THE MAYAGMAS BELT. 



369 



of the deposits of this district, the 

 Great Western and the Napa Coiisoh- 

 dated, have ah-eady been described. 

 Mr. Turner was instructed to make a 

 reconnaissance of this district as a 

 whole, and the foUowiniif information 

 is chiefly derived from his report. 



The underlying rock of the entire 

 district appears to consist of metamor- 

 phic strata. At the southeastern end 

 of the district some of these beds 

 contain Aucelhi concoitrica, and are 

 certainly, therefore, members of the 7 

 Knoxville series.^ The lithological and | 

 physical character of the metamor- | 

 phic rocks throughout the remainder - 

 of the region is identical with that of ^ 

 the rocks immediately associated with I 

 these fossils here, at Knoxville, and i 

 elsewhere, and there is no reason to | 

 suspect the presence of strata of other .^ 

 age than the Neocomian in the met- ? 

 amorphic series To the north of the = 

 Oathill mines is a small area of un- Z 

 altered rock carrying very imperfect ~ 

 fossils, the age of which is uncertain. " 

 Upon the metamorphic rocks lie great 

 quantities of andesite and basalt. The 

 andesite is for the most part glassy 

 when fresh, though asperites are al- 

 so found- This rock constitutes the 

 greater part of the mass of Mt. St. 



'The exact locality is on the cast bank of Pope 

 Creek, at the poiut at which the road from LiUell to 

 Knoxville cro.sscs it. 



MON XIII '2i 



