Reexamining the Current Soil Order Classification of Maine's Glaciomarine Sediments.

Soil classification should reflect our current knowledge and understanding of the processes and properties that occur within a soil. As such, if our concepts of a soil changes as a result of the acquisition of additional or new knowledge, the classification of those soils should change to reflect that knowledge. Since Soil Taxonomy is a hierarchical system, the most basic process and properties of the soils should be reflected at the order level of classification. In this study, we examined the basic diagnostic soil properties of soils formed in glaciomarine sediments deposited during the late Wisconsinan in New England to determine if these soils contained argillic or cambic diagnostic horizons. These soils are currently mapped at the order level as Inceptisols (cambic diagnostic horizons), but recent observation and discussion suggest that the Alfisol classification (argillic horizons) may be more appropriate. Eight pedons from three sites in New Hampshire and Maine were investigated. All but one of the pedons showed an increase in clay with depth indicative of clay illuviation. Observations of the thin sections of the B horizons showed thin oriented clay coatings along channels and other continuous voids. Point counts showed more than 1% clay coatings suggesting that all but one of the pedons we examined should be classified as having an argillic horizon and classified at the order level to Alfisols.