Diller — Mesozoic Sediments of Southwestern Oregon. 419 



and yet it should be noted that specifically determinable fossils 

 were not found in the ledges richest in quartz veins. 



Limestone. — There are six lentils of Whitsett limestone scat- 

 tered at intervals along the axis of the northeast portion. of 

 the Dillard area. They all contain the same foraminiferal 

 remains, lie approximately in line, and are interstratified with 

 the same series of sediments throughout so that there is good 

 reason to suppose they represent but one geological horizon 

 and that they belong to the same horizon as the strata with 

 which they are associated. The limestone lentil near Whit- 

 setts at the northwest base of Dodson Mountain has yielded a 

 few fossils concerning which Dr. Stanton reports as follows: 



"The collection from the Whitsett limestone is not as satis- 

 factory as those previously obtained at the same place. When 

 all of these are put together the evidence is not conclusive for 

 the Cretaceous age of the bed, through there is nothing defi- 

 nitely opposed to this reference. The lot No. 6939 which was 

 collected only 100 yards from the Whitsett limestone is cer- 

 tainly of Knoxville age. " 



The occurrence of limestone in the upper part of the Knox- 

 ville of the Dillard area is now holly exceptional, for it occurs 

 at that horizon in several places along the western side of the 

 Sacramento Valley in California. 



Chert. — Lenses and irregular masses of radiolarian chert are 

 mentioned by Londerback as very characteristic of the Dillard 

 (Franciscan) as though the mere occurrence of chert were suffi- 

 ciently distinctive. It is well to remember that in the Klamath 

 Mountains radiolarian chert is widely distributed in some of 

 the Paleozoic formations and occurs at intervals in later for- 

 mations. In the Shasta group of Tehama County, Cal., where 

 it attains perhaps its greatest known thickness, no cherts were 

 observed as far as the writer is aware, but this cannot be con- 

 sidered a valid reason for excluding them from its equivalent 

 series in Oregon. Nor, on the other hand, can it be reasonably 

 claimed that because some of the chert belong to the Dothan 

 formation of Oregon and is Jurassic, all of it in that region 

 belongs to the same horizon. 



In the Koseburg folio radiolarian chert is mapped as "Jura- 

 trias ?" The intimate association of the chert with the Myrtle 

 formation was recognized as tending to show that the chert is 

 Cretaceous, but greater weight was given to the fact " that the 

 sandstones and conglomerates of the Myrtle formation contain 

 veined fragments of chert, suggesting an age for much of the 

 chert clearly earlier than the Myrtle formation, which was 

 itself probably laid down during the early portion of the Cre- 

 taceous period. " 



