GEO 1010: The Geology of Antelope Island

The Geology of Antelope Island

Geology 1010 

Self Guided Field Trip Assignment

      The focus of this paper is the study of the shorelines that have become etched out on Antelope 
island by Lake Bonneville and the lakes that followed. The understanding and identifying of the basic types of rocks found in these shorelines are important to unlocking the geologic history of the region.

      Antelope Island is 15 miles long and 5 miles at its widest area. It covers about 40 square miles, with the tallest peak being 6,597 feet above sea level (King & Willis 2000). It was formed approximately 15 million years ago, and can be found 17 miles to the west of the Wasatch Mountain range in Davis County Utah (Stum & Miller 1999).

      Prehistoric Lake Bonneville and the connection to mineral deposits on Antelope Island have always been a point of intrigue. I took this assignment as an opportunity answer some of my unanswered questions regarding Antelope Island's formation, the rock features, as well as Lake Bonneville's impact.

      Antelope Island is geologically interesting for a number of reasons; It is surrounded by the Great Salt Lake, a remnant of lake Bonneville. Evidence of wave erosion from Lake Bonneville and preceding lakes can be seen around the island. Some of the oldest and youngest rocks in all of Utah can be found on Antelope Island.

      Lake Bonneville occupied this part of the Great Basin between 30,000-12,000 years ago (Currey, Oviatt, & Sack 1999). It is evident due to the shorelines that cut the Island into a few parallel lines, that Antelope Island was present before Lake Bonneville's time. There are many shorelines etched on Antelope Island, some from Lake Bonneville, and other shoreline benches that were eroded away by lakes that came later due to the rise and fall of lake levels.(Bissell 1968)

      Some of the oldest and youngest rocks in all of Utah can be found on and within the geological make up of Antelope Island. The oldest rocks found on the island are marginally younger than the oldest rocks found on Earth. Of the rocks found, all three of the main types of rock, Igneous, Sedimentary, and Metamorphic are represented. (Sate of Utah)

      All of the types of rocks found on Antelope Island are correlated with various time periods in accordance to when they were formed or deposited. There are rocks categorized in the Archean, Proterozoic, Cambrian, as well as Tertitary time periods(Sate of Utah) (King & Willis 2000). 

      Active faulting occurs on Antelope Island today. By observing rocks deposited/deformed from a time period of mountain building processes, geologists are able to note continual change in the tilt of tertiary rocks (King & Willis 2000). 

Reflection:

      I chose Antelope Island as my site of study because I have always had an interest in this area. I grew up in Davis county and had field trips out to the island, and always had an interest in the various rocks I could see out there. Prehistoric Lake Bonneville and the connection to mineral deposits on Antelope Island have always been a point of intrigue. I took this assignment as an opportunity answer some of my unanswered questions regarding Antelope Island's formation, the rock features, as well as Lake Bonneville's impact. While Hiking Frary peak, the tallest peak on the Island, I took down observations and photographs with this project in mind.

      Hiking to the top of Frary Peak gave me the opportunity to view these rock formations from various angles. With my observations and research, I was able to find answers to my previous questions, as well as locate and identify the various rocks along the trail. With the completion of this project, I have come to a greater appreciation for Geologists that have taken the time to write down their findings so that we are able to understand these mysterious geologic processes.

Works Cited:

Bissell, H. J. (1968). Bonneville, an ice age lake (Vol. 15, Part 4).

Bissell, H. J. (1963). Lake Bonneville: Geology of Southern Utah Valley, Utah. Washington: U.S. Govt. Print. Off.

Currey, D., Oviatt, C., & Sack, D. (1992). Radiocarbon chronology of Lake Bonneville, Eastern Great Basin, USA. Palaeogeography, Palaeoclimatology, Palaeoecology. Retrieved from Science Direct.

King, J. K., & Willis, G. C. (Eds.). (n.d.).(2000). Geology of Antelope Island, Davis County, Utah. Utah Geological Survey. Utah Department of Natural Resources.

Stum, M., & Miller, D. (1999). Visions of Antelope Island and Great Salt Lake. Logan: Utah State University Press.

State of Utah, Department of Natural Resources, & Utah Geological and Mineral Survey. (n.d.). Geology & Antelope Island State Park, Utah. Retrieved from https://ugspub.nr.utah.gov/publications/misc_pubs/mp88-02.pdf. In Cooperation with Division of Parks and Recreation.