Sr isotope stratigraphy provides a new age model for the fi rst complete section drilled through a deep-water coral mound. The 155-m-long section from Challenger Mound in the Porcupine Seabight, southwest of Ireland, is on Miocene siliciclastics and consists entirely of sediments bearing well-preserved cold-water coral Lophelia pertusa. The 87 Sr/ 86 Sr values of 28 coral specimens from the mound show an upward-increasing trend, correspond to ages from 2.6 to 0.5 Ma, and identify a signifi cant hiatus from ca. 1.7 to 1.0 Ma at 23.6 m below seafl oor. The age of the basal mound sediments coincides with the intensifi cation of Northern Hemisphere glaciations that set up the modern stratifi cation of the northeast Atlantic and enabled coral growth. Mound growth persisted throughout glacial-interglacial fl uctuations, reached a maximum rate (24 cm/k.y.) ca. 2.0 Ma, and ceased at 1.7 Ma. Unlike other buried mounds in Porcupine Seabight, Challenger Mound was only partly covered during its growth interruption, and growth restarted ca. 1.0 Ma.

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[1] Recent deep-ocean exploration has revealed unexpectedly widespread and diverse coral ecosystems in deep water on continental shelves, slopes, seamounts, and ridge systems around the world. Origin and growth history of these cold-water coral mounds are poorly known, owing to a lack of complete stratigraphic sections through them. Here we show high-resolution oxygen isotope records of planktic foraminifers from the base to the top of Challenger Mound, southwest of Ireland, which was drilled during Integrated Ocean Drilling Program Expedition 307. Challenger Mound began to grow during isotope stage 92 (2.24 million years ago (Ma)), immediately after the onset of Northern Hemisphere glaciation and the initiation of modern stratification in the northeast Atlantic. Mound initiation was likely due to reintroduction of Mediterranean Outflow Water (MOW) and ensuing development of a density gradient with overlying northeastern Atlantic water (NEAW), where organic matter was prone to be stagnated and fueled the coral ecosystem. Coral growth continued for 11 glacialinterglacial cycles until isotopic stage 72 (1.82 Ma) with glacial siliciclastic input from the continental margin. After a long hiatus that separates the lower mound and the upper mound, coral growth restored for a short time in isotope stages 19-18 (0.8-0.7 Ma) in which sediments were either eroded or not deposited during a full glacial stage. The development pattern of the water mass interface between MOW and NEAW might have changed, because of the fluctuations of the MOW production which is responsible for the amplitude in ice volume oscillations from the low-amplitude 41 ka cycles for the lower mound to the high-amplitude 100 ka cycles for the upper mound. The average sedimentation and CaCO 3 production rates of the lower mound were evaluated 27 cm/ka and 31.1 g/cm 2 /ka, respectively.