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Geologic units in San Benito county, California

Additional scientific data in this geographic area

Plio-Pleistocene and Pliocene loosely consolidated deposits (Miocene to Pleistocene) at surface, covers 20 % of this area

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

Quaternary alluvium and marine deposits (Pliocene to Holocene) at surface, covers 20 % 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 12 % of this area

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

Upper Cretaceous marine rocks, unit 1 (Upper Great Valley Sequence) (Late Cretaceous) at surface, covers 8 % of this area

Upper Cretaceous sandstone, shale, and conglomerate

Eocene marine rocks (Paleocene to Oligocene) at surface, covers 7 % of this area

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

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

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

Tertiary volcanic flow rocks, unit 1 (Quien Sabe-Burdell Mountain) (Tertiary (9.5-13 Ma)) at surface, covers 5 % of this area

Tertiary volcanic flow rocks; minor pyroclastic deposits.

Ultramafic rocks, chiefly Mesozoic, unit 3 (Coast Ranges and Western Klamath Mountains) (Middle to Late Jurassic) at surface, covers 5 % of this area

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

Miocene nonmarine rocks (Oligocene to Pleistocene) at surface, covers 4 % of this area

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

Franciscan Complex, unit 1 (Coast Ranges) (Jurassic to Cretaceous) at surface, covers 3 % 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.

Lower Cretaceous marine rocks (Early Cretaceous) at surface, covers 2 % of this area

Lower Cretaceous sandstone, shale, and conglomerate

Tertiary volcanic flow rocks, unit 2 (Pinnacles-Neenach) (Tertiary (22-24 Ma)) at surface, covers 2 % of this area

Tertiary volcanic flow rocks; minor pyroclastic deposits.

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

Sandstone, shale, and conglomerate; mostly well consolidated

Oligocene marine rocks (Eocene to Miocene) at surface, covers 1.0 % of this area

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

Franciscan schist (Early Cretaceous) at surface, covers 0.9 % of this area

Blueschist and semi-schist of Franciscan complex

Mesozoic volcanic rocks, unit 1 (Coast Ranges) (Jurassic to Cretaceous) at surface, covers 0.7 % 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

Tertiary pyroclastic and volcanic mudflow deposits, unit 3 (Pinnacles-Neenach) (Tertiary (22-24 Ma)) at surface, covers 0.6 % of this area

Tertiary pyroclastic and volcanic mudflow deposits.

Mesozoic gabbroic rocks, unit 2 (undivided) (Triassic to Cretaceous) at surface, covers 0.4 % of this area

Gabbro and dark dioritic rocks; chiefly Mesozoic

Lithology: gabbro; diorite

Cretaceous marine rocks (in part nonmarine), unit 1 (Coast Ranges) (Early to Late Cretaceous) at surface, covers 0.2 % of this area

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

Tertiary intrusive rocks (hypabyssal), unit 3 (Pinnacles Volcanic Field) (Tertiary) at surface, covers 0.2 % of this area

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

Lithology: rhyolite

Tertiary intrusive rocks (hypabyssal), unit 2 (Quien Sabe Volcanic Field) (Tertiary) at surface, covers 0.2 % of this area

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

Lithology: dacite; andesite; basalt

pre-Cenozoic metasedimentary and metavolcanic rocks undivided (Early Proterozoic to Cretaceous) at surface, covers 0.2 % 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.

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

Mesozoic granitic rocks, unit 1 (Salinian Block) (Early to Late Cretaceous) at surface, covers < 0.1 % of this area

Mesozoic granite, quartz monzonite, granodiorite, and quartz diorite

Franciscan melange (Jurassic to Cretaceous) at surface, covers < 0.1 % of this area

Melange of fragmented and sheared Franciscan complex rocks.

Lithology: melange