Sierra Nevada Batholith

The Sierra Nevada Batholith is a large batholith which forms the core of the Sierra Nevada mountain range in California, exposed at the surface as granite.[1]

Half Dome, Yosemite, a classic granite dome of the Sierra Nevada Batholith

The batholith is composed of many individual masses of rock called plutons, which formed deep underground during separate episodes of magma intrusion, millions of years before the Sierra itself first began to rise. The extremely hot, relatively buoyant plutons, also called plutonic diapirs, intruded through denser, native country rock and sediments, never reaching the surface. At the same time, some magma managed to reach the surface as volcanic lava flows, but most of it cooled and hardened below the surface and remained buried for millions of years.

The batholith – the combined mass of subsurface plutons – became exposed as tectonic forces initiated the formation of the Basin and Range geologic province, including the Sierra Nevada. As the mountains rose, the forces of erosion eventually wore down the material which had covered the batholith for millions of years. The exposed portions of the batholith became the granite peaks of the High Sierra, including Mount Whitney, Half Dome and El Capitan. Most of the batholith, however, remains below the surface.

Origins

The Sierra batholith was formed when the Farallon Plate subducted below the North American Plate. The resultant molten rock rose through the Earth's crust over the span of 100 Ma, forming several plutons, or a chain of volcanoes if the magma reached the surface. Most of the granitic rocks formed between 105 and 85 Ma, during the Cretaceous, with pluton formation ending around about 70 Ma. Erosion from 85 until 15 Ma removed the volcanic rocks and exposed the granitic core.[2][3][4]

See also

Reference
  1. Irwin, William; Wooden, Joseph (2001). "Map Showing Plutons and Accreted Terranes of the Sierra Nevada, California, With a Tabulation of U/Pb Isotopic Ages" (PDF). USGS. Retrieved 10 October 2021.
  2. "Geology of the Sierra Nevada". Yosemite Field Station. University of California, Merced. Retrieved 27 March 2022.
  3. Unger, Tanya. "Mesozoic Plutonism in the central Sierra Nevada Batholith: A review of works on mineralogy and isotopes in relation to models for batholith formation". Cooperative Institute for Research in Environmental Sciences at the University of Colorado Boulder. Retrieved 27 March 2022.
  4. Memeti, Vali; Paterson, Scott; Putirka, Keith, eds. (2014). Formation of the Sierra Nevada Batholith; Magmatic and Tectonic Processes and Their Tempos, Field Guide 34. Boulder: The Geological Society of America. ISBN 9780813700342.


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