Sevier and Laramide orogenesis produced regional highlands and intermontane basins, including Lake Flagstaff (Paleocene) in central Utah. Lake Flagstaff deposits are exposed on the Wasatch Plateau and San Pitch Mountains. Among the deposits from Lake Flagstaff, the Flagstaff Formation is dominantly interpreted as a lacustrine limestone with fluvial influence, and it is divided into three members. Along its Wasatch Plateau depocenter, the members include the Ferron Mountain Member, the Cove Mountain Member, and the Musinia Peak Member. However, these members are not easily distinguishable in the San Pitch Mountains, which is the focus of this study.
The study locality (Radio Tower) is located 3.6 km W of Sterling, UT. Research objectives include use of the physical characteristics of the oncoids, including size, shape, and contents of the nuclei, to interpret the depositional environment and hydrodynamic behavior. Additional data obtained included petrographic (thin section, acetate peel, and XRD) analysis, specifically analyzing oncoid nuclei and cortices. Oncoids from Radio Tower are small (<100mm) to large (100-400mm), with some samples as large as 30 cm x 41 cm. They are generally ellipsoidal in shape, and their nuclei are simpler, containing primarily terrigenous sediment. The nuclei and the host rock contains more spar, supporting an agitated, higher energy environment.
Sheban, Mara, "The Interpreted Depositional Environment of Large Oncoids from the Flagstaff Formation, San Pitch Mountains, Central Utah" (2018). Senior Independent Study Theses. Paper 7894.
Depositional environment, oncoids, fluvial, Utah
Bachelor of Arts
Senior Independent Study Thesis
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