Distribution and composition of impact and extraterrestrial spherules in the Kaali area (Island of Saaremaa, Estonia)

The soil in and around the Kaali meteorite craters in the SE part of Saaremaa Island contains a large number of micrometeorites and abounds in pulverized extraterrestrial and impactite matter. The explosion with accompanying high temperatures resulted in the formation of glassy silicate spherules. These spherules were distributed over a large area, and allow to estimate the age of the impact at about 7500 years BP and correlate separated sequences. The extraterrestrial and explosive material in the Kaali area is diverse in form, colour and composition. The spherules may be of different origin, including industrial. From the methodological point of view, it is especially important to study spherules in the geologically established crater fields and their surroundings. The Kaali area provides an excellent polygon for this kind of studies.