298 University of California Publications in Geology [Vol- 10 



highly colored, contain a large amount of silicified wood, leaves, and, 

 as stated above, remains of land mammals. 



As will be shown by a study of the accompanying list of species, 

 faunally the Santa Margarita differs markedly from both the 

 Vaqueros below and the Etchegoin above. Only a few of the species 

 are found in the adjoining formations. The nearest correlative of 

 the Santa Margarita appears to be the upper part of the San Pablo 

 group 12 as developed in the northern part of the Diablo Range. 



Lithologic Section of the Santa Margarita Northeast of 



Coaling a 



The sandstone member of the Santa Margarita as exposed in 

 the area northeast of Coalinga was probably deposited, unlike the 

 adjoining portions of the Vaqueros and Etchegoin, entirely under 

 marine conditions. The following tabulated section indicates in a 

 general way the lithologic character of the formation. It is to be 



Pig. 2. Detailed section across the Santa Margarita about ten miles north- 

 east of Coalinga. Horizontal distance about 2500 feet. (After Clark and 

 Euekman.) 



borne in mind, however, that the beds vary greatly within a short 

 distance and that the section can be applied in detail to only a very 

 limited area. 



Detailed Section op the Santa Margarita Ten Miles Northeast of Coalinga 



Etchegoin Feet 

 Basal gravel with silicified wood and gypsum. Neohipparion molle 

 found short distance above base 

 Santa Margarita 



Gray thin-bedded sandstone with well-rounded pebbles of brown chert, 



quartzite, and quartz monzonite 2 



Buff to white, well-rounded, medium to coarse-grained sand 18 



Hard, coarse, quartzose sand with pebbles of quartz monzonite, andesite, 



and rhyolite; cement calcareous 13 



White to bluish-white, incoherent sand consisting chiefly of well-rounded 



quartz grains 50 



Fossiliferous grayish-brown sandstone with well-rounded grains of 



quartz and feldspar 25 



12 Clark, B. L., Fauna of the San Pablo group of middle California, Univ. 

 Calif. Publ., Bull. Dept. Geo!., vol. 8, no. 22, 1915. 



