After departing Balboa, Panama, at 1515 hr (CDT) on 3 June 2002, we cleared the Bridge of the Americas then made full speed for Site 852, the intended site of the OSN-2 observatory. Torrential rain in the doldrums was superseded by fine equatorial weather. The 1921-nmi transit from Panama was completed in 179 hr at an average speed of 10.75 kt. The JOIDES Resolution arrived on location at 0015 hr on 11 June. A brief seismic survey was conducted, comprising four parallel east-west lines, each separated by 0.5 nmi in the north-south direction (Fig. F11). At the conclusion of the final east-west survey line, a north-south line was run 2 nmi southward to replicate an earlier site survey line. The survey was completed, and the ship was at the intended location of Site 1243 (5°18.0660'N, 110°04.5798' W) by 0600 hr on 11 June. The hole was relocated ~0.5 mi north of Site 852 based on the results of the site survey. The new location placed the site farther from a 100-m-deep trough to the west (Fig. F12).

From 0600 hr on 11 June 2002 to 0245 hr on 12 June, a jet-in test was conducted in preparation for installing the reentry cone and casing. We stopped the jet-in test at 58 meters below seafloor (mbsf), pulled out of the hole, and cleared the seafloor at 2000 hr on 11 June.

After recovering the drill string, we offset 20 m to the south to 5°18.0541'N, 110° 04.5798'W in preparation for spudding Hole 1243A. The reentry cone and four joints (48 m) of 20-in casing were made up, and the reentry cone was lowered through the moonpool at 0800 hr on 12 June. The seafloor was reached at 1600 hr, the reentry cone was installed, and the drill string was released at 1815 hr. Satisfactory placement of the reentry cone was confirmed with the vibration isolated television (VIT) camera.

After tripping back to the surface to remove the running tool, we returned to the hole with an 18 1/2-in bit. Reentry was achieved at 0943 hr on 13 June. It was a textbook reentry, with an elapsed time of 8 min. We then drilled down below the 20-in casing, reaching the sediment basement contact at 121 mbsf. Basement drilled well, with penetration rates ranging from 0.8 to 2.0 m/hr. Drilling concluded at 0745 hr on 14 June at a depth of 134 mbsf. We then made a wiper trip and prepared to install the 16-in casing.

At 1630 hr on 14 June, the crew commenced rigging up the casing tools to run the 16-in casing into basement. The target depth for the 16-in casing was 126 mbsf (4008 meters below rig floor [mbrf]) in order to isolate the 73 m of sediment and the top 5 m of basement as we drilled deeper. Reentry 2 occurred at 0440 hr on 15 June. The driller washed down through the 20-in casing and sediment and took weight at the basement contact at 4003 mbrf (121 mbsf). It took ~1 hr to work the 16-in casing cement shoe through the basement contact. On repeated attempts to pass through the interval from 120 to 123 mbsf, the casing (17-in outside diameter) became stuck and overpulls of up to 40 klb were required to free it, as it became wedged in the 18 1/2-in basement open hole.

On the last attempt to land the casing in the reentry cone, it became stuck firmly and took 100 klb of overpull to free it. In light of these difficulties, we decided to pull out of the hole. On recovery, the cement shoe on the 16-in casing was found to have been damaged severely in attempting to get the casing to bottom. The 10 joints of casing were laid down by 1900 hr on 15 June.

The operations plan was then revised to complete Hole 1243A without coring, as a cased hole with only 20- and 10 3/4-in casing. The target depth for the 10 3/4-in casing was 216 mbsf. Following completion of Hole 1243A, we planned to drill, RCB core, and log a second hole to 200 mbsf to obtain cores across the sediment/basement interface and into the basement. Time estimates showed that this plan could be achieved within the available time, despite the change in location of the end of Leg 203 port call. (On 13 June, we were advised that the port call had been changed from San Francisco, California, to Victoria, British Columbia, Canada, in anticipation of a longshoremen's strike in San Francisco in early July. This change added almost 4 days more to the transit from Site 1243 to port.)

The third reentry of Hole 1243A took place at 0405 hr 16 June. We washed down to 134 mbsf and then drilled ahead in basement to a depth of 224 mbsf at an average rate of 3 m/hr. At 180–184 mbsf, the drill string packed off and required 60 klb overpull to free it, but otherwise no problems were encountered.

After cleaning the hole and displacing it with 250 bbl of sepiolite, we then prepared to set the 10 3/4-in casing. Reentry 4 was achieved with the casing at 2050 hr on 18 June. The casing landed in the hole at 2345 hr, and cementing was completed by 0200 hr on 19 June. This required 100 bbl of cement and is one of the largest cement jobs done by ODP to date. We pulled out of the hole, and the running tool was back on the rig floor at 1000 hr on 19 June. We then made a cleanout trip in preparation for the future installation of the OSN-2 seismometer. Reentry 5 was achieved at 2109 hr on 19 June, and after circulating the casing clean with seawater, we pulled out of the hole, clearing the seafloor at 0025 hr on 20 June. The depth of the hole, measured to the cement, is 199 mbsf (Fig. F13).

The ship was offset 600 m to the east with the drill pipe and VIT camera down, and Hole 1243B was spudded at 0245 hr on 20 June at 5°18.0543'N, 110°4.2544'W in a water depth of 3868 m. We washed down through the sediment section to 102 mbsf, then pulled the center bit and commenced RCB coring. To improve recovery, we took half cores (4.5 m). At a depth of 142 mbsf, the hole packed off, requiring 40 klb of overpull to free it. We continued to have problems with packing off, and core recovery dropped. After repeated hole problems and poor recovery, the decision was made after Core 203-1243B-18R to abandon further attempts to core deeper. The final core returned to the surface with 5.3 m of fine black basalt cuttings.

After abandoning further attempts to core deeper in Hole 1243B because of deteriorating hole conditions, we prepared the hole for logging. Triple combo and FMS-sonic logs were run in Hole 1243B followed by a WST log in the basement section of the hole. Poor hole conditions prevented successful running of the WST in the sediment section. Eight WST receiver stations were run from bottom to top of the basement section. We then dropped a free-fall funnel in Hole 1243B and offset the ship back to Hole 1243A where we ran both inclination and cement bond logs in order to determine the characteristics of the cased hole in anticipation of future installation of the seismometer. Because the intervals to be logged at both Holes 1243B and 1243A were short, we had time to make more than one traverse with each suite of logging tools (except the WST and inclinometer) in order to verify that we were getting consistent, good quality data.

After completing the cement bond log in Hole 1243A, we snagged the first beacon dropped at Site 1243, which had ceased operating, with a grapple on the VIT frame. The VIT frame and beacon were back on deck at 0915 on 25 June, and we began the final trip out of the hole. The second (active) beacon was retrieved at 1300 hr on 25 June, and we completed tripping pipe at 1330 hr, bringing operations at Site 1243 to a conclusion. The JOIDES Resolution got under way for Victoria, British Columbia, Canada, at 1530 hr on 25 June, arriving there at 0700 on 7 July.