Editing Geology of Victoria

{{Short description|Geology of Australia}}
{{Use dmy dates|date=August 2023}}
{{Use Australian English|date=August 2023}}
[[File:Australian rock ages-MJC.png|thumb|Australian rock ages]]
[[File:Ausgeolbasic.jpg|thumb|Basic geological units of Australia]]
'''[[Victoria (Australia)|Victoria]]''' is an Australian state, situated at the southern end of the [[Great Dividing Range]]. The Great Dividing Range stretches along the east coast of the continent and terminates near the Victorian city of [[Ballarat, Victoria|Ballarat]] west of the capital Melbourne, though the nearby [[Grampians National Park|Grampians]] may be considered to be the final part of the range. The highest mountains in Victoria (just under 2,000 m) are the [[Victorian Alps]], located in the northeast of the state.

The northwest of the state is mostly [[Cainozoic]] rocks while the southeast is primarily made up of [[Palaeozoic]] rocks.<ref name="fcg">{{cite book |title=Fossil collectors guide |last=Macdonald |first=J. Reid |author2=Mary Lee Macdonald |author3=Patricia Vickers-Rich |author4=Leaellyan S. V. Rich |author5=Thomas H. Rich |year=1997 |publisher=Kangaroo Press |isbn=086417845X |page=155 <!-- |access-date=8 January 2014 -->}}</ref>  There have been no discoveries of [[Precambrian]] rocks in Victoria.

The low flat northwest of the state that borders the [[Murray River]] was once the bed of an ancient sea and the land is much afflicted with [[Salinity in Australia|salinity]]. Saline drainage from Victorian land is one of the sources of the salinity problem in the Murray–Darling River system. Commercial [[Halite|salt]] evaporation is undertaken near [[Swan Hill, Victoria|Swan Hill]].

Central and western Victoria comprise world-class [[vein (geology)#Gold-bearing veins|vein-hosted gold deposits]], hosted mostly in the extensive [[Ordovician]] [[turbidite]]s.

The southeast of the state has enormous [[Lignite|brown coal]] fields.<ref>{{Cite web|url=http://earthresources.vic.gov.au/earth-resources/victorias-earth-resources/coal|title = Coal|date = 13 May 2019}}</ref>

==Volcanism==
There is an area of extensive [[volcanism]] in central and southwestern Victoria, where there are numerous [[volcano]]es and [[volcanic lake]]s. The Western Victorian Volcanic Plains are the third largest in the world after the [[Deccan Plateau|Deccan]] in western [[India]], and the [[Snake River]] Plateau in [[Idaho]], [[United States]]. The most recent volcanic activity was at [[Mt Eccles]], which last erupted a few thousand years ago, making it an active volcanic region.<ref>{{cite web|url=http://www.volcanodiscovery.com/volcanoes/faq/active_erupting.html|title=What is the difference between an active, erupting, dormant and extinct volcano?|work=www.volcanodiscovery.com}}</ref> Large [[basalt]]ic lava flows are present on the western side of Melbourne and in the southwest of the state.

== Neoproterozoic to early Carboniferous ==
This period is covered by the recent [[Geological Survey of Victoria]] publication ''The Tasman Fold Belt System in Victoria''. The sequence of events associated with the building of southeastern Australia reveals that mineralization and magmatic processes are intimately linked with the [[Plate tectonics|tectonic]] development of the region. The history is dominated by east–west compression of predominantly oceanic [[Sedimentary rock|sedimentary]] and [[igneous rock]]s and their resultant [[Fold (geology)|fold]]ing, [[Fault (geology)|fault]]ing and [[Tectonic uplift|uplift]]. Recently, it has become increasingly apparent that major north–south movements have also been involved in constructing eastern Australia.

The [[Palaeozoic]] basement is traversed by [[thrust fault]]s more or less parallel to the north–south structural grain. The largest faults separate rocks with different ages and structural histories, and subdivide Victoria into three main structural rankings consisting of twofold belts (Delamerian and Lachlan), two terranes in the [[Lachlan Fold Belt]] (Whitelaw and Benambra), and ten structural zones (Glenelg, Grampians-Stavely, Stawell, Bendigo, Melbourne, Tabberabbera, Omeo, Deddick, Kuark, Mallacoota).<ref name="geol_of_vic">{{cite book |editor-last=Birch |editor-first=W.D. |year=2003 |title=Geology of Victoria |series=Special Publication |volume=23 |publisher=Geological Society of Australia (Victorian Division) |isbn=1876125330 }}</ref>

===Moyston Fault===
[[File:Island Archway, Great Ocean Rd, Victoria, Australia - Nov 08.jpg|thumb|right|350px|Island Archway on the [[Great Ocean Road]] in [[Victoria, Australia]]. Taken as a 6 segment panorama showing the surrounding coastline.]]
The Moyston Fault is the most important fault as it forms the terrane boundary between the Delamerian and Lachlan fold belts. These twofold belts show important differences. The Delamerian Fold Belt is mainly composed of Neoproterozoic-[[Cambrian]] rocks and was deformed in the Late Cambrian Delamerian [[Orogeny]] whereas the Lachlan Fold Belt contains mainly Cambrian-[[Devonian]] rocks with the main deformations occurring in the late [[Ordovician]] to early Carboniferous interval. The first regional deformation to affect the Lachlan Fold Belt was the Benambran Orogeny, about 450 [[mya (unit)|MYA]], after the Delamerian Orogeny.<ref name="geol_of_vic"/> [[Granite]]s comprise 20% of the total exposed area of the Lachlan Fold Belt and fall within an age range of 440 to 350 MYA. Volcanics associated with the granites are also widespread and cover an additional 5%. Blocks of older [[Crust (geology)|crust]] consisting of Neoproterozoic-Cambrian rocks, such as the '''Selwyn Block''' in central Victoria, were deformed during the late Cambrian Tyennan Orogeny prior to being incorporated into the Lachlan Fold Belt.

===Baragwanath Transform===
The second major structural break in Victoria is the Baragwanath Transform, which occurs along the eastern side of the Selwyn Block. This [[transform fault]] divides the Lachlan Fold Belt into two terranes, the Whitelaw Terrane to the west and the Benambra Terrane to the east. The main difference between these is that orogen-parallel (north-south) transport was more prevalent in the Benambra Terrane, whereas convergent east–west transport orthogonal to the orogen was dominant in the Whitelaw Terrane.

==See also==
{{Portal|Victoria|Geology}}
*[[List of volcanoes in Victoria, Australia|List of Victorian volcanoes]]
*[[Geology of Australia]]
*[[Australian gold rushes]]
*[[Murray–Darling basin]]
*[[Murray–Darling Basin Authority]]

==References==
{{Reflist}}

==External links==
{{Commons category|Geology of Victoria, Australia}}
*{{cite web |url=https://earthresources.vic.gov.au/geology-exploration/victorias-geology |title=Victoria's geology |work=Earth Resources |publisher=Dept. of Jobs Precincts & Regions, Victoria State Government |year=2019}}
*[http://er-info.dpi.vic.gov.au/sd_weave/anonymous.html GeoVIC - Victorian Government Geospatial Application]
*[https://web.archive.org/web/20070102141608/http://vic.gsa.org.au/Victorian_Geology/PreCarb.htm Victorian Geology]
*[[:simple:Western Victorian Volcanic Plains|Western Victorian Volcanic Plains]]

{{Geology of Australia}}
{{Victoria}}

[[Category:Geography of Victoria (state)]]
[[Category:Geology of Victoria (state)]]