EfiSUMfi OF LITERATURE. 107 



tatioii, but conglomerates, graywackes, quartzitic schists, and glossy 

 serpentinous schists are present. The Kawishiwin formation, apparently 

 the upper member of the series, embraces the great bulk of the greenstones, 

 chloritic schists, jaspers, and hematites. The iron ores are in lenticular 

 lodes, and stand upright, conformable with the general position of the rocks. 



6. The Keewatin sei'ies becomes more crystalline toward the bottom, 

 and passes conformably into completely crystalline mica-schists and horn- 

 blende-schists, which are named the Vermilion series. The rocks are usu- 

 ally stratiform, contain magnetic iron ore, and embrace some dark massive 

 greenstone belts, in which iio stratification bauds are visible. 



7. The Laurentian. When not disturbed by upheaval the Vermilion 

 schists pass into Laiu-eutiau gneiss, there being a gradual increase in the 

 feldspathic and siliceous ingredients. Even after the Laurentian characters 

 are apparently fully established, conformable bands of Vermilion schists 

 reappear, from which it is plain that the base of the Vermilion is an uncer- 

 tain plane, which can not be located exactly. This normal passage from 

 the Vermilion to the Laurentian is frequently disturbed by tlie intrusion of 

 numerous dikes of light-colored granitic and basic rocks. These Avere 

 both in a fluid state, the only nonfluid rocks being tlie schists which are 

 embraced within them in isolated pieces. In a similar manner small 

 areas of Laurentian granite are sometimes directly in contact with schists, 

 which have the imperfectly crystalline condition of the Keewatin. 



Nos. 3 and 4 are separable from No. 2 by divergence in dip and strike, 

 as well as by a marked difference of lithology. There is consequently some 

 evidence of unconformity between them. Below No. 4 is a great physical 

 break, which separates Nos. 1, 2, 3, and 4 from 5, 6, and 7 throughout the 

 Lake Superior region. This break is the greatest erosion interval which 

 has been discovered in Paleozoic geology. Nos. 1, 2, 3, and 4 together 

 constitute the Taconic. Nos. 5, 6, and 7 constitute the fundamental com- 

 plex or Archean, which is a unit in its grander features. 



Grant, U. S. Field observations on certain jj-ranitic areas in northeastern Minne- 

 sota: Twentieth Ann. Rept. Geol. and Nat. Hist. Surve}- Minn., for 1891, 1893, 

 pp. 35-110. One map. 



Grant, in 1893, publishes his notes made on a trip in northeastern 

 Minnesota. The areas visited were those of Kawishiwi River, Snowbank 

 Lake, Kekequabic [Cacaquabic] Lake, and Saganaga Lake. 



