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Investigating evidence of high frequency glacial eustacy in the Lower Mississippian (Tournasian) Lodgepole Formation of southwest Montana : insights from conodont oxygen isotopes

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Please use this identifier to cite or link to this item: http://hdl.handle.net/1928/13115

Investigating evidence of high frequency glacial eustacy in the Lower Mississippian (Tournasian) Lodgepole Formation of southwest Montana : insights from conodont oxygen isotopes

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Title: Investigating evidence of high frequency glacial eustacy in the Lower Mississippian (Tournasian) Lodgepole Formation of southwest Montana : insights from conodont oxygen isotopes
Author: Wallace, Zachary
Advisor(s): Elrick, Maya
Committee Member(s): Atudorei, Viorel
Fawcett, Peter
Department: University of New Mexico. Dept. of Earth and Planetary Sciences
Subject: Early Mississippian, Conodonts, Lodgepole Formation, Cycles
LC Subject(s): Geology, Stratigraphic--Mississippian.
Cyclostratigraphy--Montana.
Conodonts--Montana.
Glacial isostasy.
Degree Level: Masters
Abstract: 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.
Graduation Date: July 2011
URI: http://hdl.handle.net/1928/13115


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