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During Integrated Ocean Drilling Program (IODP) Expedition 307, three sites were drilled on Challenger Mound in Porcupine Seabight off western Ireland in May 2005 (see the “Expedition 307 summary” chapter). The aim of this expedition was to understand the origin and evolution of the coldwater coral banks in Porcupine Seabight, one of the most intensively studied provinces. In addition to the mound, one site immediately downslope of Challenger Mound and an upslope site were drilled. The mound roots on a strongly erosive unconformity and is seated partly on an enigmatic sequence of sigmoidal units and partly on a semitransparent layer. Eleven holes with a maximum depth of 270 m were drilled on and near Challenger Mound, and core sections penetrating a thick coral reef body were recovered. The mound itself consists of a repetition of floatstone and rudstone that rests on a sharp erosional boundary and contains coral (Lopheria pertusa) fragments, other bioclasts, a fine-grained clay matrix, and calcareous nannofossils (see the “Expedition 307 summary” chapter).

Through the Ocean Drilling Program (ODP) and IODP, some attempts have been made to evaluate X-ray imaging for observation and description of core samples with a computerized tomography (CT) scanner (e.g., Iturrino et al., 2004; Shirai et al., 2007). In this paper, we describe and discuss the use of medical X-ray CT to map coral fragments within host sediments. X-ray CT generates X-ray images along freely chosen sections and offers the possibility of density measurements based on X-ray attenuation. X-ray CT was performed using the archive-half section of core sample from Hole U1316A. Site U1316 is located in downslope sediment deposits ~700 m southwest of Challenger Mound. The three-dimensional (3-D) X-ray CT images were compared with split-surface digital images of the correlative half core. This paper confirms that X-ray CT is a powerful tool for core observation because it is nondestructive and provides rapid 3-D imaging.