KeiLK Geologij of a Part of the Santa Ynez River District 19 



tain. The shales and cherts of the Monterey group forming this part 

 of Loma Alta have a comparatively simple attitude, dipping to the 

 west and forming the nose of a steeply pitching anticline. To the 

 east of this main ridge, erosion has produced a cirque-like excavation 

 which has exposed the underlying rocks of the Franciscan and Tejon 

 series that form the north limb of the anticline in Redroek Canon. 

 The south flank of the fold has been faulted down, so that the strata 

 of the Monterey group have been thrown against the Franciscan. 

 The Llonterey Beds dip to the west with a north strike near the sunnuit 

 of Loma Alta and then swing to the southeast and east, forming a 

 strike ridge on the south side of the mountain. The beds near Red- 

 rock Creek become steeply tilted until they are slightly overturned in 

 the bottom of Redroek Canon. All the lower part of the Monterey, 

 including the heavy bedded sandstones, has been faulted out, leaving 

 only a thin strip of the finer grained upper members. In contrast 

 to the steeply tilted beds of the south side, the north limb of this 

 anticline is made up of comparatively gently dipping Tejon strata 

 resting unconformably upon the Franciscan rocks. On Loma Alta 

 Mountain, the Tejon is overlain by the Sespe formation and Monterey 

 group. The whole series is terminated on the north by the Little 

 Pine fault, which cuts across these beds in some places at right angles 

 to their strike. 



The more elevated region between Oso and Redroek creeks and 

 that east of Oso Cafion is occupied by an eastward pitching syncline. 

 which is tlie eojnplementary fold to the Loma Alta anticline described 

 above. Both the Eocene and Miocene rocks are involved in the fold- 

 ing, the latter being represented only east of Oso Creek. The massive 

 blulf sandstone of the Tejon stands out prominently west of Oso Creek 

 as a shallow trough which forms cliffs about five hundred feet high 

 along its margin. The Little Pine fault on the north side cuts 

 obliquely the different meml)ers of the series so that only a small part 

 of the liluff sandstone, considerably broken, remains at Oso Caiion. 

 Although the axis of the syncline is not traversed by the Little Pine 

 fault, nevertheless faulting has taken place along it. so that the 

 steeply tilted and broken remnant of the north limb lies against the 

 gently dipping southern part of the Tejon and ]\Iioeene strata. The 

 bluff sandstones as exposed here were continuous at one time with the 

 same member of the Tejon which is present on the west side of Red- 

 rock Canon. 



Along the 8anta Ynez River itself, the structures are more com- 

 plex tliaii in any other part of the district. South of Loma Alta, the 



