SAGINAW LOBE. 129 



ward by Iroquois River into Kankakee River would nave been prevented by the ice sheet from 

 draining in that direction, and it probably discharged across a low point on the western rim of 

 the basin to the east fork of Vermilion River in northern Ford Comity, 111. 1 The distribution 

 of the sand deposits in the Iroquois basin lends support to this interpretation. A sand ridge 

 leading through Onarga and Ridgeville, 111., at an altitude of about 675 feet above sea level, is 

 thought to mark the southern edge of the lake in the western part of the basin and to indicate 

 its height. There may also have been an eastward discharge from the basin past Monon, Ind., 

 into Monon Creek and thence to Tippecanoe and Wabash rivers. A long sand ridge leading 

 eastward from the meridian of Goodland, Ind., nearly to Monon stands at about 675 to 680 feet 

 and probably marks the southern edge of the lake. Nearly all the sand in the Iroquois basin 

 is below the level of these sand ridges, and the portion above does not conform to the conditions 

 of a lake shore. Its ridges rise and fall in their course across the country and seem to have been 

 developed by wind rather than by water. In places a fine silt has been deposited within the 

 area supposed to have been covered by the lake ; one such locality was noted a few miles south- 

 west of Rensselaer, Ind., and another in Iroquois County, 111., between Watseka and Donovan. 



Sandy areas farther east in the district between Monon Creek and Tippecanoe River, like 

 those east of the Tippecanoe in Pulaski and White counties, were probably laid down in con- 

 nection with the recession of the Erie-Saginaw portion of the ice sheet. The headwater portion 

 of Monon Creek is in a bowlder-strewn basin nearly surrounded by slightly higher sandy tracts. 

 This basin, which occupies an area of about 25 square miles, may perhaps have held a mass 

 of stagnant ice during the deposition of the surrounding sand deposits. Similar depressions 

 near Winamac and above that village along the borders of Tippecanoe River seem to mark 

 places where the ice persisted during the deposition of sand over the bordering district. Some 

 small areas free from sand in southeastern Starke County, both southwest and west of Bass 

 Lake, may perhaps be explained in the same way. 



Outside of the Valparaiso morainic system and its gravel outwash the Kankakee basin is 

 covered by sand except over a small area in southwestern Starke and northeastern Jasper 

 counties where a bowldery till forms the surface. The altitude of this till area is between 660 

 and 670 feet, somewhat lower than that of the surrounding sand-covered tracts and 30 to 40 

 feet lower than that of the sand 2 or 3 miles to the south. As in the districts to the east, the 

 absence of the sand from this low tract may be due to its occupation by ice during the depo- 

 sition of the sand. 



Considerable attention has been given to the slope of the sandy tracts with a view to deter- 

 mining the direction in which the waters probably flowed. In the Kankakee basin they seem 

 to have flowed westward from the time the Lake Michigan ice lobe shrank away from the south- 

 ern edge of the valley. In the Iroquois basin they probably flowed westward, though, as just 

 indicated, they may have been ponded to some extent south of the Marseilles morainic system. 

 In the Tippecanoe basin conditions are more complex: The river flows chiefly among moraines 

 for more than half its length before entering this sand area. At its point of entry near Ora 

 (see PI. VI) it is closest to Kankakee River. From this point the sandy plain slopes north- 

 westward toward the Kankakee as well as southwestward into the territory traversed by the 

 Tippecanoe, forming a very flat alluvial cone. This suggests a spreading of drainage from this 

 part of the Tippecanoe during the height of the glacial floods. The present stream for some 25 

 miles below Ora takes a zigzag course through a series of bowlder-strewn depressions which the 

 sand did not fill and which, as already suggested, may have been occupied by remnants of the 

 ice sheet during the deposition of the sand. The sand on the western side slopes away from the 

 river toward Monon Creek, continuing the southwestward slope it had on the eastern side. 

 Thus Monon Creek, although a tributary of the Tippecanoe, flows through a district lower than 

 that of the main stream. The divide between Monon Creek and the headwaters of the Iroquois 

 is very low and flat, especially south of the Marseilles morainic system, and the general south- 



i Leverett, Frank, The Illinois glacial lobe: Mon. U. S. Geol. Survey, vol. 38, 1899, pp. 289-290, 314. 

 34107°— 15 9 



