Investigation of impact spherules – a new promising method for the correlation of Quaternary deposits

During the course of the last hundred years, microscopic magnetite and glassy spherules of different genesis (extraterrestrial, volcanic, industrial, biogenic, diagenic, explosive, etc.) have often been found in various geological formations. Alongside classical geological methods, research into extraterrestrial and explosive spherules can provide valuable information, and facilitates stratigraphical correlations over large areas. During the history of the Earth, there seem to have been several peaks in the global occurrence of spherules, the best known being recorded on the K/T boundary. Several tens of impact craters, ranging from Neoproterozoic to Holocene in age, and from less than 100 m to more than 50 km in diameter, occur both in the crystalline basement and in the sedimentary cover of the old East European Craton in the Fennoscandian-Baltic region. In the Baltic States alone, at least 18 impact craters and a large number of meteorite falls have been recorded. The oldest palaeometeorite matter known in the Baltic States to date is enclosed in Lower Cambrian sandstone. This paper presents some promising results of spherule studies which were carried out surrounding Holocene meteorite craters in Estonia. On the basis of spherule studies, impact events can be precisely dated. The spherule-bearing layers serve as excellent stratigraphical markers for the correlation of sedimentary sequences.