S88 J. S. DILLER THE JURASSIC FLORA OF OREGON 



by Professors Ward and Fontaine in the Twentieth Annual Eeport of the 

 TJ. S. Geological Survey, part ii, and Monograph XLVIII. 



The plants were obtained in slates mainly in the next ravine east of 

 Morris ravine, a little west of south from the Banner mine, between the 

 wagon road and the river. 



The identity of 12 out of the 28 fossil plants found near Oroville with 

 those of the plant beds already referred to at Buck peak and Mchols, in 

 Oregon, led Ward and Fontaine to regard the beds at Oroville as belong- 

 ing to essentially the same horizon as the Oregon beds — that is, to late 

 Jurassic. 



LITEOLOar 



The Monte de Oro beds are composed of slates, sandstones, and con- 

 glomerates in small layers, irregularly interbedded. The slates, gener- 

 ally somewhat shaty, are gray to black in color and form more than half 

 of the whole mass. Exposed to the weather, they become light colored 

 and appear to be but little altered, though locally sheared and containing 

 a number of quartz veins generally parallel to the slaty cleavage. Beneath 

 the surface the slates appear more altered. They are often black, de- 

 cidedly slaty, and more frequently traversed by veins of quartz. The 

 yellowish to dark gray sandstones, ' often shaty, pass into conglomerate, 

 which generally contains, besides siliceous pebbles and dark fragments of 

 shale, numerous greenish pebbles of altered igneous rocks of andesitic 

 types. 



AURIFEROUS QUARTZ VEINS 



Several definite auriferous quartz veins of considerable size occur in this 

 belt and have been worked in the Banner mine, which is said to have 

 yielded some hundreds of thousands of dollars. In answer to my queries 

 concerning the relation of the ore bodies to the slate belt and whether there 

 may be two formations in the belt, Mr George H. Evans and Landis S. 

 Scrutton, successively superintendents of the Banner mine, have kindly 

 furnished me the following information : 



"The ore bodies of the Banner mine were found in just such slate roclis as 

 are now visible on the surface. The vein was a very persistent one in depth. 

 At the 3,000-foot level, the greatest depth attained, the vein was beautifully- 

 formed with fine smooth walls and the same character of country rock as at 

 the surface. Speaking generally, however, the values almost gave out below 

 the 500-foot level. 



"There are at least four conspicuous quartz veins outcropping in the narrow 

 Banner slate belt, but unless one is well acquainted with the spot, it is hard to 

 find them on aceoiuit of the brush. 



"There is only one formation in the said slate belt as far as we know ; 

 bunches or lenses of conglomerate and sandstone are occasionally met with 

 down to the greatest depth attained." 



