188 
blown, the materials, including the shells being collected from the terrace 
surface from the silts deposited by the valley-wide stream. This deposition 
probably occurred soon after the stream abandoned the terrace level and 
withdrew to the present deeper third of the valley width. The work was 
done mainly before the invasion by vegetation of the terrace, bluff front and 
upland border, after the retreat of the ice sheet from the region. The loess 
may be a wind deposit from the bare valley at the close of the Illinoisan 
ice invasion. This dust may have weathered through a long interglacial 
period of time to be covered with later deposits of dust and fine sand swept 
over the valley from the border of the Late Wisconsin ice which did not 
reach the present site of Terre Haute, but whose strong moraine lies fifteen 
or twenty miles upstream near Clinton and Rockville. 
