IODP Expedition 382
Iceberg Alley and Subantarctic Ice and Ocean Dynamics
Daily Science Report for 30 April 2019
Location: Hole U1537D (59°6.6597′S, 40°54.3677′W, water depth 3713.1 mbsl; proposed Site SCO-18A)
Science Update: Cores U1537D-5H to 19H penetrated from 34.8 to 177.3 mbsf and recovered 138.6 m (97%). A formation temperature measurement was made while taking Core 5H. Icebergs were monitored during the day, but none of them posed a hazard to operations.
Cores U1537D-1H to 14H were split and described. They consist of silty-clay-bearing diatom ooze, alternating with diatom-rich silty clay.
Daily Science Report for 29 April 2019
Location:
• Hole U1537B (59°6.6583′S, 40°54.3516′W; proposed Site SCO-18A)
• Hole U1537C (59°6.5197′S, 40°54.0870′W; proposed Site SCO-18A)
• Hole U1537D (59°6.640′S, 40°54.400′W; proposed Site SCO-18A)
Science Update: Hole U1537B consisted of a single core, U1537B-1H, taken for high-resolution pore water sampling, which penetrated from the seafloor to 7.4 mbsf. Hole U1537C started at 0135 h and Cores U1537C-1H to 2H penetrated from the seafloor to 15.3 m and recovered 11.9 m (78%). The Core 2H liner shattered and two large icebergs entered the red zone at 0400 h, so we ended Hole U1537C at that point. We raised the drill string clear of the seafloor and moved aside to let the icebergs pass. By 1500 h we were able to move back to the site, and at 1945 h we started Hole U1537D. Cores U1537D-1H to 4H penetrated from the seafloor to 34.8 mbsf and recovered 34.5 m (99%).
Cores U1537B-1H and U1537C-1H to 2H were split and described. They consist of diatom ooze and diatom-rich silty clay.
Daily Science Report for 28 April 2019
Location: Hole U1537A (59°6.6458′S, 40°54.3725′W, water depth 3712.9 mbsl; proposed Site SCO-18A)
Science Update: Cores U1537A-18H to 31F penetrated from 154.5 to 264.0 mbsf and recovered 108.8 m (99%). Because Core 26H was difficult to pull out of the formation, we switched to half-length piston coring at 240 mbsf. An iceberg moved into the red zone at 1830 h, so we raised the drill string to 38 mbsf. At 2020 h we ended Hole U1537A, after further encroachment of the iceberg. The rest of the day was spent monitoring iceberg trajectories and preparing to take a mudline core at a new hole.
Cores 9H to 26H were split and described. They consist of silty-clay-bearing diatom ooze, alternating with diatom-rich silty clay.
Daily Science Report for 27 April 2019
Location: Hole U1537A (59°6.6458′S, 40°54.3725′W; proposed Site SCO-18A)
Science Update: We started Hole U1537A at 0140 h, at 3712.9 m below sea level as calculated from the mudline. Cores U1537A-1H to 17H penetrated from the seafloor to 154.5 m and recovered 160.0 m (104%). Today the seas were relatively calm and no icebergs were projected to pass within 5 nmi of the ship, enabling an uninterrupted day of coring.
Cores 1H to 9H were split and described. They consist of silty-clay-bearing diatom ooze, alternating with diatom-rich silty clay.
Daily Science Report for 26 April 2019
Location:
• In transit
• Hole U1537A (59°6.640′S, 40°54.420′W; proposed Site SCO-18A)
Science Update: This morning we finished raising the drill string to the ship, which completed operations at Hole U1536E. At 0145 h we started the 20 nmi transit to Site U1537 (proposed Site SCO-18A), arriving 3.5 h later. We selected proposed Site SCO-18A because the top ~150 m of the stratigraphy appears to be uninterrupted by thin slumps compared to the other possible sites, as seen in the seismic and echosounder profiles. We started to make up the bottom-hole assembly, but high heave and roll forced us to pause operations for ~7 h. Additionally, we had to move ~1 nmi to the northwest to allow an iceberg to pass over the site location. Operations resumed at 1430 h and we lowered the drill string to within 17 m of the anticipated seafloor depth of 3710 mbsl, based on 3.5 kHz echosounder data.
Daily Science Report for 25 April 2019
Location: Hole U1536E (59°26.4496′S, 41°3.6392′W, water depth 3219.1 mbsl; proposed Site SCO-13A)
Science Update: We raised the drill string to 84 mbsf and prepared the rig floor for logging. The “quad combo” logging toolstring was assembled by 0400 h. It consisted of tools to measure the magnetic susceptibility, natural gamma radiation, electrical resistivity, sonic velocity, and density of the formation. We waited until 0630 h for an iceberg to pass the ship; its closest point of approach was ~5 nmi. We then started to lower the logging toolstring down to the seafloor. At 0830 h we started logging Hole U1536E while lowering the toolstring down at 550 m/h, reaching 643 mbsf (~3 m above the bottom of the hole), and at 1000 h we made a second logging pass while raising the toolstring back up, also at 550 m/hr. The logging tools were recovered and had been disassembled by 1515 h. The rest of the day was spent raising the drill string to the ship.
The science party met to hear a presentation about radiolarian microfossils and their use in paleoceanography.
Daily Science Report for 24 April 2019
Location: Hole U1536E (59°26.4496′S, 41°3.6392′W, water depth 3219.1 mbsl; proposed Site SCO-13A)
Science Update: Cores U1536E-27R to 33R penetrated from 578.2 to 645.4 mbsf and recovered 10.3 m (15%). After Core 33R was recovered at 1715 h, we decided to stop coring and log the hole in order to fill stratigraphic gaps in core recovery. The weather forecast predicted relatively calm seas until noon on 24 April and, although there were icebergs on the radar, they were not close or moving in our direction. This rare combination of conditions would permit a long enough time window for downhole logging. In preparation for logging, we pumped cuttings out of the hole with a 30 bbl mud sweep, released the bit at the bottom of the hole, and filled the hole with heavy mud. At midnight we were in the process of raising the drill pipe to a logging depth of 84 mbsf.
Cores 27R to 33R were split and described. Core 27R consisted solely of a core catcher with fall-in gravel. Cores 28R to 31R consist of mudstone with some limestone interbeds.
The science party met to continue yesterday’s presentations on the initial results from Site U1536.
Daily Science Report for 23 April 2019
Location: Hole U1536E (59°26.4496′S, 41°3.6392′W, water depth 3219.1 mbsl; proposed Site SCO-13A)
Science Update: Cores U1536E-25R to 26R penetrated from 559.0 to 578.2 mbsf and recovered 5.1 m (27%). At 0800 h an iceberg entered the red zone and continued on a path towards the ship. We raised the drill string clear of the seafloor at 1035 h and moved ~0.5 nmi to the east. By 1315 h the iceberg had moved clear of the site, so we repositioned and reentered Hole U1536E at 1605 h. After clearing 16 m of soft fill and 4 m of hard fill from the bottom of the hole, at the end of the day we had dropped the rotary core barrel ready to cut the next core.
The science party met to present and discuss the initial results from Site U1536.
Daily Science Report for 22 April 2019
Location: Hole U1536E (59°26.4496′S, 41°3.6392′W, water depth 3219.1 mbsl; proposed Site SCO-13A)
Science Update: The iceberg we had been tracking yesterday moved across Site U1536, and at 0730 h we were able to move back to the site. However, sea conditions were rough and vessel heave was up to 4.3 m, which was too high to safely prepare the subsea camera to guide reentry into Hole U1536E. By 1100 h the seas calmed a little and the subsea camera was deployed at 1245 h. Although the free-fall funnel had sunk into the soft seafloor sediments and/or had been covered by cuttings, the caved space above the funnel was clearly visible. We reentered Hole U1536E at 1415 h and washed down to 559 mbsf, the current depth of the hole, after removing 22 m of hard fill. From 2145 h to midnight we waited with the drill string near the base of the hole while tracking two icebergs with a projected closest point of approach of less than 5 nmi.
The science party met to hear a presentation about ODP Leg 113, Weddell Sea, and the Pliocene record from Site 697, the ODP site closest to our current location.
Daily Science Report for 21 April 2019
Location: Hole U1536E (59°26.4496′S, 41°3.6392′W, water depth 3219.1 mbsl; proposed Site SCO-13A)
Science Update: Icebergs entered and exited the red zone, approaching within 3 nmi of the ship, and preventing coring in Hole U1536E today. In the evening an iceberg headed towards the ship, and at 2145 h, when it was 1.6 nmi away, we had to raise the drill string out of the hole and move aside ~0.5 nmi to the west–northwest to let the iceberg pass.
The science party continued to work on the analyses and interpretation of the Site U1536 cores.
Daily Science Report for 20 April 2019
Location: Hole U1536E (59°26.4496′S, 41°3.6392′W, water depth 3219.1 mbsl; proposed Site SCO-13A)
Science Update: Cores U1536E-17R to 24R penetrated from 482.2 to 559.0 m and recovered 24.3 m (32%). At 1400 h an iceberg entered the red zone, so we stopped coring and raised the drill string to 50 mbsf. This iceberg moved past our location, but there was no time to resume coring because a second iceberg was approaching and entered the red zone at 2200 h. We continued to stand by.
Cores U1536E-13R to 24R were split and described. Cores U1536E-13R to 21R consist of diatom-bearing silty clay. Cores U1536E-22R to 24R consist of silty clay and have fewer and less well-preserved diatoms and radiolarians, suggesting that the opal-A/opal-CT phase transition is at ~525 mbsf at this site. The Miocene/Pliocene boundary is at ~450 mbsf, according to preliminary biostratigraphic and paleomagnetic data. Dropstones are quite common.
Daily Science Report for 19 April 2019
Location: Hole U1536E (59°26.4496′S, 41°3.6392′W, water depth 3219.1 mbsl; proposed Site SCO-13A)
Science Update: Today, Cores U1536E-4R to 16R penetrated from 359.0 to 482.2 m and recovered 63.5 m (52%). At 0315 h an iceberg entered the red zone, so we raised the drill string to 50 mbsf and waited for it to pass. We were able to resume coring at 0700 h. Weather conditions deteriorated during the day, and we had to pause rig floor operations from 2130 h to 2315 h, when ship heave reached a maximum of 5.8 m. Average wave height for the day was 4.9 m and the average swell height was 2.4 m.
Cores U1536E-2R to 12R were split and described. They consist of diatom-rich clay and diatom-rich silty clay. Dropstones appear to be more common than at shallower depths at this site. Lithification is increasing downhole.
Daily Science Report for 18 April 2019
Location: Hole U1536E (59°26.4496′S, 41°3.6392′W, water depth 3219.1 mbsl; proposed Site SCO-13A)
Science Update: We continued drilling Hole U1536E until we reached 312 mbsf. At 0850 h we deployed a free-fall funnel, which will enable reentry into the hole if icebergs force us to move from our location. Drilling then continued to 340 mbsf, where we planned to start coring. At 1300 h an iceberg entered the red zone, so we pulled the drill string up to ~50 mbsf and waited for the iceberg to pass. At 1700 h we resumed operations and lowered the drill string back down the hole. The bottom of the hole contained 3 m of soft fill. Cores U1536E-2R to 3R penetrated from 340.0 to 359.0 m and recovered 7.35 m (39%).
The science party met to hear a presentation about iron oxide minerals and applying them to find the provenance of ice-rafted debris and fine-grained sediments.
Daily Science Report for 17 April 2019
Location: Hole U1536E (59°26.4496′S, 41°3.6392′W, water depth 3219.1 mbsl; proposed Site SCO-13A)
Science Update: At the start of the day, the drill string was being raised to the ship; the bit reached the rig floor at 0630 h. After some rig maintenance, we made up the RCB bottom-hole assembly and lowered the drill string, reaching 37 m above the seafloor at 1730 h. We installed the top drive, and a core barrel with a center bit was pumped down. We started Hole U1536E at 2140 h with the aim to drill down without coring to 340 mbsf, just above the depth reached by Holes U1536A and U1536C. By midnight Hole U1536E was 81.5 m deep. During the day, seven icebergs were monitored and three of them had a projected closest approach of less than 5 nmi.
The science party met to hear a presentation on the Antarctic bottom water and changes in this water mass over the last two glacial terminations.
Daily Science Report for 16 April 2019
Location:
Hole U1536C (59°26.4604′S, 41°3.6191′W, water depth 3222.0 mbsl; proposed Site SCO-13A)
Hole U1536D (59°26.4501′S, 41°3.6198′W, water depth 3221.8 mbsl; proposed Site SCO-13A)
Science Update: As the day started, we were within an iceberg “red zone,” when the projected Closest Point of Approach (CPA) of an iceberg is less than 3 nmi and the time for it to reach the CPA is less than twice the time required to pull up the drill string to within 50 m of the seafloor. After the iceberg passed our location at 0700 h, we started to lower the drill string back down to the bottom of the hole to resume coring. Cores U1536C-38F to 40F penetrated from 341.4 to 352.0 mbsf and recovered 11.0 m (103%). At 1400 h, another iceberg entered the red zone, and we decided to end Hole U1536C, pull the drill string out of the hole, move 20 m north, and take a further mudline core for high-resolution pore water sampling. At 1940 h, Core U1536D-1H penetrated from the seafloor to 6.9 m. However, the core liner shattered and the core had to be pumped out of the barrel, so it could not be used for the intended purpose. At midnight, the drill string was being raised up to the ship in order to change over to the rotary core barrel (RCB) bottom-hole assembly.
Cores U1536C-29F to 40F were split and described. They consist of diatom-rich silty clay, with dropstones, and are late Pliocene to early Pleistocene in age.
Daily Science Report for 15 April 2019
Location: Hole U1536C (59°26.4604′S, 41°3.6191′W, water depth 3222.0 mbsl; proposed Site SCO-13A)
Science Update: Cores U1536C-18F to 37F penetrated from 236.4 to 341.4 mbsf and recovered 98.5 m (95%). There was a 1 m drilled interval to pass a hard layer at 292 m. In the morning, two icebergs were projected to approach within 5 nmi of the ship but they changed path and the alert was lifted. Throughout the day we continued to monitor icebergs within 25 nmi of the ship. At 2245 h an iceberg that was 6 nmi away was projected to pass within 3 nmi of the ship, so we stopped coring at that point. At midnight we were in the process of raising the drill string to 50 m below the seafloor.
Cores U1536C-12H to 28F were split and described. Cores 12H to 19H consist of greenish-gray diatom ooze with clay and silt, and Cores 20H to 28F consist of diatom-rich silty clay. Dropstones are present.
Daily Science Report for 14 April 2019
Location: Hole U1536C (59°26.4604′S, 41°3.6191′W, water depth 3222.0 mbsl; proposed Site SCO-13A)
Science Update: Hole U1536C was spot cored in order to fill gaps in the stratigraphy from Holes U1536A and U1536B. Cores 4H to 17F (and the drilled intervals 31, 91, 111, 131, and 161, which advanced 143.0 m without recovery) penetrated from 16.1 to 236.4 m and recovered 62.1 m (80%). We switched to half-length piston coring after encountering a hard layer at 225.3 m.
Cores U1536C-1H to 10H were split and described. They consist of greenish-gray diatom ooze with clay and silt, and are Pleistocene in age. Dropstones and volcanic tephra layers are present.
Daily Science Report for 13 April 2019
Location:
Hole U1536B (59°26.4608′S, 41°3.6399′W, water depth 3220.1 mbsl; proposed Site SCO-13A)
Hole U1536C (59°26.4604′S, 41°3.6191′W, water depth 3222.0 mbsl; proposed Site SCO-13A)
Science Update: Cores U1536B-15H to 25H penetrated from 121.6 to 226.1 m and recovered 108.7 m (104%). At 1130 h we started to raise the drill string because of approaching ice, which consisted of a large iceberg and a flotilla of smaller icebergs (bergy bits and growlers) that had calved from the main iceberg. At 1325 h the drill string cleared the seafloor, ending Hole U1536B.
From 1340 h we offset to avoid the small icebergs and continued to monitor the large iceberg until it passed us. Rig floor operations restarted at 1800 h and Hole U1536C was started at 2035 h. Cores U1536C-1H to 2H penetrated from the seafloor to 16.1 m and recovered 15.8 m (98%).
Cores U1536B-1H to 25H were split and described. They consist of greenish-gray diatom ooze with clay and silt, and are Pleistocene in age. Dropstones are present.
Daily Science Report for 12 April 2019
Location: Hole U1536B (59°26.4608′S, 41°3.6399′W, water depth 3220.1 mbsl; proposed Site SCO-13A)
Science Update: The iceberg that we were monitoring yesterday continued to approach the ship, and the decision was made to leave Hole U1536A when the iceberg was 1.7 nmi away. At 0130 h the drill string was raised above the seafloor and we moved about 1 nmi to the east–northeast to avoid the path of the iceberg. By 0320 h the iceberg had passed and we started to move back to Site U1536, while monitoring a second iceberg and a growler (a small iceberg the size of a truck).
At 0615 h the location was free of ice and we started lowering the drill string to the seafloor to start Hole U1536B. Cores U1536B-1H to 14H penetrated from seafloor to 121.6 m and recovered 122.0 m (100%). All cores were oriented and formation temperature measurements were made while taking Cores 5H, 8H, and 13H.
Cores U1536A-39F to 53F were split and described. They consist of diatom-rich silty clay. Dropstones are present.
Daily Science Report for 11 April 2019
Location: Hole U1536A (59°26.4602′S, 41°3.6596′W, water depth 3219.5 mbsl; proposed Site SCO-13A)
Science Update: Cores U1536A-31F to 53F penetrated from 244.0 to 354.4 m and recovered 114.3 m (104%). No cores were oriented and there were no formation temperature measurements today. An approaching iceberg was monitored in the afternoon, and by the evening it was still heading towards the area of the ship. At 2115 h the iceberg was 5.7 nmi and 5.5 h from the ship, and we followed the iceberg protocol: we stopped coring and raised the drill string up to about 50 m below the seafloor. At midnight we were standing by and monitoring the iceberg’s path.
Cores 18H to 38F were split and described. Cores 18H to 31F are mainly greenish-gray diatom ooze with clay and silt, and Cores 32F to 38F are mainly diatom-rich silty clay. Iceberg-rafted dropstones are present.
Daily Science Report for 10 April 2019
Location: Hole U1536A (59°26.4602′S, 41°3.6596′W, water depth 3219.5 mbsl; proposed Site SCO-13A)
Science Update: Cores U1536A-2H to 30F penetrated from 118.5 to 244.0 m and recovered 128.8 m (103%). Cores 14H to 23H were oriented and formation temperature measurements were taken with Cores 16H, 19H, and 22H. Cores 22H and 23H were difficult to pull out of the formation, so we switched to half-length piston coring for Cores 24F to 30F.
Cores 6H to 17H were split and described. They consist of greenish-gray diatom ooze with variable amounts of clay and silt.
Daily Science Report for 9 April 2019
Location: Hole U1536A (59°26.4602′S, 41°3.6596′W, water depth 3219.5 mbsl; proposed Site SCO-13A)
Science Update: Cores U1536A-2H to 13H penetrated from 4.5 to 118.5 m and recovered 121.3 m (102%). All piston cores were oriented and formation temperature measurements were taken with Cores 4H, 7H, 10H, and 13H. The coring line parted during the Core 13H run, so 50 m of line was cut and the core barrel was fished.
In the morning, the source in the X-ray core imager stopped working. After troubleshooting, the spare source was installed and the imager settings were recalibrated. We think that the original source had come to the end of its lifespan after usage during the instrument testing phase and on the last expedition. The X-radiographs will be used to quantify the iceberg-rafted detritus (IRD) content of the Iceberg Alley cores.
Cores U1536A-1F to 6H were split and described. They consist of diatom ooze with variable amounts of clay and silt. Sub-mm to cm-sized IRD clasts are seen in the X-ray images.
Daily Science Report for 8 April 2019
Location: Hole U1536A (59°26.450′S, 41°3.610′W, water depth 3219.5 mbsl; proposed Site SCO-13A)
Science Update: We started the day waiting for sea and weather conditions to improve, and at 0730 h we were able to restart operations. We made up the bottom-hole assembly and tested that the piston corer was landing correctly. The rest of the drill string was assembled and lowered to the seafloor. The top drive was installed by 1830 h. The first piston core run broke the shear pins mechanically before it could be shot as planned. The second piston corer was run with three shear pins in order to test that the system pressured up without problems. The third piston core was run with a half-length barrel, recovering 4.5 m (100%) in Core U1536A-1F, in a water depth of 3219.5 m. The core was almost full and the top 1.5 m of sediment was soupy, so an unambiguous mudline depth was hard to determine exactly.
The science party met to hear a presentation about carbon dioxide levels in the Pliocene and Pleistocene.
Daily Science Report for 7 April 2019
Location: Site U1536 (59°26.450′S, 41°3.610′W, proposed Site SCO-13A)
Science Update: At the start of the day, the drill string was being raised back to the ship in order to inspect the bottom-hole assembly (BHA) after the piston corer had misfired while attempting to start Hole U1536A. At 0815 h, with the bit at 77 m below the rig floor, sea conditions became too rough to continue operations and we waited on weather until 1500 h. At 1000 h we moved 500 m to the north to avoid an iceberg. The BHA was raised to the rig floor and no obstruction was found inside. Rough sea conditions returned at 1800 h and the rest of the day was spent waiting on weather.
The science party met at noon to discuss the current weather and ice conditions, and spent the day working on revisions to the site reports from Sites U1534 and U1535.
Daily Science Report for 6 April 2019
Location:
• In transit to Site U1536 (proposed Site SCO-13A)
• Site U1536 (59°26.450′S, 41°3.610′W, proposed Site SCO-13A)
Science Update: Today we completed the final 8 nmi to Site U1536 (proposed Site SCO-13A). During the previous day’s transit we had observed that the 3.5 kHz sub-bottom profile contained a series of reflections down to about 100 m below seafloor; based on this we decided to make two survey profiles over the site, each 4 nmi long along the site-survey seismic lines. The 3.5 kHz survey confirmed the water depth and provided details of the shallow reflectors at the site. The towed magnetometer had been deployed during the transit (in international waters) and was brought back to the deck after the survey. The thrusters were lowered at 0430 h, ending the sea voyage. The drill string was assembled and lowered to the seafloor. A pig (a cleaning device) was pumped down to remove rust from the inside of the drill pipe, but it did not emerge from the end of the drill string. This caused the piston corer to misfire twice, and despite deploying a barrel with a center bit to try to remove any remaining obstruction, the piston corer misfired a third time. At midnight, the drill string was being raised back to the ship in order to clear the obstruction.
The science party met to hear a presentation by the expedition’s ice observer about the US Arctic research vessel Sikuliaq and on ice monitoring during Expedition 382.
Daily Science Report for 5 April 2019
Location: In transit to Site U1536 (proposed Site SCO-13A)
Science Update: Today we travelled 229 nmi at an average speed of 9.5 kt. In midmorning we reduced speed because of icebergs in the general area and reduced visibility due to fog, but we were able to resume normal speed by late morning. At midnight we were 8 nmi from the site location.
The science party met to hear a presentation about the tectonic and paleoceanographic evolution of the Scotia Sea and its sub-basins. The scientists finalized the first drafts of the Site U1534 and U1535 reports, and sampling plans were confirmed for Site U1536.
Daily Science Report for 4 April 2019
Location: In transit to proposed Site SCO-13A
Science Update: The day was spent in transit to proposed Site SCO-13A in the Dove Basin study area. We travelled 283 nmi at average speed of 11.8 kt. The first iceberg of the expedition was spotted at 1600 h, at 56°20′S, 49°28′W. At midnight, 237 nmi of the transit remained, with an estimated time of arrival in the evening of 5 April.
The science party met to present and discuss the results from Sites U1534 and U1535. The scientists continued to write up the site reports and to make the remaining geochemical, paleomagnetic, and physical property analyses on samples from those two sites.
Daily Science Report for 3 April 2019
Location:
• Hole U1535A (53°11.4899′S, 58°45.6048′W, water depth 646.9 mbsl; proposed Site SFSD-02A)
• In transit to proposed Site SCO-13A
Science Update: Cores U1535A-15F to 17F penetrated from 102.9 to 117.3 m and recovered 11.4 m (79%). With operations completed at the Subantarctic Front sites, we started pulling up the drill string at 0330 h. We laid down the bottom-hole assembly, secured the rig floor for transit, and started the three-day sea voyage across the Southern Ocean to proposed Scotia Sea Site SCO-13A at 0848 h. Iceberg conditions in the region of Site SCO-13A are being monitored and the final decision on whether to start drilling at the site will be taken when we reach the area, which is currently classified as ice free.
Cores U1535A-1H to 17F were split and described. They consist of biosiliceous microfossil-bearing greenish-gray silty clay, and contain a comparable stratigraphy to the upper part of Site U1534.
Daily Science Report for 2 April 2019
Location:
Hole U1534D (53°11.3879′S, 58°45.6259′W, water depth ~606.1 mbsl; proposed Site SFSD-03A)
Hole U1535A (53°11.4899′S, 58°45.6048′W, water depth 646.9 mbsl; proposed Site SFSD-02A)
Science Update: We started Hole U1534D at 0045 h. Cores 1H to 3H penetrated from the seafloor to 28.5 m and recovered 29.6 m (104%). The purpose of this hole was to fill a gap in stratigraphic coverage and to provide more material for sampling in the upper part of the stratigraphy. From 0515 to 0930 h we transited 4 nmi east to Site U1535 (proposed Site SFSD-02A) in dynamic positioning mode so that we did not have to raise the drill string back to the ship. Cores U1535A-1H to 14F penetrated from the seafloor to 102.9 m and recovered 101.1 m (103%). Cores 9H to 11H were difficult to remove from the core barrel, so we switched to half-length piston coring at 88.5 m.
Cores U1534C-4H to 19H and U1534D-1H to 3H were split and described. They consist of biosiliceous microfossil-bearing greenish-gray silty clay. Because of the possible risk that foraminifer microfossils in the cores might dissolve after the cores are split (which has been observed in some high latitude sediments), samples were taken from Hole U1534C every 20 cm and stored frozen.
Daily Science Report for 1 April 2019
Location:
Hole U1534B (53°11.3763′S, 58°45.6298′W, water depth ~605.1 mbsl; proposed Site SFSD-03A)
Hole U1534C (53°11.3865′S, 58°45.6296′W, water depth 606.3 mbsl; proposed Site SFSD-03A)
Science Update: We started coring Hole U1534B at 0245 h. Core 1H recovered 1.5 m of sediment, but the core liner shattered and no clear mudline could be observed, so we decided to start a new hole. We started coring Hole U1534C at 0345 h. Cores 1H to 19H penetrated from the seafloor to 168.0 m and recovered 159.6 m (95%). Core 19H recovered 0.71 m and its core liner shattered, indicating that we had reached the limit of full-length piston coring, so we decided to stop coring Hole U1534C. Core 19H was on deck at 2135 h and at midnight we were pulling up the drill string in the hole.
Cores U1534A-31F to 47F, U1534B-1H, and U1534C-1H to 3H were split and described. They consist of biosiliceous microfossil-bearing greenish-gray silty clay.