ARTYKUŁY NAUKOWE Meteorytowy krater Mjølnir na Morzu Barentsa w interpretacjach stratygraficznych

Abstract

The meteorite Mjølnir crater in the Barents Sea in stratigraphical interpretations.A b s t r a c t. The Mjølnir submarine crater attaining about 40 kilometers in diameter on the Barents Shelf is one of the largest meteorite craters in the World. It was formed in the earliest Ryzanian as proved by the ammonite datings of the ejecta bearing strata in the boreholes in the Barents Sea. The iridium anomalies related to that impact were recognized also on central Spitsbergen, and in Nordvik Peninsula of northern Siberia . The Mjølnir impact resulted in a large scale reworking and redeposition of sediments in the Boreal Sea across the Late Volgian and Ryazanian transition as documented e.g. in a close neighbourhood of the crater, but also in more distal successions in central Spitsbergen. So far, no unequivocal proof of this event was documented in more southern areas in Europe, but the detailed studies of complete successionsin the nonmarine Purbeck-type facies in north-western and central Poland seem to be promising in this respect. This could allow for correlation of the Boreal ammonite subdivision with that based on the ostracodes. The palaeomagnetic studies of the continuous succession in the Nordvik Peninsula section of the uppermost Upper Volgian and Lower Ryazanian yielded also new information on the correlation between the Boreal and the Mediterranean biostratigraphical zonal schemes which is especially important for recognition of the uniform Jurassic-Cretaceous boundary in the World. The recent results of these studies indicate that the Mjølnir impact took place during magnetozone 17 r which suggests the correlation of that event with the boundary of the Jacobi and Occitanica ammonite zones corresponding to the boundary of the Lower and the Middle Berriasian of the Mediterranean domain. This confirms an opinion that the Volgian-Ryazanian boundary of the Boreal domain is placed much higher than the Tithonian Berriasian boundary in theTethyan domain – treated as a main candidate level for the uniform Jurassic-Cretaceous boundary in the World.