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IODP Expedition 391

Walvis Ridge Hotspot


Daily Science Report for 20 January 2022

Location: Underway to proposed Site CT-05A (Site U1578)

Science Update: The vessel completed 259 nmi, and a total of 269 nmi, of the 605 nmi voyage to proposed Site CT-05A (Site U1578) at an average speed of 10.8 kt. The estimated time of arrival on site is 0800 h on 22 January.

Scientists continued to collect, analyze, and write up data from Hole U1577A.


Daily Science Report for 19 January 2022

Location:

  • Hole U1577A (25°12.1439′S, 7°29.8140′E; water depth 3940.2 mbsl; proposed Site VB-13A)
  • Underway to proposed Site CT-05A (Site U1578)

Science Update: RCB coring in Hole U1577A continued. Core U1577A-26R advanced from 193.1 to 193.9 mbsf and recovered 0.35 m (44%) of igneous rock. The cutting of Core 26R was terminated early because we were unable to keep the bit on the bottom of the hole due to inclement weather with up to 5 m of ship heave. Upon stopping coring at 0215 h, we raised the drill string to 148.6 mbsf and inserted an extra knobby drilling joint on top of the drill string and waited for the weather to improve enough to resume operations. After we had spent 10.25 h waiting on the weather to improve, it was decided to terminate operations at Site U1577 given the persistent ship heave and the remaining scientific priorities of the expedition. At 1330 h, we started pulling the drill string out of Hole U1577A. When the drill string reached 104.6 mbsf at 1400 h, we set back the top drive and continued raising the drill string. The bit cleared the seafloor at 1450 h and arrived at the rig floor at 2125 h. The rig floor was secured at 2150 h, ending Site U1577. We then raised the hydrophones and thrusters, switched the vessel from DP to cruise mode, and secured the vessel for transit to proposed Site CT-05A (Site U1578). We began our sea passage to the next drill site at 2300 h, completing 10 nmi of the 605 nmi voyage by the end of the day. The estimated time of arrival on site is 0800 h on 22 January.

Cores U1577A-24R to 26R were split and described. They are made up of a massive lava flow that consists of slightly altered, highly plagioclase-pyroxene phyric basalt with minor olivine phenocrysts.

Scientists continued to collect, analyze, and write up data from Hole U1577A.


Daily Science Report for 18 January 2022

Location: Hole U1577A (25°12.1439′S, 7°29.8140′E; water depth 3940.2 mbsl; proposed Site VB-13A)

Science Update: RCB coring in Hole U1577A continued with half-length (~4.8 m) penetration. Cores U1577A-22R to 25R advanced from 173.7 to 193.1 mbsf and recovered 14.4 m (74%) of igneous rock. We pumped a 20-barrel high-viscosity mud sweep during every core to keep the hole clean.

Cores U1577A-21R to 23R were split and described. They are made up of massive lava flows that consist of slightly altered, highly porphyritic basalt showing plagioclase and pyroxene as the major phenocryst phases with variable predominance. Core 23R also contains minor olivine phenocrysts.

Scientists continued to analyze data from Hole U1576B and submitted the first draft of their Site U1576 reports.


Daily Science Report for 17 January 2022

Location: Hole U1577A (25°12.1439′S, 7°29.8140′E; water depth 3940.2 mbsl; proposed Site VB-13A)

Science Update: RCB coring in Hole U1577A continued with half-length (~4.8 m) penetration for Core U1577A-19R. When we attempted to recover Core 19R at 0400 h, we retrieved only the latch assembly for the upper section of the inner core barrel that was still in place at the end of the drill string. It was discovered that the inner core barrel parted at the swivel assembly. We then deployed a second RCB core barrel and attempted to catch the remaining lower section of the inner core barrel to no avail. A new fishing catcher was built and deployed successfully. After the inner core barrel was recovered at 0800 h, Core 19R was retrieved and repair of the inner core barrel was implemented. Coring operations resumed at 1030 h, leading to recovery of half-length Cores 20R and 21R by the end of the day. Cores U1577A-19R to 21R advanced from 158.9 to 173.7 mbsf and recovered 13.1 m (88%) of igneous rock.

Cores U1577A-10R to 20R were split and described. Cores 10R to 17R consist mainly of bioturbated clayey-nannofossil ooze and chalk with the transition from ooze to chalk observed in Section 10R-4. Occasional intercalations of ash and tuff layers occur in ooze and chalk, respectively. Tuffaceous chalk beds sporadically occur in Cores 16R to 18R. Core 18R recovered a transition from chalk to a hyaloclastite layer that forms the contact to the underlying igneous basement. Calcareous biostratigraphic markers indicate the Santonian/Campanian stage boundary of the Upper Cretaceous at the bottom of the sediment succession in Section 18R-1. The volcanic basement top is marked by a glassy chilled margin. Massive lava flows extend from the bottom of Section 18R-1 through Core 20R, consisting of slightly altered, moderately to highly plagioclase-pyroxene phyric basalt with minor olivine phenocrysts.

Scientists continued to collect, analyze, and write up data from Hole U1576B.


Daily Science Report for 16 January 2022

Location: Hole U1577A (25°12.1439′S, 7°29.8140′E; water depth 3940.2 mbsl; proposed Site VB-13A)

Science Update: RCB coring in Hole U1577A continued. Cores U1577A-7R to 18R advanced from 56.6 to 158.9 mbsf and recovered 83.9 m (82%) of sediment and igneous rock. The sediment/basement contact was intersected in Core 18R at a depth of 154.8 mbsf.

Cores U1577A-2R to 9R were split and described. They consist of nannofossil ooze to clayey-nannofossil ooze with occasional foraminifera or bioclasts and sporadically intercalated ash layers. Calcareous biostratigraphic markers indicate the early Campanian stage of the Upper Cretaceous at the base of Core 9R.

Scientists continued to collect, analyze, and write up data from Hole U1576B.


Daily Science Report for 15 January 2022

Location:

  • Underway to proposed Site VB-13A (Site U1577)
  • Hole U1577A (25°12.1439′S, 7°29.8140′E; water depth 3940.2 mbsl; proposed Site VB-13A)

Science Update: Upon completing the final 84 nmi of the 134 nmi transit from Site U1576 to proposed Site VB-13A (Site U1577), we arrived on site at 0754 h and started lowering the thrusters. When all thrusters were down and secured at 0814 h, we switched from cruise mode to DP mode. At 0815 h, the rig floor was cleared for operations. After the RCB BHA was made up, we began lowering the drill string to the seafloor while offsetting the ship 90 m eastward from the original site coordinates to a new location for Hole U1577A. We picked up the top drive at 1630 h and positioned the drill bit just above the seafloor depth of 3940.2 mbsl as obtained from the PDR. After RCB core barrels were dressed and one core barrel was lowered to the end of the drill string, we spudded Hole U1577A at 1710 h and began coring. RCB Cores U1577A-1R to 6R advanced from the seafloor to 56.6 mbsf and recovered 41.1 m (73%) of sediment.

Core U1577A-1R was split and described. It consists of an alternation of nannofossil ooze with clay and foraminifera-nannofossil ooze, including occasional intercalations of calcareous clayey sand with volcaniclasts. Calcareous biostratigraphic markers indicate an early Paleocene age (<59.2 Ma) at the base of Core 1R.

Scientists continued to collect, analyze, and write up data from Hole U1576B.


Daily Science Report for 14 January 2022

Location:

  • Hole U1576B (24°35.7711′S, 5°7.5513′E; water depth 3027.2 mbsl; proposed Site VB-14A)
  • Underway to proposed Site VB-13A (Site U1577)

Science Update: RCB coring in Hole U1576B continued. Cores U1576B-15R to 17R penetrated from 430.8 to 450.3 mbsf and recovered 17.3 m (89%) of sediment and igneous rock. After retrieving full-length Core 15R, the last two cores each made half-length (~4.8 m) advances. We pumped a 20-barrel high-viscosity mud sweep during Core 15R for hole cleaning. Upon recovering Core 17R at 1040 h, we terminated coring in Hole U1576B at a final depth of 450.3 mbsf and secured the coring equipment. At 1100 h, we started pulling the drill string out of the hole. After the top drive was set back at 1200 h, we continued pulling the drill string up to the surface. The bit cleared the seafloor at 1305 h and arrived at the rig floor at 1820 h, ending Hole U1576B. The rig floor was secured at 1915 h, ending Site U1576. We then raised the thrusters, switched the vessel from DP to cruise mode, and secured the vessel for transit to proposed Site VB-13A (Site U1577). We began our sea passage to the next drill site at 1942 h, completing 50 nmi of the 134 nmi voyage by the end of the day.

Cores U1576B-13R to 17R were split and described. They are made up of an alternation of mafic volcanic and sedimentary rocks. The latter occur as up to several meter thick interbeds in Cores 13R to 16R, consisting of foraminifera-nannofossil chalk or limestone with clay, sand, or ash. There are occasional intercalations of calcareous silty sandstone, volcanic sandstone, or siliceous chalk. Cores 13R and 14R contain minor pillow lava flows and a single massive lava flow that extends to Section 14R-2. These lavas consist of slightly to highly altered, sparsely to moderately plagioclase phyric basalt with minor pyroxene phenocrysts. The bottom of Core 14R as well as Cores 16R and 17R contain aphanitic to porphyritic pillow lava and hypo- to holocrystalline sheet lava flows made up of basalts, showing glassy margins and slightly to highly altered, sparsely plagioclase-pyroxene phyric interiors.

Scientists continued to collect, analyze, and write up data from Hole U1576A.


Daily Science Report for 13 January 2022

Location: Hole U1576B (24°35.7711′S, 5°7.5513′E; water depth 3027.2 mbsl; proposed Site VB-14A)

Science Update: RCB coring in Hole U1576B continued. Half-length (~4.8 m) Cores U1576B-9R to 14R penetrated from 401.6 to 430.8 mbsf and recovered 22.8 m (78%) of sediment and igneous rock. We pumped 20-barrel high-viscosity mud sweeps on every other core to keep the hole clean.

Cores U1576B-7R to 12R were split and described. They are made up of an alternation of mafic volcanic and sedimentary rocks. The latter occur as decimeter to meter thick interbeds in Cores 7R, 8R, and 12R, consisting of lithified foraminifera-nannofossil chalk or breccia intercalated with calcareous silty sandstone. Cores 7R to 9R contain pillow lava flows that are characterized by (glassy) chilled margins at the sediment contact. Section 9R-2 includes a contact between pillow lava and underlying massive lava. The latter is a single flow that extends through Core 12R. All lava flows consist of slightly to highly altered, hyaline to aphyric basalt.

Scientists continued to collect, analyze, and write up data from Hole U1576A.


Daily Science Report for 12 January 2022

Location: Hole U1576B (24°35.7711′S, 5°7.5513′E; water depth 3027.2 mbsl; proposed Site VB-14A)

Science Update: We continued drilling without core recovery in Hole U1576B, washing down from 121.7 mbsf to the target depth of 365.0 mbsf with a core barrel in place. At 0655 h, we retrieved the core barrel. It contained some sediment unintentionally recovered at an indeterminable depth while drilling, and was recorded as wash Core U1576B-1W. Half-length (~4.8 m) RCB coring began. Cores U1576B-2R to 8R penetrated from 365.0 to 401.6 mbsf and recovered 26.2 m (72%) of sediment and igneous rock. The first contact with igneous rock occurred on Core 5R at a depth of 385.4 mbsf. A final round of routine COVID-19 antigen testing was administered for all personnel, and all results were negative. Following 14 days of shipboard COVID-19 mitigation protocols at sea, the safety measures were lifted at 1354 h.

Cores U1576B-2R to 6R were split and described. Cores 2R to 4R and most of Core 5R consist of an intercalation of lithified, bioturbated foraminifera-nannofossil chalk with clay and calcareous silty sandstone with volcaniclasts. Siliceous chalk layers and turbidite sequences occur occasionally. Section 5R-3 contained the contact between sediment and mafic igneous rock. Pillow lava flows extend from the bottom of Section 5R-3 through Core 6R. They consist of slightly to highly altered, glassy to aphyric basalt that shows rare microphenocrysts of plagioclase and minor pyroxene.

Scientists continued to collect, analyze, and write up data from Hole U1576A.


Daily Science Report for 11 January 2022

Location:

  • Hole U1576A (24°35.7520′S, 5°7.3163′E; water depth 3032.3 mbsl; proposed Site VB-14A)
  • Hole U1576B (24°35.7711′S, 5°7.5513′E; water depth 3027.2 mbsl; proposed Site VB-14A)

Science Update: The attempts to deplug the drill bit and clear the outer core barrel continued. After we were repeatedly unable to get the inner core barrel to latch, the efforts on clearing the outer core barrel were abandoned. At 0500 h, we removed the sinker bars and started pulling the drill string out of Hole U1576A. The top drive was set back at 0615 h and the bit cleared the seafloor at 0730 h. While we were pulling up the drill string, the vessel moved 400 m at 95° to the location of Hole U1576B. The bit arrived at the rig floor at 1230 h, ending Hole U1576A. We found 1.2 m of core material clogging up the outer core barrel and bit, which were cleared out. We then made up the RCB BHA again and started lowering the bit back to the seafloor. When the drill string was lowered to 3000.8 mbsl, we picked up the top drive at 1930 h. The bit was then positioned at the seafloor depth of 3027.2 mbsl as obtained from the PDR. At 2050 h, we spudded Hole U1576B and began drilling without core recovery, advancing from the seafloor to 121.7 mbsf by the end of the day. Shipboard COVID-19 mitigation protocols continue to be followed.

Cores U1576A-26R to 41R were split and described. Cores 26R to 39R and most of Core 40R consist of consolidated to lithified, bioturbated foraminifera-nannofossil chalk that is occasionally intercalated with foraminifera siltstone, volcanic silty sandstone, and siliceous chalk layers toward the bottom of this succession. Turbidite sequences occur sporadically. Calcareous biostratigraphic markers indicate the early to middle Campanian stage of the Upper Cretaceous at the sediment/basement contact recovered at the bottom of Section 40R-3. The basement top is marked by a completely altered, highly porphyritic basalt that shows pseudomorphic plagioclase and pyroxene phenocrysts. Sections 40R-4 and 40R-5 are made up of highly to completely altered, aphyric to highly phyric basalt with the same phenocryst assemblage as found in Section 40R-3. Core 41R consists of slightly to moderately altered, aphyric basalt with rare microphenocrysts of plagioclase and pyroxene. The mafic volcanic rocks of Cores 40R and 41R were deposited as pillow and sheet lava flows.

Scientists continued to analyze data from Hole U1575A and submitted the first draft of their Site U1575 reports.


Daily Science Report for 10 January 2022

Location: Hole U1576A (24°35.7520′S, 5°7.3163′E; water depth 3032.3 mbsl; proposed Site VB-14A)

Science Update: RCB coring in Hole U1576A continued. Cores U1576A-36R to 41R penetrated from 338.3 to 396.6 mbsf and recovered 28.4 m (49%) of sediment and igneous rock. The sediment/basement contact was intersected in Core 40R at a depth of 380.2 mbsf. An unusual, highly variable standpipe pressure was observed while cutting Core 41R. After this core was recovered at 1635 h, an investigation revealed a sheared latch on the core barrel and a plugged outer core barrel in the BHA. We pumped out the blockage from the outer core barrel, applying high pressure. A bit deplugger was then deployed multiple times to verify that the outer core barrel was clear. The attempt to continue coring with Core 42R proved unsuccessful when we recovered an empty core barrel from a depth of 398.1 mbsf at 2305 h. We then continued remediation measures through the end of the day.

Routine COVID-19 antigen testing continued for all personnel, and all results were negative. Shipboard COVID-19 mitigation protocols are being followed.

Cores U1576A-12R to 25R were split and described. Cores 12R to 15R consist of bioturbated foraminifera-nannofossil ooze with clay and sporadic volcaniclastic granules. Starting in Core 16R, the sediment is predominantly consolidated. Cores 16R to 25R consist mainly of bioturbated foraminifera-nannofossil chalk with clay and subordinate volcaniclastic material. Altered ash layers are occasionally present. Minor foraminifera-nannofossil sandy claystone layers are intercalated. Calcareous biostratigraphic markers indicate the late Campanian stage of the Upper Cretaceous at the base of Core 25R.

Scientists continued to analyze data from Hole U1575A and prepare their Site U1575 reports. The laboratory groups presented their Site U1575 results at the science summary meeting.


Daily Science Report for 9 January 2022

Location: Hole U1576A (24°35.7520′S, 5°7.3163′E; water depth 3032.3 mbsl; proposed Site VB-14A)

Science Update: RCB coring in Hole U1576A continued. Cores U1576A-9R to 35R penetrated from 75.4 to 338.3 mbsf and recovered 262.9 m (84%) of sediment. Shipboard COVID-19 mitigation protocols continue to be followed.

Cores U1576A-4R to 11R were split and described. Cores 4R to 10R and the top of Core 11R consist of nannofossil-foraminifera ooze. The remainder of Core 11R consists of foraminifera-nannofossil ooze with clay, containing one thin volcaniclastic sand layer. Calcareous biostratigraphic markers indicate an early Paleocene age (<63 Ma) at the base of Core 11R.


Daily Science Report for 8 January 2022

Location:

  • Underway to proposed Site VB-14A (Site U1576)
  • Hole U1576A (24°35.7529′S, 5°7.3151′E; water depth 3032.3 mbsl; proposed Site VB-14A)

Science Update: After completing the final 85 nmi of the 183 nmi transit from Site U1575 to proposed Site VB-14A (Site U1576), we arrived on site at 0748 h and started lowering the thrusters. When all thrusters were down and secured at 0809 h, we switched from cruise mode to DP mode. At 0812 h, the rig floor was cleared for operations. After the RCB BHA was made up, we began lowering the drill string to the seafloor at 0915 h. Upon implementing a routine cut and slip of 115 feet of the drilling line, we picked up the top drive at 1500 h and positioned the drill bit at the seafloor depth of 3032.3 mbsl as obtained from the PDR. At 1640 h, we spudded Hole U1576A and began coring. RCB Cores U1576A-1R to 8R advanced from the seafloor to 75.4 mbsf and recovered 60.7 m (81%) of sediment. Routine COVID-19 antigen testing continued for all personnel, and all results were negative. Shipboard COVID-19 mitigation protocols are being followed.

Cores U1576A-1R to 3R were split and described. They consist of nannofossil-foraminifera ooze. Calcareous biostratigraphic markers indicate an early Pleistocene age (<1.6 Ma) at the base of Core 3R.


Daily Science Report for 7 January 2022

Location:

  • Hole U1575A (21°51.9659′S, 6°35.4369′E; water depth 3231.3 mbsl; proposed Site FR-01B)
  • Underway to proposed Site VB-14A (Site U1576)

Science Update: We continued RCB coring in Hole U1575A. Full-length Cores U1575A-39R to 41R penetrated from 303.1 to 332.3 mbsf and recovered 11.4 m (39%) of igneous rock. We pumped 20-barrel high-viscosity mud sweeps on every core to keep the hole clean. After recovering Core 41R, coring was terminated in Hole U1575A at a final depth of 332.3 mbsf. At 0700 h, we started pulling the drill string out of the hole. The bit cleared the seafloor at 0842 h and arrived at the rig floor at 1430 h, ending Hole U1575A and Site U1575. The rig floor was secured by 1445 h. We then raised the thrusters, switched from DP to cruise mode, and secured the vessel for transit to proposed Site VB-14A (Site U1576). We began our sea passage to the next drill site at 1515 h, completing 98 nmi of the 183 nmi voyage by the end of the day. Shipboard COVID-19 mitigation protocols continue to be followed.

Cores U1575A-36R to 41R were split and described. Cores 36R to 38R and the top of Core 39R consist of one massive holocrystalline lava flow that is made up of unaltered to slightly altered, highly plagioclase-pyroxene phyric basalt. Sections 39R-2 and 39R-3 show an intercalation of pillow lava flows and foraminifera-bearing nannofossil limestone. The pillow lavas consist of slightly altered, moderately plagioclase-pyroxene-olivine phyric basalt with glassy margins. Two massive holocrystalline lava flows extend from the bottom of Section 39R-3 through Core 41R, consisting of unaltered to moderately altered, sparsely to highly plagioclase-pyroxene phyric basalt with minor olivine phenocrysts.


Daily Science Report for 6 January 2022

Location: Hole U1575A (21°51.9659′S, 6°35.4369′E; water depth 3231.3 mbsl; proposed Site FR-01B)

Science Update: RCB coring in Hole U1575A continued. Cores U1575A-36R to 38R penetrated from 283.7 to 303.1 mbsf and recovered 13.7 m (71%) of igneous rock. We switched from full-length (~9.6 m) to half-length (~4.8 m) coring with Core 37R. We pumped 20-barrel high-viscosity mud sweeps on every core to keep the hole clean. Daily COVID-19 antigen testing continued for all personnel, and all results were negative. Shipboard COVID-19 mitigation protocols continue to be followed.

Cores U1575A-32R to 35R were split and described. They show a sequence of alternating sheet and pillow lava flows. The sheet lavas consist of unaltered to slightly altered, highly plagioclase-olivine-pyroxene phyric basalt. The pillow lavas are made up of slightly altered, aphanitic to sparsely plagioclase-olivine-pyroxene phyric basalt with glassy margins.


Daily Science Report for 5 January 2022

Location: Hole U1575A (21°51.9659′S, 6°35.4369′E; water depth 3231.3 mbsl; proposed Site FR-01B)

Science Update: RCB coring in Hole U1575A continued. Cores U1575A-31R to 35R penetrated from 254.5 to 283.7 mbsf and recovered 16.3 m (56%) of igneous rock. We switched from half-length (~4.8 m) to full-length (~9.6 m) coring with Core 35R. We pumped 20-barrel high-viscosity mud sweeps on every core to keep the hole clean. Daily COVID-19 antigen testing continued for all personnel, and all results were negative. Enhanced shipboard COVID-19 mitigation protocols continue to be followed.

Cores U1575A-26R to 31R were split and described. Cores 26R to 28R are made up of massive holocrystalline lava flows consisting of unaltered to slightly altered, highly plagioclase-olivine-pyroxene phyric basalt. Cores 29R to 31R show a sequence of alternating sheet and pillow lava flows. The sheet lavas consist of unaltered to slightly altered, highly plagioclase-olivine-pyroxene phyric basalt. The pillow lavas consist of slightly altered, aphanitic to sparsely plagioclase-olivine-pyroxene phyric basalt with glassy margins.

Further examination of calcareous biostratigraphic markers for the sediment/basement contact recovered in Section 22R-5 places the bottom of the sedimentary sequence in the Campanian stage of the Upper Cretaceous.


Daily Science Report for 4 January 2022

Location: Hole U1575A (21°51.9659′S, 6°35.4369′E; water depth 3231.3 mbsl; proposed Site FR-01B)

Science Update: RCB coring in Hole U1575A continued. Half-length (~4.8 m) Cores U1575A-26R to 30R penetrated from 229.0 to 254.5 mbsf and recovered 16.1 m (63%) of igneous rock. Daily COVID-19 antigen testing continued for all personnel, and all results were negative. Enhanced shipboard COVID-19 mitigation protocols continue to be followed.

Cores U1575A-21R to 25R were split and described. Core 21R consists of pale brown foraminifera clayey to silty sandstone with nannofossils. Core 22R consists mainly of alternating pink to reddish brown foraminifera-nannofossil chalk and nannofossil silty claystone with foraminifera, including sporadic bioclasts and a thin volcaniclastic silt layer. Calcareous biostratigraphic markers indicate the Maastrichtian stage of the Upper Cretaceous at the sediment/basement contact recovered at the bottom of Section 22R-5. The basement top is marked by a glassy chilled margin of a basaltic lava flow. Section 22R-6 and Cores 23R to 25R are made up of massive lava flows consisting of slightly altered, highly plagioclase phyric basalt with minor phenocrysts of olivine and pyroxene.


Daily Science Report for 3 January 2022

Location: Hole U1575A (21°51.9659′S, 6°35.4369′E; water depth 3231.3 mbsl; proposed Site FR-01B)

Science Update: We continued RCB coring in Hole U1575A. Cores U1575A-16R to 25R advanced from 145.4 to 229.0 mbsf and recovered 34.0 m (41%) of sediment and igneous rock. The sediment/basement contact was intersected on Core 22R at a depth of 209.9 mbsf. Daily COVID-19 antigen testing continued for all personnel, and all results were negative.

Cores U1575A-6R to 20R were split and described. They consist of nannofossil-foraminifera ooze with radiolarians. Calcareous biostratigraphic markers indicate a late Miocene age (<9.75 Ma) at the base of Core 20R. Enhanced shipboard COVID-19 mitigation protocols continue to be followed.


Daily Science Report for 2 January 2022

Location: Hole U1575A (21°51.9660′S, 6°35.4360′E; water depth 3231.3 mbsl; proposed Site FR-01B)

Science Update: We continued lowering the drill string at Site U1575, reaching a water depth of 3193.9 mbsl by 0745 h. We then picked up the top drive and pumped a “pig” (pipe cleaning device) through the drill string to remove some of the rust. The drill bit was lowered further and positioned at the seafloor depth of 3231.3 mbsl as obtained from the precision depth recorder (PDR). At 1015 h, we spudded Hole U1575A and began coring. RCB Cores U1575A-1R to 15R advanced from the seafloor to 145.4 m below seafloor (mbsf) and recovered 93.6 m (64%) of sediment. Daily COVID-19 antigen testing continued for all personnel, and all results were negative.

Cores U1575A-1R to 5R were split and described. They consist of nannofossil-foraminifera ooze with radiolarians. Calcareous biostratigraphic markers indicate a late Pliocene age (<3.6 Ma) at the base of Core 5R. Enhanced shipboard COVID-19 mitigation protocols continue to be followed.


Daily Science Report for 1 January 2022

Location:

  • Underway to proposed Site FR-01B (Site U1575)
  • Hole U1575A (21°51.9660′S, 6°35.4360′E; water depth 3231.3 mbsl; proposed Site FR-01B)

Science Update: After completing the final 258 nmi of the 967 nmi voyage from Cape Town, South Africa, to proposed Site FR-01B (Site U1575), we arrived on site at 2100 h and started lowering the thrusters. When all thrusters were down and secured at 2138 h, we switched from cruise mode to DP mode. At 2145 h, the rig floor was cleared for operations. The RCB BHA was made up and lowered to 161.1 m below sea level (mbsl) by the end of the day. Daily COVID-19 antigen testing continued for all personnel, and all results were negative.

The science party completed setting up laboratory instruments and final preparation meetings were held in anticipation of the first core on deck. Enhanced shipboard COVID-19 mitigation protocols continue to be followed.