Edeowie glass
{{short description|Natural glass found in South Australia}}
Edeowie glass is a natural glass, or lechatelierite, found in the Australian state of South Australia. It is slag-like, opaque material found as vesicular free forms or sheet-like/ropy masses. It is located throughout a semi-continuous swath in baked pod-like clay-bearing sediment in an area of about {{convert|55|km}} long by {{convert|10|km}} along the western side of the Flinders Ranges near Parachilna and east of Lake Torrens. The region in which this glass is found is mostly restricted to concentrations correlated to the ancient shoreline terrace sequence at the locality.
It is typically black in appearance, but can occur as variegated grey-green with various streak-like impurities. Pale grey and red-brownish surfaces can be caused by chemical weathering (oxidation, mineralization) and devitrification.Haines, P.W., R.J.F. Jenkins, and S.P. Kelley, 2001, [http://geology.geoscienceworld.org/cgi/content/abstract/29/10/899-a Pleistocene glass in the Australian desert: The case for an impact origin.] Geology. v. 29, no. 10, pp. 899–902.Macdonald, F.A., K. Mitchell, and S.E. Cina, 2004, [https://www.lpi.usra.edu/meetings/lpsc2004/pdf/1406.pdf Evidence for a Lightning-Strike Origin of the Edeowie Glass.] 35th Lunar and Planetary Science Conference, March 15–19, 2004, League City, Texas, abstract no.1406.Gifford, A. C., 1999, {{cite web|title=Clay soil fulgurites in the Eastern Goldfields of Western Australia|url=http://www.rswa.org.au/publications/Journal/82(4)/82(4)gifford.pdf}} Journal of the Royal Society of Western Australia, 82:165–168, 1999
Origin
Proposed origins for Edeowie and other similar lechatelierites include Pleistocene grassland fires, lightning strikes, or hypervelocity impact by one or several asteroids or comets.{{cite journal|last1=Roperch |first1=Pierrick |last2=Gattacceca |first2=Jérôme |last3=Valenzuela |first3=Millarca |last4=Devouard |first4=Bertrand |last5=Lorand |first5=Jean-Pierre |last6=Arriagada |first6=Cesar |last7=Rochette |first7=Pierre |last8=Latorre |first8=Claudio |last9=Beck |first9=Pierre |title=Surface vitrification caused by natural fires in Late Pleistocene wetlands of the Atacama Desert|journal=Earth and Planetary Science Letters |volume=469 |issue=1 July 2017 |pages=15–26 |date=2017 |doi=10.1016/j.epsl.2017.04.009|bibcode=2017E&PSL.469...15R |url=https://hal.archives-ouvertes.fr/hal-02889687 }} Some features, such as planar deformation features (PDFs) in quartz crystals found within and associated with Edeowie glass, are usually caused by extreme pressures and temperatures.{{cite web|url=http://ammin.geoscienceworld.org/content/100/7/1645.abstract |title=Lightning-induced shock lamellae in quartz |publisher=Ammin.geoscienceworld.org |date=2015-07-01 |access-date=2015-08-16}}{{cite journal |last=Melosh |first=H.J. |title=Impact geologists, beware! |journal=Geophysical Research Letters |volume=44 |issue=17 |pages=8873–8874 |doi=10.1002/2017GL074840 |year=2017 |bibcode=2017GeoRL..44.8873M }}
Interval of formation
Edeowie glass yields dates spanning 0.67–0.07 mya (~670,000–70,000 BP), but some outlier dates are as recent as the middle Holocene.
See also
References
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External links
- Geoscience Australia, 2004, [http://dbforms.ga.gov.au/pls/www/geodx.strat_units.sch_full?wher=stratno=70182 Edeowie glass.] Stratigraphic Units Database.
- Perkins, S., 2001, [http://findarticles.com/p/articles/mi_m1200/is_/ai_81110075 Desert glass: is it baked Australia?] Science News. v. 160, no. 21, p. 331.
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