Biostratigraphic Indications of the Age of the Boltysh Impact Crater, Ukraine

The Boltysh meteorite crater (diameter ≈ 23 km) on the Ukrainian shield was formed in Precambrian (~ 2.1 Ga) granites and has a classical complex structure with a central uplift (average diameter ~ 4 km). The annular trough around the uplift is filled with predominantly glassy impactites (impact melt rocks = tagamites) that are up to 230 m thick. The crater lake sediments overlie impactites and are represented by laminated siltstones, sandstones, claystones. These sediments have a maximum thickness of nearly 400 m in the center of the crater. Previous data about the geological age of the lowermost crater-fill sediments were contradictory (K1-P2), as weere the K-Ar whole rock ages of the tagamites ( 177-56 Ma).