Enigmatic linear furrows and pits on the upper continental slope, northwest Labrador Sea: are they sediment furrows or feeding traces?

Authors

  • Heiner Josenhans Atlantic Geoscience Centre, Geological Survey of Canada, Bedford Institute of Oceanography, P.O. Box 1006, Dartmouth. Nova Scotia B2Y4A2
  • Chris Woodworth Lynas Centre for Cold Ocean Resources Engineering, Memorial University of Newfoundland, St. John's, Newfoundland AIB3X5

DOI:

https://doi.org/10.4138/1647

Abstract

Linear furrows and pits were observed from a submersible on the continental slope east of Hudson Strait in water depth ranging from 1004 to 715 m (Fig. 1). The parallel to sub-parallel furrows are typically 15-40cm wide and 20-60 cm deep. These enigmatic features resemble deep-water, current-formed sedimentary furrows but differ in two significant aspects: (1) they consistently have blocky rims (berms) that appear to have been formed by the ploughing action of a rigid object, and (2) they lack any evidence of formation by bottom currents. We describe the local geological setting and compare the furrows with conventional sedimentary furrows. Our observations lead us to propose three tentative mechanisms for furrow formation: (1) formation by dragging of fins or mandibles of deep diving animals such as whales as they forage on the seafloor, (2) current driven ice which is negatively bouyant because of entrapped glacial sediment, or (3) furrowing by current-driven sponge balls which were observed in the troughs of the furrows. RÉSUMÉ Des plongées en submersible sur la pente continentale à l’est du détroit d'Hudson ont révéIé des sillons linéaires et des dépressions par une profondeur de 715 à 1004 m. Ces sillons sont parallèles on presque, typiquement d'une largeur de 15 à 40 cm et d'une profondeur de 20 à 60 cm. Ces structures énigmatiques évoquent les sillons sédimentaires dus a Taction des courants sur les grands fonds mais en différent sur deux points principaux: (1) elles présentent constamment des bordures (replats) morcelées qui semble résulter d'un labourage par un objet rigide et (2) la preuve de leur formation par des courants de fond fait défaut. On décrit le cadre géologique régional et compare ces sillons aux sillons sédimentaires conventionnels. À la lumière de nos observations, trois options s'offrent pour expliquer leur formation: (1) tralnage des nageoires ou rostres d'animaux plongeant à de grandes profondeurs, tels les baleines, qui draguent le fond, (2) reclage par des glaces vebiculies par les courants et qui sont plus denses du fait d'un lest de sédiment glaciaire ou (3) affouillement par suite de l’action des courants sur les boules spongiaires qui jalonnent le fond des sillons. [Traduit par le journal]

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Published

1988-08-01

How to Cite

Josenhans, H., & Lynas, C. W. (1988). Enigmatic linear furrows and pits on the upper continental slope, northwest Labrador Sea: are they sediment furrows or feeding traces?. Atlantic Geoscience, 24(2). https://doi.org/10.4138/1647

Issue

Vol. 24 No. 2 (1988)

Section

Articles

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