HR: 09:50h
AN: V21C-08    [Abstracts]
TI: Past and Future Directions of North Pacific Tephrochronology
AU: * Sarna-Wojcicki, A M
EM: asarna@usgs.gov
AF: U.S. Geological Survey, MS 973, 345 Middlefield Rd., Menlo Park, CA 94025 United States
AB: The north Pacific Ocean is rimmed by a complex of subduction zones that dip away from the ocean basin toward the fringing island arcs and continents. Inboard of these subduction zones is a belt of persistent volcanic activity--the Pacific "Ring of Fire"--formed by partial melting of subducted oceanic crust and overlying continental crust. Magma bodies of intermediate to silicic composition at many sites along this active volcanic belt have given rise to explosive volcanic eruptions and wide dispersal of tephra throughout the north Pacific Ocean and adjacent land areas. Moreover, along some parts of the north Pacific rim, as well as farther inboard of the subduction zones, are several persistent loci of crustal extension, translation, and hot spot activity that have also been sites of magma generation and large-volume explosive volcanism. Tephra erupted from these combined sources has been carried mostly in the direction of the prevailing winds, generally from west to east, though distributions have been complex, depending on heights of erupting columns and the prevailing weather and climate (including the seasons of eruption, positions of high- and low-pressure areas, and configurations of the jet stream). Tephra deposits formed as a consequence of this volcanic activity provide an important scientific resource for chronostratigraphy and correlation, and contribute significantly to solution of regional and topical studies in earth science. Tephra studies in Japan, the western conterminous United States, and southwestern Canada have advanced to the point that regional spatial-temporal late Noegene tephrochronological reference frameworks exist for these areas. In northwestern Canada, Alaska, Kamchatka, and eastern Siberia, the development of these stratigraphic frameworks lags, owing to lower population density, more difficult access, and shorter field seasons. Tephrochronologic studies of ocean sediment cores have been more sporadic than systematic, and lag behind tephra studies conducted on land. Promising future research directions are (1) systematic studies of ocean cores and correlation of tephra sequences between land and ocean areas, (2) systematic correlation of land and ocean stratigraphic sequences and tephra to the late Quaternary record in Greenland ice cores, (3) improvements in tephrochronometry, including cross-dating of tephrochronological, dendrochronological, and varve records, (4) improved separation and micranalytical techniques of small tephra particles and other aerosol particles, (5) closer and more systematic collaborative interdisciplinary studies between tephrochronologists and scientists studying environmental change and geologic hazards, and (6) intercalibration and integration of tephrochronologic data bases.
DE: 9350 North America
DE: 5480 Volcanism (8450)
DE: 1749 Volcanology, geochemistry, and petrology
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0370 Volcanic effects (8409)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting