IODP Expedition 401

Mediterranean–Atlantic Gateway Exchange

Daily science report for 31 January 2024

Location: Hole U1611B (36°19.3779′N, 4°34.7520′W; water depth 784.0 mbsl)

Science Update: We drilled ahead from 211.6 to 744.9 mbsf and pumped 30 bbl sepiolite mud sweeps after adding every two stands of pipe to keep the hole clear. When the center bit was retrieved, 1.7 m of sediment was found behind it in the core barrel, which was curated as a wash core, Core U1611B-2W. Coring started at 1830 h. Cores U1611B-3R to 4R penetrated from 744.9 to 764.3 mbsf and recovered 17.7 m (91%).

Cores U1611A-75R to 78R and 84R to 86R were split and described (Cores 79R to 83R were nearly empty). They are dark greenish gray Messinian silty muds and sandy silts with cm to dm scale beds of sand, dolomitic silty mud, and carbonate cemented beds.

Daily science report for 30 January 2024

Location:

Hole U1611A (36°18.7537′N, 4°34.2717′W; water depth 810.1 mbsl)
Hole U1611B (36°19.3779′N, 4°34.7520′W; water depth 784.0 mbsl)

Science Update: Downhole logging continued in Hole U1611A. The triple combo tool string made a repeat and main pass, which together cover the interval from 672.7 to 909.6 mbsf. Borehole diameter varied between narrower than 6 inch to wider than the maximum extent of the caliper measurement, 17 inch, and the logged interval of the borehole was inclined from the vertical by between 10° and 15°. The tool string was back on deck at 0410 h and a sonic-inclinometry tool string was assembled for the second logging run. This tool string was lowered into the borehole but could not pass below 743.6 mbsf. It recorded data for the short interval up to the bit, was back on deck by 0910 h, and the logging equipment was disassembled by 1100 h. The BHA was raised back to the ship, clearing the rotary table at 1400 h and ending Hole U1611A. A new mechanical bit release (MBR) and PDC RCB bit were added to the BHA and were lowered below the ship. The ship was offset to the northwest and Hole U1611B was started at 1725 h at a water depth of 784 mbsl. By midnight we had drilled ahead to 211.6 mbsf, with the aim to drill ahead to 720 mbsf and then start coring the early Pliocene and Messinian target strata.

Cores U1611A-63R to 74R were split and described. They are dark greenish gray Messinian silty muds and sandy silts with cm to dm scale beds of sand, conglomerate, and cemented carbonate.

Daily science report for 29 January 2024

Location: Hole U1611A (36°18.7537′N, 4°34.2717′W; water depth 810.1 mbsl)

Science Update: The wiper trip continued during the morning with washing down from 765.2 mbsf. Twelve tight spots were encountered and 6 m of fill was found at the base of the hole. From 0730 to 1030 h we washed out the fill and swept the hole with 30 bbl sepiolite mud in preparation for coring. Cores U1611A-84R to 86R penetrated from 1262.5 to 1281.9 mbsf and recovered 13.2 m (68%). We stopped coring after Core 86R at 1545 h and started to prepare the hole for downhole logging. The bit was released at the base of the hole, it was displaced with barite-weighted mud, and the end of pipe was raised to 672.7 mbsf. The rig floor team assembled the triple combo logging tool string, without the source, and started lowering it down the pipe at 2145 h. The tool string reached an obstruction at 909.6 mbsf, and by midnight we started the upward logging pass.

Cores U1611A-51R to 62R were split and described. They are Messinian silty muds with cm to m scale beds of sand or conglomerate, and some dm scale carbonate cemented beds. Cores 51R and 52R are mostly very dark gray, and Cores 53R to 62R are dark greenish gray.

Daily science report for 28 January 2024

Location: Hole U1611A (36°18.7537′N, 4°34.2717′W; water depth 810.1 mbsl)

Science Update: Cores U1611A-73R to 83R penetrated from 1194.6 to 1262.5 mbsf and recovered 36.7 m (54%). We switched to full-length RCB core advances with Core 77R. Core 79R returned empty, so we ran the bit deplugger and switched back to half-length advances for Cores 80R to 83R, each of which recovered less than 10 cm. At 1945 h we started a wiper trip to clear bridges in the hole prior to further coring and downhole logging. Overpulls of 20,000 to 30,000 lb were observed at 1104.9, 949.4, 881.7, and 872.0 mbsf, and by midnight the bit had been raised to 620 mbsf.

Cores U1611A-41R to 50R were split and described. They are Messinian in age and are mainly composed of very dark gray silty mud and calcareous silty mud. Sand beds, slumps, and conglomerates are present on a cm to dm scale. Wood and fish fragments continue to be found.

Daily science report for 27 January 2024

Location: Hole U1611A (36°18.7537′N, 4°34.2717′W; water depth 810.1 mbsl)

Science Update: Cores U1611A-56R to 72R penetrated from 1112.2 to 1194.6 mbsf and recovered 71.5 m (87%). Today we continued with half-core (4.65 m) advances, to attempt better core recovery as compared to full-length cores. Four 30 bbl mud sweeps were run.

Cores U1611A-33R to 40R were split and described. They are Messinian in age and are mainly composed of very dark gray mud, silty mud, and calcareous silty mud. The sediments are typically laminated at an mm scale. Sand beds and slumps on a cm to dm scale are present. Wood and fish fragments continue to be found on bedding planes. Foraminifera are present in Core 35R and below.

Daily science report for 26 January 2024

Location: Hole U1611A (36°18.7537′N, 4°34.2717′W; water depth 810.1 mbsl)

Science Update: Cores U1611A-39R to 55R penetrated from 1000.6 to 1112.2 mbsf and recovered 86.7 m (78%). After Cores 44R, we switched to half-core advances to see if that would improve core recovery. During the day, full-core advances yielded 69% recovery and half-core advances yielded 87%. Five 30 bbl mud sweeps were made to flush cuttings and loose sediment out of the borehole.

Cores U1611A-28R to 32R were split and described (Cores 25R to 27R were nearly empty). They are Messinian in age and are dominated by greenish black calcareous silty mud. The sediments are typically laminated at a mm scale, with occasional beds of coarser sediments and slumps on a cm to dm scale. Wood and leaf fragments were found, along with fish teeth and scales. Foraminifera and nannofossils are mostly absent.

Daily science report for 25 January 2024

Location: Hole U1611A (36°18.7537′N, 4°34.2717′W; water depth 810.1 mbsl)

Science Update: Cores U1611A-25R to 38R penetrated from 879.4 to 1000.6 mbsf and recovered 59.0 m (49%). After Cores 25R and 26R returned nearly empty, we ran the bit deplugger. The low recovery was likely related to coarse-grained sediments in the formation. Five 30 bbl mud sweeps were made to flush cuttings and loose sediment out of the borehole.

Cores U1611A-16R to 24R were split and described. Their age is Early Pliocene to Messinian. Cores 16R to 21R are dark greenish gray calcareous silty mud. Cores 22R to 24R are primarily calcareous mud and also contain <40 cm thick conglomerate beds, silty sands, and some slumped intervals.

Daily science report for 24 January 2024

Location: Hole U1611A (36°18.7537′N, 4°34.2717′W; water depth 810.1 mbsl)

Science Update: Cores U1611A-13R to 24R penetrated from 763.0 to 879.4 mbsf and recovered 76.8 m (66%). We ran five 30 bbl mud sweeps during the day.

Cores U1611A-5R to 15R were split and described. They contain Early Pliocene dark greenish gray calcareous mud and calcareous silty mud. Cores 12R and 13R contain four <40 cm thick beds of conglomerate. Mud clasts, shell fragments, and dolomitic sandy silt also appear in some beds in this interval.

Daily science report for 23 January 2024

Location: Hole U1611A (36°18.7537′N, 4°34.2717′W; water depth 810.1 mbsl)

Science Update: During preparation for running the core line to deploy the Sediment Temperature 2 (SET2) tool and the RCB core barrel, the core line winch electrical controller failed, specifically the Veeder-Root counter in the unit. It was replaced and the winch was back online by 0545 h. The SET2 tool run gave a temperature of 28°C at 657.3 mbsf. The Icefield MI-5 core orientation tool, usually run to orient APC cores, was run by piggybacking on the SET2 tool deployment to try to estimate any deviation of the casing from vertical. Coring started at 0815 h, and after Core U1611A-2R recovered only 3 cm of sediment, we ran the bit deplugger. Recovery improved, and Cores U1611A-2R to 12R penetrated from 656.3 to 763.0 mbsf and recovered 87.7 m (82%).

Cores U1611A-3R to 5R were split and described. They contain Early Pliocene dark greenish gray calcareous mud and calcareous silty mud.

Daily science report for 22 January 2024

Location: Hole U1611A (36°18.7537′N, 4°34.2717′W; water depth 810.1 mbsl)

Science Update: We continued to drill the casing into Hole U1611A until the reentry cone base landed on the seafloor at 810.1 mbsl with the bit at 654.6 mbsf. The subsea camera was deployed to observe the release of the casing, and at 0405 h the casing assembly was released from the pipe and BHA. The bit was raised back to the ship, clearing the rig floor at 1103 h, and completing the casing portion of operations at Hole U1611A. The rig floor team then assembled the RCB BHA with a PDC bit, lowered it to 584.9 mbsl, and deployed the subsea camera again to guide reentry into the hole. Hole U1611A was reentered at 1832 h, and the top of the cone was confirmed to be at 807.3 mbsl and the seafloor at 810.1 mbsl, within error of the PDR estimate of seafloor depth, 810.2 mbsl. The bit was lowered down the casing, meeting sediments in the casing at 613 mbsf. The top drive was installed and the bit washed down to 656.3 mbsf, followed by a 30 bbl mud sweep to clear out the casing.

The science party met for a presentation covering the operational and science objectives for Site U1611, and the noon–midnight shift scientists took a tour of the engine room.

Daily science report for 21 January 2024

Location: Hole U1611A (36°18.7537′N, 4°34.2717′W; water depth 810.2 mbsl)

Science Update: The day was spent drilling the casing into Hole U1611A from 138.7 to 604.9 mbsf. Seven 30 bbl sepiolite mud sweeps were pumped to keep the hole clear of loose sediment.

The science party met for presentations about the initial results from Site U1385, and the midnight–noon shift scientists took a tour of the engine room.

Daily science report for 20 January 2024

Location: Hole U1611A (36°18.7537′N, 4°34.2717′W; water depth 810.2 mbsl)

Science Update: The rig floor team continued to assemble the casing for Site U1611 and hang it below the ship. From 0900 to 1200 h, they made up the BHA, including the bit, underreamer bit, and mud motor. The underreamer and mud motor were tested and found to operate well. The BHA and drill pipe were lowered down through the casing until the bit and underreamer extended below the casing by 3 m. The HRT running tool was attached to the casing and the funnel was welded on. The funnel was lowered through the moonpool at 1540 h, and the whole casing system was lowered down to 792.1 mbsl before installing the top drive. Hole U1611A was started at 1730 h, and by midnight the system was drilled ahead to 138.7 mbsf.

The science party met to discuss stratigraphic correlations between three completed expedition sites, Sites U1609, U1610, and U1385.

Daily science report for 19 January 2024

Location:

In transit to Site U1611 (proposed Site WAB-03A)
Site U1611 (36°18.723′N, 4°34.307′W; water depth 810.2 mbsl)

Science Update: Today the ship traveled through the Strait of Gibraltar into the Mediterranean Sea to reach Site U1611 (proposed Site WAB-03A). We arrived on site at 1315 h, having completed the remaining 155 nmi of the 333 nmi voyage from Site U1385 at 11.6 kt. We lowered the thrusters at 1324 h and switched to DP mode at 1338 h. The rig crew cut and slip the drilling line and picked up the drill collars until the wind became too high to work in the derrick. From 1745 h to 2015 h we waited for the wind to drop before resuming operations. The hydraulic release tool (HRT) running tool was assembled and the upper guide horn was set aside.

The science party met to synthesize results from Sites U1609 and U1610.

Daily science report for 18 January 2024

Location:

Hole U1385L (37°34.0197′N, 10°7.6367′W; water depth 2584.2 mbsl)
In transit to Site U1611 (proposed Site WAB-03A)

Science Update: By 0330 h, the wind and seas had calmed enough to resume operations. The BHA was raised, disassembled, and stowed. The thrusters were raised at 0720 h, and at 0736 h we started the transit, ending operations at Site U1385. By midnight we had traveled 178 nmi of the 333 nmi transit to Site U1611 (proposed Site WAB-03A) in the Alboran Basin of the Mediterranean Sea.

The science party met to synthesize results from Site U1610.

Daily science report for 17 January 2024

Location: Hole U1385L (37°34.0197′N, 10°7.6367′W; water depth 2584.2 mbsl)

Science Update: Today was spent WOW. At midmorning the average wind speed reached 35 kt, gusting to 65 kt; then it eased throughout the day.

Cores U1385L-7X and 8X were split and described. They contain Messinian calcareous clay and clayey calcareous ooze, alternating in color between greenish gray and light greenish gray on a 1 m scale. The science party met to synthesize results from Site U1609.

Daily science report for 16 January 2024

Location: Hole U1385L (37°34.0197′N, 10°7.6367′W; water depth 2584.2 mbsl)

Science Update: We continued to drill ahead in Hole U1385L from 312.6 to 376 mbsf and started coring at 0330 h. Cores U1385L-2X to 8X penetrated from 376.0 to 443.9 mbsf and recovered 58.4 m (86%). We stopped coring at 1645 h and began to pull the bit out of the hole before the forecasted high wind and wave conditions started. The bit cleared the seafloor at 1835 h, and at 2315 h it was held at 332 mbsl while the ship began waiting on weather (WOW). We prioritized collecting core from Hole U1385L knowing that it would mean WOW the next day.

Cores U1385K-19X to 21X and U1385L-2X to 6X were split and described. Cores U1385K-19X to 21X contain Tortonian calcareous clay, alternating in color between greenish gray and light greenish gray on a sub-meter scale. Cores U1385L-2X to 6X contain Messinian calcareous clay and clayey calcareous ooze, alternating in color between greenish gray and light greenish gray on a 1 m scale.

Daily science report for 15 January 2024

Location:

Hole U1385K (37°34.0099′N, 10°7.6370′W; water depth 2584.2 mbsl)
Hole U1385L (37°34.0197′N, 10°7.6367′W; water depth 2584.2 mbsl)

Science Update: Cores U1385K-16X to 21X penetrated from 494.3 to 552.5 mbsf and recovered 56.2 m (97%). Having reached the age target in Core 21X, we stopped coring and pulled up the pipe, clearing the seafloor at 1328 h and ending Hole U1385K. We offset the ship 20 m to the north, started Hole U1385L at 1455 h, and drilled ahead without coring to 312.6 mbsf.

The science party met for a remote presentation by one of the Expedition 397 (Iberian Margin) Co-Chief Scientists about the paleoceanographic record at Site U1385. Cores U1385K-11X to 18X were split and described. They contain calcareous clay and clayey calcareous ooze, alternating in color between greenish gray and light greenish gray on a 1 m scale. These cores are Messinian and Tortonian in age.

Daily science report for 14 January 2024

Location: Hole U1385K (37°34.0099′N, 10°7.6370′W; water depth 2584.2 mbsl)

Science Update: Cores U1385K-5X to 15X penetrated from 402.4 to 494.3 mbsf and recovered 70.7 m (77%). After Cores 5X and 6X returned nearly empty, we ran a bit deplugger to ensure that the bottom of the BHA was free from obstruction. Recovery then improved to 86% for Cores 7X to 15X.

Cores U1385K-2X and 7X to 10X were split and described. They contain Messinian calcareous clay, alternating in color between greenish gray and light greenish gray on a 1 m scale.

Daily science report for 13 January 2024

Location: Hole U1385K (37°34.0099′N, 10°7.6370′W; water depth 2584.2 mbsl)

Science Update: Hole U1385K was started at 0035 h and was drilled ahead, reaching 385.0 mbsf at 1615 h. The center bit was retrieved and we started coring. Cores U1385K-2X to 4X penetrated from 385.0 to 402.4 mbsf and recovered 0.9 m (5%).

The science party met for presentations about the initial results from Site U1610.

Daily science report for 12 January 2024

Location:

Hole U1610A (36°41.9812′N, 7°25.8844′W; water depth 556.3 mbsl)
Site U1385 (preliminary: 37°34.0103′N, 10°7.6377′W; water depth 2584.5 mbsl)

Science Update: The downhole logging equipment was rigged down by 0045 h and the pipe was raised, clearing the seafloor at 0130 h and the rig floor at 0300 h. The rig floor was secured for transit, we raised the thrusters at 0336 h, and we started the sea passage to Site U1385 at 0348 h, ending Site U1610. The 154 nmi voyage took 12.8 h at a speed of 12 kt. On reaching Site U1385, we lowered the thrusters at 1622 h and switched to dynamic positioning (DP) mode at 1652 h. The advanced piston corer/extended core barrel (APC/XCB) BHA was assembled with a PDC bit and was lowered toward the seafloor. A pipe-cleaning “pig” was pumped down to clean the inside of the drill pipe. At midnight, the ship was positioned 20 m east of Hole U1385J, ready to start the new hole.

Site U1385 was cored to 151 mbsf on Expedition 339 in 2011 and to 400 mbsf on Expedition 397 in 2022. Our plan is to extend the Site U1385 record deeper than 400 mbsf and recover late Miocene sediments.

Cores U1609B-89R to 93R were split and described. They contain mostly dark greenish gray calcareous silty mud, with smaller amounts of clayey calcareous ooze, calcareous sandy silt, and calcareous silty sand. They are likely Messinian in age.