Eolianite or aeolianite is any rock formed by the

lithification Lithification (from the Ancient Greek word ''lithos'' meaning 'rock' and the Latin-derived suffix ''-ific'') is the process in which sediments compact under pressure, expel connate fluids, and gradually become solid rock. Essentially, lithificati ...

sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand an ...

deposited by

aeolian processes Aeolian processes, also spelled eolian, pertain to wind activity in the study of geology and weather and specifically to the wind's ability to shape the surface of the Earth (or other planets). Winds may erode, transport, and deposit materials ...

; that is, the

wind Wind is the natural movement of air or other gases relative to a planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few hou ...

. In common use, however, the term refers specifically to the most common form of eolianite: coastal

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

consisting of

carbonate A carbonate is a salt of carbonic acid (H2CO3), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word ''carbonate'' may also refer to a carbonate ester, an organic compound containing the carbonate g ...

sediment of shallow marine biogenic origin, formed into

coastal dune A dune is a landform composed of wind- or water-driven sand. It typically takes the form of a mound, ridge, or hill. An area with dunes is called a dune system or a dune complex. A large dune complex is called a dune field, while broad, fl ...

s by the wind, and subsequently lithified. It is also known as

kurkar Kurkar ( ar, كركار / he, כורכר) is the term used in Palestinian Arabic and modern Hebrew for the rock type of which lithified sea sand dunes consist. The equivalent term used in Lebanon is ramleh. haron Horowitz. ''The Quaternary of ...

in the Middle East, miliolite in

India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...

and Arabia, and grès dunaire in the eastern

Mediterranean The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the e ...

. eolianite has a hardness of 4.3 and is very dull. Streak is light brown.

Description

Sayles coined the term in 1931, when he described the dune-shaped hills of

Bermuda ) , anthem = "God Save the King" , song_type = National song , song = " Hail to Bermuda" , image_map = , map_caption = , image_map2 = , mapsize2 = , map_caption2 = , subdivision_type = Sovereign state , subdivision_name = , e ...

, consisting of

bioclastic Bioclasts are skeletal fossil fragments of once living marine or land organisms that are found in sedimentary rocks laid down in a marine environment—especially limestone varieties around the globe. some of which take on distinct textures and col ...

grainstone Under the Dunham classification (Dunham, 1962) system of limestones, a grainstone is defined as a grain-supported carbonate rock that contains less than 1% mud-grade material. This definition has recently been clarified as ''a carbonate-dominated ...

s. Thus, Bermuda is considered the type locality for

eolianite

facies In geology, a facies ( , ; same pronunciation and spelling in the plural) is a body of rock with specified characteristics, which can be any observable attribute of rocks (such as their overall appearance, composition, or condition of formatio ...

, with clearly defined

cross-bedding In geology, cross-bedding, also known as cross-stratification, is layering within a stratum and at an angle to the main bedding plane. The sedimentary structures which result are roughly horizontal units composed of inclined layers. The origina ...

, foresets, and topsets. Deposition is controlled by glacio-eustatic changes, with eolianites forming during

interglaciation An interglacial period (or alternatively interglacial, interglaciation) is a geological interval of warmer global average temperature lasting thousands of years that separates consecutive glacial periods within an ice age. The current Holocene in ...

s. Eolianites occur along the margins of the global carbonate belt, on the carbonate islands along northeastern Yucatan, and

Rottnest Island Rottnest Island ( nys, Wadjemup), often colloquially referred to as "Rotto", is a island off the coast of Western Australia, located west of Fremantle. A sandy, low-lying island formed on a base of aeolianite limestone, Rottnest is an A-class ...

. Eolianite occurs in many parts of the world. It occurs most extensively between the latitudes of 20° and 40° in both hemispheres, with little nearer the equator, and virtually no deposits nearer the poles. There is no apparent difference in distribution between the hemispheres, but if the extent and thickness of deposits are taken into account, the Southern Hemisphere has the bulk of eolianite. Aeolianite

Conditions favourable for formation of eolianite are: * a warm climate, favourable to the production of

by shallow marine animals; for example, the production of seashells by marine molluscs; * onshore winds to form beached sediment into

dune A dune is a landform composed of wind- or water-driven sand. It typically takes the form of a mound, ridge, or hill. An area with dunes is called a dune system or a dune complex. A large dune complex is called a dune field, while broad, f ...

s; * a relatively low onshore topography, rather than onshore cliffs, to allow the formation of

systems; * relatively low onshore rainfall, to promote rapid lithification; *

tectonic Tectonics (; ) are the processes that control the structure and properties of the Earth's crust and its evolution through time. These include the processes of mountain building, the growth and behavior of the strong, old cores of continents ...

stability; The most extensive deposits of eolianite in the world are located on the southern and western coasts of

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 ...

. On the west coast, there are over of eolianite cliffs, which are over 150 metres thick in some places. These cliffs, locally known as the

Tamala Limestone Tamala Limestone is the geological name given to the widely occurring eolianite limestone deposits on the western coastline of Western Australia, between Shark Bay in the north and nearly to Albany in the south. The rock consists of calcarenit ...

Formation, contain layers of dune origin interspersed with layers of shallow-marine origin. Other substantial deposits occur in

, the

Bahamas The Bahamas (), officially the Commonwealth of The Bahamas, is an island country within the Lucayan Archipelago of the West Indies in the Atlantic Ocean, North Atlantic. It takes up 97% of the Lucayan Archipelago's land area and is home to ...

, the southern and eastern coasts of

South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring countri ...

, the

, and oceanic islands of the

Pacific The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...

Atlantic The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe an ...

, and

Indian Indian or Indians may refer to: Peoples South Asia * Indian people, people of Indian nationality, or people who have an Indian ancestor ** Non-resident Indian, a citizen of India who has temporarily emigrated to another country * South Asia ...

Oceans.

References

* {{cite journal , author = Brooke, Brendan , year = 2001 , title = The distribution of carbonate eolianite , journal = Earth-Science Reviews , volume = 55 , issue = 1–2 , pages = 135–164 , doi = 10.1016/S0012-8252(01)00054-X Limestone Sedimentary rocks he:כורכר

Description

See also

References