OPERATIONAL/DRILLING
STRATEGY
A number of
operational, practical, and strategic factors were considered
when developing the operational plan for Leg 184. Briefly, these
include
- Sites
were selected to maximize recovery of different
stratigraphic sections and different water depths. The
northern continental margin sites comprise two transects:
an eastern pair of sites that will focus on the
Plio-Pleistocene section (Sites SCS-1 and SCS-2) at 2050
and 3190 m, respectively, and a western pair of sites
that will focus on the Oligocene to Miocene section
(Sites SCS-4 and SCS-5C) at 2093 and 3250 m,
respectively.
- All
sites are considered to be first priority, but Site
SCS-3C is considered at risk if operational time is
limited. Site SCS-5C is considered to be the highest
priority as it is the only site that will recover the
Oligocene to Miocene section of the SCS. Alternate Site
SCS-5D or 5E may become a higher priority than SCS-3C, if
the coring results at SCS-5C do not satisfactorily
recover the early history of the monsoon.
- All
sites will be triple piston cored (advanced hydraulic
piston core [APC]) and extended core barrel (XCB) cored
to total depth, with the possibility of double XCB if
critical sections are not adequately recovered. The
deeper sections of Site SCS-5C may be cored with the
rotary core barrel system (RCB), if XCB penetration and
recovery are not adequate.
- Because
of the limited number of seismic crossing lines at
proposed sites, the JOIDES Resolution will conduct
a seismic reflection survey (~2 to 2.5 days at Sites
SCS-2, 3C, 4, and 5C and, if required, Sites SCS-5D and
5E) to verify that the proposed sites are safe and to
provide a better structural framework for interpreting
the sediment accumulation patterns. Coring at all but
SCS-1 is contingent on safety panel approval, which will
be based on the survey data.
- Taking
the above operational/coring considerations into account,
the following sequence of operations is proposed: Depart
Freemantle and transit to proposed Site SCS-9 and core.
Then transit to Site SCS-1 and core. We will then conduct
a seismic survey of northern sites to collect cross lines
and select final site locations. Following the survey, we
anticipate coring proposed Sites SCS-2, SCS-5C (or
alternate), SCS-4, and SCS-3C in sequence before the
final transit to Hong Kong.
- ODP
has requested Exclusive Economic Zone (EEZ) clearance for
all proposed sites. Site SCS-9 requires drilling in
waters that are claimed by several nations and EEZ
clearance of this site may therefore be more problematic
than for the northern sites. If SCS-9 should not get
approved, the remaining time will be used to achieve the
objectives, and maximize recovery, at the other sites,
including SCS-3C.
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Logging Plan
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