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Geologic units in Marin county, California

Additional scientific data in this geographic area

Franciscan melange (Jurassic to Cretaceous) at surface, covers 40 % of this area

Melange of fragmented and sheared Franciscan complex rocks.

Lithology: melange

Franciscan Complex, unit 1 (Coast Ranges) (Jurassic to Cretaceous) at surface, covers 16 % of this area

Franciscan complex: Cretaceous and Jurassic sandstone with smaller amounts of shale, chert, limestone, and conglomerate. Includes Franciscan melange, except where separated--see KJfm.

Quaternary alluvium and marine deposits (Pliocene to Holocene) at surface, covers 9 % of this area

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

Miocene marine rocks (Oligocene to Pliocene) at surface, covers 8 % of this area

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

Pliocene marine rocks (Miocene to Pleistocene) at surface, covers 8 % of this area

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

Franciscan schist (Early Cretaceous) at surface, covers 5 % of this area

Blueschist and semi-schist of Franciscan complex

Mesozoic granitic rocks, unit 1 (Salinian Block) (Early to Late Cretaceous) at surface, covers 4 % of this area

Mesozoic granite, quartz monzonite, granodiorite, and quartz diorite

Mesozoic volcanic rocks, unit 1 (Coast Ranges) (Jurassic to 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

Ultramafic rocks, chiefly Mesozoic, unit 3 (Coast Ranges and Western Klamath Mountains) (Middle to Late Jurassic) at surface, covers 1 % of this area

Ultramafic rocks, mostly serpentine. Minor peridotite, gabbro, and diabase. Chiefly Mesozoic unit 3

Quaternary large landslide deposits (Quaternary) at surface, covers 1 % of this area

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

Lithology: landslide

Quaternary sand deposits, unit 1 (coastal) (Quaternary) at surface, covers 0.7 % of this area

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

Lithology: dune sand; beach sand

Tertiary volcanic flow rocks, unit 1 (Quien Sabe-Burdell Mountain) (Tertiary (9.5-13 Ma)) at surface, covers 0.7 % of this area

Tertiary volcanic flow rocks; minor pyroclastic deposits.

Upper Cretaceous marine rocks (?) (Cretaceous) at surface, covers 0.5 % of this area

Upper Cretaceous sandstone, shale, and conglomerate (?)

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