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doi:10.2204/iodp.proc.320321.108.2010 OperationsTimes for Site U1336 are given in local ship time, which was Universal Time Coordinated (UTC) – 9 h. Transit to Site U1336The 185 nmi transit from Site U1335 to Site U1336 took 17.8 h at an average speed of 10.4 kt. Site U1336Hole U1336AThe ship slowed as it approached Hole U1336A and was in dynamic positioning mode at 1545 h on 22 April 2009. Once the ship was stabilized over the new site, the drill string was deployed and the bit positioned 5 m shallower than the corrected precision depth recorder depth of 4300.4 m drilling depth below rig floor (DRF). Hole U1336A was spudded with the APC at 0135 h on 23 April. The seafloor depth estimated from recovery in the first core was 4296.9 m DRF (4285.3 mbsl) (Table T1). APC Cores 320-U1336A-1H through 21H were taken from 0 to 184.8 m CSF and recovered 190.2 m (103%) (Table T1). Nonmagnetic core barrels were used to obtain Cores 320-U1336A-1H through 16H; steel barrels were used for all other cores. Three cores (320-U1336A-14H, 16H, and 21H) only partially stroked and were advanced by recovery. A hard layer at ~124 DSF prevented Core 320-U1336A-14H from achieving a full stroke; the layer was ~0.5 ft thick and was not recovered. Based on how it drilled, we inferred it may have been chert. The last piston core (320-U1336A-21H) required drilling over to free the barrel from the formation. Cores 320-U1336A-22X through 35X were taken from 184.8 to 302.9 m CSF and recovered 69.0 m (58%). We stopped coring before reaching the basement objective because of decreasing rates of penetration (as low as ~3 m/h for Cores 320-U1336A-34X and 35X), relatively low recovery, and the possibility of obtaining a stratigraphically complete Miocene section by coring in a second hole. We pulled out of the hole and the bit cleared the seafloor at 0400 h on 25 April. We offset the ship 25 m south of Hole U1336A. Hole U1336BAfter positioning the bit at 4284 m DRF (5 m shallower than in Hole U1336A), we started coring in Hole U1336B at 0540 h on 25 April. Based on recovery in the first core, the seafloor depth was 4298.1 m DRF (4286.5 mbsl). Cores 320-U1336B-1H through 20H were taken from 0 to 173.9 m CSF and recovered 179.6 m (103%). Nonmagnetic core barrels were used for Cores 320-U1336B-1H through 16H; steel barrels were used for the others. Core 320-U1336B-16H only achieved a partial stroke and was advanced by recovery. Once coring was completed, the drill string was pulled out of the hole with the bit clearing the seafloor at 0400 h on 26 April. Once all drilling equipment was secured, the vessel departed for Honolulu, Hawaii, at 1315 h on 26 April. Transit to Honolulu, HawaiiThe 1954 nmi transit from Site U1336 to Honolulu, Hawaii took 7.8 days at an average speed of 10.4 kt. At 2400 on 27 April 2009, the shipboard clocks were set back one hour so that ship local time was UTC – 10 h (Hawaii Standard Time). Expedition 320 concluded with the first line ashore at 0736 h on 4 May. |
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