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A sedimentologic, stratigraphic, and geochemical study of the late Paleozoic ice age, Eastern Australia

Lauren P Birgenheier, University of Nebraska - Lincoln

Abstract

This study is a sedimentologic, stratigraphic, and geochemical analysis of the glacial record from eastern Australia, which lay at high latitudes during the late Paleozoic. Its goal is to constrain the exact timing, duration, and nature of late Paleozoic climate change. Because the understanding of glacial processes and products has changed since prior evaluation, Carboniferous and Permian units in eastern Australia were re-examined, and glacial facies were diagnosed using modern lithologic criteria. The ages of stratigraphic units were constrained using biostratigraphic and radiogenic isotopic age data. A plot of the temporal and spatial framework of glacially-influenced units in eastern Australia defines eight discrete glacial episodes (C1-C4 and P1-P4), ranging in duration from 1-8.8 m.y., which are separated from each other by periods of non-glacial deposition. The pattern of alternating glacial and non-glacial intervals demonstrates that late Paleozoic glaciation in eastern Australia was resticted to several, discrete intervals of shorter duration and climate was more dynamic than concluded by previous models. ^ Detailed sedimentologic documentation and facies analysis of Carboniferous deposits from New South Wales, Australia, such as the Spion Kop, Rocky Creek and Johnsons Creek Conglomerate and the Currabubula and Seaham Formation, demonstrate proglacial glaciofluvial and glaciolacustrine sedimentation but also documents nonglacial sediments. Age constraints on these sediments suggest that glacial advance and retreat occurred on less than 1 to 5.5 m.y. timescales. The short-term climatic fluctuations evident in Carboniferous glacial deposits may reflect orbital controls on sedimentation at high latitudes. ^ Bulk organic carbon stable isotopic analysis was performed on organic matter-rich facies from Permian glacial and non-glacial deposits across eastern Australia in order to construct a δ13Corg curve and compare resulting isotopic shifts with the stratigraphic record of glaciation from the region. Results indicate a relationship between positive and negative δ13Corg shifts and the onset and termination of glacial episodes P2-P4 in eastern Australia, respectively. Therefore, δ13Corg shifts are interpreted to record global changes in atmospheric pCO2 and climate. This study confirms (1) pCO2 was strongly coupled with climate during the Permian, and (2) bulk organic carbon isotopic records constructed from a mixed terrestrial and marine organic matter source can be a useful climate proxy. ^

Subject Area

Geology|Geochemistry

Recommended Citation

Birgenheier, Lauren P, "A sedimentologic, stratigraphic, and geochemical study of the late Paleozoic ice age, Eastern Australia" (2007). ETD collection for University of Nebraska - Lincoln. AAI3273189.
http://digitalcommons.unl.edu/dissertations/AAI3273189

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