28 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. 



no Tejon is shown, and the Temblor rests upon Cretaceous or 

 Franciscan rocks. The development of the Temblor group 

 north and south of these fault zones is as uniform in thickness, 

 lithology, and fauna, as could be expected. On the south, be- 

 tween the Temblor and Antelope valleys, the Temblor strata 

 are from 1000 to 1500 feet thick. On the north, as developed 

 about the Sunflower (McClure's) Valley, it may vary from 

 500 to 1500 feet, as exposed at different points. It is quite 

 possible that the shales overlying the terriginous sandstones in 

 this locality should be included with the Temblor. 



As regards the Monterey north and south of these fault 

 zones, there is very great discrepancy in thickness and develop- 

 ment. South of the Antelope Valley thick beds of Monterey 

 are indicated on the map, and near Carneros Springs these 

 beds are little less than 3500 feet in thickness. Earlier esti- 

 mates of these strata included beds that probably are of Santa 

 Margarita age. It is doubtful, on the other hand, if Monterey 

 strata exist at all north of the Antelope Valley, and none is 

 shown on the map of the Coalinga District. It is useless to 

 argue about the difficulty of discriminating here between 

 Temblor and Monterey upon the basis of lithology or any other 

 character. The fact remains indisputable that the Miocene 

 beds north and south of these fault zones are entirely different 

 for all parts of the section above the Temblor. These facts 

 are entirely explainable upon the assumption of distinct oro- 

 genic blocks having independent and separate diastrophic 

 movements after the close of the Temblor epoch, but they are 

 not readily explainable upon any other basis. 



A study of the Mount Diablo Range as a whole discloses the 

 fact that it consists of a number of orogenic areas that differ 

 in various parts of their Neocene stratigraphy. One of these 

 areas or blocks comprises the Temblor Range adjacent to the 

 San Juan district. A minor block is enclosed between the 

 Antelope Valley and the Bitterwater faults, and is of triangu- 

 lar shape. A larger block embraces that part of the range be- 

 tween the Antelope Valley and the Waltham Creek valley, and 

 still other blocks may be defined north of Coalinga. Many of 

 these blocks, which are in fact separate diastrophic areas, were 

 noted by Professor Whitney in his subdivisions of the Mount 

 Diablo Range. The extent to which this subdivision of the 



