752 INDEX TO THE STRATIGRAPHY OF NORTH AMERICA. 



however, shown the Eocene age of the Martinez and Tejon. Of the relationships existing 

 between these two and the Chico, or upper Cretaceous, Dr. Merriam has the following to say:" 



"The Martinez group, comprising in the typical locaHty between 1,000 and 2,000 feet of 

 sandstones, shales, and glauconitic sands, forms the lower part of a presumably conformable 

 series, the upper portion of which is formed by the Tejon. It contains a known fauna of over 

 sixty species, of which the greater portion is peculiar to itself. A number of its species range 

 up into the Tejon and a very few long-lived forms are known to occur also in the Chico. Since 

 the Martinez and Chico are faunaUy only distantly related it is probable that an unconformity 

 exists between them." 



Another fact showing the relations existing between the Eocene and the Cretaceous is 

 the occurrence in the Eocene beds in the Roseburg region, Oregon, of oysters so similar in 

 appearance to the characteristic Cretaceous fossil, Gryphsea, that without their accompanying 

 Eocene fauna these oysters would certainly be mistaken for Cretaceous forms. 



********* 



Rocks of marine origin and Eocene age are found at many localities throughout Washing- 

 ton and Oregon west of the Cascade Range and over considerable areas of the Coast Ranges 

 in central and southern California. Although Eocene rocks probably once fringed the greater 

 part of the western base of the Sierra Nevada, they are now all removed by erosion or covered 

 by later formations except at one locality near Merced Falls. For the most part the Eocene 

 rocks of the Pacific coast are either sandstone or shale. Conglomerate is found at the base 

 of the formation throughout southeastern Oregon, north of San Diego, and at a few locahties 

 along the northeastern flanks of the Coast Range; and at Port Crescent, Wash., Eocene fossils 

 are associated with tuff, but these occurrences are exceptional. Also, diatomaceous shales 

 occur at the top of the Eocene series in the vicinity of Coalinga, Cal., where they are beheved 

 to be the source of important deposits of petroleum. Coal and other indications of shallow 

 and brackish water conditions are found over much of Washington and Oregon and California, 

 usually overlying marine Eocene beds. The maximum thickness of the Eocene sediments 

 varies from 8,500 feet east of the Cascades, ^ 10,000 to 12,000 feet in western Oregon, " to 9,000 ± 

 feet in southern California. "^ 



The Tejon is the prevaiUng marine Eocene formation of CaUfornia. Notes on 

 its general relations and the extent of its occm-rence have already heen quoted 

 from Arnold. Stanton "^ discussed the stratigraphic and faunal relations with 

 the Chico and concluded that the Tejon and Chico are distinct. Gabb ^'^ had 

 described the Tejon as Cretaceous, whereas Cooper "° and White **" had regarded 

 it as a transition from Cretaceous to Eocene. 



Arnold ^^ has recently published the following classification and description of 

 the rocks in the Santa Maria district : 



a Jour. Geology, vol. 5, 1897, p. 775. 



b Smith, G. O., Mount Stuart folio. 



<: Diller, J. S., Roseburg, Cooa Bay, and Port Orford folios. 



■i Arnold, Ralph, Bull. U. S. Geol. Survey No. 321, p. 21. 



