Oxygen and silicon isotopes from diatoms (above) and other biogenic silica record important information about past environmental conditions.


Dr. Dodd in the Atacama Desert, Chile.

Salar de Llamara

Salar de Llamara, Chile.

Grad Students

Graduate students Liz Olson and Marco Castillo collecting water samples in the Salar de Llamara.


Marco and high school students from Iquique, Chile collecting water samples.

Prosopis tamarugo

Marco excavates a 9,000 yr old Prosopis tamarugo log.

Dodd Chain Saw

Dr. Dodd collects a disk of Prosopis tamarugo for isotope analyses.

Prosopis Sample

Sanded Prosopis tamarugo sample ready for ring width and isotope measurements.

Vito Valerio

Graduate student Vito Valerio with a sanded 2,500 yr old Prosopis tamarugo.


Justin P. Dodd

Justin P. Dodd

Assistant Professor
Stable Isotope Geochemistry
Office: 302C Davis Hall
Phone: 815.753.1943
Stable Isotope Lab

Educational Background

B.S., Beloit College, WI, 2003
M.S., University of Saskatchewan, 2006
Ph.D., University of New Mexico, 2011

Research Interests

My research focuses on applications of stable isotope geochemistry in a range of geological and environmental settings including paleoclimate reconstruction, paleoecology, archeology, hydrology, biology, and isotope forensics.

Research Activities >

Selected Publications >

Research Grants and Awards >

Published Conference Abstracts and Presentations >

Research Activities

Oxygen and Silicon Isotopes in Biogenic Silica

Oxygen and silicon isotope values in biogenic silica (e.g. diatoms, sponge spicules, phytoliths) provide excellent records of paleoclimatic and paleohydrologic change in freshwater and marine locations. I currently have a number of active research projects aimed at developing records of past environmental change from the Pliocene through modern times in a number of terrestrial lakes and marine environments (including Antarctic marine sediment cores).

Diagenesis and Biogenic Silica

In order to understand the variations observed in biogenic silica from sedimentary records, it is necessary to quantify variables that can cause changes in the oxygen and silicon isotope values of biogenic silica during diagenesis (post-mortem alteration). My students and I are examining the effects of diagenetic conditions on the isotopic and structural composition in biogenic silica through laboratory experiments and natural calibration studies.

Holocene Water Availability in the Atacama Desert

Oxygen and carbon isotope variations in tree-ring cellulose record multiple climate variables (including source water, temperature, and relative humidity). We are working with Chilean geologists, dendrochronologists, and archeologists to develop a record of Holocene climate and water availability in the Atacama Desert of northern Chile using isotope variations in Prosopis tamarugo (similar to mesquite) trees that are well preserved for at least the past 10ka, and perhaps longer. Additional fieldwork will be conducted in August 2014. Preliminary results of this project were presented at the 9th International Conference on Dendrochronology in Melbourne, Australia (01/17/14).

Groundwater in the Atacama

Geochemical and modeling based approaches to assessing groundwater recharge in the Pampa del Tamarugal Basin, Atacama Desert, northern Chile (w/ Dr. Pollyea, Virginia Tech).

Other Projects

    • stable isotope records (biogenic silica, organic compounds, carbonates) of late-glacial/Holocene climate and hydrologic variability in the upper Midwest (northern IL and WI)
    • oxygen isotope variability in white oak (Quercus alba) from southern WI

Selected Publications

Dodd, J.P., Fawcett, P.J., Sharp, Z.D., in review, Collapse of the summer monsoon during MIS 12 in the Southwest United States, submitted to Geology.

Rivera, M.A., and Dodd, J.P., 2013, Domesticando el Desierto. Medio Ambiente y Ocupaciones Humanas en Ramaditas (Taming the desert. Environment and human occupationsin Ramaditas, Atacama Desert), Desierto de Atacama. Dialogo Andino, v 41, 45-60.

Bojar, A.-V., Dodd, J.P., Seghedi, I., 2013, Isotope geochemistry (O, H and Sr) of Late Cretaceous volcanic rocks, Haţeg basin, South Carpathians, Romania. In Isotopic Studies in Cretaceous Research, eds. Bojar, A.-V., Melinte-Dobrinescu, M. C. and Smit, J. Geological Society of London, Special Publication. ISBN 978-1-86239-364-6.

Dodd, J.P., Sharp, Z.D., Fawcett, P.J., Brearley, A., and McCubbin, F.M., 2012, Rapid post-mortem maturation of diatom silica oxygen isotope values. Geochemistry, Geophysics, Geosystems, v. 13 (9), Q09014, doi:10.1029/2011GC004019.

Chapligin, B., Leng, M.J., Webb, E., Alexandre, A., Dodd, J.P., Lücke, A., Ijiri, A., Shemesh, A., Abelmann, A., Okazaki, T., Longstaffe, F., Herzschuh, A., Meyer, H., Moschen, R., Sharp, Z., Sloane, H.J., Sonzogni, C., Swann, G E.A., Sylvestre, F., Tyler, J.J., & Yam, R.., In press, Inter-laboratory comparison of oxygen isotopes from biogenic silica, Geochimica et Cosmochimica Acta. Available online 16 August 2011, ISSN 0016-7037, DOI: 10.1016/j.gca.2011.08.011. ( S0016703711004674)

Dodd, J.P., and Sharp, Z.D., 2010, A laser fluorination method for oxygen isotope analysis of biogenic silica and a new oxygen isotope calibration of modern diatoms in freshwater environments, Geochimica et Cosmochimica Acta, 74 (4): 1381-1390, (DOI 10.1016/j.gca.2009.11.023).

Schiff, C.J., Kaufman, D.S., Wolfe, A.P., Dodd, J.P., and Sharp, Z.D., 2009, Late Holocene storm-trajectory changes inferred from the oxygen isotope composition of lake diatoms, south Alaska. Journal of Paleolimnology, 41(1): 189-208 (DOI 10.1007/ s10933-008-9261-z).

Dodd, J.P., Patterson, W.P., Holmden, C., Brasseur, J.M., 2008. Robotic micromilling of tree rings: a new tool for obtaining subseasonal environmental isotope records. Chemical Geology, 252(1-2) 21-30. DOI 10.1016/j.chemgeo.2008.01.021.

Research Grants and Awards


Silicon isotopes in biogenic silica as a novel proxy for exploring carbon cycle dynamics throughout the Cenozoic. Pending. American Chemical Society, Petroleum Research Fund – Doctoral New Investigator Grant. $100,000. 6/2014 – 8/2016.

Holocene Climate Variability, Water Resource Availability, and Human Settlement in the Atacama Desert, Chile from Oxygen Isotope Values in Tree-Ring Cellulose. Pending. National Geographic Society, Waitt Grant. $12,000. 12/2013 – 12/2014.

Stable Isotope and Geochemical Approach to Regional Hydrologic Variability in the northern Atacama, Chile. 2013 Summer Research & Artistry Grant, Northern Illinois University. $15,000. 5/2013 – 5/2014

The Role of Groundwater in the Flooding History of Clear Lake, Wisconsin, Co-PI w/ S. K. Swanson (Beloit), Keck Geology Consortium, NSF-REU Award: 1062720, Department of Defense, the Keck Member Schools, and the ExxonMobil Foundation. $40,000. 01/2012 to 05/2013.

Climate and Precipitation Variability in the Yucatán Peninsula, Mexico and the Atacama Desert, Chile from Oxygen Isotope Values in Tree-Ring Cellulose, 2012 Summer Research & Artistry Grant, Northern Illinois University. $15,000. 5/2012 – 5/2013.

Funding Pending

Integrating Environmental Tracers and Numerical Models to Quantify Groundwater Recharge in Hyperarid Environments. Pending. Co-PI R.M. Pollyea (NIU). NSF-Hydrologic Sciences. $210,276. (Submitted 12/5/2013)

Collaborative Research: Late-Glacial Central North America “A Setting to Test Meltwater, Precipitation, and Evaporation Linkages. Pending. Co-PI T.V. Lowell, A.F. Diefendorf, D.Ward, M.A. Kelly, T.G. Fisher, K. Lepper. NSF-EAR-Global Change. $620,525. (Submitted 10/15/2013).

Diatom and Oxygen Isotope Evidence of West Antarctic Ice Sheet Dynamics and Water Mass Flux to the Ross Sea during Pliocene/Pleistocene Warm Periods. Not Funded. Co-PI R.P. Scherer and J.P. Warnock (NIU). NSF-Polar Programs. $490,104. (Submitted 4/15/2013 – Resubmit 4/15/2014)

Published Conference Abstracts and Presentations

* student research supervised by Dodd

Dodd, J.P., Olson*, E.J., Rivera, M.A., 2014, Holocene water availability in the northern Atacama Desert as recorded by oxygen isotope variations in Prosopis tamarugo: 9th International Conference on Dendrochronology, Melbourne, Australia.

Van Dussen*, E.W., Fischer, M.P., Pollyea, R.M., and Dodd, J.P., 2013, The role of geometry and internal structures on fluid system evolution in narrowly tapered orogenic wedges: Americam Association of Peterolium Geologists and Society of Exploration Geophysicists Annual Student Expo. Houston, TX.

Hackett*, H., Dodd, J.P., 2013, Preliminary insights from an isotope study on an Antarctic Pliocene diatomite: 4th International Polar Marine Diatom Workshop, Cardiff, UK.

Craig*, A. Creamer, W., Dodd, J.P., 2013, The application of organic residue analysis to archeological ceramics: a study of Andean vessels: 41 Midwest Conference on Andean and Amazonian Archaeology and Ethnohistory. Northern Illinois University, Dekalb, Illinois.

Brokus*, S.A., and Dodd, J.P., 2013, A hydrological investigation of groundwater and surface water geochemistry in the Atacama Desert of northern Chile: 41 Midwest Conference on Andean and Amazonian Archaeology and Ethnohistory. Northern Illinois University, Dekalb, Illinois.

Swanson, S.K., Dodd, J.P., 2013, The Role of Groundwater in the Flooding History of Clear Lake, Wisconsin. Proceedings of the 26 Annual Keck Research Symposium in Geology.

Icks*, N.,F. Dodd, J.P., 2013, Sedimentological evidence of a persistent ground-water dominated systin in Duck Lake, WI over the past 8000 years. Proceedings of the 26 Annual Keck Research Symposium in Geology.

Swanson, S.K., Dodd, J.P., Chew*, B., Graham*, G., Honorof*, L., Icks*, N., Karr*, N., LaBriola*, C., 2013, The role of groundwater in the flooding history of Clear Lake, Wisconsin: 37th Annual Meeting AWRA-Wisconsin Section, Milwaukee, WI.

Bojar, A.V., Dodd, J.P., Seghedi, I., 2013, Isotope geochemistry of Late Cretaceous volcanic rocks, Hateg basin, South Carpathians, Romania: Geophysical Research Abstracts, EGU General Assembly, v. 15, EGU2013-5716-1.

Dodd, J.P., Rivera, M.A., 2012,Variations in groundwater availability during the past 9,000 years in the Atacama Desert, Chile: A subannual record of oxygen isotope values from Prosopis tamarugo tree rings: EOS Transactions, American Geophysical Union, v. 93, H53A-1509.

Rivera, M.A., Dodd, J.P., & Shea, D.E., 2012, Water Availability during Prehispanic Human Settlement in the Atacama Desert: 40th Annual Midwest Conference on Andean and Amazonian Archaeology and Ethnohistory, Field Museum, Chicago, IL.

Dodd, J.P., Fawcett, P.J., & Sharp, Z.D., 2011, Rapid onset and collapse of the summer monsoon during interglacial and glacial periods MIS 11 and 12 as recorded by diatom silica δ18O values from the Valles Caldera: EOS Transactions, American Geophysical Union, v. 92, PP21A-1783.

Fawcett, P.J., Brown, E.T., Werne, J.P., Contreras, S., Anderson, R.S., Dodd, J.P., Sharp, Z.D., Heikoop, J.M., & Allen, C.D., 2011, Millennial-scale climate variability during a mid-Pleistocene glacial (MIS 12) from a terrestrial lacustrine record in the Valles Caldera, New Mexico: EOS Transactions, American Geophysical Union, v. 92.

Ziegler, K., Dodd, J.P., Sharp, Z.D., Brearley, A.J., Young, E.D., 2011, Silicon and oxygen isotopes: The maturation of lacustrine diatoms: Mineralogical Magazine, v. 75, p. 2284, Gold2011:abs:5675.