IODP Expedition 374
Ross Sea West Antarctic Ice Sheet History
Daily Science Report for 31 January 2018
Location:
• Hole U1523B (74°9.0179′S, 176°47.6660′W; water depth 828 m)
• Hole U1523C (74°9.0288′S, 176°47.6680′W; water depth 828 m)
Science Results: We continued to XCB core in Hole U1523B from Core 15X to 16X (100.7–103.3 m), which had no recovery. Since the advance for Core 16X was only 0.1 m, we dropped a center bit and drilled ahead without coring for 5.0 m to try to get through this hard layer. We then returned to XCB coring and cut Cores 18X and 19X (108.3–127.5 m), again with only minimal recovery (3%). Since drilling parameters suggested we had successfully passed the hard layers, we switched back to the half-length APC coring system for Cores 20F and 21F. Core 20F recovered 4.53 m of sediment and Core 21F recovered 3.66 m of sediment; however, we had to drill over Core 21F to retrieve it from the formation due to excessive overpull. We then switched back to the XCB coring system to cut Cores 22X to 24X (135.6–164.4 m) with minimal recovery (2.5 m; 9%). We terminated coring in Hole U1523B at that point due to unstable hole conditions causing excessive torque. The drill bit cleared the seafloor at 1740 h, ending Hole U1523B. Hole U1523C was planned to target HLAPC core within intervals of poor recovery while avoiding hard layers encountered while coring Hole U1523B. We dropped a center bit in preparation to start Hole U1523C and noticed high pump pressures indicating clogged jets in the drill bit. After attempting to clear the jets, we started Hole U1523C at 1915 h and drilled ahead without coring to 43.3 mbsf when we lost circulation through the jets on the bit, forcing us to abandon Hole U1523C. The bit cleared the seafloor at 2120 h, ending Hole U1523C. While pulling the pipe back to the rig floor, we decided to switch to the RCB coring system to core a deep hole. At the end of the day, we were still recovering the drill string.
Cores U1523B-5F through 22X were split and described. This interval included the HLAPC cores as well as six XCB cores with extremely poor recovery. The uppermost sediment consists of greenish gray to dark greenish gray diatom-rich mud with interbedded massive and laminated intervals. Pebble- and occasional cobble-sized clasts are dispersed throughout. Sand stringers, mottling, and pyrite laminae are also present. Below this are intervals of greenish gray to light olive brown massive sand and bioturbated mud with common clasts. Shell fragments are scattered on the surface of the split cores and include bryozoans, foraminifers, and worm tubes. The lowermost part of the section consists of bioturbated greenish gray diatom-rich mud, interbedded with glauconitic sandy mud. Hole U1523B contains good assemblages of moderately to well-preserved diatoms, radiolarians, and foraminifers. The age at the base of the hole is late Miocene based on diatom and radiolarian biostratigraphy.
Daily Science Report for 30 January 2018
Location: Hole U1523B (74°9.0179′S, 176°47.6660′W; water depth 828 m)
Science Results: We started the day lowering the overshot tool to recover the stuck XCB core barrel, which was freed and pulled back to the surface. We then tried to clear debris from the bottom-hole assembly (BHA), but this was unsuccessful, so the drill string was pulled to the surface; the bit arrived on the rig floor at 0450 h, ending Hole U1523A. The BHA was clogged with rock, sand, and parts of the lockable float valve. The sediment was archived as ghost core U1523A-8G. After cleaning out the BHA, a new APC/XCB BHA was assembled and lowered toward the seafloor. We picked up the top drive and started Hole U1523B at 1100 h. The mudline core (1H) recovered 8.5 m of sediment, which was sampled for shorebased high-resolution interstitial water and microbiology studies. After dropping a center bit, we drilled ahead without coring to 46.7 m. We pulled the center bit, lowered a half-length APC (HLAPC) core barrel, and collected Cores 3F to 13F (46.7–93.8 m). Core 13F was a partial stroke, so we switched to the XCB and cut Core 14X to 100.7 m. Core recovery with the HLAPC varied from no recovery to 102%. Overall recovery with the HLAPC was 25.29 m (54%). Core 14X recovered 0.14 m (2%). The recovered succession consists of Pliocene and upper Miocene sediment based on diatom and radiolarian biostratigraphy.
Cores U1523A-4F through 7F were split and described. The uppermost part of the section consists of massive dark greenish gray diatom-bearing mud with dispersed clasts, interbedded with sand. Foraminifers are common in some sand beds and shell fragments are scattered throughout. A few cobble size clasts are present and include granite, metasedimentary rock, and chert. Below this, diatom-bearing mud is laminated and interbedded with sand and gravel. Bed contacts are usually sharp. The sediment is mottled and includes sand stringers and clasts. Core U1523B-3F was also split and described and consists of sandy to silty mud interbedded with decimeter-scale diamict beds that are often bioturbated. Foraminifers and pebble-sized clasts are present.
Daily Science Report for 29 January 2018
Location:
• In transit to Site U1523 (proposed Site RSCR-14A)
• Hole U1523A (74°9.0172′S, 176°47.7067′W; water depth 828 m)
• Hole U1523B (74°9.02′S, 176°47.67′W [preliminary]; water depth 828 m)
Science Results: We continued our transit to Site U1523 (proposed Site RSCR-14A). We began to lower the thrusters at 0158 h and switched to dynamic positioning at 0218 h. After making up an advanced piston corer (APC)/extended core barrel (XCB) bottom-hole assembly (BHA), we began to lower the drill string toward the seafloor. After reaching 599.1 m below the rig floor, the drilling team pulled the upper guide horn to deploy the subsea camera for a seafloor survey to look for large rocks in the vicinity of the potential hole locations. While lowering the subsea camera, we also continued to lower the drill string. Since this site is in deeper water than the two previous sites, some of the drill pipe was drifted (checked that it was clear of internal obstructions) and strapped (measured) as it was deployed. The drilling crew then picked up the top drive and prepared an APC core barrel. We then conducted the seafloor survey, which included tagging the seafloor at four potential hole positions. All tag depths were 828 m below sea level. After moving the vessel back to the first tag location, we left the subsea camera down to observe the core barrel being shot into the seafloor to spud Hole U1523A. Core 1H recovered 8.51 m of sediment. We continued to APC core from Core 2H to 3H (8.5–27.5 m). After the core liner of Core 3H had to be pumped out of the core barrel, we decided to switch to the half-length advanced piston corer (HLAPC). We continued to core with the HLAPC to Core 7F (46.3 m). Cores 4F, 5F, and 7F had shattered liners and had to be pumped out of the core barrel. When preparing to shoot the next core, the HLAPC core barrel was unable to land. After retrieving the HLAPC core barrel, we lowered an XCB barrel with a deplugger to try to reestablish circulation; however, this attempt failed and we had to terminate coring in Hole U1523A. We pulled the drill bit out of the hole, clearing the seafloor at 2310 h and ending Hole U1523A. The attempt to retrieve the XCB core barrel resulted in a sheared overshot pin. At the end of the day, we had retrieved and repaired the overshot and we were lowering the coring line back into the hole to retrieve the XCB core barrel.
Cores 1R through 3R were split and described. The sediment consists of foraminifer-rich sand and mud, interbedded with clast-rich sandy diamict. Individual sand and mud packages are centimeter- to decimeter-scale with sharp, gradational, and bioturbated contacts. The uppermost sediment near the mudline is dark grayish brown, changing downcore to greenish gray. Decimeter-scale color alternations are apparent in the sediment. The diamict intervals contain pebble- to cobble-sized clasts of various lithologies. Near the base of the described interval, foraminifer-rich clast-rich sandy to muddy diamict is more prevalent and interbedded with moderately bioturbated mud. The age at the base of Hole U1523A is Pliocene based on diatom biostratigraphy.
Daily Science Report for 28 January 2018
Location:
• Hole U1522A (76°33.2262′S, 174°45.4652′W; water depth 558 m)
• In transit to Site U1523 (proposed Site RSCR-14A)
Science Results: We continued to run the Versatile Seismic Imager (VSI) tool string into the borehole. After hitting a bridge at 194.5 m, the tool was returned to the surface and a natural gamma ray tool was added to increase the weight of the tool string. The tool string was again lowered into the hole and made it past two narrow intervals of the borehole; however, it could not reach beyond 297.5 m. The seismic source was lowered into the water and a soft start was initiated after observation for protected species had begun. The vertical seismic profile (VSP) experiment included eight stations. Operations were halted several times due to the presence of whales and seals. After completing the last station, the tool string was returned to the surface at 0630 h. We then prepared the Formation MicroScanner (FMS) without the sonic tool, which was run on the triple combo tool string, and lowered it into the hole to 193.5 m. We conducted two upward passes, then the FMS was returned to the rig floor at 0930 h. After rigging down the logging equipment, the drilling crew pulled the remaining pipe back to the rig floor, which was secured for transit at 1325 h. The acoustic beacon was released while pulling the remaining drill string to the ship. After the thrusters were raised we began our transit to Site U1523 (proposed Site RSCR-14A) at 1324 h. Our estimated time of arrival at the site is 0300 h on 29 January. The scientists continued measurement of discrete samples for moisture and density, as well as carbonate content, total carbon, total organic carbon, and total nitrogen. They also began to write up results for the Site U1522 report. The Co-Chief Scientists presented the geological setting and site specific objectives for Site U1523.
Daily Science Report for 27 January 2018
Location: Hole U1522A (76°33.2262′S, 174°45.4652′W; water depth 558 m)
Science Results: We continued to RCB core in Hole U1522A from Core 74R to 76R (682.6–701.8 m). Total recovery for those cores was 17.19 m (60%). We terminated coring at that depth after determining that our objectives had been met. Total recovery for Hole U1522A was 279.57 m (40%). The drilling team then prepared the hole for downhole logging, which included pumping several high viscosity mud sweeps to clean out the hole and improve hole conditions, dropping the RCB bit in the bottom of the hole, and pumping additional mud and circulating to reduce torque on the drill string. We then began to pull the drill string up, leaving the top drive in until reaching 583.9 m. After displacing the hole with 10.5 ppg mud from 583.9 m to the seafloor, the drilling team set back the top drive and then continued to pull the drill string up to logging depth. The end of the pipe was set at 91.3 m and the hole was displaced with 10.5 ppg mud from that depth to the seafloor. We then prepared a modified triple combo tool string, which included tools to measure natural gamma radiation, density (without the source due to unstable hole conditions), sonic velocity, resistivity, and magnetic susceptibility. We began to lower the modified triple combo into the drill string at 1630 h. The tool string reached a total depth of 650.3 m (~50 m above the bottom of the hole). We completed a 143 m calibration log upward, then returned the tool to the bottom of the hole and logged upward to the end of the pipe. The tool string reached the surface at 2035 h. After breaking down the triple combo tool string, we prepared the Versatile Seismic Imager (VSI) tool string to complete a vertical seismic profile experiment. The tool was lowered into the hole at 2245 h and by the end of the day had reached 240 m below rig floor. While lowering the tool string in the hole, we began observation for protected species in preparation for deployment of the seismic source.
Cores 71R through 76R were split and described. The sediment primarily consists of dark greenish gray clast-poor sandy diamictite interbedded with a few short intervals of mud-rich diatomite. The diamictite ranges from massive to faintly laminated and there are several sharp contacts between these lithologies throughout the described interval. Shell fragments are present in several sections. The age at the bottom of Hole U1522A is late Miocene based on diatom biostratigraphy.
Daily Science Report for 26 January 2018
Location: Hole U1522A (76°33.2262′S, 174°45.4652′W; water depth 558 m)
Science Results: We continued to RCB core in Hole U1522A from Core 62R to 74R (558.8–682.6 m). We pumped 30-barrel mud sweeps every 1–2 cores in an attempt to clear drill cuttings and fall in out of the hole to improve hole conditions. Core recovery over this interval was generally good but somewhat variable, ranging from 16% to 93%. Total recovery for the day was 76.84 m (62%). The age at the bottom of the drilled interval is late Miocene based on diatoms.
Cores 58R to 70R were split and described. The sediment mostly consists of dark greenish gray diatom-bearing clast-poor to clast-rich sandy diamictite, with a few intervals of muddy diamictite. Clasts include a variety of lithologies (metasedimentary, igneous, chert, and basalt) and are subangular to subrounded. Shell fragments occur toward the base of the described section, together with a few slightly bioturbated intervals. A carbonate-cemented mudstone with common clasts is present near the base of the section. Total organic carbon is low (<0.6 wt%) at this site. Carbonate content is slightly higher in the lower part of the hole, reaching ~3 wt%, with the exception of a sample from the carbonate-cemented mudstone, which has much higher carbonate content.
Daily Science Report for 25 January 2018
Location: Hole U1522A (76°33.2262′S, 174°45.4652′W; water depth 558 m)
Science Results: The original operations plan for Site U1522 included a single RCB hole to 545 m (the maximum approved penetration depth). However, due to poor recovery in the upper 200 m of the hole, we requested and received permission to core to 925 m to take advantage of improved recovery at depth and to core an expanded upper Miocene record. Therefore, we continued to RCB core in Hole U1522A from Core 48R to 61R (424.5–558.9 m). We pumped 30-barrel mud sweeps every 2–4 cores, as well as a 90-barrel mud sweep after Core 56R to improve hole conditions. Core recovery over this interval was generally good, with many cores recovering 80% or more of the material cored. Lower core recovery (<40%) was usually due to a cobble blocking the core catcher. Overall recovery for the day was 96.59 m (72%). Diatoms are common throughout the cored interval and indicate a late Miocene age, although the assemblage includes a large percentage of reworked specimens.
Cores 45R through 57R were split and described. The sediment mostly consists of very dark greenish gray massive diatom-bearing clast-poor to clast-rich muddy to sandy diamictite. Some intervals are carbonate cemented and carbonate concretions are common in the upper part of the described interval. Clasts include mudstone, chert, granodiorite, and volcanic fragments. An interval of faintly laminated diatom-rich mudstone is present near the base of the described interval. Carbonate content is very low at this site (<2.5 wt%).
Daily Science Report for 24 January 2018
Location: Hole U1522A (76°33.2262′S, 174°45.4652′W; water depth 558 m)
Science Results: We continued to core in Hole U1522A from Core 31R to 35R (289.6–337.6 m). Since the core catcher repeatedly jammed with cobbles over this interval, which resulted in lower core recovery (<35%), we decided to switch to 4.6 m advances. After poor recovery in Core 36R (9%), this strategy worked for Cores 37R and 38R (342.4–352.0 m), which recovered 6.75 m of core (70%). However, this was followed by almost no recovery in Cores 39R to 41R (352.0–366.4 m). We then switched back to full 9.6 m advances with negligible recovery in Cores 42R to 44R (366.4–395.5 m). Recovery improved somewhat in Cores 45R through 47R (395.5–424.5 m), which recovered 8.24 m of core (28%). The age over the cored interval is late Miocene to early Pliocene based on diatom and radiolarian biostratigraphy.
Cores 26R through 44R were split and described. The sediment consists of dark gray massive clast-poor sandy diamictite, changing to dark greenish gray clast-poor diatom-bearing muddy diamictite downhole. Some intervals of the muddy diamictite show faint stratification. Below that, the diamictite is clast-rich and sandy, with occasional shell fragments present. At the bottom of the described interval, Cores 39R to 44R contain only washed gravel and traces of sediment. Porosity is low (around 35%) and bulk density is high (~2.1 g/cm3) in the cores recovered in the upper part of the hole. Below 200 m, porosity is generally higher (40%–50%) and bulk density lower (~1.8 g/cm3), and both are more variable. Paleomagnetic results have also been variable for this hole; however, intervals of normal and reverse polarity are present, which will help to refine the age model when combined with biostratigraphic results.
Daily Science Report for 23 January 2018
Location: Hole U1522A (76°33.2262′S, 174°45.4652′W; water depth 558 m)
Science Results: We continued to RCB core in Hole U1522A from Core 10R to 30R (87.0–289.6 m), pumping mud sweeps every 2–3 cores. Core recovery was variable over this interval. Cores 10R and 11R had reasonable recovery (34% and 48%, respectively); however, recovery decreased significantly below this and we recovered only 5.19 m (5%) from Cores 12R through 21R. Recovery improved again below that depth and we recovered 38.75 m (45%) over the remainder of the cored interval. The age at the base of the section is late Pliocene based on diatom and radiolarian biostratigraphy.
Cores 7R through 25R were split and described. The majority of the recovered sediment consists of dark gray massive clast-rich muddy to sandy diamict. The muddy diamict occurs in the upper part of the described section, grading downhole to sandy diamict. Some intervals of the diamict are diatom-bearing to diatom-rich. The abundance of clasts decreases towards the base of the described section. Clasts are variable in size, shape, and composition. The microfossil assemblages throughout the described interval show significant numbers of reworked Miocene taxa; however, this decreases near the base of the described interval.
Daily Science Report for 22 January 2018
Location: Hole U1522A (76°33.2262′S, 174°45.4652′W; water depth 558 m)
Science Results: We arrived at Site U1522 (proposed Site EBOCS-03C) at 0654 h and switched to dynamic positioning. The drilling crew prepared the bottom-hole assembly (BHA) with a new rotary core barrel (RCB) bit, then lowered the drill pipe toward the seafloor. After picking up the top drive, Hole U1522A was started at 1115 h, tagging the seafloor at 558 m water depth. We continued to RCB core from Core 1R to 9R (0–87 m). Core 1R recovered 2.89 m of sediment (30%); however, below that recovery was poor for Cores 2R to 8R (1.72 m; 3%). Recovery improved again in Core 9R (5.84 m; 60%). The age at the bottom of the recovered interval is Pliocene–Pleistocene based on diatoms; however, the assemblage includes significant numbers of reworked Miocene taxa.
The scientists worked to finish collecting data from our previous Site U1521 and prepared presentations for the site science review meeting. They also began to write up their site reports. The Co-Chief Scientists gave an introduction to the scientific objectives and geological setting of Site U1522 (proposed Site EBOCS-03C). In the laboratories, Cores U1522A-1R through 6R were split and described. The uppermost core consists of olive yellow to gray diatom-bearing sandy mud and muddy sand with clasts. Below Core 1R, the recovered material consists almost entirely of clasts of various lithologies including granite, granodiorite, marble, sandstone, and mudstone.
Daily Science Report for 21 January 2018
Location:
• Hole U1521A (75°41.0351′S, 179°40.3108′W; water depth 566 m)
• Underway to Site U1522 (proposed Site EBOCS-03C)
Science Results: We continued to lower the triple combo tool string into the drill pipe. The tools reached to 648 m (the bottom of the hole). After completing a 126.5 m calibration pass logging upward from the bottom of the hole, the tool string was lowered back to bottom at 648 m. We then completed the main pass logging upward to the end of the pipe. The tool string was back at the rig floor at 0330 h. After rigging down the triple combo, we assembled the Formation MicroScanner (FMS)-sonic tool string, which was lowered into the hole at 0630 h. The FMS-sonic tool string also reached all the way to the bottom of the hole. We completed two upward logging passes, then the tool string was returned to the rig floor at 1120 h. After rigging down the FMS-sonic, we prepared the Versatile Seismic Imager (VSI) tool string to conduct a vertical seismic profile (VSP) experiment. Observation for protected species began at 1300 h. The seismic source was lowered into the water at 1400 h and the VSP began after ramping up the source over 45 min. We collected measurements at 17 depths before the tool string was returned to the surface at 1800 h. After rigging down the VSI, the drilling crew recovered the drill string. The beacon was released during the pipe trip and was recovered at 2105 h. The drill floor was secured at 2245 h and the thrusters were raised, and at the end of the day we were underway to Site U1522 (proposed Site EBOCS-03C).
Cores U1521A-61R through 71R were split and described. Most of this interval consists of very dark greenish gray clast-poor sandy to muddy diamictite. Some intervals show very faint stratification, and shell fragments and carbonate concretions are also present. A few intervals of greenish gray mudstone are interspersed toward the bottom of the hole. A few cobble- to boulder-sized clasts are present near the bottom of the described interval. After completing description of the last cores from the site, the sedimentologists began to work towards defining lithologic units. The biostratigraphers and paleomagnetists are working together to develop a final shipboard age model for the site. Measurement of moisture and density samples, as well as samples for carbonate content and total carbon and nitrogen, should be finished within the next day.
Daily Science Report for 20 January 2018
Location: Hole U1521A (75°41.0351′S, 179°40.3108′W; water depth 566 m)
Science Update: We continued to RCB core from Core U1521A-63R to 71R (563.7–650.1 m). We then terminated coring after determining that our objectives had been met and that the hole had penetrated deeply enough for the logging tools to reach critical boundaries. Total core recovery for the hole is 411.5 m (63%). The drilling team then prepared the hole for logging, which included releasing the drill bit in the bottom of the hole, filling the hole with 217 barrels of heavy (10.5 ppg) mud, setting back the top drive, and then setting the end of pipe at 58.4 m for downhole logging. The Schlumberger engineer then began to prepare the triple combination tool string, which will record natural gamma radiation, density, resistivity, and magnetic susceptibility. The tools were lowered into the hole at 2325 h and were being lowered toward the bottom of the hole at the end of the day.
Cores U1521A-47R through 60R were split and described. The upper part of the described interval consists of massive very dark greenish gray clast-rich sandy diamictite. Shell fragments and foraminifers are occasionally present on the split-core surface. Near the base of the diamictite there are interbeds of dark greenish gray mudstone, grading into dark greenish gray sandy mudstone downhole. The mudstone is clast-poor, but contains some shell fragments and carbonate concretions. Below the mudstone is a massive very dark gray to very dark greenish gray clast-poor sandy to muddy diamictite that contains one interval of highly bioturbated very dark greenish gray mud-rich sandstone to mudstone. Shell fragments are present in this interval. Bulk density and porosity are relatively uniform within different lithologies downhole. Carbonate content increases slightly downhole, with values typically <2 wt% in the upper part of the hole, increasing to 2–5 wt% downhole.
Daily Science Report for 19 January 2018
Location: Hole U1521A (75°41.0351′S, 179°40.3108′W; water depth 566 m)
Science Update: We continued to RCB core in Hole U1521A from Core 49R through 62R (429.3–563.7 m). Except for one core with only 22% recovery, the core recovery over this interval was good to excellent, ranging from 63% to 105%. Overall recovery for the day was 118.61 m (88%). Microfossils are sparse in this interval, with rare to few diatoms that are often fragmented. Foraminifers are also present, and a few calcareous nannofossil specimens were found in two samples. Pollen grains including Nothofagus (Southern beech) are also present in this interval.
Cores 30R to 46R were split and described. The uppermost part of the interval consists of dark gray diatom-bearing clast-poor diamictite, underlain by gray to dark gray siliceous mudstone. Below this is a sequence of interbedded dark gray mudstone and clast-rich muddy to sandy diamictite. The base of the described interval is massive clast-rich silica-cemented sandy and muddy diamictite. Clast lithologies include basalt, granite, diorite, mudstone, and chert. Results from the upper part of the hole indicate low total organic carbon (0.4–0.7 wt%) and generally low calcium carbonate content (~0.4–2.0 wt%), although some calcite-cemented intervals have much higher content.
Daily Science Report for 18 January 2018
Location: Hole U1521A (75°41.0351′S, 179°40.3108′W; water depth 566 m)
Science Update: We continued to RCB core in Hole U1521A from Core 32R to 37R (294.9–352.5 m). Core recovery was poor over this interval (25%) due to jamming of the core barrel, so we opted to cut half-length cores to improve recovery. Cores 38R to 43R (352.5–390.9 m) were collected using a 4.8 m advance (instead of 9.6 m) and recovery improved significantly (80%). We switched back to cutting 9.6 m cores when the formation became somewhat softer and collected Cores 44R to 48R (390.9–429.3 m) with improved recovery (82%). The age at the bottom of the cored interval is early Miocene based on diatoms.
Cores 14R to 29R were split and described. The upper part of this interval consists of olive gray to dark gray diatom-bearing to diatom-rich mud. Some intervals are moderately to heavily bioturbated. There are dispersed shell fragments present, especially near the bottom of the interval. Some lighter-colored layers are cemented with calcite. The lower part of the interval consists of dark gray sandy diamict with varying proportions of diatoms and clasts. Volcanic clasts are common, and shell fragments and pyrite filled burrows are occasionally present. A few intervals of diatom-bearing mud are interbedded with the diamict. Magnetic reversals found over the described interval should help to refine the middle Miocene age provided by diatom biostratigraphy.
Daily Science Report for 17 January 2018
Location: Hole U1521A (75°41.0351′S, 179°40.3108′W; water depth 566 m)
Science Update: We continued to RCB core in Hole U1521A from Core 3R to 31R (17.0–294.9 mbsf). Core recovery was mixed in the upper 150 mbsf, varying from less than 5% in several cores to as high as 89%. Recovery improved markedly below 150 mbsf to the bottom of the cored section. Overall recovery for the day was better than 50%. The age at the bottom of the recovered section is middle Miocene based on diatoms. Cores 1R through 13R were split and described. The uppermost sediment consists of diatom-rich mud to diatom-bearing sandy mud with clasts. Below this the sediment consists of alternating intervals of dark gray muddy diamict and diatom-rich mud to diatom ooze. The diamicts include varying numbers of clasts. A few shell fragments were found in diatom-bearing mud near the base of the described interval.
Daily Science Report for 16 January 2018
Location:
• Underway to Site U1521 (proposed Site EBOCS-01D)
• Hole U1521A (75°41.0351′S, 179°40.3108′W; water depth 566 m)
Science Update: We arrived at Site U1521 and switched to dynamic positioning at 0938 h. The drilling crew made up and spaced out the outer core barrel, picked up the drill collars, made up the bottom-hole assembly, and then started tripping pipe toward the seafloor. During the trip, the pipe was drifted (checked to ensure that the interior was clear) and strapped (measured). After the drill bit reached 520.11 m below rig floor (mbrf), the drilling crew picked up the top drive and pumped a clean out “pig” to ensure that the interior of the drill string was free of rust and other debris. After dropping a core barrel, we started Hole U1521A at 1845 h with the rotary core barrel coring system. The driller tagged the seafloor at 573 mbrf (566 m below sea level), then slowly advanced the drill bit without rotation to collect a “push core.” After hitting a hard layer, the driller began rotating the drill string to finish cutting the first core. By the end of the day we had collected Cores U1521A-1R and 2R to a depth of 17.0 m below seafloor with average recovery of 35%.
While preparing for the beginning of coring operations later in the day, the scientists received SampleMaster training from the Curator. The Co-Chief scientists introduced the scientific objectives for Site U1521. A scientist also presented initial results from the site survey cruise conducted in this region last year. The Co-Chiefs, Operations Superintendent, Laboratory Officer, Assistant Laboratory Officer, Captain, Ice Observer, Schlumberger Engineer, and Offshore Installation Manager met to discuss drilling and logging operations for the expedition. After initiation of coring operations, the geochemists and paleontologists began processing and analyzing samples. The age of Core U1521A-2R is upper Pliocene based on diatoms and radiolarians.
Daily Science Report for 15 January 2018
Location:
• Underway to Site U1521 (proposed Site EBOCS-01D) 0.5 nmi behind the RVIB Nathaniel B. Palmer
• Underway to Site U1521 (proposed Site EBOCS-01D) without escort
Science Update: We continued to follow the RVIB Nathaniel B. Palmer, reaching the northern edge of the sea ice at ~0630 h. We cleared the southern edge of the sea ice at 1220 h, and the Palmer was released at 1300 h. Our ETA at Site U1521 is 1000 h on 16 January. The scientists continued examining legacy Antarctic cores throughout the day. The sedimentologists and paleontologists on the day shift received training on the desktop scanning electron microscope (SEM). The Co-Chief Scientists, Curator, Assistant Laboratory Officer, and Staff Scientist met with the geochemists and microbiologists conducting catwalk sampling to finalize the site-specific plan. The science party received an overview of the lithological framework of the region based on previous drilling and outcrop-based sampling. The Co-Chiefs also gave an overview of the expedition objectives for the crew and technical staff.
Daily Science Report for 14 January 2018
Location:
• In transit to rendezvous with the RVIB Nathaniel B. Palmer for escort into the Ross Sea polynya
• Underway to Site U1521 (proposed Site EBOCS-01D) 0.5 nmi behind the RVIB Nathaniel B. Palmer
Science Update: The scientists continued practicing laboratory methods and describing legacy cores. The sedimentologists and paleontologists on night shift received training on the desktop scanning electron microscope (SEM). We celebrated crossing the Antarctic Circle with cupcakes and screening of a 20 min film showing footage from past Antarctic scientific expeditions that was originally debuted at the Past Antarctic Ice Sheet (PAIS) science conference in September 2017. We began our rendezvous with the RVIB Nathaniel B. Palmer at 1930 h and commenced following 0.5 nmi behind at a speed of 10.0 kt to transit through the sea ice. The ETA for the northern edge of the sea ice is 0600 h on 15 January.
Daily Science Report for 13 January 2018
Location: In transit to rendezvous with the RVIB Nathaniel B. Palmer for escort into the Ross Sea polynya (updated ETA 2100 h on 14 January 2018)
Science Update: The scientists continued moving onto shifts. The sedimentologists began to practice visual core description and preparation and description of smear slides using legacy cores from previous Antarctic expeditions, including Deep Sea Drilling Project (DSDP) Site 270, Ocean Drilling Program (ODP) Site 1165, and Integrated Ocean Drilling Program Site U1361. They were also introduced to the Vanta handheld X-ray fluorescence (XRF) third-party tool and they used it to measure the legacy cores. The other laboratory groups also continued to practice laboratory methods. We saw our first iceberg of the expedition in midafternoon, and are scheduled to cross the Antarctic Circle at 0400 h on Sunday 14 January.
Daily Science Report for 12 January 2018
Location: In transit to rendezvous with the RVIB Nathaniel B. Palmer for escort into the Ross Sea polynya (ETA 0600 h on 15 January 2018)
Science Update: The scientists continued to work in laboratory groups throughout the day. In the morning, designated Sedimentologists and Geochemists met with the X-ray technician to discuss procedures and setup for the handheld X-ray fluorescence (XRF) tool. Three scientists presented talks on drift sedimentation and correlation of core data with seismic stratigraphy in the North Atlantic, as well as seismic stratigraphic data and facies analysis of piston cores collected on a recent cruise to the Ross Sea. In the afternoon, the Operations Superintendent gave a talk to the science party explaining coring operations on the JOIDES Resolution, after which the Staff Scientist introduced the science party to IODP depth scales. Each laboratory group submitted a first draft of their Methods section. Scientists also began to move onto shifts at the end of the day.
Daily Science Report for 11 January 2018
Location: In transit to rendezvous with the RVIB Nathaniel B. Palmer for escort into the Ross Sea polynya (ETA 0600 h on 15 January 2018)
Science Update: The Co-Chief Scientists and Staff Scientist met with the Operations Superintendent to discuss the expedition operations plan. We decided to rearrange the order of the first three sites to start with proposed Site EBOCS-01D, followed by proposed Sites EBOCS-03C and EBOCS-04B, to minimize transit and maximize operational time. After coring at Site RSCR-02B, we will then occupy Site RSCR-14A (instead of Site RSCR-11A) and Site RSCR-19A (instead of Site EBOCS-02B). Site RSCR-14A should provide a more complete record than Site RSCR-11A, and we added Site RSCR-19A to the primary plan based on the recommendation of the IODP Science Evaluation Panel. The scientists continued to work on laboratory procedures and methods. The Imaging Specialist met with the core describers to set up the microscope for smear slide observation. In the afternoon, the Curator introduced the scientists to shipboard sampling and residues, after which we discussed shipboard measurements and sampling resolution.
Daily Science Report for 10 January 2018
Location: In transit to rendezvous with the RVIB Nathaniel B. Palmer for escort into the Ross Sea polynya
Science Update: The scientists continued to work on laboratory procedures and write methods sections. The Laboratory Officer gave a presentation and showed a video on hydrofluoric acid (HF) safety to the scientists working in the Geochemistry Laboratory where HF will be used to process samples for palynomorphs. The Operations Superintendent gave three ship tours that included the rig floor, core tech shop, and mud rooms. The scheduled rendezvous with the RVIB Nathaniel B. Palmer is set for 0600 h on 15 January.
Daily Science Report for 9 January 2018
Location: In transit to rendezvous with the RVIB Nathaniel B. Palmer for escort into the Ross Sea polynya
Science Update: The Staff Scientist gave a short presentation on best practices for posting to social media. The Education and Outreach officers then introduced the science party to their plans for the expedition and explained how the scientists could participate, including blogging and posting to social media. After lunch, four scientists presented their research from IODP Expedition 318 (Wilkes Land Glacial History). The scientists also continued to work on laboratory methods and protocol. The first abandon ship and fire drill was held in the morning.
Daily Science Report for 8 January 2018
Location:
• Berth No. 7, Lyttelton, New Zealand
• In transit to rendezvous with the RVIB Nathaniel B. Palmer for escort into the Ross Sea polynya
Science Update: New Zealand customs and immigration boarded the vessel in the morning to clear it for departure. Following this, the Staff Scientist gave a core flow laboratory tour to the Paleomagnetists, Physical Property Specialists, Geochemists, and Education and Outreach team. At the same time, the Sedimentologists and Paleontologists continued to work on methods in their laboratory groups. The Imaging Specialist also worked with the Paleontologists to set up their microscopes. The scientists were given from ~1030 to 1400 h to go into town to buy last minute supplies. In the afternoon, the Staff Scientist and Publications Specialist introduced procedures and best practices for writing shipboard reports. Following this, the Staff Scientist gave a core flow laboratory tour to the Sedimentologists and Paleontologists while the other scientists continued working on methods. Port call activities concluded with an inspection for the Polar Code certificate and discharge of remaining items. The pilot boarded the vessel at 1552 h, and the vessel departed Lyttelton with the last line away at 1624 h. Sea passage to the rendezvous with the RVIB Nathaniel B. Palmer began at 1648 h when the pilot departed the vessel.
Daily Science Report for 7 January 2018
Location:
• Oil Berth, Lyttelton, New Zealand
• Berth No. 7, Lyttelton, New Zealand
Science Update: The Co-Chief Scientists introduced the scientific objectives of the Ross Sea West Antarctic Ice Sheet History expedition to start the day. We then conducted a research planning meeting. Each scientist presented a brief (~2–3 min) summary of his or her proposed postcruise research objectives and sampling plan to meet those objectives. After lunch, the science party divided into laboratory groups, with the sedimentologists and paleontologists receiving an introduction to DESClogik. The physical property specialists, paleomagnetists, and geochemists each met with the IODP JRSO technicians in their respective laboratories for an introduction to laboratory equipment and methods. We ended the day with Polar Code cold weather training for all scientists and IODP JRSO technical staff who had not previously completed the training. Port call activities included completing fueling operations, shifting the vessel back to Berth No. 7, and loading of fresh food for the expedition. Departure is planned for 1800 h on 8 January.
Daily Science Report for 6 January 2018
Location:
• Berth No. 7, Lyttelton, New Zealand
• Oil Berth, Lyttelton, New Zealand
Science Update: We began the day with a meet and greet for the scientists and IODP JRSO technical staff, followed by a presentation by the Staff Scientist that explained what we would be doing during the expedition. The Marine Computer Specialists gave the scientists an introduction to I.T. and computing aboard the JOIDES Resolution, then the scientists connected their computers to the shipboard network. After lunch, the Captain welcomed the scientists to the vessel and gave an introduction to policies and procedures aboard the vessel. The Ship’s Doctor then conducted a shipboard safety meeting. The Staff Scientist concluded the day with an introduction to the shipboard server structure. Port call activities included loading of bulk, freight, and frozen food, as well as discharging sea freight and remaining Schlumberger logging-while-drilling tools. In the afternoon the vessel shifted to the Oil Berth to begin taking on fuel for the expedition.
Daily Science Report for 5 January 2018
Location: Berth No. 7, Lyttelton, New Zealand
Science Update: The ship’s crew completed crew change and crossover at ~0730 h. The Expedition 374 science party boarded the vessel at 0930 h and were shown to their berths. After a short introductory meeting, the scientists were given time to settle in and have lunch. At 1300 h, the science party convened for presentations about life aboard the vessel. The science party then divided into three groups for a ship safety tour. Other port call activities included loading of freight for the expedition. We also conducted several tours with faculty, staff, and students from local universities.
Daily Science Report for 4 January 2018
Location: Berth No. 7, Lyttelton, New Zealand
Science Update: The Ross Sea West Antarctic Ice Sheet History Expedition 374 began with the first line ashore at 0706 h. Oncoming IODP JRSO technical staff and the Co-Chief Scientists boarded the vessel at 1000 h and completed crossover with the offgoing staff, who departed the vessel midafternoon. Port call activities included loading of IODP air freight and containers. A press conference was held in the afternoon, with the Expedition 372 Co-Chiefs giving a summary of results from their expedition and the Expedition 374 Co-Chiefs giving an introduction to the expedition scientific objectives. The press conference attendees were then given tours of the vessel. At 1745 h, the vessel was shifted to its current location at Berth No. 7.