Previous   |   Next

doi:10.2204/iodp.proc.323.104.2011

Operations

We arrived at Site U1340 on 22 July 2009 after a 1.5 day, 344 nmi transit from Site U1339. One relatively deep and three relatively shallow holes were drilled and cored with the advanced piston corer (APC) and extended core barrel (XCB) coring systems at a water depth of 1294.7 m on Bowers Ridge (Table T1). A complete set of site-specific tide tables was provided by the science party for Site U1340 and used to make adjustments relative to initial mudline core and for each successive core in each hole. The third-generation advanced piston corer temperature tool (APCT-3) was deployed four times, and three out of four data points fell on a linear curve describing a temperature gradient of +4.34°C per 100 m of depth. Overall core recovery for Site U1340 using the APC and XCB coring systems was 91.0%.

Hole U1340A

Hole U1340A was spudded at 0520 h on 23 July (all times are ship local time, Universal Time Coordinated [UTC] – 11 h). Hole U1340A was cored to 604.6 m drilling depth below seafloor (DSF) using both the APC and XCB coring systems. APC core recovery was 105%, whereas XCB core recovery averaged 61% (Table T1). APC coring using the nonmagnetic coring assemblies with the FlexIt orientation tool installed continued through Core 323-U1340A-17H to 1461.9 m drilling depth below rig floor (DRF). Standard steel coring assemblies were used from Cores 323-U1340A-18H through 42H. APC coring was terminated after Core 323-U1340A-42H after two successive short, incomplete strokes of the core barrel. The XCB coring system was then deployed for Core 323-U1340A-43X, and coring continued with the XCB system through Core 323-U1340A-62X. The APC coring system was redeployed after three straight zero-recovery runs. APC coring through Core 323-U1340A-67H was successful in recovering ~25 m of very sandy sediment. At this point, the XCB system was redeployed. The hole was terminated after Core 323-U1340A-71X when the XCB cutting shoe spacer sub failed, leaving a portion of the sub and the XCB cutting shoe at the bottom of the hole. The drill string was pulled back to the seafloor at 2103 h on 25 July, officially ending the hole. Shear pressures were consistent throughout the coring process at 2800 psi. Core recovery for Hole U1340A using the APC coring system was 105.0% with 398.8 m recovered. Core recovery for Hole U1340A using the XCB coring system was 61.0% with 136.7 m recovered. Combined core recovery for Hole U1340A using both the APC and XCB coring systems was 88.7% (Table T1).

Hole U1340B

Hole U1340B officially began when the bit cleared the seafloor at 2103 h on 25 July, ending Hole U1340A. The vessel was offset 350 m east of Hole U1340A. The top drive was picked up and the drill string was spaced out, placing the bit at 1305.4 m DRF, or 5 m above the corrected precision depth recorder (PDR) depth of 1310.4 m DRF. The first APC barrel was pressured up and fired, and the barrel recovered 6.4 m of core, establishing an official seafloor depth at 1308.5 m DRF. Hole U1340B was spudded at 2340 h on 25 July. The nonmagnetic coring assemblies and the FlexIt core orientation system were used through Core 323-U1340B-6H. Hole U1340B ended at 0400 h on 26 July when the bit cleared the seafloor. Shear pressures were consistent throughout the coring process at 2800 psi. Average core recovery for the APC was 103.0% (Table T1). The total depth of Hole U1340B was 1362.4 m DRF (53.9 mbsf).

Hole U1340C

Hole U1340C officially began when the drill string cleared the seafloor at 0400 h on 26 July. The ship was offset 300 m south of Hole U1340A. A new PDR depth was established, and the bit was placed at 1313 m DRF to optimize the core breaks between Holes U1340A and U1340B. The APC was deployed, and Hole U1339C was spudded at 0620 h on 26 July. Unfortunately, a mistake in the corrected PDR depth resulted in the first core being taken well below the mudline, and the 9.5 m of core recovered in Core 323-U1340C-1H failed to establish the seafloor depth. APC coring continued through Core 323-U1340C-3H to 1341.5 m DRF using the FlexIt core orientation system and the nonmagnetic coring assemblies. With the exception of the first core, shear pressures were consistent throughout the coring process at 2800 psi. Overall core recovery for the APC was 105.3% (Table T1). The drill string was pulled clear of the seafloor at 0835 h on 26 July, officially ending Hole U1340C.

Hole U1340D

Hole U1340D officially began when the drill string cleared the seafloor at 0835 h on 26 July. The ship was offset 20 m from Hole U1340C at 180°. Hole U1340D was spudded at 0905 h on 26 July, and the 7.3 m recovered in Core 323-U1339D-1H established the seafloor depth at 1304.7 m DRF. Three APC cores were shot to 26.3 mbsf. APC coring through Core 323-U1340D-3H used the nonmagnetic coring assemblies with the FlexIt orientation tool attached. Shear pressures were consistent throughout the coring process at 2800 psi. APC core recovery was 103.5% (Table T1). The drill string was then pulled and secured for transit. Once the drill collars were racked back and the rig floor was secured for transit, control was transferred from dynamic positioning to the bridge. The ship was placed in cruise mode at 1534 h on 26 July for the scheduled 6 h, 65 nmi transit to Site U1341.

Official APC coring for Site U1340 totaled 83 cores, 713.2 m penetrated, and 648.7 m recovered, for 91.0% core recovery.

Top of page   |   Previous   |   Next