Occasional Papers of the Museum of Zoology 3 



brian sandstone around Norway, and considerable thicknesses 

 of this rock along the road to Foster City. These earlier rocks 

 form structural, although not necessarily topographic, troughs 

 or "tongues" of Algonkian rocks between the anticlines with 

 Archean exposure.^ 



The Menominee River, south of Norway, flows along the 

 southern border of the Menominee Trough, and Brown Lake 

 and the Sturgeon River just below it are near the center of 

 the next trough to the north, the Calumet. These cylindrical 

 troughs are mostly formed of perpendicularly folded, meta- 

 morphosed, sedimentary rocks, whereas the remnants of the 

 anticlines consist of huge masses of Laurentian granite. The 

 Cambrian rocks are almost horizontal. 



The rivers of the region are mainly directed by the con- 

 figuration of the glacial deposits ; they flow through the sandy, 

 outwash plains between and in front of the moraines, although 

 they are often partially guided by the granite hills, where 

 these project above the more recent deposits. For this reason 

 they often cross the topographic features of the surface of 

 the underlying rocks, and exhibit many rapids and falls where 

 they have eroded down to the bed-rock. The Menominee, for 

 instance, at Upper Twin Falls cuts across the Ouinnesec 

 Schist, and at Sand Portage it crosses the Hanbury Slate. 



The Sturgeon River leaves the Calumet Trough, which is 

 north of the eroded Archean anticline, about four miles south- 

 east of Brown Lake, and from there flows due south to within 

 a half mile of the Menominee Trough, where it turns west 

 and enters that trough about two miles northeast of the town 

 of Loretto. Here it has formed a gorge at the Falls of the 



1 W. S. Bayley, 1904, The Menominee Iron-bearing District of 

 Michigan. U. S. Gcol. Siirv., Mon. XLVI. p. 34, PL ii. 



