Lithologic Consequences of Glacially Influenced Deposition: A Case Study from the Late Paleozoic of New South Wales, Australia

Lauren T. Birgenheier¹, Christopher R. Fielding¹, Tracy D. Frank¹, Michael C. Rygel¹, and John Roberts^2
1 University of Nebraska-Lincoln, Lincoln, NE
² University of New South Wales, Sydney, Australia

Critical diagnosis of glacial sedimentary facies is the foundation to constructing a faithful record of Icehouse climate regimes. Common glacial indicators include: diamictite, outsized clasts, rhythmically laminated siltstone/sandstone, bulleted, striated or faceted clasts, and glendonites. An understanding of glacial indicators and climate lends insight into lithology and source rock and reservoir potential. A modern diagnosis of glacially-influenced deposition relies on recognition of a number of these glacial indicators, rather than the presence of one sedimentary feature or facies. A re-evaluation of Carboniferous deposits from New South Wales, Australia, illustrates the differences between glacially-influenced deposition and distinctly non-glacial units. Glacially influenced deposition is evident in several units from New South Wales, including the Currububula and Kullatine Formations, the Spion Kop, Rocky Creek, and Johnsons Creek Conglomerates. Glacial units are spatially and temporally bounded by largely non-glacial units, such as: the Seaham, Caroda, and Youdale Formations. Source rock and reservoir potential from glacially influenced and non-glacial units are compared and contrasted. The recent recognition of the Seaham Formation as predominantly non-glacial is a significant departure from the traditional glacial interpretation from which early interpretations of the LPGIA in Australia were, in part, derived, illustrating that the use of modern sedimentological techniques can dramatically alter previous paleoclimatic interpretations. Construction of a Carboniferous stratigraphic framework highlights glacial indicators in time and space and points to two intervals of glaciation across, New South Wales, eastern Australia, that span the Namurian to Westphalian (Serpukhovian to Bashkirian), thus illustrating improved resolution regarding the timing of climatic fluctuations.