Terrestrial carbon isotope excursions and biotic change during Palaeogene hyperthermals

Journal name:
Nature Geoscience
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Pronounced transient global warming events between 60 and 50 million years ago have been linked to rapid injection of isotopically-light carbon to the ocean–atmosphere system1, 2. It is, however, unclear whether the largest of the hyperthermals, the Palaeocene–Eocene Thermal Maximum (PETM; ref. 3), had a similar origin4, 5 as the subsequent greenhouse climate events1, 6, such as the Eocene Thermal Maximum 2 and H2 events. The timing and evolution of these events is well documented in marine records7, 8, but is not well constrained on land. Here we report carbon isotope records from palaeosol carbonate nodules from the Bighorn Basin, Wyoming, USA that record the hyperthermals. Our age model is derived from cyclostratigraphy, and shows a similar structure of events in the terrestrial and marine records. Moreover, the magnitude of the terrestrial isotope excursions is consistently scaled with the marine records, suggesting that the severity of local palaeoenvironmetal change during each event was proportional to the size of the global carbon isotope excursion. We interpret this consistency as an indication of similar mechanisms of carbon release during all three hyperthermals. However, unlike during the PETM (refs 9, 10), terrestrial environmental change during the subsequent hyperthermals is not linked to substantial turnover of mammalian fauna in the Bighorn Basin.

At a glance


  1. Terrestrial carbon isotope records of the ETM2 and H2 hyperthermal events.
    Figure 1: Terrestrial carbon isotope records of the ETM2 and H2 hyperthermal events.

    Isotope results are from palaeosol carbonate in the Upper Deer Creek and Gilmore Hill sections in the Bighorn Basin, Wyoming, USA. Stratigraphic thickness is equally scaled for both sections. Magnetochrons and biozonation are given. Five distinct purple beds (1–5) are labelled at UDC (Fig. 2). The bandpass filter of the redness (a*) matrix colour reflectance record is given to denote precession-scale cyclicity. Fossil finds at UDC, and fossil localities (MP) at GH with first and last appearances (FAD and LAD) are given. A for Anacodon, B for Bunophorus, E for Ectocion, and H for Haplomylus. The correlation between UDC and GH is based on aligning the H2 event. Note that Biohorizon B occurs well before the environmental disturbance related to the hyperthermal events.

  2. Carbon isotope records in the continental and marine realms on independent astronomical timescales.
    Figure 2: Carbon isotope records in the continental and marine realms on independent astronomical timescales.

    a, Continental data are from palaeosol carbonate in the Upper Deer Creek section. Solid line represents a 5-point moving average. b, Marine data are from benthic foraminifera and shows a 4-kyr average from a stacked record of Ocean Drilling Program Sites 1262, 1263, 1265, 1267 (Walvis Ridge, southern Atlantic Ocean). Note the great similarity between the deep marine and the continental carbon isotope records indicating both coincidently recorded the carbon isotope signature of the global ocean–atmosphere reservoir.

  3. Comparison of carbon isotope excursions for PETM, ETM2 and H2 for Bighorn Basin continental and different marine records.
    Figure 3: Comparison of carbon isotope excursions for PETM, ETM2 and H2 for Bighorn Basin continental and different marine records.

    Marine data are from bulk carbonate from Mead and Dee Stream sections in New Zealand17, 27, 28 (squares), ODP Site 1265 bulk carbonate (red circles) and Site 1263 (PETM) and Site 1267 (ETM2/H2) benthic foraminifer N. truempyi (black circles) from Walvis Ridge in the southern Atlantic Ocean7, 8, 26. Uncertainty intervals represent standard errors (1σ of the mean difference between baseline and excursion values; see Supplementary Table S6). The similar scaling between CIE amplitudes implies that the factors influencing CIE amplitudes for the different proxies reacted proportionally to the carbon input to the ocean–atmosphere carbon pool.


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Author information


  1. Department of Earth Sciences, Utrecht University, 3584 CD, Utrecht, The Netherlands

    • Hemmo A. Abels,
    • Frederik J. Hilgen &
    • Lucas J. Lourens
  2. Department of Earth Sciences, University of New Hampshire, Durham, New Hampshire 03824, USA

    • William C. Clyde
  3. Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, Michigan 48109, USA

    • Philip D. Gingerich
  4. Department of Geology, Colorado College, Colorado Springs, Colorado 80903, USA

    • Henry C. Fricke
  5. Department of Earth and Atmospheric Sciences, Purdue University, West Lafayette, Indiana 47907, USA

    • Gabriel J. Bowen


H.A.A., W.C.C., P.D.G., F.J.H. and H.C.F. carried out fieldwork. H.A.A., W.C.C. and H.C.F. performed the laboratory analysis. H.A.A., W.C.C., P.D.G., H.C.F. and L.J.L. performed data integration. All authors contributed to the manuscript.

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