USING AN ARRAY OF NE PACIFIC MARGIN SEDIMENT SAMPLES TO LINK LAND AND OCEAN RESPONSES TO GLACIAL-INTERGLACIAL CLIMATE VARIABILITY

Variability in the continental fraction of marine sediments, including pollen and rock fragments, reflects the effects of regional climate change on continental runoff, ice extent, vegetation and surface ocean circulation. The transport of this continental material to the ocean, and how this transport changes over time, must be understood in order to relate vegetation and erosion changes to specific sediment sources (river catchments). This is investigated using several geochemical tracers to identify transport pathways of material from Pacific Northwest rivers to continental margin depositional sites.

We report the results of 40Ar/39Ar incremental heating and εNd of bulk detrital sediments (20-63µ fraction) from core tops in an array of fourteen sites along the continental margin of the Pacific Northwest (northern CA to southern BC). Age spectra demonstrate features that are used to relate the core tops to river mouth samples reported by VanLaningham et al. (2006). Signatures of modern sediment transport along the continental margin were found to reflect the seasonal effect of northward flow in the Davidson Current. The ultimate goal of this study is to describe down-core changes in detrital sediment source and accumulation rate, over the last 30ka, at 4 sites within this array. Comparison of such changes to highly correlated variability in pollen and plankton assemblages will distinguish terrestrial landscape changes (vegetation, erosion, runoff) from changes in ocean circulation.