LAWSON "I 

 I s A LACHeJ 



The Berkeley Hills. 



365 



brownish or yellowish gray. The relative proportion of chert and 

 shale in alternation of these two rocks is also rather variable, 

 although in general the chert beds preponderate and the shale is 

 but a thin parting. The most characteristic outcrops exhibit very 

 regular beds of chert, ranging from one inch to six inches in thick- 

 ness, with shale partings from one-eighth to one-half inch thick. 

 In this remarkable regularity and rhythm of stratification the 

 formation closely resembles the radiolarian cherts of the Franciscan 

 series. Occasionally single chert beds are a foot or even two feet 

 thick, but this is unusual; the shale appears in certain cases to 

 diminish to a mere film or to be altogether lacking in the parting 

 between the chert beds. The dark brownish or yellowish-gray 

 color of the cherts and the chocolate color of the shales appear 

 to be due to the presence of bituminous matter, since on ignition 

 the color may be discharged with the emission of a distinct bitumi- 

 nous odor. Some of the beds are composed of amorphous silica 

 of a chalky consistency, and in these cases the characteristic lam- 

 ination is not well developed. The presence of the bituminous 

 matter as a characteristic feature of a large part of the Monterey 

 series, wherever found in the Coast Ranges, whether shaly or chalky 

 or cherty, has caused them to be referred to frequently as the 

 " bituminous shale* formation." 



Fossils are scarce in this formation, the only forms known being 

 Tcllina congesta, Pecten peckhami, fish scales and casts and moulds 

 of foraminifera, all occurring in the shales. 



Sandstones and Limestones. — A careful examination of the sec- 

 tion along the ridge crest will reveal, besides the minor varia- 

 tions mentioned above, that the cherts and shales are not the only 

 constituents of this formation. On the knoll to the west of Sugar 

 Loaf there is found capping the ridge a bed of sandstone of a dark 

 bluish-gray color, resting upon the cherts and shales. This sand- 

 stone contains considerable carbonate of lime, and in it are formed 

 numerous casts of molluscs, which, though too imperfect for com- 

 plete identification, are probably of Monterey age. A collection of 

 these Molluscan remains was submitted to Dr. W. H. Dall, who 

 kindly reported that, while the fossils were too poorly preserved for 



Also "bituminous state formation;" but this is a misnomer. 



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