Properties and soil development of late-Pleistocene paleosols from Seward Peninsula, northwest Alaska

Abstract

Soils on Seward Peninsula, northwest Alaska, that were buried about 17,500 years ago and froze after burial present a unique opportunity to study soil development under the conditions of the last glacial maximum. Stratigraphic sections were excavated during the summers of 1993 and 1994. Study sites were located on steep banks of thaw lakes. We described soil morphology (including cryogenic features) and sampled for chemical and physical analyses. All paleosols are permafrost soils that developed in calcareous loess and have roots present throughout. Colors are predominantly grayish and either reflect original loess color or periodic saturation of the soils (possibly caused by the permafrost environment). Active layer thicknesses before burial ranged from 32 to 64 cm. Organic carbon contents average 3.0%, carbon/nitrogen ratios average 9, cation exchange capacities average 19.1 cmol/kg, and base saturations generally exceed 100%. There is no evidence of leaching in the profile. Soil formation occurred simultaneously to the deposition of the parent material loess. Morphological and chemical data suggest that soil development was weak and confined to organic matter accumulation, and hydrolysis of iron. All studied soils show similar morphological, chemical, and physical properties, which suggests a relatively uniform mode of soil formation in the study area. Soil-forming conditions on northern Seward Peninsula during the last glacial maximum were severe, and combined with fairly continuous loess deposition they resulted in weakly developed, nutrient-rich soils.