Different frequencies and triggers of canyon filling and flushing events in Nazaré Canyon, offshore Portugal

Allin, Joshua R.; Hunt, James E.; Talling, Peter J.; Clare, Michael A. ORCID: https://orcid.org/0000-0003-1448-3878; Pope, Ed; Masson, Douglas G.. 2016 Different frequencies and triggers of canyon filling and flushing events in Nazaré Canyon, offshore Portugal. Marine Geology, 371. 89-105. 10.1016/j.margeo.2015.11.005

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Text © 2016 Elsevier B.V. This is the author’s version of a work that was accepted for publication in Marine Geology. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was/will be published in Marine Geology (doi:10.1016/j.margeo.2015.11.005) MARGO5786R1_accepted.pdf - Accepted Version Download (7MB) | Preview

Abstract/Summary

Submarine canyons are one of the most important pathways for sediment transport into ocean basins. For this reason, understanding canyon architecture and sedimentary processes has importance for sediment budgets, carbon cycling, and geohazard assessment. Despite increasing knowledge of turbidity current triggers, the down-canyon variability in turbidity current frequency within most canyon systems is not well constrained. New AMS radiocarbon chronologies from canyon sediment cores illustrate significant variability in turbidity current frequency within Nazaré Canyon through time. Generalised linear models and Cox proportional hazards models indicate a strong influence of global sea level on the frequency of turbidity currents that fill the canyon. Radiocarbon ages from basin sediment cores indicate that larger, canyon-flushing turbidity currents reaching the Iberian Abyssal Plain have a significantly longer average recurrence interval than turbidity currents that fill the canyon. The recurrence intervals of these canyon-flushing turbidity currents also appear to be unaffected by long-term changes in global sea level. Furthermore, canyon-flushing and canyon-filling have very different statistical distributions of recurrence intervals. This indicates that the factors triggering, and thus controlling the frequency of canyon-flushing and canyon-filling events are very different. Canyon-filling appears to be predominantly triggered by sediment instability during sea level lowstand, and by storm and nepheloid transport during the present day highstand. Canyon-flushing exhibits time-independent behaviour. This indicates that a temporally random process, signal shredding, or summation of non-random processes that cannot be discerned from a random signal, are triggering canyon flushing events.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1016/j.margeo.2015.11.005
ISSN:	00253227
Additional Keywords:	Submarine canyons; Turbidity currents; Sea level; Earthquakes; Geohazards; Sediment cores
Date made live:	01 Feb 2016 14:36 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/512803

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