The Clarence Moreton Basin is a

Mesozoic The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceo ...

sedimentary basin Sedimentary basins are region-scale depressions of the Earth's crust where subsidence has occurred and a thick sequence of sediments have accumulated to form a large three-dimensional body of sedimentary rock. They form when long-term subsidence ...

on the easternmost part of the

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

n continent. It is located in the far north east of the state of

New South Wales ) , nickname = , image_map = New South Wales in Australia.svg , map_caption = Location of New South Wales in AustraliaCoordinates: , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , es ...

around Lismore and Grafton and in the

south east The points of the compass are a set of horizontal, radially arrayed compass directions (or azimuths) used in navigation and cartography. A compass rose is primarily composed of four cardinal directions—north, east, south, and west—each sepa ...

corner of

Queensland ) , nickname = Sunshine State , image_map = Queensland in Australia.svg , map_caption = Location of Queensland in Australia , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , established_ ...

. It is the part of the

Great Artesian Basin The Great Artesian Basin (GAB), located in Australia, is the largest and deepest artesian basin in the world, stretching over , with measured water temperatures ranging from . The basin provides the only source of fresh water through much of ...

that extends to the east coast in Australia's central eastern lowlands.

Description

It formed by oblique extension of the underlying Paleozoic

New England Orogen The Hunter-Bowen Orogeny was a significant arc accretion event in the Permian and Triassic periods affecting approximately 2,500 km of the Australian continental margin. The Hunter-Bowen Orogeny occurred in two main phases, a Permian accretio ...

basement. It consists of continental deposits, starting with a small amount of

Triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...

coal beds, and then mostly

Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The J ...

and

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...

sedimentary rocks. The basin covers . The basin was named when the Clarence Basin (named after the Clarence River) and Moreton Basin in Queensland were proved to be one structure. Oil is likely to be present in the basin.

Stratigraphy

The oldest rocks in the Clarence Moreton Basin of New South Wales are the

Chillingham Volcanics Chillingham can refer to: * Chillingham (game), a computer game designed for the visually impaired * Chillingham, New South Wales, a village in New South Wales, Australia * Chillingham, Northumberland, a village in Northumberland in the north of E ...

. These are from some time in the Triassic period, and crop out in a band north and south of Chillingham. They consist of conglomerate at the base, rhyolite, lithic rhyolitic tuff, and shale. The

Nymboida Coal Measures Nymboida is a village in New South Wales, Australia. It may also refer to other subjects in the area: *Nymboida National Park *Nymboida River The Nymboida River, a perennial stream of the Clarence River catchment, is located in the Northern ...

extend from Nymboida to Kangaroo Creek. They consist of lithic sandstones (wackes, minor arenites), siltstone, polymictic conglomerate, coal, rhyolitic tuff, and basalt. The total thickness is over . The outcrop is , and it forms a north west trending band long on the southwest tip of the basin. Fossils reveal a date of middle Triassic. A lower part is called Cloughers Creek Formation. The Basin Creek Formation includes the coal mined at Nymboida. The Bardool Conglomerate forming a thick layer, is also a unit in the coal measures. The conglomerate includes a thick layer of basalt exposed at Copes Creek. The

Neranleigh-Fernvale Beds The Neranleigh-Fernvale beds is a geologic formation in the north east of New South Wales and Queensland, Australia. This formation was created in the Late Devonian to the Early Carboniferous, of a thickness up to . Description This formation ...

are up to 3,500 metres thick. The Red Cliff Coal Measures date to the Late Triassic. It forms an outcropping belt wide and long from Buchanans Head through Red Cliff. The Evans Head Coal Measures are correlated with these, but are further up the north coast at

Evans Head Evans Head is a town in Richmond Valley Council of the Northern Rivers region of New South Wales, Australia. At the 2016 census, Evans Head had a population of 2,843 people. It is 726 kilometres north of Sydney, and 11 kilometres east off the ...

. The basin was next uplifted and eroded and then deepened considerably and Bundamba group rocks form a complete V shape on both sides of the basin. In the northern parts the rock is mostly friable sandstone, but in the south it is divided into conglomerate below and siltstone above. The Laytons Range Conglomerate rests on the basin floor and extends from

Baryulgil Baryulgil is a rural locality in north-eastern New South Wales, Australia. The locality is on the Clarence River in the Clarence Valley Council local government area. History According to the Geographical Names Board, the name is derived from ...

, to Nymboida. The conglomerate often appears as a cliff. The Corindi Conglomerate is a local name for a hailstone sized gravel near

Corindi Corindi River, an open mature wave dominated barrier estuary, is located in the Northern Rivers region of New South Wales, Australia. Course and features Corindi River rises below Knobbys Lookout, in hilly country located to the west of Woolgoo ...

. The Mill Creek Siltstone. are often olive green or yellow-brown with bright red joint planes. The Marburg Subgroup extends for along the western side of the basin into Queensland from Corindi. It is mostly clay cemented cross bedded quartz sandstone, but this is interbedded with

claystone Mudrocks are a class of fine-grained siliciclastic sedimentary rocks. The varying types of mudrocks include siltstone, claystone, mudstone, slate, and shale. Most of the particles of which the stone is composed are less than and are too sm ...

and shale. At the base is the Blaxland Fossil Wood Conglomerate Member at Blaxlands Creek. The fossil wood is in the form of horizontal tree trunks up to long and in diameter. The fossilization process replaced the wood with

limonite Limonite () is an iron ore consisting of a mixture of hydrated iron(III) oxide-hydroxides in varying composition. The generic formula is frequently written as FeO(OH)·H2O, although this is not entirely accurate as the ratio of oxide to hydroxid ...

and

hematite Hematite (), also spelled as haematite, is a common iron oxide compound with the formula, Fe2O3 and is widely found in rocks and soils. Hematite crystals belong to the rhombohedral lattice system which is designated the alpha polymorph of . ...

. The Towallum Basalt is a thick layer near Nymboida,

Glenreagh Glenreagh is a small town in the Clarence Valley in the Northern Rivers region of north-eastern New South Wales, Australia. At the 2016 census, Glenreagh had a population of 900 people. It is on the North Coast railway line, completed to Gl ...

and Moleton trig station overlying the Marburg formation. The Walloon Coal Measures forms a U shape around the east, south and west sides of the basin. It consists of claystone, shale, siltstone, arenites, and coal seams and the plant fossils in it show a Jurassic age. The next layer of rocks in the basin forming a nested U shape in its exposure is the Kangaroo Creek Sandstone. This sandstone has saccharoidal texture, and glistens white and cream. This is not due to angular sand grains, but results from silica crystallization. It is up to thick. The Grafton Formation is the sedimentary unit in the core of the basin. It is the youngest of the beds being between Late Jurassic and Early Cretaceous. It occurs from Grafton to

Casino A casino is a facility for certain types of gambling. Casinos are often built near or combined with hotels, resorts, restaurants, retail shopping, cruise ships, and other tourist attractions. Some casinos are also known for hosting live entertai ...

consisting of soft sandstone, siltstone and claystone. Dolerite has intruded this at

Glenugie Peak Glenugie Peak, also known as Mount Elaine or as Glen Ugie Peak, is a mountain that forms part of the ridge surrounding the Clarence Moreton Basin. It is situated in the Northern Rivers region of New South Wales, Australia, and has an elevation o ...

, and near Banyabba. Rifting along the east coast of Australia commenced and uplifted the eastern side of the Clarence Moreton Basin. This resulted in the splitting off of the

Lord Howe Rise The Lord Howe Rise is a deep sea plateau which extends from south west of New Caledonia to the Challenger Plateau, west of New Zealand in the south west of the Pacific Ocean. To its west is the Tasman Basin and to the east is the New Caledonia ...

and the opening of the ocean floor.

References

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External links

Northern Rivers Geology Blog - Clarence Moreton Basin
Sedimentary basins of Australia Mesozoic rifts and grabens Geology of New South Wales Geology of Queensland