Kaluga - Hypervelocity Impact Crater

Alternate Names
Local Language
Coordinates 54° 30' 0" N; 36° 12' 0" E
Notes
  1. Near the town of Kaluga.
Country Russia
Region Kaluga
Date Confirmed 1980
Notes
  1. PDFs in quartz (Masaitis, 1980). There are earlier references (e.g., Masaitis, 1973) but these are in Russian and it's unclear what they base an impact origin interpretation from. Also see (Masaitis, 2002) for a more recent, comprehensive overview in English.
Buried? Yes
Notes
  1. Buried under about 800 m of Upper Devonian and Lower Carboniferous sandstone and limestone (Masaitis et al., 1975).
Drilled? Yes
Notes
  1. 18 holes have been drilled, 10 into the rim area. The few holes within the depression penetrate sedimentary cover, breccias, and fractured basement complex (Masaitis et al., 1980).
Target Type Mixed
Notes
  1. Crystalline basement of granitic gneisses and schists and sandstones and siltstones of Upper Proterozoic (Masaitis et al., 1975). Middle Devonian clays, sandstones and siltstones (Masaitis et al., 1980). (Flamini, 2019) (Masaitis, 2002) describes target rock that consists of "Archean and Lower Proterozoic crystalline basement rocks (schists, gneisses, granites) covered by a [0.125-km]-thick sedimentary sequence of Upper Proterozoic argillites, silt and sandstones, and 50 m of Middle Devonian (lower horizon; D2ef1 in Fig. 3) clay, siltstones, sandstones and clayey sulfate–carbonate rocks."
Sub-Type Claystone, Gneiss, Sandstone, Schist, Siltstone, Granite
Apparent Crater Diameter (km) 15 km
Age (Ma) 383 - 394
Notes :
  1. Jourdan et al. 2009 recommend using the biostratigraphic age (youngest disturbed beds) of Middle or Upper Eigelian (Kazman and Tikhomirov, 1962; Petrov, 1969; Tikhomirov, 1995; Masaitis, 2002) because K-Ar is notoriously unreliable and the data are not availble for interrogation. Recommended age in Jourdan et al. 2009 is ~398-392 Ma; but absolute age of Eifelian has changed since so numbers are now 394-383 Ma. Isotopic dating provided a rough age of 380 ± 10 Ma; specific method not given (Masaitis et al., 1980) (Masaitis et al., 1999) (Masaitis et al., 2002). K-Ar of melt rock yielded age of 380 Ma ((Harris, 1962) according to (Masaitis, 2002)). (Harris 1962 is in Russian).

Method :
  1. Stratigraphic
Impactor Type Unknown

Advanced Data Fields

Notes

Erosion
2
  1. Ejecta and rim have been slightly eroded; the crater-fill products have been preserved (Masaitis et al., 1980).
Final Rim Diameter
Unknown
Apparent Rim Diameter
15 km
  1. Dimensions from diagram of (Masaitis et al., 1980).
Rim Reliability Index
4
  1. A central uplift is suspected but not yet revealed" (Masaitis, 2002).
Crater Morphology
Complex
Central Uplift Diameter
km
Central Uplift Height
Unknown
Uplift Reliability Index
Structural Uplift
Unknown
Thickness of Seds
0.125
Target Age
Precambrian Palaeozoic
Marine
Yes
Impactor Type
Other Shock Metamorphism
Maskelynite
  1. (Masaitis et al., 1980)
Shatter Cones
No
  1. Buried impact structure.
Planar Fractures
Yes
  1. Two sets of comparatively much wider spaced planar. Planar fractures in quartz clasts and rock fragments (Masaitis et al., 2002).
Planar Deformation Features
Yes
  1. PDF in quartz grains (Masaitis et al., 1980). Quartz in rock fragments as well as quartz mineral clasts display planar deformation features (Masaitis et al., 2002). See Fig. 4: lithic breccia has quartz clasts with PDFs (Masaitis et al., 2002). See Fig. 5: biotite clast with three sets of PDFs, oriented perpendicular to the face (0 0 1) (Masaitis et al., 2002). See Fig. 9: granite fragment of a suevite with PDFs in quartz grains (Masaitis et al., 2002).
Diaplectic Glass
Yes
  1. Some plagioclase fragments exhibit shock-induced twinning or are converted into diaplectic crystals (Masaitis et al., 2002).
Coesite
No
  1. Did not find in literature.
Stisovite
No
  1. Did not find in literature.
Crater Fill
LB, MB, M
  1. Crater-fill impactites include polymict lithic breccias (the clasts are biotite gneisses, granites and schists), melt-bearing breccias (referred to as suevites) composed of crystalline and sedimentary clasts, and glass with flow textures and vesicles, and impact melt rocks (referred to as tagamites) with a glassy to aphanitic matrix (Masaitis, 2002). Lithic breccias grade into melt (glass)-bearing breccias (suevites). Melt rocks (tagamites) are found as lenses (Masaitis, 2002). Polymict lithic breccias and melt-bearing breccias can also be found as proximal ejecta (Masaitis, 2002). *A rough estimate of melt volume: "Taking 13km for the diameter of the brecia lens and assuming a vertical cylinder geometry, these figures translate to an estimate of 8km3 of impact melt at Kaluga" (Grieve and Cintala, 1992). Published in Russian, (Masaitis et al., 1980) covers impactites.
Proximal Ejecta
LB, MB
Distal Ejecta
Dykes
Volume of Melt
8 km3 *
Depth of Melting

References

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V L Masaitis (1999) The Kaluga impact event and its proven and possible geological consequences, Berichte zur Polarforschung 343, Rainer Gersonde, Alexander Deutsch (ed.), p. 60-64, Kamloth, Bremerhaven

V L Masaitis (2002) The Middle Devonian Kaluga impact crater (Russia): New interpretation of marine setting, Deep-Sea Research. Part II: Topical Studies in Oceanography 49(6), p. 1157-1169, Pergamon, Oxford, url, doi:http://dx.doi.org/10.1016/S0967-0645(01)00142-4