This paper presents the results of microscopic observations of thin sections of sediment cores from Lakes Ni-no-Megata and San-no-Megata, Oga Peninsula, NE Japan. Micro-sedimentary structures indicate that cycles of light-dark lamina couplets represent biogenic varves, marking annual laminations. We identified complete annual cycles and partial annual cycle between the thin tephra layers of Towada-a To-a and Baitoushan-Tomakomai B-Tm in sediment cores from the two lakes, suggesting that B-Tm was deposited in AD . We also determined that To-a was deposited during early spring, while B-Tm was deposited during one or more eruption events during spring-summer. Abstract

Perla J. DELOS REYES 1) , Toshiyuki FUJIKI 3) ＋＋ , Ericson B. BARISO 1) , Mitsuru OKUNO 3 4) , Toshio NAKAMURA 5) , Tohru DANHARA 6) , Yoko SAITO-KOKUBU 7) and Tetsuo KOBAYASHI 8)

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