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IODP Expedition 402

Tyrrhenian Continent–Ocean Transition

Daily science report for 31 March 2024

Location:

  • Hole U1617B (40°0.0317′N, 13°24.4662′E; water depth 2822.3 m)
  • Underway to Site U1616

Science Update: At the beginning of the day, we had deployed the sonic logging tool to log an interval of Hole U1617B down to the obstruction at 328.4 mbsf that the triple combo tool string had been unable to pass. Because the caliper was not opened during the triple combo logging pass, we were not able to run the FMS tool with the sonic tool. The sonic tool reached the obstruction at 0100 h and began an uplog. By 0445 h the tool had been recovered and rigged down.

We picked up the top drive and washed down past the obstruction to hole bottom, then continued to circulate while pulling the pipe up to a depth of 336.8 mbsf with the goal of conducting a second logging run to total hole depth. The triple combo tool string was deployed at 1045 h, with the caliper and density tools removed to shorten the tool string and maximize the depth of data recorded by the other tools. The triple combo tool reached a depth of 364 mbsf, near the hole bottom at 370.4 mbsf. It was then recovered and the hole was displaced with heavy mud.

Pipe was tripped back to the surface and the rig floor was secured for transit at 2248 h. The vessel transitioned to cruise mode and the transit to return to Site U1616 began at 2305 h. The transit included surveying with the 3.5 and 12.0 kHz sonar systems.

Scientists held a site meeting for preliminary results from the hard rocks recovered at Site U1616E. At 0200 h, clocks were advanced by 1 h for Daylight Savings Time.

Daily science report for 30 March 2024

Location: Hole U1617B (40°0.0317′N, 13°24.4662′E; water depth 2822.3 m)

Science Update: Coring in Hole U1617B progressed from 341.0 mbsf to a final hole depth of 370.4 mbsf with Cores U1617B-17R through 22R. All cores were taken as half advances to improve recovery, with an average penetration rate of 8.2 m/h. Of the 29.4 m advance, we recovered 7.29 m of core (25%), where the low recovery is attributable to the evaporite and halite lithologies. The final core, Core 22R, crossed a lithological boundary from halite into a black shale that was observed on the catwalk to have a strong petroleum smell. Coring operations were paused while the headspace gas safety measurement for hydrocarbon content and composition was completed. The sample was found to have an anomalously low ratio of methane/ethane, indicating a thermogenic origin, halting further drilling in Hole U1617B.

Preparations then began for logging of Hole U1617B using the triple combo and FMS-sonic tool strings. Drill fluid was circulated through the hole and the core barrel deployed prior to stopping coring operations was retrieved. Pipe was tripped up to a depth of 311.6 mbsf and a 40 barrel sweep of sepiolite mud pumped. Pipe was then tripped back down to 370.4 mbsf and the rotary shifting tool was deployed to release the RCB bit at hole bottom. Finally, the pipe was set at 279.9 mbsf and the triple combo tool string was deployed at 1700 h. The tool string encountered an obstruction at 328.4 mbsf that could not be worked through. The triple combo tool string was recovered. Because we did not reach a great enough depth to open the caliper on the triple combo and measure hole diameter, we could not run the FMS tool and instead ran the sonic tool without the FMS. The tool was deployed at 2300 h.

Cores U1617B-12R through 22R were split and described. Cores 12R through 17R contain laminated intervals of sandstone, claystone, siltstone, mudstone, gypsum, and anhydrite with color varying from light gray to dark greenish gray to white to red. The gypsum and anhydrite have chicken wire structures. From the bottom of Core 18R through the top of Core 22R, the cores contain halite. The bottom of Core 22R consists of a thinly laminated black shale.

Daily science report for 29 March 2024

Location: Hole U1617B (40°0.0317′N, 13°24.4662′E; water depth 2822.3 m)

Science Update: RCB coring continued in Hole U1617B from a depth of 293.0 to 341.0 mbsf, with Cores U1617B-7R through 16R. All cores were taken as half advances to improve recovery, with an average penetration rate of 5 m/h. Of the 48.0 m advance, we recovered 26.85 m of material (56%).

Cores U1617B-4R through 11R were split and described. Cores 4R and 5R contain organic-rich mud with calcareous nannofossils and fine yellowish brown laminations, which transitions to gypsum-rich mud in the lower part of Core 5R and gypsum in Cores 6R through 9R. Cores 10R and 11R contain layers of clay, mud, and gypsum. Some of the gypsum intervals occur as breccia or conglomerate. Magnetic susceptibility is relatively low throughout this interval, but spikes in the oxide-rich gypsum layers of Core 11R. NGR is elevated in the clay and mud layers of Core 10R. Cores are Messinian in age.

Daily science report for 28 March 2024

Location: Hole U1617B (40°0.0317′N, 13°24.4662′E; water depth 2822.3 m)

Science Update: The drill ahead to 250 mbsf (drilled interval 402-U1617B-11) in Hole U1617B was completed at 1030 h. RCB drilling of sediments progressed from Cores U1617B-2R to 6R, advancing 43.0 m to a hole depth of 293.0 mbsf and recovering 34.46 m of core (80%). Recovery was high in Cores 2R through 5R, but only 10% in Core 6R. Cores will be drilled as half advances starting from Core 7R to improve recovery.

Cores U1617B-2R and 3R were split and described. The cores contain light olive gray to greenish gray nannofossil ooze with occasional glauconite-rich or foraminifera-bearing intervals. Bioturbation is mostly absent or uncommon, with one observed pyritized burrow.

Daily science report for 27 March 2024

Location:

  • Hole U1616E (40°11.0506′N, 12°33.9972′E; water depth 3567.0 m)
  • Hole U1617B (preliminary: 40°0.0324′N, 13°24.4670′E; water depth 2822.3 m)

Science Update: The triple combo logging tool string was pulled out of the hole following the unsuccessful logging attempt in which the tool string encountered an obstruction inside of the drill pipe. After the tool was recovered, we circulated drill fluid to clear any material that may be inside the pipe. A pressure increase up to 1000 psi, followed by a drop, indicated that the obstruction was cleared. Pipe was tripped back to the surface, with the bit recovered onto the rig floor at 0745 h. By 0930 h, the rig floor was secured and the vessel transitioned from DP to cruise mode, beginning the transit to Site U1617.

The transit included surveying with the 3.5 and 12.0 kHz sonar systems, crossing perpendicular to a series of ridges that may have formed during the detachment faulting. In all, the transit was 57.7 nmi and took 5.3 h at a speed of 10.9 kt. After the vessel arrived on site, we lowered the ship’s thrusters and transitioned to DP mode. By 1600 h, we were positioned over the coordinates for Hole U1617B. After making up the BHA with an RCB bit, we began tripping pipe toward the seafloor. Hole U1617B was spudded at 2330 h and will be drilled ahead without recovery to a depth of 250 mbsf prior to coring.

The science party continued analyses of samples from Hole U1616E, and they selected personal research samples from the site.

Daily science report for 26 March 2024

Location: Hole U1616E (40°11.0506′N, 12°33.9972′E; water depth 3567.0 m)

Science Update: At midnight, we were in the process of reaming Hole U1616E to hole bottom (371.0 mbsf) in preparation for logging. After cleaning the hole, we recovered the center bit and pulled most of the way out of the hole before launching the VIT camera system to observe dropping the RCB bit on the seafloor. Once the VIT had been lowered, we pulled the drill string out of the hole, clearing the seafloor at 0545 h. The vessel was offset away from the reentry cone and the bit was released using the shifting tool on the wireline. Once this operation was successfully completed, we recovered the shifting tool, reentered Hole U1616E at 0815 h, and then recovered the VIT.

The triple combo logging tool string was rigged up and deployed at 1230 h with the drill pipe set at 266.6 mbsf, ~10 m above the contact between sediment and breccia. The tool encountered an obstruction at 306.7 mbsf, directly below the breccia/basement contact at 303.5 mbsf. We made the decision to recover the triple combo tool, lower the drill pipe past this interface, and attempt a second logging run. The tool string was deployed for this second logging run at 1900 h, reaching a depth of 251.8 mbsf where it encountered an obstruction inside of the drill pipe. Attempts to clear the obstruction via circulation were not successful, with the pipe holding ~500 psi of pressure. Consequently, we ended logging operations and began pulling the Schlumberger tools out of the hole.

Cores U1616E-19R through 22R were split and described. These cores contain slightly more variable lithology than the overlying harzburgite-dominated sequence, with intervals of dunite, harzburgite, lherzolite, wehrlite, gabbro, and diabase with often strongly foliated/lineated fabric. Low recovery limits understanding of relative abundance of these rock types. Alteration was high to complete, with serpentine, clays, carbonate, amphibole, chlorite, and epidote present as alteration mineral phases.

Daily science report for 25 March 2024

Location: Hole U1616E (40°11.0506′N, 12°33.9972′E; water depth 3567.0 m)

Science Update: Coring in Hole U1616E continued with Cores U1616E-15R through 23R. All cores were taken as half advances and had an average ROP of 7.2 m/h. Of the 42.8 m advance, we recovered 10.71 m of basement rocks (25%). During drilling of Core 23R, the drill string experienced high torque and overpull at the bottom of the hole. Attempts to clean the hole bottom were unsuccessful and coring was terminated in favor of logging. Core 23R advanced 2.8 m to a final depth of 371.0 m with 0.15 m of recovery. To condition the hole for logging, a 40 bbl sweep of sepiolite mud was pumped prior to backreaming up to 212.7 mbsf. We then dropped the center bit and reamed back down to the hole bottom. At midnight, we were continuing with preparations for logging.

Cores U1616E-10R through 18R were split and described. The predominant lithology is porphyroclastic harzburgite with pervasive microveins, interspersed with gabbro, dunite, lherzolite, websterite, clinopyroxenite, and diabase. The rocks are moderately to highly altered with intervals of extensive weathering. Physical properties are relatively constant, with a slight decrease in NGR with depth, and with short intervals of moderately elevated MS.

Daily science report for 24 March 2024

Location: Hole U1616E (40°11.0506′N, 12°33.9972′E; water depth 3567.0 m)

Science Update: Cores U1616E-2R through 14R were drilled and recovered, advancing 78.2 m to a total hole depth of 328.2 mbsf. Core 2R is the first recovered core in this hole, following the casing installation operations that advanced the hole to 250 mbsf. A hard contact was encountered in Core 4R. Recovery in Cores 4R–9R was very low (10%) and all cores taken after Core 4R were half advances. Drilling parameters and formation lithology became more consistent starting from Core 10R (303.5 mbsf), which was designated as the top of basement. ROP in basement averaged 7.1 m/h and recovery in Cores 10R–14R was moderately higher (27%). Overall recovery in Cores 2R–14R was 15.16 m (19%).

Cores U1616E-2R through 9R were split and described by the sedimentologists and petrologists. Sediment in Cores 2R and 3R consists of foraminifera-rich nannofossil ooze, with sapropel layers and an interval of volcaniclastic-rich siltstone. The top sections of Core 4R contain dolomite, which then transitions into the matrix-supported consolidated breccia observed in Cores 4R–9R. Clasts in the breccia are predominantly heavily serpentinized and weathered harzburgite containing both metamorphic and magmatic vein types.

Daily science report for 23 March 2024

Location: Hole U1616E (40°11.0506′N, 12°33.9972′E; water depth 3567.0 m)

Science Update: After the successful installation of 219.4 m of 13⅜ inch casing in Hole U1616E, we prepared to RCB core the lower ~20 m of sediment, the sediment/basement interface, and the underlying basement rocks. Pipe was tripped back to the surface and the upper guide horn was reinstalled. A BHA with a 9⅞ inch RCB bit was made up and was tripped toward the seafloor. The VIT camera system was launched to facilitate reentry, which occurred at 1628 h. The VIT was then recovered prior to drilling. We washed down the distance from the end of the casing to the bottom of the drilled interval (250 mbsf) and we circulated a 40 bbl sepiolite sweep. At midnight, Core U1616E-2R was being recovered.

Scientists finished their Sites U1615 and U1617 reports.

Daily science report for 22 March 2024

Location: Hole U1616E (40°11.0506′N, 12°33.9972′E; water depth 3567.0 m)

Science Update: The 13⅜ inch casing intended for installation in Hole U1616E was rigged up and run, and the casing landed on the moonpool doors. The stinger and BHA were made up, were run through the casing, and the stinger was latched into the casing hanger. We then began tripping pipe toward the seafloor, stopping to perform a standard cut and slip of the drill line and to launch the VIT camera system to facilitate reentry in Hole U1616E. We finished tripping pipe to the seafloor and reentered Hole U1616E at 1658 h. The casing was washed in to a depth of 219.4 mbsf, landed in the reentry cone, and was released at 2045 h. This casing depth will successfully isolate the volcaniclastic gravel and tuff layers within the sediment that posed a risk to hole stability. The rest of the day was spent tripping pipe back toward the surface to prepare for RCB drilling in Hole U1616E.

Scientists finalized reports for Site U1613 and worked on reports for Sites U1615, U1616, and U1617.

Daily science report for 21 March 2024

Location: Hole U1616E (40°11.0506′N, 12°33.9972′E; water depth 3567.0 m)

Science Update: The day was spent drilling ahead in Hole U1616E in preparation for the installation of ~220 m of 13⅜ inch casing. The hole was reentered at 0120 h and the VIT camera system, which had been deployed to facilitate reentry, was recovered. The drill ahead finished at 1130 h, reaching a depth of 250.0 mbsf, and the hole was swept with sepiolite mud and then displaced with 170 bbl of barite heavy mud. We then pulled out of the hole and began tripping back to the surface. The VIT was deployed to monitor the bit clearing the reentry cone and the position of the cone on the seafloor. At midnight, the BHA had been laid out and the rig was being serviced in preparation for the casing installation.

Scientists continued to work on reporting for Sites U1615, U1616, and U1617. Staff and scientists celebrated Laboratory Officer Lisa Crowder’s 45 science expeditions and 10 transits/tie-ups on board the JOIDES Resolution.

Daily science report for 20 March 2024

Location: Hole U1616E (40°11.0520′N, 12°33.9978′E; water depth 3567.0 m)

Science Update: At midnight, we were tripping pipe toward the seafloor with the VIT camera system deployed to monitor the installation of the reentry cone with ~5 m of 20 inch casing in Hole U1616E. The hole was spudded at 0445 h, and the casing was set at a depth of 5.5 mbsf. At 0545 h, the running tool successfully unlatched from the casing. We then pulled out of the hole, recovered the VIT, and tripped pipe back to the surface. A new BHA was made up with a 14¾ inch tricone bit for drilling ahead to 250 mbsf in Hole U1616E, in preparation for the installation of ~220 m of 13⅜ inch casing. We began tripping pipe toward the seafloor, and at 2130 h we launched the VIT to observe reentry.

The science party held a site meeting for Site U1617 and worked on reports for Sites U1615, U1616, and U1617.

Daily science report for 19 March 2024

Location:

  • Hole U1616D (40°11.0520′N, 12°34.0260′E; water depth 3567.0 m)
  • Hole U1616E (preliminary: 40°11.0520′N, 12°33.9978′E; water depth 3567.00 m)

Science Update: The first 16 inch casing string was jetted into sediment at Hole U1616D to a depth of 64.64 mbsf, until the reentry cone was sitting on the seafloor. From 0430 to 0545 h, we attempted to unlatch the running tool from the DrilQuip reentry cone and casing, but we were unable to rotate it. Consequently, we made the decision to recover and inspect the reentry system and then redeploy in Hole U1616E. The casing was pulled out of the hole, experiencing strong overpull at ~10 mbsf. The VIT camera system was recovered and pipe was tripped back toward the surface.

At 1400 h, the reentry cone was brought back up through the moonpool and landed on the moonpool doors. The 16 inch casing string below the 20 to 16 inch swage was observed to be lost. It is likely that the overpull experienced while pulling out of Hole U1616E was due to the casing detaching. Two bent drill collars were removed from the BHA prior to making up the BHA again and latching it back into the reentry cone. The reentry cone with ~5 m of 20 inch casing was lowered through the moonpool and we began tripping pipe toward the seafloor. The VIT, with the Conductivity-Temperature-Depth (CTD) and Niskin water sampler attached to the frame, was launched at 2330 h and was lowered to observe casing installation and release. Hole U1616E will be offset 40 m west of Hole U1616D to avoid encountering any of the lost casing string that might be lying on the seafloor. Following installation of the reentry system, we plan to drill ahead to a depth of ~250 m and then install a second string of 13⅜ inch casing.

The science party worked on reports for Sites U1615, U1616, and U1617.

Daily science report for 18 March 2024

Location: Hole U1616D (40°11.0520′N, 12°34.0260′E; water depth 3567.0 m)

Science Update: Following the successful completion of the jet-in test in Hole U1616C, preparation began for the installation of a reentry system and a string of 16 inch casing that will sit at 64.64 mbsf in Hole U1616D. The casing was run through the moonpool and hung in the reentry cone. The stinger with the running tool and BHA were made up and latched into the reentry cone, then the moonpool doors opened and the reentry system was lowered toward the seafloor. The VIT was launched and lowered to monitor the installation of the reentry cone on the seafloor and the release of the running tool from the reentry cone. Hole U1616D was spudded at 2000 h; at midnight, casing was being jetted into the sediment and had reached a depth of 58.2 mbsf.

The science party worked on reports for Sites U1615, U1616, and U1617.

Daily science report for 17 March 2024

Location:

  • Underway to Site U1616
  • Hole U1616C (40°11.0491′N, 12°34.0397′E; water depth 3567.0 m)

Science Update: The vessel completed the final 7 nmi of the 40.1 nmi transit to Site U1616 at a speed of 8 kt. We arrived on site and transitioned to DP mode at 0112 h. To facilitate RCB drilling of basement at this site, we plan to install two casing strings and a reentry system. Prior to the casing installation, a jet-in test in Hole U1616C will verify that we will be able to successfully install the full 64.65 m of 16 inch casing as planned. In preparation for the jet-in test and casing installation, the upper guide horn was removed and a BHA with an 18½ inch tricone bit was made up. We tripped pipe toward the seafloor and spudded Hole U1616C at 1115 h. The jet-in test succeeded, penetrating 76.9 m into the sediment in ~3 h. The rest of the day was spent tripping pipe back to the surface and making up the Dril-Quip (DQ) running tool for the casing installation. A standard cut and slip of the drill line was performed.

The science party continued processing samples and data from sediments in Hole U1617A, and they took their group photos on the bow of the ship.

Daily science report for 16 March 2024

Location:

  • Hole U1617A (40°0.0211′N, 13°24.4662′E; water depth 2822.3 m)
  • Underway to Site U1616

Science Update: At midnight, we finished coring in Hole U1617A and we were conditioning the hole for logging. The drill pipe was tripped up to a depth of 74.6 mbsf and the triple combo tool string was deployed through the APC/XCB bit to log the open hole. At 0500 h, with the triple combo tool string at a depth of 135.4 mbsf, the tool encountered an obstruction and this first logging attempt was ended. The tools were recovered and three stands of drill pipe were added to the drill string, bringing the bit depth to 151.7 mbsf, past the initial obstruction. At 0845 h, the triple combo tool string was deployed a second time; however, the tool string was unable to pass out of the drill pipe into the hole. The decision was made to end logging attempts and to pull out of the hole. The rest of the day was spent tripping pipe back to the surface. At 2100 h, the rig floor was secured, the thrusters were raised, and we began the transit back to Site U1616 where we plan to install a reentry system and casing for RCB drilling in basement. By midnight the vessel had completed 33.1 nmi of the 40.1 nmi transit at a speed of 11.8 kt.

Cores U1617A-31X through 47X were split and described. Cores 31X–33X contain a gray nannofossil ooze with intervals that are nannofossil-rich or oxide-rich and contain relatively frequent pyrite nodules. Below these cores, there is a significant lithological transition to evaporite deposits similar in appearance to those found elsewhere in the Mediterranean.

Daily science report for 15 March 2024

Location: Hole U1617A (40°0.0211′N, 13°24.4662′E; water depth 2822.3 m)

Science Update: XCB coring in Hole U1617A continued with Cores U1617A-38X through 47X, advancing 45 m to a final hole depth of 339.9 mbsf. All cores were taken as half advances to improve recovery and because of slow ROP. We recovered 17.53 m of sediment, or 39%. At midnight, we had completed coring operations in the hole and were beginning to condition the hole for logging.

Cores U1617A-18H through 30X were split and described. The predominant lithology is a gray nannofossil ooze with some intervals of foraminifera-rich nannofossil ooze. Tephra deposits and some colored alteration bands (orange and greenish) are also documented throughout. Bioturbation is sparse or absent throughout most of the described interval, but it increases in Core 30X.

Daily science report for 14 March 2024

Location: Hole U1617A (40°0.0211′N, 13°24.4662′E; water depth 2822.3 m)

Science Update: Coring continued in Hole U1617A, advancing 140.7 m from 154.2 to 294.9 mbsf and recovering Cores U1617A-18H through 37X. Cores 20H and 21H were partial strokes; Cores 22F–27F were subsequently collected using the HLAPC. Cores 18H–27F all experienced overpull, ranging from 12,000 to 40,000 lb. As such, the XCB system was used starting with Core 28X. APC and HLAPC coring recovered 57.51 m out of the 55.5 m advance (104%). Recovery in Cores 28X and 30X–35X was over 100%, but Cores 29X, 36X, and 37X had low recovery. ROP slowed considerably starting in Core 36X. Overall, 126.4 m of sediment was recovered (90%).

Cores U1617A-5H through 17H were split and described. These cores contain predominantly gray nannofossil ooze, with intervals that are foraminifera-rich, glauconite-rich, or contain ash. Frequent tephra deposits and sapropels are noted. Gamma ray attenuation (GRA) bulk density and thermal conductivity both increase gradually downhole, while NGR was relatively constant with depth and only was elevated in a layer of volcaniclastic silt.

Daily science report for 13 March 2024

Location: Hole U1617A (40°0.0211′N, 13°24.4662′E; water depth 2822.3 m)

Science Update: APC/XCB Hole U1617A was spudded at 0715 h, confirming a water depth of 2822.3 m. The mudline Core U1617A-1H advanced 4.5 m with 100% recovery. At midnight, we had collected Cores U1617-1H through 17H, advancing to a depth of 154.2 mbsf and recovering 160.23 m of sediment (104%). Cores 15H and 16H were partial strokes. APCT-3 temperature measurements were made during Cores U1617A-4H, 7H, and 10H. All cores were oriented and the perfluorocarbon microbial contamination tracer was pumped with the drill fluid throughout coring.

Cores U1616B-24X through 29X were described. Cores 24X–27X are predominantly nannofossil ooze with foraminifera, with color gradations between gray and light brown. Intervals of glauconite and sapropels are noted. At the bottom of Core 27X and continuing into Core 28X, the lithology transitions to a reddish yellow dolomitic-rich nannofossil ooze with foraminifera. Core 29X contains a muddy consolidated breccia.

Cores U1617A-1H through 4H were also split and described. Section 1H-1 contains a reddish yellow pteropod ooze; otherwise, Cores 1H–4H are predominantly a gray nannofossil ooze with layers of tephra and sapropels.

Daily science report for 12 March 2024

Location:

  • Hole U1616B (40°11.0628′N, 12°34.0381′E; water depth 3567.0 m)
  • Underway to proposed Site TYR-02A (Site U1617)
  • Site U1617 (preliminary: 40°0.0216′N, 13°24.4670′E; water depth 2822.3 m)

Science Update: Cores U1616B-25X through 29X were recovered, advancing 47.5 m to a final hole depth of 302.6 mbsf. We recovered 24.87 m of material (52%). A hard contact was reached during XCB coring of Core 28X and the ROP slowed. The core was taken by advance after an hour of drilling, with only 6% recovery, but it contained clasts identified as basement material. A final core, 29X, was collected to verify the basement contact. We then began tripping pipe back to the surface. We plan to return to Site U1616 to install a casing string and to RCB drill 70 m of basement after completion of operations at proposed Site TYR-02A (Site U1617). The bit cleared the rig floor at 1700 h, ending Hole U1616B. The ship transitioned into cruise mode and transited the 40.1 nmi distance to Site U1617 at an average speed of 10.4 kt, arriving at 2150 h. At midnight, we were on location in DP mode, tripping pipe to the seafloor. The PDR water depth reading is 2822.3 m.

Cores U1616B-11X through 23X were split and described. Core 11X contains silt with volcaniclastic material, underlying the volcaniclastic gravel deposit. Core 12X consists of nannofossil ooze and diatom radiolarian rich sandy silt. Cores 13X–17X have alternating layers of nannofossil ooze and more volcaniclastic rich lithologies. Foraminifera rich intervals and layers containing sapropels, glauconite, tephra deposits, and pyrite patches are identified. Lithology in Core 18X transitions to a greenish gray nannofossil chalk, and then a poorly recovered tuff in Core 19X. Cores 20X–23X are predominantly nannofossil chalk.

Daily science report for 11 March 2024

Location: Hole U1616B (40°11.0628′N, 12°34.0381′E; water depth 3567.0 m)

Science Update: After switching to the XCB system, coring continued in Hole U1616B with Cores 7X–24X. We advanced 176.4 m and recovered 97.46 m of sediment (55%). Recovery was poor in Cores 7X–10X (3%, including Core 8X which had no recovery), but it improved in Cores 11X–24X (70%). Coring will continue until the sediment/basement contact is reached.

Cores U1616A-3H through 6H were described. Cores 3H–5H contain layers of very dark gray silty sand or olive gray volcaniclastic-rich silty sand interspersed with layers of gray nannofossil ooze. Core 6H penetrated a layer of volcaniclastic gravel. Cores 2H–10X in Hole U1616B were also split and described, where Cores U1616B-2H and 3H have overlap in depth with the bottom of Hole U1616A and contain entirely volcaniclastic gravel. The gravel extends through the top of Core U1616B-5H, then transitions back to alternating layers of sandy silt and nannofossil ooze.

Daily science report for 10 March 2024

Location:

  • Hole U1616A (40°11.0637′N, 12°34.0295′E; water depth 3567.0 m)
  • Hole U1616B (40°11.0628′N, 12°34.0381′E; water depth 3567.0 m)

Science Update: The vessel completed the 5 nmi transit between Sites U1615 and U1616 in DP mode at 0315 h. The top drive was picked up and we spaced out to spud, filling the drill string with the microbial contamination tracer prior to coring. APC/XCB Hole U1616A was spudded at 0530 h, recovering the mud line and penetrating 2.7 m into the formation (101% recovery), setting water depth as 3567.0 m. APC coring continued through Core 6H, reaching a depth of 50.2 mbsf and recovering 47.72 m of sediment (95%) overall. An APCT-3 temperature measurement was taken during Core 4H. Ship heave intensified throughout the morning and, after recovery of Core 6H, the decision was made to pull out of the hole and wait on weather (WOW), thereby ending Hole U1616A.

Hole U1616B was spudded at 1500 h, after 2 h of WOW. This hole began with drilled interval U1616B-1-1, to a depth of 31.2 mbsf, where APC/XCB coring resumed with Core 2H. Cores 2H–6H advanced 47.5 m to 78.7 mbsf, recovering 34.25 m of sediment (72%). An APCT-3 measurement was made during the collection of Core 4H. Core 7F, the first attempted HLAPC, was a misfire that resulted in a dropped core barrel. Two wireline runs were required to retrieve the empty barrel. Coring will resume with the XCB system.

Cores U1616A-1H and 2H were split and described by the sedimentologists. The cores consist of alternating layers of very dark gray silty sand with volcaniclastics and gray nannofossil ooze. When recovered, the contacts between these layers were sharp. The cores are moderately to strongly disturbed and contain soupy material.

Daily science report for 9 March 2024

Location:

  • Hole U1615A (40°11.0430′N, 12°40.6299′E; water depth 3568.6 m)
  • Underway to proposed Site TYR-15A (Site U1616)

Science Update: Coring with the XCB system continued in Hole U1615A from Cores U1615A-22X through 34X, advancing from 176.5 to 300.0 mbsf. Recovery was extremely low, 28% overall, with five cores having <0.5 m of material. Because of the poor core recovery in sediment and because the basement contact appears to be deeper than predicted at this site, we determined it would not be a suitable location for the next casing installation and we ended operations at Site U1615 at 1500 h after Core 34X. Pipe was tripped to a depth of 83 m above seafloor and a routine cut and slip of the drill line was performed. A cut and slip of the core winch line was also performed. At midnight, the vessel was moving in DP mode the 4.8 nmi distance to proposed Site TYR-15A (Site U1616) at a speed of 0.5 kt.

Cores U1615A-7H through 23X were described by the sedimentologists. Cores 7H–13F contain volcaniclastic-rich mud, sand, or gravel with sharp boundaries where the boundary was recovered. Core 14X had no recovery. Cores 15X–20X contain gray nannofossil chalk with variable amounts of silt or mud. Core 21X has a layer of tuff, before lithology transitions back to nannofossil chalk in Cores 22X and 23X. Sapropel layers and foraminifera-rich layers are noted.

Daily science report for 8 March 2024

Location: Hole U1615A (40°11.0430′N, 12°40.6299′E; water depth 3568.6 m)

Science Update: APC/XCB coring in Hole U1615A continued with Cores U1615A-3H through 21X, advancing from 16.8 to 176.5 mbsf. Advanced piston corer temperature (APCT-3) measurements were taken during Cores 4H, 7H, and 10H. Cores 8H and 10H experienced partial strokes; as such, Cores 11F–13F were taken as half-length advanced piston corer (HLAPC) cores before transitioning to XCB. Of the 159.7 m advance, we recovered 64.43 m or 40%. Eight cores had no recovery or recovery <0.5 m, including Cores 12X–14X and Cores 16X–20X.

Cores U1615A-1H through 6H were split and described. Cores 1H–4H are a mixture of dark gray to light olive brown nannofossil ooze and volcaniclastic-rich silty sand. Some horizons in Core 1H have shell fragments. Wood, pumice granules, and ash layers are also noted. Core 5H contains a gray volcaniclastic-rich gravel with mud with a slight fining-upward sequence. Physical properties are mostly constant through this interval, except for elevated magnetic susceptibility (MS) and NGR values near the top of the volcaniclastic-rich gravel.

Daily science report for 7 March 2024

Location:

  • Hole U1614C (40°15.9683′N, 12°42.3174′E; water depth 3579.0 m)
  • Underway to proposed Site TYR-16A (Site U1615)
  • Hole U1615A (preliminary: 40°11.0430′N, 12°40.6302′E; water depth 3568.6 m)

Science Update: At 0115 h, we had lowered the severing charges to a depth of 234.7 mbsf, just below the casing string, to free the stuck pipe from Hole U1614C. The charges were detonated with a 20,000 lb overpull on the pipe, and an immediate drop in string weight indicated that we were free. The Schlumberger wireline was recovered and we began pulling out of the hole. Once the seafloor was cleared at 0500 h, the vessel started to move in dynamic positioning (DP) mode at 0.5 kt toward proposed Site TYR-16A (Site U1615). The bit reached the rig floor at 1000 h, ending Hole U1614C, and an advanced piston corer/extended core barrel (APC/XCB) BHA was made up to begin operations at Site U1615. The 5.1 nmi transit was completed at 1608 h. Tripping toward the seafloor began while the ship was still in transit. Hole U1615A was spudded at 2230 h with the bit positioned 5 m above the precision depth recorder (PDR) water depth of 3571.4 m. Core U1615A-1H recovered the mudline and 7.49 m of material from a 7.3 m advance (103%), confirming the water depth as 3568.6 m. Core 2H recovered 94%.

Cores U1614C-25R through 28R were split and described. The final cores from Hole U1614C consist of slightly to highly altered serpentinized harzburgite and plagioclase-bearing harzburgite with a short interval of brecciated ophicarbonate. Alteration minerals include serpentine, magnetite, clays, and carbonate with instances of tremolite and amphibole replacing the clinopyroxene.

Daily science report for 6 March 2024

Location: Hole U1614C (40°15.9683′N, 12°42.3174′E; water depth 3579.0 m)

Science Update: Coring in Hole U1614C continued smoothly from Cores U1614C-24R through 28R. All cores were taken as half advances, for a total advance of 24.5 m to a depth of 410.6 mbsf. 12.59 m of core material were recovered (51%) with a 5.2 m/h ROP.

We lost pipe rotation and became stuck after recovery of Core U1614C-28R. Working the pipe allowed us to regain rotation and lay out two single pieces of pipe from the drill string. We became stuck again, with no rotation or vertical movement. Good circulation suggested that we were losing circulating fluids into the formation. From 1430 to 1700 h we worked the pipe without regaining movement. The vessel was offset to retrieve the core barrel and to release the bit as a last attempt to free ourselves. When this effort failed, we made the decision to deploy a severing charge and sever the pipe just below the casing, at ~231.5 mbsf. At midnight, the severing charge was being lowered to depth.

Cores U1614C-16R through 24R were described by the igneous and metamorphic petrologists as well as structural geologists. Lithologies include serpentinized harzburgite, lherzolite, dunite, and websterite. Three consecutive cores contain granitoids; NGR values are substantially higher in the granitoid intervals than in the serpentinized rocks. Alteration is moderate in Cores 16R through 19R, transitioning to highly altered downhole.

Daily science report for 5 March 2024

Location: Hole U1614C (40°15.9683′N, 12°42.3174′E; water depth 3579.0 m)

Science Update: Coring progressed in Hole U1614C from 342.0 to 386.1 mbsf (Cores U1614C-15R to 23R), with all cores taken as half advances. Of the 44.1 m advance, we recovered 24.32 m (55%), with lower recoveries in Cores 20R and 21R. The ROP was 3.6 m/h.

Cores U1614C-9R through 15R were split and described. Serpentinized lherzolite is the predominant lithology, with intervals of serpentinized dunite, harzburgite, websterite, and gabbro also observed. The degree of alteration is moderate to high. Veins include gabbro, serpentine, carbonate, and tremolite.

Daily science report for 4 March 2024

Location: Hole U1614C (40°15.9683′N, 12°42.3174′E; water depth 3579.0 m)

Science Update: Coring in basement of Hole U1614C proceeded from 307.9 to 342.0 mbsf, for a total advance of 34.1 m. All cores were taken as half advances. Recovery of basement material was 19.86 m (58%). After drilling Core U1614C-11R, we experienced high overpull and loss of rotation, but we were able to work the pipe free.

Cores U1614C-2R through 8R were split and described by the sedimentology, igneous and metamorphic petrology, and structural geology teams. Cores 2R and 3R contain dark greenish gray mudstone and clasts of plagioclase-bearing lherzolite. Cores 4R through 8R contain predominantly serpentenized lherzolite, harzburgite, and dunite, with intervals of gabbro, peridotite, websterite, and clinopyroxenite. Section 7R-4 has a zone of carbonate-cemented serpentinite. The alteration degree is moderate to high. Magnetic susceptibility and natural gamma radiation (NGR) are variable with lithology.

Daily science report for 3 March 2024

Location: Hole U1614C (40°15.9683′N, 12°42.3174′E; water depth 3579.0 m)

Science Update: At the beginning of the day, we were tripping pipe toward the seafloor to reenter Hole U1614C and begin RCB drilling. Reentry occurred at 0135 h, guided by the VIT camera system. We picked up the top drive, recovered the VIT, and dropped a core barrel with the bit at a depth of 229.7 mbsf. The core barrel was washed down to the bottom of the previous drilled interval (250.0 mbsf) before we began coring.

Cores U1614C-2R through 7R advanced 57.9 m to a depth of 307.9 mbsf and recovered 14.8 m or 26%. Recovery was particularly poor in Cores 2R and 3R, at 0.53 m (6%), and in Core 4R (12%), through relatively soft sediment at the sediment/basement interface. Cores 5R to 7R had improved recovery (43%) and a slower rate of penetration (ROP), 3.8 m/h.

Recovered cores were imaged and analyzed on the whole-round track systems for physical properties.

Daily science report for 2 March 2024

Location: Hole U1614C (40°15.9683′N, 12°42.3174′E; water depth 3579.0 m)

Science Update: Reentry into Hole U1614C to install a string of 10¾ inch casing occurred at 0030 h. We then picked up the top drive and washed in the casing to a depth of 227.3 mbsf. The casing was latched and released at ~0345 h. We recovered the VIT camera system and tripped pipe back to the surface. After racking the drill collars in the derrick and reinstalling the upper guide horn, we prepped the rotary core barrel (RCB) core barrels and made up the BHA with a C7 RCB drill bit. At midnight, we were tripping pipe toward the seafloor to begin coring, and we had launched the VIT to guide reentry.

The science party revised their methods and Site U1612 reports, then participated in a ship-wide scavenger hunt to visit different locations on the ship and learn about ship and drilling operations.

Daily science report for 1 March 2024

Location: Hole U1614C (40°15.9683′N, 12°42.3174′E; water depth 3579.0 m)

Science Update: Following the drill ahead to 250.0 mbsf, we tripped drill pipe back to the surface, racked the bottom-hole assembly (BHA), and began making up the running tool and drill collars to install the planned string of 10¾ inch casing in Hole U1614C. A standard cut and slip of drill line was performed prior to running the 20 joints of casing. With the casing hanging off the moonpool doors, we made up the BHA and latched into the casing hanger, and then began tripping toward the seafloor. The vibration isolated television (VIT) camera system was launched and lowered to guide reentry.

Scientists continued to work on site reports and methods revisions.