244 University of California Publications in Geology [Vol. 9 



rather to show the relations between the various formations consid- 

 ered. It is the opinion of the writer that the Purisima Formation is 

 the equivalent of a part of the Etchegoin and the lower portion of the 

 Merced Series at Seven Mile Beach. 



Etchegoin of the Saegent Oil Field 



Unconformably overlying the Monterey shales of the Sargent Oil 

 Field there is a formation composed of conglomerates, coarse and 

 fine-grained sandstones, and shales which was correlated by William 

 F. Jones with the San Pablo Formation of the Mount Diablo region. 

 The basis on which the correlation was made was the occurrence of 

 viviantitic sandstone. Jones separated this member into five lithologic 

 divisions ; A, the lowest member, consisted of conglomerate and 

 coarse brown sandstone ; B and C were composed of gradational series 

 of light azure blue sandstones, quite coarse at the base and grading 

 into shale at the top ; D consisted of fine and medium-grained sand- 

 stone ; E, the uppermost of the series, consisted of coarse and brown 

 sandstones. All of these members are conformable and belong to one 

 formation. The separation was doubtless made to bring out more 

 strongly the lithological variation within the formation. 



The territory covered by these beds comprises several small 

 areas a short distance west and northwest of Sargent Station. The 

 largest of these areas have been folded into an anticline and a syn- 

 eline. The axes of these folds extend from the southwest toward 

 the northeast. Both are parallel to La Brea Creek, one on either 

 side, the anticline on the north and the syncline on the south. These 

 beds grade upward into the Merced horizon which conformably 

 overlies them. 



Fauna. — The correlation of these beds with the San Pablo Forma- 

 tion was made by Jones upon a lithologic similarity, the occurrence 

 of the vivanitic sandstone. Recent collecting in this horizon lias 

 brought out some rather interesting faunal relations. The San 

 Pablo of this region has a very close faunal relationship to the 

 Etchegoin of the Coalinga district, very much closer than with the 

 San Pablo at the type locality. This is shown in two ways: (1) Of 

 the forty species obtained from the San Pablo in the Sargent Oil 

 Field nearly all occur in the Etchegoin while only sixteen occur in 

 the San Pablo near Mount Diablo, and these have a very wide 

 vertical and horizontal range; (2) The species that are most char- 



