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] Previous isotopic investigations of Aptian/Albian oceanic anoxic event (OAE) 1b from the western North Atlantic (Blake Nose) posited that increased sea surface temperatures and decreased salinity led to stratification of the upper water column, resulting in lowered dissolved oxygen and enhanced organic matter preservation. We examined calcareous nannofossils from the same site in the western North Atlantic (Blake Nose) to evaluate changes in surface water conditions prior to, during, and after the Aptian/Albian OAE1b. The results of our analysis conflict somewhat with the previous interpretation that OAE1b at Blake Nose was linked to water column stratification. The signal from calcareous nannofossils indicates that in the late Aptian, prior to OAE1b, oligotrophic conditions in the surface waters were replaced by mesotrophic conditions that persisted throughout the OAE event and into the early Albian. We speculate that increased surface water productivity facilitated to some degree the development of OAE1b at Blake Nose.

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