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Akilia island

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1 Geology
2 See also
3 References

Akilia Island is in West Greenland, about 22 kilometers south of Nuuk (Godthåb), at 63.933° N 51.667° W. Akilia is the location of a controversial rock outcropping that some geologists believe contains the oldest known sedimentary rocks on Earth, and perhaps the oldest evidence of life on Earth.

Geology

The rocks in question are part of a metamorphosed supracrustal sequence located at the south-western tip of the island. The sequence has been dated as no younger than 3.8 billion years old, placing them in the Hadean eon, based on the age of an igneous band that cuts the rock (Manning et al., 2006). The supracrustal sequence contains layers of iron-rich rocks, variously interpreted as Banded iron formation, chemical sediments from hot springs, or vein deposits. Carbon in the rock, present as graphite, shows low levels of carbon-13 (Mojzsis et al., 1996), which may suggest an origin as isotopically light organic matter derived from living organisms (Schidlowski, 1988). However, this interpretation is complicated because the Akilia rocks have undergone high-temperature metamorphism. The sedimentary origin, age and the carbon content of the rocks have been questioned (Myers and Crowley, 2000; Fedo and Whitehouse, 2002; Lepland et al, 2005).

If the Akilia rocks do show evidence of life at 3.8 Ga, it would challenge models which suggest that Earth would not be hospitable to life at this time. Research is ongoing.

References

Fedo, C. M., and Whitehouse M. J., 2002, Metasomatic origin of quartz-pyroxene rock, Akilia, Greenland, and implications for Earth's earliest life. Science, v. 296, p. 1448-1452.
Lepland, A., van Zuilen, M., Arrhenius, G., Whitehouse, M., and Fedo, C., 2005. Questioning the evidence for Earth's earliest life—Akilia revisited. Geology, v. 33, p. 77-79.
Manning, C. E., Mojzsis, S. J., and Harrison, T. M., 2006. Geology, age and origin of supracrustal rocks at Akilia, West Greenland. American Journal of Science, v. 306, p. 303-366.
Mojzsis, S. J., Arrhenius, G., McKeegan, K. D., Harrison, T. M., Nutman, A. P., and Friend, C. R. L., 1996. Evidence for life on Earth before 3,800 million years ago. Nature, v. 384, p. 55-59.
Myers, J. S., and Crowley, J. L., 2000. Vestiges of life in the oldest Greenland rocks? A review of early Archean geology in the Godthåbsfjord region, and reappraisal of field evidence for >3850 Ma life on Akilia. Precambrian Research, v. 103, p. 101-124.
Schidlowski, M., 1988. A 3,800-Million-Year Isotopic Record of Life From Carbon in Sedimentary-Rocks. Nature, v. 333, p. 313-318.