Geol.— Vol. II.] ANDERSONSTRATIGRAPHIC STUDY 1 59 



developed in accordance with the character and hardness of 

 the rocks affected. The higher portions of the range are 

 rocky and i-ugged, while the lower eastern slopes are often 

 formed of gently undulating hills extending in parallel ranks 

 and gradually sinking below the plain to the eastward. 



The principal streams of this section, flowing toward the 

 Great Valley, are the Panoche, San Carlos, Cantua, Los 

 Gatos, and Alcalde creeks, each of which cuts deep can- 

 yons into the softer formations near the valley, but heads 

 high up on the rocky ridges in the central parts of the 

 range. Farther south are the Sunflower and Antelope 

 valleys with converging streams. 



Stratigraphic Series. 

 Franciscan and Associated Rocks. 



The oldest rocks met with in the San Carlos Division of 

 the range are those generally referred to the Franciscan 

 series, including not only the well known sedimentary fac- 

 tors, but also certain basaltic and other igneous rocks closely 

 connected or involved with them. It is perhaps sufficient to 

 say that the entire series, including the eruptives, are in point of 

 age pre-Cretaceous, though they have been variously assigned 

 by different authors, wholly or in part, to the Paleozoic, 

 Jurassic, or Cretaceous periods. 



The sedimentary members of the Franciscan series repre- 

 sented in this field include the rocks ordinarily found asso- 

 ciated in this formation, such as radiolarian jaspers, sand- 

 stones, slates, and schists, and perhaps certain conglomerates. 



Closely connected with the Franciscan rocks territorially 

 are the serpentines of the range. While it is not likely that 

 the connection is anything more than territorial, as in point 

 of age the serpentines are of more recent origin and there- 

 fore more closely connected with the succeeding series, still, 

 as their association with the Franciscan rocks is habitual 

 even outside this district, they may be better classed with 

 these than with any other formations. 



