Date of Award
Doctor of Philosophy
Margaret L. Fraiser
John L. Isbell
Stephen Q. Dornbos, Mark T. Harris, Lindsay J. McHenry
Argentina, Australia, Carboniferous, Glaciers, Late Paleozoic Ice Age, Permian
The late Paleozoic ice age (LPIA; 345-280 million years ago) provides the last complete record of a major deglaciation on a vegetated Earth, and therefore can serve as a proxy for Earth's inevitable transition out of its present glaciated state. This project analyzes climate change during and following the LPIA using two different approaches:
1) Detailed sedimentology analyses of five glacially-influenced formations in Argentina and Australia in order to determine the size and thermal regime of glaciers during the LPIA.
2) An investigation of massive volcanism along the Panthalassan margin of Gondwana as a source of CO2 that may have contributed to the end of the LPIA and to two ensuing extinction events.
During the LPIA, glaciation occurred over the supercontinent Gondwana, and resulting glacial deposits are found in South America, Africa, Antarctica, India, and Australia. This project focuses on glacial and post-glacial outcrops in western Argentina and Tasmania, Australia that were deposited in western and eastern Gondwana, respectively. A study of outcrops from these two regions enables characterization and comparison of the early stages of the LPIA (when Argentina was glaciated) and when glaciation was at its peak (when Tasmania was glaciated). Glacial and post-glacial deposits are analyzed using sedimentologic field techniques to interpret depositional events, thin section analysis to determine the micromorphology of the deposits, and mineralogical (x-ray diffraction, or XRD) and elemental (x-ray fluorescence, or XRF) analysis to differentiate sediment sources and determine the oxygenation of the environments.
Atmospheric CO2 fluctuations have been linked to ice volume fluctuations during the LPIA, and CO2 input from massive volcanism is considered a major driver of the Middle and Late Permian extinctions (261 and 250 million years ago, respectively). Although these events were previously considered as unrelated, volcanism along the subducting Panthalassan margin of Gondwana occurred throughout both the deglaciation of the LPIA and the Permian extinctions. Therefore, this study will also explore the hypothesis that Panthalassan margin volcanism influenced both deglaciation and the Permian extinctions. Ultimately this dissertation will improve the understanding of
climate change during and following the LPIA and inform predictions for when and how Earth will experience deglaciation in the future.
Henry, Lindsey C., "Late Paleozoic Glaciation and Ice Sheet Collapse Over Western and Eastern Gondwana: Sedimentology and Stratigraphy of Glacial to Post-Glacial Strata in Western Argentina and Tasmania, Australia" (2013). Theses and Dissertations. 112.