Earth and Planetary Sciences ETDs

Publication Date



This study focuses on high-frequency, subtidal-carbonate cycles (1-8 m thick) within the Woodhurst Member of the Lower Mississippian Lodgepole Formation of southwest Montana. We combined conodont-oxygen isotopes (δ18Oapatite¬) and carbonate-carbon isotopes (δ13Ccarb) with cyclostratigraphy of Woodhurst cycles to test the hypothesis that the cycles developed in response to glacial eustasy, evaluate the timing and initiation of the Late Paleozoic Ice Age (LPIA), and to better understand the carbon budget in response to cycle formation. δ18Oapatite trends across targeted cycles support the hypothesis of glacial eustatic origins along with cooling surface seawater temperatures. High-resolution δ13Ccarb analysis of whole-rock limestones within eleven cycles reveal invariant or nonsystematic δ13Ccarb trends, but the long term trend confirms a major positive excursion reported in previous studies of coeval deposits, values peak at ~ 7.5 ° in the upper S. isosticha conodont Zone.

Degree Name

Earth and Planetary Sciences

Level of Degree


Department Name

Department of Earth and Planetary Sciences

First Advisor

Elrick, Maya

First Committee Member (Chair)

Atudorei, Viorel

Second Committee Member

Fawcett, Peter




Early Mississippian, Conodonts, Lodgepole Formation, Cycles

Document Type