HR: 1340h
AN: V23A-0623    [Abstracts]
TI: The Tephra Stratigraphy of two Lakes in South-Central British Columbia, Canada and its Implications for the Middle-Late Holocene Volcanic Activity at Glacier Peak, Washington, USA
AU: * Gavin, D G
EM: dgavin@life.uiuc.edu
AF: Department of Plant Biology, University of Illinois, Urbana, IL 61801 United States
AU: Foit, F F
EM: foit@mail.wsu.edu
AF: Department of Geology, Washington State University, Pullman, WA 99164 United States
AU: Hu, F
EM: fshu@life.uiuc.edu
AF: Department of Plant Biology, University of Illinois, Urbana, IL 61801 United States
AB: Several mid-late Holocene Glacier Peak tephras along with Mazama and Mount St. Helens Wn and P tephras were found in cores from Cooley and Rockslide Lakes in southeastern British Columbia, Canada approximately 300 km northeast of Glacier Peak. The sediments in Cooley Lake host the early Holocene Glacier Peak A tephra (2010 cal years BP), four separate, closely timed airfalls of Glacier Peak Dusty Creek tephra (5780-5830 cal years BP) and a Glacier Peak set D tephra (6060 cal years BP). This is the first report of Glacier Peak A and D tephras from British Columbia. The A tephra has been correlated on the basis of glass composition and age to a late Holocene Glacier Peak tephra in the sediments of Big Twin Lake, 75 km northeast of Glacier Peak. The glasses in the four Glacier Peak Dusty Creek tephra layers from Cooley Lake are compositionally indistinguishable from those in Mount Barr Cirque and Frozen Lakes in southwestern British Columbia. The layers represent four eruptions taking place over approximately 50 years (5780-5830 cal years BP). Although set D tephra has not been correlated to a known proximal/distal deposit, its glass bears the Glacier Peak glass compositional signature and its interpolated age (6060 cal. years BP) corresponds to the initiation of the set D eruptive period. The presence of Dusty Creek tephra in lake sediments across southern British Columbia and northern Washington State suggests a broad plume trajectory to the north and northeast. In contrast the apparent presence of the Glacier Peak A in only Cooley Lake in British Columbia and in lakes in Washington on the same linear trajectory suggests a narrow plume with a northeasterly direction.
DE: 8400 VOLCANOLOGY
DE: 8404 Ash deposits
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting