Published In

Marine Geology

Document Type

Post-Print

Publication Date

5-12-2016

Subjects

Wave energy, Holocene Epoch, Marine transgression, Stratigraphic geology, Bioaccumulation, Columbia River

Abstract

The Columbia River Littoral Cell (CRLC), a high-wave-energy littoral system, extends 160 km alongshore, generally north of the large Columbia River, and 10–15 km in across-shelf distance from paleo-beach backshores to about 50 m present water depths. Onshore drill holes (19 in number and 5–35 m in subsurface depth) and offshore vibracores (33 in number and 1–5 m in subsurface depth) constrain inner-shelf sand grain sizes (sample means 0.13–0.25 mm) and heavy mineral source indicators (> 90% Holocene Columbia River sand) of the inner-shelf facies (≥ 90% fine sand). Stratigraphic correlation of the transgressive ravinement surface in onshore drill holes and in offshore seismic reflection profiles provide age constraints (0–12 ka) on post-ravinement inner-shelf deposits, using paleo-sea level curves and radiocarbon dates. Post-ravinement deposit thickness (1–50 m) and long-term sedimentation rates (0.4–4.4 m ka− 1) are positively correlated to the cross-shelf gradients (0.36–0.63%) of the transgressive ravinement surface. The total post-ravinement fill volume of fine littoral sand (2.48x1010m3) in the inner-shelf represents about 2.07x106 m3 yr− 1 fine sand accumulation rate during the last 12 ka, or about one third of the estimated middle- to late-Holocene Columbia River bedload or sand discharge (5–6x106 m3 yr− 1) to the littoral zone. The fine sand accumulation in the inner-shelf represents post-ravinement accommodation space resulting from 1) geometry and depth of the transgressive ravinement surface, 2) post-ravinement sea-level rise, and 3) fine sand dispersal in the inner-shelf by combined high-wave-energy and geostrophic flow/down-welling drift currents during major winter storms.

Description

This is the author’s version of a work that was accepted for publication in Marine Geology. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published here.

Copyright © 2016. The Authors.

This is an open access article distributed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

DOI

10.1016/j.margeo.2016.05.007

Persistent Identifier

http://archives.pdx.edu/ds/psu/17311

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