Geology of the Wasatch Range – Mt. Olympus to Red Butte

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In the Wasatch Range, which appears to be overlooked by the scientific community due to the lack of studies, the geology is varied and extensive. This paper will attempt to explain the geologic processes that took place between Red Butte Canyon and Mt. Olympus. This essay will describe the sediments, mountain building events, and surface water in the canyons. With a short discussion on the human history.

The oldest formations are from early Paleozoic time and have a shallow deposition (Hintze, 2005). Looking at the Wasatch like a deck of cards fanned out on a table the oldest layers are to the south and each more recent layer moves you farther north.

The next layers visible in the rock record are from the Mississippian and Pennsylvanian period and contain mostly limestone from a shallow water period in Utah history. Weber quartzite is the predominate sandstone on the south and at the mouth of the canyon also on the north face of Mt. Olympus. (Case, 2005) Mt. Olympus has large deposits of limestone which have been weathered and eroded to the extent that there is one of the deepest caves in North America. It is extremely narrow and dangerous so few have been allowed inside.

The periods between Devonian and Mississippian and Permian and Triassic are not seen in this area of the Wasatch between Red Butte and Mt. Olympus. There is a 5million year unconformity (Parry, 2005). The Triassic has the Woodside shale, Thaynes, and Ankareh limestone layers throughout all the canyons. The Woodside shale is a dark red to purple and can be found easily. The limestone layers were the result of the ocean being west of or on top of Utah. During the Triassic period the ocean and later the inland sea fluctuated a great deal and deposited very thick layers of marine life. They are visible at the entrance to Parleys canyon on both sides of the road. The Thaynes is a visible band that traverses along the north side of Millcreek canyon from its mouth and is the most prominent feature on the north side and continues all the way into Park City. The Thaynes formation is also at the base of Spring Creek between Parley’s and Emigration. (Hintze, 2005)

Near the mouth of Parley’s Canyon there is a weather resistant formation of quartz sandstone known as the Gartra member. It is clearly seen as it traverses in an easterly direction through the Ankareh formation on the south side. It is a Triassic bed deposited at the same time as the Chinle formation in southern Utah. (Hintze, 2005) The Triassic had the largest sediment layers, 4100ft., deposited in these canyons due to the shallow sea environment (Parry, 2005).

During the Jurassic period the1300ft. thick Nugget sandstone was deposited. This layer is the result of wind swept sand dunes that covered all of Utah. It is best seen in Red Butte but there is also a band just above the Triassic limestone in the Spring Creek anticline and on Parley’s north side near its mouth (Hintze, 2005). Another formation from the Jurassic is the Twin Creek limestone. In the Wasatch it is found on the north side of Parley’s canyon. This is the top layer and continues into Emigration Canyon (Hintze, 2005).

Finally the last bit of deposition that occurred before the mountain building began was a conglomerate layer deposited during the Cretaceous period. This formation is known as the Kelvin and it can be seen in the syncline on the back side of Emigration Canyon where Emigration and Parley’s meet. (Parry, 2005)

Grandeur peak is a great example of the folding that has taken place in the formation of the Wasatch Mountains. The limestone beds that make up the Thaynes formation are visibly warped when viewed from the Salt Lake Valley. They were crushed and fractured along with folding and can be found in slides all along the north side of Millcreek. These formations contain Triassic cephalopods which help to date them. This peak has a wide range of formations that have been identified. See the map for all of them. (Hintze, 2005)

During the Devonian time, there was a small mountain building event that lifted part of the Salt Lake area. The mountains in the Wasatch Range that have the rock story from this period are farther to the north. It was a small uplift and the first to rise above the shallow seas that had covered the area off and on for millions of years. (Hintze, 2005)

The Wasatch Mountains were created in short spurts of uplift, maybe 15 to 20 feet, along the Wasatch fault. This occurred many times over a number of millennia. It is still rising but not like before. It rises about 0.4mm a year. There are no foothills on the west face. The west face of each mount is a triangle shape and steep sloped. The sediments that have eroded from the Wasatch sit in the valley and if those sediments were removed the Wasatch would be a wall 5 miles high. (Hamblin, 2004)

The limestone, siltstone and mudstone found in the Wasatch Range were deposited approximately 60 miles west of their current location. After these sediments were deposited there were mountain building events that took place to the west of Utah. The first one was during the Permian period. The Park City formation, Woodside shale and Thaynes formations were all part of this event that pushed the continental shelf east and thickened the crust in what would become Utah (Parry, 2005).

The next mountain building events that occurred were during the Mesozoic after marine sediments were deposited in Nevada and western Utah. These layers consisted of limestone and shale sandstone. The mountain building off the western edge of the continent again forced these sediments east (Parry, 2005).

Mountain building took place during the Jurassic to Cretaceous period and was the beginning of the fault block ranges we see today. The thrust belt pushed eastward and caused a foredeep basin to occur in most of Utah. (Parry,2005). This basin became an inland sea some of the time and dry some of the time. It accumulated more than 10,000ft of sediment. The Twin Creek limestone comes from this sedimentation. The Nugget sandstone was also deposited here but it was dry, sandy and wind swept during its formation. These layers can be seen clearly in Parley’s canyon (Hintze, 2005).

The Sevier Orogeny occurred during the Cretaceous. It is the first mountain building event to occur within Utah’s borders. When it rose it was the beginning of the Wasatch as we know it today (Parry, 2005).

When the basin and range began to form in the tertiary period the crust from the west coast had been shoved inland as much as 85 miles. The basin and range, caused by the collapse of the thickened crust, moved the crust westward 155 miles. This thinning of the crust caused the fault blocking to occur. The Wasatch today is due to normal faulting mostly along the Wasatch fault. (Chronic, 2010)

Weathering in the canyons has exposed many of the older features from previous mountain building events. (Parry, 2005) As the mountains rose the exposure to water, wind and rain changed what was visible. The canyons were cut by erosion from streams high on their slopes to the east. As this weathering and erosion continues the deeper sedimentary layers are exposed in the canyons of the Wasatch.

During the last ice age each of the canyons held glaciers. The glaciers in these canyons only reached as far west as the upper end of each canyon so the bowl shapes and moraine only reach part way into each canyon. The majority of canyon making has occurred due to streams cutting into the sedimentary layers which erode easily. The sediment is carried to the mouth of the canyons and deposited as alluvium (Chronic, 2010).

Lake Bonneville in the Salt Lake valley was at the highest level about 16,000 years ago. This high point is sporadically visible along the Wasatch. It is a clear shelf of sediment that makes a flat place along the steep slopes of the Wasatch Range. The Lake Bonneville shoreline is visible on Grandeur at the 5200ft level. This bench has very little vegetation due to its sandy composition which makes the shoreline visible here. (Hintze, 2005)

Humans have altered the canyons in different ways. Millcreek canyon was used for logging in the recent past and as a site for a lime kiln due to the abundance of limestone. Today Millcreek canyon has a fee station. The money collected is used for canyon improvements. This canyon is popular for hiking, mountain biking, horseback riding and picnics. (Verdant, 1998) Parley’s canyon is the highway from the Salt Lake valley to points east. The area between Parley’s and Emigration has two reservoirs that supply potable water to Salt Lake. Emigration canyon is filling with homes. Red Butte canyon has a reservoir for potable water but is the least disturbed of the canyons in Salt Lake. Red Butte can only be accessed by foot.

Looking at this section of the Wasatch as a whole unit makes it clear that the geology here is just as varied and interesting as the geology of southern Utah. Things were happening in the Wasatch all through the geologic history we have of North America. Many thousands of feet of sediment were deposited. Mountain building events occurred. Streams have eroded the canyons exposing many of the formations. Glaciers have contributed to the shape of the canyons. Lake Bonneville left a visible mark. All of which make the Wasatch a very exciting geologic place to study.

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