Soil genesis in relation to glacial history, Central Yukon.

Abstract

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Clay mineralogy and chemical properties of argillic horizons in central Yukon paleosols

“…These results are similar to those x Kaolinite-montmorillonite, as per criteria given by Foscolos et al (1977). obtained for other central Yukon pedons formed primarily on morainal and residual parent materials (Bond and Sanborn 2006;Dampier 2010). Allowing for differences in sample pretreatments, the absence of published diffraction patterns in some studies, and the semiquantitative nature of X-ray clay mineralogy, the clay mineral assemblages observed in these Wounded Moose argillic horizons appear consistent with those reported previously for a much smaller number of samples.…”

“…Therefore, as measured by this index, the upper end of the range of weathering intensity for Wounded Moose argillic horizons exceeds that of any other central Yukon soils and surficial materials previously reported. The low concentrations of organically complexed Fe and Al in these Bt horizons are comparable with those reported in B horizons of central Yukon Brunisolic soils formed beyond the Reid glacial limit in residual or colluvial parent materials (Bond and Sanborn 2006;Dampier 2010). Although this is consistent with the rarity of Podzolic soils in contemporary Yukon soil landscapes (Smith 2004), Middle Pleistocene buried Podzolic paleosols occur elsewhere in central Yukon (Jackson et al 2000), suggesting that Wounded Moose paleosols may have experienced environments conducive to podzolization during one or more earlier interglacials.…”

“…For comparison, Dampier (2010) calculated CIA values for two pre-Reid paleosols from elemental analyses published by Foscolos et al (1977), and obtained values between 56 and 76 for the IIBt horizons. On upland sites in the Lewes Plateau of central Yukon, Dampier (2010) found that ranges in CIA values of B horizons (Â50Á60) differed little between McConnell, Reid, and pre-Reid-aged soils. However, the upland sites described by Dampier (2010) were at elevations approximately 500 m higher than the sites used for this study, and had likely experienced substantially different climatic conditions and geomorphic histories during the Quaternary.…”

“…On upland sites in the Lewes Plateau of central Yukon, Dampier (2010) found that ranges in CIA values of B horizons (Â50Á60) differed little between McConnell, Reid, and pre-Reid-aged soils. However, the upland sites described by Dampier (2010) were at elevations approximately 500 m higher than the sites used for this study, and had likely experienced substantially different climatic conditions and geomorphic histories during the Quaternary. In the unglaciated Klondike Plateau south of Dawson, Bond and Sanborn (2006) examined soils formed in colluvium and saprolite derived from metamorphic bedrock.…”

“…The proportion of total Fe in these argillic horizons that has been converted to secondary forms by weathering (Â40%) is in the middle of the range (Â20Á60%) reported for B horizons in upland pre-Reid-aged soils near Carmacks (Dampier 2010) and in residual soils of unglaciated areas near Dawson (Bond and Sanborn 2006; Sanborn, unpublished data). The proportion (Â90%) of secondary Fe occurring in crystalline forms in the Wounded Moose Bt horizons is at the high end of the range (Â20Á90%) reported for B horizons in these previous central Yukon studies.…”