LAWSON "I 



PalacheJ 



The Berkeley Hills. 



44' 



HISTORICAL SUMMARY. 



The oldest rocks with which we arc in this limited field con- 

 cerned are those of the Franciscan series. These rocks are known 

 to repose, in neighboring portions of the Coast Ranges, upon the 

 worn surface of a granite, which is believed, for reasons which can 

 not be entered upon here, to be probably of the same age as the 

 post-Jurassic granites of the Sierra Nevada. This implies a post- 

 Jurassic age for the series. The paleontological evidence as to the 

 age of the Franciscan is rather scant, but its fossil foraminifera, 

 molluscs and plants have been independently interpreted by differ- 

 ent experts to indicate a place in the geological scale not older 

 than the Lower Cretaceous. Before the recognition of the Fran- 

 ciscan as a distinct series of rocks, the Knoxville had been regarded 

 as the local base of the Cretaceous in California. But it now seems 

 probable that the Cretaceous will have to be enlarged so as to 

 embrace the Franciscan in its lower part. 



These Franciscan rocks, comprising a thick accumulation of 

 sandstones, shales, foraminiferal limestones, radiolarian cherts, and 

 volcanic flows, represent a long period of geological time and 

 indicate numerous and important oscillations of level in the basin 

 in which they were accumulating. They are, moreover, traversed 

 very generally by basic intrusives, and with these intrusives are 

 very frequently found irregular zones of contact metamorphism. 



The Franciscan was subjected to orogenic deformation and 

 erosion prior to the subsidence which is represented by the Shasta- 

 Chico series of marine sediments. The strata of this series are in 

 the Strawberry Canon section not more than one-tenth as thick as 

 they are in the northern part of the state, but the general character 

 of the sediments is characteristic of the middle Coast Ranges and 

 is significant of the conditions which prevailed during their accu- 

 mulation. The Knoxville or basal division of the Shasta-Chico 

 series is prevailingly composed of clay shale or sandy shale, with, 

 in North Berkeley, some limestones, sandstones, and fine pebbly 

 conglomerates. Aucella is found equally abundantly in shale, lime- 

 stone, sandstone, and conglomerate. Belemnites occur in the sand- 

 stones, and an ammonite, probably a species of hoplites, has been 



