1913] 



Louderback: The Monterey Series 



237 



The writer has seen similar tuffs probably of the same horizon 

 in the vicinity of the Santa Ynez River. Light colored tuffs 

 (sometimes definitely stated to be rhyolite tuffs) have also been 

 found along- the coast about Point Sal, to the north of San Luis 

 Obispo, and in the vicinity of Monterey, in Contra Costa County, 

 the Mount Diablo region and Santa Catalina Island, and have 

 been reported from the interior at various points as far east as 

 the flanks of- the Sierra Nevada in the Kern River region. Be- 

 sides its occurrence in definite layers or beds, ashy material 

 (mineral grains and glass fragments) is frequently found dis- 

 seminated through the diatomaceous earths and shales. 



Lavas. — Rhyolitic lavas have been reported from the San 

 Luis region. Basic lavas are quite widespread, varied and in 

 some places abundant. Fairbanks has described pyroxene-ande- 

 site, quartz-basalt, olivine diabase and augite-teschenite from 

 the San Luis region. Other localities where basic volcanics, ex- 

 trusive or intrusive, are known in this series, are about Point 

 Sal, in the Santa Maria district, the Santa Monica mountains 

 (a thick series of lavas and breccias and associated intrusives), 

 Carmelo Bay, and the mountains bordering Carrizo plains (espec- 

 ially abundant in the southern portion, where large intrusive 

 masses occur, some of which have produced considerable meta- 

 morphism in the shales). Mr. G. C. Gester 80 has observed abun- 

 dant andesitie and basaltic volcanics associated with the Monterey 

 series in the hills about the southwest extremity of the San 

 Joaquin Valley. The volcanics of San Clemente and Santa 

 Catalina islands may also belong to this series. 



Limits of the Series 

 The upper limits of the Monterey Series are in all places so 

 far studied marked by an unconformity — generally angular. 

 The orogenic movements that took place at the end of the Mon- 

 terey period of deposition were important and widespread, the 

 next oldest succeeding formation being the San Pablo (and its 

 supposed correlatives, the Santa Margarita, etc.), considered by 

 some to correspond to the upper Miocene and by others to the 

 Pliocene. The lower limits of the series are generally also dis- 

 ss Personal communication, Aug., 1912. 



