1919] K( w: Geologii of a Part of tlic Santa Ynrz Eivcr District 13 



beds at the base, followed by other red and green sandstones, for tlie 

 most part unsorted and slightly conglomeratic. The exposures of the 

 Sespe north of the river are on the hill immediately east of Oso Creek, 

 and on the east slope of Loma Alta. 



No fossils have been found in the Sespe in the Santa Ynez district, 

 and this fact, together with its lithologic character, strongly suggests 

 that the greater part of the strata accumulated under arid conditions 

 in basins surrounded by steep slopes composed of Franciscan rocks. 

 The marked difference in thickness between the sections of opposite 

 sides of the river may be accounted for in that the surface of deposi- 

 tion was irregular, which did not allow so great an accumulation 

 of detritus in one place as in another. Regarding the age of the Sespe, 

 no definite evidence is obtained from the sections studied in this dis- 

 trict other than that it is post-Tejon and pre-Vaqueros, but it lias 

 generally been considered to be Oligocene. 



Miocene Series 

 Monterey Group 



General features. — In the Santa Ynez River district, the IMonterey 

 group is made up of four lithologic phases : ( 1 ) a lower, rather coarse 

 sandstone containing the Turritella inezana fauna in its lower beds, 

 and the Turritella ocoyana fauna in the upper part; (2) muddy sand- 

 stones, locally nodular, more shaley and enclosing impure limestone 

 lenses; (3) a thin series of cream-colored clay shales containing an 

 abundance of fish scales; (4) an upper zone composed of calcareous 

 and siliceous cherty shales of the type which is so characteristic of the 

 Monterey group over California. The first two are included with the 

 Vaqueros sandstone member of the Monterey group, while the latter 

 two members have been mapped as the Salinas shale" formation of the 

 same group, a name recently adopted by the U. S. Greological Survey 

 for these beds in Monterey County. 



Vaqueros sandstone. — Both faunal zones of the Vaqueros, the Tu)-- 

 ritella inezana and 2\ ocoyana zones are represented, though the former 

 was found only in the west fork of Blue Cafion. At this place, strati- 

 graphic relations have. been obscured by faulting. A fauna, in which 

 Pecten magnolia and Turritella inezana are abundant, is present in 



8 English, W. A., Geology and oil prospects of the Salinas Valley-Parkfield 

 area, Cal., U. S. Geol. Surv. Bull. 601-11., 1916. 



