Strangways - Hypervelocity Impact Crater

Alternate Names
Local Language
Coordinates 15° 10' 50" S; 133° 34' 38" E
Notes
  1. W of the Strangways River, approximately 75 km SE of Elsey Station, near Mataranka, Northern Territory, Australia.
Country Australia
Region Northern Territory
Date Confirmed 1971
Notes
  1. PFs in quartz and feldspars and shatter cones found (Guppy et al., 1971). Note: (Brett et al., 1970) finds suevites, and "abundant...impact metamorphism" but does not elaborate in the paper on what types of shcok are present.
Buried? No
Notes
  1. Cretaceous sandstones and Cenozoic sediments unconformably overly about 1/4 of the structure (Ferguson et al., 1978).
Drilled? No
Target Type Mixed
Notes
  1. Granitic gneiss and amphibolite; and quartzite and siltstone of the Proterozoic Roper Group (Ferguson et al., 1978).
Sub-Type Amphibolite, Gneiss, Quartzite, Siltstone
Apparent Crater Diameter (km) 26 km
Age (Ma) 657 ± 43
Notes :
  1. 657 ± 43 Ma determined by 40Ar/39Ar of impact melt rocks (Spray et al., 1999), recalculated by (Schmieder and Kring, 2020); the pre-recalculated age was 646 ± 42 Ma. Additional age constraints: <470 Ma by 40Ar/39Ar interpreted as a maximum age by (Bottomley et al., 1990). Quaternary limestone lies unconformably on disturbed strata, apparently these strata were deposited after the event.

Method :
  1. 40Ar/39Ar
Impactor Type Achondrite
Notes
  1. Ir and Ni along with Os, Pd and Cr are more abundant in melt roks than in country rocks; and olivine-rich achondrite, urelite or nakhlite is suggested (Morgan et al., 1981).

Advanced Data Fields

Notes

Erosion
5
  1. Up to 15 m of the melt rock is preserved and overlies breccia and crystalline rocks of the core zone (Morgan et al., 1981).
Final Rim Diameter
Unknown
Apparent Rim Diameter
26 km
  1. Estimates vary between 24-26 km based on disturbance of regional geology (Spray et al., 1999) and 26-29 km based on remote sensing and mapped distribution of shatter cones (Zumsprekel and Bishoff, 2005).
Rim Reliability Index
2
  1. Consists of a central uplift of granitic gneiss, a collar, generally 5 km wide, of upturned and overturned quarzite and siltstone and an outer zone of disturbance (Ferguson et al., 1978). (Spray et al., 1999) discuss stratigraphy of the crater. Unconformities and generally advanced erosion hinder an estimate of stratigraphic uplift.
Crater Morphology
Complex
Central Uplift Diameter
10km
Central Uplift Height
Unknown
Uplift Reliability Index
4
Structural Uplift
Unknown
Thickness of Seds
Target Age
Precambrian
Marine
No
Impactor Type
Achondrite
  1. Ir and Ni along with Os, Pd and Cr are more abundant in melt roks than in country rocks; and olivine-rich achondrite, urelite or nakhlite is suggested (Morgan et al., 1981).
Other Shock Metamorphism
  1. Did not find in literature.
Shatter Cones
Yes
  1. Shatter cones poorly developed in granitoid rocks (Spray et al., 1999). Poorly developed shatter cones occur locally in sandstone (Guppy et al., 1971). "Shatter fracturing, more commonly intersecting sets of striated cleavage surfaces than well-formed cones, is well displayed in the inner quartzites" (Ferguson et al., 1978). Central uplift locally intensely shatter-coned (Shoemaker and Shoemaker, 1996). The original crater dimensions were re-estimated recently at 26-29 km by combining remote sensing data with the distribution of shatter cones localised in the field (Zumsprekel and Bischoff, 2005). Shatter cones occur in granite and in the Limmen Sandstone; the distribution of shatter cones is mapped (Fig. 8; Zumsprekel and Bischoff, 2005). Shatter cones occur within a circle of ~14.5 km in diameter.
Planar Fractures
No
  1. Did not find in literature.
Planar Deformation Features
Yes
  1. PDF in quartz grains (Guppy et al., 1971) (Morgan et al., 1981). See also (Zumsprekel and Bischoff, 2005), esp. Fig. 3C.
Diaplectic Glass
Yes
  1. Presence of diaplectic glasses noted by (Zumspreckel and Bischoff, 2005) in samples of melt rock. However, only mentioned in passing; further info needed.
Coesite
No
  1. Did not find in literature.
Stisovite
No
  1. Did not find in literature.
Crater Fill
LB, MB, M
  1. "Only remnants of the melt sheet now remain as erosional outliers resting as veneers or larger masses on the granitoid gneiss core... Thicknesses of 5 to 30 m are preserved in the main melt exposures near the western margin of the core... The absence of any indication of more slowly cooled melt suggests that the original thickness did not greatly exceed that of the largest mass now exposed." (Spray et al., 1999). Polymict breccias and clast-rich melt rocks with aphanitic matrices (Spray et al., 1999).
Proximal Ejecta
Distal Ejecta
Dykes
Volume of Melt
Depth of Melting

References

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J W Morgan, G A Wandless (1983) Strangways Crater, Northern Territory, Australia; siderophile element enrichment and lithophile element fractionation, Journal of Geophysical Research 88, Suppl.(B2), William V Boynton, Thomas J Ahrens (ed.), p. A819-A829, American Geophysical Union, Washington, DC, url, doi:http://dx.doi.org/10.1029/JB088iS02p0A819

J G Spray, S P Kelley, M R Dence (1999) The Strangways impact structure, Northern Territory, Australia; geological setting and laser probe (super 40) Ar/ (super 39) Ar geochronology, Earth and Planetary Science Letters 172(3-4), p. 199-211, Elsevier, Amsterdam, url

P W Haines (2005) Impact Cratering and distal ejecta: the Australian record, Australian Journal of Earth Sciences 52(4-5), p. 481-507, url

H Zumsprekel, L Bischoff (2005) Remote sensing and GIS analyses of the Strangways impact structure, Northern Territory, Australian Journal of Earth Sciences 52(4-5), p. 621-630, Blackwell Scientific Publications for the Geological Society of Australia, Melbourne, Victoria, url, doi:http://dx.doi.org/10.1080/08120090500181077

S Staffieri, A Coletta, M L Battagliere, M Virelli (2019) Strangways, Australia, Encyclopedic Atlas of Terrestrial Impact Craters, p. 305-207, Springer, Cham, url, doi:https://doi.org/10.1007/978-3-030-05451-9_78

C Koeberl, B A Ivanov (2020) An impact crater possibly formed during a snowball earth period: Strangways, Lunar & Planetary Science Conference, p. 1288, pdf