The Magellan mound province in the Porcupine Basin

Abstract

The Magellan mound province is one of the three known provinces of carbonate mounds or coldwater coral banks in the Porcupine Seabight, west of Ireland. It has been studied in detail using a large and varied data set: 2D and 3D seismic data, sidescan sonar imagery and video data collected during ROV deployment have been used to describe the mounds in terms of origin, growth processes and burial. The aim of this paper is to present the Magellan mounds and their setting in an integrated, holistic way.More than 1,000 densely spaced and mainly buried mounds have been identified in the area. They all seem to be rooted on one seismic reflection, suggesting a sudden mound start-up. Their size and spatial distribution characteristics are presented, together with the present-day appearance of the few mounds that reach the seabed. The underlying geology has been studied by means of fault analysis and numerical basin modelling in an attempt to identify possible hydrocarbon migration pathways below or in the surroundings of the Magellan mounds.Although conclusive evidence concerning the processes of mound initiation proves to be elusive, the results of both fault analysis and 2D numerical modelling failed to identify, with confidence, any direct pathways for focused hydrocarbon flow to the Magellan province. Diffuse seepage however may have taken place, as drainage area modelling suggests a possible link between mound position and structural features in the Hovland-Magellan area. During mound development and growth, the interplay of currents and sedimentation seems to have been the most important control. Mounds which could not keep pace with the sedimentation rates were buried, and on the few mounds which maintained growth, only a few corals survive at present.

The Holocene occurrence of cold water corals in the NE Atlantic: Implications for coral carbonate mound evolution

“…Within Porcupine Seabight, along Porcupine Bank and on Rockall Bank, numerous carbonate mound provinces have been found at water depth between 400 m and 1100 m (Hovland et al, 1994;de Mol et al, 2002;Huvenne et al, 2003;Kenyon et al, 2003;van Weering et al, 2003;Wheeler et al, 2005;van Rooij et al, 2006;van Wheeler et al, 2007;Foubert et al, 2007;Huvenne et al, 2007).…”

X-ray imagery and physical core logging as a proxy of the content of sediment cores in cold-water coral mound provinces: a case study from Porcupine Seabight, SW of Ireland

“…4a, 5a). A detailed study of this area has been performed by Huvenne et al (2003Huvenne et al ( , 2006. On the TOBI sidescan imagery the Magellan province appears as an area with a homogeneous acoustic facies of medium, although rather 'grainy' backscatter strength , which can be linked to bioturbated muddy or silty hemipelagic sediments (Kenyon et al 1998).…”

Carbonate mounds: From paradox to World Heritage

“…The giant mounds, which started to grow some 2.5 Ma (Exp. 307, Kano et al, 2007), are also often molded by moderate to strong currents (Magellan mounds, Huvenne et al, 2007) and draped by contourite drifts (Van Rooij et al, 2003) (Fig. 2).…”

“…An interesting experiment would be to drill a sequence of mounds from exposed ones to recently buried ones, to track in particular the diagenetic expression of the switch from open diagenetic system (the "mound flushing" stage of exposed mounds) to encapsulation, both in a proven pathway of advecting fluids (Melilla mound province, Alboran Sea, Morocco, Comas et al, 2009) and in a setting, possibly not affected by migrating fluids (Magellan -Perseverance mound suite, Porcupine Seabight, Huvenne et al, 2007;Pirlet et al, 2010).…”