INTERPRETING CRYOGENIC FEATURES IN SOILS AND PALEOSOLS: QUANTITATIVE PALEOCLIMATE RECONSTRUCTION FROM LATE PLEISTOCENE TO HOLOCENE FROST-AFFECTED SOILS AND SEDIMENTS

Cryogenic features are perhaps one of the most diagnostic indicators of frigid paleoclimate in terrestrial sedimentary environments. Characterized by cryoturbation, or the disruption and churning of soil fabric by differential frost heave, frost-affected soils are clear indicators of either permafrost or deep seasonal freezing. Because most cryogenic features are physical, rather than geochemical, they have a high preservation potential and are useful indicators of past climate. Cryoturbation can be highly variable, depending on a variety of soil properties including moisture availability, temperature, mineralogy, base saturation, salt content, pore pressure, and texture. Although cryogenic features and the mechanisms which create them have been extensively characterized, quantitative investigation of the soil conditions leading to their formation has never been attempted. This study characterizes the suites of cryogenic features occurring in loess-parented upland buried soils in central Alaska using micromorphology. Bulk soil geochemistry and mineralogy have then been used to reconstruct mean annual precipitation (MAP), mean annual ground temperature (MAGT), pH, base saturation, and salinity for these soils in order to determine the unique climatic conditions leading to the formation of various suites of cryogenic features. This study intends to enable semi-quantitative reconstruction of paleoclimate of cryogenic soils and sediments based solely on soil micromorphology, without the need for additional characterization of physical and chemical properties.