LOGGING
Wireline logging will be carried out at all three sites. At the drift site, Site PBD-12B, and fan (slope)
site, Site PBF-6A, we will run a triple or quad combination (from natural gamma, porosity, density,
resistivity, and sonic velocity tools), and the geological high-sensitivity magnetometer (GHMT;
magnetic tool string: magnetic field, magnetic susceptibility, and natural gamma). If time becomes
available, running the Formation MicroScanner (FMS) toolstring (a micro-resistivity imager),
and/or performing some check shots using the well seismic tool (WST) will provide valuable
additional information for these sites. At the shelf site, Site PBS-2A, we will run the triple
combination (natural gamma, porosity, density, and resistivity tools), FMS-sonic, and GHMT (as
above) tool strings.
Logging-while-drilling-light tool (LWD-L; compensated dual resistivity [CDR] tool: natural
gamma and resistivity tools) will be used strategically for intervals at Sites PBS-2A and PBF-6A
where core recovery is anticipated to be poor and in the top 80 to 100 mbsf, where the bottomhole
assembly (BHA) prevents wireline log acquisition. At Site PBS-2A, we will use LWD-L down to
100 mbsf, as previous ODP holes in similar Antarctic shelf environments (Legs 119, 178) have had
very poor core recovery in the top 100 m. At Site PBF-6A, we will use LWD-L to 330 mbsf, while
drilling ahead at the RCB hole to the depth achieved at the XCB hole.
The logs will provide continuous in situ records of the physical and chemical properties of the
sediment, which can be interpreted in terms of sediment lithology. This information can be used to
complement core data, fill gaps in core recovery, and enable core data to be located at its correct
depth position. The continuous nature of the log data makes it ideal for studies of cyclicity (where
every cycle counts). The GHMT is likely to provide a magnetic polarity stratigraphy at the drift site,
and possibly also at the fan site (depending mostly on the sediment grain size). The FMS resistivity
images can be used to identify diamictites, fine-scale bedding, and fabric, including orientation.
Synthetic seismograms (and WST check shots, if taken) can be used to correlate hole depths with
travel times on the seismic section.
UNDERWAY GEOPHYSICS
To ensure that sites are precisely located, particularly for sites selected on seismic lines that were
shot prior to the advent of the Global Positioning System (GPS), some additional seismic data will
be collected on approaching these sites. Standard ODP practice of collecting 3.5-kHz and 12-kHz
data will be followed at all sites and in transit and an 80 cu. inch water gun and hydrophone
streamer line will be run across each site.
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