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Akilia Island is in West Greenland, about 22 kilometers south of Nuuk (Godthåb), 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
Papers
- Gilmour I, Wright I, Wright J, Origins of Earth and Life, The Open University, 1997, ISBN 0749281820
- Lepland A, van Zuilen M, Arrhenius G, Whitehouse M and Fedo C, Questioning the evidence for Earth's earliest life—Akilia revisited, Geology; January 2005; v. 33; no. 1; p. 77-79; DOI: 10.1130/G20890.1
- Schidlowski, M., A 3,800-Million-Year Isotopic Record of Life From Carbon in Sedimentary-Rocks, Nature, 333(6171):313 -- 318, (1988).
- Nisbet, E. The realms of Archaean life. Nature, 2000; 405(6787):625 -- 626.
External links
"Akilia island"