Australia: The Land Where Time Began

A biography of the Australian continent 

Late Cretaceous Land Plants

Information about terrestrial plants from Australia from the Late Cretaceous has been gathered from impressions, stems, cones (reproductive structures), mineralised wood, cuticles, spores and pollen. According to the authors3 there is evidence in the fossil record from the Late Cretaceous that changes in rainforest and woodland communities, though a large part of the record is geographically and stratigraphically patchy.

Species of forest and woodland communities have been found in the macrofloras of the Winton Formation from the uppermost-Cenomanian. Conifers are mainly the dominant type of vegetation that includes several araucarians (Araucaria), Elatocladus (a podocarp), Ginkgo and sequoias (Taxodiaceae) such as Athrotaxus and Australosequoia wintonensis. The authors3 have suggested probable understorey plants that include pentoxylaceans (Taeniopteris) and ferns such as Sphenopteris and Microphyllopteris, and along the edges of lakes and swamps, horsetails and quillworts. There have also been a number of angiosperms recorded. Leaf impressions have allowed the identification of magnolias, mineralised flowers Lovella wintonensis, and fruiting structures. In localities in the Gippsland Basin and the Otway Basin, southern Victoria, similar macrofloras, with spores and pollen,  from the Cenomanian have been found. Regional differences are apparent in the fossil record such as lower angiosperm diversity and a flora that is adapted to wet zones that is generally more pervasive.

Apart from some cuticle and leaf fragments found in drill cores from the Otway Basin, microfossils are almost the only evidence of plants from the Late Cretaceous. What evidence there is indicates that around the Cenomanian-Turonian boundary there were profound changes in the vegetation, including the introduction of modern elements such as Ilex (holly) and proteas such as Banksia. The authors3 suggest the migration routes taken by the new arrivals in Australia were probably via southern high-latitude regions, the new taxa becoming established elements of the flora by the Santonian. Proteacean lineages of the present such as Macadamia had begun to differentiate, as well as other austral angiosperms that were characteristic of the Australian vegetation such as Winteraceae and Nothofagus (southern beech) by the Campanian-Masstrichtian. The authors3 suggest that somewhere in South America-Antarctic Peninsula appears to be the place of origin of Nothofagus. At the present it is widely distributed throughout many continental fragments of Gondwana, such as Australia, New Guinea, New Zealand, New Caledonia and South America.

 

 

 

 

Triassic Australia
Jurassic Australia
Cretaceous Australia

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