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doi:10.2204/iodp.proc.338.203.2015 Data report: boron isotope ratios in interstitial waters from Sites C0021 and C00221Tomohiro Toki,2 Kota Higa,2 and Ryuichi Shinjo3AbstractSurface sediment was sampled from Sites C0021 and C0022 in the Nankai accretionary prism during Integrated Ocean Drilling Program (IODP) Expedition 338. Interstitial waters were extracted from the sediments, and boron isotope ratios (δ11B) in the interstitial waters were measured. Just below the seafloor at both sites, boron concentrations were higher than that of seawater, and δ11B values were rich in 10B relative to seawater. Boron concentrations decreased and δ11B increased with increasing depth at both sites. At Site C0022, these values were almost constant around 100 meters below seafloor, and at the bottom of the hole, boron concentrations were increasing and δ11B values were increasing. We did not find anomalies related to lithologic unconformities such as faults and mass transport deposits. This may indicate that it has been some time since the events forming these unconformities, assuming that anomalies existing just after the events were smoothed by diffusion. Thus, these faults and mass transport deposits might currently be inactive. |
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