Morphological characteristics and superficial structure of submarine mounds in the lower slope of the Canary continental margin (W of Canary Islands)

Abstract

Extrusive edifices and structural reliefs, catalogued as mounds and located on the seafloor to the west of Canary Islands were analyzed by acoustic data obtained with multibeam and parametric echosounders during several oceanographic expeditions. They were carried out at deep waters, from 4800 to 5200 m, and they have allowed characterizing 41 newly discovered submarine structures which occur either as isolated edifices or clustered mounds. These features have circular to elongated shapes with diameters of 2-24 km and relief heights of 10 to 250 m, showing different flank slopes of 2-50°. They generally display mounded forms and show morphological elements as ridges, near-circular rock outcrops, depressions and fault scarps together with mass flow and slide deposits located at the vicinity of the edifices. Two types of extrusive features are evidenced by the morphological and seismic data analyses, the first one probably corresponds to high velocity extrusions that reach the seafloor surface and the second one is probably formed by the combination of faulted structures and low velocity extrusions that produce singular domes in the shallower sedimentary records. Based on both analyses, extrusive phenomena represent the dominant mechanism for mound field evolution in the Canary lower slope region.