Research Articles

These are all peer-reviewed journal articles published by me and my research group. PDF's are available for download by clicking on the titles; they are for personal use only and may not be redistributed. A few selected Other Publications are also available. Scroll down to see everything chronologically, or select a year:

2016 2015 2014  2013 2012  2011  2010  2009  2008  2007  2006  2005  2004  2002  2001  1999


◆ Wirth SB and Sessions AL (2016) Plant-wax D/H ratios in the southern European Alps record multiple aspects of climate variability. Quaternary Science Reviews 148, 176-191. doi:10.1016/j.quascirev.2016.07.020

◆ Osburn MR, Dawson KS, Fogel ML, Sessions AL (2016). Fractionation of Hydrogen Isotopes by Sulfate- and Nitrate-Reducing Bacteria. Frontiers in Microbiology 7, 1166. doi:10.3389/fmicb.2016.01166

◆ Piasecki A, Sessions AL, Peterson B, Eiler JM (2016) Prediction of equilibrium distributions of isotopologues for methane, ethane, and propane using density functional theory. Geochimica et Cosmochimica Acta 190, 1-12. doi:10.1016/j.gca.2016.06.003.

◆ Raven MR, Sessions AL, Adkins JF, Thunell RC (2016) Rapid organic matter sulfurization in sinking particles from the Cariaco Basin water column. Geochimica et Cosmochimica Acta 190, 175-190. doi: 10.1016/j.gca.2016.06.030.

◆ Douglas PMJ, Stolper DA, Smith DA, Walter Anthony KM, Paull CK, Dallimore S, Wik M, Crill PM, Winterball M, Eiler JM, Sessions AL (2016) Diverse origins of Arctic and Subarctic methane point source emissions identified with multiply-substituted isotopologues. Geochimica et Cosmochimica Acta 188, 163-188. doi:10.1016/j.gca.2016.05.031.

◆ Meshoulam A, Ellis GS, Ahmad WS, Deev A, Sessions AL, Tang Y, Adkins JF, Jinzhong L, Gilhooly WP, Aizenshtat Z, Amrani A. (2016) Study of thermochemical sulfate reduction mechanism using compound specific sulfur isotope analysis. Geochimica et Cosmochimica Acta 188, 73-92. doi:10.1016/j.gca.2016.05.026.

◆ Piasecki A, Sessions AL, Lawson M, Ferreira AA, Santos Neto EV, Eiler JM (2016) Analysis of the site-specific carbon isotope composition of propane by gas source isotope ratio mass spectrometry. Geochimica et Cosmochimica Acta 188, 58-72. doi:10.1016/j.gca.2016.04.048.

◆ Raven MR, Sessions AL, Fischer WW, Adkins JF (2016) Sedimentary pyrite δ34S differs from porewater sulfide in Santa Barbara Basin: proposed role of organic sulfur. Geochimica et Cosmochimica Acta 186, 120-134. doi: 10.1016/j.gca.2016.04.037.

◆ Niedermeyer E, Forrest M, Beckmann B, Sessions AL, Mulch A, Schefuß E (2016) The stable hydrogen isotopic composition of sedimentary plant waxes as quantitative proxy for rainfall in the West African Sahel. Geochimica et Cosmochimica Acta 184, 55-70. doi: 10.1016/j.gca.2016.03.034.

◆ Sessions AL (2016) Factors controlling the deuterium contents of sedimentary hydrocarbons. Organic Geochemistry 96, 43-54. doi: 10.1016/j.orggeochem.2016.02.012.

◆ Schimmelmann A, Qi H, and 22 others (2016) Organic Reference Materials for Hydrogen, Carbon, And Nitrogen Stable Isotope-Ratio Measurements: Caffeines, n‑Alkanes, Fatty Acid Methyl Esters, Glycines, L‑Valines, Polyethylenes, and Oils. Analytical Chemistry 88, 4294-4302. doi:10.1021/acs.analchem.5b04392.


◆ Kopf SH, Sessions AL, Cowley ES, Reyes C, Van Sambeek L, Hu Y, Orphan VJ, Kato R, and Newman DK (2015) Trace incorporation of heavy water reveals slow and heterogeneous pathogen growth rates in cystic fibrosis sputum. Proceedings of the National Academy of Sciences, doi: 10.1073/pnas.1512057112.

◆ Hansman RL and Sessions AL (2015) Measuring the in situ carbon isotopic composition of distinct marine plankton populations sorted by flow cytometry. Limnology and Oceanography: Methods, doi:10.1002/lom3.10073.

◆ Pacheco JJ, Labinger JA, Sessions AL, and Davis ME (2015) Route to renewable PET: Reaction pathways and energetics of Diels-Alder and dehydrative aromatization reactions between ethylene and biomass-derived furans catalyzed by Lewis acid molecular sieves. ACS Catalysis 5, 5904-5913.

◆ Rice K, Sessions AL, Lai K, and Takeuchi GT (2015) New technique to remove asphalt from microfossil-rich matrix from Rancho La Brea. in La Brea and Beyond: The Paleontology of Asphalt-Preserved Biotas, ed John M. Harris. Natural History Museum of LA County Science Series 42, 169-174.

◆ Dawson KS, Osburn MR, Sessions AL, and Orphan VJ (2015) Metabolic associations with archaea drive shifts in hydrogen isotope fractionation in sulfate-reducing bacterial lipids in cocultures and methane seeps. Geobiology DOI:10.1111/gbi.12140.

◆ Neubauer C, Dalleska NF, Cowley ES, Shikuma NJ, Wu C-H, Sessions AL, and Newman DK (2015) Lipid remodeling in Rhodopseudomonas palustris TIE-1 upon loss of hopanoids and hopanoid methylation. Geobiology DOI:10.1111/gbi.12143.

◆ Stolper DA, Martini AM, Clog M, Douglas PM, Sessions AL, Shusta SS, Valentine DL, and Eiler JM (2015) Distinguishing and understanding thermogenic and biogenic sources of methane using multiply substituted isotopologues. Geochimica et Cosmochimica Acta 161, 219-247.

◆ Raven MR, Adkins J.F, Werne JP, Lyons TW and Sessions AL (2015) Sulfur isotopic composition of individual organic compounds from Cariaco Basin sediments. Organic Geochemistry 80, 53–59.


◆ Summons RE, Sessions AL, Allwood AC, Barton HA, Beaty DW, Blakkolb B, Canham J, Clark BC, Dworkin JP, Lin Y, Mathies R, Milkovich SM, Steele A (2014) Planning considerations related to the organic contamination of Martian samples and implications for the Mars 2020 rover. Astrobiology 14, 970-1024.

◆ Crowe SA, Paris G, Katsev S, Jones CA, Kim S-T, Zerkle AL, Nomosatryo S, Fowle DA, Adkins JF, Sessions AL, Farquhar J, Canfield DE (2014) Sulfate was a trace constituent of Archean seawater. Science 346, 735-739. 

◆ Paris G, Adkins JF, Sessions AL, Webb SM, Fischer WW (2014) Neoarchean carbonate-associated sulfate records positive Δ33S anomalies. Science 346, 739-741.

◆ Niedermeyer EA, Sessions AL, Feakins SJ, Mohtadi M (2014) Hydroclimate of the western Indo-Pacific Warm Pool during the past 24,000 years. PNAS 111, 9402-9406.

◆ Greenwood PF, Amrani A, Sessions AL, Raven MR, Holman A, Dror G, Grice K, McCulloch MT, and Adkins JF (2014) Chapter 10: Development and initial biogeochemical applications of compound-specific sulfur isotope analysis. in Principles and Practice of Analytical Techniques in Geosciences, ed K. Grice, Royal Society of Chemistry, pp 285-312.

◆ Paris G, Fehrenbacher JS, Sessions AL, Spero HJ, Adkins JF (2014) Experimental determination of carbonate-associated sulfate d34S in planktonic foraminifera shells. Geochemistry, Geophysics, Geosystems 15, 1452-1461. 

◆ Stolper DA, Lawson M, Davis CL, Ferreira AA, Santos Neto EV, Ellis GS, Lewan MD, Martini AM, Tang Y, Schoell M, Sessions AL, Eiler JM (2014) Formation temperatures of thermogenic and biogenic methane. Science 344, 1500-1503. DOI: 10.1126/science.1254509

◆ Stolper DA, Sessions AL, Ferreira AA, Santos Neto EV, Schimmelmann A, Shusta SS, Valentine DL, Eiler JM (2014) Combined 13C-D and D-D clumping in methane: methods and preliminary results. Geochimica et Cosmochimica Acta 126, 169-191.

◆ Doughty DM, Dieterle M, Sessions AL, Fischer WW, Newman DK (2014) Probing the subcellular localization of hopanoid lipids in bacteria using NanoSIMS. PLoS One 9, e84455.

◆ Ricci JN, Coleman ML, Welander PV, Sessions AL, Summons RE, Spear JR, Newman DK (2014) Diverse capacity for 2-methylhopanoid production correlates with a specific ecological nicheThe ISME Journal 8, 675-684.


◆  Lee C, Fike DA, Love GD, Sessions AL, Grotzinger JP, Summons RE, Fischer WW (2013) Carbon isotopes and lipid biomarkers from organic-rich facies of the Shuram Formation, Sultanate of Oman. Geobiology 11, 406-419.

◆  Summons RE, Bird LR, Gillespie AL, Pruss SB, Roberts M, Sessions AL (2013) Lipid biomarkers in ooids from different locations and ages: evidence for a common bacterial flora. Geobiology 11, 420-436.

◆  Paris G, Sessions AL, Subhas AV, Adkins JF (2013) MC-ICP-MS measurement of δ34S and Δ33S in small amounts of dissolved sulfate. Chemical Geology 345, 50-61.

◆  Sessions AL, Zhang L, Welander PV, Doughty D, Summons RE, Newman DK (2013) Identification and quantification of polyfunctionalized hopanoids by high temperature gas chromatography-mass spectrometry. Organic Geochemistry 56, 120-130.

◆ Wang Y, Sessions AL, Nielsen RJ, Goddard WA (2013) Equilibrium 2H/1H fractionations in organic molecules: III. Cyclic ketones and hydrocarbons. Geochimica et Cosmochimica Acta 107, 82-95.

◆ Morrill PL, Kuenen JG, Johnson OJ, Suzuki S, Rietze A, Sessions AL, Fogel ML, Nealson KH (2013) Geochemistry and geobiology of a present-day serpentinization site in California: The Cedars. Geochimica et Cosmochimica Acta, 109, 222-240.

◆  Eiler JM, Clog M, Magyar P, Piasecki A, Sessions AL, Stolper D, Deerberg M, Schlueter H-J, Schwieters J (2013) A high-resolution gas-source isotope ratio mass spectrometerInternational Journal of Mass Spectrometry, 335, 45-56.


◆  Amrani A, Deev A, Sessions AL, Tang Y, Adkins JF, Hill RJ, Moldowan JM, Wei Z (2012) The sulfur-isotopic compositions of benzothiophenes and dibenzothiophenes as a proxy for thermochemical sulfate reduction. Geochimica et Cosmochimica Acta 84, 152-164.

◆  Sachse D, Billault I, Bowen GJ, Chikaraishi Y, Dawson TE, Feakins SJ, Freeman KH, Magill CR, McInerney FA, van der Meer MTJ, Polissar P, Robins RJ, Sachs JP, Schmidt HL, Sessions AL, White JWC, West JB, Kahmen A (2012) Molecular paleohydrology: Interpreting the hydrogen-isotopic composition of lipid biomarkers from photosynthesizing organisms. Annual Reviews of Earth and Planetary Science 40, 221-249.

◆  Ferreira AA, Santos Neto EV, Sessions AL, Schimmelmann A, Aquino Neto FR (2012) 2H/1H ratios of hopanes, tricyclic and tetracyclic terpanes in oils and source rocks from the Potiguar Basin, Brazil. Organic Geochemistry 51, 13-16.

◆ Bontognali TRR, Sessions AL, Allwood AC, Fischer WW, Grotzinger JP, Summons RE, Eiler JM (2012) Sulfur isotopes of organic matter preserved in 3.45-billion-year-old stromatolites reveal microbial metabolism. Proceedings of the National Academy of Sciences 109, 15146-15151.


◆  Doughty DM, Coleman ML, Hunter RC, Sessions AL, Summons RE, and Newman DK (2011) The RND-family transporter, HpnN, is required for hopanoid localization to the outer membrane of Rhodopseudomonas palustris TIE-1. Proceedings of the National Academy of Sciences 108, E1045-E1051.

◆  Bennett SA, Hansman RL, Sessions AL, Nakamura K, and Edwards KJ (2011) Tracing iron-fueled microbial carbon production within the hydrothermal plume at the Loihi seamount. Geochimica et Cosmochimica Acta 75, 5526-5539.

◆  Osburn MR, Sessions AL, Pepe-Ranney C, and Spear JR (2011) Hydrogen-isotopic variability in fatty acids from Yellowstone National Park hot spring microbial communities. Geochimica et Cosmochimica Acta 75, 4830-4845.

◆  Li C, Sessions AL, Thiagarajan N, Valentine D (2011) D/H variations of terrestrial lipids from Santa Barbara Basin over the past 1400 years: A preliminary assessment of paleoclimatic relevance. Organic Geochemistry 42, 15-24.


◆  Feakins SJ and Sessions AL (2010b) Crassulacean acid metabolism influences D/H ratio of leaf wax in succulent plants. Organic Geochemistry41, 1269-1276.

◆  Niedermeyer E, Schefuss E, Sessions AL, Mulitza S, Mollenhauer G, Schulz M, Wefer G (2010) Orbital- and millennial-scale changes in the hydrologic cycle and vegetation in the western African Sahel: insights from individual plant wax δD and δ13C. Quaternary Science Reviews 29, 2996-3005.

◆  Redmond MC, Valentine DL, Sessions AL (2010) Identification of novel methane-, ethane-, and propane-oxidizing bacteria at marine hydrocarbon seeps identified by stable isotope probing. Applied and Environmental Microbiology 76, 6412-6422.

◆  Welander PV, Coleman ML, Sessions AL, Summons RE, Newman DK (2010) Identification of a methylase required for 2-methylhopanoid production and implications for the interpretation of sedimentary hopanes. Proceedings of the National Academy of Sciences 107, 8537-8542.

◆  Li C, Love GD, Lyons TW, Fike DA, Sessions AL, and Chu X (2010) A stratified redox model for the Ediacaran Ocean. Science 328, 80-83.

◆  Feakins SJ and Sessions AL (2010) Controls on the D/H ratios of plant leaf waxes in an arid ecosystem. Geochimica et Cosmochimica Acta 74, 2128-2141.


◆  Amrani A, Sessions AL, Adkins JF (2009) Compound-specific d34S analysis of volatile organics by coupled GC/ICPMS. Analytical Chemistry 81, 9027-9034.

◆  Wang Y, Sessions AL, Nielsen RJ, and Goddard WA (2009) Equilibrium 2H/1H fractionations in organic molecules. I. Experimental calibration of ab initio calculations. Geochimica et Cosmochimica Acta 73, 7060-7075.

◆ Wang Y, Sessions AL, Nielsen RJ, and Goddard WA (2009) Equilibrium 2H/1H fractionations in organic molecules. II. Linear alkanes, alkenes, ketones, carboxylic acids, esters, alcohols and ethers. Geochimica et Cosmochimica Acta 73, 7076-7086.

◆  Marshall AO, Corsetti F, Sessions AL, and Marshall C (2009) Raman spectroscopy and biomarker analysis reveal multiple carbon inputs in a Precambrian glacial sediment. Organic Geochemistry 40, 1115-1123.

◆  Sessions AL, Doughty DM, Welander PV, Summons RE, and Newman DK (2009) The continuing puzzle of the great oxidation event. Current Biology 19, R567-R574.

◆  Welander PV, Hunter RC, Zhang L, Sessions AL, Summons RE, Newman DK (2009) Hopanoids play a role in membrane integrity and pH homeostasis in Rhodopseudomonas palustris TIE-1. Journal of Bacteriology 191, 6145-6156.

◆  Zhang X, Gillespie A, Sessions AL (2009). Large D/H variations in bacterial lipids reflect central metabolic pathways. Proceedings of the National Academy of Science, USA 106(31), 12580-12586.

◆  Li C, Sessions AL, Kinnamen F, Valentine DL (2009). Hydrogen-isotopic variability in lipids from Santa Barbara Basin sediments. Geochimica et Cosmochimica Acta 73, 4803-4823.

◆  Campbell BJ, Li C, Sessions AL, and Valentine DL (2009) Hydrogen isotopic fractionation in lipid biosynthesis by H2-consuming Desulfobacterium autotrophicumGeochimica et Cosmochimica Act73, 2744-2757.

◆  Sauer PE, Schimmelmann A, Sessions AL, and Topalov K (2009). Simplified batch equilibration for D/H determination of non-exchangeable hydrogen in solid organic material. Rapid Communications in Mass Spectrometry 23, 949-956.


◆  Wang Y and Sessions AL (2008).Memory Effects in Compound-Specific D/H Analysis by GC/P/IRMS. Analytical Chemistry 80, 9162-9170.

◆  Jones A, Sessions AL, Campbell BJ, Li C, Valentine DL (2008). D/H ratios of fatty acids from marine particulate organic matter in the California Borderland Basins. Organic Geochemistry 39, 485-500.

◆  Pearson A, Kraunz KS, Sessions AL, Dekas AE, Leavitt WR, Edwards KJ (2008). Quantifying microbial utilization of petroleum hydrocarbons in salt-marsh sediments using the 13C content of bacterial rRNA. Applied and Environmental Microbiology 74, 1157-1166.


◆  Rashby SE, Sessions AL, Summons RE, and Newman DK (2007). Biosynthesis of 2-methylbacteriohopanepolyols by an anoxygenic phototroph. Proceedings of the National Academy of Science 104, 15099-15104.


◆  Eek KM, Sessions AL and Lies DP (2006). Carbon-isotopic analysis of microbial cells sorted by flow cytometry. Geobiology 5, 85-95.

◆  Sessions AL (2006). Isotope-ratio detection for gas chromatography. Journal of Separation Science 29, 1946-1961.

◆  Schimmelmann A, Sessions AL, and Mastalerz M (2006). Hydrogen isotopic (D/H) composition of organic matter during diagenesis and thermal maturation. Annual Reviews of Earth and Planetary Sciences 34, 501-533.

◆  Sessions AL (2006) Seasonal changes in lipid D/H fractionation by Spartina alternifloraGeochimica et Cosmochimica Acta70, 2153-2162.


◆  Olcott AN, Sessions AL, Corsetti FA, Kaufmann AJ, de Olieviera TF (2005) Biomarker evidence for photosynthesis during Neoproterozoic glaciation. Science 310, 471-474.

◆  Sessions AL, Sylva SP and Hayes JM (2005) A moving-wire device for carbon-isotopic analyses of nanogram quantities of nonvolatile organic carbon. Analytical Chemistry 77, 6519-6527.

◆  Sessions AL and Hayes JM (2005) Calculation of hydrogen isotopic fractionations in biogeochemical systems. Geochimica et Cosmochimica Acta 69, 593-597.


◆  McDuffie KE, Eglinton TI, Sessions AL, Sylva SP, Wagner T, and Hayes JM (2004) Rapid analysis of 13C in plant-wax n-alkanes for reconstruction of terrestrial vegetation signals from aquatic sediments. Geochemistry, Geophysics, Geosystems 5, Q10004.

◆  Pearson A, Sessions A L, Edwards KJ, and Hayes JM (2004) Phylogenetically specific separation of rRNA from prokaryotes for isotopic analysis. Marine Chemistry 92, 295-306.

◆  Valentine DL, Sessions AL, Tyler SC, and Chidthaisong, A (2004) Hydrogen isotope fractionation during H2/CO2 acetogenesis: hydrogenase efficiency and the origin of lipid-bound hydrogen. Geobiology 2, 179-188.

◆  Schimmelmann A, Sessions AL, Boreham CJ, Edwards DS, Logan GA, and Summons RE (2004) D/H ratios in terrestrially sourced petroleum systems. Organic Geochemistry 35, 1160-1195.

◆  Sessions AL, Sylva SP, Summons RE, and Hayes JM (2004) Isotopic exchange of carbon-bound hydrogen over geologic timescales. Geochimica et Cosmochimica Acta 68,1545-1559.

◆  Schneider RJ, Kim S-W, von Reden KF, Hayes JM, Wills JSC, Griffin V, Sessions AL, and Sylva SP (2004). A gas ion source for continuous-flow AMS. Nuclear Instruments and Methods in Physics Research (B) 223-224, 149-154


◆  Sessions AL, Jahnke LL, Schimmelmann A, and Hayes JM (2002) Hydrogen isotope fractionation in lipids of the methane-oxidizing bacterium Methylococcus capsulatusGeochimica et Cosmochimica Acta 66, 3955-3969.


◆  Sauer PE, Eglinton TI, Hayes JM, Schimmelmann A, and Sessions AL (2001) Compound-specific D/H ratios of lipid biomarkers from sediments as a proxy for environmental and climatic conditions. Geochimica et Cosmochimica Acta 65, 213-222.

◆  Sessions AL, Burgoyne TW, and Hayes JM (2001) Correction of H3+ contributions in hydrogen isotope ratio monitoring mass spectrometry. Analytical Chemistry 73, 192-199.

◆  Sessions AL, Burgoyne TW, and Hayes JM (2001) Determination of the H3 Factor in hydrogen isotope ratio monitoring mass spectrometry. Analytical Chemistry 73, 200-207.


◆  Sessions AL, Burgoyne TW, Schimmelmann A, and Hayes JM (1999) Fractionation of hydrogen isotopes in lipid biosynthesis. Organic Geochemistry 30, 1193-1200.

Other Stuff

◆ Coplen, Tyler B. (2011) Guidelines and recommended terms for expression of stable-isotope-ratio and gas-ratio measurement results. Rapid Communications in Mass Spectrometry 25, 2538-2560.

The definitive guideline for nomenclature and definitions related to stable isotopes. The definition of a delta value does not include a factor of 1000...!

◆ Brocks, Jochen J. and Summons, Roger E. (2004) Sedimentary hydrocarbons, biomarkers for early life. Treatise on Geochemistry, volume 8, chapter 3.

This is the most recent and complete review of biomarker information on ancient rocks, and an excellent reference source.

◆ Hayes, John M. (2004) An Introduction to isotopic calculations. Unpublished manuscript, 10p.

A practical description of calculations using isotopes that are relevant to biogeochemical systems. Especially useful for its evaluation of systematic errors that arise from common approximate forms of calculations involving mass balance and Rayleigh distillation.

◆ Hayes, John M. (2002) Practice and Principles of Isotopic Measurements in Organic Geochemistry. Electronic version edited by A. Sessions.

Originally published in 1983, I think this is one of the best introductions to the usage of stable isotopes in biogeochemistry. It was updated in 2002 by JMH to include sections on primary standards of stable isotopic abundance, statistical limits on the determination of isotopic ratios, and uncertainties associated with blank-corrected isotope ratios.

◆ Hayes, John M. (2001) Fractionation of the Isotopes of Carbon and Hydrogen in Biosynthetic Processes. Chapter prepared for a short course sponsored by the Mineralogical Society of America and organized by John W. Valley and David R. Cole.

This document contains a comprehensive review of the known isotope effects associated with a variety of biosynthetic pathways.

◆    Sessions, Alex L. (2001) Hydrogen isotope ratios of individual organic compounds. Ph.D. thesis, Indiana University.

Most of this material has appeared in five published research articles. Chapters 4 and 5 contain some additional data on hydrogen exchange and sulfate-reducing bacteria, respectively.

Copyright 2015 by Alex Sessions. All rights reserved.