Roadside Geology of Yosemite Valley
This map was scanned from the Geologic Map of Yosemite National Park and Vicinity, California, U.S. Geologic Survey Miscellaneous Investigations Series Map I-1874 by N. King Huber, Paul C. Bateman, and Clyde Wahrhaftig, published in 1989. The entire map is available from the U.S. Geological Survey: http://mapping.usgs.gov/esic/to_order.html#map
For a general explanation of plutonic rocks, click here.
Explanation of Symbols:
Qal: Quaternary Alluvium
Includes stream deposits, meadow deposits, and glacial outwash (Quaternary)
Qtl: Talus (Holocene)
Rock waste derived from cliffs. Only especially extensive areas shown
Qti: Tioga Till
Moraines usually sharp crested with abundant boulders at surface (Pleistocene)
Qta: Tahoe Till
Moraines usually crested, but subdued, with scattered, weathered boulders at surface.
Qpt: Pre-Tahoe Till
Moraines hummocky and dissected. May include Sherwin tills (Pleistocene).
Medium grained biotite hornblende granodiorite with conspicuous crystals of sphene. Locally porphyritic with abundant large phenocrysts of potassium feldspar. Age 86-88 Ma
Kkc: Granodiorite of Kuna Crest
Dark-colored, fine- to medium-grained, biotite-hornblende granodiorite. Age 88 Ma
Ks: Sentinel Granodiorite
Coarse-grained, dark-gray, biotite-hornblende granodiorite with abundant sphene. Age 93 Ma
Kbv: Bridalveil Granodiorite
Fine-grained hornblende-biotite granodiorite and granite.
Kic: Granodiorite of Illilouette Creek
Medium- to coarse-grained mafic hornblende-biotite granodiorite, tonalite and granite. Age about 100 Ma
Kid: Quartz diorite
Dark fine-grained rock rich in hornblende. Occurs as irregular intrusive masses cross-cutting El Capitan and Taft Granites on north side of Yosemite Valley.
Kt: Taft Granite
Fine- to coarse-grained white to gray biotite granite and biotite granodiorite. Locally porphyritic with phenocrysts of potassium feldspar. Age 96 Ma
Kec: El Capitan Granite
Coarse-grained, white to light-gray biotite granite and biotite granodiorite. Commonly porphyritic with blocky phenocrysts of potassium feldspar and conspicuous quartz grains. Age about 102 Ma
Kga: Tonalite of the Gateway
Also known as Bass Lake Tonalite. Medium-grained biotite-hornblende tonalite. Varies to granodiorite and quartz diorite. Age 114 Ma
Kar: Granodiorite of Arch Rock
Medium-grained, biotite granodiorite, commonly with poikilitic potassium feldspar. Age 116 Ma
KJdg: Diorite and gabbro
Occurs as generally small, irregularly shaped bodies throughout map area, including the Rockslides adjacent to El Capitan. Age Jurassic to Cretaceous
Jms: Metasedimentary rock
Hornfels and other metamorphic rocks. Jurassic (?)