IODP Expedition 382
Iceberg Alley and Subantarctic Ice and Ocean Dynamics
Daily Science Report for 19 May 2019
Location: Prat Terminal, Punta Arenas, Chile
Science Update: Today we travelled 144 nmi at an average speed of 7.9 kt. The pilot boarded at 0754 h near the entrance to the Straits of Magellan and we proceeded to Prat Terminal, Punta Arenas, Chile. The first line went ashore at 1530 h, ending Expedition 382.
Daily Science Report for 18 May 2019
Location: In transit to Punta Arenas, Chile
Science Update: Today we travelled 190 nmi at an average speed of 7.9 kt. There are 144 nmi remaining to Punta Arenas, Chile.
The science party finalized the site reports for the expedition.
Daily Science Report for 17 May 2019
Location: In transit to Punta Arenas
Science Update: Today we travelled 250 nmi at an average speed of 10.4 kt. There are 334 nmi remaining to Punta Arenas, Chile. Our course took us over the first two sites of the expedition, Sites U1534 and U1535. At 0930 h we slowed to 5 kt to make a single east–west 3.5 kHz subbottom profiler survey over the sites. The survey recorded reflections down to about 70 mbsf, and the profile will help to correlate the stratigraphies between the two sites. The survey was completed at 1100 h and we resumed normal speed.
The science party continued to work on Site U1538 reports and discuss postexpedition research plans.
Daily Science Report for 16 May 2019
Location: In transit to Punta Arenas
Science Update: Today we travelled 245 nmi at an average speed of 10.2 kt. There are 584 nmi remaining to Punta Arenas, Chile.
The science party continued to work on Site U1538 reports and discuss postexpedition research plans.
Daily Science Report for 15 May 2019
Location: In transit to Punta Arenas
Science Update: Today we completed 141 nmi of the 1045 nmi sea voyage from Site U1538 to Punta Arenas at an average speed of 5.9 kt. 816 nmi remain to reach Punta Arenas.
The science party met to present and discuss the initial results from Site U1538.
Daily Science Report for 14 May 2019
Location: In transit to Punta Arenas
Science Update: Having completed operations at Site U1538, we started the sea voyage at 0000 h. We had to leave Site U1538 earlier than planned because of deteriorating weather and sea conditions. This earlier departure briefly opened a short time window to core an additional ~100 m at Site U1534 drilled earlier in the expedition, which lies almost directly along the course from Site U1538 to Punta Arenas. However, headwinds slowed our progress to the extent that we no longer had time to carry out this plan, so we are proceeding directly to Punta Arenas. At midnight, we had completed 88 nmi of the voyage at an average speed of 3.7 kt.
Daily Science Report for 13 May 2019
Location: Hole U1538D (57°26.5335′S, 43°21.4723′W, water depth 3130.4 mbsl; proposed Site SCO-11A)
Science Update: Cores U1538D-3H to 14H penetrated from 12.4 to 126.4 mbsf and recovered 102.9 m (90%). A formation temperature measurement was made while taking Core 12H. The last core came on deck at 1240 h and the bit was clear of the seafloor at 1430 h, ending Hole U1538D. We had to stop coring in order to leave time to raise the drill string and secure the bottom-hole assembly for transit before stormy weather and high seas arrived early on 14 May. At 2345 h the rig floor was secure and we raised the thrusters for transit.
Cores U1538D-1H to 14H were split and described. They consist of silty clay–bearing diatom ooze, alternating with diatom-rich silty clay on a 10 m scale. The science party met to discuss postexpedition research plans.
Daily Science Report for 12 May 2019
Location: Hole U1538D (57°26.5335′S, 43°21.4723′W, water depth 3130.4 mbsl; proposed Site SCO-11A)
Science Update: Most of the day was spent waiting on sea conditions to improve. The ship’s heave (being the maximum peak to peak heave over a 10 min interval) remained above 5 m until ~1930 h. At that time we were able to resume rig floor operations. Hole U1538D started at 2145 h. Cores U1538D-1H to 2H penetrated from the seafloor to 12.4 mbsf and recovered 11.7 m (94%).
The science party met to discuss postexpedition research plans.
Daily Science Report for 11 May 2019
Location: Hole U1538C (57°26.5387′S, 43°21.4521′W, water depth 3130.2 mbsl; proposed Site SCO-11A)
Science Update: Cores U1538C-3H to 12H penetrated from 15.6 to 105.9 mbsf and recovered 91.3 m (101%). One half-length piston core, Core 6F, was taken to adjust the depth offset to splice over core breaks in Hole U1538A. At 1000 h, the sea and wind conditions had deteriorated to the extent that we could not safely handle the core barrel on the rig floor. We waited with the drill string in the hole, but it was apparent that conditions would not improve today, so at 1500 h we raised the drill string clear of the seafloor, ending Hole U1538C. The rest of the day was spent waiting on weather. The ship’s average pitch, roll, and heave were 3.5°, 3.8°, and 6 m, respectively.
Cores U1538C-1H to 12H were split and described. They consist of silty-clay-bearing diatom ooze, alternating with diatom-rich silty clay on a 10 m scale. The science party met to discuss postexpedition research plans.
Daily Science Report for 10 May 2019
Location:
Hole U1538A (57°26.5248′S, 43°21.4691′W, water depth 3130.6 mbsl; proposed Site SCO-11A)
Hole U1538B (57°26.5368′S, 43°21.4454′W, water depth 3129.8 mbsl; proposed Site SCO-11A)
Hole U1538C (57°26.5387′S, 43°21.4521′W, water depth 3130.2 mbsl; proposed Site SCO-11A)
Science Update: Cores U1538A-70X to 75X penetrated from 621.8 to 676 mbsf and recovered 10.4 m (19%). We stopped coring after reaching the maximum depth permitted by the IODP Safety Panel for this site. We decided to forego downhole logging of Hole U1538A because ship heave exceeded 3 m and was forecast to become higher, which would pose a risk to the downhole logging tools and increase uncertainty in the depth registration of the logging data. However, the hole has a free-fall funnel, and after completing coring we filled it with 10.5 ppg heavy mud, so in principle we could return to Hole U1538A and log it if sea and heave conditions become calmer before the end of operations at this site. Instead, we raised the pipe above seafloor, offset 20 m to the east, and started Hole U1538B at 1900 h. Core U1538B-1H recovered 7.8 m and was this hole’s only core, which we sampled for pore water at high resolution. We then offset 20 m to the south and started Hole U1538C at 2135 h. Cores U1538A-1H to 2H penetrated from the seafloor to 15.6 mbsf and recovered 15.7 m (100%).
Cores U1538A-56X to 75X were split and described. They consist mostly of silty-clay-rich diatomite, with a lesser proportion of biosilica-rich silty clay. Cores 57X to 75X are early Pliocene in age. Gravel to pebble-sized clasts of diverse petrologies were present, particularly as fall-in at the top of the first section of each core, but also occurring in place in stratigraphic sequence.
Daily Science Report for 9 May 2019
Location: Hole U1538A (57°26.5248′S, 43°21.4691′W, water depth 3130.6 mbsl; proposed Site SCO-11A)
Science Update: Cores U1538A-64X to 69X penetrated from 574.1 to 621.8 mbsf and recovered 8.8 m (19%). Coring was interrupted from 0415 to 0900 h when an iceberg passed through the red zone. We raised the drill string to 45 mbsf and waited until after the iceberg passed, with a closest distance of 1.2 nmi from the ship. We then lowered the drill string back down to the bottom of the hole and resumed coring from 597.9 mbsf. From 1930 to 2100 h ship heave was about 4 m, which was too high to maintain a consistent weight on bit, so we waited for the heave to subside before taking Core 69X, the last core of the day.
Cores U1538A-44X to 55X were split and described. They consist mostly of diatom-rich and diatom-bearing silty clay, apart from Core 53X, which consisted of silty-clay-rich diatomite. Gravel to pebble-sized clasts of diverse petrologies were present in the cores below Core 47X in greater concentrations than the upper part of the hole.
Daily Science Report for 8 May 2019
Location: Hole U1538A (57°26.5248′S, 43°21.4691′W, water depth 3130.6 mbsl; proposed Site SCO-11A)
Science Update: Cores U1538A-53X to 63X penetrated from 468.6 to 574.1 mbsf and recovered 51.1 m (48%).
Cores U1538A-30H to 43X were split and described. They consist mostly of silty-clay–rich diatom ooze, alternating with diatom-rich silty clay. Ice-rafted debris is present throughout, though usually in lower concentrations than in the Dove Basin to the south at Sites U1536 and U1537. Cores U1538A-1H to 48X are Pleistocene age, and Cores U1538A-51X to 62X are late to early Pliocene age.
Daily Science Report for 7 May 2019
Location: Hole U1538A (57°26.5248′S, 43°21.4691′W, water depth 3130.6 mbsl; proposed Site SCO-11A)
Science Update: Cores U1538A-38X to 52X penetrated from 325.5 to 468.6 mbsf and recovered 96.9 m (68%). From 1300 to 1500 h we waited for a large iceberg to pass the edge of the red zone (3 nmi from the ship), with the drill string close to the bottom of the hole. Coring then continued until 2145 h, when another iceberg approached close to the red zone, but it changed direction away from the ship and we resumed coring at 2230 h.
The science party met to hear a presentation on bioavailable iron and the Southern Ocean.
Daily Science Report for 6 May 2019
Location: Hole U1538A (57°26.5248′S, 43°21.4691′W, water depth 3130.6 mbsl; proposed Site SCO-11A)
Science Update: Today, Cores U1538A-23H to 37X penetrated from 207.3 to 325.5 mbsf and recovered 102.4 m (87%). Core 30H was difficult to extract from the formation and required a drillover to retrieve it, so we switched to half-length piston coring for Cores 31F to 34F, reaching 294.4 mbsf. At that point the hole was deep enough that we would want to reenter it if forced off site by an iceberg, so we deployed a free-fall funnel to enable reentry. We resumed coring at 1830 h, taking Core 35F, which also required a drillover, so we switched to extended core barrel (XCB) coring for Cores 36X and 37X.
The science party met to discuss the schedule for the remaining two weeks of the expedition. We also held a ceremony on the bow to commemorate the life of Wally Broecker, geochemist and paleoceanographer.
Daily Science Report for 5 May 2019
Location: Hole U1538A (57°26.5248′S, 43°21.4691′W, water depth 3130.6 mbsl; proposed Site SCO-11A)
Science Update: Today, Cores U1538A-8H to 22H penetrated from 64.8 to 207.3 mbsf and recovered 143.0 m (100%). Formation temperature measurements were made while taking Cores 9H, 12H, 15H, and 18H. At 1130 h an iceberg and a bergy bit entered the red zone, so we raised the drill string to 45 mbsf and offset 35 m to the northwest to allow the bergy bit to pass. At 1530 h the iceberg was clear of the red zone and we resumed rig floor operations, lowering the drill string back to 150 mbsf and recovering Cores 18H–22H. At 2245 h another iceberg entered the edge of the red zone and at midnight we were standing by with the drill string at 189 mbsf.
The science party met to hear a presentation on ocean circulation in the Northwest Pacific and the Southern Ocean.
Daily Science Report for 4 May 2019
Location:
• In transit to Site U1538 (proposed Site SCO-11A)
• Hole U1538A (57°26.5248′S, 43°21.4691′W, water depth 3130.6 mbsl; proposed Site SCO-11A)
Science Update: We arrived at Site U1538 at 0245 h after completing the remaining 18 nmi of the transit. The whole 127 nmi transit took 15 h at an average speed of 8.4 kt. We assembled the drill string and lowered it to the seafloor. The drill line was slipped and cut as part of regular maintenance. We started Hole U1538A at 1615 h, at 3130.6 m below sea level as calculated from the mudline. Cores U1538A-1H to 7H penetrated from the seafloor to 64.8 mbsf and recovered 63.8 m (98%). A formation temperature measurement was made while taking Core 6H.
The science party met to present and discuss the first results from Site U1537.
Daily Science Report for 3 May 2019
Location:
• Hole U1537D (59°6.6597′S, 40°54.3677′W, water depth 3713.1 mbsl; proposed Site SCO-18A)
• In transit to Site U1538 (proposed Site SCO-11A)
Science Update: This morning we finished raising the drill string to the ship, which completed operations at Hole U1537D. At 1030 h we started the 127 nmi transit to Site U1538 (proposed Site SCO-11A). At midnight we had completed 109 nmi of the voyage at an average speed of 8.7 kt. At times we had to reduce speed because of low visibility foggy conditions.
The science party met to hear a presentation about dating and temperature reconstruction of Holocene Antarctic sediments.
Daily Science Report for 2 May 2019
Location: Hole U1537D (59°6.6597′S, 40°54.3677′W, water depth 3713.1 mbsl; proposed Site SCO-18A)
Science Update: Cores U1537D-38F to 50F penetrated from 291.9 to 354.3 mbsf and recovered 62.9 m (101%). About eight icebergs were visible on the horizon all day, and from 1345 to 1430 h we waited to monitor an iceberg that was at the edge of the red zone, but it turned away from the ship and we could resume coring. Although today the skies were clear and the seas were relatively calm, high winds and combined wave and swell of 7 m were forecast for 3 May. We decided to end the hole and the site in the early evening in order to leave enough time to raise the drill string to the ship before bad weather set in, and also to leave sufficient time for the coring and logging program at the next site, proposed Site SCO-11, in the Pirie Basin area. The bit cleared the seafloor at 2140 h. Some rig floor maintenance was made to the dolly roller, and at midnight the drill string was being raised to the ship.
Cores U1537D-30F to 50F were split and described. Cores U1537D-30F to 39F mainly consist of biosilica-bearing silty clay. Cores 40F to 50F consist of slumped interbedded silty clay and diatom ooze. The lowest in-place sediments are Pliocene in age. The science party met to hear a presentation about dating the transition from C3 to C4 plants and role of the transition in the carbon cycle.
Daily Science Report for 1 May 2019
Location: Hole U1537D (59°6.6597′S, 40°54.3677′W, water depth 3713.1 mbsl; proposed Site SCO-18A)
Science Update: Cores U1537D-20F to 37F penetrated from 177.3 to 291.9 mbsf and recovered 112.9 m (99%). We took two half-length piston cores (Cores 20F and 21F) across a hard layer that had been found in Hole U1537A at ~182 m, before returning to full length piston coring for Cores 22H to 27H. Below 244 mbsf the formation was too hard for full-length coring, so we used half-length coring from that point down (Cores 28F to 37F). Some of the core liners cracked along their length when the first cut was made to divide the cores into 1.5 m sections. To alleviate this problem, we have been warming up the core liners around the section boundaries before cutting them. So far this seems to have worked.
Cores U1537D-15H to 29F were split and described. Cores 15H to 21F predominantly consist of silty-clay-rich diatom ooze, and Cores 22H to 29F predominantly consist of biosilica-bearing silty clay. The science party met to hear a presentation about reconstructing past marine communities using ancient DNA.