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A Physiographic Survey of the Terre Haute Area- 

 Report OF Progress. 



By Charles R. Dryer. 



The physiogv.nphie survey of the Terre Hante area reported hist year 

 has been continued during the past season and extended across the Wabash 

 valley to the top of the east bluffs. A strip six miles wide, north and south, 

 has been completed, and we have been brought face to face with the prob- 

 lem of the sand and gravel terrace, three miles and more In width, 50 feet 

 above the river and more than 100 feet deep, which extends along the east 

 side of the valley a distance of 30 miles. AVithin the area surveyed its 

 generallj' level surface is traversed by several irregular north-south 

 ridges, which rise to n nearly uniform height of 510 feet A. T. These are 

 interpreted as being bars laid down by a loaded and probably braided 

 stream. In some places these bars are capped by subsequent eolian de- 

 posits. The materials of the terrace are everywhere fairly well assorted 

 and stratified, with frequent cross bedding, where the strata dip down 

 stream and suggest local delta formation. The strata in vertical section 

 often display a great variety and testify to frequent local changes in the 

 velocity of the depositing stream. Boulders up to two or three feet in 

 diameter are common and are attributed to the melting of floating ice. 



The terrace heads 12 miles north of Terre Haute in Parke Co., where 

 the Shelbyville moraine of the Wisconsin ice sheet crossed the Wabash 

 valley. At this point the problem is complicated by the extension of the 

 terrace up the valley of Raccoon creek to the northeast where it is more 

 than a mile wide. The final solution requires the extension of the survey 

 to the Shelbyville moraine and up the Raccoon valley to a distance not j'et 

 determined. This work has been begun, but is not yet completed. So far 

 as studied, the terrace appears to be an outwash plain, or valley train, 

 laid down by a constantly overloaded stream, or streams, which issued 

 from the margin of the Wisconsin ice sheet. Whether this is the true in- 

 terpretation, wlH^ther the train oiiginally occupied the whole width of tlie 

 valley, and, if so, what wei-c tlii' agonci(^s and conditidns of its removal from 



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