Brittle-Ductile Deformation Behaviour in the Middle Crust as Exemplified by Mullions (Former "Boudins") in the High-Ardenne Slate Belt (Aardkundige Mededelingen) (v. 14)

In the High-Ardenne slate belt multilayer sequences occur, consisting of pelite intercalated with psammite layers. The psammite layers are commonly characterized by the particular occurrence of arrays of quartz veins, which are oriented at high angle to the bedding. In between two adjacent veins, the pelite-psammite interface is characterized by a cylindrical cuspate-lobate geometry.

Describing the structures and their geometry introduced the terms "boudin" and "boudinage." In the current literature, boudinage refers to the process of layer-parallel extension of competent layers embedded in a more incompetent matrix. Confronted with this kinematic definition, it remained until recently a matter of controversy whether or not this definition applies to the structures in the High-Ardenne slate belt, i.e. the "boudinage" question.