Genesis of upland soils, Lewes Plateau, central Yukon. Part 2: Soils formed in weathered granitic bedrock

Abstract

Dampier, L., Sanborn, P., Smith, S., Bond, J. and Clague, J. J. 2011. Genesis of upland soils, Lewes Plateau, central Yukon. Part 2: Soils formed in weathered granitic bedrock. Can. J. Soil Sci. 91: 579–594. Polygenetic soils have formed on weathered granitic bedrock at high elevation (>1200 m asl) beyond the penultimate glacial limit on the Lewes Plateau in central Yukon Territory. Solum thickness in four Brunisols that were examined exceeds the depths of excavated pits (85–110 cm), but data indicate limited chemical weathering. Clay mineralogy is dominated by vermiculite and kaolinite. Smectite and chlorite are present in horizons derived, respectively, from residuum and colluvium. Sola are strongly cryoturbated, in spite of the lack of permafrost at these sites today. Three scenarios are proposed to explain these soils: preservation of relict soil features beneath cold-based ice, prolonged interglacial soil formation following erosion of till deposited by warm-based ice, and ice-free conditions throughout the Quaternary, with soil evolution shaped by multiple glacial-interglacial cycles.

Relict periglacial soils on Quaternary terraces in the Central Ebro Basin (NE Spain)

“…The clay coatings described cannot be primarily associated with periglacial conditions as they require a temperate climate with moist periods both for the initial formation of clay‐sized material and its subsequent mobilization leading to the formation of the coatings . Furthermore, the reddish color of these soils, with a hue of 5YR or 7.5YR that is related to the presence of hematite, suggests a much warmer climate than even the present one …”