18 University of California Publications in Geology [Vol. 12 



Santa Ynez River the fold is evit by a cross fault, beyond which it is 

 materially narrowed, though the syncline can be traced considerably 

 farther to the east. The other syncline forms the top of Little Pine 

 Mountain. It is quite shallow, as the Salinas shale lies nearly flat 

 at the summit. The northward extent of these rocks has not been 

 traced. The most important structure related to this area is the Little 

 Pine fault, which limits it on the south. The fault is remarkably 

 straight and topography characteristic of faulting is common along it. 

 Tlie trace of the fault is usually distinct as it separates the soft Tejon 

 shales from the Franciscan in some places, and in others, the Knox- 

 ville sliales from the IMonterey group, being thus a noticeable feature 

 in the topography of the country. The altered serpentine in which 

 the cinnabar occurs is present only on this fault zone. The rock is 

 somewhat harder than the adjacent strata, and it weathers into a 

 rather prominent "reef" along the fault. The dip of the fault plane 

 is nearly vertical, though a dip of eighty degrees to the south was 

 noticed in a few places. A minor cross fault dislocates this main 

 fracture in the caiaon north of the big bend in the Santa Ynez River. 

 To the west of Redrock Creek, the fault is overlapped by the Fer- 

 nando strata, thus placing its age as pre-Fernando. In its eastward 

 extension, it is cut off by a cross fault at the mouth of Blue Canon. 

 At this point it is quite close to the Santa Ynez fault, the two being 

 about a mile apart. This indicates that structural lines of both the 

 San Rafael and Sana Ynez mountains ai'e convergent in this region. 



Santa Ynez River Area 

 The most highly folded Tertiary strata in this district lie within 

 the belt of formations that trends in a northwest direction along the 

 course of the Santa Ynez River. It is about a mile wide at its eastern 

 end. where it is cut off' by a cross fault near the mouth of Blue 

 Caiion; to the west it broadens until, at Loma Alta, the width is 

 somewhat more than five miles. Complicated folding and faulting 

 are a characteristic of the area. The most interesting piece of struc- 

 ture is that of Loma Alta and the adjacent region to the east, includ- 

 ing the high hill east of Oso Creek. Loma Alta is made up of a 

 series of strata ranging in age from the Tejon through the Monterey 

 group, the oldest of which rest upon the Franciscan series. The 

 essential structure is anticlinal, broken by the Redrock fault along the 

 ea.stern end of its axis. Although the beds are fractured close to the 

 main ridge of Loma Alta, the fault does not pass through the moun- 



