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Geologic units in Orange county, California

Additional scientific data in this geographic area

Miocene marine rocks (Oligocene to Pliocene) at surface, covers 40 % of this area

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

Upper Cretaceous marine rocks, unit 1 (Upper Great Valley Sequence) (Late Cretaceous) at surface, covers 13 % of this area

Upper Cretaceous sandstone, shale, and conglomerate

Oligocene nonmarine rocks, unit 2 (Central and Southern California) (middle Eocene to early Miocene) at surface, covers 12 % of this area

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

Eocene marine rocks (Paleocene to Oligocene) at surface, covers 8 % of this area

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

Quaternary alluvium and marine deposits (Pliocene to Holocene) at surface, covers 7 % of this area

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

Pliocene marine rocks (Miocene to Pleistocene) at surface, covers 5 % of this area

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

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

Mesozoic granitic rocks , unit 2 (Peninsular Ranges) (Middle Jurassic to Late Cretaceous) at surface, covers 3 % of this area

Mesozoic granite, quartz monzonite, granodiorite, and quartz diorite

Paleocene marine rocks, unit 1 (Central and Southern California) (Paleocene) at surface, covers 3 % of this area

Sandstone, shale, and conglomerate; mostly well consolidated

Jurassic marine rocks, unit 4 (Peninsular Ranges and Western Transverse Ranges) (Paleozoic(?) to Late Jurassic) at surface, covers 0.8 % of this area

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

Cretaceous marine rocks (in part nonmarine), unit 1 (Coast Ranges) (Early to Late Cretaceous) at surface, covers 0.7 % of this area

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

Tertiary volcanic flow rocks, unit 8 (Southern California Basin) (Tertiary (8-25 Ma; most near 15)) at surface, covers 0.5 % of this area

Tertiary volcanic flow rocks; minor pyroclastic deposits.

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