Strangways crater

Strangways is a large impact structure (or astrobleme), the eroded remnant of a former impact crater, situated in the Northern Territory, Australia. It was named after the nearby Strangways River. The location is remote and difficult to access.

The circular topographic feature that marks the site was originally thought to be volcanic, with an impact origin first proposed in 1971 after the discovery of evidence diagnostic of impact including shatter cones and shocked quartz.cite journal | author=Guppy DJ, Brett R, Milton DJ | title=Liverpool and Strangways craters, Northern Territory; two structures of probable impact origin | journal=Journal of Geophysical Research | volume=76 | issue= | year=1971 | pages=5387–93 | id= | doi=10.1029/JB076i023p05387 ] The circular topographic feature is about 16 km in diameter and lies within Mesoproterozoic sedimentary rocks of the McArthur Basin. However, this is only a relic of the original crater after considerable erosion. Estimates of the original rim diameter vary between different researchers in the range 24–40 kmcite journal | author=Haines PW | title=Impact cratering and distal ejecta: the Australian record | journal=Australian Journal of Earth Sciences | volume=52 | issue= | year=2005 | pages=481–507 | doi=10.1080/08120090500170351 [http://journalsonline.tandf.co.uk/link.asp?id=n0396841487037g4 Abstract] ] ; the Earth Impact Database [http://www.unb.ca/passc/ImpactDatabase/images/strangways.htm Strangways] . "Earth Impact Database". Retrieved on 2007-02-20.] prefers a diameter of 25 km. The age of the impact event has been determined at 646 ± 42 Ma (Neoproterozoic) based on radiometric dating of impact melt rocks.cite journal | author=Spray JG, Kelley SP, Dence MR | title=The Strangways impact structure, Northern Territory, Australia: geological setting and laser probe ⁴⁰Ar/³⁹Ar geochronology | journal=Earth and Planetary Science Letters | volume=172 | issue= | year=1999 | pages=199–211 | doi=10.1016/S0012-821X(99)00206-X [http://dx.doi.org/10.1016/S0012-821X(99)00206-X Abstract] ]

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