W. D. Smith — Notes on Badiolarian Cherts in Oregon. 299 



Akt. XXXIII. — Notes on Radiolarian Cherts in Oregon ; 

 by Warren D. Smith. 



The age of certain cherts found in our West Coast strati- 

 graphy has long been a matter of conjecture. Diller described 

 occurrences of these in both the Port Orford Folio (U. S. G. S.) 

 and that for Roseburg and assigned provisionally the rocks to 

 the Cretaceous. No genera or species were given, as far as I 

 know, nor were any very definite field relations mentioned, on 

 account of the unsatisfactory nature of the exposures. 



During the summer of 1915, the writer was in the field for 

 the Oregon Bureau of Geology and Mines investigating some 

 problems connected with the stratigraphy of the Cascades, dur- 

 ing the course of which he obtained some data relative to 

 these cherts which may be of interest now and are here given 

 with the permission of the Director of that Bureau. 



In the cow pasture back of Mr. Engles' house at Feel F. O., 

 about 25 miles east of Foseburg on the Little Fiver, a branch 

 of the Umpqua, there is an almost hopeless mixture of rocks, 

 hornblende schists with small patches of these cherts inclosed 

 by them. 



At the time of the writer's visit to Peel, he was fortunate in 

 being able to see these outcrops after some excavating had 

 been done for road metal. The value of this for road surfac- 

 ing is due doubtless to the combination of the chert and the 

 iron, for they are ferruginous at this place. An examination 

 of the outcrops as opened up by them showed the stratification 

 lines very plainly. The strike was found to be JX 8° E. and 

 the dip 70°-90°. The direction of the dip varies, in places 

 being to the N.W., and a few feet away, about the same amount 

 in the opposite direction. About a quarter of a mile farther 

 up the Little River, Eocene sandstone and shales were found 

 dipping about 20° to the east (as already noted by Diller), so 

 that if these beds do not reverse their direction of dip in the 

 intervening distance (no outcrops visible to determine this) 

 they would come far above these chert beds and there would 

 be a marked angular unconformity between them. 



Thin sections of these cherts were made which showed species 

 of the following genera of radiolaria : Cenosphsera, Dictyomi- 

 tra and Spongodiscus. In most cases, however, only small 

 round areas filled with cryptocrystalline silica showed where 

 the. tests had been. 



Identical forms have been found by the writer* in material 

 lithologically similar and in about the same stratigraphic posi- 



* Smith, W. D., Philippine Jour. Science, vol. v, No. 5, p. 327. 



