AMS radiocarbon dates for tephra layers in Adak Island, Aleutian Islands, Alaska

Okuno, Mitsuru*; Wada, Keiji*; Torii, Masayuki*; Danhara, Toru*; Nakamura, Toshio*; Kokubu, Yoko   ; Gualtieri, L.*; Brenn, S.*

Adak Island, a member of the Andreanof Islands in the Aleutian Islands, Alaska is covered with Holocene sequences of soil-tephra complexes. Tephra layers are useful for establishing a chronographic framework on the island. Black (1976) described the three conspicuous tephra deposits (Main, Intermediate and Sandwich in ascending order). In order to re-evaluate the chronological framework, we conducted AMS radiocarbon dating and petrographic analysis on cored peat deposits collected from near Haven Lake. Charcoal fragments collected from around Three Arm Bay, southwestern area, are also dated. This poster presents petrography and radiocarbon dates. Based on our results, eruption ages of the Main, Intermediate, Sandwich, YBO and Forty Yeartephra were dated to approximately 9.5, 7.2, 4.7, 3.6 and 0.4 cal ka BP, respectively.