16 University of California Publications in Geology [Vol. 12 



fact that they rest upon beds of upper Fernando age, suggests that 

 they may be correlated with the Paso Robles formation, which is well 

 developed in the Salinas Valley. Arnold^^ mentions similar land-laid 

 deposits from the Santa ]\Iaria district and says that they are probably 

 the equivalent of the Paso Robles formation. None of the beds in this 

 district are of Miocene age, and the faunal evidence indicates that 

 they are upper Pliocene and do not represent the lower Fernando 

 occurring in the Elsmere Canon section of the Santa Clara Valley. 



QUATERNARY SYSTEM 

 Terrace Deposits 

 At least six distinct deposits of terrace material are present along 

 the Santa Ynez River, the highest one being at an elevation of 1500 

 feet. Their extent is not large enough to show on the map and the 

 deposits forming any one terrace are never over 100 feet thick. They 

 are composed of unsorted material, usually unconsolidated, which has 

 been washed down from the higher areas at their rear. Where made 

 up of the diatomaceous sliale, the material is much finer than when 

 derived from the hard Tejon or Cretaceous rocks, and huge boulders 

 several feet in diameter are a common occurrence in the beds that 

 are well exposed in the vicinity of IMateo Potrero. 



STRUCTURE 

 GENERAL FEATURES 

 The structure of the California Coast Ranges is relatively complex, 

 but in general, the folding and faulting has a definite northwest trend 

 which is reflected topographically. In the Santa Ynez River district, 

 the San Rafael ^Mountains conform to this general habit, whereas the 

 Santa Ynez Mountains are anomalous in that their trend is almost 

 east-west. The general structure of the latter range is that of an 

 anticline, dislocated on the north side by the Santa Ynez fault, the 

 faulting having occurred in post-Fernando time. In the vicinity of 

 San Marcos Pass, the fold is comparatively simple, whereas on the 

 south side of the range, east of La Cumbre Peak, the strata are over- 

 turned to the south. Another set of folds within the range has 

 a northwest strike, and probably was formed prior to the general 

 anticlinal folding of the mountains but at the same time as the 



11 Arnold, Ralph, Geology and oil resources of the Santa Maria oil district, 

 Santa Barbara County, California, U. S. Geol. Surv. Bull. 322, p. 55, 1907. 



