The Impact Cratering Record of Fennoscandia — A Close Look at the Database

Abstract

Currently thirty meteorite impact structures are identified in Fermoscandia, which corresponds to similar to19 % of the known global record. Eleven of them have been discovered or confirmed during the last decade. This high number is due to intensive, determined research, including deep drilling, and high-resolution geophysical regional mapping. The ages and diameters of Fermoscandian impact structures vary considerably, but many are relatively small (<10 km) and mostly of early Paleozoic age. The latter is probably an effect of the regional geological evolution. The majority of craters were formed in complex targets composed of crystalline basement, a sedimentary cover and frequently a water pile on top. Only those that were excavated in the crystalline shield contain bodies of coherent impact melt rock or reveal indications of such. Distal impact-related deposits of some structures have locally survived, especially those that formed in platform areas with virtually uninterrupted sedimentation after impact. These deposits are useful stratigraphic markers. Apart from the confirmed structures, there are presently some sixty additional structures for which an impact origin has been suggested.