USGS Home
Contact USGS
Search USGS

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

Geologic units in San Francisco county, California

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

Franciscan Complex, unit 1 (Coast Ranges) (Jurassic to Cretaceous) at surface, covers 19 % 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

Pliocene marine rocks (Miocene to Pleistocene) at surface, covers < 0.1 % of this area

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

Lithology: sandstone; mudstone; siltstone; claystone; conglomerate

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

Lithology: granodiorite; quartz monzonite; tonalite; quartz diorite; granite; alkali-granite (alaskite); gabbro

Quaternary alluvium and marine deposits (Pliocene to Holocene) at surface, covers 25 % 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)

Franciscan melange (Jurassic to Cretaceous) at surface, covers 0.3 % of this area

Melange of fragmented and sheared Franciscan complex rocks.

Lithology: melange

Quaternary sand deposits, unit 1 (coastal) (Quaternary) at surface, covers 39 % of this area

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

Lithology: dune sand; beach sand

Mesozoic volcanic rocks, unit 1 (Coast Ranges) (Jurassic to Cretaceous) at surface, covers 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 5 % of this area

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

Lithology: serpentinite; peridotite