Faculty, Staff and Students

< Back to list

Aaron Diefendorf

Title: Associate Professor, Organic and Isotope Geochemistry
Office: 610 Geology-Physics Building
Tel: 513-556-3787
Email: aaron.diefendorf@uc.edu
Web: http://aarondiefendorf.weebly.com

My research uses stable isotope and organic biogeochemical tools to solve critical questions in the areas of global climate change, carbon cycling, Earth’s climate sensitivity, paleoclimatology, and paleoecology.


  • Ph.D., Pennsylvania State University, 2010 (Geosciences and Biogeochemistry).
  • M.S., University of Saskatchewan, Canada, 2005 (Geological Sciences).
  • B.S., University of Tennessee, 2002 (Honors Geology).
  • B.F.A., University of Tennessee, 2002 (Studio Art Ceramics).

Research Information

Research Interests

Earth’s climate is warming at a pace and magnitude unprecedented in recent times, with profound consequences for terrestrial ecology and hydrology. My research aims to contribute to our understanding of future global change by examining Cenozoic changes in climate, ecology, and the carbon cycle. Fossil chemical signatures—biomarkers—and their carbon isotope ratios integrate and track the ancient carbon cycle and provide unique paleoecological information in sediments where other proxies are not often preserved. The combination of biomarkers and carbon isotopes provides new insights into the feedbacks between global change, terrestrial ecology, and the carbon cycle.

Please see my website for current information, a curriculum vitae, information about our organic and isotope geochemistry facilities.

Research Support

  • (PI), Diefendorf, MRI: Acquisition of Stable Isotope Instrumentation for Biogeochemistry Research and Teaching at the University of Cincinnati , NSF. (EAR-1229114), $400,000 ($571,428 total). 09/15/2012 to 08/31/2015. Status: Active.
  • (PI), Diefendorf, In support of NSF Grant., Ohio Board of Regents Action Fund. (OBR AF), $85,714. 09/15/2012 to 08/31/2015. Status: Active.
  • (PI), Diefendorf, Aaron, Terrestrial Biomarker Transport Mechanisms and Implications for Interpreting Terrestrial Signals in Oils and Bitumens, American Chemical Society - National Chapter. (PRF 5187-DN12), $100,000.00. 01/01/2012 to 08/31/2016. Status: Active.
  • (PI), Diefendorf, Aaron, North Hemisphere mid-latitude paleovegetation response to moisture changes during the late Quaternary, Korea Institute of Geoscience and Mineral Resources. (KIGMR 2015-2016), $29,000.00. 07/01/2015 to 04/30/2016. Status: Awarded.
  • (Collaborator), Diefendorf, Aaron; Havig, Jeff, Agouron Small Grant in Aid conference funds for 10/15/16 event (Grant No.AI-SGIA-203.16.1), Agouron Institute. (AI 010348-002), $8,000.00. 06/01/2016 to 05/31/2017. Status: Awarded.
  • (PI), Diefendorf, Aaron, Evaluating plant carbon isotope fractionation as a pCO2 proxy for the geologic record, National Science Foundation. (EAR-1636546), $138,189.00. 09/01/2016 to 08/31/2018. Status: Active.
  • (PI), Diefendorf, Aaron; Lowell, Thomas, Collaborative Research: Identifying basin-specific controls on isotopic and chronological offsets of lake sediment leaf wax hydrogen isotope records, National Science Foundation. (EAR-1636740), $222,636. 08/01/2016 to 07/31/2018. Status: Active.
  • (PI), Diefendorf, Aaron, Hydrologic conditions in western North America during the Last Interglacial , Korea Institute of Ocean Science and Technology. (KIGMR 2016-2017), $31,284.71. 06/01/2016 to 04/30/2017. Status: Active.
  • (Collaborator), Czaja, Andrew; Diefendorf, Aaron; Hamilton, Trinity; Havig, Jeff, Midwest Geobiology Conference , National Aeronautics and Space Administration. (OSGC Student-Innovative-Creative-Hands-on Project (SICHOP) grant), $2,000.00. 06/06/2016 to 12/31/2016. Status: Awarded.


Peer Reviewed Publications

  • Diefendorf A., & Patterson W. (2005). Survey of stable isotope values in Irish surface waters. Journal of Paleolimnology, 34(2), 257-269.
  • Diefendorf, A.F., Freeman, K.H., Wing, S.L., 2012. Distribution and carbon isotope patterns of diterpenoids and triterpenoids in modern temperate C3 trees and their geochemical significance. Geochimica et Cosmochimica Acta 85, 342-356
  • Diefendorf A.F., Mueller K.E., Wing, S.L., Koch P.L, & Freeman, K.H. (2010). Global patterns in leaf 13C discrimination and implications for studies of pa. Proceedings of the National Academy of Sciences of the United States of America, 107(13), 5738-5743.
  • Cui, Y., Kump, L.R., Ridgwell, A.J., Charles, A.J., Junium, C.K., Diefendorf, A.F., Freeman, K.H., Urban, N.M., Harding, I.C., 2012. Reply to 'Constraints on hyperthermals'. Nature Geoscience 5, 231-232.
  • Cui, Y. Kump, L.R., Ridgwell, A.J., Charles, A.J., Junium, C.K., Diefendorf, A.F., Freeman, K.H., Urban, N.M., Harding, I.C., (2011). Slow release of fossil carbon during the Paleocene-Eocene Thermal Maximum. Nature Geoscience. 4, 481-485.
  • Freeman, K.H., Mueller, K.E., Diefendorf, A.F., Wing, S.L., & Koch, P.L. (2011). Clarifying the influence of water availability and plant types on carbon isotope discrimination by C. Proceedings of the National Academy of Sciences of the United States of America, 108(16).
  • Mueller, K.E., Diefendorf, A.F., Freeman, K.H. & Eissenstat, D.M. (2010). Appraising the roles of nutrient availability, global change, and functional traits during the angiosperm rise to dominance. Ecology Letters, 13, E1-E6.
  • Diefendorf A., Freeman K., Graham H., & Wing S. (2011). Production of n-alkyl lipids in living plants and implications for the geologic past. Geochimica et Cosmochimica Acta, 75(23), 7472-7485.
  • Wing, S.L., Bloch, J.I., Bowen, G.J., Boyer, D.M., Chester, S., Diefendorf, A.F., Harrington, G.J., Kraus, M.J., Secord, R., Smith, F.A. (2009). Coordinated sedimentary and biotic change during the Paleocene-Eocene Thermal Maximum in the Bighorn Basin, Wyoming, USA, in: Crouch, E.M., Strong, C.P., Hollis, C.J. (Eds.), Climatic and Biotic Events of the Paleogene (CBEP 2009). GNS Science Miscellaneous Series, 18, 156-162.
  • Cui Y., Kump L., Ridgwell A., Diefendorf A., & Junium C. (2010). A high-resolution record from Svalbard of carbon release during the Paleocene-Eocene thermal maximum. Journal of Earth Science, 21(SUPPL. 1), 190.
  • Schouten, S., Hopmans, E.C., van der Meer, J., Mets, A., Bard, E., Bianchi, T.S., Diefendorf, A., Escala, M., Freeman, K.H., Furukawa, Y., Huguet, C., Ingalls, A., Menot-Combes, G., Nederbragt, A.J., Oba, M., Pearson, A., Pearson, E.J., Rosell-Mele, A., Schaeffer, P., Shah, S.R., Shanahan, T.M., Smith, R.W., Smittenberg, R., Talbot, H.M., Uchida, M., Van Mooy, B.A.S., Yamamoto, M., Zhang, Z.H., Damste, J.S.S. (2009). An interlaboratory study of TEX86 and BIT analysis using high-performance liquid chromatography-mass spectrometry. Geochemistry Geophysics Geosystems, 10, 13.
  • Diefendorf A., Freeman K., & Wing S. (2012). Distribution and carbon isotope patterns of diterpenoids and triterpenoids in modern temperate C. Geochimica et Cosmochimica Acta, 85, 342-356.
  • Diefendorf, A.F., Patterson, W.P., Holmden, C., Mullins, H.T. (2008). Carbon isotopes of marl and lake sediment organic matter reflect terrestrial landscape change during the late Glacial and early Holocene (16, 800 to 5, 540 cal yr BP): a multiproxy study of lacustrine sediments at Lough Inchiquin, western Ireland. Journal of Paleolimnology, 39, 101-115.
  • Close, H.G., Shah, S.R., Ingalls, A.E., Diefendorf, A.F., Brodie, E.L., Hansman, R.L., Freeman, K.H., Aluwihare, L.I., & Pearson, A. (2013). Export of submicron particulate organic matter to mesopelagic depth in an oligotrophic gyre. Proceedings of the National Academy of Sciences of the United States of America, 110(31), 12565-12570.
  • Tibert, N.E., Patterson, W.P., Diefendorf, A.F., Martini, A., Stanton, C. (2007). Holocene temperature variability in western Ireland: Evidence from limnic ostracode assemblages and stable isotope values. Stratigraphy, 4, 353-361.
  • Clyde, W. C.; Gingerich, P. D.; Wing, S. L.; Röhl, U.; Westerhold, T.; Bowen, G.; Johnson, K.; Baczynski, A. A.; Diefendorf, A.; McInerney, F.; Schnurrenberger, D.; Noren, A.; Brady, K.; Acks, R.; Belcher, C.; Collinson, M.; D'Ambrosia, A.; Denis, E.; Freeman, K.; Harrington, G.; Jardine, P.; Kraus, M.; Maibauer, B.; Riedel, J.; Schouten, S.; Tsukui, K.; Weijers, J.; Welter, G.; Wittkopp, F. and Wood, A.(2013). Bighorn Basin Coring Project (BBCP): A continental perspective on early Paleogene hyperthermals. Scientific Drilling (16), 21-31.
  • Diefendorf, A.F., Patterson, W.P., Mullins, H.T., Tibert, N., Martini, A. (2006). Evidence for high-frequency late Glacial to mid-Holocene (16, 800 to 5500 cal yr B.P.) climate variability from oxygen isotope values of Lough Inchiquin, Ireland. Quaternary Research, 65, 78-86.
  • Diefendorf A., Freeman K., & Wing S. (2014). A comparison of terpenoid and leaf fossil vegetation proxies in Paleocene and Eocene Bighorn Basin sediments. Organic Geochemistry, 71, 30-42.
  • Marin-Spiotta, E., Chaopricha, N.T., Plante, A., Diefendorf, A.F., Muller, C.W., Grandy, S., Mason, J.A., (2014). Long-term stabilization of deep soil carbon by fire and burial during early Holocene climate change. Nature Geoscience, 7(6), 428-432.
  • Diefendorf A., Giri S., & Lowell T. (2015). Origin and sedimentary fate of plant-derived terpenoids in a small river catchment and implications. Organic Geochemistry, 82, 22-32.
  • Diefendorf A., Freeman K., Wing S., Currano E., & Mueller K. (2015). Paleogene plants fractionated carbon isotopes similar to modern plants. Earth and Planetary Science Letters, 429, 33-44.
  • Diefendorf A., Leslie A., & Wing S. (2015). Leaf wax composition and carbon isotopes vary among major conifer groups. Geochimica et Cosmochimica Acta, 170, 145-156.
  • Kallenbach, C.M., Grandy, A.S., Frey, S.D., & Diefendorf, A.F. (2015). Microbial physiology and necromass regulate agricultural soil carbon accumulation. Soil Biology and Biochemistry, 91, 279-290.
  • Diefendorf A., Sberna D., & Taylor D. (2015). Effect of thermal maturation on plant-derived terpenoids and leaf wax n-alkyl components. Organic Geochemistry, 89-90, 61-70.
  • Diefendorf A., & Freimuth E. (2017). Extracting the most from terrestrial plant-derived n-alkyl lipids and their carbon isotopes from the. Organic Geochemistry, 103, 1-21.
  • Diefendorf A., Freimuth E., & Lowell T. (2017). Hydrogen isotopes of n-alkanes and n-alkanoic acids as tracers of precipitation in a temperate fores. Geochimica et Cosmochimica Acta, 206, 166-183.
  • Date, P., Crowley-Gill, A., Diefendorf, A.F., & Rollmann, S.M, (2017). Population differences in host plant preference and the importance of yeast and plant substrate to v. Ecology and Evolution, 7(11), 3815-3825.
  • Vrazo, M.B., Diefendorf, A.F., Crowley, B.E., and Brett, C.E., 2018. Late Cretaceous marine arthropods relied on terrestrial organic matter as a food source: evidence from the Coon Creek Lagerstätte in the Mississippian Embayment. Geobiology 2018, 1-19. 
  • Suh, Y.J., and Diefendorf, A.F., 2018. Seasonal and canopy height variation in n-alkanes and their carbon isotopes in a temperate forest. Organic Geochemistry 116, 23-34. 
  • Arnold, T.E., Diefendorf, A.F., Brenner, M., Freeman, K.H., and Baczynski, A.A., 2018. Subtropical climate response to Heinrich Events in the North Atlantic. Quaternary Science Reviews 194, 1-11. 

Experience & Service

Work Experience

  • 2011 to Present, Assistant Professor, University of Cincinnati.

Other Experience and Professional Memberships

  • Geological Society of America
  • American Geophysical Union
  • Sigma Xi
  • American Association for the Advancement of Science

Courses Taught

    Level: Undergraduate

    Level: Undergraduate

  • Organic Geochemistry
    Organic Geochemistry
    Level: Both

  • Stable Isotope Biogeochemistry
    Stable Isotope Biogeochemistry
    Level: Both

  • Geoscience Workshop: Techniques in Stable Isotopes
    Geoscience Workshop: Techniques in Stable Isotopes
    Level: Graduate