IODP Expedition 374
Ross Sea West Antarctic Ice Sheet History
Daily Science Report for 7 March 2018
Location:
• Berth #2 West, Port of Lyttelton, New Zealand
• In transit to Port of Timaru, New Zealand
Science Results: We started the day tied up alongside Berth #2 West in Lyttelton, New Zealand. We loaded a 40 ft container of Siem Offshore freight, as well as additional IODP air freight. We gave a ship tour to a group of Christchurch/Lyttelton community and business leaders. Two Expedition 375 scientists delivered osmosampler equipment to the vessel for the upcoming expedition. The remaining Expedition 374 Co-Chief Scientist and one scientist disembarked the vessel. Due to a scheduled strike at Lyttelton port, we opted to move the ship to Timaru prior to the start of the shutdown. The pilot boarded the vessel at 1456 h and the last line was released at 1518 h. The pilot departed the vessel at 1536 h and we began our sea voyage to Timaru.
Daily Science Report for 6 March 2018
Location: Berth #2 West, Port of Lyttelton, New Zealand
Science Results: We are tied up alongside Berth #2 West in Lyttelton, New Zealand. We loaded some of the IODP air freight shipment, fresh food for Expedition 375, and the bulk mud dust collector. The IODP technicians completed final cleaning of the laboratories. The Staff Scientist completed the introductory section for the expedition Methods chapter. All expedition science reports are now complete, with the exception of adding the final operations after the end of the expedition.
Daily Science Report for 5 March 2018
Location: Berth #2 West, Port of Lyttelton, New Zealand
Science Results: We are tied up alongside Berth #2 West in Lyttelton, New Zealand. We loaded the contents of a 40 ft IODP container onboard. We also loaded IODP material into a 20 ft container to be returned to College Station. The Staff Scientist finalized the Operations sections for each site, excluding the final operations during the last few days of the expedition.
Daily Science Report for 4 March 2018
Location: Berth #2 West, Port of Lyttelton, New Zealand
Science Results: We are tied up alongside Berth #2 West in Lyttelton, New Zealand. The oncoming Expedition 375 Staff Scientist visited the ship to meet with the current Staff Scientist, Operations Superintendent, Laboratory Officer, Manager of Technical and Analytical Services, and the port agent to discuss logistics for critical equipment to be transferred to the ship and assembled before Expedition 375 departs. The Staff Scientist completed final edits of the Expedition 374 visual core description (VCD) summary descriptions for consistency, spelling, and grammar.
Daily Science Report for 3 March 2018
Location: Berth #2 West, Port of Lyttelton, New Zealand
Science Results: We are tied up alongside Berth #2 West in Lyttelton, New Zealand. We loaded the last three flats of Expedition 375 CORK equipment. The Staff Scientist completed the Preliminary Report, minus the final Operations section that will be turned in at the end of the expedition. Two scientists disembarked the vessel.
Daily Science Report for 2 March 2018
Location: Berth #2 West, Port of Lyttelton, New Zealand
Science Results: We are tied up alongside Berth #2 West in Lyttelton, New Zealand. We loaded four flats of equipment for Expedition 375. We also offloaded Expedition 374 frozen samples for shipment. The remaining Expedition 374 scientists met to revisit results from Sites U1523, U1524, and U1525. The scientists assisting with postcruise X-ray fluorescence (XRF) scanning finalized the scanning schedule.
Daily Science Report for 1 March 2018
Location: Berth #2 West, Port of Lyttelton, New Zealand
Science Results: We are tied up alongside Berth #2 West in Lyttelton, New Zealand. We loaded 52 joints of 10¾ inch casing into the riser hold in preparation for IODP Expedition 375. The Expedition 374 cores were loaded into a refrigerated container for transport to the Gulf Coast Repository in College Station, Texas, USA. Expedition 374 scientists who will help with postcruise X-ray fluorescence (XRF) scanning compiled lists of cores to scan for each site, together with time estimates to complete the scanning prior to an XRF scheduling discussion.
Daily Science Report for 28 February 2018
Location: Berth #2 West, Port of Lyttelton, New Zealand
Science Results: We are tied up alongside Berth #2 West in Lyttelton, New Zealand. We loaded 22 joints of 10¾ inch casing plus four pup joints, as well as 75 joints of 4½ inch casing plus six pup joints to the riser hold in preparation for IODP Expedition 375. We also loaded 12 oxygen and six acetylene bottles. The remaining Expedition 374 scientists met to revisit results from Sites U1521 and U1522, and they made plans to discuss the remaining sites in the coming days. The Staff Scientist collated the Expedition Summary figures and also corrected several inconsistencies in location names on the expedition maps for all Background and Objectives sections, as well as for the Expedition Summary.
Daily Science Report for 27 February 2018
Location: Berth #2 West, Port of Lyttelton, New Zealand
Science Results: We are standing by waiting on port call operations and will load Expedition 375 items as they become available.
Daily Science Report for 26 February 2018
Location:
• Oil Berth, Port of Lyttelton, New Zealand
• Berth #2 West, Port of Lyttelton, New Zealand
Science Results: We finished taking on fuel, and then the pilot boarded the vessel at 1624 h. The last line was released at 1645 h to shift to Berth #2 West, where we arrived at 1700 h. We will remain at Berth #2 West until departing for Expedition 375. We are currently standing by waiting on port call operations and will load Expedition 374 items as they become available. The Staff Scientist began assembling sections of the Expedition Summary into a single document.
Daily Science Report for 25 February 2018
Location:
• Berth #7 East, Port of Lyttelton, New Zealand
• Oil Berth, Port of Lyttelton, New Zealand
Science Results: The pilot boarded the vessel at 0558 h and the last line was released at 0626 h to shift to the Oil Berth to begin loading fuel. We arrived at the Oil Berth at 0640 h. By the end of the day we had loaded 1100 metric tons of marine gas oil. The Staff Scientist compiled operations tables and worked to complete remaining operations text for the site chapters.
Daily Science Report for 24 February 2018
Location: Berth #7 East, Port of Lyttelton, New Zealand
Science Results: We are tied up alongside Berth #7 East in Lyttelton, New Zealand. We crated the liquid nitrogen generator for shipment back to College Station. We also offloaded scrap metal (drilling and coring line) from Expedition 374. One scientist disembarked for his return flight home.
Daily Science Report for 23 February 2018
Location: Berth #7 East, Port of Lyttelton, New Zealand
Science Results: We are tied up alongside Berth #7 East in Lyttelton, New Zealand. We loaded refrigerated catering containers and 5½ inch drill pipe, and offloaded an empty core liner box. Several additional scientists disembarked for return flights home.
Daily Science Report for 22 February 2018
Location:
• Berth #2 West, Port of Lyttelton, New Zealand
• Berth #7 East, Port of Lyttelton, New Zealand
Science Results: We shifted to Berth #7 East, arriving at 0949 h. The Co-Chief Scientists and Staff Scientist finalized most of the Expedition Summary. Only the Operations section remains to be completed. We held the final science meeting to review what we had accomplished during the expedition and synthesize future research. The Staff Scientist also gave the science party a final review of postexpedition activities. Scientists who changed their departure flights began to disembark in the afternoon.
Daily Science Report for 21 February 2018
Location: Berth #2 West, Port of Lyttelton, New Zealand.
Science Results: We are tied up alongside Berth #2 West in Lyttelton, New Zealand. The scientists completed all site reports and Methods sections, and also reviewed the Expedition Summary. The Co-Chief Scientists and Staff Scientist continued to work towards finalizing the Expedition Summary. We held meetings to discuss Pliocene and Pleistocene research plans and sample requests.
Daily Science Report for 20 February 2018
Location: Berth #2 West, Port of Lyttelton, New Zealand.
Science Results: We are tied up alongside Berth #2 West in Lyttelton, New Zealand, to shelter from Cyclone Gita. The scientists continued to finalize site reports and Methods sections. We also had a meeting to discuss research plans and sample requests for the Miocene.
Daily Science Report for 19 February 2018
Location:
• Underway to Lyttelton, New Zealand
• Berth #2 West, Port of Lyttelton, New Zealand
Science Results: We arrived at a point 12 nmi offshore Lyttelton at 0148 h and lowered the thrusters. After confirming berth availability and permission to come into port, we raised the thrusters at 1142 h and transited toward Lyttelton. The pilot boarded the vessel at 1342 h and we arrived in port with the first line ashore at 1512 h. The scientists continued to work on revising site reports and Methods sections. The Co-Chief Scientists and Expedition Project Manager/Staff Scientist continued to work on the Expedition Summary. Science party members will continue working onboard to complete all expedition-related reports by 22 February.
Daily Science Report for 18 February 2018
Location: Underway to Lyttelton, New Zealand
Science Results: We are underway to the pilot station at Lyttelton, New Zealand, with an estimated arrival time of 1300 h on 19 February. We are currently investigating if we can move to a berth in Lyttelton on 19 February to shelter from approaching Tropical Storm Gita. The scientists continued to work on finalizing reports. We also held small group discussions for research planning. The Co-Chief Scientists and Staff Scientist worked to finalize the Preliminary Report.
Daily Science Report for 17 February 2018
Location: Underway to Lyttelton, New Zealand
Science Results: We are underway to the pilot station at Lyttelton, New Zealand, with an estimated arrival time of 1300 h on 19 February. We will take on supplies at the pilot station and then move offshore to undertake repairs. The Co-Chief Scientists gave a presentation to summarize the expedition achievements and remind everyone of the scientific objectives for each site in preparation for final research planning. The scientists continued to work on finalizing reports.
Daily Science Report for 16 February 2018
Location: Underway to Lyttelton, New Zealand
Science Results: We are underway to the pilot station at Lyttelton, New Zealand, with an estimated arrival time of 1300 h on 19 February. We will take on supplies at the pilot station and then move offshore to undertake repairs. The scientists turned in drafts of their Site U1524 reports and continued to work on revising and finalizing other site reports and Methods text. The Staff Scientist gave an update on repair plans and estimated arrival into port, with updated timeline for the remainder of the expedition. The Operations Superintendent gave tours of the Bridge and Dynamic Positioning system to interested scientists.
Daily Science Report for 15 February 2018
Location: Underway to Lyttelton, New Zealand
Science Results: We are underway to the pilot station at Lyttelton, New Zealand, with an estimated arrival time of 1300 h on 19 February. The scientists continued to work on writing up site reports and finalizing Methods text. The Staff Scientist gave an end-of-expedition presentation to lay out a (tentative) schedule for the remainder of the expedition and to explain what happens following the end of the expedition, including publication of the Preliminary Report, the postcruise editorial meeting, sampling party, and science meeting, and manuscript submission deadlines to fulfill the obligation to conduct research and publish those results. The Operations Superintendent also gave tours of the engine room to interested scientists.
Daily Science Report for 14 February 2018
Location: Underway to Lyttelton, New Zealand
Science Results: After receiving confirmation that we have to return to port to fix the mechanical problem, we began to prepare for the end of the expedition as there is not enough time remaining to return to any of our sites for continued operations. The scientists presented results from Site U1524 and worked on writing up those results. They also worked to finalize previous site reports and began updating Methods text.
Daily Science Report for 13 February 2018
Location: Underway north toward Lyttelton, New Zealand
Science Results: We continued to transit north toward Lyttelton, New Zealand, with a mechanical breakdown issue while awaiting further instructions from shore. The scientists finished writing up their results from Site U1525 and turned in drafts of the site report. They also continued to analyze data from Site U1524 in preparation for the science review meeting. Our education team conducted a workshop for interested scientists on how to explain their science using only the 1000 most common words in the English language.
Daily Science Report for 12 February 2018
Location: Underway north toward warmer water/Lyttelton, New Zealand
Science Results: We continued transiting north toward Lyttelton, New Zealand, while attempting to resolve the mechanical problem. The scientists completed measurement of the remaining samples from Hole U1524C. Carbonate content remains low in Hole U1524C (<1.5 wt%), with the exception of a single sample of carbonate-cemented mudstone with a carbonate content of 64 wt%. Total organic carbon content is also generally low (<1 wt%). Discrete bulk density and porosity measurements are variable, with no discernible downhole trend. The scientists presented science results from Site U1525 and worked on writing up the site reports.
Daily Science Report for 11 February 2018
Location:
• Hole U1524C (74°13.0537′S, 173°37.9338′W; water depth 2394 m)
• Underway north toward warmer water/Lyttelton, New Zealand
Science Results: We continued to RCB core from Core U1525C-15R to 20R, which penetrated to 441.9 m. Core recovery was 9.21 m (16%). We terminated coring at that point due to a mechanical breakdown of the port stern tube and shaft arrangement. After pumping a 30-barrel high-viscosity mud sweep, we began to pull the drill string out of the hole, setting back the top drive when the bottom of the drill string reached 372.8 m. We disassembled the bottom-hole assembly and secured the drill floor at 1835 h. The thrusters were raised and we departed Site U1524 at 1900 h. We are headed north toward Lyttelton, New Zealand; however, we are attempting to fix the mechanical problem while underway and will return to our area of operations if the problem can be resolved.
Cores U1524C-12R through 20R were split and described; however, only Cores 12R, 16R, and 20R had any significant recovery. The sediment consists of interbedded dark greenish gray to light greenish gray diatom-rich mud and sandy mud. Dispersed clasts (primarily mudstone) are present throughout. Sandy mud beds have bioturbated, gradational lower contacts and sharp upper contacts. Diatom-rich mud beds are occasionally laminated but often show burrowing. The upper part of the described interval contains some coarser-grained (sand to gravel size) laminae, typically at the top of sandy mud beds. Pyrite staining is present throughout. The age at the base of Hole U1524C is late Miocene based on diatom biostratigraphy.
Daily Science Report for 10 February 2018
Location: Hole U1524C (74°13.0537′S, 173°37.9338′W; water depth 2394 m)
Science Results: We continued to drill without coring in Hole U1524C from 88.2 to 260.5 m. After reaching that depth, we retrieved the center bit and started RCB coring. Cores 2R through 14R pentetrated to 384.3 m with poor core recovery (9.99 m, 8%). Diatoms and radiolarians suggest a late Miocene age at the bottom of the drilled interval; however, this is preliminary due to significant reworking of fossils. Cores 2R through 11R were split and described. The upper part of the recovered core material consists of interbedded greenish gray and light greenish gray diatom ooze. Some intervals are laminated and beds often have sharp contacts. Bioturbation is common in the light greenish gray diatom ooze. A few small (~1 cm) clasts are also present. Below this, dark greenish gray diatom-rich mud is interbedded with decimeter- to meter-thick beds of light greenish gray clast-poor muddy diamict. The diamict is burrowed and contains lenses of pyrite. Most clasts are <1 cm, although some range up to a few centimeters in size. Cores with very poor recovery consist of cobble-sized clasts.
Daily Science Report for 9 February 2018
Location:
• Hole U1525A (75°0.0603′S, 173°55.2028′W; water depth 1776 m)
• In transit to Site U1524
• Hole U1524C (74°13.0537′S, 173°37.9338′W; water depth 2394 m)
Science Results: We continued to raise the drill string back to the ship at Hole U1525A. After setting back the drill collars, we disassembled and inspected the outer core barrel. The bit cleared the rotary table at 0535 h and the rig floor was secured at 0542 h, ending operations at Site U1525. We then transited back to Site U1524 and the drill floor was cleared to begin operations at 1006 h. We prepared a RCB bottom-hole assembly and lowered the drill string towards the seafloor. After the drill bit reached 1766 m, we deployed the subsea camera to recover the seafloor beacon that had failed to release when we abandoned the site due to approaching sea ice. We recovered the beacon at 1800 h and returned the subsea camera to the ship, with the beacon arriving on deck at 1915 h. After securing the subsea camera we continued to prepare for drilling operations. Hole U1524C was started at 2110 h and we drilled without coring from the seafloor to 88.2 m by the end of the day. We plan to start coring at 260 m.
The last cores from our previous Site U1525 (U1525A-30X though 33X) were split and described. Of these, only Core 30X was of good quality; the core barrels shattered for Cores 31X to 33X, resulting in highly disturbed cores. The sediment consists of laminated dark greenish gray diatom-rich mud that is interbedded with greenish gray diatom-rich mud. The greenish gray mud is massive to slightly laminated, with gradational and often bioturbated lower contacts. Millimeter- to centimeter-scale beds of silt, sand, and gravel are common. The lower contacts of the dark greenish gray beds are sharp. The age at the bottom of Hole U1525A is Pliocene based on diatom and radiolarian biostratigraphy.
Daily Science Report for 8 February 2018
Location: Hole U1525A (75°0.0603′S, 173°55.2028′W; water depth 1776 m)
Science Results: APC coring with nonmagnetic core barrels continued from Core U1525A-17H to 19H (88.8–111.8 m). Since Core 19H recorded a partial stroke, we advanced 4.1 m based on recovery and switched to half-length APC (HLAPC) coring, collecting Cores 20F to 24F (111.8–131.2 m). Core 24F also recorded a partial stroke, so we switched to XCB coring. We cut Cores 25X to 33X to a total depth of 213.2 m. Five out of the nine XCB cores had shattered liners, which we suspect resulted from a combination of very cold seawater (−2°C) circulating through the hole and the small space between the core liner and the core barrel, which allows vibration. Since ice conditions at our previous Site U1524 are forecast to improve by noon tomorrow, we opted to stop coring after Core U1524A-33X. Recovery over the cored interval was 84.67 m (68%). We began to pull the drill string out of the hole, clearing the seafloor at 2150 h. At the end of the day we were conducting routine rig maintenance (slip and cut of 115 ft of drill line).
Cores 5H through 29X were split and described. The sediment consists of interbedded olive gray diatom-bearing mud and greenish gray diatom-bearing mud, although some intervals are diatom-rich. The olive gray mud packages are thicker than the greenish gray mud beds and usually have sharp bases. There are coarser grained beds and sand lenses, particularly in the olive gray beds. Carbonate content is slightly higher in the upper part of this site, usually in the range of 2–4 wt%, whereas total organic carbon content is very low (<0.2 wt%).
Daily Science Report for 7 February 2018
Location:
• Underway to Site U1525 (proposed Site RSCR-03A)
• Hole U1525A (75°0.0603′S, 173°55.2028′W; water depth 1776 m)
Science Results: We arrived at Site U1525 (proposed Site RSCR-03A) at 0215 h and switched to dynamic positioning. After preparing the APC/XCB bottom-hole assembly, we began to lower the drill string toward the seafloor. We picked up the top drive and lowered the drill bit to tag the seafloor, which indicated that it was soft. We then prepared a nonmagnetic APC core barrel and started Hole U1525A at 1000 h. Core 1H collected 8.62 m of sediment, establishing a seafloor depth of 1776 m. We continued to core with nonmagnetic core barrels through Core 4H (28.9 m), which was a partial stroke. We switched to the half-length APC (HLAPC) coring system to collect Cores 5F through 8F (28.9–43.0 m). Since Core 8F was a partial stroke with no recovery, we switched to the XCB to cut Cores 9X and 10X (43.0–55.7 m) to get through an indurated zone. We then returned to the HLAPC system for Cores 11F to 15F (55.7–79.2 m). Since the sediment seemed conducive to piston coring, we switched back to the full-length APC and by the end of the day we had collected Core 16H to 88.7 m. Core recovery was poor (3%) over the XCB interval; however, overall core recovery was good, with 74.03 m (83%) collected for the day. The age at the bottom of the cored interval is late Pliocene based on diatom and radiolarian biostratigraphy.
Cores U1524A-28H through 34X were split and described. The sediment consists of thick beds of olive gray diatom-bearing mud interbedded with thinner intervals of greenish gray diatom-bearing mud. The olive gray mud contains coarse silt to sand laminae and lenses. The greenish gray mud typically has a gradational lower contact, is bioturbated, and contains some dispersed clasts. Pyrite staining is common throughout. On average, calcium carbonate content is somewhat higher (1–2.5 wt% compared with <1 wt%) in the lower half of Hole U1524A. Cores U1525A-1H through 4H were also split and described. The uppermost part of the hole consists of brownish yellow to light yellowish brown sandy mud and muddy sand with dispersed clasts. The color grades downhole into gray, although there is no discernible change in lithology. Below this the gray sandy mud/muddy sand is interbedded with meter-thick beds of light olive brown to dark grayish brown clast-rich diamict.
Daily Science Report for 6 February 2018
Location:
• Hole U1524A (74°13.0427′S, 173°38.0185′W; water depth 2394 m)
• Hole U1524B (74°13.0440′S, 173°37.9834′W; water depth 2394 m)
• Underway to Site U1525 (proposed Site RSCR-03A)
Science Results: Oriented APC coring with nonmagnetic core barrels continued from Core U1524A-28H to 30H (246.3–270.3 m). After Core 30H recorded a partial stroke, we switched to the half-length APC (HLAPC) and collected Core 31F. This core also recorded a partial stroke and only recovered 0.4 m of sediment. We advanced the hole by recovery (0.4 m) and switched to the XCB coring system. Cores 31X through 34X were cored to 299.5 m; all core liners were shattered upon recovery resulting in highly disturbed sediment. At that point we had to terminate coring and pull out of the hole due to approaching sea ice. Overall recovery in Hole U1524A was 282.35 m (94%). After pulling the drill bit up to 249.5 m, we set back the top drive and continued to pull out of the hole, clearing the seafloor at 0950 h. We attempted to retrieve the acoustic beacon, but it would not release. We continued to monitor the approaching ice while picking up the top drive so that we could take a single mudline core for high resolution interstitial water and microbiological studies. Hole U1524B was started at 1155 h and consisted of a single core (1H) that recovered 7.76 m. We then continued to retrieve the drill and used the dynamic positioning system to move away from the floating ice. After the drill string was recovered and the rig floor secured for transit, we departed for Site U1525 (proposed alternate Site RSCR-03A) at 2030 h. We decided to go to this alternate site because it is close to Site U1524 (47 nmi) but outside the sea ice edge, and the Ross Sea unconformity RSU3 (primary objective for Site U1524) is located at a much shallower depth. We intend to continue coring at this site until the sea ice moves away from Site U1524, which is projected to occur in 2–3 days.
Diatom biostratigraphy indicates an early Pliocene age for the base of Hole U1524A. Diatoms are consistently present throughout the hole and radiolarians are present over most of it. Cores U1524A-14H through 27H were split and described. The sediment consists of interbedded olive gray and greenish gray diatom-bearing/rich mud. The bases of the olive gray mud beds are typically sharp. Some intervals are laminated, and sand/silt lenses and pyrite staining are consistently present throughout this lithology. The greenish gray mud typically has a gradational lower contact and often shows burrows. Greenish gray mud beds are typically thinner (centimeter to decimeter scale), whereas the olive gray mud beds are thicker (decimeter to meter scale). Total organic carbon and calcium carbonate contents are low throughout this site (<0.6 wt% and <2.5 wt%, respectively).
Daily Science Report for 5 February 2018
Location: Hole U1524A (74°13.0427′S, 173°38.0185′W; water depth 2394 m)
Science Results: Oriented APC coring with nonmagnetic core barrels continued in Hole U1524A from Core 5H to 27H (32.5–246.3 m). Core recovery over this interval was 227.03 m (102%). The age at the bottom of the hole is Pliocene based on diatom and radiolarian biostratigraphy. Cores 1H through 13H were split and described. The uppermost sediment consists of interbedded brown, light brown, and greenish gray diatom-bearing mud with dispersed clasts. Color alternations occur at decimeter scale, often with sharp bases. Downhole, the sediment changes to olive gray and greenish gray diatom-bearing mud interbedded at decimeter to meter scale. The olive gray mud typically has a sharp base and includes sand laminae. The greenish gray beds have gradational basal contacts. Dispersed clasts up to cobble size are sporadically present. Burrows become more common toward the base of the described section. An ~17 cm thick ash bed is present in the middle of the described interval.
Daily Science Report for 4 February 2018
Location:
• Hole U1523E (74°9.0290′S, 176°47.7491′W; water depth 828 m)
• In transit to Site U1524 (proposed Site RSCR-10A)
• Hole U1524A (74°13.0427′S, 173°38.0185′W; water depth 2394 m)
Science Results: After we finished recovering Core U1523E-25F (the final core of Site U1523), we pumped a 30-barrel mud sweep and then began to retrieve the drill string back to the vessel. We left the top drive in until the drill bit cleared the seafloor at 0150 h due to unstable hole conditions causing excessive torque and overpull. The bit cleared the rotary table at 0555 h, ending operations at Site U1523. After securing the rig floor for transit, we departed for Site U1524 (proposed Site RSCR-10A), which is an alternate site for the original primary proposed Site RSCR-02B. We decided to occupy the alternate site because the seismic facies displayed less evidence for transported sediment, the sea ice edge is further away, and the primary target is slightly shallower. We arrived at the site and switched to dynamic positioning at 1044 h. We then prepared an APC/XCB bottom-hole assembly and began to lower it toward the seafloor. Since this location is in deeper water than the previous sites, some of the drill pipe was strapped and drifted as it was deployed. After positioning the drill string with the bit at 2400 m below rig floor, we installed the Icefield core orientation tool and started APC coring in Hole U1524A at 1825 h. Core U1524A-1H recovered 4.02 m, indicating a seafloor depth of 2394 m. We continued to APC core with orientation and nonmagnetic core barrels to Core 4H (32.5 m). The age at the bottom of the cored section is Pleistocene based on diatom biostratigraphy.
Cores U1523E-18F through 25F from our previous site were split and described. The upper part of the described interval consists of pale green to greenish gray diatom-rich mud to diatom-bearing/rich sandy mud with dispersed clasts. Decimeter-thick alternations between different colored sediment is apparent. Sand stringers are present throughout the described section. The bottom two cores are heavily disturbed due to shattered core liners. Total organic carbon is low at this site (<0.6 wt%), and carbonate content is mostly very low (<1 wt%) except in some intervals with foraminifers where carbonate content is higher (5–15 wt%).
Daily Science Report for 3 February 2018
Location:
• Hole U1523D (74°9.0288′S, 176°47.7087′W; water depth 828 m)
• Hole U1523E (74°9.0290′S, 176°47.7491′W; water depth 828 m)
Science Results: After completion of downhole logging, we recovered the drill string with the end of the drill string arriving back on the rig floor at 0240 h. We then prepared an APC/XCB bottom-hole assembly and began to lower the drill string to the seafloor to spot core Hole U1523E over some intervals poorly recovered in Holes U1523A and U1523B. The first core was taken with the drill bit at the seafloor, and Core 1H recovered a full barrel (9.86 m). After drilling without coring 9.5 m, we switched to the half-length APC coring system (HLAPC) and proceeded with spot coring. Over the upper ~90 m, this consisted of 1–3 HLAPC cores, followed by a drill ahead interval ranging from 2.8 to 12.3 m. Depths were chosen to avoid gravel encountered in our previous holes. Below ~90 m, we deployed a center bit to drill through hard layers (93–95 m, 104–108 m, and 116–117 m) and took HLAPC cores in between. This proved particularly successful for the interval below 100 m, allowing us to fill in substantial gaps in the stratigraphy. The last core (25F) in Hole U1523E arrived on deck at 2350 h. We collected 17 cores in Hole U1523E that recovered 54.08 m (64%).
Cores U1523E-1H through 16F (0–90.82 m) were split and described. The uppermost part of the section consists of greenish gray to grayish brown interbedded sandy mud, muddy sand, and foraminifer-rich sand. Pebble-sized clasts are common and bioturbation is present in some intervals. Glauconite, shell fragments, and pyritized burrows are also present. Below this is a poorly recovered interval of sandy mud with abundant clasts. In the lower part of the described interval, the sediment consists of olive gray mud, greenish gray diatom-bearing/rich sandy mud, and muddy diatomite. Clasts, glauconite, burrows, and pyrite stains are common in the mud and sandy mud. Several layers of shell hash are also present within this interval. Occasional cobble-sized clasts are present throughout the described interval and include granite and gneiss. Radiolarian and diatom biostratigraphy confirms late Miocene, Pliocene, and Pleistocene ages for the section recovered in Hole U1523E. Dinoflagellate cysts are consistent with these ages. Several paleomagnetic reversals were identified in the section and should help to refine the age model when combined with the biostratigraphic results.
Daily Science Report for 2 February 2018
Location: Hole U1523D (74°9.0288′S, 176°47.7087′W; water depth 828 m)
Science Results: We continued to RCB core in Hole U1523D from Core 14R through 19R (250.2–307.8 m) with essentially no recovery. After reaching our target depth (~300 m) for downhole logging, we terminated coring. We pumped two 50-barrel high viscosity mud sweeps, dropped the RCB bit in the bottom of the hole, and then displaced the hole with 94 barrels of 10.5 ppg mud. We then pulled the drill string to 258.5 m, set back the top drive, and continued to pull the drill string up to logging depth, with the end of the pipe set at 82.3 m. After displacing the upper part of the hole with heavy mud, we prepared for downhole logging operations. The modified triple combo tool string included tools to measure natural gamma radiation, resistivity, sonic velocity, and magnetic susceptibility. The density tool was run without the source for the caliper. The triple combo was lowered into the hole at 1320 h and reached to 292 m (within 15 m of the bottom of the hole). After a calibration log to 152 m, the tools were lowered back to 292 m, the caliper was opened, and a final log was collected. When the tool string neared the end of the pipe, it was raised to 67 m to provide additional coverage of the borehole. The tools were back at the surface at 1630 h. We then prepared the Formation MicroScanner (FMS) tool string, which was lowered into the hole at 1820 h. The FMS reached to 289.6 m and two passes were completed before the tool string was retrieved to the surface at 2130 h. The unprocessed logging data look very good and will provide constraints on unrecovered intervals of the site. After securing all logging tools, we began to retrieve the drill string towards the surface, with the end of pipe clearing the seafloor at 2315 h. The scientists continued to analyze discrete samples from Hole U1523B for moisture and density, as well as carbonate and total organic carbon. They also worked on revision of previous site reports.
Daily Science Report for 1 February 2018
Location:
• Hole U1523C (74°9.0288′S, 176°47.6680′W; water depth 828 m)
• Hole U1523D (74°9.0288′S, 176°47.7087′W; water depth 828 m)
Science Results: We continued to pull the drill string back to the rig floor, with the bit arriving back on the rig floor at 0130 h, ending Hole U1523C. We then prepared a RCB bottom-hole assembly and lowered the pipe toward the seafloor. After picking up the top drive, we started Hole U1523D, 20 m west of Hole U1523C. We drilled without coring from the seafloor to 135 m. After retrieving the center bit, RCB Cores 2R through 13R penetrated to 250.2 m with very poor recovery (0.84 m; 1%) due to the unconsolidated and coarse-grained nature of the sediment. We plan to core to ~300 m and then log the hole with a modified triple combo tool string. Most of the core recovered consists of washed cobble-sized clasts; however, a few cores contained small amounts of sediment that yielded a late Miocene age based on diatom biostratigraphy for the upper part of the cored interval.
Cores U1523B-23X and 24X (145.20–155.57 m) were split and described. The sediment consists of greenish gray diatom-rich/bearing mud and sandy mud interbedded with clast-rich muddy to sandy diamict. Glauconite is present within this interval. The mud is laminated and mottled in places and distinct gravel beds are present in the diamict. Despite the presence of frequent to common numbers of foraminifers, carbonate content is low at this site (<3.5 wt%). It is highest in the upper ~40 mbsf, then decreases downhole.