PINE MOUNTAIN SECTION 425 



valley over Pine mountain to San Simeon. Franciscan strata with in- 

 trusives are the oldest rocks exposed in this section. Their outcrops 

 extend from the Pacific to the eastern base of Pine mountain, a width 

 of 10 miles or more. Overlying the Franciscan on the east, in the valley 

 of the Nacimiento, are coarse conglomerate beds which closely resemble 

 the upper conglomerate of the Miocene (?) group. White shale of the 

 Monterey (Miocene) succeeds them and is in turn followed by the chalky 

 San Pablo (marine Pliocene) strata. The Miocene and Pliocene* for- 

 mations, including the conglomerate, are involved in an extensive syn- 

 clinorium. The structure was obvious in the outcrops passed over en 

 route and was traceable at a distance in consequence of the individuality 

 of the Miocene (?) conglomerate and especially of the white San Pablo 

 formation. A feature of the distant landscape east of Pine mountain is 

 an isolated synclinal height in which San Pablo strata are maintained 

 probably more than 2,500 feet above sea (see plate 28) 



The magnitude of this synclinorium argues for its original develop- 

 ment by simple subsidence before it was exaggerated and rendered com- 

 plex by compression. Such a subsidence has already been inferred from 

 the Miocene (?) formations. The broad facts of structure not only sup- 

 port the previous inference, but also define the areal extent of subsidence, 

 inasmuch as the axis of the synclinorium trends with the axis of the 

 original depression, northwest-southeast, and the anticlinorium of the 

 Avestern Santa Lucia range presumably coincides with a district which 

 did not share or lagged behind the downward movement. 



From the character and distribution of strata east of the Santa Lucia 

 range and from their broad structural relations, it thus appears that the 

 geographic conditions of Miocene and Pliocene time included a bay or 

 strait northeast of a western land. 



Pliocene to Present 

 » physiography of the coastal slope 



The western Santa Lucia range in the stretch of 60 miles from near point 

 Sur to Pine mountain carries no strata younger than the Miocene (?) sand- 

 stones. If the district was submerged at any time subsequent to the 

 Miocene (?), whatever sediments formed have been eroded. The history 

 is therefore to be read in the physiographic aspects, of which the western 

 slope of the range bears the more legible features. 



To the writer's eye the Santa Lucia range presents two distinct stages 

 of topographic development. An earlier is recorded in the aspects of 



* Identified by Doctor Fairbanks. 

 LXI— Bull. Geol. Soc. Am., Vol. 11, 1899 



