96 PLEISTOCENE OF INDIANA AND MICHIGAN. 



the descent to this northern plain is abrupt, but as a rule it extends over a distance of 2 miles 

 or more. The east-west trend of the north border of this elevated undulating tract probably 

 conforms to a late position of the ice border during the development of the Bloomington 

 morainic system, or a bowlder belt and weak moraines which are thought to be close successors 

 of the Bloomington system parallel it a few miles to the north. During the early development 

 of the morainic system the ice border seems to have had a northwest-southeast trend and to 

 have passed from southwestern Lafayette County across northeastern Montgomery County. 



Montgomery County. — The strong moraines of southwestern Tippecanoe County are paral- 

 leled on the inner or northeast border by a gently undulating but very bowldery tract 3 to 2 

 miles wide which leads from the Wabash Valley near the Fountain-Tippecanoe county line 

 southeastward to Linden, in northern Montgomery County, and thence past Darlington to the 

 eastern edge of the county, about 10 miles east of Crawfordsville, beyond which it is not clearly 

 marked. This tract is commonly known as the Linden-Darlington bowlder belt and is thought 

 to mark a position of the ice border, but not the maximum position held during the develop- 

 ment of the Bloomington morainic system. 



The moraines of southwestern Tippecanoe County do not continue with strength into 

 Montgomery County. The outer one is traceable no farther than the Coal Creek valley in the 

 north edge of the county. The second one, though easily traced to Sugar Creek near Craw- 

 fordsville, lacks the strength displayed nearer the Wabash Valley. Its knolls are not closely 

 aggregated, but inclose nearly plane tracts that occupy about half the surface. Few of them 

 exceed 25 feet and most of them are but 10 to 15 feet high. Between Sugar Creek and the 

 Boone County line the knolls are so scattered that it is difficult to trace the border. 



Boone and Clinton counties. — Boone County, though owing its high altitude to a very thick 

 deposit of drift, does not present definite morainic ridges. By combining a series of bowldery 

 strips, chains of gravelly knolls, and heads of peculiar troughlike valleys that may be lines of 

 glacial drainage, a sort of rough outline for the ice border may be drawn through the southern 

 portion of the county. The valleys referred to are along the headwaters of Eel River and 

 seem to have been cut by large streams which headed very abruptly in these southern town- 

 ships of Boone County, as if emerging from the ice sheet. Possibly they are to some extent 

 subglacial, but in any case they are excavated so deeply that the present streams are filling 

 instead of eroding them. The bluffs range from 20 to 50 feet in height and are in places bor- 

 dered by chains of knolls that add much to the irregularity of the surface, some of them being 

 20 to 30 feet in height. 



In the southeastern part of Boone County bowlders as well as knolls abound. Fishback 

 and Eagle creeks run through belts of undulating drift which in places take on a morainic 

 appearance, especial^ where the knolls are thickly strewn with bowlders. In contrast to these 

 irregularities of the southern townships the central and northeastern parts of the county are 

 remarkably smooth, there being wide areas in which there is scarcely a knoll. 



Farther north, in Clinton County, an undulating surface continues that of southern Tippe- 

 canoe County and, like it, stands above a plain on the north. It is therefore probable that 

 during the development of the Bloomington morainic system the ice receded from southern 

 Boone northward into central Clinton County, a distance of about 25 miles, leaving only scat- 

 tered knolls and short strips of bowlders in its retreat. 



Hamilton County. — The undulating tract which traverses central Clinton County from 

 west to east curves around to the south through southwestern Tipton County and runs south- 

 ward through the western part of Hamilton County. In places, as in the vicinity of Sheridan 

 east of Horton and southeastward from Westfield to White River, sharp knolls are closely 

 aggregated and give a decidedly morainic appearance to the surface. But on the whole the 

 surface is gently undulating or nearly plane. 



Marion County. — This undulating topography continues down the west side of White River 

 to Indianapolis and also appears on the east bluff immediately above the city. Some of the 



