56 PLEISTOCENE OF INDIANA AND MICHIGAN. 



The average altitude of the entire southern peninsula of Michigan (not including the beds 

 of the Great Lakes) is estimated to be 835 feet. The range in altitude is from 573 to 1,710 

 feet. The highest points are morainic knobs a few miles southeast of Cadillac in Sherman 

 Township, Osceola County, and the lowest are on the border of Lake Erie. As planimeter 

 measurements of the bedrock contours (see PI. II) made by W. F. Cooper, of the Michigan Geo- 

 logical Survey, show an average altitude of 554 feet, an average thickness of nearly 300 feet of 

 drift is indicated. The bedrock ranges from a little below sea level to fully 1,100 feet above. 



The average altitude of Indiana has been estimated by Gannett J to be 700 feet and by 

 Gorby 2 to be 800 feet; the estimate by Gorby, being based more largely on field observations, 

 is perhaps the closer approximation. The altitude ranges from 314 feet at the mouth of the 

 Wabash to 1,285 feet on the morainic hills in southern Randolph County. 



Outside of the prominent drift belt in the northeastern counties only one large area in 

 Indiana rises above 1,000 feet. This is in the eastern part of the State, chiefly in Wayne and 

 Randolph counties, and is due to the rock surface, which reaches fully 1,100 feet and bears 

 morainic knolls that rise above 1,200 feet. It is in this area that the reentrant between the 

 Miami and East White lobes is found. Only here and in the "thumb" of Michigan do rock 

 elevations seem to have had much influence on ice movements; the low basins now occupied 

 by the Great Lakes were the features which had greatest control. 



In northern Indiana and in nearly all of the southern peninsula of Michigan the rock surface 

 is entirely concealed beneath the thick glacial deposits. In southern Indiana, however, a 

 succession of rock formations from the Ordovician to Pennsylvanian is exposed from east to 

 west. (See PI. III.) These formations trend from west of north to east of south about parallel 

 to the western or main branch of the Cincinnati axis. As they vary greatly in their power to 

 resist weathering and erosion, they have given rise to a series of troughs or basins separated by 

 ridges and highlands. These, however, have exerted but little influence on the flow of the ice 

 or the outline of the ice border. 



The hills in the more resistant formations rise to a somewhat regular elevation that suggests 

 a peneplain, and a few hills in the softer formations reach nearly the same altitude. Most of 

 the divides in the friable rocks of the southwestern part of the State, however, are 50 to 150 feet 

 lower than the level of the suggested peneplain, and only isolated hills rise to its level. Some 

 of the hills of friable rock carry deposits of bronzed gravel, presumably of Tertiary age, that 

 antedate the erosion of the formation elsewhere; for example, two hills north of Princeton, 

 Ind., some knobs bordering White River near Shoals, and other knobs in Washington County 3 

 carry a little bronzed gravel similar to the Tertiary gravel of southern Illinois. 



Throughout much of the drift-covered portion of Indiana the surface is monotonously 

 smooth, both on slopes of 10 to 20 feet to the mile and on nearly dead-level surfaces. Many 

 moraines also are inconspicuous. 



Sharply morainic tracts with prominent knob and basin topography are found mainly 

 in three localities. The largest and most prominent is in the northeastern part of the State 

 and covers a considerable part of Steuben, Lagrange, Noble, and Kosciusko counties and parts 

 of Dekalb, Whitley, Wabash, Miami, and Fulton counties. In this tract are many knolls 30 

 to 50 feet high and a few 75 to 100 feet or more; among them are numerous basins containing 

 lakes and marshes. The second large morainic tract sweeps around the head of Lake Michigan 



i Gannett, Henry, Thirteenth Ann. Rept. V. S. Geol. Survey, pt. 2, 1893, p. 289. 



2 Gorby, S. S., Sixteenth Rept. Dept. Geology and Nat. Hist. Indiana, 1891, p. 217. 



3 Cox, E. T., Third Rept. Geol. Survey Indiana, 1872, p. 138. Leverett, Frank, Eighteenth Ann. Rept. U. S. Geol. Survey, pt. 4, 1897, p. 433; 

 also Mon. U. S. Geol. Survey, vol. 41, 1902, p. 111. Fuller, M. L., and Ashley, G. H., Ditney folio (No. 84), Geol. Atlas U. S., TJ. S. Geol. Survey, 

 1902, p. 6. Blatchley, W. S., Thirtieth Ann. Rept. Dept. Geology and Nat. Res. Indiana, 1905, p. 936. 



