The Moira Mounds, small cold-water coral mounds in the Porcupine Seabight, NE Atlantic: Part B—Evaluating the impact of sediment dynamics through high-resolution ROV-borne bathymetric mapping

Carbonate mounds: From paradox to World Heritage

“…The most likely limiting factor in the baffling process is the maximal height of saltation of the sediment grains within the bedload transport layer. As Foubert et al (2011) already had concluded for the Moira Mounds, such small buildups should be regarded as simple responses to stressed conditions in strong bottom currents and high sediment fluxes, rather than as an initial phase of extensive mound growth. The giant mounds, which started to grow some 2.5 Ma (Exp.…”

“…The remarkable resolution achieved in seismic imaging, multibeam bathymetry and habitat mapping in Porcupine Seabight, in the Bay of Biscay and on the Moroccan North-Atlantic margin in water depths ranging between 300 and 1300 m has shed light on vast fields of small cold-water coral capped hummocks, barely a few meters in amplitude (Masson et al, 2003;Wheeler et al, 2008;Huvenne et al, 2009;De Mol et al, 2011;Foubert et al, 2011;Wheeler et al, 2011), or coralcapped giant ripples, up to 10 to 20 m in amplitude (Mienis, 2007;Correa et al, 2012). In the early days of modern mound exploration on the Irish margin, the frequent spatial association of such fields of coral-capped hummocks and giant cold-water coral mounds fuelled the hypothesis that those small mounded features possibly could represent the embryonic stage of giant mounds, and still recently, contrasting views persist on this matter (Wilson et al, 2007;Foubert et al, 2011;Wheeler et al, 2011).…”

“…In the early days of modern mound exploration on the Irish margin, the frequent spatial association of such fields of coral-capped hummocks and giant cold-water coral mounds fuelled the hypothesis that those small mounded features possibly could represent the embryonic stage of giant mounds, and still recently, contrasting views persist on this matter (Wilson et al, 2007;Foubert et al, 2011;Wheeler et al, 2011). In a depression between outcropping giant carbonate mounds in the Belgica Mound province in Porcupine Seabight, small mounded features abound on sediment waves and small ridges and furrows: the Moira Mounds ( Fig.…”

“…1) (Wheeler et al, 2008. Foubert et al (2011) argue that they can be explained by the interaction of cold-water coral growth and sediment baffling, in response to strong bottom currents and high sediment fluxes. The targeted coring of minimounds on Odet Spur, south of the Guilvinec Canyon in the Bay of Biscay furthermore revealed that the debris of skeletal benthos, in general cold-water corals, formed no more than a centimeter-to decimeter-thick veneer at the surface of those small topographic elevations, which apparently had been shaped in a clayey substratum by strong bottom currents.…”

“…It should be noted that such fields of sediment waves topped with corals can also climb the flanks of larger mound structure (e.g. Thérèse Mound, Belgica Mound province, Foubert et al, 2011). The patchy settlement of opportunistic cold-water corals on the highs and the concurrent sediment baffling could actually mold small hummocks on these wave fields, and stabilize them.…”