Earth Sciences Commons^™

Ediacaran Depositional Age And Subsequent Fluid-Rock Interactions In The Mutual And Browns Hole Formations Of Northern Utah, Ashley W. Provow

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Constraining the depositional age of Neoproterozoic stratigraphy in western North America has implications for correlating global glaciation and tectonic events. The depositional ages of the Neoproterozoic Mutual and Browns Hole formations of northern Utah are controlled by two conflicting datapoints. However, new U-Pb geochronological data from 95 detrital apatite grains refines the maximum depositional age of the volcanic member of the Browns Hole Formation to 613 ± 12 Ma (2σ). This places new restrictions on the time available for the deposition of underlying units. Due to debate regarding the age models for underlying stratigraphy, two scenarios for sediment accumulation rates …

New Ca-Id-Tims Detrital Zircon Constraints On Middle Neoproterozoic Sedimentary Successions, Southwestern United States, Abigail R. Bullard

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Three related sedimentary successions located in Arizona, Utah, and California were deposited in basins on proto-North America during the early rifting of Rodinia (~780 Mya). Previous detrital zircon U-Pb maximum ages for the units are inexact, making it difficult to piece together what happened at this point in Earth history.

We report better maximum age constraints on these units obtained by subjecting detrital zircons to high-precision CA-ID-TIMS analysis, which provide more exact ²⁰⁶Pb/²³⁸U ages. These new data significantly improve the precision for the base of the ChUMP units, with an average age of 775.63 ± 0.27 Ma …

Two Scenes From Utah's Stratigraphic Record: Neoproterozoic Snowball Earth, Before And After, Dawn Schmidli Hayes

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

This research is focused on rock units deposited in northern Utah before and after global glacial events of unprecedented magnitude, commonly referred to as
“Snowball Earth” glaciations. The rock units deposited prior to the beginning of these glaciations (~770 to 740 million years ago) include the Uinta Mountain Group in Utah’s Uinta Mountains. Rock units deposited after the glaciations (either ~665 or ~635 million years ago) include parts of the Kelley Canyon Formation on Antelope Island in the Great Salt Lake. These rocks, deposited in shallow ocean environments, record the history of life and ocean chemistry just before and after …

Stratigraphic, Microfossil, And Geochemical Analysis Of The Neoproterozoic Uinta Mountain Group, Utah: Evidence For A Eutrophication Event?, Dawn Schmidli Hayes

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Several previous Neoproterozoic microfossil diversity studies yield evidence for a relatively sudden biotic change prior to the first well‐constrained Sturtian glaciations. In an event interpreted as a mass extinction of eukaryotic phytoplankton followed by bacterial dominance, diverse assemblages of complex acritarchs are replaced by more uniform assemblages consisting of simple leiosphaerid acritarchs and bacteria. Recent data from the Chuar Group of the Grand Canyon (770‐742 Ma) suggest this biotic change was caused by eutrophication rather than the direct effects of Sturtian glaciation; evidence includes total organic carbon increases indicative of increasing primary productivity followed by iron speciation values that suggest …

Correlation, Paleogeography, And Provenance Of The Neoproterozoic Eastern Uinta Mountain Group, Goslin Mountain Area, Northeastern Utah, Daniel J. Rybczynski

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Geologic mapping, facies analysis, sedimentary petrography, and detrital zircon analyses of undivided eastern Uinta Mountain Group stratigraphy are presented to better understand the depositional environments and tectonic setting of the Uinta Mountain Group basin. Subdivided units have been modified and correlated from previous work and include the Red Pine Shale, Hades Pass, Crouse Canyon, Outlaw Trail, and Diamond Breaks formations. Three lower-order maximum flooding surfaces associated with the lower Outlaw Trail formation, lower Hades Pass formation, and Red Pine Shale are interpreted. The relative magnitude of each lower-order transgression increases up section along with increasing diversity of palynomorph assemblages found …

Sedimentology, Stratigraphy, And Organic Geochemistry Of The Red Pine Shale, Uinta Mountains, Utah: A Prograding Deltaic System In A Mid-Neoproterozoic Interior Seaway, Caroline Amelia Myer

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The Red Pine Shale (RPS; ~1120m thick), uppermost formation of the Neoproterozoic Uinta Mountain Group, Utah, is an organic-rich sedimentary succession interpreted as a marine deltaic system that delivered immature sediment from the north that mixed with mature sediment from the east. Multiple data sets suggest regional climate and sea-level changes associated with changing organic-carbon burial rates.

Six facies were identified and represent wave-, tidal-, and river-influenced parts of the distal prodelta to delta front in a marine system. These include the shale facies and associated concretion facies (distal prodelta), the shale-sandstone facies (proximal prodelta to delta front), the slump …