Structural analysis of sheath folds with horizontal X-axes, northeast Canada

Abstract

Early Proterozoic supracrustal rocks occur below a thick nappe of Archaean basement gneiss in the Melville Peninsula where sheath folds are exposed in a wide zone of middle Proterozoic dynamothermal metamorphism. Outcrop patterns of truncated isoclinal sheath folds resemble cylindrical folds except in relatively small areas around the paraboloidal caps. Bulk extension axes are parallel to strike in the belt as shown by isoclinal sheath folds with horizontal central axes ( X-axes), as well as similarly aligned mullion structure and rotated scapolite prisms. Extension axes converge from northeast to southwest in the apparent flow direction.