New approach to Ice Complex investigation

Abstract:

Ice Complex (IC) is the most well-known type of syncryogenic permafrost deposit. ICs are widely distributed in the northern-eastern part of Russia (Siberia) and in Alaska. These deposits are an important source of paleo-climatic information, because they contain well-preserved remains of flora and fauna typical for the time of preservation. The isotope signature of ice preserved in an IC can help to reconstruct specific features of the freezing period and freezing conditions. However, the best methods to use to determine the origin and age of ICs and what constitutes typical IC morphological structure are still being discussed. Conventionally, syncryogenic permafrost deposits of Pleistocene age, consisting of an ice-wedge net, are considered ICs. In our multi-year study, we applied a new approach, defining ICs using cryolithological criteria. Our results allow us to conclude that the initial composition of an IC is determined by the sediments (silt, sand, gravel) and processes (fluvial, slope, aeolian) involved in IC genesis. Further alteration of IC composition occurs via cryogenic processes during glacial epochs and partial/complete thawing during inter-glacial epochs; usually such alteration leads to an increase in the fine-grain fraction of IC sediments and the formation of separate IC layers, which should be considered as separate stratigraphic units. Only the uppermost unit of an IC should be called an edoma ice complex (EIC); this unit creates specific relief features, for which EICs are known, in Siberia and Yakutia. The most important task to which attention should be paid in further investigations is the development of criteria that will allow reconstructive modeling of the processes and conditions that existed in the past, processes and conditions which determined initial IC composition and alteration of properties over time.