University of Massachusetts  |  UMass College of Natural Sciences  |  UMass Geosciences


Steven Petsch

Associate Professor of Geosciences


265 Morrill Science Center

Dept. of Geosciences

UMass Amherst


phone: (413) 545-4413

email: spetsch<at>      


Life on our planet is constrained within bounds set by the transport and transformations of the elements. Carbon cycling in particular plays a central role in Biogeochemistry on a range of scales in time and space.

My research addresses what happens after deposition of organic matter in sediment, and as it turns out, what happens is … a lot! Processes such as diagenesis, chemical decomposition and the existence of metabolically active microorganisms at the deepest and most extreme extent of our exploration lead us to wonder why and how organic matter is preserved for millions of years in rocks.

To address this, my research test the limits of what it means to be refractory, labile or biologically available, by exploring the degradation, dissolution and utilization of ancient organic matter in soils, aquatic systems and the deep subsurface.


Research Interests:

Š      transport and transformation of organic matter within and between sedimentary and earth surface environments

Š      delivery of rock-derived fossil organic matter to earth surface reservoirs such as soils, rivers and sediment

Š      long-term fate of rock-derived fossil organic matter in the geologic carbon cycle

Š      microbe-rock-water interactions in subsurface environments

Š      anaerobic biodegradation of shale and coal organic matter associated with methanogenesis

Š      interactions between chemical, physical, microbiological and human processes in sedimentary and earth surface environments

Š      global biogeochemical cycles of carbon, sulfur, oxygen

Š      analytical techniques for characterization of natural organic matter in geologic materials


Courses taught:

Š     GeoSci 285  Environmental Geology.  This course uses case-studies and real-world data to explore 3 fundamental environmental challenges that are being addressed through Geosciences research: Water, Energy and Climate Change.  (Fall 2011 syllabus)

Š     GeoSci 307  Geologic Writing.  This course is required for all Geology and Earth Systems majors.  In this course we discuss professional communication (resumes, cover letters, email), scientific writing (referencing, scientific papers), experiment design, hypothesis testing and data analysis.  (Spring 2012 syllabus)

Š     GeoSci 517  Sedimentary Geochemistry.  In this course we review the fundamentals of carbonate chemistry, redox biogeochemistry, diagenetic models of sedimentary reactive transports, global geochemical cycles, and the chemical composition of marine sediments. (Fall 2010 syllabus)

Š     GeoSci 615 Organic Geochemistry.  This course explores the chemistry of naturally-occurring forms of organic matter on the Earth, including structure and nomenclature, analytical methods, biosynthesis, isotope systematics, and applications in carbon cycling and paleoenvironmental reconstruction.  (Fall 2011 syllabus).

Š     NatSci 190H  Global Challenges – Scientific Solutions.  This is the first-year course in the iConS program (Integrated Concentration in Science), open through competitive application to all majors in the College of Natural Science.  This sources uses team-based, inquiry-based learning to explore case studies of compelling societal challenges and approaches towards their scientific solution.  For more information, visit the iConS program website  (Spring 2011 syllabus).



* denotes student author/co-authored publications and presentations

Brantley, S.L., Megonigal, J.P., Scatena, F.N., Balogh-Brunstad, Z., Barnes, R.T., Bruns, M.A., van Cappellen, P., Dontsova, K., Hartnett, H., Hartshorn, T., Heimsath, A., Herndon, E., Jin, E., Keller, C.K., Leake, J.R., McDowell, W.H., Meinzer, F.C., Mozdzer, T., Petsch, S., Pett-Ridge, J., Pregitzer, K.S., Raymond, P., Riebe, C.S., Shumaker, K., Sutton-Grier, A., Walter, R., Yoo, K.. Thirteen hypotheses to test how biology and weathering interact within the Critical Zone (2011). Geobiology 9,140-165.

Allison, M.A., Dellapenna, T.M., Gordon, E.S., Mitra, S., Petsch, S.T. (2010) Impact of Hurricane Katrina (2005) on shelf organic carbon burial and deltaic evolution.  Geophysical Research Letters 37, doi: 10.1029/2010GL044547.

Caraco, N., Bauer, J.E., Cole, J.J., Petsch, S.T., Raymond, P. (2010) Millenial-aged organic carbon subsidies to a modern river food web.  Ecology 91, 2385-2393.  doi: 10.1890/09-0330.1

McIntosh, J., Martini, A., Petsch, S., and Huang, R. (2008) Biogeochemistry of the Forest City Basin coalbed methane play.  International Journal of Coal Geology, 76, 111-118. invited submission.

Formolo, M., Martini, A., and Petsch, S. (2008) Biodegradation of sedimentary organic matter in the Powder River and San Juan Basins: The impact of thermal maturity. International Journal of Coal Geology, 76, 89-97. invited submission.

Schillawski, S.J. and Petsch, S. (2008) Release of biodegradable dissolved organic matter from ancient sedimentary rocks. Global Biogeochemical Cycles, 184, 137-144.

Formolo, M.F., Salacup, J., Petsch, S.T., Martini, A.M., and Nüsslein, K. (2008) A new model linking atmospheric methane sources to Pleistocene glaciation via methanogenesis in sedimentary basins. Geology 36, p. 139-142.

Longworth, B.E., Petsch, S.T., Raymond, P.A., and Bauer, J. E. (2007) Linking lithology and land use to sources of dissolved and particulate organic matter in headwaters of a temperate, passive-margin river system.  Geochimica et Cosmochimica Acta. 71, 4233-4250.

Waldron, P., Petsch, S.T., Martini, A.M., and Nüsslein, K. (2007) Salinity constraints on subsurface archaeal diversity and methanogenesis in sedimentary rock rich in organic matter.  Applied and Environmental Microbiology 73, 4171-4179.

GoĖi, M.A., Alleau, Y., Corbett, R., Walsh, J.P, Mallinson, D., Allison, M.A., Gordon, E., Petsch, S.T., Dellapenna, T.S. (2007)  The effects of Hurricanes Katrina and Rita on the seabed of the Louisiana Shelf.  SEPM The Sedimentary Record 5, 5-9.

Bolton, E.W., Berner, R.A., Petsch, S.T., and Wildman, R.A. (2006)  The weathering of sedimentary organic matter as a control on atmospheric O2: II. Theoretical Modeling.  American Journal of Science 306, 575-615.

Petsch, S.T., Edwards, K.J., and Eglinton, T.I. (2005)  Microbial transformations of organic matter in black shales and implications for global biogeochemical cycles.  Palaeogeography, Palaeoclimatology, Palaeoecology (special issue: Geobiology) 219, 157-170. invited submission.

Raymond, P.A., Bauer, J.E., Caraco, N.F., Cole, J.J., Longworth, B.E., and Petsch, S.T. (2004)  Controls on the variability of organic matter and dissolved inorganic carbon age in northeast U.S. rivers. Marine Chemistry (special issue honoring John Hedges) 92, 353-366. . invited submission. 

Wildman, R.A., Berner, R.A., Petsch, S.T., Bolton, E.W., Eckert, J.O., Mok, U. and Evans, J.B. (2004)  The weathering of sedimentary organic matter as a control on atmo-spheric O2: I. Analysis of a black shale. American Journal of Science 304, 234-249. [4]

Petsch, S.T., Edwards, K.J., and Eglinton, T.I. (2003) Abundance, distribution and d13C analysis of microbial phospholipid-derived fatty acids in a black shale weathering profile. Organic Geochemistry 34, 731-743.

Jaffe, L.A., Peucker-Ehrenbrink, B., and Petsch, S.T. (2002) Effects of weathering of organic-rich sedimentary rocks on the mobility of rhenium, platinum-group elements and organic carbon. Earth and Planetary Science Letters. 198, 339-353.

Petsch, S.T., Eglinton, T.I., and Edwards, K.J. (2001) 14C-dead living biomass: evidence for microbial assimilation of ancient organic carbon during shale weathering. Science, 292, 1127-1131.

Petsch, S.T., Smernik, R.J., Eglinton, T.I., and Oades, J.M. (2001) A solid state 13C NMR study of kerogen degradation during black shale weathering. Geochimica et Cosmochimica Acta, 65, 1867-1882.

Berner, R.A., Petsch, S.T., Beerling, D.J., Popp, B.N., Lane, R.S., Laws, E.A., Westley, M.B., Cassar, N. Woodward, F.I., and Quick, W.P. (2000) Isotope fractionation and atmospheric oxygen: implications for Phanerozoic O2 Evolution. Science, 287, 1630-1633.

Petsch, S.T., Berner, R.A., and Eglinton, T.I. (2000) A field study of the chemical weathering of ancient sedimentary organic matter. Organic Geochemistry, 31, 475-487.

Petsch, S.T. (1999) Comment on “Carbon isotope ratios of Phanerozoic marine cements: re-evaluating global carbon and sulfur systems”. Geochimica et Cosmochimica Acta, 63, 307-310.

Berner, R.A. and Petsch, S.T. (1998) The sulfur cycle and atmospheric oxygen. Science, 282, 1426-1427.

Petsch, S.T. and Berner, R.A. (1998) Coupling the geochemical cycles of C, P, Fe and S: the effect on atmospheric O2 and the isotopic records of carbon and sulfur. American Journal of Science, 298, 246-262.

Fisler, D. K., Mackwell, S. J., and Petsch, S. T. (1997) Grain boundary diffusion in enstatite. Physics and Chemistry of Minerals, 24, 264-273.



UMass Biogeochemistry Laboratory

UMass Stable Isotope Geochemistry Laboratory




photos from the field …

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At a natural gas field in Kansas hosted in Pennsylvanian shales and coals, sampling production water.  Dissolved gas and water chemistry reveal that this methane is largely microbial in origin, and culture-dependent and –independent molecular tools confirm the activity of Bacteria and Archaea in these rocks at great depth in the subsurface. 


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Big scale and small scale view of our field site in eastern Kentucky, where the Devonian New Albany Shale is exposed in a spectacular road cut.  My work at this site has documented the chemical changes in shale organic matter that accompany rock weathering (visible as transition from gray-black shale to light brown regolith in upper left corner of photo on left).  On cm-scale, cores of unweathered rock are surrounded by lighter colored weathered shale, in which the organic matter has been lost and degraded, and new Fe- and S-bearing minerals are precipitating on the face of the outcrop.


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A small stream near the base of the outcrop shown above reveals copious amounts of thick, globular iron oxides.  These are host to communities of iron-oxidizing bacteria that help to break down the shale. 


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This watershed of small stream (left) in eastern upstate NY is underlain by Ordovician and Devonian shales.  Waters collected from this stream and its headwaters (on left, being sampled by former graduate student Brett Longworth) contain particulate and dissolved organic matter with very low amounts of radiocarbon.  This tells us that organic matter from the watershed’s rocks is contributed to the modern aquatic carbon cycle.  Radiocarbon analysis of benthic invertebrates and zooplankton from here and downstream in the Hudson River also show a depletion in radiocarbon, telling us that ancient rock-derived carbon is being incorporated into the foodwebs of this ecosystem.