Samantha Hamilton
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B.Sc. (Honours) Thesis
(PDF - 45 Mb)
Silurian Carbon Isotope Excursions (SCIE) are characterized by extreme spikes in the positive stable isotope of carbon-13. These events are marked across the globe and are unvarying in their instance of appearance, making them an easily traceable event in the rock record. Although they are well documented, it remains unknown as to why there would be climactic variation to the degree that we observe with SCIE. Because of the relatively unaltered fossiliferous carbonate rocks found in the Arisaig Group, Nova Scotia, as well as their dating to known SCIE at the Wenlock/ Ludlow boundary as well as the Silurian/ Devonian boundary, this may provide an ideal study location for SCIE to add to the database of geographic locations in which they are observed. These rocks are also suitable for environmental analysis to provide an approximation of the conditions that might have given rise to SCIE. In this study, samples were taken across a section of the Upper Silurian of the Arisaig Group spanning from the Ludfordian Green member of the Moydart Formation to the Pridolian Stonehouse Formation. Electron Microprobe analysis was conducted to establish a complete chemical stratigraphy of the study location. A model was proposed to simulate paleoenvironmental conditions throughout the section, focusing on paleothermometry. Additionally, microtextural and Mn, Mg, Sr and Fe elemental concentrations were used to determine the degree of diagenetic effects in the section. Major environmental differences were observed across the section in locations we would expect to observe SCIE and that are consistent with global !O18 data . These rocks also display minimal amounts of diagenesis, and are therefore well suited for future stable isotope work.
Keywords:Silurian Arisaig Group, Calcite, Coquinite, Electron Microprobe, Chemostratigraphy
Pages: 116
Supervisor: Richard Cox