EXPEDITION 301T OPERATIONS AND PRINCIPAL RESULTS
Astoria 2 Port Call
Expedition 301T, the second part of the first expedition of IODP, officially began at the Astoria, Oregon (USA), port call with the first line tied up at 0424 h on 20 August 2004. The Astoria port call was an abbreviated port call with normal port call activities kept to a minimum. The original plan called for offloading Expedition 301 materials and samples in Astoria, taking on fuel, water, food supplies, spares, and bulk material. Shortly after arrival, the vessel was informed by customs that they had not been notified 48 h in advance of material to be offloaded in Astoria. This requirement had not been in place during the first Astoria port call. This problem could not be resolved on 20 August (Friday) and the quick departure schedule precluded a solution by departure time on the morning of 22 August (Sunday). The vessel was forced to reload all material that had already been offloaded onto the dock including all scrap iron from Expedition 301 and had to sail with all material originally scheduled for offloading in Astoria.Transit to Site 1253
The last line was cast off from Pier 1 at 0645 h on 22 August. The forward and aft tugs were released, and the JOIDES Resolution proceeded down the Columbia River and across the Columbia Bar. The pilot was dispatched via helicopter, and at 0824 h the vessel was under way at full speed on a course of 183°T for Site 1253. The transit was uneventful, making the 3411 nmi transit in 314.7 h at an average speed of 10.87 kt.
After a 13 day transit from Astoria, the vessel arrived at Site 1253 in Costa Rican waters on 4 September, approximately 1 day ahead of schedule. After reducing speed upon approach to the site, the thrusters/hydrophones were lowered and the vessel was switched to dynamic positioning (DP) control.Site 1253
After a smooth transit from Astoria, Oregon, the ship arrived at Site 1253 at 1112 h. Alvin operations had left the two Site 1253 OsmoSampler packages seated at depth, the tools and ~550 m of Spectra line attached, and a ring and float attached ~20 m above the CORK wellhead. Operations commenced with the attempts to retrieve the OsmoSampler packages. A sunflower-shaped fishing tool with grooves located between the petals was used to "fish" the rope suspended by a float above the CORK. After fishing for just over 3 h, we started pulling the rope that we hoped was secured to the OsmoSampler. We found that we had captured the float, some of the spectra rope, and the metal ring used to tie onto the float. The remainder of the fished components either dropped to the seafloor during the trip out or remained in Hole 1253A. The explanation is that the OsmoSampler string made it close to the surface with the line wrapped around the drill pipe and caught on the vibration-isolated television (VIT) camera frame. When the VIT frame came clear of the water, the fleet angle to the camera winch pulled on the frame, which was being held back by the Spectra rope wrapped around the drill pipe. The camera winch was capable of pulling far more than the rating on the Spectra rope (10,000 lb). During recovery the camera swings 180° to get closer to the overhead sheave, and that may be when the Spectra rope parted. The dropped components were left to be found and recovered after we completed operations in Hole 1255A.Site 1255
After the initial attempted retrieval of OsmoSamplers at Site 1253, the ship was offset to Site 1255 in dynamic positioning (DP) mode and a new BHA was made up for connecting to the CORK in Hole Site 1255A. It was run into the hole to 4270 m, and the subsea TV camera was deployed to assist in latching onto the CORK. At midnight on 5 September, the ship was maneuvering to latch onto the CORK in Hole 1255A. The first latching attempt lasted 9 h, and erratic currents seemed to cause problems with all attempts to latch. After latching onto the CORK, the core line was run in and latched onto the OsmoSampler string inside the 4.5 inch casing. The OsmoSampler string was retrieved, the drill pipe was disconnected from the CORK, and the OsmoSampler was recovered and laid out on the core receiving platform. A new OsmoSampler string was made up and inserted into the drill pipe. It took 1.75 h to reconnect to the CORK, and then the OsmoSampler was lowered to depth. After attempts to disconnect the coring line from the OsmoSampler string, the pipe was disconnected from the CORK to discover that the OsmoSampler shear pin did not shear as intended. After two attempts the coring line was successfully disconnected from the instrument strings, with the float assembly properly deployed just above the CORK. After disconnecting from the CORK in Hole 1255A, the ship moved in DP mode back to Site 1253.
The OsmoSamplers recovered from Hole 1255A were subsampled for shipboard measurements of alkalinity, pH, ammonium, and salinity and for further postcruise chemical and isotopic time series analyses. Maximum values of 17.1 mM for alkalinity and 1828 µM ammonium are elevated relative to Site 1253 and are the result of bacterially mediated diagenesis of organic matter. Inspection indicated the osmotic pumps worked well throughout the period deployed. In addition, osmotic flowmeter fluids were subsampled for postcruise analyses to determine relative flow rates and direction. The temperature loggers recovered are in excellent shape.Return to Site 1253
Upon completing successful operations at Site 1255, we returned to Site 1253 and reentered Hole 1253A with a fishing tool to inspect for the OsmoSampler packages and any remaining hardware. The hole was found to be completely clear. The OsmoSamplers were not found; thus, it was assumed they had been removed from the hole and dropped onto the seafloor when the Spectra line parted during initial fishing operations. Attempts to pull the coring line from the hole resulted in the realization that it was stuck. The line was worked up and down until it was freed, and the coring line was pulled from Hole 1253A. The new OsmoSampler packages (upper level within a screen and lower level in the open hole) were assembled with a new sinker bar and 500 m line to a seafloor float and deployed in Hole 1253A without incident. Visual inspection with the VIT camera confirmed that the float assembly was properly deployed just above the CORK.
After unlatching from the Hole 1253A CORK, a bottom survey was initiated to find the OsmoSampler string that was dropped during the first recovery attempt at Site 1253. The vessel was moved in DP mode on 150 m parallel lines spaced on 10 m centers. The initial track was on a course of 045°, returning on the reciprocal course of 225°T. Each pass moved 10 m farther from the CORK. After reaching 90 m northwest of the CORK, the vessel returned to the CORK/reentry cone and conducted the same search to the southeast. The OsmoSampler was located after 7.5 h, ~20 m southeast of the CORK. The vessel stabilized position over the OsmoSampler. A four-pronged grapple assembly was rigged to the underwater TV camera, and a successful pass was made with the fishing tool. The camera and VIT frame arrived at the surface with the upper OsmoSampler, wireline jars, 500 m of Spectra rope, and other miscellaneous hardware left by the submersible Alvin. The lower OsmoSampler was not recovered. After successful recovery of the upper OsmoSampler from Site 1253, the drill string was pulled up and beacons were recovered from Sites 1253 and 1255. Schlumberger sheaves were rigged up for a test of the active heave compensating wireline logging winch. After concluding the Schlumberger test, the sheaves were rigged down and the BHA was pulled out of the hole and laid out. All components were secured for transit to Panama.
Hole 1253A fluid coils from two of the Teflon OsmoSamplers were subsampled for shipboard measurements of alkalinity, pH, ammonium, and salinity and for a wide variety of postcruise analyses. Maximum values for alkalinity and ammonium are low: 0.8 mM and 170 µM, respectively. Two further copper coils will also be analyzed for gases and organic components postcruise. Initial salinity analyses in the two separate fluid coils have very similar profiles, suggesting two complete years of fluids were obtained.Transit to Panama
Transit to Panama began at 1130 h on 8 September. The total transit distance was 522 nmi. First line was ashore at Berth 15, Balboa, Panama, at 1950 h on 10 September 2004.
Next Section | Table of Contents