390 



University of California Publications in Geology [Vol. 9 



in Science, suggested an Eocene age for the lone and associated for- 

 mations. 



Stratigraphy 



The base of the Eocene strata of South Table Mountain is exposed 

 in the old Miocene Hydraulic Mine, one mile north of Oroville. The 

 basal conglomerate, about twenty feet in thickness, rests upon Chieo 

 rocks from which Mr. Ruckman obtained specimens of Trigonia 

 evansana, and Citcullaea, sp. Twenty feet of clay strata rest upon 

 this conglomerate. These two lithologic members were recognized 

 in the Rumble Mine, one-half mile northwest of this locality, at 

 County Hospital Hill, one mile west, and in the Dyer mining shaft, 

 two and one-half miles north of Oroville. A study of the sediments 

 as exposed in the Dyer shaft and the south face of South Table 

 Mountain gives in descending order the following approximate 

 sequence : 



Feet 



(9) Older basalt 100 to 150 



(8) Andesitic tuff breccia 10 to 20 



(7) Alternating sandstone, clay and carbonaceous shales 100 



(6) Conglomerate 50 



(5) Tuffaceous clay 20 



(4) Yellow, tan sandstone 100 



(3) Dark gray shales interbedded with lignite containing fos- 



siliferous strata, and thin-bedded fossiliferous sandstone 40 



(2) Clay with tuff fragments 20 



(1) Conglomerate resting upon Chico sandstone 20 



The remaining sedimentary series on the west side of Oroville 

 Table Mountain and South Table Mountain are composed of similar 

 sediments and are beyond doubt the same as those south of South 

 Table Mountain. Turner 47 reports finding Corbicula, sp. in these 

 strata at a point about one and one-half miles south of Pentz (form- 

 erly called Pence's Ranch), where they rest upon Chico rocks which 

 contain a very abundant upper Cretaceous fauna. 



The conditions of sedimentation in Morris Ravine and at the 

 Cherokee mine have been described admirably by Lindgren 48 as 

 follows : 



The well-known Cherokee hydraulic mine ... is situated at the 

 north end of Table Mountain. . . . The bedrock of the channel mined 



47 Turner, H. W., The Rocks of the Sierra Nevada, Fourteenth Ann. Rept., 

 U. S. Geol. Survey, pt. 2, p. 463, 1894. 



is Lindgren, W., Tertiary Gravels of the Sierra Nevada of California, 

 pt. 2, p. 90, 1911. 



