Eocene-Oligocene coals of the Gippsland and Australo-Antarctic basins – Paleoclimatic and paleogeographic context and implications for the earliest Cenozoic glaciations
Abstract Australia's Gippsland Basin contains a semi-continuous Eocene-Oligocene (41.5–28.4 Ma) near-coastal coal record that formed adjacent to Pacific Ocean. Traralgon and Morwell Formation brown coals include 4 main seams (T2, T1, T0, M2). Coal seam palynology records show late Middle Eocene (T2) coals formed under megathermic conditions characterized by high-gymnosperm contents, Late Eocene (T1) coals formed under mesothermic conditions characterized by reduced-gymnosperm contents and earliest indications of palaeoclimate cooling. Earliest Oligocene T0 coal record (33.9–31.5 Ma) contains high-gymnosperm palynology profile, very similar to the T2 coals. The earliest indication of cooler climes only begins after this coal formed as indicated by low-gymnosperm high-Nothofagus (southern beech) pollen proportions. We suggest in Gippsland the earliest evidence for major glacial cooling (by inference the Oi1 event) be placed immediately above the T0 coal seam where Early to Late Oligocene Morwell Formation sands, clays and coals contain low counts of gymnosperms ( A number of contemporaneous Middle to Late Eocene brown coals occurred in near-coastal settings across 1200 km of southern Australia. Palaeogeographically, all these coal basins faced the Australo-Antarctic Gulf and have a much lower gymnosperm proportion (