SMALL-SCALE FAULTING AS AN INDICATOR OF DEFORMATION MECHANISM IN THE TERTIARY SEDIMENTS OF THE NORTHERN DANISH CENTRAL TROUGH

The Tertiary sediments in the northern part of the Danish Central Trough are characterized by a large number of small faults (25-50 m offset). Models for the accommodation of the deformation of the sediments are presented and it is shown quantitatively that a bending model best explains the observed strain distribution. From this we infer that the internal deformation of the Tertiary sediments is due to differential subsidence along older fault trends and not caused by applied extemal stresses on the Tertiary sediments. The effect of rock rheology and excess fluid pressure is discussed in order to explain the size of the throw and the smaller number of reverse faults compared to normal faults. Although the rocks are brittle they may in regions of shortening suffer more grain-scale creep deformation than in regions of extension. The strain distribution is determined on seismic sections and the main limitations of the method is thus the vertical and horizontal resolution of the seismic surveys used.