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IODP Expedition 340:
Lesser Antilles Volcanism and Landslides
Week 3 Report (19-25 March 2012)
PDF file is available for download.
Week 3 of Lesser Antilles Volcanism and Landslides Expedition (340)
began with an uneventful pipe trip to spud Hole U1397A. The bit was initially
set at 2484.5 mbrf and the hole was spudded at 0422 h
(UTC-4h) on 19 March. The first 9 cores were oriented with the FLEXIT tool.
Non-magnetic core barrels were used for APC coring from Core U1397A-1H through
-17H. APCT-3 temperature measurements were taken on Cores U1397A-5H through
-7H. An APCT-3 core was attempted on Core U1397A-3H, but the electronics failed
and data could not be downloaded. The majority of the piston cores were incomplete
strokes and the hole was advanced by recovery. After reaching APC refusal, XCB
coring continued to 265.5 mbsf. Because of time constraints, coring was
terminated after Core U1397A-35X at 265.5 mbsf - shallower than the target
depth of 314 mbsf. Difficult hole conditions
contributed to increasing the coring time required to advance the hole. Overall
core recovery for Hole U1397A was 55%. After the completion of coring, the
drill string was pulled back with the top drive still installed. The bit
cleared the seafloor at 0055 h on 21 March ending Hole U1397A. The total time
spent on Hole U1397A was 53.25 h.
After clearing the seafloor from Hole U1397A, the vessel was offset 20
meters to the east and Hole U1397B was spudded at 0252 h on 21 March.
Non-magnetic core barrels were used on all cores. APCT-3 temperature
measurements were taken on Cores U1397B-3H, -4H, and -7H. Similarly to Hole
U1397A, most of the piston cores were partial strokes and the hole was advanced
by recovery. After reaching APC refusal on Core U1397B-17H, XCB coring
continued to 265.5 mbsf. Because of time constraints, coring was terminated
after Core U1397A-33X at 253.5 mbsf - short of the 314 mbsf target depth. Difficult hole conditions contributed to increasing the coring time required to advance the hole. Overall core recovery for Hole U1397B was 53%.
At the conclusion of coring, Hole U1397B was conditioned with a 30-barrel
high viscosity mud sweep. Hole conditions at the end of coring were very bad
and the top drive had to be left in to pull upward. Both rotation and
circulation were required until ~220 mbsf. The hole was not displaced with
logging mud since the mud would have simply pumped away during the circulation
required to keep the drill string free. The drill string was then pulled up to
2645 mbrf, the wireline rigged up for logging, and
the triple combo was deployed. Because of the poor hole
conditions, the two nuclear sources typically used in this logging string were
not included. Two successful passes were made to 221.1 mbsf. The tool string
was then pulled back to surface and rigged down. The FMS-sonic tool string was
then picked up and the tool was run to 210.3 mbsf. Two passes were made over
the length of the open hole. The second pass was only able to reach ~205 mbsf
as the hole slowly deteriorated. The tools were then pulled back to surface and
rigged down. At the beginning of the last logging run, the driller noted a drill
string overpull of 70 klbs. After the FMS-sonic was recovered, the top drive was picked up and using rotation and overpull the drill string was worked
free from the formation. The bit cleared the rotary table at 0240 h and the
drill floor was secured at 0245 h on 24 March ending Hole U1397B and Site U1397
(CARI-010B). The total time spent on Hole U1397B was 73.75 h. The vessel then
proceeded to Site U1398 (CARI-09B).
After a 46.0 nmi transit from Site U1397
(CARI-09B), the vessel arrived at Site U1398 (CARI-09B). The vessel stabilized
over Site U1398 (CARI-09B) at 0706 h on 24 March and Hole U1398A was spudded at
1551 h on 24 March. Core orientation was performed with the FLEXIT tool and
non-magnetic core barrels used through Core U1398A-6H. On the third core, the
APC system was unable to penetrate the formation so the XCB system was deployed
for Cores U1398A-3X and -4X. The APC system was then redeployed on Core
U1398A-5H. APCT-3 temperature measurements were taken on Cores U1398A-5H and
-6H. Once again, the hole was advanced by recovery after partial APC strokes.
Week 3 ended on Core U1398A-27X.
We started our third week with coring operations off Martinique at Site
U1397 (CARI-10B) and at the end of the week we are in the middle of our coring
operations on Site U1398 (CARI-09B).
Site U1397 (14°54.41'N, 61°25.35'W), located west of Martinique, was chosen to characterize the eruptive history of this volcanic island in space
and time. Previous studies on short piston cores (7 m long) have revealed a
large number of tephra layers within the marine sediment and shown that the
sedimentation rate in this area is about 20 cm/ky.
Taking into consideration the proposed total depth at this site the sediments
recovered would span a time interval of about 1 Ma. It was also expected to be
able to identify and date layers related to the emplacement of debris
avalanches from Montagne Pelée and Pitons du Carbet volcanoes as well as to sample the region related to the transition of volcanism from the Pitons du Carbet and Mont Conil volcanoes to the Montagne Pelée from the retrieved material. The end of their volcanic activity (~0.3-0.5 Ma) preceedes, or is synchronous with, the beginning of the Montagne Pelée activity.
This site was also thought to contain tephra from volcanoes of Dominica, which can
be distinguished from Martinique lavas based on their geochemistry and
micro-textural characteristics. Even though we did not reach our depth objectives for this site the retrieved material will allow us to study the eruptional and depositional history of Martinique extending back to ~350 ka. A
distinct volcanic marker as well as the bio- and magnetostratigraphy
assign the base reached at this site to an age of 350 to 400 ka. Generally, the material retrieved consist, similar to the other sites cored so far, of hemipelagic muds, volcaniclastic or mixed (bioclastic-volcaniclastic)
turbidites, and tephra layers of variable thickness. The amount of hemipelagic
background sediment retrieved at this site is lower compared to the other
sites. The degree of lithification increases with
depth, and at the base of both holes the retrieved sediments are
semi-consolidated. The mainly normally graded volcaniclastic
turbidites consist of fresh as well as altered andesitic lava clasts, pumice, and crystals. The non-volcanic components
observed in some of the turbidite units are composed
of biogenic and detrital carbonate. In the uppermost 28 m at this site we cored
around 200 tephra layers, followed by more but not quite as abundant tephra
layers going deeper into the formation. The tephra layers consist of ash and
pumice of variable grain size and are highly variable in thickness.
So far at Site U1398, we recovered similar material as at Site U1397.
The sediments recovered from this site will be used to characterize the sedimentation processes (distinguishing between the processes related to volcanic and non-volcanic activity) in the backarc Grenada Basin. We
plan to retrieve a complete sedimentation record down to ~264 mbsf at this site.
The material recovered so far consists of tephra layers (being less frequent
than at the last site, Site U1397) and volcaniclastic turbidites intercalated with hemipelagic background sedimentation. The proportion of hemipelagic sediment is larger at this site compared to Site U1397.
Education and Outreach
Live videoconferences continued during the third week of our
expedition. On Monday we had live broadcasts with students from the Brockenhurst College (Hampshire, UK) and from the Don Callejon Middle School (Santa Clara California, US) featuring scientists Martin Palmer and Martin Jutzeler. On
Tuesday, scientists Martin Palmer and Anne Le Friant
hosted a live broadcast with students from the Abbotswood
Jr School (Hampshire, UK; ages 8-11 years), and the
College Eugene Yssap (Sainte Anne, Guadeloupe; ages
13-16 years). On Thursday our education and outreach activities continued with a
live video conference with the Primary School Marseille (Aoz-en-Provence, France) featuring our co-chief scientist Anne Le Friant and another one
with the Fairlands Elementary (Pleasanton California,
US) featuring our staff scientist Nicole Stroncik. On
Friday we continued our broadcasts with the Admiral Farragut Academy (St.
Petersburg, FL) and the University of Leicester (Leicester, UK) featuring our
education and outreach officer Teresa Greely as well as one of our logging
staff scientists, Sally Morgan. In addition blogging with our scientists
continued over the entire week.
Technical Support and HSE Activities
Science Mission Support: Technical staff remains fully engaged
in providing support for coring operations.
Other Technical Activities:
data reduction: While logging, full background as well as an edge correction
test was conducted. Analysis of data
is in progress.
Lab ceiling lights installed and work is proceeding on the ceiling
Numerous data management and processing issues encountered
The weekly fire and abandon ship drill was held as scheduled.