The Jurassic in Washington, US

Paleontology and geology

The rocks of the Nooksack exotic terrane include exposures of fossiliferous, Jurassic sedimentary rocks on the west side of Mt. Baker. This thick sequence of marine sandstones and dark shales lies over volcanic rocks that were formed in an island arc. The sedimentary rocks were deposited in deep water on the flanks of these volcanic islands. Fossils of clams, snails and ammonites can be found in the black shales.