IODP Expedition 385
Guaymas Basin Tectonics and Biosphere
Daily Science Report for 15 November 2019
Location:
• Underway to San Diego, USA
• 10th Avenue Marine Terminal, San Diego, USA
Science Update: Today we completed the final 140 nmi of the 1191 nmi voyage to San Diego. The transit was concluded at an average speed of 10.4 kt. Pilots boarded the ship at 1600 h for the last 10 nmi of pilotage into the port. Expedition 385 ended with the first line ashore at 1724 h. Port call activities commenced with offloading of 129 joints of 5 inch drill pipe to the dock. U.S. Customs and Border Protection agents boarded the ship and cleared all personnel by 2000 h.
We cleaned the laboratories and scientists finalized all remaining science reports. We circulated the list of all planned postexpedition research projects and tentative publications.
Daily Science Report for 14 November 2019
Location: Underway to San Diego, USA
Science Update: Today we completed 216 nmi, and a total of 1041 nmi, of the 1191 nmi voyage to San Diego. We are underway at a speed of ~9.0 kt, with a currently estimated time of arrival at the San Diego pilot station of 1600 h on 15 November 2019.
We backed up the database. Scientists revised shipboard reports and held the second science summary meeting for Sites U1551 and U1552, with half of the laboratory groups presenting their results. Postexpedition research plans were discussed in small working groups.
Daily Science Report for 13 November 2019
Location: Underway to San Diego, USA
Science Update: Today we completed 249 nmi, and a total of 825 nmi, of the 1191 nmi voyage to San Diego. We are underway at a speed of ~9.3 kt, with a currently estimated time of arrival at the San Diego pilot station of 1600 h on 15 November 2019.
Scientists submitted the first draft their Site U1552 reports and held the first science summary meeting for Sites U1551 and U1552, with half of the laboratory groups presenting their results.
Daily Science Report for 12 November 2019
Location: Underway to San Diego, USA
Science Update: Today we completed 290 nmi, and a total of 576 nmi, of the 1191 nmi voyage to San Diego. We are underway at a full speed of ~12.1 kt, with a currently estimated time of arrival at the San Diego pilot station of 1600 h on 15 November 2019.
Scientists continued to analyze data from Hole U1552C and prepare their Site U1552 reports. Updated Site U1547/U1548 reports were submitted by the laboratory groups as a consequence of four holes added to these sites during the last week of operations.
Daily Science Report for 11 November 2019
Location: Underway to San Diego, USA
Science Update: Today we completed 277 nmi, and a total of 286 nmi, of the 1182 nmi voyage to San Diego. We are underway at a speed of ~11.5 kt, with an estimated time of arrival at the San Diego pilot station of 0630 h on 16 November 2019.
Cores U1552C-7H to 11H have been split and described. They consist of olive gray homogenous and laminated diatom clay and ooze alternating with numerous centimeter- to decimeter-thick, gray silty clay and foraminifer-bearing sand layers. Biostratigraphic analysis revealed the occurrence of calcareous nannofossil Emiliania huxleyi at the bottom of the hole, indicating a deposition age younger than 0.29 Ma for the entire sediment sequence in Hole U1552C.
Daily Science Report for 10 November 2019
Location:
• Hole U1552C (27°33.2181′N, 111°32.8557′W; water depth 1844.3 mbsl)
• Underway to San Diego, USA
Science Update: We continued APC coring in Hole U1552C. Cores U1552C-7H to 11H penetrated from 51.8 to a final depth of 99.3 mbsf and recovered 41.9 m (88%). We made formation temperature measurements with the APCT-3 tool on Cores 7H and 10H. Upon accomplishing the target depth objective, coring was terminated after recovering Core 11H. We pulled the drill string out of the hole and the bit cleared the seafloor at 0545 h and arrived at the rig floor at 1045 h, ending Hole U1552C and Site U1552. This concluded the coring operations on Expedition 385. Next, we disassembled the bottom-hole assembly and cleared the rig floor. The next 11.25 h were spent laying out 43 stands of drill pipe (129 joints) to the riser hatch. We then secured the vessel for transit and switched from dynamic positioning to cruise mode at 2235 h. We began our sea passage back to San Diego at 2300 h, completing 9 nmi of the 1191 nmi voyage by the end of the day.
Cores U1548C-8X to 10X have been split and described. They contain slightly to moderately altered, sparsely to moderately vesicular, sparsely to moderately plagioclase-phyric basalt that is occasionally mingled with sedimentary rock (mainly carbonate). Glassy margins are often present throughout the recovered igneous succession. Veins filled with calcite or sediment are abundant and surrounded by halos.
Cores U1552A-5H to 12H have been split and described. They consist of olive gray homogenous and laminated diatom clay and minor ooze alternating with several centimeter- to decimeter-thick, gray silty clay and foraminifer-bearing sand layers. Biostratigraphic analysis carried out in in Hole U1552A revealed the occurrence of calcareous nannofossil Emiliania huxleyi at the bottom of the hole, indicating a deposition age younger than 0.29 Ma for the entire sediment sequence in Hole U1552A.
Cores U1552B-1H to 6H have been split and described. They comprise diatom clay intercalating with diatom-bearing or diatom-rich clayey silt and silty clay. No biostratigraphic analysis was done in Hole U1552B.
Cores U1552C-1H to 6H have been split and described. They consist of diatom clay showing alternating homogenous and laminated intervals that intercalate with clayey to sandy silt and silty sand layers that are a few centimeters thick. Biostratigraphic assessment has not yielded any age-diagnostic species yet.
Daily Science Report for 9 November 2019
Location:
• Underway to Site U1552 (proposed Site GUAYM-10B)
• Hole U1552A (27°33.2906′N, 111°32.9665′W; water depth 1841.6 mbsl)
• Hole U1552B (27°33.2885′N, 111°32.9640′W; water depth 1841.1 mbsl)
• Hole U1552C (27°33.2181′N, 111°32.8557′W; water depth 1844.3 mbsl)
Science Update: We continued moving to Site U1552 (proposed Site GUAYM-10B) and arrived at the site coordinates at 0200 h. The drill string with the APC coring system was then lowered to the seafloor. At 0315 h, we deployed the subsea camera system to conduct a survey of the seafloor at this site. The survey did not find any vent communities. Upon retrieving the subsea camera by 0615 h, we picked up the top drive and spudded Hole U1552A at 0730 h. Mudline Core U1552A-1H recovered 3.1 m, which established a seafloor depth of 1841.6 mbsl. Cores U1552A-1H to 12H penetrated from the seafloor to a final depth of 107.5 mbsf and recovered 73.9 m (69%). Gas hydrates were recovered in Core U1552A-4H. The APCT-3 tool was deployed to make formation temperature measurements on Cores U1552A-4H, 7H, 10H, and 12H. Upon accomplishing the target depth objective on Core U1552A-12H, coring was terminated. We pulled the drill string out of the hole and the bit cleared the seafloor at 1547 h, ending Hole U1552A. We then shifted the vessel to establish Hole U1552B to recover cores for extensive microbiology and biogeochemistry sampling. Hole U1552B was spudded at 1620 h. Mudline Core U1552B-1H recovered 7.6 m, which determined a seafloor depth of 1841.1 mbsl. Cores U1552B-1H to 6H penetrated from the seafloor to a final depth of 55.0 mbsf and recovered 40.0 m (73%). Gas hydrates were recovered in Cores U1552B-4H and 5H. Upon accomplishing the target depth and microbial sampling objectives, coring was terminated after recovering Core U1552B-6H. We pulled the drill string out of the hole and the bit cleared the seafloor at 1957 h, ending Hole U1552B. After moving the vessel over the Hole U1552C coordinates, we positioned the bit above the seafloor to start coring. We spudded Hole U1552C at 2037 h. Mudline Core U1552C-1H recovered 4.4 m, establishing a seafloor depth of 1844.3 mbsl. Cores U1552C-1H to 6H penetrated from the seafloor to 51.8 mbsf and recovered 36.4 m (70%). We made a formation temperature measurement with the APCT-3 tool on Core U1552C-4H.
Cores U1548E-4H to 12H have been split and described. They consist of an alternation between olive gray, clay-rich diatom ooze and micrite-rich diatom clay, with the former being the predominant lithology. No biostratigraphic examination was carried out in Hole U1548E.
Cores U1552A-1H to 4H have been split and described. They show high lithologic variability over a relatively small depth interval. Core 1H contains homogenous diatom clay with shell fragments mostly of Lucinidae bivalves. Core 2H mainly consists of clay-rich, laminated diatom ooze. Core 2H also includes the first appearance of a micrite concretion and disseminated accessory micrite mixed with diatom and clay in the rest of the core. The bottom of Core 2H shows diatom-rich silt that constitutes the top of a ~6 m thick depositional unit that has a sandy base in the middle of Core 3H. Its bottom part consists of olive gray clay-rich diatom ooze which contains micrite as a minor component. Visible deformation and gas expansion characterize the clay-rich diatom ooze recovered in Core 4H. At this depth, gas hydrates were observed during core retrieval. Biostratigraphic assessment has not revealed any age-diagnostic species yet.
Scientists submitted the first draft of their Site U1551 reports.
Daily Science Report for 8 November 2019
Location:
• Hole U1548D (27°30.5316′N, 111°41.3855′W; water depth 1729.3 mbsl)
• Hole U1548E (27°30.4829′N, 111°41.2922′W; water depth 1729.9 mbsl)
• Underway to Site U1552 (proposed Site GUAYM-10B)
Science Update: We continued coring in Hole U1548D, deploying the APC and half-length APC (HLAPC) coring tools. Cores U1548D-9H to 13F penetrated from 72.8 to 110.0 mbsf and recovered 44.4 m (119%). We made a formation temperature measurement with the APCT-3 tool on Core U1548D-12H. We deployed the HLAPC tool on Core 13F. After recovering this core that penetrated to the target depth of 110 mbsf, we terminated coring in Hole U1548D. The drill string was pulled out of the hole and the bit cleared the seafloor at 0450 h, ending Hole U1548D. We then offset the vessel to the Hole U1548E coordinates, while cutting and reheading the core line. The bit was positioned above the seafloor and Hole U1548E was spudded at 0655 h. Mudline Core U1548E-1H recovered 5.7 m, which established a seafloor depth of 1729.9 mbsl. Cores 1H to 12H penetrated from the seafloor to 110.0 mbsf and recovered 115.2 m (105%). The APCT-3 tool was deployed to make formation temperature measurements on Cores U1548E-4H, 7H, and 10H. Upon penetration to the target depth of 110 mbsf on Core 12H, coring was terminated. We pulled the drill string out of the hole and the bit cleared the seafloor at 1705 h. We began to move the vessel in dynamic positioning mode to Site U1552 (proposed Site GUAYM-10B) at 1715 h, ending Hole U1548E and Site U1548. By the end of the day, we were still in transit to Site U1552 located ~22 km northwest of the northern axial graben of Guaymas Basin.
Cores U1547E-21R to 24R have been split and described. They contain slightly altered, nonvesicular to sparsely vesicular, dark greenish gray, sparsely to moderately plagioclase-pyroxene phyric dolerite. Sparse vesicularity is present. Vesicles are subangular and mostly filled with zeolite minerals. Calcite veinlets are occasionally present in different intervals.
Cores U1548D-6H to 13F have been split and described. They consist of an intercalation of olive gray, clay-rich diatom ooze and micrite-rich diatom clay, with the former being the major lithology. Biostratigraphic examination revealed the calcareous nannofossil species Emiliania huxleyi in Cores 7H and 13F, suggesting a deposition age of <0.29 Ma.
Cores U1548E-1H to 3H have been split and described. They comprise an alternation between laminated and homogenous, clay-rich diatom clay and diatom ooze.
Daily Science Report for 7 November 2019
Location:
• Hole U1548C (27°30.2704′N, 111°40.8468′W; water depth 1737.0 mbsl)
• Hole U1548D (27°30.5316′N, 111°41.3855′W; water depth 1729.3 mbsl)
Science Update: The day began while we were positioning the drill string above the seafloor to start coring in Hole U1548C with the advanced piston corer (APC) system. At 0055 h, we spudded Hole U1548C. Mudline Core U1548C-1H recovered 7.6 m, which established a seafloor depth of 1737.0 mbsl. Cores 1H to 10X penetrated from the seafloor to 69.8 mbsf and recovered 71.0 m (102%). We made formation temperature measurements on Core 4H with the APCT-3 tool and after Cores 5H, 6H, and 7H with the SET2 tool. The third deployment of the SET2 tool bent the tip of the tool upon encountering a hard formation at ~65 mbsf. We then switched to the extended core barrel (XCB) tool on Core 8X, which recovered a sediment/sill contact. Upon recovering Core 10X, we terminated coring in Hole U1548C at a final depth of 69.8 mbsf, as our microbiology sampling and target depth objectives were accomplished. We started pulling the drill string out of the hole and the bit cleared the seafloor at 1610 h, ending Hole U1548C. Upon offsetting the vessel to the coordinates of Hole U1548D, we positioned the bit above the seafloor to start APC coring. We spudded Hole U1548D at 1902 h. Mudline Core U1548D-1H recovered 6.4 m, which determined a seafloor depth of 1729.3 mbsl. Cores 1H to 8H penetrated from the seafloor to 72.8 mbsf and recovered 76.2 m (105%).
Cores U1547E-17R to 20R have been split and described. Core 17R consists of slightly to moderately altered, sparsely vesicular aphyric equigranular basalt. Vesicles are either open or filled with calcite. A few observed veins are filled with carbonate and pyrite. Mingling with sediment is partially present. Cores 18R to 21R consist of slightly to moderately altered, sparsely to nonvesicular, inequigranular dolerite. Rare veinlets of calcite are observed.
Cores U1548C-1H to 7H have been split and described. Cores 1H and 2H contain homogenous, clay-rich diatom clay with shell fragments and open burrows. Starting with Core 3H, the sediment is mainly composed of alternations between laminated and homogenous diatom clay and diatom ooze with occasional gray silty beds mixed with diatom and clay. An important lithologic change occurs in Core 4H marked by the occurrence of authigenic carbonate precipitates. Sand- and silt-rich layers, a few centimeters thick, also become more frequent. The bottom of Core 7H contains siliceous clay. No biostratigraphic assessment took place in Hole U1548C.
Cores U1548D-1H to 5H have been split and described. They consist of homogenous, clay-rich diatom clay with shell fragments in Core 1H, and alternations between laminated and homogenous diatom clay and diatom ooze in Cores 2H to 5H. Biostratigraphic analysis has not revealed any age-diagnostic species yet.
Scientists held the science summary meetings for Sites U1549 and U1550.
Daily Science Report for 6 November 2019
Location:
• Hole U1547E (27°30.3598′N, 111°40.7756′W; water depth 1732.1 mbsl)
• Hole U1548C (27°30.2704′N, 111°40.8468′W; water depth 1737.0 mbsl)
Science Update: We continued RCB coring in Hole U1547E. Cores 21R to 24R penetrated from 177.3 to 191.2 mbsf and recovered 10.2 m (73%). In view of the remaining science objectives of the expedition, we decided to stop coring in Hole U1547E at a final depth of 191.2 mbsf. At 0900 h, we started pulling the drill string out of the hole, and the bit cleared the seafloor at 1045 h. While we were continuing to raise the drill string to the surface, the vessel was moved to Site U1548 at 1120 h to recover another set of microbiology samples from the hydrothermally influenced sediment formation associated with the Ringvent structure. At 1142 h, the vessel arrived over the Hole U1548C coordinates. At 1440 h, the bit arrived at the rig floor, ending Hole U1547E and Site U1547. We then made up an ACB/XCB bottom-hole assembly and started lowering the drill string to the seafloor. At 2100 h, we pulled the upper guide horn and deployed the subsea camera system to conduct a survey of the seafloor at the intended location of Hole U1548C. At 2223 h, we moved the vessel to new hole coordinates 5 m to the southwest from the original coordinates to avoid a clam bed. By the end of the day, the subsea camera system was retrieved.
Cores U1547E-10R to 16R have been split and described. They contain igneous rocks that mainly consist of equigranular, aphyric basalt. The bottom of Core 11R and top of Core 12R show plagioclase-phyric basalt with glomeroporphyritic texture. Glassy margins occur in Core 13R. All recovered rocks are slightly to moderately altered and sparsely to moderately vesicular. Vesicles are either open or filled with calcite. Veins are present at different intervals and are filled with carbonate and pyrite.
Daily Science Report for 5 November 2019
Location: Hole U1547E (27°30.3598′N, 111°40.7756′W; water depth 1732.1 mbsl)
Science Update: We continued RCB coring in Hole U1547E. Cores 11R to 20R penetrated from 134.8 to 177.3 mbsf and recovered 21.9 m (52%).
Cores 2R to 9R have been split and described. Cores 2R and 3R consist of diatom-bearing micrite. Cores 4R to 9R contain slightly to moderately altered, equigranular to inequigranular, aphyric basalt. These rocks are nonvesicular to moderately vesicular, showing subrounded vesicles that are filled with calcite and subordinate pyrite. There is infrequent occurrence of dendritic calcite veins. Glassy margins were observed in Cores 4R and 5R.
Scientists submitted the first draft of their Site U1550 reports.
Daily Science Report for 4 November 2019
Location:
• Underway to Site U1547 (proposed Site GUAYM-12A)
• Hole U1547E (27°30.3598′N, 111°40.7756′W; water depth 1732.1 mbsl)
Science Update: We continued our transit to Site U1547 (proposed Site GUAYM-12A) and arrived at the site coordinates at 0115 h. We lowered the thrusters and switched to dynamic positioning mode at 0137 h, starting operations at Hole U1547E, located 77 m southwest of Hole U1547D. We made up the rotary core barrel (RCB) bottom-hole assembly and started lowering the drill string to the seafloor. At 0645 h, we picked up the top drive, dropped the center bit, and the end of the drill string tagged the seafloor at 1732.1 mbsl. We spudded Hole U1547E at 0800 h and drilled ahead without core recovery to 61.8 mbsf. At 0915 h, we retrieved the center bit and started RCB coring. Cores 2R to 10R penetrated from 61.8 to 134.8 mbsf and recovered 12.1 m (17%).
Cores U1551A-10H to 19F have been split and described. Core 10H consists of unconsolidated sand that marks the end of a very thick sand interval, and olive green homogenous diatom clay that starts at the bottom of the core. This lithology continues through the upper part of Core 11H. The rest of Core 11H through Core 13H is made up of diatom clay alternating with sand and silty sand. Cores 14H to 16F consist of sand only. Finally, Cores 17F to 19F are characterized by fine-scaled alternation between diatom clay, silty sand, and sand layers. Scanning electron microscopy confirmed the presence of calcareous nannofossil Emiliania huxleyi at the bottom of Hole U1551A, indicating a depositional age of Holocene to Middle Pleistocene (0–0.29 Ma).
Cores U1551B-1H to 6H have been split and described. As observed in Hole U1551A, the lithologies include homogenous clay- and nannofossil-rich diatom ooze at the very top, followed by a 7 m thick turbidite in Cores 2H and 3H. Core 3H also includes the same dark, organic-rich clay interval observed in Hole U1551A. Cores 4H to 6H contain carbonate concretions and are highly deformed, probably as a consequence of synsedimentary slumps mainly composed of diatom clay and thin silty sand layers.
Daily Science Report for 3 November 2019
Location:
• Hole U1551A (27°12.3887′N, 111°13.1943′W; water depth 1844.1 mbsl)
• Hole U1551B (27°12.3832′N, 111°13.1841′W; water depth 1843.9 mbsl)
• Underway to Site U1547 (proposed Site GUAYM-12A)
Science Update: We continued coring in Hole U1551A, deploying the APC and HLAPC coring tools. Cores U1551A-9H to 19F penetrated from 53.9 to 120.3 mbsf and recovered 12.5 m (113%). Partial strokes were encountered on Cores 4H to 9H, 11H, and 13H to 15H. We made formation temperature measurements with the APCT-3 tool on Cores 4H, 7H, 10H, and 13H. We switched to the HLAPC coring system after Core 15H at 108.2 mbsf. We terminated coring in Hole U1551A after recovering Core 19F from a final depth of 120.3 mbsf because unconsolidated sand layers prevented us from reaching our deeper drilling objectives. We pulled the drill string out of the hole and the bit cleared the seafloor at 1025 h, ending Hole U1551A. The vessel then moved 20 m east to start APC coring in Hole U1551B. We spudded Hole U1551B at 1130 h. Mudline Core U1551B-1H recovered 4.9 m. This established a seafloor depth of 1843.9 mbsl. Cores 1H to 6H penetrated from the seafloor to 48.5 mbsf and recovered 50.0 m (103%). We encountered partial strokes on Cores 3H to 6H. We terminated coring in Hole U1551B after recovering Core 6H at a final depth of 48.5 mbsf. We pumped perfluorocarbon tracers (PFTs) for drilling fluid (seawater) contamination monitoring on all cores. At 1645 h, we started pulling the drill string out of the hole. The bit cleared the seafloor at 1700 h and arrived at the rig floor at 2100 h. The vessel was then secured for transit to return to Site U1547 (proposed Site GUAYM-12A). We switched from dynamic positioning to cruise mode at 2130 h, ending Hole U1551B and Site U1551. The thrusters were raised and our sea passage began at 2200 h.
Cores U1546D-31X to 47F have been split and described. They consist of greenish brown diatom clay.
Cores U1551A-1H to 9H have been split and described. Core 1H is dominated by homogenous clay- and nannofossil-rich diatom ooze. Cores 2H and 3H consist of resedimented depositional intervals that include a ~7 m thick megaturbidite. Below the turbidite, tiltled beds, folds, and small faults become a common feature of the cores. Core 3H also contains light-colored intervals composed of micrite and an ~1.5 m thick interval of organic-rich clay. Carbonate concretions and bedding deformation continue through Cores 4H, 5H, and the upper part of Core 6H. Starting around the middle of Core 6H through the bottom of Core 9H, the majority of the sediment is composed of sand and silty sand with rare intercalations of small, clayey, silty layers. Biostratigraphic assessment revealed barren layers or few nannofossil and marine diatom tests only. None of them represents an age-diagnostic species.
Daily Science Report for 2 November 2019
Location:
• Hole U1546D (27°37.8943′N, 111°52.7812′W; water depth 1585.9 mbsl)
• Underway to Site U1551 (proposed Site GUAYM-15A)
• Hole U1551A (27°12.3887′N, 111°13.1943′W; water depth 1844.1 mbsl)
Science Update: We continued coring in Hole U1546D, alternating between the HLAPC and XCB coring tools. Cores 45X to 47F penetrated from 289.0 to 300.1 mbsf and recovered 12.5 m (113%). The XCB coring system was deployed on Core 45X to core through a hard carbonate layer. We pumped perfluorocarbon tracers (PFTs) for drilling fluid (seawater) contamination monitoring on all cores. Upon accomplishing our microbiology sampling objectives in Hole U1546D, we terminated coring at a final depth of 300.1 mbsf. We pulled the drill string out of the hole and the bit cleared the rig floor at 0715 h. We then secured the ship for transit to Site U1551 (proposed Site GUAYM-15A), located ~29 km southeast of the northern axial graben of Guaymas Basin. At 0742 h, we switched from dynamic positioning (DP) to cruise mode, which ended operations in Hole U1546D and thus at Site U1546. Upon completing our ~34 nmi sea passage, we arrived at the Site U1551 coordinates at 1213 h, lowered the thrusters, and switched to DP mode at 1219 h. We then made up an APC/XCB bottom-hole assembly and started lowering the drill string to the seafloor to start APC coring in Hole U1551A. At 1530 h, we picked up the top drive and positioned the bit above the seafloor at a water depth of 1836.8 mbsl. The orientation tool and APC core barrel were installed, and Hole U1551A was spudded at 1700 h. Mudline Core U1551A-1H recovered 2.6 m. This determined a seafloor depth of 1844.1 mbsl. Cores U1551A-1H to 8H penetrated from the seafloor to 53.9 mbsf and recovered 55.2 m (103%).
Cores U1546D-7H to 30H have been split and described. They consist of diatom ooze and clay, showing overall decreasing lamination and increasing bioturbation with predominance of diatom clay from Core 21H onwards. Carbonate-rich indurated intervals and dolostones occur regularly.
Scientists submitted the first draft of their Site U1549 reports.
Daily Science Report for 1 November 2019
Location: Hole U1546D (27°37.8943′N, 111°52.7812′W; water depth 1585.9 mbsl)
Science Update: We continued coring in Hole U1546D, alternating between the APC, HLAPC, and XCB coring tools. Cores 2H to 44F penetrated from 4.0 to 289.0 mbsf and recovered 298.2 m (105%). On Cores 2H to 30H, we primarily deployed the APC coring system and switched to XCB coring whenever we had to drill through hard carbonate layers. This happened on Cores 13X, 26X, and 29X. After APC tool refusal and recovering XCB Core 31X from a depth of 235.5 mbsf at 1735 h, we switched to the HLAPC coring tool that was predominantly deployed from Cores 32F to 44F. The XCB coring system needed to be deployed for breaking through a hard layer on Core 39X. We pumped perfluorocarbon tracers (PFTs) for drilling fluid (seawater) contamination monitoring on all cores.
Cores U1545C-41F to 63F have been split and described. They consist of light olive to olive-gray micrite-rich diatom ooze and diatom clay, as well as silty clay.
Cores U1546D-1H to 6H have been split and described. They consist of alternating finely laminated and homogenous diatom clay and diatom ooze. Soft sediment deformation has occasionally been observed.