Slate Islands - Hypervelocity Impact Crater

Alternate Names
Local Language
Coordinates 48° 39' 11" N; 87° 0' 29" W
Notes
  1. In Lake Superior, 13 km S of Terrace Bay.
Country Canada
Region Ontario
Date Confirmed 1976
Notes
  1. Previous to this study, Sage had reported "shatter cone-like" structures, but this paper goes into detail describing shatter cones and shock deformation (PFs and PDFs) in quartz and feldspars (Hall and Grieve, 1976).
Buried? No
Notes
  1. Only central uplift is emergent.
Drilled? No
Target Type Mixed
Notes
  1. Archean granite greenstone, minor Keweenawan basalt and minor sandstone. Geologically complex rocks of the Superior Province; Archean to Keweenawan felsic to mafic metavolcanics and metasediments and pyroclastics with dioritic and felsic intrusives (Sage, 1978).
Sub-Type Basalt, Sandstone, Granite
Apparent Crater Diameter (km) 30 km
Age (Ma) ~450
Notes :
  1. ~450 Ma determined by 40Ar/39Ar of pseudotachylite (Dressler et al., 1979). Additional age constraints: Slightly more eroded than the comparably sized Charlevoix structure (Halls and Grieve, 1976). 500-800 Ma estimated stratigraphically (Sharpton et al., 1997).

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

Advanced Data Fields

Notes

Erosion
7
  1. No crater-fill remains. Only remnants of the breccia remain and the crater floor is exposed. Originally the metavolcanics were overlain by Keweenawan basalts and sediments. Glaciation has modified both the subaerial and submarine areas (Ogilvie et al., 1984).
Final Rim Diameter
Unknown
Apparent Rim Diameter
30 km
  1. Apparent diameter of 30 km (Osinski and Ferriere, 2016). Diameter estimates include 30 km (Halls and Grieve, 1976) and in more recent papers the diameter is noted as 30-32 km (Sharpton et al., 1996) (Dressler and Sharpton, 1997).
Rim Reliability Index
4
  1. Based on geophysics (Bengston, 1984).
Crater Morphology
Complex
Central Uplift Diameter
12km
Central Uplift Height
Unknown
Uplift Reliability Index
Structural Uplift
Unknown
Thickness of Seds
Target Age
Precambrian
Marine
No
Impactor Type
Other Shock Metamorphism
No
Shatter Cones
Yes
  1. The exposed Keweenawan is about 400 feet (120 m) thick; 16 flow units were identified and more are undoubtedly present. The metavolcanics, and at least one of the sandstone beds, have a well developed cone-shaped or plumose fracture pattern (shatter cone-like) which is well displayed on several wave washed shoals along the west coast of the island. The axes of these shatter cone-like features have a shallow east ward plunge with their apices showing a strongly preferred orientation towards the east. (Sage, 1974). Shatter cones were first observed by R. Sage during field mapping in 1973 (Sharpton et al., 1996). Shatter cones are present in practically all target rocks of the Slate Islands, including shatter cone clasts within breccia (Sharpton et al., 1996). They are especially well developed in Keweenawan metabasalts and interflow sediments. Shatter cones typically range in size from ~2-3 cm to ~1 m long. The smallest cones are most common in fine-grained metasediments; cones somewhat larger, well-developed, 10-30 cm occur in Keweenawan metabasalts (Sharpton et al., 1996). A minimum 10 m long shatter cone is visible in Archean felsic metavolcanic rocks on the shoreline (in McGreevy Harbour) (Sharpton et al., 1996). Shatter-coned fragments occur within polymict impact breccia (Dressler et al., 1999). Shatter cones with apices pointing in opposite or diverging directions occur but are not common" (Dressler et al., 1999). "The target rocks exhibit shatter cones (Fig. 23.3a) and are in places, brecciated and locally from autochthonous breccias (Grieve, 2006). Breccia dykes containing shatter cones (Grieve, 2006). Shatter cones best developed in the unmetamorphosed Keweenawan lithologies reaching up to 30 cm in axial length (Halls and Grieve, 1976). "On the Slate Islands shatter cones are found in almost all rock types, but are best developed in Keweenawan basalt flows and chilled margins of associated feeder dykes, and in Archean diorite, feldspar porphyry, felsic metavolcanics, and iron formation" (Stesky and Halls, 1983). "Shatter cones occur in practically all impact units except for impact melts rocks, which, however, contain shatter-coned inclusions as observed at one location on the west-central shore of Patterson Island" (Dressler et al., 1995). Shatter cones range in size from 1 to 2 cm to several meters long, the largest occuring in felsic metavolcanic rocks on the eastern shore of McGreevy Harbor are at least 10 m long (Dressler et al., 1995).
Planar Fractures
Yes
  1. PF in quartz (Dressler et al., 1999).
Planar Deformation Features
Yes
  1. PDF in quartz and feldspar (Grieve and Robertson, 1976) (Halls and Grieve, 1976) (Dressler et al., 1995) (Dressler et al., 1999). PDFs in feldspars and carbonate (Dressler et al., 1995). PDF in quartz (Sharpton et al., 1996). PDF in quartz grains, 6-15 GPa (Grieve and Robertson, 1976) (Wu et al., 1993).
Diaplectic Glass
No
Coesite
No
Stisovite
No
Crater Fill
  1. The structure has been eroded below the crater floor. Crater-fill impactites are not preserved. Poorly sorted (clast size varies between less than 1 cm, up to 10s of meters) polymict lithic breccia dykes occur in the target rocks. Pseudotachylite veins up to 5 cm wide with clasts of less than 3 mm in size are also present (Kerrigan et al., 2014). Melt-bearing breccias (suevites) have been reported by (Dressler et al., 1998). However, (Kerrigan et al., 2014) could not identify these breccias based on macroscopic analysis.
Proximal Ejecta
Distal Ejecta
Dykes
LB, P
Volume of Melt
Depth of Melting

References

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H C Halls, R A F Grieve (1976) The Slate Islands; a probable complex meteorite impact structure in Lake Superior, Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre 13(9), p. 1301-1309, National Research Council of Canada, Ottawa, ON, url, doi:http://dx.doi.org/10.1139/e76-131

R A F Grieve, P B Robertson (1976) Variations in shock deformation at the Slate Islands impact structure, Lake Superior, Canada, Contributions to Mineralogy and Petrology 58(1), p. 37-49, Springer International, Heidelberg-New York, url

H C Halls, R A F Grieve (1976) The Slate Islands; the central uplift of a meteorite impact crater?, Proceedings and Abstracts - Institute on Lake Superior Geology. Meeting(22), p. 27, Institute on Lake Superior Geology

R A F Grieve, P B Robertson (1977) The Slate Islands structure; a partially submerged impact crater in Lake Superior, Geos, p. 15-17, Canada Department of Energy, Mines and Resources, Ottawa, ON, url

H C Halls (1977) The paleomagnetic signature of a complex meteorite impact structure, Slate Islands, Lake Superior, Eos, Transactions, American Geophysical Union 58(8), p. 727, American Geophysical Union, Washington, DC

R M Stesky (1978) Elastic properties of shocked rocks from the Slate Islands meteorite impact structure, northern Lake Superior, Eos, Transactions, American Geophysical Union 59(12), p. 1033, American Geophysical Union, Washington, DC

H C Halls, R M Stesky (1978) Paleomagnetic and shatter cone measurements from the Slate Islands, northern Lake Superior, Eos, Transactions, American Geophysical Union 59(12), p. 1035, American Geophysical Union, Washington, DC

H C Halls (1979) Diatremes and shock features in Precambrian rocks of the Slate Islands, northeastern Lake Superior; discussion, Geological Society of America Bulletin 90(11), p. 1084-1086, Geological Society of America (GSA), Boulder, CO, url

R P Meyer, J H Karl, H C Halls, M E Bengtson (1980) The Slate Islands; an astrobleme?, Eos, Transactions, American Geophysical Union 61(17), p. 366, American Geophysical Union, Washington, DC

M E Bengtson, R P Meyer (1981) Investigations of the Slate Islands Crater, Eos, Transactions, American Geophysical Union 62(45), p. 1039, American Geophysical Union, Washington, DC, url

M E Bengtson, R P Meyer, P Pomeroy (1981) Seismic characteristics of an ancient shock structure; Slate Islands, Canada, Earthquake Notes 52(3), p. 10, Seismological Society of America, Eastern Section, [El Cerrito, CA]

R M Stesky, H C Halls (1983) Structural analysis of shatter cones from the Slate Islands, northern Lake Superior, Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre 20(1), p. 1-18, National Research Council of Canada, Ottawa, ON, url, doi:http://dx.doi.org/10.1139/e83-001

D D'Aria, J B Garvin (1988) Thermal infrared reflectance spectroscopy of impact-related rocks; implications for geologic remote sensing of Mars and Earth, Abstracts of Papers Submitted to the Lunar and Planetary Science Conference 19, Part 1, p. 243-244, Lunar and Planetary Science Conference, Houston, TX

P E Jupp, B D Spurr (1989) Statistical estimation of a shock center; Slate Islands astrobleme, Mathematical Geology 21(2), p. 191-198, Plenum [for the] International Association for Mathematical Geology, New York-London, url

H C Halls (1990) The Slate Island meteorite impact site; a study of shock remanent magnetization, Fennoscandian impact structures, L J Pesonen, H Niemisara (ed.), p. 27, Geol. Surv. Finl., Espoo, url

V L Sharpton, B O Dressler, B Schnieders, J Scott (1995) Shock metamorphism and impact melts at the Slate Islands impact structure, Lake Superior, Ontario, Canada, Eos, Transactions, American Geophysical Union 76(46, Suppl.), p. 337, American Geophysical Union, Washington, DC

B O Dressler, V L Sharpton, B Schneiders, J Scott (1995) New observations at the Slate Islands impact structure, Lake Superior, Ontario Geological Survey Miscellaneous Paper, J A Ayer, C L Baker, J A Fyon, J A Junkin, C A Kaszycki, D G Laderoute, G Merlino, J W Newsome, L Owsiacki, J M Richardson, G Spiers, P C Thurston (ed.), p. 53-61, Ontario Geological Survey, Toronto, ON, url

B O Dressler, V L Sharpton, B Schnieders, J Scott (1996) Formation of impact breccias at the Slate Islands Structure, northern Lake Superior, Ontario, Canada, Abstracts of Papers Submitted to the Lunar and Planetary Science Conference 27, Part 1, p. 325-326, Lunar and Planetary Science Conference, Houston, TX, url

B O Dressler, V L Sharpton (1996) Breccias of the Slate Islands impact structure, northern Lake Superior, Ontario, Abstract Volume (Geological Association of Canada) 21, p. 1, Geological Association of Canada, Waterloo, ON

V L Sharpton, B O Dressler (1996) The Slate Islands impact structure; structural interpretation and age constraints, Abstracts of Papers Submitted to the Lunar and Planetary Science Conference 27, Part 3, p. 1177-1178, Lunar and Planetary Science Conference, Houston, TX

V L Sharpton, B O Dressler, R R Herrick, B Schnieders, J Scott (1996) New constraints on the Slate Islands impact structure, Ontario, Canada, Geology 24(9), p. 851-854, Geological Society of America (GSA), Boulder, CO, url, doi:http://dx.doi.org/10.1130/0091-7613(1996)024<0851:NCOTSI>2.3.CO;2

B O Dressler, V L Sharpton, B Schnieders, J Scott (1996) Clastic breccias at the Slates Islands complex impact structure, Northern Lake Superior, LPI Contributions, p. 38-45, url

B O Dressler, V L Sharpton, B R Schnieders, J F Scott (1996) Clastic breccias at the Slate Islands complex impact structure, northern lake Superior, Ontario Geological Survey Miscellaneous Paper, C L Baker, P C Thurston, M C Gerow, C A Kaszycki, D G Laderoute, G Merlino, J W Newsome, L Owsiacki, G Spiers, J A Fyon (ed.), p. 38-45, Ontario Geological Survey, Toronto, ON, url

R A F Grieve, P B Robertson (1997) New constraints on the Slate Islands impact structure: Comment, Geology 25(7), p. 666-667

B O Dressler, V L Sharpton (1997) Breccia formation at a complex impact crater; Slate Islands, Lake Superior, Ontario, Canada, Tectonophysics 275(4), p. 285-311, Elsevier, Amsterdam, url

V L Sharpton, P Copeland, B O Dressler, T L Spell, D Black, D P Blanchard (1997) New age constraints on the Slate Islands impact structure, Lake Superior, Canada, Abstracts of Papers Submitted to the Lunar and Planetary Science Conference 28, Part 3, p. 1287-1288, Lunar and Planetary Science Conference, Houston, TX, url

R Sage (1999) The Slate Islands; a uniquely sited cryptoexplosion structure, Open File Report - Ontario Geological Survey, p. 28.1-28.13, Ministry of Natural Resources, Toronto, ON

B O Dressler, V L Sharpton, P Copeland (2000) Slate islands, lake superior, canada: a mid-size, complex impact structure, Large meteorite impacts and planetary evolution II 38, Lunar and Planetary Inst., Houston, TX USA: NASA, Suite 1M32, Washington, DC, 20546-0001, USA, [mailto:public-inquiries@hq.nasa.gov], [URL:http://www.nasa.gov], url

B O Dressler, W U Reimold, V L Sharpton, Roger L Gibson (2001) Pseudotachylites in central parts of impact craters - orientation and timing of emplacement, Lunar & Planetary Science Conference 39, p. 1023, Witwatersrand Univ., Impact Cratering Research Group, Johannesburg, South Africa: NASA, Suite 1M32, Washington, DC, 20546-0001, USA, [mailto:public-inquiries@hq.nasa.gov], [URL:http://www.nasa.gov], url

A M Nuhn, G R Osinski, L L Tornabene (2013) Remote sensing study of the Slate Islands impact structure, Canada, Abstracts of Papers Submitted to the Lunar and Planetary Science Conference 44, p. Abstract 2389, Lunar and Planetary Science Conference, Houston, TX, url

M C Kerrigan, J Clayton, A M Nuhn, A E Pickersgill, G R Osinski (2014) The Slate Islands impact structure, Lake Superior, Canada; field and petrographic observations of impact breccias, Abstracts of Papers Submitted to the Lunar and Planetary Science Conference 45, p. Abstract 1588, Lunar and Planetary Science Conference, Houston, TX, pdf

E Flamini, A Coletta, M L Battagliere, M Virelli (2019) Slate Islands, Canada, Encyclopedic Atlas of Terrestrial Impact Craters, p. 613-615, Springer, Cham, url, doi:https://doi.org/10.1007/978-3-030-05451-9_170