Mbkriam.] 



Jolin Day Basin. 



313 



on a terrace about 75-100 feet above the river. Twenty-five feet 

 below this is the sagebrush flat made up of alluvium with numerous 

 angular boulders and pebbles from the hills near by. At another 

 locality, about two miles farther up the river, water-worn gravels 

 were again seen on well-marked benches. 



Along a considerable part of the river, terraces representing 

 parts of ancient alluvial fans or slopes are very common. On the 

 north side of Bridge Creek near Allen's ranch numerous broad, 

 gently-sloping tables separated by gullies sometimes several hun- 

 dred feet deep represent an old and very regular alluvial slope. 

 The stream cuttings here show in places a considerable thickness 

 of the John Day beds capped by irregularly stratified wash from the 

 adjacent lava bluffs. 



In terrace deposits remains of Elephas and Eqmis have been 

 found at several localities. Near Mt. Vernon, on the East Fork, a 

 nearly complete skeleton of Elephas primigenius was discovered in 

 an alluvial deposit not much above the level of the river. Whether 

 or not the other remains have been worked over from older depos- 

 its, this skeleton has evidently not been disturbed. 



Canon Cutting. — The discovery of typical Quaternary forms 

 in deposits so near the valley floor shows that the canon cutting 

 had been practically finished for some time when Quaternary 

 mammals were still in this region. In other words, the period 

 of active canon-cutting did not extend to the close of the Qua- 

 ternary. The backward extension of this period is limited by 

 the Rattlesnake. Though the drainage was probably established 

 before the close of that epoch, the great work of corrasion was 

 accomplished after the river began cutting into the uppermost 

 Rattlesnake beds. A palaeontological determination of the age 

 of the Rattlesnake would very materially aid in fixing more 

 exactly the probable earlier limit of the era of canon-cutting. 

 The greatest probable extension of this epoch is from late 

 Pliocene to middle Quaternary. On these broad lines a correla- 

 tion of this period with the Sierran * epoch of Le Conte would seem 

 to be justified. 



Jour. Geol., 1899, V. 7, p. 525. 



