Australia: The Land Where Time Began

A biography of the Australian continent 

Australian Pollen Record - The Bassian Plain

The vegetation of much of the Bassian Plain during the LGM is indicated by pollen cores from southern Victoria, western Tasmania and King Island. Cores from Lake Wangoom and E55-6 record a change at about 100,000 BP from eucalypt forest, with some cool-temperate rainforest species and some grass, to grasses, non-grass herbs and a few scattered eucalypts on an open steppe. By about 20,000 BP some casuarinas are present. There are also some aquatic plants at the LGM, indicating swamps and wetlands (Harle, 1997) according to pollen cores from the E55-6 site. The Wyelangata cores, in what is now a cool temperate rainforest of Antarctic beech in a high-rainfall area (Mckenzie and Kershaw, 2000). Pollen concentrations indicate Nothofagus was present, though scattered sparsely, throughout the LGM. The area was apparently swampy during the LGM, as indicated by the presence of sedges, heath plants and grasses.

The Tasmanian pollen record shows that during the LGM the previously dominant Nothofagus forest had been replaced by open steppe, vegetated almost entirely with grasses and daisies, and a few alpine shrubs. There were only isolated forests of eucalypt and Nothofagus, isolated remnants on valley floors in coastal areas (Colhoun, 2000).

At about 120,000 BP, cores from Egg Lagoon on King Island, indicate that sclerophyll forests were present, with an increasing Casuarinaceae component, that was gradually replacing closed forest. At about 35,000 BP, grasslands and herb fields replaces forests (D'Costa, 1997).

It appears the vegetation of the Bassian Plain at times of low sea level was probably mixed shrubland and grassland, with few if any trees. There are indications in the pollen record of some wetlands, and isolated pockets of remnant forest lingered on in some humid areas. Flinders Island, on the eastern highlands, and King Island, then the western highlands, are believed to have been separated by a basin that probably held a large freshwater lake when the Plain was dry land. There may also have been marshes and or lakes in the many scattered depressions on the Plain (Lambeck & Chapell, 2001).

 

Sources & Further reading

  • Mary E. White, The Greening of Gondwana, the 400 Million Year story of Australian Plants, Reed, 1994
  • Chris Johnson, Australia's Mammal Extinctions, a 50,000 year history, Cambridge University Press, 2006

 

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                                                                                           Author: M.H.Monroe  Email: admin@austhrutime.com     Sources & Further reading