Ile Rouleau - Hypervelocity Impact Crater

Alternate Names
Local Language
Coordinates 50° 40' 54" N; 73° 52' 48" W
Notes
  1. Within Lac Mistassini in central Quebec, approximately 90 km N of Chibougamau.
Country Canada
Region Quebec
Date Confirmed 1976
Notes
  1. Confirmed by shatter cones found throughout the island, planar features found in quartz grains within the breccia (Caty et al., 1976).
Buried? No
Notes
  1. Covered by water except for the central island (Caty et al., 1976).
Drilled? No
Target Type Sedimentary
Notes
  1. Argillaceous and micritic dolomite of the Albanel Formation (Proterozoic); Mistassini Group (Ogilvie et al., 1984).
Sub-Type Dolomite
Apparent Crater Diameter (km) 4 km
Age (Ma) 0.011 - 1800
Notes :
  1. A rough age of 11 ka - 1800 Ma is recommended based on stratigraphic constraints. (Caty et al. 1976). See also (Ogilvie et al., 1984) who suggestes the structure's survival at such a comparatively small size implies an age no greater that 300 Ma. Extensive Pleistocene glacial erosion has taken place (Caty et al., 1976). The Mistassini group (target rock) is upper Aphebian (1.8 b.y.) (Caty et al. 1976) Structure covered by Pleistocene [Wisconsin] Glacial deposits (Caty et al. 1976) [Note: Wisconsin glaciation began 75 ka-100 ka and ended ~11 ka]

Method :
  1. Stratigraphy
Impactor Type Iron
Notes
  1. (Evangelatos, 2009)

Advanced Data Fields

Notes

Erosion
6
  1. Only remnants of the brecciated rock remain and the crater floor is exposed. Extensive Pleistocene glacial erosion has taken place (Caty et al., 1976).
Final Rim Diameter
~4
Apparent Rim Diameter
4 km
  1. (Caty et al., 1976). The maximum rim-to-rim diameter of the crater is estimated at ∼4 km based on the absence of conspicuous impact features on adjacent Ile Manitounouc (Grieve 2006). However, considering the high degree of erosion and the lack of detailed geological work at the impact site, this assumption remains speculative.
Rim Reliability Index
3
  1. The island, forming the central uplift, is roughly comma-shaped with a width of 1 km. A glacial tail comprises the SW side. There is no suggestion of a deformed circular structure surrounding this uplift (Caty et al., 1976).
Crater Morphology
Complex
Central Uplift Diameter
1km
Central Uplift Height
Unknown
Uplift Reliability Index
3
Structural Uplift
Unknown
Thickness of Seds
Target Age
Precambrian
Marine
No
Impactor Type
Iron
  1. (Evangelatos, 2009)
Other Shock Metamorphism
Planar features
  1. A large irregular mass of breccia on the north shore contains siltstone clasts with planar features in quartz (Caty et al., 1967).
Shatter Cones
Yes
  1. Shatter cones were first observed by (Caty, 1973). Very well-developed shatter cones occur on the eastern and southwestern shores of the central island (Caty et al., 1976). The size of the shatter cones is limited to the thickness of the dolomitic beds (~5-15 cm). Shatter cones occur in micritic and argillaceous dolomite. Full cones are rarely visible. Some cones have a "trumpet shape" due to the smaller apical angle near the apex. Average apical angle of 94° with cones pointing upwards and inwards to the centre of the island (Caty et al., 1975) (Caty et al., 1976). Bedding-to-cone-axis angle varies from 45 to 70° (Caty et al., 1975). Fragments of shatter cones also occur within breccia outrcoping in the north section of the island (Caty et al., 1976). Cones over one meter in height are reported by (White, 1977). Well-developed shatter cones in dolomite beds on the eastern and southwestern shores (Grieve, 2006). Sizes are limited to the thickness of the beds, 5-15cm (Grieve, 2006). The cones have an average apical angle of 94° and generally point upwards and inwards to the centre of the island (Grieve, 2006).
Planar Fractures
Yes
  1. PFs in quartz grains are present (White, 1977) (Evangelatos et al., 2009).
Planar Deformation Features
Yes
  1. PDF in quartz grains (Caty et al., 1976) (Ogilvie et al., 1984).
Diaplectic Glass
No
Coesite
No
Stisovite
No
Crater Fill
  1. Polymictic breccia dykes (Caty et al., 1976) (Evangelatos et al., 2009). Crater-fill impactites? "Breccia dikes are found all around the island. Most are thin, 20 cm or less (exaggerated in Fig. 2), although some are from 1 to 6 m thick" (Caty et al., 1976). "The dikes (Fig. 2) have a crudely radial orientation with respect to the island. Most dip steeply or are vertical, although they vary in orientation and dip. The dikes have a sharp contact with the FIG. 3. Multiple sets of planar features in silty quartz grain from a breccia fragment. Bar is 0.1 mm long. enclosing rocks, with apophyses cutting off into some beds. Some dikes form discontinuous lenses, which reappear along strike. The breccia dikes of Ile Rouleau are unique in the Mistassini basin" (Caty et al., 1976). "Most of the breccias are composed of small (1 to 2 cm), angular to subrounded fragments of micritic dolomite, shale, chert, and other lithologies known in the Mistassini Group. Some of the dolomite fragments are as large as 1.5 m. A few clasts are composed of breccia, suggesting two phases of brecciation. The earlier phase may well be a sedimentary breccia. The matrix is finely comminuted rock particles. The breccias have a pale tan color, in contrast to the general gray color of the dolomites; they are also slightly more resistant to weathering than the dolomites. The lithic fragments of the breccias, although diverse, are almost entirely composed of dolomite and clay minerals. Several fragments in breccia specimens contain silty quartz grains, however, and many of these show planar fea- tures (Carter, 1968). A few grains show multiple sets of features (Fig. 3). The planar features are decorated (P. B. Robertson, pers. comm. 1976) and suggest a low level of shock deformation" (Caty et al., 1976).
Proximal Ejecta
Distal Ejecta
Dykes
LB
Volume of Melt
Depth of Melting

References

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J-L Caty, E H Chown, D W Roy (1976) A new astrobleme: Ile Rouleau Structure, Lake Mistassini, Quebec, Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre 13(6), p. 824-831, National Research Council of Canada, Ottawa, ON, url, doi:http://dx.doi.org/10.1139/e76-085

J Evangelatos, K E Butler, J G Spray (2007) A marine magnetic study of the Ile Rouleau impact structure, Lake Mistassini, Quebec, Canada, Meteoritics & Planetary Science 42, Supple, p. 1, Meteoritical Society, Fayetteville, AR, url

J Evangelatos, K E Butler, J G Spray (2009) A marine magnetic study of a carbonate-hosted impact structure: Ile Rouleau, Canada, Geophysical Journal International 179(1), p. 171-181, Wiley-Blackwell on behalf of The Royal Astronomical Society, the Deutsche Geophysikalische Gesellschaft and the European Geophysical Society, url, doi:http://dx.doi.org/10.1111/j.1365-246X.2009.04304.x

E Flamini, A Coletta, M L Battagliere, M Virelli (2019) Ile Rouleau, Canada, Encyclopedic Atlas of Terrestrial Impact Craters, p. 531-533, Springer, Cham, url, doi:https://doi.org/10.1007/978-3-030-05451-9_148