Geologic units in Riverside county, California

Quaternary alluvium and marine deposits (Pleistocene to Holocene) at surface, covers 33 % of this area

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

Older Quaternary alluvium and marine deposits (Pleistocene) at surface, covers 14 % of this area

Older alluvium, lake, playa, and terrace deposits.

Mesozoic granitic rocks, unit 2 (Peninsular Ranges) (Middle Jurassic to Late Cretaceous) at surface, covers 13 % of this area

Mesozoic granite, quartz monzonite, granodiorite, and quartz diorite

Mesozoic granitic rocks, unit 3 (Sierra Nevada, Death Valley area, Northern Mojave Desert and Transverse Ranges) (Permian to Tertiary; most Mesozoic) at surface, covers 7 % of this area

Mesozoic granite, quartz monzonite, granodiorite, and quartz diorite

Precambrian igneous and metamorphic rock complex (Early Proterozoic to Miocene) at surface, covers 5 % of this area

Complex of Precambrian igneous and metamorphic rocks. Mostly gneiss and schist intruded by igneous rocks; may be Mesozoic in part.

Precambrian rocks, undivided, unit 2 (Mojave Desert and Transverse Ranges) (Early Proterozoic to Miocene) at surface, covers 4 % of this area

Conglomerate, shale, sandstone, limestone, dolomite, marble, gneiss, hornfels, and quartzite; may be Paleozoic in part

Plio-Pleistocene and Pliocene loosely consolidated deposits (Miocene to Pleistocene) at surface, covers 4 % of this area

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

Quaternary sand deposits, unit 2 (inland) (Quaternary) at surface, covers 4 % of this area

Extensive marine and nonmarine sand deposits, generally near the coast or desert playas

pre-Cenozoic granitic and metamorphic rocks undivided (Early Proterozoic to Late Cretaceous) at surface, covers 3 % of this area

Granitic and metamorphic rocks, mostly gneiss and other metamorphic rocks injected by granitic rocks. Mesozoic to Precambrian.

pre-Cenozoic metasedimentary and metavolcanic rocks undivided (Early Proterozoic to Cretaceous) at surface, covers 3 % 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.

Jurassic marine rocks, unit 4 (Peninsular Ranges and Western Transverse Ranges) (Paleozoic(?) to Late Jurassic) at surface, covers 2 % of this area

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

Undated granitic rocks, unit 3 (Southern California) (Jurassic(?) to Cretaceous(?)) at surface, covers 1 % of this area

Undated granitic rocks, unit 3 (Southern California)

Precambrian granitic rocks, unit 1, (Eastern Mojave Desert) (Early Proterozoic to Miocene) at surface, covers 1 % of this area

Precambrian granite, syenite, anorthosite, and gabbroic rocks in the San Gabriel Mountains; also various Precambrian plutonic rocks elsewhere in southeastern California

Cretaceous marine rocks (in part nonmarine) (?), unit 1 (Blythe) (Middle Jurassic(?) to Late Cretaceous) at surface, covers 1 % of this area

Undivided Cretaceous sandstone, shale, and conglomerate; minor nonmarine rocks in Peninsular Ranges (?)

Mesozoic gabbroic rocks, unit 2 (undivided) (Triassic to Cretaceous) at surface, covers 0.8 % of this area

Gabbro and dark dioritic rocks; chiefly Mesozoic

Mesozoic volcanic rocks, unit 4 (Peninsular Ranges) (Late Jurassic to Early Cretaceous) at surface, covers 0.6 % 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.

Paleozoic marine rocks, undivided, unit 1 (Mojave Desert and Death Valley area) (Late Proterozoic to Jurassic) at surface, covers 0.5 % of this area

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

Schist of various types and ages, unit 2 (Southern and West-central California) (Late Cretaceous to Eocene) at surface, covers 0.5 % of this area

Schists of various types; mostly Paleozoic or Mesozoic age; some Precambrian.

Tertiary volcanic flow rocks, unit 15 (Southern Mojave Desert) (Tertiary (8-28 Ma)) at surface, covers 0.5 % of this area

Tertiary volcanic flow rocks; minor pyroclastic deposits.

Oligocene nonmarine rocks, unit 2 (Central and Southern California) (middle Eocene to early Miocene) at surface, covers 0.4 % of this area

Sandstone, shale, and conglomerate; in part Miocene and Eocene.

Undated granitic rocks, unit 1 (Chocolate Mountains) (Oligocene to Miocene) at surface, covers 0.3 % of this area

Undated granitic rocks, unit 1 (Chocolate Mountains)

Mesozoic volcanic rocks, unit 3 (Mojave Desert, Death Valley area, and Eastern Sierra Nevada) (Triassic to Cretaceous) at surface, covers 0.2 % of this area

Paleocene marine rocks, unit 1 (Central and Southern California) (Paleocene) at surface, covers 0.1 % of this area

Sandstone, shale, and conglomerate; mostly well consolidated

Tertiary intrusive rocks (hypabyssal), unit 6 (Southern Mojave Desert) (Tertiary) at surface, covers 0.1 % of this area

Tertiary intrusive rocks; mostly shallow (hypabyssal) plugs and dikes. Includes some Mesozoic rocks.

Miocene nonmarine rocks (Oligocene to Pleistocene) at surface, covers 0.1 % of this area

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

Quaternary volcanic flow rocks, unit 7 (Mojave Desert) (Quaternary) at surface, covers < 0.1 % of this area

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

Eocene marine rocks (Paleocene to Oligocene) at surface, covers < 0.1 % of this area

Shale, sandstone, conglomerate, and minor limestone; in part Oligocene and Paleocene.

Tertiary pyroclastic and volcanic mudflow deposits, unit 7 (Southern Mojave Desert) (Tertiary (8-28 Ma)) at surface, covers < 0.1 % of this area

Tertiary pyroclastic and volcanic mudflow deposits.

Tertiary nonmarine rocks, undivided (Paleocene to Pliocene) at surface, covers < 0.1 % of this area

Undivided Tertiary sandstone, shale, conglomerate, breccia, and ancient lake deposits.

Holocene river alluvium (Holocene) at surface, covers < 0.1 % of this area

Unconsolidated to weakly consolidated sand and gravel in river channels and sand, silt, and clay on floodplains. Also includes young terrace deposits fringing floodplains. (0-10 ka)

Quaternary volcanic flow rocks, unit 8 (Peninsular Ranges) (Quaternary) at surface, covers < 0.1 % of this area

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

Limestone of probable Paleozoic or Mesozoic age (Paleozoic to Mesozoic) at surface, covers < 0.1 % of this area

Limestone, dolomite, and marble whose age is uncertain but probably Paleozoic or Mesozoic

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

Selected large landslides, such as Blackhawk slide on north side of San Gabriel Mountains; early to late Quaternary.

Cretaceous marine rocks (in part nonmarine), unit 1 (Coast Ranges) (Early to Late Cretaceous) at surface, covers < 0.1 % of this area

Undivided Cretaceous sandstone, shale, and conglomerate; minor nonmarine rocks in Peninsular Ranges

Upper Cretaceous marine rocks, unit 1 (Upper Great Valley Sequence) (Late Cretaceous) at surface, covers < 0.1 % of this area

Upper Cretaceous sandstone, shale, and conglomerate

Miocene marine rocks (Oligocene to Pliocene) at surface, covers < 0.1 % of this area

Sandstone, shale, siltstone, conglomerate and breccia; in part Pliocene and Oligocene.

Undivided pre-Cenozoic metavolcanic rocks, unit 2 (undivided) (Paleozoic(?) to Mesozoic(?)) at surface, covers < 0.1 % of this area

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

Pliocene marine rocks (Miocene to Pleistocene) at surface, covers < 0.1 % of this area

Sandstone, siltstone, shale, and conglomerate; in part Pleistocene and Miocene.

Tertiary volcanic flow rocks, unit 13 (Plush Ranch-Vasquez-Diligencia) (Tertiary (19-23 Ma)) at surface, covers < 0.1 % of this area

Tertiary volcanic flow rocks; minor pyroclastic deposits.

Tertiary volcanic flow rocks, unit 16 (Northern Mojave Desert) (Tertiary (4-22 Ma)) at surface, covers < 0.1 % of this area

Tertiary volcanic flow rocks; minor pyroclastic deposits.

Tertiary intrusive rocks (hypabyssal), unit 7 (Northern Mojave Desert) (Tertiary) at surface, covers < 0.1 % of this area

Tertiary intrusive rocks; mostly shallow (hypabyssal) plugs and dikes. Includes some Mesozoic rocks.