USGS Home
Contact USGS
Search USGS

Mineral Resources > Online Spatial Data > Geology > by state > California Geology

Geologic units in Ventura county, California

[Additional scientific data in this geographic area]

Miocene marine rocks (Oligocene to Pliocene) at surface, covers 14 % of this area

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

Lithology: sandstone; mudstone; siltstone; evaporite; conglomerate

Paleocene marine rocks, unit 1 (Central and Southern California) (Paleocene) at surface, covers 0.7 % of this area

Sandstone, shale, and conglomerate; mostly well consolidated

Lithology: sandstone; mudstone; conglomerate

Oligocene nonmarine rocks, unit 2 (Central and Southern California) (middle Eocene to early Miocene) at surface, covers 8 % of this area

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

Lithology: sandstone; conglomerate; mudstone; siltstone; sedimentary breccia; evaporite; limestone

Precambrian rocks, undivided, unit 2 (Mojave Desert and Transverse Ranges) (Early Proterozoic to Miocene) at surface, covers 5 % of this area

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

Lithology: gneiss; granitoid; amphibolite; quartzite; schist; hornfels; marble; granofels; granite; syenite; carbonatite; chert

Eocene marine rocks (Paleocene to Oligocene) at surface, covers 23 % of this area

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

Lithology: mudstone; sandstone; conglomerate; limestone; siltstone; sedimentary breccia

Tertiary intrusive rocks (hypabyssal), unit 5 (Southern California Basin) (Tertiary) at surface, covers < 0.1 % of this area

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

Lithology: basalt; andesite; dacite

Tertiary volcanic flow rocks, unit 13 (Plush Ranch-Vasquez-Diligencia) (Tertiary (19-23 Ma)) at surface, covers 0.2 % of this area

Tertiary volcanic flow rocks; minor pyroclastic deposits.

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

Quaternary alluvium and marine deposits (Pliocene to Holocene) at surface, covers 19 % 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)

Mesozoic granitic rocks, unit 3 (Sierra Nevada, Death Valley area, Northern Mojave Desert and Transverse Ranges) (Permian to Tertiary; most Mesozoic) at surface, covers 4 % 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

Tertiary nonmarine rocks, undivided (Paleocene to Pliocene) at surface, covers 3 % of this area

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

Lithology: conglomerate; sandstone; sedimentary breccia; volcanic rock (aphanitic); mudstone; limestone; siltstone

Tertiary volcanic flow rocks, unit 8 (Southern California Basin) (Tertiary (8-25 Ma; most near 15)) at surface, covers 3 % of this area

Tertiary volcanic flow rocks; minor pyroclastic deposits.

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

Plio-Pleistocene and Pliocene loosely consolidated deposits (Miocene to Pleistocene) at surface, covers 9 % 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

Pliocene marine rocks (Miocene to Pleistocene) at surface, covers 7 % of this area

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

Lithology: sandstone; mudstone; siltstone; claystone; conglomerate

Tertiary pyroclastic and volcanic mudflow deposits, unit 5 (Southern California Basin) (Tertiary (8-25 Ma)) at surface, covers 0.3 % of this area

Tertiary pyroclastic and volcanic mudflow deposits.

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

Upper Cretaceous marine rocks, unit 1 (Upper Great Valley Sequence) (Late Cretaceous) at surface, covers 2 % of this area

Upper Cretaceous sandstone, shale, and conglomerate

Lithology: sandstone; mudstone; conglomerate