HR: 1340h
AN: V23A-0618    [Abstracts]
TI: Life on the Edge: Holocene Tephra Stratigraphy of Tanginak Anchorage, Sitkalidak Island, Kodiak Archipelago, Alaska
AU: * Mahrt, E
EM: bmahrt@u.washington.edu
AF: University of Washington Department of Earth and Space Sciences, PO Box 351310, Seattle, WA 98195 United States
AU: Bourgeois, J
EM: jbourgeo@u.washington.edu
AF: University of Washington Department of Earth and Space Sciences, PO Box 351310, Seattle, WA 98195 United States
AU: Fitzhugh, J B
EM: fitzhugh@u.washington.edu
AF: University of Washington Department of Anthropology, Box 353100, Seattle, WA 98195 United States
AB: Geologic hazards associated with volcanism in the North Pacific have profound if usually temporary effects on the environment and human populations. Ash falls associated with these events are often preserved across large areas providing time specific markers. In the past century, volcanic activity and its effects in the North Pacific have been recorded, but much of the Holocene volcanic record in the Alaskan region is still being investigated. The Kodiak Archipelago, while not volcanic itself, is located near both Aleutian and Alaskan peninsula volcanoes. However, little has been published about the Holocene tephrochronology of the Kodiak region. This study focuses on the area around Tanginak Spring Site (KOD481). Located on Sitkalidak Island it is the earliest known human occupation in the Kodiak archipelago. We are documenting Holocene environmental changes on Sitkalidak Island and relating these changes to the archaeological record. As part of this work, we will establish a local tephrochronology using stratigraphy and geochemistry which will allow us to better correlate sedimentary changes across large areas as well as study human interaction with ashfall events. Herein we report a preliminary tephrochronology in peat excavations on Sitkalidak Island dating back to the earliest Holocene. Dates are radiocarbon years BP on peat directly below tephra. Marker tephra present in our reference sections are Katmai 1912, light gray (historic?), medium gray (3370), medium gray (3720), beige 1 (4340), apricot (5390), beige 3 (6790), black (9280), and white (11,520). Geochemical and petrographic analysis will help to determine with which volcanic events these tephra are associated. Establishing a local tephrochronology is important not only for local correlation but also to ascertain the tephra stratigraphy of the Kodiak Archipelago and beyond. The frequency of tephra in Tanginak Anchorage sections suggests that tephra will be a very useful stratigraphic tool in this region.
DE: 8404 Ash deposits
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting