632 



E. M. KINDLE CANADIAN PLEISTOCENE CONCRETIONS 



indurated in any degree and remain as soft as the clay in the beds below 

 the sand from which they were derived. The stratigraphic relations of 

 these structures to the clays and the sands are shown in figure 4. 



The origin of these highly irregular-shaped fillings affords an interest- 

 ing problem. The sand beds associated with them are traversed by 

 numerous burrows of insects or worms which now live in these beds. 

 These tubes of recent origin are, however, invariably circular in cross- 

 section and without clay fillings, while the clay fillings show in most 





"^ 







Figure 4. — Sketch at Rideau Junction, Ontario 



Showing relations of sand and underlying clay, together with the occurrence of cal- 

 careous root concretions (plate 11, figures 1-4), along the slope of the sand bank and the 

 pseudoconcretions near base of sand beds in lower right-hand corner. 



cross-sections a wide divergence from a circular outline. Since none of 

 the many insect or worm burrows of recent origin present the extraor- 

 dinary shape of these clay-filled perforations of the sand beds, the latter 

 do not appear to have been formed under conditions now existing. If, 

 however, we go back to the conditions which existed shortly after the 

 lower part of the sand beds were laid down, the probable conditions of 

 their origin can be inferred. Marine animals of various species may 

 then have been accustomed to burrow through the sand to the clay. 



