HR: 09:30h
AN: U31A-05 INVITED     [Abstracts]
TI: Erosional Fluxes of the Cascadia Forearc High
AU: * Gosse, J
EM: john.gosse@dal.ca
AF: Dalhousie University, Earth Sciences 3006 LSC Edzell Castle Circle, Halifax, NS B3H3J5 Canada
AU: Brandon, M
EM: mark.brandon@yale.edu
AF: Yale University, Department of Geology and Geophysics 210 Whitney Ave, New Haven, CT 06520 United States
AU: Pazzaglia, F
EM: fjp3@lehigh.edu
AF: Lehigh University, EES, 31 Wiliams Drive, Bethlehem, PA 18015 United States
AU: Antinao, J
EM: jrojas@dal.ca
AF: Dalhousie University, Earth Sciences 3006 LSC Edzell Castle Circle, Halifax, NS B3H3J5 Canada
AB: Catchment-wide 10Be inventories have been used to estimate average erosion rates for drainages over timescales of ca. 10 ka along the Cascadia Forearc High. Samples comprise 150-350 micrometer sand from modern and terrace sediment. Terrace sediment ranged from a few hundred to ca. 11,000 years old and was considered to represent pre-logging inventories. The 10Be catchment-average erosion rate estimates in the Clearwater River drainage of western Olympic Peninsula range from 0.18­O0.07 mm/a (2Ÿa unc) for Miller Creek, a tributary in a low relief zone close to the coast to 0.39­O0.16 mm/a for the upper reach of the mainstem with higher relief. The pattern and magnitude of erosion matches incision rates for similar time scales. That incision rates are similar to the average erosion rates for similar timescales may indicate that steady state has been achieved. The 10Be erosion rate for the entire catchment is 0.34­O0.25 mm/a, similar to a modern suspended sediment load erosion rate estimate of 0.32 from the neighbouring Hoh River. Long-term cooling history derived estimates of Olympic Peninsula exhumation reveal a similar pattern (highest rates in highest relief regions) and magnitude of exhumation over long time periods. Samples collected from 6 additional catchments from Vancouver Island to southern Oregon yield erosion estimates that range from 0.52­O0.05 mm/a (Myra River) to 0.12­O0.01 mm/a (Umpqua River). A weak relationship between relief or slope and erosion rate can be distilled, however these erosion rates may reflect differential rates of sediment accretion along the Forearc.
DE: 1130 Geomorphological geochronology
DE: 1150 Cosmogenic-nuclide exposure dating (4918)
SC: Union [U]
MN: Fall Meeting 2005