Professor of Earth Sciences
Wilford and Daris Zinsmeyer Chair in Marine Studies
National Taiwan University, B.Sc., 1959
Columbia University, Ph.D., 1966
Postdoctoral, Lamont-Doherty Earth Observatory, 1966-67
Assistant Scientist, Chemistry Department, Woods Hole Oceanographic Institution,
Associate Professor of Geological Sciences, University of Southern California, 1969-75
Professor of Earth Sciences, University of Southern California, 1975-present
Visiting Scholar, Centre des Faibles Radioactivites, France, 1975-76, 1984
Visiting Professor, Harwell Laboratory, United Kingdom, 1983
Visiting Professor, Institute of Geology (1980), Institute of Geochemistry
(1984), Institute of
Salt Lakes (1987), Chinese Academy of Sciences, People's Republic of China
Visiting Professor, Institute of Oceanography, National Taiwan University
and Institute of
Earth Sciences, Academia Sinica, 1991
Visiting Professor, Kanazawa University, Japan, 1991
John Simon Guggenheim Fellow, 1983
Fulbright Senior Scholar to France, 1983-84
Fellow, Japan Society for the Promotion of Science, 1991
Fellow, American Geophysical Union, 1996-
Achievement Award, Chinese Engineers and Scientists Association of Southern
California (CESASC), 1997
Wilford and Daris Zinsmeyer Chair in Marine Studies, University of Southern
Hsi-tze-wan Foundation Professor, National Sun Yet-Sen University, Taiwan,
Exploration and application ofnaturally-occurring isotopes, including actinide
nuclides,cosmogenic 10Be, 26Al and 36Cl, andstable isotopes of oxygen and carbon, as time and
property tracers in the ocean and onland.
Publications in marine and terrestrial geochronology, ocean mixing,water-column
dynamics, sediment diagenesis, kinetics of rock-waterinteraction, paleoceanography,
paleoclimate, closed-basin lake paleohydrology, Quaternary geology,archaeology, and
Recent Research Activities
My research applies geochemistry to problems in oceanography, paleoclimatology,
environmental concerns on a variety of timescales. To undertake these problems, I use naturally
occurring isotopic variations due to radioactive decay or mass fractionation as time and process
tracers and combine modeling techniques with radiochemical assay and mass spectrometry.
An important component of my research program has been to develop means
natural deposits. I have explored theuse of decay-series isotopes and cosmogenic nuclides
(10Be and 26Al) to determine ages and sedimentation rates of such deposits as marine
sediments and ferromanganese nodules, fossil corals, and pedogeniccarbonates, and the use of
the fallout 137Cs/135Cs for recent sedimentationand erosion rates. In recent years, my
colleagues/students and I designed an extraction technique which enables us to measure 26Al in
marine sediments thus paving the way of effectively using this cosmic-ray produced isotope for
sediment chronology and other geophysical studies. Our exploratory research on the use of
226Ra/Ba ratios for dating biogenic carbonates has yielded promising results which not only
show the datability of coastal mollusc shells in Antarctica, but also should aid in tackling the
14C reservoir age problem in Southern Oceans. We have also developed the U-series isochron
method for dating a variety of sedimentary materials ranging from travertine to soil carbonate to
evaporitic salts. Successful applications of this technique have led us to the establishment of
late Quaternary chronologies of closed-basinlake salt deposits in the western U.S., western
China, and South America. Considerable efforts have also been spent to push the frontier in the
useof 226Ra and 226Ra as watermass time tracers.
Seeking new ways of extracting information about past environments in terms
of climate and
ocean productivity changes constitutes another part of my research effort. On paleoclimate
studies, our isotopic (oxygen and carbon), chemical, and mineralogical studies on lake
sediments allow us to decipher the regional changes in climate and hydrology in great detail.
From a mass balance of 18O and water, and from an understanding of the factors controlling
the d13C-d18O covariance in lake sediments, we can deduce the volume change of a
closed-basin lake, hence changes in regional precipitation versus evaporation. Such
paleoclimatic reconstructions are being made in very high-resolution (subdecadal) for the
Mono and Owens Lakes of the Great Basin in the western U.S. We are pushing the
time-resolution limit (interannual to subdecadal) for deciphering the paleoclimatic signals
archived in the speleothem deposits of limestone caves. Results from our study of the Shihua
Cave near Beijing clearly revealed a climatic cyclicity that may tie to past variations of the
summer monsoon strength. We are studying a series of caves in eastern China from25o to 40o
N, in an attempt to unravel temporal shifts in the positions of the Intertropical Convergence
Zone (ITCZ) and the Northwest Pacific Subtropical High, hence possible linkage between the
Asian Summer Monsoons and El Ni*±o-Southern Oscillation (ENSO). We are confident that
this research will contribute to our understanding of not only the climate history of eastern
Asia, but also the factors influencing the monsoon fluctuations that are rooted in the global
climate variability. On paleoceanographic research, we have been critically evaluating the use of
particle-reactive isotope pairs of 230Th-231Pa and our newly proposed 26Al-10Be as proxies for
past oceanic productivity. These proxies have the advantage of being less affected by
post-depositional dissolution/mobility, in addition to having known production ratio for each of
Also going on are two environmental research projects which deal with problems
concern of a more direct and immediate nature. Prior to the 1970s, coastal ocean off southern
California received significant amounts of man-made organic contaminants such as chlorinated
pesticides (DDTs), polychlorinated biphenyls (PCBs) and linear alkylbenzenes (LABs).
Although the contaminants are largely buried by sedimentation, an investigation of their
post-depositional movement and fate in the coastal marine environment is urgently needed. We
have launched studies to address this issue in the Palos Verdes Shelf area and in the San Diego
Bay. In collaboration with scientists from the Southern California Coastal Water Research
Project (SCCWRP), we measured the organic contaminants and some naturally-occurring
radioisotopes in seawater and sediment cores collected in the vicinity of the Whites Point
sewage outfall. As DDTs are largely bound to particles due to their large partition coefficients,
we can use the particle-reactive 234Th (half-life 24.1 d) in relation to its radioactive parent 238U
to trace the pollutants in sediments and seawater. The radioactivity distributions enabled us to
estimate the fluxes of the buried DDTs and PCBs across the seafloor and, upon reentry into the
sea, their water-column residence times in the region. A similar study is being carried out on the
resuspension, redistribution, and dispersal of PCBs and polycyclic aromatic hydrocarbons
(PAHs) in the San Diego Bay.
The second project related to environmental concerns is directed toward
and quantitative assessment of subsurface transport of radioactive waste contaminants at U.S.
DOE sites such as Hanford, Washington and the Idaho National Engineering and
Environmental Laboratory (INEEL). The long-term migration behavior of radionuclides in
underground aquifers can be understood through a study of the cumulative effects of transport
over geological times, and these effects can be assessed from the naturally occurring U and Th
decay-series disequilibria observed in the rock-water system. The decay series consist of
elements with diverse chemical properties and with isotopes having a range of decay mean lives.
Different geochemical behaviors of the nuclides lead to significant radioactive
between parents and daughters in the interstitial fluids and associated solids. Both
thermodynamic and kinetic factors play a role in creating and maintaining the disequilibria. By
modeling the local mass balance of the various radioisotopes, with constraints placed by their
different decay rates and the parent-daughter relationships, one can derive information on
kinetics of rock-water interaction under a given geochemical and hydrologic environment, on
time scales of a few days to over a million years. Adopting this natural analog approach, we
have been studying the radionuclide and groundwater movements at INEEL. The study gives us
information on (1) sorption-desorption rate constants and retardation factors of various
radionuclides, (2) rates of precipitation and dissolution of rocks and their influence on
radionuclide transport, and (3) transit time and flow path of groundwaters at the site. Such
site-specific information is also of fundamental value for evaluating in-situ, long-term migration
of radionuclides in the far field of a nuclear waste disposal site.
The above-outlined research programs are the collaborative undertakings
of many researchers
and institutions. The principal ones include:
USC Geochemistry Laboratory: T. L. Ku, S. Luo, H. C. Li, L. Stott, L. Wang,
Tang, H. Huang, J, Peng, D. Paulsen.
Lawrence Livermore National Laboratory: J. R. Southon.
Los Alamos National Laboratory: M. Murrell, R. Roback.
Binghamton University: T. K. Lowenstein.
Ohio State University: P. A. Berkman.
Southern California Coastal Water Research Project: E. Zeng.
Japan Marine Science and Technology Center: M. Kusakabe.
Institute of Earth Sciences, Academia Sinica: T. Lee, C.A. Huh.
Geology 412, Oceans, Climate, and the Environment
Geology 460, Geochemistry and Hydrogeology
Geology 560, Marine Geochemistry
Geology 564, Isotope Geochemistry
Geology 555, Chemical Equilibria in Geology
Geology 566, Geochemistry Seminar
Click here to see a list of PUBLISHED PAPERS SINCE 1995
Science Hall, Room 325E
USC Earth Sciences
Los Angeles, CA 90089-0740
phone: (213) 740-5826
fax: (213) 740-8801
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Last modified: January 18, 2000.
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