IODP Expedition 359
Maldives Monsoon and Sea Level
Daily Science Report for 30 November 2015
Location: Colombo, Sri Lanka
Science Update: The 1.5 d transit to Colombo, Sri Lanka, was quick and uneventful. The Sri Lanka harbor pilot came on board at 1013 h, and Expedition 359 officially ended when the first line went ashore at the Unity Container Terminal berth at 1100 h on 30 November.
Daily Science Report for 29 November 2015
Location: In transit to Colombo, Sri Lanka
Science Update: We continued our transit to Colombo, Sri Lanka. Estimated time of arrival at the pilot station is 0700 h on 30 November. The science party completed all shipboard work and submitted their Sites U1471 and U1472 reports.
Daily Science Report for 28 November 2015
Location: In transit to Colombo, Sri Lanka
Science Update: We departed Site U1472 after securing the rig floor at 0212 h. The short transit to the Malé pilot station was completed at 0718 h. The Maldivian harbor pilot came aboard and we proceeded to anchorage for formal procedures to clear the vessel out of Maldivian waters. At anchorage, the Maldivian Minister of Fisheries and Agriculture came aboard for a meeting with the expedition Co-Chief Scientists who gave him a briefing on the expedition results. At 0943 h, the Minister and his entourage departed the vessel along with the two Maldivian coastal observers. The vessel was cleared to depart and we began our transit to Colombo, Sri Lanka, at 1512 h.
In the laboratories, all measurements of cores and samples from Site U1472 were completed and scientists continued to work and submit their Site U1471 and U1472 reports.
Daily Science Report for 27 November 2015
Location: Hole U1472A (MAL-06B, 4°46.2653′N, 73°4.0111′E; 379 mbsl)
Science Update: We arrived at Site U1472 at 0222 h. With limited time available because we needed to depart to Malé no later than 0200 h on 28 November, we decided to core one final APC hole as deep as possible with the remaining time. The drill string was run to the seafloor and Hole U1472A was started at 0415 h. We cut and recovered Cores U1472A-1H through 34F from 0 to 251.9 mbsf, recovering 233.75 m of core (93%). The last core of Expedition 359 arrived on deck at 2015 h. By midnight, we were retrieving the drill string back on board.
In the laboratories, Cores U1472A-1H through 22H were measured for physical properties and described. Because of the limited time available, core samples were only studied for biostratigraphic, interstitial water (chloride and alkalinity), and gas analyses. Planktonic foraminifera and calcareous nannofossils provide an age of 8.8 Ma for the base of the section. The cores described today consist of unlithified planktonic foraminifera-rich packstone, grading downhole to a partially lithified to lithified planktonic foraminifera-rich grainstone interlayered with packstone and wackestone. Scientists started to submit their Site U1471 reports.
Daily Science Report for 26 November 2015
Location: Hole U1471E (MAL-07A, 4°45.9829′N, 73°8.0929′E; 419 mbsl)
Science Update: After the completion of coring in Hole U1471E, the hole was prepared for wireline logging. A 30-barrel mud sweep was pumped, the RCB bit was released at the bottom of the hole, and the pipe was pulled up to a logging depth of 99.7 mbsf. The triple combo tool string was rigged up and deployed in the hole at 0545 h. A downlog was completed to 1003.7 mbsf (the total drilled depth), a short repeat pass was logged, and the main pass of the tool string was recorded from the bottom of the hole up past the seafloor. Borehole diameter in the upper section of the hole was at the maximum reach of the caliper arm (~17 inch), but much of the lower section was in-gauge. The Versatile Seismic Imager (VSI) tool string was rigged up next and run into the hole at 1245 h for a vertical seismic profile (VSP) experiment. The tool string reached an unpassable obstruction at ~615 mbsf where the borehole had been observed to be very narrow during the triple combo run. Therefore, only shallow VSP stations could be reached; clear waveforms were recorded at three depth stations between 233 and 606 mbsf. The VSI tool string was run one more time into the hole to attempt one deeper station but on the second attempt, an obstruction was encountered at 454 mbsf, also a narrow section observed during the triple combo run. A third logging run was made with a sonic tool string, measuring gamma ray and sonic velocity, with the aim of recording velocity data in the available open hole interval. The Formation MicroScanner (FMS) tool that is usually combined with the sonic tool has a maximum caliper reach of ~15 inch, and so would not have made contact with the borehole walls in sections where borehole diameters exceeded 17 inch. The sonic tool string was run into the hole at 1620 h and a downlog was recorded down to 454 mbsf, the same location where an obstruction blocked passage of the VSI tool string. After several unsuccessful attempts to pass below the blocked section, the sonic tool string was pulled up from 454 mbsf to record a main pass through the shallow section of open hole up to the seafloor. The sonic tool string was rigged down and logging operations for Hole U1471E and Expedition 359 were completed by 1940 h. The drill string was pulled aboard and the seafloor positioning beacon was recovered as the ship began to move using the dynamic positioning system to the next site, U1472 (MAL-6B).
Daily Science Report for 25 November 2015
Location: Hole U1471E (MAL-07A, 4°45.9829′N, 73°8.0929′E; 419 mbsl)
Science Update: We completed coring operations in RCB Hole U1471E. Cores U1471E-32R through 44R deepened the hole from 887.3 mbsf to just past our target seismic reflector at 1003.7 mbsf. Calcareous nannofossils and planktonic foraminifera biostratigraphy provided an age of >13.5 Ma, and thus confirmed that our deep coring objective at Site U1471 had been achieved. Core recovery with the RCB coring system was very good throughout the entire cored interval, ranging from 29% to 89%, and averaging 55%. Total core recovery at Site U1471 was 771.2 m (58%).
Cores U1471E-33R through 44R were described today. The major lithology throughout this interval is very fine to fine grained, white to light gray, lithified foraminifera-rich packstone to wackestone. Bioclasts and moldic porosity are abundant. Bioturbation is common with many burrows with pyrite and glauconite alteration rims with Thalassinoides, Teichichnus, Planolites, Palaeophycus, and Chondrites as recognizable ichnofossils. The minor lithology is very fine to fine grained, grayish brown to dark gray interlayered wackestone (<10 cm thick layers). These layers are compacted with flattened burrows, horsetail structures, and abundant dissolution features. Bioturbation is common and characterized by small burrowing communities dominated by Phycosiphon.
Daily Science Report for 24 November 2015
Location: Hole U1471E (MAL-07A, 4°45.9829′N, 73°8.0929′E; 419 mbsl)
Science Update: We continued to RCB core Hole U1471E. Cores U1471E-11R through 19R penetrated from 683.6 to 770.9 mbsf and recovered 27.2 m of core (31%). At that point we deployed the RCB bit deplugger because back flow was coming up from the drill pipe. Once the bit was cleared, we continued RCB coring, and we cut and recovered Cores U1471E-20R through 31R to 887.3 mbsf. Core recovery for this interval was 52.4 m (45%). The hole remains in good condition and core recovery has been improving.
Cores U1471E-2R through 7R consist of a light brownish gray, medium grain planktonic foraminifera-rich packstone. Benthic foraminifera are common. Cores U1472E-8R to 25R consist of fine- to medium-grained, light gray to grayish brown planktonic foraminifera-rich packstone and wackestone. Benthic foraminifera are rare. Bioturbation is intense with Thalassinoides, Teichichnus, Planolites, Palaeophycus, and Chondrites as recognizable ichnofossils.
We continued to discuss the findings of the expedition and plan our postcruise research.
Daily Science Report for 23 November 2015
Location: Hole U1471E (MAL-07A, 4°45.9829′N, 73°8.0929′E; 419 mbsl)
Science Update: Today we continued rotary drilling Hole U1471E. The hole was deepened to 596.3 m, where the formation became hard and we determined that the center bit should be pulled. RCB coring followed, and we cut and recovered Cores U1471E-2R through 10R to 683.6 mbsf by midnight. Total core recovered for this interval was 28.03 m (32.1%).
Cores U1471E-2R through 7R were described today. They consist of a light brownish gray, medium grain planktonic foraminifera-rich packstone. Benthic foraminifera are common.
The scientific party presented the scientific highlights of the expedition so far and discussed postcruise research. We are excited to report that all the scientific objectives of the expedition have been achieved, and new findings have been made.
Daily Science Report for 22 November 2015
Location:
• Hole U1471D (MAL-07A, 4°45.9828′N, 73°8.1035′E; 419 mbsl)
• Hole U1471E (MAL-07A, 4°45.98′N, 73°8.09′E; 419 mbsl)
Science Update: After completing coring operations in Hole U1471D, the planned test of the motion decoupled hydraulic delivery system (MDHDS) took place with mixed results. The handling of the tool on the rig floor was greatly improved, reducing the deployment time from 1.5 h required during its first test at Site U1467 to 30 min. The Electrical Release System (ERS) tool was opened and closed several times, working flawlessly each time, and the Sediment Temperature Tool (SET2) functioned well and successfully recorded data, although it was not inserted into the formation because the MDHDS became stuck at the flapper valve in the bottom-hole assembly (BHA). The drill string and the MDHDS tool were brought back to the rig floor at 0545 h and laid out. Later, it was determined that entrained sand in the flapper valve had restricted the downhole deployment of the tool. Following the test, the ship was offset 20 m west, and a new BHA with an RCB bit was made up. The drill string was lowered once again to the seafloor, and we began to rotary drill Hole U1471E at 1110 h. We continued to drill ahead with the RCB center bit reaching 421.4 mbsf at midnight. Our plan is to continue drilling until ~610 mbsf and then to start RCB coring until we reach our target seismic reflector.
In the laboratories, all cores from Holes U1471C and U1471D have been measured for physical properties and described. Paleomagnetic measurements are ongoing. Scientists are finalizing their reports for the previous sites and starting to work on their Site U1471 reports.
Daily Science Report for 21 November 2015
Location:
• Hole U1471A (MAL-07A, 4°45.9825′N, 73°8.1358′E; 419 mbsl)
• Hole U1471B (MAL-07A, 4°45.9825′N, 73°8.1263′E; 420 mbsl)
• Hole U1471C (MAL-07A, 4°45.9831′N, 73°8.1147′E; 419 mbsl)
• Hole U1471D (MAL-07A, 4°45.9828′N, 73°8.1035′E; 419 mbsl)
Science Update: Hole U1471B was started 20 m west of Hole U1471A at 0440 h. Core U1471B-1H recovered 6.62 m of sediment but the core liner was shattered, yielding a questionable mudline depth (420.4 m) for stratigraphic correlation. As a result, the hole was terminated and the ship was moved 20 m west to start Hole U1471C. With the APC bit positioned at 428.6 m below the rig floor, we cut and recovered Core U1470C-1H, retrieving 7.85 m of core and establishing a seafloor depth of 419 m. APC coring continued through Core U1471C-19H to 178.8 mbsf with a final recovery of 170.2 m (95.2%). Recovery with the APC system in this hole was <100%; Core U1471C-5H was retrieved with less than 100% recovery because the core barrel was deployed without a core catcher. Unfortunately, the core gap in this hole prevented us from building a complete stratigraphic section between Holes U1471A and U1471C for the upper ~200 m at Site U1471; therefore, we had to APC core another hole to at least ~70 mbsf, which initially we tried to avoid in order to save time for the deep RCB and logging hole we plan to drill at this site. The ship was offset another 20 m west and, using the offset seafloor depth from Hole U1471C, at 2105 h we started APC coring Hole U1471D one meter below the seafloor. By midnight, we had cut and recovered Cores U1471D-1H through 7H to 58 mbsf (core recovery 100%), but the liner of Core U1471D-7H was also shattered.
In the laboratories, we measured and described Cores U1471C-1H through 12H (0 to 112.3 m). The main lithology is medium- to fine-grained, light gray to light brownish gray, unlithified to partly lithified planktic foraminifera-rich packstone. Benthic microfossils and organic material are common. Measurements of core physical properties and of carbonate and organic carbon content of discrete sediment samples are ongoing.
Daily Science Report for 20 November 2015
Location: Hole U1471A (MAL-07A, 4°45.98′N, 73°8.13′E; 419 mbsl)
Science Update: XCB coring in Hole U1471A continued with Cores U1471A-68X through 82X penetrating from 568.7 to 685.7 mbsf and recovering 31.7 m of core. Core recovery varied from 6% to 88% over this interval, averaging 27%. Despite the much improved core recovery obtained in Cores U1471A-74X to 82X (44.5%), we decided to terminate the hole before reaching our depth and age objectives due to the very slow penetration rate (<8 m/h) we were achieving with the XCB system in the hard rock. Our plan is reach our objective (the base of the drift deposits, which we expect to be around 13 Ma) in an RCB hole to be drilled after completing two more APC holes to 180 and 140 mbsf.
In the laboratories, we measured and described Cores U1471A-51X through 82X. The main lithology in Cores U1471A-51X to 73X is fine- to medium-grained interlayered unlithified, partially lithified and lithified planktic foraminifera-rich packstone. Cores U1471A-74X and 82X consist of fine-grained, light gray and light brownish gray and dark grayish brown lithified wackestone and packstone. Bioturbation is moderate to intense. Planktic foraminifera and nannofossil biostratigraphy provide an estimated age of 10.7 Ma for the base of Hole U1471A. Measurements of core physical properties and of carbonate and organic carbon content of discrete sediment samples are ongoing.
Daily Science Report for 19 November 2015
Location: Hole U1471A (MAL-07A, 4°45.98′N, 73°8.13′E; 419 mbsl)
Science Update: We cut and recovered Cores U1471A-46X through 59X (388.7 to 515.1 m). Core recovery varied from 2% to 27% over this interval, averaging 8%. Core recovery remained problematic in the interbedded material because the hard limestone rock continuously jammed in the cutting shoe and the soft rock washed away. In an attempt to improve core recovery we switched to the half-length advanced piston coring system (HLAPC) and cut Cores U1471A-60F, 61F, and 63F (recovery varied from 24% to 96%), but as the formation became harder again, we switched back to the XCB system. By midnight, Cores U1471A-64X through 67X had extended the hole to 568.7 mbsf, retrieving just 1.84 m of core (5%).
In the laboratories, we measured and described Cores U1471A-29H through 50F. The main lithology of this interval is light gray to light brownish gray, fine- to medium-grained interlayered unlithified, partially lithified and lithified planktic foraminifera-rich packstone. Calcareous nannofossil biostratigraphy provide an estimated age of 8.8 Ma between Cores U1471A-54X and 55X. Measurements of geochemical and physical properties are ongoing. Scientists submitted the initial drafts of the Sites U1469 and U1470 reports.
Daily Science Report for 18 November 2015
Location: Hole U1471A (MAL-07A, 4°45.98′N, 73°8.13′E; 419 mbsl)
Science Update: We continue to deepen Hole U1471A with the full- and half-length APC, and the XCB coring systems. APC Cores U1471A-10H through 32H penetrated from 80.6 to 295.1 mbsf and returned 218 m of core (102%). However, drillover and high overpull were required to free the APC core barrels from Cores U1471A-26H on down. When Core U1471A-32H achieved only a partial stroke and required drilling over to free the core barrel, we switched to the half-length APC system and cut and recovered Cores U1471A-33F through 37F to 318.6 mbsf (recovery 58%); however, the formation had become more lithified and that point we switched to the XCB coring system. Cores U1471A-38X through 44X advanced the hole to 384 mbsf, but with very low recovery (9%). Then we decided to switch back to the half-length APC system (45F), but core recovery remained problematic. At that point the driller noticed that the wash pipe on the top drive was leaking. Coring was temporarily halted around 2000 h to allow the drill crew to make a wiper trip in the hole and to replace the leaking wash pipe assembly.
In the laboratories, scientists continue to process cores and samples from Hole U1471A. Cores U1471A-2H to 19H consist of light brown to grayish brown, fine to medium-grained, unlithified planktic foraminifera-rich packstone. In the deeper cores, decimeter-thick layers of partially lithified packstone are present. Preservation of calcareous microfossils deteriorates below Core U1471A-10H with most shells showing pervasive recrystallization. ICP analyses of major and minor elements have been completed for Sites U1469 and U1470. Scientists began to submit the initial drafts of the Site U1469 and U1470 reports.
Daily Science Report for 17 November 2015
Location:
Hole U1470B (MAL-05A, 4°45.9818′N, 72°59.0210′E; 400 mbsl)
Transit to Site U1471
Hole U1471A (MAL-07A, 4°46′N, 73°8.1′E; 419 mbsl)
Science Update: Similarly to the previous platform sites, RCB coring of the loosely cemented limestone formation in Hole U1470B continued to be problematic due to loss of circulation, high drill torque, and slow and poor recovery. Eventually, because of the very low recovery and the desire to log the hole, coring was terminated after recovering Core U1470B-19R to 343.7 mbsf shortly after 0400 h. Total core recovered in Hole U1470B was 7.35 m (4%). Following this we attempted to wireline log the hole; due to uncertainty about the hole stability, a single logging run was planned with a tool string designed to measure the highest priority data (gamma ray, sonic velocity, electrical resistivity, and borehole diameter). We ran this sonic-resistivity tool string into the hole, but unfortunately, it was not able to pass a collapsing section of the borehole securely just 52 m below the depth of the end of the pipe at 100.2 mbsf. We pulled the tool string back into the pipe and up to the rig floor, where it was rigged down, and logging operations in Hole U1470B were concluded. We continued to retrieve the drill string, and then released and recovered the seafloor positioning beacon. The thrusters were raised, and by 1448 h we were underway to Site U1471. Transit to the next site was concluded in just over an hour, and by 1636 h we had started to make up the APC/XCB bottom-hole assembly and rig up for coring operations at the new site. We tagged the seafloor with the APC bit, establishing a depth of 414 mbsl, and started coring of Hole U1471A at 2050 h. By midnight, we had cut and recovered Cores U1471A-1H through 9H to 80.6 mbsf with a recovery of 97%.
In the laboratories, RCB Cores 8R through 19R from Hole U1470B and the mudline core (1H) from Hole U1471A were split and described. Cores U1470B-8R to 19R contained significantly reworked and dolomitized reefal material consisting of grayish brown, lithified granule-grained dolomitic coral-rich packstone to grainstone and lithified bioclastic floatstone, with a very fine-grained crystalline matrix. The main components of this succession are common to abundant red algae (as nodules and encrustations), and coral fragments (massive and branching). Serpulids and mollusks are common (as molds). Moldic porosity is pervasive with abundant casts of bioclasts, commonly partially to totally infilled by calcitic cement. Crystalline structures are observed on the walls of the molds, with botryoidal-like geometries. Fine-crystals of dolomite are present as well-developed large euhedral dolomite crystals. Core U1471A-1H contains a grayish brown, fine to medium-grained, unlithified planktic foraminifera-rich packstone. Benthic foraminifer, gastropods, and pteropods are common. Cores U1471A-1H through 9H were sampled for interstitial water chemistry and gas analyses, and they are being measured for physical properties.
Daily Science Report for 16 November 2015
Location: Hole U1470B (MAL-05A, 4°45.9818′N, 72°59.0210′E; 400 mbsl)
Science Update: Today we started rotary drilling Hole U1470B at 0230 h. The hole was deepened to 169 m before RCB coring started. Cores U1470B-2R through 14R penetrated from 169 to 295.1 mbsf and recovered 6.15 m of core (5%). RCB coring was difficult from the start due to the loosely cemented limestone formation, causing elevated drill string torque and overpull and requiring two mud sweeps and reaming operations to clean the hole. By midnight we had cut and recovered Core U1470B-14R to 295.1 mbsf, and we plan to continue rotary coring to at least 300 mbsf.
Cores U1470B-2R to 7R were split and described today. They contain dolomitized red algae-rich grainstone to rudstone, with abundant branching and massive corals, bivalve, and gastropod fragments. Fossil components are often present as molds. Discrete measurements for paleomagnetics, physical properties, and solid phase geochemistry from Site U1470 are ongoing.
Daily Science Report for 15 November 2015
Location: Hole U1470A (MAL-05A, 4°45.9828′N, 72°59.0324′E; 400 mbsl)
Science Update: We started coring Hole U1470A at 0335 h, cutting and recovering Cores U1470A-1H through 24X (0 to 190 mbsf) using the full- and half-length APC and XCB coring systems. The top of the buried platform was reached at 150 mbsf. The lithology is a reefal limestone. Loosely cemented reef rubble below 150 mbsf was hard to recover and caused coring and recovery problems to the XCB system. This led us to terminate operations in Hole U1470A at 190 mbsf in favor of starting a new hole using the rotary coring system. The drill string was retrieved back on board and by midnight the RCB BHA had been assembled in preparation to start Hole U1470B.
Cores U1470A-1H through 3H (0 to 21.1 mbsf) consist of well sorted unlithified grainstone to rudstone, dominated by skeletal grains and planktic foraminifera, with pteropods, echinoderms, bryozoans, benthic foraminifera, and ostracods as minor components. Cores U1470A-4H through 14H (21.1 to 125.6 mbsf) yielded a medium grained, moderately to well sorted, unlithified to partially lithified planktic foraminifera-rich packstone. Planktic foraminifera and calcareous nannofossil biostratigraphy provide an estimated age of 5.57 Ma for the bottom of Core U1470A-7H (59.1 mbsf). Discrete measurements for paleomagnetics, physical properties, and porewater and sediment geochemistry from Sites U1469 and U1470 are ongoing.
Daily Science Report for 14 November 2015
Location:
• Hole U1469A (MAL-08A, 4°54.4143′N, 73°0.4910′E; 427 mbsl)
• Hole U1469B (MAL-08A, 4°54.4166′N, 73°0.4694′E; 427 mbsl)
• Transit to Site U1470
• Hole U1470A (MAL-05A, 4°45.98′N, 72°59.03′E; 380 mbsl)
Science Update: We cut and recovered Cores U1469A-11R through 17R from 93 to 161 mbsf with a core recovery of just over 5%. Increased pump pressures and elevated drill string torque impacted coring operations in Hole U1469A from the start, leading us to terminate the hole after Core U1469A-17R was recovered. In an attempt to avoid the problematic upper part of the formation, Hole U1469B (40 m west of Hole U1469A) was drilled ahead with an RCB center bit to 122 m before RCB coring began. Then we cut and recovered Cores U1469B-2R to 4R to 151.4 mbsf (recovery 2%) while experiencing excessive torque and overpull once again. Due to the difficult coring conditions and poor recovery, we decided to abandon the hole and to stop coring operations at Site U1469. We retrieved the drill string and secured the rig for transit to Site U1470 (MAL-05A). We arrived over the site coordinates at 2230 h, deployed the seafloor positioning beacon, and switched to dynamic positioning. By midnight, we were making up the APC/XCB bottom-hole assembly to start operations in Hole U1470A.
The cores described today consist of medium- to coarse-grained, pale yellow, partially lithified to lithified grainstone to packstone (Cores U1469A-1R to 16R, and U1469B-2R-3R), with abundant bivalve molds and fragments, benthic foraminifera, and echinoderm spines; and lithified dolomitic coral-rich floatstone (in Cores U1469A-17R and U1469B-4R).
Scientists submitted the first drafts of the Site U1468 reports.
Daily Science Report for 13 November 2015
Location:
• Hole U1468B (MAL-03A, 4°55.9823′N, 73°4.2888′E; 521.5 mbsl)
• Transit to Site U1429
• Hole U1469A (MAL-08A, 4°54.42′N, 73°0.49′E; 427 mbsl)
Science Update: We rigged up the triple combo tool string and ran it into Hole U1468B at 0240 h. The tool string reached ~835 mbsf where it tagged bottom, indicating ~40 m of infill in the hole (originally drilled to 874.5 mbsf). A short pass was logged from the bottom of the hole up to ~735 mbsf, showing reasonable hole diameter. The tool string was run back to total depth and the main pass started at 835 mbsf, recording gamma ray, density, porosity, electrical resistivity, and magnetic susceptibility. Borehole diameter varied smoothly, ranging from ~17 to 12 inch, until a narrow section (<6 inch) was encountered at ~465 mbsf. Significant overpull was required to continue pulling the tool string up to ~290 mbsf. This suggested that the borehole had deteriorated in this interval. Above ~290 mbsf, hole diameter increased and the main pass continued up to the depth of the drill pipe at 140 mbsf. Logging data were recorded continually throughout the main pass with the triple combo tool string, but further logging operations could not be carried out due to the state of the borehole. The tool string was returned to the rig floor and rigged down, and logging operations in Hole U1468B were complete by 0915 h. Following this, we recovered the seafloor positioning beacon and began to pull the drill string back aboard and make up an RCB bottom-hole assembly (BHA) while moving to the coordinates of the next site, Site U1469. Once on location, we lowered the drill string to the seafloor, deployed an RCB core barrel, tagged the seafloor with the bit at 427 mbsl, and started coring in Hole U1469A at 1825 h. RCB coring continued, cutting Cores U1469A-1R through 10R from the seafloor to 93 mbsf. Core recovery for this interval was 0.5 m (<1%). From the start, coring in this hole has been extremely problematic, experiencing increased pump pressures and excessive drill string torque.
In the laboratories, scientists continue to work on and turn in the reports for Site U1468, and we presented the highlights from this site at the science meeting.
Daily Science Report for 12 November 2015
Location: Hole U1468B (MAL-03A, 4°55.9823′N, 73°4.2888′E; 521.5 mbsl)
Science Update: We finished drilling the dedicated logging Hole U1468B to 874.7 mbsf at ~2030 h. Following this, the hole was swept with high viscosity mud and the drill bit was released at the bottom of the hole. By midnight, the end of the pipe had been pulled back to 801.5 mbsf. We plan to deploy all three logging strings in this hole.
Scientists are preparing the first drafts of the reports for Site U1468 and their presentations for tomorrow’s science meeting.
Daily Science Report for 11 November 2015
Location: Hole U1468B (MAL-03A, 4°55.9′N, 73°4.2′E; 521.5 mbsl)
Science Update: We started the day recovering the drill string after finishing coring operations in Hole U1468A. Following, we changed the APC/XCB bottom-hole assembly (BHA) for one with a drilling bit. Once the new BHA was made up, we lowered the pipe back to the seafloor and spudded Hole U1468B at 0810 h. We started drilling without coring, deepening Hole U1468B. At 131.7 mbsf we experienced elevated drill string torque. We worked the pipe back to 43.5 mbsf, pumped a mud sweep, deployed a wash barrel, and reamed the hole back to total depth. After recovering the wash barrel, we continued drilling with the hole still in good condition. By midnight, we had drilled down to 335.7 mbsf.
All cores from Hole U1468A have been processed through the laboratories. Analyses of discrete sediment samples for moisture and density measurements have been completed. All interstitial water samples have been analyzed by ICP and ion chromatography. Scientists are analyzing their data and preparing the first drafts of the reports for Site U1468.
Daily Science Report for 10 November 2015
Location:
• Hole U1468A (MAL-03A, 4°55.9832′N, 73°4.2780′E; 521.5 mbsl)
• Hole U1468B (MAL-03A, 4°55.9′N, 73°4.2′E; 521.5 mbsl)
Science Update: Today we completed coring operations in Hole U1468A with the recovery of XCB Cores U1468A-96X through 111X from 718.9 to 874.7 mbsf. Core recovery for Hole U1468A was 458.7 m or 53%. The hole terminated 10 m into a densely cemented shallow-water carbonate platform. The calcareous nannofossils and planktic foraminifers above this platform provided an age of 24 Ma, and thus confirmed that our deep coring objective at Site U1468 of reaching just over the Oligocene/Miocene boundary had been achieved. The drill string was pulled out of the hole, clearing the seafloor at 2215 h, and the vessel was offset 20 m to the east. After recovering the drill string, our next operation at Site U1468 will be to drill a dedicated hole to 874 mbsf for wireline logging.
The major lithologies of the cores described today are fine-grained lithified planktic foraminifera-rich wackestone to packstone, locally interbedded by convolute laminae consistent with turbiditic deposits (Cores U1468A-69X to 96X); and very fine-grained, white semi-lithified calcareous nannofossils and planktic foraminifera-rich mudstone (chalk) interlayered with organic rich dark gray brown to black wackestone (Cores U1468A-97X to 98X). Over 1150 discrete samples from Hole U1468A are being analyzed for biostratigraphic, paleomagnetics, sediment physical properties, and porewater and sediment geochemistry.
Daily Science Report for 9 November 2015
Location: Hole U1468A (MAL-03A, 4°55.98′N, 73°4.28′E; 521.5 mbsl)
Science Update: Cores U1468A-66X through 95X penetrated from 427.7 to 718.9 mbsf and recovered 140.6 m (48%). Cores described today (U1468A-31F to 68X) consist of light olive gray to pale yellow, very fine-grained and well-sorted lithified planktic foraminifera-rich packstone to wackestone. Benthic foraminifera (Lepidocyclina and Amphistegina) are common. Bioturbation ranges from moderate to intense, with Thalassinoides, Teichichnus, Planolites, Palaeophycus, and Chondrites as recognizable ichnofossils. Calcareous nannofossil and planktic foraminifera biostratigraphy indicates an age of about 17 Ma for Core U1468A-90X. Discrete measurements for paleomagnetics, physical properties, and porewater and sediment geochemistry are ongoing.
Daily Science Report for 8 November 2015
Location: Hole U1468A (MAL-03A, 4°55.98′N, 73°4.28′E; 521.5 mbsl)
Science Update: We continued to deepen Hole U1468A using the half-length APC and XCB coring systems. Cores U1468A-31F through 65X penetrated to 427.7 mbsf and recovered 103 m of core (44%). A hard layer of chert at ~345 mbsf tore up the XCB cutting shoe on Core U1468A-55X; therefore, an XCB center bit was deployed and the hard layer was drilled through from 345 to 346 mbsf. After recovering the center bit with the wireline, we resumed XCB coring. By midnight, the hole remained in good condition.
Cores described today (U1468A-11H to 30F) recovered a sequence of medium to coarse grained, unlithified to lithified large benthic foraminifera-rich grainstone to packstone. The abundant large benthic foraminifera (Sphaerogypsina globulus, Lepidocyclina, and Amphistegina) indicate deposition in shallow water. The absence of planktic foraminifera or calcareous nannofossils in this sediment package has prevented us from estimating an age for the base of the cored sequence. Measurements of sediment physical properties and geochemical analyses of sediment and interstitial water samples from Hole U1468A are ongoing.
Daily Science Report for 7 November 2015
Location: Hole U1468A (MAL-03A, 4°55.98′N, 73°4.28′E; 521.5 mbsl)
Science Update: We completed the transit to Site U1468 (MAL-03A) in under 2 h, switching to dynamic positioning mode at 0232 h. We spudded Hole U1468A at 0830 h and the mudline core established the seafloor at 521.5 mbsl. Cores U1468A-1H to 30F extended from the seafloor to 192.4 m and recovered 160 m of core (83%). The first 13 cores and Core U1468A-27H were taken with the full-length APC system; the remainder were taken with the half-length APC system (HLAPC).
Cores described today recovered a sequence of unlithified planktic foraminifera-rich grainstone (U1468A-1H to 6H-3, 125 cm) overlying unlithified to partially lithified benthic foraminifera-rich grainstone with interlayered packstone in Cores U1468A-6H-3, 125 cm, to 10H. The lower section contains abundant large shallow benthic foraminifera Sphaerogypsina, Lepidocyclina, and Amphistegina, as well as echinoderm spines, mollusk shell fragments and bryozoans. All reports for Site U1467 have been submitted.
Daily Science Report for 6 November 2015
Location: Hole U1467E (MAL-09A, 4°51.0137′N, 73°17.0312′E; 487 mbsl)
Science Update: Hole U1467E was successfully logged using the triple combo, FMS-sonic and VSI tool strings. Deployment of the triple combo was completed at 0600 h, reaching the bottom of the hole at 714 mbsf. Taking advantage of daylight and following the marine mammal protection protocol, the vertical seismic profile (VSP) experiment was conducted next. The VSP reached ~684 mbsf or ~30 m off bottom, apparently due to fill in the borehole, but a very good signal was received at each station, thus providing the necessary information for an accurate time-depth conversion of the seismic data. The FMS-sonic was deployed last at 1200 h and run down to 664 mbsf, where it stopped because of further filling at the bottom of the borehole. Following wireline logging, we deployed the VIT/subseafloor camera down to the seafloor to pressure test all its components and the new fiber optic cable. The test was successful and collected excellent video quality. By midnight, we had secured the rig for transit to the next site, U1468 (MAL-03A).
Scientists continued to work on shipboard reports and started to submit the reports for Site U1467.
Daily Science Report for 5 November 2015
Location: Hole U1467E (MAL-09A, 4°51.0137′N, 73°17.0312′E; 487 mbsl)
Science Update: Drilling of the dedicated logging Hole U1467E to 714 mbsf was completed at ~2030 h. In preparation for wireline logging, we released the drill bit at the bottom of the hole, raised the end of the pipe up to 98.6 mbsf, and had finished assembling the triple combo logging tool string just before midnight. Our logging plan in this hole includes deploying all three logging tool strings: the triple combo, the Formation MicroScanner (FMS)-sonic, and the Versatile Seismic Imager (VSI).
All analyses of samples from Site U1467 were completed. We presented the highlights of our results at today’s science meeting and we are working on the site reports.
Daily Science Report for 4 November 2015
Location:
• Hole U1467D (MAL-09A, 4°51.0475′N, 73°17.0201′E; 487 mbsl)
• Hole U1467E (MAL-09A, 4°51.04′N, 73°17.02′E; 487 mbsl)
Science Update: APC coring in Hole U1467D started at 0130 h. Cores U1467D-1H through 22H penetrated to 201 mbsf (102% recovery). At 1030 h, we started to retrieve the drill string. Our final operation at Site U1467 will be to drill a hole to ~714 mbsf, drop the bit, and collect downhole logs. We assembled a new bottom-hole assembly with a tri-cone drilling bit and a mechanical bit release, lowered the drill string to the seafloor, moved the ship 20 m east of Hole U1467A, and started drilling without coring in Hole U1467E at 1710 h. At midnight the bit had reached 245.2 mbsf.
All cores from Holes U1467C and U1467D have been processed through the laboratories. As in the uppermost section of the previous holes at this site, Cores U1467D-1H to 15H consist of unlithified to partially lithified planktic foraminifera-rich wackestone with common bioturbation. Stratigraphic correlation of the four holes at Site U1467 have produced a good composite section for Site U1467.
Daily Science Report for 3 November 2015
Location: Hole U1467C (MAL-09A, 4°51.0362′N, 73°17.0197′E; 487 mbsl)
Science Update: We completed coring operations in Hole U1467C after cutting and recovering Cores U1467C-27H through 37X to 714 mbsf. Recovery for Hole U1467C was 87%. Following this we made up the triple combo tool string and positioned the end of the drill pipe at 102 mbsf in preparation for downhole logging. The tool string was run to the total depth of the hole without any problems, but after completing the first logging run it was determined that the borehole diameter was too large for collecting useful data with the FMS-sonic and the VSI tool strings. Therefore, we decided to end logging operations and core a fourth APC hole to refusal, followed by drilling a dedicated RCB hole to collect downhole log data.
Cores U1467C-23H to 37XH consist of unlithified to partially lithified planktic foraminifera-rich wackestone to packstone.
Daily Science Report for 2 November 2015
Location: Hole U1467C (MAL-09A, 4°51.0361′N, 73°17.0198′E; 487 mbsl)
Science Update: Today we extended Hole U1467C to 607.7 mbsf, recovering Cores U1467C-13H through 22H from 111.2 to 198.7 mbsf, and later Cores U1467C-24X through 26X from 578.6 to 607.7 mbsf. Recovery for these two cored intervals was good (92%). We drilled without coring from 198.7 to 578.6 mbsf because this section was already cored in Hole U1467B, and our priority was to deepen Hole U1467C to 714 mbsf to recover the older part of the stratigraphic section and to conduct downhole measurements.
Cores U1467C-1H to 22H consist of unlithified planktic foraminifera-rich wackestone with thick inter-layered partially lithified wackestone. Bioturbation is common.
Daily Science Report for 1 November 2015
Location:
• Hole U1467B (MAL-09A, 4°51.0155′N, 73°17.0204′E; 487 mbsl)
• Hole U1467C (MAL-09A, 4°51.01′N, 73°17.02′E; 487 mbsl)
Science Update: After cutting and recovering Cores U1467B-74X through 77X from 617.2 mbsf, the same problem that we experienced in Hole U1467A with the XCB latch sleeve occurred. As a result, coring to the target depth of 714 mbsf could not be completed and the hole was abandoned. Recovery in Hole U1467B was 560.9 m or 91%. Site U1467 is a dedicated paleoceanographic site that requires an integrated stratigraphic correlation of multiple holes. Unfortunately, paleomagnetic correlation has been complicated by a strong magnetic overprint in the upper half of every core during this expedition. Since rust inside the drill pipe may be hampering the data, we pumped a wiper pig to clean the pipe annulus before pulling out of the hole. After the XCB sleeve was replaced, we lowered the drill string back to the seafloor and spudded Hole U1467C at 1620 h, 3 m deeper than Hole U1467B to provide a good overlap for stratigraphic correlation. Core U1467C-1H recovered 6.66 m, establishing a seafloor depth of 487 mbsl. We continued APC coring, extending the hole to 111.2 mbsf (Cores U1467C-2H through 12H; 100% recovery) by midnight.
In the laboratories, Cores U1467B-40H to 77X were described and measured and sampled for physical properties and geochemical analyses. These analyses are ongoing. The cores from this interval consist of very fine-grained, partially lithified planktic foraminifera-rich wackestone to packstone. Bioturbation is common, with Planolites, Chondrites, and Thalassinoides as the main trace fossils recognized. The age at the base of Hole U1467B is estimated at 11.7 Ma. Scientists continued to work on the reports for Sites U1465 and U1466.