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doi:10.2204/iodp.proc.346.108.2015

Site U1427¹

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 U1427 is in the Yamato Basin at 35°57.92′N, 134°26.06′E and 330 meters below sea level (mbsl). The site is situated on the outer margin of the southeast-northwest–trending continental shelf ~35 km from the northern coast of Honshu Island and ~110 km south of Site U1426 (Fig. F1). Today, this site is under the influence of the first branch of the Tsushima Warm Current (TWC), which is flowing along the outer margin of the continental shelf of Honshu Island (Hase et al., 1999). A piston core obtained during a preexpedition site survey cruise suggests an average sedimentation rate of ~300 m/m.y. (www.godac.jamstec.go.jp/​catalog/​data/​doc_catalog/​media/​KR07-12_all.pdf). This is significantly higher than any other sites drilled in the marginal basin, and coring at this site should provide an extremely high resolution record spanning most of the Pleistocene. In addition, the proximity to the southwestern portion of Honshu Island will provide a rare opportunity to examine the interrelationship between terrestrial climate and oceanography in the southern part of the marginal basin.

Site U1427 is the southernmost site of the IODP Expedition 346 latitudinal transect and is also the shallowest site of the depth transect. The location of Site U1427 was selected to obtain a high-resolution record of changes in the intensity of the influx of the first branch of the TWC during the last 2 m.y. We anticipate that this site will allow high-resolution and continuous reconstruction of the oxygen isotope record because the shallow depth of Site U1427 assures that the site has always been located above the calcium carbonate compensation depth. Accordingly, benthic foraminifers have likely survived burial and resisted corrosion even during glacial maxima climate stages when euxinic deepwater conditions prevailed deeper than 500 mbsl (Ikehara et al., 1994). Together with the results from IODP Sites U1425 and U1426, Site U1427 will enable us to reconstruct sea-surface temperature changes associated with the north–south movement of the Subpolar Front, which is considered to be related to the strength of the TWC (Isoda, 2011).

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 U1427. 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.346.108.2015

² Expedition 346 Scientists’ addresses.

Publication: 28 March 2015
MS 346-108

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