Geologic units in Glenn county, California

Additional scientific data in this geographic area

Quaternary alluvium and marine deposits (Pleistocene to Holocene) at surface, covers 40 % of this area

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

Franciscan schist (Early Cretaceous) at surface, covers 13 % of this area

Blueschist and semi-schist of Franciscan complex

Lower Cretaceous marine rocks (Early Cretaceous) at surface, covers 9 % of this area

Lower Cretaceous sandstone, shale, and conglomerate

Plio-Pleistocene and Pliocene loosely consolidated deposits (Miocene to Pleistocene) at surface, covers 9 % of this area

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

Franciscan Complex, unit 1 (Coast Ranges) (Jurassic to Cretaceous) at surface, covers 7 % 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.

Jurassic marine rocks, unit 2 (Coast Ranges) (Late Jurassic to Early Cretaceous) at surface, covers 7 % of this area

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

Franciscan melange (Jurassic to Cretaceous) at surface, covers 3 % of this area

Melange of fragmented and sheared Franciscan complex rocks.

Ultramafic rocks, chiefly Mesozoic, unit 3 (Coast Ranges and Western Klamath Mountains) (Middle to Late Jurassic) at surface, covers 2 % of this area

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

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.

Older Quaternary alluvium and marine deposits (Pleistocene) at surface, covers 0.2 % of this area

Older alluvium, lake, playa, and terrace deposits.

Tertiary pyroclastic and volcanic mudflow deposits, unit 9 (Cascade Range) (Tertiary (2-24 Ma)) at surface, covers 0.2 % of this area

Tertiary pyroclastic and volcanic mudflow deposits.

Tertiary volcanic flow rocks, unit 19 (Lovejoy) (Tertiary (14-16 Ma)) at surface, covers 0.1 % of this area

Tertiary volcanic flow rocks; minor pyroclastic deposits.

Cretaceous marine rocks (in part nonmarine), unit 1 (Coast Ranges) (Early to Late Cretaceous) at surface, covers < 0.1 % of this area

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