650 



T. T. QUIRKE BOUDIXAGE, AX UNUSUAL PHENOMENON 



This leads to the consideration of the possibility of a reversal of the 

 position of shortening in a parallel fold. 



Whereas in the type parallel fold the center is shortened and the flanks 

 remain unchanged, would it not be possible for the center to be nnshort- 

 ened and for the flanks to suffer rotational shortening both upward and 

 downward? This would lead to a parallel fold growing more and more 

 folded on opposite sides of the central plane, the degree of curvature 

 again being a function of the radius. In any case, the extent of the 

 feature must depend on the persistence of the homogeneous containing 



vA^^^^^^^^^^^^; 



jjaxjmu^m^ shortening Is^lon^^erftr&i axis^ 



Figure 1. — Theoi etiral Parallel Foldina 



layer, without which such a feature would be impossible. Boudinage 

 may ^^rovide such a case. 



The Boudins 



During the early part of August, under the leading of Prof. Max 

 Lohest, certain members of the International Geological Congress visited 

 the region of Bastogne, in southeastern Belgium. There one has the 

 opportunity to see, in the local quarries, a type of deformation which is 

 so rare as to be almost imknown in any other place, Tliis is the develop- 

 ment of "boudinage," as it is called by Lohest (figures 2, 3, and 4). 



