28 PLEISTOCENE OF INDIANA AND MICHIGAN. 



The moraines of the Huron-Erie lobe east of the reentrant differ in type from those formed 

 by the Lake Michigan lobe on the west. They lack the strong bold ridges of the moraines of the 

 Lake Michigan lobe and vary greatly in expression from place to place. A portion- of pronounced 

 morainic type with closely aggregated bowlder-strewn hummocks inclosing numerous basins 

 may be followed within a few miles by a stretch where the knolls or hummocks are very scat- 

 tered, and the whole aspect is vague. In places bowldery strips tie together well-defined sec- 

 tions, but in some places even these fail, leaving the ice border without definite trace. The 

 bowldery belts also take singular turns away from the moraines, some of them in fact lying 

 more nearly coincident with the direction of ice movement than with the trend of the ice border. 

 This lack of continuity characterizes all the moraines of Wisconsin drift in Indiana outside the 

 Mississinawa morainic system of the Huron-Erie lobe. 1 That system and later ones in the series 

 formed by the Huron-Erie lobe, though less bulky than the moraines of the Lake Michigan lobe, 

 are weU-defined ridges that control the drainage and admit of easy tracing. 



EARLIER AND LATER WISCONSIN. 



The contrast between the features of the Lake Michigan lobe and those of the Huron-Erie 

 lobe and especially the contrast in topography were at first thought to show a difference in age, 

 the sharp hummocky shapes east of the reentrant angle being thought to be fresher than the 

 gentle undulations of the drift of the Lake Michigan lobe west of it. This idea has been widely 

 introduced into the literature and on it is based the division into earlier and later Wisconsin, 

 the moraines of the Lake Michigan lobe, from the Shelbyville to the Marseilles, having been 

 placed in the earlier Wisconsin, and nearly all those of the Huron-Erie lobe of the ice field hav- 

 ing been classed as later Wisconsin. 



The argument drawn from the differences in contour was supported by an overlapping 

 upon the eastern ends of the moraines of the Lake Michigan lobe by bowldery strips that have 

 a trend in harmony with the moraines of the Huron-Erie lobe and that contain rocks character- 

 istic of the Huron-Erie ice. Thus the four moraines in the Bloomington morainic system of 

 the Lake Michigan lobe, which trend west-southwest and east-northeast near their eastern ends, 

 are crossed about at right angles by a bowldery belt which runs north-northwest and south- 

 southeast from eastern Iroquois County, 111., across western Benton and Warren counties, Ind., 

 to the Wabash Valley at Attica, and which to the south of the Wabash is associated with a 

 moraine -of the Huron-Erie lobe. It was thought that the bowlder belt north of Attica, hke 

 that south of the Wabash Valley, was formed at the border of the Huron-Erie ice and that its 

 incursion into the region occupied by moraines and till plains of the Lake Michigan lobe neces- 

 sitated the earlier disappearance of the Lake Michigan lobe. In the vicinity of the bowldery 

 strip certain deposits of till, among which is the gray till on Stone Creek near Wilhamsport, 

 appear to be a product of movement from the east. 



.Another feature which was thought to support the division into earlier and later Wisconsin 

 is the cross striation in western Indiana; one set of striae bears southward as if formed by the 

 Lake Michigan lobe, and a later set bears westward as if formed by the Huron-Erie ice movement. 

 It now appears, however, that the southward-pointing striae were produced at the Illinoian 

 rather than at the Wisconsin stage, for they occur farther east than the Lake Michigan glacier 

 is known to have extended in the Wisconsin stage and farther south than the Wisconsin drift 

 limit. For this reason they can not be 'used for differentiating the so-called earlier and later 

 Wisconsin movements. 



The early hypothesis implies great discordance in glaciation in the Lake Michigan and 

 Huron-Erie portions of the Labrador ice field. Under it not only must the Lake Michigan ice 

 have melted back about to the limits of the Lake Michigan basin, and have developed 

 several very bulky moraines in the course of its recession while the Huron-Erie ice held 

 nearly its maximum position, but the Lake Michigan ice border must afterward have 

 maintained its position just outside the limits of the Lake Michigan basin and have formed 



> Mon. U. S. Geol. Survey, vol. 41, 1902, pp. 494-509. 



