Numerous piercement structures occur on the Queen Elizabeth Islands of the Canadian Arctic Archipelago. The exposed cores of these structures are composed chiefly of Pennsylvanian anhydrite, which may be underlain by rock salt. The cores are surrounded by Mesozoic rocks.A geometric analysis of two well-exposed domes on Axel Heiberg Island was made to learn whether the anhydrite behaved as an active source material or as a passive overburden during doming. Attitudes of bedding and lenticular limestone boudins were measured in both domes, and the axial traces of macroscopic folds were constructed.The flow pattern in the anhydritic domal cores corresponds to that predicted by model studies, suggesting that layered anhydrite behaved essentially as a source material for the domes. The South Fiord Dome is composed of three sub-cores, whereas the Mokka Fiord Dome rose as a single unit.During late stages of doming, large radial fractures developed in upper levels of the anhydrite cores. These fractures seem to correspond to the radial cracks in model overburdens, and indicate a change in the mechanical behaviour of anhydrite.

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