The two Suvasvesi impact structures, Finland: Argon isotopic evidence for a “false” impact crater doublet

• Published in: Meteoritics & Planetary Science
• Main Authors: Schmieder, Martin, Schwarz, Winfried H., Trieloff, Mario, Buchner, Elmar, Hopp, Jens, Tohver, Eric, Pesonen, Lauri J., Lehtinen, Martti, Moilanen, Jarmo, Werner, Stephanie C., Öhman, Teemu
• Other Authors: Division of Arctic Sciences
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2016
• Subjects: Fennoscandian
• Online Access: http://dx.doi.org/10.1111/maps.12636; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fmaps.12636; https://onlinelibrary.wiley.com/doi/pdf/10.1111/maps.12636; https://onlinelibrary.wiley.com/doi/full-xml/10.1111/maps.12636; https://onlinelibrary.wiley.com/doi/am-pdf/10.1111/maps.12636

Abstract The two neighboring Suvasvesi North and South impact structures in central‐east Finland have been discussed as a possible impact crater doublet produced by the impact of a binary asteroid. This study presents 40 Ar/ 39 Ar geochronologic data for impact melt rocks recovered from the drilling into the center of the Suvasvesi North impact structure and melt rock from glacially transported boulders linked to Suvasvesi South. 40 Ar/ 39 Ar step‐heating analysis yielded two essentially flat age spectra indicating a Late Cretaceous age of ~85 Ma for the Suvasvesi North melt rock, whereas the Suvasvesi South melt sample gave a Neoproterozoic minimum (alteration) age of ~710 Ma. Although the statistical likelihood for two independent meteorite strikes in close proximity to each other is rather low, the remarkable difference in 40 Ar/ 39 Ar ages of >600 Myr for the two Suvasvesi impact melt samples is interpreted as evidence for two temporally separate, but geographically closely spaced, impacts into the Fennoscandian Shield. The Suvasvesi North and South impact structures are, thus, interpreted as a “false” crater doublet, similar to the larger East and West Clearwater Lake impact structures in Québec, Canada, recently shown to be unrelated. Our findings have implications for the reliable recognition of impact crater doublets and the apparent rate of binary asteroid impacts on Earth and other planetary bodies in the inner solar system.