Smithsonian Report. I'fM). Richar/ 



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Farm Creek Exposuhc. 7 Miles East of Peoria. III. 



, Bowlder clay, ileposilcd frimi the iiieltiii(! i(e sheet of the hist ghiciatioii, fre.^ih 

 on the hoiioin, wealhereil on top. Overlain by pravel hrought by the nieltinn 

 waters of the reeeilinu ice; 2, loess, an ejliaii deposit during an interglacial 

 period; In and 1'), bow Ider clay of an earlier ice sheet, ih is its \veathere<l jior- 

 tion, at least l', feet thick (down to the dark band in the pholopraiih); la is a 

 fresh blue bow Ider clay. The jiholopraph illustrates a feature ( (.ninicn to such 

 deposits of the Ice .Vge, both in .\merica and iti Kiiroi e. 'I'l.e earlier placial 

 lK)wlder clay (li is weathered to a much greater depth tli;;n the upper one (3i. 

 although the latter, at the locality of the picture, be( aiiie exposeil to the inllu- 

 ence of the atniospiiere about 2(l,0(Jt) years ago. Moreover, the deconipusilion 

 of the oilier glacial ileposit must have been completed before the region w;is 

 covered by the lii.>;t ice sheet, becaii.se later this ice sheet and its ileposils pro- 

 tected the older bowliler clays ag;iinsl decomposition. Therefore, a much 

 longer time was neeileil for tlie inlerglacial period than the postglacial 1>i,(MK» 

 to jo.oorj years. (Photo by Hev. Henry Helzek.) 



