Nevadan orogeny

[2] The latter stages of orogenesis, in contrast, saw multiple oceanic arc terranes accreted onto the western margin of North America in a "Cordilleran type" accretionary orogen.

[8] This is analogous to the "Andean" style of orogenesis where subduction of an oceanic plate to approximately 110 km beneath the surface of Earth results in melting of the down-going slab and convecting asthenosphere.

[10] These mostly undeformed dikes were dated using the K-Ar method and were determined to be between 169 and 209 Ma in age, which implies they were placed well before any deformation related to the Nevadan Orogeny would have occurred.

[2] 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.

[11] The Klamath Mountains tell a similar story to the Sierra Nevada in that they are the product of multiple different accretionary events of island arc terranes.

[12] Continued convergence in the Klamath Mountains region would eventually lead to the emplacement of dikes and sills within the Josephine Ophiolite at approximately 153 Ma.

[12] The youngest of the accretionary ophiolite sequence in the Klamath Mountains appears to be the Josephine Ophoilite, which is dated to be about 155 to 150 Ma in age using both argon-argon (Ar-Ar) and lead-uranium (Pb-U) methods.

[13] In the Klamath Mountains it has also been observed that there are two other plutons of rock that were accreted during the Nevadan Orogeny, the Abrams and Salmon mica schists of the Stuart Fork Formation.

[3] Using the potassium-argon (K-Ar) method of isotopic dating on phyllite, the age of metamorphism in the Stuart Fork Formation was determined to be about 148 Ma.

[8][12] As the Nevadan Orogeny progressed, the Tuolumne River Terrane was accreted to the Sierra Nevada at approximately the same time as the formation of the Josephine Ophiolite in the Klamath Mountains (150-155 Ma).

[12][2] During the last stages of orogenesis, the sedimentary rocks of the Western Belt were accreted to the Sierra Nevada while the Abrams and Salmon mica schists were thrust on top of the Stuart Fork Formation in the Klamath Mountains.