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IODP Expedition 317:
Canterbury Basin Sea Level
Week 7 Report (20-26 December 2009)
PDF file is available for download.
28 December 2009
week began tripping drill pipe out of Hole U1352C after completing coring
operations. 400 barrels of high
viscosity logging mud were displaced into Hole U1352C. The trip out of the hole
experienced excessive drag and required the top drive to be re-installed. The
trip out continued with rotation until the end of the string reached 545 m DRF.
The upper guide horn was removed and the VIT camera was deployed to observe and
document the cone of cuttings at the sea floor while logging. The drill string
was set to a logging depth of 458 m DRF and the logging string was rigged up to
run a modified version of the triple combo. The first logging run indicated
that the hole had collapsed and the tool string was unable to pass 562 m WRF.
The tool string was pulled back to surface and rigged down. The drill string
was tripped back and operations at Hole U1352C ended at 2200 h on 20 December.
the time operations at Hole U1352C were concluded, the winds and swells were
too high for operations at the next site in shallow (<200 m) water. In
anticipation of a delay of ~24 h due to weather, it was decided to core Hole
U1352D while waiting on weather. Hole U1352D operations commenced at 2200 h on
20 December and Cores U1352D-1H through 14H to a depth of 127.0 m DSF recovered
130.8 m of core (103%). Non-magnetic coring assemblies were used and core
orientation was measured on all cores.
an 18 nm transit the vessel was positioned at Site U1353 (proposed site CB-01A;
water depth 84.2 m) at 2320 h on 21 December. Coring in Hole U1353A began at 0230 h on 22 December with
the APC/XCB system and continued through Core U1353A-8H (56.0 m DSF) using
non-magnetic coring assemblies. Orientation was measured on the first six cores
and a temperature measurement was taken with Core U1353A-5H. Contamination
testing was done on all cores with microspheres. Total recovery for Hole U1353A
was 56.4 m (101%).
at Hole U1353A ended and those at Hole U1353B began at 1530 h on 22 December.
The vessel was positioned 20 m south of Hole U1353A and Hole U1353B was piston
cored to a depth of 80.2 m DSF with a total recovery of 80.7 m (101%). Because of the rough piston coring
conditions in Hole U1353A, the core orientation tool was not deployed. The APC
system was pushed hard because it offered nominal recovery of ~100% (recovery
by advance). However, strokes were incomplete and penetrations short. Moreover,
liners got regularly shattered and much of the recovered material consisted of
shell hash and other sediment that fell into the bottom of the hole or was
disturbed by the coring process. The XCB system allowed for faster penetration
but was essentially unable to recover any significant amount of core. From Core
U1353B-1H to 60H (0-258 m DSF), the APC was used 51 times and recovered 188.3 m
over an interval of 188.0 m (average advancement 3.7 m; average recovery 100%);
and the XCB system was deployed 9 times and recovered 2.63 m over an interval
of 69.7 m (average advancement of 7.7 m; average recovery 4%). Below 258 m DSF,
the XCB was deployed exclusively to the total depth of 614 m DSF with a
recovery of rate of 6%.
cement plug was pumped per IODP policies for drilling on a continental shelf
and operations at Hole U1353B were completed at 2050 h on 26 December. A total
of 212 m of core were recovered over an interval of 614 m (average recovery
rate of 34%). At 2230 h on 26 December, drilling Hole U1353C as a dedicated
logging hole began.
deepest core (U1352C-148R: 1918 to 1924 m CSF) from Hole U1352C was opened and
described. It contained white, silty limestone with up to 3-cm thick intervals
of well laminated, light greenish gray very fine sandy marlstone. Fourteen
cores (U1352D-1H to 14H) were retrieved from Hole U1352D (0-127 m CSF) with an
average nominal recovery of 103%. These cores were described by
sedimentologists. Lithology is same as that of Holes U1352A and U1352B.
from the second shelf site, Site U1353, opened to date are Cores U1353A-1H to
8H (0 - 56 m CSF) and U1353B-1H to 97X (0 - 604 m CSF). Cores U1353A-1H through
8H and U1353B-1H to 11H consist of green muddy very fine-grained sand, greenish
gray mud with rare shells, and thick (1-6 m) beds of very fine-grained,
well-sorted massive sand with scattered shell fragments (beach sand). The
Holocene interval was ~6-7 m thick.
80 m CSF, poor coring conditions persisted, with short APC advances and XCB
coring attempts with no recovery. Much of the recovered sediment comprised
shell hash and shelly gravels interpreted as cave-in. Short intervals of gray
mud were recovered and they were considered to represent the in situ formation.
At least one significant lithologic boundary was recovered in Core U1353B-28H.
This boundary may be correlate with similar surfaces at other sites drilled
during Expedition 317. Hole U1352C was terminated after retrieval of Core
U1353B-98X (614 m DSF).
age of Core U1353B-11H is ~0.44 Ma and that of Core U1353B-30H is 2.7-3.1 Ma,
based on calcareous nannofossils. The age of Cores U1353B- 60X to 65X is ~3.7
Ma based on macrofossils and nannofossils. Precise shipboard age determination
is difficult because of poor preservation of nannofossils and planktonic
foraminifera. It is difficult to determine the age of the bottom of the Hole
because of low abundance of diagnostic microfossils. However, nannofossils
suggest an early middle Miocene age. If so, we will have reached an
unconformity that has already been recognized at both Sites U1351 and U1352,
but had not been interpreted on seismic profiles. This provides an excellent
basis for a revised and improved seismic interpretation in this interval.
measurements of IW samples show a zone of low salinity and chloride at ~50 m
CSF. This may indicate a fresh water wedge extending from the shore beneath the
shelf floor or, alternatively, residual fresh water from periods of shelf
exposure during sea-level lowstands.
Technical Support and HSE Activities
shipboard labs were processing cores and samples from Site U1353. Off going
shipments are being prepared. A fire and boat drill was held on December 20 for
the entire ship's complement.