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Pliocene marine fossils in the Paso Robles Formation, California

August 1, 1973

Marine invertebrates from the Paso Robles Formation recently discovered near Atascadero, Calif., indicate that the basal part of this chiefly nonmarine deposit is of provincial early Pliocene age. Heretofore the lack of direct fossil or radiometric evidence of the age of the Paso Robles has made it a difficult unit to place in the late Cenozoic history of the Coast Ranges. The assemblage is dominated by Ostrea vespertina and by Nettastomella rostrata, a rock-boring bivalve; its mode of preservation indicates that the fossils are in place and have
not been recycled from older marine formations. This occurrence suggests that during the early Pliocene a seaway connected the present
southern Salinas Valley area with the northern part of the Santa Maria basin; the fossils occur about halfway between the southernmost
exposures of the Pancho Rico Formation near San Miguel and fossiliferous strata east of Pismo Beach, both marine units of early Pliocene age.

Publication Year 1973
Title Pliocene marine fossils in the Paso Robles Formation, California
Authors Warren O. Addicott, Jon S. Galehouse
Publication Type Article
Publication Subtype Journal Article
Series Title Journal of Research of the U.S. Geological Survey
Index ID 70161865
Record Source USGS Publications Warehouse