Paleoclimate reconstruction of Pennsylvanian paleoequatorial environments: Coupling terrestrial and marine proxies

The geological record is replete with archives of environmental information. As the earth transitions from a global icehouse to greenhouse climate, there is an increasing need for deep-time studies that will provide insight into how the both the terrestrial and marine realm may respond to such a climate change. The Late Paleozoic Ice Age (LPIA) represents a particularly attractive interval for this endeavor, as it encompasses the only complete icehouse to greenhouse transition on the vegetated earth, providing the closest deep-time analogue to the modern ice age.;This dissertation examines the evolution of paleotropical climate during the LPIA through coupled lithostratigraphic and geochemical investigations of intercalated terrestrial and marine strata preserved within North American cyclothems. The morphological, mineralogical, and geochemical content of paleosols preserved within Pennsylvanian cyclothems of the Illinois basin serve as a terrestrial paleoclimate proxy and are used to investigate the interplay of basin-scale to global-scale controls responsible for their evolution during the LPIA. Deconvolution of these controls reveals that the development of Pennsylvanian-age paleosols in the Illinois basin can readily be related to Late Paleozoic glacioeustatic fluctuations, and associated climate change, as well as topographic position on the ancient landscape. The oxygen and hydrogen isotope composition of paleosol phyllosilicates are used as a quantitative terrestrial paleotemperature proxy for the Pennsylvanian tropics and reveal a significant temperature increase (~ 6ºC) at low-latitudes across the Desmoinesian-Missourian (~Moscovian-Kasimovian) boundary. Conodont apatite delta 18O values from organic-rich marine black shales in the Illinois basin serve as a marine paleoclimate proxy. These data reveal significant variations in conodont apatite delta18O values from a single black shale member across the basin that is attributed to local factors such as enhanced continental runoff in the Illinois basin as a result of its proximity to the ancient shoreline Appalachian highlands. Collectively, the results presented in this dissertation help resolve the responses of terrestrial and marine systems to the waxing and waning of late Paleozoic Gondwanan ice sheets and provide insight into the suite of mechanisms responsible for tropical paleoenvironmental change during LPIA glacial-deglacial episodes.