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IODP Expedition 339:
Week 2 Report (21-27 November 2011)
PDF file is available for download.
Just prior to concluding the port call in Ponta Delgada, the home port of registry for the JOIDES Resolution was changed from Monrovia, Liberia to Limassol, Cyprus. The vessel departed for Site U1385 (proposed site SHACK-04A), the first site of the expedition, at 0800 hr on 22 November. We
covered the 741 nmi transit in 68 hours at an average cruising
speed of 11.1 knots. During the voyage, the co-chief scientists, ancillary
program proponent and senior USIO and Siem Offshore
personnel met for a final clarification of operations at Site U1385. The clock
was advanced one hour placing the vessel on Lisbon time. This is the same time
zone as UTC or +6 hours relative to Central Standard Time.
The vessel arrived on site at 0400 hr
on 25 November. The initial pipe trip was extended by the
routine measuring and "rabbiting" that occurs on the first deployment of
the drill string. Following a three-hour VIT survey of the seabed during which
no obstructions were observed, Hole U1385A was spudded with the APC at 2300 hr on 25 November. The recovery of the first core
established the seafloor depth at 2598.0 mbrf (2586.7
mbsl). Piston coring with non-magnetic core barrels advanced
to a total depth of 151.1 mbsf (17 cores), which was the depth objective of the
site. Cores U1385A-4H through -17H were oriented. There were APCT deployments
at 30.0 (-4H), 58.5 (-7H), 87.0 (-10H), and 115.5 (-13H) mbsf. The APC
experienced partial strokes on -14H and -17H. The last core only advanced 7.7 m
when the formation firmed up and abruptly stopped the APC. The drill crew
experienced difficultly extracting the sinker bars from the drill string prior
to pulling out of the hole. It required 4.5 hours of IODP rig time to remove a
deformed section of coring line before operations could resume. This involved
the removal of 100 m of coring line, the re-heading of the line, and the
redressing of the oil saver.
Following a vessel offset of 20 m east of Hole U1385A, operations on Hole U1385B began at 0030 hr on 27 November. The water depth calculated
from the recovery of the first core is 2597.9 mbrf (2586.6 mbsl). Piston coring using non-magnetic core barrels continued to a total depth of 147.9 mbsf (16 cores). The week ended beginning operations in Hole U1385C.
During the second week of Expedition 339, all science teams
underwent training on analytical equipment, software, and the lithostratigraphy team on description techniques used during the core description process. Particular attention was paid to training on DESCLogik, the software used to capture core
description data. All teams also worked to define and prepare their methods for
the expedition scientific activities and we conducted science seminars related
to the expedition objectives.
By week's end, we completed coring operations in two holes
at Site U1385, the deepest site of the expedition. The overall objective of this
site, located on the western Iberian Margin, is to recover a late Pleistocene
sediment record that will greatly improve the precision with which marine
sediment records of climate change can be correlated to and compared with ice
core and terrestrial records.
Seventeen cores were retrieved from Hole U1385A recovering
155.87 m of sediment (102.9% recovery) and sixteen cores were retrieved from
Hole U1385B recovering 150.73 m of sediment (103%). Core sections are being
processed in the ship's core laboratory using the multisensor track systems to
measure the sediment's physical and paleomagnetic
properties and the archive section halves are being described lithologically and digitally imaged. Sediment and interstitial water samples are being measured for inorganic and organic geochemistry and water samples are also being measured for oxygen isotopic composition.
All cores recovered from Holes U1385A and U1385B were logged
on the special track multisensor logger (STMSL), which measures magnetic
susceptibility and density. All cores from Hole U1385A and Cores 1H through 8H
from Hole U1385B were logged using the whole round multisensor logger (WRMSL)
and the natural gamma radiation logger (NGR). The WRMSL measures magnetic
susceptibility, gamma ray attenuation bulk density, and P-wave velocity at a
higher resolution than the STMSL. Obtained results are coherent with those
expected for mud/ooze pelagic sediments. Thermal conductivity was measured in one section per core for Hole U1385A. Samples for moisture and density
(MAD) measurements were taken from Hole U1385A. Preliminary results indicate a
coherent pattern with a progressive increase in density when increasing depth.
By noon 27 November, the Lithostratigraphy
team has described through Core Section U1385A-12H-2. Cores 339-U1385A-1H and
2H are composed of nannofossil ooze and silty or clayey nannofossil ooze,
with abundant silt- and clay-sized detrital carbonate and a notable absence of siliciclastic clays. The sediment colors in the upper 2
cores are primarily varying shades of gray. Cores 339-U1385A-3H through -4H-7
contain more siliciclastic material, classified as nannofossil muds and nannofossil clays. From Section 339-U1385A-4H-7
through 339-U1385A-12H-2, the nannofossil content
increases again, so that these sediments are classified as muddy nannofossil ooze to nannofossil ooze with clay. Bioturbation
throughout these cores ranges from sparse to moderate, with scattered
occurrences of recognizable ichnofauna. The most notable physical features observed are at least 3 subvertical faults in Sections 339-U1385A-10H-3, -10H-4, and -12H-2. Each of these faults is traceable for several decimeters along the core, and shows offset of 5-10 cm.
Core catcher samples from Holes U1385A and U1385B were
prepared for calcareous nannofossil, planktonic and
benthonic foraminifer, ostracod, and pollen studies.
In order to elaborate a more accurate chronology based on nannofossil
data, additional samples were taken at selected sections. Biostratigraphic
data were mainly based on the identification of nannofossil,
as well as planktonic and benthonic foraminifer events that allowed us to
estimate an age of circa 1.2/1.4 Ma for the bottom of Hole U1385A. Micropaleontological
analyses of core catcher samples from Hole U1385B are in progress.
performed detailed measurements of the response function of the magnetometer to
aid in the deconvolution of the long-core paleomagnetic measurements and are in the process of conducting a full range of paleomagnetic analyses on
cores and samples from Site U1385. The aims of these analyses are to determine
the magnetostratigraphy, the geomagnetic field
behavior, and to study the environmental magnetism of the cores. Shipboard
analyses conducted so far suggest that a useful magnetic signal is preserved in
the APC cored intervals, helped by the use of an orientation tool ("Flexit") during coring. Preliminary comparison with biostratigraphic data and consistently positive magnetic paleoinclinations suggest the recovery of the Brunhes magnetochron in Cores U1385-1H through 10H and the Brunhes/Matuyama boundary in Core U1385-11H. Paleomagnetic
directions from discrete samples for comparison with the split-core results
will be determined when time permits.
Education and Outreach
This week education and outreach activities included two
ship-to-shore videoconferences. One with a classroom of 5th graders
from a U.S. School in Washington, DC and a second one with two high school
classes that were visiting the Science Museum Centro Ciência
Viva de Tavira (Algarve, Portugal) in the framework of the Portuguese National Science and Technology Week 2011 (Semana C&T 2011).
members of the shipboard science party and technical staff have started to
share their experiences on the JR Web Portal blog (www.thejr.org website), social
networks (e.g. Facebook, Twitter), or their University websites.
Technical Support and HSE Activities
The USIO technical staff assisted the scientific party in
preparing the laboratories for coring and processing core samples. The
Operations Superintendent gave three tours of the drill floor for the science
party. The gun array for VSP work was made ready. A Fire and Boat Drill was held
for all participants on 22 November.