Holocene soils/paleosols in the okstindan mountains, nordland: stratigraphy and extractable fe and al

Abstract

A chronosequence of surface and buried soils in moraines and outwash, ranging in age from Middle to Late Holocene, i.e., Little Ice Age, and forming under alpine and subalpine vegetation in the Okstindan Mountains of centralnorth Norway (66 o N) (Oksskolten) was studied to determine if topographic/stratigraphic setting, weathering characteristics, soil/paleosol properties, SEM/EDS analysis, and extractable Fe and Al could be used to elucidate information on paleoenvironment and age. The geochemical data previously published and geological mapping by the Norwegian Geological Survey indicate a uniform parent material in these profiles. Slight geochemical anomalies of higher U, Th and Br in organic-rich horizons are related to vegetation and/or higher water content at various times, confirmed by extractable Fe evidence. The data interpretation also shows that extractable Fe, principally Feo, is useful in identifying previous perched water tables, possibly generated by permafrost. The activity ratio of Feo/Fed (oxalate to dithionite) and the ratio Fed/Fet (dithionite to total Fe) appear useful in distinguishing older from younger soils on the basis of the conversion of ferrihydrite to goethite+hematite. Pyrophosphate extracts, proved useful in determining movement of organically bound Al, and showed a pronounced difference between the alpine and subalpine environments. Oxalateextractable and dithionite-extractable Al proved of little value in relative age determination, presumably because sodium dithionite does not extract all crystalline Al.