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Title

Negative-relief features reworking contourite deposits in the Motril marginal plateau (Alboran Sea, Western Mediterranean)

AuthorsPalomino, Desirée; Vázquez, J. T.; Ercilla, Gemma ; López-González, Nieves; Alonso, Belén ; Díaz del Río, Víctor
Issue Date28-Jan-2013
CitationDialogue Between Contourite and Oceanography processes International Workshop: 53 (2013)
AbstractThe analysis of high-resolution (sparker, 3-channel Airgun) and very high-resolution (TOPAS, Parasound) seismic reflection profiles and multibeam bathymetry compiled during several oceanographical cruises in the northern Alboran Sea (SW Mediterranean), have allowed to study the morphology and origin of negative-relief features located on the contourite deposits developed in the vicinity of the seamounts - Avempace, Herradura, and Djibouti Ville (Al-ldrissi) - on the Motril Marginal Plateau (northern Alboran Sea). Two types of negative-relief features have been identified according to their circular or elongated morphology. Circular-like shapes match with pockmark and scour mark morphologies. The pockmarks are placed at the N and NW of the Avempace Seamount from 672 to 740 m water depth. 48 pockmarks have been described and they al1 display V-shaped cross-section. They are 1-19 m high and 50-400 m wide and but only some show higher backscatter than the surrounding areas. The scour marks occur isolated or clustered in the surroundings of the Herradura Seamount at 750-900 water depth. These negative-relief features are both V- and U-shaped in cross-sections. Ushaped scour marks display flat-bottom and truncated reflectors along their walls. Elongated-like shapes match with tectonic depressions and furrows. Tectonic depressions are NNE-SSW linear features, isolated and forming groups with a rhombshape distribution, that locate at 650-1,000 m water depth. The furrows are smallsized erosive ENE-WSW features 1-5 m high and 200 m wide, located at the NW of Avempace and Herradura seamounts from 720 to 900 m water depth. They show Ushaped cross-section running parallel the regional slope. The pockmark formation is attributed to the escape of seepage of gas and interstitial fluids from contourite sediments they affect. The Pockmark field location could be also related to normal basement faults that have favoured the upward migration of the fluid following pre-existing pathways. Scour marks are associated with the vorticity arising when bottom currents flow around a seamount. Upstream of the seamount, a turbulence are develops favouring the whirls occurrence that erode seafloor creating the scour marks. Tectonic depressions are related to the vertical displacement of a NNW-SSE strike-slip fault system and associated to seafloor rupture along the Pliocene Quaternary Faults that have affected even the most recent sediments. Additionally, they can perform as small channels that control the water flow to the SW. Furrows
DescriptionDialogue Between Contourite and Oceanography processes International Workshop, University of Hull, 28-26 January 2013, University of Hull, UK
URIhttp://hdl.handle.net/10261/89691
Appears in Collections:(ICM) Comunicaciones congresos
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