772 INDEX TO THE STEATIGRAPHY OF NORTH AMERICA. 



See Harris " on the correlation of the Tejon. There seems to be a strong probability that 

 part of the beds heretofore referred to the Tejon represent the basal Eocene, but at present we 

 are without sufficient evidence to speak positively. 



Diller describes the. Arago group in the Coos Bay ^''^ and Port Orford ^^^ foKos 

 and the Umpqua in the Roseburg foUo."* The following quotation is from the 

 Coos Bay folio: 



The rocks of the Eocene period in this region have been called the Arago formation, but in 

 this quadrangle they are grouped into two formations — the Pulaski and the Coaledo. These 

 formations occupy almost the whole of the Coos Bay region. They are composed generally of 

 sandstones and shales, which are especially well exposed near the mouth of Coos Bay and at 

 Cape Arago, where they contain Cardita planicosta and numerous other characteristic Eocene 

 fossils. Heavy-bedded sandstones prevail in the eastern part of the area, toward the Coast 

 Rainge, where the Eocene rocks have a wide distribution, and shales become abundantly inter- 

 stratified with the sandstones in the western part, near the coast. In the eastern part of the 

 quadrangle the sandstones are penetrated and separated by dark, heavy intrusions of igneous 

 rock, basalt, and the overlying sandstone near by generally contains much sediment derived 

 from it. 



The strata among which the coal beds are found contain at a number of places the fossils 

 which characterize the Arago formation, and it is therefore evident that the coal-bearing strata 

 are of the same age as that formation and form part of it. 



L 10. JOHN DAY BASIN, OREGON. 



Merriam distinguished as probably Eocene the Clarno formation, a deposit of 

 "tuffs, ashes, and lavas," which overlies the Chico (Upper Cretaceous) and is over- 

 lain by the John Day formation (Oligocene) at Clarno Ferry, on John Day River, 

 Oregon. He says : ^'"^ 



At numerous localities along the western side of the John Day Basin there are exposed, 

 either below the lowest John Day beds or above the Chico Cretaceous, several hundred feet of 

 strata which certainly do not belong to either of these horizons. To these beds the name 

 Clarno formation has been applied by the writer. 



Typical exposures of the Clarno are to be seen at Clarno's Ferry, on the John Day east of 

 Antelope, near the town of Fossil, on Cherry Creek, and near Burnt Ranch. 



The Clarno formation is made up almost entirely of erupted materials. Part of the section 

 consists of rhyolite and andesite flows, but the most characteristic portion comprises sedi- 

 mentary beds grading from ashy shale to coarse tuff. The ash and tuff beds frequently contain 

 plant remains in abundance and were evidently, at least in part, deposited in water. The 

 strata seem in some places to have accumulated very rapidly. At one locahty where large 

 specimens of Equisetum have been found in shaly beds, the stems are standing erect and cutting 

 across the stratification planes. This could occur only where deposition or shifting of the 

 ashy mud was taking place verj^ rapidly. The wide extent of the plant beds, which seem to 

 be present at nearly all of the well-known occurrences of the formation, indicates the existence 

 of lacustrine conditions, intermittently at least, OA^er this region during the Clarno epoch. 



The thickness of the Clarno formation is not less than 400 feet. It wiU probably be found 

 to exceed that limit. The strata are usually gray to buff but sometimes show brilliant coloratipn 

 in shades of red, green, and blue. 



The relations of the Clarno to the Cretaceous may be seen just east of the town of Mitchell, 

 where a considerable thickness of andesite and tuff is resting upon the Chico. Again, on the 

 wagon road between Allen's ranch and Mitchell, the Clarno appears to rest upon the western 

 side of the KJioxville anticline. 



a Science, vol. 22, Aug. 18, 1893, p. 97. 



