Soil development indices in a soil chronosequence formed on Lower Pleistocene terraces in the north-western Duero basin (León, Spain)

EN A study was carried out in a soil chronosequence developed on alluvial deposits, comprising six terraces displaying marked variations due to altitudinal differences. Many of their morphological properties, such as their original red colour, have become obscured beneath a variety of colours as a result of the intense hydromorphism acting upon the impermeable Miocene clay substrate which underlies these formations. The accumulation indices (AI) for total clay and fine clay, and most especially those corresponding to the iron oxides (Fed/Fet), were found to be good indicators, highlighting developmental and evolutionary differences between the six soils.