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The Physiography of Indianapolis. 



Charles R. Dryer, Indiana State Normal School. 



In 1820, the Indiana Commissioners fixed upon a point in the unin- 

 habited wilderness, "on White river at the head of navigation" and 

 within ten miles of the geographical center of the State for the location 

 of the future capital. Congress had granted to the State four square 

 miles for use as a seat of government, and in 1821 a plat of one square 

 mile was surveyed which now comprises the official and commercial 

 center of the city. The area was situated near the eastern border of the 

 flood plain of White River and a few feet above it, but was traversed by 

 Pogues Run, a small tributary. Fall Creek, a much larger stream, 

 entered the river from the northeast just above the city and Pleasant 

 Run a short distance below. On the opposite side of the river, Eagle 

 Creek came in from the west. 



The present metropolitan district would be enclosed by a parallelo- 

 gram 8 by 10 miles, of which about 35 square miles are built up. The 

 underlying bed rocks are Devonian limestones and shales too deeply 

 buried beneath glacial material to influence topography. The Illinoian 

 drift sheet of compact blue clay, varies from 20 to 80 feet in thickness. 

 A few feet of sand and gravel separate it from the usual bouldery till of 

 Wisconsin age, the whole forming a mantle 70 to 170 feet thick. This 

 glacial subtratum has been eroded and replaced by gravel to an extent 

 presently to be described. 



In the absence of a topographic map relief can be described only 

 in approximate terms. Central Marion County is crossed from north- 

 west to southeast by a belt of undulating drift in part morainic about 

 ten miles wide, its surface lying about 800 feet A. T. It is bordered on 

 the south by massive gravel ridges and other morainic features.* 

 Through this belt nearly at right angles. White River and Fall Creek cut 

 a trench about 200 feet deep, having its bottom on or near bed rock. 

 During the period of glacial retreat this trench was filled half full of 

 gravelly outwash. A readvance of the ice margin, accompanied by the 



* Leverett, Frank. U. S. Geol. Surv. Monograph LIII, p. 96. 



