Further cryostratigraphic observations in the CRREL permafrost tunnel, Fox, Alaska

Cryostratigraphic mapping in the main shaft of the CRREL tunnel indicates secondary modification of original Pleistocene-age syngenetic permafrost. Layered, lenticular-layered and micro-lenticular cryostructures within undisturbed silt characterise the syngenetic permafrost. Thawed and refrozen deposits are characterised by massive and reticulate-chaotic cryostructures. The micro-morphology of typical cryostructures, as observed through an environmental scanning electron microscope (ESEM), is described. It is inferred that preferential cryogenic modification has occurred due to fluvio-thermal erosion operating along ice wedges. Soil and ice pseudomorphs are the manifestation of this process. Gravel, silt, ice and mixed (silt/ice) pseudomorphs occur within silt. Ice pseudomorphs are formed by thermokarst-cave ice ('pool ice') which filled thermokarst pits, channels and gullies. Copyright (C) 2006 John Wiley & Sons, Ltd.