Development of Cretaceous transpressional cleavage synchronous with batholith emplacement, Central Sierra Nevada, California

Metamorphosed strata of the Ritter Range pendant record structures formed during the emplacement of granitic plutons at upper crustal levels (40Ar/39 Ar plateau ages ranging from about 85 to 80 Ma. Hornblende, and possibly muscovite, are expected to retain 40Ar at or near estimated peak metamorphic temperatures of ~500 °C, thus their 40Ar/39Ar ages closely correspond to the time of cleavage formation. Granitic plutons adjacent to the Ritter Range pendant have yielded U-Pb and other ages that cluster from 91 to 82 Ma. We conclude that bedding-inclined cleavage and metamorphism in the Ritter Range wall rocks developed in a dextral transpressive strain regime penecontemporaneously with emplacement of adjacent granitic plutons.