Hershey — Some Western Klamath Stratigraphy, 65 



ward one will frequently arrive at a point where the strata 

 bend up and presently igneous rocks appear. They usually 

 have the characters of surface volcanics and always are in belts 

 parallel to the strike of the slates and sandstones. Such 

 features as I usually accept as criteria in the determination of 

 the fact of intrusion in the Blue Chert and JNordheimer forma- 

 tions are positively absent here. Even these igneous rocks do 

 not appear in the 4- to 7-mile belt of pure Bragdon next to the 

 Orleans fault. I have gone 12 miles north from Orleans with 

 out seeing anything but Bragdon and have had similar experi- 

 ences on long trips in other directions. The significance of 

 this will be apparent when I say that in the course of several 

 hundred miles travel in Blue Chert areas and several score in 

 the IsTordheimer area, I have probably not for any five minutes 

 been out of sight of nearby igneous rocks. 



The only theory in explanation of this distribution of the 

 intrusives which seems to me to have a natural ring is that at 

 the time of their formation (granite, peridotite and all later 

 igneous rocks excepted), the Bragdon formation of the western 

 area was not in existence. Otherwise, the igneous material 

 has exercised a most remarkable selection. I am aware that 

 intrusives will to a certain extent concentrate into certain 

 formations which are most easily penetrated, but this objection 

 does not apply in this case. There is nothing about the Brag- 

 don to make it especially resistant to melted rock. On the 

 contrary, it is the softest and most easily broken formation of 

 pre-Cretaceous age in the Klamath region west of the Sacra- 

 mento River. Granite and peridotite found little difficulty in 

 cutting through it. My observation of intrusives in other 

 regions such, as eastern Nevada lends no encouragement to the 

 idea that the Bragdon resisted the penetration by such mate- 

 rial as intimately injected every other formation of the region. 



The hypothesis of " localization " is not pertinent because we 

 are dealing with a territory several thousand square miles in 

 extent and an asserted contrast which is not based on very 

 limited observation. Remember, we have on one side tens of 

 thousands of dikes and scores of large batholiths and on the 

 other side nothing. 



If the Bragdon formation goes down under the Blue Chert 

 series east of the Orleans fault, it must necessarily be intimately 

 intruded by the igneous rock which is so abundant in all parts 

 of the other series. This would break down any theory based 

 on an alleged resistance to intrusion and would make it unrea- 

 sonable to suppose the intrusives rapidly gave out in the half 

 mile accounted for by the fault. (This fault is far younger 

 than any igneous rock entering into this discussion.) There- 

 fore, it appears to me improbable, almost to the extent of cer- 



Am. Jour. Sci. — Fourth Series, Vol. XXI, No. 121.— January, 1906. 

 5 



