A 30,000 year Record of 13C and 18O changes in Organic Matter from an Equatorial Peatbog

  1. P. K. Swart,
  2. K. C. Lohmann,
  3. J. Mckenzie and
  4. S. Savin
  1. Anne-Marie Aucour1,
  2. Claude Hillaire-Marcel1 and
  3. Raymonde Bonnefille2

Published Online: 2 APR 2013

DOI: 10.1029/GM078p0343

Climate Change in Continental Isotopic Records

Climate Change in Continental Isotopic Records

How to Cite

Aucour, A.-M., Hillaire-Marcel, C. and Bonnefille, R. (1993) A 30,000 year Record of 13C and 18O changes in Organic Matter from an Equatorial Peatbog, in Climate Change in Continental Isotopic Records (eds P. K. Swart, K. C. Lohmann, J. Mckenzie and S. Savin), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM078p0343

Author Information

  1. 1

    Centre de Recherche en Géochimie Isotopique et en Géochronologie (GEOTOP(, Université du Québec à Montréal

  2. 2

    Laboratoire De Géologie du Quaternaire, CNRS, Marseille-Luminy

Publication History

  1. Published Online: 2 APR 2013
  2. Published Print: 1 JAN 1993

ISBN Information

Print ISBN: 9780875900377

Online ISBN: 9781118664025

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Keywords:

  • Climate changes;
  • Paleoclimatology;
  • Isotope geology;
  • Radioactive tracers

Summary

Coring of the Kashira peatbog in Burundi (core Ka-2, 3° 28′S, 29°34′E, altitude: 2240 m) allowed the recovery of a 30,000 year palaeoclimatic record for Equatorial Africa. The δ13C values of total organic matter (TOM) in core Ka-2 vary primarily as a function of C3/C4 plant inputs (essentially Gramineae and Cyperacae versus other plants). Maximum 13C contents of TOM are observed between 30 and 15 ka, which suggests the dominance of C4 plants in the local palaeovegetation during that period. Fossil plant remains are derived from emergent plants and their cellulose 18O/16O ratios are measured. They reflect (1) the isotopic composition of the meteoric waters used by the plants, (2) the evapotranspiration which is mostly controlled by the relative humidity of the air, and (3) the type of plant. The 30-12 ka and 3-0 ka intervals show high 18O contents (δ18O values of 24–27.5‰ and 26–28.5 °/∞ versus SMOW respectively). The much lower δ18O values (19–24‰) observed during the 7-3 ka interval indicate relatively high humidity and 18O-depleted precipitation during that period. Combined with pollen data, the isotopic composition of organic matter in peatbogs provides additional information on vegetational mass budgets (C3/C4 plants) and on past water cycle in the equatorial atmosphere.