Date of Award:

8-2013

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Geosciences

Department name when degree awarded

Geology

Committee Chair(s)

Carol M. Dehler

Committee

Carol M. Dehler

Committee

Dave Liddell

Committee

John Shervais

Committee

Paul Link

Committee

Adolph Yonkee

Abstract

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 the largest-magnitude glaciations in the history of our planet.

The results of this research indicate that shallow ocean conditions before the Snowball Earth glaciations fluctuated between oxic and anoxic, with smaller-scale
fluctuations (millions of years) not seeming to affect shallow marine life but larger-scale changes (occurring over several tens of millions of years) corresponding with
changes in the types of organisms present. After the glaciations, major & geologically “instant” ocean chemical changes are documented in Utah’s rocks; the results of this research challenge some existing ideas about the popular yet hotly contested Snowball Earth hypothesis and have the potential to change the Precambrian part of the geologic timescale.

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