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Troy Rasbury Associate Professor Office: ESS 320 Phone: (631) 632-1488 Fax: (631) 632-8240 E-mail Address: Troy.Rasbury@sunysb.edu B.S., Midwestern State University, 1984 M.S., Tulane University, 1990 Ph.D., SUNY Stony Brook, 1998 Assistant Professor at Queens College 1998-1999 Faculty member at Stony Brook starting Fall 1999 Visit our isotope lab on the web |
Carbonate petrography, Chronostratigraphy, and U-Pb Geochronology
The main focus of my research is exploring the potential for U-Pb
dating of sedimentary materials for the purpose of improving time resolution in the sedimentary rock
record. This effort has mainly centered on syn-sedimentary carbonates that are common in space
and time. Even though we can rarely obtain two sigma age uncertainties of less than 1% (and the
current best is about 0.3%), this research has vast potential for improving our understanding
of rates because of the common occurrence of carbonates. The research involves looking
carefully at sedimentary rocks to understand their history in terms of the environment of
deposition as well as to understand the diagenetic history of the rock. We target minerals
that form at the time of sedimentation, or, that is to say, they form so close to the time of
sedimentation that within the uncertainty of dating techniques they form at the time of
sedimentation. This requires careful petrographic investigation of rocks from well-constrained
rapidly deposited stratigraphic sections to avoid samples that have complex histories. With
such screening, the hope is that the age of the carbonate accurately dates the time of sedimentation
within the stated precision. This can be determined by evaluation of the U-Pb system and by
obtaining multiple ages from a sequence that occur in a stratigraphically sensible arrangement.
However the most powerful tests will be from comparing ages from high precision techniques in
sections where such tests are possible.
My current focus is on long-term marine and terrestrial records with high-resolution
cycles that should provide multiple temporally widely spaced ages allowing tests of the
cyclicity as well as the ages themselves (by the principle of superposition). I have ongoing
research projects related to providing better time resolution for the late Paleozoic using
U-Pb dating of paleosol carbonates and in marine cements that were originally aragonite.
Some of these ages are shown below in a cycle versus age diagram. This will be coupled
with
Sr chemostratigraphy to provide an additional means of exploring global correlations.
Below is a diagram illustrating the constraints that cycles can provide if we can assume
they are periodic and that we have recognized all of them. These are assumptions that
require testing as well and certainly more dates will facilitate this research.
The solid red line is a weighted least squares fit to the ages obtained from paleosols from the Sacramento Mountains in New Mexico and from cores from the Central Basin Platform. The positions of the dated horizons and biostratigraphically (fusulinids and conodonts) identified boundaries are shown in terms of cycle position. The uncertainties in the boundary ages is a function of the uncertainty in the dated horizons AND the uncertainty in cycle position. We have used +/- 5 cycles and based on linear extrapolation assuming the cycles are quasi-equal duration (a far better guess than that the rate of sedimentation is constant) we obtain an age for the Carboniferous-Permian (C-P) boundary of 301 +/- 2 Ma and a cycle duration of 147 +/- 64 ky for the late Paleozoic cyclothems [Rasbury et al. 1998]. The dashed red lines have slopes of 100 ky/cycle (flatter) and 400 ky/cycle. If one takes the most precise age from the left side of this diagram (298 +/- 1 Ma) and uses 400 ky/cycle then the estimated age of the C-P boundary is 307 and the Missourian-Virgilian (M-V) boundary is 319 (instead of 307 +/- 3 Ma as estimated by simply using the data and not assuming a cycle duration but rather calculating this).
I approach sample selection from several directions including 1) a focus on the controls on U speciation in depositional environments and how this controls its incorporation into carbonates, 2) petrographic evaluation, 3) trace element (see fish below) and fission track maps, 3) autoradiography, and 4) I am working with Shelly Kelly (APS), Paul Northrup and Tony Lanzirotti (NSLS), Drew Tait and Robert Donohoe (LANL) to determine the U oxidation state and U complexes using spectrographic techniques.
Th La map of a Green River fish fossil. Th concentrations exceed 700 ppm [Cole et al., 2003].
Publications
Jennifer M. Cole, E. Troy Rasbury, Gilbert N. Hanson, Isabel P. Montañez and Vicki A. Pedone, accepted August 2004, Using U-Pb ages of Miocene tufa for correlation in a terrestrial succession, Barstow Formation, California: Geological Society of America Bulletin.
E. T. Rasbury, W. B. Ward, N. G. Hemming, H. Li, J. A. D. Dickson, G. N. Hanson, and R. P. Major, 2004, Concurrent U-Pb age and seawater 87Sr/86Sr value of marine cement: Earth and Planetary Science Letters, v. 221, p. 355-371.
Jennifer M. Cole, E. Troy Rasbury, Isabel P. Montañez, Vicki A. Pedone, Antonio Lanzirotti, and Gilbert N. Hanson, 2004, Petrographic and trace element analysis of uranium-rich tufa calcite, middle Miocene Barstow Formation, California: Sedimentology, v. 51, p. 433-453.
M. L. Becker, E. T. Rasbury, W. J. Meyers, and G. N. Hanson, 2004, U-Pb calcite age of the Late Permian Castile Formation, Delaware Basin: constraint on the age of the Permian-Triassic Boundary? Reply to a comment by Ian Metcalfe: Earth and Planetary Science Letters, v. 217, p. 469-471.
Jennifer M. Cole, Jessica Nienstedt, Glenn Spataro, E. Troy Rasbury, Antonio Lanzirotti, Aaron J. Celestian, Melanie Nilsson, Gilbert N. Hanson, 2003, A method for determining relative uranium concentrations in geological samples on a hand specimen scale: Chemical Geology, v. 193, p. 127-136.
R. L. Folk and E. T. Rasbury, 2002, Nanometer-scale spheroids on sands, Vulcano, Sicily: possible nannobacterial alteration: Terra Nova, v. 14, p. 467-475.
E. T. Rasbury, 2002, Geochronology: McGraw-Hill Yearbook of Science & Technology, p. 143-145.
K. McCall, A. Lanzirotti and E. T. Rasbury, 2001, U (VI) Incorporation in Paleosol Calcite: Evidence for Sequestration of U on Geologic Time Scales: NSLS Activity Report 2001
M. L. Becker, E. T. Rasbury, G. N. Hanson and W. J. Meyers, 2001, Refinement in the age of the Carboniferous-Permian boundary based on U-Pb dating of beostratigraphically constrained syn-sedimentary carbonates in the Appalachian region of North America: Carboniferous Newsletter, v. 19, p. 18-20.
M. L. Becker, E. T. Rasbury, W. J. Meyers, and G. N. Hanson, 2002, U-Pb calcite age of the Late Permian Castile Formation, Delaware Basin: constraint on the age of the Permian-Triassic Boundary: Earth and Planetary Science Letters, v. 203, p. 681-689.
Mona L. Becker, Jennifer M. Cole, E. Troy Rasbury, Vicki A. Pedone, Isabel P. Montaņez , Gilbert N. Hanson , 2001, Cyclic variations of uranium incorporation in tufa from the Miocene Barstow Formation, Rainbow Basin, Mojave, California: Geology, v. 29, p. 139-142.
E. Troy Rasbury, William J. Meyers, Gilbert N. Hanson, Robert H. Goldstein, and Arthur H. Saller, 2000, Relationship of uranium to petrography of caliche paleosols with application to precisely dating the time of sedimentation: Journal of Sedimentary Research, v. 70, p. 604-618.
S. R. Hemming and E. T. Rasbury, 2000, Pb isotope measurements of sanidine monitor standards: Implications for provenance analysis and tephrochronology: Chemical Geology, v. 165, p. 331-337.
A.H. Saller, J.A.D. Dickson, E.T. Rasbury, T. Ebato, 1999, Effects of long-term accommodation changes on short-term cycles, late Paleozoic platform limestones, West Texas: in Harris, Saller, and Simo, eds, SEPM Special Publication No. 63, Introduction to advances in carbonate sequence stratigraphy- application to reservoirs, outcrops and models, p. 227-246.
E. Troy Rasbury, Gilbert N. Hanson, William J. Meyers, William E. Holt, Robert H. Goldstein and Arthur H. Saller, 1998, U-Pb dates of paleosols: Constraints on late Paleozoic cycle durations and boundary ages: Geology, v. 26, 403-406.
Z. S. Wang, E. T. Rasbury, G. N. Hanson, W. J. Meyers, 1998, Dating the time of sedimentation of clastic sedimentary rocks using U-Pb system of calcretes: Geochimica et Cosmochimica Acta, v. 62, p. 2823-2835.
F. Marcantonio, S. Higgins, R. F. Anderson, M. Stute, P. Schlosser and E. T. Rasbury, 1998, Terrigenous helium in deep-sea sediments: Geochimica et Cosmochimica Acta, v. 62, p. 1535-1543.
E. T. Rasbury, G. N. Hanson, W. J. Meyers and A. H. Saller, 1997, Dating of the time of sedimentation using U-Pb ages of paleosol calcite: Geochimica et Cosmochimica Acta, v. 61, p. 1525-1529.
Recent Abstracts:
S. D. Kelly, J. F. Banfield, S. C. Brooks, J. K. Fredrickson, E. T. Rasbury, C. Spötl, N. C. Sturchio, Y. Suzuke, K. M. Kemner, 2004, Uranium in Calcium Carbonate Systems, Third Worksjop on Speciation, Techniques, and Facilities for Radioactive Materials at Synchrotron Light Sources, Berkeley, California, September 14-16, 2004.
E. Troy Rasbury, Elizabeth H. Gierlowski-Kordesch, Jennifer M. Cole, Cherri Sookdeo, Glenn Spataro, and Jessica Nienstedt, 2004, Calcite cements in fluvial deposits of the New Haven Arkose, Hartford Basin, Connecticut, 32cd International Geological Congress, Florence, Italy.
F. D. Winsolw III, E. T. Rasbury, S. R. Hemming, 2004, Petrologic complexities of the Manicouagan melt sheet: Implications for 40Ar-39Ar geochronology, 35th Lunar and Planetary Science Conference, League City, Texas.
J. M. Cole, E. T. Rasbury, I. P. Montañez, V. A Pedone, A. Lanzirotti, and G. N. Hanson, 2004, Uranium and other trace element incorporation into tufa calcite, 14th Annual V. M. Goldschmidt Conference, Copenhagen, Denmark.
P. E. Olsen, M. Machlus, T. Rasbury, D. V. Kent, 2004, The full spectrum of Milankovitch precession-related periodicities in Triassic age lacustrine strata of Eastern North America: from 10 ky to 3.5 m.y, European Union of Geosciences meeting, Nice, France.
E. Troy Rasbury, C. Drew Tait, Robert J. Donohoe, 2003, Uranyl incorporation in organic-bearing soil calcite, Fall American Geophysical Union meeting, San Francisco, CA.
Brian C. Titone, E. Troy Rasbury, Scott M. McLennan, Tony Lanzirotti and Malka Machlus, 2003, Actinide enrichment in phosphate bone fossils of the Green River Formation, Annual Geological Society of America meeting, Seattle, WA.
E. Troy Rasbury, Carol B. DeWet, and Jessica Nienstedt, 2003, U-Pb age of stromatolite cacite from the Triassic Passaic Formation of the Newark Basin, Annual Geological Society of America meeting, Seattle, WA.
J. Cole, D. Nest, A. Lanzirotti, T. Rasbury, and G. Hanson, 2002, Incorporation of Uranium and Other Trace Elements in Lacustrine Tufa Calcite, 2002 National Synchrotron Light Source Activity Report.
B. Titone, T. Rasbury, A, Lanzirotti, and M. Machlus, 2002, Th Incorporation in Phosphatic Fossils of the Green River Formation, 2002 National Synchrotron Light Source Activity Report.
J. Neinstedt, K. Claeson, G. Spataro, J. Cole, T. Rasbury, A. Lanzirotti, 2002, A Petrographic Study of Devonian Teeth from Clinton County, Pennsylvania: extended abstract, Long Island Geologists: http://pbisotopes.ess.sunysb.edu/lig/Conferences/abstracts_02/nienstedt/index.htm
C. Sookdeo, G. Spataro, and T. Rasbury, 2002, Calcite Cements in a Fluvial Cycle, Hartford Basin, Connecticut: extended abstract, Long Island Geologists: http://pbisotopes.ess.sunysb.edu/lig/Conferences/abstracts_02/sookdeo/calcite_cements_in_a_fluvial_cyc.htm
Jennifer M. Cole, E. Troy Rasbury, Gilbert N. Hanson, and Gail M. Ashley, 2001. Evaluating the effect of initial isotopic disequilibrium on U-Pb ages of Quaternary sedimentary carbonates from Olduvai Gorge, Tanzania. 11th Annual V. M. Goldschmidt Conference. Hot Springs, VA. Abstract 3594.
Kasey McCall, E. Troy Rasbury, and
Antonio Lanzirotti, 2001, Trace Element Incorporation in Caliche Paleosols. 11th Annual V.
M. Goldschmidt Conference, Hot Springs, VA.
E. T. Rasbury M. L. Becker, G. N. Hanson, G. N., and W. J. Meyers 2001, Problems with Correlation of the Carboniferous-Permian Boundary in North America. Eos Transactions AGU 82(47), Fall Meeting Suppl., Abstract V42F-06.
A. Lanzirotti, S. Sutton, S., T. Rasbury, M. Becker, and G. N. Hanson, 2001, Coupled U-Pb isotopic studies and synchrotron x-ray microbeam analysis of geologic systems. Eos Transactions AGU 82(47), Fall Meeting Suppl., Abstract V42F-10.
H. Li, E. T. Rasbury, and G. N. Hanson, 2001, Determining the age and original seawater 87Sr/86Sr from altered aragonite marine cements of the Laborcita Formation, New Mexico. Eos Transactions AGU 82(47), Fall Meeting Suppl., Abstract V42F-11.
Jennifer M. Cole, E. Troy Rasbury, Isabel P. Montaņez, Vicki A. Pedone, Sideny R. Hemming, Antonio Lanzirotti, Mona L. Becker, and Gilbert N. Hanson, 2001. Uranium-lead ages of lake margin tufa calcite from the middle Miocene Barstow Formation, southern California. Eos Transactions AGU 82(47), Fall Meeting Suppl., Abstract V42F-04.
Vicki A. Pedone, E.Troy Rasbury,
Sidney Hemming, and Isabel Montaņez, 2001, U-Pb and Ar-Ar age constraints on Miocene
terrestrial rocks: An example from the Barstovian Land Mammal Stage of North America,
International Geological Society of America meeting, Edinburgh, Scotland, June 2001.
J. Neinstedt, G. Spataro, C. Sookdeo,
T. Rasbury, C. deWet, 2001, A Petrographic Comparison of Triassic Caliches from the Gettysburhg
and Hartford Basins, Long Island Geologists
Meeting; http://pbisotopes.ess.sunysb.edu/lig/Conferences/abstracts-01/4_01_program.htm#POSTERS
Jennifer M. Cole, Antonio Lanzirotti, E. Troy Rasbury, and Gilbert N. Hanson, 2001, XRF and XANES studies of uranium incorporation into Miocene tufa calcite, 2001 National Synchrotron Light Source Activity Report.
K. McCall, E.T. Rasbury, and A. Lanzirotti, 2001, Uranium Incorporation Into Pedogenic Carbonates, 2001 National Synchrotron Light Source Activity Report. http://www.pubs.bnl.gov/nsls01/pdf/section%206%20abstracts/mcca433.pdf
J. Nienstedt, C. Drayer, A. Lanzirotti, T. Rasbury, A. Celestian, and C. Forester, 2001, Incorporation of U and Th in Phosphatized Fossils, 2001 National Synchrotron Light Source Activity Report. http://www.pubs.bnl.gov/nsls01/pdf/section%206%20abstracts/nien478.pdf
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