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J. Kirk Cochran


Ph.D., 1979, Yale University

Marine geo-chemistry, use of radionuclides as geochemical tracers; diagenesis of marine sediment


Research Interests

My research group and I are using natural radionuclides to study Earth surface processes. The fact that different chemical elements are represented in the suite of radioactive nuclides permits studies of chemical behavior, and the property of radioactivity provides a clock with which to measure rates. Much of my recent research has focused on using naturally occurring radionuclides to determine rates of particle cycling and particulate organic carbon fluxes in the open ocean. This work has as its goal an understanding of the fate of carbon in the ocean and has been carried out in the North Atlantic, Pacific and Southern Oceans, as well as the Mediterranean Sea Radionuclides such as 234Th and 210Po provide a means of determining the export of particulate organic carbon from the upper ocean and provide information on this important aspect of the carbon cycle.

In coastal waters and estuaries, naturally occurring particle-reactive radionuclides provide tracers to determine rates of removal of contaminants from the water column and the subsequent transport and deposition of sediments and associated contaminants. Radionuclides that tend to remain in solution, such as the Ra isotopes, serve as tracers of submarine groundwater discharge to the coastal ocean. These applications are part of ongoing projects in New York’s coastal lagoons (Jamaica Bay, Great South Bay) and in Long Island Sound. A related area of research in regional settings is the health and resiliency of the area’s salt marshes. Marshes are increasingly being lost and we seek to understand the causes of loss. I am applying an integrated approach to examine both the biogeochemical and physical dynamics of natural and restored salt marshes.

In addition to broad applications of natural radionuclides to recent Earth surface processes, I am collaborating with colleagues in the Stony Brook Dept. of Geosciences, the American Museum of Natural History and Brooklyn College (CUNY) to characterize the geochemical setting of the Late Cretaceous (~70 Ma) Western Interior Seaway of North America and oceanographic conditions prior to and immediately after the Cretaceous-Paleogene boundary (66 Ma). This research involves measurements of carbon, oxygen and strontium isotopes in well-preserved shells of fossil molluscs, authigenic carbonate deposits and sediment formations.

Selected Publications

Krishnaswami, S. and J. K. Cochran. 2008. U-Th Series Nuclides in Aquatic Systems, Elsevier, New York, 458 pp.

Cochran, J.K. and P. Masqué. 2003. Short-lived U/Th series radionuclides in the ocean: Tracers for scavenging rates, export fluxes and particle dynamics. In: Uranium Series Geochemistry (B.P. Bourdon, G. Henderson, C.C. Lundstrom, S.P. Turner eds.), Reviews in Mineralogy and Geochemistry, vol. 52, Mineralogical Society of America, pp. 461-492.

Cochran, J. K., J. C. Miquel, R. Armstrong, S. Fowler, P. Masqué, B. Gasser, D. Hirschberg, J. Szlosek, A. M. Rodriguez y Baena, E. Verdeny, and G. Stewart (2009) Time-series measurements of 234Th in water column and sediment trap samples from the northwestern Mediterranean Sea. Deep-Sea Research II, doi:10.1016/j.dsr2.2008.12.034.

Cochran, J. K., N. H. Landman, N. L. Larson, K. C. Meehan, M. Garb, and J. Brezina (2015) Geochemical evidence (C and Sr isotopes) for methane seeps as ammonite habitats in the Late Cretaceous (Campanian) Western Interior Seaway. Swiss J Palaeontol. doi: 10.1007/s13358-015-0087-9.

Hayes, C. T., E. E. Black, R. F. Anderson, M. Baskaran, K. O. Buesseler, M. A. Charette, H. Cheng, J. K. Cochran, R. L. Edwards, P. Fitzgerald, P. J. Lam, Y. Lu, S. O. Morris, D. C. Ohnemus, F. J. Pavia, G. Stewart and Y. Tang (2018) Flux of particulate elements in the North Atlantic Ocean constrained by multiple radionuclides. Global Biogeochem. Cycles,  <

Landman, N. H., J. K. Cochran, M. Slovacek, N. L. Larson, M. P. Garb, J. Brezina, and J. D. Witts (2018) Isotope sclerochronology of ammonites (Baculites compressus) from methane seep and non-seep sites in the Late Cretaceous Western Interior Seaway, USA: Implications for ammonite habitat and mode of life. American Journal of Science 318: 603-639

Tamborski, J. J., J. K. Cochran, and H.J. Bokuniewicz (2017) Submarine groundwater discharge driven nitrogen fluxes to Long Island Sound, NY: Terrestrial vs. marine sources. Geochimica et Cosmochimica Acta 218: 40–57.

Witts, J. D., N. H. Landman, M. P. Garb, C. Boas, E. Larina, R. Rovelli, L. E. Edwards, R. M. Sherrell and J. K. Cochran (2018) A fossiliferous spherule-rich bed at the Cretaceous-Paleogene (K-Pg) boundary in the Mississippi Embayment and Eastern Gulf Coastal Plain. Cretaceous Research 91: 147-167.

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SoMAS Convocation 2019

Photo above: Dean Shepson welcomes the Class of 2019 at the SoMAS Convocation. Congratulations to our graduates!  The annual SoMAS Convocation occurred on Friday, May 24, 2019 at the Center for Leadership and Service. Students gathered with their friends and family...

SoMAS Research featured as EOS Research Spotlight

The recent publication by SoMAS alum Shaily Rahman (PhD, 2016) and her advisors, Robert Aller and J. Kirk Cochran: "The Missing Silica Sink: Revisiting the Marine Sedimentary Si Cycle Using Cosmogenic 32Si" published in Global Biogeochemical Cycles 31, 1559 - 1578, is...

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