Diller — Klamath Mountain Section, California. 343 



the southwestern and northeastern. The southwestern belt 

 embraces South Fork Mountain and all the country bordering 

 the Salmon Mountains and Bully Choop upon the southwest, 

 while the northeastern belt, beginning in the Bully Choop and 

 Salmon Mountains, extends northeast to the Great Bend of Pit 

 River. It is of importance to note that in each belt the oldest 

 rocks lie upon the southwest, decreasing in age to the northeast, 

 and in the northeastern belt the succession extends up through 

 the Triassic, Jurassic and Cretaceous. 



PrE-DeVONIAN. 



Southwestern belt of schists. — The oldest rocks of the region 

 are schists,* of which the southwestern belt forms North Yallo 

 Bally and South Fork Mountain and may be traced from the 

 western part of Tehama County northwest between the South 

 Fork of Trinity and Mad River to the coast at the mouth of 

 Red Wood Creek, while the northeastern belt passes through 

 Bully Choop and Salmon Mountains. 



The principal rock of South Fork Mountain is a gray or 

 greenish gray, more or less silky, mica-schist in which the mica 

 is sericite. Although in well denned folia and fibers giving 

 the mass a decided schistose structure, the mica is not well 

 crystallized in distinct scales. The quartz is generally in 

 excess of the mica and the mass is locally full of quartz veins. 

 Another type of rock in this belt occurs in North Yallo Bally 

 and locally along the lower portion of the southwestern slope 

 of South Fork Mountain. The rock is greenish, generally 

 more or less schistose, and composed chiefly of quartz and 

 epidote. The occasional presence of blue hornblende in this 

 rock suggests that it may be the result of contact metamor- 

 phism, but the Held relations as far as known are not decisive. 



The rocks bordering the schists of the South Fork Moun- 

 tain upon both flanks are strongly contrasted with each other 

 as well as with the schists. Upon the northeast are Devonian 

 limestones, sandstones and shales cut by many igneous masses 

 and decidedly metamorphosed. Upon the southwest between 

 Mad River and the coast are conglomerates, sandstones and 

 shales, at least in part of Cretaceous age. They are but little 

 metamorphosed and are associated with comparatively few 

 igneous rocks. The change from the schist to these rocks near 

 Mad River is striking and indicates a profound break which may 

 be most conveniently considered as the southwestern limit of 

 the Klamath Mountains. 



The general dip of the less altered sedimentary formations 

 bordering the schists of South Fork Mountain belt upon both 



* Included in the Abrams and Salmon formations of Hersliey. Am. Geol., 

 June, 1901, and manuscript map. 



