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Acraman impact structure
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== Ejecta layer == A widespread layer of ejecta, believed to be from the Acraman impact structure, is found within Ediacaran rocks of the [[Flinders Ranges]] at least {{convert|300|km|mi}} east of the crater,<ref name="Gostin1986" /> and in [[diamond drilling|drill holes]] from the [[Officer Basin]] to the north.<ref name=Wallace1989>{{cite journal | author = Wallace, M.W. |author2= Gostin, V.A.|author3= Keays, R.R. | date = 1989 | title = Geological Note: Discovery of the acraman impact ejecta blanket in the officer basin and its stratigraphic significance | journal = Australian Journal of Earth Sciences | volume = 36 | issue = 4 | pages = 585β587 | url = http://www.informaworld.com/index/781041341.pdf | doi = 10.1080/08120098908729511|bibcode = 1989AuJES..36..585W }}</ref> At the time these areas were shallow sea, and the ejecta settled into mud on the sea floor. The ejecta, containing shocked minerals and small shatter cones, is composed of rock similar in age and composition to that at the crater,<ref name="Gostin1986" /> and is associated with an [[iridium anomaly]] suggesting contamination with extraterrestrial material.<ref name=Gostin1989>{{cite journal | author = Gostin, V.A. |author2= Keays, R.R.|author3= Wallace, M.W. | date = 1989 | title = Iridium anomaly from the Acraman impact ejecta horizon: impacts can produce sedimentary iridium peaks | journal = Nature | volume = 340 | issue = 6234 | pages = 542β544 | doi = 10.1038/340542a0 |bibcode = 1989Natur.340..542G |s2cid= 4310570}}</ref> An [[Adaptive radiation|evolutionary radiation]] within marine microorganisms ([[acritarch]]s) occurs just above the level as the ejecta layer, and some authors believe there may be a connection.<ref name=Grey2003>{{cite journal | author = Grey, K. |author2= Walter, M.R.|author3= Calver, C.R. | date = 2003 | title = Neoproterozoic biotic diversification: Snowball Earth or aftermath of the Acraman impact? | journal = Geology | volume = 31 | issue = 5 | pages = 459β462 | doi = 10.1130/0091-7613(2003)031<0459:NBDSEO>2.0.CO;2|bibcode = 2003Geo....31..459G }}</ref><ref name=Williams2003>{{cite journal | last1 = Williams | first1 = George E. | name-list-style = amp | date = 2003 | title = The Acraman asteroid impact, South Australia: magnitude and implications for the late Vendian environment | journal = Journal of the Geological Society of London | volume = 160 | issue = 4 | pages = 545β554 | doi = 10.1144/0016-764902-142 | last2 = Wallace | first2 = Malcolm W.| bibcode = 2003JGSoc.160..545W | s2cid = 129728586 }}</ref> The proximity of the crater to the type area for the [[Ediacara biota|Ediacara Biota]] is noted, though probably not significant given the likely global consequences of the impact.
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