Geology of Australia

The geology of Australia includes with virtually all known rocks of all geological periods, a period of more than 3.8 billion years of Earth's history.

• 5.1 Cambrian
• 5.2 Ordovician
• 5.3 Silurian
• 5.4 Devon
• 5.5 carbon

• Permo - Triassic 6.1
• 6.2 Jura
• 6.3 chalk

• 7.1 Tertiary and Quaternary

Geological Survey

Australia can be geologically divided into several main regions: the archaic shields, the Proterozoic fold belt and Phanerozoic sedimentary basins, and the sedimentary basins and their metamorphic and igneous rocks.

Today's Australian land mass has a thick crust: the thickness of the lithosphere beneath Australia is up to 150 km, of which approximately 70 km continental crust. This is set up primarily of archaic, Proterozoic and Paleozoic granites and gneisses some. Only a thin veil of Phanerozoic deposits covered the ancient rocks of the Australian craton.

Erosion carries these rocks in a steady process and produces by aeolian and fluvial processes extensive dune systems, salt pan deposits and unconsolidated rock, and a profound weathering leads to the formation of powerful and lateritic soil profiles saprolithischen.

Kratonische areas

The large cratonic blocks of the Australian continent lie mainly in the west. These are

• The Yilgarn craton Archean
• The Pilbara craton Archean to Proterozoic
• The Gawler Craton and Willyama block, also with archaic age to proterozoischem

These in turn are bordered by several Proterozoic mountain belts and sedimentary basins, especially

• The Musgrave block of granulite - gneiss and igneous rocks
• The Arunta block with amphibolitfaziell metamorphic rocks and granites
• The Gascoyne Complex, the Glengarry Basin and the Bangemall Basin, which are sandwiched between the Yilgarn Craton and the Arunta Block.

Plate tectonic situation

Australia as a continent is on the Australian plate and is surrounded to the north edge on all sides by oceanic crust. The Australian Plate was part of all super continents, but particularly noteworthy is its relation to Gondwana: from the correspondence of many geological units and the geological development in Australia, Africa, South America and Antarctica Alfred Wegener had derived his theory of continental drift.

The formation of Australia as its own continent began after the fall of Gondwana in the Permian by it solved together with Antarctica from Africa and India. After the separation of Gondwana took place the elimination of Antarctica over a longer period, and Antarctica split only in the Jura completely from Australia. The initial rifting began at the edge of the southern Australian Basin and also had the separation of Tasmania from Australia to the result.

Today, the Australian plate moves with about five centimeters a year in northern direction towards Eurasia. Your North Rim is therefore already occurred in a collision with the Sunda arc and Papua New Guinea, and the outermost Australian shelf is subducted under the group of island arcs. Tensions of this is still in the early stages continent - island arc collision build on data already in the interior of Australia, they are manifested in earthquakes and incipient thrusts up into the Flinders Ranges, far to the south of the continent.

Geological History

The geological history covers wide areas of the Australian continental mass extraordinarily long periods of time.

Archean

In the Archean, the three major cratons of Australia were formed, their history is very complicated and took a long time to complete. Output of the Archean and early Mesoproterozoikum the cratons were in a series of mountain building ( orogenies ) 2400-1600 mya ( million years ago, millions of years before present) combined to form a contiguous land mass. The Capricorn orogeny was responsible for the unification of the Yilgarn Craton with the Pilbara craton to the land mass that makes Western Australia today. Areas affected by this orogeny rocks are in Bangemall basin, open in the Gascoyne Complex and in the basins of Glengarry, Yerrida and Padbury. The connection between the Yilgarn and Gawler craton is not known, since it is covered by younger, Proterozoic - Paleozoic Officer and Amadeus Basin. Maybe these unknown Proterozoic fold belt are formed similarly to the Albany complex and Musgrave Block in southern Western Australia.

Paleoproterozoic

Western Australia

On the southern edge of the Pilbara Craton encamped in the Paleoproterozoic before about 2.77 to 2.3 billion years ( 2.77 to 2.3 Gigajahre, Ga) in the Hamersley Basin with river and marine sediments, the last evidence of a prospective of mountain building environment between the Pilbara craton and the Yilgarn craton from.

The union of the two cratons began about 2.2 billion years in the Capricorn orogeny. In this long-running association process resulted in several sedimentary basins: those formed in the interior of cratons Ashburton and Blair Basin ( ~ 1.8 Ga), the Edmund and Collier basins ( 1.6 to 1.07 Ga), the northern Gascoyne complex ( 1.84 to 1.62 Ga), the Glenburgh - Terrane ( 2 to 1.78 Ga) and the Errabiddy shear zone at the north western edge of the Yilgarn craton.

Between about 2 and 1.8 Ga was formed in Verlaufer the collision on the northern edge of the Yilgarn Craton, a backarc basin, which Bryah Basin, whose volcanic deposits that Narracoota volcanics, could be dated to an age of 1.89 Ga. The lying to the east basin ( Yerrida and Eerarheedy Basin) formed as sedimentary basins on the passive continental margin in the north of the Yilgarn Craton. The climax of the collision of the two cratons led to the deformation of the Bryah and the Padbury Basin in the foothills of the mountains, as well as the western edge of the Yerrida Basin was included. It came to the outflow of flood basalts. The Eerarheedy Basin was verfaltet while the slightly younger Yapungku orogeny, in which also the archaic- Proterozoic fold belt of northern Australia were welded together.

Eastern Australia

The Paleoproterozoic in southeastern Australia is represented by the frequently deformed, highly metamorphosed gneiss areas of the Willyama Supergroup, Olary of the block and the Broken Hill block in South Australia and New South Wales. In northern Australia, the Paleoproterozoic especially in Mount Isa block and complicated folds and - thrust belt occurs. These rocks not only lay witness to an intense deformation, but also a widespread deposition in grave fractures of the continental crust, the development of dolomitic carbonate platforms and the emergence of deep-sea sediments phosphoritischer.

Mesoproterozoikum

Mesoproterozoische rocks build the oldest formations on in Tasmania, they are found on King and Iceland in Tyennan block.

Neoproterozoic

In the Neoproterozoic, the Giles Complex, a series of mafic to ultramafic intrusions in the Musgrave block, which were dated to about 1.08 Ga formed. Widely used are also the same old warehouse aisles in Bangemall basin and in the area of Glenayle and in the igneous Greater Region Warukurna ( Warukurna Large Igneous Province ).

Paleozoic

Cambrian

The Stavely Zone in Victoria is a Terran, which consists of boninitischen to MOR basalts, a connection with the Boniniten the Vulkanitfolge the Mount Read in northern Tasmania is assumed. In New South Wales and Victoria, the Adaminaby layers are widely used, which were deposited in deep water. The Lachlan Fold Belt contains ophiolite sequences, which are classified in the Cambrian, and the autopsies were performed during the Ordovician Lachlan orogeny.

In Central Australia, the Petermann orogeny occurred in the Cambrian. From the rising mountain ranges from a powerful, intracontinental sequence of fluvial sediments in the interior of the central Australian landmass spilled. Randliche platforms and marginal basin on a passive continental margin in South Australia had been formed in the foothills of Delamerischen orogeny. At this time began in Western Australia the formation of marginal basins and marginal union platforms. A supra-regional reference horizon in Western Australia are the flood basalts of the Antrim Plateau, which cover an area of ​​more than 12,000 km ².

Ordovician

In the Ordovician, the Lachlan Fold Belt formed during the Lachlan orogeny, which has a alpinotype tectonics and led to the emergence of the great serpentine belt of western New South Wales. As part of this orogeny the flysch and molasse sediments were annexed, which are now preserved in the slate belts of Victoria and eastern New South Wales.

In Victoria the Ordovician turbidite sediments of the deep water were deposited in the transition from Cambrian, namely the St Arnaud Group and the Castlemaine Group, which are now open in the Stawell and Bendigo zone. In the middle Ordovician the Sunbury Group was deposited, which is now open in the Melbourne zone. At the same time, the Bendoc Group was deposited, and the Molong volcanic arc formed, arising from a lime - alkaline magmas arc which is related to the deposition of the turbidites of the Kiandra Group.

Silurian

During the Silurian was the west and the center of the Australian continent dry land. Between Geraldton and Exmouth Gulf on the outermost coast of Western Australia, however, there was a sedimentary basin, where the river deposits accumulated. In Kalbarri on the Murchison River the footprints of a large Seeskorpions were found, the order was one of the first animals that entered the Australian country. Under the current Great Sandy Desert was at that time a gulf, which was connected to the open sea.

In the area of the basin of Cowra, Tumut and Hill End deep sea sediments were deposited. In the east there were volcanic arcs: in New England, west of Townsville and Cairns, in New South Wales and Victoria, at Yass and Molong, and in the Australian Capital Territory. In New South Wales and Victoria, there was moreover between 435-425 mya to the intrusion of granites, which succeeded about 400 million years of the Bega Batholith. At the granites of New South Wales for the first time ( igneous rocks melted from igneous rocks, engl. ) ( Sedimentary rocks of sedimentary rocks melted, engl. ) Was the difference between the I-type granites and S-type granites found.

Devon

During the Devonian, there was a warm climate in Australia. The majority of Central and Western Australia was the country in the area of the Great Sandy Desert was a great bay, grew up in the coral reefs. Between the north of Rockhampton to the south of Grafton consisted of Calliope bow. From river sands, the sandstones, today make up the Western Australian Bungle Bungle Ranges formed.

In an area of the sea is now off the east coast of Australia, a chain of volcanic mountains eroded, sediments delivered in a basin in parts of present-day East Coast. Here sandstone and limestone came to deposit. In central New South Wales, in the Snowy Mountains, in Eden, New England and near Clermont andesitic and rhyolitic volcanic rocks originated. Baragwanathia longifolia, a plant from the class of Bärlapppflanzen, appeared at this time as the first Australian land plant. The interior of the continent drained a large river system that flowed eastward at Parkes.

The east coast was about 385-380 mya covered by the Tabberabberan orogeny, which squeezed Tasmania, Victoria and southern New South Wales in the east-west direction and folded. Also the northern New South Wales and Queensland was between 377 and 352 mya concentrated.

Carbon

In the Carboniferous collision folded with parts of South America to the Eastern Highlands, their counterparts are today in the Sierras de Córdoba, and in New Zealand. A special feature of the Carboniferous are the notes on a then staged large ice age that gripped more than half of the Australian continent. Remnants of this continuing in the late Carboniferous and the Permian Karoo Ice Age to be found not only in glacial sediments, but also in fossil GELISOL formations, soil formation of an Arctic climate, which today can be found for example in the Hunter River Basin.

Mesozoic

Permo - Triassic

The Permian and Triassic in Australia are dominated by the subduction of the Hunter - Bowen Orogeny on the eastern edge of the continent. During this orogeny, a larger island arc was accreted, and it formed a backarc basin. The process went on for a long time back: he began in the late Carboniferous and lasted until the Middle Triassic. Its end is dated to 229-225 mya.

In western and central Australia the then vast mountain ranges were as the Petermann Ranges removed by the Permo-Carboniferous glaciation, so that powerful navy emerged to fluvial, glacial tillites, and fossil- rich limestones and broad platform sediments were formed. The rifting of the Australian plate from India and Africa began in the Permian, it triggered the formation of a long-standing Riftbeckens from the Perth Basin. In the Swan Coastal Plain (Swan Coastal Plain ) and Pilbara petroleum arose during this rifting, possibly in an oxygen-depleted grave breach basin, which can be compared with the present-day Lake Tanganyika.

Law

In Western Australia, there was a partial merging into jungle tropical savannah during the Jurassic. This testifies to the profound tropical weathering of the regolith in the Yilgarn craton, which can still be seen today. In the Jura to Australia broke away from Antarctica, and led to the formation of the basins of Gippsland, Bass and Otway in Victoria and the shelf basin off the coast of South and Western Australia. Today there are large deposits of oil and natural gas in all these basins. Coal was formed in sedimentary basins of the north-central Queensland, and the deposits of a shallow Epikontinentalmeeres covered most part of Central Australia. Reduction of the passive continental margin and marine transgression covered the Perth Basin. Sediments were poured into the basin from the land, including the Jurassic Cattamarra - coal layers.

Chalk

Begun in the Jurassic rift between Australia and Antarctica continued into the Cretaceous continued, and in the sea, a fully developed mid oceanic ridge formed as the spreading axis from. Even Tasmania dissolved in this process of Australia. The page shifts between Antarctica and Australia during the Cretaceous resulted in the formation of the Stirling Range. These were the last orogenic events in Australia.

Cretaceous volcanism off the coast of Queensland is evidence of a short episode in which an island arc was formed ( today, for example in the Whitsunday Islands handed ). This was followed by the development of a carbonate platform, the formation of sedimentary basins on a passive continental margin tectonics and volcanism in the otherwise quiet Hunter - Bowen - mountain belt. Scattered evidence of volcanism can be found in the form of volcanic sticks also at the edge of the Great Artesian Basin.

Cretaceous deposits are further from the Suratbecken known, and in the Perth Basin the sedimentation continued.

Cenozoic

Tertiary and Quaternary

At the tertiary almost all tectonic processes in Australia found its end. A few examples of continental volcanism can be found for example in the Glasshouse Mountains in Queensland. Here form a series of volcanic buildings whose age decreases from north to south, to terminate in the Quaternary, about 10,000 year-old maars and basalt flows of the Newer Volcanics Province of Victoria small volcanic sticks.