THE MARSEILLES MORAINE. 31 J 



Kendall County and is represented on the Marseilles topographic sheet. A 

 water parting occurs in this valley-like gap at the inner border of the 

 moraine near the line of Grundy and Kendall counties. It stands only 640 

 feet above tide, while neighboring portions of the moraine on the north and 

 west are about 100 feet higher. About 6 miles southwest from this gap 

 there is a shallower one in which the water parting is 690 feet, or 40 to 60 

 feet below neighboring portions of the morainic crest. At the Illinois 

 Valley the moraine is interrupted by a gap about li miles in width. It 

 stands 675 to 700 feet above tide at the south bluff and 650 to 675 feet at 

 the north bluff. The broad bottom of the valley stands only about 500 

 feet; but this, as shown below, has been lowered by the "Chicago Outlet." 

 These gaps, like the indentations, seem referable to streams issuing from 

 the ice sheet during the formation of the moraine, and perhaps also during 

 the withdrawal of the ice from the plain on the east. 



In eastern Livingston and northern Ford counties the main ridge lies 

 near the north border of the belt. Outside of it, extending nearly to the 

 east fork of Vermilion River (a distance of about 6 miles), there is an 

 undulatory tract probably of morainic character. The surface of much of 

 this tract is fully as undulatory as on the main part of the moraine, and 

 stands nearly as high as the crest of the moraine. Plane tracts one-half 

 mile to a mile or more in width and 25 to ,40 feet in depth extend north 

 from the east fork of Vermilion River nearly to the crest of the moraine, 

 greatly interrupting the continuity of the undulatory tract just noted and 

 giving the appearance of spurs leading out to the south. There is, however, 

 at the east a well-defined crest in this outer belt with a trend approximately 

 parallel with that of the main crest. This suggests the interpretation that 

 the moraine consists of a double ridge in this region, and that its outer ridge 

 has been imperfectly developed or greatly eroded. If the imperfection is 

 due to erosion, it seems necessary to restrict the eroding agency chiefly to 

 water escaping from the ice sheet, for there has been apparently but little 

 postglacial erosion in this locality. 



THICKNESS OF THE DRIFT. 



The thickness of the drift along the Marseilles moraine has a known 

 range from less than 100 feet up to 360 feet. In eastern Kane and western . 

 Dupage counties the thickness along the crest is generally 100 to 150 feet. 



