1913] Dickerson: Fauna of Eocene at Marysville Buttes 261 



cussion of the lone and Tejon given in the Marysville Folio, and 

 in addition gives a list of marine fossils fonnd two miles east 

 of South Buttes. 



Stratigraphic Relations and Lithology op Marysville Buttes 



Eocene 



According to the authors of the Marysville Folio, the buttes 

 consist of a central core of coarse grained andesite which was 

 forced up in the valley floor, a ring of sedimentary beds which 

 were upturned when the lava was forced out, and a ring of 

 andesitic muds which were thrown out from secondary craters 

 on the edge of the sedimentary ring. In general, the sedimentary 

 beds dip away from the central core. The only Eocene area 

 which is mapped in the Marysville folio is a strip about a mile 

 and a quarter long by a quarter mile wide on the west side of 

 the buttes two miles east of the South Buttes. The Eocene in 

 this area is overlain by the lone formation which has a dip of 

 15° W., while the Eocene has in most places a dip of 35° to 

 40° W., strike N 90? W., although the dip is nearly vertical near 

 West Butte peak. The lone consists of gravels and sands, for 

 the most part unconsolidated. Cross-bedding is very common 

 and intricate. These sediments were probably deposited on the 

 Eocene as an alluvial fan. The lone in turn is overlain by 

 andesitic mud flows — now firmly cemented — which dip to the 

 west about 4° -5°. 



An east-west section through West Butte largely adapted 

 from the Marysville Folio shows the following sequence on the 

 west side : 



100 feet of green-gray sandstone and shale with limestone con- 

 cretions marking the upper limit of the Eocene. 



300 feet of green-gray, glauconitic shale. 



200 feet of massive, thin-bedded, buff sandstone. 



100 feet of impure, gray limestone with thin strata of hard gray, 

 medium-grained sandstone. 



600 feet of massive, medium-grained, yellow, non-fossiliferous sand- 

 stone in contact with the andesitic core. 



