Australia: The Land Where Time Began

A biography of the Australian continent 

The Pollen Record in Australia

The pollen record of gymnosperms in Australia starts in the Middle Mesozoic. The first Angiosperm pollen, Ilex, a Holley, appeared in the Late Cretaceous. Soon after it is followed by that of Antarctic Beech and proteaceous species. The Myrtaceae first appear in the Palaeocene. The appearance of taxa throughout the Tertiary is in quick succession, more herbaceous taxa appearing in the Late Tertiary.

66-57 Ma, in the Palaeocene, there were 10 different pollen types of Gymnosperm, the dominant group of the time. 23 different pollen types of Proteaceae are also very abundant, many becoming extinct during the Tertiary, Myrtaceae and Antarctic Beech are present, but not in great abundance. There is continued diversification of the Angiosperms.

57-36 Ma, the Eocene, the assemblages present are similar to those of the Palaeocene. Then about 40 Ma, in the Middle Eocene, Antarctic Beech become dominant over a short period. Antarctic Beech produces large amounts of wind dispersed pollen, resulting in all samples being over-represented. Just as it comes to dominance, many other proteaceous types, as well as some other Angiosperm types disappear from the record.

23-5.3 Ma, Miocene, the early pollen floras are unchanged from the Oligocene. In the Middle Miocene, Myrtaceae come to dominance, with 8 different types, at the expense of Antarctic Beech. The Eucalypt pollen type, also found in genera other than Eucalyptus, is present but not common. Most of the pollen are of the Tristania, Backhousia, Baeckea, Syzyigium and Acmena. There were probably other genera as well.

5.3-1.6. Ma, Pliocene, Myrtaceae is dominant, but small amounts of Antarctic Beech remain, as well as other early Tertiary forms. Pollen of grasses and Asteraceae (daisy family) are usually present, often in low numbers.

Pleistocene, Antarctic Beech and most Gymnosperms have gone from most of the continent, and the Myrtaceae is dominant, and the daisy family and grasses have greatly increased.

There are some plant groups, such as the Laurales, that have pollen that doesn't survive fossilisation. This was one of the earliest known Angiosperm types, many of the first Angiosperms in Australia were probably of this type. The result is a problem interpreting the flora from the pollen record. A further complication is that wind-blown pollen is always over-represented in a sample. Fossilisation is likely to occur only in climatic zones where there is at least moderate rainfall. The pollen record gives a much better picture of the flora at a particular time than the macrofossil record, it is still far from a complete picture of the flora.

Sites where pollen has been recovered in cores

  1. Banda Sea
  2. Lombok Ridge
  3. Site GC17, off Western Australia
  4. ODP820, marine sediment core 45 km off Cairns
  5. Lynchs Crater, Atherton Tablelands (Kershaw et a., 1993; Moss & Kershaw, 2000)
  6. Old Lake Coomboo, Fraser Island
  7. Cuddie Springs, New South Wales
  8. Lake George
  9. Lake Wangoom
  10. Site E55-6
  11. Wyelangta
  12. Egg Lagoon
  13. Lake Selina, Tasmanis
  14. Darwin Crater, Tasmania

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
Author: M. H. Monroe
Email:  admin@austhrutime.com
Last updated 09/08/2012 

 

 

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