Fractures and Biopores in Weichselian Clayey Till Aquitards at Flakkebjerg, Denmark: Selected Paper – Conference, Copenhagen May 14-16, 1998, on “Mass Transport in Fractured Aquifers and Aquitards”

The distribution of fractures and biopores in a clayey and sandy till aquitard was investigated in two excavations, on southern Zealand, Denmark. A large number of fracture data were measured and quantitative fracture properties calculated. The formation of fractures can be related to the depositional history of the tills during two glacier-advances/retreats and subsequent climatic changes during the Quaternary. The fractures including faults are separated into four systems: 1) Large vertical/subvertical fractures related to the oldest glacier-advance or interstadial climatic influence. 2) Horizontal -subhorizontal fractures related to subglacial drag/shear during a glacial advance from northeast and in an initial stage of a younger glacier-advance from southeast. 3) Normal faults related to subglacial loading during a late stage of the youngest glacier-advance and, 4) Minor desiccation and freeze-thaw fractures related to post-glacial climatic influence. A conceptual macropore distribution model was developed that consists of three zones with different macropore characteristics.