Leg 172 Operations Report

To Site 1055
To Site 1056
To Site 1057
To Site 1058


The JOIDES Resolution (JR) departed Charleston, South Carolina at 1900 hr (local time) on 18 February 1997. At 0700 hr on 19 February, the ship was slowed to deploy and test new seismic gear, which included a generator injector (GI) air gun, on loan from Seismic Systems Incorporated, and two new multichannel seismic streamers produced by Innovative Transducers Incorporated. By 1200 hr, we began a 46-km-long seismic survey over the first two drill sites‹Sites 1054 and 1055. Very good seismic images were obtained using a combination of the GI gun source and the Teledyne single-channel oil-filled streamers, the latter of which are due to be replaced by the new multichannel streamers. Unfortunately, the first of the two multichannel streamers failed when deployed. The total transit to Site 1054, including the seismic survey, was 156 nmi, which was traveled at an average speed of 9.9 knots (kt).

SITE 1054
(Proposed Site CS-3B)

Drilling operations commenced at 1817 hr on 19 February at Site 1054 using the advanced hydraulic piston corer (APC) coring system and, for the lower part of Hole 1054A, the extended core barrel (XCB) system. Cores 172-1054A-3H through 10H and 12H, 1054B-4H through 12H, and 1054C-3H through 13H were oriented with the Tensor tool.

At Hole 1054A, the APC system reached 84.8 mbsf (Core 1054A-10H) with its usual high recovery (91%-108%), but failed to penetrate on the next try. One XCB core was taken from 84.8 to 93.5 mbsf and penetrated a small hard claystone zone, which was underlain by ooze. Piston coring was resumed on the next core and advanced with a full stroke to 103.0 mbsf. When an attempt with another piston core failed to advance due to indurated sediments, the remainder of the hole was cored with the XCB.

After the vessel was offset ~30 m south of the initial hole, Hole 1054B was spudded at a depth of 1304.8 mbrf. APC coring advanced to refusal, which was 103.2 mbsf. The vessel was offset another 30 m south and Hole 1054C was cored to 101.0 mbsf. By 1700 hr on 21 February, the drilling equipment was secured and the vessel was underway on a 14-nmi transit to the next site.

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SITE 1055
(Proposed Site CS-2)

Coring operations started at Site 1055 at 0025 hr on 22 February. All holes were APC cored with recovery ranging from 98% to 118%. Cores 1055B-3H through 14H, 1055C-3H through 14H, and 1055B-3H through 14H were oriented with the Tensor tool.

The first core barrel in Hole 1055A contained 9.82 m of sediment, and therefore did not give a reliable indication of the mudline depth. Thus, Hole 1055B was spudded ~15 m to the west, and the mudline was obtained in the first core. A seafloor depth of 1809.0 mbrf was estimated from this core.

The vessel was offset ~30 m north of Hole 1055B, and Hole 1055C was spudded at a mudline depth calculated as 1809.0 mbrf. Hole 1055D was spudded ~30 m north of Hole 1055C at a mudline depth calculated as 1809.9 mbrf. The final two cores were collected at Hole 1055E, which is ~40 m north of Hole 1055D, in order to have multiple copies of the glacial-to-interglacial transition recorded by the near surface sediments at this site. The JR was on its way to Site 1056 by 1145 hr on 23 February.

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SITE 1056
(Proposed Site BBOR-8C)

At 1300 hr (local time) on 23 February 1997, the JR slowed to deploy the seismic gear for a survey over Sites 1056 and 1057. A north-south survey line was collected over Site 1056 at 6 kt followed by a west-to-east crossing line. The survey gear was left in as the ship followed a southeast course toward Site 1057 at 8 kt. The JR again slowed to 6 kt as it crossed over Site 1057, first on a northwest-to-southeast course and then again on an east-to-west crossing line. The total survey length was 85 km. The multichannel streamer failed again during this survey, but was later fixed by changing the polarity of its pin configuration.

Because the water depth was ~400 m deeper at Site 1056 than the previous site, additional joints of pipe were used, which included the reconditioned drill pipe loaded in Charleston. This reconditioned pipe was first measured and "rabbited" (a process in which a small piece of bar or tubing of known diameter is passed through the drill pipe to ensure that it is free of obstructions or diameter restrictions).

At 0340 hr on 24 February, the initial attempt at a mudline core in Hole 1056A was obtained, but the core barrel was full and the seafloor depth could not be determined with any accuracy. Hole 1056B was then started ~7 m northeast of Hole 1056A and 6 m shallower. A mudline core was retrieved, and the seafloor depth at this hole was estimated at 2177.9 mbrf, which was 5.5 m shallower than the depth estimated by the Precision Depth Recorder (PDR).

The ship was offset after Holes 1056B and 1056C, with Hole 1056C located ~25 m northwest of Hole 1056B and Hole 1056D ~30 m northwest of Hole 1056C. The total core recovered at the site was 480.5 m with 108.8% recovery. The large recovery probably results from gas expansion. By 1945 hr on 25 February, the drilling equipment was secured and the vessel was underway on a southeasterly heading to the next site.

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SITE 1057

(Proposed Site BBOR-7A)

Coring operations at Site 1057 began at 2246 hr on 25 February after a 31-nmi transit from Site 1056. All holes were APC cored with recovery ranging from 100% to 115%. Starting with the third core in each hole, all cores downhole were oriented with the Tensor tool.

The seafloor depth was established at 2595.0 m at Hole 1057A, which was 6 m deeper than the PDR measurement. Hole 1057B is ~35 m south of Hole 1057A, and Hole 1057C is another ~33 m south of Hole 1057B. Relative to the drill string position for Hole 1057A, the drill string was raised 3 m higher for Hole 1057B and only then lowered 2 m for Hole 1057C. During operations on Hole 1057B, a chartered tuna boat, The Winds of Fortune, came alongside at 1345 hr on 26 February and disembarked two crew members, who joined us for the remainder of the cruise. By 1515 hr on 27 February, the vessel was underway to the next location.

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SITE 1058
(Proposed Site BBOR-9)

The 30-nmi transit to Site 1058 was traveled at an average speed of 12 kt. At 1745 hr, the vessel slowed as the seismic gear was deployed about 8 nmi before Site 1058. The survey proceeded over Sites 1058 and 1059 along a southeasterly course. The vessel came about and performed a northeast to southwest crossing over Site 1059 and then a southwest to northeast crossing over Site 1058. During the 24-km-long survey, data was collected simultaneously with a single-channel and a six-channel streamer. Accurate survey and drilling positions were obtained owing to the availability of differential global positioning system (GPS).

At 2045 hr on 27 February, the seismic equipment was retrieved and the vessel returned to Site 1058, and coring operations began at 2109 hr on 27 February. All holes were APC cored with recovery ranging from 98% to 114%. Starting with the third core in each hole, all cores downhole were oriented with the Tensor tool.

The seafloor depth was established at 2996.0 mbrf in Hole 1058A, which was 4 m shallower than the PDR measurement. Hole 1058B is ~24 m south of Hole 1058A, and Hole 1058C is another ~30 m south and ~5 m west of Hole 1058B. The starting drill string position was vertically offset 3 m shallower for Hole 1058B than Hole 1058A and then another 3 m shallower for Hole 1058C.

On the evening of 28 February, we received sad news of a death in the family of an ODP crew member. After assessing all options, including queries to the local military installations in North and South Carolina, looking into the availability and suitability of local transport (air and boat), and exploring the possibility of using a vessel of opportunity, it was decided to interrupt operations in order to divert the vessel to Charleston for a humanitarian evacuation. At 0515 hr on 2 March, operations ceased at Site 1058 and we proceeded to Charleston.

At 0354 hr on 3 March, the JR arrived at the Charleston pilot station where it rendezvoused with the tug Robert B. Turecaro. Bill Stevens disembarked the vessel at 0414 hr and by 0418 hr the vessel was underway to Site 1059. The total round trip distance for this unscheduled transit was 447 nmi and consumed 41.2 hr.

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