Submarine Mass Movements Along a Sediment Starved Margin: The Menorca Channel (Balearic Islands - Western Mediterranean)

Abstract

Sediment starved passive margins, particularly those of insular slopes, display significant mass transport activity despite the absence of environmental stresses from high sedimentation rates. The “Menorca Channel” represents the up to 120 m deep shelf sector connecting the Menorca and Mallorca Islands (Balearic Islands – Western Mediterranean). South of the Menorca Channel submarine gravitational processes have been mapped and interpreted from swath-bathymetry, TOPAS parametric echosounder and deep-towed videos. The shelf-break is located at an average depth of 140 m, and sediment instability is a widespread phenomenon. The slope region south the Menorca Channel shows a number of submarine canyons disrupting the outer shelf. The north-easternmost canyon is the more active feature, with an incised axis and scars shaping the flanks up to their edges. Headwall scarps, between 140 and 700 m depth, are up to 20 m high. The shallower scarps producing slab-type failures have carved the outer edges of planar sedimentary bodies interpreted as formed in shallow environments during previous glacial stages. Results show that a variety of sediment instability processes extensively shape the southern upper slope of the Menorca Channel. Submarine canyons develop on the Emile Bodout Escarpment (EBE), a passive tectonic feature which bounds the slope region of the study area. A number of knickpoints within the canyons suggest backward erosion control on mass wasting and, at the same time, that slope failure is one of the main drivers for canyon upslope migration. Steep gradients of the upper slope, the presence of weak layers and the action of major storms during lowstand stages are additional factors likely to influence the distribution and frequency of mass wasting processes in this area