Radiocarbon, isotope, biogenic, and 230Th measurements for sediment core RC10-196 ...

• Main Authors: Kohfeld, Karen E, Chase, Zanna
• Format: Article in Journal/Newspaper
• Language: English
• Published: PANGAEA 2011
• Subjects: Piston corer; RC10; Robert Conrad; Planktonic foraminifera; Subarctic
• Online Access: https://dx.doi.org/10.1594/pangaea.772835; https://doi.pangaea.de/10.1594/PANGAEA.772835

The subarctic North Pacific Ocean holds a large CO2 reservoir that is currently isolated from the atmosphere by a low-salinity layer. It has recently been hypothesized that the reorganization of these high-CO2 waters may have played a crucial role in the degassing of carbon dioxide to the atmosphere during the last deglaciation. This reorganization would leave some imprint on paleo-productivity records. Here we present 230Th-normalized biogenic fluxes from an intermediate depth sediment core in the Northwest Pacific (RC10-196, 54.7°N, 177.1°E, 1007 m) and place them within the context of a synthesis of previously-published biogenic flux data from 49 deep-sea cores north of 20°N, ranging from 420 to 3968 m water depth. The 230Th-normalized opal, carbonate, and organic carbon fluxes from RC10-196 peak approximately 13,000 calendar years BP during the Bølling/Allerød (B/A) period. Our data synthesis suggests that biogenic fluxes were in general lowest during the last glacial period, increased somewhat in the ... : Methods: 230Th-normalization was used to reconstruct particle flux to an intermediate depth sediment core, RC10-196 (54.7°N, 177.1°E, 1007 m). An age model was determined using a combination of radiocarbon dates and oxygen isotope stratigraphy. Oxygen isotope values were measured on N. pachyderma (sinistral coiling) from the 150-250 µm size fraction at the Saskatchewan Isotope Laboratory at the University of Saskatchewan. Radiocarbon analysis was conducted on three samples (two of N. pachyderma (sinistral coiling), one of mixed planktonic foraminifera), at Lawrence Livermore National Laboratory. These dates were converted to calendar age using the CALIB program (Stuiver and Reimer, 1993 (version 6.0)). Prior to calibration, a reservoir correction of 450 years was applied, using estimates obtained by Sarnthein et al. (2007) on cores from the NW Pacific region. Using this age model, sedimentation rates at RC10-196 ranged from 4.2 to 5.9 cm/ka over the last 30,000 years. Samples for U-series measurement were ...