Tephrochronology of the Kamchatka–Kurile and Aleutian arcs: evidence for volcanic episodicity

Volcanic ash layers in North Pacific deep-sea sediment provide a record of episodic explosive volcanism in the Kamchatka–Kurile and Aleutian arcs over the past five million years. We counted 450 ash layers, determined layer thickness and cumulative ash thickness to quantify the flux of ash with time. We use this record to investigate the eruptive history of these arcs, test the reliability of the marine ash record, and inquire into the regional episodicity of North Pacific explosive volcanic history. Episodes of explosive volcanism occurred at approximately 0.2–0.5, 0.7–0.9, 1.5–1.7, and 2.5–2.65 Ma in the Kamchatka arc and 0.15–0.4, 1.7–1.8, 2.55–2.65, and at 3.0–3.1 Ma in the eastern Aleutian arc. These generally coeval eruptive episodes suggest that the pulses in explosive volcanism in the North Pacific enumerated here and recognized by others are regionally episodic over a wide portion of the Pacific rim and not just a response to local volcanogenic processes.