Daily bathymetric surveys document how stratigraphy is built and its extreme incompleteness in submarine channels

Turbidity 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 m(3)) 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. (C) 2019 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Keyword(s)

stratigraphic completeness, submarine channel, turbidity current, crescentic bedform, submarine landslide, channel-lobe transition zone

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176 Mo
MMC. One summer offshore Squamish Delta, British Columbia.
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Video 1. Time-lapse animation of stratigraphic evolution of the Northern Channel.
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Video 2. Time-lapse animation of stratigraphic evolution of proximal to medial parts of Northern Channel.
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Video 3. Time-lapse animation of stratigraphic evolution of medial to distal parts of Northern Channel.
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Video 4. Time-lapse animation of stratigraphic evolution of the Central Channel.
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Video 5. Time-lapse animation of stratigraphic evolution of proximal to medial parts of Central Channel.
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Video 6. Time-lapse animation of stratigraphic evolution of medial to distal parts of Central Channel.
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Video 7. Time-lapse animation of stratigraphic evolution of the Southern Channel.
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Video 8. Time-lapse animation of stratigraphic evolution of proximal to medial parts of Southern Channel.
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Video 9. Time-lapse animation of stratigraphic evolution of the channel lobe transition zone of Southern Channel.
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Video 10. Time-lapse animation of stratigraphic evolution of the channel lobe transition zone of Southern Channel – zoom in.
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Video 11. Time-lapse animation of stratigraphic evolution of across-profile A.
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Video 12. Time-lapse animation of stratigraphic evolution of across-profile B.
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Video 13. Time-lapse animation of stratigraphic evolution of across-profile C.
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Video 14. Time-lapse animation of stratigraphic evolution of across-profile D.
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Video 15. Time-lapse animation of stratigraphic evolution of across-profile E.
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Video 16. Time-lapse animation of stratigraphic evolution of across-profile F.
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Video 17. Time-lapse animation of stratigraphic evolution of across-profile G.
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Video 18. Time-lapse animation of stratigraphic evolution of across-profile H.
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How to cite
Vendettuoli D., Clare M. A., Clarke J. E. Hughes, Vellinga A., Hizzet J., Hage Sophie, Cartigny M. J. B., Talling P. J., Waltham D., Hubbard S. M., Stacey C., Lintern D. G. (2019). Daily bathymetric surveys document how stratigraphy is built and its extreme incompleteness in submarine channels. Earth And Planetary Science Letters. 515. 231-247. https://doi.org/10.1016/j.epsl.2019.03.033, https://archimer.ifremer.fr/doc/00730/84236/

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