Genesis of Turbic Cryosols on north-facing slopes in a dissected, unglaciated landscape, west-central Yukon Territory

Abstract

The characteristics and landscape distribution of Histic Dystric Turbic Cryosols were examined on a steep (>30%) northerly slope in the unglaciated Klondike Plateau, near Dawson City, Yukon Territory. Based on texture, major element geochemistry, and clay mineralogy, the mineral parent materials were crudely stratified, with a silty material of likely aeolian origin overlying sandy gravelly colluvium. Discontinuous organic matter-enriched horizons occurred 50 cm or more below the active layer, and contained abundant partially decomposed plant detritus. Eight accelerator radiocarbon dates, ranging from 350 ± 40 to 3680 ± 40 14C years BP, suggested that incorporation of organic materials within and below the active layer was geologically recent, and had likely occurred by a combination of cryoturbation and slope processes. The widespread and rapid initiation of mass movements on slopes containing permafrost that followed forest fires in 2004 on the Klondike Plateau may be an analogue for the processes that contributed to organic matter burial in these Cryosols. These soils may represent a significant reservoir of C, as similar sites occupy at least 15% of a representative portion of the Plateau. This reservoir may be vulnerable to mobilization if future climatic warming increases the frequency of forest fires and resulting slope instability.Key words: Tyrbic Cryosol, Yukon Territory, cryoturbation, soil organic carbon, mass movement

The detailed palaeoecology of a mid‐Wisconsinan interstadial (ca. 32 00014C a BP) vegetation surface from interior Alaska

“…Concentrations of oxalate‐extractable Fe and Al were generally low, indicating a limited degree of chemical weathering prior to burial. The occurrence of a higher Fe concentration in the Abff1 is consistent with the pattern of Fe accumulation in buried organic matter noted in modern Gelisols in the Klondike Goldfields (Smith et al , 2009).…”

Soil genesis in relation to glacial history, Central Yukon.

“…The first studies of soils on Quaternary deposits in the central Yukon attempted to relate soil development at low-elevation sites to paleoclimate (Foscolos et al 1977;Rutter et al 1978;Tarnocai et al 1985;Smith et al 1986;Tarnocai and Valentine 1989;Tarnocai and Smith 1989). More recently, researchers have begun to examine soils developed on other deposits, such as loess (Laxton et al 1996;Sanborn et al 2006) and colluvium (Bond and Sanborn 2006;Smith et al 2009), as well as soils at higher elevations (Jackson et al 1999). This section provides information on previous soil research in central Yukon as it relates to glacial history.…”

“…Although this work established a framework for viewing soil landscapes in the central Bond and Sanborn (2006) showed that Brunisolic soils on unglaciated, upland areas in the west-central Yukon were strongly modified by slope processes. Smith et al (2009) investigated the distribution and pedogenic characteristics of Histic Dystric Turbic Cryosols on a steep, unglaciated slope with a northern aspect near Dawson City. They determined that these soils are a significant reservoir for carbon which is vulnerable to climatic warming.…”