Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Elevated weathering rates in the Rocky Mountains during the Early Eocene Climatic Optimum


During the chemical weathering of silicate minerals, atmospheric carbon dioxide is incorporated into carbonate minerals and buried. As the rate of silicate weathering is thought to increase in response to increasing atmospheric CO2 concentrations, this represents an important negative feedback mechanism1. Quaternary records of weathering reflect a narrow range of pCO2 (180–300 p.p.m.v.)2; therefore, the extent of this feedback has been difficult to predict for increasing concentrations of atmospheric CO2. However, high CO2 levels of up to 1,125 p.p.m.v. have been suggested for the Early Eocene Climatic Optimum (52 to 50 million years ago)3,4,5. Here, we combine 40Ar/39Ar ages6 and the measured volumes of river-derived sediments and sodium-bearing evaporites to determine rates of physical erosion and chemical weathering in the Green River Basin, western United State of America, during the Early Eocene Climatic Optimum7. We find physical erosion rates of 420±79 t km2 yr−1 and chemical weathering rates of 62.5±21.9 t km2 yr−1. The calculated denudation rates of 175±30 m Myr−1 rival the highest documented non-glacial Quaternary rates for crystalline bedrock8. We suggest that elevated atmospheric CO2 levels during the Early Eocene epoch led to enhanced silicate dissolution rates9, and thus to increased production of loose rock material and higher rates of physical weathering and denudation.

This is a preview of subscription content, access via your institution

Relevant articles

Open Access articles citing this article.

Access options

Rent or buy this article

Get just this article for as long as you need it


Prices may be subject to local taxes which are calculated during checkout

Figure 1: Map of the central Rocky Mountain lake province showing the Early Eocene palaeocatchment of the GGRB6.
Figure 2: Early Eocene strata in the GGRB.
Figure 3: Comparison of Eocene chemical weathering, physical erosion and overall denudation rates to Quaternary rates for unglaciated granitic catchments.


  1. Suchet, P. A. & Probst, J. L. A global model for present-day atmospheric/soil CO2 consumption by chemical erosion of continental rocks (GEM-CO2). Tellus B 47, 273–280 (1995).

    Article  Google Scholar 

  2. Petit, J. R. et al. Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica. Nature 399, 429–436 (1999).

    Article  Google Scholar 

  3. Lowenstein, T. K. & Demicco, R. V. Elevated Eocene atmospheric CO2 and its subsequent decline. Science 313, 1928 (2007).

    Article  Google Scholar 

  4. Zachos, J., Pagani, M., Sloan, L., Thomas, E. & Billups, K. Trends, rhythms, and aberrations in global climate 65 Ma to present. Science 292, 685–693 (2001).

    Google Scholar 

  5. Fletcher, B. J., Brentnall, S. J., Anderson, C. W., Berner, R. A. & Beerling, D. J. Atmospheric carbon dioxide linked with Mesozoic and early Cenozoic climate change. Nature Geosci. 1, 43–48 (2008).

    Article  Google Scholar 

  6. Smith, M. E., Carroll, A. R. & Singer, B. S. Synoptic reconstruction of a major ancient lake system: Eocene Green River Formation, Western United States. Geol. Soc. Am. Bull. 120, 54–84 (2008).

    Article  Google Scholar 

  7. Einsele, G. & Hinderer, M. Quantifying denudation and sediment-accumulation systems (open and closed lakes): Basic concepts and first results. Palaeogeogr. Palaeoclimatol. Palaeoecol. 140, 7–21 (1998).

    Article  Google Scholar 

  8. Riebe, C. S., Kirchner, J. W. & Finkel, R. C. Erosional and climatic effects on long-term chemical weathering rates in granitic landscapes spanning diverse climate regimes. Earth Planet. Sci. Lett. 224, 547–562 (2004).

    Article  Google Scholar 

  9. West, A. J., Galy, A. & Bickle, M. Tectonic and climatic controls on silicate weathering. Earth Planet. Sci. Lett. 235, 211–228 (2005).

    Article  Google Scholar 

  10. Dickinson, W. R. et al. Paleogeographic and paleotectonic setting of Laramide sedimentary basins in the central Rocky Mountain region. Geol. Soc. Am. Bull. 100, 1023–1039 (1988).

    Article  Google Scholar 

  11. Wiig, S. V., Grundy, W. D. & Dyni, J. R. Trona resources in the Green River Basin, southwest Wyoming. US Geological Survey Open-File Report OF 95-476 (1995).

  12. Pietras, J. T. & Carroll, A. R. High-resolution stratigraphy of an underfilled lake basin: Wilkins Peak Member, Eocene Green River Formation, Wyoming, USA. J. Sedim. Res. 76, 1197–1214 (2006).

    Article  Google Scholar 

  13. Bradley, W. H. The geology of the Green River Formation and associated Eocene rocks in southwestern Wyoming and adjacent parts of Colorado and Utah. US Geological Survey Professional Paper 496-A (1964).

  14. Roehler, H. W. Description and correlation of Eocene rocks in stratigraphic reference sections for the Green River and Washakie Basins, southwest Wyoming. US Geological Survey Professional Paper 1506-D (1992).

  15. Carroll, A. R., Chetel, L. M. & Smith, M. E. Feast to famine: Sediment supply control on Laramide basin fill. Geology 34, 197–200 (2006).

    Article  Google Scholar 

  16. Cullers, R. L. The controls on the major- and trace-element evolution of shales, siltstones and sandstones of Ordovician to Tertiary age in the Wet Mountains region, Colorado, U.S.A. Chem. Geol. 123, 107–131 (1995).

    Article  Google Scholar 

  17. Hansen, W. R. Geology of the Flaming Gorge area Utah-Colorado-Wyoming. US Geological Survey Professional Paper 490 (1965).

  18. Kunk, M. J. et al. 40Ar/39Ar ages of late Cenozoic volcanic rocks within and around the Carbondale and Eagle collapse centers, Colorado; constraints on the timing of evaporite-related collapse and incision of the Colorado River. Geological Society of America Special Paper 366, 213–234 (2002).

  19. Kelley, S. A. & Chapin, C. E. Denudation history and internal structure of the Front Range and Wet Mountains, Colorado, based on apatite-fission-track thermochronology. New Mexico Bureau of Geology and Mineral Resources Bulletin 160, 41–77 (2004).

  20. Wilf, P. Late Paleocene-early Eocene climate changes in southwestern Wyoming: Paleobotanical analysis. Geol. Soc. Am. Bull. 112, 292–307 (2000).

    Article  Google Scholar 

  21. Taylor, J. R. An Introduction to Error Analysis (Univ. Science Books, Mill Valley, 1982).

    Google Scholar 

  22. Mason, G. M. Mineralogic Aspects of Stratigraphy and Geochemistry of the Green River Formation, Wyoming. Thesis, Univ. of Wyoming, Laramie (1987).

  23. Sueker, J. K., Clow, D. W., Ryan, J. N. & Jarrett, R. D. Effect of basin physical characteristics on solute fluxes in nine alpine/subalpine basins, Colorado, USA. Hydrol. Process. 15, 2759–2769 (2001).

    Article  Google Scholar 

  24. Andrews, J. A. & Schlesinger, W. H. Soil CO2 dynamics, acidification, and chemical weathering in a temperate forest with experimental CO2 enrichment. Glob. Biogeochem. Cycles 15, 149–162 (2001).

    Article  Google Scholar 

  25. Syvitski, J. P. M. & Milliman, J. D. Geology, geography, and humans battle for dominance over the delivery of fluvial sediment to the coastal ocean. J. Geol. 115, 1–19 (2007).

    Article  Google Scholar 

  26. Kirchner, J. W. et al. Mountain erosion over 10 yr, 10 k.y., and 10 m.y. time scales. Geology 29, 591–594 (2001).

    Article  Google Scholar 

  27. Dethier, D. P. & Lazarus, E. D. Geomorphic inferences from regolith thickness, chemical denudation and CRN erosion rates near the glacial limit, Boulder Creek catchment and vicinity, Colorado. Geomorphology 75, 384–399 (2006).

    Article  Google Scholar 

  28. Summerfield, M. A. & Hulton, N. J. Natural controls of fluvial denudation rates in major world drainage basins. J. Geophys. Res. 99, 871–883 (1994).

    Article  Google Scholar 

  29. Matmon, A. et al. Temporally and spatially uniform rates of erosion in the southern Appalachian Great Smoky Mountains. Geology 31, 155–158 (2003).

    Article  Google Scholar 

  30. Roehler, H. W. Chart showing identification of oil-shale and trona beds and their geophysical log responses in the Union Pacific Railroad Company El Paso corehole no. 44-3, Eocene Green River Formation, southwest Wyoming. US Geological Survey Miscellaneous Field Studies Map MF-2188 (1991).

Download references


We thank B. S. Singer, J. R. Dyni, J. C. Knox, D. C. Kelly, B. Tikoff and J. P. Smoot for assistance or discussions, and appreciate the thoughtful review by R.S. Anderson. Financial support was provided by National Science Foundation grants EAR-0230123, EAR-0114055 and EAR-0516760, and the Bailey Distinguished Graduate Fellowship at the University of Wisconsin.

Author information

Authors and Affiliations


Corresponding author

Correspondence to M. Elliot Smith.

Supplementary information

Supplementary Information

Supplementary tables S1-S3 and figure S1 (PDF 243 kb)

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Elliot Smith, M., Carroll, A. & Mueller, E. Elevated weathering rates in the Rocky Mountains during the Early Eocene Climatic Optimum. Nature Geosci 1, 370–374 (2008).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:

This article is cited by


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing