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OCR for page 97
c
Workshop White Papers
SCIENTIFIC OCEAN DRILLING: The most important difference in how this “cutting
PAST, PRESENT AND FUTURE edge” (for 1968) technology was used by DSDP scientists
as opposed to how it was being used by the oil industry lay
in the overall purpose of the drilling. The purpose of drilling
Ted Moore
for oil is to create a hole through which to extract hydro-
University of Michigan
carbons. The purpose of the scientific drilling is to recover
the sedimentary and rock section in the deep sea and avoid
U.S. oceanographic institutions banded together in
encountering oil and gas at all costs. From the start, a safety
1968 to take the first steps toward exploring the sedimentary
advisory panel of oil company experts was set up to review
record and the crustal rocks of the deep ocean basins. It was
required surveys and seismic data from every site drilled to
auspicious timing. The new paradigms of seafloor spreading
assure there was no likelihood that reservoirs of oil and gas
and plate tectonics had only recently been accepted by the
would be encountered in the drilling.
broad scientific community. Based on the early results and
The desire by scientists to recover a complete, undis-
technological developments of the Moho Project and on
turbed section of the uppermost crustal material has required
a careful consideration of all the potential scientific ques-
some technological development by the scientific commu-
tions that might be addressed by drilling in the deep sea,
nity. The greatest advance in this regard for the recovery of
a new effort was proposed that led to the development of
sediments was the development of a hydraulic piston core
the Deep Sea Drilling Project (DSDP). Unlike the Moho
that can be triggered to shoot out ahead of the drill bit and
Project, DSDP would not involve large-scale technological
recover a virtually undisturbed 9 m section of sediment.
development. Rather it would use “off the shelf” technology
When the sediment becomes too stiff to core in this way, an
developed by the offshore oil drilling industry and placed on
extended core barrel with a thin cutting face can be pushed
a single deep-water, dynamically positioned drillship. This
ahead of the massive roller-cone drill bit and recover rela-
did, of course, limit the scope of the problems addressed by
tively undisturbed sections, until finally when the section
the project. There would be no deep drilling down to the
becomes totally lithified, the standard roller-cone drill bit
Mohorovičić discontinuity; drilling in ice-covered regions
with an open center can core and recover the section.
could not be undertaken; and drilling in very shallow water
In addition to the technical enhancements that were
was not appropriate for the deep-water drill ship. But this
achieved during DSDP and the subsequent Ocean Drilling
still left a vast, unexplored region of the deep oceans open
Program (ODP), there was a continued improvement in how
to investigation. In addition to limits on the range of opera-
these devices were used to achieve the recovery of a complete
tions, the technology of that day did not allow drilling with
section and how the recovered section was described and
a riser in deep water. Seawater rather than drilling “mud”
documented. Initially in DSDP on-board core description
was usually used as the drilling fluid to clear debris from the
was rather rudimentary: physical core/rock description, bio-
hole and expel it onto the seafloor. This approach to deep-sea
stratigraphic age, smear slide description, core photographs,
drilling has effectively limited the depth of section drilled
physical properties, and carbonate content. This could all be
and recovered to about 2 km.
done on board with about 10 scientists and 6 technicians. By
97
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98 SCIENTIFIC OCEAN DRILLING
the end of the ODP program the greatly improved quality of New Jersey and the reefs of Tahiti to delve into the history
the cores permitted the useful employment of core scanning of sea level changes and its impact on the sedimentary archi-
devices that measure density, magnetic susceptibility, P-wave tecture of shallow water environments. And we are beginning
velocity, natural gamma radiation, color, and magnetic polar- an ambitious program of exploring the tectonic, depositional,
ity. These digital measurements are in addition to pore water and hydrologic environment of convergent margins. We no
chemistry, physical properties, microbiological samples, longer have to drill lacking the well control provided by a
biostratigraphy, and other measurements that were standard riser and will hopefully extend the water depth in which we
in the days of DSDP. In ODP the shipboard scientific party can operate in the riser (or “well control”) mode beyond the
grew to as many as 30 scientists who operated the machines, present 2,500 m.
did the descriptions, made the measurements, and carried The envisioned scope of the great exploration that await-
out the scientific studies. Their efforts over 12-hour shifts, 7 ed us in the beginning days of scientific ocean drilling has
days/week, on a 56-day expedition constitute an aggregate been exceeded. Not only have we applied crucial tests to the
9 to 10 man-years of work achieved during the at-sea time. plate tectonic theory but also we have created a whole new
These expeditions are very productive efforts. scientific field—paleoceanography. Through the exploration
The substantial improvements made in the recovery and of the deep-sea environment we have also expanded the sci-
documentation of the recovered section came in parallel to ence we address far beyond that envisioned in the early days
improvements in how we used the holes that were drilled. of DSDP. The chemistry and hydrology of water in the sedi-
Logging of the holes has come very close to keeping pace ments and the crust are now thought to play a key role in the
with developments in the industry. Other measurements such chemistry of the oceans and the weathering of the basalt both
as heat flow and vertical velocity profiles have also been near the ridge axes and far off the axes into the older crust.
commonly made. Perhaps one of the most elegant innova- The structure of the oceanic crust itself is gradually being
tions in down-hole instrumentation has been the circulation revealed as we penetrate deeper into the basaltic sections.
obviation retrofit kit (CORK), a device that seals off one or And we are just beginning to realize the great importance
more sections of the drill hole and allows measurements of of microbes in the ocean environment. These are just some
the chemical and physical nature of the waters in that sec- of the aspects of scientific ocean drilling that continue to
tion to be made over time. Thus, the holes themselves can intrigue the scientific mind and expand both the science and
become deep-sea observatories or laboratories for chemistry, the scientific community that use scientific ocean drilling to
microbiology, and seismology. increase the scope of our knowledge.
As our knowledge of the deep-sea environment and
the scientific questions we address expands, our technical
Supporting References
capabilities continue to improve. Now with the Integrated
Coffin, M.F. and J.A. McKenzie. 2001. Earth, Oceans and Life: Scientific
Ocean Drilling Program (IODP) we have also been able
Investigation of the Earth System Using Multiple Drilling Platforms and
to go beyond the limitations first accepted as necessary in
New Technologies, Initial Science Plan, 2003-2013. Integrated Ocean
the early days of DSDP. We have drilled in the ice-covered Drilling Program, Texas A&M University, College Station, Texas.
region of the high Arctic and brought back a startling record Gornitz, V. 2009. Encyclopedia of Paleoclimatology and Ancient Environ-
of climate change associated with the CO2 rich atmosphere ments. Springer, The Netherlands.
of the Eocene. We have drilled on the very shallow shelf off
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99
APPENDIX C
THE RECORD OF HYDROTHERMAL The felsic-hosted PACMANUS hydrothermal system
PROCESSES IN THE OCEANIC CRUST (~3°S, Manus Basin) provided the opportunity to investigate
the characteristics of hydrothermalism in a back-arc basin.
Drilling beneath active hydrothermal systems revealed a cap
Susan E. Humphris
of unaltered dacites and rhyolites, below which the volcanics
Woods Hole Oceanographic Institution
are pervasively and intensely altered rather than alteration
being confined to a narrow upflow zone, with clay miner-
Hydrothermal chemical exchange between the crust and
als dominating the alteration assemblage. In addition, fluid
oceans is a fundamental component of global geochemical
inclusion data provided clear evidence for a magmatic com-
cycles, affecting the composition of the lithosphere, the
ponent to the hydrothermal fluid that played a fundamental
oceans and, through subduction, the mantle and arc magmas.
role in the nature of alteration—a clear distinction from the
In addition, this process provides the energy and nutrients
TAG and Middle Valley hydrothermal sites.
for chemosynthetic organisms. Understanding the processes
Although drilling seafloor sulfide deposits has been
that control chemical fluxes resulting from water-rock reac-
technologically challenging, often with poor recovery, it
tions requires direct sampling of in situ crust, and has been
has nevertheless revealed previously unrecognized shallow
an overarching goal of the lithosphere community for more
subseafloor processes—entrainment of seawater, mixing of
than 40 years. Scientific ocean drilling has played a critical
hydrothermal fluids with seawater and magmatic compo-
role in (i) advancing our understanding of subsurface water-
nents, deposition of secondary phases that play key roles in
rock reactions and the mechanisms of formation of seafloor
deposit construction but are not preserved in ancient depos-
massive sulfide deposits in active hydrothermal systems at
its—that are now demonstrated to be critical in the formation
mid-ocean ridges, and (ii) the development of a conceptual
of massive sulfide deposits.
model for the alteration reactions that occur in off-axis con-
vection systems driven by lithospheric cooling.
THE RECORD OF OFF-AXIS CONVECTION
SYSTEMS
ACTIVE HYDROTHERMAL SYSTEMS AT
OCEANIC SPREADING CENTERS As the crust spreads, hydrothermal alteration continues
in off-axis convection systems driven by lithospheric cool-
Scientific drilling at three active hydrothermal sites in
ing. This process is believed to continue to an age of ~65
different geotectonic settings has revolutionized our under-
myr when the crust effectively becomes “sealed.” Hence, the
standing of the formation and subsurface structure of seafloor
ocean crust provides a time-integrated record of water-rock
massive sulfide deposits. Drilling at the basalt-hosted active
reactions that occurred both on- and off-axis.
TAG hydrothermal mound (~26°N, Mid-Atlantic Ridge)
Scientific ocean drilling has provided many sections
revealed abundant anhydrite (CaSO4)—a mineral that is
of the uppermost few hundred meters of ocean crust. These
very uncommon in ancient deposits due to its retrograde
have predominantly been focused in young (< 20 Ma) and
solubility—attesting to considerable entrainment and heat-
ancient (> 110 Ma) crust. Of particular note are two long
ing of seawater into the subsurface. Although its formation
sections of upper ocean crust formed at intermediate (Hole
provides a framework for construction of the deposit, the ulti-
504B on 6 Ma crust) and superfast spreading rates (Hole
mate dissolution of anhydrite was recognized as an important
1256D on 15 Ma crust) in the eastern Pacific. No holes pen-
mechanism for the formation of sulfide breccia—a lithology
etrate greater than 50 m in 45-80 Ma basement, the interval
that had been previously interpreted in ancient ophiolite
in which the crust becomes sealed. Although details vary,
massive sulfide deposits to result from post-depositional
the mineralogical and geochemical characteristics of all the
weathering.
upper crustal sections support a model whereby greenschist
Drilling at the sediment-hosted Middle Valley hydro-
alteration of dikes at low water/rock ratios is overprinted
thermal sites (~48°N, Juan de Fuca Ridge) resulted in the first
by fracture-controlled alteration and mineralization by
successful recovery of feeder zone mineralization underlying
upwelling hydrothermal fluids, a conductive boundary layer
a seafloor massive sulfide deposit. Feeder zones in ancient
above gabbroic intrusions, leaching of metals from dikes
deposits commonly account for a significant portion of
and gabbros in the deep “root zone,” and stepped thermal
the economic reserves of a deposit. An unexpected finding
and alteration gradients in the basement. The prediction that
was the presence of a stratified zone of high-grade Cu-rich
conductive boundary layers separate hydrothermal systems
replacement mineralization (~16 wt.% Cu) at the base of the
from the heat source that drives them has been confirmed
feeder zone formed by lateral flow of hydrothermal fluids
by the identification of recrystallized sheeted dikes at the
beneath an impermeable silicified mudstone horizon. This
dike–gabbro transition at all locations. Incipient alteration
type of mineralization had not been previously recognized
of the uppermost gabbros occurs at high temperatures, with
below seafloor mineral deposits, and hence has implications
fluid flow along fracture networks occurring over very short
for land-based mineral exploration.
timescales.
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100 SCIENTIFIC OCEAN DRILLING
Drilling at oceanic core complexes on the more litho- magma chamber. Investigations of this interplay, and of the
logically heterogeneous slow spreading ridges (e.g., the hydrological-geochemical-microbiological feedbacks in
Atlantis Massif [30°N, Mid-Atlantic Ridge] and Atlantis aging oceanic lithosphere—the largest fractured aquifer on
Bank [Southwest Indian Ridge]) has provided access to Earth—require access to in situ oceanic crust and subsurface
lower ocean crust that has been tectonically exhumed at the experimentation that can be provided only by drilling.
seafloor. The combination of regional-scale geophysical and
geological surveys with deep drill holes at these locations
Supporting References
indicate that detachment zones act to focus fluids at high
Alt, J. 2004. Alteration of the upper oceanic crust: Mineralogy, chemistry,
and low temperatures. Gabbroic rocks are variably altered
and processes. In Hydrogeology of the Oceanic Lithosphere, Elderfield,
at these two sites, and preserve complex, but different,
H. and E. Davis (Eds.). Cambridge University Press, New York.
records of metamorphism, brittle failure, and hydrothermal Humphris, S.E., P.M. Herzig, D.J. Miller, J.C. Alt, K. Becker, D. Brown,
alteration. At the Atlantis Massif, greenschist facies altera- G. Brügmann, H Chiba, Y. Fouquet, J.B. Gemmell, G. Guerin, M.D.
tion occurred at depths at least 1 km below seafloor, with Hannington, N.G. Holm, J.J. Honnorez, G.J. Iturrino, R. Knott, R.
Ludwig, K. Nakamura, S. Petersen, A.L. Reysenbach, P.A. Rona, S.
variable degrees of interaction with seawater at temperatures
Smith, A.A. Sturz, M.K. Tivey, and X. Zhao. 1995. The internal structure
generally >250 °C. In contrast, at Atlantis Bank, patchy high
of an active sea-floor massive sulphide deposit. Nature 377:713-716.
temperature alteration (up to 600 °C) by hydrothermal fluids Zierenberg, R.A., Y. Fouquet, D.J. Miller, J.M. Bahr, P.A. Baker, T.
over a wide range of temperatures likely occurred at or very Bjerkgard, C.A. Brunner, R.C. Duckworth, R. Gable, J. Gieskes, W.D.
near the spreading axis, while later, low temperature altera- Goodfellow, H.M. Groschel-Becker, G. Guerin, J. Ishibashi, G.J.
Iturrino, R.H. James, K.S. Lackschewitz, L.L. Marquez, P. Nehlig, J.M.
tion is likely related to cooling during uplift.
Peter, C.A. Rigsby, P.J. Schultheiss, W.C. Shanks, B.R.T. Simoneit, M.
In summary, drilling to date has highlighted the critical,
Summit, D.A.H. Teagle, M. Urbat, and G.G. Zuffa. 1998. The deep
but highly variable, interplay between fluid flow, lithol- structure of a sea-floor hydrothermal deposit. Nature 392:485-488.
ogy, and magmatism from the seafloor down to the axial
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101
APPENDIX C
HEAT AND FLUID FLOW flowing down the cased section into upper basement, and it
was shown that these data could be interpreted to estimate
both downhole flow rate and permeability of the formation
Keir Becker
into which the flow was directed (Becker et al., 1983). This
University of Miami
method has been applied to numerous holes since then,
including some less common examples that were drilled in
From the time of Project Mohole, researchers have rec-
sediment-covered basement highs and actually produced
ognized the opportunities that scientific ocean drilling pres-
formation fluids up the hole (e.g., Fisher et al., 1997). Since
ents to investigate heat and fluid flow processes in oceanic
1979, drillstring packer experiments have been conducted
sediments and crust (e.g., Von Herzen and Maxwell, 1964).
deeper in Hole 504B and in the upper basement sections
The early Deep Dea Drilling Project (DSDP) measurements
of several crustal holes. The combined datasets have docu-
were made primarily in sediments (see review by Erickson et
mented a reduction over several orders of magnitude of per-
al., 1975), before the discovery of hydrothermal circulation
meability with depth in young oceanic crust and a reduction
in the mid-1970s and the subsequent realization that fluid
of permeability of uppermost crust with crustal age (e.g.,
flow in subseafloor formations is a key process in nearly all
Fisher, 1998; Fisher and Becker, 2000; Becker and Fisher,
subsea geological type settings from spreading centers to
2000, 2008) that are often used in current numerical models
continental margins. Hence, the COSOD I (Conference on
of hydrothermal circulation in oceanic crust. It is probably
Scientific Ocean Drilling) report recognized the importance
an oversimplification, but there seems to be a rough identity
of subseafloor fluid flow, and understanding it fully became
among the most permeable and porous upper few hundred m
a focal point/major theme of DSDP/ODP (Ocean Drill-
of young oceanic basement, seismic Layer 2A, and the zone
ing Program)/IODP (Integrated Ocean Drilling Program)
of oxidative alteration.
scientific drilling starting with the 1987 COSOD II report.
While the down- or uphole flow in many crustal reentry
Since subseafloor fluid circulation occurs in most seafloor
holes can be interpreted to estimate permeability, it also
geological type settings, this summary overlaps several oth-
represents a significant perturbation to the in situ subsea-
ers from the workshop (e.g., S. Humphris on hydrothermal
floor hydrological systems that we are trying to understand
circulation, K. Edwards on deep biosphere, C. Ruppel on gas
with scientific ocean drilling. This led to the development
hydrates, and J.C. Moore on convergent margins). The table
in 1989-1990 of a new experimental approach to seal these
below summarizes in a historical context the main technical
reentry holes, simultaneously emplacing long-term instru-
and scientific contributions of scientific ocean drilling in
mentation to record in situ temperatures and pressures and
understanding subseafloor heat and fluid flow. This written
to sample formation fluids. This concept was named the
summary touches on some of the themes covered by other
CORK (Circulation Obviation Retrofit Kit) hydrogeological
speakers, but mainly features the off-axis, low-temperature,
observatory (Davis et al., 1992). CORKs have allowed for
ridge-flank setting that for technical reasons has been the
determination of in situ temperature and pore pressure state
main setting to date for scientific ocean drilling into oceanic
after the perturbation due to drilling has decayed (e.g., Davis
crust.
and Becker, 2002). The subseafloor pressure data show an
The early- to mid-1970s deduction of the likelihood of
attenuated and phase-lagged seafloor tidal loading signal
hydrothermal circulation in young oceanic crust was roughly
that can be interpreted to constrain hydraulic diffusivity and
coincident with the internationalization of DSDP (the IPOD
derived permeability at formation scales (Davis et al., 2000).
or International Phase of Ocean Drilling) and a special IPOD
In addition, once the tidal signals are filtered out, the sub-
focus on penetrating significantly into ocean basement. The
seafloor pressures also show formation responses to tectonic
last started with several important young Atlantic crustal
events, acting essentially as crustal strain meters (e.g., Davis
holes, and borehole temperature measurements in some
et al., 2001). The combination of CORK and packer observa-
of them revealed a new phenomenon: that ocean bottom
tions in ridge-flank sites indicates high lateral fluids fluxes
water was being drawn down the holes into the upper levels
and short residence times in very permeable upper basement
of basement beneath the sediment cover required to spud
under relatively small pressure differentials (e.g., Davis and
the holes (e.g., Hyndman et al., 1976). It was deduced that
Becker, 2002). This conclusion is supported by geochemi-
the upper oceanic basement in young crust is much more
cal analyses of pore waters and long-term “OsmoSamplers”
permeable than the overlying sediments. The first direct
recovered from the CORKs (e.g., Elderfield et al., 1999;
measurements of the upper basement permeability—the key
Wheat et al., 2000, 2003).
parameter that controls fluid flow through the formation—
During the late 1990s, newer CORK concepts were
were made in 1979 with a drillstring packer experiment in
developed to separately seal multiple zones in a single hole;
the famous crustal reference Hole 504B, located in thickly
these models include the “Advanced CORK,” “CORK-II,”
sedimented young crust on the south flank of the Costa Rica
and a “wireline CORK” that can be installed from oceano-
Rift (Anderson and Zoback, 1982). Thermal measurements
graphic vessels. More than 20 CORKs of various models
in Hole 504B also indicated that ocean bottom water was
have been installed to date, primarily in ridge-flank settings
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102 SCIENTIFIC OCEAN DRILLING
Selected Program
Timeline/Program Historical Context Highlights Technical Contributions Scientific Contributions
Mohole Pre-plate tectonics Deep sediment First sediment temperature
1961-1966 Pre-hydrothermal temperatures measured at probe
Reconnaissance deep heat flow
Mohole pilot site
measurements and pore fluid
sampling
Early DSDP Pre-hydrothermal Exploration scientific Deep heat flow measurements
1968-1974 drilling around the world, validated shallow oceanographic
primarily in sedimentary heat flow probe technique
sections
Later DSDP Hydrothermal circulation Deep Atlantic crustal holes Uyeda probe Interpretation of downhole flow
1974-1983 deduced/verified in crustal holes
Guaymas Basin Barnes probe
JOIDES Hydrogeology First recorded uphole flow
Working Group Galapagos Mounds Water Sampler Temperature
Probe (WSTP) Vertical flow through sediments
Costa Rica Rift – 504B verified
Hydraulic Piston Corer
(HPC) T-tool Deep sedimentary pore fluids as
proxy for basement fluids
First packer experiments
First crustal permeability values
First pore pressure probe
Permeable, oxidative upper
basement ~ Layer 2A
First studies of fluids in prisms
Early ODP Reentries of deep ODP/IODP straddle packer Crustal permeability-depth
1985-1990 crustal holes (418A, profile through sheeted dikes
395A, 504B) Borehole fluid samplers
Direct evidence for fluid flow in
Barbados + Nankai prism subduction plate boundary faults
studies
Late ODP Boreholes as long-term First- and second- Original CORK Expansion of crustal
1991-2003 observatories generation CORK in-situ long-term permeability-depth profile
hydrogeological OsmoSamplers
Initiative in In-situ observatories deployed medium-T (up to 200 °C) Documentation of age variation
Monitoring of Geological in sedimented ocean sediment T and pore fluid of upper crustal k
Processes ridges, ridge flanks, and probes
Pilot Project in Deep subduction settings In ridge flanks: huge lateral
Biosphere Hi-T borehole T-tool (up to fluid fluxes with small
Targeted drilling of 360 °C) pressure differentials and high
Hydrogeology Program hi-T (270-365 °C) permeabilities
Planning Group (2001) hydrothermnal systems Multi-zone Advanced
CORK, CORK-II, and First direct measurement of fluid
First targeted gas hydrates wireline CORK pressure at subduction plate
drilling in context of fluid boundary fault
flow
First in situ video in oceanic
crust, showing microbiota
IODP Initiatives in Deep Juan de Fuca 3-d CORK Addition of microbiological First crustal-scale cross-hole
2004-2011 Biosphere and Hydrates array capabilities to CORKs + hydrogeological experiments
shipboard labs
NanTroSEIZE seismic + First in situ microbiological
fluid observatories Improvement of downhole incubation experiments
tools
Gulf of Mexico margin First network cable-ready
overpressured zone borehole observatories
Three major biosphere/fluid Excess fluid pressures measured
programs to come in Gulf of Mexico margin
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103
APPENDIX C
and in subduction zones. In the latter setting, a prime goal Becker, K., E.E. Davis, F.N. Spiess, and C.P. deMoustier. 2004. Temperature
and video logs from the upper oceanic curst, Holes 504B and 896A,
has been to document fluid pressures in plate boundary faults
Costa Rica Rift flank: Implications for the permeability of upper oceanic
and the relationship between fluid processes and subduction crust. Earth and Planetary Science Letters 222(3-4):881-896.
earthquakes. To date, overpressures as high as 1 MPa have Davis, E.E. and K. Becker. 2002. Observations of natural-state fluid pres-
been documented in the monitored plate boundary faults, but sures and temperatures in young oceanic crust and inferences regard-
this is significantly less than lithostatic pressure and thus not ing hydrothermal circulation. Earth and Planetary Science Letters
204(1-2):231-248.
enough to enable slip along the faults. In the Hydrate Ridge
Davis, E.E., K. Becker, T. Pettigrew, B. Carson, and R. MacDonald. 1992.
subduction setting offshore Oregon, a CORK through a thrust CORK: A hydrologic seal and downhole observatory for deep-ocean
fault apparently recorded the transient thermal signal of an boreholes. In Proceedings of the Ocean Drilling Program, Initial
up-fault fluid flow event. Even more ambitious observatories Reports, Volume 139, Davis E.E., M.J. Mottl, A.T. Fisher, et al. (Eds.).
are planned for the IODP NanTroSEIZE program, combining Ocean Drilling Program, Texas A&M University, College Station, Texas.
Davis, E.E., K. Wang, K. Becker, and R.E. Thomson. 2000. Formation-scale
seismic and strain instruments with the CORK hydrological
hydraulic and mechanical properties of oceanic crust inferred from pore
concept. pressure response to periodic seafloor loading. Journal of Geophysical
In the process of installing wireline CORKs in Hole Research 105(B6):13423-13435.
504B and a companion Hole 896A ~1km away in 2001, it Davis, E.E., K. Wang, R.E. Thomson, K. Becker, and J. Cassidy. 2001. An
was determined that Hole 896A was producing crustal fluids episode of seafloor spreading and associated plate deformation inferred
from crustal fluid pressure transients. Journal of Geophysical Research
and the first (only?) true video from within oceanic basement
106(B10):21953-21963.
was collected (Becker et al., 2004). That video seems to show Elderfield, H., C.G. Wheat, M.J. Mottl, C. Monnin, and B. Spiro. 1999. Fluid
copious microbiota within the hole and images individual and geochemical transport through oceanic crust: A transect across the
formations that are producing fluids into the hole and prob- eastern flank of the Juan de Fuca Ridge. Earth and Planetary Science
ably represent most of the bulk permeability of the formation. Letters 172(1-2):151-165.
Erickson, A.J., R.P. Von Herzen, J.G. Sclater, R.W. Girdler, B.V. Marshall,
That serves to emphasize the fact that the permeability of
and R. Hyndman. 1975. Geothermal measurements in deep-sea drill
oceanic crust—and probably most other subseafloor forma- holes. Journal of Geophysical Research 80(17):2515-2528.
tions—is fracture-dominated and multi-scalar, so it cannot Fisher, A.T. 1998. Permeability within basaltic oceanic crust. Reviews of
be accurately represented as a single-valued parameter (e.g., Geophysics 36(2):143-182.
Fisher, 1998; Becker and Davis, 2003; Fisher et al., 2008). Fisher, A.T. and K. Becker. 2000. Channelized fluid flow in oceanic crust
reconciles heat-flow and permeability data. Nature 403:71-74.
In summer 2010, IODP Expedition 327 to the Juan de Fuca
Fisher, A.T., K. Becker, and E.E. Davis. 1997. The permeability of young
Ridge flank featured the first attempt to resolve directional oceanic crust east of Juan de Fuca Ridge determined using borehole ther-
variation of crustal permeability and natural fluid flow via mal measurements. Geophysical Research Letters 24(11):1311-1314.
the first planned hole-to-hole pumping tests in an array of Fisher, A.T., E.E. Davis, and K. Becker. 2008. Borehole-to-borehole
CORKs penetrating upper basement. (An unplanned hole-to- hydrologic response across 2.4 km in the upper oceanic crust: Impli-
cation for crustal-scale properties. Journal of Geophysical Research
hole experiment in the same array is described by Fisher et
113(B7):B07106.
al., 2008.) That array of CORKs has also involved the first Hyndman, R.D., R.P. Von Herzen, A.J. Erickson, and J. Jolivet. 1976. Heat
in situ microbiological cultivation experiments in oceanic flow measurements in deep crustal holes on the Mid-Atlantic Ridge.
basement, and so represents an important new future direc- Journal of Geophysical Research 81(23):4053-4060.
tion for CORKs and scientific ocean drilling discussed in Von Herzen, R.P. and A.E. Maxwell. 1964. Measurements of heat flow at the
preliminary Mohole site off Mexico. Journal of Geophysical Research
more detail by K. Edwards.
69(4):741-748.
Wheat, C.G., H. Elderfield, M.J. Mottl, and C. Monnin. 2000. Chemical
composition of basement fluids within an oceanic ridge flank: Impli-
Supporting References
cations for along-strike and across-strike hydrothermal circulation.
Anderson, R.N. and M.D. Zoback. 1982. Permeability, underpressures, Journal of Geophysical Research 105(B6):13437-13447.
and convection in the oceanic crust near the Costa Rica Rift, eastern Wheat, C.G., H.W. Jannasch, M. Kastner, J.N. Plant, and E.H. DeCarlo.
equatorial Pacific. Journal of Geophysical Research 87(B4):2860-2868. 2003. Seawater transport and reaction in upper oceanic basaltic base-
Becker, K. and E.E. Davis. 2003. New evidence for age variation and scale ment: Chemical data from continuous monitoring of sealed borehole
effects of permeabilities of young oceanic crust from borehole thermal in a ridge flank environment. Earth and Planetary Science Letters
and pressure measurements. Earth and Planetary Science Letters 216(4):549-564.
210(3-4):499-508.
Becker, K. and A.T. Fisher. 2000. Permeability of upper oceanic base-
ment on the eastern flank of the Juan de Fuca Ridge determined with
drill-string packer experiments. Journal of Geophysical Research
105(B1):897-912.
Becker, K. and A.T. Fisher. 2008. Borehole packer tests at multiple depths
resolve distinct hydrologic intervals in 3.5-Ma upper oceanic crust on
the eastern flank of the Juan de Fuca Ridge. Journal of Geophysical
Letters 113(B07105):1-12.
Becker, K., M.G. Langseth, R.P. Von Herzen, and R.N. Anderson. 1983.
Deep crustal geothermal measurements, Hole 504B, Costa Rica Rift.
Journal of Geophysical Research 88(B4):3447-3457.
OCR for page 104
104 SCIENTIFIC OCEAN DRILLING
SUBSURFACE MICROBIAL OBSERVATORIES the lateral dimension of the experimental environment (i.e.,
TO INVESTIGATE THE DEEP OCEAN CRUST all instruments must fit within the innermost borehole casing,
BIOSPHERE: DEVELOPMENT, TESTING, AND which is typically on the order of 9 cm diameter). Downhole
FUTURE instruments also must provide necessary power for the dura-
tion of the deployment (4-5 years).
The continuing adaptation of technologies from other
Katrina J. Edwards
disciplines will advance capabilities to observe and sample
University of Southern California
the subseafloor crustal biosphere. Technologies that are
suitable for long-term deployment, with ultra-low power
Scientific ocean drilling has historically yielded some
consumptions and minimal impact by biofouling, are ideal
of the most transformative advances in the Earth sciences,
for crustal biosphere observatories. Instrumentation for mak-
cross-cutting many of its disciplines, and providing funda-
ing remote measurements of downhole conditions is also
mental advances to our knowledge of how the Earth works.
required. This includes designing downhole electrochemical
Today, ocean drilling is poised to offer these same transfor-
and mass spectrometer analyzers, for measuring changes in
mative advances to disciplines within the life sciences, and
fluid and gas compositions, and also developing new ways
provide insight into how life operates and interacts with Earth
to measure rates of chemical reactions in situ. For example,
processes at and below the seafloor. To date, many exciting
a protoype downhole sampler for manipulative experiments
discoveries have been made about the nature of the deep
is nearly ready for field trials. Another promising adaptation
microbial biosphere in marine sediments. In comparison,
would be instrumentation for measuring deep ultraviolet
there is relatively little information about the nature, extent,
fluorescence downhole, permitting the detection of the native
and activity of microorganisms living in the volcanic oce-
fluorescence of microbial cells without the use of stains or
anic crust. Because of the size and hydrodynamics of this
dyes or interference from auto-fluorescent mineral particles.
potential biome, crustal life may have profound influence on
Future observatory experiments will also benefit from
global chemical cycles and, as a consequence, the physical
the utilization of components that are compatible with objec-
and chemical evolution of the crust and ocean. Hence, it is
tives in multiple disciplines (microbiology, hydrogeology,
imperative that the scientific community develops a more
chemistry, etc.).
complete understanding of life in ocean crust. To do this,
researchers must develop the appropriate tools for studying
Supporting References
this unique habitat, and recent engineering and methodologi-
cal advancements make now a particularly opportunistic Becker, K. and E.E. Davis. 2005. A review of CORK designs and operations
time to do so. Subseafloor borehole observatories (Circula- during the Ocean Drilling Program. In Proceedings of the Integrated
tion Obviation Retrofit Kits or CORKs) can help to provide Ocean Drilling Program, Volume 301, Fisher, A.T., T. Urabe, A. Klaus,
and the Expedition 301 Scientists (Eds.). Integrated Ocean Drilling
representative samples of crustal fluids and microbiological
Program, Texas A&M University, College Station, Texas.
samples, reducing the extent of contamination associated
Bhartia, R., W.F. Hug, E.C. Salas, R.D. Reid, K. Sijapat, A. Tsapin, K.H.
with drilling, coring, and other operations. Nealson, A.L. Lane, and P.G. Conrad. 2008. Native fluorescence spec-
troscopy: Classification of organics with deep UV to UV excitation.
Applied Spectroscopy 62(10):1070-1077.
SUBSURFACE MICROBIAL OBSERVATORY Cowen, J.P., S.J. Giovannoni, F. Kenig, H.P. Johnson, D. Butterfield, M.S.
TECHNOLOGY Rappé, M. Hutnak, and P. Lam. 2003. Fluids from aging ocean crust
that support microbial life. Science 299(5603):120-123.
Tools available for CORK-associated microbial observa- D’Hondt, S., B.B. Jørgensen, D.J. Miller, A. Batzke, R. Blake, B.A. Cragg,
tory experiments can be broken down into two categories: H. Cypionka, G.R. Dickens, T. Ferdelman, K.U. Hinrichs, N.G. Holm,
those that are deployed down hole (“subsurface”) within the R. Mitterer, A. Spivack, G. Wang, B. Bekins, B. Engelen, K. Ford, G.
Gettemy, S.D. Rutherford, H. Sass, C.G. Skillbeck, I.W. Aiello, G.
CORK casing, and those that are deployed at the seafloor
Guèrin, C.H. House, F. Inagaki, P. Meister, T. Naehr, S. Niitsuma, R.J.
and connected to the horizon of interest via pumping of
Parkes, A. Schippers, D.C. Smith, A. Teske, J. Wiegel, C.N. Padilla,
fluids through umbilicals. Redundancy between seafloor and J.L.S. Acosta. 2004. Distributions of microbial activities in deep
and subsurface sampling and experimental units allows for subseafloor sediments. Science 306(5705):2216-2221.
a higher confidence of capturing representative samples for Davis, E.E., K. Becker, T. Pettigrew, B. Carson, and R. MacDonald. 1992.
CORK: A hydrological seal and downhole observatory for deep-ocean
targeted questions.
boreholes. In Proceedings of the Ocean Drilling Program, Initial Re-
First-generation downhole observatory technology con-
ports, Volume 139, Davis, E.E., M.J. Mottl, A.T. Fisher, and the ODP Leg
sisted of subsurface temperature and pressure loggers and 130 Scientists (Eds.). Ocean Drilling Program, Texas A&M University,
osmotically driven fluid samplers (“OsmoSamplers”), which College Station, Texas.
collect a continuous record of temperature, pressure, and
composition of the fluid within CORKed boreholes. Second-
generation downhole devices couple these to microbial colo-
nization experiments. All downhole technology is limited by
OCR for page 105
105
APPENDIX C
Fisher, A.T., C.G. Wheat, K. Becker, E.E. Davis, H. Jannasch, D. Schroeder, Orcutt, B., C.G. Wheat, and K.J. Edwards. 2010. Subseafloor ocean crust
R. Dixon, T.L. Pettigrew, R. Meldrum, R. MacDonald, M. Nielsen, M. microbial observatories: Development of FLOCS (Flow-through Osmo
Fisk, J. Cowen, W. Bach, and K.J. Edwards. 2005. Scientific and techni- Colonization System) and evaluation of borehole construction materials.
cal design and deployment of long-term subseafloor observatories for Geomicrobiology Journal 27(2):143-157.
hydrogeologic and related experiments, IDOP Expedition 301, eastern Parkes, R.J., B.A. Cragg, S.J. Bale, J.M. Getliff, K. Goodman, P.A. Rochelle,
flank of Juan de Fuca Ridge. In Proceedings of the Integrated Ocean J.C. Fry, A.J. Weightman, and S.M. Harvey. 1994. Deep bacterial bio-
Drilling Program, Volume 301, Fisher, A.T., T. Urabe, A. Klaus, and the sphere in Pacific Ocean sediments. Nature 371:410-413.
Expedition 301 Scientists (Eds.). Integrated Ocean Drilling Program, Preston, C., R. Marin, III, S. Jenson, J. Feldman, E. Massion, E. DeLong,
Texas A&M University, College Station, Texas. M. Suzuki, K. Wheeler, D. Cline, N. Alvarado, and C. Scholin. 2009.
Girguis, P.R., J. Robidart, and G. Wheat. 2008. The BOSS: A novel approach Near real-time, autonomous detection of marine bacterioplankton on a
to coupling temporal changes in geochemistry and microbiology in the coastal mooring in Monterey Bay, California, using rRNA-targeted DNA
deep subsurface biosphere. Eos, Transcripts American Geophysical probes. Environmental Microbiology 11(5):1168-1180.
Union 89(53):B51F-03. Storrie-Lombardi, M.C., W.F. Hug, G.D. McDonald, A.I. Tsapin, and K.H.
Inagaki, F., T. Nunoura, S. Nakagawa, A. Teske, M. Lever, A. Lauer, Nealson. 2001. Hollow cathode ion laser for deep ultraviolent Raman
M. Suzuki, K. Takai, M. Delwiche, F.S. Colwell, K.H. Nealson, K. spectroscopy and fluorescence imaging. Review of Scientific Instruments
Horikoshi, S. D’Hondt, and B.B. Jørgensen. 2006. Biogeographical dis- 72(12):4452-4459.
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rine sediments on the Pacific Ocean Margin. Proceedings of the National Kyriazi, P.R. Girguis. 2010. New constraints on methane fluxes and rates
Academy of Sciences of the United States of America 103(8):2815-2820. of anaerobic methane oxidation in a Gulf of Mexico brine pool via in
Jannasch, H.W., E.E. Davis, M. Kastner, J.D. Morris, T.L. Pettigrew, J.N. situ mass spectrometry. Deep-Sea Research II 57:2022-2029.
Plant, E.A. Solomon, H.W. Villinger, and C.G. Wheat. 2003. CORK-II: Wheat, C.G., H.W. Jannasch, M. Kastner, J.N. Plant, and E.H. DeCarlo.
Long-term monitoring of fluid chemistry, fluxes, and hydrology in in- 2003. Seawater transport and reaction in upper ocean basaltic basement:
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and the ODP Leg 205 Scientists (Eds.). Ocean Drilling Program, Texas 216(4):549-564.
A&M University, College Station, Texas. Wheat, C.G., H.W. Jannasch, M. Kastner, J.N. Plant, E.H. DeCarlo, and
Luther, G.W., B.T. Glazer, S.F. Ma, R.E. Trouwborst, T.S. Moore, E. G. Lebon. 2004. Venting formation fluids from deep sea boreholes in a
Metzger, C. Kraiya, T.J. Waite, G. Druschel, B. Sundby, M. Taillefert, ridge flank setting: ODP sites 1025 and 1026. Geochemistry, Geophys-
D.B. Nuzzio, T.M. Shank, B.L. Lewis, and P.J. Brendel. 2008. Use of ics, Geosystems 5(8):Q08007.
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OCR for page 106
106 SCIENTIFIC OCEAN DRILLING
SCIENTIFIC OCEAN DRILLING AND GAS tives, focusing on the extensive gas hydrates province in
HYDRATES STUDIES the fine-grained sediments of the Blake Ridge. For the first
time, ODP purposely cored and logged the entire hydrates
stability zone and the underlying free gas zone, countering
Carolyn Ruppel
critics concerned about the safety of such activities. Many
U.S. Geological Survey
accomplishments of ODP Leg 164 have stood the test of
time, with similar phenomena being rediscovered in other
Gas hydrates and the huge quantities of methane that
marine hydrates provinces even today. ODP Leg 164 proved
they sequester in marine sediments are typically linked to
that gas hydrates occurred even in the absence of the bottom
three broad scientific themes: carbon cycling and global
simulating reflector (BSR) that sometimes marks the base
climate change (e.g., Dickens et al., 1995, 1997a; Dickens,
of gas hydrates stability (Dillon et al., 1996) and provided
2003; Kennett et al., 2003), submarine slope stability (e.g.,
strong evidence that small-scale permeability variations
Kvenvolden, 1999; Grozic, 2010; Maslin et al., 2010), and
(e.g., slightly coarser-grained sediments or dual-porosity/
energy resources (e.g., Collett, 2002). The last element—
diatomaceous layers) locally control preferential accumula-
the energy resource potential of gas hydrates—renders gas
tion of gas hydrates in seemingly homogeneous sediments
hydrates unique within the scientific ocean drilling (SOD)
(Ginsburg et al., 2000; Kraemer et al., 2000). The expedition
community: There has always been the expectation that rou-
yielded a rich dataset for calibration of logging, vertical seis-
tine gas hydrates drilling for resource issues would someday
mic profiles (VSP), and geochemical constraints on in situ
reach such maturity that SOD would no longer be appropri-
hydrates concentrations (e.g., Holbrook et al., 1996; Collett
ate. We are largely operating in this era now, with no gas
and Ladd, 2000; Lorenson et al., 2000); demonstrated that
hydrates drilling having been conducted by the Integrated
gas hydrates filled only a small percentage of available pore
Ocean Drilling Program (IODP) since 2005 (Expedition
space despite the widespread occurrence of a BSR; and
311; Riedel et al., 2006). Over the past decade, government/
marked a first attempt at shipboard microbiology within SOD
private-sector operators in Japan, the United States, South
(Wellsbury et al., 2000).
Korea, India, China, and Malaysia (e.g., Collett et al., 2008a,
By the late 1990s, it was clear that ODP Leg 164,
b, 2009; Hadley et al., 2008; Jones et al., 2008; Park et al.,
despite far exceeding initial expectations, had yielded a
2008; Ruppel et al., 2008; Wu et al., 2008; Yang et al., 2008;
largely static picture of gas hydrates systems that are more
Tsuji et al., 2009; National Energy Technology Laboratory,
properly considered dynamic and hydrologically driven.
2010) completed and/or have begun planning deepwater
With the publication of studies that linked the evolution of
drilling operations to investigate the resource potential of gas
gas hydrates provinces to fluxes of fluids, gas, and energy
hydrates and, in some cases, to assess geohazards related to
(Rempel and Buffett, 1998; Xu and Ruppel, 1999; Ruppel
drilling and eventual production. None of this government/
and Kinoshita, 2000) and with the increasing emphasis on
private-sector activity would have been possible without the
gas hydrates “plumbing systems,” the Gas Hydrates PPG, the
fundamental knowledge and technological developments
Hydrogeology PPG (Ge et al., 2002), and subsequently the
provided by SOD activities during the Ocean Drilling Pro-
IODP science plan all alluded to a strategy of drilling in gas
gram (ODP) and IODP. In this brief, I review the contribu-
hydrates provinces characterized by different flux regimes.
tions of ODP/IODP to gas hydrates science, highlight special
ODP Leg 204 (Tréhu et al., 2003) was the second SOD expe-
technology developed by SOD for studying hydrates-bearing
dition fully committed to the exploration of gas hydrates,
sediments (known as HBS), and make recommendations
this time in the highly dynamic setting of Hydrate Ridge, an
about the appropriate niche for SOD in future gas hydrates
accretionary ridge offshore Oregon. Leg 204 yielded impor-
investigations.
tant constraints on processes and gas hydrates distributions
Gas hydrates research has had a long history in the SOD
in three dimensions (Tréhu et al., 2004a), sometimes with the
community, even before its elevation to a focus area within
additional fourth dimension of time. Leg 204 had unusually
the theme of “Subseafloor Ocean and Deep Biosphere” dur-
rich ancillary data-sets (e.g., 3D seismic [Tréhu et al., 2002]
ing IODP’s formulation. Before the early 1990s, most of the
and CSEM [Weitemeyer et al., 2006]), included sophisticated
direct knowledge about subseafloor gas hydrates had been
microbiology (e.g., Colwell et al., 2008; Nunoura et al.,
acquired when gas hydrates were encountered, sometimes
2008), and provided detailed insights into the nature of flux
accidentally, during DSDP and ODP expeditions focused
regimes and gas/hydrates dynamics at hydrates-bearing seeps
on other scientific goals. Leg 146 in 1992 (Westbrook et al.,
(e.g., Torres et al., 2004; Tréhu et al., 2004b; Liu and Flem-
1994) was an exception, having been designed to conduct
ings, 2006). A few years later, Expedition 311 (Riedel et al.,
limited gas hydrates investigations within the context of
2006) became the only IODP activity exclusively focused on
broader-scale fluids research on the Oregon and Vancouver
gas hydrates, completing a drilling transect from the subduct-
parts of the Cascadian margin.
ing plate onto the overriding plate on the northern Cascadia
In 1995, ODP Leg 164 (Dillon et al., 1996) was the first
margin. The project highlighted lateral heterogeneity in gas
expedition committed exclusively to gas hydrates objec-
hydrates distributions and discovered concentrations of gas
OCR for page 107
107
APPENDIX C
hydrates in coarse-grained sediments well above the base Villinger Temperature Tool (DVTP) and DVTP-P; Graber et
of the gas hydrates stability zone, a finding that challenges al., 2002), SOD’s model of rapid, post-drilling publication
simple models (e.g., Hyndman and Davis, 1992; Rempel of archival initial reports, and the shipboard deployment of
and Buffett, 1998; Xu and Ruppel, 1999) for gas hydrates imaging equipment capable of determining the distribution
system dynamics (e.g., Malinverno, 2010). In September and character of gas hydrates in recovered cores (e.g., Abegg
2010, Site 889, which was drilled on Leg 146 and which et al., 2006).
lies close to IODP Expedition 311 Sites U1327/U1328, will The international focus on developing deepwater
be re-instrumented and prepared for eventual linkage of the hydrates as an energy resource means that SOD will not play
borehole instrumentation to Canada’s NEPTUNE cabled a leading role in most future gas hydrates drilling. SOD’s
observatory (Davis et al., 2010). While the primary focus drilling platforms may on occasion be suitable for use for
of this effort is not gas hydrates, it is noteworthy that SOD non-SOD projects that involve straightforward gas hydrates
boreholes drilled originally for gas hydrates objectives will investigations, little advanced mud handling, and few special
be the first on the North American Margin to be part of a logging requirements.
cabled observatory. SOD does have an important role to play in non-resource
Gas hydrates are unique among geologic materials stud- aspects of gas hydrates in a future program. First, marine
ied by SOD: They are highly accessible to the drill (within gas hydrates at the upper feather edge of stability on the
the uppermost 10s to 100s of meters subseafloor), are stable continental slopes (e.g., Westbrook et al., 2009) and those
over a specific pressure and temperature range, and rapidly associated with subsea permafrost in shallow circum-Arctic
dissociate to water and large volumes of gas. The dissocia- areas (e.g., Rachold et al., 2007; Ruppel, 2009; Shakhova et
tion process is strongly endothermic, which has led to reli- al., 2010) are probably actively deteriorating now in response
ance on routine thermal infrared imaging (e.g., Ford et al., to climate change on relatively short timescales (contempo-
2003; Weinberger et al., 2005) to locate gas hydrates nodules rary to 20 ka). The dynamics of these gas hydrates systems
in recovered conventional cores. Because the removal of represents a compelling, multidisciplinary problem that is
hydrates-bearing cores from the gas hydrates stability field well-suited for the future of SOD under the auspices of the
leads to rapid degassing, the destruction of sediment textures, “Earth in Motion” theme. Second, despite decades’ worth of
and irreversible changes in bulk sediment properties (e.g., anecdotal studies exploring possible links between subma-
Francisca et al., 2005), pressure coring—coring that main- rine slope stability and gas hydrates (e.g., Carpenter, 1981;
tains in situ hydrostatic pressure—has long been viewed as Kayen and Lee, 1991; Paull et al., 1991), there remains no
a necessity for gas hydrates studies. Even in the mid-1980s, proof that gas hydrates and/or free gas play a causal role in
SOD was experimenting with pressure coring, but true suc- triggering failures or exacerbate major failures once they are
cess with the Pressure Core Sampler (PCS; Pettigrew, 1992) initiated (e.g., Bryn et al., 2005; Tappin, 2010). In light of
was not attained until ODP Leg 164 (Dickens et al., 1997b, (a) the tsunamogenic potential of major slope failures that
2000). The success of the PCS set the stage for larger, more occur in or near gas hydrates areas (e.g., Long et al., 1990;
sophisticated pressure corers (e.g., Hydrate Autoclave Cor- Hornbach et al., 2007), (b) advances in understanding the
ing Equipment (HYACE)/deployment of HYACE tools in geomechanics of hydrate-bearing and gas-charged slope
new tests on hydrates (HYACINTH); Fugro corer) that are sediments (e.g., Sultan et al., 2004; Nixon and Grozic, 2007;
now routinely deployed to obtain high-quality, hydrates- Kwon et al., 2008; Liu and Flemings, 2009); and (c) inferred
bearing samples, particularly in relatively fine-grained sedi- climate-induced dissociation of marine gas hydrates (e.g.,
ments. Subsequent technical innovations made for sampling Westbrook et al., 2009) under way now in areas near previ-
and testing of HBS at in situ hydrostatic pressure (e.g., Park ously documented slope failures, the time is ripe for a fresh
et al., 2009) also owe a great deal to the initial work done focus on the links between gas hydrates and slope stability
within SOD. These outside-SOD developments include: (a) issues within SOD.
the pressure-temperature core sampler (PTCS), a chilled
3-m-long pressure corer developed for Nankai Trough
Supporting References
drilling (Takahashi and Tsuji, 2005); (b) a chilled vessel to
Abegg, F., G. Bohrmann, and W. Kuhs. 2006. Data report: Shapes and
transfer pressure cores into imaging/measurement devices
structures of gas hydrates imaged by computed tomographic analyses,
(PCATS) and an instrument to provide pressure core sub-
ODP Leg 204, Hydrate Ridge. In Proceedings of Ocean Drilling Pro-
samples for microbiological and other studies (Schultheiss gram, Scientific Results, Volume 204, Tréhu, A.M., G. Bohrmann, M.E.
et al., 2006, 2010; Parkes et al., 2009); and (c) devices to Torres, and F.S. Colwell (Eds.). Ocean Drilling Program, Texas A&M
measure the physical properties of pressure cores both at University, College Station, Texas.
Bryn, P., K. Berg, C.F. Forsberg, A. Solheim, and T. Kvalstad. 2005. Explain-
hydrostatic pressure (IPTC; Yun et al., 2006) and with effec-
ing the Storegga slide. Marine and Petroleum Geology 22(1-2):11-19.
tive stress restored (Ruppel et al., 2008). Other key technical
Carpenter, G. 1981. Coincident sediment slump/clathrate compexes on the
contributions of SOD to the numerous international non- U.S. Atlantic continental slope. Geo-Marine Letters 1(1):29-32.
SOD gas hydrates drilling projects are the development of Collett, T.S. 2002. Energy resource potential of natural gas hydrates. AAPG
reliable borehole pressure-temperature tools (e.g., the Davis- Bulletin 86(11):1971-1992.
OCR for page 134
134 SCIENTIFIC OCEAN DRILLING
WHAT MAJOR TECHNOLOGICAL ADVANCES Innovations and improvement of drilling and coring
AND INNOVATIONS HAVE DEVELOPED systems on JR over time include: unique bare-rock, spud-in
FROM THE DRILLING PROGRAM? guide-base allowing use of rotary coring bit (RCB); extended
core barrel (XCB) for improved recovery in formations too
hard for piston coring; motor-driven core barrel for environ-
Hans Christian Larsen
ments of highly alternating formation strength; and advanced
IODP Management International, Inc.
piston coring (APC) system (developed from the previous
hydraulic piston coring [HPC]) for ultra-high recovery
This white paper summarizes some major technological
(~100 percent) within soft sediments. Recent “drill over”
advances and innovations made over the 40+ years since the
technology has pushed the limit of APC to 458 m below
inception of scientific ocean drilling by the Deep Sea Drill-
seafloor (HPC: ~100 m). True orientation of cores can also
ing Project (DSDP) in 1966. The focus is on the more recent
be achieved. Information systems for in-situ monitoring of
developments from the later part of the Ocean Drilling Pro-
drill bit conditions are being developed to further enhance
gram (ODP) and from the Integrated Ocean Drilling Program
recovery.
(IODP). Limits on report length only allow highlights to be
In addition, IODP saw two major new inventions: the
included. Funding of many of the technical developments is
deepwater, riser drilling vessel D/V Chikyu, purpose-built
from outside the program, which traditionally deploy most
for SOD by Japan; and application of the mission-specific
of its funds for operations. According to AGI (American
platform (MSP) approach to coring within uniquely chal-
Geosciences Institute), scientific publications underpinned
lenging environments.
by these technologies now exceed 26,000 (>1,500 in Science
Chikyu is one of the most capable drillships worldwide.
or Nature).
Her current riser capability is 2,500 m water depth, amongst
Scientific ocean drilling (SOD) deployed the first ever
the deepest at time of ship design. A 4,000+ m deepwater,
deepwater drill-ship, the CUSS 1 for project Mohole in
benchmark-setting riser is currently being explored through
1961 in a water depth of 3,500 m. The thruster-supported
optimization of conventional riser technology (material
positioning system laid the groundwork for modern dynamic
standards, downsizing of blowout preventors [BOPs]) and
positioning (DP) systems. The offshore hydrocarbon indus-
a riserless (or dual gravity) mud recovery system (RMR).
try that subsequently developed is now a top global industry
Chikyu’s double rig design is uniquely well suited for RMR,
with development budgets many orders of magnitude higher
but RMR could also be applied on JR and may be considered
than within SOD. SOD therefore piggy-backs on industry
for a new SOD vessel planned by China. Another ongoing
developments, such as coring, sampling from boreholes, core
riser innovation is a monitoring and vibration mitigation sys-
description, core-log integration, borehole observatories,
tem for operation under strong currents (a condition offshore
and development of new research tools and environmental
Japan), pushing the envelope of current industry standards.
proxies. SOD set the benchmark in these fields using a truly
The innovative application of the MSP concept to the
unique set of tools and expertise, and is at the forefront of
high Arctic (2004) resulted in a transformative technical
coring within extreme environments. Four key topics of
achievement of the first ever deep coring within the central
technology developments and spin-offs are reviewed.
Arctic Ocean. This was achieved through sophisticated ice
management in conjunction with two powerful ice breakers
PLATFORMS, DRILLING, AND CORING and a purpose fitted, ice-breaking drilling vessel (a concept
TECHNOLOGY now adapted by industry). Application of a piggy-back,
narrow kerf coring system to a DP positioned vessel for
The DSDP R/V Glomar Challenger was a purpose-built,
high-recovery drilling of carbonate reef material is another
first-generation deepwater drillship, globally breaking new
noteworthy innovation that increased core recovery with one
ground drilling in water as deep as 7,044 m (open hole,
order (+) of magnitude.
non-riser). ODP was served by the R/V JOIDES Resolution
Developments by SOD partners (e.g., BGS and
(JR), an oil exploration platform converted to a non-riser
MARUM) are pushing the shallow (0-100 m) coring from
scientific drilling vessel. Superior to Glomar Challenger in
seabed frames (e.g., MeBo of MARUM), which can provide
all aspects (e.g., tonnage, drill string capabilities, DP perfor-
high-recovery cores from young oceanic crust, otherwise
mance, heave compensation), JR drilled deeper, in shallower
proven impossible to effectively core. SOD is also develop-
waters, in higher latitudes, and with improved core recovery.
ing high-temperature core barrels for such environments.
JR underwent major refurbishment during IODP years 2006-
Because of these many incremental innovations in
2008, extending vessel lifetime, improving accommodations
drilling technology, SOD can effectively core in almost any
and laboratory space, further improving heave compensation,
environment, and maintains leadership in deepwater coring,
and adding newly developed, state-of-the-art coring analyti-
despite being the David compared to the Goliath in the global
cal facilities.
drilling industry.
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135
APPENDIX C
SHIPBOARD AND LAB-BASED academic-industry collaboration, IODP supported a logging-
TECHNOLOGIES AND MEASUREMENTS while-coring system that measures an electrical image of the
borehole while taking a core sample, thereby enhancing core
Core splitting and processing tools and protocols still in
log integration. SOD also developed formation temperatures
use by IODP were developed by DSDP and laid the founda-
tools and is the global source of deep temperature data for
tion for an unparalleled collection of legacy data from below
the sub-seafloor. Large-diameter drill pipe (6-5/8”) will in the
the oceans. Of course, major advances in both discrete and
future allow for development of better pore fluid sampling
continuous core measurements have been made over time. In
and formation testing, geochemical logging, nuclear mag-
this field, SOD can claim credit per se for innovations within
netic resonance for pore size distribution, and high-coverage
continuous core descriptions and measurements, laying the
electrical imaging.
groundwork for development of different physical/chemical
Gas hydrates and associated logging and sampling tools
proxies for environmental change and temporal constraints:
is an area where SOD has led the initial research and develop-
(1) A core cryogenic magnetometer, which contributed to
ment. Hydrates are unstable at surface conditions. Through
the commercial product now in use, provides onboard rapid
core-log integration an estimate of gas hydrate content that
paleomagnetic stratigraphy; (2) Multi-Sensor Track (MST),
is continuous at depth can be made. An SOD-developed
which is applied pre-core splitting to provide density, mag-
pressure core sampler (PCS) paved the way for recovery
netic susceptibility, p-wave velocity, and resistivity; (3) rapid
of gas hydrate to the surface without sublimation of the
measurement color spectrophotometry; (4) spectral natural
hydrate. SOD partners (including Geotek Ltd) then devel-
gamma ray analysis rapidly measuring cores at comparable
oped the PCS into the HYACINTH for in situ pressure and
resolution to downhole logging tools (unique for core-log
temperature-preserving sampling tool for gas hydrates. This
integration); (5) rapid, high-resolution, high dynamic range
tool is pivotal in the many governmental and commercial
linescan split core imager; (6) continuous XRF high-reso-
investigations of gas hydrates as a possible new hydrocarbon
lution core scanning (split core); (7) ultra-clean sample and
energy source.
curation protocols for microbiological sampling; (8) infrared
In 2009 SOD took borehole-hosted vertical seismic
cameras to identify gas hydrate horizons in core before sub-
profiling (VSP) to a new level by conducting a wide-angle,
limation; and (9) non-destructive rhizon porewater sampler.
semi-3D walk-away experiment over the drill site location
Ocean drilling has adapted a number of other advanced
offshore Japan that is targeted for ultra-deep (7 km) riser
facilities for use. Of these, the continuous core computed
drilling and instrumentation of a seismic plate boundary. In
tomography (CT) scanning stands out and has opened a new
this location SOD activities eventually will enable surface
world of 3D imaging before core splitting.
3D seismic data, advanced VSP data, borehole logging,
The opportunities offered by these advanced core scan-
sampling, and long-term borehole observatory data to be
ning and analytical tools are vastly supplemented by a large
integrated in a unique collage of plate-boundary data.
number of (non-program) state-of-the-art analytical facili-
ties for mainly discrete samples (e.g., isotopes, magnetic
DEEP EARTH OBSERVATORY SCIENCE
properties including paleo-intensity, microbiology, and DNA
sequencing). More than 13,000 scientists are using SOD
Following successful advances in downhole sampling
samples. Approximately 2.2 million ODP samples have
and logging, the concept of actually installing downhole
been taken; this number is increasing, with a recent record
observatories that could sample time series (e.g., fluids, pres-
of 53,000 samples provided by a SOD core repository.
sure, and temperature) was introduced during the ODP by the
CORK (Circulation Obviation Retrofit Kit) concept. IODP
DOWNHOLE MEASUREMENTS/LOGGING is making big strides toward establishing a permanent pres-
AND ADVANCED SAMPLING ence of subseafloor observatories within critical ocean floor
locations, and with a vastly expanded set of observations.
Because of its unique expertise in core-log integration,
These include time-series of pore water geochemistry from
SOD is a respected partner of world-leading geophysical
osmosamplers (resolution of ~a few days) and geochemical
logging companies. Downhole logging has grown in SOD
tracer flow-meter allowing estimates of lateral fluid flow
drilling, with logged drill sites increasing from 14 percent
rates; microbiological observatory elements into hydro-
during DSDP to 64 percent during IODP. Most technology
logical observatories via use of substrates; vastly improved
used in scientific drilling originates from the hydrocarbon
pressure resolution (order of 1 ppb full scale) as a sensitive
industry, from wireline logs to logging-while-drilling mea-
proxy for strain, and with sampling frequency <1Hz linking
surements. However, SOD likely has the globally best core-
deformation to seismological data; and tilt meter and seismic
log integration data, and specialty tools developed by SOD
broadband sensors. Implementation protocols to co-locate
include magnetic properties, high-resolution natural gamma
multiple sensors for hydrological-geodetic-seismological
ray radioactivity, borehole temperature, pressure-measuring
purposes or hydrological-thermal-microbiological purposes
penetrometers, and laser imaging for microbiology. Through
are being developed and planned for upcoming experiments.
OCR for page 136
136 SCIENTIFIC OCEAN DRILLING
Supporting References
Extending these subseafloor observatories to the high-pres-
sure and -temperature regimes at 6-7 km depth (seismogenic Fisher, A. and K. Becker. 1993. A Guide to ODP Tools for Downhole Mea-
zones) is currently under development, and links to land by surements: Technical Note 10. [Online]. Available: http://www-odp.
fiberoptical networks for real-time monitoring are being tamu.edu/publications/tnotes/tn10/10toc.html [2010, November 29].
Goldberg, D. 1997. The role of downhole measurements in marine geology
implemented offshore Japan and Northwest America in two
and geophysics. Reviews of Geophysical 35(3):315-342.
seismically active zones. This SOD development is in coop-
Goldberg, D., G. Myers, G. Iturrino, K. Grigar, T. Pettigrew, and S.
eration with and co-funded by other entities and programs. Mrozewski. 2006. Logging-while-coring: New technology for the si-
These novel technologies, combined with the experience multaneous recovery of downhole cores and geophysical measurements.
gained to implement them via drillships, submersibles, and Geological Society, London, Special Publications 267:219-228.
Graber, K.K., E. Pollard, B. Jonasson, and E. Schulte. (Eds.). 2002. Over-
remotely operated vehicles (ROVs), underpins a new sci-
view of Ocean Drilling Program engineering tools and hardware. In
entific paradigm of observing processes as they happen (as
Ocean Drilling Program Technical Note 31. Ocean Drilling Program,
opposed to simply studying the lasting imprint of processes Texas A&M University, College Station, Texas.
in the geological record). Naturally, the new science plan (in Huey, D.P. and M.A. Storms. 1995. New downhole tools improve recovery.
preparation) for SOD beyond 2013 makes this emerging field Oil and Gas Journal 23:42-48.
Huey, D.P. and M.A. Storms. 1995. Modified wire line tools improve open
of “Earth in Motion” science one of its four grand challenges.
hole logging operations. Oil and Gas Journal 30:94-96.
Malinverno, A., M. Kastner, M.E. Torres, and U.G. Wortmann. 2008. Gas
SOD STUDY OF ACTIVE LIFE BELOW THE hydrate occurrence from pore water chlorinity and downhole logs
in a transect across the northern Cascadia margin (Integrated Ocean
SEAFLOOR
Drilling Program Expedition 311). Journal of Geophysical Research
113(B13):1-18.
Rapid and ongoing technology development underpins
Miller, J.E. and D.P. Huey. 1992. Development of a mud-motor-powered
another emerging field of science: the study of active micro-
coring tool. In Offshore Technology Conference, Houston, Texas.
bial life, below, in part deeply below (~1,600 m), the seafloor Miyazaki, E., M. Ozaki, S. Nishioka, and J. Minamiura. 2008. Application
(a second grand challenge of the new science plan). Technol- of riser fairings to the D/V “CHIKYU” during drilling in high current
ogy development in this field takes place globally, and with area. In Proceedings of Oceans ’08 Mts/Ieee Kobe-Techno-Ocean ’08,
Kobe, Japan.
many different entities and constituencies involved. Special
Peter, S., M. Holland, and G. Humphrey. 2009. Wireline coring and analysis
contributions by SOD, apart from making sampling pos-
under pressure: Recent use and future developments of the HYACINTH
sible, are laboratories (on platforms and at core repositories), system. Scientific Drilling 7:44-50.
protocols for clean sampling, curation processes and storage Pettigrew, T.L. 1993. Design and operation of a Drill-In-Casing system
(long-term and legacy), computer-automated cell counts (DIC). In Ocean Drilling Program Technical Note 21. Ocean Drilling
Program, Texas A&M University, College Station, Texas.
(living cells), and DNA replication from limited amount of
Saffer, D., L. McNeill, E. Araki, T. Byrne, N. Eguchi, S. Toczko, K. Taka-
material. Initial findings and technology developments by
hashi, and the Expedition 319 Scientists. 2009. NanTroSEIZE Stage 2:
SOD have generated very significant spin-off activities by NanTroSEIZE riser/riserless observatory. In Proceedings of the Inte-
other groups. grated Ocean Drilling Program, Volume 319. Integrated Ocean Drilling
Program, Texas A&M University, College Station, Texas.
Stahl, M.J. 1994. Automated stress analysis and design of drill strings for
riserless offshore coring operations. Oil and Gas Journal 4:43-48.
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137
APPENDIX C
DRILLING THE OCEAN CRUST magma bodies, an absence of large magma chambers, melt-
rock reaction, mass transfer by upward percolation of melts
through the lower crust, and vertical rafting of intrusions and
Henry J. B. Dick
altered mantle peridotite all having been recognized as major
Woods Hole Oceanographic Institution
accretionary processes.
Ocean crust drilling began in earnest in 1974 with Leg
Formation of the ocean lithosphere is the principle mag-
37 of DSDP (Deep Sea Drilling Project), which drilled a four
matic process on the planet, generating some three-fifths of
hole transect at 37°N on the Mid-Atlantic Ridge (MAR) in
the Earth’s crust by surface area and representing the major
shallow ocean crust from 3.5 to 13 myr. The sites included a
transfer of heat, mass, and volatiles between the Earth’s
planned deep hole at Site 332 that penetrated 583 m before
interior, crust oceans, and atmospheres. At the present time
abandoned. At Site 334, a tectonically emplaced layer of ser-
we do not have direct knowledge of the composition of the
pentinized peridotite and gabbro was recovered beneath 50 m
ocean crust or a full understanding of how it forms. What we
of pillow basalts. Ironically, this first in situ section of lower
do know is largely the result of ocean drilling both in intact
crustal rocks proved to be atypical of what was later drilled
sections of the ocean crust and in tectonic windows where
on seven legs in the Pacific, Atlantic, and Indian Oceans.
the lower ocean crust and mantle have been unroofed to
In all, about 50 holes were drilled into “intact” sections of
the seafloor. The initial stimulus for drilling was to test two
oceanic crust up to the start of the Integrated Ocean Drilling
competing models for the ocean crust, which at the time was
Program (IODP) in 2004, when it was believed that layered
assumed to be a relatively simple layered sequence some 6-7
crust, such as described in the Penrose model, existed in the
km thick. Harry Hess, in his landmark paper, History of the
Atlantic and Pacific Oceans. At Hole 504B south of the Costa
Ocean Basins (Hess, 1962), proposed that the ocean crust
Rica Rift, and possibly at Hole 418A in the 108-million-year-
largely consisted of mantle peridotite hydrothermally altered
old MAR crust, seismic layer 2B was penetrated, with only
to serpentine with the Mohorovičić discontinuity (Moho)
Hole 504B possibly reaching the very top of seismic layer
representing the upper temperature limit for the stability of
3 (Dick et al., 1992; Alt et al., 1993; Detrick et al., 1994).
this mineral. The opposing model, which had gained general
Drilling in young Pacific crust was particularly difficult, with
acceptance from the Earth sciences community, was a layer
10 holes in crust less than 30 million years old reaching a
cake consisting of pillow lavas overlying sheeted dikes and
maximum penetration of only 178 m—a result attributed to
gabbro, with the Moho representing the igneous crust-mantle
the difficulty of drilling abundant glassy sheet flows. Suc-
boundary. In the latter, known as the Penrose ophiolite model
cess was better at slower-spreading ridges, with 11 holes
(Conference Participants, 1972) the lower ocean crust rep-
penetrating greater than 200 m, and 7 reaching greater than
resented the remains of a large magma chamber in which
500 m. This drilling showed that seismic layer 2A was com-
mantle melts pooled and underwent fractional crystalliza-
posed of basalt lavas and rubble, and that at an intermediate
tion, while the dikes represented the conduits through which
spreading ridge, seismic layer 2B at Hole 504B was sheeted
differentiated magmas erupted to the seafloor to form a layer
dikes as in the Penrose model. Unexpectedly, however, the
of pillow lavas. Obvious differences in the morphology of
layer 2B-layer 3 seismic boundary there corresponded to an
the seafloor between relatively low relief smooth seafloor
alteration front in dikes, rather than the dike-gabbro transi-
formed at the fast spreading East Pacific Rise (EPR) and
tion. Surprisingly, short sections of often brecciated serpen-
slower spreading ridges were largely ignored in this model.
tinized peridotite and gabbro, exhibiting high-temperature
The ultimate goal of ocean drilling initially was to
alteration and crystal-plastic deformation, were found in six
achieve a full penetration of the crust from pillow lavas to
Atlantic holes drilled in supposedly “intact” crust. Drilling
mantle. Given the presumed simplicity of the ocean crust, a
at slow spreading ridges demonstrated unexpected tectonic
single core would answer all questions. A total penetration of
complexity that did not fit the Penrose model and proved a
“intact” crust has not been achieved, although we now know
harbinger of things to come.
that it is technically feasible given the will. Thirty-five years
The early failure to drill deeply into intact oceanic crust
of ocean drilling, in combination with seafloor mapping,
was a huge disappointment. Recoveries were low, averag-
however, has radically transformed our view of the ocean
ing ~20 percent. Other than sporadic drilling at Hole 504B,
crust, which is now viewed as highly varied in composition
no serious attempt to drill ocean crust was made for many
and architecture, with radically different models for fast and
years after DSDP Leg 53 in 1977. Drilling difficulties were
slow spread crust. Ironically, both the Hess and the Penrose
attributed to highly fractured basalt and diabase and possibly
models have proved to describe the ocean crust as it forms
thermal problems deep in Hole 504B, although these were
under different tectonic conditions. The mechanisms of
likely due as much to not properly designing holes for deep
accretion of the lower crust now believed to exist are also
penetration. Thus, a new strategy was adopted during the
radically different from the simple closed-system magma
Ocean Drilling Program (ODP), using “tectonic windows”
chamber that was the widely accepted paradigm at the start
to drill lower crust and mantle (Dick, 1989; Dick and Mével,
of ocean drilling, with direct intrusion of numerous small
1996). This drilling strategy targeted peridotite and gabbro
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138 SCIENTIFIC OCEAN DRILLING
exposed at topographic highs at oceanic core complexes: stratigraphy produced by upward compaction of interstitial
Atlantis Bank on the Southwest Indian Ridge; the MARK melt to produced numerous high-level Fe-Ti rich oxide gab-
area at 23°N; the MAR Atlantis Massif and tectonic blocks bro layers. In addition, olivine-rich troctolites occur in the
in the rift mountains near the 15°20′ fracture zone; and Hess mid-section at Hole 1309D. These rocks form by reaction
Deep in the Pacific, where the amagmatic tip of the Cocos- between basalt melt and mantle peridotite at the base of the
Nazca rift propagates into young (1.5–2 million-year-old) crust, and are subsequently mechanically rafted up through
EPR crust. the section (Drouin et al., 2007a, b, 2009; Suhr et al., 2008).
Drilling at Hess Deep recovered important sections of Overall, the large majority of gabbros drilled at these sites
tectonically disturbed lower crust and mantle that was con- and by Leg 153 at MARK are far too evolved to crystallize
sistent with the Penrose model. These sections included the directly from MORB. Thus, to date, we have not recovered
important Hole 894G 154-m section of fine-grained gabbros anything like the full lower crustal suite at either slow or fast
with a few diabase dikes, which are believed to represent a spreading ridges, which is critical, because until we do we
section of lower crust formed in the melt lens beneath the will have only indirect knowledge of the processes that shape
EPR and resembled part of the Oman Ophiolite section. They MORB—the most abundant magma on earth.
are believed to be the precursor to a similar thick underly- Leg 209 examined what was once thought to be atypical
ocean crust. It is drilled 19 holes at eight sites from 14°43 ′N
ing gabbro section. The gabbros are too evolved, however,
to represent crystallization products of the relatively primi- to 15°39’N on the MAR where dredging found extensive
tive pillow basalts that characterize the East Pacific Rise, mantle outcrops intruded by small gabbro bodies. This find-
in conflict with the generally accepted hypothesis that the ing led to the hypothesis that the crust was largely serpen-
melt lens is their primary source. A second result was a tinized peridotite with local small magmatic centers cut by
series of holes at Site 895 that represent a transect across a small dike swarms and local eruptive sequences (Cannat et
melt transport conduit through a mantle section. The host al., 1997, 2006). This was what Leg 209 drilled, confirming
peridotites were highly depleted residues of partial melting, the existence of crustal sections that form by direct intrusion
consistent with a fractional melting model, while the dunite and hydrothermal alteration of mantle rock along a signifi-
conduits contained gabbroic segregations that demonstrated cant portion of slower spreading ridges. Moreover, the crust
for the first time that the mid-ocean ridge basalt (MORB) consisted of one tectonic block cutting another with alternate
is formed within the mantle itself, rather than represent- fault capture, leading to spreading of blocks in opposite
ing mixing of diverse magmas in a lower crustal magma directions from the rift valley (Schroeder et al., 2007)—a
chamber. The segregations also showed that basaltic melts new form of seafloor spreading, which morphological analy-
can crystallize at near constant temperature by reaction with sis of the seafloor suggests makes up a substantial portion
the host mantle—a result whose importance was not fully (~40 percent) of the crust at slower spreading ridges (e.g.,
appreciated until analysis of the Hole 1309D gabbro section Escartin et al., 2008).
in the Atlantic. One of the great successes of IODP has been Drilling in lower crust at slower spreading ridges shows
the penetration of an intact section of EPR crust down to the that its accretion occurs by mechanisms previously not
dike-gabbro transition at Hole 1256 penetrating 1257.1 m of considered: direct intrusion of small batches of melts at all
the upper crust, including a 345.7 m sheeted dike complex levels, upward compaction of interstitial melts by permeable
and 100.5 m into gabbro near the depth predicted by seis- flow, and rafting of deeper intrusions and material formed by
mologists for the layer 12-3 boundary. Besides affirming the reaction between melts and mantle at the base of the crust.
results from Hess Deep, Hole 1256D proved the hypothesis Moreover, it has also shown that both Penrose- and Hess-type
that the shallow ocean crust (dikes and lavas) thins at the sections exist along slow and ultraslow spreading ridges.
fastest spreading rates, confirming the utility of seismology
in shallow Pacific crust.
Supporting References
Drilling lower crustal rocks in tectonic windows at slow
Alt, J.C., H. Kinoshita, and L.B. Stokking, S. Allerton, W. Bach, K. Becker,
and ultraslow spreading ridges is one of the dramatic suc-
V.K. Boehm, T.S. Brewer, Y. Dilek, F. Filice, M.R. Fisk, H. Fujisawa, H.
cesses of ODP and IODP. Hole 735B penetrated 1,508 m of
Furnes, G. Guerin, G.D. Harper, J. Honnorez, H. Hoskins, H. Ishizuka,
gabbro at the Atlantis Bank core complex on the southwest C. Laverene, A.W. McNeil, A.J. Magenheim, S. Miyashita, P.A. Pezard,
Indian Ridge, while Hole 1309D penetrated 1,415 m at the M.H. Salisbury, P. Taratotti, D.A. Teagle, D.A. Vanko, R.H. Wilkens, and
Atlantis Massif on the MAR. Recovery was ~87 percent of H.U. Worm. 1993. Costa Rica Rift. In Proceedings of the Ocean Drilling
Program, Initial Reports, Volume 148. Ocean Drilling Program, Texas
both sites. These successes show unequivocally for the first
A&M University, College Station, Texas.
time that thick gabbro sequences do exist at slower spread-
Cannat, M., Y. Lagabrielle, H. Bougault, J. Casey, N. de Coutures, L.
ing ridges, but that they are the remains of numerous small Dmitriev, and Y. Fouquet. 1997. Ultramafic and gabbroic exposures at
intrusive swarms, not of large magma chambers. Moreover, the Mid-Atlantic Ridge: Geologic mapping in the 15°N region. Tecto-
the sections are riddled with microgabbro dikes and solution nophysics 279(1-4):193-213.
channels representing melt transport from depth through pre-
existing gabbro. Equally startling is a superimposed igneous
OCR for page 139
139
APPENDIX C
Cannat, M., D. Sauter, V. Mendel, E. Ruellan, K. Okino, J. Escartin, V. Drouin, M., M. Godard, and B. Ildefonse. 2007b. Origin of olivine-rich
Combier, and M. Baala. 2006. Modes of seafloor generation at a melt- troctolites from IODP Hole U1209D in the Atlantis Massif (Mid-At-
poor ultraslow-spreading ridge. Geology 34(7):605-608. lantic Ridge): Petrostructural and geochemical study. Eos, Transactions,
Conference Participants. 1972. Penrose field conference on ophiolites. American Geophysical Union 88:52.
Geotimes 17:24-26. Drouin, M., M. Godard, B. Ildefonse, O. Bruguier, and C.J. Garrido. 2009.
Detrick, R., J. Collins, R. Stephen, and S. Swift. 1994. In situ evidence for Geochemical and petrographic evidence for magmatic impregnation in
the nature of the seismic layer 2/3 boundary in oceanic crust. Nature the oceanic lithosphere at Atlantis Massif, Mid-Atlantic Ridge (IODP
370:288-290. Hole U1309D, 30°N). Chemical Geology 264(1-4):71-88.
Dick, H.J.B. (Ed.). 1989. JOI/USSAC Workshop Report: Drilling the Oce- Escartin, J., D.K. Smith, J.R. Cann, H. Schouten, C.H. Langmuir, and S.
anic Lower Crust and Mantle. Woods Hole Oceanographic Institution, Escrig. 2008. Central role of detachment faults in accretion of slow-
Woods Hole, Massachusetts. spreading oceanic lithosphere. Nature 455:790-794.
Dick, H.J.B. and C. Mével. (Eds.). 1996. The Ocean Lithosphere and Scien- Hess, H.H. 1962. The history of the ocean basins. In Petrologic Studies: A
tific Drilling into the 21st Century. JOI/U.S. Science Support Program Volume in Honor of A.F. Buddington, Engel, A.E.J., H.L. James, and
and the InterRidge Office, Washington, DC. B.F. Leonard (Eds.). Geological Society of America, Boudler, Colorado.
Dick, H.J.B., J.A. Eringer, L.B. Stokking, P. Agrinier, S. Allerton, J.C. Alt, Suhr, G., E. Hellebrand, K. Johnson, and D. Brunelli. 2008. Stacked
L.O. Boldreel, M.R. Fisk, P.K.H. Harvey, G.J. Iturrino, K.T.M. Johnson, gabbro units and intervening mantle: A detailed look at a section of
D.S. Kelley, P.K. Kepezhinskas, C. Laverne, F.C. Marton, A.W. McNeill, IODP Leg 305, Hole U1309D. Geochemistry, Geophysics, Geosystems
H.R. Naslund, J.E. Pariso, N.N. Pertsev, P. Pezard, E.S. Schandi, J.W. 9(Q10007):1-31.
Sparks, P. Tartarotti, S. Umino. D.A. Vanko, and E. Zuleger. 1992. 2. Schroeder, T., M.J. Cheadle, H.J.B. Dick, U. Faul, J.F. Casey, and P.B.
Site 504. In Proceedings of the Ocean Drilling Program, Initial Reports, Kelemen. 2007. Nonvolcanic seafloor spreading and corner-flow rota-
Volume 140, Dick, H.J.B., J.A. Erzinger, and L.B. Stokking (Eds.). tion accommodated by extensional faulting at 15N on the Mid-Atlantic
Ocean Drilling Program, Texas A&M Univeristy, College Station, Texas. Ridge: A structural synthesis of ODP Leg 209. Geochemistry, Geophys-
Drouin, M., M. Godard, and B. Ildefonse. 2007a. Origin of olivine-rich ics, Geosystems 8:Q06015.
gabbroic rocks from the Atlantis Massif (MAR 30°N, IODP Hole
U1309D): Petrostructural and geochemical study. Geophysical Research
Abstracts 9(06550).
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140 SCIENTIFIC OCEAN DRILLING
LARGE IGNEOUS PROVINCES Focused investigations of oceanic plateaus have tar-
geted the two largest features globally, the ~120 Ma Ontong
Java Plateau (Pacific Ocean) and ~120-95 Ma Kerguelen
Millard F. Coffin
Plateau/Broken Ridge (Indian Ocean), each encompassing
University of Tasmania, Australia
an area approximately one-fourth the size of the contigu-
ous United States. Several expeditions have drilled multiple
Large igneous provinces (LIPs)—oceanic plateaus, volca-
holes penetrating the igneous basement of each. In late 2009,
nic rifted margins, and continental flood basalts—result from
igneous basement of a third oceanic plateau, the ~145-130
fundamental processes in Earth’s interior and have been impli-
Ma Shatsky Rise (Pacific Ocean), was drilled in various
cated as a cause of major worldwide environmental changes.
locations. These three features constitute the only oceanic
Although the plate tectonics paradigm successfully explains
plateaus where igneous basement has been drilled at more
volcanic activity on Earth’s surface associated with seafloor
than one site.
spreading and plate subduction, it does not elucidate the mas-
Drilling results from Ontong Java Plateau basement
sive “hotspot” volcanism that produces LIPs, which dominates
rocks are complemented by studies of obducted plateau
the record of volcanism on all other terrestrial planets and
rocks exposed in the Solomon Islands. All basement rocks
satellites in our solar system and the cause of which is debated
recovered to date are remarkably homogeneous—submarine
vigorously. Temporal correlations between LIP emplacements
tholeiitic basalts with minor variations in elemental and iso-
and environmental phenomena such as mass extinctions and
topic composition. Partial batch melting (≥30 percent) gener-
oceanic anoxic events (OAEs) are well documented, yet the
ated the basalts, with melting and fractional crystallization
underlying mechanisms causing these global catastrophes are
at depths of <6 km. The lavas and their overlying sediment
only beginning to be grasped. Scientific ocean drilling has
indicate relatively minor uplift accompanying emplacement
played a central and critical role in illuminating solid Earth
and relatively minor subsidence since emplacement. Primar-
processes causing LIPs and in comprehending the effects of
ily on the basis of drilling results, multiple models—plume,
LIP formation on Earth’s environment.
bolide impact, and upwelling eclogite—have been proposed
Reconnaissance drilling of oceanic plateaus and volca-
for the feature’s origin. The Ontong Java Plateau correlates
nic rifted margins began soon after scientific ocean drilling
temporally with oceanic anoxic event (OAE-1a), and inter-
started in 1968, but the first targeted LIP investigations
pretation of strontium, osmium, and lead isotopic systems
involving drilling, focusing on the ~55 Ma North Atlantic
during the time of OAE-1a points to a close linkage between
volcanic rifted margins, commenced in the 1980s. Drilling
the two, with CO2, Fe, and trace metal emissions from the
on the UK margin confirmed a hypothesis that submarine
massive magmatism potentially triggering the event.
“seaward-dipping reflectors” (SDRs) observed on seismic
Uppermost igneous basement of the Kerguelen Plateau/
reflection data were stacks of originally subaerial lava flows
Broken Ridge is dominantly subaerial tholeiitic basalt, and it
that subsequently cooled and subsided beneath sea level,
shows two apparent peaks in magmatism at 119-110 Ma and
where they were buried by sediment—a nearly ubiquitous
105-95 Ma. Geochemical differences among these basalts
characteristic of submarine LIPs that precludes their volcanic
are attributable to varying proportions of components from
and plutonic rocks from being sampled by any means other
the primary mantle source (plume?), depleted mid-ocean
than drilling. Further focused drilling of the North Atlantic
ridge basalt (MORB)-related asthenosphere, and continental
LIP, on the Norwegian Margin in the 1980s and the conjugate
lithosphere. Proterozoic-age zircon and monazite in clasts
East Greenland Margin in the 1990s, documented extreme
of garnet-biotite gneiss in a conglomerate intercalated with
magmatic productivity over a distance of at least 2,000 km
basalt at one drill site demonstrate the presence of fragments
during continental rifting and breakup, provided the first
of continental crust in the Kerguelen Plateau, inferred previ-
age data from an oceanic LIP showing that construction of
ously from geophysical and geochemical data. For the first
these margins was geologically “instantaneous” (ca. 1 mil-
time from an intra-oceanic LIP, alkalic lavas, rhyolite, and
lion years), and yielded geochemical evidence that landward
pyroclastic deposits were sampled. Flora and fauna preserved
SDRs were contaminated during ascent through continental
in sediment overlying igneous basement record long-term
crust and that oceanward SDRs formed at a seafloor spreading
plateau subsidence, beginning with terrestrial and shallow
center resembling Iceland. A proposed mechanism for these
marine deposition and continuing to deep water deposition.
~55 Ma magmas triggering the Paleocene-Eocene Thermal
The first results of 2009 basement drilling on the Shatsky
Maximum is intrusion of voluminous mantle-derived melts
Rise include evidence for initial shallow water or subaerial
into carbon-rich sedimentary strata in the northeast Atlantic
eruption of predominantly massive lava flows, subsequent
that caused explosive release of methane into the ocean and
deeper water eruption of mainly pillow lava flows, and post-
atmosphere via hydrothermal vent complexes. More than
emplacement subsidence resembling that of normal oceanic
50 percent of passive margins globally are “volcanic,” but
crust.
to date scientific ocean drilling has only sampled the North
Future LIP drilling has the potential to transform our
Atlantic LIP at one site.
understanding of the Earth system through investigating:
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141
APPENDIX C
Supporting References
(1) magma (and hence mantle source) variability through
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ics 32(1):1-36.
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Eldholm, O. and M.F. Coffin. 2000. Large igneous provinces and plate tec-
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OCR for page 142
142 SCIENTIFIC OCEAN DRILLING
CONTINENTAL BREAKUP AND km to the east of the peridotite ridge, indicating that there is
SEDIMENTARY BASIN FORMATION a wide zone of upper mantle rocks exhumed to the seafloor
and presumably separating extended continental crust from
oceanic crust. Some of the sampled peridotite contained
Dale S. Sawyer
strong remnant magnetization, explaining the presence of
Rice University
apparent seafloor spreading anomalies over crust that is
not oceanic. ODP Leg 173 (Whitmarsh and Wallace, 2001)
In the study of continental breakup (and other large-scale
showed that the continental crust was thinned to nearly
tectonic systems), scientific ocean drilling is not a capstone
zero thickness by low-angle detachment faulting, which in
activity, but rather is part of an iterative process comprising
some places brought upper mantle peridotite to within a few
drilling, improved geophysical (primarily controlled source
hundred meters of the seafloor at the time of breakup. The
seismology) and geological (including onshore exposures
peridotites are most likely to be subcontinental mantle. Mafic
where available) characterization, ongoing geodynamic
cores were shown to have been emplaced in or just below the
modeling, and drilling again. Continental breakup and ensu-
thinned lower continental crust. Surprisingly no samples of
ing seafloor spreading inherently separate the “field area”
upper continental crust or synrift melt were obtained, which
for a study into a pair of conjugate rifted margins. Typically
is attributed to gradual breakup and transition to seafloor
both margins must be studied comprehensively to learn about
spreading. During Leg 173 shipboard scientists noted strong
the whole. Every rifted margin is a blend of end-member
similarities between cores obtained from the Iberia Abyssal
types: (1) magma-dominated or magma-poor, (2) actively
Plain and the character and history of rifted margins and
rifting or no longer rifting, (3) normal spreading, obliquely
transition zones exposed in the modern Alps (Manatschal and
spreading, and transform, and (4) sediment-dominated or
Bernoulli, 1998). This line of research has been very fruitful
sediment starved. Examination of any single rifting system
in expanding our understanding of both systems. ODP Leg
cannot reveal details of all the important breakup processes.
210 (Tucholke and Sibuet, 2007) drilled off Newfoundland
Successful drilling studies will include geodynamic model-
in a position conjugate to the Legs 149/173 transect. The
ing efforts before, during, and after each coordinated drilling
primary site bottomed in a pair of diabase sills dated at 98 and
activity
105 Ma. The upper sill is intruded at the level of the promi-
In 1991, the Ocean Drilling Program (ODP) Planning
nent and widespread “U” reflection, suggesting that sills
Committee formed a North Atlantic Rifted Margins Detailed
may be pervasive at this stratigraphic level. No equivalent
Planning Group (NARM-DPG) with a charge to explore
to these sills was observed on the Iberia Margin. A second
options and make recommendations for conducting drilling
site off Newfoundland sampled exhumed peridotite in a shal-
on volcanic and non-volcanic conjugate rifted margins. The
low basement high that is similar to peridotites sampled off
NARM-DPG recommended that ODP efforts focus on the
Iberia. As in Iberia, these peridotites showed little evidence
Newfoundland-Iberia conjugate pair for studies of magma-
of melting even though they were coincident with apparently
poor rifting and the southeast Greenland–northeast Atlantic
normal lineated magnetic anomalies.
for studies of magma-dominated rifting.
Extensive reinterpretation of seismic profiles after Legs
Drilling on the magma-poor Newfoundland and Iberia
173 and 210, synthesis of Alps analogs (Peron-Pinvidic et
rifted margins comprises DSDP (Deep Sea Drilling Project)
al., 2007), comparison to drilling results, comparison to slow
Leg 47 and ODP Legs 103, 149, 173, and 210. DSDP Leg
spreading midocean ridge analogs (Cannat et al., 2009), and
47B (Sibuet and Ryan, 1979) drilled a deep sedimentary hole
geodynamic modeling (Lavier and Manatschal, 2006) has led
that provided stratigraphic information about the breakup
to a new understanding of the Newfoundland–Iberia breakup
of Newfoundland and Iberia. ODP Leg 103 (Boillot and
(Peron-Pinvidic and Manatschal, 2009). This understanding
Winterer, 1988) drilled a transect across the Deep Galicia
moves past thinking of continental breakup as mono-phase
Basin and demonstrated that (1) a prominent seismic reflec-
and laterally uniform rifting followed by an abrupt breakup
tor “S,” later to be characterized as a detachment fault,
and formation of a sharp continent-ocean boundary. The
is within or overlain by rotated, fault-bounded blocks of
new model describes rifting as a process of progressive
continental crust, (2) peridotite, which ascended from 30
strain localization, stacking different modes of extension
km depth and shows a history of partial melting, stretching,
in temporally and spatially varying domains. It defines the
serpentinization, and fracturing, is exposed in a margin par-
end of rifting and onset of seafloor spreading neither as a
allel ridge at the foot of the margin, and (3) obtained dates
moment in time, nor a mappable boundary, but as a transi-
for the syn- and post-rift sediments reflect the last stage
tion zone in which a series of processes interact and overlap
of breakup. ODP Leg 149 (Whitmarsh and Sawyer, 1996)
in complex ways. Features that we could not explain are
drilled a transect across the Iberia Abyssal Plain margin
now comprehensible. Furthermore, this new understanding
segment. Peridotite was again sampled at the top of a ridge,
is revolutionizing the way academic and petroleum industry
providing additional information about its exhumation his-
scientists interpret other magma-poor rifted margins around
tory. However, serpentinized peridotite was also sampled 20
the world (Reston, 2009).
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143
APPENDIX C
Drilling on the magma-dominated southeast Greenland Larsen, H.C. and R.A. Duncan. 1996. Introduction: Leg 163 background and
objectives. In Proceedings of the Ocean Drilling Program, Initial Re-
and northeast Atlantic volcanic margins comprises DSDP
ports, Volume 163, Duncan, R.A., H.C. Larsen, J.F. Allan, Y. Aita, N.T.
Legs 38 and 81 and ODP Legs 104, 152, and 163. DSDP Leg Arndt, C.J. Bücker, H. Cambray, K.V. Cashman, B.P. Cemey, P.D. Clift,
38 (Talwani and Udintsev, 1976) found that acoustic base- J.G. Fitton, B. Le Gall, P.R. Hooper, Y. Nakasa, Y. Niu, H. Philipp, S.
ment of Vøring Plateau was composed of basaltic volcanics. Planke, J. Rehacek, A.D. Saunders, D.A.H. Teagle, and C. Tenger (Eds.).
DSDP Leg 81 (Roberts et al., 1984) drilled Rockall Margin, Ocean Drilling Program, Texas A&M University, College Station, Texas.
Larsen, H.C. and A.D. Saunders. 1998. Tectonism and volcanism at the
suggesting that seaward dipping reflectors (SDRs) were
Southeast Greenland Rifted Margine: A record of plume impact and
subaerial volcanic constructions. ODP Leg 104 (Eldholm later continental rupture. In Proceedings of the Ocean Drilling Program,
et al., 1989) drilled 900 m of subaerial flows of the SDR Scientific Results, Volume 152, Saunders, A.D., H.C. Larsen, and S.W.
at the Vøring Margin and was able to characterize events Wise, Jr. (Eds.). Ocean Drilling Program, Texas A&M University, Col-
during the initial opening of a volcanic margin. ODP Leg lege Station, Texas.
Lavier, L.L. and G.A. Manatschal. 2006. A mechanism to thin the continen-
152 (Larsen and Saunders, 1998) drilled a transect of holes
tal lithosphere at magma-poor margins. Nature 440:324-328.
across the southeast Greenland SDR from the middle shelf Manatschal, G. and D. Bernoulli. 1998. Rifting and early evolution of
to deep water. They distinguished continental and oceanic ancient ocean basins: The record of the Mesozoic Tethys and of
flow sequences and located the seaward extent of rifted the Galicia-Newfoundland Margins. Marine Geophysical Research
continental crust. They showed that the SDR overlies fully 20(4):371-381.
Peron-Pinvidic, G. and G. Manatschal. 2009. The final rifting evolution at
oceanic crust and that it formed in the manner of the present-
deep magma-poor passive margins from Iberia-Newfoundland: A new
day Iceland rift zone. They were able to infer features of the point of view. International Journal of Earth Sciences 98(7):1581-1597.
plume associated with the formation of the margin. ODP Leg Peron-Pinvidic, G., G. Manatschal, T.A. Minshull, and D.S. Sawyer.
163 (Larsen and Duncan, 1996) was not able to achieve its 2007. Tectonosedimentary evolution of the deep Iberia-Newfound-
primary tectonic objectives because of “a drilling accident land margins: Evidence for a complex breakup history. Tectonics
26(TC2011):1-19.
and damage to the ship sustained during extreme storm con-
Reston, T.J. 2009. The extension discrepancy and syn-rift subsidence deficit
ditions” (Initial reports 163). During this period of drilling, at rifted margins. Petroleum Geoscience 15(3):217-237.
1976 to 1995, and complementary seismic, geological, and Roberts, D.G., J. Backman, A.C. Morton, J.W. Murray, and J.B. Keene.
modeling studies, the understanding of magma-dominated 1984. Evolution of volcanic rifted margins: Synthesis of Leg 81 results
continental breakup moved forward, as did our conception on the West Margin of Rockall Plateau. In Initial Reports of the Deep
Sea Drilling Project, Volume 81, Roberts D.G., D. Schnitker, et al.
about the global extent and importance of these margins
(Eds.). Deep Sea Drilling Project, U.S. Government Printing Office,
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Future opportunities in the study of continental breakup Sibuet, J.C. and W.B.F. Ryan. 1979. Site 398: Evolution of the West Iberian
will depend not just on access to ocean drilling, but also Passive Continental Margin in the framework of the early evolution of
on coordinated high-quality, two- and three-dimensional the North Atlantic Ocean. In Initial Reports of the Deep Sea Drilling
Project, Volume 47, Part II, Sibuet, J.C., W.B.F. Ryan, et al. (Eds.). Deep
multichannel seismic reflection profiling and companion
Sea Drilling Project, U.S. Government Printing Office, Washington, DC.
long-offset seismic surveys. The INVEST report mentions Talwani, M. and G. Udintsev. 1976. Tectonic synthesis. In Initial Reports
several times the need for increased collaboration with of the Deep Sea Drilling Project, Volume 38. Deep Sea Drilling Project,
industry. The study of continental breakup is one of the most U.S. Government Printing Office, Washington, DC.
obvious and important touch points between academic and Tucholke, B.E. and J.C. Sibuet. 2007. Leg 210 synthesis: Tectonic, mag-
matic, and sedimentary evolution of the Newfoundland-Iberia rift. In
industry science.
Proceedings of the Ocean Drilling Program, Scientific Results, Volume
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