Bringelly Shale is a component of the Wianamatta group of sedimentary rocks in the

Sydney Basin The Sydney Basin is an 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 eastern side now subsided beneath the Tasman Sea ...

of eastern Australia. Formed in the

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 ...

Period Period may refer to: Common uses * Era, a length or span of time * Full stop (or period), a punctuation mark Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (or rhetorical period), a concept ...

, it has an extensive outcrop in the western parts of Sydney. The shale has its greatest geographical extent at

Bringelly Bringelly is a suburb of Sydney, in the state of New South Wales, Australia. It is located on the Northern Road between Penrith and Camden. It has a public school. Bringelly is also the name of a local hill. History Bringelly was a name given t ...

, near the suburb of Liverpool.

Lithology

The shale is the topmost layer of sedimentary rock laid down by a river delta over the older

Hawkesbury sandstone Sydney sandstone is the common name for Sydney Basin Hawkesbury Sandstone, one variety of which is historically known as Yellowblock, and also as "yellow gold" a sedimentary rock named after the Hawkesbury River north of Sydney, where thi ...

in the

Triassic Period 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 ...

. It is similar to

Ashfield Shale Ashfield Shale is part of the Wianamatta group of sedimentary rocks in the Sydney Basin. It lies directly on contemporaneously eroded Hawkesbury sandstone or the Mittagong formation. These rock types were formed in the Triassic Period. It is nam ...

in that both have low porosities, though differing in having a greater amount of

calcareous Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines. In zoology ''Calcareous'' is used as an adje ...

graywacke Greywacke or graywacke ( German ''grauwacke'', signifying a grey, earthy rock) 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 li ...

-type, lithic sandstone bands and lenses,

carbonaceous Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon makes up o ...

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 sma ...

siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility.Blatt ''et al.'' 1980, ...

laminite Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles ...

, but would lack sideritic mudstone bands that Ashfield Shale has. Bringelly Shale has lumpy clay minerals, and it swells and decays rapidly on submergence in water and is generally less durable.

Description

The average thickness is around 60 metres. It was deposited in a swampy

alluvial Alluvium (from Latin ''alluvius'', from ''alluere'' 'to wash against') is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. Alluv ...

plain with winding streams that formed sporadic beds of sandstone. The shale is dark when unweathered just like the Ashfield Shale. The shale is usually a typical olive-green colour when weathered. Alloyed

coal Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal is formed when dead ...

bands and lenses and

iron oxide Iron oxides are chemical compounds composed of iron and oxygen. Several iron oxides are recognized. All are black magnetic solids. Often they are non-stoichiometric. Oxyhydroxides are a related class of compounds, perhaps the best known of which ...

concretions have been observed in the shale. The shale is quarried in many western suburbs of Sydney for brick and miscellaneous ceramic manufacture.

References

{{Reflist Geology of New South Wales Geologic formations of Australia Triassic Australia Shale formations

Lithology

Description

See also

References