The Nevadan orogeny occurred along the western margin of North America during the Late Jurassic to Early Cretaceous approximately 155 Ma to 145 Ma. It is noted that the Klamath Mountains and the Sierra Nevada share similar stratigraphy indicating that they were both formed by the Nevadan orogeny. In comparison with other orogenic events, it appears that the Nevadan Orogeny occurred rather quickly taking only about 10 million years as compared to hundreds of millions of years for other orogenies around the world (ex. Trans-Hudson orogeny).
Order of events
thumb|"Cordilleran" style of arc terrane accretion onto a continental land mass. Continued subduction transports the arc terrane to the margin of the continent where it is too buoyant to be subducted so it gets accreted to the continent.
The Nevadan Orogeny began with the formation of a continental volcanic arc due to east dipping subduction of the Farallon Plate beneath the North American Plate. The accretion of arc terranes resulted in the generation of three distinct belts in the Sierra Nevada: the Western belt, Central belt, and Eastern Belt. This melting may be assisted by the presence of water in what is known as flux melting. It was determined that the deformation was minimal in the Eastern Belt by looking at dikes that had intruded the rocks which appeared to be mostly undeformed.
The Calaveras-greenschist complex is located in the western half of the Central Belt and essentially consists of volcanic arc rocks along with small amounts of chert and argillite. In the southern part of the Western Belt the rocks have undergone folding as the main type of deformation. The age of these rocks was dated using K-Ar dating. These dikes are proposed to have been formed when the North American plate underwent a change in motion direction so that subduction was no longer occurring in a northeast direction but in the southeast direction. Once the Western Hayfork Terrane was formed (and had subsequently stopped forming) the region was intruded by mafic dikes attributed to some form of extension at approximately 160 Ma. Rather than being thrust on top of North America, the Josephine Ophiolite was accreted through a different process that involved being thrust underneath North America and then eventually being exhumed at the surface. Using the K-Ar method of isotopic dating on phyllite, the age of metamorphism in the Stuart Fork Formation was determined to be about 148 Ma.