Kaali craters of Estonia and their meteoritic material

The Kaali craters are located on Saaremaa island, Estonia, in an area of 1 sq km. The main crater, which has a diameter of 104-110 m and initial depth of 22 m, has a natural body of water (d = 30- 60 m) on its bottom. The diameters of the eight smaller craters range from 12 to 40 m and their depths from 1 to 4 m. The craters were formed about 3500 to 3900 years ago in the clayey basal moraine and underlying Upper Silurian thick microbedded dolomites and filled with the mixture of dolomite pieces and the basal moraine and humus. The structure of the craters and the distribution of dispersed material in the craters and surroundings allows us to conclude that a gigantic meteorite fell from the east-northeast at an angle of about 35 degrees. The estimations of the initial weight and the velocity at the moment of impact are about 1000 t and 200 km/s respectively. The chemical composition of the meteorite fragments, found only in the small craters, indicates that the Kaali meteorite belongs to a class of coarse octahedrites. The fragments weighing usually from 0.5 to 2 g are concentrated in the central part of the craters. The biggest meteorite fragment from Kaali weighs 20.4 g. The soil in the crater field has also yielded abundantly dispersed and partly metamorphosed magnetic matter (microfragments and -meteorites, magnetic globules, platelets, magnetic-silicate crusts, and globules) with the mean content of 5-10 g/m^3 and the grain size less than 1 mm. Generally, the content of meteoritic dust and magnetic-silicate material increases farther from the crater field. However, there is a zone of a higher concentration corresponding to the supposed fall trajectory of the meteorite.