Lavvson ~j 



t'ALACM H J 



The Berkeley Hills. 



another longitudinal fault, to be described later as the Canon fault. 

 The differential downthrow along the entire length of the fault is to 

 the northward. 



The conglomerate referred to in the preceding section as inter- 

 vening between the Knoxville and the Chico, traces of which are 

 found near the head of Dwight Way, is significant of an important 

 change in the conditions of sedimentation at the close of the Knox- 

 ville. The fine shales are replaced by coarse pebbles, indicating a 

 disturbance of the region from which the sediments were derived, 

 whereby the streams had their grades accentuated and their powers 

 of erosion and transportation greatly increased. 



THE MONTEREY SERIES. 



Unconformity . — The general trend of the crest line of Skyline 

 Ridge is transverse to the strike of the formations, and, as the gen- 

 eral dip of the latter is northeasterly, we meet with successively 

 higher or later formations as we pass along the ridge towards the 

 summit of the range. The next formations, therefore, which we 

 should naturally expect to find in this section lying upon the Chico 

 would be those of the Eocene. There are two main divisions of 

 this series, viz., the lower or Martinez formation, and the upper or 

 Tejon formation. But, although both of these are represented by 

 thick accumulations of sandstone replete with fossils in the neigh- 

 borhood of Martinez, not many miles distant, they are not found in 

 our section, and the next rocks that we meet with in ascending 

 order are those of the Monterey series (Miocene). We have here, 

 therefore, a fine illustration of a geological gap or hiatus, there 

 being a long interval of time between the Chico and the Monterey, 

 for which we have nothing to show in the shape of sedimentary 

 deposits. There are of course two possible explanations of such a 

 hiatus. Either the region now occupied by the Berkeley Hills was 

 dry land during Martinez and Tejon time, so that no marine sedi- 

 ments were ever laid down upon the Chico, or the sea of these 

 periods extended over the region as elsewhere in the Middle Coast 

 Ranges, and the Martinez and Tejon formations, which were then 

 deposited, were removed by erosion in consequence of an uplift 

 which intervened prior to the Monterey submergence. Without 



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