Eucla Basin
Encyclopedia
The Eucla Basin is an artesian
depression
located in Western Australia
and South Australia
. The onshore-offshore depression covers approximately 1,141,000 km² and slopes southward to an open bay known as the Great Australian Bight
. It extends more than 500 km offshore and about 350 km inland from the coastline. The Eucla Basin is a Cainozoic basin consisting mostly of carbonate
sediment
s and sedimentary rocks
. The basin contains a sandstone
acquifer at its base (confined), and an unconfined limestone
acquifer.
The surface area of the basin (and Nullarbor Plain
) consists mostly of grazing and rangeland, but nickel
and gold
are mined at the western end. Very few people live in this part of the country, with most of the region having fewer than one inhabitant per km². In normal years, the area receives less than 250 mm of precipitation
. Due to a shortage of regional seals and source rock
s, the basin has poor petroleum
prospects, but it is forming as a major zircon
producing area.
. It includes the smaller Eyre Coastal Plain
and Eucla Shelf physiographic sections.
Artesian aquifer
An artesian aquifer is a confined aquifer containing groundwater under positive pressure. This causes the water level in a well to rise to a point where hydrostatic equilibrium has been reached. This type of well is called an artesian well...
depression
Depression (geology)
A depression in geology is a landform sunken or depressed below the surrounding area. Depressions may be formed by various mechanisms.Structural or tectonic related:...
located in Western Australia
Western Australia
Western Australia is a state of Australia, occupying the entire western third of the Australian continent. It is bounded by the Indian Ocean to the north and west, the Great Australian Bight and Indian Ocean to the south, the Northern Territory to the north-east and South Australia to the south-east...
and South Australia
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...
. The onshore-offshore depression covers approximately 1,141,000 km² and slopes southward to an open bay known as the Great Australian Bight
Great Australian Bight
The Great Australian Bight is a large bight, or open bay, off the central and western portions of the southern coastline of mainland Australia.-Extent:...
. It extends more than 500 km offshore and about 350 km inland from the coastline. The Eucla Basin is a Cainozoic basin consisting mostly of carbonate
Carbonate
In chemistry, a carbonate is a salt of carbonic acid, characterized by the presence of the carbonate ion, . The name may also mean an ester of carbonic acid, an organic compound containing the carbonate group C2....
sediment
Sediment
Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....
s and sedimentary rocks
Rock (geology)
In geology, rock or stone is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock. In general rocks are of three types, namely, igneous, sedimentary, and metamorphic...
. The basin contains a 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,...
acquifer at its base (confined), and an unconfined 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....
acquifer.
The surface area of the basin (and Nullarbor Plain
Nullarbor Plain
The Nullarbor Plain is part of the area of flat, almost treeless, arid or semi-arid country of southern Australia, located on the Great Australian Bight coast with the Great Victoria Desert to its north. It is the world's largest single piece of limestone, and occupies an area of about...
) consists mostly of grazing and rangeland, but nickel
Nickel
Nickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...
and gold
Gold
Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...
are mined at the western end. Very few people live in this part of the country, with most of the region having fewer than one inhabitant per km². In normal years, the area receives less than 250 mm of precipitation
Precipitation (meteorology)
In meteorology, precipitation In meteorology, precipitation In meteorology, precipitation (also known as one of the classes of hydrometeors, which are atmospheric water phenomena is any product of the condensation of atmospheric water vapor that falls under gravity. The main forms of precipitation...
. Due to a shortage of regional seals and source rock
Source rock
In petroleum geology, source rock refers to rocks from which hydrocarbons have been generated or are capable of being generated. They form one of the necessary elements of a working petroleum system. They are organic-rich sediments that may have been deposited in a variety of environments including...
s, the basin has poor petroleum
Petroleum
Petroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...
prospects, but it is forming as a major zircon
Zircon
Zircon is a mineral belonging to the group of nesosilicates. Its chemical name is zirconium silicate and its corresponding chemical formula is ZrSiO4. A common empirical formula showing some of the range of substitution in zircon is 1–x4x–y...
producing area.
Physiography
The Eucla Basin is one of the distinct physiographic provinces of the larger West Australian ShieldAustralian Shield
The Australian Shield, also called the Western Australian Shield or Western Plateau, occupies more than half of the continent of Australia. It occupies the portion of Australia west of a line running north-south roughly from the eastern shore of Arnhem Land on the Bay or Gulf of Carpentaria to the...
. It includes the smaller Eyre Coastal Plain
Eyre Peninsula
Eyre Peninsula is a triangular peninsula in South Australia. It is bounded on the east by Spencer Gulf, the west by the Great Australian Bight, and the north by the Gawler Ranges. It is named after explorer Edward John Eyre who explored some of it in 1839-1841. The coastline was first explored by...
and Eucla Shelf physiographic sections.
See also
- Encyclopædia Britannica - http://www.britannica.com/eb/article-9033177 (note: Britannica lists the basin's area at 180,000 km²—a 2005 report by the Australian government gives a figure of more than 1.1 million km²).
- Eucla Basin, Geoscience Australia (Australian government report) - https://www.ga.gov.au/bin/htsqr?file=oracle/provinces/web_provs_report.htsqr&prov_list=20936&report=html
- National Geographic Atlas of the World
- World Mining News - http://www.mbendi.co.za/a_sndmsg/news_view.asp?I=72039&PG=15