GONDWANA TIMELINE (by Dr. Keith Corbett)
GEOLOGICAL HISTORY AND AUSTRALIAN FLORA

JURASSIC PERIOD:   - from 208 to 144 million years ago.
 
Climate: 

Continental movement: 

Australia: 

Tasmania: 

Vegetation History:

Wet and warm everywhere. No polar ice.

Gondwana and Laurasia. Stretching and rifting begin about 150 m.y.a.

Stretching.

Dolerite intrusion. 

Ancient flora only - conifers, ferns, cycads, gingkos, lycopods,
horsetails.  Many of these species survive today. Basalt eruption buries Jurassic forest at Lune River (in Tasmania’s far south). Fossils of ferns, conifers and cycads occur.

CRETACEOUS PERIOD: - from 144 to 65 million years ago. (A Gondwana Connection?)
 
Climate: Sudden cooling event and widespread flooding by sea - Great Artesian Basin formed. 
Between 100 and 80 m.y.a. the climate is mostly warm again. 
From 80 to 65 m.y.a. a time of change. 
Terminal Cretaceous Event 65 m.y.a. 
Sudden cooling, many extinctions, volcanic activity, possibly caused by asteroid/comet impact.
Continental Movement: 125 m.y.a. Africa leaves Antarctica. India separates from Antarctica and Australia and bolts north at 20cm a year.
100 m.y.a. Africa separates from South America.
  80 m.y.a. New Zealand separates from Australia. 
Australia: Stretching and rifting. Australia stays attached to Antarctica long after other continents depart - Tasmania is the “problem”.
Tasmania: Bass Strait Basin partly fills but does not quite split.
Vegetation History: 100 m.y.a. Flowering plants evolve in West Gondwana. Great Rift  valley between Africa and South America is centre of evolution.
 90 m.y.a. Flowering plants migrate to all continents and begin to compete with conifers etc.
  80 m.y.a. First Nothofagus seen in Antarctica. Southern conifers still dominant in Australia - Huon Pine, Phyllocladus, Callitris. First Proteaceae in Australia. Nothofagus arrives via Antarctica and South America, but does not reach Africa.
Ilex is first flowering plant to occur in Australia.

TERTIARY PERIOD:  - from 65 to 1.6 million years ago, divided into five epochs;
        Palaeocene, Eocene, Oligocene, Miocene and Pliocene

PALAEOCENE:  - from 65 to 58 million years ago.       EOCENE:  - from 58 to 40 million years ago.
 
 
Climate: 

Continental movement: 

Australia: 
 

Tasmania: 
 

Vegetation History:

“A Golden Age” - mainly warm and wet again.

50 m.y.a. India collides with Asia and forms Himalayas

Seafloor spreading in Bight. Australia “un-zips” and finally separates from Antarctica 45 m.y.a.

Tasmania hangs on to Antarctica - Tasmania and South Tasman Rise continue to provide land connection to Antarctica until 45 m.y.a.

First occurrence of Casuarinas, Banksia, Myrtaceae, Restioneaceae Winteraceae and Epacridaceae during Palaeocene. 
Grass pollen appears in early Eocene. 
Rich sub-tropical rainforest covers much of Australia during Eocene (now confined to N.E. Queensland. New Guinea and New Caledonia.)

OLIGOCENE      - from 40 to 24 million years ago.
 
Climate: 

Continental movement:

Australia: 

Tasmania: 

Vegetation History: 

First glaciers on Antarctica. Cooler and drier - more seasonal.

Drake Passage opens. Circum-polar current formed.

Australia colliding with New Guinea.

Carried north on Australian plate from about 65º S.

45 m.y.a. Australia departs with its cargo of Gondwanan plants which now evolve in isolation for 30 million years.
Temperate rainforest widespread with much Nothofagus. (Also in Antarctica and South America)
c.25 m.y.a. Acacia and Eucalyptus pollen first recognised in Australia.

MIOCENE :           - from 24 to 5.3 million years ago.
 
Climate: 
 
 
 
 

Continental movement: 

Australia and Tasmania:

Vegetation History:

Warm and wet for a short period initially.
 - 20 m.y.a. Isolation and cooling of Antarctica.
 - 15 m.y.a. Southern ice cap formed.
 - 10 m.y.a. Australia drying out and arriving in sub-tropics.
 - 5.3 m.y.a. Terminal Miocene Event. Cold, dry, arid period

20 m.y.a. Antarctica stranded over South Pole - begins to cool.

Drifting north at 6-7cm/yr.

c.17 m.y.a. Antarctic flora succumbs to cold.
c.15 m.y.a. Change from closed forest to wet sclerophyll forest, dry forest to open woodland and grasses. Eucalypts, Acacias, Casuarinas, grasses become dominant.
c.10 m.y.a. Fire becomes important factor

PLIOCENE:       - from 5.3 to 1.6 million years ago.
 
Climate: 
 
 
 

Continental movement:

Australia: 

Tasmania:

Vegetation History:

Antarctica freezes over.
Brief warm period.
Colder again.
Northern ice cap forms.

Continues.

Colliding with Timor region. Migration of plants and animals from north.

Gets to latitude 42ºS. Cool, temperate and moist.

5 m.y.a. Sub-tropical forest species migrate to refuges in Queensland and New Guinea.
Invasion by Asian plants from north. Myrtaceae dominate.
2 m.y.a. Dry sclerophyll, woodlands and deserts expand.

QUATERNARY PERIOD: - from 1.6 million years ago to present day, divided into two epochs;
            Pleistocene and Holocene.

PLEISTOCENE:    - from 1.6 to 0.1 million years.
 
Climate:

Australia: 

Tasmania: 

Vegetation History: 

ICE AGE. Sea levels rise and fall many times.

Climate drying. Man arrives c.60,000 years.

Intermittent land bridge across Bass Strait.

Man has major impact on flora. Rainforest reduced to 1% of land area.

HOLOCENE:        The modern era - continental movement continues

(Return to the Story of Gondwana)

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