Textural analyses of sidescan sonar imagery from two mound provinces in the Porcupine Seabight

Huvenne, V.A.I., Blondel, Ph. and Henriet, J.P. (2002) Textural analyses of sidescan sonar imagery from two mound provinces in the Porcupine Seabight. Marine Geology, 189 (3-4), 323-341. (doi:10.1016/S0025-3227(02)00420-6).

Abstract

Large mound structures have been discovered in the Porcupine Seabight (Northeast Atlantic) at a depth of 500–1200 m, associated with the growth of cold-water deep-sea coral species such as Lophelia pertusa (L.) or Madrepora oculata (L.). During the Training Through Research cruise in 1997, high-resolution OREtech sidescan sonar data were acquired over two provinces of these structures. This article focuses on the presentation and quantitative interpretation of representative sections of these sidescan data from areas around the Belgica and Hovland mounds. Several image analysis tools were used, but texture analysis, based on grey level co-occurrence matrices, gave the best results. Entropy and homogeneity indices were calculated, and the resulting images made it possible to discriminate between different seabed features on a quantitative basis. Mounds, moats and background sediments could be delineated accurately, and the image textures could be linked to the actual seafloor appearance through core descriptions and deep-towed video data. A major difference was found in the acoustic returns from the two provinces studied: the Belgica province shows much rougher textures. This is due to an actual difference in seabed roughness, caused by a difference in bottom currents and sediment dynamics in the two areas. The combined effect of the northward-directed North Atlantic slope current and superimposed internal waves and tides appears to be much stronger in the Belgica province. The reported difference in current strength might well influence the growth of the deep-water coral species in both areas.

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Contributors

Author: V.A.I. Huvenne

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