Effect of Crystalline Iron Oxides on Development and Classification of Podzolic Soils in Western Labrador, Newfoundland

Abstract

AbstractSeven pedons from western Labrador with various amounts of crystalline Fe oxides in the parent material were studied to determine how Fe oxides inherited from the parent material influence Podzolic soil development in a boreal environment. Amounts of total amorphous Fe oxides did not increase with increasing amounts of crystalline Fe oxides in the soils. Consequently, the ratio of amorphous to crystalline Fe oxide contents decreased sharply with increasing crystalline Fe oxide contents. This decrease is attributed to the resistance of crystalline Fe oxides to weathering and decomposition. Goethite was the only form of crystalline Fe oxide identified in the clays of soils with low crystalline Fe oxide contents. About equal amounts of goethite and hematite were identified in the clays of soils with medium and high crystalline Fe oxide contents. Smectite and vermiculite were the major clay minerals in the E horizon of soils with low and medium crystalline Fe oxide contents. However, only small amounts of these minerals were present in the E horizon of the soil with high crystalline Fe oxide contents in spite of relatively large amounts of potentially expandable silicates such as mica. One of the current criteria of the spodic horizon, (Fe + Al)p/(Fe + Al)d, was found to be too restrictive for soils developed on materials containing medium to high crystalline Fe oxide contents and should be deleted.