398 University of California Publications in Geology [Vol. 9 



Relation of the Auriferous Gravels to the Ione Formation 



Essentially the same relations as were found at Oroville 51 exist be- 

 tween the Auriferous Gravels in the vicinity of lone and the lone 

 formation. Along the Calaveras River three miles east of Stone 

 Corral the intimate relationship of the Auriferous Gravels to the 

 lone is shown by the mapping in the Jackson Folio. Both rest di- 

 rectly upon the diabase of the basement complex and they are only 

 a quarter of a mile apart in one locality. The mapping in the vicin- 

 ity of Campo Seco shows a direct relation between the marine lone 

 and the gravels. The lone area at Mule Town two miles north of 

 lone has all the characteristics of the Auriferous Gravels and might 

 have been mapped as such but for its evident close association with 

 the lone a short distance further west. A direct connection seems 

 to exist between the marine lone and the stream deposits of the 

 Sierra Nevada. Probably short consequent high-grade streams 

 emptied into the Eocene embayment now represented by the lower 

 member of the lone. Apparently the shore line passed through the 

 present sites of the towns of lone, Buena Vista, and Valley Springs. 



These facts show that the lone is the marine or estuarine equiv- 

 alent of the Auriferous Gravels, stream-laid deposits of the Sierra 

 Nevada. 



THE IONE FORMATION NEAR MERCED FALLS 



Until these three members were studied at the type locality, the 

 relationship of the small area south of Merced Falls, which was 

 mapped by Ransome and Turner as Tejon, to the adjoining lone tuffs 

 and clays was obscure. The clays, sands and tuffs exposed one mile 

 west of Merced are lithologically identical with those of the lower- 

 most member, and the red sandstone mapped as Tejon found here 

 is identical with that of the second or sandstone member of the lone 

 of the type locality. The same condition evidently prevailed here 

 as in the area between Waters Peak and Buena Vista Peak, that is, 

 a deposition along the shore line of a rapidly transgressing western 

 sea. In this sandstone, casts of the Yenericardia planicosta merriami 

 were found near the top. The authors of the Sonora Folio, Messrs. 

 Turner and Ransome, 52 described this as follows : 



si Dickerson, R. E., Note on the Faunal Zones of the Tejon Group, Univ. 

 Calif. Publ. Bull. Dept. Geol., vol. 8, p. 23, 1914. 



52 Turner, H. W., and Ransome, F. L. Sonora Folio, U. S. Geological 

 Survey, p. 2, 1897. 



