Saaksjarvi - Hypervelocity Impact Crater

Alternate Names N/A
Coordinates 61° 24' 34" N; 22° 22' 30" E
Notes
  1. In SW Finland, ~25 km E of the town of Pori.
Country Finland
Region Western Finland
Date Confirmed 1969
Notes
  1. Confirmed based on PDF's found in quartz grains and feldspars in melt-bearing breccia (Papunen, 1969).
Buried? No
Drilled? Yes
Notes
  1. One hole (105 m), breccia and brecciated basement.
Target Type Crystalline
Notes
  1. Proterozoic granite gneiss, quartz diorites, mica-gneiss and migmatite (Papunen, 1973) and Jotnian sandstones (Mutanen, 1979).
Sub-Type Diorite, Gneiss, Migmatite, Sandstone, Volcanics
Apparent Crater Diameter (km) 5 km
Age (Ma) 602 ± 17
Notes :
  1. 602 ± 17 Ma determined by U-Pb of zircon in impact melt rock (Mänttäri et al., 2004). Additional age constraints: 40Ar/39Ar provides an age of 560 ± 12 Ma (Muller et al., 1990). (Bottomley et al., 1990) suggest an age of <300 Ma.

Method :
  1. U-Pb
Impactor Type Ordinary chondrite
Notes
  1. Enrichment of Ir, Ni, Co and Cr in 5 samples analyzed suggest a chondritic projectile (Palme et al., 1980).

Advanced Data Fields

Notes

Local Language
N/A
Erosion
7
  1. Heavily eroded by glaciation; the floor has been removed and the substructure exposed (Papunen, 1969).
Final Rim Diameter
Unknown
Apparent Rim Diameter
5 km
  1. Anomalous circular area is ~5 km in diameter (Elo et al., 1992).
Rim Reliability Index
2?
  1. Only the lake basin and boulder erratics on the shoreline indicate a crater (Papunen, 1969).
Crater Morphology
Complex
Central Uplift Diameter
Unknown
Central Uplift Height
Unknown
Uplift Reliability Index
4
Structural Uplift
Unknown
Thickness of Seds
Unknown
Target Age
Precambrian
Marine
No
Impactor Type
Ordinary chondrite
  1. Enrichment of Ir, Ni, Co and Cr in 5 samples analyzed suggest a chondritic projectile (Palme et al., 1980).
Other Shock Metamorphism
Maskelynite
  1. (Papunen, 1973)
Shatter Cones
No
Planar Fractures
No
Planar Deformation Features
Yes
  1. PDF in quartz grains and feldspars. (Papunen, 1969).
Diaplectic Glass
No
Coesite
No
Stisovite
No
Crater Fill
LB, MB, M
  1. Melt rocks have a glassy matrix and melt-bearing breccias (referred to as suevites) contain vesicles filled with clays and zeolites. Both are present as lenses in LB (no melt sheet was found). The crater-fill impactites have a total thickness of 180 m (Pihlaja and Kujala, 2000). Melt rocks can also be found as floats in the shore of Lake Saaksjarvi (Tagle et al., 2009). Float and drill samples.
Proximal Ejecta
Unknown
Distal Ejecta
Unknown
Dykes
Unknown
Volume of Melt
Unknown
Depth of Melting
Unknown

References

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H Papunen (1969) Possible impact metamorphic textures in the erratics of the lake Saeaeksjaervi area in southwestern Finland, Bulletin of the Geological Society of Finland 41, p. 151-155, Geological Society of Finland, Helsinki, pdf

H Papunen (1973) Chemical composition and origin of the shock metamorphic rocks of the Saaksjarvi area, Finland, Bulletin of the Geological Society of Finland(45, Part 1), p. 29-34, Geological Society of Finland, Helsinki, pdf

T Koljonen, R J Rosenberg (1976) Major elements and REE in tektites and three probable shock-metamorphic rock series of the baltic shield, Geochemical Journal 10(1), p. 1-11, Geochemical Society of Japan, Nagoya, url

Richard J Bottomley, D York, R A F Grieve (1977) 40Ar-39Ar dating of Scandinavian impact craters, Meteoritics 12, p. 182-193, url

T Mutanen (1979) Lake Saaksjarvi; an astrobleme after all, Geologi 31(9-10), p. 125-130, Suomen Geologinen Seura, Helsinki, url

A J Ellis (1979) Explored geothermal systems, Geochemistry of Hydrothermal Ore Deposits, H L Barnes (ed.), p. 632-683, New York: John Wiley and Sons

H Palme, W Rammensee, U Reimold (1980) The meteoritic component of impact melts from European impact craters, Lunar and Planetary Science Conference 11, p. 848-850, url

Carlton C Allen, K Keil (1981) Hydrothermal alteration of melt rocks in impact craters, Meteoritics 16(4), p. 288-289, Arizona State University, Center for Meteorite Studies, Tempe, AZ, url

R A F Grieve (1982) The record of impact on Earth: Implications for a major Cretaceous/Tertiary impact event, Geological Society of America 190(Special Paper), p. 25-37, url

Y P Gurov, Y P Gurova (1987) Impact structures on the Earth's surface, Geologicheskiy Zhurnal 47(1), p. 117-124, Naukova Dumka, Kiev, url

N Mueller, J B Hartung, E K Jasseberger, W U Reimold (1990) 40Ar-39Ar dating of some Fennoscandian impact craters, Fennoscandian impact structures, L J Pesonen, H Niemisara (ed.), p. 37, Geol. Surv. Finl., Espoo, url

N Müller, J B Hartung, E K Jessberger, W U Reimold (1990) 40Ar-39Ar ages of Dellen, Jänisjärvi, and Sääksjärvi impact craters, Meteoritics 25(1), p. 1-10, Wiley/Blackwell (10.1111), url, doi:10.1111/j.1945-5100.1990.tb00964.x

S Elo, L Kivekas, H Kujala, S I Lahti, P Pihlaja (1990) Recent studies of lake Saaksjarvi meteorite impact crater, southwestern Finland, Fennoscandian impact structures, L J Pesonen, H Niemisara (ed.), p. 44, Geol. Surv. Finl., Espoo, url

H Henkel, L J Pesonen (1992) Impact craters and craterform structures in Fennoscandia, Tectonophysics 216(1-2), p. 31-40, doi:10.1016/0040-1951(92)90153-W

S. Elo, L. Kivekäs, H. Kujala, S. I. Lahti, P. Pihlaja (1992) Recent studies of the Lake Sääksjärvi meteorite impact crater, southwestern Finland, Tectonophysics 216(1-2), doi:10.1016/0040-1951(92)90163-Z

S F Simmons, P R L Browne (1996) Smectite, Atlas of Alteration, A J B Thompson, J F H Thompson (ed.), p. 96-97, Geological Association of Canada, Mineral Deposits Division

K A Kinnunen, K Lindqvist (1998) Agate as an indicator of impact structures: An example from Saaksjarvi, Finland, Meteoritics & Planetary Science 33(1), p. 7-12, Meteoritical Society, Fayetteville, AR, url

P J Pihlaja, H Kujala (2000) Some geochemical features of impact melts, suevites and target rocks at Saaksjarvi impact structure, Finland, Workshop of the European Science Foundation (ESF) Impact Programme, Juri Plado, Lauri J Pesonen (ed.), p. 50, Geological Survey of Finland, Espoo, url

R Tagle, R T Schmitt, J Erzinger (2009) Identification of the projectile component in the impact structures Rochechouart, France and Saaksjarvi, Finland: Implications for the impactor population for the Earth, Geochimica et Cosmochimica Acta 73(16), p. 4891-4906, Elsevier, New York, NY, url, doi:http://dx.doi.org/10.1016/j.gca.2009.05.044

S Staffieri, A Coletta, M L Battagliere, M Virelli (2019) Sääksjärvi, Finland, Encyclopedic Atlas of Terrestrial Impact Craters, p. 417-418, Springer, Cham, url, doi:https://doi.org/10.1007/978-3-030-05451-9_111