Dating constituent formation in soils to determine rates of soil processes: a review.

摘要

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.