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Omar
An Omar with a hemispherical bubble and a coin to demonstrate a size reference
An Omar with a hemispherical bubble visible
General
Category Native Minerals
A cupstone or nutting stone used in antiquity to process nuts

Omarolluks, usually referred to today in both general and scientific discourse as "omars," (a term coined by V.K. PRest in 1990[1] in response to a theory first advanced by Upham in 1896) are stones that have hemispherical bubbles in them. They were formed when round mineral bubbles of precipitation formed around some kind of nucleus in fine-grained sediment before that sediment hardened into rock. When these mineral bubbles weathered out, they left the bubble-like holes. Visually, some say they resemble cupstones. J.A. Donaldson and V.K. Prest have specified criteria for identifying omars [2][3]

According to current understanding, omars were formed only in the Belcher Islands, an archipelago limited to only about a quarter of 1% of Hudson Bay. [4]

Glaciers moved omars from the southeastern part of Hudson Bay to central Canada and into the U.S. where they were deposited on moraines. Because scientists know precisely where they (probably) came from they are very valuable in documenting the movement of glaciers.[5]

References

  1. ^ http://74.125.95.132/search?q=cache:dTH5nvtwi_UJ:id.erudit.org/iderudit/005654ar+Omarolluk+calcareous&cd=4&hl=en&ct=clnk&gl=us
  2. ^ Donaldson,A and Prest,V (1997) Criteria for recognizing omars, widely dispersed indicators of Pleistocene history in North America. GAC/MAC Abs. 22, 40, Ottawa.
  3. ^ Prest,VK, Donaldson,JA and Mooers,HD (2000) The omar story: the role of omars in assessing glacial history of west-central North America. GĂ©ographie Physique et Quaternaire 54, 257-270.
  4. ^ Dutch, S. (n.d.) Leaverites - Features in Sedimentary Rocks. Downloaded October 28, 2009 from http://www.uwgb.edu/dutchs/PETROLGY/Leaverite-SedFeat.HTM
  5. ^ (2007, August). An omar (siltstone erratic). Downloaded October 28, 2009 from http://www.turnstone.ca/rom74om.htm
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