Late-Pleistocene Syngenetic Permafrost in the CRREL Permafrost Tunnel, Fox, Alaska

Abstract

Late-Pleistocene syngenetic permafrost exposed in the walls and ceiling of the CRREL permafrost tunnel consists of ice-and organic-rich silty sediments penetrated by ice wedges. Evidence of long-continued syngenetic freezing under cold-climate conditions includes the dominance of lenticular and micro-lenticular cryostructures throughout the walls, ice veins and wedges at many levels, the presence of undecomposed rootlets, and organic-rich layers that reflect the former positions of the ground surface. Fluvio-thermal modifications are indicated by bodies ofthermokarst-cave ('pool') ice, by soil and ice pseudomorphs, and by reticulate-chaotic cryostructures associated with freezing ofsaturated sediments trapped in underground channels.