This paper presents the initial results of an inner-shelf vibracoring project along the USrnsouthwest Washington and northwest Oregon coast within the 165-km long Columbia River littoralrncell. The project was designed to investigate the role of the inner shelf (also herein the lowerrnshoreface) in shaping the evolution of the barriers. Vibracores were collected along transectsrnstarting on the upper shoreface (shallower than 12 m), crossing the toe of the progradational wedge,rnand ending in water depths of 40-75 m. Core sites were selected where the record of sedimentaryrndeposits contained within vibracores could be analyzed relative to results of previously collectedrndata including historical bathymetric change, seismic, side-scan, surface sediments, barrier drillingrnand ground penetrating radar, as well as process measurements and beach and nearshore morphologyrndata. Preliminary interpretations, based on limited radiocarbon dating, suggest that upper shorefacernaggradation corresponds to barrier progradation while the lower shoreface may act as a sink, source,rnor bypass of sand depending upon its configuration relative to equilibrium. In general, thernaccumulation of modern shoreface sand appears to be significantly less than that suggested byrnpreviously collected data. The results of this project are providing insights into shoreface behaviourrnand the effect of the inherited shelf substrate slope and structure on the transport and accumulationrnpatterns of sand originally supplied by the Columbia River.
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