Adelaide Geosyncline
Encyclopedia
The Adelaide Geosyncline (also known as Adelaide Rift Complex) is a major geological province in central South Australia
. It stretches from the northernmost parts of the Flinders Ranges
, narrowing at the Fleurieu Peninsula
and extending into Kangaroo Island, and composes the two major mountain ranges of the State: the Flinders Ranges
and the Mount Lofty Ranges
. The sediments in the rift complex were deposited between about 870 Ma (the middle Neoproterozoic
) to ~500 Ma (the end of the Cambrian
). They consist of a thick pile of sedimentary rocks and minor volcanic rocks that were deposited on the eastern margin of Australia during the time of break up of the supercontinent Rodinia
. A number of authors have noted the similarity in these sedimentary rocks with rocks found in western North America and have suggested that they were formerly adjacent to each other in Rodinia. This is one major correlation in the so-called SWEAT (SW USA against East Antarctica) reconstruction
of Rodinia (Moores 1991; Dalziel 1991).
s, shale
s, and sandstone
s indicate a predominantly marine environment.
(mountain-building period) extending into the Ordovician
. Foden et al. (2006) suggest that this orogeny lastet from ~514 Ma to 500 Ma. This event is called the Delamerian Orogeny, named after a small town on the Fleurieu Peninsula where evidence was found for the event. The orogeny caused substantial folding, buckling, and faulting of the strata, and resulted in the creation of a major mountain range, the eroded stumps of which can today be seen as the Mount Lofty and Flinders Ranges.
Accompanying this folding and faulting were several intrusion
s: the granites at Victor Harbor
were intruded at this time, as were those at Palmer
in the eastern South Mount Lofty Ranges.
Not all of the Geosyncline experienced tectonic activity; the deposits in the Stuart Shelf to the northwest remained undisturbed (and still do today), while limestones and shales were deposited in the Cooper and Pedirka Basins to the north and northeast.
of the northern Flinders in 1946 are of worldwide significance for being some of the oldest examples of fossilised animal life ever found. They date from the very end of the Neoproterozoic
, and in 2004 the location gave its name to the last geological period of the era, the Ediacaran
.
The ranges formed during the Delamerian orogeny continue to erode, and intra-plate subsidence is occurring. In the South Mount Lofty Ranges this has resulted in rifting and the formation of graben
structures, creating the long parallel faults which shape the Adelaide Plains
.
South Australia
South Australia is a state of Australia in the southern central part of the country. It covers some of the most arid parts of the continent; with a total land area of , it is the fourth largest of Australia's six states and two territories.South Australia shares borders with all of the mainland...
. It stretches from the northernmost parts of the Flinders Ranges
Flinders Ranges
Flinders Ranges is the largest mountain range in South Australia, which starts approximately north west of Adelaide. The discontinuous ranges stretch for over from Port Pirie to Lake Callabonna...
, narrowing at the Fleurieu Peninsula
Fleurieu Peninsula
The Fleurieu Peninsula is a peninsula located south of Adelaide in South Australia, Australia. It was named after the French explorer and hydrographer Charles Pierre Claret de Fleurieu by the French explorer Nicolas Baudin as he mapped the south coast of Australia in 1802.Towns of interest in the...
and extending into Kangaroo Island, and composes the two major mountain ranges of the State: the Flinders Ranges
Flinders Ranges
Flinders Ranges is the largest mountain range in South Australia, which starts approximately north west of Adelaide. The discontinuous ranges stretch for over from Port Pirie to Lake Callabonna...
and the Mount Lofty Ranges
Mount Lofty Ranges
The Mount Lofty Ranges are the range of mountains just to the east of Adelaide in South Australia.-Location and description:The Mount Lofty Ranges stretch from the southernmost point of the Fleurieu Peninsula at Cape Jervis northwards for over before petering out north of Peterborough...
. The sediments in the rift complex were deposited between about 870 Ma (the middle Neoproterozoic
Neoproterozoic
The Neoproterozoic Era is the unit of geologic time from 1,000 to 542.0 ± 1.0 million years ago. The terminal Era of the formal Proterozoic Eon , it is further subdivided into the Tonian, Cryogenian, and Ediacaran Periods...
) to ~500 Ma (the end of the Cambrian
Cambrian
The Cambrian is the first geological period of the Paleozoic Era, lasting from Mya ; it is succeeded by the Ordovician. Its subdivisions, and indeed its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latin name for Wales, where Britain's...
). They consist of a thick pile of sedimentary rocks and minor volcanic rocks that were deposited on the eastern margin of Australia during the time of break up of the supercontinent Rodinia
Rodinia
In geology, Rodinia is the name of a supercontinent, a continent which contained most or all of Earth's landmass. According to plate tectonic reconstructions, Rodinia existed between 1.1 billion and 750 million years ago, in the Neoproterozoic era...
. A number of authors have noted the similarity in these sedimentary rocks with rocks found in western North America and have suggested that they were formerly adjacent to each other in Rodinia. This is one major correlation in the so-called SWEAT (SW USA against East Antarctica) reconstruction
Plate reconstruction
Plate reconstruction is the process of reconstructing the positions of tectonic plates relative to each other or to other reference frames, such as the earth's magnetic field or groups of hotspots, in the geological past...
of Rodinia (Moores 1991; Dalziel 1991).
Formation
The Adelaide Geosyncline is a great belt of sediments, deposited in a depression during a time of lithospheric stretching in an arc approximately a thousand kilometres long and several hundred kilometres wide. The thickest parts of the belt are approximately 24,000 m thick. LimestoneLimestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
s, shale
Shale
Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable. Shale is characterized by breaks along thin laminae or parallel layering...
s, and sandstone
Sandstone
Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...
s indicate a predominantly marine environment.
Delamerian Orogeny
This sedimentation ended towards the Cambrian, when plate movements changed and the area experienced an orogenyOrogeny
Orogeny refers to forces and events leading to a severe structural deformation of the Earth's crust due to the engagement of tectonic plates. Response to such engagement results in the formation of long tracts of highly deformed rock called orogens or orogenic belts...
(mountain-building period) extending into the Ordovician
Ordovician
The Ordovician is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 488.3±1.7 to 443.7±1.5 million years ago . It follows the Cambrian Period and is followed by the Silurian Period...
. Foden et al. (2006) suggest that this orogeny lastet from ~514 Ma to 500 Ma. This event is called the Delamerian Orogeny, named after a small town on the Fleurieu Peninsula where evidence was found for the event. The orogeny caused substantial folding, buckling, and faulting of the strata, and resulted in the creation of a major mountain range, the eroded stumps of which can today be seen as the Mount Lofty and Flinders Ranges.
Accompanying this folding and faulting were several intrusion
Intrusion
An intrusion is liquid rock that forms under Earth's surface. Magma from under the surface is slowly pushed up from deep within the earth into any cracks or spaces it can find, sometimes pushing existing country rock out of the way, a process that can take millions of years. As the rock slowly...
s: the granites at Victor Harbor
Victor Harbor, South Australia
Victor Harbor is a city located on the coast of the Fleurieu Peninsula, about 80 km south of Adelaide, South Australia. The city is the largest population centre on the peninsula, with an economy based upon agriculture, fisheries and various industries...
were intruded at this time, as were those at Palmer
Palmer, South Australia
Palmer is a town just east of the Adelaide Hills region of South Australia along the Adelaide-Mannum Road, 70 kilometres east-north-east of the state capital, Adelaide and 15 km west-north-west of Mannum . It is located in the Mid Murray Council local government area...
in the eastern South Mount Lofty Ranges.
Not all of the Geosyncline experienced tectonic activity; the deposits in the Stuart Shelf to the northwest remained undisturbed (and still do today), while limestones and shales were deposited in the Cooper and Pedirka Basins to the north and northeast.
Stratigraphic column
| Eon | Era | Period | Local division | General name | Mt Lofty Ranges | Flinders Ranges |
|---|---|---|---|---|---|---|
| Phanerozoic Phanerozoic The Phanerozoic Eon is the current eon in the geologic timescale, and the one during which abundant animal life has existed. It covers roughly 542 million years and goes back to the time when diverse hard-shelled animals first appeared... |
Palaeozoic | Unconformity Unconformity An unconformity is a buried erosion surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval of time before deposition of the younger, but the term is used to describe... overlaid by Permian Permian The PermianThe term "Permian" was introduced into geology in 1841 by Sir Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian... glacial sediments |
||||
| Cambrian Cambrian The Cambrian is the first geological period of the Paleozoic Era, lasting from Mya ; it is succeeded by the Ordovician. Its subdivisions, and indeed its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latin name for Wales, where Britain's... |
Mid-late | Lake Frome Lake Frome Lake Frome is a large endorheic lake in South Australia, east of the Northern Flinders Ranges. It is a large, shallow, unvegetated salt pan, 100 km long and 40 km wide, lying mostly below sea level and having a total surface area of 259,615 hectares... group |
not exposed | Limestone Limestone Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera.... s, sandstone Sandstone Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,... s |
||
| Early | Kanmantoo group | Metamorphosed Metamorphism Metamorphism is the solid-state recrystallization of pre-existing rocks due to changes in physical and chemical conditions, primarily heat, pressure, and the introduction of chemically active fluids. Mineralogical, chemical and crystallographic changes can occur during this process... schist Schist The schists constitute a group of medium-grade metamorphic rocks, chiefly notable for the preponderance of lamellar minerals such as micas, chlorite, talc, hornblende, graphite, and others. Quartz often occurs in drawn-out grains to such an extent that a particular form called quartz schist is... s, greywacke Greywacke Greywacke or Graywacke is a variety of sandstone generally characterized by its hardness, dark color, and poorly sorted angular grains of quartz, feldspar, and small rock fragments or lithic fragments set in a compact, clay-fine matrix. It is a texturally immature sedimentary rock generally found... s, gneiss Gneiss Gneiss is a common and widely distributed type of rock formed by high-grade regional metamorphic processes from pre-existing formations that were originally either igneous or sedimentary rocks.-Etymology:... es |
Shale Shale Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable. Shale is characterized by breaks along thin laminae or parallel layering... s, siltstone Siltstone Siltstone is a sedimentary rock which has a grain size in the silt range, finer than sandstone and coarser than claystones.- Description :As its name implies, it is primarily composed of silt sized particles, defined as grains 1/16 - 1/256 mm or 4 to 8 on the Krumbein phi scale... s |
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| Normanville Normanville, South Australia Normanville is a small rural town near the coast on the Fleurieu Peninsula, South Australia. It is situated next to the mouth of the Bungala River.-Location and geography:... group / Hawker Hawker, South Australia Hawker is a town in the Flinders Ranges area of South Australia, 365 km north of Adelaide. It is in the Flinders Ranges Council, the state Electoral district of Stuart and the federal Division of Grey. At the 2006 census, Hawker had a population of 229.... group |
Limestones | |||||
| Proterozoic Proterozoic The Proterozoic is a geological eon representing a period before the first abundant complex life on Earth. The name Proterozoic comes from the Greek "earlier life"... |
Neoproterozoic Neoproterozoic The Neoproterozoic Era is the unit of geologic time from 1,000 to 542.0 ± 1.0 million years ago. The terminal Era of the formal Proterozoic Eon , it is further subdivided into the Tonian, Cryogenian, and Ediacaran Periods... |
Ediacaran Ediacaran The Ediacaran Period , named after the Ediacara Hills of South Australia, is the last geological period of the Neoproterozoic Era and of the Proterozoic Eon, immediately preceding the Cambrian Period, the first period of the Paleozoic Era and of the Phanerozoic Eon... |
Marinoan Marino, South Australia Marino is a suburb in the south of Adelaide, South Australia. It sits on coastal hills overlooking Gulf St Vincent, within the City of Marion Local Government Area. It neighbours Seacliff, Hallett Cove and Kingston Park.... |
Wilpena Wilpena Pound Wilpena Pound is a natural amphitheatre of mountains located north of Adelaide, South Australia, Australia in the heart of the Flinders Ranges National Park. The Pound is the most northern point with access via a sealed road in this part of the Flinders Ranges... group |
Pound Wilpena Pound Wilpena Pound is a natural amphitheatre of mountains located north of Adelaide, South Australia, Australia in the heart of the Flinders Ranges National Park. The Pound is the most northern point with access via a sealed road in this part of the Flinders Ranges... subgroup: quartzite Quartzite Quartzite is a hard metamorphic rock which was originally sandstone. Sandstone is converted into quartzite through heating and pressure usually related to tectonic compression within orogenic belts. Pure quartzite is usually white to gray, though quartzites often occur in various shades of pink... s, massive sandstones |
|
| Limestones | ||||||
| ABC Range quartzite | ||||||
| Brachina formation: purple siltstones | ||||||
| Dolomite Dolomite Dolomite is a carbonate mineral composed of calcium magnesium carbonate CaMg2. The term is also used to describe the sedimentary carbonate rock dolostone.... s |
Nuccaleena formation dolomite (marker bed) | |||||
| Cryogenian Cryogenian The Cryogenian is a geologic period that lasted from . It forms the second geologic period of the Neoproterozoic Era, preceded by the Tonian Period and followed by the Ediacaran... |
Umberatana group | Reynella Reynella, South Australia Reynella is a metropolitan suburb of Adelaide, South Australia.It is located 20km south of the Central Business District of Adelaide in the north of the City of Onkaparinga... formation: shales, siltstones |
Glaciation event: Yerelina subgroup tillites | |||
| Angepena formation: shales, siltstones | ||||||
| Sturtian | Brighton Brighton, South Australia Brighton is a coastal suburb of Adelaide, South Australia, situated between Seacliff and Glenelg and aside Holdfast Bay. Some notable features of the area are the Brighton-Seacliff Yacht Club, the Brighton Surf Lifesaving Club, the Brighton Jetty, and its excellent beach... limestone |
Dolomites | ||||
| First of the Sturtian-Varangian glaciations: Sturt tillite | ||||||
| Burra Burra, South Australia Burra is a pastoral centre and historic tourist town in the mid-north of South Australia. It lies east of the Clare Valley in the Bald Hills range, part of the northern Mount Lofty Ranges, and on Burra Creek. The town began as a single company mining township that, by 1851, was a set of townships ... group |
Belair Belair, South Australia Belair is a suburb situated in the southern foothills of Adelaide, South Australia.-Geography:A leafy suburb, Belair was established during the settlement of Adelaide as a source of timber. Parts of Belair have views of the city of Adelaide, the Adelaide Plains and the coast... subgroup: shales, sandstones |
Shales, siltstones, etc. | ||||
| Torrensian River Torrens The River Torrens is the most significant river of the Adelaide Plains and was one of the reasons for the siting of the city of Adelaide, capital of South Australia. It flows from its source in the Adelaide Hills near Mount Pleasant, across the Adelaide Plains, past the city centre and empties... |
Glen Osmond Glen Osmond, South Australia Glen Osmond is a small suburb of Adelaide, South Australia in the City of Burnside located in the foothills of the Adelaide Hills.-References:... slate |
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| Beaumont Beaumont, South Australia Beaumont is a suburb of Adelaide in the City of Burnside. Founded as a purpose-built village by Sir Samuel Davenport in 1848, it initially struggled due to high land prices in the area. However, with Adelaide's inevitable expansion residents eventually settled... dolomite |
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| Stonyfell Stonyfell, South Australia Stonyfell is a prestigious suburb in the foothills of Adelaide in the City of Burnside. It has many parks with walking tracks, waterfalls and bike tracks. St Peter's Collegiate Girls' School is the only school in Stonyfell. The historic Stonyfell Winery is one of Australia's oldest. There is also a... quartzite |
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| Dolomites | ||||||
| Aldgate Aldgate, South Australia Aldgate is a South Australian town located 21 kilometres south-east of Adelaide, in the Adelaide Hills.The town of Aldgate was supposedly named in 1882 after the local hotel the Aldgate Pump, which was named by Richard D. Hawkins, who had additionally opened the nearby Crafers Inn... sandstone |
Conglomerate Conglomerate (geology) A conglomerate is a rock consisting of individual clasts within a finer-grained matrix that have become cemented together. Conglomerates are sedimentary rocks consisting of rounded fragments and are thus differentiated from breccias, which consist of angular clasts... s |
|||||
| Willouran | Callanna beds / Mount Painter complex | not exposed | Wooltana volcanics | |||
| Sandstones | ||||||
| Unconformity underlain by metamorphosed Mesoproterozoic Mesoproterozoic The Mesoproterozoic Era is a geologic era that occurred between 1600 Ma and 1000 Ma . The Mesoproterozoic was the first period of Earth's history with a respectable geological record. Continents existed in the Paleoproterozoic, but we know little about them... basement |
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Fossil life
Fossils are to be found in the Geosyncline; those discovered in the Ediacara HillsEdiacara Hills
Ediacara Hills are a range of low hills in the northern part of the Flinders Ranges of South Australia, around 650 km north of Adelaide. The area has many old copper and silver mines from mining activity in the late 19th century...
of the northern Flinders in 1946 are of worldwide significance for being some of the oldest examples of fossilised animal life ever found. They date from the very end of the Neoproterozoic
Neoproterozoic
The Neoproterozoic Era is the unit of geologic time from 1,000 to 542.0 ± 1.0 million years ago. The terminal Era of the formal Proterozoic Eon , it is further subdivided into the Tonian, Cryogenian, and Ediacaran Periods...
, and in 2004 the location gave its name to the last geological period of the era, the Ediacaran
Ediacaran
The Ediacaran Period , named after the Ediacara Hills of South Australia, is the last geological period of the Neoproterozoic Era and of the Proterozoic Eon, immediately preceding the Cambrian Period, the first period of the Paleozoic Era and of the Phanerozoic Eon...
.
Recent geological history
- See also: Geomorphology of the Mount Lofty Ranges
The ranges formed during the Delamerian orogeny continue to erode, and intra-plate subsidence is occurring. In the South Mount Lofty Ranges this has resulted in rifting and the formation of graben
Graben
In geology, a graben is a depressed block of land bordered by parallel faults. Graben is German for ditch. Graben is used for both the singular and plural....
structures, creating the long parallel faults which shape the Adelaide Plains
Adelaide Plains
The Adelaide Plains is the area in South Australia between the Mount Lofty Ranges on the east and Gulf St Vincent on the west. The plains are generally fertile with annual rainfall of about per year....
.
Further reading
- Foden J., Elburg M.A., Smith P.B., Dougherty-Page J. and Burtt A. 2006. The timing and duration of the Delamerian orogeny: correlation with the Ross Orogen and implications for Gondwana assembly. The Journal of Geology, 114, 189-210.
- Ludbrook N.H., A guide to the geology and mineral resources of South Australia. Government Printer, 1980.
- Preiss W.V. 1987. The Adelaide Geosyncline, late Proterozoic stratigraphy, sedimentation, palaeontology and tectonics. Bulletin of Geological Survey, South Australia, 53, 438 pp.
- Atlas of South Australia