Kousuke Kurisaki

The extraction of past environmental information using 137Cs and some elements in terrestrial carbonate deposits

Abstract Terrestrial carbonate deposits with a banded layer structure can be good tools for the extraction of past environmental information on global and local scales. The absolute age dating is most important for the reconstruction of an environmental chronicle. The terrestrial carbonate deposits(tufa) was collected at Hirao-dai Plateau in Fukuoka, Japan. Tufa has wide banded layers in which the growth rates are about a few mm a year. The activity of 137Cs that was a global or local fallout radionuclide was measured in each layer of the tufa sample. The absolute age was determined by the numbering of a banded layer and 137Cs activity profiles. The trace of the atomic bombing at Nagasaki was detected. The growth rate of the tufa is related to the environment of the year. The variations of a depositional condition of tufa sample were checked by some metal concentrations determined by neutron activation analysis. The relationship between the variation of environmental condition and the historical event at Hirao-dai was discussed using these metal concentration profiles.