May 30, 2000
Shipboard Scientific Party, Leg 190
WEEKLY REPORT, 11 - 27 May 2000
SCIENCE: Leg 190 is the first of a two-leg program of drilling along a transect in the Nankai Trough, the type example of a convergent margin accreting a thick section of clastic sediments. The proposed sites will define the interrelationship of the dynamics of deformation and fluid flow processes in an accretionary prism characterized by thick terrigenous sediments. Our integrated structural, geochemical, and physical properties program will fully characterize the factors controlling development of this accretionary prism.
Leg 190 will focus on core recovery from sites in undeformed to highly deformed zones along the transect to investigate variability in deformational and hydrologic character. The second leg, Leg 196 in 2001, will involve logging the sites drilled on Legs 131 and 190 with LWD to obtain a first order picture of how physical properties change during accretion. Leg 196 will also install borehole seals (ACORKs) for long-term monitoring of fluid flow processes and fluid geochemistry.
Leg 190 Drilling Strategy: To provide structural, physical properties, and geochemical gradients across the accretionary prism, Leg 190 will core a series of sites along the eastern Nankai transect, including a reference site (Site ENT-1A), one into the proto thrust zone (PTZ; Site ENT-03A), two sites into the out-of-sequence thrusts (OOSTs) higher on the slope (Sites 06A and 07A), and a reference site along the western transect (WNT-01A). Alternate sites are in the OOST (Sites ENT-04A and ENT-05A), the landward dipping reflector zone (LDRZ; Sites ENT-08A and 09A), and the western PTZ (Site WNT-03B). Experience on Legs 87 and 131 has shown that the shallow sedimentary section usually contains thick beds of poorly consolidated sand. Casing the upper part of Hole 808C on Leg 131 provided enough stability to allow drilling to proceed to more than 1300 m. Since Site ENT-03A is close to Hole 808, we have included a deployment of drill-in casing (DIC) in the operations time estimate to ~100 mbsf at this site. We will have additional drill-in-casing capabilities for other sites, if required. Core recovery on Leg 131 was good after stabilizing the shallow sands, so we anticipate similar success on Leg 190. Sites ENT-01A, 03A, and 06A will use advanced hydraulic piston corer (APC)/extended core barrel (XCB) to ~350 mbsf and rotary core barrel (RCB) to total depth (TD). Site ENT-07A will use only APC/XCB and, and Site WNT-01A will use only RCB.
As of 1900 May 29, we have occupied Site 1173 (ENT-01A) and have recovered the first four cores (0-45.1 mbsf) which contain Nankai Trough silty turbidites.
OPERATIONS: Port Call - Townsville, Australia: Leg 190 began at 1315 hr 11 May when the first line was passed ashore to Pier #2, Townsville, Australia. Hardware and equipment taken aboard during port call included 1,160 sacks of Sepiolite, 10 joints of 13-3/8" flush joint casing, 24 joints of 11-3/4" casing, and 2 boxes of core liners. Hardware and equipment off loaded during the port call included, 3 reefers of core, 2 empty core liner boxes, and a top drive motor for rewinding. At 0840 hr 15 May, the pilot boarded the vessel. The last line was released from the pier at 0900 hr and the JOIDES Resolution maneuvered out of the harbor. The pilot departed the vessel at 0942 and the JOIDES Resolution began steaming at full speed to Guam to pick up the science party.
Transit - Townsville, Australia to Guam: The 2,207 nmi transit from Townsville, Australia to Guam was accomplished at an average speed of 11.2 knots, in 196.5 hours. Calm seas were enjoyed during the entire transit. Tasks completed during the transit included, refurbishment of cabins, repair of propulsion motor P-18A, installation of new sealed motors in the A/C system on the top of the labstack, calibration of the ICP and development of methods for analyzing water and rock samples, a variety of repairs and upgrades to several labs, installation of instrumented load pins in the traveling block (although these had to be removed for repair as they were unstable when the temperature varied), servicing of the rig instrument system (RIS), refurbishment of Weco valves on cementing lines, rebuilding of the top drive tilt cylinder, installation of new fiber grating on core receiving cat walk, installation of new ceiling panels in accommodations, fabrication of catwalk under pipe racker, painting of the emergency generator room, and eradication of polliwogs from ship by King Neptune.
Port Call - Guam: The first line was passed ashore at Hotel Berth, Orote Point, Guam at 1600 hr 23 May ending the transit. The Leg 190 science party boarded the ship. The instrumented load pins installed during the transit from Townsville were taken off the ship and sent back for modification and recalibration. The last line from shore was passed at 2054 hr 23 May ending the brief Guam port call.
Transit - Guam to Site ENT-01A: The 1210 nmi transit from Guam to Site ENT-01A began at 2118 hr, 23 May. Calm seas were enjoyed over most of the transit.