Archaean

Akilia island is in West Greenland, about 22 kilometers south of Nuuk (Godthab), at . Akilia is the location of a controversial rock outcropping that some geologists believe is the oldest known sedimentary rocks, and perhaps the oldest evidence of life on Earth or anywhere else. ==Geology== The formation in question, at the southern tip of the island has been dated as no younger than 3.85 Ga ( Hadean), based on the age of an igneous band that cuts the rock. As a result, they may be older. It has been claimed that the Akilia sediments include banded iron beds, thought to be the result of oxygen released by photosynthetic organisms combining with dissolved iron to form insoluble iron oxides. Carbon deposits in the rock show low levels of Carbon-13. Kerogen deposits (derived from organic matter) are isotopically light (i.e. more negative δ13C values) which is indicative of photosynthesis (see Schidlowski, 1988). However, this interpretation is under doubt as the Akilia rocks have undergone high-temperature metamorphosis which is known to be fractionating itself (Gilmour & Wright, 1997). There is also a lack of corroborating sulfur isotope fractionation (Nisbet, 2000). Both the sedimentary origin and the carbon content of the rocks have been questioned (Lepland et al, 2005). If the Akilia rocks do show evidence of life at 3.85Ga, the time available for life to organize itself on Earth would be tightly limited, since other evidence suggests the Earth would not be hospitable to life before 3.9Ga. Research is continuing. ==See also== * Origin of life * Panspermia ==Papers== *Gilmour I, Wright I, Wright J, Origins of Earth and Life, The Open University, 1997, ISBN 0749281820 ...more on Wikipedia about "Akilia island"

Anorthosite is a phaneritic, intrusive igneous rock characterized by a predominance of plagioclase feldspar (90-100%), and a minimal mafic component (0-10%). Pyroxene, ilmenite, magnetite, and olivine are the mafic minerals most commonly present. ...more on Wikipedia about "Anorthosite"

The Archean (Archaean; also formerly known as the Archaeozoic) is a geologic eon that refers to the time before the Proterozoic, 2500 Ma (million years ago). Instead of being based on stratigraphy, this date is defined chronometrically. The lower boundary has not been officially recognized by the International Commission on Stratigraphy, but it is usually set to 3800 Ma at the end of the Hadean eon. ...more on Wikipedia about "Archean"

Arctica was an ancient continent approximately 2.5 billion years ago in the Neoarchean era. It consisted of Canadian and Siberian shields. ...more on Wikipedia about "Arctica"

In the geologic timescale, the Eoarchean was an era that lasted from 3800 Ma to 3600 Ma (million years ago). It is the first part of the Archaean Eon. During this era, prokaryotes (simple single-celled life) are thought to have originated. The Hadean eon was prior to the Eoarchean. In chronostratigraphy, its zone rank is an erathem. ...more on Wikipedia about "Eoarchean"

Kenorland was a supercontinent that existed in the Paleoproterozoic Era about 2450 - 2100 million years ago. It comprised at least Laurentia, Baltica, Australia, and Kalahari cratons. ...more on Wikipedia about "Kenorland"

The Mesoarchean is a geologic era within the Archean, spanning 3200 Ma to 2800 Ma (million years ago). The period is defined chronometrically and is not referenced to a specific level in a rock section on Earth. Fossils from Australia show that stromatolites have lived on earth since the Mesoarchean. ...more on Wikipedia about "Mesoarchean"

The Neoarchean is a geologic era within the Archaean. It spans the period of time 2800 Ma to 2500 Ma (million years ago)—the period being defined chronometrically and not referenced to a specific level in a rock section on Earth. ...more on Wikipedia about "Neoarchean"

The Paleoarchean is a geologic era within the Archaean. It spans the period of time 3600 Ma to 3200 Ma (million years ago)—the period being defined chronometrically and not referenced to a specific level in a rock section on Earth. ...more on Wikipedia about "Paleoarchean"

Ur is the name of the first known continent that probably formed 3 billion years ago in the early Archean Eon. Ur joined with the continents Nena and Atlantica about one billion years ago to form the supercontinent Rodinia. It now forms parts of Africa, Australia, India, and Madagascar. In the early period of its existence, it was probably the only continent on Earth, and is so considered by some to be a supercontinent, even though it was probably smaller than Australia is now. ...more on Wikipedia about "Ur (continent)"

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