PRE-WISCONSIN DRIFT AND ASSOCIATED DEPOSITS. 67 



glacial ridges, a conspicuous instance being a ridge that rises 30 to 50 feet above the railway 

 station east of Fort Branch. This ridge is composed of loose-textured reddish drift carrying 

 considerable sand and a moderate number of bowlders and coarse pebbles. The wells alono- 

 it enter what is termed "blue mud" at about the level of the base of the ridge and continue 

 in it for 40 to 60 feet until they reach rock. 



South of the west-flowing parts of East White and White rivers in Dubois, Pike, Gibson, 

 Posey, and Vanderburg counties there is very little typical till. The clayey parts of the drift 

 carry few pebbles and exceedingly few bowlders. Both the clayey and the sandy deposits 

 indicate that lake or water action was so combined with glacial action as to influence nearly 

 all the glacial deposits. The uplands carry only scanty glacial material, a thickness of 10 feet 

 being rare, but the valleys contain 75 to 100 or more feet, including the silt deposits above 

 described. 



The general presence of till in the district north and west of White River puts it in contrast 

 with the district to the south and east, and the amount of drift on the uplands is much greater, 

 reaching depths of 20 to 60 feet or more. 



The deposits in some preglacial valleys are described as black mud, though their color is 

 usually blue or gray. The most conspicuous occurrences are in the valleys of Eel River and 

 White River in Clay and Greene counties, and are possibly flood-plain deposits antedating the 

 glacial invasion, though the absence of samples makes it difficult to judge. 



INTERBEDDED DEPOSITS. 

 BURIED SILT OB LOESS. 



In scattered exposures in the southwestern counties of Indiana fossiliferous silt very similar 

 to the loess that overlies the till occurs beneath or is interbedded with the till. It may, however, 

 be of small extent and may not represent widespread conditions such as prevailed during the 

 main loess deposition. Several occurrences were examined in 1902 by M. L. Fuller and the 

 writer. 



Loess was found interbedded with till about 5 miles south of Hazleton in eastern White 

 River Township, Gibson County. The overlying till is of the ordinary clayey type characteristic 

 of the Ilhnoian drift sheet and is thickly set with pebbles. The underlying deposit seems to 

 have fewer pebbles but is apparently glacial. The loess is gray and contains many fossils. 

 The exposures were not sufficient to determine whether both the drift sheets and the included 

 loess belong in the Ulinoian stage or whether the lower drift belongs in an earlier stage of 

 glaciation. The lower sheet appears to be fully as much oxidized as the upper. The loess 

 outcrops in a gully at the roadside and appears to be 12 to 15 feet thick. 



Buried loess was also found on the north bluff of the Ohio about 16 miles below Rockport, 

 Ind., in sec. 4, T. 8 S., R. 7 W., where it is separated from the surface loess by a bed of pebbly 

 clayey alluvium. The following section was observed along the newly graded road leading down 

 to the Ohio Valley from the residence of Mr. Deyss on the bluff: 



Section of Ohio River bluff at Deyss -private road, sec. 4, T. 8 S., R. 7 W. 



Feet. 



Loess, brown, loose textured 11 



Clay, brown, slightly pebbly, becoming gray near base 14 



Loess, gray, very thickly set with fossils 15 



Clay, sandy, of marbled brown color, containing pebbly layers 13 



Gravel, bronzed, apparently redeposited from the preglacial gravels outcropping in the bluff far- 

 ther up the Ohio 17 



70 



