Using the ship's dynamic positioning system, we moved ~5 nmi to Site 1269 (Fig. F1). During the move a two-stand bottom-hole assembly was built consisting of six 8.25-in drill collars. This was done to minimize the risk of losing additional drill collars and jeopardizing further operations. As at Site 1268, all collars were inspected before inclusion in the drill string.
Prior to initiating Hole 1269A, we undertook a 1.25-hr subsea camera survey to verify our location as compared to site survey videotapes. The drilling target for Site 1269 was along the track of Shinkai 6500 submersible Dive 423 in 1998, which recovered samples of peridotite and gabbro from a series of steep outcrops separated by flat, sedimented seafloor along the western flank of the Mid-Atlantic Ridge axial valley. Our camera survey for Hole 1269A began at a depth where the site survey dive had recovered dunite (Shinkai 6500 Dive 423, sample R007) (Fig. F2). After moving downslope 60 m to ensure we were above an outcrop and in sediment free of talus, we released a positioning beacon from the camera frame 30 m east of our selected drilling target, retrieved the camera, and spudded Hole 1269A.
Hole 1269A was initiated at 1005 hr on 27 May 2003 with a seafloor tag depth of 2809 meters below sea level (mbsl). Coring continued to a depth of 15.3 meters below seafloor (mbsf) (Table T1) before high drilling torque, collapsing hole, and low recovery (2.6%) consisting of only fragments of basalt led us to terminate coring. At 1425 hr on 27 May the bit cleared the seafloor, ending Hole 1269A.
Our second subsea camera survey at Site 1269 began with the drill pipe over the positioning beacon. We surveyed 60 m west, continuing along a flat, sedimented seafloor, free of talus shed from uphill. A push-in test indicated the sediment was <5 m thick, so we retrieved the camera and spudded Hole 1269B.
At 1950 hr on 27 May, Hole 1269B was initiated with a seafloor tag depth of 2799 mbsl. The first core was recovered after 11.1 m of penetration and again contained only a few pieces of basalt. As in Hole 1269A, high torque and recovery of only basalt fragments suggested we would not reach our drilling objectives without first drilling through an unknown thickness of unstable basaltic lava, so we abandoned the hole. The bit cleared the seafloor at 2215 hr on 27 May, ending Hole 1269B. Anticipating a move of ~1 km, we recovered the positioning beacon.
With two holes at our most promising target yielding only basalt, we elected to move farther uphill (west) for our next hole at Site 1269. After offsetting the drill ship ~1.1 km west, we conducted our third subsea camera survey at this site. This location was near the top of the western rift valley wall, in a flat, sedimented terrain above a moderate slope from which four samples of gabbro were collected during Shinkai 6500 Dive 423 (Fig. F2). After surveying 275 m upslope, we returned to a position ~65 m west of the start of our camera survey to begin Hole 1269C (Fig. F1).
Hole 1269C was initiated at 1118 hr on 28 May. Coring was again hampered by high and erratic torque, and the two core barrels (to a depth of 18.3 mbsf) that were recovered contained only a few fragments of basalt. Recognizing that our favored drilling targets at Site 1269 were all covered with a basaltic carapace beneath a few meters of pelagic sediment, we elected to terminate coring at this site and to move to one of our alternate sites. The drill string and positioning beacon were recovered, and we completed operations at Site 1269 at 2000 hr on 28 May.
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Ms 209IR-104