Date of Award

6-2018

Degree Name

Master of Science

Department

Geosciences

First Advisor

Dr. Stephen E. Kaczmarek

Second Advisor

Dr. William B. Harrison III

Third Advisor

Dr. Peter Voice

Fourth Advisor

Jay Zambito

Access Setting

Masters Thesis-Campus Only

Restricted to Campus until

12-2018

Abstract

Handheld energy dispersive x-ray fluorescence spectrometry (ED-XRF) is routinely used to observe elemental variability in fine-grained siliciclastics but has been applied rarely in fine-grained carbonates. Here, ED-XRF chemostratigraphy is utilized in the texturally homogenous, mudstones of the Silurian A-1 Carbonate (A-1C), Michigan Basin. Previous studies on the A-1C focused on the stratigraphic relationship with the underlying Niagaran reefs, so little is known about the geological variability in the basin center. In this study, high-resolution elemental data from nine cores were integrated with petrographic and mineralogical observations to evaluate two hypotheses: (1) Texturally homogeneous, basin-center mudstones in the A-1C have spatially correlative elemental signatures (i.e. chemofacies); (2) Elemental variations reflect temporal changes in relative sea-level, redox conditions, and sedimentation rate.

Spatially correlative temporal variations in Si, Al, K, and S are observed between basin-center wells. High abundances of Si, Al, and K associated with siliciclastic minerals are interpreted to reflect intensification of clastic sedimentation during low sea-level. Associated S increases are interpreted as diagenetically altered gypsum that was deposited during periods of low sea-level. Chemofacies successions indicate 6 low-order transgressive-regressive cycles and up to 14 high-order cycles. These findings demonstrate the ability of ED-XRF to provide geologically relevant elemental data that can be used to refine sequence stratigraphic interpretations in fine-grained carbonates.

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