Multiple crenulation cleavages as kinematic and incremental strain indicators

Well-foliated metasedimentary rocks within strike-slip shear zones from the Narragansett Basin of Rhode Island are deformed by superposed crenulation cleavages. Overprinting relationships between cleavage generations is consistently clockwise or anti-clockwise in sinistral and dextral shear zones, respectively, indicating that the cleavages formed during progressive non-coaxial deformation. These shear zones have a nearly ideal geometry relative to the pre-existing foliation that allowed sequential formation and rotation of each crenulation generation. s paper, we explore the formation of these superposed crenulation cleavages and propose a method for measuring the incremental strains recorded by the cleavages. The effects of a variably oriented pre-existing foliation are considered and incorporated into the model. The superposed crenulation cleavages provide a new kinematic indicator for well-foliated rocks that records the deformation path and the associated incremental strains.