Brent - Hypervelocity Impact Crater

Alternate Names
Local Language
Coordinates 46° 4' 32" N; 78° 28' 59" W
Notes
  1. 4 km north of Brent, Ontario, within the northern boundary of Algonquin Park. Two lakes are located within the crater, Gilmour and Tecumseh.
Country Canada
Region Ontario
Date Confirmed 1960
Notes
  1. (Millman et al., 1960) concludes the site is of an impact origin based on aerial and terrestrial investigation, with additional gravity, magnetic, and seismic surveys supporting this theory. Additionally, cores taken near the centre of the crater contain evidence for PDFs in quartz (Dence, 1964).
Buried? Yes
Notes
  1. Sedimentary fill, ~250m thick, Lower to Middle Ordovician in age, covers the breccia; the crater depression is still noticeable in surface morphology (Allen et al., 1981).
Drilled? Yes
Notes
  1. 5 km of core from 12 holes penetrate sedimentary fill, a brecciated zone, a melt zone and into fractured crystalline basement (Grieve and Cintala, 1981).
Target Type Crystalline
Notes
  1. The igneous-metamorphic basement complex is mainly gneiss of granodioritic composition of the Grenville structural province (Grieve, 1978).
Sub-Type Gneiss
Apparent Crater Diameter (km) 3.4 km
Age (Ma) 453.2 ± 6.0
Notes :
  1. A U-Pb (LA-ICP-MS) age of 453.2 ± 6.0 Ma was obtained from melt-grown apatites and zircons (McGregor et al., 2020). Additional age constraints: K-Ar studies on the coarsest crystalline melt rocks provide an age of 450 ± 30 Ma (Hartung et al., 1971). Schmieder and Kring (2020) also cite: Lozej and Beales (1975); Grahn and Ormo¨ (1995)

Method :
  1. U-Pb
Impactor Type Ordinary chondrite
Notes
  1. Based on PGE geochemistry the impactor is likely L or LL chondrite (Evans et al., 1993).

Advanced Data Fields

Notes

Erosion
4
  1. Rim is largely eroded, although the crater-fill products are preserved. The vertical depth from the original ground plane to the present erosional surface is estimated at 220 m (Grieve and Cintala, 1981).
Final Rim Diameter
3.8 km
Apparent Rim Diameter
3.4 km
  1. These are reconstructed dimensions (Grieve and Cintala, 1981).
Rim Reliability Index
2
  1. Largest known terrestrial crater with a simple, bowl-shaped form. The ejecta and rim are absent and the depression is filled with Ordovician sediments (Grieve and Cintala, 1981).
Crater Morphology
Simple
Central Uplift Diameter
km
Central Uplift Height
Unknown
Uplift Reliability Index
1
Structural Uplift
Unknown
Thickness of Seds
Target Age
Precambrian
Marine
No
Impactor Type
Ordinary chondrite
  1. Based on PGE geochemistry the impactor is likely L or LL chondrite (Evans et al., 1993).
Other Shock Metamorphism
Shatter Cones
Yes
  1. The occurrence of shatter cones in gneiss from the target rock is reported in borehole B-1-59, at depths between 2896 and 3035 feet (Matthews, 1974) (page 21). [Shatter cones questionable]. The fracturing and brecciation observed deep in the central hole are accompanied by curved, fluted fracture surfaces resembling portions of shatter cones (Dence, 1964).
Planar Fractures
Yes
  1. PF quartz in lithic clasts of mesoperthite gneiss in allochthonous breccia from drill hole B1-59 (Fig. 1.4) (Grieve, 2006).
Planar Deformation Features
Yes
Diaplectic Glass
No
Coesite
No
Stisovite
No
Crater Fill
LB, MB, M
  1. Polymict lithic and monomict breccias (Coney et al., 2007). V.o.M. via Table 1 of (Grieve and Cintala, 1981) 600 m of crater-fill impactites: polymict and monomict lithic breccias interbedded with melt-bearing breccias, overlying a lenticular basal melt sheet of 200 m in radius and 42 m thick at the center of the structure. These melt rocks are clast-rich at the contacts with the fractured basement and the overlying breccias, and clast-poor in the middle of the sheet (Dence, 1964), (Grieve, 1978) (Grieve and Cintala, 1981) (McGregor et al., 2020).
Proximal Ejecta
Distal Ejecta
Dykes
Volume of Melt
1 x 10-3 km3 or 2x10^-2 km^3
Depth of Melting

References

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P M Millman, B A Liberty, J F Clark, P L Willmore, M J S Innes (1960) The Brent Crater, Publications of the Dominion Observatory Ottawa XXIV(1)

C S Beals, M J S Innes, J A Rottenberg (1960) The Search For Fossil Meteorite Craters - I, Current Science Association 29(6), p. 205-218, url

M J S Innes (1961) The Use of Gravity Methods to Study the Underground Structure and Impact Energy of Meteorite Craters, Journal of Geophysical Research 66(7), p. 2225-2239, url, doi:10.1029/JZ066i007p02225

Michael R Dence (1964) A comparative structural and petrographic study of probable Canadian meteorite craters, Meteoritics 2(3), p. 249-270, url, doi:10.1111/j.1945-5100.1964.tb01432.x

A E Beck, Z Logis (1964) Terrestrial Flow of Heat in the Brent Crater, Nature 201, p. 383-383, url, doi:10.1038/201383a0

Michael R Dence (1965) The extraterrestrial origin of Canadian craters, Annals of the New York Academy of Sciences 123(2), p. 941-969, doi:10.1111/j.1749-6632.1965.tb20411.x

K L Currie, M Shafiqullah (1967) Carbonatite and Alkaline Igneous Rocks in the Brent Crater, Ontario, Nature 215, p. 725-726, url, doi:10.1038/215725a0

M Shafiqullah, W M Tupper, T J S Cole (1968) K-Ar ages on rocks from the crater at Brent, Ontario, Earth and Planetary Science Letters 5, p. 148-152, url, doi:10.1016/S0012-821X(68)80031-7

R A F Grieve, Michael R Dence, P B Robertson (1971) Cratering processes: As interpreted from the occurrence of impact melts*, Impact and Explosion Cratering, p. 791-814

Jack B Hartung, Michael R Dence, John A S Adams (1971) Potassium-argon dating of shock-metamorphosed rocks from the Brent Impact Crater, Ontario, Canada, Journal of Geophysical Research 76(23), p. 5437-5448, American Geophysical Union (AGU), url, doi:10.1029/jb076i023p05437

Michael R Dence, J B Hartung, J F Sutter (1971) Old K-Ar mineral ages from the Grenville province, Ontario, Canadian Journal of Earth Sciences 8(11), p. 1495-1498, url, doi:10.1139/e71-138

K L Currie (1971) A Study of Potash Fenitization around the Brent Crater, Ontario,-A Paleozoic Alkaline Complex, Canadian Journal of Earth Sciences 8(5), url

P B Robertson (1973) Durham E-Theses: Shock metamorphism of potassic feldspars, url

G P Lozej, F W Beales (1975) The Unmetamorphosed Sedimentary Fill of the Brent Meteorite Crater, Southeastern Ontario, Canadian Journal of Earth Sciences 12, p. 606-628, url, doi:10.1139/e75-055

P B Robertson, R A F Grieve (1975) Impact structures in Canada: Their recognition and characteristics*, The Journal of the Royal Astronomical Society of Canada 69(1), p. 1-21

F W Beales, G P Lozej (1975) Ordovician Tidalites in the Unmetamorphosed Sedimentary Fill of the Brent Meteorite Crater, Ontario, Tidal Deposits, p. 315-323, url, doi:10.1007/978-3-642-88494-8_36

E K Jessberger, Michael R Dence, B Dominik, J Hartung, T Kirsten, O A Schaeffer (1976) Crater Chronology: Resetting of K-AR Ages by Craters of 1-20KM Size from Studies on the Ries and Brent Craters, LPI Contributions 262, p. 19, url

A E Beck, V M Hamza, C C Chang (1976) Analysis of heat flow data - correlation of thermal resistivity and shock metamorphic grade and its use as evidence for an impact origin of the Brent Crater, Canadian Journal of Earth Sciences 13(7), p. 929-936, url, doi:10.1139/e76-095

O V Parfenova, O I Yakovlev (1977) Some peculiarities of selective evaporation in target rocks after meteoritic impact, Impact and Explosion Cratering, p. 843-859, url

P B Robertson, R A F Grieve (1977) Shock attenuation at terrestrial impact structures*, Impact and Explosion Cratering; Planetary and Terrestrial Implications, p. 687-702, url

Michael R Dence, R A F Grieve, P B Robertson (1977) Terrestrial impact structures: Principal characteristics and energy considerations*, Impact and Explosion Cratering, p. 247-275, url

R A F Grieve, Michael R Dence (1978) Principal Characteristics of the Impactites at Brent Crater, Ontario, Canada, Lunar and Planetary Science IX, p. 416-418, url

Richard A F Grieve (1978) The Petro-Chemistry of the Melt Rocks at Brent Crater and Their Implications for the Conditions of Impact, Meteoritics 13, p. 484-486, url

Richard A F Grieve (1978) The melt rocks at Brent Crater, Ontario, Canada, Lunar Planetary Science Conference, 9th, p. 2579-2608, url

Herbert Palme, Rainer Wolf, Richard A F Grieve (1978) New Data on Meteoritic Material at Terrestrial Impact Craters, Lunar and Planetary Science IX, p. 856-858, url

D Stoeffler, H-D Knoell, U Maerz (1979) Terrestrial and lunar impact breccias and the classification of lunar highland rocks, Lunar and Planetary Science Conference Proceedings 10, N W Hinners (ed.), p. 639-675, url

O I Yakovlev, V I Vernadsky (1980) The role of vaporization and condensation in the formation of the chemical composition of impactites, Lunar and Planetary Science XI, p. 1285-1287

R A F Grieve, Mark J Cintala (1981) Brent Crater, Ontario: Observation and Theory, Lunar and Planetary Institute Science Conference Abstracts 12, p. 362-364, url

P H Schultz (1981) The Impact of Impacts Explored, Geotimes 26, p. 25-26, url

Herbert Palme, Richard A F Grieve, Rainer Wolf (1981) Identification of the projectile at the Brent crater, and further considerations of projectile types at terrestrial craters*, Geochimica et Cosmochimica Acta 45, p. 2417-2424, url, doi:10.1016/0016-7037(81)90095-8

Carlton C Allen, James L Gooding, Klaus Keil (1981) Hydrothermally altered impact melt from Brent and Ries craters, Lunar and Planetary Science XII, p. 16-18, url

Carlton C Allen, J L Gooding, K Keil (1982) Altered Impact Melt Rock and Breccia: Contribution to Martian "soil", Lunar and Planetary Institute Science Conference Abstracts 13, p. 7-8, url

K A Holsapple (1982) A Comparison of Scaling Laws for Planetary Impact Cratering: Experiments, Calculations, and Theory, Lunar and Planetary Institute Science Conference Abstracts 13, p. 331-332, url

James B Garvin, R A F Grieve (1982) An Analytical Model for Simple Terrestrial Craters: Brent and Meteor, Lunar and Planetary Science XIII, p. 251-252, url

Richard A F Grieve, Mark J Cintala (1982) A Method for Estimating the Initial Impact Conditions of Terrestrial Cratering Events, Exemplified by its Application to Brent Crater, Ontario, 12th Lunar Planetary Science Conference, p. 1607-1621, url

R A F Grieve, James B Garvin (1984) A geometric model for excavation and modification at terrestrial simple impact craters, Journal of Geophysical Research 89, p. 11561-11572, url

R A F Grieve, James B Garvin (1984) A Test of a Model for the Development of Terrestrial Simple Craters, Lunar and Planetary Institute Science Conference Abstracts 15, p. 324-325, url

R M Schmidt, K R Housen, M D Bjorkman (1985) Centrifuge impact cratering experiments, Reports of Planetary Geology and Geophysics Program, p. 167-169, url

R E Chavez (1986) An optimisation of the gravity data from the Brent crater, Ontario, Canada, First Break 4(2), url, doi:10.3997/1365-2397.1986004

Noreen J Evans, D C Gregoire, R A F Grieve, W D Goodfellow, J Veizer (1993) Use of platinum-group elements for impactor identification: Terrestrial impact craters and Cretaceous-Tertiary boundary, Geochimica et Cosmochimica Acta 57, p. 3737-3748, url, doi:10.1016/0016-7037(93)90152-M

Gerhard Schmidt, H Palme, K L Kratz (1995) The Fractionation of Highly Siderophile Elements (HSE) in Impact Melts and the Determination of the Meteoritic Components, Meteoritics 30, p. 573-573, url

Jens Ormö, Maurits Lindström (2000) When a cosmic impact strikes the sea bed, Geological Magazine 137(1), p. 67-80, url, doi:10.1017/S0016756800003538

C O'Dale (2002) Exploring Meteorite Craters From the Air, Meteorite - The International Quarterly of Meteorites and Meteorite Science 8, p. 34-37, url

Michael R Dence (2003) WIRGO in TIC's? [What (on Earth) is Really Going On in Terrestrial Impact Craters?] or Structural Evidence from Shock Metamorphism, Impact Cratering: Bridging the Gap Between Modeling and Observations, p. 20-20, url

Bart Vleminckx (2010) Universiteit Gent: Geochemistry of the Brent impact structure, Ontario, Canada, url

Drew Branson (2018) The Brent Crater: an alkaline igneous complex, 12th I@Q Conference Proceedings, url, doi:10.24908/iqurcp.11561

Enrico Flamini, A Coletta, M L Battagliere, Maria Virelli (2019) Brent, Canada, Encyclopedic Atlas of Terrestrial Impact Craters, p. 461-462, Springer International Publishing, doi:10.1007/978-3-030-05451-9_126

Maree McGregor, Michael R Dence, Christopher R M McFarlane, John G Spray (2020) U–Pb geochronology of apatite and zircon from the Brent impact structure, Canada: a Late Ordovician Sandbian–Katian boundary event associated with L-Chondrite parent body disruption, Contributions to Mineralogy and Petrology 175(7), Springer, doi:10.1007/s00410-020-01699-9