MORAINIC SYSTEMS AT HEADS OF LAKE MICHIGAN AND SAGINAW BASINS. 175 



by the Valparaiso morainic system, unless perchance it is represented in what has been con- 

 sidered the outer portion of that system in northwestern Indiana and northeastern Illinois. One 

 feature which suggests its westward continuation from South Bend toward Laporte is the bowl- 

 dery, somewhat undulating gravelly district known as Rolling Prairie, which lies east of the sta- 

 tion of that name and which stands above the level of the neighboring portion of the Valparaiso 

 system and of the outwash apron connected with that system. Another feature is the great 

 gravel plain which lies north of the Kankakee Marsh in Laporte and Porter counties, Ind., at 

 a level higher than that of the lines of glacial drainage which head in the Valparaiso morainic 

 system and lead through this plain. The plain appears to be older than that connected with 

 the Valparaiso morainic system and to be composed of outwash from an ice border which is 

 largely concealed, as above suggested, by the extension of the Valparaiso system. The alti- 

 tude near New Carlisle and westward from there to Laporte is 50 to 75 feet above the gravel 

 plains that head in the Valparaiso morainic system. 



It is possible that the Kalamazoo system embraces a bowlder-strewn gravel tract known 

 as Sumption Prairie, which lies south of the head of Kankakee River just west of the city of 

 South Bend, but with this exception it seems to lie entirely north of the Kankakee. Aside 

 from basins both Sumption and Rolling prairies have nearly plane surfaces, and both seem to 

 be composed entirely of assorted material capped with a bowlder-strewn loamy deposit a few 

 feet thick. Were it not for the large number of bowlders these tracts would naturally be classed 

 as outwash aprons, and they seem on the whole to be more closely allied to outwash than to 

 moraine. 



The great width of the gravel plain on the north side of the Kankakee east of the meridian 

 of Valparaiso may be best explained on the interpretation that the plain was built up by the 

 Lake Michigan lobe in the course of a recession across the area thus covered, and that it buried 

 any morainic features which may have developed during the recession. From the meridian 

 of Valparaiso westward into Illinois, though there is very little outwash between the morainic 

 system and the Kankakee Marsh or between the different members of the morainic system, 

 the bulk of the morainic system is fully as great as the combined bulk of the moraines and 

 gravel plains on the north side of the Kankakee east from Valparaiso and of the combined Kala- 

 mazoo and Valparaiso morainic systems in southwestern Michigan. It may, therefore, as 

 above suggested, embrace both the Kalamazoo and the Valparaiso morainic systems, though 

 as yet the two have not been differentiated in that region. 



TOPOGRAPHY. 



ALTITUDE. 



The Kalamazoo morainic system appears to attain its greatest elevation in the imme- 

 diate vicinity of its junction with the correlative morainic system of the Saginaw lobe near 

 Prairieville, Mich., where its altitude is about 1,050 feet above sea level; at only a few points, how- 

 ever, does it rise above 1,000 feet. The altitude of the outwash apron at Prairieville is nearly 

 if not quite 1,000 feet. The crest of the outer ridge throughout much of its course from Prairie- 

 ville to the Michigan-Indiana State line is between 900 and 1,000 feet, though for a few miles 

 near the State line it does not quite reach 900 feet. The inner ridge has a crest above 900 

 feet as far southwest as the vicinity of Dowagiac, but from that city southwestward to the State 

 line it exceeds 800 feet at few points. The highest points on the bowlder-strewn Rolling Prairie 

 and on the neighboring portions of the gravel plain in Laporte County, Ind., are about 825 

 feet, but the crest of the morainic system in northwestern Indiana in few places rises above 

 800 feet and in some places drops to about 700 feet. 



The outer border of the morainic system shows comparatively slight relief, for the gravel 

 plain which follows it for its entire length from Prairieville to South Bend has been built up 

 nearly to the level of its crest. Nor does either morainic ridge show more than slight relief 



