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IODP Expedition 323:
Bering Sea Paleoceanography
Week 3 Report (19-25 July 2009)
PDF file is available for download.
25 July 2009
Hole U1339C, in the Umnak Plateau, was spudded at 2230 hr on
July 18th and at the start of the third week we were recovering Core
U1339C-3H with the APC system. Core advance was a continuous 9.5 m except for
Core U1339C-16H which contacted a drop stone at 4.5 m stopping the APC core
barrel. A portion of the drop stone was recovered at the top of the next core.
APC coring continued through Core U1339C-17H to a depth of 156.8 m DSF using
the FLEXIT core orientation system and non-magnetic coring assemblies. The
standard APC coring system was then used through Core U1339C-21H to a depth of
194.8 m DSF. Overall core recovery for the APC was 102.2%. The drill string was
pulled clear of the seafloor at 1610 hr July 19th officially ending
The ship was offset 28 m and 195° from Hole U1339C and Hole
U1339D was spudded at 1725 hr on July 19th. Core U1339D-1H recovered
6.6 m of sediments establishing a seafloor depth of 1879.4 m DSF. Twenty-two
APC cores were cut to a depth of 200 m. Hole U1339D was cored using
non-magnetic core barrels down through Core U1339D-17H. Steel core barrels were
then used as APC coring continued through Core U1339D-22H. Apart from the first
mudline core there was one other short core caused by a premature firing of the
APC. This was most likely caused by damage to the shear pins caused by running
the core barrel assembly into the landing seat at too high a speed. APC core recovery was 102.9%. The
coring tools were secured and the hole was swept clean with 50 barrels of
attapulgite mud. There was no fill identified at total depth. The LFV was
locked open, and the end-of-pipe (EOP) was placed at ~80 m DSF. Rig-up for
wireline logging began at 1130 hr on July 20th. Wireline logging in
Hole U1339D was successfully completed using the Triple Combo and the FMS-sonic
tool and all logging equipment was rigged down by 0200 hr on July 21st.
Two logging strings were deployed to total hole depth of 200 m. The drill
string was then pulled out and secured for transit. The ship was placed in
cruise mode at 0745 hr on July 21st for the scheduled 1.4 day (344
NMI) transit to Site U1340 (BOW-12B) on the Bowers Ridge. Official APC coring
totals for Site U1339 include 69 cores, 624.2 m penetrated, 643.67 m recovered,
for 103.1% recovery.
After a 1.6 day transit to Site U13340 (BOW-12B), rig floor
operations commenced at 2315 hr on July 22nd. The pipe trip to the
seafloor was uneventful. The top drive
was picked up and the drill string was spaced out placing the bit at 1300.4 m
DSF or 5 m above the "corrected" PDR depth of 1305.4 m DSF. The first APC
barrel was pressured up and fired and the barrel recovered 3.9 m of core and an
official seafloor depth was established at 1306 m. APC coring continued through
Core U1340A-17H to a depth of 1461.9 m DSF (or 156.5 m in the hole) using
non-magnetic coring assemblies and with the FLEXIT orientation tool installed.
The non-magnetic coring equipment was changed to the standard APC coring system
and coring continued. Coring with the APC system was suspended after Core
U1340A-42H with two successive short, incomplete strokes of the core barrel.
The XCB coring system was deployed from Core U1340A-43X through U1340A-62X.
After 3 successive zero recovery cores and an apparent formation change, a
decision was made to redeploy the APC coring system at 543.9 m DSF. The APC
system recovered very sandy core sections to 566 m DSF. The XCB system was then
again deployed for Cores U1340A-68X through U1340A-71X. The hole was terminated
after Core U1340A-71X when the cutting shoe spacer sub fractured, leaving half
the sub and the XCB cutting shoe in the hole. The drill string was pulled back
to the seafloor at 2100 hr on July 25th officially ending the hole.
Overall recovery for Hole U1340A using the APC coring systems was 105 % with
398.8 m recovered. Overall recovery for Hole U1340A with the XCB coring system
was 61% with 136.7 m recovered.
The vessel was then moved eastward 350 m and Hole U1340B was
spudded at 2340 hr at the end of the third week of Expedition 323.
This week, we recovered a total of 543.51 m of sediments at
Site U1339 (Holes U1339A, U1339B, U1339C, and U1339D) in the Umnak Plateau and
642.87 m at Site U1340 (Holes U1340A, U1340B, U1340C, U1340D) in the Bowers
Early in the week we completed the description of all
remaining sediment cores from Site U1339. The stratigraphic section recovered
in these holes is predominantly green to grayish green diatom ooze and silty
diatom ooze with variable amounts of dispersed vitric ash, isolated pebbles,
distinct ash layers as well as bioturbated ash/diatom ooze layers and laminated
intervals. Bioturbation varies from slight to strong although areas described
as having no visible bioturbation may be intensely bioturbated. Rare dolomite
indurated layers are found in bottom half of the section. All core sections
were successfully measured with the core laboratory track systems for natural
gamma radiation, density, magnetic susceptibility and thermal conductivity
tools and the data uploaded to the Library Information Management System (LIMS).
The age interval recovered at Site U1339 covers from the
Recent to about 0.74 m.y. based on silicoflagellate, radiolarian and diatom
biostratigraphy. The more recent age estimates are well supported by our
physical property records that are in good agreement with other records from
piston cores from the region.
We performed chemical analysis of interstitial water (IW)
and squeeze cakes samples collected from Holes U1339A and U1339B. We determined
concentrations of dissolved sulfate, ammonium, sulfide, major (i.e., Ca, Na,
etc.) and minor (i.e., Fe, Mn) elements among other chemical species. Analysis
of solid phase fractions included nitrogen and carbon. In addition, we
performed extensive sampling for postcruise microbiological analyses at Hole
We completed logging operations in Hole U1339D between
midday and midnight on July 20th. Two tool strings were deployed:
the Triple Combo (natural gamma ray, porosity, density, resistivity) and the
FMS-Sonic string (electrical images and sonic velocity). Operations proceeded
smoothly and the caliper logs indicate hat the hole was in good conditions and
that all data should be of good quality. Some time was dedicated during
operations for the continuing evaluation of performance of the new wireline
heave compensator. All logging data were processed on site and transmitted to
LDEO for quality control before online publication. Preliminary data were
distributed to the science party for integration with the ongoing core
measurements and description. Comparison with the gamma ray and density core
track data show an excellent agreement that will allow tying precisely the logs
with the stratigraphy and deposition history of the Umnak Plateau.
We arrived at Site U1440 (BOW-12B) on Jul 22nd at
2300 hr and Hole U1340A was spudded at 0520 hr on July 23rd. The
stratigraphic section at this Bowers Ridge site contains light to dark green to
grayish green diatom ooze and silty diatom ooze with minor foraminifera-bearing
diatom ooze. Cores U1340A-4H through 7H, as well as 10H and 11H, contained
slumped sediment intervals. There are occasional thin dark- and light-colored
ash layers and bioturbated ash-rich layers and rare silicoflagellate rich- and
monospecific diatom laminae. A dark gray sand layer composed of diatom-bearing,
sponge spicule-rich coarse-ashy sand was recovered in Core U1340A-64H.
Bioturbation varies from slight to strong throughout.
Technical Support and HSE Activities
During this week, the technical staff was fully engaged with
processing cores from Sites U1339 and U1340, assisting scientists with
instruments and data processing, and solving equipment issues as they arise.
USIO staff continue to fine tune issues with analytical
systems. On a time available basis, work continues on the reorganization of the
ship's storerooms. Ship's crew has completed the painting of the decks in the
Science Pallet and Logistic Store room. There are no facility infrastructure
issues to report.
The weekly fire and boat drill was held as scheduled.