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IODP Expedition 400

NW Greenland Glaciated Margin

Daily science report for 30 September 2023

Locations:

  • Hole U1608A (proposed Site MB-06D): 74°7.6818′N, 60°58.3172′W; water depth 606.9 m
  • Hole U1606B (preliminary): 74°14.261′N, 61°1.606′W; water depth 656.4 m

Science Update: Following a complete pass of Hole U1608A, the quad combo was pulled to the rig floor and broken down. The FMS (without sonic) tool string was then assembled and deployed at 0235 h. After two successful logs, the FMS tool was brought back onboard and broken down. The VSI was rigged up and deployed and the protected species watch began at 0730 h. Stations were measured up hole every 20 m and the VSI was back onboard by 1300 h. With logging completed we tripped the pipe out of Hole U1608A, clearing the rig floor at 1555 h. The drill floor was secured for transit and the thrusters were raised and secured for transit at 1630 h, ending Hole U1608A and Site U1608. The vessel began the 6.6 nmi transit back to Site U1606 and arrived at 1715 h. The thrusters were lowered and secured and the ship was fully in DP mode at 1738 h. The rig crew made up an RCB BHA and the drill string was tripped to near the seafloor. Hole U1606B was spudded at 2125 h, tagging the seafloor at 656.4 mbsl. Core U1606B-1R advanced 4.6 m and recovered 2.64 m (57%).

Cores U1608A-57R to 60R were split and described. The cores primarily consist of dark greenish gray muddy sand, sandy mud, and mud. An interval of calcareous mud is also present. Dispersed clasts and bioturbation occur variably throughout the cores. Cores contain sparse fossils.

Daily science report for 29 September 2023

Location: Hole U1608A (proposed Site MB-06D): 74°7.6818′N, 60°58.3172′W; water depth 606.9 m

Science Update: Cores U1608A-31R to 49R advanced from 274.1 to 458.4 mbsf and recovered 104.11 m (56%).

Cores U1608A-50R to 60R advanced from 458.4 to 561.0 mbsf and recovered 75.85 m (75%). Sepiolite (drilling mud) was swept into the hole and the bit was released in the hole at 1555 h to prepare for logging Hole U1608A. The hole was displaced with heavy mud (barite) and the pipe was tripped up, with the end of the pipe ultimately placed at 103.9 mbsf due to concerns about the condition and stability of the hole. The quad combo tool string was deployed to the base of Hole U1608A and tagged the bottom at 558.6 mbsf. We then began running the tool up the hole.

Cores U1608A-39R to 56R were split and described. The cores primarily consist of medium to dark greenish gray and dark brown muddy sand, sandy mud, and mud. Intervals of calcareous mud are also present. Dispersed clasts and bioturbation occur variably throughout the cores and some burrows are pyritized. Cores contain sparse fossils.

Daily science report for 28 September 2023

Location: Hole U1608A (proposed Site MB-06D): 74°7.6818′N, 60°58.3172′W; water depth 606.9 m

Science Update: Cores U1608A-31R to 49R advanced from 274.1 to 458.4 mbsf and recovered 104.11 m (56%).

Cores U1608A-23R to 38R were split and described. The cores primarily consist of medium to dark greenish gray muddy sand and sandy mud. Intervals of calcareous mud are also present. Dispersed clasts and bioturbation occur variably throughout the cores. Cores contain sparse fossils.

Daily science report for 27 September 2023

Location: Hole U1608A (proposed Site MB-06D): 74°7.6818′N, 60°58.3172′W; water depth 606.9 m

Science Update: Cores U1608A-10R to 30R advanced from 82.1 to 274.1 mbsf and recovered 83.37 m (41%).

Cores U1608A-8R to 22R were split and described. The cores primarily consist of medium to dark greenish gray muddy sand and sandy mud. Intervals of calcareous mud are also present. Dispersed clasts and bioturbation occur variably throughout the cores. Cores contain sparse fossils. Scientists worked on the reports and continued site summary presentations for Site U1607.

Daily science report for 26 September 2023

Locations:

  • Underway to proposed Site MB-06D (Site U1608)
  • Hole U1608A (proposed Site MB-06D): 74°7.6818′N, 60°58.3172′W; water depth 606.9 m

Science Update: The vessel completed the final 3 nmi of the transit to proposed Site MB-06D (Site U1608). The thrusters were lowered and secured and the ship was fully in DP mode at 0051 h. The rig crew made up an RCB BHA and the drill string was tripped to near the seafloor. Hole U1608A was spudded at 0435 h, tagging the seafloor at 606.9 mbsl. Cores U1608A-1R to 9R advanced from 0 to 82.1 mbsf and recovered 4.02 m (5%).

Cores U1608A-1R to 7R were split and described. The cores consist of severely disturbed washed gravel, including cobbles and pebbles of granite and gneiss. Scientists worked on the reports and began site summary presentations for Site U1607.

Daily science report for 25 September 2023

Locations:

  • Hole U1607A (proposed Site MB-07B): 74°29.5499′N, 60°34.9900′W; water depth 738.6 m
  • Underway to proposed Site MB-06D (Site U1608)

Science Update: The end of pipe was raised to 59.6 mbsf and the quad combo tool string was deployed to the base of Hole U1607A. At 938 mbsf (40 m from the bottom of the hole) a hard contact was encountered. The pipe was raised to 42.1 mbsf for the main pass. Following a complete pass of the hole, the quad combo was pulled up to the rig floor and broken down. The VSI was rigged up and the protected species watch began at 0930 h. The VSI was deployed to 930 mbsf and stations were measured every 30 m up hole until 1715 h, at which time the protected species watch also concluded. The VSI was brought back onboard and with logging completed we tripped the pipe out of Hole U1607A, clearing the rig floor at 2111 h. The drill floor was secured for transit and the thrusters were raised and secured for transit at 2124 h, ending Hole U1607A and Site U1607. The vessel began the transit to proposed Site MB-06D (Site U1608), completing 20 nmi of the voyage.

Scientists continued to process discrete samples and worked on the reports for Site U1607.

Daily science report for 24 September 2023

Location: Hole U1607A (proposed Site MB-07B): 74°29.5499′N, 60°34.9900′W; water depth 738.6 m

Science Update: Cores U1607A-92R to 103R advanced from 867.0 to 978.0 mbsf and recovered 30.97 m (28%). Sepiolite (drilling mud) was swept into the hole and the bit was released into the hole at 1940 h to prepare for logging Hole U1607A. The hole was displaced with heavy mud (barite) and the pipe was tripped up with the end of the pipe at 42.1 mbsf.

Cores U1607A-87R to 103R were split and described. Cores 87R to 94R consist primarily of dark brown mud, and sandy mud and glauconite is often present. Cores 95R to 103R consist primarily of dark grayish brown mud, with intervals of yellow calcareous mud. Bioturbation is variable and some pyritized burrows are present throughout. Cores contain sparse fossils that are consistent with an Oligocene age.

Daily science report for 23 September 2023

Location: Hole U1607A (proposed Site MB-07B): 74°29.5499′N, 60°34.9900′W; water depth 738.6 m

Science Update: Cores U1607A-81R to 91R advanced from 760.3 to 867.0 mbsf and recovered 86.77 m (81%).

Cores U1607A-76R to 86R were split and described. The cores consist primarily of grayish brown muddy sand. Intervals of grayish yellow calcareous mud are also present. Bioturbation is variable and laminations and shell fragments are present. Cores are barren or contain sparse microfossils.

Daily science report for 22 September 2023

Location: Hole U1607A (proposed Site MB-07B): 74°29.5499′N, 60°34.9900′W; water depth 738.6 m

Science Update: Cores U1607A-69R to 80R advanced from 643.9 to 760.3 mbsf and recovered 103.38 m (87%).

Cores U1607A-63R to 75R were split and described. The cores consist primarily of gray and brown sandy mud and muddy sand. Intervals of grayish yellow calcareous mud are also present. Bioturbation is common and shell fragments are present. Cores are barren or contain sparse microfossils.

Daily science report for 21 September 2023

Location: Hole U1607A (proposed Site MB-07B): 74°29.5499′N, 60°34.9900′W; water depth 738.6 m

Science Update: Hole U1607A was reentered at 0042 h. The subsea camera was back on board at 0130 h. The drill string was lowered to 516.7 mbsf, and we washed back to 566.3 mbsf. Cores U1607A-61R to 68R advanced from 566.3 to 643.9 mbsf and recovered 63.05 m (81%).

Cores U1607A-49R to 62R were split and described. The cores consist primarily of gray and brown sandy mud and muddy sand with dispersed clasts. Bioturbation is common, including pyritized burrows. Cores are barren or contain sparse fossils.

Daily science report for 20 September 2023

Location: Hole U1607A (proposed Site MB-07B): 74°29.5499′N, 60°34.9900′W; water depth 738.6 m

Science Update: Cores U1607A-54R to 60R advanced from 498.4 to 566.3 mbsf and recovered 61.5 m (91%). We then began to trip the drill string up in preparation for a bit change. The pipe was raised to 53.4 mbsf and a FFF was deployed at 1542 h. The subsea camera system was then deployed at 1652 h to observe that the FFF had landed in position and to ensure a clean exit from Hole U1607A. The bit cleared the seafloor at 1753 h and the subsea camera system was back on board by 1834 h. The drill string was then tripped up, with the bit at the surface at 2037 h. A RCB BHA was made up with a new C-4 bit and the drill string was tripped back to the seafloor. The subsea camera system was deployed at 2245 h to assist with reentering Hole U1607A.

Cores U1607A-33R to 48R were split and described. The cores consist primarily of gray and brown sandy mud and muddy sand with dispersed clasts. Bioturbation is common to moderate, including pyritized burrows. Cores are barren or contain sparse fossils.

Daily science report for 19 September 2023

Location: Hole U1607A (proposed Site MB-07B): 74°29.5499′N, 60°34.9900′W; water depth 738.6 m

Science Update: Cores U1607A-38R to 53R advanced from 348.1 to 498.4 mbsf and recovered 119.05 m (79%).

Cores U1607A-23R to 32R were split and described. The cores consist primarily of gray and brown sandy mud and muddy sand with dispersed clasts. Bioturbation is present in the mud intervals, including pyritized burrows. Cores are barren or contain sparse fossils.

Daily science report for 18 September 2023

Location: Hole U1607A (proposed Site MB-07B): 74°29.5499′N, 60°34.9900′W; water depth 738.6 m

Science Update: Cores U1607A-23R to 37R advanced from 207.9 to 348.1 mbsf and recovered 121.23 m (87%).

Cores U1607A-12R to 22R were split and described. The cores consist primarily of gray and brown sandy mud and muddy sand with dispersed clasts. Bioturbation is present in the mud intervals, including pyritized burrows. Shells and shell fragments are also present. Cores are barren or contain sparse fossils that are consistent with an upper Miocene age.

Daily science report for 17 September 2023

Location: Hole U1607A (proposed Site MB-07B): 74°29.5499′N, 60°34.9900′W; water depth 738.6 m

Science Update: Cores U1607A-8R to 22R advanced from 65.0 to 207.9 mbsf and recovered 111.88 m (78%).

Cores U1607A-5R to 11R were split and described. The cores consist primarily of gray and brown sandy mud and muddy sand with dispersed clasts. Bioturbation is present in the mud intervals, including pyritized burrows. Cores are barren or contain sparse fossils.

Daily science report for 16 September 2023

Location: Hole U1607A (proposed Site MB-07B): 74°29.5499′N, 60°34.9900′W; water depth 738.6 m

Science Update: Cores U1607A-1R to 7R advanced from 0 to 65.0 mbsf and recovered 56.81 m (87%).

Cores U1607A-1R to 4R were split and described. The cores consist primarily of gray and brown sandy mud and muddy sand, with dispersed clasts present in Cores 2R to 4R. Bioturbation is present in the mud intervals, including pyritized burrows. Intervals of calcareous mud are also present. Cores are barren or contain sparse fossils.

Daily science report for 15 September 2023

Locations:

  • Hole U1606A: 74°13.9380′N, 61°2.2426′W; water depth 652.6 m
  • Hole U1607A (proposed Site MB-07B; preliminary): 74°29.55′N, 60°34.994′W; water depth 738.6 m

Science Update: Cores U1606A-12R to 20R advanced from 103.0 to 182.4 mbsf and recovered 13.23 m (15%). At 1030 h ice moved within 3 nmi of the vessel and we raised the drill string to 24.6 mbsf by 1215 h. The ice was slow moving (nearly stationary) and was expected to linger over the site for more than a day while moving closer to the vessel. The decision was made to pull out of Hole U1606A and move to proposed Site MB-07B (Site U1607). The drill string was tripped up, with the bit at the surface at 1424 h. The drill floor was secured for transit and the thrusters were raised and secured for transit at 1500 h. The vessel transited 17 nmi to proposed Site MB-07B (Site U1607). The thrusters were lowered and secured and the ship was fully in DP mode at 1707 h. The rig crew made up an RCB BHA and the drill string was tripped to near the seafloor. Hole U1607A was spudded at 2225 h, tagging the seafloor at 738.6 mbsl.

Cores U1606A-5R to 19R were split and described. The cores consist primarily of grayish green to greenish gray sandy mud and muddy sand with dispersed clasts. Bioturbation is sparse to common. Diatoms and benthic foraminifers are present and the cores span Pleistocene to Pliocene in age.

Daily science report for 14 September 2023

Location: Hole U1606A (proposed Site MB-17A): 74°13.9380′N, 61°2.2426′W; water depth 652.6 m

Science Update: The drill string was partially lowered while we waited on ice to clear the site. By 0230 h we positioned the vessel over the site and Hole U1606A was spudded at 0415 h. Cores U1606A-1R to 11R advanced from 0 to 103.0 mbsf and recovered 16.91 m (16%).

Cores U1605A-40R to 47R were split and described. The cores consist of gray clast-poor and clast-rich sandy or muddy diamicton and gravel. Large clasts of igneous and metamorphic rock are present and all cores are slightly to severely disturbed. Cores are barren or contain sparse fossils. Cores U1606A-1R to 4R were also split and described and consist primarily of brown and gray sandy diamicton with varying clast abundance. Core U1606A-1R also contains biosilica-bearing sandy mud and diatoms are present. Scientists worked on the reports for Sites U1604 and U1605.

Daily science report for 13 September 2023

Locations:

  • Hole U1605A: 73°33.6421′N, 62°9.0687′W; water depth 528.7 m
  • Hole U1606A (proposed Site MB-17A; preliminary): 74°13.937′N, 61°2.247′W; water depth 648.1 m

Science Update: Cores U1605A-41R to 47R advanced from 216.7 to 282.0 mbsf and recovered 7.96 m (12%). We then began pulling the drill string out of the hole, clearing the seafloor at 1535 h. The drill string was tripped up, with the bit at the surface at 1720 h. The drill floor was secured for transit and the thrusters were raised and secured for transit at 1748 h, ending Hole U1605A and Site U1605. The vessel transited 44 nmi to proposed Site MB-17A (Site U1606). The thrusters were lowered and secured and the ship was fully in DP mode at 2200 h. Ice monitoring began and the vessel made the final approach to the site slowly as ice vacated the area. The rig crew made up an RCB BHA in preparation for Hole U1606A.

Cores U1605A-26R to 39R were split and described. The cores consist of gray clast-poor and clast-rich sandy or muddy diamicton and gravel. Large clasts of igneous and metamorphic rock are present and all cores are slightly to severely disturbed. Cores are barren or contain sparse fossils. Scientists worked on the reports for Site U1604.

Daily science report for 12 September 2023

Location: Hole U1605A (proposed Site MB-31A): 73°33.6421′N, 62°9.0687′W; water depth 528.7 m

Science Update: Cores U1605A-20R to 40R advanced from 92.7 to 216.7 mbsf and recovered 15.99 m (13%). Cores 20R through 35R were half advances (4.7–4.8 m).

Cores U1605A-14R to 25R were split and described. The cores consist of gray clast-poor and clast-rich sandy or muddy diamicton and gravel. Large clasts of igneous and metamorphic rock are present and all cores are slightly to severely disturbed. Cores are barren or contain sparse fossils. Scientists worked on the reports and continued site summary presentations for Site U1604.

Daily science report for 11 September 2023

Location: Hole U1605A (proposed Site MB-31A): 73°33.6421′N, 62°9.0687′W; water depth 528.7 m

Science Update: Cores U1605A-5R to 19R advanced from 21.4 to 92.7 mbsf and recovered 7.91 m (11%). All cores were half advances (4.7–4.8 m) and the rate of penetration is ~5 m/h.

Cores U1605A-4R to 13R were split and described. The cores consist primarily of gray clast-poor and clast-rich sandy diamicton and gravel. Large clasts of igneous and metamorphic rock are present and all cores are slightly to severely disturbed. Cores are barren of fossils. Scientists worked on the reports and began site summary presentations for Site U1604.

Daily science report for 10 September 2023

Location: Hole U1605A (proposed Site MB-31A): 73°33.6421′N, 62°9.0687′W; water depth 528.7 m

Science Update: The RCB BHA was tripped down and we attempted to spud Hole U1605A based on a water depth of 524.1 mbsl. Following a 3 m advance, the core barrel returned empty. The pipe was lowered and Hole U1605A was spudded at 0340 h and recovered 3.2 m from an 8.0 m advance. Cores U1605A-1R to 4R advanced from 0 to 21.4 mbsf and recovered 6.59 m (32%).

Cores U1605A-1R to 3R were split and described. The cores consist of gray clast-poor and clast-rich sandy diamicton. Large clasts of igneous and metamorphic rock are common and all cores are moderately to severely disturbed. Cores are barren of fossils. Scientists worked on the reports for Site U1604.

Daily science report for 9 September 2023

Locations:

  • Hole U1604B (proposed Site MB-02C): 73°06.9077′N, 63°47.3996′W; water depth 1943.6 m
  • Hole U1605A (proposed Site MB-31A; preliminary): 73°33.642′N, 62°9.064′W; water depth 535.4 m

Science Update: The quad combo tool string was deployed to the base of Hole U1604B. Following a complete pass of the hole the quad combo was pulled to the rig floor and broken down. The FMS-sonic tool string was then assembled and deployed at 0640 h. The FMS-sonic tool string was run and the tools were back on deck by 1200 h. With logging completed we tripped the pipe out of Hole U1604B, clearing the rig floor at 1720 h. The drill floor was secured for transit and the thrusters were raised and secured for transit at 1824 h, ending Hole U1604B and Site U1604. The vessel transited 39 nmi to proposed Site MB-31A (Site U1605), arriving on location at 2200 h. Observing that ice was a sufficient distance away from the vessel, the thrusters were lowered and secured at 2224 h and the ship was fully in DP mode at 2229 h. The precision depth recorder calculated the seafloor at 535.4 mbsl. A RCB BHA was made up in preparation for Hole U1605A.

Cores U1604B-48X to 55X were split and described. The cores alternate between mud, sandy mud, and interlaminated mud and sand. Cores vary between brown and gray in color. Intervals of dispersed clasts and intervals of calcareous mud are present. Cores are barren or contain sparse fossils.

Daily science report for 8 September 2023

Location: Hole U1604B (proposed Site MB-02C): 73°06.9077′N, 63°47.3996′W; water depth 1943.6 m

Science Update: Cores U1604B-43X to 55X advanced from 304.8 to 429.6 mbsf and recovered 42.5 m (34%). Sepiolite (drilling mud) was swept into the hole and heavy barite mud was added in preparation for logging Hole U1604B. The drill string was tripped up and the end of pipe set at 58.7 mbsf. The quad combo tool string was rigged up and prepared to deploy.

Cores U1604B-24H to 47X were split and described. The cores alternate between mud, sandy mud, and interlaminated mud and sand. Cores vary between brown and gray in color. Intervals of dispersed and common clasts are frequent and intervals of calcareous mud are present. Cores are barren or contain sparse fossils.

Daily science report for 7 September 2023

Location: Hole U1604B (proposed Site MB-02C): 73°06.9077′N, 63°47.3996′W; water depth 1943.6 m

Science Update: Cores U1604B-29H to 30H were advanced by recovery from 208.1 to 216.8 mbsf and recovered 8.78 m (102%). We then switched to the HLAPC coring system and Cores U1604B-31F to 35F advanced from 216.8 to 237.6 mbsf and recovered 16.89 m (81%). With ice still in the general area we decided to install a FFF to allow us to complete coring and logging of the site in Hole U1604B. The FFF was deployed at 1530 h and by 1630 h we resumed coring Hole U1604B. Cores U1604B-36X to 42X advanced from 237.6 to 304.8 mbsf and recovered 45.75 m (68%).

Cores U1604B-11H to 23H were split and described. The cores alternate between mud and interlaminated mud and sand and are predominantly dark grayish brown and greenish gray in color. Dispersed clasts and intervals of calcareous mud are present. Cores are barren or contain sparse fossils. Scientists continued to collect samples for sedimentary ancient DNA from Hole U1604B.

Daily science report for 6 September 2023

Location: Hole U1604B (proposed Site MB-02C): 73°06.9077′N, 63°47.3996′W; water depth 1943.6 m

Science Update: Cores U1604B-8H to 14H advanced from 60.6 to 105.3 mbsf and recovered 46.72 m (100%). However, Core 14H only recovered 0.2 m of material. An XCB core barrel was dropped and Core 15X advanced from 105.3 to 105.5 mbsf and recovered 0.22 m of hard material. We then switched back to APC coring and Cores 16H to 22H advanced from 105.5 to 163.1 mbsf and recovered 59.68 m (103%). Cores 21H and 22H were only partial strokes so we switched to the HLAPC system for Core 23F, which advanced from 163.1 to 167.9 mbsf and recovered 4.78 m (100%). We switched back to APC coring and Cores 24H to 28H advanced from 167.9 to 208.1 mbsf and recovered 41.09 m (102%).

Cores U1604B-1H to 10H were split and described. The cores alternate between mud and interlaminated mud and sand and are predominantly dark grayish brown in color. Dispersed clasts and intervals of calcareous mud are present. Cores are barren or contain sparse fossils. Scientists collected samples for sedimentary ancient DNA from Hole U1604B.

Daily science report for 5 September 2023

Locations:

  • Hole U1604A (proposed Site MB-02C): 73°06.9002′N, 63°47.4227′W; water depth 1942.2 m
  • Hole U1604B (proposed Site MB-02C): 73°06.9077′N, 63°47.3996′W; water depth 1943.6 m

Science Update: The drill string was lowered back into Hole U1604A and washed back to 233.0 mbsf. Cores U1604A-31X to 32X advanced from 233.0 to 250.6 mbsf and recovered 11.05 m (63%). At 0430 h ice moved within 3 nmi of the vessel and we raised the drill string to 16.7 mbsf by 0545 h and began WOI. Ice then entered the 1 nmi exclusion zone and we raised the drill string, clearing the seafloor at 0715 h. The vessel was moved 700 m north and then 700 m west to maintain a safe distance from the ice. By 1600 h we began to move back toward the site and the vessel was in position over Hole U1604B (20 m northeast of Hole U1604A) by 1630 h. Hole U1604B was spudded at 1755 h and the seafloor established as 1943.6 mbsl. Cores U1604B-1H to 7H advanced from 0 to 60.6 mbsf and recovered 51.42 m (86%).

Cores U1604A-19H to 32X were split and described. The cores alternate between mud and interlaminated mud and sand and are predominantly dark grayish brown in color. Dispersed clasts and intervals of diamicton are present. Cores are barren or contain sparse fossils. Scientists collected catwalk samples for sedimentary ancient DNA and Rhizon water samples from Hole U1604B.

Daily science report for 4 September 2023

Location: Hole U1604A (proposed Site MB-02C): 73°06.9002′N, 63°47.4227′W; water depth 1942.2 m

Science Update: Cores U1604A-14H to 26H advanced from 116.0 to 206.8 mbsf and recovered 93.84 m (103%). We switched to the HLAPC coring system, however Core U1604A-27F only recovered 2.85 m after a partial stroke. We then switched to the XCB coring system and Cores U1604-28X to 30X advanced from 209.6 to 233.0 mbsf and recovered 23.71 m (103%). At 1930 h ice moved within 3 nmi of the vessel and we raised the drill string to 16.2 mbsf by 2045 h and began WOI. By 2300 h the ice had moved a sufficient distance away from the vessel and we began to lower the drill string back into Hole U1604A.

Cores U1604A-4H to 18H were split and described. The cores alternate between mud and interlaminated mud and sand and are predominantly gray in color. Dispersed clasts and intervals of calcareous mud are present. Cores are barren or contain sparse fossils. The science party continued site summary presentations for Site U1603.

Daily science report for 3 September 2023

Locations:

  • Hole U1603F (72°59.0361′N, 62°58.8180′W; water depth 1801.3 m)
  • Hole U1604A (73°06.9002′N, 63°47.4227′W; water depth 1942.2 m)

Science Update: The drill string was tripped up, with the bit at the surface at 0030 h. The drill floor was secured for transit and the thrusters were raised and secured for transit at 0145 h, ending Hole U1603F and Site U1603. The vessel transited 16 nmi to proposed Site MB-02C (Site U1604), arriving on location at 0306 h. The thrusters were lowered and secured at 0324 h and the ship was fully in DP mode at 0337 h. The rig crew made up an APC/XCB BHA and began tripping the drill pipe. Hole U1604A was spudded at 1020 h and Core U1604A-1H recovered 2.04 m. The seafloor was calculated as 1942.2 mbsl. Cores U1604A-1H to 13H advanced from 0 to 116.0 mbsf and recovered 101.52 m (89%). Temperature measurements were made on Cores 4H, 7H, 10H, and 13H.

Cores U1603F-6H to 15H and Cores U1604A-1H to 3H were split and described. Cores U1603F-6H to 15H alternate between mud and interlaminated mud and sand and are predominantly gray and brown in color. Dispersed clasts are present. Cores U1604A-1H to 3H are primarily composed of mud and are gray and brown in color. Diamicton and calcareous mud are present in some intervals. Cores are barren or contain sparse fossils. The science party began site summary presentations for Site U1603.

Daily science report for 2 September 2023

Locations:

  • Hole U1603E (72°59.0551′N, 62°58.8829′W; water depth 1800.4 m)
  • Hole U1603F (72°59.0361′N, 62°58.8180′W; water depth 1801.3 m)

Science Update: Core U1603E-7F advanced from 54.4 to 59.1 mbsf and recovered 0.31 m (7%). It was decided to abandon Hole U1603E due to lack of recovery and the drill string was tripped out, clearing the seafloor at 0140 h. The vessel was offset 10 m southeast of Hole U1603A and Hole U1603F was spudded at 0235 h. Cores U1603F-1H to 5H advanced from 0 to 44.0 mbsf and recovered 45.49 m (103%). Core U1603F-6F (44.0–48.80 mbsf; 4.73 m recovered) was cored with the HLAPC system to help adjust core spacing to cover gaps in Hole U1603A. Cores U1603F-7H to 15H advanced from 48.8 to 134.3 mbsf and recovered 66.71 m (78%). We then began pulling the drill string out of the hole, clearing the seafloor at 1935 h.

Cores U1603E-1H to 7F and U1603F-1H to 5H were split and described. The cores alternate between mud and interlaminated mud and sand and are predominantly gray and brown in color. Dispersed clasts are present. Scientists collected samples for sedimentary ancient DNA in Hole U1603F. Scientists also continued to work on reports for Site U1603.

Daily science report for 1 September 2023

Locations:

  • Hole U1603D (72°59.0506′N, 62°58.8735′W; water depth 1800.8 m)
  • Hole U1603E (72°59.0551′N, 62°58.8829′W; water depth 1800.4 m)

Science Update: The FMS-sonic tool string was run and the tools were back on deck by 0345 h. With logging completed we tripped the pipe out of Hole U1603D, clearing the rig floor at 0900 h and ending Hole U1603D. An APC/XCB BHA was made up and we began tripping the drill pipe back to the seafloor at 1200 h. The vessel was offset 10 m northwest and the pipe was pumped with a cleanout tool while the tracer pumps were running. Hole U1603E was spudded at 1745 h and Core U1603E-1H recovered 6.94 m. Core 2H advanced to 16.4 m and recovered 9.75 m (103%). Cores 3H through 6H each advanced 9.5 m but recovered almost no material (less than 20 cm each). The deplugger was run in the pipe.

Scientists collected catwalk samples for sedimentary ancient DNA, and Rhizon water samples from the upper 16 m of Hole U1603E. Scientists also continued to work on reports for Site U1603.