46 research outputs found
230 Th normalization: new insights on an essential tool for quantifying sedimentary fluxes in the modern and quaternary ocean
© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Costa, K. M., Hayes, C. T., Anderson, R. F., Pavia, F. J., Bausch, A., Deng, F., Dutay, J., Geibert, W., Heinze, C., Henderson, G., Hillaire-Marcel, C., Hoffmann, S., Jaccard, S. L., Jacobel, A. W., Kienast, S. S., Kipp, L., Lerner, P., Lippold, J., Lund, D., Marcantonio, F., McGee, D., McManus, J. F., Mekik, F., Middleton, J. L., Missiaen, L., Not, C., Pichat, S., Robinson, L. F., Rowland, G. H., Roy-Barman, M., Alessandro, Torfstein, A., Winckler, G., & Zhou, Y. 230 Th normalization: new insights on an essential tool for quantifying sedimentary fluxes in the modern and quaternary ocean. Paleoceanography and Paleoclimatology, 35(2), (2020): e2019PA003820, doi:10.1029/2019PA003820.230Th normalization is a valuable paleoceanographic tool for reconstructing highâresolution sediment fluxes during the late Pleistocene (last ~500,000 years). As its application has expanded to ever more diverse marine environments, the nuances of 230Th systematics, with regard to particle type, particle size, lateral advective/diffusive redistribution, and other processes, have emerged. We synthesized over 1000 sedimentary records of 230Th from across the global ocean at two time slices, the late Holocene (0â5,000 years ago, or 0â5 ka) and the Last Glacial Maximum (18.5â23.5 ka), and investigated the spatial structure of 230Thânormalized mass fluxes. On a global scale, sedimentary mass fluxes were significantly higher during the Last Glacial Maximum (1.79â2.17 g/cm2kyr, 95% confidence) relative to the Holocene (1.48â1.68 g/cm2kyr, 95% confidence). We then examined the potential confounding influences of boundary scavenging, nepheloid layers, hydrothermal scavenging, sizeâdependent sediment fractionation, and carbonate dissolution on the efficacy of 230Th as a constant flux proxy. Anomalous 230Th behavior is sometimes observed proximal to hydrothermal ridges and in continental margins where high particle fluxes and steep continental slopes can lead to the combined effects of boundary scavenging and nepheloid interference. Notwithstanding these limitations, we found that 230Th normalization is a robust tool for determining sediment mass accumulation rates in the majority of pelagic marine settings (>1,000 m water depth).We thank Zanna Chase and one anonymous reviewer for valuable feedback. K. M. C. was supported by a Postdoctoral Scholarship at WHOI. L. M. acknowledges funding from the Australian Research Council grant DP180100048. The contribution of C. T. H., J. F. M., and R. F. A. were supported in part by the U.S. National Science Foundation (USâNSF). G. H. R. was supported by the Natural Environment Research Council (grant NE/L002434/1). S. L. J. acknowledges support from the Swiss National Science Foundation (grants PP002P2_144811 and PP00P2_172915). This study was supported by the Past Global Changes (PAGES) project, which in turn received support from the Swiss Academy of Sciences and the USâNSF. This work grew out of a 2018 workshop in AixâMarseille, France, funded by PAGES, GEOTRACES, SCOR, USâNSF, AixâMarseille UniversitĂ©, and John Cantle Scientific. All data are publicly available as supporting information to this document and on the National Center for Environmental Information (NCEI) at https://www.ncdc.noaa.gov/paleo/study/28791
\u3csup\u3e230\u3c/sup\u3eTh Normalization: New Insights on an Essential Tool for Quantifying Sedimentary Fluxes in the Modern and Quaternary Ocean
230Th normalization is a valuable paleoceanographic tool for reconstructing highâresolution sediment fluxes during the late Pleistocene (last ~500,000 years). As its application has expanded to ever more diverse marine environments, the nuances of 230Th systematics, with regard to particle type, particle size, lateral advective/diffusive redistribution, and other processes, have emerged. We synthesized over 1000 sedimentary records of 230Th from across the global ocean at two time slices, the late Holocene (0â5,000 years ago, or 0â5 ka) and the Last Glacial Maximum (18.5â23.5 ka), and investigated the spatial structure of 230Thânormalized mass fluxes. On a global scale, sedimentary mass fluxes were significantly higher during the Last Glacial Maximum (1.79â2.17 g/cm2kyr, 95% confidence) relative to the Holocene (1.48â1.68 g/cm2kyr, 95% confidence). We then examined the potential confounding influences of boundary scavenging, nepheloid layers, hydrothermal scavenging, sizeâdependent sediment fractionation, and carbonate dissolution on the efficacy of 230Th as a constant flux proxy. Anomalous 230Th behavior is sometimes observed proximal to hydrothermal ridges and in continental margins where high particle fluxes and steep continental slopes can lead to the combined effects of boundary scavenging and nepheloid interference. Notwithstanding these limitations, we found that 230Th normalization is a robust tool for determining sediment mass accumulation rates in the majority of pelagic marine settings (\u3e1,000 m water depth)
Principles of igneous petrology, par S. Maaloe, 1985
Kienast Jean-Robert. Principles of igneous petrology, par S. Maaloe, 1985. In: Bulletin de Minéralogie, volume 109, 3, 1986. p. 318
The deep proterozoic crust in the North Atlantic Provinces â Series C : Mathematical and Physical Sciences. Vol. 158
Kienast Jean-Robert. The deep proterozoic crust in the North Atlantic Provinces â Series C : Mathematical and Physical Sciences. Vol. 158. In: Bulletin de MinĂ©ralogie, volume 109, 6, 1986. pp. 700-701
Microtextures of igneous and metamorphic rocks, par J. P. Bard, édité par D. Reidel
Kienast Jean-Robert. Microtextures of igneous and metamorphic rocks, par J. P. Bard, édité par D. Reidel. In: Bulletin de Minéralogie, volume 110, 1, 1987. p. 119
W-Sn skarn deposits and related metamorphic skarns and granitoids par T. A. P. Kwak
Kienast Jean-Robert. W-Sn skarn deposits and related metamorphic skarns and granitoids par T. A. P. Kwak. In: Bulletin de Minéralogie, volume 111, 5, 1988. pp. 552-553
The deep proterozoic crust in the North Atlantic Provinces â Series C : Mathematical and Physical Sciences. Vol. 158
Kienast Jean-Robert. The deep proterozoic crust in the North Atlantic Provinces â Series C : Mathematical and Physical Sciences. Vol. 158. In: Bulletin de MinĂ©ralogie, volume 109, 6, 1986. pp. 700-701