442 



University of California. 



[Vol. 2. 



found in the shales in addition to the aitccllce. These beds rest 

 indifferently upon the various formations of the Franciscan, and the 

 latter afford many evidences of disturbance which have not affected 

 the overlying Knoxville. Notwithstanding this fact, however, and 

 the further fact that the Franciscan is made up of characteristic 

 resistant rocks well adapted to yielding pebbles, no fragments of 

 the Franciscan have as yet been found in the Shasta of this region. 

 The radiolarian cherts and glaucophane schists of the Franciscan 

 occur abundantly in the Tertiary conglomerates, and one would 

 naturally expect to find them in the first over-lying unconformable 

 beds. Their absence is in harmony with the generally fine-grained 

 character of the Knoxville beds. These facts clearly indicate that 

 the floor of the basin upon which the Knoxville sediments accu- 

 mulated was a surface of exceedingly low relief, and that as it 

 subsided beneath sea level there were no insular masses to afford 

 beach material or high-grade streams contributing coarse detritus. 



If high land bordered the Knoxville sea, it was so distant from 

 the middle Coast Ranges that the streams contributed practically 

 only suspended matter to the accumulation. It is rare in stratig- 

 raphy that such a fine-grained sediment as the Knoxville shales 

 should be so extensively developed immediately above an uncon- 

 formity, and it is not certain that in the middle Coast Ranges we 

 fully understand the conditions which obtained during the accumu- 

 lation of these strata. In the southern Coast Ranges conglomer- 

 ates, with numerous pebbles of characteristic Franciscan rocks, 

 occur, according to Fairbanks,* at the base of the Knoxville. 



Above the Knoxville and intervening between it and rocks 

 referred to the Chico, is a stratum of rather coarse pebble conglom- 

 erate. This conglomerate barely comes within the limits of our 

 map at the head of Dwight Way, but is traceable for many miles 

 along' the front of the range to the southeast, in which direction the 

 stratum increases in volume very noticeably. This formation is 

 certainly significant of a very radical change in the conditions of 

 deposition from those which prevailed in the immediately pre- 

 ceding epoch. We may safely infer the deformation of the region 

 to such an extent as to determine a much higher grade for streams 



*Jour. Geol., Sept.-Oct., 1898. 



