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doi:10.2204/iodp.proc.345.107.2014

Holes U1415F and U1415G¹

K.M. Gillis, J.E. Snow, A. Klaus, G. Guerin, N. Abe, N. Akizawa, G. Ceuleneer, M.J. Cheadle, Á. Adrião, K. Faak, T.J. Falloon, S.A. Friedman, M.M. Godard, Y. Harigane, A.J. Horst, T. Hoshide, B. Ildefonse, M.M. Jean, B.E. John, J.H. Koepke, S. Machi, J. Maeda, N.E. Marks, A.M. McCaig, R. Meyer, A. Morris, T. Nozaka, M. Python, A. Saha, and R.P. Wintsch²

Operations

The locations for Integrated Ocean Drilling Program Holes U1415F and U1415G (see Fig. F8 in the “Expedition 345 summary” chapter [Gillis et al., 2014b]) were selected to test sediment thickness and subseafloor drilling conditions, with the aim of finding a suitable site for establishing a deep hole. Hole operations are summarized in Table T1 and outlined below. All times are ship local time (UTC – 7 h).

Near-bottom 3.5 kHz pinger and camera survey

At the end of operations in Hole U1415E and while still at that location, we assembled a new bottom-hole assembly (BHA) and lowered the bit to just above the seafloor. The previous problem with the 3.5 kHz pinger was ascribed to dead batteries, so the batteries were charged and the pinger was operational once again. We lowered the camera system with the 3.5 kHz pinger attached and conducted a new survey of the seafloor and near-subbottom in an attempt to locate an area on the bench with thin sediment and little or no rubble in evidence. This survey lasted from 1615 to 2000 h on 26 December 2012 (see Table T1 and Fig. F3 in the “Bench site survey” chapter [Gillis et al., 2014a]).

Hole U1415F drilling operations

A new location was selected, the top drive picked up, and a jet-in test was started at 2100 h on 26 December 2012. The seafloor depth for this hole was established as 4857.0 meters below rig floor (mbrf). The bit was jetted into the formation only 1.5 m before the test was terminated. The bit was pulled clear of the seafloor, and the camera system was recovered.

Hole U1415G drilling operations

The drill string was spaced out, and Hole U1415G was spudded at 2355 h on 26 December 2012 without offsetting the ship from the location of Hole U1415F. Rotary core barrel coring continued to 4869.94 mbrf (12.9 meters below seafloor) before being terminated. Core 345-U1415G-1R recovered 0.29 m (2%). Hole conditions were the same as in earlier holes, making it highly risky to attempt making connections with the bit in the hole. The bit was pulled clear of the seafloor at 0445 h on 27 December, ending Hole U1415G.

¹ Gillis, K.M., Snow, J.E., Klaus, A., Guerin, G., Abe, N., Akizawa, N., Ceuleneer, G., Cheadle, M.J., Adrião, Á., Faak, K., Falloon, T.J., Friedman, S.A., Godard, M.M., Harigane, Y., Horst, A.J., Hoshide, T., Ildefonse, B., Jean, M.M., John, B.E., Koepke, J.H., Machi, S., Maeda, J., Marks, N.E., McCaig, A.M., Meyer, R., Morris, A., Nozaka, T., Python, M., Saha, A., and Wintsch, R.P., 2014. Holes U1415F and U1415G. In Gillis, K.M., Snow, J.E., Klaus, A., and the Expedition 345 Scientists, Proc. IODP, 345: College Station, TX (Integrated Ocean Drilling Program). doi:10.2204/iodp.proc.345.107.2014

² Expedition 345 Scientists’ addresses.

Publication: 12 February 2014
MS 345-107

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