Hershey — Some Western Klamath Stratigraphy. 61 



The volcanic series dips at a much lower angle than the 

 Blue Chert series beneath it, suggesting marked nonconform- 

 ity by reason of pre-volcanic uplift and great erosion. Else- 

 where in the western Klamath region masses of volcanic rocks 

 rest nonconformably on the Blue Chert series. I have never 

 seen any evidence of volcanic rocks interbeclded with this 

 series. In one place, below Cecil ville in the valley of the 

 South Fork of Salmon River, tuffs and lavas occur under Pale- 

 ozoic limestone and chert, but the contact is a nonconformity 

 reversed by overturning. It is my impression that in the 

 western portion of the Klamath region, all the clearly volcanic 

 rocks are younger than the Devonian Blue Chert series. 



Above the rhyolite in Pearch Creek valley, there is a forma- 

 tion of black slaty shale whose maximum thickness I estimate 

 at 3000 feet. At the base there is a slight development of 

 coarse sandstone, apparently made up of debris from the 

 underlying quartz-bearing rhyolite. It hardly anywhere attains 

 a thickness of 50 feet, but may be traced along the contact for 

 several miles ; and there is little doubt of its having been laid 

 down on the surface of the volcanic series. I have found no 

 evidence of nonconformity at this contact and it is my impres- 

 sion that the deposition of the sandstone followed closely that 

 of the rhyolite. 



Excepting this thin basal sandstone, the formation contains 

 no conglomerate, sandstone and limestone, and only a few thin 

 layers of chert. Its most characteristic feature is that it is 

 largely composed of layers of the thickness of coarse paper. 

 It resists weathering so well that it stands in high rugged 

 ridges and peaks, often bare of soil, and having a rusty color 

 on outcrop. The ' reddish brown high ridge at the head of 

 Pearch Creek, a prominent feature in Orleans scenery, is largely 

 of this formation. 



So far as known, it is confined to a basin-like depression in 

 the surface of the older rocks, in an area possibly 20 miles 

 long (north-south) and 10 miles wide, lying west of Know- 

 nothing Creek, south of Salmon River, east of the Orleans 

 fault and north of " Trinity Summit." As the valley of 

 JS[ ordheimer Creek is largely cut in it, I propose to designate 

 it the Nordheimer formation. 



Its dips are prevailingly toward the center of the basin but 

 usually not at high angles, contrasting with the dips of the 

 Blue Chert series lower. Their relation is certainly that of 

 marked nonconformity although they are separated by igneous 

 rocks. 



The ]STordheimer formation is badly shattered by intrusive 

 rocks. They are clearly plutonic, being largely in the form of 

 batholithic masses of gray and greenish, fine-grained crystal- 



