Cleavage in east‐central Vermont

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Abstract
Two types of cleavage, schistosity (flow cleavage) and slip cleavage, are common in the metamorphosed sediments of east‐central Vermont. Two generations of cleavage are also recognized. Cleavage of the earlier stage of deformation is schistosity, and is generally parallel to bedding. Just west of the Monroe Fault, along the eastern border of the area, only this earlier schistosity is present; farther west, a slip cleavage cuts the earlier schistosity. This slip cleavage is more and more intensely developed toward the west, and about three or four miles west of the Monroe Fault it grades without deflection into a true schistosity. This later schistosity apparently has obliterated the earlier schistosity that is presumed to have been present here. Both the later schistosity and its more easterly equivalent, the slip cleavage, are parallel to the axial planes of numerous minor folds in the rocks. The passage without deflection of slip cleavage into schistosity is taken as evidence that slip cleavage and schistosity are here mechanically equivalent. Schistosity forms in the higher metamorphic environment (staurolite zone of metamorphism in this area).

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