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Site U14241

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 U1424 is in the eastern part of the marginal sea surrounded by the Japanese Islands, the Korean Peninsula, and the Eurasian continent at 40°11.40′N, 138°13.90′E and 2808 meters below sea level. The site is at the same location as Ocean Drilling Program (ODP) Site 794 and is ~200 km southwest of the entrance of the Tsugaru Strait (Fig. F1). Site U1424 is near the boundary between the Japan and Yamato Basins and ~10 km west of the submarine Toyama Channel that extends from the central part of Honshu Island. The site is mainly under the influence of the second branch of the Tsushima Warm Current and close to the present position where the third branch merges with the second branch of the Tsushima Warm Current during the present summer. Previous drilling at Site 794 revealed that the site is characterized by very slow (~30 m/m.y.) yet continuous sedimentation during the last 4 m.y. (Tada, 1994), which is ideal to detect the contribution of eolian dust from the Asian continent. Preliminary examination of the Pleistocene sediment suggests possible occurrence of ice-rafted debris (IRD), suggesting its potential utility for the study of IRD.

Site U1424 is the southernmost site of the northern half of the latitudinal transect targeted by IODP Expedition 346 and is also the second deepest site of the depth transect. The location of Site U1424 was selected specifically to identify the southern limit of IRD events. Together with the results from IODP Sites U1422 and U1423, identification of IRD events at this site and correlation with previous sites will allow us to reconstruct temporal changes in the southern limit of sea ice in the marginal sea during the last 4 m.y.

Site U1424 is also ideal for reconstruction of eolian dust flux, grain size, and provenance changes since ~4 Ma, considering the very low sedimentation rate observed at Site 794. Although IRD may contribute to the total terrigenous flux in several intervals, the grain size range of eolian dust (4–32 µm) may allow differentiation of the eolian dust component from other terrigenous components.

This site is also useful to reconstruct changes in deepwater oxygenation and calcium carbonate compensation depth during the last 4 m.y., particularly because Site U1424 is the second deepest site drilled during Expedition 346. At the deepest site previously drilled during this expedition, Site U1422, this objective was negatively impacted by the presence of numerous turbidites in the interval older than ~2.5 Ma.

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 U1424. 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.346.105.2015

2Expedition 346 Scientists’ addresses.

Publication: 28 March 2015
MS 346-105