensively utilized. Silver made Beaver County famous for a while. Higher terraces show well east of town, particularly near the block letter
156.1 Bridge and the South Beaver interchange. East of the bridge a gravel quarry in the terrace veneer shows the internal structure of the deposit. The marshy area in the vicinity of the road is produced by water which is forced to surface because of a bedrock sill at the west end of the valley.
161.4 Road cuts through pink and green Tertiary Bullion Canyon volcanic rocks on the southwest side of the Tushar volcanic center.
163.5 Late Tertiary tuffaceous rocks and basalt exposed in road cuts.
164.0 Beaver County-Iron County Line. To the south the highway drops into the valley of Fremont Wash. Varicolored volcanic rocks are poorly exposed on either side of the valley and weather to produce a thick soil over grown by sagebrush and juniper woodlands.
170.8 Junction of Utah State Highway 20 with Interstate 15. High peaks to the east and west of the north end of Parowan Valley are in younger Tertiary volcanic rocks.
177.6 Roadside rest area off the southbound lane. Reddish Wasatch or Cedar Breaks Formation is now exposed beneath the volcanic rocks along the base of the fault escarpment to the east. This red formation rises toward the south and forms the Pink Cliffs and much of the scenic area around Cedar Breaks National Monument (fig. 3.14) and the high rim of the Markagunt Plateau.
181.1 A gentle anticline is expressed at the fault escarpment where tan Cretaceous rocks are exposed beneath the pink Wasatch or Cedar Breaks Formation. The escarpment here is part of the Hurricane Cliffs that are along the Hurricane Fault and which are traceable as a topographic break from here well into Arizona.
182.9 Paragonah Exit. Cretaceous Kaiparowits rocks are exposed along the cliffs beneath the pink Wasatch Formation (fig. 3.15). Fault-repeated Wasatch beds are dropped down to near valley level at the base of the escarpment. Young basalt from a volcano on the plateau flank has covered the fault slices south of town.
Figure 3.15.View eastward of faulted upper Cretaceous and Wasatch beds near Paragonah. The Hurricane Fault trace is along the base of the escarpment.
187.8 Bridge Over Exit to Parowan. State Highway 143 leads southeast to Parowan and to Cedar Breaks National Monument. Pinkish Tertiary Wasatch Formation, purplish Tertiary volcanic rocks, and tan Cretaceous Kaiparowits Formation (fig. 3.16) are in fault-repeated exposures east of town. Volcanic rocks cap the Markagunt Plateau to the east. Cedar Breaks Monument is visible on the skyline to the southeast up Parowan Canyon.
190.6 Bridge over freeway at the southern edge of Parowan. Volcanic rubble and fault slices of Tertiary and Cretaceous rocks still form the west face of the Markagunt Plateau. West of the highway fault-repeated and down-faulted Wasatch or Claron Formation shows in Parowan Gap beyond Little Salt Lake playa.
197.2 Summit exit. South of here Tertiary volcanic rocks rest upon Cretaceous Kaiparowits Formation in fault slices that repent the section, in general, downdropped toward the west.
199.8 Crest of hill north of Cedar City. Southwest and west from here are the multipeaked laccoliths of the Iron Springs mining district. Tertiary intrusions have domed into Mesozoic rocks and have reacted with the Jurassic Carmel Limestone to produce moderately extensive iron deposits of magnetite and hematite in the intrusion and around the intrusion borders. Three Peaks laccolith is to the west. Granite Mountain is beyond and in front of Iron Mountain which is to the southwest.
202.9 Double road cut through Tertiary volcanic rocks on a large spur leading out from the Hurricane Cliffs. Kaiparowits Formation is exposed at the escarpment.
205.2 Bridge over Union Pacific Railroad at the west end of Cedar City. Cedar Breaks National Monument in Tertiary Wasatch or Cedar Breaks Formation is visible on the skyline beyond the varicolored Jurassic and Triassic rocks which are exposed in Cedar Canyon. Mesozoic rocks are involved in pre-Hurricane Fault folds.
207.4 Bridge at the West Cedar City Interchange. College of Southern Utah is in the western edge of town east of the highway. Cross Hollow Hills to the southwest are composed of Tertiary and Quaternary volcanic rocks. To the southeast Cedar Mountain along the Hurricane Cliffs is capped by Cretaceous Straight Cliffs Sandstone. Tropic Shale and Dakota Sandstone form the wooded slope below. Reddish slopes and ledges in the lower part of the escarpment are on the Carmel Formation. Navajo Sandstone is exposed as the white cliff-former above the reddish Triassic rocks near the base of the cliffs. Volcanoes high on the plateau provided basalt which has poured over the escarpment to the southeast of town (fig. 3.17).
Figure 3.17.Hummocky topography on dark lava flows which have poured over the Hurricane escarpment south of Cedar City at approximately Mile 208 from volcanos high on the plateau.
211.9 Double road cuts through basalt which is offset by small faults with displacements of 10 to 15 feet. Crude columns are developed in the lava which has flowed over alluvial fan material obviously derived from the Triassic and Jurassic rocks to the east. Iron Mountain and its associated iron mines are visible to the west.
216.5 South of the Kanarraville Interchange, Jurassic Navajo Sandstone forms cliffs above folded Triassic rocks. Tertiary Wasatch Formation overlies Navajo Sandstone unconformably and in turn is overlain by Quaternary basalt.
219.9 Permian Kaibab Limestone appears at the base of the Hurricane Cliffs east of the Hurricane Fault trace (fig. 3.18). Reddish Triassic Moenkopi, Chinle and Moenave Formations form the slope below cliffforming white Navajo Sandstone. Cretaceous Straight Cliffs Formation forms the caprock above the slope on the Dakota and Tropic Formations. Kaibab Limestone is overturned on the Kanarra Anticline.
Figure 3.18.View southeastward from south of Cedar City at approximately Mile 220 of Kaibab Limestone and older rocks exposed in the Hurricane Fault escarpment in the low hills, and the Navajo Sandstone and younger rocks in the White Cliffs escarpment along the skyline.
221.3 Rest area on the southbound lane. Kaibab Limestone is exposed near the base of the cliffs which are still capped by Cretaceous rocks. The Pine Valley Mountains to the southwest are carved in a large laccolith.
223.3 Fault slivers of red Triassic Moenkopi rocks are dropped down against Kaibab Limestone near the New Harmony exit.
223.9 Iron County-Washington County Line. Triassic Moenkopi Formation forms the reddish cliffs on the skyline to the east.
225.9 Bridge of the Kolob Canyon Interchange. Fins and buttresses of Navajo Sandstone show well on the skyline to the east up some of the canyons. Gray and tan Kaibab Limestone forms the lower set of cliffs associated with some fault slivers of red Moenkopi Formation.
229.0 Bridge over Ash Creek. The reservoir here does not hold water because of the jointed bedrock over which it was constructed. Black Ridge to the south is composed of Quaternary basalt which is the same age as basalt on the Hurricane Cliffs to the east, indicating the relatively recent major movement on the Hurricane Fault. Younger basalts have poured over the escarpment, however, indicating several periods of volcanic activity.
232.9 Underpass beneath Snowfield Exit. Northeast of the exit tan massive Coconino Sandstone is visible below gray Toroweap Formation and tan Kaibab Limestone in the cliffs. Pink and red beds at the base are Triassic rocks. The Kanarra fold shows in various attitudes of the Kaibab Limestone. Most of the Interstate highway is still built over young basalt or on debris swept out from the Pine Valley Mountains to the west (fig. 3.19).
234.5 Bridge at the Pintura Exit. Coarse bouldery debris on the west side of the road is mudflow or alluvial fan material from the Pine Valley Mountains. East of the road westerly dipping Kaibab Limestone is exposed next to the trace of the Hurricane Fault.
237.9 Steeply folded Kaibab Limestone (fig. 3.20) is exposed on the east side of the Kanarra fold and the Hurricane Fault.
239.0 Cross Over Toquerville-Zion National Park Exit to Utah State Highway 17. Quaternary basalt caps Navajo Sandstone on both sides of the road as part of inverted valleys.
Figure 3.19.The northern part of the Pine Valley Mountains as seen westward from near the Snowfield exit at approximately Mile 231. The Pine Valley Mountains are carved out of a large igneous intrusion which appears to be laccolithic. Tree-covered slopes in the foreground are alluvial fans which are spreading eastward from the Pine Valley Mountains.
Figure 3.7.0.Steep eastward-dipping Kaibab Limestone forming the prominent cliff at the top of the Hurricane escarpment. Toroweap and Coconino Formations are "posed in the less well-bedded lower parts of the faulted face. Steep dips are eastward off the Kanarra Fold which diagonals across the fault escarpment. The Hurricane Fault trace is at the base of light-colored exposures near the brush line.
241.9 Navajo Sandstone and younger rocks are exposed to the west in front of the Pine Valley Mountain intrusion. Shinarumpcapped terrace above the Moenkopi Formation rises above the Kaibab exposures in the Hurricane Cliffs to the east.
242.9 Bridge over access road north of Leeds. The small mine dump to the east is in the Silver Reef Sandstone Member of the Chinle Formation. Toward the west the Moenave Formation forms the brick red sandstone cliffs in front of the higher and lighter colored Navajo Sandstone, near the base of the Pine Valley Mountains.
243.5 Bend in the highway. Silver Reef Sandstone caps the cuesta to the northwest and the middle of three prominent sandstones in the Chinle Formation crosses the road approximately here and forms the cuesta to the southwest. Shinarump Sandstone member is exposed on to the southeast. Chinle beds begin to swing from the west flank over the northern nose of the Harrisburg Dome to the east. Beyond the bend a short distance, dumps of some of the mines of the Silver Reef district (fig. 3.21) are visible to the southwest in the sandstone cuesta.
244.1 Leeds Interchange. Leeds was an old silver mining district where fossil leaves and other organic material were replaced by native silver or copper-uranium-vanadium minerals. The ore was mined from the Silver Reef Sandstone Member of the Chinle Formation which occurs approximately 175 feet above the Shinarump Sandstone Member. To 1953 production from the district approached eight million dollars. To the south of the interchange the freeway continues in a subsequent valley between cuestas formed of the two lower sandstone members of the Chinle Formation.
245.5 A gap in the cuesta along a small drainage shows the mining area of the Silver Reef District to the northwest.
Figure 3.21.View southeastward into the northern part of the Silver Reef Mining District from approximately Mile 243. Rocks in the foreground and near the mine dump are in the Chinle Formation. The ledge-forming sandstone above tire dump is the Silver Reef Sandstone Member of the Chinle Formation and was the main ore bearer for the silver, copper, uranium, and vanadium minerals in the district.
246.3 Double road cuts on both lanes through varicolored lower mudstones of the Chinle Formation above the Shinarump Conglomerate which holds up the cuesta to the east. Interstate Highway 15 continues toward the southwest across alluvial fill and poor exposures.
247.7 View toward the north and northwest from near the brow of the hill shows the Silver Reef Mine dumps in the cuesta a short distance west of the highway.
249.2 Double road cuts through coarse terrace gravel deposited across a cut surface on Moenave Formation. The gravel is largely of igneous pebbles and boulders derived from the Pine Valley Mountains to the northwest. The prominent cuesta to the east is held up by the Shinarump Member. Contact of the Chinle and Moenave Formations is somewhere in the middle of the alluvial blanketed valley at approximately the position of the highway. The highway swings onto Moenave beds toward the southwest.
250.6 Bridge Over Interchange of Utah State Highway 15 at Hurricane and Zion National Park Turnoff. For a description of the geology along Utah State Highway 9 east to Zion Canyon and Mt. Carmel Junction see HW-9 Road Guide. The prominent red sandstone toward the northwest is the Springdale Member of the Moenave Formation and the interchange is on the less wellexposed Dinosaur Canyon Member of the formation. Light-colored Navajo Sandstone forms the next series of cliffs to the northwest around the base of the Pine Valley Mountains (fig. 3.22).
Figure 3.22.View northwestward from approximately Mile 250 of the Pine Valley Mountains and their foothill belt. Relatively flat country in the foreground is a gravel cap over a pedimon carved on Chinle Formation. Navajo Sandstone forms the prominent light-colored exposures at the top of the cuesta in the middle distance. The Pine Valley intrusion is exposed in the high peak of the mountains on the skyline.
252.0 Deep double road cuts through the middle part of the Moenave Formation. Sandstone near the top is lower Springdale Member. The basalt which caps the ridge shows excellent columnar jointing and rests upon a lag gravel over the Moenave beds (fig. 3.23). The linear basalt ridge represents an inverted valley. When the basalt flowed into the Virgin River Valley from the northwest it flowed down a valley and protected it from subsequent major erosion. Softer Moenave rocks on either side of the lava flow have been removed by subsequent erosion, by the displaced stream and associated streams, leaving the former valley now standing high.
Figure 3.23.Columnar jointed basalt flow which delimits an inverted valley. Basalt initially flowed down a low point in the topography but because of its resistance to erosion it has protected the valley while more easily eroded beds on either side have been removed. Thus the former valley now rises as a ridge. Basalt here tests on red Moenave beds.
253.6 Cross drainage and bridge over access road in eastern Washington. Spring area a short distance to the west is along the Washington Fault which has dropped upper Moenave beds on the west down against lower Moenave beds on the east.
254.7 Cross Bridge In Washington-Middleton Interchange. Springdale Sandstone forms the prominent reddish bluff to the north and continues north of the highway westward to St. George.
256.5 Deep stepped road cuts through Moenave Formation (fig. 3,24) capped by another basalt-armoured inverted valley. This basalt is less well jointed than that to the east but the linear ridge apparently formed in the same way. Moenave beds here appear similar to rocks interpreted elsewhere to have been deposited on tidal flats of an and coastline.
Figure 3.24.Crudely jointed basalt capping an extensive exposure of the lower part of the Moenave Formation at Mile 256.5. The long basalt ridge expresses an inverted valley, where basalt protected the gravelly sediments deposited in the valley fill while unprotected
257.1 Center of Bridge Over Interstate 15 at the Interchange East of St. George. The access road which separates from the freeway short of the bridge leads into the eastern end of the main business street in St. George, noted for its white Mormon Temple (fig. 3.25).
Figure 3.25.Mormon Temple in St. George. The temple was built of red Moenave Sandstone but has been plastered and painted white.
from Field Guide: Northern Colorado Plateau by J. Keith Rigby - Purchase Information
