3D spatial and morphological analysis of a buried mound province

Mound structures were discovered in 3 provinces in the Porcupine Seabight, along the continental margin southwest of Ireland. One of them, the Magellan Province, contains mainly buried mound structures, although a few mounds also protrude up to the seabed, at 600 to 750 m depth. Comparison with other (seabed) mounds in the area allowed their identification as coral banks or carbonate mounds, associated with the growth of deep-sea coral species such as Lophelia pertusa and Madrepora oculata. The mounds in the Magellan Province were studied by means of high-resolution 2D and industrial 3D seismic data. The 3D data set consisted of the upper 400 ms TWT of a 830 km2 industrial data block, provided by Statoil Exploration (Ireland) Ltd., and its partners, Conoco (U.K.) Ltd., Enterprise Energy Ireland Ltd. and Dana Petroleum plc. Time structure maps of key reflections and horizon slices were further processed in a GIS-system using mathematical morphology and geostatistical toolsThe resulting images revealed 305 mounds (>30 m) within an area of 350 km2. They all are rooted on the same reflection. Smaller buildups can be seen in the seismic profiles too, but were excluded from the statistical analyses. The mounds are significantly elongated in a N/S direction, and are associated with moat structures containing the same - even stronger- elongation. A N/S directed current influence seems to have played an important role in the mound history. The location and spatial pattern of the mounds however, is different. Investigations showed that mound positions are not linked to any fault information present in the shallow 3D data block. A possible relationship with the depth contours of key horizons or erosional unconformities, or with the morphology of an underlying enigmatic slope failure seems more promising. According to spatial trend analysis, the mounds are larger on the western edge of the province, while the burying sediment packages are thicker towards the (S)E. Sedimentation rates hence seem to have influenced the mound growth and vitality as well.From the 2 and 3D seismic analysis of the Magellan Mound Province, one learns that the mounds started to grow at 1 confined moment in time and space. Their positioning does not seem to be influenced by shallow faults, but rather by the location of erosional unconformities and a deeper lying slope failure. Currents and sedimentation patterns on their turn clearly played a role in the mound development