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Guyot Science 2005Guyot Science 2005

Department of Geosciences, Princeton University

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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.

Guyot Science 2005A Summary of the Research Progress and Accomplishments

Made by the Faculty Members of theDepartment 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 for-mer 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 en-dowed 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 fi rst 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 teleseis-mic 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 fi eld 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 member-ship 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.

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Michael Bender Professor Ph.D., 1970, Columbia Universityemail: bender@princeton.edu

The activities of my laboratory focus on studies of the geochemistry of O

2, with applications to understanding the

global carbon cycle and glacial-interglacial climate change. The geochemical properties we study are the concentration of O

2 in air (which we measure to very high precision), and

the relative abundance of the three stable O isotopes (16O, 17O, and 18O) in O

2. There are two subjects for the isotopic

studies: O2 in fossil air extracted from ice cores, and dis-

solved O2 in seawater.

The results inform us about a range of topics. Studies of the O

2 concentration (or ratio of O

2/N

2) in air constrain the

fate of fossil fuel CO2 that does not remain in the atmo-

sphere. These measurements allow us to partition the “miss-ing” CO

2 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 O

2 in ice core trapped

gases refl ect the relative fertility of Earth’s biosphere, averaged over about 1,000 years. The triple isotope composition of O

2in seawater refl ects the fraction of dissolved O

2 from photo-

synthesis. O2 supersaturation refl ects net production (pho-

tosynthesis in excess of respiration); by combining measure-ments of O

2 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 measure-ments can be made on large numbers of samples collected by colleagues on cruises of opportunity, and returned to the lab.Supplementing the O

2 studies are studies of Ar. In seawa-

ter samples, Ar gives a measure of physical supersaturation due to warming of waters and bubble entrainment. In air samples, the Ar/N

2 ratio refl ects seasonal outgassing and

ingassing due to temperature-driven solubility changes, and also to atmospheric mixing.

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 O

2/N

2/Ar ratio of air, of trapped

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 specfi c accomplishments.

1. We prepared for publication papers on the meridional gradient of O

2 in air and its implications for the ocean car-

bon cycle, on the concentration and isotopic composition of O

2 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).

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 dat-ing 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 confi rmed 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 BibliographyRefereed articles:Hendricks, Melissa B., Michael L. Bender and Bruce A. Barnett Bender and Bruce A. Barnett Bender

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, 1541-1561, 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 millennial-scale 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 Atmo-spheric O

2/N

2 changes, 1993–2002: Implications for the

partitioning of fossil fuel CO2 sequestration, Global Biogeo-

chemical 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 O

2 in the equatorial Pacifi c:

a tracer of mixing and biological production, Journal of

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F. Anthony DahlenDepartment ChairProfessorPh.D., 1969, University of Cali-fornia, San Diegoemail: fad@princeton.edu

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.

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.

Suwa, Makoto, Josepth C. von Fischer, Michael L. Bender, Amaelle Landais, and Edward J. Brook Chronology recon-struction for the disturbed bottom section of the GISP2 and the GRIP ice cores: implications for Termination II in Green-land, 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 O

2/Ar ratios

and the triple isotope composition of O2, Deep Sea Re-

search, in review, 2005.

In 2005 I continued my longstanding collaboration with Guust Nolet and postdoctoral fellow Raffaella Montelli, to account for fi nite-frequency wavefront healing effects in global seismic traveltime tomography. Raffa and I spent much of the summer repairing a minor error in our ray-theo-retical crustal traveltime corrections. As expected, the repairs led to only minor changes in her P-wave velocity images P-wave velocity images P(Science 2004), and do not alter the important conclusion Science 2004), and do not alter the important conclusion Sciencthat 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 kilome-ters, 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 G3G3G , Raffa has gone on to invert S-wave traveltimes using fi nite-frequency sensi-S-wave traveltimes using fi nite-frequency sensi-Stivity kernels, in order to provide an independent check on her very exciting P-wave results. In fact, her recently obtained P-wave results. In fact, her recently obtained PS-wave images confi rm the presence of the six well-resolved S-wave images confi rm the presence of the six well-resolved Sdeep-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-wave tomography extending down to the core-mantle P-wave tomography extending down to the core-mantle P

boundary beneath Cape Verde, Cook Island and Cape Verde. This strong confi rmation of the deep-mantle plumes seen in Raffa’s earlier P-wave results is signifi cant not only because P-wave results is signifi cant not only because Pthe raypath coverage differs, but also because the off-path sensitivity of fi nite-frequency S waves differs from that of S waves differs from that of SP waves. Raffa left Princeton in September to begin a new P waves. Raffa left Princeton in September to begin a new Pcareer 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 sym-metric 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 com-ponents 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 fl uid outer core. Preliminary results have been submitted for publication as two back-to-back papers Geophysical Journal International. The next steps Geophysical Journal International. The next steps Geophysical Journal Internationalare 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 con-ducted 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 fi nite-frequency Fréchet sensitivity kernels for surface-wave group-delay and attenuation measurements. Quite unexpect-edly, we found that a fi nite-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

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Thomas S. DuffyAssociate ProfessorPh.D., 1992, California Institute of Technologyemail: duffy@princeton.edu

My research program focuses on understanding the large-scale 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

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 Princ-eton mathematic department, to use wavelets and possibly curvelets as a basis for fi nite-frequency tomographic inver-sions. 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-di-mensional time-frequency multitapers of Slepian and Thom-son to the case of a double polar cap, for application to the so-called “polar gap” problem in satellite geodesy.

Two-Year BibliographyRefereed 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, Geo-phys. 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 ampli-tudes 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.

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.

Articles in press or submitted:Simons, F. J., Dahlen, F. A. & Weiczorek, M., Spatiospectral con-

centration on a sphere, SIAM Review, in press, 2005.Zhou, Y., Nolet, G., Dahlen, F. A. & Laske, G., Global upper-man-

tle structure from fi nite-frequency surface-wave tomography, J. Geophys. Res., in press, 2005.

Dahlen, F. A. & Zhou, Y., Surface-wave group-delay and attenua-tion 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 spectral-element method for computing 3-D spherical-earth seismo-grams, Geophys. J. Int., submitted, 2005.

Montelli, R., Nolet, G., Dahlen, F. A. & Masters, G., A catalogue of deep-mantle plumes: new results from fi nite-frequency tomography, Geoshem., Geophys, Geosystems, submitted, 2005.

Montelli, R., Nolet, G. & Dahlen, F. A., 2005. Comment on ‘Ba-nana-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.

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 dramati-cally 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.

Phase transitions and crystal structures of deep Earth mineralsPhase transformation in CaSiO

3Phase transformation in CaSiO

3Phase transformation in CaSiO perovskiteExperimental studies have shown that the main rock types of the Earth’s mantle (e.g. peridotite, basalt) transform under

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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 condi-tions was also obtained. We have recently carried out experiments using glass starting materials with compositions along the MgSiO

3-

Al2O

3 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 En

85Co

15 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 fi eld is narrow, although analysis is complicated by the slug-gish reaction kinetics. We also fi nd 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 MgSiO

3 are challenging. Germanates are known to

be excellent analogs for silicates as similar phase transitions occur but at signifi cantly lower pressures in germanates. We have carried out a detailed set of synchrotron x-ray diffrac-tion experiments on the post-perovskite phase of MgGeO

3 in

which we have synthesized the phase, measured its equation of state and refi ned the crystal structure (Rietveld method) over broad pressure intervals. Our equation of state mea-surements span a range from 7-201 GPa and place new constraints on the compressibility and structural anisotropy of the new phase (Kubo et al., 2005). We could successfully Kubo et al., 2005). We could successfully Kubo et al., 2005conduct Rietveld refi nements at very high pressures using data obtained between 80 and 110 GPa with both Ar and NaCl pressure media, including high temperature (1400-1700 K) data at ~90 GPa. Our structure refi nements provide the fi rst 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 refi nement 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 sensi-tive 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” con-stituents such as the post-perovskite phase. In collaboration

lower mantle conditions to assemblages dominated by miner-als in the perovskite crystal structure. CaSiO

3 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 diffrac-tion experiments reported over ~20 years. We conducted the fi rst high-resolution diffraction study of this material at 20-50 GPa [Shim et al., 2002] and showed that the sym-metry of CaSiO

3 perovskite at room temperature after laser

heating is not cubic, but of lower symmetry, most likely tetragonal. Our result is consistent with theoretical calcula-tions 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 signifi cant anomalies in elastic properties and may therefore have relevance for interpretation of seismic profi les of the mantle.

Post-perovskite phase transition in silicates and germanatesThe 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 evolu-tion. Thus, the recent discovery of a post-perovskite phase in MgSiO

3 at 125 GPa, close to conditions expected for the

D” region has major potential implications for understand-ing 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 Mg-SiO

3 perovskite to 108 GPa [Shim et al., 2001] and reported

evidence for a potential modifi cation within the perovskite structure. The existence of the post-perovskite phase was later confi rmed in MgSiO

3 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-pres-sure experiments. Using the laser-heated diamond anvil cell, we have recently investigated the equation of state of coex-isting perovskite and post-perovskite (CaIrO

3-type) phases

synthesized from a natural pyroxene composition with Fe content close to that expected for the lower mantle (Shieh et al., 2005). Our measured pressure-volume data for the post-al., 2005). Our measured pressure-volume data for the post-al., 2005perovskite phase from 12-106 GPa yield a bulk modulus of 219(5) GPa and a zero-pressure volume of 164.9(6) Å3 when K

0’=4. The bulk modulus of post-perovskite is 575(15) GPa

at a pressure of 100 GPa. These results are broadly consis-tent 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 CaIrO

3-type phases at

80-106 GPa demonstrates that the post-perovskite phase has a smaller volume than perovskite by 1.1(2)%. Using mea-sured volumes together with the bulk modulus calculated from EOS fi ts, we fi nd that the bulk sound velocity decreasesby 2.3(2.1)% across this transition at 120 GPa, again con-

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with R. Wenk’s group at Berkeley, we have carried out the fi rst experimental deformation study of the post-perovskite phase (of MgGeO

3 composition) in the diamond anvil cell at

104-130 GPa and ambient temperature (Merkel et al., 2005). Merkel et al., 2005). Merkel et al., 2005Previous 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 compari-son 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 inter-mediate 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.

Phase transitions in SnO2

Phase transitions in SnO2

Phase transitions in SnO to megabar pressures2 to megabar pressures

2There 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 uncov-ered. 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 investi-gated as analogs for SiO

2 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 SnO

2 demonstrates the existence of four phase transitions

during compression to 117 GPa. The observed sequence of high-pressure phases for SnO

2 is rutile-type (P4

2P4

2P4 /mnm

2/mnm

2) →

CaCl2-type (Pnnm) → pyrite-type (

is rutile-type ( is rutile-type ( is rutile-type () → ZrO

2 ortho-

rhombic phase I (Pbca) → cotunnite-type (Pnam). The latter two phases were observed here for the fi rst time in this system. The bulk moduli for the Pbca (259 GPa) and Pbca (259 GPa) and Pbca Pnam(417 GPa) phases of SnO

2 determined by fi tting pressure-

volume data to the second-order Birch-Murnaghan equa-tion of state indicate these high-pressure phases are highly incompressible – although the potential role of deviatoric stress still needs better characterization. Rietveld refi nements 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 fi rst transformation may be associated with the formation of the Pbca phase whereas the second transformation is consistent Pbca phase whereas the second transformation is consistent Pbcawith the cotunnite-type phase.

Finite element simulations of the laser-heated diamond cellWe have examined the thermal structure of the laser-heated

diamond anvil cell using fi nite element calculations (Kiefer and Duffy, 2005). We carried out simulations using a and Duffy, 2005). We carried out simulations using a and Duffy, 2005realistic experimental geometry (including insulation layers between the diamonds and sample) to investigate the factors controlling development of axial and radial thermal gradi-ents 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 sys-tematically quantifi ed 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 CO

2and 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-fur-nance geometry. We have also systematically investigated the effects of different laser modes. The results in some cases confi rm preconceptions, but in several cases rather surpris-ing 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.

Elastic properties of minerals and structure of the mantleThe 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. De-spite this importance, the elastic properties of many mantle minerals are poorly constrained, particularly for low-sym-metry 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 single-crystal elastic properties of a variety of minerals at pressures corresponding to depths as great 1000 km.

Elasticity of olivines and garnetsThe single-crystal elasticity of fayalite (Fe

2SiO

4) was mea-

sured to 12 GPa by Brillouin scattering at ambient tempera-ture (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 (ortho-rhombic), and good crystals are rare. Nevertheless, we could recover the 9 elastic stiffness moduli as well as crystal orien-tation 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 C

44 and C

55 show non-linear

pressure dependence at P>5 GPa, and this leads to non-linear behavior in the aggregate shear modulus as well. The soften-ing of C

44 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-

9

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., andradite) to above 11 GPa (Jiang et al., 2004a; Jiang et al., andradite) to above 11 GPa (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 min-eral 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 pyrope-almandine 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. Bril-louin 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 measure-ments 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 et al., 2005). Speziale et al., 2005). Speziale et al., 2005Logarithmic 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 fi ndings from this study, the very different responses of olivines and garnets to iron substitution gives rise to signifi -cant 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 af-fected 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 veloc-ity heterogeneity.

Elasticity of hydrous mineralsThe 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 mea-suring 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 et al., 2005GPa (Jiang et al., 2005GPa ( ). Brucite shows highly anomalous Jiang et al., 2005). Brucite shows highly anomalous Jiang et al., 2005elastic properties including the largest shear modulus pres-sure derivative (Gʹ=3.6) yet measured. The elastic anisotropy of brucite changes strongly with pressure. The ratio of the

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 fi rst 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-crys-tal 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 scat-tering at simultaneous high pressures and temperatures, and to extend measurements to higher pressures, particularly for polycrystalline samples.

Yield strength at high pressuresThe yield strength of materials at high pressure is a funda-mental property that has not yet been well characterized. Static strength determination is a preliminary step toward eventual characterization of the complete fl ow laws that govern rheological properties at high pressure or deep Earth conditions. Among the basic questions are how pressure af-fects 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 opti-mizing the design and performance of high-pressure appara-tus. Quantitative evaluation of differential stresses developed under various pressure-transmitting media is one example in this regard. Elasticity and strength are interconnected prop-erties that play a mutual role in several basic areas of high-pressure science such as development of accurate pressure calibration. Interest in strength properties is also driven by several themes in current materials research including theo-retical 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-hy-drostatic 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, equa-tion 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 met-als, oxides, silicates, and nitrides. Our recent studies have included: tungsten (He and Duffy, 2005), platinum (He and Duffy, 2005), platinum (He and Duffy, 2005 Kavner and Duffy, 2003); MgGeO

3 post-perovskite (Merkel et al.,

2005), SiO2005), SiO20052 (Shieh et al., 2002), CaSiOShieh et al., 2002), CaSiOShieh et al., 2002

3 (perovskite) (Shieh

et al., 2004), CaO (2004), CaO (2004 Speziale et al., 2005), B6O (He and Duffy,

2004), and cubic-Si3N

4 (Kiefer et al., 2005). In general,

10

strength increases with compression at a rate greater than the shear modulus, implying signifi cant 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) Gcompared with four-coordinated silicates (4-7% G). Strong G). Strong Gcovalent 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 B

6O at 65 GPa confi ning pressure. The general increase

in strength with pressure for all material classes implies that most materials are “strong” at megabar pressures if one recog-nizes 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 em-pirical 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 tech-nique for constraining mechanical properties at high pres-sures. 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 et al., 2005). Cal-Speziale et al., 2005). Cal-Speziale et al., 2005cium oxide supports a low differential stress of ~1% of the shear modulus (<2 GPa at high pressures). The Brillouin results show a softening of C

44 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 modifi -cation to stress/strain continuity relationships. There are a number of directions for future develop-ments 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.

Two-Year BibliographyBooks: Rubie, D. C., T. S. Duffy, and E. Ohtani, editors, New Develop-

ments 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 Ap-plications, Elsevier, Amsterdam, pp. 512, 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.

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, Phys-ics 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, 3624-3626, 2004.

Shim, S.-H., T. S. Duffy, R. Jeanloz, C.-S. Yoo, and V. Iota, Ra-man 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, 16, S1041-S1052, 2004.Condensed Matter, 16, S1041-S1052, 2004.Condensed Matter

Speziale, S., F. Jiang, and T. S. Duffy, Compositional depen-dence 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 plane-tary 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 inte-grated silicon and silicon-germanium thin fi lms using compli-ant substrates, Applied Physics Letters, 87, 061922, 2005.

Kiefer, B., S. R. Shieh, T. S. Duffy, and T. Sekine, Strength, elas-ticity, 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 laser-heated diamond anvil cell, Journal of Applied Physics, 97, 114902, 2005.

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, Warren-dale, Pa, vol. 809, pp. B3.6.1-B.3.6.3, 2004.

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.

11

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 post-perovskite 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 elastic-ity of calcium oxide: A comparison between Brillouin scat-tering 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 post-perovskite phase to 2 Mbar, Geophysical Research Letters, submitted, 2006.

Lincoln S. HollisterProfessorPh.D., 1966, California Institute of Technologyemail: linc@princeton.edu

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 fi eld 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.

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 becom-ing stable continental crust, the original island arc composi-tion is modifi ed by processes that are not understood. This is a fundamental problem in the earth sciences. The disci-plines 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 sched-uling problems and to complexities in obtaining Canadian environmental permits. For information on the permitting process, see http://www.eos.ubc.ca/research/batholiths/

Bhutan. With my colleague Djordje Grujic at Dalhausie University, we have defi ned 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 fl ow in Bhutan. This rationalizes seemingly contradictory fi eld data to the theoretically based channel fl ow model of Beaumont and others. I have helped recruit Bhutanese students to study geol-ogy in USA. Two recently received MS degrees at UTEP, and one of these, Tobgay Tobgay, is expected to come to Princ-eton for a Ph.D.

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 contro-versy, which holds that parts of western Canada traveled from latitudes corresponding to Baja California during the latest Cretaceous.

Two-Year BibliographyRefereed 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. Earth and Planetary Science Letters v. Earth and Planetary Science Letters221, 397 407, 2004.

Other miscellaneous publications:Clowes, R.M., L.S. Hollister, G.Woodsworth, BATHOLITHS:

How the Coast Mountains of British Columbia Formed. Infor-mational Brochure for EA and Outreach. 16pp. http://www.eos.ubc.ca/research/batholiths/, 2005.

Clowes, R.M., L.S. Hollister, G. Woodsworth, Batholiths: learn-ing 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 Publica-tion 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 re-sponse to Late Tertiary extension near Prince Rupert, British Columbia. Canadian J. Earth Sciences.

12

Gerta KellerProfessorPh.D., 1978, Stanford Univer-sityemail: gkeller@princeton.edu

During the past two years the 15 year long research proj-ect on the Cretaceous-Tertiary boundary impact and mass extinction has culminated in spectacular success with the coming together of empirical evidence from sedimentol-ogy, 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 fi lms 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, (re-leased 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 confi rm previous studies. New drilling of K-T sequences near Recife in Brazil, also funded by NSF, commenced in Septem-ber and fi nished 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 ef-fects of the Chicxulub impact at 8000km from its crater. The cores will be shipped to Princeton in early 2006.

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=NSG2349857238495

Two-Year BibliographyRefereed 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 Cenomanian-Turonian Stratotype Section (GSSP) at Pueblo, Colorado. Marine Micropleontology, 51: 95-128, 2004.

Keller, G., Stueben, D., Berner, Z. and Adatte, T., Cenomanian-Turonian 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., Chicxu-lub 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 Kra-mar: 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 Micropale-ontology, 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 Te-thys (Israel): mineralogy, trace element and platinum group elements, biostratigraphy and faunal turnovers. BulletinSociété 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., Rindfl eisch, 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 lime-stone 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.

Other miscellaneous publications:Keller, Suche nach der Ursache des Massensterbens vor 65 Mil-

lionen 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. Creta-ceous 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.

13

Nadine McQuarrieAssistant ProfessorPh.D., 2001, Arizona Universityemail: nmcq@princeton.edu

My research focuses on the kinematic evolution of moun-tain 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 fi eld studies, typically through the creation of new geologic maps at previously unpublished scales or resolutions. Projects also typically involve the cre-ation 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-Pacifi c plate boundary over the last 36 Myr, 2) the interaction be-tween erosion and deformation in fold-thrust belts in Bolivia 3) the fundamental controls on the width of mountain belts, specifi cally looking at the northern edge of the Andean Pla-teau in Peru and 4) how has deformation evolved in time and space during arc-continent collision in Timor.

Tectonic reconstructions of the North America-Pacifi c plate boundary: Precise displacement fi elds 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 displace-ment fi elds 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 (im-plying where more fi eld-based data are needed). The maps can also be displayed as a movie that illustrates how exten-sion varies with time and as velocity fi elds over 2-5-10 m.y. increments that can be compared to the modern GPS strain fi eld. The fi rst version of these reconstructions was published

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 fi eld research to constrain the amount and timing of fault offset in the Mo-jave 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 off-sets 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 fi eld test for kinematic compatibility models. 2) The palinspastic reconstructions allow us to restore other data sets of inter-est, such as the volcanic eruptive centers through the Basin and Range. For her Sr. Thesis, Margee Prat started integrat-ing 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.

Interaction between erosion and deformation in fold-thrust belts: Quantifying the interactions of lithology, tectonics and climate on multi-scale morphologies of moun-tain 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 forma-tion and development of orogens. Active research in Bolivia (collaborative research with Dr. Todd Ehlers and graduate student Jason Barnes at University of Michigan) use low-temperature thermochronometry, fi eld-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 fi eld will be the input into 2D and 3D thermo-mechanical models that link uplift and erosion to an evolving thermal fi eld. This thermal history is used to calculate and predict apatite fi ssion track and apatite and zircon (U-Th)/He sample ages.

Controls on orogen width: The Andes mountains extend over 8000 km along the western side of the South American continent. Signifi cant along strike changes in morphology, structure and zonal climate regimes make the South Ameri-can Andes an ideal location to look at the factors that control

14

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 transi-tions abruptly into a signifi cantly narrower (150 km) moun-tain 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 signifi cant 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 sur-prising things that we found was although the stratigraphy varies signifi cantly 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 accom-panying geologic cross section will be products of Nicole’s fi rst year project.

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 conti-nental 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 eleva-tion that once was at sea level, 2, Young, marine sedimen-tary rocks record the progressive shoaling of ocean water depths. 3) Deformed rocks suffi ciently exposed to reveal their

deformation history and 4) Rocks which can provide cool-ing ages of apatite grains which indicate the window of time these rocks were cooled through uplift and erosion. These factors allow is to quantify both rates of crustal shortening factors allow is to quantify both rates of crustal shortening fas well as rates of surface uplift in East Timor. Th e colli-sion history of the Banda arc is also signifi cant because the obliquity of the collision provides a unique insight into the temporal evolution of the orogen through trading space for time along strike. Th e westward propagation of the orogen (110 km/m.y.) provides a way to simultaneously observe this active arc-continent collision at various stages of develop-ment. Th is last summer Sarah Johnston (graduate student) and I undertook a six-week fi eld 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 fi nished, She will be able to use the section to estimate the amount of shortening and thicken-ing for this location, thus producing an estimate of thicken-ing-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 BibliographyRefereed 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 Pla-teau: Tectonophysics, v. 399, p. 15-37, 2005.

McQuarrie, N. and Wernicke, B.P., An Animated Tectonic Recon-struction of Southwestern North America since 36 MA: Geo-sphere, v. 1, p 147-172. doi: 10.1130/GES00016.1, 2005.

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 East-ern California shear zone: Journal of Geology.

Barnes, J., Ehlers, T.A., McQuarrie, N., O’ Sullivan, P.B., (in re-view), Erosion, Climate and plateau growth in the central An-des, northern Bolivia: Earth and Planetary Science Letters.

15

François M. M. MorelAlbert G. Blanke, Jr., Professor of GeosciencesDirector, Princeton Environmental Institute Director, Center in Envi-ronmental BioInorganic ChemistryPh.D., 1971, California Institute of Technologyemail: morel@princeton.edu

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 fi x is exported to the deep sea; some of the SiO

2 precipitated

by diatoms and of the CaCO3 precipitated by coccolitho-

phores 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 phy-toplankton precipitate hard parts: what physiological and ecological benefi ts diatoms obtain from their silica frustule? and coccolithophores from their calcite liths? We’ve been working on the hypothesis that the hard parts of phytoplank-ton are important in key extracellular enzymatic processes. We have shown that the silica frustule of diatoms is an excel-lent buffer for hydrogen ion that enables the rapid conver-sion of HCO

3- to CO

2 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 coccolitho-phores likewise enhance the activity of extracellular alkaline phosphatase –an enzyme that liberates orthophosphate from organic compounds. The biogeochemistry of cadmium continues to be a re-search focus in our group. Because of its excellent correlation with phosphate, cadmium is used as a paleotracer of nutri-ents in the sea. We have obtained mounting evidence from laboratory and fi eld work that cadmium is an important micronutrient for marine phytoplankton. From our previ-ous 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 acquisi-tion of inorganic carbon for photosynthesis. Having now obtained the full DNA sequence for this enzyme (the fi rst 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 coccolitho-phores which we have found to accumulate unusually high

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 Uni-versity) we have continued our work on the mechanism of inorganic carbon uptake and fi xation in diatoms. By follow-ing the rates of CO

2 uptake and O

2 evolution in the presence

of various inhibitors, we have obtained convincing data sup-porting our earlier (and controversial) report of unicellular C

4 photosynthesis --a pathway that involves accumulation of

carbon as a C4 compound prior to fi xation-- in these organ-

isms. 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 sys-tem 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 reactivat-ed our research on the iron physiology of marine phytoplank-ton. 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 intracel-lular 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 fi eld 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 identifi ed 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 fi rst 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 organ-ism thought to be responsible for the bulk of N

2 fi xation in

the ocean. Our continuing work on the biogeochemistry of mer-cury is presently focused on mercury methylation. Since methyl mercury is the species accumulated in fi sh 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 methyla-tion 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 concentra-tion 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

16

Satish MyneniAssociate ProfessorPh.D., 1995, Ohio State Universityemail: smyneni@princeton.edu

reducing bacteria has shown that, contrary to what is com-monly 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 BibliographyRefereed articles:Shaked, Y., A.B. Kustka, F.M.M. Morel and Y. Erel, Simultaneous

determination of iron reduction and uptake by phytoplank-ton, 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 fi xation 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. Mo-rel, 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 pCO

2Limnol. 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 Tech-niques, 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.

Amyot, M., F.M.M. Morel and P. A. Ariya, Dark oxidation of dissolved and liquid elemental mercury in aquatic environ-ments, 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 bioavail-abilty. 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. Lim-nol. And Oceanogr., 50(3) 872-882, 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 charac-terization of an iron storage and DNA-binding Dpsprotein from Trichodesmium erythraeum. , Applied Env. Microbiol-ogy, in press.

Shaked, Y., Y. Xu, K. Leblanc and F. M. M. Morel, Zinc availability and alkaline phosphatase activity in Emiliania huxleyi: Im-plications 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 phospho-huxleyi (Prymnesiophyceae) and its regulation by phospho-huxleyi (rus, 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.

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 environ-ment, which includes mineral oxides, biota and their byprod-ucts, and the atmosphere. One of the challenges in environ-mental sciences is to gain a better understanding of interac-tions 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

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 explor-ing one of these fundamental interactions, which include the evaluation of the chemical state of water in different geologic media and how this modifi es the biogeochemical behavior of different inorganic and organic moieties in the natural sys-tems. I am also interested in evaluating the chemical state(s) of important geochemical species to develop predictive pat-terns for explaining their macroscale behavior. A summary of my current research projects, and accom-plishments in the last one year are provided below.

Speciation of Aluminum and Iron in Aqueous Solutions and in Solid phasesAluminum 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 con-taminants 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-

17

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 infl uence of different environmental variables that modify their transformation. My group members, Laura Harrington and Michael Hay are participating in this inves-tigation. 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 spectro-microscopy to evaluate the heterogeneity in size and compo-sition 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 Fe3+ in the environment is infl uenced by the speciation of these ions in aqueous solutions. It is well understood that these ions exist as hexaqua complexes (e.g. Al(H

2O)

63+)

in highly acidic solutions and hydroxylated species (e.g. Al(OH)

m(H

2O)

nl+/-l+/-l ) 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 spec-troscopy, 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 H

2O 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 coordina-tion 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 sev-eral 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 occur-rence of H-bonding complexes of sulfate with Fe-oxyhy-droxide 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 MoleculesOrganic molecules are found everywhere on the surface of the Earth, and their composition, molecular structure and concentration modifi es 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. Min-eral., 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 environ- ment: 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 fi eld 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 organo-halogens 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 signifi cant contributor to the organohalogen burden in the environment. With the help of my research group members, I made signifi cant 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 spe-ciation variations in soils are directly related to the weather-ing 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 investiga-tors. Specifi c molecules identifi ed in our investigation are chlorinated xanthones (probably associated with lichens), and several other aliphatic and aromatic chlorinated mol-ecules (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

18

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 dehalogena-tion in sediments. Although iodine is present at trace concen-trations, we are fi nding that iodide and iodate present in soils react with naturally occurring organic molecules and form organoiodines in short time. The presence of Ca is signifi -cantly 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 equilib-rium 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 reac-tive 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 com-plexes (chelation) with aqueous metals and mineral surfaces. This information is important in understanding the reactiv-ity 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 funda-mental biogeochemical processes in the environment.

Two-Year BibliographyRefereed 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.

Maria S., Russell L. M., Gilles M. K., Myneni S. C. B. Organic aerosol growth mechanisms and their climate forcing impli-cations. Science, 306: 1921-1924 2004.

Wei J. Saxena A., Song B., Ward B. B., Beveridge T.J ., MyneniSCB. Elucidation of functional groups on Gram-positive and Gram-negative bacterial surfaces using infrared spectros-copy. Langmui,r 20: 11433-11442 2004.Langmui,r 20: 11433-11442 2004.Langmui,r

Edwards, D. C., Nielsen S. B., Jarzecki A. A., Spiro T. G., MyneniS. C. B. Experimental and theoretical vibrational spectros-copy 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: 10249-10256. 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., A109: 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 fi ne structure spectroscopies. J. App. Phys-ics ,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 environ-mental science beamline at the Advanced Light Source. J. Electron Spectosc. Relat. Phenom., 150: 86-104 2005.

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 sys-tems, 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.

19

Guust NoletGeorge J. Magee Professor of Geophysics and Geological EngineeringPh.D., 1976, University of Utre-cht (The Netherlands)email: nolet@princeton.edu

With Raffaella Montelli and Tony Dahlen, we continued the exploration of the effects of fi nite frequency – introduced by us fi ve years ago – into the imaging of the Earth’s interior. An investigation of long period S, ScS and SS waves led to a spectacular confi rmation of the earlier results that showed a number of mantle plumes reach deep down into the lower mantle. This fi nding has important implications for the geo-dynamics of the Earth. This is probably the last time we in-vert 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 fi lters that will allow us for the fi rst time to measure arrival times and amplitudes of body waves from shallow earthquakes – the complicating interacting of the ghost refl ections from the Earth’s surface are fully taken into account in the fi lter. The measurements can be done in different frequency windows, thus fully exploiting the power of fi nite frequency tomogra-phy, the new method of interpretation pioneered at Princ-eton in the past decade. Using the matched fi ltering method, Karin has recently been able to show that fi nite 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 pres-ent cleaning up the fi nite-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 fi nite-frequency tomography, but also the various methods of data analysis, model parameter-ization and inversion. No such book exists at present.

With Stephanie Gautier and Jean Virieux, both at Geosciences Azur in France, I have developed a new method to compute the fi nite-frequency sensitivity of arrival times and amplitudes of local seismic waves in complicated, three-dimensional media. A fi rst application, to image the seis-mogenic zone in the area of the Gulf of Corinth (Greece) is under way.

Two-Year BibliographyBooksLevander, 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 tomo-graphic models, Geophys. J. Int., 161, 365-372, 2005.

Nolet, G., F.A. Dahlen and R. Montelli, Traveltimes and ampli-tudes 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 Mono-graph Series, 1-6, 2005.

Dahlen, F.A. and G. Nolet, Comment on the paper “On sensitiv-ity 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.

Articles in press or submitted:Sigloch, K. and G. Nolet, Measuring fi nite-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 fi nite-frequency to-mography, subm. to Geochemistry, geophysics, geosystems (G3), 2006.

Montelli, R., G. Nolet and F.A. Dahlen, Comment on `Banana-doughnut 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 Upper-Mantle Structure from Finite-Frequency Surface-Wave Tomography, J. Geophys. Res., in press, 2006.

20

Tullis C. OnstottProfessorPh.D., 1980, Princeton Universityemail: onstott@princeton.edu

Deep Permafrost Environments and the Mars Deep Drill-ing MissionThe past year’s IPTAI astrobiology effort has experienced some signifi cant 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 develop-ments at Ulu for this coming summer. This campaign will be the fi rst 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 detec-tion experiments on these same samples in the fi eld 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 technol-ogy required has reached fl ight capability as of yet. In this context we have resubmitted a proposal to NASA’s ASTID, Astrobiology Science and Technology In-strument 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

abiogenic or biotic origin. No instruments are currently fl ight 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 ori-gins. The bad news is that the shuttle back to fl ight 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!

The South African Deep Microbiology ProjectThe 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 diffi cult to understand and microscopic features that a frankly so bizarre that their origin is a mystery. For these reasons we’ve had great diffi culty in publishing the fi ndings of this project, but this past year has seen a confl u-ence of efforts by the co-investigators participating in this project, which at long last had led to the acceptance for pub-lication 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:

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 repre-sents a new genus of Firmicutes with genetic capabilities that Firmicutes with genetic capabilities that Firmicutesare 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 envi-ronmental samples, discover the function of specifi c 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 instrument-ing 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. Nev-ertheless, 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.

21

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 fi nd 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 fi nal stages of the DUSEL. These two sites will submit proposals to NSF in July ’06. The fi nal 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 justifi cation of the facility. We will be complet-ing 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 fi eld of terrestrial subsurface microbiology.

Two-Year BibliographyRefereed 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 composi-tions of radiolytic H

2 and the implications for deep biosphere

in continental crust. Geochim. Cosmochim. Acta, 69, 893-903, 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 fl uorescent 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: 1680-1687, 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 Ramifi cations for the Surface Biosphere. In The CO

2 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 H

2 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., Pfi ffner, 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.

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 H

2-based autotrophy and methanogenesis in

the deep subsurface. Chem. Geol., in press, 2006.Onstott, T. C., Lin, L.-H., Davidson, M., Mislowack, B., Borc-

sik, M., Hall, J., Slater, G., Ward, J., Sherwood Lollar, B., Lippmann-Pipke, J., Boice, E., Pratt, L. M., Pfi ffner, 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,Geomicrobiol. Jour,Geomicrobiol. Jour in press

Pfi ffner, 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 Profi les 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-Cou-loume, G., Onstott, T.C., Sherwood Lollar, B. 14C distribution in methane and DIC in South African gold mines: Implica-tions 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: Biofi lms 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 On-stott, T. C. Heterogeneous microbial communities associ-ated 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., Pfi ffner, S. M., Lin, L.-H. and Onstott, T. C. (2005) Desulfotomacu-lum 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 CH

4: sources, fl ux

and detection. Astrobiology Journal, in press, 2006.DeFlaun, M. F., Fredrickson, J. K,., Dong, H., Pfi ffner, S. M.,

Onstott, T. C., Balkwill, D .L., Streger, S. H., Stackebrandt, E., Knoessen, S. and van Heerden, E. Isolation and char-acterization 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 biofi lm. 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 Atlan-tic 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

22

Michael Oppenheimer(Woodrow Wilson School and De-partment of Geosciences)Albert G. Millbank Professor of Geosciences and International AffairsPh.D., 1970, University of Chicagoemail: omichael@princeton.edu

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 caus-ing warming. Specifi c 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 cy-cle. 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 warm-ing. 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 plansMy 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

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.

Two-Year BibliographyRefereed 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. Environmen-tal Hist., 9, 327-8, 2004.

The infl uence 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. Don-ner, W.J.Skirving, C.M. Little, and O. Hoegh-Guldberg). Global Change Biology, 11, 1–15, doi: 10.1111/j.1365-2486.2005.01073.x, 2005.

Article 2 of the UNFCCC: Historical Origins, Recent Interpreta-tions (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. Brad-ford). Climatic Change, 73, 227-238, 2005.

Defi ning 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.

Published (or submitted or in press) chapters in books:What is the Economic Value of Information about Climate Thresh-

olds? (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.

23

nents (which affects the frequency of volcanic eruptions and hence the composition of the atmosphere), is mainly respon-sible 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 relative-ly 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 refl ect 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 amplifi cation of obliquity but not precession cycles in global ice volume. Another concerns fl uctuations in equato-rial sea surface temperatures, very similar to those in the bot-tom panel, which lead fl uctuations 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 infl uence 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 in-creases signifi cantly. 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

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 tempera-tures, 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

S. George H. PhilanderKnox Taylor Professor of GeosciencesPh.D., 1970, Harvard Universityemail: gphlder@princeton.edu

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 dra-matic fl uctuations between prolonged ice-ages that persisted for some 100,000 years, and brief, temperate interglacials. (Variations in O18 in seafl oor 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 con-centration 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 under-stand what had happened in the past. Two sets of processes determine the climate variations described above. One, associated with the drifting of conti-

24

water rises to the surface, depends on oceanic factors, specifi -cally 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 trans-port, 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 accompa-nied by a gradual elevation of the oceanic thermocline which, around 3 Ma, was so shallow that tropical air-sea interac-tions started infl uencing 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.

Two-Year BibliographyRefereed articles:Boccaletti G., R. Pacanowski, S.G. Philander and A. Fedorov Philander and A. Fedorov Philander

The Thermal Structure of the Ocean, J. Phys. Oceanogr., 34, 888-902, 2004.

Fedorov A.V., R.C. Pacanowski, S. G. Philander and G. Boc-Philander and G. Boc-Philandercaletti: 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: Simula-tions 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 Philander S.G. El Niño and the Uncertain Science of Global Philander

Warming. Daedalus, Journal of the American Academy of Arts and Sciences pp 105-108, Spring 2004.

Philander S.G. Science in an Uncertain World, Philander S.G. Science in an Uncertain World, Philander News from ICTP, Trieste, Italy, Autumn, 2004.

Philander S.G. State of Fear The Day After Tomorrow, Philander S.G. State of Fear The Day After Tomorrow, Philander 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 Land-Philander S.G. Sextant to Satellite; the Education of a Land-Philander

based OceanographerChapter in History of Physical Oceanography - Developments

since 1960. Editors M. Jochum and R. Martugudde. Pub-lisher 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. Physi-cal Oceanography, submitted.

Allan RubinProfessorPh.D., 1988, Stanford Universityemail: arubin@princeton.edu

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 cross-correlation as a tool for obtaining precise relative locations of microearthquakes. Because the number of earthquakes in-creases exponentially with decreasing magnitude, earthquakes near the detection threshold of a given seismic network rep-resent a potential wealth of data for both structural geologists and seismologists. A major impediment to exploiting these

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 signifi cant 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 thou-sands 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 nu-cleation, a spin-off of one of our ongoing projects designed

25

haps more signifi cantly, 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 (in-elastic dilation and pore pressure reduction within the fault zone; frictional heating of pore fl uids, 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 compet-ing 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 BibliographyRefereed articles:Rubin, A. M., and J.-P. Ampuero, Earthquake nucleation on (ag-

ing) 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.

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 chemi-cal 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 tempo-ral 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 fi rst time, we have succeeded in obtaining ana-lytic approximations for the size and timescale of earthquake nucleation that are consistent with full numerical simula-tions. These approximations are based on well-established principles of fracture mechanics, allowing much greater in-sight into the complex behaviors that result when the nonlin-ear 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-

Jorge L. SarmientoProfessorPh.D., 1978, Columbia Universityemail: jls@splash.princeton.edu

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 diffi cult 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

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 fi ll 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 fi eld, 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 magnum opus of 1982, Tracers in magnum opusthe 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 fi nish 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 refl ect the culmination of several ongoing projects that carried over from previous years, as well as refl ecting my ever-deepening interest in understanding the critical role of the Southern Ocean in controlling ocean biogeochemistry and its

26

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 pro-cesses in this region.

Two-Year BibliographyBooks:Sarmiento, J. L., and N. Gruber, Ocean Biogeochemical Dynam-

ics, Princeton University Press, in press.

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 ventila-tion 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 CO

2. 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. Bullis-ter, 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. Mar-shall, 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. Geo-phys. Res. Lett., 31, L07303, doi:10.1029/2003GL018970, 2004.

Mignone, B. K., J. L. Sarmiento, R. D. Slater, and A. Gnanadesi-kan, Sensitivity of sequestration effi ciency to mixing process-es 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. Mon-fray, 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 acidifi cation over the 21st century and

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 briefl y below, with reference to the in press and submitted papers.

Ocean Biogeochemical Processes and Modeling: The Orr et al. (2005) Science paper, my only 2005 journal publica-tion, discusses the impact of ocean acidifi cation by anthropo-genic carbon on the depth of the saturation horizon of arago-nite, 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.

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 CO

2observations 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 implica-tions 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 CO

2 fertilization sink has

major negative implications for the future growth rate of atmospheric CO

2 – mitigation will be much more diffi cult

than had been previously been thought.

Southern Ocean Circulation and Biogeochemistry: Refer-ence (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 CO

2 (confi ned 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 identifi ed 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 dif-

27

its impact on marine calcifying organisms. Nature, 437: 681-686, 2005.

Articles in press or submitted:Dunne, J. P., R. A. Armstrong, A. Gnanadesikan, and J. L.

Sarmiento, Empirical and mechanistic models for the par-ticle export, Global Biogeochem. Cycles, in press.

Jin, X., N. Gruber, J. P. Dunne, J. L. Sarmiento, and R. A. Armstrong, Diagnosing CaCO

3 and opal export and phyto-

plankton 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. Mil-ligan, Climate-driven trends in contemporary ocean produc-tivity, 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 anthropo-genic carbon uptake, transport, and storage by the ocean, Global Biogeochem. Cycles, in press.

Jacobson, A. R., S. E. Mikaloff-Fletcher, N. Gruber, J. L. Sarmiento, M. Gloor, and TransCom Modelers, A joint atmo-sphere-ocean inversion for surface fl uxes of carbon dioxide: I. Methods and global-scale fl uxes, Global Biogeochem Cycles, submitted.

Jacobson, A. R., S. E. Mikaloff-Fletcher, N. Gruber, J. L. Sarmiento, M. Gloor, and TransCom Modelers, A joint atmo-sphere-ocean inversion for surface fl uxes 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.

Daniel SigmanAssistant ProfessorPh.D., 1997, MIT and Woods Hole Oceanographic Institutionemail: sigman@princeton.edu

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 (NO

3-) and dissolved organic nitrogen) to provide integrative

constraints on nitrogen cycle processes in modern environ-ments, 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 phys-ical and biogeochemical fl uxes 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:

• 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?

• What terms and rates compose the budgets of “fi xed” (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?

My research activities over the past year are summarized below under the following headings: (1) isotope method de-velopment, (2) laboratory studies of isotope discrimination, (3) studies in the modern ocean, (4) studies in the terrestrial biosphere, the atmosphere, and ice cores, (5) paleoceano-graphic 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 measure-ments, to the development of the background information needed to make those measurements useful, to their appli-cation to important questions, and fi nally to a quantitative consideration of the fi ndings in a broader environmental context. The citations below refer to manuscripts listed in the publications section of the annual review form.

Isotope method developmentIn 2005, building on my group’s previously developed meth-ods for isotopic analysis of nitrate, graduate student Angela Knapp published the fi rst 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 isotopi-cally [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 high-sensitivity method for measuring the 15N/14N of dissolved ammonium (NH

4+), as described in Houlton’s 2005 Ph.D.

dissertation. Also building upon Knapp’s dissolved organic N method, Becky Robinson and Brigitte Brunelle have estab-lished, 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

28

budget for the surface ocean at the Bermuda Atlantic Time-series Station (BATS), indicating that N

2 fi xation accounts

for <10% of the N supply at this site and reopening the ques-tion of the N source for the large summertime drawdown in CO

2 at BATS.

Nitrate N and O isotope data are also contributing to our understanding of fi xed N loss from the ocean. In 2005, Moritz Lehmann published a study of the Bering Sea in which we fi nd that the down-slope transport of organic matter from the productive Bering shelf drives denitrifi ca-tion in the deep sea sediments, leading to the development of a previously observed nitrate defi cit in the deep basin of the Bering Sea [Lehmann et al., 2005]. These fi ndings sug-gest that sedimentary denitrifi cation 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 fi xed 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 concen-tration 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 comple-ment our lab studies of algal physiology and our paleoceano-graphic studies.

Studies in the terrestrial biosphere, the atmosphere, and ice coresRecent Ecology and Evolutionary Biology graduate stu-dent 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 denitrifi cation in tropical sys-tems [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 fl uxes, the Maui gradient suggests that the plants in these forests are not so much driving the N fl uxes as fi nding a solu-tion for their N demand that is consistent with the condi-tions 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 down-core 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].

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.

Laboratory studies of isotope discriminationThe utility of isotopic distributions in the environment is premised on knowledge of the magnitudes of isotope dis-crimination by individual biogeochemical reactions, which is most often gained through lab studies of cultured organ-isms. Julie Granger’s focus is on the isotope effects of nitrate-consuming processes, in particular, nitrate assimilation by photosynthetic organisms (central to studies of nutrient sup-ply and uptake in the surface ocean) and denitrifi cation by heterotrophic bacteria (central to studies of the global ocean’s input/output budget of fi xed N). In previous years, we have studied the relationship between N and O isotope fraction-ation during nitrate assimilation. In 2005, our investigations were extended to denitrifi ers. Because we believe that nitrate reductase is the driver of isotope fractionation during both nitrate assimilation and denitrifi cation, 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 denitrifi er demonstrated different and unexpected behavior, which we believe relates to the several forms of nitrate reductase found in certain denitrifi ers (manuscript in preparation).

Studies in the modern oceanIn projects carried out in various regions of the open ocean and in previously well-studied isolated basins, we are devel-oping 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 fi xed N has been proposed to augment the subsurface nitrate pool, the 15N/14N of this nitrate converges toward the 15N/14N of newly fi xed N and thus appears consistent with this process [Knapp et al., 2005]. Ongoing work described in Knapp’s Ph.D. disserta-tion seeks to combine the isotope data with constraints on circulation to quantify the rate of N

2 fi xation in the overly-

ing 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 (low-15N/14N) newly fi xed N in a region of intense nitrate loss by denitrifi cation [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 cy-cling that is known to take place in the surface ocean. Angie Knapp’s measurements of DON completes the N isotope

29

Although post-depositional artifacts cannot be ruled out for glacial-age ice, the 15N/14N data suggest a major cli-mate-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 fi eld.

Paleoceanographic studiesFormer 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 CO

2. New

down-core records from the Subantarctic Zone of the South-ern 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 fi rst evidence for natu-rally 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 Subant-arctic Zone may also explain observations of lower nutrient content, higher dissolved O

2 content, and less denitrifi cation

in the tropical thermocline during the last ice age, with im-plications 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 demon-strating that the Subarctic North Pacifi c and the most polar Southern Ocean respond similarly to climate change, includ-ing 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 stratifi cation during cold climates. The reconstructed polar ocean changes have the capacity to affect atmospheric CO

2 in the observed

sense of its glacial/interglacial change.

Model studies of past ocean changesI have recently begun to consider a physical mechanism for the apparent climate/polar stratifi cation 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 signifi cant 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 stratifi cation in the Pleistocene

cycles in CO2 and climate.

Two-Year BibliographyRefereed articles: Hastings, M. G., E. J. Steig, and D. M. Sigman, Seasonal varia-

tions 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, Lim-nology and Oceanography, 49, 5 , 1763-1773, 2004.

Robinson, R. S., B. G. Brunelle and D. M. Sigman, Revisiting nu-trient utilization in the glacial Antarctic: Evidence from a new method for diatom-bound N isotopic analysis, Paleoceanog-raphy, 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 illumi-nated by the 15N/14N of intracellular nitrate, Journal of Phycol-ogy, 40, 517–522, 2004.

Sigman, D. M., S. L. Jaccard, and G. H. Haug, Polar ocean stratifi cation in a cold climate, Nature, 428, 59-63, 2004.

Hastings, M. G., D. M. Sigman, and E. J. Steig, Glacial/intergla-cial 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 Pacifi c 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 ori-gin of the deep Bering Sea nitrate defi cit -- Constraints from the nitrogen and oxygen isotopic composition of water col-umn nitrate and benthic nitrate fl uxes, Global Biogeochemi-cal 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 Pacifi c stratifi cation, Science, 308,1003-1006, 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 Pacifi c seasonal-ity 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 compo-sition of dissolved organic nitrogen and nitrate at the Ber-muda Atlantic time-series study site, Global Biogeochemical Cycles, 19, GB1018, 10.1029/2004GB002320, 2005.

30

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 biogeo-chemistry, 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 diatom-bound nitrogen isotopes for Subarctic Pacifi c stratifi cation during the last ice age and a link to North Pacifi c denitrifi ca-tion 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 analy-sis, 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 (2Marine Environment (2Marine Environment nd 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.

John SuppeBlair Professor of GeologyPh.D., 1969, Yale Universityemail: suppe@princeton.edu

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 fi rst part of a total of one-year of sojourns supported by an honorifi c award from the Alexander von Humboldt Foundation. I spent much effort in the spring as the scientifi c orga-nizer of an “International Conference on Theory and Ap-plication 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 fi eld 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 signifi cant assumptions about material properties. This is an important contribution to the long-standing controversy over the strength of major plate-bound-

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.

Two-Year BibliographyBooks(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.” Ameri-can 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 Asso-ciation of Petroleum Geologists Memoir, 82, p. 438-452, 2004.

(with L. M. Strayer and S. G. Erickson) Infl uence of growth strata on the evolution of fault-related folds: Distinct-element mod-els. . 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 fold-ing. 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.

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(with Li-Fan Yue and Jih-Hao Hung) Structural geology of a classic thrust belt earthquake: the 1999 Chi-Chi earthquake Taiwan (M

w7.6). Journal of Structural Geology v, 27, 2058-Journal of Structural Geology v, 27, 2058-Journal of Structural Geology

2083, 2005.

Other miscellaneous publications:(with Dengfa He) Guidebook for fi eldtrip in souh and north Tian-

shan 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:Articles in press or submitted:Articles in press or submitted(with Kauan-Yin Lai,Yue-Gau Chen, Jih-Hao Hung and Ya-Wen

Chen) Fault geometry related surface deformation of an ac-tive fault: evidence from geomorphic features and coseismic slip. Quaternary International, in press, 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 detach-ment 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 Fold-ing, American Association of Petroleum Geologists Memoir,(chapter manuscripts in review), 2005.

Bess B. WardWilliam J. Sinclair Professor of GeosciencesPh.D., 1982 University of Washington

My research concerns the marine and global nitrogen cycle, using molecular and immunological probes for marine bacteria and bacterial processes (especially nitrifi cation and denitrifi cation), and measuring the rates of N transforma-tion processes. We have ongoing research on denitrifi cation in several suboxic zones of the world ocean (Arabian Sea, Eastern Tropical North and South Pacifi c) and in Antarctica, the genes involved in nitrogen assimilation by phytoplank-ton, 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 infl uence climate; they utilize and produce nutrients that are involved in eutrophica-tion; 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 microorgan-isms 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 nitrifi ers, autotrophs that oxidize ammonium to nitrite and nitrate, and the deniti-fi ers, heterotrophs that can respire nitrate in the absence of oxygen. The linked activities of these two groups can be cru-cial in determining the chemical form and supply of nitrogen

to planktonic communities and in determining the net nitro-gen 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/ecomi-crobio.html

1. “Biocomplexity of Aquatic Microbial systems: Relat-ing diversity of Microorganisms to Ecosystem Function” (O’Mullan, Adhitya) (http://geoweb.princeton.edu/research/biocomplexity/index.html) 2005 was the last offi cial year of this collaborative project, in-volving several other institutions, all working in Chesapeake Bay and coordinated through Princeton as the lead institu-tion. Microbial biogeochemical cycling of the elements regu-lates a dynamic environment in which the cycles of different elements are linked through the physiology of microorgan-isms. Our present understanding of ecosystem function has been gained through physical/chemical approaches to mea-surement and modeling of the net transformations. These approaches necessarily rely on gross simplifi cations 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 diversi-ty and complexity at every level: redundancy and duplication of functional genes within a single organism; molecular di-versity 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 communi-ties 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 num-bers 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 func-tional genes in natural systems. The gene arrays, along with

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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 fi ve ammonia-and nitrite-oxidizing bacteria. Nitrobacter hambur-gensis 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 under-way. 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.

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 signifi cant denitrifi cation occurs in the water column. Nitrous oxide is an intermediate in the denitrifi cation path-way, and is also produced during aerobic nitrifi cation 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 char-acteristic pattern in oxygen minimum zones (OMZs), such as that found in the Arabian Sea. In previous work (Granger and Ward, 2003), we showed that denitrifi cation by cultured bacteria in the lab could be limited by copper availability, leading to the accumulation of denitrifi cation intermediates in the medium. We hypothesized that copper availability in OMZs might be quite low, low enough in fact to limit de-nitrifi cation 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 communi-ties in trace metal clean incubations, we have shows that Carbon is probably the most important limitation in these systems, that denitrifi cation is very Anammox (anaerobic ammonium oxidation) is a recently discovered step in thee N cycle, that performs essentially thee same role as denitrifi ca-tion. We have made some of the fi rst measurements of this process in Chesapeake Bay, and in the OMZ regions of thee ocean (Jeremy Rich). Contrary to the fi rst reports by Danish and German investigators, we fi nd the anammox occurs in both sediments and the water column, but is not the domi-nant 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 in-volved and plan to continue working (pending proposals).

a full suite of ecosystem process measurements, are deployed along a transect that spans the eutrophic -oligotrophic gradi-ent 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 fi xation, N fi xation, nitrifi cation, denitrifi cation, urea assimilation). The goal of these experiments is to determine how microbial species diversity affects the major energy and nutrient fl ows within ecosystems, and to assess the degree of stability or instability associated with changes in redundancy within guilds of microorganisms responsible for major nitro-gen and carbon pathways. The fi eld work for this project has been completed (~20 fi eld trips/research cruises have been completed in Chesa-peake 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 nitroge-nase, 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 fi rst successful second generation array to analyze phy-toplankton 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.

2. “What limits denitrifi cation and bacterial production in Lake Bonney, Antarctica?” (Tuit) During the two recent fi eld seasons, we developed and tested a series of fl ow cytometric assays for bacterial abundance and physiological state in samples from Lake Bonney, where denitrifi cation appears to proceed normally in one lobe of the lake but not the other. Hypotheses about the ability of trace metals to limit denitrifi cation in natural environments were tested on laboratory cultures and on incubation experiments in the lake. It appears that copper availability can indeed regulate denitrifi cation but this is probably not the funda-mental 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 distrib-uted across the Bacterial and Archaeal domains in a great diversity of microorganisms. Because trace metal availability can limit denitrifi cation in the lab, we hypothesized that metal distributions might infl uence the type of nir found in natural marine assemblages. The fi rst 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 fi rst reported for a water column environment, and are quite different from those previously reported from sediment environments.

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6. “Functional diversity of phytoplankton N assimila-tion” (Adhitya, Allen) Diatoms are an important component of marine photo-synthetic assemblages, and tend to be especially important in coastal and upwelling systems. We hypothesize that their ability to utilize variable and high nitrate concentra-tions 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 fi rst 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 quanti-tative assays of diatom gene expression, which we will use to study differential success of various phytoplankton groups in response to N availability.

Two-Year BibliographyRefereed 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 spec-troscopy. Langmuir, 20:11433-11442, 2004. Langmuir, 20:11433-11442, 2004. Langmuir

Song, B., and B. B. Ward. Molecular characterization of the as-similatory nitratereductase gene and its expression in the marine green alga Dunaliella tertiolecta. Journal of Phycol-ogy, 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 Chesa-peake Bay by using a DNA macroarray. Applied and Environ-mental Microbiology, 70: 1767-1776, 2004.

Steward, G. F., B. D. Jenkins, B. B. Ward and J. P. Zehr. Devel-opment and testing of a DNA macroarray to assess nitro-genase (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 Ecol-ogy, 34: 69-78, 2004.

Ward, B. B., J. Granger, M. T. Maldonado, K. L. Casciotti, S. Harris and M. L. Wells. Denitrifi cation 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.

Ward, B. B. Temporal variability in nitrifi cation rates and related biogeochemical factors in Monterey Bay. Marine Ecology-Progress 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 nitrifi ca-tion 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 identifi ed in ammonia-oxidizing bacteria. FEMS Micro-bial Ecology, 52: 197-205, 2005.

Song, B., and B. B. Ward. Genetic diversity of benzoyl coen-zyme A reductase genes detected in denitfi ying isolates and estuarine sediment communities. Applied and Environmental Microbiology, 71:2036-2045, 2005.

Articles In PressTaroncher-Oldenburg, G. and B. B. Ward. Oligonucletoide micro-

arrays for the study of microbial communities. In: DNA Analy-sis 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 cy-cling in the Southern California Bight, Deep-Sea Research.

Ward, B. B. and G. D. O’Mullan. Community level analysis: Ge-netic andbiogeochemcial approaches to investigate commu-nity 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.

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. Nitrifi cation 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

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Guyot Hall, front entrance.

Princeton UniversityDepartment of GeosciencesGuyot HallPrinceton, NJ 08544-1003