The Geologic History of Utah Valley
Stephen R. Ott
Geology 112
Table of Contents
Introduction
Phase 1: Metamorphic Basement Phase
Phase 2: Miogeoclinal Platform Phase
Phase 3: Oquirrh-Paradox Basin Phase
Phase 4: Interior Basin and Navadan Orogeny Phase
Phase 5: Sevier Compressional Orogeny and Foreland Basin Phase
Phase 6: Laramide uplifts-Uinta Basin Phase
Phase 7: Explosive Caldera and Stratovolcano Phase
Phase 8: Regional Uplift, Basin-range Faulting, Bimodal Volcanism, and Lake Bonneville Phase
Conclusion
References
Appendix
Table 1. Utah Geologic Phases and Geologic Time
Table 2. Geologic Formations of Provo
Table of Figures
Figure 1. Location of Utah Valley
Figure 2. Map of Phase 1
Figure 3. Map of Phase 2
Figure 4. Map of Phase 3
Figure 5. Map of Phase 4
Figure 6. Map of Phase 5
Figure 7. Map of Phase 8
Figure 8. Map of the Wasatch Fault
Figure 9. Map of Lake Bonneville region
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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 Table1 in the appendix, where 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 Figure1, 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 ValleyPhase 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 Figure2, 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 1Phase 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 2In 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 Table2 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 Figure3.) 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).
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 Table2 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 Figure4.)
Figure 4. Map of Phase 3It 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 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 (Table2 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 4During 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).
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 Figure5).
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 5The 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, 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 Figure6.) 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 one-fifth of that mass consists of the ores that have been identified (Chronic, 1990, p. 223-226).
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 8The volcanism described in the name for this phase took place mostly in the south-west 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 Figure8).
Figure 8. Map of the Wasatch FaultAs 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 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). Figure9 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 regionAt 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. 209-213).
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. (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 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.
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.
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Appendix
Table 1. Utah Geologic Phases and Geologic Time
Phase / Age / Era / Period / Epoch8 / 15 million / Cenozoic / Quaternary / Recent
Pleistocene
Tertiary / Pliocene
Miocene
7 / 37 million
Oligocene
6 / 66 million / Eocene
Paleocene
5 / 100 million / Mesozoic / Cretaceous
4 / 250 million
Jurassic
Triassic
3 / 360 million / Paleozoic / Permian
Pennsylvanian
Mississippian
2 / 1,000 million / Devonian
Silurian
Ordovician
Cambrian
Proterozoic
1 / 3,000 million
Archean
Table 2. Geologic Formations of Provo
Quaternary / Alluvium, colluvium, soil / 0-50 ftLake Bonneville deposits / 0-200 ft
Miocne – Pliocene / Buried valley fill / 0-13,000 ft
Triassic / Woodside Shale / 300 ft
Park City Group / Franson Formation / 800 ft
Permian / Meade Peak Tongue / 280 ft
Grandeur Formation / 310 ft
Diamond Creek Sandstone / 670 ft
Kirkman Limestone / 310 ft
Oquirrh Group / Granger Mountain Formation / 10,300 ft
Pennsylvanian / Wallsburg Ridge Formation / 5300 ft
Shingle Mill Limestone / 1100 ft
Bear Canyon Formation / 7900 ft
Bridal Veil Falls Limestone / 1050 ft
Manning Canyon Shale / 1650 ft
Mississippian
Great Blue Ls / Upper Limestone member / 1800 ft
Long Trail Shale member / 300 ft
Topliff Limestone member / 700 ft
Humbug Formation / 540 ft
Deseret Limestone / 840 ft
Gardison Limestone / 600 ft
Devonian / Fitchville Dolomite / 50-270 ft
Cambrian / Maxfield Limestone / 0-850 ft
Ophir Formation / 300-500 ft
Tintic Quartzite / 1200-1300 ft
Proterozoic / Mutual Formation / 0-1300 ft
Mineral Fork Tillite / 0-200 ft
Big Cottonwood Formation / 1350+ ft
(Hintze, 1988, p. 151)