Date of Final Oral Examination (Defense)
Type of Culminating Activity
Doctor of Philosophy in Geosciences
Mark Schmitz, Ph.D.
James Crowley, Ph.D.
Matthew J. Kohn, Ph.D.
Clyde J. Northrup, Ph.D.
Neoproterozoic sedimentary successions contain evidence for some of the most extreme climate fluctuations, breakup of the paleo-supercontinent Rodina, multiple low-latitude global glaciations, and the resultant evolution and radiation of complex life. The stratigraphic record of these events are found on all major continents and have been associated with, in part, global ‘Snowball Earth’ events. However, the understanding and integration of these, and related phenomenon, are limited by disparate and imprecise age constraints that prohibit clear correlation between locations.
This research focused on high-precision geochronology within an integrated framework of sedimentology, stratigraphy, and geochemistry to resolve the timing and duration of Neoproterozoic Rodinian rifting and ‘Snowball Earth’ glaciation recorded in rock units across Idaho. A tandem approach to U-Pb zircon geochronology and geochemistry, combining laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) and high-precision U-Pb chemical abrasion-isotope dilution thermal ionization mass spectrometry (CA-IDTIMS), was used to establish a high-fidelity record of pre-, syn-, and post-Rodinian rift sediments, glacigenic sediments, and rift-related magmatism across Idaho.
Results from this research have: 1) documented prolonged pre-to-post Rodinian rifting and basin subsidence; 2) provided the first geochronologic evidence of Cambrian – Ordovician strata in central Idaho; 3) placed firm age constraints on long-duration Sturtian glaciation; 4) provided evidence of Marinoan glaciation; 5) documented duration and pulse of regional rift-related magmatism; 6) showed the need for in situ and isotope dilution analytical techniques to establish clear age constraints in this time and place.
Isakson, Vincent H., "Geochronology of the Tectonic, Stratigraphic, and Magmatic Evolution of Neoproterozoic to Early Paleozoic, North American Cordillera and Cryogenian Glaciation" (2017). Boise State University Theses and Dissertations. 1262.