The Geologic History of Utah Valley
Stephen R. Ott
Geology 112
Table of Contents
Introduction ......................................................................................................................... 1
Phase 1: Metamorphic Basement Phase ............................................................................. 3
Phase 2: Miogeoclinal Platform Phase ............................................................................... 4
Phase 3: Oquirrh-Paradox Basin Phase............................................................................... 5
Phase 4: Interior Basin and Navadan Orogeny Phase ......................................................... 6
Phase 5: Sevier Compressional Orogeny and Foreland Basin Phase ................................. 7
Phase 6: Laramide uplifts-Uinta Basin Phase ..................................................................... 8
Phase 7: Explosive Caldera and Stratovolcano Phase ........................................................ 8
Phase 8: Regional Uplift, Basin-range Faulting, Bimodal Volcanism, and Lake
Bonneville Phase .................................................................................................. 9
Conclusion ........................................................................................................................ 12
References ......................................................................................................................... 14
Appendix ........................................................................................................................... 15
Table 1. Utah Geologic Phases and Geologic Time ..................................................... 16
Table 2. Geologic Formations of Provo ....................................................................... 17
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Table of Figures
Figure 1. Location of Utah Valley ..................................................................................... 2
Figure 2. Map of Phase 1 ................................................................................................... 3
Figure 3. Map of Phase 2 ................................................................................................... 4
Figure 4. Map of Phase 3 ................................................................................................... 5
Figure 5. Map of Phase 4 ................................................................................................... 6
Figure 6. Map of Phase 5 ................................................................................................... 7
Figure 7. Map of Phase 8 ................................................................................................... 9
Figure 8. Map of the Wasatch Fault ................................................................................. 10
Figure 9. Map of Lake Bonneville region ........................................................................ 11
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Introduction
This report is about the geologic history of Utah Valley. I’m writing this report for
the Historical Geology class (Geology 112) at BYU-Idaho as part of the course
requirements. I choose to write on this topic because I grew up in Orem, Utah, located in
Utah Valley, and I wanted to investigate many of the interesting geologic features that I
have seen there.
Hintze divides the geologic history of the entire state of Utah into eight different
phases (1988, p. 1). I have used those phases as a guide for describing the geologic
history of Utah Valley by identifying which phases participated in the development of
that area. This report will briefly describe each of the eight phases, which Hintze lists as
follows:
1. The metamorphic basement phase.
2. The miogeoclinal platform phase.
3. The Oquirrh-Paradox Basin phase.
4. The interior basin and Navadan orogeny phase.
5. The Sevier compressional orogeny and foreland basin phase.
6. The Laramide uplifts-Uinta Basin phase.
7. The explosive caldera and stratovolcano phase.
8. The regional uplift, basin-range faulting, bimodal volcanism, and Lake
Bonneville phase.
As a matter of general overview and contrary to the present status of the state, most
of Utah has been just above or below sea level for the vast majority of the Earth’s history.
Only during the last 10 million years has it developed the observable geologic features
that we recognize today. The reader may need to refer to Table 1 in the appendix, where
1
I have correlated each of the phases with the recognized geologic periods of Earth’s
history.
In each of the important phases, I have constructed a map of the state of Utah based
upon drawings shown by Hintze (1988, p. 2). The maps will help the reader understand
how the events that influenced the state of Utah influenced Utah Valley. In the map,
which is shown in Figure 1, Utah Valley is located as the light-gray elliptical region in
the middle of the state, with Utah Lake is the dark irregular shape in the middle.
Figure 1. Location of Utah Valley
2
Phase 1: Metamorphic Basement Phase
The metamorphic basement phase of Utah geologic history began three billion
years ago in the Archean era and lasted for two billion years into the early Proterozoic era
(Hintze, 1988, p. 2). As can be seen in Figure 2, only the northern area of the state was
affected by the development of the craton in the Archean era. The development of the
land southward, including Utah Valley, began approximately 1.6 billion years ago during
the early part of the Proterozoic era. This additional area was probably created through
both sedimentary deposition and volcanic deposition from island arcs which were
colliding with the craton up until two billion years ago. Only in an area west of
Santaquin are any rocks from the craton or added terrane visible in Utah Valley (Stokes,
1986, p. 39), and all visible remnants from this age throughout the state have been
metamorphosed into gneiss, schist, or quartzite (Chronic, 1990, p. v; Hintze, 1988, p. 14).
Figure 2. Map of Phase 1
3
Phase 2: Miogeoclinal Platform Phase
The miogeoclinal platform phase began approximately one billion years ago in
the late Proterozoic era and continued through the Devonian period, which ended 360
million years ago (Hintze, 1988, p. 1)
Figure 3. Map of Phase 2
In the early part of this phase, most of Utah was above water, and there must have
been mountains sufficiently high enough to host glaciers. The resulting glacial erosion
produced tillite in sections of Utah. The Mineral Fork Tillite at Provo were deposited
during this age (Hintze, 1988, p. 151; see Table 2 in the appendix). After the glacial
period, the sea slowly transgressed across the western side (Chronic, 1990, p. v).
For the remainder of this phase, the state was separated with a north-south line
that ran just west of Utah Valley. (See Figure 3.) Although the state was almost entirely
covered by a shallow sea, the west side was under deeper water and slowly subsiding as
deposition occurred. One author explained that the only possibility for the thousands of
feet of deposition that occurred during this time period was if the ground was continuing
to subside at about the same rate as deposition was taking place (Hintze, 1988, p. 5).
4
Progressing from the Precambrian through the Devonian, Utah had significant
amounts of limestone, sandstone, and dolomite deposits. There were significant amounts
of fossils in these formations, particularly corals and brachiopods, which is indicative of a
tropical sea (Chronic, 1990, p. v; see Table 2 in the appendix). The position of the early
North American continent, in fact, places Utah at a 90º angle from its current orientation,
in a position just above the equator (Hintze, 1988, p. 25).
Phase 3: Oquirrh-Paradox Basin Phase
The Paradox Basin phase began 360 million years ago in the Mississippian period
and continued for over 100 million years through the Permian period (Hintze, 1988, p. 1).
The main events in this period were the development of the Oquirrh Basin, Paradox
Basin, and Uncompahgre Highland. Only the Oquirrh Basin had a significant effect on
the geology of Utah Valley, so this section will focus on that. (See Figure 4.)
Figure 4. Map of Phase 3
It has been suggested that the Oquirrh Basin developed through slight rotation of
one section of the continent (Hintze, 1988, p. 5). Utah Valley lies in what was the
southern quarter of this basin. In some areas of this basin many miles of limestone and
5
shale accumulated between the Pennsylvanian and Permian periods (Chronic, 1990,
p. 223-226). From the stratigraphic information in Hintze (1988, p. 151), there are
apparently over ten formations and five miles thick of these rocks (Table 2 in the
appendix). Fossils of brachiopods, corals, and bryozoans are contained in these layers
(Chronic, 1990, p. v).
Phase 4: Interior Basin and Navadan Orogeny Phase
The interior basin and Navadan orogeny phase began 250 million years ago in the
Triassic period and continued for 50 million years through the early part of the
Cretaceous period (Hintze, 1988, p. 1).
Figure 5. Map of Phase 4
During this phase, erosion of the Uncompahgre Highland in eastern Utah
produced thick deposits over the entire state including Utah Valley (Hintze, 1988, p. 6).
Many of these deposits are now famous in other parts of the state outside Utah Valley,
including the formations that created Zion National Park and Arches National Park.
However, these deposits are not visible in western Utah because they were later covered
by a major thrust resulting from the Sevier orogeny in Phase 5 (Hintze, 1988, p. 6).
6
Also during this phase, since the land is slowly rising, the sea is retreating
westward and the area is drying out, depositing evaporites in the Arapain Basin just south
of Utah Valley (Hintze, 1988, p. 6). And finally in the later part of this phase, granitic
intrusions are forming just to the west of Utah Valley (Hintze, 1988, p.24; Chronic, 1990,
p. v; see Figure 5).
At this point in Earth’s history, the supercontinent of Guandwandaland is
breaking up, and the entire North American continent is slowing moving away from the
equator toward the north (Hintze, 1988, p. 24).
Phase 5: Sevier Compressional Orogeny and Foreland Basin Phase
The Sevier compressional orogeny and foreland basin phase began 100 million
years ago in the later part of the Cretaceous period and continued for 44 million years
(Hintze, 1988, p. 1).
Figure 6. Map of Phase 5
The Sevier orogeny is attributed to subduction of an oceanic plate off the western
coast of North America, in what is now Nevada (Chronic, 1990, p. v). The thrusting was
so strong that later thrusts were often pushed on top of previous thrusts (Chronic, 1990,
7
p. v). This pushed older rock layers on top of younger ones (Chronic, 1990, p. v) and
actually shortened Utah by about 40 miles (Chronic, 1990, p. 204) also creating the
Sevier Mountains western Utah. (See Figure 6.) Erosion of the mountains produced a
wide band of conglomerate rocks throughout the Utah Valley area (Hintze, 1988, p. 2)
and the region just to the east of Utah Valley consisted of some coastal plains and coal
swamps (Hintze, 1988, p. 2).
This period transformed Utah from being mostly a coastal or shallow marine region
to a region of high uplift and mountains (Chronic, 1990, p. v).
Phase 6: Laramide uplifts-Uinta Basin Phase
The Laramide uplifts and Uinta Basin phase began 66 million years ago in the
Paleocene epoch of the Tertiary period and continued for almost 30 million years through
the Eocene epoch (Hintze, 1988, p. 1). There is no description of anything happening in
Utah Valley at this time although to the west a series of volcanic events are taking place
and to the east sections of uplift and basin-filling are taking place.
Phase 7: Explosive Caldera and Stratovolcano Phase
The explosive caldera and stratovolcano phase began 37 million years ago in the
Oligocene epoch and continued for over 15 million years through the early Miocene
epoch (Hintze, 1988, p. 1)
Although one author stated that all areas of the state were affected by igneous
activity except for the Uintah Basin (Hintze, 1988, p. 8), I was not able to find any
specific events in Utah Valley. However, just to the north, the igneous action caused
intrusions into earlier rock and enriched the formations with copper, molybdenum, gold,
lead, and zinc. This enrichment is now the Bingham Copper mine in south Salt Lake
Valley. Half a million tons of rock are recovered each day from the mine, and about one8
fifth of that mass consists of the ores that have been identified (Chronic, 1990, p. 223226).
Phase 8: Regional Uplift, Basin-range Faulting, Bimodal Volcanism, and Lake
Bonneville Phase
The final phase of Utah geologic history began 15 million years ago in the late
Miocene epoch and continues today (Hintze, 1988, p. 1). This is the phase that I am most
interested in because it created the features which I became familiar with growing up.
Figure 7. Map of Phase 8
The volcanism described in the name for this phase took place mostly in the southwest portion of the state, from Delta to St. George (Hintze, 1988, p. 9-10), and so will not
be addressed in this report.
The uplift and faulting occur because of regional stretching of the continental crust
from California to Colorado. Stretching has caused tensional stress which creates breaks
perpendicular to the stress in the form of north-south running normal faults (Hintze,
1988, p. 9-10). One of the major faults in this region lies along the east side of Utah
Valley and is called the Wasatch Fault (Chronic, 1990, p. 223-226; see Figure 8).
9
Figure 8. Map of the Wasatch Fault
As a result of the excessive faulting, the mountains along the Wasatch Fault expose
rock of very old age. One example of this is the hike up to Timpanogos cave in
American Fork Canyon. On the path to the cave, the hiker goes all the way from
Cambrian Quartzite at the bottom of the canyon up to Mississippian-age limestone (Kiver
& Harris, 1999, p. 613-616). The caves are formed inside the Deseret formation of this
limestone.
Some of the mountains have been affected by Pleistocene glaciation, and the sharp
peak of Timpanogos is a glacial horn that still contains a remnant of the glacier on the
south side (Kiver & Harris, 1999, p. 613-616). Emerald Lake lies just below the glacier
remnant in a huge, U-shaped valley. Its existence is probably a result of a glacial
morraine which has dammed the water of the melting snow.
Another result of the faulting and the cold climate of the ice age was the creation of
Lake Bonneville. Between 130,000 and 30,000 years ago, volcanic eruptions in southeast
Idaho blocked the earlier course of the Bear River and diverted its flow into central Utah.
This river and others filled up some of the deeper grabens caused by the range-faulting
10
and Lake Bonneville was created. This lake reached its maximum height about 16,000
years ago when it overflowed through an outlet by Downey, Idaho, into the Snake River.
It was so large that it filled up one-third to one-fourth of the state, all the way over to
Nevada and up into southern Idaho (Chronic, 1990, p. 209-213). Figure 9 below
represents the general area of Lake Bonneville, although the lake was much more
irregular than the oval shape shown.
Figure 9. Map of Lake Bonneville region
At its maximum depth it reached about 250 feet above the current level of Great
Salt Lake, and it remained there for about 1500 years. Then, about 14,500 years ago, it
broke through its threshold and created a catastrophic flood into the Snake River. The
level of the water dropped 350 feet in less than a year to a new level at Red Rock Pass.
The lake level stayed at that level for another 1,000 years, building up the currently
visible shoreline all the way from Brigham City to Spanish Fork (Chronic, 1990, p. 209213).
One of the important deltaic regions that were created from the deposition of the
Provo River into Lake Bonneville was the “Provo Bench” where Orem now sits.
11
(Chronic, 1990, p. 223-226). This bench is obvious from every side of the city,
especially at the south end, where drivers have to go up “Orem hill” traveling into the
city on State Street. Because of the bench’s position close to the ancient Provo River
outlet, large, erosion-rounded rocks and later fine silt was deposited at the mouth of the
river in the Orem area. As a result, in our area of Orem our gardens were grown in very
loose, medium-fine soil mixed with “Orem potatoes,” or smooth (river-eroded), fist-sized
rocks.
An even larger deltaic region is at the south end of the valley at the mouth of
Spanish Fork Canyon. Large volumes of very soft Tertiary sediments have been eroded
to form this buildup (Chronic, 1990, p. 223-226). Where these sediments originated, the
soft sediments, high moisture content and steep mountain slopes contributed to the huge
mud slide that blocked the canyon and created “Thistle Lake” in the summer of 1983.
Although publications indicate that this deltaic region is very easy to view (Chronic,
1990, p. 223-226), I’ve never noticed where this “bench” lies. I’m guessing that a main
road doesn’t cut across the bench like the Orem bench.
About 13,500 years ago, this latest Lake Bonneville threshold was breached
several times and then as a result of the drying climate, the level of the water fell below
the outlet and the water gradually became salty about 10,000 years ago to become the
Great Salt Lake (Chronic, 1990, p. 209-213). Utah Lake is also a remnant of Lake
Bonneville, but it is not salty because its water flows out into the Great Salt Lake through
the Jordan River.
Conclusion
As a concluding note, this latest phase in Utah’s geologic history results from
continual tensional stress and climatic variations. As a result both more earthquakes
12
along the Wasatch Fault, some of large magnitude, and more fluctuations in the water
level of Great Salt Lake are a guarantee for the geologic future of Utah Valley.
13
References
Chronic, Halka (1990). Roadside Geology of Utah. Missoula, Montana: Mountain Press
Publishing Company.
Hintze, Lehi F. (1988). Geologic History of Utah: A Field Guide to Utah’s Rocks.
Provo, Utah: Brigham Young University Geology Studies.
Kiver, Eugene P. and Harris, David V. (1999). “Timpanogos Cave National Monument,”
Geology of U.S. Parklands, Fifth Edition. John Wiley & Sons, Inc.
Stokes, William Lee (1986). Geology of Utah. Salt Lake City, Utah: Utah Museum of
Natural History.
14
Appendix
15
Table 1. Utah Geologic Phases and Geologic Time
Phase
Age
Era
Period
Quaternary
8
15 million
Cenozoic
7
66 million
5
100 million
Miocene
Tertiary
37 million
6
Oligocene
Eocene
Paleocene
Cretaceous
4
3
250 million
Mesozoic
360 million
Paleozoic
2
1,000 million
Jurassic
Triassic
Permian
Pennsylvanian
Mississippian
Devonian
Silurian
Ordovician
Cambrian
Proterozoic
1
3,000 million
Epoch
Recent
Pleistocene
Pliocene
Archean
16
Table 2. Geologic Formations of Provo
Quaternary
Miocne –
Pliocene
Triassic
Alluvium, colluvium, soil
Lake Bonneville deposits
Buried valley fill
0-50 ft
0-200 ft
0-13,000 ft
Woodside Shale
Park City Group Franson Formation
Permian
Meade Peak Tongue
Grandeur Formation
Diamond Creek Sandstone
Kirkman Limestone
Oquirrh Group Granger Mountain Formation
Pennsylvanian
Wallsburg Ridge Formation
Shingle Mill Limestone
Bear Canyon Formation
Bridal Veil Falls Limestone
Manning Canyon Shale
300 ft
800 ft
280 ft
310 ft
670 ft
310 ft
10,300 ft
5300 ft
1100 ft
7900 ft
1050 ft
1650 ft
Mississippian
Great Blue Ls
Devonian
Cambrian
Proterozoic
Upper Limestone member
Long Trail Shale member
Topliff Limestone member
Humbug Formation
Deseret Limestone
Gardison Limestone
Fitchville Dolomite
Maxfield Limestone
Ophir Formation
Tintic Quartzite
Mutual Formation
Mineral Fork Tillite
Big Cottonwood Formation
(Hintze, 1988, p. 151)
17
1800 ft
300 ft
700 ft
540 ft
840 ft
600 ft
50-270 ft
0-850 ft
300-500 ft
1200-1300 ft
0-1300 ft
0-200 ft
1350+ ft