Geologic units in Placer county, California

Tertiary pyroclastic and volcanic mudflow deposits, unit 9 (Cascade Range) (Tertiary (2-24 Ma)) at surface, covers 23 % of this area

Tertiary pyroclastic and volcanic mudflow deposits.

Lithology: andesite; rhyolite; basalt; tuff; ash-flow tuff; ignimbrite

Mesozoic granitic rocks, unit 3 (Sierra Nevada, Death Valley area, Northern Mojave Desert and Transverse Ranges) (Permian to Tertiary; most Mesozoic) at surface, covers 14 % of this area

Mesozoic granite, quartz monzonite, granodiorite, and quartz diorite

Lithology: granodiorite; quartz monzonite; tonalite; quartz diorite; diorite; granite; monzodiorite; quartz syenite; quartz monzodiorite; gabbro; trondhjemite; alkali-granite (alaskite); pegmatite; monzonite; aplite

Plio-Pleistocene and Pliocene loosely consolidated deposits (Miocene to Pleistocene) at surface, covers 12 % of this area

Pliocene and/or Pleistocene sandstone, shale, and gravel deposits; in part Miocene.

Lithology: sandstone; conglomerate; claystone; shale; siltstone; limestone; evaporite; coal; sedimentary breccia

Mesozoic volcanic rocks, unit 2 (Western Sierra Foothills and Western Klamath Mountains) (Jurassic) at surface, covers 9 % of this area

Undivided Mesozoic volcanic and metavolcanic rocks. Andesite and rhyolite flow rocks, greenstone, volcanic breccia and other pyroclastic rocks; in part strongly metamorphosed. Includes volcanic rocks of Franciscan Complex: basaltic pillow lava, diabase, greenstone, and minor pyroclastic rocks

Lithology: mafic volcanic rock; intermediate volcanic rock; felsic volcanic rock; chert; sandstone; conglomerate

Quaternary alluvium and marine deposits (Pliocene to Holocene) at surface, covers 8 % of this area

Alluvium, lake, playa, and terrace deposits; unconsolidated and semi-consolidated. Mostly nonmarine, but includes marine deposits near the coast.

Lithology: alluvium; terrace; lake or marine deposit (non-glacial)

Tertiary volcanic flow rocks, unit 17 (Cascade Range) (Tertiary (2-24 Ma)) at surface, covers 7 % of this area

Tertiary volcanic flow rocks; minor pyroclastic deposits.

Lithology: andesite; basalt; rhyolite; dacite; volcanic breccia (agglomerate)

Jurassic marine rocks, unit 5 (Northern Sierra Nevada and Eastern Klamath Mountains) (Devonian to Late Jurassic) at surface, covers 5 % of this area

Shale, sandstone, minor conglomerate, chert, slate, limestone; minor pyroclastic rocks

Lithology: slate; sandstone; argillite; mudstone; conglomerate; limestone; quartzite; chert; pyroclastic; andesite; intrusive rock

Quaternary volcanic flow rocks, unit 1 (Cascade Volcanic Field) (Quaternary) at surface, covers 3 % of this area

Quaternary volcanic flow rocks; minor pyroclastic deposits; in part Pliocene and Miocene.

Lithology: andesite; basalt; rhyolite; dacite; volcanic breccia (agglomerate)

Undivided pre-Cenozoic metavolcanic rocks, unit 2 (undivided) (Paleozoic(?) to Mesozoic(?)) at surface, covers 2 % of this area

Undivided pre-Cenozoic metavolcanic rocks. Includes latite, dacite, tuff, and greenstone; commonly schistose.

Lithology: intermediate volcanic rock; mafic volcanic rock; felsic volcanic rock; greenstone; amphibolite; gabbro

Ultramafic rocks, chiefly Mesozoic, unit 2 (Western Sierra Nevada and Klamath Mountains) (Late Proterozoic(?) to Early Jurassic) at surface, covers 2 % of this area

Ultramafic rocks, mostly serpentine. Minor peridotite, gabbro, and diabase. Chiefly Mesozoic unit 2

Lithology: peridotite; serpentinite; pyroxenite

Mesozoic volcanic rocks, unit 5 (Northern Sierra Nevada and Eastern Klamath Mountains) (Late Permian(?) to Jurassic) at surface, covers 2 % of this area

Lithology: intermediate volcanic rock; felsic volcanic rock; clastic

pre-Cenozoic metasedimentary and metavolcanic rocks undivided (Early Proterozoic to Cretaceous) at surface, covers 2 % of this area

Undivided pre-Cenozoic metasedimentary and metavolcanic rocks of great variety. Mostly slate, quartzite, hornfels, chert, phyllite, mylonite, schist, gneiss, and minor marble.

Lithology: schist; gneiss; quartzite; argillite; phyllite; metavolcanic rock; slate; hornfels; marble; chert; sandstone; mudstone; conglomerate

Quaternary glacial deposits (Pleistocene) at surface, covers 1 % of this area

Glacial till and moraines. Found at high elevations mostly in the Sierra Nevada and Klamath Mountains.

Lithology: glacial drift

Eocene nonmarine rocks, unit 1 (Northern and Central California) (Eocene) at surface, covers 0.7 % of this area

Sandstone, shale, and conglomerate.

Lithology: sandstone; mudstone; conglomerate; siltstone; coal

Mesozoic gabbroic rocks, unit 2 (undivided) (Triassic to Cretaceous) at surface, covers 0.6 % of this area

Gabbro and dark dioritic rocks; chiefly Mesozoic

Lithology: gabbro; diorite

Paleozoic marine rocks, undivided, unit 4 (Western Sierra Nevada) (Ordovician to Triassic) at surface, covers 0.4 % of this area

Undivided Paleozoic metasedimentary rocks. Includes slate, sandstone, shale, chert, conglomerate, limestone, dolomite, marble, phyllite, schist, hornfels, and quartzite

Lithology: argillite; quartzite; phyllite; schist; marble; mudstone; sandstone; conglomerate; sedimentary breccia; limestone; chert; basalt

Jurassic marine rocks, unit 1 (Western Sierra Nevada and Western Klamath Mountains) (Triassic to Late Jurassic) at surface, covers 0.4 % of this area

Shale, sandstone, minor conglomerate, chert, slate, limestone; minor pyroclastic rocks

Lithology: slate; graywacke; siltstone; pyroclastic; conglomerate; chert; basalt

Paleozoic marine rocks, undivided, unit 6 (Northwestern Sierra Nevada) (Permian(?) to Jurassic(?)) at surface, covers 0.2 % of this area

Undivided Paleozoic metasedimentary rocks. Includes slate, sandstone, shale, chert, conglomerate, limestone, dolomite, marble, phyllite, schist, hornfels, and quartzite

Lithology: argillite; phyllite; slate; chert; marble; greenstone; sandstone

Miocene nonmarine rocks (Oligocene to Pleistocene) at surface, covers 0.2 % of this area

Sandstone, shale, conglomerate, and fanglomerate; in part Pliocene and Oligocene.

Lithology: sandstone; conglomerate; siltstone; mudstone; sedimentary breccia; limestone; dolostone (dolomite); chert; felsic volcanic rock (aphanitic); basalt

Triassic marine rocks, unit 5 (Northern Sierra Nevada) (Middle to Late Triassic) at surface, covers < 0.1 % of this area

Shale, conglomerate, limestone and dolomite, sandstone, slate, hornfels, quartzite; minor pyroclastic rocks

Lithology: slate; limestone; conglomerate; andesite

Andesite and related rocks of intermediate composition (Late Miocene to Middle Miocene) at surface, covers < 0.1 % of this area

ANDESITE AND RELATED ROCKS OF INTERMEDIATE COMPOSITION-Flows and breccias

Lithology: andesite; latite; trachyte; dacite

Granitic rocks (Cretaceous) at surface, covers < 0.1 % of this area

GRANITIC ROCKS-Mostly quartz monzonite and granodiorite

Lithology: granodiorite; quartz monzonite; granite; peraluminous granite

Morainal deposits (Quaternary) at surface, covers < 0.1 % of this area

MORAINAL DEPOSITS

Lithology: glacial drift