Nested Cyclicity in the Carboniferous Glacial Record from New South Wales, Australia

Birgenheier, Lauren P.¹, Christopher R. Fielding², Tracy D. Frank³, Michael C. Rygel⁴ (1) University of Nebraska - Lincoln, Lincoln, NE (2) University of Nebraska-Lincoln, Lincoln, NE (3) University of Nebraska - Lincoln, Lincoln (4) SUNY Potsdam, Potsdam, NY

Evidence of glaciation contained within Carboniferous deposits from New South Wales, Australia fueled early 20th century theories of late Paleozoic Gondwanan glaciation. A modern examination of these deposits offers insight into the details of ancient icehouse climate dynamics and sedimentation style that have been previously overlooked. Stratigraphic placement of these glacially-influenced deposits using detailed biostratigraphic and geochronological data have resulted in the recognition of four discrete glacial episodes (C1-C4) that span the Namurian (Serpukhovian) to late Westphalian (mid Moscovian), increasing in duration through time (~1 to 5.5 m.y.). This stratigraphic framework reveals a ~1 to 5.5 m.y. pacing of climate through the Carboniferous within an overall pattern of climatic deterioration that peaked during the early Permian. Facies analysis of the formations that record each ~1 - 5.5 m.y. glacial episode, such as the Seaham and Currabubula Formations and the Rocky Creek, Spion Kop, and Johnson's Creek Conglomerate, reveal features consistent with a higher order cyclicity within each period of glaciation. While the current age constraints limit our ability to determine the duration of the shorter-term cycles observed within glacially-influenced units, the recognition of climatic variation at multiple time scales, or nested cyclicity, during the late Paleozoic is strikingly similar to the character of Cenozoic climate variation. This suggests the principle drivers of Cenozoic climate change were also operating during the late Paleozoic and offers the late Paleozoic ice age as a promising ancient analogue to study modern and predict future climate change.