NONCONFORMITY liKLOW THE OrilGO.- 195 



cause their relative age is not sharply enough defined. Unfortunately, pos- 

 itive structural evidence on this point also is as yet wanting. 



The evidence of the existence of this important non-conformity may 

 be recapitulated in a few words. Tlie pebbles in the conglomerates of the 

 WaUala and the (Jhico groups show that metamorphic rocks existed near 

 them when these beds were deposited, and these pebbles entirely resemble 

 rocks known to be of Knoxville age. If they are really of this age, the 

 metamorphism and upheaval of the Knoxville beds must have preceded the 

 Wallala period and theie must be an unconformity. Again, the strati- 

 graphical relations of the Wallala beds on the coast and of the Chico beds 

 at New Idria to the adjoining metamorphic areas seem inexplicable except- 

 ino- on the tlieory of a non-conformity. Furthermore, a great non-con- 

 formity certainly exists somewhere between the Knoxville beds and the 

 Miocene. None sucli is found between the Miocene and the Ti^jon or be- 

 tween the Tejon and the Chico. Hence the non-conformity must be be- 

 tween the Chico and the Knoxville. Finally, the fossils prove that an im- 

 mense time elapsed between the end of the Knoxville and the beginning 

 of the Chico, while the Chico is now found in contact with the Knoxville 

 at various points. This could not be the case unless an upheaval had inter- 

 vened. 



Identity of the Mariposa and Knoxville beds. TllC gold belt of California, aS llitliertO 



traced out by miners and geologists, is an area of peculiar form. From Mari- 

 posa County to Nevada City, in Nevada County, a distance of about one 

 hundred and fifty miles, the belt is a strip of country nearly parallel to the crest 

 of the Sierra and about thirty miles in width. Northward from Nevada City 

 it rapidly widens, becoming at the same time less well defined. To the north 

 it is finallv terminated by extensive lava fields, while toward the northwest 

 the country gradually loses its auriferous character as the coast is approached. 

 Within the goldl)earing region three fossiliferous areas are known to exist. 

 From the McCloud River to Pence's ranch extends a belt of highly indu- 

 rated limestone containing Carboniferous fossils. In Oenesee Valley the 

 State survey found fossils regarded as Triassic and Jurassic. Both of these 

 localities are far removed from the narrow strip of country lying along the 

 foot-hills from Miiriposa to Nevada, which is often known as the gold belt 



