790 FREDERIC H. LAHEE 



bowlders inclosed in the evenly banded slates (Fig. i). These were 

 thought to have been carried by the floating ice-blocks, and to have 

 dropped as the ice melted. Mr. R. W. Sayles's study of the tilHte 

 of Squantum, cited above, is also confirmatory evidence. 



The Auhurndale deposits described. — Last November, at Auburn- 

 dale, Massachusetts, the writer came upon a beautiful exposure of a 

 structure exactly resembling the Squantum zones of deformation, 

 but this time in unconsolidated deposits of a Pleistocene sand plain, 

 (Fig. 3). The structure was seen in a sand pit. The deposit con- 

 sists of fine and coarse sand and some clay, all regularly stratified 

 with frequent variations in texture. As at Squantum, the zones 

 are repeated at several stratigraphic levels and with no definite 

 spacing or order. Here, then, is an example of aqueous deposition 

 undeniably associated with glacial action. The likeness between 

 the two cases is highly significant, particularly as regards the origin 

 suggested. 



Definition. — -The relations described above are those of local 

 unconformity associated with deformation of the upper layers of 

 the subjacent strata. The structure is really local angular uncon- 

 formity. Since erosion producing local unconformity is often called 

 contemporaneous erosion, we may term the folding and faulting 

 resulting from such erosion contemporaneous deformation. 



