MICRO TEPHRA PARTICLES IN H15 ICE CORE, ANTARCTICA -POSSIBLE TEPHRO-CHRONOLOGICAL DATING FOR ANTARCTIC ICE CORE-

Antarctic glacier ice records the information of climate change, huge volcanic activity in the world etc, during more than 350 thousand years in Quaternary period. However the accurate age of ice cannot get easily. Tephra particles precipitate on surface snow of Antarctica in short period. Snow convert into ice gradually. Tephra in glacier ice move with the ice. Therefore we can get the age of ice form the eruption age of tephra. To get the eruption age, we have to know the source volcano of tephra, because amount of tephra grains lacks for the direct age determination. Size of ice core is too small to collect enough amount of tephra grains for dating the eruption age. When we found micro tephra particles in ice cores and prove the source volcanoes for those particles, we can get the age of ice. So, we have to confirm the existence of such tephra particles in ice cores for establishment of this ice core dating method.

We found 10 micro m size micro tephra particles in the several positions of H15 ice core(~60 m long), Antarctica. SEM observations indicate these particles have typical shape of pieces of broken glass. And also EDS analyses of these particles show strong Si peak. The most positions of micro tephra layers in the core are correlate to the high electric conductivity peaks on the ice core scan and to the points of high SO42- contents (volcanic signals) in the ice core. These micro tephra particles were possibly derived by worldwide volcanic activity such as 1991 eruptions of Pinatubo volcano, Philippine.