The 83-nmi transit to Site 1239 (proposed Site CAR-1C) required 7.5 hr at an average speed of 11.1 kt. The 3.5-kHz precision depth recorder (PDR) profiler was used to check the site characteristics by comparison with precruise survey data. The vessel was positioning on the site coordinates by 1945 hr on 10 May, and a beacon was deployed at 2005 hr.
After the bottom-hole assembly was made up and the drill string deployed to a depth of 1412 meters below rig floor (mbrf), the top drive was picked up and spaced out to a depth of 1420 mbrf. Hole 1239A was initiated with the advanced piston corer (APC) at 0115 hr on 11 May. The seafloor depth that was estimated by the amount of recovery of the first core was 1426.1 mbrf, 2.3 m shallower than the corrected PDR depth of 1428.4 mbrf. Piston coring advanced to 88.9 meters below seafloor (mbsf). Core barrels (Cores 10H through 12H) required drilling over to free them from the sediment. The barrels with Cores 13H through 16H (107.9-145.9 mbsf) did not need to be drilled over. The next two piston cores (17H and 18H; 145.9-164.9 mbsf) had to be drilled over. Piston coring in the hole was terminated when the last core (19H; 164.9-174.4 mbsf) did not achieve a full stroke and was recovered with a bent barrel and twisted piston rods. The APC cored 174.4 m and recovered 182.5 m (recovery = 105%).
The nonmagnetic core barrel was deployed on even-numbered cores up to and including Core 12H (Table T1). The nonmagnetic core barrel was not used after this to prevent possible damage to hardware as a consequence of the drilling-over process. The piston cores were oriented starting with Core 3H. Downhole temperature measurements were taken with the APC temperature (APCT) tool as listed in Table T1. Most of the cores were odoriferous (H2S) and were stored on the catwalk rack after splitting to allow degassing and to reduce the smell in the laboratory stack. Headspace measurements on the cores yielded moderate amounts of methane (<60,000 ppm) and slight amounts of ethane (<20 ppm). Traces of C3-C5 (<3 ppm) were measured. No higher molecular weight hydrocarbon compounds were detected.
The hole was deepened with the extended core barrel (XCB) from 174.4 to 515.4 mbsf (341.0 m cored interval) with an excellent 97.5% average recovery. XCB refusal was encountered at 515.4 mbsf when the last core (55X) contacted acoustic basement. The average rate of penetration of the XCB section was ~50 m/hr. The total recovery of the hole was 515.1 m, representing 99.9% of the cored interval (Table T1).
To prepare the hole for logging, the hole was flushed with 30 bbl of sepiolite mud and then displaced with 242 bbl of 8.9-lb/gal sepiolite mud. Downhole logging operations began at 1530 hr on 12 May. The bit was placed at the logging depth of 95.5 mbsf. The triple combination (triple combo) tool string with the Lamont-Doherty Earth Observatory (LDEO) Multi-Sensor Spectral Gamma Ray Tool (MGT) on top was deployed first followed by the Formation MicroScanner (FMS)-sonic tool string. Hole 1239B was another unusually smooth hole for the Ocean Drilling Program (ODP). Data quality was excellent, similar to that from Hole 1238A. One pass with the triple combo tool string was conducted from total depth (517 mbsf) to the mudline, followed by one full pass from 517 mbsf to the bit and one repeat pass from 155 mbsf to the bit with the LDEO MGT. Two subsequent passes with the FMS-sonic tool string also reached the bottom of the hole. The hole diameter ranged from ~11.5 to 15 in, allowing good pad contact. Hole deviation increased with depth, reaching 7.5° at the bottom. Logging operations were completed by 0800 hr on 13 May, and the bit was pulled free of the seafloor at 0910 hr on 13 May.
The vessel was offset 20 m west of Hole 1239A. Prior to coring, a bottom water temperature measurement was obtained with the APCT tool with the bit positioned just above the seafloor. From this and the downhole temperatures measured in Hole 1239A, a temperature gradient of 9.4°C/100 m was calculated. To obtain the desired stratigraphic overlap with the first hole, the bit was then placed at 1423.0 mbrf and Hole 1239B was initiated with the APC at 1055 hr. The seafloor depth calculated from the recovery of the first core was 1424.7 mbrf. Piston coring combined with a 2-m drilled interval (102.8-104.8 mbsf) deepened the hole to 171.3 mbsf. The cored interval was 169.3 m with 177.34 m recovered (recovery = 104.7%).
The nonmagnetic core barrel was deployed on odd-numbered cores up to and including Core 15H. Three core barrels were drilled over in this hole (Cores 16H, 17H, and 18H). The cores were oriented starting with Core 3H.
XCB operations extended the total depth of this hole to 398.7 mbsf. The XCB cored 227.4 m with an average recovery of 101.2%. The total cored interval in Hole 1239B was 396.7 m, with 407.4 m recovered (recovery = 102.7%) (Table T1). The bit was pulled free of the seafloor at 1315 hr on 14 May.
The vessel was moved 20 m west of Hole 1239B. Hole 1239C was initiated with the APC at 1420 hr on 14 May. The bit was positioned at a depth of 1426.0 mbrf or 1.3 mbsf above the calculated mudline depth of Hole 1239B (1424.7 mbrf). Piston coring deepened the hole to 117.3 mbsf to ensure complete stratigraphic recovery to a depth of 170 mbsf. Two intervals were drilled to maintain the proper overlap with the data from the previous two holes (0.0-1.3 and 39.3-41.3 mbsf). The cored interval was 114.0 m, with 119.7 m recovered (Table T1). The nonmagnetic core barrel was deployed on even-numbered cores. No core barrels were drilled over. Cores were oriented starting with Core 3H.
The total cored interval at Site 1239 was 1026.1 m, with 1042.1 m recovered, representing an average recovery of 101.6%. The vessel was secured and departed for Site 1240 at 0218 hr on 15 May.