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This article in SSSAJ

  1. Vol. 53 No. 1, p. 201-210
     
    Received: Mar 14, 1988


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doi:10.2136/sssaj1989.03615995005300010037x

The Stable Isotope Chemistry of Pedogenic Carbonates at Kyle Canyon, Nevada

  1. Ronald G. Amundson ,
  2. Harvey E. Doner,
  3. Oliver A. Chadwick and
  4. Janet M. Sowers
  1. Dep. of Plant and Soil Biology, 108 Hilgard Hall, Univ. of Calif., Berkeley, CA 94720
    Jet Propulsion Lab., Calif. Inst. of Technology, Pasadena, CA 91109
    U.S. Geological Survey, Menlo Park, CA 94025

Abstract

Abstract

The C and O isotopic composition and radiometric ages of laminar pedogenic CaCO3 coatings were examined in limestone-derived alluvium along an elevational and climatic transect of the Mojave Desert of Nevada. The δ13C of the soil CO2 decreased with increasing elevation and was related to plant density and available soil moisture. Laminar pedogenic carbonate coats which formed on the bottoms of clasts were separated into inner and outer laminae. The δ13C of carbonates in the outer laminae decreased with increasing elevation as a result of a decrease in the percentage of detrital carbonate in the sample and a decrease in the δ13C of the soil CO2. The δ18O of the outer laminae also decreased with elevation and, after correcting for contamination by detrital carbonate, appeared to correspond to changes in the isotopic composition of the precipitation. The δ13C of the carbonate in the inner laminae also decreased with increasing elevation; however, carbonate in the inner laminae was much purer than the outer laminae and appeared to be predominantly pedogenic in origin. The δ13C of these layers reflects the δ13C of soil CO2 and, for most samples, corresponded to expected values for modern carbonate. Based on uncertainties in dating techniques and the estimated range in isotopic composition of pedogenic carbonate, however, it was not possible to determine if some of the inner laminae formed in the latest pluvial period and reflect past pedogenic conditions.

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