CRYOSTRUCTURES IN PERMAFROST, TUKTOYAKTUK COASTLANDS, WESTERN ARCTIC CANADA

The shape and distribution of ice and sediment within frozen ground co nstitute its cryostructure. Observations on perennially frozen sedimen ts in the Tuktoyaktuk coastlands enable six cryostructures to be ident ified: (1) structureless, (2) lenticular, (3) layered, (4) reticulate, (5) crustal, and (6) suspended. These cryostructures can be transitio nal or composite. Five cryofacies types can also be identified accordi ng to volumetric ice content and grain size. They can be grouped into cryofacies assemblages. The utility of the descriptive classification of ice-rich sediments is illustrated from a palaeothaw layer at Crumbl ing Point.