Evidence for Glacial and Polar Impacts in the Permian Coal Measures of the Sydney Basin

Abstract

This paper recognises that the Permian sequence of the Sydney Basin formed at a time the basin is indicated by polar wander curves to have been very close to the South Pole. That same Permian sequence contains some evidence for sometimes subtle Polar and Glacial impacts. In particular, Arctic Holocene geomorphological features, such as eskers, and ephemeral lacustrine environments, provide possible analogues for elements within the Permian coal measures and adjacent strata of the Sydney Basin. This paper also suggests more evidence for repeated climate change should become apparent with closer inspection of Sydney Basin strata. The flat lakebeds of huge, but little recognised, ice dammed lakes, recently existed throughout much of North America. These are seen as the modern equivalents of those that contributed to the regions post Triassic geology, especially in Alberta and Saskatchewan where accommodation, created by subsidence associated with uplift of the adjacent Rocky Mountains, has ensured preservation of the sedimentary succession. Only the most recent such lake sediments are preserved further east in Manitoba, where repeated glaciation may have obliterated many previous deposits. These lakes are seen as the possible environments in which floating plants, probably with nitrogen fixing physiology similar to the Azolla genus, may have formed extensive peat deposits. This hypothesis is reinforced by the ability of Azolla to grow rapidly in the long daylight hours peculiar to summer in the polar regions. Subsequent burial under ice sheets up to 3 or 4 kilometres in thickness may have contribute to lithification processes - including coalification. The recent lake deposits are interleaved with huge linear gravel deposits, originating as eskers and possibly moraines, which are similar in many ways to the conglomerate strata that are so prominent in the Newcastle Coal Measures and also exist elsewhere in the Sydney Basin.