Dr. Hailemichael Soils of the Past: an introduction to paleopedology (G.J. Retallack) contains a concise answer to your question. To summarize, in dry climates carbonate in soil builds up from dust and leftover weathering products at the rate of .26 g/cm2/yr (for cool desert regions-Las Cruces) to half that in a wetter and cooler climate or twice the Las Cruces value in a wetter an somewhat warmer climate (0.51-Roswell). Hope this helps, but again the Retallack text is more detailed, as I’m sure other texts are as well. Dave Mrofka UC Riverside Earth Sciences -----Original Message----- From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On Behalf Of Million Hailemichael Sent: Wednesday, August 06, 2003 2:55 PM To: [log in to unmask] Subject: [ISOGEOCHEM] pedogenic carbonates in semiarid soil Dear all How long does it takes for a pedogenic carbonate to be formed. Not neccesarly in the form of a nodule, but even in the form of fine powder in semi arid environment. Hundreds of years? Or do we get pedogenic carbonate in 20 or 30 years. Thank you ************************************************************* Million Hailemichael, Ph.D. Senior Research Associate Texas A&M University Department of Rangeland Ecology and Management Stable Isotope Laboratory 2126 TAMU College Station, TX 77843-2126 Phone: (979)845-1497 Fax: (979)845-6430 **************************************************************