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IODP Leg 311
- Cascadia Margin Gas Hydrates
Gilles Guerin and Alberto Malinverno
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Figure
1. A) Location
of IODP Expedition 311 on
the Cascadia margin. B) Bathymetry
and location of the different
sites visited (bathimetry
courtesy of D. Kelley, J.
Delaney, and D. Glickson,
University of Washington,
and C. Barnes, C. Katnick,
NEPTUNE Canada, University
of Victoria; funded by the
University of Washington
and the W.M. Keck Foundation).
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Figure
2. Seismic section (line
89-08) showing the position
of the Expedition 311 sites
across the accretionary front.
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Figure 1. A) Location of IODP Expedition 311 on the Cascadia margin.
B) Bathymetry and location of the different sites visited (bathimetry
courtesy of D. Kelley, J. Delaney, and D. Glickson, University
of Washington, and C. Barnes, C. Katnick, NEPTUNE Canada, University
of Victoria; funded by the University of Washington and the W.M.
Keck Foundation).
Figure 2. Seismic section (line 89-08) showing the position of
the Expedition 311 sites across the accretionary front.
Expedition 311 of the Integrated Ocean Drilling Program (IODP)
investigated the occurence and the
formation of gas hydrate in the accretionary prism of the northern
Cascadia margin. The five sites visited during the expedition defined
a SW-NE transect across a ~30km wide Bottom Simulating Reflector
(BSR) that runs parallel to the coast alongmost of the continental
slope (see Figure 1).
From Site U1326, at the SW tip of the accretionary prism, to Site
U1329, the shallowest site located at the landward limit of the
BSR, the transect was designed to sample the complexity of the
evolution of a gas hydrate system (see Figure 2).
To constrain the formation of gas hydrates in subduction zones,
Expedition 311 had an ambitious drilling
program including extensive pressure coring to recover gas hydrate
at in situ conditions. Because of the unstability of gas hydrate
at surface conditions, and of the strong response of some logging
tools such as electrical and acoustic logs to the presence of gas
hydrate, logging was a critical component of the operations. The
logging program consisted of two phases - the first week of the
expedition was dedicated to Logging While Drilling (LWD), in order
to identify intervals likely to contain gas hydrate where pressure
coring tools should be deployed; the second phase consisted in
wireline logging following coring operations in order to complete
the geophysical characterization of the sites.
Expedition 311 Preliminary
Report
Expedition
311 Logging Summary
Log
Data
ODP
Leg 204 - Hydrate Ridge:
Dave Goldberg, Gilles Guerin
During Ocean Drilling Program (ODP) Leg 204, a total of nine sites were
drilled through the gas hydrate stability zone on the southern part of
Hydrate Ridge on the Cascadia accretionary margin, offshore Oregon. For
further information regarding gas hydrates and the background geological
setting see the Leg 204 Preliminary Report. The first part of Leg 204 was
dedicated entirely to logging while drilling (LWD) to identify potential gas
hydrate bearing intervals prior to coring. The data were of excellent
quality, thus allowing optimization of the use of time-consuming special
tools to measure in situ temperature and pressure and to retrieve cores at
in situ pressure. The leg also included an extensive wireline logging
program and a two-ship seismic program with the R/V Maurice Ewing to acquire
offset and walkaway vertical seismic profiles (VSP). The log data are
available from the ODP Logging Services database.
Preliminary
Report
Logging Summary
Log
Data
Electrical and Nuclear Resonance measurements of Tetrahydrofuran Hydrate:
Ann Cook, Dave Goldberg
Tetrahydrofuran (THF) hydrate (20% weight THF with 80% weight deionized
water) was synthesized in the laboratory at LDEO and brought to the
Schlumberger-Doll research laboratory in Ridgefield, Connecticut for
measurements of their surface area, nuclear magnetic relaxivity, and
dielectric properties. Surface area data was collected at liquid nitrogen
temperatures. NMR and dielectric
experiments were conducted at
about 0°
Celsius.
Photo 1
Photo 2
Photo 3
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