Carbon stable isotope composition of modern calcareous soil profiles in California: Implications for CO2 reconstructions from calcareous paleosols

Neil J. Tabor, Timothy S. Myers, Erik Gulbranson, Craig Rasmussen, Nathan D. Sheldon

Research output: Chapter in Book/Report/Conference proceedingChapter

23 Scopus citations


Fourteen soil profiles from California were collected in order to measure the δ13C of coexisting soil calcite and organic matter. Thirteen of the profiles contained a measurable amount of calcite ranging from 0.04 to 54.6 wt %. Soil calcite δ13CPDB (δ13C value vs. the calcite standard Peedee Belemnite) values range from -14.4 to 1.3%, whereas organic matter δ13CPDB values range from -24.0 to -27.7. The hydrology of these profiles is divided into two broad groups: (1) soils characterized by gravity-driven, piston-type vertical flow through the profile and (2) soils affected by groundwater within the profile at depths where calcite is present. The difference between soil calcite and organic matter δ13CPDB values, Δ13Ccc-om, is smaller in profiles affected by groundwater saturation as well as most Vertisols and may be a product of waterlogging. The larger Δ13C cc-om values in soils with gravity-driven flow are consistent with open-system mixing of tropospheric CO2 and CO2 derived from in situ oxidation of soil organic matter with mean soil PCO2 values potentially in excess of ;20,000 ppmV at the time of calcite crystallization. There is a correlation between estimates of soil PCO 2 and a value termed "EPPT-U" (kJm 2/yr) among the soil profiles characterized by gravity-driven flow. EPPT-U is the energy flux through the soil during periods of soil moisture utilization, and it is the product of water mass and temperature in the profile during the growing season. Thus, soils with high water-holding capacity/storage and/or low/high growing season temperature may form soil calcite in the presence of high soil PCO2, and vice versa. The results of this research have important implications for reconstructions of paleoclimate from stable carbon isotopes of calcareous paleosol profiles.

Original languageEnglish (US)
Title of host publicationNew Frontiers In Paleopedology And Terrestrial Paleoclimatology
Subtitle of host publicationPaleosols And Soil Surface Analog Systems
PublisherSEPM Society for Sedimentary Geology
Number of pages18
ISBN (Print)9781565763227
StatePublished - 2013

Publication series

NameSEPM Special Publications
ISSN (Print)1060-071X


  • California
  • Carbon isotope
  • Oxygen isotope
  • Soil
  • Water balance

ASJC Scopus subject areas

  • Geology
  • Stratigraphy


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