Earth and Atmospheric Sciences, Department of
Date of this Version
2010
Abstract
Recent research in eastern Australia has established that rather than being a single, long-lived epoch, the late Palaeozoic Ice Age comprised a series of glacial intervals each 1–8 million years in duration, separated by non-glacial intervals of comparable duration. In order to test whether the glacial events recognized in New South Wales and Queensland have broader extent, we conducted a reappraisal of the Parmeener Supergroup of Tasmania, southeast Australia. A facies analysis of the Pennsylvanian to Permian section was carried out, allowing rationalization of the succession into four recurrent facies associations: a) glacigenic facies association, restricted to the basal Pennsylvanian/earliest Permian Wynyard Formation and correlatives, b) glacially/cold climate-influenced to open marine shelf facies association, which accounts for large parts of the Permian succession, c) deltaic facies association, which specifically describes the Lower Permian “Lower Freshwater Sequence” interval, and d) fluvial to estuarine facies association, which specifically addresses the Upper Permian Cygnet Coal Measures and correlatives. Indicators of sediment accumulation under glacial influence and cold climate are restricted to four discrete stratigraphic intervals, all of which indicate that glaciation was temperate in nature. The lowermost of these, incorporating the basal Wynyard Formation and its correlatives, and overlying Woody Island Formation, shows evidence of proximal glacial influence (subglacial, grounding-line fan and ?fjordal facies), and is likely a composite of one or more Pennsylvanian glacial event(s) and an earliest Permian (Asselian) glacial. The second, of late Sakmarian to early Artinskian age, comprises an initial more proximal ice-influenced section and an overlying more distal ice-influenced interval. The third (Kungurian to Roadian) and fourth (Capitanian) intervals are both distal glacimarine records. The four intervals are of comparable age to glacials P1–P4, respectively, recognized in New South Wales and Queensland (notwithstanding apparent discrepancies of < 2 million years in age), and display similar facies characteristics and vertical contrasts to those intervals. Accordingly, it is concluded that the late Palaeozoic stratigraphy of Tasmania preserves a glacial/cold climate record correlatable to that of mainland eastern Australia, lending support to the hypothesis that these events were widespread across this portion of Gondwana.
Comments
Published in Palaeogeography, Palaeoclimatology, Palaeoecology 298 (2010), pp. 70–90; doi:10.1016/j.palaeo.2010.05.023 Copyright © 2010 Elsevier B.V. Used by permission.