Full-glacial paleosols in perennially frozen loess sequences, Klondike goldfields, Yukon Territory, Canada

摘要

Perennially frozen loess deposits in the Klondike goldfields include paleosols formed in full-glacial environments, correlated by Alaskan distal tephra with Marine Isotope Stages (MIS) 2 and 4. Patterns of organic and inorganic carbon and clay distribution, microstructures, and profile morphologies indicate that soil formation occurred in a base-rich environment in which organic matter accreted predominantly as root detritus. At sites approximately 20 kin apart, the expression of cryoturbation and ice wedge development decreases in strength upward in loess-paleosol sequences correlated with MIS 4, suggesting increasing aridity. Configurations of cryoturbation features and ice-wedge thaw unconformities, the presence of numerous ground squirrel burrows, and an absence of peat accumulation suggest that these substrates were predominantly well-drained, with active layers of equal or greater thickness than in modem soils on similar sites in the west-central Yukon. Some characteristics of these paleosols are similar to those of modem steppe and tundra soils, consistent with plant macrofossil evidence for local ecological diversity during full-glacial conditions in eastern Beringia. (c) 2006 University of Washington. All rights reserved.