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Date of Award

Summer 2025

Document Type

Masters Thesis

Department or Program Affiliation

Geology

Degree Name

Master of Science (MS)

Department

Geology

First Advisor

Ponton, Camilo

Second Advisor

Housen, Bernard Arthur

Third Advisor

Foreman, Brady

Abstract

Terrestrial organic carbon (OC) is transported by rivers to continental margins and eventually deposited on the ocean floor by turbidity currents. Plant and wood fragments have been found to contribute significantly to the carbon load deposited on river-dominated continental margins, but carbon quantification is often exclusively performed on the fine-grained particles (< 2mm) excluding the coarse particulate fractions (> 2mm). Turbidites samples from the Nitinat Fan in the Cascadia Basin within the Pacific Northwest were analyzed to quantify OC, determine OC sourcing, and characterize “sedimentary wood” using stable carbon isotope ratios and Raman microscopy.

The results from this research show that OC sourcing in the Nitinat Fan is mostly from terrestrial C3 vascular vegetation based on carbon isotopes and C:N ratios. In some wood-containing sedimentary layers, more than 90% of the carbon is stored as woody debris rather than dispersed organic carbon. On average, coarse (>2mm) woody debris have a higher carbon content (60%) than finer (< 2mm) woody debris (40%) and therefore contributes more to bulk organic carbon (OCbulk ), 77% vs. 23% respectively. Sedimentary layers that incorporate wood were found to contain 6 times more carbon than regular fan sediment suggesting previous studies may have underestimated carbon storage in the ocean sink.

Raman microscopy was used to characterize woody debris (sedimentary wood), but while initial applications proved to be challenging for sedimentary wood samples that are degraded, the method was efficient at determining wood type (angiosperm vs. gymnosperm) and sometimes offer identification at the species level, when the wood is unaltered.

Type

Text

Keywords

Submarine fans, turbidity currents, turbidites, terrestrial organic carbon, wood fragments, Raman microscopy, ocean carbon sink

Publisher

Western Washington University

OCLC Number

1524901934

Subject – LCSH

Submarine fans--Northwest, Pacific; Water--Organic compound content--Northwest, Pacific; Carbon--Environmental aspects--Northwest, Pacific; Wood--Biodegradation--Northwest, Pacific; Marine sediments--Northwest, Pacific--Analysis; Sedimentation and deposition--Northwest, Pacific; Carbon sequestration--Northwest, Pacific; Turbidites--Northwest, Pacific; Turbidity currents

Geographic Coverage

Northwest, Pacific; Cascadia Subduction Zone

Format

application/pdf

Genre/Form

masters theses

Language

English

Rights

Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author’s written permission.

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