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Submarine canyons, slope failures and mass transport processes in southern Cascadia

May 20, 2020

The marine turbidite record along the southern Cascadia Subduction Zone has been used to interpret paleoseismicity and suggest a shorter recurrence interval for large (>M7) earthquakes along this portion of the margin; however, the sources and pathways of these turbidity flows are poorly constrained. We examine the spatial distribution of sediment storage, downslope transport, and slope failures across the margin using multibeam bathymetry, sparker multichannel seismic and chirp subbottom data. Although deep-sea seismoturbidites are often linked to turbidity flows in submarine canyons, the morphology and stratigraphy of southern Cascadia suggests few of the canyons have been active sediment conduits during the recent sea level highstand. Stepped, intraslope basins trap most of the sediment from Rogue and Sixes canyons. Smith and Klamath canyons appear to be isolated, lower slope incisions with no connection to upper slope canyons or gullies. Aggradation and infilling of channels on the upper slope of Trinidad Canyon indicate limited sediment bypass during the Holocene. In contrast, there is evidence of extensive mass wasting of the lower slope, and non-channelized downslope flows outside of the canyon systems that appear to be likely sources of seismoturbidites in southern Cascadia, rather than routing of shelf sediment through submarine canyon systems.

Publication Year 2020
Title Submarine canyons, slope failures and mass transport processes in southern Cascadia
DOI 10.1144/SP500-2019-169
Authors Jenna C. Hill, Janet Watt, Daniel S. Brothers, Jared W. Kluesner
Publication Type Article
Publication Subtype Journal Article
Series Title Geological Society, London, Special Publications
Index ID 70210742
Record Source USGS Publications Warehouse
USGS Organization Pacific Coastal and Marine Science Center