Date of Award
Master of Science
Geological and Environmental Sciences
Dr. Stephen E. Kaczmarek
Dr. William B. Harrison III
Dr. Peter Voice
A-1 carbonate, chemostratigraphy, Michigan Basin, ED-XRF, sequence stratigraphy
Masters Thesis-Open Access
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.
Hemenway, "Application of Handheld ED-XRF for High-Resolution Chemostratigraphy in Texturally Homogeneous Carbonate Mudstones: Salina A-1 Carbonate (Silurian), Michigan Basin" (2018). Master's Theses. 3704.