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Site U14221

R. Tada, R.W. Murray, C.A. Alvarez Zarikian, W.T. Anderson Jr., M.-A. Bassetti, B.J. Brace, S.C. Clemens, M.H. da Costa Gurgel, G.R. Dickens, A.G. Dunlea, S.J. Gallagher, L. Giosan, A.C.G. Henderson, A.E. Holbourn, K. Ikehara, T. Irino, T. Itaki, A. Karasuda, C.W. Kinsley, Y. Kubota, G.S. Lee, K.E. Lee, J. Lofi, C.I.C.D. Lopes, L.C. Peterson, M. Saavedra-Pellitero, T. Sagawa, R.K. Singh, S. Sugisaki, S. Toucanne, S. Wan, C. Xuan, H. Zheng, and M. Ziegler2

Background and objectives

Integrated Ocean Drilling Program (IODP) Site U1422 is located in the northeastern part of the marginal sea between the Eurasian continent and the Japanese Islands at 43°45.99′N, 138°49.99′E and 3429 meters below sea level. The site is ~40 km southwest of Ocean Drilling Program (ODP) Leg 127 Site 795 and near the northeastern edge of the topographic depression of the Japan Basin (Fig. F1). The site is mainly under the influence of the Liman (Cold) Current but may also be slightly influenced by the Tsushima Warm Current (TWC) (Yoon and Kim, 2009). Although more than one-half (1.4 Sv) of the TWC (~2.5 Sv) flows out of the marginal sea through the Tsugaru Strait, ~300 km south of Site U1422, the rest of the TWC (~1.1 Sv) flows further north and out through the Soya Strait at present (e.g., Talley et al., 2006). Because the sill depth of the Soya Strait (~300 km northeast of Site U1422) is only 55 m, the influence of the TWC should have been significantly affected by glacioeustatic sea level changes during the Quaternary. Results from previous drilling at Site 795 suggest continuous deposition of hemipelagic sediment since the middle Miocene, at an average linear sedimentation rate of ~55 m/m.y. for the upper 200 m (Tada, 1994). This sedimentation rate is slow enough to detect the contribution of eolian dust from the Asian continent. The Pliocene–Pleistocene sediment of Site 795 also contains occasional dropstones in the upper 300 m of the sequence, suggesting its appropriateness for ice-rafted debris (IRD) study.

Site U1422 is the northernmost site of the latitudinal transect targeted by IODP Expedition 346 and is also the deepest site of the depth transect. The location of Site U1422 was selected specifically to identify the timing of the onset of IRD events and to reconstruct temporal variations in its intensity and frequency. Because sea ice formation in the marginal sea, which occurs along the northwestern margin as a result of strong winter cooling (Talley et al., 2003), is closely related to the intensity of Siberian High (e.g., Tada, 2004), we expected the intensity of the IRD events to reflect the strength of the East Asian winter monsoon. Therefore, at Site U1422 we hoped to reconstruct the winter monsoon intensity through examination of IRD abundance and distribution along the northern latitudinal transect in the Japan Basin. At present, stronger winter monsoon wind produces deep water, called Japan Sea Proper Water (JSPW), through sea ice formation in the northwestern part of the marginal sea (Talley et al., 2003). Consequently, sea ice formation and deepwater ventilation could also reflect winter monsoon intensity. Ikehara (2003) described millennial-scale IRD events in the northern part of the marginal sea during the last 160 k.y. Correlation of these IRD data with the lightness (L*) profile of piston Core MD01-2407 suggests that many of these IRD events coincide with intervals of high L* values, further suggesting intense deepwater ventilation that in turn coincides with Heinrich events.

1 Tada, R., Murray, R.W., Alvarez Zarikian, C.A., Anderson, W.T., Jr., Bassetti, M.-A., Brace, B.J., Clemens, S.C., da Costa Gurgel, M.H., Dickens, G.R., Dunlea, A.G., Gallagher, S.J., Giosan, L., Henderson, A.C.G., Holbourn, A.E., Ikehara, K., Irino, T., Itaki, T., Karasuda, A., Kinsley, C.W., Kubota, Y., Lee, G.S., Lee, K.E., Lofi, J., Lopes, C.I.C.D., Peterson, L.C., Saavedra-Pellitero, M., Sagawa, T., Singh, R.K., Sugisaki, S., Toucanne, S., Wan, S., Xuan, C., Zheng, H., and Ziegler, M., 2015. Site U1422. In Tada, R., Murray, R.W., Alvarez Zarikian, C.A., and the Expedition 346 Scientists, Proc. IODP, 346: College Station, TX (Integrated Ocean Drilling Program). doi:10.2204/iodp.proc.346.103.2015

2Expedition 346 Scientists’ addresses.

Publication: 28 March 2015
MS 346-103