248 ROLLIN T. CHAMBERLIN 



the unaltered red drift, from whose ice-sheet they are unquestionably 

 the outwash. Occurring beneath the gray drift nearly everywhere 

 between the Franconia moraine and the river, they belong to the 

 glacio-fluvial work at the Franconia stage. No limestone pebbles 

 are found in situ within these deposits, though much limestone 

 frequently has rattled down, as talus, from the gray drift above, 

 and the gravel has often been cemented into a Pleistocene conglom- 

 erate by the calcareous waters from the later till-sheet. 



In July, 1904, beds of humus material and clay containing pelecy- 

 pod and gastropod shells, apparently of land types, were reported 

 to have been found between the red till and the stratified drift above, 

 in one of the gullies south of Franconia. In August these beds could 

 not be found. Evidences of slumping were everywhere, induced by 

 the unusually heavy rains of July; possibly the reported interglacial 

 beds had been buried; perhaps they themselves were earlier slumps 

 partially covered with gravel talus. Elsewhere in the same gully, 

 and in the various tributaries where good exposures of the till and 

 outwash gravels could be examined, the contact was clearly marked 

 without any indication of a soil line. The same conditions obtain 

 in the numerous cuts and sections in the strip between the moraine 

 and the river. Vegetable matter and fossiliferous clay, in place, 

 between the red till and red overwash, would mean that, after the 

 unstratified drift was deposited, the ice retreated west far enough 

 and for a time long enough to permit the growth of vegetation and 

 the immigration of mollusks, and that it again advanced, producing 

 the Franconia moraine and the overwash gravels. 



West of the Franconia terminal is a gently rolling ground-moraine 

 topography for several miles beyond the boundaries of the quadrangle. 

 Still farther in this direction, a region of many lakes and some moraine 

 belts was seen from the train; but, since the gray drift becomes 

 thicker toward the west, it was not apparent how much of the topog- 

 raphy is to be assigned to the red ice. The main fact is that the 

 red glacier retreated toward Lake Superior before the gray ice invaded 

 the region. How far the red had receded by the time the gray 

 appeared, and where the two ice-sheets met, if they ever did come 

 together, are questions which cannot be answered from a knowledge 

 of the St. Croix region alone. Upham 1 reports a soil line between 



1 Geology of Minnesota, Vol. II, p. 414. 



