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TitleDaily bathymetric surveys document how stratigraphy is built and its extreme incompleteness in submarine channels
AuthorVendettuoli, D; Clare, M A; Hughes Clarke, J E; Vellinga, A; Hizzett, J; Hage, S; Cartigny, M J BORCID logo; Talling, P J; Waltham, D; Hubbard, S M; Stacey, CORCID logo; Lintern, D GORCID logo
SourceEarth and Planetary Science Letters vol. 515, 2019 p. 231-247, Open Access logo Open Access
Alt SeriesNatural Resources Canada, Contribution Series 20190056
PublisherElsevier BV
Mediapaper; on-line; digital
File formatpdf (Adobe® Reader®); html
ProvinceBritish Columbia; Western offshore region
AreaHowe Sound; Squamish River; Squamish Delta
Lat/Long WENS-123.2333 -123.1333 49.7167 49.5500
Subjectsmarine geology; surficial geology/geomorphology; stratigraphy; sedimentology; geophysics; geophysical surveys; acoustic surveys, marine; bathymetry; submarine features; channels; turbidity currents; sediment transport; sediment distribution; depositional environment; depositional history; marine sediments; stratigraphic analyses; sediment reworking; bedforms; erosion; erosional surfaces; marine sediment cores; Infrastructures; marine deltaic sediments
Illustrationstime series; schematic representations; location maps; geoscientific sketch maps; bathymetric profiles; stratigraphic correlations
Released2019 04 04
AbstractTurbidity currents are powerful flows of sediment that pose a hazard to critical seafloor infrastructure and transport globally important amounts of sediment to the deep sea. Due to challenges of direct monitoring, we typically rely on their deposits to reconstruct past turbidity currents. Understanding these flows is complicated because successive flows can rework or erase previous deposits. Hence, depositional environments dominated by turbidity currents, such as submarine channels, only partially record their deposits. But precisely how incomplete these deposits are, is unclear. Here we use the most extensive repeat bathymetric mapping yet of any turbidity current system, to reveal the stratigraphic evolution of three submarine channels. We re-analyze 93 daily repeat surveys performed over four months at the Squamish submarine delta, British Columbia in 2011, during which time >100 turbidity currents were monitored. Turbidity currents deposit and rework sediments into upstream-migrating bedforms, ensuring low rates of preservation (median 11%), even on the terminal lobes. Large delta-lip collapses (up to 150,000 m3) are relatively well preserved, however, due to their rapidly emplaced volumes, which shield underlying channel deposits from erosion over the surveyed timescale. The biggest gaps in the depositional record relate to infrequent powerful flows that cause significant erosion, particularly at the channel-lobe transition zone where no deposits during our monitoring period are preserved. Our analysis of repeat surveys demonstrates how incomplete the stratigraphy of submarine channels can be, even over just 4 months, and provides a new approach to better understand how the stratigraphic record is built and preserved in a wider range of marine settings.

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