Couture - Hypervelocity Impact Crater

Alternate Names Lac Coutoure
Local Language
Coordinates 60° 7' 50" N; 75° 18' 19" W
Notes
  1. Ungava Peninsula in northern Quebec, about 150 km SW of the New Quebec crater and 100 km E of Povungnituk.
Country Canada
Region Quebec
Date Confirmed 1967
Buried? No
Notes
  1. A significant amount of sediment had accumulated before glaciation scraped most of it from the crater floor (Beals et al., 1967).
Drilled? No
Target Type Crystalline
Notes
  1. Superior Province, granitic to granodiorite Archean gneisses (Beals et al., 1967).
Sub-Type Gneiss
Apparent Crater Diameter (km) 8 km
Age (Ma) 429 ± 25
Notes :
  1. 429 ± 25 Ma determined by 40Ar/39Ar of 4 samples of impact melt rock from the western side of the lake (Bottomley et al., 1990, recalculated by Schmieder and Kring 2020); the pre-recalculated age was 425 ± 25 Ma.

Method :
  1. 40Ar/39Ar
Impactor Type Unknown

Advanced Data Fields

Notes

Erosion
6
  1. Only remnants of the melt rock and breccia remain. All vestiges of a rim have been removed by glaciation (Robertson, 1965). The original ground plane is approximately 200 m above the present surface (Beals et al., 1967).
Final Rim Diameter
Unknown
Apparent Rim Diameter
8 km
  1. Lake is 13 km diameter; estimate for crater is 8 km diameter, considered very unreliable (Robertson, 1965) (Grieve, 1987). See also (Beals et al., 1967).
Rim Reliability Index
3
  1. The lake is more circular and deeper than other lakes in the area; the structure occupies a central, island free portion of the lake, 8 km in diameter. A low submerged central uplift rises 25 m above the lake bottom (Robertson, 1965).
Crater Morphology
Complex
Central Uplift Diameter
4km
Central Uplift Height
25 m
Uplift Reliability Index
3
Structural Uplift
Unknown
Thickness of Seds
Target Age
Precambrian
Marine
No
Impactor Type
Other Shock Metamorphism
Decorated fine fractures
  1. Strong, fine fractures in quartz, decorated with minute inclusions or cavities (Beals et al., 1976).
Shatter Cones
No
  1. Yes (Short and Bunch, 1968). (Robertson, 1965) reports an apparent absence of shatter cones, althougth (Beals et al., 1967) report shatter cone surfaces found in some fragments are similar to surfaces observed in gneisses of similar compsition and primary texture from the Carswell Lake structure and Clearwater Lake.
Planar Fractures
No
  1. See "Other
Planar Deformation Features
Yes
  1. PDF in quartz grains (Beals et al., 1967) and in feldspar grains (Bunch, 1968). PDFs in quartz fragments occurring with-in breccia and, in one case PDFs were present in a quartz grain of a rock fragment within breccia (Robertson, 1965). Two, and sometimes three or more sets of planes are present in a single grain (Robertson, 1965). See Fig. 13-1 for PDF orientations measured for 201 sets of planes and plotted on a histogram. Similar planes were observed in a few plagioclase grains within breccias, but are less distinct than the lamellae seen in quartz (Robertson, 1965). PDFs in quartz and feldspars within gneiss clasts in both the clastic breccias and impact melt rocks (Grieve, 2006), although (Robertson, 1965) reports a complete absence of PDFs in gneiss. Fig. 10 (Robertson et al., 1968) shows quartz with basal (vertical) and ω (inclined) decorated planar features.
Diaplectic Glass
No
Coesite
No
  1. (Robertson, 1965) did not observe any coesite in the 18 breccia samples examined via x-ray of hydrofluoric digested breccia residue.
Stisovite
No
  1. (Robertson, 1965) did not observe any stishovite in the 18 breccia samples examined via x-ray of hydrofluoric digested breccia residue.
Crater Fill
LB, MB, M
  1. Only remnants of the melt rock and breccia remain. All vestiges of a rim have been removed by glaciation (Robertson, 1965). (Bottomley et al., 1990) dated impact melt rocks with a cryptocrystalline matrix
Proximal Ejecta
Distal Ejecta
Dykes
Volume of Melt
Depth of Melting

References

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E Kitzes (1964) Exploring craters in the Earth, Nature and Science 1(8), p. 10-12, url

B Robertson (1966) Deformation lamellae from the Lac Couture Crater, Quebec, Special Paper - Geological Society of America, p. 138, Geological Society of America (GSA), Boulder, CO, url

C S Beals, I Halliday (1967) Impact Craters of the Earth and Moon, Journal of the Royal Astronomical Society of Canada 61(5), p. 295-313

R A F Grieve, M Pilkington (1996) The signature of terrestrial impacts, AGSO Journal of Australian Geology and Geophysics 16(4), Andrew Y Glikson (ed.), p. 399-420, Australian Geological Survey Organisation, Canberra, A.C.T., url

A Berclaz, A M Cadieux, K N M Sharma, J David, M Parent, A Leclair (2001) Geology of the Lac Aigneau area (NTS 24E and 24F/04), Bibliothèque nationale du Québec