IODP Expedition 354

Bengal Fan

Daily Science Report for 31 March 2015

Location: Transit to Colombo, Sri Lanka

Science Update: After a 513 nmi transit, we arrived at Colombo, Sri Lanka. The Bengal Fan Expedition (354) concluded with the first line ashore at 0842 h on 31 March.

Daily Science Report for 30 March 2015

Location: Transit to Colombo, Sri Lanka

Science Update: The vessel is in transit to Colombo, Sri Lanka.

Daily Science Report for 29 March 2015

Location: Hole U1455C (MBF-1A, DSDP Site 218) (8°0.40′N, 86°17.00′E, 3732.5 mbsl)
Transit to Colombo, Sri Lanka

Science Update: This morning we finished retrieving the drill string at 0535 h. After the rig floor was secured and the thrusters were raised, we started our transit to Colombo, Sri Lanka, at 0630 h.

Daily Science Report for 28 March 2015

Location: Hole U1455C (MBF-1A, DSDP Site 218) (8°0.4081′N, 86°17.0090′E, 3732.5 mbsl)

Science Update: Cores 54R to 60R penetrated from 880.8 to 949.0 m (68.2 m) and recovered 19.26 m (28%). The last core of IODP Bengal Fan Expedition 354 arrived on deck at 1435 h. As we pulled the drill string out of the hole, the pipe became stuck a couple of times. The second time, it took 2 h to free the pipe when the bit was at 161.4 m. The bit cleared the seafloor at 2120 h. These final Expedition 354 cores are interbeded dark gray claystone and dark gray siltstone. Ages extend back to the top of the middle Miocene.

Daily Science Report for 27 March 2015

Location: Hole U1455C (MBF-1A, DSDP Site 218) (8°0.4081′N, 86°17.0090′E, 3732.5 mbsl)

Science Update: Cores 44R to 53R penetrated from 782.8 to 880.8 m (98.0 m) and recovered 37.17 m (38%). These cores are late Miocene dark gray claystone, dark gray parallel laminated silt(stone) with plant fragments, and mottled calcareous clay with nannofossils.

Daily Science Report for 26 March 2015

Location: Hole U1455C (MBF-1A, DSDP Site 218) (8°0.4081′N, 86°17.0090′E, 3732.5 mbsl)

Science Update: After drilling ahead without coring from 431 to 773 m (DSDP Site 218 had cored to 773 m), we retrieved the center bit, circulated mud to clean cuttings out of the hole, and started RCB coring at 2030 h. The first RCB core arrived just before midnight; Core U1455C-43R penetrated from 773.0 to 782.8 m (9.8 m) and recovered 2.92 m (30%). This core is a late Miocene succession of normal-graded and parallel-laminated beds of silt with plant fragments fining upwards into clay.

Daily Science Report for 25 March 2015

Location: Hole U1455C (MBF-1A) (8°0.4081′N, 86°17.0090′E, 3732.5 mbsl)

Science Update: We finished retrieving the drill string and the APC bit was back on the rig floor at 0145 h. After a couple of hours servicing the rig (drill line slip and cut, lubricating crown sheave and main blocks, 0230 to 0445 h), we assembled an RCB bottom-hole assembly with a mechanical bit release and lowered it to the seafloor. The camera system was deployed and we reentered the Hole U1455C free-fall funnel at 1540 h after only ~15 min of maneuvering. The camera system was retrieved and we lowered the bit to 219.4 m before it encountered any resistance. We installed the top drive and we washed and reamed back down to the bottom of the hole (431 m). We deployed a center bit and started to drill ahead without coring at 2215 h. We plan to drill ahead to ~770 m and RCB core until the operational time for the expedition expires.

Daily Science Report for 24 March 2015

Location: Hole U1455C (MBF-1A) (8°0.4081′N, 86°17.0090′E, 3732.5 mbsl)

Science Update: Cores U1455C-33F and 41F penetrated from 390.0 to 431.4 m (41.4 m) and recovered 29.46 m of sediment (71%). Since the formation was getting quite firm and we had obtained suitable cores from this section, we decided to stop piston coring. We plan to reenter this hole with the RCB system to core our deep objectives. We circulated 30 barrels of mud to clear cuttings out of the hole, and at 1530 h we started raising the bit back up the hole. After pulling a couple stands of pipe, we removed the top drive and continued pulling out of the hole. When the bit reached 77.4 m, we assembled a free-fall funnel (FFF) around the drill string and dropped it through the moonpool at 1850 h. We waited 1 h to allow the FFF to land. The bit was pulled out of the hole at 1955 h and we spent the rest of the day retrieving the drill string. Cores described today (U1455C-28F to 32F) are late Miocene nannofossil-rich calcareous clay, silty sand, and clayey silt.

Daily Science Report for 23 March 2015

Location: Hole U1455C (MBF-1A) (8°0.4081′N, 86°17.0090′E, 3732.5 mbsl)

Science Update: Cores U1455C-23F and 24F penetrated from 112.0–122.3 m (9.4 m) and recovered 5.63 m of sediment (60%). We then drilled without coring from 122.3 to 359.8 m and resumed continuous HLAPC coring to obtain a high-resolution record of an interval that records a major shift in terrestrial vegetation that occurred in the Miocene. Cores 26F to 32F penetrated from 359.8 to 390.0 m (30.2 m) and recovered 19.36 m of sediment (64%). Cores described today (U1455C-28F to 32F) are late Miocene nannofossil-rich calcareous clay underlain by silty sand and clayey silt.

Daily Science Report for 22 March 2015

Location: Hole U1455C (MBF-1A) (8°0.4081′N, 86°17.0090′E, 3732.5 mbsl)

Science Update: Coring in Hole U1455A, started at 0105 h, was intended to be a single mudline core for microbiologic and geochemical studies. Since Core U1455A-1H recovered only 0.9 m, we offset the ship 20 m to the east and started coring in Hole U1455B at 0225 h. Core U1455B-1H recovered 6.88 m and this core was sampled for these studies. The ship was offset 20 m to the south and coring in Hole U1455C started at 0350 h. Cores U1455-1H to 3H penetrated from the seafloor to 23.2 m and recovered 22.42 m of sediment (97%). Since Core 3H was only a partial stroke and the core liner cracked, we switched to the half-length APC (HLAPC) system. The hole was deepened to 112.9 m with 15 HLAPC cores and four 4.8 m advances without coring. Cores 4F to 22F sampled 70.5 m of this interval and recovered 61.82 m of sediment (88%). Cores described today are middle to early Pleistocene gray mottled calcareous clay (Cores 1H–2H), dark gray fine sand and gray clay with silt interbeds (3H–14F), and gray mottled calcareous clay (15F).

Daily Science Report for 21 March 2015

Location: Hole U1454D (MBF-7A) (8°0.4083′N, 85°51.0025′E, 3710.3 mbsl)
Transit to Site U1455
Site U1455 (MBF-1A) (8°0.42′N, 86°17.00′E, 3745 mbsl)

Science Update: Coring in Hole U1454D started at 0020 h. Cores U1454D-1H to 5F penetrated to 37.1 m and recovered 24.46 m (66%). We pulled the bit out of the seafloor (0630 h) and retrieved the drill string. Once the bit was back on the rig floor, we secured the rig floor, raised the thrusters, and departed for Site U1455 (MBF-1A) at 1336 h. After the 26 nmi transit, we arrived at Site U1455 at 1640 h. We assembled an APC bottom-hole assembly with a 9.875 inch PDC bit with a lockable float valve and started lowering it to the seafloor. At midnight, the bit was just above the seafloor and we were preparing to start coring in Hole U1455A.

Daily Science Report for 20 March 2015

Location: Holes U1454B and U1454C (MBF-7A) (8°0.40′N, 85°51.99′E, 3710.3 mbsl)

Science Update: Coring in Hole U1454B continued with Cores 20F–32F penetrating from 100.7 to 161.8 m (61.1 m) and recovering 56.56 m of sediment (93%). Having achieved our depth objectives, we decided to core two more holes to obtain a more complete section in the upper ~37 m. We pulled the bit out of Hole U1454B, offset the ship 20 m to the south, and started coring in Hole U1454C at 1650 h. Cores U1454C-1H to 6F penetrated to 37.2 m and recovered 30.16 m (81%). We pulled the bit out of Hole U1454C and were preparing to start Hole U1454D just before midnight. Cores described today (8F–32F) are early Pleistocene gray clay with silt interbeds, dark gray sand, and grayish white to light brown nannofossil-rich calcareous clay.

Daily Science Report for 19 March 2015

Location: Hole U1454B (MBF-7A) (8°0.4083′N, 85°51.0025′E, 3710.3 mbsl)

Science Update: We completed lowering the drill string to the seafloor and took a single mudline core in Hole U1454A (1H, 0–7.5 m) for microbiologic and geochemical studies. We offset the ship 20 m to the east and started coring in Hole U1454B at 0255 h. The full-length APC penetrated from the seafloor to 32.1 m (Cores U1454B-1H to 4H, 30.28 m recovered, 94%). We switched to the half-length APC. Twelve HLAPC cores and three 4.8 m advances without coring penetrated to 100.7 m. Cores U1454B-5F to 19F sampled 54.2 m and recovered 43.22 m of sediment (80%). Coring was interrupted for 2 h (1400–1600 h) when a broken strand on the coring line snagged in the top drive; ~1500 m of coring line was cut off and the coring line re-terminated. Cores described today (1H–8H) are middle to early Pleistocene gray clay with silt interbeds and dark gray fine sands with mica.

Daily Science Report for 18 March 2015

Location: Hole U1453A (MBF-4A) (8°0.4193′N, 86°47.8973′E, 3679.5 mbsl)
Transit to Site U1454
Site U1454 (MBF-7A) (8°0.4067′N, 85°50.9882′E, 3709.9 mbsl)

Science Update: Following yesterday’s successful wireline logging in Hole U1453A, all of the logging equipment was cleared off the rig floor at 0055 h. We then spent 45 min getting the pipe free from the formation with the bit clearing the seafloor at 0200 h. We retrieved the drill string, secured the rig floor, raised the thrusters, and departed for Site U1454 (MBF-7A) at 1130 h. After a 56 nmi transit, we arrived at Site U1454 at 1706 h, started assembling an APC/XCB bottom-hole assembly, and just before midnight we were preparing to start coring in Hole U1454A. At our noon crossover the logging scientists gave an overview of some the preliminary log data from Hole U1453A.

Daily Science Report for 17 March 2015

Location: Hole U1453A (MBF-4A) (8°0.4193′N, 86°47.8973′E, 3679.5 mbsl)

Science Update: Today we deepened Hole U1453A from 168.2 to 215.7 m. Cores 34F to 42F penetrated 23.5 m of formation and recovered 16.91 m of core (72%). The cores described today (U1453A-23F to 42F) are a Pleistocene succession of dark gray sand, gray clay with silt interbeds, and calcareous clay. Since we achieved our primary coring objectives at this site, we started to prepare the hole for downhole logging. We circulated 25 barrels of mud to clean cuttings out of the hole. To ensure the lockable float valve was functioning well for logging, we also activated it with a go-devil and an XCB barrel. We then filled the hole with 180 barrels of 12.0 ppg mud and raised the bit up to logging depth (78.5 m). The triple combo logging string was assembled and lowered down the drill string. At ~2170 m DRF within the drill pipe well above the seafloor, the string began losing weight. We inferred it had encountered the weighted mud, so we circulated the mud down to the seafloor and resumed lowering the logging tool string. Log data was collected to the full depth of the hole and indicated good hole conditions. After the triple combo was recovered, we ran the FMS-sonic tool string, which also reached the bottom of the hole. The tool string was back on the rig floor just before midnight (2355 h).

Daily Science Report for 16 March 2015

Location: Hole U1453A (MBF-4A) (8°0.4193′N, 86°47.8973′E, 3679.5 mbsl)

Science Update: Cores U1453A-14F to 33F penetrated from 71.9 to 168.2 m (96.3 m) and recovered 89.2 m of core (93%). One full-length APC was attempted in this interval (29H), but it only penetrated ~7 m. The cores described today (U1453A-6F to 22F) are a Pleistocene succession of clays with silt interbeds and intervals of homogenous silty sand with mica.

Daily Science Report for 15 March 2015

Location: Hole U1453A (MBF-4A) (8°0.4193′N, 86°47.8973′E, 3679.5 mbsl)

Science Update: We finished lowering the drill string to the seafloor and started coring in Hole U1453A at 1020 h. Except for one 5 m interval advanced without coring (29.3–34.3 m), APC and HLAPC coring penetrated from the seafloor to 71.9 m (Cores U1453A-1H to 13F) and recovered 58.7 m of core (88%). The cores described today (1H–4H) are Pleistocene light gray clayey calcareous ooze, a light brown ash layer, gray clay, and dark gray fine sand.

Daily Science Report for 14 March 2015

Location: Site U1452 (8°0.42′N, 87° 10.90′E, 3670.5 mbsl)
Transit to Site U1453
Site U1453 (MBF-4A) (8°0.42′N, 86°47.90′E, 3682.8 mbsl)

Science Update: After finishing coring in Hole U1452B, we pulled out of the hole with the bit clearing the seafloor at 0300 h. We then offset the ship 20 m south of Hole U1452B and started APC coring in Hole U1452C. Hole U1452C consisted of continuous coring from the seafloor to 41.3 m to obtain a more complete sampling of the uppermost levee sequence. Coring in Hole U1452C started at 0245 h on 14 March. After a successful mudline core (U1452C-1H), we used the XCB system to core from 7.0 to 11.0 m; in Hole U1452B, this interval had poor recovery and appeared to be a hard layer. Unfortunately, this core came back empty. APC coring resumed and Cores 3H–6H extended from 11.0 to 41.3 m (30.3 m) and recovered 30.3 m of core (87%). When the last core recovered sand, our objective for this hole had been reached (we had passed below the targeted levee section) so we pulled out of the hole and recovered the drill string. After the bit was back on board, we secured the rig floor, raised the thrusters, and departed for Site U1453 (MBF-4A) at 1900 h. After a short 23 nmi transit, we arrived at Site U1453 (MBF-4A) at 2145 h and started lowering the drill string to the seafloor. The major lithology of the Hole U1452B cores described today (32F–43F) are Pleistocene sand with mica, nannofossil rich clay with foraminifers, fine sand, and some silty clay.

Daily Science Report for 13 March 2015

Location: Site U1452 (8°0.42′N, 87°10.90′E, 3670.5 mbsl)

Science Update: Today, we deepened Hole U1452B from 94.9 to 217.7 m. Five half-length APC cores (HLAPC, 18F–26F) alternating with five 4.8 m advances without coring extended from 94.9 to 142.4 m and recovered 14.49 m of core (62%). Nearly continuous HLAPC coring (Cores 28F to 43F, except for a single 4.8 m advance without coring) penetrated from 142.4 to 217.7 m and recovered 62.49 m of core (89%). We decided our primary deep coring objectives at this site had been achieved, so we pulled out of Hole U1452B. Hole U1452B penetrated a total of 217.7 m of which 174.5 m was cored and recovered 140.33 m of core (64%). The major lithology of the cores described today (U1452B-7F to 31F) are Pleistocene dark gray fine sands; minor lithologies include dark gray clay and silt, as well as greenish-gray nannofossil-rich clay.

Daily Science Report for 12 March 2015

Location: Site U1452 (8°0.42′N, 87°10.90′E, 3670.5 mbsl)

Science Update: After lowering the drill string to the seafloor, we attempted to take the mudline APC core in Hole U1452A at 0315 h, but the system would not fire (shear pins did not fail). After recovering the APC core barrel and diagnosing/fixing the problem, we redeployed the APC core barrel and started coring in Hole U1452A at 0540 h. Core U1451A-1H penetrated 8 m. This single core from this hole is dedicated to high-resolution studies around the Toba ash layer, so it was only run through the whole-round track systems and then stored for postcruise splitting and sampling. We then offset the ship 20 m to the east and started coring in Hole U1452B at 0700 h. Core U1452B-1H to 5H penetrated to 41.4 m and recovered 8.21 m of sediment (80%). All of these cores were orientated. Core 5H was a partial stroke and inferred to have only penetrated ~4.7 m based on the amount of competent material recovered in the top of the core. We then switch to the half-length APC system. Cores 6F to 12F penetrated from 41.4 to 71.1 m (29.7 m) and recovered 23.32 m of core (79%). Based on evidence on the outside of the core barrel, Core 6F only penetrated 1.5 m into the formation, so it was advanced this amount; all other cores were advanced 4.7 m. We then started alternating 4.7 m long HLAPC cores with 4.8 m intervals drilled without coring. Cores 14F and 16F penetrated 9.4 m and recovered 6.92 m of core. Two intervals drilled without coring penetrated 9.6 m. Cores described today (1H–6F) are Pleistocene nannofossil-rich calcareous ooze with a volanic ash layer, clayey silt, silty clay, and silty fine sand.

Daily Science Report for 11 March 2015

Location: Hole U1450B (8°0.4192′N, 87°40.2586′E, 3655.4 mbsl)
Transit to Site U1452
Site U1452 (8°0.4196′N, 87°10.9001′E, 3670.5 mbsl)

Science Update: We finished assembling and testing the first logging tool string (triple combo) at 0115 h. We lowered it through the drill string and out of the open end of the drill string that was at 82.7 m. The bottom of the tool string encountered an obstruction in the hole at 133.7 m. The tool string was raised and lowered a few times in an attempt to pass through this obstruction, but the tool became stuck in the hole. After applying the maximum amount of force to the logging wireline, the tool string was freed from the formation. The tool string was recovered on the rig floor at 0615 h. We decided logging was not possible due to the hole conditions. After the rig floor was cleared of the logging setup, the driller started to pull the string out of the seafloor. However, the pipe had become stuck and the drillers had to apply 40 klbs of overpull to extract the bottom-hole assembly out of the seafloor. After the drill string was retrieved, the rig floor secured, the thrusters raised, and the seafloor positioning beacon recovered, we departed for Site U1452 at 1430 h on 11 March. We arrived at Site U1452 (MBF-5A) at 1700 h, prepared an APC/XCB bottom-hole assembly, and lowered it to the seafloor. We anticipate starting coring in Hole U1452A tomorrow morning.

Daily Science Report for 10 March 2015

Location: Hole U1450B (8°0.4192′N, 87°40.2586′E, 3655.4 mbsl)

Science Update: Cores U1450B-12R to 22R penetrated from 705.1 to 811.9 m (106.8 m) and recovered 15.77 m of core (29%). We decided our primary coring objectives had been mostly achieved, so we started to prepare the hole for downhole logging. We circulated 35 barrels of mud to clear cuttings out of the hole (before retrieving the last core), deployed the rotary shifting tool (RST) to release the bit in the bottom of the hole, filled the hole with weighted mud, and raised the bottom of the drill string up to 82.7 m. At 2300 h, we started assembling the first logging tool string (triple combo). Cores described today (12R–22R) are gray claystone, gray clayey silt with plant fragments, mottled marlstone and limestone with burrows. These cores extend back to the upper Miocene.

Daily Science Report for 9 March 2015

Location: Hole U1450B (8°0.42′N, 87°40.23′E, 3655.4 mbsl)

Science Update: At 0414 h we finished drilling down without coring to 608.0 m (Hole U1450A was cored to 687.4 m). After retrieving the center bit, RCB coring started at 0515 h. Cores U1450B-2R to 11R penetrated from 608.0 to 705.1 m (97.1 m) and recovered 15.77 m of core. Due to poor recovery for Cores 3R–6R (3.72 m; 8%), slow penetration rate, and sediment jammed in those core catchers, we ran a bit deplugger after Core 6R to clear the bit; subsequent core recovery improved. Cores described today (2R–11R) are predominantly gray silty clay and clayey silt layers with plant fragments; limited intervals contain light gray mottled marlstone and limestone. These cores extend back to the upper Miocene.

Daily Science Report for 8 March 2015

Location: Hole U1450B (8°0.42′N, 87°40.23′E, 3655.4 mbsl)

Science Update: We continued drilling without coring in Hole U1450B from 25.7 to 465.0 m. Due to the low penetration rate, at 1945 h we retrieved the center bit for inspection and then redeployed it. Drilling resumed at 2100 h and by midnight the bit had reached 530.7 m. We plan to start RCB coring at 600 m (Hole U1450A cored to 687.4 m), core below that depth, and then log.

Daily Science Report for 7 March 2015

Location: Hole U1451B (8°0.4203′N, 88°44.4745′E, 3607.3 mbsl)
Transit to Site U1450
Hole U1450B (8°0.42′N, 87°40.23′E, 3655.4 mbsl)

Science Update: We finished retrieving the drill string from Hole U1451B, secured the rig floor for transit, recovered the seafloor positioning beacon, raised the thrusters, and at 0800 h departed Site U1451. After a 64 nmi transit we arrived back at Site U1450 at 1342 h. Most of the rest of the day was spent assembling an RCB coring bottom-hole assembly and lowering it to the seafloor. Drilling in Hole U1450B started at 2305 h, and by midnight the bit had penetrated to 25.7 m. We plan to drill without coring to 600 m (Hole U1450A cored to 687.4 m), core below that depth, and then log.