MORAINES OF NORTHERN" LIMB OF HURON-ERIE LOBE IN INDIANA. 173 



Grant County. — In Grant County, which, lies south, of Wabash and Huntington counties, the 

 surface portion of the drift is a clayey till. West from the Mississinawa system the drift is thin, 

 often but 20 feet or less in depth, but from that system eastward the thickness generally exceeds 

 100 feet and may average 150 feet. In the preglacial valleys it is 300 feet. Where the drift is 

 thick the deeper portions are often largely of sand and gravel. 



Blackford County. — In Blackford County, as in northeastern Grant County, the drift is 100 

 to 150 feet thick. In the northeast corner, however, over a few square miles along Salamonie 

 Kiver, it is but 20 or 30 feet thick. The main part of the drift is a clayey till, but beds of sand 

 and gravel at various depths supply water for the wells. The deeper borings show thin beds of 

 sand in the till. 



Jay County. — Jay County, which lies east of Blackford and extends to the Ohio State line, 

 is traversed by the Mississinawa and Salamonie moraines. The former is very largely of clayey 

 till and the latter carries gravel knolls only locally. North of the Salamonie moraine the drift is 

 thin, with rock at 10 to 20 feet. The drift is only 30 to 60 feet in the vicinity of Portland, the 

 county seat, which stands between the two moraines. Along the moraines its thickness prob- 

 ably averages about 100 feet. In preglacial valleys it reaches a depth of about 350 feet. Where 

 thickest and especially in the preglacial valleys its lower part is largely sand and gravel. 



