OLDER DRIFTS IN THE ST. CROIX REGION 545 ' 



Pebbles in this exposure of the drift were small and scarce. They 

 were mostly soft, showing evidence of much weathering and age. 

 The classification of the pebbles collected shows the unmistakable 

 Keewatin character of the drift even in the absence of limestone. 

 The abundance of chert suggests the former presence of the calcareous 

 element. This occurrence of western drift is three miles east of the 

 limiting terminal moraine of the Keewatin glacier of the Wisconsin 

 epoch, showing that this earlier Keewatin ice-advance was more 

 powerful than the last. 



The upper oxidized portion of this old Keewatin drift has now been 

 recognized in limited sections in various other portions of the quad- 

 rangle. It has been brought to light in constructing the new rail- 

 way spur from St. Croix Falls station down to the electric-power 

 dam, and evidences of it have been seen on the Taylor's Falls side of 

 the river. These occurrences suggest that if the entire region had 

 not been buried beneath such heavy deposits of Wisconsin drift this 

 supposed Kansan drift would be found to constitute an important 

 sheet. 



THE LOWER RED DRIFT 



In the gully in which the true grayish-black till was first detected 

 no pre- Wisconsin red drift was exposed to view, but in the next 

 ravine to the north there was visible an intensely red, firmly con- 

 solidated till, or hardpan, upon which rested a rather ferruginous 

 sand, and above that the fresher-appearing sand and gravel of Wis- 

 consin age. A much,, better section is afforded by the wide, open 

 ravine in the N.W. ^, Section 15, Franconia (i^ miles southeast of 

 Franconia). Near the head of this ravine the gray Keewatin drift 

 of Wisconsin age is seen resting upon the red Wisconsin sands and 

 gravels from Lake Superior and Labrador. Lower down toward the 

 river is a bank of reddish-brown to pinkish-red sandy till which is 

 bright carmine red at the top. Though a true red drift, it contains 

 many limestone pebbles in some places and locally boils up briskly 

 with acid. The Wisconsin red drift of this region is indifferent to 

 acid and it is very seldom that a fragment of limestone is found with- 

 in it. A sharply defined contact separates the hard red calcareous 

 till from the overlying unconsolidated sands which undoubtedly 

 belong to the Wisconsin red drift. At the top of the underlying red 



