PLATE LXXXV. 



PIGEON POINT PLATE, 1899. N. H. WINCHELL. 



There is no part of the state of equal size which is so mountainous. Along the 

 northern boundary the Pigeon river descends, like nearly all the streams that enter 

 lake Superior from Minnesota, rather suddenly from 600 to 700 feet. It presents, 

 below the "grand portage," a continuous series of rapids and waterfalls as far as 

 Pigeon River falls, below which, with some difficulty, small canoes can float in the 

 river to the head of Pigeon bay, which is a fine harbor for large vessels. 



The hills are abrupt and rocky, consisting of great dikes of diabase and gabbro 

 that lift their heads up through the slates which they penetrate sometimes with 

 perpendicular walls from 50 to 200 feet above the slates which they cut. As these 

 dikes, which are often several hundred feet wide, must have been confined between 

 rock walls when the molten matter was intruded, there is evidence of the removal 

 of that amount of strata of the Animikie by circumdenudation from the dikes. As 

 there is no other place in the state where such a phenomenon is thus displayed, it 

 is evident that the enclosing rock must have been one that was easily destroyed, 

 quite unlike the Animikie that is known on the boundary line further west and on 

 Pigeon point. This, indeed, is known to be the character of the Grand Portage gray- 

 wacke. The hills are rudely arranged in ridges which extend easterly and north- 

 easterly, though with exceptions, the most remarkable of which is the peninsula of 

 Hat point, which is at right angles to the prevailing direction and may be in part a 

 lava flow from mount Josephine. 



The geological history of this little tract, so far as known at present, is about 

 as follows, beginning at the bottom: 



1. The Animikie strata were formed. On the area included within this plate 

 only two of those parts of the Animikie that prevail further west are known, viz., 

 the fissile black slates and the quartzyte, but there is, in addition, above (?) the 

 Wauswaugoning quartzyte, the imperfectly slaty, greenish-gray member, or Grand 

 Portage graywacke. 



2. Surface eruptives and flows of basic rock, probably of minor importance. 

 These are seen on some of the Lucille islands south of Pigeon point, where they seem 

 to lie on the upper portion of the Animikie, cut by the great dikes of the country. 



3. Epoch of profound igneous intrusion (Cabotian) forming the most of the 

 dikes and sills of gabbro that invaded the Animikie. This event cannot probably be 

 definitely separated from the last. The rocks of these two epochs doubtless run 

 together in other places, especially where the ancient surface is preserved. But 



