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history:evolution_australia

How Australia evolved in geological terms and evolution

In the beginning

  • The Australian landmass has been part of all major supercontinents, but its association with Gondwana is especially notable as important correlations have been made geologically with the African continental mass and Antarctica.

Archaean

  • There are three main cratonic shields of recognised Archaean age within the Australian landmass: The Yilgarn, the Pilbara and the Gawler cratons.
  • Wave Rock in WA is thought to have been created 2700mya with its current form due to erosion since then
  • The cratons appear to have been assembled to form the greater Australian landmass (2,400-1,600mya)
  • 2.229 billion years ago, the 70km wide Yarrabubba impact crater in WA the result of an asteroid impact (the oldest known impact crater although controversially, the “oldest-known impact structure” should go to the Maniisoq formation in southwest Greenland, which is around 3 billion years old although this may have been tectonic rather than impact) which is thought to have helped end the “snowball earth” period

Columbia / Nuna super-continent

  • the super-continent of Columbia or Nuna containing almost all of Earth's continental blocks is thought to have assembled following global scale collisional events in 2.1-1.8 billion years ago.
    • 1.8bya Kimberely collides with NT creating initial white Argyle diamonds 150km below the surface
  • The eastern coast of India was attached to western North America, with southern Australia in the northern hemisphere against western Canada.
  • Most of South America was rotated such that the western edge of modern-day Brazil lined up with eastern North America, forming a continental margin that extended into the southern edge of Scandinavia.
  • 1600mya: the Gawler Ranges Sth Australia super-volcano - one of the largest ever on earth - creates the unique pink rhyolite of the Gawler Ranges and the “Organ Pipes” formation some of which are 300m thick - in the 1-2 million years it erupted, estimated total lava output was a million times the volume of Sydney Harbour covering ~500km diameter! IKt is the world's only felsic shield volcano. This produced the vast mineral deposits of Olympic Dam region.
  • Tasmania has a very different origin to the rest of Australia as it formed sandwiched between Arizona and Antarctica in the northern hemisphere
    • during much of this time it was under the ocean and was being covered in sediment and under water land slides from both Arizona and East Antarctica
    • this sediment would gradually construct the land mass of Tasmania to form an island
    • ~1400mya, a tectonic rift event occurred between the land mass that would be Tasmania and Arizona forming a sea between Tasmania and Arizona and an increasing separation on Nth America and Antarctica leaving a part of Tasmania attached to Arizona and another part of Tasmania attached to East Antarctica
    • Tasmania, attached to East Antarctica, then gradually drifted towards southern Australia and collided with southern Australia by around 500mya which helped to lift SE Victoria up from under the ocean as well as cause an orogeny within Tasmania and bring mineral deposits including gold to the surface of both Tasmania and Victoria
    • Antarctica then broke away from Tasmania and migrated southwards
  • 1500-1100mya, South Australian Craton collides with the already joined West Australian Craton and the North Australian Craton creating the Musgravian Orogeny and the Albany-Fraser Orogeny and later the Petermann Ranges
  • 1300mya, break up of Nuna results in volcanic eruptions which pushed the white Argyle diamonds from 150km below the surface to the surface at 70kph in a carrot shaped volcanic pipe of magma called a diatreme and the increased pressures resulted in the diamonds warping and becoming pink Argyle diamonds

Rodinia

  • the Rodinia supercontinent was assembled c1300-1230mya
  • tectonic activity between 1300-1100 Mya led to the assembly of Proterozoic Australia from collision of the 3 main cratons as an early component of the supercontinent of Rodinia.
  • Australia was well north of the equator and adjacent Eastern Antarctica, India, South China and Laurentia
  • c 850-800mya a rift developed between the continental masses of present-day Australia, East Antarctica, India and the Congo and Kalahari cratons on one side and later Laurentia, Baltica, Amazonia and the West African and Rio de la Plata cratons on the other.
  • Adelaide Rift Complex of sedimentary deposits begin to form 870mya through to 500 mya (hence the Ediacaran fossils in this region) with the southern parts ending with the Delamerian Orogeny 514-500mya (the northern parts such as Cooper and Perdirka Basins still continue to have deposition
  • 830mya - rifting to the east formed the “Adelaide Geosyncline”
  • 830-750mya - the Centralian Superbasin developed over the junction of the North, South, and West Australian cratons
  • 620-540mya - King Leopold, Paterson, Petermann Ranges, and Pinjarra orogenies
    • Petermann Ranges formed 600-550mya due to the colliding of SthAust and Nth Australia and reached elevations of some 9000m and was 2000km long however these rapidly eroded and the sedimentary fans would form Uluru
  • Rodinia broke up in four stages between 825–550
  • Rodinia existed before complex life colonized dry land

rodinia_reconstruction.jpg

Gondwana

  • several cratons joined to form a supercontinent the size of 2/3rds of current continental area on earth called Gondwana
    • this commenced between 800-650mya with the East African Orogeny – the collision of India and Madagascar with East Africa
      • Note that southern parts of the Australia craton lay just north of the magnetic equator c750mya
      • the break up of Rodinia resulted in the Terra Australis Orogen (TAO) which became the oceanic southern margin of Gondwana which stretched from South America to Eastern Australia and encompassed South Africa, West Antarctica, New Zealand and Victoria Land in East Antarctica
      • Snowball Earth of the Cryogenian Period with extreme cooling of global climate 717–635 mya
      • Ediacaran soft bodied fauna lived in shallow seas in Australia c670 mya
      • the Cambrian animal life explosion commenced around 600 mya but these were all living in water (1st air breathing animal and first vascular plant did not evolve until c400mya)
    • it completed b 600-530mya with the collision of South America with Africa and the addition of Australia and Antarctica
    • the final stages of Gondwanan assembly overlapped with the opening of the Iapetus Ocean between Laurentia (which would later become north America) and western Gondwana. During this interval, the Cambrian explosion occurred.
    • 620-540mya - King Leopold, Paterson, Petermann Ranges, and Pinjarra orogenies
      • the mantle underlying the Musgrave Province (former Petermann Ranges now Woodroffe Thrust on WA-NT border) and the Arunta Region (Ormiston Gorge, West Macdonnell Ranges near Alice Springs) has been uplifted some 20-30km in an east-west orientation through the 50km thick crust and can be seen on gravity images of the area 1)
    • 580mya massive Acraman impact crater, Gawler Ranges, Sth Australia which had fall out ~4“ thick layer of pink rhyolite ejectiles in the Flinders Ranges 300km to the east - now a salt lake / salt pan
      • bolide diameter 4.8km; velocity 25km/sec; energy 5.2 x 10^6 Mt TNT; transient cavity 40km; collapse crater 90km; ejecta blanket >540km;
    • 560mya - Mt William in central Victoria forms from an undersea volcano producing Victoria's oldest rocks - greenstone which was used by Aborigines for tools
    • 550mya, erosion of the Petermann Ranges starts to form the sandstone deposit that will eventually form Uluru
    • 550mya volcanic activity laid down rock in southern Gippsland in Victoria (eg. around Cape Liptrap)
    • Tasmania (still attached to East Antarctica) collides with south-eastern Australia causing Victoria to be uplifted from the ocean floor

upload.wikimedia.org_wikipedia_commons_2_22_positions_of_ancient_continents_2c_550_million_years_ago.jpg

the splitting of Gondwana and the separation of Australia

  • Cambrian era (539-485mya)
    • eastern two thirds of Victoria is an oceanic floor that commences to be uplifted east of the Moyston Fault Line by a subducting Pacific plate creating a volcanic arc 525-511mya - the Stavely Volcanic Arc stretching from Victoria to the closely connected Antarctica and now sits between Ballarat and the Grampians - the final burst of volcanic activity from these arcs c500mya are what generally push up mineral rich magma to the surface such as gold - hence the Golden Triangle in western Victoria was formed (gold deposits in the eastern Victorian fields was formed separately)
    • 550-470mya: Delamerian Orogeny forms and by 514-500mya ends the sedimentary deposits on the Adelaide Rift Complex
      • this resulted in the creation of a major mountain range, the eroded stumps of which can today be seen as the Mount Lofty and the Flinders Ranges
    • 500mya: 1st Ice Age occurred
  • Ordovician period (485-444 mya)
    • deepwater sedimentation of the St Arnaud and Castlemaine Group turbidites, which are now emplaced in the Stawell and Bendigo Zones followed by deposition of the Sunbury Group in the Melbourne Zone, Bendoc Group and formation of the Molong Arc
    • shallow marine limestone and mudstone deposition Melbourne Zone, Tabberabbera zone eastern central Victoria until c405mya
    • 450-340mya: Lachlan Orogeny forms in eastern Australia
  • Silurian period (444-420mya)
    • 445.2 and 443.8mya - Hirnantian glaciation stage, Ordovician-Silurian extinction event killed 85% of species - may have been triggered by a massive asteroid impact in Deniliquin, NSW causing a 520km wide impact crater, although this may have occurred as early as 514mya
    • a giant water scorpion, the first animal found to walk on the Australian continent in NW of WA
    • volcanic arcs in eastern Australia
    • Granite intrusions as well as gold-bearing quartz reefs formed from hot salty fluids in New South Wales and Victoria
      • repeated minor earthquakes result in immediate deposition of quartz and gold from pressurised supersaturated silica and minerals in water within the fault lines - a magnitude 2 earthquake results in 130-fold reduction in pressure while a magnitude 6 event could reduce pressures by 13,000 fold - each event laying down more gold-laden quartz reefs and a fault line could have hundreds of magnitude 2 events per year
    • Deep water sediments formed in the Cowra, Tumut and Hillend Troughs
    • the Lachlan Orogen / Lachlan Fold Belt (LBF) of southeastern Australia had a varied paleogeography with deep marine, shallow marine, subaerial environments and widespread igneous activity reflecting an extensional backarc setting. This changed to a compressional–extensional regime in the Devonian associated with episodic compressional events, including the Bindian, Tabberabberan and Kanimblan orogenies.
      • The Lachlan Orogen includes Cambrian to Carboniferous rocks in central and eastern NSW west of the Sydney Basin and extending southwards into Victoria and northeastern Tasmania
      • The western boundary of the Lachlan Orogen in western Victoria is generally taken along the Moyston Fault, although the Grampians Supergroup west of the Moyston Fault has characteristics of the Lachlan Orogen including probable Silurian to Early Devonian sedimentation and deformation.2)
      • The Grampians Group may possibly have been deformed in the Silurian to Early Devonian associated with either the Benambran Orogeny or the Bindian Orogeny
      • the Great Artesian Basin has been laid down over the top of the LFB in northwestern New South Wales and western Queensland and the Murray-Darling Basin covers the southwest of New South Wales
    • 444-435mya, phase 1 Benambran Orogeny in Wagga-Omeo zone, Bega, Murda Syncline, and ? in eastern Tasmania
    • 435-427mya, phase 2 Benambran Orogeny in Tabberabbera zone, western Victorian highlands east of Moyston fault
    • 423-419mya Silurian sedimentary deposits carry gold across much of Victoria's gold fields Ballarat - Bendigo and including under Melbourne - the Silurian Melbourne Formation (these were deposited in deep water in contrast to Devonian sediments which deposited in shallow waters and were later largely covered by volcanic flows laying down basalt in the past 5 million years)
  • Devonian period (420-360mya)
    • conditions were warm in Australia
    • 439-400mya, the hard sandstone deposit from erosion of the Petermann Ranges folded and tilted 85deg in the Alice Springs Orogeny to form Uluru 3)
    • 420-408mya, The Early Devonian Bindian Orogeny was associated with SSE transport of the Wagga–Omeo Zone that was synchronous with thick sedimentation in the Cobar and Darling basins in central and western NSW.
    • 411-386mya, the granites of Melville Caves and adjacent regions in NW Vic form
    • 405-385mya, Tabberabberan Orogeny eastern part of the Melbourne Zone
    • 400-385mya, Bulla Granites of the western part of the Melbourne Zone form
    • Buchan Rift Zone in Victoria
    • 372mya: Frasnian-Fammenian extinction event 50% of genera and 90% of families become extinct and was followed by a glaciation event
      • this could have been triggered by the c358-372mya Woodleigh Crater in Western Australia
        • could have been a 5-6km diameter asteroid - 4th largest since Hadean era causing megatsunamis, volcanism in Victoria, global forest fires, volcanic winters, brief glaciation event and could have triggered the global Devonian extinctions due to mass plankton die off and disruption of the food chain
    • Victoria experiences a very high level of volcanism which may have been further increased after the Woodleigh crater impact event in WA and the volcanism alone could have been responsible for the Devonian extinction event
      • 374mya: Cerberean Caldera supervolcano forms the Marysville Igneous Complex within the Lake Eildon Nat Park and last eruption 365mya with 27km caldera diameter which then collapsed 1-2km into the earth
      • Acheron caldera (same magma chamber as Cerberean)
      • Mt Macedon erupts
      • Mt Dandenong erupts
      • massive volcanoes in western Victoria near Rocklands forming the:
        • Moralla gemfields of geodes and smoky quartz due to unique slowly erupting rhyolitic lava now covered in 2-6m of sediment
        • various ignimbrite layers
    • From the middle Devonian period to the beginning of the Cretaceous period (a span of some 250 million years), most of Victoria was no longer covered by ocean and several thousand metres of sediments were eroded away to form a nearly level plain and which exposed granite formed in the Middle Devonian period.
    • 365mya: the You Yangs batholith magma chamber very slowly cooled and solidifies deep under the sea which then receded and eroded the overlying sedimentary material to form the granite which is the exposed residual You Yangs
    • 360mya: Hangenberg extinction event lasting 100,000-300,000yrs due to profound oceanic anoxia and which would result in crude oil deposits forming
      • this could have been triggered by the dual East Warburton impact craters in central Australia dated at 300-360mya which again increased volcanic eruptions in Victoria
  • Carboniferous period (360-mya)
    • Pangaea supercontinent formed
    • 330mya: north-south Temperance Reef of gold/quartz deposited under Nth Ballarat (at depth of 300m present day Ballarat but southern end abruptly disappeared and has not been found)
      • horst and graben event presumably moved the southern end deeper in a depression which then became buried by sediment from erosion of Black Hill horst section and then also later by volcanic activity which would suggest the reef is at ~180m depth under Ballarat East
    • a major ice age left over half of Australia glaciated
    • the great Coal Forests in Australia and the beginning of the evolution of ferns, seed ferns, horsetails and gymnosperms
    • presumably the Gondwanide orogeny created the orogenic Great Dividing Range on Australia's east coast region which formed 300mya and they are believed to have been as high as any mountains on the planet today, but they have been almost completely eroded since

Pangaea supercontinent, much of Pangaea was in the southern hemisphere and surrounded by a superocean, Panthalassa.

Fossil evidence to support Pangaea concept

Permo-Triassic period (289-201mya)

  • sea levels had dramatically fallen from around 150m higher than current to around current levels by 300mya and then continued to rise for the next 200 million years until they peaked at around 100mya
  • formation of a rift basin on the West Australian coast creating de-oxygenated rift valley lakes in the Swan Coastal Plain and Pilbara resulting in petroleum
  • Antarctica has been near or at the South Pole since the formation of Pangaea about 280 Ma
  • a major Permian ice age which left over half of the continent glaciated and this eroded then extensive central Australian mountain ranges such as the Petermann Ranges
  • 280-160mya: ice sheets covered most of south and southeastern Australia (eg. Werribee Gorge)
  • c250mya a massive asteroid slammed into Antarctic's Wilkes Land and by weakening the earth's crust in that region, appears to have created the necessary catalyst for the separation of Australia and Antarctica, the formation of the Rift Valley, and presumably, the Permian Extinction event, the massive NSW volcanic complex as well as perhaps an antipodal effect to cause the Siberia Traps Flood Basaltic Volcanic Eruption
  • Permian Extinction event 252mya greatly impacted insects and resulted in the loss of over 90% of marine and 70% of terrestrial species
  • the Triassic (252-201mya) was getting hotter and dryer in Australia but a large part of Australia was under the influence of a monsoonal regime.
  • the South Pole was over eastern Australia but there were no ice caps and carbon dioxide levels were about three times higher than today and coal swamps had virtually disappeared. Most of Australia was land but some large sedimentary basins persisted.
  • 240mya - giant amphibian Arenaerpeton supinatus inhabited freshwater rivers

Jurassic period (200-145mya)

  • western Australia had a tropical savannah to jungle environment
  • 182mya initial rifting of East-Gondwana starts in a SE orientation 4)
  • Pangaea supercontinent begins breaking up 175 mya
  • Australia was mainly at 45-60degS, Australia begins rifting away from Antarctica in the Jurassic, this caused subsidence which formed the Gippsland, Bass and Otway Basins in Victoria and the offshore shelf basins of South Australia and Western Australia, all of which host significant oil and gas deposits
    • a 600km wide Rift Valley formed and the crust at the inner 350km thinned from 40km to 10km thick allowing the hot lithosphere to rise closer to the surface resulting in magma being forced upwards
    • the rifting commenced at the West Australian end c160mya and would result in the North-West oil and gas deposits
    • this large Rift Valley basin then started slowly filling up with sandstone and mudstone sediments from rivers which reached thicknesses of 3000m
    • accumulated swamp material would later be compacted to form coal seams such as at Wonthaggi
  • c150mya, an extensive sea forms between Africa and Antarctica
  • c150 Mya a strip of terrain separated the present coast of eastern Australia from the proto-Pacific Ocean. This terrain is now marked by the Lord Howe Rise, Queensland Plateau and New Caledonia.
  • Most of Australia was land with large sedimentary basins developing in both eastern and western Australia, but there is not much evidence for dinosaurs in Australia during this period, unlike the rest of the world
  • evolution of Wollemi pines (100-200mya) which once grew across most of Australia but now only some 200 wild specimen remain, hidden in a secret part of Wollemi NP in NSW 5)
  • there were no polar ice caps and the world climate was warm and increasingly humid with little differentiation into climatic belts. Carbon dioxide levels were about seven times higher than today.

Cretaceous period (145-66mya)

  • 160-132mya, 1st phase of rifting, the West Australian end of the rift had opened up as far as the Great Australian Bight.6)
  • 140mya Africa separates from Sth America
  • by 132mya the position of the South Pole had shifted, bringing Australia's most southerly point at the time, somewhere near the Queensland-New South Wales border to about 80deg South. By 120mya the South Pole was close to Tasmania.
  • 132-96 mya, the remainder of Australia separated. During this phase, India started rotating northwestward from Australia. As a result of this the Perth Basin subsided allowing the sea to flow in. Australia was joined to Antarctica along the eastern edge of that continent. What is now Australia's east coast was then it's southern coast.
    • it is probable during this period that the two remaining Eidothea sp. which include Nightcap Oak found only in northern NSW and another species found near Cairns, both belong to Proteaceae subfamily Proteoideae suggesting an origin in Africa - earliest known fossils are 15-20mya from Ballarat, the fruit of which are little changed from today7)
    • 2nd phase, rifting shifted direction. Australia rotated to the northwest, so that the southern (now eastern) end of the rift opened forming the Otway Basin and Torquay Basin. About 15 million years later rifting of an arm of the Tasman Sea formed the Gippsland Basin. This rotation squeezed the West Australian section, forcing thinner basin crust, with overlying sediments, against the solid Yilgarn Block. This resulted in the heaving up of the Stirling Ranges.
  • 130mya: Gosse's Bluff meteorite impact crater 20-25km wide (now 6km wide)
  • 125mya, small dinosaurs on the present south Victorian coastline (formerly, the Australian-Antarctic rift valley) such as Galleonosaurus dorisae, Qantassaurus intrepidus and 12 million years later, Diluvicursor pickeringi - these ornithopods are closely related to those from Patagonia in Argentina 8)
    • 110mya elaphrosaur found at Eric the Red West area of the Eumeralla Formation in the Otways in 2015
    • 107mya a new large megaraptorid Theropod dinosaur bones with 20cm long hand claw found in the Eric the Red West area of the Eumeralla Formation in the Otways in 2011-2017
    • 95mya Australovenator megaraptorid Theropod dinosaur, ornithopods and large long necked sauropods (Diamantinasaurus and Savannasaurus) lived in Queensland
  • pre-109mya, Eucalypts evolve somewhere in the Weddellian Biogeographic Province (which includes southern South America, western Antarctica and south-eastern Australia), in an area with high natural fire frequency
  • 110mya, Australia's 1st mammals evolved such as the 1st monotremes (ancestors of the platypus) which appeared before the 1st marsupials (evolved 100mya in Nth America) migrated from South America and which arrived in Australia c55 mya (Tasmania was still connected to Antarctica until 30mya)
  • 112-65mya, the first Varanidae family of monitor lizards evolved in Asia, migrated to Africa 49-33mya (possibly via Iran), and to Indonesian archipelago 39-26mya, thence to Australia
  • Atlantica, today's South America and Africa, finally separated from eastern Gondwana (Antarctica, India and Australia)
  • India moved northwards from Pangaea then 40mya later, Australia starts moving northwards with continued rifting from Antarctica resulting subsidence and the formation of a rift valley and vast flood plain where Bass Strait is
    • Victoria's southern coast (especially around Inverloch) has areas of early Cretaceous period layers of siltstone and sandstone as well as conglomerate exposed which contains dinosaur fossils as well as early amphibians and mammals from 105-120mya when Victoria was located at latitude 70-75deg South and the climate was cool temperate similar to current day Tasmania uplands. Vulcanism dated to 99.9mya extruded igneous rock over some areas. The swampy backwaters were to form the coal seams as well as the oil and gas deposits in the region.
  • Whitsunday Islands formed from volcanism
  • Madagascar separates from India (100-90mya)
  • sea level rise and water entering the Carpentaria Basin resulted in flooding of central Australia, peaking in 115-110mya, forming the muddy, stagnant Eromanga Sea (the size of 1/3rd of the continent but poorly connected to the oceans) which broke the continent into four distinct islands which resulted in local diversification of flora - South Western Australia, Adelaide Region and South-Eastern Australia
    • fossils of a 6m long 100mya elasmosaur, a type of plesiosaur, which was an aquatic reptile, was found near the remote western Queensland town of McKinlay in 2022 9)
    • the marine deposits of sandstone and limestone between these islands meant that:
      • the deep underground freshwater sediments became covered with an impermeable layer and thus formed the Great Artesian Basin which continued to be fed with fresh water from the east as at the eastern edge of the basin the layers of sandstone are warped up sufficiently to allow water to seep into it from the rain falling on the western slope of the Great Divide, but this water takes 2 million years to reach Lake Eyre!
      • once the flood was over, the flora could not migrate to other islands due to the pH of the limestone soils and the high salinity of the sandy soils between them, and this forced plants to evolve to tolerate these soils
      • the acidic oxidative weathering resulted in this region having the highest prevalence of opals in the world
  • Australia had a cool, wet climate
  • much of Australia was covered with conifer forests, cycads and ferns while dinosaurs still dominated
  • 96mya, Great Dividing Range formed
  • 85mya: New Zealand, New Caledonia and the rest of the now submerged continent of Zealandia begin to separate from Australia forming the Gippsland Basin (and the Thorpdale volcanic group active 66-5mya; Carrajung volcanic group 59-47.8mya), Tasman Rift Zone and the Tasman Sea and possibly the Port Phillip Sunklands - this halted 55mya 10)
  • 85-65 Ma, Tasmania was still connected to Antarctica by the stretched crust of the South Tasman Rise. Climate was hot and humid. Australia was separated from Antarctica by 100km. Bass Strait was then the Bassian Plain - a rift valley of river flood plains, swamps and lakes.
  • Australia appears to have been largely spared in the global mass extinction event of 65-66mya when 75% of animal species died out including all the dinosaurs - this is now confirmed to be due to an asteroid hitting Mexico's Yucatan Peninsula where it created a 200km crater. There had been a preceding increased volcanic activity in the Deccan which was in fact responsible for a brief warming phase 200,000 years before the mass extinction, but this had no long-term effect on life and the climate.
  • 65mya the southern tip of Sth America was still connected to Antarctica, as was Australia, but Africa, Madagascar and India were well separated, having broken away 200-250mya.
  • late Cretaceous and early Tertiary extensive volcanic lava flows down many valleys in South Gippsland (eg Warragul, Mirboo, Leongatha as well as on the southern Mornington Peninsula around Red Hill)

www.abc.net.au_cm_lb_10889396_data_gondwana-1-data.jpg

125mya there was a 4000km long volcanic region along Australia's east coast.11)

Tertiary period (65-2.6mya)

  • In the Tertiary period (65 mya) the climate was moist and mild. The entire Australian continent was probably covered by a subtropical rainforest-type vegetation.
  • 65mya, further drifting away from Antarctica results in three interconnected marine basins (Otway, Gippsland and Bass basins) forming along the southern edge of Victoria’s continental plate and significant marine sediments were laid down in shallow seas. Some parts of these basins now lie onshore but most are to be found beneath Bass Strait where commercial oil and gas reserves have been found within these sediments.
  • 63mya, the islands of Indonesia start to form from volcanic activity resulting from the Indian and Australian plates colliding and slipping under the Sunda Plate.
  • 60mya, south-eastern South Australia started to sink and rivers began to deposit sediment into the newly forming Lake Eyre Basin
  • 56mya: start of the eocene epoch
  • 55mya: Tasman Rift event ends perhaps due to start of a subducting event under NZ which is ongoing and is now possibly pulling on Victoria as the southern island is subducting eastwards while to the north of NZ it is subducting westwards and Australia continue moves northwards
  • 55mya, small marsupials migrate to Australia from Sth America via Antarctic
    • perhaps the ancestors of the Hickmaniidae spider migrated from Andes to Tasmania at this time
  • at 50mya, earth had tropical conditions as far as latitude 40deg, there was no continental glaciation and even at the south pole, the climate was cool temperate, thanks largely to CO2 levels being 6x higher than pre-industrial levels at 1700ppm and thus sea levels were 150-200m higher than present, but then started a prolonged global cooling phase which we are still in and has resulted in glaciation events which have intensified over the last 1 million years
  • 50mya, the Transantarctic Mountains were thrust up.
  • 50mya: Pacific Ring of Fire formed as Zealandia continued to sink in a “subduction rupture event” 12)
  • 40mya, whales evolved from ancestors of the hippopotamus
  • 38-36mya, Australia's climate changed becoming much drier and duricrusts formed over much of the continent, as the large-scale ice sheets became established in East Antarctica
  • 33.9mya: start of the oligocene epoch
  • From 30-35mya, there was a period of global drying and cooling (perhaps due to the formation of the Himalayas which increased Earth's total rainfall, increased rock weathering which washed out carbon dioxide levels, while the uplift of the Tibetan Plateau above the snow line increased the albedo effect, which combined with less greenhouse gases made the earth more sensitive to small changes in orbital variations - solar flux at 60deg latitude can vary 25% due to orbital variations)
  • 27mya, the circum-polar Southern Ocean formed with the last connections of Sth America and of Tasmania to Antarctica gone which then allowed the Antarctic to freeze, being isolated from the warmer ocean currents.
  • 26-27mya: volcanic eruptions of the Glasshouse Mountains in Queensland
  • 28-20mya: Port Phillip sunklands form in Victoria from a mountainous past due to rift event and sea level rise flooding the area from the Otways, across Port Phillip Bay and to the north of Melbourne
  • late Oligocene (c25mya?) to Middle Miocene (c10mya?): green to grey richly fossiliferous silt marine sediments known as the Fyansford Formation laid down on top of older volcanic basalts. These were in some places with calcareous lenses, or even limestone such as at Green Gully, near Keilor
  • 25mya: NZ mountains form from the subducting events under NZ and this may have pulled on Victoria forming the Port Phillip Sunklands
  • 25mya Australian continent colonised with Elapid snakes - presumably an early sea krait
  • 25mya fossil of a large 50kg wombat like creature Mukupirna fortidentata discovered near Alice Springs in 2023 shared a common ancestor with wombats and is an intermediate evolution with koala-like animals
  • 25mya: 2500kg Diprotaton optatum marsupial evolved (extinct ~25000yrs ago) 13)
  • 24mya: small Thylacoleonidae carnivorous marsupials evolved from wombat ancestors
    • Microleo attenboroughi evolvd 18mya
  • 23mya: miocene epoch starts
  • a period of thawing of Antarctica ice
  • the rise of the Eucalypts which were a minority of plant life in Australia 30-50mya but eventually flourished from 21mya (the oldest known fossil in Australia) onwards, initially in the drier interior but as these areas became too dry, in the Miocene, they migrated to the margins and overtook the previously dominant coastal non-Eucalypt forests thanks to their evolutionary advantages with fires which their design promotes, and their tough sclerophyll leaves which tolerate drought and heat, their opercula which cover the flowers preventing it from drying out or being attacked by insects. However, frequent fires will wipe out even Eucalypts locally as they are unable to re-seed or regenerate from lignotubers or budding and presumably this then leads to desertification.
  • 22mya, “modern” penguins evolve in Australia and NZ then migrate to Antarctica and 12mya when the Drake Passage between Sth America and Antarctica opened, they migrated to the other continents14) Penguins had split from the sister group of Procellariiformes 60mya.
  • 20mya, Australia had drifted far enough north for its northernmost parts to move into the zone of influence of the tropical monsoon climate
  • 17-19mya - Riversleigh, Boodjamulla National Park, N-W Queensland World Heritage Site of limestone fossils (“D-site”) and New Riversleigh
    • cells are so well preserved even the nuclei are fossilized
    • desert sloth - “marsupials the size of sheep, which graze in treetops and hang upside down like sloths”
    • sabre-toothed bandicoot
    • snakes
  • 15mya the Antarctic ice sheet re-formed
  • 15mya goannas migrated to Australia from the Nth Hemisphere
  • 10mya increasing aridity and prolonged droughts was being caused in Australia, especially in the interior, by the greatly expanding ice sheets in Antarctica. This led to reduced erosion and deposition.
  • c8mya Pythonidae migrate to Australia from Asia although some had migrated to NW Australia 14mya? 15)
  • 4-20mya Australian Elapid snakes evolve into the modern genera of Elapids
  • 6-7mya 1st humans evolve in Africa
  • 6-7mya Hanging Rock, Camel's Hump, The Jim Jim and Brock's Monument volcanic eruptions which would leave the unique mamelons we see today due to the viscous magma plugging the vents
  • 5.3mya: start of the pliocene epoch
  • Sand deserts and large inland salt lakes formed in Australia within the last 5 million years
  • the Australian megafauna evolved
  • 80% of Australian native flora species are found only in Australia
  • Australian and Indian rainforests share 47 genera thanks to the close proximity in Gondwana
  • 2-5mya: volcanic eruptions in Victoria produce extensive laval sheets forming the Werribee and Keilor basalt plains
    • west-east running Yarrowee River in Ballarat forms after volcanic activity 4-7mya covered the old north-south running Deep Lead ancient rivers which had been uplifted as Black Hill by a Horst and Graben events due to the splitting of Antarctica from Australia and which then formed sedimentary deep leads such the under Bakery Hill reef then covered by basalt
  • 2.8mya - the connection of North and South America at the Isthmus of Panama cut off the warm ocean currents from the Pacific Ocean entering the Atlantic Ocean leaving only the newly created Gulf Stream to transfer heat to the Arctic Ocean, driving warm, wet weather over northern Europe which allowed increased rainfall and thus ice production over the Arctic Cap, laying part of the foundation for the Quaternary Ice Age Event

Quaternary Period (2.58mya-present)

Pleistocene

  • 2.58mya, the Quaternary Glaciation / Quaternary Ice Age event resulted in:
    • formation of the Arctic ice cap
    • a rapid desertification of the Lake Eyre Basin
    • cycles of glaciation with ice sheets advancing and retreating on 40,000- and 100,000-year time scales called glacial periods which occurred at 350,000yrs ago, 250,000yrs ago, 140,000 yrs ago and the most recent one peaked 18,000yrs ago and ended 10,000yrs ago, over this time there have been several “warm periods” when temperatures rapidly rose similar to present day but they only last 3000-4000yrs before steadily cooling into another glaciation period 16)
      • 129,000-116,000 years ago in the last inter-glacial era when the West Antarctic ice sheet melted due to <2degC ocean warming, sea levels possibly rose 6-9m17)
    • sea levels falling by 110m
  • 2.5-2.7mya: substantially reduced sea surface temperatures and thus humidity results in groundwater levels dropped between 10m and 20m and the Nullarbor Plain changing from lush forests to arid land and severing the ecological connections between east and west Australia (eg Eucalypts and black cockatoos)
  • 2mya: Volcanoes to the north of Melbourne.Lava flows erupted from Hayes Hill near Mernda, flowed down the ancestral Merri Creek and Darebin Creek valleys into the Yarra Valley at Fairfield and down that valley onto the Yarra delta as far as the present site of Spencer Street bridge. Yarra River became entrenched along the boundary between the these lava flows and the softer Silurian bedrock
  • Murray Canyons form, as sea levels were much lower, the pleistocene Murray River flowed to the edge of the Continental Shelf and carved out 5km deep canyons (twice as deep as the Grand Canyon) - these are now under the Southern Ocean south-east of Kangaroo Island
  • 2mya: Wolf Creek Meteorite Crater nickel-iron meteorite impact in the Kimberleys 850m wide
  • 2mya: Thylacoleo carnifex the 50-160kg carnivorous marsupial lion evolved 18) 19)
  • 1.5-1.6mya H. erectus man lived in Indonesia but no evidence he made it to Australia
  • 1.5mya megalania - a giant monitor lizard (became extinct c50,000yrs ago)
  • 1.5mya: Anakies in Victoria last eruption
  • 1mya: last eruption of Mt Warrenheip near Ballarat
  • 900,000 yrs ago - weathering of mountains result in quartz sediment from northern NSW rivers such as the Hawkesbury travel northwards due to South-east trade currents and form the sandy beaches along the coast, culminating in the development of Fraser Island, the world's largest sand island, and what is though to have allowed the development of the Great Barrier Reef as further sand gets pushed north-eastwards into deep waters off the continental shelf allowing the coast northwards to become dominated by corals.
  • 470,000yrs ago: Mt Franklin last eruption (near Daylesford, Vic)
  • 100-150,000yrs ago: Mt Buninyong 1st erupts producing a steep scoria cone and the 6km Clarendon lave flow travelling SE. Later a lava lake formed on Mt Buninyong and resulted in the westward lava flow over what is now Buninyong
  • 120,000yrs ago: the Last Interglacial period when global temperatures were similar to current temperatures (0.5 – 1.5degC warmer than preindustrial levels)
    • sea levels were 5-10m higher than current and this appears to be due to the collapse of the West Antarctic Ice Sheet (WAIS) at that time which would account for 3-5m of the sea level rises and is evidenced by DNA in octopus of the region 20)
  • 70,000yrs ago: modern course of the Murray River was carved when a series of earthquakes and aftershocks that went for years lifted the ground along the 80km Cadell fault line which stretches from Deniliquin through Echuca, to Rochester in northern Victoria. A series of six very large earthquakes events occurring every 5000-10000yrs formed the fault scar, which is up to 10 to 15 metres high at Mathoura resulting in the river being diverted from Mathoura to Echuca. This fault line is regarded as being dormant as no quakes have occurred in the past 20,000yrs, although it could be overdue for its 1 in 10,000yr magnitude quake.
  • 20,000-50,000 yrs ago, placental mammals such as bats and rodents made their reappearance in Australia as Australia continued to move closer to Indonesia
  • Australian flora was largely unaffected by the 4 main Ice Ages, as unlike the very thick widespread ice glaciation up to 3km thick in northern continents, these were mainly only 10m thick and only reached 30m thick in the higher altitudes of Tasmania and the Snowy Mountains
  • c50,000yrs ago Aboriginal indigenous peoples migrated to northern Australia from Sri Lanka region
    • the Gulf of Carpentaria was a massive fresh water lake at the time and most likely a very attractive place for the founding population
    • genetic lineages show that the first Aboriginal populations swept around the coasts of Australia in two parallel waves over a period of 2000-3000 years. One went clockwise and the other counter-clockwise, before meeting somewhere in South Australia.
    • genetic patterns suggest that populations quickly settled down into specific territory or country, and have moved very little since and stayed connected within their realms for up to 50,000 years despite huge environmental and climate change.21)
  • Australian megafauna die out
    • Varanus priscus, a giant goanna formally known as Megalania prisca, became extinct c50,000yrs ago
    • 2.4kg giant skink Tiliqua frangens 22)
    • c40,000yrs ago, 13 species of super-sized megafauna species, including five reptilian megapredators, a marsupial “lion” and the world’s largest wombats and kangaroos became extinct near Mackay, Qld and the cause seems to be successive loss of water flow, intensified drying, increased burning and vegetation change although the arrival of Aborigines several thousand years earlier may also have contributed 23)
  • 37,000yrs ago - Tower Hill volcanic eruption in SW Victoria covers indigenous axes and presumably forms the oldest known oral history still being told by Aboriginal Gunditjmara people of the area 24)
  • c20,000yrs ago the entire north-west shelf was dry land and inhabited by Tiwi people
  • the glaciation maximum which occurred 18,000 yrs ago resulted in the central basin of Bass Strait being enclosed by raised sills forming a large shallow lake
  • rapid global sea level rises between 14,500 - 14,100 years ago (during Meltwater Pulse 1A) and between 12,000 and 9,000 years ago resulted in the rapid inundation of approximately 50% of the Northwest Shelf
  • ~12,000yrs ago, Mt Buninyong has another major eruption destroying the previous scoria cone

www.abc.net.au_news_image_10914308-3x2-700x467.jpg

Migration of Australian indigenous tribes based on Hep B virus strains to Sahul (the connected landmass of New Guinea, Australia and Tasmania 50,000yrs ago) 25)

Holocene

  • 11,650 yrs ago marked the end of the last glaciation event and the start of an interglacial period
  • sea levels rose resulting in:
    • the sills of the Bassian Basin were breached resulting in the formation of Bass Strait 8000 yrs ago which now has an average depth of 60m and Port Philip Bay filling with sea water instead of being just a depressed swamp land
    • Sundaland (greater Indonesia) was submerged under shallow sea, creating Malacca Strait, South China Sea, Karimata Strait and Java Sea and forming Malay peninsula, Sumatra, Java, Borneo and other islands.
    • New Guinea and Aru Islands became separated from the Australia mainland
  • 8000 yrs ago - peak of natural interglacial warming period but the expected fall in CO2 levels and temperatures due to orbital effects have not been realised initially due to agricultural clearing of land, then 5,000yrs ago rice terracing cultivation and beef cattle domestication which caused a rise in methane levels, and now industrialisation usage of fossil fuels which add 9 gigatons of CO2 into the air each year (volcanoes add 0.2 gigatons per year) has further contributed to rapidly rising greenhouse gases which has averted another glaciation period
  • 5000 yrs ago - south coast Australia and SW coast of NZ hit my a 200m mega tsunami caused by comet impact into Indian Ocean - the Burckle Crate, depositing seismic chevrons and causing coastal scarring (and building the 600 foot high mountains in Madagascar)
  • 5000 yrs ago - most of Australia suffered a drought for several centuries with only small wetter pockets being unaffected - The Grampians, Mount Buffalo, Flinder's Ranges. This drier period with nutrient poor soils and frequent fires allowed Eucalypts and Acacias to evolve from the northern rainforests and dominate the dry sclerophyll regions.
  • c5000 yrs ago - the dingo is introduced into mainland Australia probably via New Guinea - it is closely related to East Asian domestic dogs
  • 4850 years ago the latest of the volcanic activity occurred in the Mt Gambier region in South Australia, and about 4500 years ago at Tower Hill in Victoria.
history/evolution_australia.txt · Last modified: 2023/12/22 20:54 by gary1

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