Grain size,La/Yb and Th/Sc of settling particles in the western North Pacific: Evidence for lateral transport of small Asian loess |
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| Authors: | Nobuhiro Maeda Shinichiro Noriki Hisashi Narita |
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| Institution: | (1) Graduate School of Environmental Earth Science, Hokkaido University, Sapporo 060-0810, Japan;(2) Faculty of Environmental Earth Science, Hokkaido University, Sapporo 060-0810, Japan;(3) Present address: The General Environmental Technos Co., Ltd., Azuchimachi, Chuo-ku, Osaka 541-0052, Japan |
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| Abstract: | To understand the transport process of lithogenic particles in the ocean, we measured the grain size distributions of lithogenic
particles and measured the opal, La, Yb, Th, and Sc concentrations of the settling particles collected from time-series sediment
traps at Sta. KNOT (44°N, 155°E, water depth 5320 m) from June 2002 to May 2004. The annual mean lithogenic particle flux
observed at the lower sediment trap (5100 m) was twice as high as that at the upper sediment trap (770 m). The contribution
of Asian loess estimated by the La/Yb and the Th/Sc ratios in the lower layer was greater than that in the upper layer. The
fluxes of small lithogenic particles with sizes of 3–4 μm at the lower layer (5 to 65 mg/m2/day) were approximately four times larger than that at the upper layer (0.6 to 27 mg/m2/day). These results indicate that the horizontal addition of small particle sizes of Asian loess is a main factor in the
increase of lithogenic particles at the lower layer. The temporal variations in the small lithogenic particle flux at the
lower layer had a positive correlation with those at the upper layer (r = 0.71). The small lithogenic particle fluxes showed
a strong positive correlation with the opal fluxes (r = 0.9). We therefore conclude that the small lithogenic particles were
laterally transported and scavenged by the formation of aggregates with opal. |
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| Keywords: | Western North Pacific sediment trap lithogenic particle grain size La/Yb Th/Sc |
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