Kink-bands: Shock deformation of biotite resulting from a nuclear explosion

Microscopic examination of granodiorite samples from the shock region around a nuclear explosion reveals sharply folded lens-shaped zones (kink-bands) in the mineral biotite. Fifty percent of these zones are oriented approximately 90 degrees to the direction of shock-wave propagation, but other zones are symmetrically concentrated at shear angles of 50 degrees and 70 degrees to the direction of shock-wave propagation.