Cornu,S., Montagne,D. and Vasconcelos,P.M.(2009): Dating constituent formation in soils to determine rates of soil processes: A review. Geoderma, 153, 293-303.


 Rates of soil processes are poorly known. One approach to determine them could be through the radiogenic isotopic dating of soil constituents. Such methods have been recently used to date minerals in soils and weathering profiles thanks to the development of high-resolution techniques such as 40Ar/39Ar, U-series of micro-drilled samples, U-series by laser ablation and (U-Th)/He and to the development of suitable methodology expanding application of the techniques to a variety of supergene minerals (e.g. Fe- and Mn-oxihydroxides, carbonates, etc.).
 In this paper we identify (i) the main soil constituents that can be dated through these isotopic methods - that are mainly Fe-oxides, Mn-oxides, pedogenic carbonates and organic matter, (ii) the main pedogenic processes that leads to their formation in soils and (iii) the different soil settings that allow transforming soil constituent ages into rates of soil processes, namely growth bands, transformation fronts and chronosequences.

Keywords: Isotopes; Chronosequences; Oxides; Carbonates; Organic matter; Pedogenesis 』

1. Introduction
2. Precipitation of Fe-oxides in soils: ferruginisation and degradation
 2.1.Formation of Fe-oxides in soils
  2.1.1. Formation of Fe-oxides under oxic conditions
  2.1.2. Degradation
 2.2. Dating methods
  2.2.1. U-series Principle Application to Fe-oxide dating
  2.2.2. (U-Th)/He and 4He/3He Principle Application to Fe-oxide dating
3. Processes responsible for the formation of Mn-oxides in soil profiles
 3.1. Formation of Mn-oxides in soils
 3.2. Dating by 40Ar/39Ar
  3.2.1. Principle
  3.2.2. Application to Mn-oxide dating
4. Processes responsible for the precipitation of pedogenic carbonates in soils
 4.1. Formation of pedogenic carbonates
 4.2. Dating methods
  4.2.1. Application of U-series to carbonate dating
  4.2.2. Radiocarbon Principle Application to carbonate dating
5. Organic matter accumulation into soils
 5.1. Process
 5.2. Dating by radiocarbon
6. From dating soil constituents to rating soil processes
 6.1. Dating growth bands
 6.2. Progression of a transformation front at the profile scale
 6.3. Use of chronosequences
7. Conclusion