AFTONIAN INTERGLACIAL STAGE 497 



erous trees, which were very abundant in northeastern Iowa, so that their 

 wood is found in the sections of many wells, forming a broadly preserved 

 forest bed. Leaves and wood of deciduous trees, as oak, elm, ash, walnut, 

 and hickory, are also found, indicating a temperate climate similar to 

 that of the present time. 



Near Toronto, about 750 miles east-northeast from Afton, extensive 

 interglacial beds contain remains of numerous species of mammals and 

 trees identical with those of the Aftonian stage in Iowa and Nebraska, 

 so that the Toronto formation is referred by Prof. A. P. Coleman to the 

 same time. He also well refers more northern Canadian forest beds and 

 lignite to Aftonian time, of which he writes as follows : 



"Another widespread tract of interglacial deposits lies 350 or 400 miles north 

 of Toronto, along river valleys of the James Bay region, with an extent from 

 east to west of 100 miles and from north to south of 50. It includes 27 known 

 outcrops of interglacial lignite or peat, scattered over an area of several thou- 

 sand square miles. Logs of wood 17 inches in diameter have been found in 

 the beds." 5 



In twelve counties of southern Minnesota, wells in the glacial drifts 

 encounter interglacial beds containing wood, layers of peat, and occasion- 

 ally shells of fresh-water and air-breathing mollusks, which layers are 

 underlain and overlain by till, the direct deposit of an ice-sheet. These 

 counties, described by the State geologist, the late Prof. N". H. Winchell, 

 and by the present writer, in the first volume of the Final Eeport of the 

 Geological and Natural History Survey of Minnesota, are, in their order 

 from east to west, Fillmore, Mower, Freeborn, Steele, Faribault, Martin, 

 Jackson, Cottonwood, Brown, Redwood, Lyon, and Rock counties. 



Professor Winchell recorded many such wells in Mower County and 

 adjacent parts of Fillmore County that penetrate a bed of peat carrying 

 pieces of wood thought to be pine and cedar. This interglacial peat bed, 

 varying from about one foot to six or eight feet in thickness, lies at 20 to 

 25 feet beneath the surface of Le Roy and Grand Meadow townships and 

 the city of Austin. In other parts of Mower County it occurs at depths 

 of 35, 45, and 50 feet. It probably is continuous with the extensive inter- 

 glacial forest bed of Aftonian age in northeastern Iowa which was studied 

 early and well reported by McGee. The other counties to the west have 

 less abundant records of wells that pass through or into interglacial forest 

 and peat beds, which would indicate that there they were largely removed 

 by the erosion of the ensuing stages of glaciation. 



Evidence of a long interglacial stage, here regarded as the Aftonian, 



5 Report of the International Geological Congress in Toronto, 1913, pp. 435-449. 



