Geophysical Research AbstractsVol. 12, EGU2010-9522, 2010EGU General Assembly 2010© Author(s) 2010Magnetic fabric study of rock deformation during alpine tectonicevolution on a cross section through the Eastern Alps (Austria)K. Gruber, R. Scholger, and E. L. PueyoDepartment of Applied Geological Sciences and Geophysics, Chair of Geophysics. Univ. of Leoben. PaleomagneticLaboratory. Leoben, Austria.Measurements of anisotropy of magnetic susceptibility (AMS) were carried out on samples from more thanseventy sites collected in the Eastern Alps. The sites were taken alongside a North-South transect (about 15°30‘East Longitude) from Scheibbs in the North to Kapfenberg in the South, comprising most of the NorthernCalcareous Alps (NCA) nappes, Helvetic and Penninic Flysh units as well as the greywacke zone. Sampleswere taken in detail mostly in Mesozoic rocks of the NCA, from North to South: Bajuvaric (Frankenfels, Lunz,Sulzbach and Reisalpen nappes), Tirolic (Ötscher, Göller, Rotwald-Gindelstein nappes) and Juvavic (Mürzalpennappe) system. Two to six sites per thrust sheet or nappe were analysed for a structural investigation of therelationship between magnetic fabric and tectonic strain.Standard paleomagnetic drill cores were taken. All measurements were performed in the Petrophysics andPaleomagnetic laboratories of the University of Leoben using AGICO MFK1-Kappabridge susceptibility systemand a 2-G cryogenic magnetometer. Statistical evaluation of the AMS data was perfomed using the softwarepackage AGICO ANISOFT 4.2. (Chadima et al., 2009).Throughout the Eastern Alps transect distinct changes of the magnetic fabric are observed. Primary sed-imentary fabrics and very low susceptibility values are dominant in most cases in the northernmost andsouthernmost part of the transect. Some inverse fabrics were found in few sites of the nappes and the percentageincreases towards the south which might be related to tectonic events. Contrastingly, isotropic fabrics dominate inthe middle part.The Helvetic and Penninic Flysh units yield in general weak oblate fabrics. A few sites show a tendency toinverse fabrics which indicate the presence of a certain amount of strain within this unit. The oblate fabrics ofthe Helvetic and Flysh units show either shallow NE dipping or slightly steeper SW dipping k1-axis orientation.Within the inverse fabrics, even steeper NE or SW dipping k1-axis are present. In a previous paleomagnetic studyof the same samples (Pueyo et al., 2002) both, primary and secondary remanent magnetization vectors wereobserved. No significant rotations were detected in the Flysh units.All samples from the Bajuvaric system show dominantly very low susceptibility values and isotropic fab-rics and were therefore excluded from further investigations. Bajuvaric nappes hardly show any significantrotations based on paleomagnetic data (Pueyo et al., 2002).The nappes of the Tirolic and Juvavic systems have very low susceptibility values but they increase slightlytowards the south. The shape of the anisotropy ellipsoid remains oblate (group A) in most cases and the degree ofanisotropy is very weak. Also more prolate fabrics (group B) are present. Group A and B show a trend to shallowN or S dipping k1-axis in the North. Further in the south the k1-axis of group A tend to dip steeply NE. ShallowNE or SW dipping and slightly steeper NE or SW dipping oriented prolate susceptibility ellipsoids are dominantin group B. Tirolic and Juvavic units display clockwise rotation ranging between 30 and more than 100° (Pueyo etal., 2002), which was assigned to block rotation.Shallow E dipping and NNW dipping oblate susceptibility ellipsoids are dominant in the Basement. A gen-
