Leg 202 began at 1120 hr on 29 March 2002, when the first line was passed ashore in Valparaiso, Chile. The scientific party was aboard by 2 April. Two Chilean (Pedro Crignola and Flavia Velásquez Ruiz) and one Peruvian (Robert Herrera) observers joined the scientific party in compliance with demands associated with the permissions to operate in their national waters. The three individuals were to leave the ship later in the cruise upon exiting Peruvian waters and be replaced by an Ecuadorian observer. The port call was extended by 24 hr because we had to leave the pier and anchor in the harbor to allow a fruit freighter to occupy the berth.
At 0718 hr on 4 April, the last line was released and the vessel began the journey to the first site of the leg. Based on an assessment of available time and scheduled drilling program, we added the top-priority contingency Site SEPAC-19A to the operational plan. Because this site is positioned farther south than any of the first-priority sites, it was most effective to drill it as the first site. A 3.5-kHz survey was conducted over proposed Sites SEPAC-14A and SEPAC-13B before we proceeded to Site SEPAC-19A.
By midnight, the winds were gusting to 38 kt and the seas began to build. The vessel's speed had to be reduced to limit violent rolling and pitching. The next morning up to 60-kt gusts and blinding rain followed, and the seas and swell were estimated to be 30 ft and greater. As the vessel approached the position of Site SEPAC-19A, the captain ordered the vessel to reverse course. The speed was reduced to ~4 kt to maintain heading into the Force 8 storm. As the vessel proceeded on this northwesterly course, the weather gradually improved, but not to the extent that would have allowed us to return to Site SEPAC-19A. The most effective option was to proceed to Site SEPAC-9A. As the storm gradually abated, the speed of the vessel increased to 8 kt.
In the morning of 7 April, the vessel slowed and approached the Global Positioning System (GPS) coordinates of Site 1232 (proposed Site SEPAC-9A). The thrusters were lowered, and at 1100 hr the vessel was holding station at Site 1232 using the GPS. The voyage from Valparaiso lasted 74.5 hr and covered 645 nmi at an average speed of 8.6 kt.
The corrected precision depth recorder measurement indicated a depth of 4091.4 meters below rig floor (mbrf), relative to the dual elevator stool on the rig floor. A 136-m-long advanced piston corer (APC) and extended core barrel (XCB) bottom-hole assembly (BHA) was made up. This type of BHA was used at all sites during Leg 202. The initial pipe trip of the leg was extended to accomplish routine preparations and maintenance.
Hole 1232A was initiated with the APC at 0505 hr on 8 April with the bit placed at 4089 mbrf. The first core was a full recovery (Table T1), and hole-to-hole correlation later showed that the core top was 6.1 m below the seafloor (mbsf). Piston coring advanced to 112.5 mbsf, where the formation became too stiff to continue with the APC. Although the last two cores (11H and 12H) achieved full stroke, the barrels became firmly stuck in the formation and could not be released with a force of 80 klb. The core barrels were subsequently drilled over and released. The APC portion of the hole cored 112.5 m and recovered 104.5 m (recovery = 93%). Cores were oriented starting with Core 3H. Four attempts at collecting downhole temperature data were unsuccessful because of tool problems (Cores 3H, 6H, and 7H) or excessive motion at the bit (Core 8H).
The wireline parted during the recovery of Core 5H, and the core barrel dropped from ~150 mbrf. The core barrel, tensor tool, and sinker bars were successfully recovered in the first fishing attempt with the wireline.
Vessel heave was responsible for the mechanical parting of the APC shear pin when the core barrel for Core 5H apparently landed too hard in the BHA. The barrel was actually pumped into the formation during the pressuring up of the drill string and did not successfully fire in the normal fashion. The resulting core was mostly flow-in, which probably occurred during the extraction of the barrel from the sediment.
Following APC refusal, the XCB was deployed and advanced from 112.5 to 371.3 mbsf. We planned originally to deepen the hole to acoustic basement at ~500 mbsf. This plan was abandoned and the hole was terminated because (1) the recovered sequence consisted of Pleistocene turbidites, and seismic data indicated that this sequence continued to basement and (2) inferred sediment accumulation rates were much higher than expected, which made the prospect of recovering pre-Pleistocene sediments unlikely. The XCB cored 258.8 m and recovered 184.31 m (recovery = 71.2%). In total, 371.3 m was cored and 288.8 m was recovered in Hole 1232A (recovery = 78%) (Table T1).
The vessel was offset 30 m north, and Hole 1232B was initiated with the APC at 1820 hr on 10 April. In an attempt to obtain a good mudline core and a stratigraphic overlap with the initial hole, the bit was positioned at 4080 mbrf. The core was still too deep by 2.2 m, however, as determined later. Based on the drill string measurement, the seafloor depth was 4080.4 m. Piston coring advanced to 90.1 mbsf, where the hole was terminated. The average recovery was 106.9% (Table T1). Cores were oriented starting with Core 2H. A bottom-water temperature measurement (1.60°C) was obtained with the APC temperature (APCT) tool before we initiated the hole. Four attempts at collecting downhole temperature data were unsuccessful because of tool problems (Cores 3H, 4H, 6H, and 8H). The bit was pulled free of the seafloor at 0815 hr on 11 April.
The vessel was offset 30 m north, and Hole 1232C was initiated with the APC at 1010 hr on 11 April. The bit was positioned at 4075 mbrf. The mudline was recovered in Core 1H, and the seafloor depth was determined to be at 4079.8 mbrf based on the drill string measurement. Piston coring was concluded after advancing to 33.2 mbsf. The average recovery was 95.4%. Because of the shallow depth objective, no cores were oriented. One downhole temperature measurement was attempted (Core 4H) but yielded bad data. The overall cored interval at this site was 494.6 m with 416.8 m recovered (recovery = 84.3%) (Table T1).
The vessel was secured for transit and left location at 2330 hr on 12 April.