Squeezing paleomagnetic information using virtual directions; an example from the Bielsa granite (Axial Pyrenees)

Abstract

The Bielsa granite is located within the Bielsa thrust sheet, one of the basement thrusting units in the Central Southern Pyrenees. Internal deformation of this nappe during the Pyrenean compression is evidenced by folding of the unconformable Triassic red beds overlying the granite, that has been intensely fractured both during the Late-Variscan and Pyrenean stages. Detailed directional analysis of paleomagnetic data in the Bielsa granite by means of the VD (virtual direction) method indicates that in spite of the poor results obtained by means of conventional directional analysis, reasonable means can be produced from the application of the VD software. The results obtained indicate that a post-folding remagnetization with normal polarity involving the Bielsa granite may have taken place during the Cenozoic, correlating with similar processes in the Axial Zone and the Internal Sierras.