1914 | 



Dickerson : Eocene of the Santa Ana Mountains 



267 



That a great erosion interval occurred between the deposition of 

 the Martinez and the overlying Tejon is strongly suggested by the 

 areal distribution of these two groups and their relation to the 

 underlying Chico. The small area of Tejon at the mouth of Sierra 

 Canon lies only a mile from both of the Martinez exposures. (See 

 plate 26.) These two areas of Martinez were once connected and, in 

 all probability, extended across the present site of the small Tejon area 

 mentioned above. The Tejon sandstone at this place rests upon Chico. 

 the Martinez evidently having been removed during a period of emerg- 

 ence before the deposition of the Tejon. The small area of Tejon in 

 Sierra Canon has a westerly dip of about five degrees, while the under- 

 lying Chico dips twenty degrees to the northeast. This Chico sand- 

 stone is the lower member of a local anticline whose north-south axis 

 is a quarter of a mile west of the contact described above. This anti- 

 cline appears to have been the locus of more than one movement. One 

 of these movements was in pre-Martinez time, as is shown by the uncon- 

 formable relations described above, and another period of folding 

 appears to have taken place between the deposition of the Martinez 

 and the Tejon. The basis for this statement is derived from a study 

 of the relations between the Martinez two and one-half miles north 

 of Santiago Coal Mine and the Chico in contact with it. The Martinez 

 in this vicinity appears to have been preserved by this folding. This 

 period of folding is further shown by the finding of a very small area 

 of Martinez in a slight fold of Chico very near the crest of the range 

 on a ridge between two small branches of Sierra Canon. The Tejon 

 of Sierra Canon evidently did not partake in this last folding, as its 

 westerly dip shows. The areal distribution of the two groups of the 

 Eocene and their structural relations show that a period of erosion 

 must have occurred between the deposition of the Martinez and the 

 Tejon. 



LOWEK MIOCENE 



Mr. J. P. Buwalda describes the distribution and stratigraphy of 



the Vaqueros as follows : 



The Vaqueros formation, of lower Miocene age, was found in contact with the 

 Tejon at the locality one mile and a half west of Santiago Coal Mine. The 

 lowermost Miocene overlaps the Tejon at its eastern end and rests directly 

 upon the Chico. No clear contact was found at this locality, but the area' 

 distribution of the Vaqueros in this area and in the upper portion of Santiago 

 Creek can be explained only upon the basis of an unconformity between the 

 two groups. In the upper portion of Santiago Creek, the Vaqueros rests 

 unconformable' upon the Chico, the Martinez and Tejon being absent. In 



