Doctor of Philosophy (PhD)
Geology and Geophysics
Magnetic susceptibility (χ) has gained increased usage as a stratigraphic correlation tool. This project evaluates the utility of a χ correlation tool, including its shortcomings, and attempts its integration with other datasets. The Upper Ordovician of eastern North America represent the stratigraphic interval in which these experiments were conducted. 4566 samples were collected for the purposes of this study, and χ was measured on 3345 of the samples. This project includes three major facets, 1) the spatial variability of χ, 2) correlation of Sandbian-Katian boundary interval strata in eastern North America using χ, and 3) utility of χ for interpreting stratigraphic sequences. 1) Testing the spatial variability of χ was conducted by sampling a single isochronous Upper Ordovician limestone horizon across the lateral extent of the Cincinnati Arch. A small but predictable decrease in χ values with increased distance from the clastic sediment source was documented. These observations match the hypotheses of the Episodic Starvation model of sedimentation on the Cincinnati Arch. Facies changes in proximal positions of the basin, and interbedding of muddy carbonates with shales, result in the deterioration of the χ signature, and correlation becomes increasingly difficult using this method. Based upon this, correlation using χ profiles is most suited for distal portions of basins. 2) Application of the χ technique has been used for correlation of the Sandbian-Katian boundary interval in eastern North America. A series of correlation hypotheses have been proposed but a unique correlation has not been found. Due to a series of unconformities, and biostratigraphic discrepancies it has not been possible to find a datum to hang χ profiles upon. The leading hypothesis is that deepening strata of the Logana-Napanee interval correlates to the lower wackestone unit of the Viola Springs Formation, and upper Womble Shale. 3) In order to incorporate χ datasets into sequence stratigraphic analyses a series of χ samples have been collected across sequence stratigraphic surfaces of know interpretation. Large shifts to lower measured χ values at some sequence boundaries and shifts to higher χ values at most flooding surfaces may be used to aid in sequence stratigraphic interpretation.
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Secure the entire work for patent and/or proprietary purposes for a period of one year. Student has submitted appropriate documentation which states: During this period the copyright owner also agrees not to exercise her/his ownership rights, including public use in works, without prior authorization from LSU. At the end of the one year period, either we or LSU may request an automatic extension for one additional year. At the end of the one year secure period (or its extension, if such is requested), the work will be released for access worldwide.
Schramm, Thomas J., "Magnetic Susceptibility of North American Ordovician Epicontinental Seas: Spatial Variability and Sandbian-Katian Boundary Correlation" (2015). LSU Doctoral Dissertations. 3629.