The area includes fragments of an ancient island arc scraped off of a subducting plate in the Mesozoic and later affected by the much more recent tilting up of the Sierra Nevada batholith and igneous intrusions. It also contains ancient sea floor and mantle hundreds of millions of years old.
The area consists of remnants from an ancient island arc stripped away by a subducting plate during the Mesozoic era, followed by more recent tilting and igneous activity in the Sierra Nevada batholith. It also includes old sea floor and mantle that are hundreds of millions of years old.