  Markers of brittle faulting are widely used for recovering past deformation
phases. Rocks often have oriented magnetic fabrics, which can be interpreted as
connected to ductile deformation before cementation of the sediment. This paper
reports a novel statistical procedure for simultaneous evaluation of AMS
(Anisotropy of Magnetic Susceptibility) and fault-slip data.The new method
analyzes the AMS data, without linearization techniques, so that weak AMS
lineation and rotational AMS can be assessed that are beyond the scope of
classical methods. This idea is extended to the evaluation of fault-slip data.
While the traditional assumptions of stress inversion are not rejected, the
method recovers the stress field via statistical hypothesis testing. In
addition it provides statistical information needed for the combined evaluation
of the AMS and the mesotectonic (0.1 to 10m) data. In the combined evaluation a
statistical test is carried out that helps to decide if the AMS lineation and
the mesotectonic markers (in case of repeated deformation of the oldest set of
markers) were formed in the same or different deformation phases. If this
condition is met, the combined evaluation can improve the precision of the
reconstruction. When the two data sets do not have a common solution for the
direction of the extension, the deformational origin of the AMS is
questionable. In this case the orientation of the stress field responsible for
the AMS lineation might be different from that which caused the brittle
deformation. Although most of the examples demonstrate the reconstruction of
weak deformations in sediments, the new method is readily applicable to
investigate the ductile-brittle transition of any rock formation as long as AMS
and fault-slip data are available.
