IODP Expedition 397T
Transit and Return to Walvis Ridge Hotspot
Daily Science Report for 23 September 2022
Location: Hole U1585A (30°10.0160′S, 1°10.6491′E; water depth 3457 mbsl; proposed Site TT-04A)
Science Update: Core U1585A-39R was retrieved from 489.2 to 498.8 mbsf and recovered 5.76 m of 9.6 m cored (60% recovery). At 0615 h we began retrieving the drill string and the bit cleared the rig floor at 1555 h, ending Hole U1585A. The drill floor was secured, the thrusters raised, and the voyage to Lisbon, Portugal began at 1715 h. By midnight we had completed 77 nmi of the 4458 nmi voyage.
Cores 33R through 39R consist of sparsely to highly phyric basalt with varying proportions of pyroxene, plagioclase, and rare olivine phenocrysts. The interval is interpreted as one or more massive lava flows.
The plan for the small science party on board is to use the next two weeks underway to Lisbon to complete all shipboard measurements, refine core descriptions, share all shipboard data with the full Expedition 391 project team, write site reports, and negotiate and extract samples from Hole U1584A and U1585A cores for shorebased studies by the project team.
Daily Science Report for 22 September 2022
Location: Hole U1585A (30°10.0160′S, 1°10.6491′E; water depth 3457 mbsl; proposed Site TT-04A)
Science Update: Cores U1585A-35R through 38R were retrieved from 450.8 to 489.2 mbsf and recovered 38.8 m of 38.4 m cored, with an average recovery of 101%. The hole was swept with 30 barrels of sepiolite mud after Core 35R (470.0 mbsf).
Core 30R and the upper half of Core 31R consist of reddish breccia-conglomerate with highly altered basalt clasts. In the top of Core 30R, an exceptionally large clast (>60 cm) was recovered. At ~408 mbsf (Core 31R), and through Core 38R, we finally penetrated and recovered ~80 m of massive basalt. The basalt in Cores 31R and 32R described so far is sparsely to highly olivine phyric, moderately pyroxene phyric, and moderately pyroxene-plagioclase phyric. A thin chilled margin is present at the top of the basalt, and veins and vesicles are present in some intervals.
Daily Science Report for 21 September 2022
Location: Hole U1585A (30°10.0160′S, 1°10.6491′E; water depth 3457 mbsl; proposed Site TT-04A)
Science Update: Cores U1585A-28R through 32R were retrieved from 383.6 to 450.8 mbsf and recovered 45.2 m of 67.2 m cored, with recovery ranging from 11% to 95% (average 67%). Hard rock drilling rates were encountered from Core 31R downwards. The hole was swept with 30 barrels of sepiolite mud after Cores 29R (402.8 mbsf) and 32R (431.6 mbsf).
Cores 23R through 29R consist of alternations of dark green, greenish-gray, reddish-brown, and dark brown intervals of cm to several dm thick basaltic breccia-conglomerate, laminated basaltic sand (coarse ash) layers, and fine-grained silt-clay (fine ash) intervals. The redder the sediment the more severely altered the clasts. The fine-grained intervals typically are mottled and fossiliferous, whereby the fossil fragments are severely recrystallized or altered to clay. The succession is tentatively interpreted as a series of mass-wasting deposits.
At midnight, we had completed the mandated 6 days of COVID mitigation that started after the last recorded positive case on board was quarantined, as per COPE protocol. This ends the daily COVID testing, and wearing of masks will no longer be mandatory.
Daily Science Report for 20 September 2022
Location: Hole U1585A (30°10.0160′S, 1°10.6491′E; water depth 3457 mbsl; proposed Site TT-04A)
Science Update: Cores U1585A-16R through 27R were retrieved from 268.4 to 383.6 mbsf and recovered 72.0 m of 115.2 m cored, with recovery ranging from 26% to 100% (average 62%). The hole was swept with 30 barrels of sepiolite mud seven times, after every one or two cores.
The top half-meter of Core U1585A-15R is the basal continuation of the volcanic breccia in Core 14R, which we tentatively interpret as a hyaloclastite grading upwards into mass-wasted breccia. Below that interval, Cores 15R through 22R consist mostly of gray, light and dark grayish-brown, dark greenish-gray, and bluish-gray fine-grained sediment that is variably calcareous, displays dark-light cycles with smooth color transitions, and recrystallized microfossils in the lightest intervals. Some intervals have a homogeneous and featureless appearance whereas others are pervasively mottled as a result of bioturbation in the variegated sediments. These pelagic sediments have a few intervals with small-scale faults and in situ breccia, and are interlayered with a 1.4 m thick volcanic breccia unit in Cores 18R–19R and several thin volcanic breccia layers in Core 21R.
COVID-19 mitigation protocols continue to be followed with mask wearing, social distancing, and antigen testing of all personnel.
Daily Science Report for 19 September 2022
Location: Hole U1585A (30°10.0160′S, 1°10.6491′E; water depth 3457 mbsl; proposed Site TT-04A)
Science Update: Cores U1585A-6R through 15R were retrieved from 172.4 to 268.4 mbsf and recovered 48.5 m of 96.0 m cored, with recovery ranging from 25% to 87% (average 51%). The driller noted a hard tag at 250 mbsf, followed by a drilling break at 262 mbsf. The hole was swept with 30–40 barrels of sepiolite mud after Cores 7R (191.6 mbsf), 10R (220.4 mbsf), and 13R (249.2 mbsf).
Core U1585A-6R and the upper part of Core 7R consist of massive lapillistone. From the lower part of Core 7R through Core 11R, the lapillistone layers grade into tuff layers that are typically finely laminated and often display ripples and cross-bedding, forming fining-upward sequences on the order of 1 m thick. Cores 9R and 10R have ~2 m thick light tan, chalky layers with nanofossils. From Cores 11R through 13R, volcanic breccia with basalt and tuff rip-up clasts, and lapilli/tuff matrix becomes more prevalent. Core 14R, with a top depth of 249 mbsf corresponding to the driller’s observation of a hard tag, contains a 6 m thick massive basalt breccia unit with green-reduced tuff matrix in the lower part and red-oxidized matrix in the upper part.
COVID-19 mitigation protocols continue to be followed with mask wearing, social distancing, and antigen testing of all personnel.
Daily Science Report for 18 September 2022
Location: Hole U1585A (30°10.0160′S, 1°10.6491′E; water depth 3457 mbsl; proposed Site TT-04A)
Science Update: We continued to lower the drill string from 3416.4 mbrf to just above the seafloor based on the PDR signal. Next we picked up the top drive, pumped the “pig” to clear the newly installed pipe from potential rust and other obstructions, dropped the RCB barrel, and began to spud Hole U1585A. The first attempt advanced from 3450 to 3459.7 mbrf. No tag was observed and the barrel returned empty. On the second attempt from 3459.7 to 3469.4 mbrf the driller observed a tag at 3468.5 mbrf. The barrel again returned empty; however, it showed evidence of contact in the coring shoe. At 0340 h we declared the seafloor depth at 3468.5 mbrf. At 0430 h a wash barrel was dropped, followed by a center bit, and we drilled ahead to 144.1 mbsf. The wash barrel and center bit were retrieved and a 30 barrel sepiolite mud sweep was conducted. At 1815 h, the core barrel was dropped and coring began. Cores U1585A-3R through 5R from 144.1 to 172.4 mbsf recovered 13.2 m of 28.3 m cored, with recovery ranging from 12% to 60% (average 47%).
Core U1585A-3R and the upper 4 m of Core 4R consist of bioturbated tan chalk. The lower part of Core 4R and all of Core 5R consist of massive lapillistone with coarse ash tuff matrix, and a few fine-ash tuff layers that in some cases are laminated.
COVID-19 mitigation protocols continue to be followed with mask wearing, social distancing, and antigen testing of all personnel.
Daily Science Report for 17 September 2022
Location: Hole U1585A (30°10.0160′S, 1°10.6491′E; water depth 3457 mbsl; proposed Site TT-04A)
Science Update: We retrieved the drill string from Hole U1584A, with the bit clearing the rig floor at 0605 h. The rig floor was secured, the thrusters were raised, and we departed Site U1584 at 0700 h. We completed the 111 nmi transit to Site U1585 (proposed site TT-04A) at a speed of 11.4 kt and arrived at 1615 h. Dynamic positioning (DP) mode was established and we were ready for operations at 1650 h. A bit and bit sub were made up to the RCB BHA, which was deployed to 3416.4 mbrf by midnight.
COVID-19 mitigation protocols continue to be followed with mask wearing, social distancing, and antigen testing of all personnel.
Daily Science Report for 16 September 2022
Location: Hole U1584A (31°20.3217′S, 2°50.2205′E; water depth 2304.8 mbsl; proposed Site GT-06A)
Science Update: We completed drilling the interval from 28.1 to 141.8 without coring and retrieved the center bit and wash barrel. We switched to coring and retrieved Cores U1584A-3R through 9R from 141.8 to 208.2 mbsf, with core recovery ranging from 0% to 95% (average 36%). The hole was swept with 30 barrels of mud after Cores 5R (170 mbsf) and 9R (208.2 mbsf).
We decided to abandon Site U1584 at this point because the seismic basement reflector was the top of a potentially thick succession of volcaniclastic sediments rather than the targeted basaltic lava flows.
Cores U1584A-3R to 5R consist of bioturbated clay to fine sand size material, ranging from tan mud in Core 3R to gray sandy mud in Core 4R and reddish-brown sandy mud in Core 5R. Based on the abundance of black opaque and lithic grains, particularly in Cores 5R and 6R, the bulk of this material is of volcanic origin. Core 6R was lost in the coring process and had no recovery. Cores 7R through 10R consist of polymict volcanic breccia-conglomerate or lapillistone with mostly fine pebble-size (lapilli) clasts, occasional large pebble-size basalt clasts, and conspicuous black mineral grains in the sandy matrix.
COVID-19 mitigation protocols continue to be followed with mask wearing, social distancing, and antigen testing of all personnel.
Daily Science Report for 15 September 2022
Location: Hole U1584A (31°20.3217′S, 2°50.2205′E; water depth 2304.8 mbsl; proposed Site GT-06A)
Science Update: At 0200 h the ship’s clock was set back one hour to UTC + 1 h, which will be our local time for the remainder of the expedition. We completed the final 110 nmi of the 810 nmi voyage from Cape Town and arrived at Site U1584 (proposed Site GT-06A) at 0830 h. The thrusters were deployed and a drill string with a rotary core barrel (RCB), bottom-hole assembly (BHA), and a C-4 coring bit was made up. At 1630 h the top drive was engaged and a “pig” was deployed to clear potential rust and other obstructions from the drill pipe. We estimated the seafloor at 2313 meters below rig floor (mbrf) based on the corrected precision depth recorder (PDR) signal. At 1800 h the first core barrel was dropped from 2310 mbrf and the liner returned empty. The driller had observed a tag at 2316 mbrf while lowering the core barrel. For the second attempt, the barrel was dropped from 2316 mbrf. The liner returned empty again except for sediment residue smeared all along its length, indicating that the barrel had penetrated the formation but couldn’t hold the sediment. At 2005 h we declared the seafloor depth at 2315.9 mbrf and deployed the core barrel with a center bit in place. The center bit had to be deployed a second time because no indication of landing was detected the first time. We started to drill down without coring to the target at 145 meters below seafloor (mbsf) and reached 28.1 mbsf by midnight.
COVID-19 mitigation protocols continue to be followed with mask wearing, social distancing, and antigen testing of all personnel.
Daily Science Report for 14 September 2022
Location: Underway to proposed Site GT-06A
Science Update: Today we completed 277 nmi for a total of 700 nmi of the 810 nmi voyage to proposed Site GT-06A. Our expected time of arrival is 0900 h on 15 September. The scientists and JRSO technicians attended a series of planning meetings to clarify shipboard laboratory measurement objectives and sampling strategies.
COVID-19 mitigation protocols continue to be followed with mask wearing, social distancing, and antigen testing of all personnel.
Daily Science Report for 13 September 2022
Location: Underway to proposed Site GT-06A
Science Update: Today we completed 272 nmi for a total of 423 nmi of the 810 nmi voyage to proposed Site GT-06A. Our expected time of arrival is late morning of 15 September. All scientists and JRSO key personnel attended the pre-spud meeting to review planned operations at proposed Site GT-06A. The first boat drill was held.
COVID-19 mitigation protocols were followed with mask wearing, social distancing, and antigen testing of all personnel.
Daily Science Report for 12 September 2022
Location: Underway to proposed Site GT-06A
Science Update: One more JRSO staff member came on board before the pilot boarded and the ship departed Cape Town at 1018 h. By midnight we had completed 151 nmi of the 810 nmi transit to proposed Site GT-06A. Our expected time of arrival is late morning of 15 September.
Daily Science Report for 11 September 2022
Location: Duncan Dock E, Cape Town, South Africa
Science Update: Port call activities continued, including the loading of 500 mt of fuel and fresh food. All shipboard personnel received another COVID-19 PCR test. COVID mitigation protocols continue to be followed.
The expected time of departure is tomorrow at 1000 h local time.
Daily Science Report for 10 September 2022
Location: Duncan Dock E, Cape Town, South Africa
Science Update: IODP Expedition 397T, Transit and Return to Walvis Ridge Hotspot, officially began in the port of Cape Town, South Africa, at 0800 h. All oncoming Expedition 397T personnel, including JRSO staff and scientists, moved onto the ship following a four day hotel quarantine. The quarantine included a PCR and an antigen test according to the COVID-19 mitigation protocol. Once aboard, all shipboard personnel received another COVID-19 PCR test. All tests have been negative so far.
The Expedition 397T science party consists of eight members of the larger Expedition 391 science party (project team), and the JRSO Expedition Project Manager (EPM). Two scientists who did not sail on Expedition 391 received required laboratory safety training. The scientists and JRSO technicians had already held a virtual kickoff meeting during the hotel quarantine, where they received a science overview from the Co-Chief Scientist, and discussed shipboard measurements, sampling strategies, and outreach plans.