Bigach - Hypervelocity Impact Crater

Alternate Names N/A
Coordinates 48° 34' 30" N; 82° 1' 42" E
Notes
  1. S of the village of Bigach in the Kokpekty district of the Semipalatinsk province.
Country Kazakhstan
Region East Kazakhstan
Date Confirmed 1986
Notes
  1. Confirmed by the presence of shatter cones (Kiselev and Korotushenko, 1986).
Buried? No
Notes
  1. Minor deposits of clay and alluvium fill the depression (Kiselev and Korotushenko, 1986).
Drilled? Yes
Notes
  1. Two holes, drilled to the N and S of the centre of the crater, reached depths of 180 m and 206 m. No core description given (Kiselev and Korotushenko, 1986).
Target Type Mixed
Notes
  1. \"Crystalline (volcanic) and sedimentary. Devonian and Carboniferous sandstone, andesite, basalt, dacite, tuff (all folded). Devonian basalts, overlain by Carboniferous andesite and basaltic tuff and rhyolite. Palaeozoic rocks are covered by Palaeogene clays (Kiselev and Korotushenko, 1986).\"
Sub-Type Claystone, Sandstone, Volcanics
Apparent Crater Diameter (km) 8 km
Age (Ma) 6 ± 3
Notes :
  1. Based on stratigraphy, the impact age is 6 ± 3 Ma (Grieve, 1982).

    Additional age constraints: Formed between 10 and 1 Ma (Kiselev and Korotushenko, 1986).

Method :
  1. Stratigraphy
Impactor Type Unknown

Advanced Data Fields

Notes

Local Language
N/A
Erosion
2
  1. Vestiges of a rim and an ejecta blanket of allochthonous breccia up to 50 m thick remain (Kieselev and Korotushenko, 1986).
Final Rim Diameter
Unknown
Apparent Rim Diameter
8 km
  1. (Kiselev and Korotushenko, 1986)
Rim Reliability Index
2
  1. A circular depression with an elevated rim (basaltic wall) contains >200 m of beccia and is surrounded by a zone of allogenic breccia ejecta (Kiselev and Korotshenko, 1986).
Crater Morphology
Complex
Central Uplift Diameter
Unknown
Central Uplift Height
Unknown
Uplift Reliability Index
Unknown
Structural Uplift
Unknown
Thickness of Seds
Unknown
Target Age
Palaeozoic Cenozoic
Marine
No
Impactor Type
Unknown
Other Shock Metamorphism
Unknown
Shatter Cones
Yes
  1. Shatter cones, described as \"horsetail\"-type structure occur in blocks/fragments of igneous rocks (diabases, gabbros, and basal lavas) within allogenic breccia [ejecta outside the crater] (Kiselev and Korotushenko, 1986). Poor shatter cone (clasts?) occur in fractured/brecciated rocks of the crater rim (Masaitis, 1999). CHECK REFS
Planar Fractures
No
Planar Deformation Features
No
Diaplectic Glass
No
Coesite
No
Stisovite
No
Crater Fill
Unknown
  1. Several outcrops of ejected breccia composed of blocks up to 20 m across of Paleozoic rocks, cemented by fine-grained material (Masaitis, 1999). The crater has been drilled (taken from the drilling column) and an ejecta blanket of allochthonous breccia is mentioned in the \"Erosional Level\" column but could not access this reference (Kiselev and Korotushenko, 1986).
Proximal Ejecta
Unknown
Distal Ejecta
Unknown
Dykes
Unknown
Volume of Melt
Unknown
Depth of Melting
Unknown

References

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N P Kiselev, Y G Korotushenko (1986) The Bigach astrobleme in eastern Kazakhstan, Meteoritika 45, p. 119-121, url

V L Masaitis (1999) Impact structures of northeastern Eurasia: The territories of Russia and adjacent countries, Meteoritics & Planetary Science 34, p. 691-711