The Narrabeen group of sedimentary rocks occurs in the Sydney Basin

Sydney Basin

The Sydney Basin is a sedimentary basin on the east coast of New South Wales, Australia consisting of Permian and Triassic sedimentary rocks...

 in eastern Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

. This series of rocks was formed in the triassic

Triassic

The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...

 period.

It includes various rock types including lithic 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,...

, quartz

Quartz

Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...

 sandstone, 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, claystone

Claystone

Claystone is a geological term used to describe a clastic sedimentary rock that is composed primarily of clay-sized particles ....

s, 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...

 and shales

Shalës

Shalës is a municipality in the Elbasan District, Elbasan County, central Albania. The municipality consists of the villages Shalës, Licaj, Kurtalli, Xibrake, Xherie and Kodras....

, some of which have fossil

Fossil

Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

s of plants and fish.

Above the Narrabeen group is the younger less fertile Hawkesbury sandstone. Below are 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...

 sedimentary rocks including measures of coal

Coal

Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...

.

The Narrabeen group is most famously seen as The Three Sisters

Three Sisters (Australia)

The Three Sisters is a rock formation in the Blue Mountains of New South Wales, Australia. They are close to the town of Katoomba and are one of the Blue Mountains' best known sites, towering above the Jamison Valley. Their names are Meehni , Wimlah , and Gunnedoo .-Geology:The Sisters were formed...

 in Blue Mountains. It can also be seen in various places in the Sydney Basin, such as Long Reef near Narrabeen, and at sea level around Broken Bay

Broken Bay

Broken Bay is a large inlet of the Pacific Ocean located about 50 km north of Sydney on the coast of New South Wales, Australia, and is the first major bay north of Sydney's Port Jackson.- Geography :...

.

See also

Sydney Basin

Sydney Basin

The Sydney Basin is a sedimentary basin on the east coast of New South Wales, Australia consisting of Permian and Triassic sedimentary rocks...

, Hawkesbury sandstone, Wianamatta shale

Wianamatta shale

Wianamatta Shale is the uppermost outcropping unit in the Sydney Basin in New South Wales, Australia. It dates from the Triassic Period and generally comprises fine grained sedimentary rocks such as shales and laminites with less common sandstone units...

, Mittagong formation

Mittagong Formation

The Mittagong Formation is a type of sedimentary rock occurring in the Sydney Basin in eastern Australia. Formed in the triassic period. It may be seen as a narrow band of fine grained sandstone between the shale and the Hawkesbury sandstone . The maximum thickness is ten metres.In northern Sydney...