1919] Kew: Geology of a Part of the Santa Ynez Biver District 21 



The folding of the later period is shown in the main structure of 

 the mountains, namely, the Santa Ynez anticline. This deformative 

 movement has continued to comparatively recent times, for late 

 Pliocene strata of marine origin along the beach at Santa Barbara have 

 been tilted to an angle of forty-five degrees and raised considerably 

 above sea level. The axis of the fold extends approximately along the 

 crest of the range, but east of the San Marcos Pass it swings slightly 

 northward, and passing to the north of La Cumbre Peak is terminated 

 by the Santa Ynez fault. To the east of La Cumbre in this district the 

 north limb of the anticline has been faulted out, and the Miocene beds 

 have been let down against the Tejon along the axis of the fold. Near 

 San Marcos Pass, the fold is broad, the gently dipping massive sand- 

 stones forming the slopes of the mountain in this vicinity. Farther 

 to the east, the strata become tilted to a much greater angle, and east 

 of La Cumbre Peak the major part of the beds constituting the south 

 limb of the anticline is overturned. The foothills of the range are made 

 up of post-Eocene formations resting upon the Tejon. Arnold'- has 

 described the geology and structure of the mountains in the vicinity 

 of Summerland, which is similar to that in the western pai't of the 

 district. 



CONCLUSIONS 



Although the stratigraphy of the Santa Ynez district is similar to 

 that usually occurring througliout the California Coast Ranges, a few 

 observations of interest should be emphasized. (1) The Sespe forma- 

 tion and IMonterey group in the Santa Ynez district were laid down 

 without the interruption of deformative movements, during which time 

 the sea transgressed upon the land; (2) at least two periods of folding 

 and faulting have taken place since the Miocene : the first before the 

 deposition of the Fernando formation, the second after the Fernando 

 and probably continuing into Recent time; (3) the Santa Ynez Moun- 

 tains are genetically as well as geographically distinct from the San 

 Rafael Mountains, the former having been formed during the later 

 diastrophic movements (post-Pliocene), and the latter during the 

 earlier ones (pre-Pliocene) , in which the forces acted in a different 

 direction. 



Transmitted April S3, 1919. 



12 Arnold, Ralph, Geology and oil resources of the Summerland district, Cali- 

 fornia, U. S. Geol. Surv. Bull. 321. 



