The Mittagong Formation is a

sedimentary rock Sedimentary rocks are types of rock (geology), rock formed by the cementation (geology), cementation of sediments—i.e. particles made of minerals (geological detritus) or organic matter (biological detritus)—that have been accumulated or de ...

unit in the

Sydney Basin The Sydney Basin is an Interim Biogeographic Regionalisation for Australia, interim Australian bioregion and is both a structural entity and a depositional area, now preserved on the east coast of New South Wales, Australia and with some of its ...

in eastern

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

Formation

Laid down in the

Triassic The Triassic ( ; sometimes symbolized 🝈) is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is t ...

Period, it may be seen as an interval of interbedded fine-grained

sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...

and shale between the Ashfield Shale (above) and the

Hawkesbury sandstone Sydney sandstone, also known as the Hawkesbury sandstone, yellowblock, and yellow gold, is a sedimentary rock named after Sydney, and the Hawkesbury River north of Sydney, where this sandstone is particularly common. It forms the bedrock f ...

(below). The maximum thickness around Sydney may be ten metres. Near Town Hall railway station, the formation is 8 metres thick. In the type area at Mittagong it is 15 metres thick.

Whereabouts

In northern

Sydney Sydney is the capital city of the States and territories of Australia, state of New South Wales and the List of cities in Australia by population, most populous city in Australia. Located on Australia's east coast, the metropolis surrounds Syd ...

it can be seen in several areas, such as

West Pymble West Pymble is a suburb on the Upper North Shore (Sydney), Upper North Shore of Sydney in the state of New South Wales, Australia north-west of the Sydney Central Business District in the Local government in Australia, local government area of ...

and Mount Ku-ring-gai. This rock formation is associated with the

critically endangered An IUCN Red List critically endangered (CR or sometimes CE) species is one that has been categorized by the International Union for Conservation of Nature as facing an extremely high risk of extinction in the wild. As of December 2023, of t ...

Sydney Turpentine-Ironbark Forest Sydney is the capital city of the state of New South Wales and the most populous city in Australia. Located on Australia's east coast, the metropolis surrounds Sydney Harbour and extends about 80 km (50 mi) from the Pacific Ocean in ...

References

Geologic formations of Australia Triassic Australia Sandstone formations Shale formations Geology of New South Wales {{Australia-geology-stub

Formation

Whereabouts

See also

References