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Study of meteoritic matter for precise regional stratigraphy

Raukas Anto

Geologos

2000

Vol. 5

77--86

New physical and isotope-geochemical methods and improvement of old classical methods have considerably enlarged our knowledge not only of the physical age of the deposits but also of the palaeogeographic situation in the past. During the last hundred years, microscopic glassy and ferrous spheroids of different origin have often been found in various geological formations. In 1996, IGCP project 384 “Impact and Extraterrestrial Spherules: New Tools for Global Correlation” with a duration of five years (1996-2000) was launched. Estonia with its two well-known astroblems (Kardla, Neugrund) and three groups of Holocene craters (Kaali, Ilumetsa, Tsoorikmae) serves as a key region for this kind of studies. The concentration of magnetite-silicate microimpactites in certain layers of peat in the surroundings of the Kaali and Ilumetsa craters suggests that the Holocene impact events can be precisely dated on the basis of l4C dates and pollen evidence, and serve as good regional chronostratigraphical markers. The age of the Kaali craters is approximately 7500 and Ilumetsa craters about 6600 years BP.