Y. Tamura , C.J. Busby , P. Blum , G. Guèrin , G.D.M. Andrews , A.K. Barker , J.L.R. Berger , E.M. Bongiolo , M. Bordiga , S.M. DeBari , J.B. Gill , C. Hamelin , J. Jia , E.H. John , A.-S. Jonas , M. Jutzeler , M.A.C. Kars , Z.A. Kita , K. Konrad , S.H. Mahony , M. Martini , T. Miyazaki , R.J. Musgrave , D.B. Nascimento , A.R.L. Nichols , J.M. Ribeiro , T. Sato , J.C. Schindlbeck , A.K. Schmitt , S.M. Straub , M.J. Vautravers , Y. and Yang
30 May 2015
International Ocean Discovery Program (IODP) Hole U1436A lies in the western part of the Izu fore-arc basin, ~60 km east of the arc-front volcano Aogashima, ~170 km west of the axis of the Izu-Bonin Trench, and 1.5 km west of Ocean Drilling Program (ODP) Site 792, at 1776 meters below sea level (mbsl). It was drilled as a 150 m deep geotechnical test hole for potential future deep drilling (5500 meters below seafloor [mbsf]) at proposed Site IBM-4 using the D/V Chikyu. Core from Site U1436 yielded a rich record of Late Pleistocene explosive volcanism, including a distinctive black glassy mafic ash layer that may record a large-volume subaqueous eruption on the Izu arc front. Because of the importance of this discovery, Site U1436 was drilled in three additional holes (U1436B, U1436C, and U1436D), as part of a contingency operation, in an attempt to get better recovery on the black glassy mafic ash layer and its enclosing sediments and to better constrain its thickness. IODP Site U1437 is located in the Izu rear arc, ~330 km west of the axis of the Izu-Bonin Trench and ~90 km west of the arc-front volcanoes Myojinsho and Myojin Knoll, at 2117 mbsl. The primary scientific objective for Site U1437 was to characterize “the missing half of the subduction factory” because numerous ODP/IODP sites had been drilled in the arc-front to fore-arc region, but this was the first site to be drilled in the rear-arc region of the Izu arc. A complete view of the arc system is needed to understand the formation of oceanic arc crust and its evolution into continental crust. Site U1437 on the rear arc had excellent core recovery in Holes U1437B and U1437D, and we succeeded in hanging the longest casing ever in the history of R/V JOIDES Resolution scientific drilling (1085.6 m) in Hole U1437E and cored to 1806.5 mbsf.