GEOLOGIC RELATIONS OF THE MARTINEZ GROUP 769 
Lithologically there are some differences between the Mar- 
tinez and the adjoining formations, the most important of which 
are the slightly different aspect of its sandstones and the fre- 
quent presence in them of considerable quantities of glauconite. 
The sandstones are often grayish, differing from the yellowish 
or bluish rocks of the Chico and the massive white to dull red 
Tejon sandstones. In many places the Martinez contains large 
quantities of glauconite disseminated evenly through the sand- 
stones in rounded grains of considerable size. Glauconite does 
not seem to occur at all in the Chico but may possibly be found 
toward the base of the true Tejon. The truly glauconitic rocks 
belong principally to the Martinez. 
While the group shows little which would serve to separate 
it stratigraphically or lithologically from the over and under- 
lying formations, its fauna, on which Gabb based his classifica- 
tion, contains numerous elements throwing light on its geologic 
relations. Between the Chico-Cretaceous and the Miocene there 
are two distinct faunas present, viz., the Martinez (in part) and 
Tejon of Gabb, or the Lower and Upper Tejon of Mr. Stanton. 
As other criteria failed to separate satisfactorily the Chico, Mar- 
tinez, and Tejon, extensive fossil collections were made by the 
writer at all possible points. A series of rich localities running 
across the strike from the Chico to the Tejon furnished the 
sequence of faunas as shown in the table on pages 770 and 771. 
An examination of these lists shows that the lower Martinez 
beds, as stated by Mr. Stanton, have a fauna distinct from that 
of the Chico, and that, while the two sets of rocks may seem to 
be conformable, an unconformity, as yet unobserved, probably 
exists. “here are mo, Species “common to localities 1-and 2 
excepting Dentalium Coopert which ranges up into the Tejon and 
appears to be identical with a form occurring in the lowest Mio- 
cene. Other localities furnishing a few imperfect fossils are 
known in beds perhaps somewhat lower down than Locality No. 
2 but as yet no distinct overlapping of the two faunas has been 
discovered. 
Locality No. 3, higher up in the group, furnishes a fauna of 
