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Guyot Science 2005
Department of Geosciences, Princeton University
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Guyot Science 2005
A Summary of the Research Progress and Accomplishments
Made by the Faculty Members of the
Department of Geosciences During the Year 2005
Last year, January–December 2005, was a transitional year for a number of faculty members of the Princeton Department
of Geosciences. In June Bob Phinney transferred to emeritus status, following a distinguished career as a professor and former department chair. We are pleased that Bob has agreed to remain at Princeton, and plans to continue to teach his popular
freshman seminar, Active Geological Processes, which has long been an attraction for prospective departmental majors. In July
Satish Myneni was promoted to the rank of associate professor with continuing tenure. Two professors were named to endowed chairs: George Philander is now the Knox Taylor Professor of Geosciences and Bess Ward is now the William J. Sinclair
Professor of Geosciences. In April, George was inducted into the National Academy of Sciences, raising the departmental
membership to four. Nadine McQuarrie, a structural geologist who studies mountain building and other active tectonic
processes, completed her first highly successful year as our newest assistant professor. Next year, we will be joined by two new
assistant professors, Adam Maloof, a geologist who applies paleomagnetism and other tools to the study of the ancient earth,
and Frederik Simons, a geophysicist who is developing a variety of innovative new tools to study the structure and evolution
of planetary lithospheres as well as pioneering in the development of a freely drifting submersible vehicle to increase teleseismic coverage in the world’s oceans. In December, François Morel was awarded the Maurice Ewing Medal of the American
Geophysical Union and the U.S. Navy, “for his leadership in the revolution in low-temperature aqueous geochemistry that has
resulted in a new field of studies at the interface between marine chemistry and biology.” Finally, Allan Rubin was inducted as
a Fellow of the American Geophysical Union; this is a prestigious honor restricted to no more than 0.1 percent of the membership each year. More than half of the faculty members in the Department of Geosciences are now Fellows of the AGU. The
recent research accomplishments of each member of the geosciences faculty are described in the individual reports that follow.
A list of faculty publications during the past two years, 2004-2005, is appended to each narrative report.
Back Row: Rob Hargraves (deceased), Satish Myneni, Greg van der Vink, Guust Nolet, Tony
Dahlen, Jorge Sarmiento, John Suppe. Middle Row: Bob Phinney (emeritus), Lincoln Hollister,
Peter Bunge, Ken Deffeyes (emeritus), François Morel, Michael Bender, Nadine McQuarrie, Bess
Ward, Tullis Onstott. Front Row: Jason Morgan (emeritus), Tom Duffy, Franklyn van Houten
(emeritus), Gerta Keller, George Philander, Bill Bonini (emeritus), Allan Rubin. Photo by Pryde
Brown, with additions by Laurie Wanat.
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gases in ice cores, and of dissolved gases in seawater. We also
made a modest beginning on 2 new programs of ice core
research. Here are some specfic accomplishments.
Michael Bender
Professor
Ph.D., 1970, Columbia University
email: [email protected]
1. We prepared for publication papers on the meridional
gradient of O2 in air and its implications for the ocean carbon cycle, on the concentration and isotopic composition of
O2 in Southern Ocean surface waters and their implications
for the fertility of these waters, and on technical aspects of
deriving a timescale climate records in slowly accumulating
ice in East Antarctica. These papers are now either accepted
or in revision. We also worked on several other manuscripts
that are now in review.
2. Jan Kaiser participated in 2 cruises of the “Atlantic
Meridional Transect” program and made measurements that
strongly contradict the hypothesis that shallow, nutrient-poor
ocean waters are chronically net heterotrophic (i. e., that
respiration exceeds photosynthesis).
The activities of my laboratory focus on studies of the
geochemistry of O2, with applications to understanding the
global carbon cycle and glacial-interglacial climate change.
The geochemical properties we study are the concentration
of O2 in air (which we measure to very high precision), and
the relative abundance of the three stable O isotopes (16O,
17
O, and 18O) in O2. There are two subjects for the isotopic
studies: O2 in fossil air extracted from ice cores, and dissolved O2 in seawater.
The results inform us about a range of topics. Studies of
the O2 concentration (or ratio of O2/N2) in air constrain the
fate of fossil fuel CO2 that does not remain in the atmosphere. These measurements allow us to partition the “missing” CO2 between the oceans and the land biosphere. They
also constrain rates of seasonal biological production by the
oceans. Finally, they provide a test of models describing the
global interaction of ocean circulation and biogeochemistry.
The isotopic measurements of O2 in ice core trapped
gases reflect the relative fertility of Earth’s biosphere, averaged
over about 1,000 years. The triple isotope composition of O2
in seawater reflects the fraction of dissolved O2 from photosynthesis. O2 supersaturation reflects net production (photosynthesis in excess of respiration); by combining measurements of O2 concentrations and isotopes, we can determine
rates of photosynthesis, respiration, and net production in
aquatic ecosystems. Of course rate determinations of these
processes in seawater have been made for many years; what
makes our work new is that our approach does not require
labor-intensive bottle incubations at sea, and our measurements can be made on large numbers of samples collected by
colleagues on cruises of opportunity, and returned to the lab.
Supplementing the O2 studies are studies of Ar. In seawater samples, Ar gives a measure of physical supersaturation
due to warming of waters and bubble entrainment. In air
samples, the Ar/N2 ratio reflects seasonal outgassing and
ingassing due to temperature-driven solubility changes, and
also to atmospheric mixing.
3. We began measurements in a collaboration with David
Marchant, Boston University, to study ice of apparently great
antiquity in the Dry Valleys, Antarctica. This ice underlies
volcanic ash deposits dated as old as 10,000,000 years. The
evidence suggests that the ice is older than the overlying
ash, but this conclusion is highly controversial. If proved, it
would allow us to measure the concentrations of greenhouse
gases in bubbles of air trapped in the ice, and determine the
carbon dioxide concentration of the atmosphere at times
when Earth was much warmer than at present. We showed
that the gases in the bubbles are original samples of trapped
air, and we are currently developing isotopic methods for dating the ice.
4. We began a collaboration with Lonnie Thompson,
Ohio State University, to date climate records of ice cores he
has collected from tropical and temperate regions. To date
our results confirmed the relatively recent age of the deep
part of one core (ruling out the possibility that the bottom of
this core might date back to the last ice age).
Two-Year Bibliography
Refereed articles:
Hendricks, Melissa B., Michael L. Bender and Bruce A. Barnett
Net and gross O2 production in the southern ocean from
measurements of biological O2 saturation and its triple
isotope composition, Deep-Sea Research Part I, 51, 15411561, 2004.
Brook, E. J., J. W. C. White, Annie S. M. Schilla, Michael L.
Bender, Bruce Barnett, Jeffery P. Severinghaus, Kedrick C.
Taylor, Richard B. Alley, Eric J. Steig Timing of millennialscale change at Siple Dome, West Antarctica, during the last
glacial period, Quaternary Science Reviews, 24, 1333-1343,
2005.
Bender, M. L., D. T. Ho, M. B. Hendricks, R Mika, M. O. Battle, P.
P. Tans, T. J. Conway, B. Sturtevant, and N. Cassar Atmospheric O2/N2 changes, 1993–2002: Implications for the
partitioning of fossil fuel CO2 sequestration, Global Biogeochemical Cycles, 19, GB4017, doi:10.1029/2004GB002410,
2005.
Hendricks, Melissa B., Michael L. Bender, Bruce A. Barnett,
Peter Strutton, and Francisco Chavez The triple oxygen
isotope composition of dissolved O2 in the equatorial Pacific:
a tracer of mixing and biological production, Journal of
Highlights of our research during the past year:
Our primary focus was on preparing papers for publication
and writing proposals for research funding. We continued
our measurements of the O2/N2/Ar ratio of air, of trapped
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Geophysical Research - Oceans, 110, C12021, doi:10.1029/
2004JC002735, 2005.
Kaiser, Jan, Matthew K. Reuer, Bruce Barnett, and Michael L.
Bender, Marine productivity estimates from continuous
oxygen/argon ratio measurements by shipboard membrane
inlet mass spectrometry, Geophysical Research Letters,32,
L19605, doi:10.1029/2005GL023459, 2005.
Suwa, Makoto, Josepth C. von Fischer, Michael L. Bender,
Amaelle Landais, and Edward J. Brook Chronology reconstruction for the disturbed bottom section of the GISP2 and
the GRIP ice cores: implications for Termination II in Greenland, Journal of Geophysical Research - Atmospheres, in
press. 2005.
Bender, M. L., G. Floch, J. Chappellaz, M. Suwa, J._M. Barnola,
T. Blunier, G. Dreyfus, J. Jouzel, and F. Parrenin Gas age-ice
age differences and the chronology of the Vostok ice core,
0-100 ka, Journal of Geophysical Research – Atmospheres
(in review), 2005.
Reuer, Matthew K., Bruce A. Barnett, Michael L. Bender, Paul
G. Falkowski, and Melissa B. Hendricks New estimates of
Southern Ocean biological production rates from O2/Ar ratios
and the triple isotope composition of O2, Deep Sea Research, in review, 2005.
Articles in press or submitted:
Battle, Mark, Sara Mikaloff Fletcher, Michael L. Bender, Ralph F.
Keeling, Andrew C. Manning, Nicolas Gruber, Pieter P. Tans,
Melissa B. Hendricks, David T. Ho, Caroline Simons, Robert
Mika, and Bill Paplawsky Atmospheric potential oxygen: New
Observations and their implications for some atmospheric
and oceanic models of the global oxygen and carbon dioxide
cycles, Global Biogeochemical Cycles, in press, 2005.
boundary beneath Cape Verde, Cook Island and Cape Verde.
This strong confirmation of the deep-mantle plumes seen in
Raffa’s earlier P
P-wave results is significant not only because
the raypath coverage differs, but also because the off-path
sensitivity of finite-frequency S waves differs from that of
P waves. Raffa left Princeton in September to begin a new
career as a research geophysicist for ExxonMobil in Houston.
Fourth-year graduate student Tarje Nissen-Meyer made
substantial progress during 2005 on his dissertation project,
to compute exact waveform and traveltime sensitivity kernels
in a background spherical earth model, using an axially symmetric spectral element method. Once the method is fully
developed, it will be capable of computing the response of a
spherical earth to a moment tensor or point force source up
to 1-Hz frequency, substantially better than can be achieved
with normal-mode summation codes. Individual 2-D codes
are required for the monopole, dipole and quadrupole components of the source. At the present time, these three source
types have been successfully implemented in the simple case
of an earth model lacking a fluid outer core. Preliminary
results have been submitted for publication as two back-toback papers Geophysical Journal International
International. The next steps
are to account for the core using a displacement potential
representation, to optimize the mesh for a realistic spherical
earth model such as PREM, and to parallelize the code for
implementation on a small cluster. This work is being conducted in collaboration with Alex Fournier, who defended
his Princeton Ph.D. dissertation in December 2003, and who
is now a member of the faculty at the University of Toulouse.
During the summer of 2005, I collaborated with Ying
Zhou, who is now a postdoctoral fellow working with Jeroen
Tromp at the Caltech Seismological Laboratory, to develop
finite-frequency Fréchet sensitivity kernels for surface-wave
group-delay and attenuation measurements. Quite unexpectedly, we found that a finite-frequency group delay exhibits
strong sensitivity to the local phase velocity perturbation
δc/c as well as to the local group-velocity perturbation δC/C.
This dual dependence makes the inversion of measured
surface-wave group delays for 2-D maps of δC/C a dubious
F. Anthony Dahlen
Department Chair
Professor
Ph.D., 1969, University of California, San Diego
email: [email protected]
In 2005 I continued my longstanding collaboration with
Guust Nolet and postdoctoral fellow Raffaella Montelli,
to account for finite-frequency wavefront healing effects
in global seismic traveltime tomography. Raffa and I spent
much of the summer repairing a minor error in our ray-theoretical crustal traveltime corrections. As expected, the repairs
led to only minor changes in her P
P-wave velocity images
(Science
Science 2004), and do not alter the important conclusion
Scienc
that there least six well-resolved plumes—Ascension, Azores,
Canary, Easter, Samoa and Tahiti—that originate in the
vicinity of the core-mantle boundary, as originally proposed
by Jason Morgan more than thirty years ago. All of the
observed plumes have a diameter of several hundred kilometers, indicating that plumes convey a substantial fraction of
the internal heat escaping from the earth. In a recent paper
submitted to the AGU electronic journal G3, Raffa has gone
on to invert SS-wave traveltimes using finite-frequency sensitivity kernels, in order to provide an independent check on
her very exciting P
P-wave results. In fact, her recently obtained
SS-wave images confirm the presence of the six well-resolved
deep-mantle plumes listed above, as well as the existence
of starting plumes that have not yet risen all the way to the
earth’s surface beneath the Coral Sea, east of Solomon and
south of Java, and plume conduits that are poorly resolved in
the P
P-wave tomography extending down to the core-mantle
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Ampuero, J.-P. & Dahlen, F. A., Ambiguity of the moment tensor,
Bull. Seismol. Soc. Amer., 95, 390-400, 2005.
Dahlen, F. A., Finite-frequency sensitivity kernels for boundary
topography perturbations, Geophys. J. Int., 162, 525-540,
2005.
Nolet, G., Dahlen, F. A. & Montelli, R., Travel times of seismic
waves: a reassessment, in Seismic Earth: Array Analysis
of Broadband Seismograms, edited by Levander, A. & Nolet,
G., Geophysical Monograph 157, American Geophysical
Union, Washington, D.C., pages 37-47, 2005.
Dahlen, F. A. & Nolet, G., Comment on ‘Onsensitivity kernels for
‘wave-equation’ transmission tomography’ by de Hoop and
van der Hilst, Geophys. J. Int., 163, 949-951, 2005.
Zhou, Y., Dahlen, F. A., Nolet, G. & Laske, G., Finite-frequency
effects in global surface-wave tomography, Geophys. J. Int.,
163, 1087-1111, 2005.
procedure, unless the lateral variations in group velocity are
extremely smooth.
Guust Nolet and I are both very excited about a recently
launched collaboration with Ingrid Daubechies in the Princeton mathematic department, to use wavelets and possibly
curvelets as a basis for finite-frequency tomographic inversions. We will be joined in this project by Huub Douma,
a new postdoctoral fellow, who recently received his Ph.D.
from the Colorado School of Mines.
Finally, in 2005, I was pleased to be able to continue my
collaboration with Frederik Simons, who is now a member of
the faculty at University College London, but who will join
the geosciences department as our newest assistant professor
in September 2006.
We extended our spherical generalization of the one-dimensional time-frequency multitapers of Slepian and Thomson to the case of a double polar cap, for application to the
so-called “polar gap” problem in satellite geodesy.
Articles in press or submitted:
Simons, F. J., Dahlen, F. A. & Weiczorek, M., Spatiospectral concentration on a sphere, SIAM Review, in press, 2005.
Zhou, Y., Nolet, G., Dahlen, F. A. & Laske, G., Global upper-mantle structure from finite-frequency surface-wave tomography,
J. Geophys. Res., in press, 2005.
Dahlen, F. A. & Zhou, Y., Surface-wave group-delay and attenuation kernels, Geophys. J. Int., in press, 2005.
Nissen-Meyer, T., Dahlen, F. A. & Fournier, A., Spherical-earth
Fréchet sensitivity kernels, Geophys. J. Int., submitted, 2005.
Nissen-Meyer, T., Fournier, A. & Dahlen, F. A., A 2-D spectralelement method for computing 3-D spherical-earth seismograms, Geophys. J. Int., submitted, 2005.
Montelli, R., Nolet, G., Dahlen, F. A. & Masters, G., A catalogue
of deep-mantle plumes: new results from finite-frequency
tomography, Geoshem., Geophys, Geosystems, submitted,
2005.
Montelli, R., Nolet, G. & Dahlen, F. A., 2005. Comment on ‘Banana-doughnut kernels and mantle tomography’ by van der
Hilst and de Hoop, Geophys. J. Int., submitted, 2005.
Simons, F. J. & Dahlen, F. A., Spherical Slepian functions and the
polar gap in geodesy, Geophys. J. Int., submitted, 2005.
Two-Year Bibliography
Refereed Articles:
Montelli, R., Nolet, G., Dahlen, F. A., Masters, G., Engdahl, E. R.
& Hung, S.-H., Finite-frequency tomography reveals a variety
of plumes in the mantle, Science, 303, 338-343, 2004.
Dahlen, F. A., Resolution limit of traveltime tomography, Geophys. J. Int., 157, 315-331, 2004.
Zhou, Y., Dahlen, F. A. & Nolet, G., 3-D sensitivity kernels for
surface-wave observables, Geophys. J. Int., 158, 142-168,
2004.
Baig, A. M. & Dahlen, F. A., Statistics of traveltimes and amplitudes of waves in random 3-D media, Geophys. J. Int., 158,
187-210, 2004.
Montelli, R., Nolet, G., Master, G., Dahlen, F. A. & Hung, S-H.,
Global P and PP traveltime tomography: rays versus waves,
Geophys. J. Int., 158, 637-654, 2004.
Baig, A. M. & Dahlen, F. A., Traveltime biases in random media
and the S-wave discrepancy, Geophys. J. Int., 158, 922-938,
2004.
temperature of the deep mantle. We are exploring crystal
structures, phase relations, elasticity, and other fundamental
properties at these ultra-high pressure conditions.
Experimental capabilities for studying materials at
planetary interior conditions are progressing rapidly. For
example, advances in synchrotron diffraction methods have
expanded the P-T range accessible to direct measurements all
the way up to 200 GPa and 3000 K, while at the same time
leading to improved resolution that has resulted in dramatically better ability to recover crystallographic details. In
combination with new geophysical observations of the Earth,
we can now better address such fundamental questions as
the origin of seismic discontinuities, chemical heterogeneity
in the mantle, and the nature of the core-mantle boundary
region.
Thomas S. Duffy
Associate Professor
Ph.D., 1992, California Institute
of Technology
email: [email protected]
My research program focuses on understanding the largescale physical and chemical behavior of Earth and other
planets through experimental study of geological materials
directly under extreme pressure and temperature conditions.
We are using the diamond anvil cell together with laser
heating and optical spectroscopy techniques at pressures and
Phase transitions and crystal structures of deep Earth
minerals
Phase transformation in CaSiO3 perovskite
Experimental studies have shown that the main rock types of
the Earth’s mantle (e.g. peridotite, basalt) transform under
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lower mantle conditions to assemblages dominated by minerals in the perovskite crystal structure. CaSiO3 perovskite is
an important phase because it is thought to be the repository
for many high-charge trace elements (including radioactive
elements). This phase was long thought to possess cubic
symmetry on the basis of many low-resolution x-ray diffraction experiments reported over ~20 years. We conducted
the first high-resolution diffraction study of this material at
20-50 GPa [Shim et al., 2002] and showed that the symmetry of CaSiO3 perovskite at room temperature after laser
heating is not cubic, but of lower symmetry, most likely
tetragonal. Our result is consistent with theoretical calculations using density functional theory (DFT) and more recent
experiments which suggest that the transformation from the
low-symmetry to cubic form may occur under certain mantle
conditions. Such a transition could be accompanied by
significant anomalies in elastic properties and may therefore
have relevance for interpretation of seismic profiles of the
mantle.
sistent with theoretical predictions. Upon decompression
without further heating, it was found that the post-perovskite
phase could still be observed at pressures as low at 12 GPa
and evidence for at least partial persistence to ambient conditions was also obtained.
We have recently carried out experiments using glass
starting materials with compositions along the MgSiO3Al2O3 join to investigate the effects of Al content on the
equation of state, transformation pressure, and stability
limits of the new phase (Kubo et al., in preparation). The
post-perovskite phase was synthesized for compositions with
0, 5, 15, and 20 mol. % corundum at maximum pressures
between 145-164 GPa. For the En85Co15 composition,
the perovskite to post-perovskite phase transformation was
found to occur at 130 GPa and 1800 K, which is higher by
~10 GPa than the transition pressure in Al-free samples. In
contract to earlier studies on pyrope compositions, our work
suggests the two-phase (perovskite + post-perovskite) stability
field is narrow, although analysis is complicated by the sluggish reaction kinetics. We also find that incorporation of Al
has only a negligibly small effect on the unit cell volume of
the post-perovskite phase in the 80-160 GPa pressure range.
Due to the extreme high pressures of the transition and
sluggish transformation rates, studies of the post-perovskite
phase of MgSiO3 are challenging. Germanates are known to
be excellent analogs for silicates as similar phase transitions
occur but at significantly lower pressures in germanates. We
have carried out a detailed set of synchrotron x-ray diffraction experiments on the post-perovskite phase of MgGeO3 in
which we have synthesized the phase, measured its equation
of state and refined the crystal structure (Rietveld method)
over broad pressure intervals. Our equation of state measurements span a range from 7-201 GPa and place new
constraints on the compressibility and structural anisotropy
of the new phase (Kubo
Kubo et al., 2005
2005). We could successfully
conduct Rietveld refinements at very high pressures using
data obtained between 80 and 110 GPa with both Ar and
NaCl pressure media, including high temperature (14001700 K) data at ~90 GPa. Our structure refinements provide
the first experimental constraints on the evolution of bond
distances and angles with compression, thereby providing
insight into the mechanisms by which the structure responds
to compression (Kubo et al., in preparation). The structural
response appears to be generally smooth over the pressure
range investigated. Average Mg-O and Ge-O bond lengths at
room temperature are consistent with those determined for
other germanates and silicates. It is also notable that trends
in structure parameters obtained by Rietveld refinement are
qualitatively consistent with results of our theoretical (DFT)
calculations. The temperature effect on average Mg-O bond
length is strong while average Ge-O bond length is less sensitive to temperature.
One of the most interesting properties of the D” region
is that it possesses strong (and variable) seismic anisotropy.
Interpretation of this anisotropy has been limited due to poor
constraints on the lattice preferred orientation of D” constituents such as the post-perovskite phase. In collaboration
Post-perovskite phase transition in silicates and germanates
The Earth’s core-mantle boundary region, 2900 km below
the surface, is highly complex and potentially holds the key
to a host of questions about the planet’s interior and evolution. Thus, the recent discovery of a post-perovskite phase
in MgSiO3 at 125 GPa, close to conditions expected for the
D” region has major potential implications for understanding geophysics of the deep mantle. We have been pursuing
a number of lines of research related to the post-perovskite
phase. We had previously demonstrated the stability of MgSiO3 perovskite to 108 GPa [Shim et al., 2001] and reported
evidence for a potential modification within the perovskite
structure. The existence of the post-perovskite phase was
later confirmed in MgSiO3 on the basis of angle-dispersive
diffraction at 144 GPa [Shim et al., 2004].
Besides the crystal structure, the equation of state (EOS)
is the most fundamental parameter obtained from high-pressure experiments. Using the laser-heated diamond anvil cell,
we have recently investigated the equation of state of coexisting perovskite and post-perovskite (CaIrO3-type) phases
synthesized from a natural pyroxene composition with Fe
content close to that expected for the lower mantle (Shieh et
al., 2005
2005). Our measured pressure-volume data for the postperovskite phase from 12-106 GPa yield a bulk modulus of
219(5) GPa and a zero-pressure volume of 164.9(6) Å3 when
K0’=4. The bulk modulus of post-perovskite is 575(15) GPa
at a pressure of 100 GPa. These results are broadly consistent with theoretical calculations and put limits on the effect
of Fe content on the bulk modulus. Our x-ray diffraction
data indicate the post-perovskite phase can be formed in this
composition at P-T conditions corresponding to ~400-550
km above the core-mantle boundary. Direct comparison of
volumes of coexisting perovskite and CaIrO3-type phases at
80-106 GPa demonstrates that the post-perovskite phase has
a smaller volume than perovskite by 1.1(2)%. Using measured volumes together with the bulk modulus calculated
from EOS fits, we find that the bulk sound velocity decreases
by 2.3(2.1)% across this transition at 120 GPa, again con7
with R. Wenk’s group at Berkeley, we have carried out the
first experimental deformation study of the post-perovskite
phase (of MgGeO3 composition) in the diamond anvil cell at
104-130 GPa and ambient temperature (Merkel
Merkel et al., 2005
2005).
Previous phenomenological considerations had suggested
that (010) or (001) may be the dominant slip planes, based
on either the nature of layering in the structure or comparison of theoretical elastic constants with seismic constraints.
However, our results showed that slip on (100) or (110)
planes dominated plastic deformation, in good agreement
with a recent independent theoretical study which found that
(110) slip could produce a series of polytype structures intermediate between perovskite and post-perovskite. With the
assumption that silicate post-perovskite behaves similarly at
lower mantle conditions, a quantitative model of this phase’s
contribution to seismic anisotropy in D” was constructed.
Studies of the post-perovskite phase remain challenging and
there are many unanswered questions that will be a focus
for future research. Our equation of state studies will be
extended to more complex compositions and new analytical
techniques for examining the quenched samples are being
adopted. Plastic deformation studies will soon be extended
to silicate compositions.
diamond anvil cell using finite element calculations (Kiefer
and Duffy, 2005
2005). We carried out simulations using a
realistic experimental geometry (including insulation layers
between the diamonds and sample) to investigate the factors
controlling development of axial and radial thermal gradients for optically thin samples. The two key parameters for
controlling the axial thermal gradient are the ratio of sample
to insulator thermal conductivity and the ratio of the sample
thickness to total gap between the diamonds. We also systematically quantified the magnitude of the axial temperature
gradients as these parameters are varied. On-going work
is focused on simulating more closely the actual complex
sample geometries that are used in practice for both CO2
and Nd:YLF laser heating. For example, we have simulated
single- and double-sided hot plate geometries, single- and
double-sided heating of metallic samples and the micro-furnance geometry. We have also systematically investigated
the effects of different laser modes. The results in some cases
confirm preconceptions, but in several cases rather surprising results are obtained. These calculations promise to yield
insights that will lead to improved experimental designs to
yield more homogeneous pressure-temperature conditions in
the sample.
Phase transitions in SnO2 to megabar pressures
There are many other systems with potentially interesting
phase relations in the Mbar regime to be explored. As one
example, the metal dioxides exhibit extensive polymorphism
at high pressures, and a variety of transformation pathways
leading to highly coordinated structures have been uncovered. Some high-pressure polymorphs in these systems have
very high bulk moduli and may qualify as strong or even
superhard solids. Many of these phases have been investigated as analogs for SiO2 as they exhibit similar sequences of
transitions but at lower pressures compared with silica. Our
high-pressure and high-temperature x-ray diffraction study
of SnO2 demonstrates the existence of four phase transitions
during compression to 117 GPa. The observed sequence of
high-pressure phases for SnO2 is rutile-type ((P4
P42/mnm) →
CaCl2-type (Pnnm) → pyrite-type (
) → ZrO2 orthorhombic phase I (Pbca) → cotunnite-type (Pnam). The
latter two phases were observed here for the first time in this
system. The bulk moduli for the Pbca (259 GPa) and Pnam
(417 GPa) phases of SnO2 determined by fitting pressurevolume data to the second-order Birch-Murnaghan equation of state indicate these high-pressure phases are highly
incompressible – although the potential role of deviatoric
stress still needs better characterization. Rietveld refinements
of powder diffraction patterns for both phases have been
successfully carried out. Our static high-pressure results also
enable us to provide an interpretation for previous shock
compression data that show evidence for two discontinuities
along the Hugoniot curve. Our results indicate that the first
transformation may be associated with the formation of the
Pbca phase whereas the second transformation is consistent
with the cotunnite-type phase.
Elastic properties of minerals and structure of the mantle
The elastic tenor is fundamental to a range of solid-state
phenomena including elastic wave propagation, mechanical
stability, interatomic interactions, material strength, equation
of state, and phase transition mechanisms. The single-crystal
elastic properties of minerals are essential for interpretation
of the seismic velocity structure of the Earth’s mantle. Despite this importance, the elastic properties of many mantle
minerals are poorly constrained, particularly for low-symmetry species at elevated pressures. Brillouin scattering is a
method whereby one can measure the complete elastic tensor
by recording the frequency shift induced in scattered laser
light by thermally generated sound waves. We are using this
technique in the diamond anvil cell to investigate the singlecrystal elastic properties of a variety of minerals at pressures
corresponding to depths as great 1000 km.
Elasticity of olivines and garnets
The single-crystal elasticity of fayalite (Fe2SiO4) was measured to 12 GPa by Brillouin scattering at ambient temperature (Speziale et al., 2004), more than an order of magnitude
higher pressure than previous investigations. Fayalite is
challenging because it is Fe-rich, of low symmetry (orthorhombic), and good crystals are rare. Nevertheless, we could
recover the 9 elastic stiffness moduli as well as crystal orientation information by an extensive measurement program
using several natural crystals. Our results demonstrate
unequivocally that the bulk modulus of olivine increases with
iron content, and this effect is enhanced by the application of
pressure. The shear constants C44 and C55 show non-linear
pressure dependence at P>5 GPa, and this leads to non-linear
behavior in the aggregate shear modulus as well. The softening of C44 is comparable to the behavior observed in Mg-rich
olivines, but softening of C55 is much stronger in the Fe-rich
composition. This shear softening of high-pressure meta-
Finite element simulations of the laser-heated diamond cell
We have examined the thermal structure of the laser-heated
8
stable fayalite is likely connected to the previously observed
pressure-induced amorphization above 35 GPa.
We have also carried out single-crystal elasticity studies
of three natural garnets (grossular, almandine-pyrope, and
andradite) to above 11 GPa ((Jiang et al., 2004a; Jiang et al.,
2004b). Garnets are major constituents of the Earth’s upper
mantle. They have high symmetry and exhibit a great deal
of compositional variability, making them an ideal testing
ground for our understanding of elasticity variations in mineral systems. In combination with other Brillouin scattering
data for pyrope, our results allow us to constrain the effect
of Fe-Mg substitution on the dodecahedral site in pyropealmandine and Fe-Al substitution on the octahedral site in
andradite-grossular at high pressures. This was not possible
previously due to systematic differences between results at
high pressures from different experimental techniques. Brillouin scattering measurements (at ambient or high pressures)
and pressure-volume equation of state data were shown to
be a powerful combination for evaluating the reliability and
potential pitfalls of static compression measurements (e.g.
deviatoric stress effects, parameter tradeoffs).
Global seismological and geodynamic models require an
assessment of not only thermal effects on seismic velocities
but also compositional effects. Our new elasticity measurements together with selected values from the literature have
allowed us to comprehensively evaluate the sensitivity of
seismic velocity to composition, pressure, and temperature
for major upper mantle minerals (Speziale
Speziale et al., 2005
2005).
Logarithmic compressional and shear velocity variations with
respect to iron content are most strongly sensitive to crystal
structure but pressure and temperature effects may also be
important at upper mantle conditions. As one example of
the findings from this study, the very different responses of
olivines and garnets to iron substitution gives rise to significant variations in the sensitivity of different rock types to
iron concentration in accordance with their garnet content.
Velocities in mid-ocean ridge basalts are thus much less affected by variations in iron content than other rock types
such as harzburgite. These differences need to be accounted
for in evaluating the effects of Fe variability on seismic velocity heterogeneity.
longitudinal moduli, C11/C33, decreases from 3.3 at ambient
pressure to 1.2 at 15 GPa.
The epidote family is a group of hydrous Ca-Al silicates
that may be important water carriers in cold subducting
slabs. In general, little is known about the elastic properties
of Ca-Al silicates. Our measurements of the elastic tensor
of the epidote-member zoisite at ambient pressure (Mao et
al., in preparation) place the first experimental constraint on
zoisite’s shear modulus and resolve discrepancies in the bulk
modulus from static compression experiments.
In addition to continued characterization of single-crystal elastic properties of important mantle phases and their
variation with chemistry and structure, we are also focusing
future efforts on examining elastic anomalies associated with
high-pressure phase transitions. Over the longer term, we
plan to develop equipment for carrying out Brillouin scattering at simultaneous high pressures and temperatures, and
to extend measurements to higher pressures, particularly for
polycrystalline samples.
Yield strength at high pressures
The yield strength of materials at high pressure is a fundamental property that has not yet been well characterized.
Static strength determination is a preliminary step toward
eventual characterization of the complete flow laws that
govern rheological properties at high pressure or deep Earth
conditions. Among the basic questions are how pressure affects yield strength, how relative strengths of different classes
of materials compare at ~1 Mbar, and whether theoretically
predicted strength inversions (e.g. strengths of rare gas solids
exceeding those of metals) can occur at ultrahigh pressures.
Knowledge of strength properties is also important for optimizing the design and performance of high-pressure apparatus. Quantitative evaluation of differential stresses developed
under various pressure-transmitting media is one example in
this regard. Elasticity and strength are interconnected properties that play a mutual role in several basic areas of highpressure science such as development of accurate pressure
calibration. Interest in strength properties is also driven by
several themes in current materials research including theoretical determinations of ideal shear strength, the connection
between strength and particle size in the nano-crystalline
realm, and the search for new super hard solids.
In the radial x-ray diffraction technique, a sample is
compressed in a diamond cell under intentionally non-hydrostatic conditions and the lattice strain is measured as a
function of angle from the loading axis using synchrotron
x-rays. Such studies can constrain yield strength and provide
insights into other properties including elastic moduli, equation of state, and texture development to very high pressures.
In ongoing research over the last seven years, we have used
this method to characterize the strength of a suite of metals, oxides, silicates, and nitrides. Our recent studies have
included: tungsten (He
He and Duffy, 2005
2005), platinum (Kavner
and Duffy, 2003); MgGeO3 post-perovskite (Merkel et al.,
2005), SiO2 (Shieh
2005
Shieh et al., 2002
2002), CaSiO3 (perovskite) (Shieh
et al., 2004
2004), CaO (Speziale et al., 2005), B6O (He and Duffy,
2004), and cubic-Si3N4 (Kiefer et al., 2005). In general,
Elasticity of hydrous minerals
The elastic properties of subduction zone minerals are
necessary for understanding basic features of the subduction
factory including the existence and distribution of hydrous
phases and the effect on seismic wavespeeds of thermal and
metamorphic processes. Modeling of seismic velocities in
subduction zones is greatly limited by lack of constraints on
the elastic properties of the metamorphic phases expected to
exist there. We have begun to address this problem by measuring the elastic tensors (at ambient and high pressures) of a
suite of hydrous minerals including brucite, diaspore, alunite,
and zoisite. The elasticity of brucite has been measured to 14
GPa ((Jiang
Jiang et al., 2005
2005).
). Brucite shows highly anomalous
elastic properties including the largest shear modulus pressure derivative (Gʹ=3.6) yet measured. The elastic anisotropy
of brucite changes strongly with pressure. The ratio of the
9
He, D. W. and T. S. Duffy, Equation of state and strength of
boron suboxide from radial x-ray diffraction in a diamond cell
under nonhydrostatic compression, Physical Review B, 70,
184121, 2004.
Jiang, F., S. Speziale, and T. S. Duffy, Single-crystal elasticity of
grossular- and almandine-rich garnets to 11 GPa, Journal of
Geophysical Research, 109, B10201, 2004.
Shieh, S. R., T. S. Duffy, and G. Shen, Elasticity and strength of
calcium silicate perovskite at lower mantle pressures, Physics of the Earth and Planetary Interiors, 143 144, 93-106,
2004.
Shim, S.-H., T. S. Duffy, R. Jeanloz and G. Shen, Stability and
crystal structure of MgSiO3 perovskite to the core-mantle
boundary, Geophysical Research Letters, L10603, 2004.
Yin, H. Z., K. D. Hobart, F. J. Kub, S. R. Shieh, T. S. Duffy, J. C.
Sturm, High-Ge content SiGe islands formed on compliant
oxide by SiGe oxidation, Applied Physics Letters, 84, 36243626, 2004.
Shim, S.-H., T. S. Duffy, R. Jeanloz, C.-S. Yoo, and V. Iota, Raman spectroscopy and x-ray diffraction of phase transitions
in Cr2O3 to 61 GPa, Physical Review B, 69,144107, 2004.
Jiang, F., S. Speziale, S. R. Shieh, and T. S. Duffy, Single-crystal
elasticity of andradite garnet to 11 GPa, Journal of Physics:
Condensed Matter
Matter, 16, S1041-S1052, 2004.
Speziale, S., F. Jiang, and T. S. Duffy, Compositional dependence of the elastic wave velocities of mantle minerals:
Implications for seismic properties of mantle rocks, Structure,
Composition, and Evolution of Earth’s Mantle, edited by R.
van der Hilst, J. D. Bass, J. Matas, and J. Trampert, AGU,
Washington, DC, 303-323, 2005.
Duffy, T. S., Synchrotron facilities and the study of deep planetary interiors, Reports of Progress in Physics, 68, 1811-1859,
2005.
Yin, H., K. D. Hoburt, R. L. Peterson, S. R. Shieh, T. S. Duffy, J.
C. Sturm, Tunable uniaxial vs biaxial in-plain strain in integrated silicon and silicon-germanium thin films using compliant substrates, Applied Physics Letters, 87, 061922, 2005.
Kiefer, B., S. R. Shieh, T. S. Duffy, and T. Sekine, Strength, elasticity, and equation of state of nanocrystalline cubic silicon
nitride (c-Si3N4) to 68 GPa, Physical Review B, 014102,
2005.
Shieh, S. R., T. S. Duffy, and G. Shen, X-ray diffraction study
of phase stability in SiO2 at deep lower mantle conditions,
Earth and Planetary Science Letters, 235, 273-282, 2005.
Kiefer, B. and T. S. Duffy, Finite element simulations of the laserheated diamond anvil cell, Journal of Applied Physics, 97,
114902, 2005.
strength increases with compression at a rate greater than
the shear modulus, implying significant strain hardening
under diamond cell loading conditions. At pressures of 20-80
GPa, metals typically exhibit strengths of 1-3% of the shear
modulus, G. For silicates, six-coordinated silicates exhibit
lower strengths relative to their shear modulus (2-4% G)
G
compared with four-coordinated silicates (4-7% G
G). Strong
covalent oxides, silicates, and nitrides such as ringwoodite,
boron suboxide, and spinel-structured silicon nitride possess
yield strengths that can approach 10% of the shear modulus.
The maximum strength value we have measured is 28 GPa
for B6O at 65 GPa confining pressure. The general increase
in strength with pressure for all material classes implies that
most materials are “strong” at megabar pressures if one recognizes that the strength of high-grade steel at ambient pressure
is ~2 GPa. Furthermore, the consistency of general strength
trends across material classes suggests that reasonable empirical predictions of strength in the multimegabar pressure
regime can now be made, and this is borne out by our recent
data on tungsten metal.
Combination of radial x-ray diffraction and Brillouin
scattering at high pressures is a potentially powerful technique for constraining mechanical properties at high pressures. We carried out a study of calcium oxide, CaO, by both
Brillouin scattering (to 23 GPa) and by radial nonhydrostatic
x-ray diffraction (to 65 GPa) (Speziale
Speziale et al., 2005
2005). Calcium oxide supports a low differential stress of ~1% of the
shear modulus (<2 GPa at high pressures). The Brillouin
results show a softening of C44 and consequent increase in the
elastic anisotropy in qualitative agreement with theoretical
predictions. Over the common pressure range, Brillouin and
radial diffraction data yield results in very good agreement
for the elastic tensor. However, the radial diffraction data
diverge from the extrapolation of Brillouin results at higher
pressures, perhaps related to the onset of plasticity or modification to stress/strain continuity relationships.
There are a number of directions for future developments in this area. Additional measurements are needed for
both the softest and hardest materials; the former to better
quantify stress states actually achieved in experiments, and
the latter to better characterize the properties of ultrahard
solids. On the technical side, advances in diamond cell
technology will be pursued to improve the capabilities of the
diamond cell as a deformation device with the goal toward
eventual direct examination of rheological properties at very
high P-T conditions.
Other miscellaneous publication:
Duffy, T. S., Deeper understanding, Nature, 430, 409-410, 2004.
Rubie, D. C., T. S. Duffy, and E. Ohtani, New developments in
high-pressure mineral physics and applications to the Earth’s
interior, introduction to special issue, Physics of the Earth
and Planetary Interiors, 143-144, 1-3, 2004.
Yin, H., K. D. Hobart, S. R. Shieh, R. L. Peterson, T. S. Duffy,
and J. C. Sturm, Interference-enhanced Raman Scattering
in Strain Characterization of Ultra-thin Strained SiGe and Si
Films on Insulator, in High-Mobility Group-IV Materials and
Devices, edited by M. Caymax, E. Kasper, S. Zaima, K. Rim,
and P. F. P. Fichtner, Materials Research Society, Warrendale, Pa, vol. 809, pp. B3.6.1-B.3.6.3, 2004.
Two-Year Bibliography
Books:
Rubie, D. C., T. S. Duffy, and E. Ohtani, editors, New Developments in High-Pressure Mineral Physics and Applications to
the Earth’s Interior, Elsevier, Amsterdam, pp. 625, 2004.
Chen, J., Y. Wang, T. S. Duffy, G. Shen, and L. Dobrzhinetskaya,
Advances in High Pressure Technology for Geophysical Applications, Elsevier, Amsterdam, pp. 512, 2005.
Articles in press or submitted:
Jiang, F., S. Speziale, and T. S. Duffy, Single-crystal elasticity of
brucite, Mg(OH)2, to 14 GPa by Brillouin scattering, Physical
Review B, submitted, 2005.
7He, D. W., and T. S. Duffy, Static strength of tungsten to 69
GPa, Physical Review B, submitted, 2005.
Refereed articles:
Speziale, S., T. S. Duffy, and R. J. Angel, Single-crystal elasticity
of fayalite to 12 GPa, Journal of Geophysical Research, 109,
B10201, 2004.
10
Merkel, S., A. Kubo, L. Miyagi, S. Speziale, H.-k. Mao, T. S.
Duffy, and H.-R. Wenk, Plastic deformation of MgGeO¬3
post-perovskite at lower mantle pressures, Science, in press,
2005.
Shieh, S. R., A. Kubo, T. S. Duffy, V. B. Prakapenka, and G.
Shen, High-pressure phases in SnO2 to 117 GPa, Physical
Review B, in press, 2005.
Shieh, S. R., T. S. Duffy, A. Kubo, G. Shen, V. B. Prakapenka, N.
Sata, K. Hirose, and Y. Ohishi, Equation of state of the postperovskite phase synthesized from a natural (Mg,Fe)SiO3
orthopyroxene, Proceedings of the National Academy of
Sciences, in press, 2005.
Speziale, S., S. R. Shieh, and T. S. Duffy, High-pressure elasticity of calcium oxide: A comparison between Brillouin scattering and radial x-ray diffraction, Journal of Geophysical
Research, in press, 2005.
Kubo, A., B. Kiefer, G. Shen, V. Prakapenka, R. J. Cava, and T.
S. Duffy, Stability and equation of state of MgGeO¬3 postperovskite phase to 2 Mbar, Geophysical Research Letters,
submitted, 2006.
Bhutan. With my colleague Djordje Grujic at Dalhausie
University, we have defined a process in mountain building,
based on our studies in Bhutan. This process involves the
rapid extrusion of a low viscosity, partially melted orogenic
channel from lower crustal depths. It was published in 2002.
In 2005 we completed an article on pulsed channel flow in
Bhutan. This rationalizes seemingly contradictory field data
to the theoretically based channel flow model of Beaumont
and others.
I have helped recruit Bhutanese students to study geology in USA. Two recently received MS degrees at UTEP, and
one of these, Tobgay Tobgay, is expected to come to Princeton for a Ph.D.
Lincoln S. Hollister
Professor
Ph.D., 1966, California Institute
of Technology
email: [email protected]
Lamellar magnetism. Following up on our hypothesis
(Hollister, et al, 2004) that reheating of ilmenohematite
may explain anomalous remanent magnetization in rocks
along the west coast of North America, I am collaborating
on a NSF proposal funded through UC Berkeley to test the
hypothesis. The graduate student working on the project
is one of our former undergraduate students. We may be
headed for a solution to the Baja British Columbia controversy, which holds that parts of western Canada traveled from
latitudes corresponding to Baja California during the latest
Cretaceous.
How are mountains and continental crust made? These
are the major questions driving my research and teaching.
I interpret the pressure-temperature-time-strain history of
rocks in the context of the tectonic processes operating on
the continental crust. My contributions are based on direct
observation of the products of mountain building. I have
forged collaborations with people in other disciplines and
work in an interdisciplinary mode where the objective is to
achieve results unattainable by individual investigators. I
also help students learn how to use field observations in the
construction of hypotheses, and for eliminating alternatives.
My research is on three fronts: the origin of the Coast
Mountains of British Columbia, the origin of the Himalayas
in Bhutan, and the application of lamellar magnetism for
resolving the Baja British Columbia controversy.
Two-Year Bibliography
Refereed articles:
Hollister, L. S., R. B. Hargraves, T. S. James, and P. R. Renne,
The paleomagnetic effects of reheating the Ecstall pluton,
British Columbia. Earth and Planetary Science Letters v.
221, 397 407, 2004.
Batholiths. My biggest research commitment for the next
few years is the new multidisciplinary collaboration, called
BATHOLITHS, which proposes to resolve the continental
crust composition paradox: although continental crust begins
as accreted island arcs the average composition of continental
crusts is more silicic than that of island arcs. Before becoming stable continental crust, the original island arc composition is modified by processes that are not understood. This
is a fundamental problem in the earth sciences. The disciplines of BATHOLITHS include active and passive source
seismology, geochemistry, structural geology, and petrology.
Most of these endeavors are underway, but the active source
seismology experiment has been delayed due to ship scheduling problems and to complexities in obtaining Canadian
environmental permits. For information on the permitting
process, see http://www.eos.ubc.ca/research/batholiths/
Other miscellaneous publications:
Clowes, R.M., L.S. Hollister, G.Woodsworth, BATHOLITHS:
How the Coast Mountains of British Columbia Formed. Informational Brochure for EA and Outreach. 16pp. http://www.
eos.ubc.ca/research/batholiths/, 2005.
Clowes, R.M., L.S. Hollister, G. Woodsworth, Batholiths: learning how the Coast mountains of British Columbia formed.
Informational sheet; 2 pp. http://www.eos.ubc.ca/research/
batholiths/, 2005.
Articles in press or submitted:
Hollister, L.S. & D. Grujic,, in press, Pulsed Channel Flow in
Bhutan. Geological Society of London Special Publication on Channel Flow, Ductile Extrusion and Exhumation of
Lower-mid Crust in Continental Collision Zones.
Hollister, L.S., J. Diebold, T. Das, in revision, Whole crustal response to Late Tertiary extension near Prince Rupert, British
Columbia. Canadian J. Earth Sciences.
11
Two-Year Bibliography
Gerta Keller
Refereed articles:
Keller, G., Paleoecology of Late Maastrichtian-early Danian
planktic foraminifera in the eastern Tethys (Israel and Egypt).
J. Foram. Res., 34(1): 49-73, 2004.
Keller, G. and Pardo, A., Paleoecology of the CenomanianTuronian Stratotype Section (GSSP) at Pueblo, Colorado.
Marine Micropleontology, 51: 95-128, 2004.
Keller, G., Stueben, D., Berner, Z. and Adatte, T., CenomanianTuronian δ13C, δ18O, sea-level and salinity variations at
Pueblo, Colorado. Paleoclimatol. Paleoecol. Paleogeogr.,
211, 19-43, 2004.
Keller, G., Adatte, T., Stinnesbeck, W., Rebolledo-Vieyra, M.,
Urrutia Fucugauchi, J., Kramar, U. and Stueben, D., Chicxulub crater predates K-T boundary mass extinction.PNAS,
101(11): 3721-3992, 2004.
Keller, G., Adatte, T., Stinnesbeck, W., More Evidence that
Chicxulub predates KTboundary. Meteoritics and Planetary
Science (MAPS), 39,(6/7), 1127-1144, 2004.
Wolfgang Stinnesbeck, Gerta Keller, Thierry Adatte,
Markus Harting, Doris Stüben, Georg Istrate and Utz Kramar: Yaxcopoil-1 and the Chicxulub impact. International
Journal of Earth Sciences, Volume 93, Number 6, pp. 1042
- 1065, 2004.
Keller, G. and Pardo, A., Disaster Opportunists Guembelitrinidae
– Index for Environmental Catastrophes. Marine Micropaleontology, 53, 83-116, 2004.
Adatte, T. Keller, G., Stueben, D., Harting, M., Kramar, U.,
Stinnesbeck, W., Abramovich, S. and Benjamini, C., Late
Maastrichtian and K/T paleoenvironment of the eastern Tethys (Israel): mineralogy, trace element and platinum group
elements, biostratigraphy and faunal turnovers. Bulletin
Société Géologique de France, 176, 1, 35-53, 2005.
Keller, G., Biotic effects of late Maastrichtian mantle plume
volcanism: implications for impacts and mass extinctions.
Lithos, 79, 317-341, 2005.
Keller, G. Impacts, volcanism and mass extinctions: random
coincidence or cause & effect? Australian Journal of Earth
Sciences, 52, 725-757, 2005.
Stueben, D., Harting, M., Kramar, U., Stinnesbeck, W., Keller,
G., and Adatte, T., High resolution geochemical record in
Mexico during the Cretaceous-Tertiary transition. Geochmica
et Cosmochimica Acta, 69, (10), 2559-2579, 2005.
Stinnesbeck, W., Ifrim, C., Schmidt, H., Rindfleisch, A., Buchy,
M-C., Frey, E., González-González, A.H., Vega, H.J., Cavin,
L., Keller, G. and Smith, K.T., 2005. A new lithographic limestone deposit in the Upper Cretaceous Austin Group at El
Rosario, County of Muzquiz, Coahuila, Northeastern Mexico.
Revista Mexicana Ciencias Geologicas, v. 22 (3), 401-418.
Professor
Ph.D., 1978, Stanford University
email: [email protected]
During the past two years the 15 year long research project on the Cretaceous-Tertiary boundary impact and mass
extinction has culminated in spectacular success with the
coming together of empirical evidence from sedimentology, stratigraphy, paleontology, mineralogy, geochemistry
and paleomagnetic stratigraphy. The environmental history
revealed by all of these disciplines indicates that the current
impact mass extinction scenario can no longer be supported.
The Chicxulub impact, commonly believed to be the cause
for the KT mass extinction, predates this mass extinction by
300,000 years. A second impact together with major Deccan
volcanism is the likely cause for the mass extinction.
Our new theory and its supporting evidence has been
carried by news outlets all over the world and more than
100 news articles have appeared in international magazines,
including top journals like Nature, The Economist, La
Recherche, Der Spiegel, Focus, Facts etc. and the Geological
Society of London has sponsored a debate on my team’s work
(Geoscientist, November, 2003).
Six documentary films have been made over the past
year, including BBC Horizon (released in October 2004 in
the UK), ABC, the History Channel, Swiss TV (released
Nov. 24), The New York Museum of Natural History, (released May 2005) and TV interview with Alexander Kluge
for German Film, TV and Media released October 2005.
Accomplishments during 2005 include the successful
drilling of the K-T boundary sequences along the Brazos
River in Texas funded by NSF. These cores form a critical
part in testing the new impact theory and preliminary results
confirm previous studies. New drilling of K-T sequences near
Recife in Brazil, also funded by NSF, commenced in September and finished at the end of December 2005 with nearly
100% core recovery. The three core localities recovered K-T
sequences with the purpose of assessing the environmental effects of the Chicxulub impact at 8000km from its crater. The
cores will be shipped to Princeton in early 2006.
Other miscellaneous publications:
Keller, Suche nach der Ursache des Massensterbens vor 65 Millionen Jahren. Werdenberger Jahrbuch, p. 189-200, 2004.
Keller, La Météorite innocentée. La Recherche, 379, 30-36, 2004.
Articles in press or submitted:
Keller, G. and Pardo, A., Guembelitria and Heterohelix Blooms
– Planktonic proxies for Environmental Catastrophes. Cretaceous Research, in press.
Harting, M., Keller, G., Stinnesbeck, W., Volker, Z. and Fotouh,
M., Geochemical characterisation of Chicxulub-Impact
ejecta: New constraints from the Gulf of Mexico and the
Caribbean. EPSL, in prep.
A 2000 word summary of our results is published in the
Geoscientist and can be downloaded at
http://www.geolsoc.org.uk/template.cfm?name=NSG23498
57238495
12
in the December issue of Geospheres, 2005. The power of
these sequential reconstructions come from 1) highlighting
areas that are not strain compatible and require additional
research on the timing, magnitude and style of deformation.
Richard Lease for his Sr. Thesis conducted field research to
constrain the amount and timing of fault offset in the Mojave portion of the Eastern California Shear Zone (ECSZ).
The palinspastic reconstructions modeled through the Arc
GIS script required large fault displacements through the
eastern Mojave, but the geologic data to support model offsets were unavailable. Richard found a unique marker offset
along the fault, which suggests 22± 5 km of offset (15-25 km
more than previous estimates), and provided a positive field
test for kinematic compatibility models. 2) The palinspastic
reconstructions allow us to restore other data sets of interest, such as the volcanic eruptive centers through the Basin
and Range. For her Sr. Thesis, Margee Prat started integrating the ARC GIS database of extension in the central Basin
and Range with the NAVDAT (North American Volcanic)
Database. Together these data sets have the potential to show
how mantle lithospheric thickness has evolved with time in
conjunction with crustal thinning, as well as provide insight
into geodynamical links between extension and volcanism in
this region.
Nadine McQuarrie
Assistant Professor
Ph.D., 2001, Arizona University
email: [email protected]
My research focuses on the kinematic evolution of mountain belts. My interests range from evaluating the sequential
accumulation of strain in folds and faults that form a wide
(350-350 km), high elevation plateau to the kinematics and
dynamics of diffuse continental extension. Research projects
start with structurally based field studies, typically through
the creation of new geologic maps at previously unpublished
scales or resolutions. Projects also typically involve the creation and sequential restoration of cross sections to evaluate
viable kinematic deformation histories. Current projects I
am working on in conjunction with colleagues and students
are: 1) tectonic reconstructions of the North America-Pacific
plate boundary over the last 36 Myr, 2) the interaction between erosion and deformation in fold-thrust belts in Bolivia
3) the fundamental controls on the width of mountain belts,
specifically looking at the northern edge of the Andean Plateau in Peru and 4) how has deformation evolved in time and
space during arc-continent collision in Timor.
Interaction between erosion and deformation in foldthrust belts: Quantifying the interactions of lithology,
tectonics and climate on multi-scale morphologies of mountain ranges is at the forefront of current geological research.
One of the central facets to this research is the magnitude of
control climate and the associated erosion has on the formation and development of orogens. Active research in Bolivia
(collaborative research with Dr. Todd Ehlers and graduate
student Jason Barnes at University of Michigan) use lowtemperature thermochronometry, field-constrained structural
analysis, and numerical models to delineate the kinematic
evolution of the fold-thrust belts, and the impact of erosional
variations on their formation. In Bolivia we have obtained
cooling ages and structural data that has been combined in
a preliminary kinematic model of how the fold thrust belt
has developed through time. We have used new mapping
to construct a balanced cross section across the Andean
plateau from the volcanic arc to the undeformed foreland.
The restored cross section was imported into 2-D MOVE
(a cross section restoration program) and the displacement
along folds and faults was forward modeled providing a
quantitative description of the kinematics (displacement,
velocity, velocity change) of fold-thrust belt deformation.
The simulated velocity field will be the input into 2D and
3D thermo-mechanical models that link uplift and erosion
to an evolving thermal field. This thermal history is used to
calculate and predict apatite fission track and apatite and
zircon (U-Th)/He sample ages.
Tectonic reconstructions of the North America-Pacific
plate boundary: Precise displacement fields of continental
deformation are becoming increasingly more common and
exact through the advent and expansion of global positioning
systems (GPS). However, displacement histories over much
longer scales (105-107) are required for addressing questions
of how the lithosphere responds to major changes in plate
geometry and kinematics. For many regions on earth the
detailed geologic history necessary for long-term displacement fields is just not available. However, in western North
America more is known about timing, amount, and spatial
variations of deformation than any other comparable region.
By using an Arc GIS (global information systems) database
of timing, magnitude and direction of deformation, we can
sequentially restore deformation through western North
America with time creating a series of palinspastic maps from
36 million years ago to present. The data from these maps
can be displayed in a variety of ways that highlight not only
the areas where the reconstructions are accurate, but more
importantly where the reconstructions are inaccurate (implying where more field-based data are needed). The maps
can also be displayed as a movie that illustrates how extension varies with time and as velocity fields over 2-5-10 m.y.
increments that can be compared to the modern GPS strain
field. The first version of these reconstructions was published
Controls on orogen width: The Andes mountains extend
over 8000 km along the western side of the South American
continent. Significant along strike changes in morphology,
structure and zonal climate regimes make the South American Andes an ideal location to look at the factors that control
13
orogen width. Interesting, the widest portion of the Andes,
between 12° and 27° S, is also the driest suggesting the lack
of erosion is an important factor in broad (350-550 km)
high (4-5 km) plateaus. One of the most abrupt along strike
changes in morphology of the Andes is along the northern
edge of the Andean plateau in Peru. Here a wide zone (~350
km) of high topography with minimal vertical relief transitions abruptly into a significantly narrower (150 km) mountain range with a narrow drainage divide. This west stepping,
right angle bend in topography is mimicked in the structural
elevation (i.e. stratigraphic erosion level) of lower Paleozoic
rocks. This significant change in topographic and structural
width provides a unique opportunity to evaluate the factors
that govern the width of orogens.
This last summer, Nicole Gotberg (graduate student)
and I mapped 2 transects through the Peruvian Andes. The
northern transect was through the narrow portion of the
mountain range and the southern transect was across wide,
northern border of the Andean plateau. One of the surprising things that we found was although the stratigraphy
varies significantly across the Northern Plateau boundary,
the cumulative stratigraphic thickness if each region (north
and south) is essentially the same. This fall Nicole has been
digitally combining her mapping with Peruvian geologic
maps to create new geologic maps that can be used as the
bases for balanced cross sections across each region. A map
of the northern edge of the Andean Plateau and an accompanying geologic cross section will be products of Nicole’s
first year project.
deformation history and 4) Rocks which can provide cooling ages of apatite grains which indicate the window of time
these rocks were cooled through uplift and erosion. These
ffactors allow is to quantify both rates of crustal shortening
as well as rates of surface uplift in East Timor. The collision history of the Banda arc is also significant because the
obliquity of the collision provides a unique insight into the
temporal evolution of the orogen through trading space for
time along strike. The westward propagation of the orogen
(110 km/m.y.) provides a way to simultaneously observe this
active arc-continent collision at various stages of development. This last summer Sarah Johnston (graduate student)
and I undertook a six-week field season in East Timor to
collect structural data along a roughly N-S transect across
the island of Timor in the country of East Timor. Sarah is
in the process of compiling her preliminary mapping with
pre-existing published and unpublished data of collaborators
into a comprehensive GIS database. This database alone will
be an important contribution to the current understanding
of East Timor geology. As the map is being compiled, Sarah
will construct an orogen-scale balanced cross section along
the transect line. When finished, She will be able to use the
section to estimate the amount of shortening and thickening for this location, thus producing an estimate of thickening-induced uplift. The construction of the section will also
pinpoint geographic areas in need of more research and data
collection for future work.
Two-Year Bibliography
Refereed articles:
McQuarrie, N., Crustal-scale geometry of Zagros fold-thrust belt,
Iran. Journal of Structural Geology, v.26, p. 519-535, 2004.
McQuarrie, N., Horton, B.K., Zandt, G., Beck, S., and DeCelles,
P.G., The lithospheric evolution of the central Andean Plateau: Tectonophysics, v. 399, p. 15-37, 2005.
McQuarrie, N. and Wernicke, B.P., An Animated Tectonic Reconstruction of Southwestern North America since 36 MA: Geosphere, v. 1, p 147-172. doi: 10.1130/GES00016.1, 2005.
4-D Evolution of arc-continent collision in East Timor:
The island of Timor in southeast Asia formed and is actively
growing by the processes of island arc collision with a continental margin. Collision of the Indonesian volcanic islands
(the Banda arc) with the Australian continental margin
caused the growth and emergence of Timor, Rote, Savu and
Sumba islands in the Banda forearc. In the mountainous
region of East Timor, maximum elevations reach ~ 3000 m.
Preserved in these mountains are: 1) Flights of coral terraces
that record the emergence of the islands by marking an elevation that once was at sea level, 2, Young, marine sedimentary rocks record the progressive shoaling of ocean water
depths. 3) Deformed rocks sufficiently exposed to reveal their
Articles in press or submitted:
Lease, R.O., McQuarrie, N., Oskin, M., (in review), Dextral Shear
on the Bristol-Granite Mountains Fault Zone: Successful
Geologic Prediction from Kinematic Compatibility of the Eastern California shear zone: Journal of Geology.
Barnes, J., Ehlers, T.A., McQuarrie, N., O’ Sullivan, P.B., (in review), Erosion, Climate and plateau growth in the central Andes, northern Bolivia: Earth and Planetary Science Letters.
14
François M. M.
Morel
Albert G. Blanke, Jr., Professor of
Geosciences
Director, Princeton Environmental
Institute Director, Center in Environmental BioInorganic Chemistry
Ph.D., 1971, California Institute of
Technology
email: [email protected]
Marine phytoplankton are responsible for about half of the
global primary production and for a major fraction of reverse
weathering on the Earth. Some of the carbon dioxide they
fix is exported to the deep sea; some of the SiO2 precipitated
by diatoms and of the CaCO3 precipitated by coccolithophores is accumulated in sediments and eventually subjected
to diagenesis. What physical and chemical factors control
the growth and activity of phytoplankton is the overarching
question addressed in my research group. Our focus is on
trace metals, some of which are essential for phytoplankton
growth (e.g., Fe), some are toxic (e.g., Hg), some are both
(e.g., Cd).
An outstanding question of oceanography is why phytoplankton precipitate hard parts: what physiological and
ecological benefits diatoms obtain from their silica frustule?
and coccolithophores from their calcite liths? We’ve been
working on the hypothesis that the hard parts of phytoplankton are important in key extracellular enzymatic processes.
We have shown that the silica frustule of diatoms is an excellent buffer for hydrogen ion that enables the rapid conversion of HCO3- to CO2 through the activity of an extracellular
carbonic anhydrase enzyme, a key step in the acquisition
of inorganic carbon by diatoms. We have now obtained
evidence that the calcium carbonate liths of coccolithophores likewise enhance the activity of extracellular alkaline
phosphatase –an enzyme that liberates orthophosphate from
organic compounds.
The biogeochemistry of cadmium continues to be a research focus in our group. Because of its excellent correlation
with phosphate, cadmium is used as a paleotracer of nutrients in the sea. We have obtained mounting evidence from
laboratory and field work that cadmium is an important
micronutrient for marine phytoplankton. From our previous work, we know that Cd promotes the growth of diatoms
under low zinc conditions as the result of the synthesis of a
Cd-carbonic anhydrase. Cadmium thus catalyses the acquisition of inorganic carbon for photosynthesis. Having now
obtained the full DNA sequence for this enzyme (the first Cd
enzyme discovered) and over-expressed it in a bacterial host,
we are in the process of characterizing it in collaboration
with protein chemists at Pen. Our next goal is to elucidate
the biochemical/physiological role of Cd in coccolithophores which we have found to accumulate unusually high
15
concentrations of this metal. The biochemical utilization of
cadmium by diatoms and coccolithophores is, we believe, the
key to the ocean biogeochemistry of Cd and also, perhaps, to
the ecology of these dominant phytoplankton taxa.
In collaboration with John Reinfelder (at Rutgers University) we have continued our work on the mechanism of
inorganic carbon uptake and fixation in diatoms. By following the rates of CO2 uptake and O2 evolution in the presence
of various inhibitors, we have obtained convincing data supporting our earlier (and controversial) report of unicellular
C4 photosynthesis --a pathway that involves accumulation of
carbon as a C4 compound prior to fixation-- in these organisms. This project, in concert with our work on Cd-carbonic
anhydrase and on the physiological role of the silica frustule
indicate that a particularly effective carbon acquisition system may be in part responsible for the ecological success of
diatoms in the oceans.
After a hiatus of several years (during which iron became
the fashionable element in oceanography), we have reactivated our research on the iron physiology of marine phytoplankton. Our present foci are the mechanism of uptake of iron
complexed in organic chelates or precipitated as colloidal
oxides (the major form of iron in the oceans), and intracellular Fe storage. 1) Fe uptake. A considerable amount of
laboratory data show that the uptake of Fe by phytoplankton
is modulated by the free Fe(III) concentration in seawater.
But some laboratory and field data also show that Fe uptake
depends on the reduction of Fe(III)complexes by surface
enzymes. We have posited a new model of Fe uptake that
reconciles these results by making the uptake dependent on
the Fe(II) concentration at the surface and obtained new
data supporting the validity of this “Fe(II)s” model. 2) Fe
storage. We have identified in the recently published genome
of the marine cyanobacterium Trichodesmium two sequences
with high homology to genes known to code for ferritin, the
major iron storage protein in living organisms. This is the
first evidence of ferritin in marine microorganisms and we
are in the process of isolating and characterizing this protein
to study its role in the ecology of Trichodesmium, the organism thought to be responsible for the bulk of N2 fixation in
the ocean.
Our continuing work on the biogeochemistry of mercury is presently focused on mercury methylation. Since
methyl mercury is the species accumulated in fish via the
food chain, this is a key transformation, but it has received
surprisingly little attention over the past 20 years. The two
questions we are trying to answer are: 1) where is methylation occurring in the ocean and by what mechanism? and
2) what controls the rate of methylation by sulfate reducing
bacteria in freshwater systems? New data on the concentration of mercury in tuna caught off Hawaii show that this
concentration has not changed in thirty years. Mercury in
tuna thus does not respond to the increase in mercury in
the atmosphere and in the surface of the oceans caused by
anthropogenic inputs. We thus propose that methyl mercury
in the open ocean may originate from the deep sea, perhaps
from hydrothermal vents. Our biochemical work with sulfate
Amyot, M., F.M.M. Morel and P. A. Ariya, Dark oxidation of
dissolved and liquid elemental mercury in aquatic environments, Environ. Sci. Technol., 39(1) p. 110, 2005.
Sternberg, E., D. Tang, T.-Y. Ho, C. Jeandel and F.M.M. Morel,
Barium Uptake and Adsorption in Diatoms, Geochemica
Acta, Vol. 69(11) 2745-2752, 2005.
Kustka, A. B., Y. Shaked, A.J. Milligan, D. W. King, F.M.M. Morel,
Extracellular production of superoxide by marine diatoms:
Contrasting effects on iron redox chemistry and bioavailabilty. Limnol. and Oceanogr., 50(4) 1172-1180, 2005.
Shaked, Y., A.B. Kustka and F.M.M. Morel, A general kinetic
model for iron acquisition by eukaryotic phytoplankton. Limnol. And Oceanogr., 50(3) 872-882, 2005.
reducing bacteria has shown that, contrary to what is commonly believed, the acetylCoA pathway is not necessary for
Hg methylation in these organisms. We are now trying to
elucidate what enzymes are actually involved in methylation
and what control their activity in these organisms.
Two-Year Bibliography
Refereed articles:
Shaked, Y., A.B. Kustka, F.M.M. Morel and Y. Erel, Simultaneous
determination of iron reduction and uptake by phytoplankton, Limnol. and Oceanography: Methods, http://www.aslo.
org/lomethods/free/2004/0137.pdf, Vol 2, 137-145, 2004.
Reinfelder, J.R., A.J. Milligan, F.M.M. Morel, The role of the C4
pathway in carbon accumulation and fixation in a marine
diatom. Plant Physiolog, Vol. 135, 2106-2111, 2004.
Lalonde, J.D., M. Amyot, J. Orvoine, F.M.M. Morel, J-C. Auclair,
P.A. Ariya, Photoinduced Oxidation of Hg0(aq) in the Waters
from the St. Lawrence Estuary Environ. Sci. Technol., 38 (2)
508-514, 2004.
Kraepiel, A.M.L., K. Keller, H.B. Chin, E.G. Malcolm, F.M.M. Morel, Response to Comment on “Sources and Variations of
Mercury in Tuna” Environ. Sci. Technol., 38(14) 4048, 2004.
Milligan, A. J. and F.M.M. Morel. Dynamics of silicon metabolism
and silicon isotopic discrimination in a marine diatom as a
function of pCO2 Limnol. Oceanogr., 49 (2), 322-329, 2004.
Morel, F.M.M. and E.G. Malcolm, “The biogeochemistry of
Cadmium” in Biogeochemical Cycles of Elements, Vol. 43
of Metal Ions Biological Systems; ( A. Sigel, H. sigel, and
R.K.O. Sigel, eds), M. Dekker, New York, pp. 301, 2005.
Sunda, W., N.M. Price, F.M.M. Morel “Trace Metal ion buffers
and their use in culture studies” in Algal Culturing Techniques, R. Anderson Editor, Academic Press p. 35-63, 2005.
Lane, T.W, M.A. Saito, G.N. George, I.J. Pickering, R.C. Prince,
F.M.M. Morel, A cadmium enzyme from a marine diatom,
Nature, Vol. 435 p. 42, 2005.
Articles in press or submitted:
Castruita, M., M. Saito, P.C. Schottel, L.A.Elmegreen, S. Myneni,
E.I. Stiefel, and F.M.M. Morel, Overexpression and characterization of an iron storage and DNA-binding Dpsprotein
from Trichodesmium erythraeum. , Applied Env. Microbiology, in press.
Shaked, Y., Y. Xu, K. Leblanc and F. M. M. Morel, Zinc availability
and alkaline phosphatase activity in Emiliania huxleyi: Implications for Zn-P co-limitation in the ocean Limnology and
Oceanography, in press.
Tang, D. and F.M.M. Morel, Distinguishing between cellular and
Fe-oxide associated trace elements in phytoplankton Marine
Chemistry, in press, 2005
Xu, Y., T.M. Wahlund, L. Feng, Y.Shaked, and F. M.M. Morel, A
novel alkaline phosphatase in the coccolithophore Emiliania
huxleyi ((Prymnesiophyceae) and its regulation by phosphorus, J. of Phycology, submitted, 2005.
Park, H., B.Song, and F.M.M. Morel, Diversity of the Cadmium
Containing Carbonic Anhydrase (CDCA) in Marine Diatoms
and Seawater, Env. Microbiology, submitted, 2005.
fate and transport of contaminants in the environment. This
area of research is gaining importance, and researchers from
different disciplines began conducting studies to explore
these interactions in greater detail. I am interested in exploring one of these fundamental interactions, which include the
evaluation of the chemical state of water in different geologic
media and how this modifies the biogeochemical behavior of
different inorganic and organic moieties in the natural systems. I am also interested in evaluating the chemical state(s)
of important geochemical species to develop predictive patterns for explaining their macroscale behavior.
A summary of my current research projects, and accomplishments in the last one year are provided below.
Satish Myneni
Associate Professor
Ph.D., 1995, Ohio State
University
email: [email protected]
Speciation of Aluminum and Iron in Aqueous Solutions
and in Solid phases
Aluminum and iron are one of the most abundant elements
in the Earth’s crust and form common minerals of all soils
and sediments. The oxides (Fe only) and oxyhydroxides
of these elements are highly reactive towards aqueous contaminants and nutrients and play an important role in the
geochemical cycling of several elements. However, several
oxides and oxyhydroxides of Al3+ and Fe3+ exist in the form of
amorphous and poorly crystalline precipitates and aqueous
polymers, whose genesis, structure, composition and reactiv-
Water is essential for the origin and survival of life on our
planet and perhaps plays an important role on the existence
of life on other planetary bodies as well. In several different
forms, water mediates the physical and chemical interactions
between various components of the Earth’s surface environment, which includes mineral oxides, biota and their byproducts, and the atmosphere. One of the challenges in environmental sciences is to gain a better understanding of interactions between these different components in nature, and to
use it to predict a variety of biogeochemical processes such as
elemental cycling, biological chemistry of elements, and the
16
ity are poorly understood. These metastable phases occur
as nanosize particulates, and convert to crystalline phases if
given enough time. The rates of transformation depend on
several physico-chemical variables in the environment, and
vary from a few hours to several months. My research focuses
on the structural chemistry of these metastable phases, and
on the influence of different environmental variables that
modify their transformation. My group members, Laura
Harrington and Michael Hay are participating in this investigation.
We use different X-ray scattering and spectroscopy
techniques to evaluate the coordination environment of Al3+
and Fe3+ in the stable and metastable phases, and vibrational
spectroscopy to understand the coordination environment of
bridging and terminal hydroxyls. We also use X-ray spectromicroscopy to evaluate the heterogeneity in size and composition of these phases. In collaboration with Dr. Ann Chaka
at the National Institute of Standards and Technology, we are
conducting quantum chemical calculations to complement
the experimental investigations.
The formation of different oxyhydroxides of Al3+ and
3+
Fe in the environment is influenced by the speciation of
these ions in aqueous solutions. It is well understood that
these ions exist as hexaqua complexes (e.g. Al(H2O)63+)
in highly acidic solutions and hydroxylated species (e.g.
l
Al(OH)m(H2O)nl+/) at all other pH values, and exhibit least
solubility at near neutral pH. The chemical behavior of these
two ions in aqueous solutions and their species is primarily
determined by the hydroxylation of these ions, which in turn
is dictated by different aqueous chemical conditions. We
built a new synchrotron experimental chamber to evaluate
the electronic states of the hydroxylated species of these ions
in aqueous solutions. Although Al-speciation in aqueous
solutions and precipitates is well studied using NMR spectroscopy, variations in the structural environment of Al in
these systems are not well understood. Our preliminary X-ray
studies on aluminum indicate that Al3+ forms octahedral
complex with H2O in highly acidic solutions, and converts to
a tetrahedral complex with 4OH- in alkaline solutions, which
are in agreement with previous NMR spectroscopy studies.
However, Al3+ converts to a pentacoordinate species when it
reacts with an OH- in moderately acidic solutions. Although
recent theoretical studies lend support to this observation,
experimental evidence is missing. Changes in the coordination of Al3+ modify its electronic state and thus its reactivity.
The behavior of Fe3+ follows the chemistry of Al3+ closely.
Since Fe3+ exhibits stronger interactions with sulfate among
all inorganic ligands, and both of them occur together in several natural systems, our initial studies focused on Fe3+-sulfate
interactions. Our infrared and X-ray spectroscopy studies of
these systems provided unequivocal evidence for the occurrence of H-bonding complexes of sulfate with Fe-oxyhydroxide polymers (Myneni et al. submitted). These studies
unravel the mystery of solution and solid phase speciation of
Fe3+ in acidic environments (Majlan and Myneni, Environ.
Sci. Technol., 2005). The current emphasis is also on the
understanding of the structural environments of soluble Fe3+-
polymers in aquatic and biological systems (e.g. ferritins),
and their precipitates.
Chemistry of Natural Organic Molecules
Organic molecules are found everywhere on the surface of
the Earth, and their composition, molecular structure and
concentration modifies the biogeochemical processes in the
environment. One of the bottlenecks in our understanding of
the elemental cycles is related to the speciation of C, N, and
S associated with the organic molecules, and their variation
in the environment. For the past several years, my research
group has been using and developing X-ray spectroscopy and
spectromicroscopy methods for studying the chemistry of
natural organic molecules in their pristine state (Rev. Mineral., 2002). Using these methods I am investigating the:
• Functional group composition and macromolecular
structure of natural organic molecules in soils and
sediments,
• Role of minerals in the retention and fractionation of
organic molecules in the environment,
• Chemistry of natural organohalogens in the environment: coordination chemistry, rates of formation in
the environment and their role in various biogeo
chemical reactions, and
• Reactions at the microorganism-water interfaces.
To investigate the biogeochemical processes involved in
organic molecule halogenation in terrestrial systems and their
rates in detail, we built a field station in Princeton University
campus. In addition, we are monitoring the speciation of
C, N, and S in organic molecules to evaluate the association
of these elemental cycles with the halogen-cycle. We found
several interesting results on these systems, and some of the
highlights are as follows.
Chemistry of natural organohalogens. While manmade organohalogens are widely distributed throughout the biosphere
and are characterized by varying degrees of persistence and
toxicity, natural production of organohalogen compounds
is gaining recognition as a significant contributor to the
organohalogen burden in the environment. With the help
of my research group members, I made significant progress
in understanding the chemistry of natural organohalogens
in the past 3-4 years. Using X-ray spectroscopy, I directly
showed that the formation of organochlorines and their speciation variations in soils are directly related to the weathering of plant material. Dr. Deshmukh (post-doctoral scholar)
conducted a detailed speciation of organochlorines in the
O-horizons of soils, and his studies indicated that a majority
of chlorinated organic molecules in weathering plant material
are associated with the soluble polyphenol fraction, but not
with stable lignins, as thought by several previous investigators. Specific molecules identified in our investigation are
chlorinated xanthones (probably associated with lichens),
and several other aliphatic and aromatic chlorinated molecules (sources uncertain at this stage). The X-ray microscopy
studies conducted by Ms. Leri (graduate student) indicated a
heterogeneous distribution of organochlorines in weathering
leaves, which we are attributing to the differences in organic
17
Maria S., Russell L. M., Gilles M. K., Myneni S. C. B. Organic
aerosol growth mechanisms and their climate forcing implications. Science, 306: 1921-1924 2004.
Wei J. Saxena A., Song B., Ward B. B., Beveridge T.J ., Myneni
SCB. Elucidation of functional groups on Gram-positive and
Gram-negative bacterial surfaces using infrared spectroscopy. Langmui,r 20: 11433-11442 2004.
Edwards, D. C., Nielsen S. B., Jarzecki A. A., Spiro T. G., Myneni
S. C. B. Experimental and theoretical vibrational spectroscopy studies of acetohydroxamic acid and desferrioxamine
B in aqueous solutions: Effects of pH and iron complexation.
Geochim. Cosmochim. Acta, 69: 3237-3248 2005.
Edwards D. C., Myneni S. C. B. Hard and soft X-ray absorption
spectroscopic investigation of aqueous Fe(III)-hydroxamate
siderophore complexes J. Phys. Chem., A 109: 1024910256. 2005
Strathmann T. J., Myneni S. C. B. Effect if soil fulvic acid on
nickel (II) sorption and bonding at the aqueous-boehmite
(γ-AlOOH) interface. Environ. Sci. Technol., 39: 4027-4034
2005.
Majzlan J., Myneni S. C. B. Speciation of iron and sulfate in acid
waters: Aqueous clusters to mineral precipitates. Environ.
Sci. Technol., 39: 188-194 2005.
Naslund L., Edwards D. C., Wernet P., Bergmann U., Ogasawara
H., Pettersson L. G. M., Myneni S. C. B., Nilsson A. X-ray
absorption spectroscopy study of the hydrogen bond network
in the bulk water of aqueous solutions. J. Phys. Chem., A
109: 5995-6002 2005.
Li W., Seal S., Rivero C., Lopez C., Richardson K., Pope A.,
Schulte A., Myneni S. C. B., Jain H., Antoine K., Miller A. C.
Role of S/Se ratio in chemical bnding of As-S-Se glasses
investigated by Raman, X-ray photoelectron, and extended
X-ray absorption fine structure spectroscopies. J. App. Physics ,98: 053503 2005.
Bluhm H., Andersson K., Araki T., Benzerara K., Brown G.
E., Dynes J. J., Ghosal S., Gilles M. K., Hansed H. –Ch,
Heminger J. C., Hitchcock A. P., Ketteler G., Kilcoyne A. L.
D., Kneedler E., Lawrence J. R., Leppard G. G., Majzlan
J., Mun B. S., Myneni S. C. B., Nilsson A., Ogasawara H.,
Ogletree D. F., Pecher K., Salmeron M., Shuh D. K., Tonner
B., Tyliszczak T., Warwick T., Yoon T. H. (2005) Soft X-ray
microscopy and spectroscopy at the molecular environmental science beamline at the Advanced Light Source. J.
Electron Spectosc. Relat. Phenom., 150: 86-104 2005.
molecule halogenation processes.
Researches conducted by Ms. Hakala (senior) and Leri
have shown that organobromines, like organochlorines, are
common in terrestrial and marine environments. Since they
are present at high concentrations in marine systems, we are
planning detailed studies on their formation in the photic
zone of ocean water, and their accumulation and dehalogenation in sediments. Although iodine is present at trace concentrations, we are finding that iodide and iodate present in soils
react with naturally occurring organic molecules and form
organoiodines in short time. The presence of Ca is significantly affecting the sensitivity of X-ray spectroscopy methods
in detecting organoiodines in all natural samples. However,
we found that the reactions of inorganic iodine with organic
molecules are slow, and take about a week to reach equilibrium in laboratory microcosms. Rachel Zwillinger, a senior in
my research group, conducted these investigations.
Reactive Carboxylic Acids in Natural Organic Molecules.
Carboxylic acid groups are one of the most important reactive groups in naturally occurring organic molecules. It has
been widely assumed that a majority of these carboxylic acids
are present as aromatic carboxylic acids (such as in salicylic
acid). However, a combination of multidimensional NMR
and infrared spectroscopy studies indicated that a majority
of carboxylic groups in natural organics are associated with
the aliphatic fraction, and have an electron withdrawing
group on the adjacent C-atom (in the α- and β-positions).
The presence of such groups makes the carboxyl group much
more reactive and promotes the formation of strong complexes (chelation) with aqueous metals and mineral surfaces.
This information is important in understanding the reactivity of common stable biomacromolecules and their origin in
aquatic systems.
In summary, my research group is developing into a diverse
and interdisciplinary research group to address the fundamental biogeochemical processes in the environment.
Two-Year Bibliography
Articles in press or submitted:
Myneni S. C. B. Applications of X-ray and infrared spectroscopy
methods in studying microbe-mineral interfaces, in press.
Myneni S. C. B., Waychunas G. A., Traina S. J., Brown Jr. G. E.
Understanding the speciation of oxoanions in aquatic systems, Proc. Natl. Acad. Sci., in review.
Bellenger J., Arnaud-Neu F., Asfari Z., Myneni S. C. B., Stiefel
E. I., Kraepiel A. Complexation of oxoanions and cationic
metals by the bis(catecholate) siderophore azotochelin,
Inorganic Chemistry, in review.
Refereed articles:
Strathmann T., Myneni S. C. B., Speciation of aqueous Ni(II)Carboxylate and Ni(II)-Fulvic Acid Solutions: Combined
ATR-FTIR and XAFS Analysis. Geochim. Cosmochim. Acta,
68: 3441-1458, 2004.
Xue S., Leri A., Myneni S. C. B., Jaffe P. Uptake of bromide by
two wetland plants (Typha latifolia and Phragmites australis
(Cav.) Trin. Ex Steud). Environ. Sci. Technol.,38: 5642-5648
2004.
Reina R., Leri A., Myneni S. C. B. Cl K-edge X-ray spectroscopic
investigation of enzymatic formation of organochlorines in
weathering plant material. Env. Sci. Technol., 38: 783-789
2004.
18
With Stephanie Gautier and Jean Virieux, both at
Geosciences Azur in France, I have developed a new method
to compute the finite-frequency sensitivity of arrival times
and amplitudes of local seismic waves in complicated, threedimensional media. A first application, to image the seismogenic zone in the area of the Gulf of Corinth (Greece) is
under way.
Guust Nolet
George J. Magee Professor of
Geophysics and Geological
Engineering
Ph.D., 1976, University of Utrecht (The Netherlands)
email: [email protected]
Two-Year Bibliography
Books
Levander, A. and G. Nolet (eds.), Seismic Earth: Analysis of
broadband seismograms, AGU Monograph Series, 2005.
Refereed articles:
Montelli, R., G. Nolet, F.A. Dahlen, G. Masters, E.R. Engdahl,
S.-H. Hung, Finite-frequency tomography reveals variety of
plumes in the mantle, Science, 303, 338-343, 2004.
Montelli, R., G. Nolet, F.A. Dahlen, G. Masters, E.R. Engdahl, S.H. Hung, Global P and PP travel time tomography: rays vs.
waves, Geophys. J. Int., 158, 637-654, 2004.
Zhou, Y., F.A. Dahlen and G. Nolet, Three-dimensional sensitivity
kernels for surface wave observables, Geophys. J. Int., 158,
142-168, 2004.
Nolet, G. and R. Montelli, Optimum parameterization of tomographic models, Geophys. J. Int., 161, 365-372, 2005.
Nolet, G., F.A. Dahlen and R. Montelli, Traveltimes and amplitudes of seismic waves: a re-assessment, in A. Levander
and G. Nolet (eds.), Seismic Earth: Analysis of broadband
seismograms, AGU Monograph Series, 37-48, 2005.
Levander, A. and G. Nolet, Perspectives on array seismology
and US Array, in A. Levander and G. Nolet (eds.), Seismic
Earth: Analysis of broadband seismograms, AGU Monograph Series, 1-6, 2005.
Dahlen, F.A. and G. Nolet, Comment on the paper “On sensitivity kernels for wave-equation transmission tomography” by
de Hoop and van der Hilst, Geophys. J. Int., 163, 949-951,
2005.
Zhou, Y., F.A. Dahlen, G. Nolet and G. Laske, Finite-frequency
effects in global surface-wave tomography, Geophys. J. Int.,
163, 1087-1111, 2005.
With Raffaella Montelli and Tony Dahlen, we continued the
exploration of the effects of finite frequency – introduced by
us five years ago – into the imaging of the Earth’s interior.
An investigation of long period S, ScS and SS waves led to
a spectacular confirmation of the earlier results that showed
a number of mantle plumes reach deep down into the lower
mantle. This finding has important implications for the geodynamics of the Earth. This is probably the last time we invert data sets that exist in the pubic domain or that we obtain
by collaboration with others. Since 2002, Karin Sigloch has
been developing a new method based on matched filters that
will allow us for the first time to measure arrival times and
amplitudes of body waves from shallow earthquakes – the
complicating interacting of the ghost reflections from the
Earth’s surface are fully taken into account in the filter. The
measurements can be done in different frequency windows,
thus fully exploiting the power of finite frequency tomography, the new method of interpretation pioneered at Princeton in the past decade. Using the matched filtering method,
Karin has recently been able to show that finite frequency
effects are clearly visible in the arrival times and amplitudes
of teleseismic P waves recorded by the RISTRA array in the
western United States. She, and new graduate student Yue
Tiang, have embarked upon an ambitious project to develop
our own data base of amplitudes and arrival times, which will
include complete dispersion information.
Raffaella Montelli has left for Exxon, and we are at present cleaning up the finite-frequency tomography software
that she developed, making it more general and user friendly.
I have started writing a book that summarizes not only the
theory of classical as well as finite-frequency tomography, but
also the various methods of data analysis, model parameterization and inversion. No such book exists at present.
Articles in press or submitted:
Sigloch, K. and G. Nolet, Measuring finite-frequency body wave
amplitudes and travel times, subm. to Geophys. J. Int., 2005.
Montelli, R., G. Nolet, F.A. Dahlen and G. Masters, A catalogue
of deep mantle plumes: new results from finite-frequency tomography, subm. to Geochemistry, geophysics, geosystems
(G3), 2006.
Montelli, R., G. Nolet and F.A. Dahlen, Comment on `Bananadoughnut kernels and mantle tomography’ by van der Hilst
and de Hoop, subm. to Geophys. J. Int., 2006.
Zhou, Y., G. Nolet, F.A. Dahlen and G. Laske, Global UpperMantle Structure from Finite-Frequency Surface-Wave
Tomography, J. Geophys. Res., in press, 2006.
19
abiogenic or biotic origin. No instruments are currently
flight ready that are capable of performing C and H isotopic
analyses of methane. In a paper that has been accepted for
publication by Astrobiology Journal, I outlined the possible
origins of the Martian methane and what type of analyses
would be required to distinguish between the different origins. The bad news is that the shuttle back to flight program
is bleeding NASA’s science programs dry and the funding
prospects for Mar’s related initiatives over the next several
years is bleak. It’s time to seek a well endowed benefactor!
Tullis C. Onstott
Professor
Ph.D., 1980, Princeton University
email: [email protected]
The South African Deep Microbiology Project
The environments sampled over the past 5 years in the deep
mines of South Africa have revealed new microbial phyla that
have never been reported elsewhere, unusual biogeochemical
phenomena that are difficult to understand and microscopic
features that a frankly so bizarre that their origin is a mystery.
For these reasons we’ve had great difficulty in publishing the
findings of this project, but this past year has seen a confluence of efforts by the co-investigators participating in this
project, which at long last had led to the acceptance for publication of numerous manuscripts describing the microbial
diversity and geochemistry of the deep subsurface of South
Africa. A great deal more research remains to be performed
including the following:
Deep Permafrost Environments and the Mars Deep Drilling Mission
The past year’s IPTAI astrobiology effort has experienced some
significant setbacks. Lupin Mine, a Au mine in the Canadian
Arctic that was our sole access to brine situated beneath 500
meters of permafrost and rock, was closed. We were able to
obtain some high quality planktonic samples prior to the
closure in March and Daniel McGown has been successful
in amplifying 16SrDNA from these samples. This was not a
trivial undertaking given that the biodensity in these brines
appears to be 100 to 1000 times less than we’ve experienced
in South Africa. Despite his success, the low biodensity
doesn’t bode well for obtaining complete genomic analyses of
these environments using large fragment DNA cloning and
sequencing. The investigators involved in research at Lupin
will be gathering in January ’06 to share their results and
plan publications based on the data in hand. The lead IPTAI
investigator, Prof. Pratt of Indiana University, and I prepared
a proposal to the NAI to support drilling into the permafrost
at another Au mine further north called Ulu. This proposal
went through two reviews and now it appears to be funded
pending quotation from the drilling contractor and developments at Ulu for this coming summer. This campaign will be
the first of several designed to develop the technology required
for 1) locating subsurface brines beneath deep permafrost on
Mars, 2) retrieving samples of permafrost and brine with little
organic or microbial contamination, 3) performing life detection experiments on these same samples in the field or in the
borehole and 4) determining how sensitive the organic and
inorganic constituents are to the thermal histories that Martian
samples will be subjected to upon their return from Mars be
robotic craft. It is anticipated that such a mission would take
place in the 2018-2020 time frame and none of the technology required has reached flight capability as of yet.
In this context we have resubmitted a proposal to
NASA’s ASTID, Astrobiology Science and Technology Instrument Development, program for perfecting the means of
contaminant removal on the surface of Mars by Mars rovers
with Honeybee Robotics Ltd. and development of a laser
spectrometer of methane isotope analyses. Our group has
focused upon methane as a biomarker of Martian life since
the discovery of methane in the Martian in 2004 by several
investigators led to a plethora of papers speculating on its
1. The Joint Genomics Institute completed sequencing of
the complete genome of the DNA of the microorganism
which appears to dominate the microbial ecosystem at depths
greater than 1.5 km. in South Africa. This organism represents a new genus of Firmicutes with genetic capabilities that
are surprising when compared to what we thought were the
characteristics of deep subsurface organisms. Now we have
to agree upon a name for this organism, utilize the genomic
information to try to isolate the microbe from more environmental samples, discover the function of specific genes by
performing cloning experiments and complete annotation
of the sequence. A manuscript to be submitted to Science is
being prepared for the release of the genome.
2. Over the past year we have been installing and instrumenting boreholes at 3.7 km depth at Tau Tona mine as part of
an NSF funded project to monitor earthquake seismicity and
relate that activity to geochemical and microbial properties.
Progress, however, has been much slower than anticipated
primarily because of safety issues regarding the site. Nevertheless, the borehole for in situ monitoring of microbial
and geochemical transients will be completed in January ’06
and if all goes well this will represent the deepest site in the
world for long term observation of subsurface phenomena.
This is truly an international effort as the ICDP has paid for
the acquisition of pristine cores from the site, the German
government is supporting a group from Univ. of Potsdam to
investigate changes in gas chemistry and the South African
NRF is supporting out colleagues from the Univ. of Free
State to run the site. Having the capability for long term in
situ studies will hopefully lead to an understanding of some
of the mysterious relationships we’ve been observing with
spot samples.
20
Articles in press or submitted:
Sherwood Lollar, B., Lacrampe-Couloume, G., Slater, G.F., Ward,
J., Moser, D.P., Lin, L.-H. and Onstott, T.C. Abiogenic
gases support H2-based autotrophy and methanogenesis in
the deep subsurface. Chem. Geol., in press, 2006.
Onstott, T. C., Lin, L.-H., Davidson, M., Mislowack, B., Borcsik, M., Hall, J., Slater, G., Ward, J., Sherwood Lollar, B.,
Lippmann-Pipke, J., Boice, E., Pratt, L. M., Pfiffner, S. M.,
Moser, D. P., Gihring, T. M., Kieft, T., Phelps, T. J., van
Heerden, E., Litthaur, D., DeFlaun, M., Rothmel, R., Wanger,
G. and Southam, G. The origin and age of biogeochemical
trends in deep fracture water of the Witwatersrand Basin,
South Africa. Geomicrobiol. Jour
Jour, in press
Pfiffner, S. M., Cantu, J.M., Smithgall, A., Peacock, A., White,
D.C., Moser, D. P., Onstott, T. C. and van Heerden, E.
Phospholipid Fatty Acid Profiles and Biodensity Estimates for
Water, Rock and Air Samples Recovered from Witwatersrand
Basin Mines. Geomicrobiol. Jour., in press, 2006.
Slater, G. F., Lippmann-Pipke, J., Reddy, C. M., Lacrampe-Couloume, G., Onstott, T.C., Sherwood Lollar, B. 14C distribution
in methane and DIC in South African gold mines: Implications to timing of methanogenesis. Geomicrobiol. Jour., in
press, 2006.
Wanger, G., Onstott, T. C. and Southam, G. Structural and
Chemical Characterization of a Natural Fracture Surface
from 2.8 Kilometers Below Land Surface: Biofilms in the
Deep Subsurface. Geomicrobiol. Jour., 2006.
Gihring, T. M., Moser, D. P., Lin, L.-H., Davidson, M., Onstott, T.
C., Morgan, L., Milleson, M., Kieft, T., Trimarco, E., Balkwill,
D.L. and Dollhopf, M. The distribution of microbial taxa in
the subsurface water of the Kalahari Shield, South Africa.
Geomicrobiol. Jour., in press, 2006.
Lihung, L.-H., Gihring, T. M., Sherwood Lollar, B., Boice, E., Pratt,
L. M., Lippmann-Pipke, J., Bellamy, R.E.S., Hall, J. and Onstott, T. C. Heterogeneous microbial communities associated with a 0.7 to 1.4 kmbls section of the continental crust.
Geomicrobiol. Jour., in press, 2006.
Moser, D. P., Gihring, T. M., Brockman, F. J., Fredrickson, J. K.,
Balkwill, D. L., Dollhopf, M. E., Sherwood-Lollar, B., Pratt, L.
M., Boice, E., Southam, G., Wanger, G., Baker, B. J., Pfiffner,
S. M., Lin, L.-H. and Onstott, T. C. (2005) Desulfotomaculum spp. and Methanobacterium spp. Dominate 4-5 km Deep
Fault. Appl. Environ. Microbiol., in press, 2006.
Onstott, T. C., McGown, D., Kessler, J., Sherwood Lollar, B.,
Lehmann, K. K. and Clifford, S. Martian CH4: sources, flux
and detection. Astrobiology Journal, in press, 2006.
DeFlaun, M. F., Fredrickson, J. K,., Dong, H., Pfiffner, S. M.,
Onstott, T. C., Balkwill, D .L., Streger, S. H., Stackebrandt,
E., Knoessen, S. and van Heerden, E. Isolation and characterization of a novel Geobacillus thermoleovorans species
from an ultra-deep South African gold mine. Systematic and
Applied Microbiology, in press, 2006.
Lihung, L.-H., Wang, P-L, Rumble, D., Lippmann-Pipke, J., Boice,
E., Pratt, L. M., Sherwood Lollar, B., Brodie, Eoin, Hazen, T.,
Andersen, G., DeSantis, T., Moser, D. P., Kershaw, D. and
Onstott, T. C. Long term biosustainability in a high energy,
low diversity crustal biotome. Science, submitted, 2006.
Mac Lean, L.C.W., Pray, T.J., Onstott, T.C. and Southam, G.
High-resolution structural and chemical studies of framboidal
pyrite formed within a bacterial biofilm. Geology, submitted,
2006.
Mailloux, B. J., Devlin, S., Fuller, M. E., Onstott, T. C., DeFlaun, M.
F., Choi, K-H, Green, M., Swift, D. J.P. and McCarthy, J. The
Role of Aquifer Heterogeneity on Metal Reduction in an Atlantic Coastal Plain Aquifer. App. Geochem., submitted, 2006.
Mailloux B. J., Devlin S., Fuller M. E., Onstott T. C., Sigman D.
M., Williams K. H., and Hubbard S. S. The fate of nitrate
during stimulation of coastal plain sediments. Environmental
3. A new weirdophile? In a Pt mine in South Africa we’ve
discovered a star-shaped microbe that probably represents a
new phylum of Archaea. Although we returned to this mine
to collect additional samples and attempted to isolate the
organism in culture, we failed to find it in the new collection.
This is probably because the original seep had been sealed
with cement. In January ’06 we’ll try to return to see if we
can obtain a sample of this organism for further study.
Deep Underground Science and Engineering Laboratory
(DUSEL)
The NSF has selected two candidates to compete in the final
stages of the DUSEL. These two sites will submit proposals
to NSF in July ’06. The final winner will be selected in early
’07 for funding to be used to develop an MRI proposal that
would go to Congress in ’09. As an S1 Investigator I will be
coauthor of the “glossy” report on DUSEL that will be used
by NSF for justification of the facility. We will be completing this document early in ’06. Given the funding trends at
NSF, DOE and NASA, the DUSEL may actually represent
the best candidate for supporting long term investment in
the field of terrestrial subsurface microbiology.
Two-Year Bibliography
Refereed articles:
Hall, J.A., Mailloux, B.J., Onstott, T.C., Scheibe, T.D., Fuller,
M.E., Dong, H. and DeFlaun, M.F., Physical versus chemical
effects on bacterial transport as determined during in situ
sediment core pulse experiments, Jour. Cont. Hydrology, 76:
295-314, 2004.
Lin, L-H, Slater, G. F., Sherwood Lollar, B., Lacrampe-Couloume,
G. and Onsott, T. C., Yields and hydrogen isotopic compositions of radiolytic H2 and the implications for deep biosphere
in continental crust. Geochim. Cosmochim. Acta, 69, 893903, 2004.
Fuller M. E., Mailloux B. J., Streger S., Hall J. A., Zhang P.,
Vainberg S., Johnson W. P., Onstott T. C., and DeFlaun
M. F. Application of a vital fluorescent staining method for
simultaneous, near-real-time concentration monitoring of two
bacterial strains in an Atlantic Coastal Plain aquifer in Oyster,
Virginia. Applied and Environmental Microbiology, 70: 16801687, 2004.
Ward, J.A., Slater, G.F., Lacrampe-Couloume, G., Lin, L.-H., Hall,
J.A., Moser, D.P., Bonin , A., Bellamy, R.E.S., Onstott, T.C.
and Sherwood Lollar, B., Microbial Hydrocarbon Gases in
the Witwatersrand Basin, South Africa: Implications for Deep
Biosphere, Geochim. Cosmochim. Acta, 68; 3239-3250,
2004.
Onstott, T.C. Impact of CO2 Injections on Deep Subsurface
Microbial Ecosystems and Potential Ramifications for the
Surface Biosphere. In The CO2 Capture and Storage Project,
Vol. II, D.C. Thomas and S.M. Benson, eds., 1207-1239,
2004.
Lin, L-H, Hall, J.A., Lippmann, J., Ward, J.A., Sherwood-Lollar,
B. and Onstott, T.C., Radiolytic H2 in the continental crust:
Nuclear power for deep subsurface microbial communities,
Geochem. Geophys. Geosys., 6: 10.1029/2004GC000907,
2005.
Kieft, T.L., McCuddy, S.M, Onstott, T. C., Davidson, M., Lin, L-H,
Mislowack, B., Pratt, L.M., Boice, E., Sherwood Lollar, B.,
Lippmann-Pipke, J., Pfiffner, S. M., Phelps, T. J., Gihring, T.,
Moser, D., and van Heerden, A. Geochemically Generated,
Energy-Rich Substrates and Indigenous Microorganisms
in Deep, Ancient Groundwater, Geomicrobiology Journal,
22:325-355, 2005.
21
of risk assessment. The “dangerous warming” project and
the “negative learning” project will be the focus of my main
efforts in the near future. I will also continue to supervise
postdoctoral students and graduate students in efforts to
include the nitrogen cycle and ice-ocean interactions in the
aforementioned Earth System Model.
Michael Oppenheimer
(Woodrow Wilson School and Department of Geosciences)
Albert G. Millbank Professor of
Geosciences and International
Affairs
Ph.D., 1970, University of Chicago Two-Year Bibliography
email: [email protected]
Refereed Articles:
The West Antarctic Ice Sheet and Long Term Climate Policy (with
R.B. Alley). Climatic Change, 64, 1-10, 2004.
Climate Change Impacts Sensitive to Path to Stabilization (with
B.C. O’Neill).Proc. Nat. Acad. Sci. 101, 16411–16416,
doi_10.1073_pnas.0405522101, 2004.
Book Review: The Discovery of Global Warming. J. Environmental Hist., 9, 327-8, 2004.
The influence of climate on in-stream removal of nitrogen (with
S.D. Donner and C.J. Kucharik). Geophys. Res. Letters, 31,
L20509, doi:10.1029/2004GL020477, 2004.
Ice Sheets, Global Warming, and Article 2 of the UNFCCC (with
R.B. Alley). Climatic Change, 68, 257-267, 2005.
Global Assessment of Coral Bleaching and Required Rates
of Adaptation under Climate Change (with S.D. Donner, W.J.Skirving, C.M. Little, and O. Hoegh-Guldberg).
Global Change Biology, 11, 1–15, doi: 10.1111/j.13652486.2005.01073.x, 2005.
Article 2 of the UNFCCC: Historical Origins, Recent Interpretations (with A. Petsonk). Climatic Change, 73, 195-226, 2005.
Attribution of Regional Radiative Forcing due to Tropospheric
Ozone: A Step Toward Climate Credit for Reductions in
Emissions of Ozone Precursors (with V. Naik, D. Mauzerall,
L. Horowitz, D. Schwarzkopf, V. Ramaswamy). J. Geophys.
Res.,in press, 2005.
Avoiding Dangerous Anthropogenic Interference with the Climate
System (with K. Keller, M. Hall, S.-R. Kim, and D. F. Bradford). Climatic Change, 73, 227-238, 2005.
Defining Dangerous Anthropogenic Interference: The Role of
Science,The Limits of Science. Risk Analysis, 25, 1-9, 2005.
The Potential Impacts of Sea Level Rise on the Coastal Region
of New Jersey, USA (with M.P. Cooper and M.D. Beevers).
Submitted to Climatic Change, 2005.
The broadest frame for my research is the question of what
constitutes a dangerous level of climate change. Within that
framework, I have explored particular outcomes or impacts
of climate change that might have important consequences
for people and societies, and therefore could produce useful
benchmarks for policy makers on an appropriate approach
for limiting the greenhouse gas emissions that are causing warming. Specific studies have focused on the effect
of warming on 1)the Antarctic and Greenland ice sheets 2)
coral reef ecosystems and 3)the nitrogen biogeochemical cycle. In each case, attempts are being made to use modeling,
observations, and paleo-climatic data to provides bounds on
the probability of various outcomes for given levels of warming. The most important outcome has been recognition that
a warming in excess of two degrees Celsius is likely to lead to
outcomes that would be widely recognized as dangerous.
Most recent research and future research plans
My recent research has focused on the stability of the West
Antarctic and Greenland ice sheets, a global assessment of
coral reef ecosystems, construction of a nitrogen sub model
within the Geophysical Fluid Dynamics Laboratory’s Earth
System Model and the construction of new decision making
models appropriate to the global warming problem,including
the recognition of a new phenomenon, “negative learning”.
As a lead author of the Fourth Assessment Report of the
Intergovernmental Panel on Climate Change, I am spending
considerable time this year on developing a comprehensive
framework for evaluating the question of what constitutes
dangerous levels of warming, within a context that recognizes
uncertainty, learning, and the group and individual aspects
Published (or submitted or in press) chapters in books:
What is the Economic Value of Information about Climate Thresholds? (with K. Keller, S-R Kim, J. Baehr, and D. F. Bradford),
Integrated Assessment of Human-Induced Climate Change,
M. Schlesinger, ed., submitted October 14, 2004.
Emissions Pathways to Avoid Dangerous Climate Change: A
Transatlantic View (with C. Jaeger) in Options for Future
Climate Policy: Transatlantic Perspectives, German Institute
for International and Security Affairs, Berlin, 2005.
22
nents (which affects the frequency of volcanic eruptions and
hence the composition of the atmosphere), is mainly responsible for the long-term global cooling. The other associated
with the Milankovitch cycles, the periodic variations in
sunlight. The global cooling affected the response to relatively constant Milankovitch forcing by introducing feedbacks
at certain times. For example, the global cooling led to the
appearance of northern glaciers around 3 Ma, bringing into
play the ice-albedo feedback. (White glaciers reflect sunlight,
thus promoting the growth of glaciers by depriving the Earth
of heat.) This mechanism has been studied extensively in
connection with the ice-ages, but many puzzles remain. One
is the amplification of obliquity but not precession cycles in
global ice volume. Another concerns fluctuations in equatorial sea surface temperatures, very similar to those in the bottom panel, which lead fluctuations in ice volume by several
thousand years. This, and other evidence, clearly indicate
that the ice-ages involve more than ice, that the tropics
played a role.
Equatorial sea surface temperature patterns depend on
the winds and in turn influence the winds. This implies that
interactions between the ocean and atmosphere amount
to positive feedbacks. Their impact on the global climate
is evident during El Niño episodes when the atmospheric
concentration of the powerful greenhouse gas water vapor increases significantly. Sea surface temperature patterns depend
critically on the subsurface thermal structure of the ocean,
especially the depth of the thermocline, the interface between
the shallow layer of warm surface waters and the much colder
water at depth. El Niño corresponds to changes in the slope
S. George H.
Philander
Knox Taylor Professor of
Geosciences
Ph.D., 1970, Harvard University
email: [email protected]
These geological records show that the present is an unusual
moment in the recent history of our planet. Super-imposed
on the global cooling that started some 50 million years
(Ma) ago when polar temperatures were close to100C, are
periodic oscillations that were modest in amplitude up to ~3
million years but then started to amplify, culminating in dramatic fluctuations between prolonged ice-ages that persisted
for some 100,000 years, and brief, temperate interglacials.
(Variations in O18 in seafloor cores, the top panel, are a
measure of polar temperatures.) Our species took advantage
of the current interglacial -- it started 10,000 years ago -- to
advance rapidly, from the invention of farming to industrial
activities that are causing a rapid rise in the atmospheric concentration of greenhouse gases. This rise, the vertical red bar
in the lower panel which shows measurements from Antarctic
glaciers, is occurring at a time when those concentrations are
at a natural maximum. That it is also occurring in an era, the
past 1 Ma, of great climate sensitivity, follows from the cause
of the recurrent ice-ages: very modest, periodic variations in
the distribution of sunlight because of periodic variations
in orbital parameters such as the tilt of the Earth’s axis. To
anticipate what will happen next it will be helpful to understand what had happened in the past.
Two sets of processes determine the climate variations
described above. One, associated with the drifting of conti-
of the equatorial thermocline as in the sketch on the left.
Changes in the spatially averaged depth of the thermocline,
as in the sketch on the right, also alter sea surface temperatures, by means of entirely different (diabatic) processes that
involve changes in the heat budget of the ocean.
Whereas the oceanic heat gain, in low latitudes where cold
23
Two-Year Bibliography
water rises to the surface, depends on oceanic factors, specifically the depth of the thermocline, the oceanic heat loss
in high latitudes depends on atmospheric factors, the air
temperature for example. In a state of equilibrium, heat gain
balances heat loss so that a warm world, with a small loss of
heat from the oceans, must have a small gain and hence a
deep tropical thermocline. Atmospheric conditions in high
latitudes can therefore determine the depth of the tropical
thermocline, and the intensity of air-sea interactions. These
connections between low and high latitudes depend on the
oceanic circulation which has two main components: the
deep, slow thermohaline circulation, and the shallow, rapid
wind-driven circulation. Both effect a poleward transport
of heat by means of meridional overturning; surface waters
sink in the extra-tropics and rise back to the surface in lower
latitudes. The sinking depends on the buoyancy of the water
and hence on its temperature and salinity. The heat transport, and consequently the depth of the tropical thermocline,
can therefore be affected by several high latitude factors that
include temperature, rainfall, and the melting of snow.
The global cooling that started 50 Ma ago was accompanied by a gradual elevation of the oceanic thermocline which,
around 3 Ma, was so shallow that tropical air-sea interactions started influencing the global climate. Such insights,
from studies of oceanic connections between low and high
latitudes, are shedding light on phenomena that range from
the decadal modulation of El Niño, to the perennial (rather
than intermittent) El Niño conditions of the early Pliocene,
to the recurrent ice-ages of the past million years. The
theories help explain the geological record of past climates,
which in turn provide valuable checks for computer models
of future global warming.
Refereed articles:
Boccaletti G., R. Pacanowski, S.G. Philander and A. Fedorov
The Thermal Structure of the Ocean, J. Phys. Oceanogr.,
34, 888-902, 2004.
Fedorov A.V., R.C. Pacanowski, S. G. Philander and G. Boccaletti: The effect of salinity on the wind-driven circulation
and the thermal structure of the upper ocean, J. Phys.
Oceanogr., 31, 1949-1966, 2004.
Boccaletti G., R. Pacanowski, and S.G. Philander: A diabatic
mechanism for decadal variability in the tropics, Dynamics
of Atmospheres and Oceans, 39, 3-19, 2005.
Barreiro M., S.G. Philander, R. Pacanowski, A. Fedorov: Simulations of warm tropical conditions with application to middle
Pliocene atmospheres. Climate Dynamics, doi:10.1007/
s00382-005-0086-4, 2005.
Other miscellaneous publications:
Philander S.G. El Niño and the Uncertain Science of Global
Warming. Daedalus, Journal of the American Academy of
Arts and Sciences pp 105-108, Spring 2004.
Philander S.G. Science in an Uncertain World, News from
ICTP, Trieste, Italy, Autumn, 2004.
Philander S.G. State of Fear The Day After Tomorrow, P-ROK,
Vol. 1 No. 2, 2005.
(P-ROK = Princeton Report on Knowledge)
Articles in press or submitted:
Philander S.G. Sextant to Satellite; the Education of a Landbased Oceanographer
Chapter in History of Physical Oceanography - Developments
since 1960. Editors M. Jochum and R. Martugudde. Publisher Springer/New York, 2006.
Fedorov A., C. Ravelo, P. Dekens, M. Barreiro, R. Pacanowski,
S.G. Philander: The Pliocene Paradox, Science, submitted.
Fedorov A, G. Boccaletti, R. Pacanowski and S. G. Philander:
The Freshening of Surface Waters in High Latitudes; Effects
on the Thermohaline and Wind-driven Circulations, J. Physical Oceanography, submitted.
datasets has been that location errors are typically ~1 km,
a value that exceeds both the earthquake dimensions (tens
of meters for magnitude 1 events) and the length scales of
significant structures within fault zones. By cross-correlating
the seismograms of “similar” earthquakes (those with similar
locations and focal mechanisms), it is possible to determine
relative arrival times with errors that are less than one-tenth
the sampling rate. From such measurements I and students
and post-docs working with me have relocated many thousands of microearthquakes recorded by seismic networks in
California and Hawaii. In most of our study regions we have
reduced errors in relative location to meters to tens of meters
for events separated by tens to hundreds of meters. This
increased resolution allows us to image fault-zone structures
that previously were invisible, and to obtain catalogs of many
thousands of events in which relative location errors are
much smaller than the earthquakes themselves. For studies
of earthquake interaction, which can be conducted sensibly
only in a statistical sense, such large numbers are essential
and cannot be obtained using standard catalogs.
For the past year most of my research has been devoted
to developing a theoretical understanding of earthquake nucleation, a spin-off of one of our ongoing projects designed
Allan Rubin
Professor
Ph.D., 1988, Stanford University
email: [email protected]
For the past few years I have been studying earthquake
physics both observationally and theoretically. The primary
impetus for this work has been the advent of waveform crosscorrelation as a tool for obtaining precise relative locations
of microearthquakes. Because the number of earthquakes increases exponentially with decreasing magnitude, earthquakes
near the detection threshold of a given seismic network represent a potential wealth of data for both structural geologists
and seismologists. A major impediment to exploiting these
24
to study the very asymmetric distribution of earthquake
aftershocks in our central San Andreas fault catalog. The
modern view of fault friction is that it depends upon both
the fault sliding velocity and the evolving physical or chemical state of the fault surface, which together comprise the
“rate” and “state” aspects of “rate-and-state” friction. Despite
the fact that the standard rate-and-state equations have been
around for over 20 years, their implications for earthquake
nucleation on elastically-deformable faults (meaning any
fault in the Earth, as opposed to small laboratory versions)
have remained elusive. The interest in this topic stems from
the fact that if nucleation occurred on large enough temporal and spatial scales, precursory signals could be detected
and interpreted prior to damaging earthquakes. While the
observational record in this regard has not been promising,
there have been numerous suggestions of “nucleation events”,
occurring on timescales of fractions of a second to hours, that
scale with the ultimate size of the earthquake.
For the first time, we have succeeded in obtaining analytic approximations for the size and timescale of earthquake
nucleation that are consistent with full numerical simulations. These approximations are based on well-established
principles of fracture mechanics, allowing much greater insight into the complex behaviors that result when the nonlinear friction equations operate in an elastic system. We found,
for example, that under the most popular of the laws for the
evolution of the fault “state”, nucleation near the base of the
seismogenic zone takes the form of an expanding crack that
might often be detectable using surface seismometers. Per-
haps more significantly, we showed that the aspect of this law
that leads to such large nucleation zones (possibly hundreds
of meters across) is clearly contradicted by existing laboratory
experiments. A second popular state evolution law leads to
much smaller “pulses” of slip that travel in one direction only.
Because all variants of these laws are strictly empirical and
are certainly inadequate at some level, it seems much more
important to obtain a generic understanding of, for example,
the conditions under which the nucleation zone expands or
contracts, rather than to just run computer simulations using
the currently favored friction law. Only then can one be in a
position to predict the outcome when other physics (inelastic dilation and pore pressure reduction within the fault
zone; frictional heating of pore fluids, etc.) comes into play.
This is where my efforts are now focused. In addition, our
theoretical work has pointed to non-traditional rock friction
experiments that might better distinguish between competing state evolution laws; I am currently working with Chris
Marone at Penn State and Nick Beeler at the USGS to design
and implement these.
Two-Year Bibliography
Refereed articles:
Rubin, A. M., and J.-P. Ampuero, Earthquake nucleation on (aging) rate and state faults, J. Geophys. Res., 110, B11312,
doi:10.1029/2005JB003686, 2005.
Peng, Z., J.E. Vidale, C. Marone, and A. Rubin, Systematic
variations in recurrence interval and moment of repeating
aftershocks, Geophys. Res. Lett., 32 (15): Art. No. L15301
AUG 2 2005.
reasons it took so long to complete (10 years) is because there
was a great deal of new research we needed to do in areas
that were just not adequately understood. I estimate that I
published more than two-dozen papers over the past decade
that grew primarily out my attempts to fill in the gaps in our
understanding. The gathering of several major new data sets
as part of the WOCE and JGOFS programs in the decade
of the 1990’s provided a basis for a new look at the field, but
much of the analysis of these data had not been done when
I started writing during an earlier sabbatical. In addition,
while some areas had a great deal of exciting new research
that we could base our book on, no one had successfully
attempted to pull all of this together into a new synthesis
since Broecker and Peng’s magnum opus of 1982, Tracers in
the Sea. Our ambition was to provide a modern analogue to
that wonderful textbook that has served as an introduction
for a whole generation of ocean biogeochemists. We will be
delighted if we succeed even partially in accomplishing that
goal.
As a result of the exceptional efforts required to finish up
the book over the last year, my journal publications dropped
from a high of nine achieved in 2004 to one in 2005.
However, I have eight journal articles in press or submitted
that reflect the culmination of several ongoing projects that
carried over from previous years, as well as reflecting my everdeepening interest in understanding the critical role of the
Southern Ocean in controlling ocean biogeochemistry and its
Jorge L. Sarmiento
Professor
Ph.D., 1978, Columbia University
email: [email protected]
The primary focus of my research over the past year was the
completion of my textbook cum research monograph on
ocean biogeochemistry (Ocean Biogeochemical Dynamics,
now in press with Princeton University Press) together with
my old post doc and now UCLA faculty member (soon to be
ETH faculty member), Nicolas Gruber. We have reviewed
the galley proofs, and the book is scheduled to come out
in May. It is of course difficult to anticipate how it will be
received, but there are already quite a few colleagues who
have been happily using earlier versions of the book in their
courses for some years.
The book represents much more than just a synthesis
of our present knowledge and understanding. One of the
25
carbon cycle. These new journal articles can be categorized
into three broad areas: (1) ocean biogeochemical processes
and modeling, (2) modeling and observational constraints on
ocean and land carbon sinks for anthropogenic carbon, and
(3) Southern Ocean biogeochemistry and circulation. Each
of these areas is discussed briefly below, with reference to the
in press and submitted papers.
ferences have major consequences for the rate of CO2 uptake
estimated by these models. We are developing a new ocean
model in collaboration with colleagues at GFDL that we
hope will provide us with an improved simulation of processes in this region.
Two-Year Bibliography
Books:
Sarmiento, J. L., and N. Gruber, Ocean Biogeochemical Dynamics, Princeton University Press, in press.
Ocean Biogeochemical Processes and Modeling: The Orr
et al. (2005) Science paper, my only 2005 journal publication, discusses the impact of ocean acidification by anthropogenic carbon on the depth of the saturation horizon of aragonite, and its likely outcropping at the surface of the Southern
Ocean during the middle of this century. The possible
consequences of this are very disturbing. The in press and
submitted articles (1) and (2) by Dunne et al. and Jin et al.
present results from our latest efforts to develop new ocean
biogeochemistry models. This is ongoing research aimed at
model development with the goal of providing new analyses
of the impact of global warming on ocean biology and the
ocean carbon cycle. Article (3) (Behrenfeld et al., submitted)
is a byproduct of a parallel effort to develop empirically based
ocean ecosystem models based on a new analysis of satellite
color observations.
Refereed articles:
Doney, S. C., K. Lindsay, K. Caldeira, J.-M. Campin, H. Drange,
J.-C. Dutay, M. Follows, Y. Gao, A. Gnanadesikan, N.
Gruber, A. Ishida, F. Joos, G. Madec, E. Maier-Reimer, J.C.
Marshall, R.J. Matear, P. Monfray, A. Mouchet, R. Najjar,
J.C. Orr, G.-K. Plattner, J. Sarmiento, R. Schlitzer, R. Slater,
I.J. Totterdell, M.-F. Weirig, Y. Yamanaka, and A. Yool, 2004.
Evaluating global ocean carbon models: The importance of
realistic physics, Global Biogeochem. Cycles, 18, GB3017,
doi:10.1029/2003GB002150.
Edmonds, J., F. Joos, N. Nakicenovic, R. G. Richels, and J. L.
Sarmiento, Scenarios, targets, gaps, and costs. In: The
Global Carbon Cycle, ed. C. B. Field and M. R. Raupach,
Island Press, Washington, D.C., pp. 77-102. 2004.
Gnanadesikan, A., J. P. Dunne, R. M. Key, K. Matsumoto, J. L.
Sarmiento, R. D. Slater, and P, S. Swathi, Oceanic ventilation and biogeochemical cycling: Understanding the physical
mechanisms that produce realistic distributions of tracers
and productivity. Global Biogeochem. Cycles, 18, GB4010,
doi:10.1029/2003GB002097, 2004.
Greenblatt, J. B., and J. L. Sarmiento, Variability and climate
feedback mechanisms in ocean uptake of CO2. In: The
Global Carbon Cycle, ed. C. B. Field and M. R. Raupach,
Island Press, Washington, D.C., pp. 257-275, 2004.
Marinov, I., and J. L. Sarmiento, The role of the oceans in the
global carbon cycle: An overview. In: The Ocean Carbon
Cycle and Climate, ed. M. Follows and T. Oguz, NATO ASI,
Ankara, Turkey, Kluwer Academic Publishers, pp. 251-295,
2004.
Matsumoto, K., J.L. Sarmiento, R.M. Key, O. Aumont, J.L. Bullister, K. Caldeira, J.-M. Campin, S.C. Doney, H. Drange, J.-C.
Dutay, M. Follows, Y. Gao, A. Gnanadesikan, N. Gruber,
A. Ishida, F. Joos, K. Lindsay, E. Maier-Reimer, J.C. Marshall, R.J. Matear, P. Monfray, A. Mouchet, R. Najjar, G.-K.
Plattner, R. Schlitzer, R. Slater, P.S. Swathi, I.J. Totterdell,
M.-F. Weirig, Y. Yamanaka, A. Yool, J.C. Orr, Evaluation of
ocean carbon cycle models with data-based metrics. Geophys. Res. Lett., 31, L07303, doi:10.1029/2003GL018970,
2004.
Mignone, B. K., J. L. Sarmiento, R. D. Slater, and A. Gnanadesikan, Sensitivity of sequestration efficiency to mixing processes in the global ocean. Energy, 29: 1467-1478, 2004.
Sarmiento, J. L., N. Gruber, M. A. Brzezinski, and J. P. Dunne,
High latitude controls of the global nutricline and low latitude
biological productivity. Nature, 427: 56-60, 2004a.
Sarmiento, J. L., R. Slater, R. Barber, L. Bopp, S. C. Doney, A.
C. Hirst, J. Kleypas, R. Matear, U. Mikolajewicz, P. Monfray,
V. Soldatov, S. A. Spall, and R. Stouffer, Response of ocean
ecosystems to climate warming. Global Biogeochem .
Cycles, 18, GB3003, doi:1029/2003GB002134, 2004b.
Orr, J. C., V. J. Fabry, O. Aumont, L. Bopp, S. C. Doney, R.
M. Feely, A. Gnanadesikan, N. Gruber, A. Ishida, F. Joos, R.
M. Key, K. Lindsay, E. Maier-Reimer, R. Matear, P. Monfray, A. Mouchet, R. G. Najjar, G.-K.Plattner, K. B. Rodgers,
C. L. Sabine, J. L. Sarmiento, R. Schlitzer, R. D. Slater,
I. J. Totterdell, M.-F. Weirig, Y. Yamanaka, and A. Yool,
Anthropogenic ocean acidification over the 21st century and
Modeling and Observational Constraints on Carbon
Sinks: A major research directions that my group has taken
in the past years is estimation of the magnitude, spatial
distribution, and temporal variability of carbon sources and
sinks by inverse modeling of atmospheric and oceanic CO2
observations and by evaluation of models with the major
new data sets that were gathered by the global surveys of the
past decade. This work culminated during previous years in
several papers that converged on an estimate for the oceanic
carbon sink of 2.0 ± 0.3 Pg C yr—1 for the 1990’s. In a series
of new papers (references (4) to (6) by Fletcher et al., and
Jacobson et al, a and b) my group has explored the implications of this oceanic constraint for our estimates of land
carbon sources and sinks. The submitted papers by Jacobson
et al., a and b suggest that the large anthropogenic carbon
sink postulated to exist in tropical rain forests is probably
a chimera. The absence of this CO2 fertilization sink has
major negative implications for the future growth rate of
atmospheric CO2 – mitigation will be much more difficult
than had been previously been thought.
Southern Ocean Circulation and Biogeochemistry: Reference (7) (Marinov et al., submitted) demonstrates that there
is a clear separation in the Southern Ocean between regions
that control the air-sea balance of CO2 (confined primarily to
high latitude regions of deep-water formation), and regions
that control the return of nutrients from the deep ocean to
the surface (lower latitude areas where Subantarctic Mode
Water forms; see Sarmiento et al.,, 2004a). In Mignone et
al., in press (reference (9)), we show that major differences in
the representation of Southern Ocean circulation previously
identified and analyzed by Matsumoto et al. (2004) can be
explained as resulting from differences in the representation
of wind forcing and mixing in the ocean models. These dif26
its impact on marine calcifying organisms. Nature, 437: 681686, 2005.
Jacobson, A. R., S. E. Mikaloff-Fletcher, N. Gruber, J. L.
Sarmiento, M. Gloor, and TransCom Modelers, A joint atmosphere-ocean inversion for surface fluxes of carbon dioxide:
I. Methods and global-scale fluxes, Global Biogeochem
Cycles, submitted.
Jacobson, A. R., S. E. Mikaloff-Fletcher, N. Gruber, J. L.
Sarmiento, M. Gloor, and TransCom Modelers, A joint atmosphere-ocean inversion for surface fluxes of carbon dioxide:
II. Regional results, Global Biogeochem Cycles, submitted.
Marinov, I. A. Gnanadesikan, J. R. Toggweiler, and J. L.
Sarmiento, The Southern Ocean biogeochemical divide,
Nature, submitted.
Mignone, B. K., A. Gnanadesikan, J. L. Sarmiento, R. D. Slater,
Central role of southern hemisphere winds and eddies in
modulating the oceanic uptake of anthropogenic carbon,
Geophys. Res. Lett., in press.
Articles in press or submitted:
Dunne, J. P., R. A. Armstrong, A. Gnanadesikan, and J. L.
Sarmiento, Empirical and mechanistic models for the particle export, Global Biogeochem. Cycles, in press.
Jin, X., N. Gruber, J. P. Dunne, J. L. Sarmiento, and R. A.
Armstrong, Diagnosing CaCO3 and opal export and phytoplankton functional groups from global nutrient and alkalinity
distributions, Global Biogeochem. Cycles, in press.
Behrenfeld, M., R. O’Malley, D. A. Siegel, C. McClain, J.
Sarmiento, G. Feldman, P. Falkowski, E. Boss, and A. Milligan, Climate-driven trends in contemporary ocean productivity, Science, submitted.
Fletcher, S. E., N. Gruber, A. R. Jacobson, S. C. Doney, S.
Dutkiewicz, M. Follows, K. Lindsay, D. Menemenlis, A.
Mouchet, and J. Sarmiento, Inverse estimates of anthropogenic carbon uptake, transport, and storage by the ocean,
Global Biogeochem. Cycles, in press.
• What terms and rates compose the budgets of “fixed”
(biologically available) N in the modern ocean, on
land, and in the atmosphere? What are the sensitivities
of the different inputs and outputs? How have the N
budgets in these systems changed over climate cycles,
and how have these changes affected the fertility of
ocean and land? What has been the role of such
changes in the global carbon cycle?
Daniel Sigman
Assistant Professor
Ph.D., 1997, MIT and Woods Hole
Oceanographic Institution
email: [email protected]
My research activities over the past year are summarized
below under the following headings: (1) isotope method development, (2) laboratory studies of isotope discrimination,
(3) studies in the modern ocean, (4) studies in the terrestrial
biosphere, the atmosphere, and ice cores, (5) paleoceanographic studies, and (6) model studies of past ocean changes.
My group’s entire body of work in these areas represents our
effort to progress from the introduction of new measurements, to the development of the background information
needed to make those measurements useful, to their application to important questions, and finally to a quantitative
consideration of the findings in a broader environmental
context. The citations below refer to manuscripts listed in the
publications section of the annual review form.
My group members and I are focused on two distinct but
complementary research goals. First, we use of the isotopic
composition of dissolved nitrogen species (such as nitrate
(NO3-) and dissolved organic nitrogen) to provide integrative
constraints on nitrogen cycle processes in modern environments, mostly in the ocean but also in terrestrial systems
and the atmosphere. Second, we treat the past, as recorded
in marine sediments and glacial ice, as an archive of natural
experiments from which the underlying controls on the physical and biogeochemical fluxes of the environment can be
determined; we study the past N cycle both in its own right
and as an indicator of broader environmental change.
A unifying goal of all of this work is to understand the
role of plant nutrients in the interaction between life and the
environment. Two sets of questions, focused on the ocean,
have most centrally motivated our studies:
Isotope method development
In 2005, building on my group’s previously developed methods for isotopic analysis of nitrate, graduate student Angela
Knapp published the first method for the 15N/14N analysis of
bulk dissolved organic matter in seawater, a major N pool in
the ocean that had not previously been characterized isotopically [Knapp et al., 2005]. In turn, on the basis of this work,
a collaboration among Moritz Lehmann, Ben Houlton, and
Masha Prokopenko has resulted in the development of a highsensitivity method for measuring the 15N/14N of dissolved
ammonium (NH4+), as described in Houlton’s 2005 Ph.D.
dissertation. Also building upon Knapp’s dissolved organic N
method, Becky Robinson and Brigitte Brunelle have established, improved, and tested a new technique for the 15N/14N
of diatom microfossil-bound N, for paleoclimate studies
[Robinson et al., 2005, Brunelle et al., in review]. Finally, Julie
Granger has developed a versatile method for the removal of
• The polar oceans are special domains in the ocean
where the “major nutrients” nitrogen (N) and
phosphorus (P) are not completely consumed by algal
growth. What factors control the physical conditions
and nutrient status of the polar surface ocean? Over
the ice age/interglacial cycles of the last 3 million
years, how have the characteristics of the polar ocean
affected other regions of the ocean, atmospheric
carbon dioxide, and climate?
27
nitrite (NO2-) from aqueous samples to prevent this species
from contaminating the isotopic analysis of nitrate [Granger
et al., in review]. This method is particularly relevant to
Granger’s culture studies of denitrifying bacteria (see below),
in which there were large accumulations of nitrite.
budget for the surface ocean at the Bermuda Atlantic Timeseries Station (BATS), indicating that N2 fixation accounts
for <10% of the N supply at this site and reopening the question of the N source for the large summertime drawdown in
CO2 at BATS.
Nitrate N and O isotope data are also contributing to
our understanding of fixed N loss from the ocean. In 2005,
Moritz Lehmann published a study of the Bering Sea in
which we find that the down-slope transport of organic
matter from the productive Bering shelf drives denitrification in the deep sea sediments, leading to the development
of a previously observed nitrate deficit in the deep basin of
the Bering Sea [Lehmann et al., 2005]. These findings suggest that sedimentary denitrification is likely at the heart of
unexplained variations in the nitrate-to-phosphate ratio of
deep waters, with implications for globally integrated rates of
nitrate loss from the ocean.
Finally, the isotopes of nitrate also represent a potentially
powerful constraint on the internal cycling of fixed N in the
ocean, with implications for ocean circulation and the carbon
cycle. My strongest interest in this regard is in the supply,
transport, and consumption of nitrate in regions of the polar
ocean, the Southern Ocean in particular. Combined concentration and isotope data, interpreted with a numerical model,
allowed Peter DiFiore to quantify the different physical
mechanisms of nitrate supply, the rate of biological export
production, and the isotope effect of nitrate assimilation in
the Subantarctic Zone of the Southern Ocean [DiFiore et al.,
in review]. These studies of the modern polar ocean complement our lab studies of algal physiology and our paleoceanographic studies.
Laboratory studies of isotope discrimination
The utility of isotopic distributions in the environment is
premised on knowledge of the magnitudes of isotope discrimination by individual biogeochemical reactions, which
is most often gained through lab studies of cultured organisms. Julie Granger’s focus is on the isotope effects of nitrateconsuming processes, in particular, nitrate assimilation by
photosynthetic organisms (central to studies of nutrient supply and uptake in the surface ocean) and denitrification by
heterotrophic bacteria (central to studies of the global ocean’s
input/output budget of fixed N). In previous years, we have
studied the relationship between N and O isotope fractionation during nitrate assimilation. In 2005, our investigations
were extended to denitrifiers. Because we believe that nitrate
reductase is the driver of isotope fractionation during both
nitrate assimilation and denitrification, we had predicted
that the N-to-O isotope coupling would be the same for
both processes. This prediction has been borne out by Julie’s
culture experiments, but one exotic denitrifier demonstrated
different and unexpected behavior, which we believe relates
to the several forms of nitrate reductase found in certain
denitrifiers (manuscript in preparation).
Studies in the modern ocean
In projects carried out in various regions of the open ocean
and in previously well-studied isolated basins, we are developing and applying the N and O isotope ratios of nitrate
and dissolved organic N as integrative signals of spatially and
temporally variable processes. Important results have begun
to arise.
In regions where the input of newly fixed N has been
proposed to augment the subsurface nitrate pool, the 15N/14N
of this nitrate converges toward the 15N/14N of newly fixed N
and thus appears consistent with this process [Knapp et al.,
2005]. Ongoing work described in Knapp’s Ph.D. dissertation seeks to combine the isotope data with constraints on
circulation to quantify the rate of N2 fixation in the overlying surface ocean. Perhaps more surprising is the tentative
evidence from our coupled nitrate 15N/14N and 18O/16O
measurements for a previously unrecognized input of (low15
N/14N) newly fixed N in a region of intense nitrate loss by
denitrification [Sigman et al., 2005].
With our new ability to measure the 15N/14N of dissolved
organic N (DON), we have begun to study this enigmatic
N pool, which has been hypothesized to be an important
N source and sink for algae growing in the surface ocean as
well as a form in which N can be exported from the surface
ocean [Knapp et al., 2005]. In general, we have found the
bulk DON pool of the tropical and subtropical surface ocean
to be remarkably stable in isotopic composition, implying
that this pool is not a direct participant in the rapid N cycling that is known to take place in the surface ocean. Angie
Knapp’s measurements of DON completes the N isotope
Studies in the terrestrial biosphere, the atmosphere, and
ice cores
Recent Ecology and Evolutionary Biology graduate student Ben Houlton has measured the isotopic composition
of nitrate, dissolved organic N, and ammonium in cloud
water, rainfall, soil extracts, soil water, and streams across a
well-constrained rainfall gradient on the island of Maui, as
described in his 2005 Ph.D. dissertation. The resulting N
isotope budgets for these forests indicate an important and
rainfall-dependent role for denitrification in tropical systems [Houlton et al., in review]. Associated with changes in
the forest N budget across the rainfall gradient, we found a
remarkably abrupt transition in the form of N fueling plant
growth, from nitrate to ammonium with increasing rainfall.
In contrast to a widely held view that plants control forest
N fluxes, the Maui gradient suggests that the plants in these
forests are not so much driving the N fluxes as finding a solution for their N demand that is consistent with the conditions of microbial growth.
With recent Princeton Ph.D. Meredith Hastings, I have
worked on the nitrate N and O isotopes in rain, snow, and
ice as tracers of reactive nitrogen sources and processing
in the modern and ancient atmosphere. Hastings’s downcore study in the GISP2 ice core from Greenland indicates
a dramatically (~20‰) higher nitrate 15N/14N in ice from
the last ice age than in the Holocene [Hastings et al., 2005].
28
Although post-depositional artifacts cannot be ruled out
for glacial-age ice, the 15N/14N data suggest a major climate-driven change in the relative contributions of different
sources of atmospheric reactive N, such as may result from a
reorganization of the terrestrial biosphere. While the isotopic
signatures of reactive N sources and processing require better
description to realize the true potential of the isotope tracers
of atmospheric reactive N, our new methods are expediting
progress in this field.
cycles in CO2 and climate.
Two-Year Bibliography
Refereed articles:
Hastings, M. G., E. J. Steig, and D. M. Sigman, Seasonal variations in N and O isotopes of nitrate in snow at Summit,
Greenland: Implications for the study of nitrate in snow and
ice cores, Journal of Geophysical Research – Atmospheres,
109, D20306, 10.1029/2004JD004991, 2004.
Deutsch, C., D. M. Sigman, R. C. Thunell, N. Meckler, and G. H.
Haug, Isotopic constraints on glacial/interglacial changes in
the oceanic nitrogen budget, Global Biogeochemical Cycles,
18, GB4012, 10.1029/2003GB002189, 2004.
Granger, J., D. M. Sigman, J. A. Needoba, and P. J. Harrison,
Coupled nitrogen and oxygen isotope fractionation of nitrate
during assimilation by cultures of marine phytoplankton, Limnology and Oceanography, 49, 5 , 1763-1773, 2004.
Robinson, R. S., B. G. Brunelle and D. M. Sigman, Revisiting nutrient utilization in the glacial Antarctic: Evidence from a new
method for diatom-bound N isotopic analysis, Paleoceanography, 19, 3, PA3001, 10.1029/2003PA000996, 2004.
Thunell, R. C., D. M. Sigman, F. Muller-Karger, Y. Astor and R.
Varela, The nitrogen isotope dynamics of the Cariaco Basin,
Venezuela, Global Biogeochemical Cycles, 18, 3, GB3001,
10.1029/2003GB002185, 2004.
Lehmann, M. F., D. M. Sigman, and W. M. Berelson, Coupling
the 15N/14N and 18O/16O of nitrate as a constraint on benthic
nitrogen cycling, Marine Chemistry, 88, 1-20, 2004.
Needoba, J. A., D. M. Sigman, P. J. Harrison, The mechanism of
isotope fractionation by algal nitrate assimilation as illuminated by the 15N/14N of intracellular nitrate, Journal of Phycology, 40, 517–522, 2004.
Sigman, D. M., S. L. Jaccard, and G. H. Haug, Polar ocean
stratification in a cold climate, Nature, 428, 59-63, 2004.
Hastings, M. G., D. M. Sigman, and E. J. Steig, Glacial/interglacial changes in the isotopes of nitrate from the Greenland
Ice Sheet Project 2 (GISP2) ice core, Global Biogeochemical
Cycles, 19, GB4024, doi:10.1029/2005GB002502, 2005.
Sigman, D. M., J. Granger, P. DiFiore, M. F. Lehmann, A. v.
Geen, R. Ho, and G. Cane, Coupled nitrogen and oxygen
isotope measurements of nitrate along the eastern North
Pacific margin, Global Biogeochemical Cycles, 19, GB4022,
doi:10.1029/2005GB002458, 2005.
Lehmann, M. F., D. M. Sigman, D. C. McCorkle, B. G. Brunelle,
S. Hoffmann, M. Kienast, G. Cane, and J. Clement, The origin of the deep Bering Sea nitrate deficit -- Constraints from
the nitrogen and oxygen isotopic composition of water column nitrate and benthic nitrate fluxes, Global Biogeochemical Cycles, 19, GB4005, 10.1029/2005GB002508, 2005.
Jaccard, S. L., Haug, G. H., Sigman, D. M., Pedersen, T. F.,
Thierstein, H. R., Röhl. U., Glacial/interglacial changes in
Subarctic North Pacific stratification, Science, 308,10031006, 2005.
Robinson, R. S., D. M. Sigman, P. J. DiFiore, M. M. Rohde,
T. A. Mashiotta, and D. W. Lea, Diatom-bound 15N/14N:
New support for enhanced nutrient consumption in the
ice age Subantarctic, Paleoceanography, 20, PA3003,
10.1029/2004PA001114, 2005.
Haug, G. H., A. Ganopolski, D. M. Sigman, A. Rosell-Mele, G. E.
A. Swann, R. Tiedemann, S. L. Jaccard, J. Bollmann, M. A.
Maslin, M. J. Leng, and G. Eglinton, North Pacific seasonality and the glaciation of North America 2.7 million years ago,
Nature, 433, 821-825, 2005.
Knapp, A. N., D. M. Sigman, and F. Lipschultz, N isotopic composition of dissolved organic nitrogen and nitrate at the Bermuda Atlantic time-series study site, Global Biogeochemical
Cycles, 19, GB1018, 10.1029/2004GB002320, 2005.
Paleoceanographic studies
Former postdoctoral researcher Rebecca Robinson and
current graduate student Brigitte Brunelle have used their
recently developed method for diatom microfossil-bound N
isotope analysis to generate down-core records from polar
ocean regions, where the nutrient status and physics of the
surface layer can strongly affect atmospheric CO2. New
down-core records from the Subantarctic Zone of the Southern Ocean provide evidence for more complete nutrient
drawdown in the region during the last ice age [Robinson et
al., 2005]. This represents some of the first evidence for naturally driven, long term iron fertilization of the ocean, in this
case due to greater dust inputs to the region during the last
ice age, much as had been predicted by the late John Martin.
Ice age enhancement of nitrate consumption in the Subantarctic Zone may also explain observations of lower nutrient
content, higher dissolved O2 content, and less denitrification
in the tropical thermocline during the last ice age, with implications for climate-related changes in global ocean fertility
and the N budget. In 2005, my collaborators (in particular,
Gerald Haug) and I have published several papers demonstrating that the Subarctic North Pacific and the most polar
Southern Ocean respond similarly to climate change, including glacial/interglacial cycles [Haug et al., 2005; Jaccard et al.,
2005]. These studies and a manuscript in review by graduate
student Brigitte Brunelle on the ice age Bering Sea greatly
strengthen the case for a pervasive and general tendency for
these polar ocean regions to undergo vertical stratification
during cold climates. The reconstructed polar ocean changes
have the capacity to affect atmospheric CO2 in the observed
sense of its glacial/interglacial change.
Model studies of past ocean changes
I have recently begun to consider a physical mechanism for
the apparent climate/polar stratification link mentioned
above that involves the reduced sensitivity of seawater density
to temperature at low temperatures: in the case of a globally
colder ocean, temperature gradients become less important
in polar ocean density structure, reducing their opposition
to the stratifying effect of the net atmospheric deposition of
fresh water on polar ocean regions. Postdoctoral researcher
Agatha de Boer has used a general ocean circulation model
to investigate this effect [de Boer et al., in review]. The results
provide proof of concept for a significant role for whole
ocean temperature change in polar ocean overturning. They
also point to interactions among the polar regions of the
different ocean basins that, along with the inclusion of other
feedbacks, are leading us toward a more complete hypothesis
for the role of polar ocean stratification in the Pleistocene
29
Articles in press or submitted:
de Boer, A. M., D. M. Sigman, and J. R. Toggweiler, The effect of
global ocean temperature change on deep ocean ventilation,
Paleoceanography, in review.
DiFiore, P. J., D. M. Sigman, T. W. Trull, A. J. Lourey, and K. L.
Karsh, Nitrogen isotope constraints on Subantarctic biogeochemistry, Journal of Geophysical Research – Oceans, in
review.
Brunelle, B. G., D. M. Sigman, M. S. Cook, L. D. Keigwin, G. H.
Haug, B. Mingram, and G. Schettler, Evidence from diatombound nitrogen isotopes for Subarctic Pacific stratification
during the last ice age and a link to North Pacific denitrification changes, Paleoceanography, in review.
Granger, J., D. M. Sigman, M. Prokopenko, and P. D. Tortell, A
method for nitrite removal in nitrate N and O isotope analysis, Limnology and Oceanography: Methods, in review.
Galbraith, E. D., D. M. Sigman, R. S. Robinson, T. F. Pedersen,
“Nitrogen in Past Marine Environments”, in Nitrogen in the
Marine Environment (2nd edition), edited by D. A. Bronk, M.
R. Mulholland, and D. G. Capone, in review.
Houlton, B. Z., D. M. Sigman, and L. O. Hedin, Isotopic evidence
for large gaseous nitrogen losses from tropical rainforests,
Proceedings of the National Academy of Sciences, in review.
ary faults. Results using this new theory indicate very weak
faults in Taiwan, Japan and Niger delta. Furthermore this
work shows that the upper crust is relatively strong, which
raises the fundamental question of how a crust containing
weak faults is able to be strong.
John Suppe
Blair Professor of Geology
Ph.D., 1969, Yale University
email: [email protected]
Two-Year Bibliography
Books
(with J. Shaw, C. Connors, editors) Seismic Interpretation of
Contractional Fault-Related Folds: an AAPG Seismic Atlas.
American Association of Petroleum Geologists, 156pp, 2005.
Refereed articles:
San Andreas fault in southern California: Three-dimensional fault
models and earthquake scenarios. Journal of Geophysical
Research, v. 109, B04313, 17 pp, 2004.
Essay Review of John Rodgers “The Company I Kept.” American Journal of Science, v. 304, p. 285-286, 2004.
(with Erickson, S. G., and Strayer, L. M.) Numerical modeling of
hinge-zone migration in fault-bend folds. . In McClay, K. ed.,
“Thrust Tectonics and Hydrocarbon Systems” American Association of Petroleum Geologists Memoir, 82, p. 438-452, 2004.
(with L. M. Strayer and S. G. Erickson) Influence of growth strata
on the evolution of fault-related folds: Distinct-element models. . In McClay, K. ed., “Thrust Tectonics and Hydrocarbon
Systems” American Association of Petroleum Geologists
Memoir, 82, p. 413-437, 2004.
(and Chris Connors and Yikun Zhang) Shear fault-bend folding. In McClay, K. ed., “Thrust Tectonics and Hydrocarbon
Systems” American Association of Petroleum Geologists
Memoir, 82, p. 303-323, 2004.
(with A. Ferrari, X. Wang and C. Jia) The Yakeng detachment fold,
China. In J. Shaw, C. Connors, J. Suppe, editors, Seismic
Interpretation of Contractional Fault-Related Folds. American
Association of Petroleum Geologists, p. 110-113, 2005.
(with J. H. Shaw and S. C. Hook) Pitas Point anticline, California,
USA. In J. Shaw, C. Connors, J. Suppe, editors, Seismic
Interpretation of Contractional Fault-Related Folds. American
Association of Petroleum Geologists, p. 60-62, 2005.
(with J. H. Shaw and C. D. Connors) Part 1: Structural Interpretation
Methods. In J. Shaw, C. Connors, J. Suppe, editors, Seismic
Interpretation of Contractional Fault-Related Folds. American
Association of Petroleum Geologists, p. 1-58, 2005.
(with F. Corredor and J. H. Shaw) Shear fault-bend fold, deep water
Niger Delta. In J. Shaw, C. Connors, J. Suppe, editors, Seismic
Interpretation of Contractional Fault-Related Folds. American
Association of Petroleum Geologists, p. 87-92, 2005.
(with A. Hubert-Ferrari and Jerome Van Der Woerd) Irregular
earthquake cycle along the southern Tianshan, China (Aksu
area). Journal of Geophysical Research, v. 110, B06402,
doi:10.1029/2003JB002603, 2005.
Since I am in the midst a one-year sabbatical I should
be brief. I am currently Visiting Professor of Tectonics at
Caltech and in the second half of the sabbatical will be at
the Ludwig Maximillians University in Munich. The stay
in Germany is the first part of a total of one-year of sojourns
supported by an honorific award from the Alexander von
Humboldt Foundation.
I spent much effort in the spring as the scientific organizer of an “International Conference on Theory and Application of Fault-Related Folding in Foreland Basins” which
was attended by a stellar cast of ~70 international experts
and ~140 Chinese, held in Beijing 25-27 June, followed by
a logistically ambitious one-week field trip for 110 people to
remote areas of far western China to observe many examples
of actively growing anticlines, which was the phenomenon of
interest to this conference. The conference was enormously
successful and is being followed by two major collections
of papers; one is a Memoir of the American Association of
Petroleum Geologists and the other a special section of the
Journal of Geophysical Research. I am involved in many
papers and with the editing. So many of my former students
and friends were involved in the conference that it could be
considered a Festschrift.
However my main current focus is completing a major
monograph on fault-related fold theory to be published by
Princeton University Press. In addition I have obtained a
surprising result in critical-taper wedge theory which allows
one to determine absolute fault strength from wedge taper
data, independent of significant assumptions about material
properties. This is an important contribution to the longstanding controversy over the strength of major plate-bound30
(with Li-Fan Yue and Jih-Hao Hung) Structural geology of a
classic thrust belt earthquake: the 1999 Chi-Chi earthquake
Taiwan (Mw7.6). Journal of Structural Geology v, 27, 20582083, 2005.
(with A. Hubert-Ferrari, Ramon Gonzalez-Mieres, X. Wang)
Active folding of the landscape in the southern Tianshan,
China. Journal of Geophysical Research, submitted, 2005.
(with Ramon Gonzalez-Mieres) Relief and shortening in detachment folds. Journal of Structural Geology, submitted, 2005.
Mass balance and thrusting in detachment folds. (In K. McClay,
J. H. Shaw and J. Suppe, editors) Thrust-Related Folding,
American Association of Petroleum Geologists Memoir,
submitted, 2005.
(with K. McClay and J. H. Shaw), editors, Thrust-Related Folding, American Association of Petroleum Geologists Memoir,
(chapter manuscripts in review), 2005.
Other miscellaneous publications:
(with Dengfa He) Guidebook for fieldtrip in souh and north Tianshan foreland basin, Xinjiang Uygur Autonimous Region,
China: International Conference on Theory and Application
of Fault-Related Folding in Foreland Basins, 78 pp, 2005.
Articles in press or submitted
submitted:
(with Kauan-Yin Lai,Yue-Gau Chen, Jih-Hao Hung and Ya-Wen
Chen) Fault geometry related surface deformation of an active fault: evidence from geomorphic features and coseismic
slip. Quaternary International, in press, 2005.
to planktonic communities and in determining the net nitrogen budget of ecosystems. A new project on phytoplankton
nitrogen dynamics now makes the link between the carbon
and nitrogen cycles explicit, by investigating the potential for
N assimilation to control the composition of photosynthetic
planktonic assemblages.
Ward lab has a web page where all of this is described.
http://geoweb.princeton.edu/research/ecomicrobio/ecomicrobio.html
Bess B. Ward
William J. Sinclair Professor of
Geosciences
Ph.D., 1982 University of
Washington
1. “Biocomplexity of Aquatic Microbial systems: Relating diversity of Microorganisms to Ecosystem Function”
(O’Mullan, Adhitya) (http://geoweb.princeton.edu/research/
biocomplexity/index.html)
2005 was the last official year of this collaborative project, involving several other institutions, all working in Chesapeake
Bay and coordinated through Princeton as the lead institution. Microbial biogeochemical cycling of the elements regulates a dynamic environment in which the cycles of different
elements are linked through the physiology of microorganisms. Our present understanding of ecosystem function has
been gained through physical/chemical approaches to measurement and modeling of the net transformations. These
approaches necessarily rely on gross simplifications about the
role and regulation of the various functional groups (guilds)
involved. Recent advances in molecular microbial ecology
have shown the microbial world to contain immense diversity and complexity at every level: redundancy and duplication
of functional genes within a single organism; molecular diversity among functional genes that encode the same process
in different organisms; large genetic diversity among different
organisms apparently engaged in the same biogeochemical
function within single communities; great variability in the
species composition of different communities that apparently
perform equally well.
The goal of this project is to investigate the functional
relationship between complexity in microbial communities and the physical/chemical environment at a range of
biological and ecological scales. Previously, such analysis was
technologically limited by the inability to assay large numbers of samples simultaneously for a large number of genes
and phylotypes. Using gene array technology, we will be able
to detect the distribution and differential expression of functional genes in natural systems. The gene arrays, along with
My research concerns the marine and global nitrogen cycle,
using molecular and immunological probes for marine
bacteria and bacterial processes (especially nitrification and
denitrification), and measuring the rates of N transformation processes. We have ongoing research on denitrification
in several suboxic zones of the world ocean (Arabian Sea,
Eastern Tropical North and South Pacific) and in Antarctica,
the genes involved in nitrogen assimilation by phytoplankton, diversity of functional guilds of bacteria involved in the
nitrogen cycle of aquatic systems, and the role of metals in
nitrogen redox biogeochemistry. Some of the main projects
are summarized explicitly below.
Microbes control many of the important biogeochemical
processes that occur in the oceans as well as on land. They
contribute to the trace gas cycles that influence climate; they
utilize and produce nutrients that are involved in eutrophication; and they are even capable of cleansing the environment
by degrading a vast variety of chemical compounds, both
naturally occurring and anthropogenically produced. My
research focuses on the nitrogen cycle and the microorganisms involved in transformations of inorganic and organic
nitrogen in the ocean and in sediment environments. This
research makes use of technical approaches that range from
molecular biology to stable isotope biogeochemistry. The two
main bacterial groups we study are the nitrifiers, autotrophs
that oxidize ammonium to nitrite and nitrate, and the denitifiers, heterotrophs that can respire nitrate in the absence of
oxygen. The linked activities of these two groups can be crucial in determining the chemical form and supply of nitrogen
31
4. “Draft Level Sequencing of a Selection of Nitrifying
Bacteria” (O’Mullan) and “Microbial genome sequencing;
The complete genome sequence of a mini consortium of
marine ammonia oxidizers”
Sequencing is nearly complete for the entire genome of five
ammonia-and nitrite-oxidizing bacteria. Nitrobacter hamburgensis 14X was grown in our lab and I extracted the DNA
that was used for sequencing. Ward lab is the lead on the N.
hamburgensensis genome and annotation is currently underway. In the NSF project, we are sequencing two additional
ammonia oxidizers, including Nitrosococcus oceanus. The
Moore foundation microbial genome project has agreed to
sequence another N. oceanus genome, and that project is now
underway.
a full suite of ecosystem process measurements, are deployed
along a transect that spans the eutrophic -oligotrophic gradient from the inland waters of the Chesapeake Bay out to the
Sargasso Sea. Experiments and functional gene studies focus
on key transformations in the carbon and nitrogen cycles
(C fixation, N fixation, nitrification, denitrification, urea
assimilation). The goal of these experiments is to determine
how microbial species diversity affects the major energy and
nutrient flows within ecosystems, and to assess the degree of
stability or instability associated with changes in redundancy
within guilds of microorganisms responsible for major nitrogen and carbon pathways.
The field work for this project has been completed (~20
field trips/research cruises have been completed in Chesapeake Bay, the Choptank River and the Sargasso Sea). Both
microarrays (using 70-bp oligomer probes) and macroarrays
(using ~350 bp PCR products) derived from functional genes
for ammonia monooxygenase, nitrite reductase and nitrogenase, have been developed and applied in this system. The
array technology is robust and “works” for most genes. Genes
encoding the essential enzymes RuBisCO (rbcL) and nitrate
reductase (NR) in eukaryotic phytoplankton were used in
the first successful second generation array to analyze phytoplankton communities in the English Channel. This array
detected both community composition (DNA) and gene
expression (mRNA) in natural assemblages and demonstrated
the power of the approach.
5. “Diversity and distribution of denitrifying bacteria in
relation to chemical distributions in theoxygen minimum
zone of the Arabian Sea” (Jayakumar, Tuit, Rich)
The Arabian Sea is one of three regions in the open ocean
where significant denitrification occurs in the water column.
Nitrous oxide is an intermediate in the denitrification pathway, and is also produced during aerobic nitrification at low
oxygen tensions. It is very effective as a greenhouse gas, and
what controls its production and release from marine systems
is not well understood. Nitrous oxide accumulates in a characteristic pattern in oxygen minimum zones (OMZs), such
as that found in the Arabian Sea. In previous work (Granger
and Ward, 2003), we showed that denitrification by cultured
bacteria in the lab could be limited by copper availability,
leading to the accumulation of denitrification intermediates
in the medium. We hypothesized that copper availability in
OMZs might be quite low, low enough in fact to limit denitrification at the nitrous oxide reduction step, thus leading
to accumulation of nitrous oxide. Copper limitation might
also lead to accumulation of nitrite in denitrifying bacteria
that possess the copper type nitrite reductasae, rather than
the iron enzyme. Thus, if copper limitation were a fact of life
in the OMZ, we might expect that the iron NiR should be
more common than the copper NiR.
We have now completed three major cruises in the last
three years, one each to the three major oxygen minimum
zones of the world ocean. Using chelators and various carbon
and nutrient additions to manipulate the natural communities in trace metal clean incubations, we have shows that
Carbon is probably the most important limitation in these
systems, that denitrification is very Anammox (anaerobic
ammonium oxidation) is a recently discovered step in thee N
cycle, that performs essentially thee same role as denitrification. We have made some of the first measurements of this
process in Chesapeake Bay, and in the OMZ regions of thee
ocean (Jeremy Rich). Contrary to the first reports by Danish
and German investigators, we find the anammox occurs in
both sediments and the water column, but is not the dominant process. We hypothesize that our methods, which were
designed to minimize artifacts we perceived in the original
methods, may be responsible for the different conclusions.
This is a very controversial area in which we are keenly involved and plan to continue working (pending proposals).
2. “What limits denitrification and bacterial production
in Lake Bonney, Antarctica?” (Tuit)
During the two recent field seasons, we developed and tested
a series of flow cytometric assays for bacterial abundance
and physiological state in samples from Lake Bonney, where
denitrification appears to proceed normally in one lobe of the
lake but not the other. Hypotheses about the ability of trace
metals to limit denitrification in natural environments were
tested on laboratory cultures and on incubation experiments
in the lake. It appears that copper availability can indeed
regulate denitrification but this is probably not the fundamental reason for the dysfunctional N cycle in Lake Bonney.
3. “Center for Environmental Bioinorganic Chemistry”
(Jayakumar, Tuit)
The two forms of dissimilatory (respiratory) nitrite reductase,
the cd-NiR (nirS gene) and Cu-NiR (nirK gene), are distributed across the Bacterial and Archaeal domains in a great
diversity of microorganisms. Because trace metal availability
can limit denitrification in the lab, we hypothesized that
metal distributions might influence the type of nir found in
natural marine assemblages. The first step in addressing this
hypothesis is to describe the distribution and diversity of nir
genes in marine systems. One paper (Jayakumar, Francis and
Ward, 2004) describes the diversity and distribution of nirS
genes in the low oxygen coastal waters of the Arabian Sea in
the continental shelf region of India. The sequences found
here are the first reported for a water column environment,
and are quite different from those previously reported from
sediment environments.
32
Ward, B. B. Temporal variability in nitrification rates and related
biogeochemical factors in Monterey Bay. Marine EcologyProgress Series, 292: 97-109, 2005.
Allen, A. E., B. B. Ward and B. K. Song. Characterization of
diatom (Bacillariophyceae) nitrate reductase genes and their
detection in marine phytoplankton communities. Journal of
Phycology, 41:95-104, 2005.
O’Mullan, G. D. and B. B. Ward. Comparison of temporal and
spatial variability of ammonia-oxidizing baceria to nitrification rates in Monterey Bay, CA. Applied and Environmental
Microbiology, 71: 697-705, 2005.
Casciotti, K. L. and B. B. Ward. Nitric oxide reductase (norB)
genes identified in ammonia-oxidizing bacteria. FEMS Microbial Ecology, 52: 197-205, 2005.
Song, B., and B. B. Ward. Genetic diversity of benzoyl coenzyme A reductase genes detected in denitfiying isolates and
estuarine sediment communities. Applied and Environmental
Microbiology, 71:2036-2045, 2005.
6. “Functional diversity of phytoplankton N assimilation” (Adhitya, Allen)
Diatoms are an important component of marine photosynthetic assemblages, and tend to be especially important
in coastal and upwelling systems. We hypothesize that
their ability to utilize variable and high nitrate concentrations and to grow more rapidly on nitrate than many other
phytoplankton, is partly responsible for their success. We
will investigate the response of important diatom groups
to changing N and light regimes in an upwelling scenario
to test this hypothesis. Initial work on the key gene, nitrate
reductase, was done by Andy Allen (a post doc) who found
the first diatom NR gene, and by Anita Adyhitya (student),
who investigated the NR gene diversity in diatoms associated
with seagrass beds. This work lays the foundation for quantitative assays of diatom gene expression, which we will use to
study differential success of various phytoplankton groups in
response to N availability.
Articles In Press
Taroncher-Oldenburg, G. and B. B. Ward. Oligonucletoide microarrays for the study of microbial communities. In: DNA Analysis by Nonradioactive Probes (Ed.) Hilario, E. and Mackay,
J.F., Humana Press, Totowa, NY, USA.
Bronk, D. A. and B. B. Ward. Inorganic and organic nitrogen cycling in the Southern California Bight, Deep-Sea Research.
Ward, B. B. and G. D. O’Mullan. Community level analysis: Genetic andbiogeochemcial approaches to investigate community composition and function inaerobic ammonia oxidation.
In: Method in Enzymology. Ed: J. Leadbetter.
Glatz, R. E., P. W. Lepp, B. B. Ward and C. A. Francis. Microbial
diversity in the watercolumn of permanently ice-covered
Lake Bonney, Antarctic, Geobiology.
Two-Year Bibliography
Refereed articles:
Jiang, W., A. Saxena, B. Song, B. B. Ward, T. J. Beveridge, S. C.
B. Myneni. Elucidation of functional groups on Gram-positive
and Gram-negative bacterial surfacesusing infrared spectroscopy. Langmuir
Langmuir, 20:11433-11442, 2004.
Song, B., and B. B. Ward. Molecular characterization of the assimilatory nitratereductase gene and its expression in the
marine green alga Dunaliella tertiolecta. Journal of Phycology, 40: 721-731, 2004.
Jenkins, B. D., G. F. Steward, S. M. Short, B. B. Ward and J. P.
Zehr. Fingerprinting diazotroph communities in the Chesapeake Bay by using a DNA macroarray. Applied and Environmental Microbiology, 70: 1767-1776, 2004.
Steward, G. F., B. D. Jenkins, B. B. Ward and J. P. Zehr. Development and testing of a DNA macroarray to assess nitrogenase (nifH) gene diversity. Applied and Environmental
Microbiology, 70: 1455-1465, 2004.
Jayakumar, D. A., C. A. Francis, S. W. A. Naqvi and B. B. Ward.
Diversity of nitrite reductase genes in the denitrifying water
column of the coastal Arabian Sea. Aquatic Microbial Ecology, 34: 69-78, 2004.
Ward, B. B., J. Granger, M. T. Maldonado, K. L. Casciotti, S.
Harris and M. L. Wells. Denitrification in the hypolimnion of
permanently ice-covered Lake Boney, Antarctica. Aquatic
Microbial Ecology, 38: 295-307, 2005.
Ward, B. B. Molecular approaches to marine microbial ecology
and the marine nitrogen cycle. In: Annual Review of Earth
and Planetary Science, 33:301-333, 2005.
Submitted
Jackson, G. A., B. B. Ward, G. D. O’Mullan, C. A. Francis, M. A.
Voytek, D. Eveillard.Estimating total numbers of microbial
operational taxonomic units (OTUs) using DNA sequence
data, Applied and Environmental Microbiology.
Ward, B. B., Nitrogen Cycling in Aquatic Environments. In:
Manual ofEnvironmental Microbiology.
Ward, B. B. Nitrification in marine systems. In: Nitrogen in the
Marine Environment, Eds. D. G. Capone, D. A. Bronk and M.
Mulholland.
Adhitya, A., F. I. M. Thomas and B. B. Ward. Diversity of nitrate
reductase genes from planktonic and epiphytic environments
in seagrass communities, Microbial Ecology.
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Princeton Geosciences 2006
35
Guyot Hall, front entrance.
Princeton University
Department of Geosciences
Guyot Hall
Princeton, NJ 08544-1003
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