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Data from: Flood-driven turbidite deposition in a highstand-detached submarine canyon

Lahr, Evan1; Ogston, Andrea1; Keil, Rick1; Neibauer, Jaqui1; Al-Thani, Jassem1

Published Oct 10, 2025 on Dryad. https://doi.org/10.5061/dryad.v6wwpzh7k

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Abstract

Turbidites on active margins represent key archives of great earthquakes, yet turbidity currents triggered by nonseismic events complicate paleoearthquake records and influence geochemical budgets. Sediment cores collected from Astoria Canyon address whether ocean-process-triggered turbidity currents are preserved in “highstand-inactive” canyon stratigraphy. Detailed analysis of a turbidite-bearing core indicates fluvial origin on the basis of sedimentology, geochronology, and organic matter composition. Turbidites are 15 cm thick, graded, and laminated. Turbidite 210Pb activity is low, and depositional ages align with major Columbia River floods. Turbidite organic matter is terrestrial and modern (-26‰ δ13Corg, 18 C:N, ~6 mg lignin per 100 mg OC). These deposits provide the first direct evidence of turbidite deposition that post-dates the latest megathrust earthquake in northern Cascadia, with implications including that highstand stratigraphy preserves nonseismic events, turbidite composition reflects sediment source, and turbidite deposition represents a significant component of sediment and carbon accumulation.