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IODP Expedition 390

South Atlantic Transect 1

Daily Science Report for 17 May 2022

Location: Hole U1557D (30°56.4651′S, 26°37.7892′W, water depth 5010.7 mbsl)

Science Update: Cores U1557D-11R through 14R advanced 38.9 m to a depth of 684.7 mbsf and recovered 26.0 m of material (67%). All cores were full length with a mud sweep pumped after every core. Penetration rates were <2.5 m/h. After completing coring, we began tripping out of the hole to drop the bit on the seafloor and reenter for logging.

Cores U1557D-10R to 12R consist of clast-supported sedimentary breccia and contain highly or completely altered basalt clasts with cryptocrystalline groundmass. In most cores, alteration made it difficult to evaluate phenocryst abundance. Downhole, some basalt clasts could be identified as sparsely to moderately plagioclase olivine phyric. Chilled margins are present in some clasts.


Daily Science Report for 16 May 2022

Location: Hole U1557D (30°56.4651′S, 26°37.7892′W, water depth 5010.7 mbsl)

Science Update: At midnight, the subsea camera system was deployed and lowered to the seafloor to guide reentry in Hole U1557D after waiting on weather. We reentered the hole at 0246 h and pulled the subsea camera system back to the rig floor. With the top drive in, we tripped pipe inside the casing to 637.1 mbsf. The top drive was then set back in order to replace the wash pipe. After this repair, we continued coring from 637.1 mbsf. Core U1557D-10R advanced 8.7 m to 645.8 mbsf and recovered 8.47 m of material (97%).

The science party finished final chemistry and micropaleontology analyses from APC/XCB sediment holes at Site U1556 and worked on their site reports.


Daily Science Report for 15 May 2022

Location: Hole U1557D (30°56.4651′S, 26°37.7892′W, water depth 5010.7 mbsl)

Science Update: The day was spent waiting on weather with the drill pipe and RCB BHA set at 3227 mbrf. At 1800 h, weather marginally improved and the process of tripping to the seafloor began. The subsea camera system was deployed at 2130 h to guide reentry in Hole U1557D. At midnight, we were preparing to reenter with the drill pipe spaced out to 5005.3 mbrf.

The science party worked on reports describing sediment at Sites U1556 and U1561. Cores U1557D-8R and 9R were described for igneous and alteration petrology. They consist of clast-supported sedimentary breccia and contain highly or completely altered basalt clasts with cryptocrystalline groundmass. Glass clasts are altered to palagonite. A color change in alteration from orange or brown to dark green occurs in Core 9R. The science party and JRSO staff took part in a lifeboat drill.


Daily Science Report for 14 May 2022

Location: Hole U1557D (30°56.4651′S, 26°37.7892′W, water depth 5010.7 mbsl)

Science Update: Core U1557D-8R advanced 9.8 m and recovered 5.3 m (54%). Drilling began on Core 9R, but after only 1 m advance, the core was recovered due to poor weather and drilling conditions. Core 9R advanced to 637.1 mbsf and recovered 0.57 m (57%). We then pulled out of the hole, tripped to a depth of 3227 mbrf, and waited for weather conditions to improve.

Scientists worked on reports describing sediment at Sites U1556 and U1561. Cores U1557D-5R through 7R were described for igneous and alteration petrology. They consist of clast-supported sedimentary breccia and contain highly or completely altered basalt clasts with cryptocrystalline groundmass.


Daily Science Report for 13 May 2022

Location: Hole U1557D (30°56.4651′S, 26°37.7892′W, water depth 5010.7 mbsl)

Science Update: Cores U1557D-3R to 7R advanced 44.6 m to 626.3 mbsf with good penetration rates and high recovery (28.96 m recovered, 65%).

Cores U1557D-2R to 4R are clast-supported sedimentary breccias containing aphyric basalt with cryptocrystalline groundmass. Glass occurs along chilled margins and as clasts. The matrix is micritic limestone.


Daily Science Report for 12 May 2022

Location: Hole U1557D (30°56.4651′S, 26°37.7892′W, water depth 5010.7 mbsl)

Science Update: Tripping pipe toward the seafloor at Hole U1557D with the RCB BHA continued. At 0415 h, tripping paused to open the moonpool and deploy the subsea camera system to guide reentry. We located and reentered Hole U1557D at 0653 h, recovered the subsea camera system, and began tripping pipe through the casing to the hole bottom. Hole U1557D was cased several meters into basement during Expedition 395E, with a total hole depth of 575.6 mbsf. Core U1557D-2R, the first recovered core in this hole, arrived on deck at 1925 h. The core advanced 6.1 m to 581.7 mbsf and recovered 1.98 m of material (32%).

Cores U1556D-1H and U1556E-1H through 5H were split and described following analysis of whole rounds for oxygen content and Rhizon sampling of interstitial waters (IW). Core U1556D-1H was a missed mudline and contains brown silty clay as well as an interval of pinkish-gray or light greenish-gray organic-rich diatom ooze. Cores U1556E-1H through 5H contain brown silty clay and pinkish-gray calcareous nannofossil ooze.

Cores U1561A-1H through 9X, U1561B-1H, and U1561C-1H, collected during Expedition 395E, were also described. These cores contain brown silty clay with zeolites transitioning to light yellowish-brown calcareous nannofossil ooze downhole at Hole U1561A. Cores U1561A-8X and 9X contain aphyric basalt emplaced as pillow lava flows. The sediment/basement interface dates to the Paleocene.


Daily Science Report for 11 May 2022

Location:

  • Hole U1556E (30°56.5622′S, 26°41.9472′W, water depth 5003.1 mbsl)
  • Hole U1557D (30°56.4651′S, 26°37.7892′W, water depth 5010.7 mbsl)

Science Update: Cores U1556E-2H through 5H advanced 38.0 m and recovered 38.21 m of sediment. Core 5H was the final core for Site U1556 during this expedition. In total, Hole U1556E penetrated to a depth of 43.1 mbsf and recovered 43.33 m (100.5%). We then pulled out of the hole and began tripping pipe toward the surface. During tripping, the ship moved in dynamic positioning (DP) mode from Site U1556 to U1557 at a speed of 0.5 kt, arriving at 1436 h. The APC/XCB bit reached the rig floor at 1530 h, marking the end of Hole U1556E. The BHA for RCB coring in Hole U1557D was made up and we began tripping drill pipe toward the seafloor to reenter Hole U1557D, stopping once to fill the pipe with water.

Cores U1556C-27X to 32X were split and described. The sediment consists of predominantly brown nannofossil-rich calcareous chalk or clayey calcareous chalk with thin intervals of silty clay. Core 30X contains the sediment/basement interface, consisting of volcanics and gray foraminiferal nannofossil chalk, and dates to the Paleocene. Cores 31X and 32X consist of sedimentary breccias with sparsely to moderately phyric basalt as well as glass clasts. The matrix is calcareous sediments with clay.


Daily Science Report for 10 May 2022

Location:

  • Hole U1556C (30°56.5412′S, 26°41.9482′W, water depth 5005.7 mbsl)
  • Hole U1556D (30°56.5514′S, 26°41.9472′W, water depth 5003.1 mbsl)
  • Hole U1556E (30°56.5622′S, 26°41.9472′W, water depth 5003.1 mbsl)

Science Update: Cores U1556C-26X through 30X advanced 48.6 m to a depth of 276.3 mbsf, where we contacted a hard layer. These cores recovered 43.17 m of material (89%). Two additional cores (Cores 31X and 32X) were drilled as 2 m advances using the polycrystalline diamond compact (PDC) cutting shoe to collect material at the sediment/basement interface. Core 31X appeared to have jammed and only recovered 0.53 m of material, but Core 32X successfully recovered 1.54 m, reaching a depth of 280.3 mbsf. Hole U1556C ended at 1920 h when we tripped pipe out of the hole to the seafloor. The ship was offset 20 m south of Hole U1556C for Hole U1556D. This additional APC hole will recore the top five cores at Site U1556 to achieve less disturbed samples for microbiological, chemical, and paleoceanographic sampling. We spudded Hole U1556D at 2120 h but recovered a core with a full liner and missed mudline. Hole U1556D was abandoned, and the ship offset another 20 m south. Hole U1556E was spudded at 2300 h from a shot depth of 5010.0 mbrf. Core U1556E-1H recovered 5.12 m, establishing water depth as 5003.1 mbsl.

Cores U1556C-18X to 26X were split and described. The cores span from the Miocene to Eocene and contain alternating intervals of pinkish-white calcareous nannofossil chalk and reddish-brown silty clay. Bioturbation, where it occurs, is sparse to moderate and consists mostly of trails, tracks, and burrows.


Daily Science Report for 9 May 2022

Location: Hole U1556C (30°56.5412′S, 26°41.9482′W, water depth 5005.7 mbsl)

Science Update: Cores U1556C-16H through 25X advanced 96.9 m to a depth of 227.7 mbsf and recovered 96.33 m (99%). We switched from APC to XCB coring after Core 16H.

Cores U1556C-7H to 17X contain alternating intervals of brown silty clay and pinkish-white or gray calcareous nannofossil ooze. The clay transitions to a reddish-brown color downcore. Occasional intervals of foraminiferal nannofossil ooze are observed. Core 17X contains more lithified calcareous nannofossil chalk instead of ooze. Core 9H dates to the late Miocene. Physical properties data correlate with lithology.


Daily Science Report for 8 May 2022

Location: Hole U1556C (30°56.5412′S, 26°41.9482′W, water depth 5005.7 mbsl)

Science Update: Cores U1556C-2H through 15H advanced 125.8 m to 130.8 mbsf. The cores recovered 134.57 m of sediment (107%). Advanced piston corer temperature (APCT-3) tool temperature measurements were made on Cores 4H, 7H, 10H, and 13H. All cores were collected using nonmagnetic core barrels and oriented with the Icefield MI-5 magnetic orientation tool.

Cores U1556C-1H through 6H contain alternating intervals of brown silty clay and pinkish-white calcareous nannofossil ooze. An organic-rich diatom ooze is present in Core 1H. Cored material is moderately to severely disturbed or destroyed, including soupy intervals, uparching, fall-in, and voids.

Siem Offshore personnel conducted testing of the ship’s general alarm system.


Daily Science Report for 7 May 2022

Location: Hole U1556C (30°56.5412′S, 26°41.9482′W, water depth 5005.7 mbsl)

Science Update: After finishing operations at Hole U1556B, we continued tripping pipe toward the surface. Hole U1556B ended at 0405 h when the bottom-hole assembly (BHA) and MBR reached the rig floor. The crew preformed a cut and slip of the drill line, then began tripping pipe toward the seafloor with the advanced piston corer/extended core barrel (APC/XCB) BHA for sediment coring in Hole U1556C. Tripping paused twice to fill the drill pipe with water. Core U1556C-1H was shot from a depth of 5012.5 meters below rig floor (mbrf) and recovered 7.61 m of sediment as well as the mudline. The core was received on deck at 2315 h. It was significantly disturbed, so seafloor depth was assumed to be 5005.7 mbsl, offset from Hole U1556A.

The science party held a meeting to present their preliminary findings about material recovered from Hole U1556B, covering igneous unit boundaries, alteration features, physical properties, paleomagnetism, chemistry, and micropaleontology.


Daily Science Report for 6 May 2022

Location: Hole U1556B (30°56.5244′S, 26°41.9472′W, water depth 5001.8 mbsl)

Science Update: At midnight, our second logging tool string, containing the Ultrasonic Borehole Imager (UBI) tool and Accelerator Porosity Sonde (APS) tool, was lowered to a hole depth of 622 mbsf. The upward pass generated high-quality borehole image data. The tool string was recovered at 0605 h and the final logging tool string, the Formation MicroScanner (FMS)-sonic, was lowered until it tagged the bottom at 633.4 mbsf wireline depth. The tool logged two upward passes and reached the surface for recovery at 1710 h. After the rig floor was cleared of logging equipment, we began tripping pipe back toward the surface, clearing the seafloor at 1830 h. The ship was repositioned 30 m south to prepare for Hole U1556C and we continued tripping pipe back to the surface.

Scientists collected their final discrete shipboard samples from Hole U1556B and selected “pooled” samples that will be distributed to scientists to generate a common geochemical dataset postexpedition.


Daily Science Report for 5 May 2022

Location: Hole U1556B (30°56.5244′S, 26°41.9472′W, water depth 5001.8 mbsl)

Science Update: With the rotary core barrel (RCB) bit dropped at the bottom of Hole U1556B and the pipe tripped up to 41 mbsf, we rigged up for logging operations. The triple combo tool string, including tools for measuring formation density, resistivity, and magnetic susceptibility (MS), was lowered to 634 mbsf and the first upward pass started. Tool string telemetry failed after only a few meters of logging, and the string was pulled back to the surface and recovered at 0900 h. The Multi-Senor Spectral Gamma Ray Tool (MGT) was identified as the source of the problem and a spare tool was substituted into the string. The second attempt at logging was successful, with two passes of the triple combo completed before pulling it back to surface at 1930 h. At midnight, we were lowering the second tool string, containing the Ultrasonic Borehole Imager (UBI) and porosity tool.

Igneous and alteration petrology description of Hole U1556B was completed by the science party. Cores U1556B-56R to 59R contain highly plagioclase olivine-augite phyric basalt. Glass occurs in chilled margins. Alteration is moderate with a pseudomorphic texture and is gray to light gray in color. Fill includes veins, rare vesicles, and breccias. Intervals of breccia are cemented with micritic limestone.


Daily Science Report for 4 May 2022

Location: Hole U1556B (30°56.5244′S, 26°41.9472′W, water depth 5001.8 mbsl)

Science Update: Cores U1556B-57R to 59R advanced from 620.5 to 633.2 mbsf and recovered 11.14 m (88%). All cores were half length, with a mud sweep conducted after every core. Penetration rates in Cores 53R to 59R slowed considerably to <1.5 m/h. Core 59R is the last from Hole U1556B, arriving on deck at 1505 h. We then dropped the bit into the bottom of the hole using the mechanical bit release (MBR) process, pulled it out of the hole to 41 mbsf, and began preparing for logging operations.

Cores U1556B-50R to 55R were described for igneous and alteration petrology. Core 50R through Section U1556B-54R-3 contain aphyric basalt with cryptocystalline groundmass emplaced as a pillow lava flow. From Section 54R-4 downcore, core lithology is highly plagioclase olivine phyric with microcrystalline groundmass, emplaced as a massive lava flow. Olivine in this interval is 100% altered. Physical properties data also show substantial changes across this interval. Glass occurs in chilled margins and as discrete clasts. Intervals of hyaloclastite in Cores 54R and 55R have a micritic limestone matrix.


Daily Science Report for 3 May 2022

Location: Hole U1556B (30°56.5244′S, 26°41.9472′W, water depth 5001.8 mbsl)

Science Update: Cores U1556B-53R to 56R advanced from 601.0 to 620.5 mbsf and recovered 16.1 m (82%). All cores were half length, with a mud sweep conducted after every core.

Cores U1556B-46R to 49R contain aphyric basalt emplaced as pillow lava flows, except for a single section containing moderately olivine phyric basalt emplaced as a massive lava flow. The basalts are moderately to highly altered with pervasive orange halos. Fill includes veins, rare vesicles, and hyaloclastite breccias.


Daily Science Report for 2 May 2022

Location: Hole U1556B (30°56.5244′S, 26°41.9472′W, water depth 5001.8 mbsl)

Science Update: Cores U1556B-49R to 52R advanced from 581.6 to 601.0 mbsf and recovered 9.85 m (51%). All cores were half length, with a mud sweep conducted after every core. During initial drilling of Core 51R, we experienced high pump pressures and recovered the core barrel. Circulating pressure returned to normal after additional pumping. The deplugger tool was run as a precaution.

Cores U1556B-41R to 45R contain aphyric basalt with cryptocrystalline groundmass, emplaced as pillow lava flows. Glass in chilled margins is moderately to completely altered. Core 43R contains an interval of hyaloclastite breccia. Downhole measurements scientists, the Co-Chief Scientists, and select JRSO staff held a meeting to go over details of planned logging operations. JRSO staff took part in a training on using the Emergency Escape Breathing Devices (EEBD).


Daily Science Report for 1 May 2022

Location: Hole U1556B (30°56.5244′S, 26°41.9472′W, water depth 5001.8 mbsl)

Science Update: Cores U1556B-42R to 48R advanced from 547.5 to 581.6 mbsf and recovered 20.26 m (59%). All cores were half length. Mud sweeps were pumped after every half core.

Cores U1556B-35R to Section U1556B-38R-2 contain moderately or sparsely olivine phyric basalt. From Section 38R-3 through Core 40R, basalt is aphyric with cryptocrystalline groundmass. Most sections are emplaced as pillow lava flows, except for a dike in Core 38R. Fill includes veins and interpillow hyaloclastite. The science party and JRSO staff took part in a fire and boat drill followed by a lifeboat tour.