Avak - Hypervelocity Impact Crater

Alternate Names
Local Language
Coordinates 71° 14' 25" N; 156° 30' 7" W
Notes
  1. 12 km SE of Barrow, Alaska on coastal plain (Kirschner et al., 1992).
Country United States of America
Region Alaska
Date Confirmed 1992
Notes
  1. Confirmed by PDFs in quartz and shatter cones from drill core from the central high (Kirschner et al., 1992).
Buried? Yes
Notes
  1. Buried by ~30 m of permanently frozen Pliocene and Pleistocene sand and gravel. No surface expression, on swampy, lake dotted tundra (Kischner et al., 1992). Buried beneath ~1 km of sedimentary cover (Banet and Fenton, 2008).
Drilled? Yes
Notes
  1. ~17 drill holes.
Target Type Sedimentary
Notes
  1. \"Ordovician to Lower Cretaceous sediments. Ordovician-Cretaceous shale, sandstone, argillite.\"
Sub-Type Argillite, Sandstone, Shale
Apparent Crater Diameter (km) 10 km
Age (Ma) 90 - 94
Notes :
  1. 90-94 Ma (late Turonian) based on palynological data from above, within, and below the breccia (Banet and Fenton, 2008) Previous age constraints: Minimum age: impact overlain by Late Pliocene/Quaternary deposits (~3 Ma) (Kirschner et al., 1992) Maximum age: lack of ejecta in nearby Albian and Cenomanian deposits, suggests impact post-dates Cenomanian (~95 Ma) (Kirschner et al., 1992)

Method :
  1. Palynology
Impactor Type Unknown

Advanced Data Fields

Notes

Erosion
4
  1. Very limited information available from drill cores. Appears to be no ejecta preserved (Banet and Fenton, 2008).
Final Rim Diameter
Unknown
Apparent Rim Diameter
10 km
  1. ~10 km in diameter (Banet and Fenton, 2008). Based on geophysics. Uplift is a minimum.
Rim Reliability Index
2
  1. Central uplift ~4 km in diameter. Surrounding annular depression, high rim with discontinuous ring. Central uplift and annular structural low, clearly defined by its gravity signature (Kirschner et al., 1992).
Crater Morphology
Complex
Central Uplift Diameter
4km
Central Uplift Height
Unknown
Uplift Reliability Index
2
Structural Uplift
500 m
Thickness of Seds
Target Age
Palaeozoic Mesozoic
Marine
No
Impactor Type
Other Shock Metamorphism
Kinked chlorite clays
Shatter Cones
Yes
  1. Well-developed shatter cones, up to 10 cm high and more than 8 cm wide (parts of larger cones), occur in quartz sandstone of the Lower Jurassic Barrow sand and in calcareous concretions in Kingak (?) Shale (Kirschner et al., 1992) (Therriault and Grantz, 1995) [recovered between 538 and 576 m (from a large clast/block?), in core U.S. Navy Avak 1, drilled close to the centre of the structure]. Thin dark gray lutite lie on surfaces of some shatter cones (Kirschner et al., 1992).
Planar Fractures
No
Planar Deformation Features
Yes
  1. PDF in quartz grains, good ones are rare (Therriault and Grantz, 1995).
Diaplectic Glass
No
Coesite
No
Stisovite
No
Crater Fill
LB
  1. Breccia clasts in mudstone. Also appears to be breccia clasts, believed to be Avak ejecta (Kirschner et al., 1992) (Banet and Fenton, 2008).
Proximal Ejecta
Distal Ejecta
LB
Dykes
Volume of Melt
Depth of Melting

References

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F R Collins, M C Brewer (1961) Core tests and test wells, Barrow Area, Alaska, p. 569-644, US Government Printing Office

J R Woolson (1962) Seismic and gravity surveys of naval petroleum reserve No. 4 and adjoining areas, Alaska 1944-53

R J Lantz (1980) Barrow Gas Fields, North Slope, Alaska, AAPG Bulletin 64(5), p. 737-737, url

C E Kirschner, A Grantz, M W Mullen (1992) Impact Origin of the Avak Structure, Arctic Alaska, and Genesis of the Barrow Gas Fields, The American Association of Petroleum Geologists Bulletin 76(5), p. 651-679

R A F Grieve, V L Masaitis (1994) The economic potential of terrestrial impact craters, International Geology Review 36(2), p. 105-151, url, doi:10.1080/00206819409465452

Richard R Donofrio (1998) North American impact structures hold giant field potential, Oil & Gas Journal, p. 69-83

Arthur C Banet, J P G Fenton (2007) An examination of the Simpson core test wells suggests an age for the Avak impact feature near Barrow, Alaska, Special Paper of the Geological Society of America 437, p. 139-145, Geological Society of America, url, doi:10.1130/2008.2437(08)

Arthur C Banet, J P G Fenton, T P Walsh, T C Morahan, P Stokes (2009) Palynological and core data suggest middle-late Turonian age for the Avak impact, Barrow, Alaska, American Association of Petroleum Geologists

Enrico Flamini, A Coletta, M L Battagliere, M Virelli (2019) Avak, USA, Encyclopedic Atlas of Terrestrial Impact Craters, E Flamini, Di Martino M, Coletta A (ed.), p. 451-453, Springer International Publishing, doi:10.1007/978-3-030-05451-9_123