THE DULUTH PLATE, 1899. N. H. WINCHELL. 



surface eruptives. This marks an important physical event as transpiring in the 

 immediate neighborhood between the date of the Fond du Lac sandstones and that 

 of the quartzyte and conglomerate. This physical change in the environment is 

 indicated by the change in the nature of the accumulating cotemporary sediments, 

 viz., from coarse, siliceous sediments to sediments of eruptive fragments, although, 

 at the river, there is no apparent stratigraphic break. 



The gabbro, as such, is wanting, and in its place is a series of eruptive basic 

 flows which are identical with those seen at Duluth along the lake shore. This indi- 

 cates that the gabbro intrusion was, at the site of this deep well, represented by a 

 succession of extrusions at the surface. 



The bottom of this lower series of eruptives is characterized by the usual fea- 

 tures where the gabbro comes into contact with the Animikie, viz., fusion and blend- 

 ing of the fragmental rocks with the basic eruptives, producing two sorts of igneous 

 rock, one acid, the result of fusion of the elastics, and the other basic, from a deep 

 source. N. H. w. 



