Clearwater West - Hypervelocity Impact Crater

Alternate Names West Clearwater
Coordinates 56° 12' 45" N; 74° 31' 39" W
Notes
  1. 112 km E of Hudson Bay and 200 km NE of Poste-de-la-Baleine in northern Quebec.
Country Canada
Region Quebec
Date Confirmed 1964
Notes
  1. Suggested to be of impact origin based on air photos (Beals et al., 1956). First report of shatter cones was in 1964 (Dence, 1964).
Buried? No
Notes
  1. Some post-crater-fill, within the lake.
Drilled? Yes
Notes
  1. 5 holes have been drilled within the island ring. General descriptions in (Dence et al., 1965).
Target Type Mixed
Notes
  1. Archean granodiorite, quartz monzonites, and granitic gneisses, with minor mafic granulite and meta-grabbro with a thin cover of Middle-Upper Ordovician limestones (Ogilvie et al., 1984). (Rosa et al., 2010) describe "thin veneer" of "totally eroded" Paleozoic dolomitic limestone that was present at time of impact.
Sub-Type Gneiss, Granodiorite, Limestone, Monzonite
Apparent Crater Diameter (km) 36 km
Age (Ma) 286.2 ± 2.6
Notes :
  1. 286.2 ± 2.6 Ma determined by 40Ar/39Ar of 2 samples of melt rock (Schmeider et al., 2015). Previous age constraints: 300 ± 30 Ma and 285 ± 30 Ma derived from K-Ar whole rock ages of the melt rocks (Wanless et al., 1965). 280 ± 2 Ma (Bottomley et al., 1990).

Method :
  1. 40Ar/39Ar
Impactor Type Unknown
Notes
  1. No meteorite component has been detected in the melt rocks (Palme et al., 1978).

Advanced Data Fields

Notes

Local Language
Lac Wiyâshâkimî
Erosion
4
  1. Glaciation has removed the ejecta and the rim, leaving only some of the melt sheet and breccia (Simonds et al., 1978).
Final Rim Diameter
Unknown
Apparent Rim Diameter
36 km
  1. Dimensions based on digital terrain model (Hische, 1994).
Rim Reliability Index
2
  1. The lake fills an annular trough surrounding a ring of islands which reflect the eroded centrally uplifted rocks (Wood and Head, 1976).
Crater Morphology
Complex
Central Uplift Diameter
8 km
Central Uplift Height
Unknown
Uplift Reliability Index
2
Structural Uplift
Unknown
Thickness of Seds
Unknown
Target Age
Precambrian Palaeozoic
Marine
No
Impactor Type
Unknown
  1. No meteorite component has been detected in the melt rocks (Palme et al., 1978).
Other Shock Metamorphism
Maskelynite Planar features Pressure
  1. (Dence, 1964) (Bunch et al., 1967) (Bostock, 1969). Planar features in quartz samples from central islands (Simonds et al., 1978) (Part I). Planar features mentioned in: Table 1. Distribution of Shock features in Quartz and Feldspar clasts (Phinney et al., 1978). Minerals at different stages of shock metamorphism (Dence et al., 1974). Peak shock pressures of 200-250 kb (Simonds et al., 1978).
Shatter Cones
Yes
  1. Poorly-formed shatter cones occur in the island ring (Grieve, 2006). Shatter cones in gneisses (Fig. 8) (Dence, 1964). Shattered granite passes into microbreccias having numerous deformation lamellas in the quartz (McIntyre, 1962). Shatter cones preserved in the fractured basement on the island ring 6-10 km from the centre (Simonds et al., 1978) (Part I). Poorly formed shatter cones on the central islands with axes that appear to plunge at more than 45° (Simonds et al., 1978) (Part I).
Planar Fractures
Yes
  1. Fig. 9 (Robertson et al., 1968) shows a quartz grain "non-decorated cleavage fractures" {1011} orientation. Fig.6 (Robertson et al., 1968) shows a quartz grain with shear fractures that continue in the adjoining plagioclase grain as a number of curved surfaces, and decorated PDFs.
Planar Deformation Features
Yes
  1. PDF in quartz grains (Simonds et al., 1978) (Bostock, 1969) (Ogilvie et al., 1984), with peak shock pressures of 200 to 250 kb (Simonds et al., 1978). PDFs in quartz common in the more granitic rocks from the island ring (Fig. 4.6b) (Grieve, 2006). PDFs in feldspar and quartz clasts of allochthonous breccia overlying the fractured basement rock (Grieve, 2006). Angular quartz fragments within granitic microbreccias show an extraordinary richness in various PDFs (McIntyre, 1968). Fig. 9 (Robertson et al., 1968) shows a quartz grain with decorated planar features (ω). ***See Table 1 for class two planar feature (PDF Types and orientations). Planar elements in shocked quartz grains from Clearwater Lake and the Ries basin are parallel to {OOOI I, {lOI31, {WIlL {IOI21, {IOIOI (Engelhardt et al., 1968). PDFs in quartz and pyroxenes (Scott et al., 1997). **see (Stoffler, 1972) (Stoffler, 1974).
Diaplectic Glass
Yes
  1. The metagabbro of the central islands contains maskelynite (Fig. 4.6a) (Grieve, 2006). Maskelynite in clasts of allochthonous breccia overlying the fractured basement rock (Grieve, 2006). "Samples from central island display partial to complete transformation of feldspar to maskelynite" (Simonds et al., 1978) (Part I). Very fresh gabbro with maskelynite (Palme et al., 1978). Maskelynite, see Table 1. Distribution of Shock features in Quartz and Feldspar clasts (Phinney et al., 1978). Presence of maskelynite (shock-vitrified plagioclase) in drill core (Rosa, 2004). Maskelynite and diaplectic quartz (Scott et al., 1997).
Coesite
No
Stisovite
No
Crater Fill
LB, MB, M
Proximal Ejecta
Unknown
Distal Ejecta
Unknown
Dykes
Unknown
Volume of Melt
80 km3
Depth of Melting
Unknown

References

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Wolf von Engelhardt, F Hoerz, D Stoeffler, W Bertsch (1968) Observations on quartz deformation in the breccias of West Clearwater Lake, Canada, and the Ries Basin, Germany, Shock metamorphism of natural materials, Bevan French, Nicholas M Short (ed.), url

Michael R Dence, W V Engelhardt, L S Walter, A G Plant (1970) Spheroids in impact glass from west Clearwater Lake crater, Quebec, Eos, Transactions, American Geophysical Union 51(4), p. 342, American Geophysical Union, Washington, DC, url

Michael R Dence, Wolf von Engelhardt, A G Plant, L S Walter (1974) Indications of fluid immiscibility in glass from West Clearwater Lake impact crater, Quebec, Canada, Contributions to Mineralogy and Petrology 46(2), p. 81-97, Springer International, Heidelberg-New York, url

C H Simonds, W C Phinney, P E McGee, A Cochran (1978) West Clearwater, Quebec impact structure; Part I, Field geology, structure, and bulk chemistry, Proceedings of the Lunar and Planetary Science Conference(9, Vol. 2), R B Merrill (ed.), p. 2633-2658, Pergamon, New York, NY, url

W C Phinney, C H Simonds, A Cochran, P E McGee (1978) West Clearwater, Quebec impact structure; Part II, Petrology, Proceedings of the Lunar and Planetary Science Conference(9, Vol. 2), R B Merrill (ed.), p. 2659-2693, Pergamon, New York, NY, url

K Benes (1981) Kanadsky krater Clearwater West a jeho typove protejsky na Mesici, Merkuru a Marsu, Geologicky Pruzkum 23(6), p. 180-182, Zamestnavatelsky Svaz Dulniho a Naftovho Prumyslu, Prague, url

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R R Herrick, V L Sharpton (1994) Gravity analysis of impact basins at spacecraft altitudes; lessons from Chicxulub, Abstracts of Papers Submitted to the Lunar and Planetary Science Conference 25, Part 2, p. 537-538, Lunar and Planetary Science Conference, Houston, TX, url

B C Schuraytz, V L Sharpton (1994) Siderophile-element distribution in Chicxulub melt rocks; forensic chemistry on the KT smoking gun, LPI Contribution 825, p. 106-108, Lunar and Planetary Institute, Houston, TX, url

P H Schultz (1994) Chicxulub as an oblique impact, Abstracts of Papers Submitted to the Lunar and Planetary Science Conference 25, Part 3, p. 1211-1212, Lunar and Planetary Science Conference, Houston, TX, url

K A Holsapple (1994) Estimation of the measures of the Chicxulub cratering event, LPI Contribution 825, p. 50-52, Lunar and Planetary Institute, Houston, TX, url

Noreen J Evans, T J Ahrens, B I A McInnes, D C Gregoire (1994) New evidence for primary fractionation of ruthenium and iridium in the Chicxulub ejecta cloud, LPI Contribution 825, p. 34-36, Lunar and Planetary Institute, Houston, TX, url

B A Ivanov, D D Badjukov, O I Yakovlev (1994) Shock degassing of sedimentary rocks due to the Chicxulub impact; hydrocode simulation, LPI Contribution 825, p. 54-55, Lunar and Planetary Institute, Houston, TX, url

J S Alexopoulos, W B McKinnon (1994) Large impact craters and basins on Venus, with implications for ring mechanics on the terrestrial planets, Special Paper - Geological Society of America 293, B O Dressler, R A F Grieve, V L Sharpton (ed.), p. 29-50, Geological Society of America (GSA), Boulder, CO, url

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