238 Recent Advances and New Voices in Marine and Coastal Geoscience

We seek abstracts on physical oceanography, marine geology, geomorphology, sediment transport, geophysics, tectonic processes, climate change, paleobiology, or any aspect of oceans and coasts, past and present. We encourage students to participate in this session.

Wednesday, 22 October 2025
8:00 AM - 12:00 PM
HBGCC, 213AB

Quantifying the Carbon Storage Potential of Submarine Fans: an example from the Nitinat Fan in the Cascadia Margin

Paper number: 238-2
Program: Technical Sessions
Time: 8:30 AM – 8:45 AM

Authors

Abstract

Submarine fans, formed by the deposition of turbidity currents represent the largest sediment accumulations on earth and constitute an important carbon sink. Plant and wood fragments are known to contribute significantly to the carbon content in turbidites, but sedimentary carbon quantification is often exclusively performed on fine-grained sediments (< 2mm), excluding the coarse particulate fractions. Here, we analyzed turbidite samples from the Nitinat Fan in the Cascadia Basin (ODP Leg 146, site 888B) to quantify organic carbon (OC) and determine its provenance. The wood-bearing sedimentary layers contain 6 times more carbon than regular fan sediments. Elemental analysis of wood fragments (d13C = -27.1‰ VPDB; C/N = 104) and Raman microscopy spectra confirm sedimentary wood in the fan is sourced from terrestrial vascular C3 plants of the gymnosperm lineage. On average, coarse (> 2mm) woody debris have a higher carbon content (60%) than fine (< 2mm) woody debris (40%) and disproportionately contribute to the sedimentary OC. In fact, in wood-bearing sediments, 77% of the carbon is stored as coarse woody debris. We report an OC burial flux of 0.44 ± 0.12 MtC/yr and estimate that since the mid Pleistocene, the Nitinat Fan has stored 1291 ± 704 MtC. This estimate is 62 - 37% higher than those obtained by traditional methodologies that for the most part exclude coarse wood fragments. This study demonstrates that woody debris significantly increases the OC burial efficiency of marine sediments and must be recognized as an important component of the carbon cycle.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-412657

© Copyright 2025 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.