Carbon and Oxygen Stable Isotopic Measurements of Carbonate and Water Samples using Mass Spectrometer with Gas Bench

We verified the appropriate conditions and the precisions of stable isotopic analyses for carbonate and water samples using a mass spectrometer with Gas Bench. Standard deviation and reproducibility of the analyses are dependent on the amount of carbon dioxide obtained from samples, and are minimized when the amount of carbonate sample of 0.09-0.14 mg. Isotopic equilibrium is obtained in l hour at 50℃ after the reaction of carbonate and purified phosphoric acid. On these conditions, the reproducibility was±0.19‰ forδ^13C, and±0.22‰ for δ^18O(2SD). In the case of water samples, the appropriate sample amount was 0.75-1.0 mL for seawater, and 0.5 mL for calcareous freshwater that includes 3-4 mM of dissolved inorganic carbon. Reproducibility of ±0.04‰ (2SD) is gained for δ^13C after the reaction for 20 hours at 25℃. Oxygen isotope reaches the equilibrium in 24 hours after the reaction, which reveals the reproducibility of ±0.18‰(2SD). Standard deviation and reproducibility in any cases are within a required level for geoscientific researches on the marine and terrestrial specimens

Strontium isotopic ages from IODP Exp307

Sr isotope stratigraphy provides a new age model for the first complete section drilled through a deep-water coral mound. The 155-m-long section from Challenger Mound in the Porcupine Sea-bight, southwest of Ireland, is on Miocene siliciclastics and consists entirely of sediments bearing well-preserved cold-water coral Lophelia pertusa. The 87Sr/86Sr 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 significant hiatus from ca. 1.7 to 1.0 Ma at 23.6 m below seafloor. The age of the basal mound sediments coincides with the intensification of Northern Hemisphere glaciations that set up the modern stratification of the northeast Atlantic and enabled coral growth. Mound growth persisted throughout glacial-interglacial fluctuations, 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

Age constraints on the origin and growth history of a deep-water coral mound in the northeast Atlantic drilled during Integrated Ocean Drilling Program Expedition 307

Sr isotope stratigraphy provides a new age model for the first complete section drilled through a deep-water coral mound. The 155-m-long section from Challenger Mound in the Porcupine Sea-bight, southwest of Ireland, is on Miocene siliciclastics and consists entirely of sediments bearing well-preserved cold-water coral Lophelia pertusa. The 87Sr/86Sr 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 significant hiatus from ca. 1.7 to 1.0 Ma at 23.6 m below seafloor. The age of the basal mound sediments coincides with the intensification of Northern Hemisphere glaciations that set up the modern stratification of the northeast Atlantic and enabled coral growth. Mound growth persisted throughout glacial-interglacial fluctuations, 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.<br/