1914] 



Dicker so ii : Fauna! Zones of the Tejon Group 



25 



youngest Tejon sediments which have heretofore heen regarded as 

 lone. Many oscillations of the coastline are recorded in the Tejon 

 strata, but most of these are apparently local. Thus the coal horizons 

 north of Mount Diablo are not trustworthy guides except in the im- 

 mediate vicinity of the mountain, as lignitic horizons occur near the 

 base of the Tejon on the south side of the peak as well. These oscil- 

 lations are sometimes marked by local unconformities, such as between 

 the coal strata in the Tejon north of Mount Diablo and their inter- 

 bedded sandstones. In the upper beds of the Tejon south of Mount 

 Diablo a well-marked irregular contact between coal strata and the 

 underlying white sandstone was found in a locality a quarter mile 

 east of Tassajero Creek. A comparison between the faunas above 

 and below some of the stratigraphic breaks has been made, but almost 

 invariably no great difference can be discerned, hence the writer re- 

 gards these unconformities as local and inconsequential. 



SUMMARY 



Taken as a whole, the 2600 feet of the Tejon south of Mount Diablo 

 may be divided into three main divisions, viz.. the lowermost; the 

 middle, consisting of the three bluffs and their intervening strata, 

 and the upper. Within these are recognized several faunal zones : 

 (1) zone 1; (2) zone 2; (3) zone 3. A fourth, the Siphonalia sut- 

 terensis zone, occurs typically in the Marysville Buttes. 



The Tejon group was deposited by a transgressing sea, and as a 

 consequence the youngest known sediments were deposited along the 

 western edge of the Sierras upon rocks of various ages, the older 

 members of the Tejon group being absent. 



Transmitted December SO, WIS. 



