CBICO-TfiJON SERIES. 237 



face of the synclinals will afford paths of least resistance. Metamorphism 

 thns induced will therefore affect the synclinals more than the anticlinals, 

 and, if erosion follows, not only will the relief and the fractured surface of 

 the anticlinals tend to their degradation, l)ut the resistance of the synclinals 

 will be increased by the silicitication and cementation of the mass. It is 

 quite conceivable that the combined effect of plication and metamorphism 

 as liere imagined should be such as to result in a much more regular mod- 

 eling of the surface liy erosion than would have been induced had either 

 plication or metamorphism alone influenced the course of degradation.' 



The ch.co-T^jon scries. —To Ward tlio soutlicm Olid of the map the Chico-Tc'jou 

 series appears. It consists chiefly of soft sandstones of a tawny hue where 

 exposed to oxidizing influences, but bluish -in color below the water-line, 

 as is usual with sediments containing a small amount of iron. This series, 

 though tilted and disturbed, is not crushed or plicated like the older strata 

 to the north. It also inchules conglomerates full of metamorphic pebbles, 

 in some cases showing an unusually brilliant polish. These pebbles are 

 highly siliceous and on this account do not at first sight appear to resemble 

 the extensivel}' developed metamorphic series. In cases of this kind, how- 

 ever, it is necessary to rememl^er that even feldspathic rocks are rapidly 

 disintegrated in moving water and that quartz is almost the only mineral 

 which will long retain the form of pebbles. Concretions are common in 

 these rocks, occasionally with fossil nuclei, but usually without any dis- 

 tinguisliable nucleus. They sometimes weather more and sometimes less 

 rapidly than the rock in which they are embedded and are often composed 

 of concentric shells. Some argillaceous deposits and a little limestone 

 occur in this formation. The Chico-T^jon series of this region is fos- 

 siliferous, though organic remains are by no means generally distributed 

 through it. Mr. Gabb collected a considerable number of fossils here, and 

 so also did my party. 



The Chico-Tejon series does not come in contact with the metamorphic 

 rocks in such a way as to demonstrate a non-conformity, alluvium and lava 

 intervening on the surfiice ; but the sudden change in lithological character 

 and the comparatively trifling disturbance of the iinmetamorphosed rocks 



' See Dana, Manual of Geology, p. 750. 



