Sedimentary Geology, 64 (1989), 25-41

I.P. MARTINI¹ and M.R. BANKS²

1Department of Land Resource Science, University of Guelph, Guelph, Ont. N1G 2W1 Canada)
²Department of Geology, University of Tasmania, Hobart, Tasmania 7001 (Australia)

The Lower Permian "Lower Freshwater Sequence" of Tasmania consists of fluvial and coastal sediments deposited in a cold-climate setting adjacent to ice-ridden, shallow seas. The sequence represents a regressive pulse during the filling of a marine basin, possibly a fjord, up to 150 km wide and more than 270 km long, occupied by glaciers in the late Carboniferous.
    The climatic conditions during the early Permian in Tasmania are revealed by (1) well-developed continental scree breccias, (2) the flora (Glossopteris-Gangamopteris assemblage), (3) rarity of fossils in tidal deposits, (4) the structure of the trace fossil population (intense bioturbation in offshore muds), (5) the foramol nature of the fauna of the marine beds below and above the Lower Freshwater Sequence, a fauna dominated by brachiopods and bryozoa and containing Eurydesma, and (6) features of the sediments themselves, such as "lonestones" in muddy offshore marine deposits, and oxygen isotopes of associated marine carbonates.
    Although the sedimentation in the Lower Freshwater Sequence is qualitatively analogous to that of the Quaternary of Canada, the fluvial and coastal sediments do not show evidence of ice rafting nor of frozen ground. Lack of such evidence suggests a cold-temperate rather than a subpolar setting.