PREGLACIAL RIVERS IN THE SAINT CROIX VALLEY 17 



region that tlie occurrence of the two short, grandly ])ictures(iue rock 

 gorges, or canyons, known as the Upper and Lower Dalles of the Saint 

 Croix, so named by the French voyageurs in allusion to their inclosing 

 walls of rock, strongly suggests that there the stream is now flowing in 

 a course which it has cut during and since the Ice age. No closel}^ ad- 

 jacent belt, however, seems to be })robably identifiable as a drift-filled 

 preglacial valley. Therefore, from my studies, for the IMinnesota Geo- 

 logical Survey, of the country extending many miles westward from the 

 Saint Croix, I conclude that in preglacial times this river was repre- 

 sented by two quite independent rivers, each flowing into the Mississippi. 



The greater part of the Saint Croix drainage basin, including all above 

 the rapids, six miles long, which end at Saint Croix Falls and Ta3dors 

 Falls, I think to have belonged before the Ice age to a river flowing south 

 and southwest from the principal elbow of the present Saint Croix, taking 

 approximately the course of the Sunrise river, which, however, now runs 

 northward, and traversing Anoka count}^ to a junction with the Missis- 

 sippi somewhere between Anoka and Minneapolis. Thence, as Professor 

 N. H. Winchell has shown, the preglacial course of the Mississippi 

 probably passed southeastward.* It may have coincided nearly with 

 the site of lake Phalen, close northeast of Saint Paul, running thence 

 south two miles to join the present valley near the State Fish Hatchery, 

 where the northeastern bluff of the Mississippi for a distance of about 

 a mile consists of morainic glacial drift without rock outcrops. Between 

 lake Phalen and this place, a well at the Saint Paul Harvester works, 

 about 863 feet above the sea, penetrated 235 feet of drift deposits before 

 reaching the bed-rock, thus revealing the existence of a preglacial chan- 

 nel eroded there by a river that flowed at a level 55 feet below the present 

 Mississippi. t 



A broad, low belt of sand and gravel plains stretches across the dis- 

 tance of nearly 40 miles from the Saint Croix to the Mississippi at Anoka, 

 nowhere having a greater height than 150 feet above the elbow of the 

 Saint Croix and the mouth of the Sunrise river. On the east, between 

 that low tract and the Saint Croix valley, a belt of rolling and hilly 

 glacial drift or till underlain in part by the bed-rocks at a greater alti- 

 tude than the sand and gravel area westward divides it from this valley. 

 It seem to me more likel}^ therefore that the old river passed far west 

 and south, to Anoka and Saint Paul, than that it took the course sug- 



*"An approximate interglacial chronometer," Am. Geologist, vol. 10, pp. 69-80, with sections 

 and a map, August, 1892. On this map the probaltle preglacial and interglacial channels of the 

 Mississippi in the vicinity of Minneapolis and Saint Paul are delineated, differing much from its 

 present course, 



t Geology of Minnesota, Final Report, vol. 2, 1888, pp. 3G1-3G3. 



