1916] 



Dickcrson : Tejon Eocene of California 



455 



(Arnold) may be a derivative of Cardium cooper ii, as Arnold sug- 

 gested by its original name Cardium cooperii variety lorenzanum. 

 Aturia ziczac Sowerby which is reported from the San Lorenzo of 

 Santa Cruz County may be the same as Aturia mathewsonii Gabb. 

 Cedyptraea excentrica (Gabb) appears to be common to both the Tejon 

 and San Lorenzo. A species of Solen which occurs in the Agasoma 

 gravidum zone at Walnut Creek closely resembles Solen parcdlelus 

 Gabb if it is not identical with it. The cast of the San Lorenzo fauna 

 of California is eocenic but any very direct connection between this 

 Oligocene fauna and the Tejon Eocene has not been discovered. This 

 lack of close faunal relationship seems to indicate that a time-interval 

 of considerable duration may have occurred between the periods, or 

 that a fauna which developed elsewhere may have entered suddenly 

 upon the opening of a portal which had been closed during Tejon 

 time or that both conditions as stated above may have taken place. 

 The writer is inclined to believe that a time-interval represented by 

 unconformity will be found although the invasion of a foreign fauna 

 may be an element as well. 



SUMMARY OF STRATIGRAPHY 



Typical Tejon sections are given below and a series of columnar 

 sections in figure 10 accompany them. The zonal divisions indicated 

 are only approximate, as fossiliferous Tejon horizons are not present 

 with sufficient frequency to warrant great accuracy. The broken 

 connecting lines indicate in a diagrammatic fashion the writer's cor- 

 relations between the different sections in the state. The descriptions 

 of the sections are generalized in many cases. 



Of these sections, the one north of Coalinga is probably most com- 

 plete stratigraphically, but the one south of Mount Diablo exhibits the 

 best faunal succession on the whole, and hence zonal divisions are more 

 accurately placed. In no one place is there a section complete in all 

 respects. Thus at lone, Oroville and Marysville Buttes only the upper- 

 most phase, the Siphonalia sutterensis zone, is represented. At San 

 Diego and at Grapevine Creek, the type locality of the Tejon, only 

 the Rimella simplex zone is present. The upper Eocene in the Santa 

 Ana Mountains is probably but a residual of the same zone. Another 

 residual occurs in northern California near Lower Lake and it prob- 

 ably represents portions of the Rimella simplex and Balanophyllia 

 variabilis zones. 



