Lawson i 

 PalacheJ 



The Berkeley Hills, 



359 



slickensided and seamed with small veins; and in both these respects 

 are in contrast to the Shasta-Chico beds. The Franciscan beds 

 have very generally been invaded by the intrusions of a basaltic 

 rock which never pierces the Knoxville. The Knoxville beds are 

 never affected by metamorphism so as to develop the contact 

 zones of glaucophane and other schists which are common features 

 of the Franciscan. 



These facts clearly indicate that the Franciscan rocks have 

 passed through a history which has not been participated in by the 

 overlying Shasta-Chico. The Knoxville shales lie indifferently 

 upon the various formations of the Franciscan, and we are, there- 

 fore, forced to the conclusion that the latter must have been 

 orogenically disturbed and worn down by erosion to afford the 

 surface upon which the Knoxville beds were deposited. We are 

 thus warranted in the belief, that we are here dealing with one of 

 those epochs in geological history in which the record of geo- 

 logical time is marked, not by the accumulation of sediments, but 

 by their erosion and removal. It is sometimes spoken of as a hiatus 

 in the geological record, but it is only a gap in the record of sedi- 

 mentation not in the record of geological events. Structurally it 

 is referred to as an unconformity, and the Knoxville strata repose, 

 therefore, unconformably upon the Franciscan. 



Chico Sandstones. — As we continue the ascent of the hill, follow- 

 ing Panoramic Way, we meet with sandstones with subordinate 

 intercalations of shale all the way to the summit of Skyline Ridge. 

 In the cuttings by the side of Panoramic Way we may see that 

 these sandstones are in places distinctly bedded, but away from the 

 road the outcrops usually show no evidence of stratification, and on 

 the roadside where the stratification may be best observed it is also 

 very apparent that the strata, locally at least, have suffered con- 

 siderable disturbance. Dislocations and thrusts of limited extent 

 traverse the beds in various directions, and the softer shale beds, 

 between the harder and more resistant sandstone beds, have been 

 intensely deformed and crumpled. Inasmuch as phenomena of this 

 kind are not commonly observable in other parts of this set of 

 rocks, we may conclude that the shattering of the rock is indicative 

 of a local zone of disturbance. This shattering must not be con- 



