362 Diller — Klamath Mountain Section, California. 



Resume. 



The sedimentary rocks of the Klamath Mountains, except- 

 ing those which are pre-Devonian, belong to the following 

 groups: Devonian, Carboniferous, Triassic, Jurassic, Creta- 

 ceous, Eocene, Miocene, Pliocene, and Pleistocene. 



The general conclusions concerning their distribution and 

 structural relations may be summarized as follows : 



1. The Klamath Mountains, although composed in large 

 part of igneous rocks, are made up chiefly of pre-Devonian 

 schists with Devonian and Carboniferous sediments, among 

 which fossiliferous limestones occur. 



2. Triassic and Jurassic sediments form but a small part of 

 the Klamath Mountains, occurring, as far as yet definitely 

 known, only in the southeastern projection between the 

 McCloud River and the Great Bend of Pit River. 



3. The Cretaceous strata of marine origin practically sur- 

 round the Klamath Mountains and occur also in separate 

 basins within their northern and southern portions. 



4. The Eocene, Miocene, Pliocene and Pleistocene sedi- 

 ments near the coast are of marine origin, but inland among 

 the Klamath Mountains some, if not all, of the basins containing 

 marine Cretaceous beds contain also fresh water Eocene, Mio- 

 cene, Pliocene, and Pleistocene sediments. 



5. The older sedimentary rocks, including those of Paleozoic 

 or greater age, forming the bulk of the Klamath Mountains, are 

 arranged in two belts running northwest from the end of the 

 Sacramento Valley to the coast between Red Wood Creek in 

 California and the mouth of Rogue River in Oregon. 



6. The dividing line between the belts is occupied largely 

 by igneous rocks. It lies near the southwestern base of the 

 Bully Choop and Salmon Mountains. 



7. Both belts embrace pre-Devonian, Devonian and Carbon- 

 iferous sediments. The oldest rocks of each belt are upon the 

 southwest side and decrease in age -to the northeast. The pre- 

 vailing dip of the strata throughout the greater part of the 

 Klamath Mountains and the northern end of the Coast range is 

 in the same direction. 



8. This repetition of beds in the same order in the direction 

 of the prevailing dip suggests faulting and that a great fault 

 runs northwest and southeast near the southwest base of Bully 

 Choop and Salmon Mountains. 



9. West of the ancient schists of the South Fork Mountain, 

 bordering the coast, lies the North Coast Range of California, 

 composed of shales, sandstones and conglomerates which are at 

 least in part Cretaceous and perhaps wholly of Mesozoic age. 



10. Between these unaltered sediments and the pre-Devonian 

 schists toward which they dip, there is a great break along the 

 southwest line of South Fork Mountain marking the line 

 between the Klamath Mountains and the Coast Range proper. 



U. S. Geological Survey, Washington, D. C. 



