Abstract

An analysis of 1168 modern soil profiles from the U.S. Natural Resources Conservation Service yields no correlation between mean annual precipitation and depth to the top of the carbonate horizon (r2 = 0.03; p < 0.001). Parent material and soil texture both play negligible roles in this regression. When combined with similar published studies (n = 1481), r2 improves slightly (r2 = 0.31; p < 0.001). Caution is therefore advised in using this or any previously published regression for inferring paleoprecipitation from paleosols. However, in the combined data set, carbonate horizon–bearing soils correlate with a mean annual precipitation of < 760 mm (p < 0.05). Thus the presence vs. absence of pedogenic calcium carbonate is a good indicator of paleoprecipitation above or below this value.

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