346 C. W. HALL KEEWATIN OF EASTERN AND CENTRAL MINNESOTA 



contacts and a few artesian wells. The last afford evidence of the super- 

 position of the Cretaceous shales over the granitic rocks. At Glenwood, 

 on the northwestern border, granitic rocks occur at a depth scarcely 

 greater than 50 feet below the water of lake Minnewaska. At Paynes- 

 ville, southwest Stearns county, not more than 12 miles from outcrops 

 of granitic rocks, Cretaceous shales were discovered at 70 feet below the 

 surface. . How deep the crystalline rocks lie was not determined. At 

 Glencoe, directly south of Saint Cloud, red quartzite rocks were reached 

 at 936 feet and bored into 700 feet farther. Just where the southern 

 subglacial boundary lies has not yet been determined. At Anoka, 40 

 miles from the most southerly granites, wells determine the presence of 

 the Paleozoics, which extend thence down the Mississippi valle3^ At 

 Minneapolis granitics were reached in the T^akewood Cemetery well at 

 2,150 feet from a point 975 feet above the sea. Along the east side of 

 the district along which the crystallines disappear beneath Cambrian 

 sandstones these disappear abruptly against the Great fault, determin- 

 ing the western limit of the Keweenawan lava flows. 



The geographic limits of the rock series under consideration may thus 

 be summarized : On the south, while disappearing beneath the Paleozoic, 

 they continue beneath these beyond Minneapolis, Winona, and La Crosse, 

 where well-borings have established the presence of granitic rocks ; to the 

 east as far north as township 46, range 16 west, while beneath Cambrian 

 sandstones westward the schists are abruptly broken by the great Ke- 

 weenawan fault; northeastward they slope beneath the Keweenawan; 

 northward they must be overlain by the westerly stretching Mesaba; 

 but to the west the glacial drift and Cretaceous so comi)letely obscure 

 the relations of the older rocks that it is now impossible to correlate with 

 positiveness the central Minnesota granites and the Minnesota Valley 

 gneisses and gabbro-schists. 



Keewatin of THE Saint Louis River District 



ROCKS OF THE SERIES AND THEIR RELATIONS 



In the bed of Mission creek, sections 30 and 31, township 49, range 15 

 west, near the boundary between Saint Louis and Carlton counties, lies 

 the easternmost exposure of the Thomson slates. In the gorge of the 

 Saint Louis river, where Mission creek joins it, the slates form the river 

 bed. From this point they are practically continuous to Knife falls, a 

 distance by river of 15 miles. The strike is east and west, the dip gen- 

 erally south, at a varying angle. Above Knife falls occasional exposures 

 are seen as far as section 27, township 51, range 19 west. 



