Iron and aluminum soil/paleosol extractions as age/environment indicators: Some examples from a catchment in southern Ontario, Canada

• Fluvial soil/paleosol chronosequence
• Fe and Al extracts
• Environmental reconstruction
• Fluvial deposit correlation with Late Pleistocene glaciation

Various chemical extractions of Fe and Al from bulk soil samples, including Na-pyrophosphate (Fep, Alp), acid ammonium oxalate (Feo, Alo), and Na-dithionite (Fed, Ald), have been used over the last half century to distinguish soil ages over varying time frames from 102 to 106 years and even as far into antiquity as the Oligocene (30 × 106) years. Problems with mineral/chemical uniformity of sediments, free drainage of open system profiles, and variable climate over long time frames have produced problems and uncertainties as to just what each extraction removes from the bulk material analyzed. Some problems have been resolved by the work of Parfitt and Childs (1988); but some persist, especially with respect to the solubility of some extractant forms and the actual composition of others, particularly Alp, Alo, and Ald. A recent test of soils and paleosols in a fluvial chronosequence in southern Ontario illustrates the soil-paleosol evolutionary time trend over a period of ~ 11 ky, essentially post-Iroquois time in the Ontario basin (Jackson et al., 2000). This work highlights the importance of isolated, free draining weathering systems, mineral uniformity, and new relationships between secondary forms of Fed and Ald, the latter previously considered of little importance in age relationship quests.