A Middle-Late Triassic 40Ar/39Ar age for the Paasselka impact structure (SE Finland)

作者：Schmieder Martin^*; Schwarz Winfried H; Buchner Elmar; Trieloff Mario; Moilanen Jarmo; Oehman Teemu

来源：Meteoritics & Planetary Science, 2010, 45(4): 572-582.

DOI：10.1111/j.1945-5100.2010.01041.x

40Ar/39Ar dating of recrystallized feldspar glass particles separated from clast-rich impact melt rocks from the approximately 10 km Paasselka impact structure (SE Finland) yielded a Middle to Late Triassic (Ladinian-Karnian) pseudo-plateau age of 228.7 +/- 3.0 (3.4) Ma (2 sigma). This new age makes Paasselka the first known Triassic impact structure dated by isotopic methods on the Baltic Shield. The new Paasselka impact age is, within uncertainty, coeval with isotopic ages recently obtained for the Lake Saint Martin impact structure in Canada, indicating a new Middle to Late Triassic impact crater population on Earth. The comparatively small crater size, however, suggests no relationship between the Paasselka impact and a postulated extinction event at the Middle/Late Triassic boundary.

• 出版日期2010-4