Marine fossils were recently discovered east of Marysville, California, by Theo Crook, in a conglomerate resting on the bedrock of the lower western slopes of the Sierra Nevada. Crook kindly turned over his collections to the University of California and suggested that the writers make a more complete examination. Additional fossils have been collected and the local stratigraphy has been studied, resulting in the recognition of a new formation, herein called the Wheatland formation. On the basis of the fauna, the formation is correlated with the lower portion of the Gaviota formation of the Santa Ynez mountains, California, and with the Gries Ranch beds of southwestern Washington. These are tentatively considered of Upper Eocene age, but they may be Lower Oligocene.
This formation is of importance for two reasons: (1) it is the first record of a marine invasion in this area in Upper Eocene or possibly . . .