IODP Expedition 395
Reykjanes Mantle Convection and Climate
Daily science report for 11 August 2023
Location: In transit to Reykjavík, Iceland
Science Update: The vessel continued the transit from Site U1564 to Reykjavík, Iceland. The ship completed 221 nmi of the 293 nmi transit at an average speed of 9.2 kt and is expected to reach the pilot station at 0700 h on 12 August.
The science party finalized the reports for Site U1564 and the methods chapters. A results meeting for Site U1564 was held and the science party discussed the achievements of the cruise.
Daily science report for 10 August 2023
Location: Hole U1564F (59°51.036′N, 23°15.984′W; water depth 2208.2 m)
Science Update: Two passes of the borehole were made with the FMS-sonic tool string. At 0530 h, the FMS-sonic reached the rig floor and was broken down. The Ultrasonic Borehole Imager (UBI) was run to a depth of 1164.7 mbsf, 5 m above the base of the hole. The average heave over the course of the day was 1.8 m, which made it difficult to run imaging tools. Because of the weather conditions, the UBI was to be run at a lower resolution scan. However, the basement section was first logged at high resolution to test the image quality and because there was enough time in the program. The UBI was then lowered back to 1164.7 mbsf and the entire hole was logged at a lower resolution. The UBI was retrieved and broken down. The rig crew pulled the drill pipe out of the hole, with the bit clearing the seafloor at 1525 h. The BHA was broken down and the end of the pipe reached the rig floor at 2130 h. The vessel was secured for transit, and at 2206 h, the vessel was switched from DP to cruise mode, ending Site U1564. The thrusters were raised and the transit to Reykjavík, Iceland, began at 2230 h. At the end of the day, the vessel had completed 14.0 nmi of the 293 nmi transit.
The science laboratory teams continued to work on site reports and methods chapters.
Daily science report for 9 August 2023
Location: Hole U1564F (59°51.036′N, 23°15.984′W; water depth 2208.2 m)
Science Update: The drill pipe continued to be pulled out of the hole. At 0215 h, the subsea camera was deployed and descended to near the seafloor. At 0325 h the bit cleared the seafloor, and the vessel was offset 20 m from Hole U1564F. The mechanical bit release sleeve was activated, and the drill bit fell to the seafloor. The end of the drill pipe reentered Hole U1564F at 0625 h. The end of the pipe was positioned at 59.3 mbsf within the casing string for logging operations. The triple combo tool string was rigged up and deployed to the base of the hole (1169.7 mbsf). On the upward pass, the Accelerator Porosity Sonde (APS) malfunctioned and porosity measurements were not collected. Following a complete pass of the hole, the triple combo was pulled to the rig floor and broken down. The Formation MicroScanner (FMS)-sonic was made up and deployed in the hole. On the downward pass, the Dipole Sonic Imager (DSI) malfunctioned and was not used. At 2330 h, the FMS-sonic tool string reached the base of the hole and began the first upward pass of the open hole.
The laboratory teams continue to finalize discrete sample measurements from Hole U1564F, including inductively coupled plasma–atomic emission spectroscopy (ICP-AES) of the basalt, thin section descriptions, moisture and density (MAD), and paleomagnetic cubes. The final site reports and revisions to the methods chapter are in progress.
Daily science report for 8 August 2023
Location: Hole U1564F (59°51.036′N, 23°15.984′W; water depth 2208.2 m)
Science Update: Coring continued with the recovery of Cores U1564F-70R to 76R (1136.7–1169.7 mbsf). Erratic standpipe pressure was observed while cutting Core 74R and the core barrel was retrieved after only a 3.9 m advance. It was suspected that the core barrel had come unlatched from the BHA and there was rock blocking the bit throat. A bit deplugger was deployed, but there was no indication that anything was jammed in the bit. Hole U1564F was terminated at a final depth of 1169.7 mbsf.
A total of 434.15 m of core was recovered from a 571.7 m interval (76%). The recovery within the basement section was high (69%) with 119.46 m of core recovered over 172.4 m.
Following the completion of coring operations, the hole was cleaned with a 50-barrel high viscosity mud sweep in preparation of downhole logging operations. At the end of the day, the drill pipe began to be pulled from the hole to drop the bit on the seafloor.
Expedition 395 completed coring operations at 11 holes across four sites. A final total of 3825.76 m of core was recovered across a 4397.6 m interval, with 87% recovery.
Cores U1564F-68R to 76R (1126.9–1167.1 mbsf) were split and described. Cores 68R to 70R contain sparsely plagioclase phyric basalt that are moderately to completely altered. Cores 71R to 76R contain aphyric basalt with glassy intervals. These cores range from being slightly to completely altered. When present, vesicles are filled with a variety of minerals, including celadonite, clay, calcite, and oxides. Veins that range in color between white, pink, dark green, and brown continue to be abundant.
Daily science report for 7 August 2023
Location: Hole U1564F (59°51.036′N, 23°15.984′W; water depth 2208.2 m)
Science Update: Coring continued with the recovery of Cores U1564F-62R to 69R (1097.7–1136.7 mbsf). A total of 23.31 m of basalt was recovered over the interval (60%).
Cores U1564F-62R to 67R (1097.7–1125.59 mbsf) were split and described. These cores contain sparsely plagioclase phyric basalt. Aphryic basalt was recovered in Core 66R. The basalt is moderately to completely altered. When present, vesicles are filled with a variety of minerals including celadonite, clay, calcite, and oxides. Veins that range in color between white, pink, dark green, and brown continue to be abundant. Small (20–40 cm) intervals of mudstone are present in Cores 63R, 65R, and 66R.
Daily science report for 6 August 2023
Location: Hole U1564F (59°51.036′N, 23°15.984′W; water depth 2208.2 m)
Science Update: Coring continued with the recovery of Cores U1564F-53R to 61R (1053.9–1097.7 mbsf). A total of 35.34 m of core was recovered over the 43.8 m interval (81% recovery). The average ROP was 2.8 m/h. A 65 cm package of sediment was recovered in Core 53R.
Cores U1564F-52R to 61R (1049.0–1096.0 mbsf) were split and described. The dominant lithology is fine to medium grained sparsely plagioclase phyric basalt. Aphyric basalt is present in Cores 55R and 56R. The degree of alteration ranges from moderate to completely altered. Veins that are primarily white in color continue to be abundant. When present, vesicles are filled with a variety of minerals including celadonite, chlorite, clay, and oxides.
The sediment recovered in Sections U1564F-52R-2 to 4 is reddish brown nannofossil chalk with silty clay. Interval U1564F-53R-1, 6–71 cm, contains reddish brown, reddish gray, greenish gray, and white nannofossil chalk with silty clay. The nannofossil assemblage provides an age estimate of early Oligocene.
Daily science report for 5 August 2023
Location: Hole U1564F (59°51.036′N, 23°15.984′W; water depth 2208.2 m)
Science Update: The drill pipe was run from the ship to near the seafloor for reentry into Hole U1564F. At 0315 h, the subsea camera was deployed. The bit was spaced out, and after nearly 2 h of searching for the reentry cone, the bit entered Hole U1564F at 0725 h. The drill pipe was run in the hole and the subsea camera retrieved. Coring resumed at 1115 h. Cores U1564F-50R to 52R (1039.2–1053.9 mbsf) were retrieved with 76% recovery. Core 52R was cut in 20 min over a 4.9 m interval and contained 3.83 m of sediment.
Cores U1564F-48R to 51R (1024.7–1047.68 mbsf) were split and described. These cores contain sparsely plagioclase pyroxene phyric basalt and aphyric basalt. The basalts are moderately to completely altered with numerous white veins.
Daily science report for 4 August 2023
Location: Hole U1564F (59°51.036′N, 23°15.984′W; water depth 2208.2 m)
Science Update: Coring continued with the recovery of Cores U1564F-46R to 49R (1015.0–1039.2 mbsf). A total of 17.69 m of core was recovered (73%). Cores 46R, 47R, and 49R were half advances (4.7 or 5.0 m). The average ROP over this interval was 2.4 m/h. Following Core 49R, the drill bit had reached 59.7 rotating h and the drill string was pulled out of the hole to change the bit. At 1640 h, the bit cleared the seafloor, and the vessel was offset 20 m east of Hole U1564F. At 2030 h, the bit cleared the rig floor. A C-7 RCB bit and mechanical bit release were made up.
Section U1564F-44R-2 through Core U1564F-47R (997.23–1023.91 mbsf) were split and described. These cores contain sparsely olivine plagioclase or sparsely plagioclase phyric basalt. The basalts are highly altered with numerous white veins.
Daily science report for 3 August 2023
Location: Hole U1564F (59°51.036′N, 23°15.984′W; water depth 2208.2 m)
Science Update: Coring continued with the recovery of Cores U1564F-39R to 45R (957.0–1015.0 mbsf). The rate of penetration (ROP) dropped significantly from the previous day, to less than 2 m/h, during the cutting of Core 39R. The penetration rates varied throughout the day, but overall remained low with an average of ~4 m/h. The basaltic basement was reached at ~997.2 mbsf in Core 44R. This core recovered 7.03 m of material (74%), including 1.43 m of sediment and the remainder basalt. Core recovery remained high in Core 45R, with 7.32 m recovered (75%).
Core U1564F-35R through Section U1564F-44R-1 (918.3–997.23 mbsf) were split and described. The base of the sedimentary section records complex lithologic changes. Cores 35R to 39R are silty nannofossil chalk and silty claystone with glauconite. The cores are primarily greenish gray but transition to reddish brown in Core 39R. This interval is marked by soft sediment deformation and several fractures and veins. Glauconite is present in the form of very small grains to 2 cm clasts. Core 40R to Section 44R-1 contain white, greenish gray, reddish gray, and reddish brown nannofossil chalk. Fractures and glauconite are present within this interval as well. The base of the sedimentary section is ~32 Ma, which is consistent with the magnetic anomaly age prediction for the ocean crust.
Daily science report for 2 August 2023
Location: Hole U1564F (59°51.036′N, 23°15.984′W; water depth 2208.2 m)
Science Update: Coring continued with Cores U1564F-29R to 38R recovering 76.54 m of core from 859.9 to 957.0 mbsf (79% recovery).
Cores U1564F-25R to 34R (821.2–918.45 mbsf) were split and described. The primary lithologies are greenish gray to gray nannofossil chalk and silty clay/claystone. Bioturbation is moderate to abundant, and pyrite is present. Soft sediment deformation is observed in Cores 26R and 32R. Fractures and veins are found throughout the described section. The age of the described cores is early to middle Miocene.
Daily science report for 1 August 2023
Location: Hole U1564F (59°51.036′N, 23°15.984′W; water depth 2208.2 m)
Science Update: Coring continued with Cores U1564F-18R to 28R recovering 89.13 m of core from 753.0 to 859.9 mbsf (83% recovery).
Cores U1564F-14R to 24R (714.1–819.94 mbsf) were split and described. The primary lithologies are greenish gray nannofossil chalk and silty claystone. Bioturbation is present throughout, and several fractures were logged in Cores 23R and 24R. These cores are middle Miocene in age.