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

Geologic units in Trinity county, California

Mesozoic gabbroic rocks, unit 1 (Trinity Ophiolite) (Ordovician) at surface, covers 2 % of this area

Gabbro and dark dioritic rocks; chiefly Mesozoic

Lithology: gabbro; diorite

Paleozoic marine rocks, undivided, unit 7 (Southeastern Klamath Mountains) (Devonian(?)) at surface, covers 0.2 % of this area

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

Lithology: gneiss; amphibolite

Schist of various types and ages, unit 7 (Klamath Mountains) (Devonian) at surface, covers 9 % of this area

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

Lithology: schist; amphibolite; marble

Quaternary glacial deposits (Pleistocene) at surface, covers 1 % of this area

Glacial till and moraines. Found at high elevations mostly in the Sierra Nevada and Klamath Mountains.

Lithology: glacial drift

Lower Cretaceous marine rocks (Early Cretaceous) at surface, covers 0.2 % of this area

Lower Cretaceous sandstone, shale, and conglomerate

Lithology: mudstone; sandstone; conglomerate

Paleozoic marine rocks, undivided, unit 9 (Western Klamath Mountains) (Devonian to Jurassic) at surface, covers 27 % of this area

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

Lithology: argillite; chert; quartzite; phyllite; schist; sandstone; mudstone; conglomerate; limestone; marble; volcanic rock (aphanitic); amphibolite; melange

Lower Cretaceous marine rocks (?) (Cretaceous (?)) at surface, covers < 0.1 % of this area

Lower Cretaceous sandstone, shale, and conglomerate (?)

Lithology: conglomerate; sandstone; mudstone

Ultramafic rocks, chiefly Mesozoic, unit 2 (Western Sierra Nevada and Klamath Mountains) (Late Proterozoic(?) to Early Jurassic) at surface, covers 2 % of this area

Ultramafic rocks, mostly serpentine. Minor peridotite, gabbro, and diabase. Chiefly Mesozoic unit 2

Lithology: peridotite; serpentinite; pyroxenite

Mesozoic gabbroic rocks, unit 2 (undivided) (Triassic to Cretaceous) at surface, covers 0.6 % of this area

Gabbro and dark dioritic rocks; chiefly Mesozoic

Lithology: gabbro; diorite

Franciscan Complex, unit 1 (Coast Ranges) (Jurassic to Cretaceous) at surface, covers 21 % 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.

Lithology: sandstone; mudstone; chert; limestone; conglomerate; greenstone; serpentinite; gabbro; amphibolite; schist; felsic volcanic rock

Carboniferous marine rocks, unit 4 (Eastern Klamath Mountains) (Mississippian to Early Permian) at surface, covers 5 % of this area

Shale, sandstone, conglomerate, limestone, dolomite, chert, hornfels, marble, quartzite; in part pyroclastic rocks

Lithology: mudstone; pyroclastic; conglomerate; sandstone; limestone; greenstone

Paleozoic metavolcanic rocks, unit 1 (Eastern Klamath Mountains) (Devonian and Permian) at surface, covers 0.9 % of this area

Undivided Paleozoic metavolcanic rocks. Mostly flows, breccia and tuff, including greenstone, diabase, and pillow lavas; minor interbedded sedimentary rocks

Lithology: intermediate volcanic rock; mafic volcanic rock; felsic volcanic rock; mudstone; sandstone; conglomerate

Undated granitic rocks, unit 2 (Western Klamath Mountains) (Late Triassic to Early Jurassic) at surface, covers 0.3 % of this area

Undated granitic rocks unit 2

Lithology: plutonic rock (phaneritic)

Mesozoic volcanic rocks, unit 1 (Coast Ranges) (Jurassic to Cretaceous) at surface, covers 0.2 % 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

Lithology: greenstone; basalt; diabase; blueschist; chert; felsic volcanic rock

Ultramafic rocks, chiefly Mesozoic, unit 3 (Coast Ranges and Western Klamath Mountains) (Middle to Late Jurassic) at surface, covers 0.3 % of this area

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

Lithology: serpentinite; peridotite

Oigocene nonmarine rocks (?), unit 1 (Klamath Mountains) (Oligocene(?) to Pleistocene(?)) at surface, covers < 0.1 % of this area

Lithology: sand; gravel

Oligocene nonmarine rocks, unit 1 (Northern California) (Oligocene to Miocene) at surface, covers 2 % of this area

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

Lithology: sandstone; conglomerate; mudstone; coal; pyroclastic

Mesozoic granitic rocks, unit 5 (Klamath Mountains) (Jurassic to early Cretaceous) at surface, covers 10 % of this area

Mesozoic granite, quartz monzonite, granodiorite, and quartz diorite

Lithology: diorite; quartz diorite; granite; tonalite; granodiorite; monzodiorite; gabbro; pyroxenite; trondhjemite; pegmatite; aplite

Ultramafic rocks, chiefly Mesozoic, unit 1 (Trinity Ophiolite) (Ordovician) at surface, covers 8 % of this area

Ultramafic rocks, mostly serpentine. Minor peridotite, gabbro, and diabase. Chiefly Mesozoic unit 1

Lithology: peridotite; pyroxenite; serpentinite

pre-Cenozoic metasedimentary and metavolcanic rocks undivided (Early Proterozoic to Cretaceous) at surface, covers 0.1 % 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.

Lithology: schist; gneiss; quartzite; argillite; phyllite; metavolcanic rock; slate; hornfels; marble; chert; sandstone; mudstone; conglomerate

Franciscan schist (Early Cretaceous) at surface, covers 4 % of this area

Blueschist and semi-schist of Franciscan complex

Lithology: blueschist; metasedimentary rock; metavolcanic rock

Jurassic marine rocks, unit 1 (Western Sierra Nevada and Western Klamath Mountains) (Triassic to Late Jurassic) at surface, covers 3 % of this area

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

Lithology: slate; graywacke; siltstone; pyroclastic; conglomerate; chert; basalt

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

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

Lithology: intermediate volcanic rock; mafic volcanic rock; felsic volcanic rock; greenstone; amphibolite; gabbro

Quaternary alluvium and marine deposits (Pliocene to Holocene) at surface, covers 0.3 % 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)