IODP Expedition 385
Guaymas Basin Tectonics and Biosphere
Daily Science Report for 30 September 2019
Location: Hole U1545A (27°38.2325′N, 111°53.3406′W; water depth 1593.5 mbsl)
Science Update: Coring continued in Hole U1545A. XCB Core 74X penetrated from 498.6 to 503.3 mbsf and recovered 8.7 m (184%). This was followed by circulation of 20 barrels of mud for hole cleaning and a formation temperature measurement (SET2 tool). Coring was then terminated in Hole U1545A based on a low C1/C2 value and the safety monitoring protocol. Upon circulating high-viscosity mud in the hole, we ran the Kuster Flow Through Sampler (FTS) tool and successfully recovered a borehole fluid sample from 490 mbsf at 0530 h. After circulating another sweep of high-viscosity mud, we started the deployment of wireline logging tool strings. We raised the end of the drill string to a logging depth of 75 mbsf, made up the triple combination (triple combo) logging tool string (with natural gamma ray, porosity, and density sondes), and lowered it into the hole. Once the tool string reached fill at ~488 mbsf, we performed a short calibration pass followed by a full logging run up to the seafloor. The tool string returned to the rig floor at 1500 h. After disassembling the triple combo tool string, we rigged up the Formation MicroScanner (FMS)-sonic (resistivity imaging) logging tool string. The tool string was lowered in the hole until it reached the fill at the bottom of the hole. The FMS-sonic tool string returned to the rig floor at 2300 h and was disassembled.
Cores 58X to 74X have been split and described. They consist of silty clay, with subordinate pyrite framboids. Even though the cores are affected by drilling disturbance, including brecciation and biscuiting, very fine-scaled lamination as well as dolomitized yellowish layers are regularly visible. In Core 71X, we observed an ~80 cm thick hard rock layer at a depth of ~482 mbsf. Preliminary data indicate an igneous nature, but this awaits further confirmation. No new age-diagnostic microfossils were observed, so the age remained in the Middle Pleistocene at the base of Core 74X.
Daily Science Report for 29 September 2019
Location: Hole U1545A (27°38.2325′N, 111°53.3406′W; water depth 1593.5 mbsl)
Science Update: We continued XCB coring in Hole U1545A all day. Cores 60X to 73X penetrated from 372.1 to 498.6 mbsf and recovered 67.7 m (54%). We made formation temperature measurements (SET-2 tool) after Cores 61X, 66X, and 70X. Prior to each SET-2 tool deployment, we circulated 20 barrels of mud for hole cleaning.
Cores 32H to 57X have been split and described. They consist of light olive to olive gray micrite-rich diatom clay, showing a decrease in both authigenic micrite content and abundance of carbonate concretions compared to shallower cores. Volcanic ash layers were observed in Cores 35F and 36F. Starting with Core 42F, the recovered material commonly shows drilling disturbance. No new age-diagnostic microfossils have been observed, so the biostratigraphic age remains in the Middle Pleistocene at the base of Core 57X.
Daily Science Report for 28 September 2019
Location: Hole U1545A (27°38.2325′N, 111°53.3406′W; water depth 1593.5 mbsl)
Science Update: We continued coring in Hole U1545A throughout the day, alternating between the HLAPC and extended core barrel (XCB) coring tools. Cores 33F to 59X penetrated from 212.4 to 372.1 mbsf and recovered 95.7 m (60%), with an overall reduced recovery rate due to sporadic occurrence of lithified carbonate layers. We made formation temperature measurements (APCT-3 temperature shoe) on Cores 36F, 43F, and 47F. After encountering hard carbonate, we recorded partial stroke and a damaged HLAPC cutting shoe, so we switched to XCB for Core 40X. We then resumed HLAPC coring through Core 50F, with the exception of XCB Core 49X that was recovered upon coring through another hard layer. Following HLAPC Core 50F, we decided to switch back to the XCB coring tool continuously.
Cores 13H to 31H have been split and described. They mainly consist of light olive-gray diatom ooze with laminated and homogenous textures. Interbedded carbonate layers and nodules are common. Starting with Core 27F, micrometer-sized authigenic carbonate is a main component of the sediment and the lithology ranges between light olive (more carbonate) to olive gray (less carbonate) micrite-rich diatom clay. No new age-diagnostic microfossils have been observed so that the age remains in the Middle Pleistocene ( 290 ka) at the base of Core 31H.
Daily Science Report for 27 September 2019
Location: Hole U1545A (27°39.2315′N, 111°53.3396′W; water depth 1593.5 mbsl)
Science Update: We continued coring in Hole U1545A throughout the day, alternating between the APC and half-length APC (HLAPC) coring tools. Cores 2H to 32H penetrated from 4.5 to 212.4 mbsf and recovered 212.4 m (103%). All APC cores were oriented and we made formation temperature measurements (APCT-3 temperature shoe) on every third core starting with Core 4H through Core 13H. After encountering hard layers, we recorded partial strokes and overpull upon retrieval on Cores 14H–16H. We switched to HLAPC for Cores 17F to 31F to improve core quality. APCT-3 measurements were made on Cores 18F, 24F, and 30F. Upon switching back to APC for taking Core 32H, we recorded another partial stroke with strong overpull. We thus resumed HLAPC coring just before midnight.
Cores 1H to 12H have been split and described. They consist of olive-gray laminated diatom ooze with varying subordinate proportions of clay, silt, authigenic carbonate, and other biosiliceous and calcareous microfossils. Changes in physical properties reflect variation in clay abundance on a centimeter- to meter-scale. Calcareous biostratigraphic markers indicate a Middle Pleistocene age (<290 ka) at the base of Core 12H.
Daily Science Report for 26 September 2019
Location:
• Underway to Site U1545 (proposed Site GUAYM-01B)
• Hole U1545A (27°39.2315′N, 111°53.3396′W; water depth 1593.1 mbsl)
Science Update: After completing the final 158 nmi of the 1152 nmi voyage from San Diego to Guaymas Basin (Gulf of California), we arrived at Site U1545 (proposed Site GUAYM-01B) at 1300 h. We lowered the thrusters and then switched to dynamic positioning mode. Rig floor operations commenced at 1345 h. The APC/XCB bottom-hole assembly was made up and the drill string was lowered to 1558.1 m below sea level (mbsl). We then pumped a “pig” (pipe cleaning device) through the drill string to remove some of the rust. By 2300 h, the drill bit was lowered to 1588.1 mbsl, and we installed the sinker bars and the core orientation tool. Upon positioning the bit for taking the first core, we spudded Hole U1545A at 2322 h. Mudline Core U1545A-1H arrived on deck at 2335 h, recovering 4.4 m. This established a seafloor depth of 1593.1 mbsl.
While still in transit, the Co-Chief Scientists presented the expedition scientific objectives to technicians and Siem Offshore personnel working on the night shift. The Core Description team received training on the core X-ray Imaging Logger by technical staff. In the early afternoon, the Co-Chief Scientists gave a presentation on the science objectives of northwestern Guaymas Basin Sites U1545 (GUAYM-01B) and U1546 (GUAYM-02B) and what we anticipate to encounter. Technical staff then introduced the Chemistry and Microbiology Laboratory groups to the capabilities of the Kuster Flow Through Sampler (FTS) tool that is going to be deployed to recover borehole fluids. All laboratory teams finished their preparations and are ready to receive the first core.
Daily Science Report for 25 September 2019
Location: Underway to Site U1545 (proposed Site GUAYM-01B)
Science Update: Today we completed 306 nmi, and a total of 994 nmi, of the 1152 nmi voyage from San Diego to Site U1545 (proposed Site GUAYM-01B) in the Gulf of California. We are underway at full speed, with the estimated time of arrival at 1500 h on 26 September 2019.
The laboratory teams finalized and submitted drafts of their Methods for the expedition, and continued setting up their laboratories for receiving core. At 1300 h, we held a pre-spud meeting with Siem Offshore staff to discuss operations for the first two drill sites, located ~50 km northwest of the axial trough of Guaymas Basin. The Co-Chief Scientists presented the expedition scientific objectives to technicians and Siem Offshore personnel working on the day shift. The Operations Superintendent guided two tours of the vessel for half of the science party and new technical staff. The first two live ship-to-shore outreach events were successfully conducted as scheduled.
Daily Science Report for 24 September 2019
Location: Underway to Site U1545 (proposed Site GUAYM-01B)
Science Update: Today we completed 304 nmi, and a total of 688 nmi, of the 1152 nmi voyage from San Diego to Site U1545 (proposed primary Site GUAYM-01B) in the Gulf of California. We are underway at full speed (~13 kt), and the estimated time of arrival on site is now 1500 h on 26 September 2019. Throughout the day, the scientists continued preparing their laboratories for receiving core, including setting up instruments in the Radiation (RAD) and Department of Energy (DOE) vans that are dedicated to performing microbial rate measurements with radioactive and stable isotope tracers, respectively. The Curatorial Specialist concluded in-depth training on core sampling to laboratory teams. The Operations Superintendent guided two tours of the vessel for half of the science party and new technical staff.
Daily Science Report for 23 September 2019
Location: Underway to Site U1545 (proposed Site GUAYM-01B)
Science Update: Today we completed 293 nmi, and a total of 384 nmi, of the 1152 nmi voyage from San Diego to Site U1545 (proposed primary Site GUAYM-01B) in the Gulf of California. We are underway at full speed, and the current estimated time of arrival on site is 0100 h (0800 h UTC) on 27 September. The scientists continued setting up their laboratories and drafting corresponding methods throughout the day. The Curatorial Specialist continued providing in-depth training on core sampling to different laboratory teams. We held a sampling discussion meeting to finalize the extensive biogeochemical and microbial shipboard sampling plan for personal postcruise research at Site U1545. Throughout the expedition, this plan will be adjusted for other drill sites as needed. The science party started moving to shifts at noon.
Daily Science Report for 22 September 2019
Location:
• B-Street Pier Terminal, Port of San Diego, USA
• In transit to Ensenada, Mexico
• At anchorage in Ensenada, Mexico
• Underway to Site U1545 (proposed Site GUAYM-01B)
Science Update: After securing the vessel for transit, the pilot boarded the ship at 0642 h. The vessel departed the B-Street Pier Terminal with the last line away at 0742 h, beginning our sea voyage. It started with a transit to Ensenada, Mexico, to clear customs and immigration. The transit ended at 1442 h. We anchored the vessel at 1512 h. The port agent and one final member of the science party then boarded the ship at 1515 h. All clearance formalities were completed by 1555 h. The anchor was fully lifted and secured at 1632 h. We then resumed our sea voyage at 1636 h. The rest of the day was spent in transit to Site U1545 (proposed Site GUAYM-01B). The scientists continued setting up their laboratories and drafting methods. The Curatorial Specialist provided in-depth training on core sampling on the core deck to different laboratory teams over the course of the day.
Daily Science Report for 21 September 2019
Location: B-Street Pier Terminal, Port of San Diego, USA
Science Update: In the morning, one experienced sedimentologist, who had already sailed on several JOIDES Resolution expeditions, gave a seminar on sediment core description to the entire science party. Then, all laboratory teams continued preparing their laboratories and drafting methods. In the afternoon, the Expedition Project Manager and Publications Specialist introduced the science party to IODP publications, as well as their obligations during the expedition and afterwards. Scientists were given the rest of the afternoon off in light of the last evening in port. We completed loading of freight, offloaded trash prior to sailing, and secured all equipment for our transit.
Daily Science Report for 20 September 2019
Location: B-Street Pier Terminal, Port of San Diego, USA
Science Update: After the science party received an orientation on IODP terminology, all laboratory groups met in their corresponding laboratories to continue the preparation of their working spaces and methods. This was followed by two presentations giving an overview of planned operations: (1) on coring operations by the Operations Superintendent, and (2) on downhole measurements by the Expedition Project Manager. In the afternoon, the Outreach Officer provided the scientists with an overview of his plans for the expedition. The scientists were given the afternoon off in anticipation of a departure as planned. However, our departure was delayed to avoid stormy weather systems on our sea passage to Guaymas Basin. Our new estimated time of departure is 0700 h on 22 September. Port call activities continued with unloading and loading of freight, including bunkering of another ~1000 metric tons of fuel. Remaining PR tours of the ship took place as scheduled. In total, 180 visitors were given a tour over the course of port call.
Daily Science Report for 19 September 2019
Location: B-Street Pier Terminal, Port of San Diego, USA
Science Update: Today started with the scientists presenting their individual research objectives and plans. In the afternoon, the Captain, Ship’s Doctor, Offshore Installation Manager, First and Second Mates, and the Camp Boss met the science party and new IODP JRSO technical staff, and gave a presentation on environment and safety of the vessel. Subsequently, all laboratory teams met with their technical staff to learn their working spaces and start preparing instruments. This included an introduction to the descriptive information system, given by JRSO staff to the core describers. PR tours of the ship took place as planned. Port call activities continued with loading of hardware and supplies all day, such as food and lube oil.
Daily Science Report for 18 September 2019
Location: B-Street Pier Terminal, Port of San Diego, USA
Science Update: The day began with introductions of the Expedition 385 scientists and IODP JRSO staff. This was followed by a talk on the expedition science objectives by the Co-Chief Scientists and a presentation of the expedition work plan by the Expedition Project Manager (EPM). In the afternoon, the scientists were introduced to core handling and sampling by the Curatοrial Specialist followed by core flow tours conducted by the EPM. Another science party member boarded the vessel at 1530 h. At the end of the day, the Geochemistry and Microbiology Laboratory team convened for an initial meeting with their technical staff to learn their laboratory and start the preparation of the complex geochemical and biogeochemical studies planned in Guaymas Basin. Numerous PR tours of the ship took place as scheduled, including tours for Scripps Institution of Oceanography staff and local media. Routine port call activities continued as planned, including loading of casing and food, as well as a derrick inspection.
Daily Science Report for 17 September 2019
Location: B-Street Pier Terminal, Port of San Diego, USA
Science Update: The majority of the Expedition 385 science party boarded the vessel at 0830 h, got settled in their rooms, started to connect their computers with the ship’s network, and had their photos taken. At 1300 h, after another nine scientists had boarded the vessel upon solving issues with their Mexican cooperation visa documents, the science party was given a short introductory talk and presentation on information technology aboard the JOIDES Resolution. The initial orientation talks were then concluded with presentations about life at sea and general safety. This was followed by a general ship safety tour. Several PR tours of the vessel took place as scheduled. Other port call activities included the arrival of the oncoming Siem Offshore crew that crossed over with their offgoing counterparts. Loading and unloading of cargo continued throughout the day, including discharge of Expedition 379T cores and staging of casing and core winch line shipments for loading. By the end of the day, almost 1000 metric tons of fuel were bunkered.
Daily Science Report for 16 September 2019
Location: B-Street Pier Terminal, Port of San Diego, USA
Science Update: The Guaymas Basin Tectonics and Biosphere Expedition (385) officially began at 0815 h with the Co-Chief Scientists and IODP JRSO staff boarding the vessel at the B-Street Pier Terminal in San Diego. The JRSO staff conducted crossover with the offgoing staff who departed in the late afternoon. Prior to that, all technical staff attended a radiation safety training course. The Co-Chief Scientists got their computer network connections set up and were given a tour of the ship. Other port call activities included handling offgoing and incoming freight, such as loading of drill pipe (150 joints) and casing (20 joints). Also, third-party instrument and supply shipments of the Expedition 385 science party were received. The Department of Energy van was loaded and placed on the Core Tech Shop roof, enabling implementation of microbial stable isotope studies at sea.
An afternoon “Expedition to Guaymas Basin” Science Symposium was held by Scripps Institution of Oceanography (UC San Diego) in La Jolla with ~160 people in attendance, including science party members of the pioneering DSDP Leg 64 that first drilled Guaymas Basin more than 40 years ago.