Paleomagnetic evidence for crustal and thin‐skinned rotations in the European Hercynides

Abstract

Devonian and Carboniferous paleomagnetic data from the European Hercynides show a coherent pattern in inclination but significant dispersion in declination. The declination anomalies with respect to expected declinations for stable Europe indicate a strong correlation with the regional changes in the structural trend of the mountain belt. Detailed analysis of the paleomagnetic and structural data revealed the highest degree of correlation between changes in strike and declination anomalies for external parts of the orogen, where thin‐skinned nappe emplacement has been most prevalent. The correlation between changes in strike and declination anomalies from interior parts of the Hercynides is less well defined and displays a greater degree of scatter. Nevertheless the partly secondary character of the arcuate shape can be demonstrated. Thus the internal Hercynides are at least in part a true orocline with secondary bending in the sense of S.W. Carey. We infer that the bending of the European Hercynides resulted from the combination of multiple deep‐reaching deformations of the European lithosphere as well as the effects of thin‐skinned rotations. The decreasing degree of rotations toward the crystalline interior of the belt appears to favor a geodynamic model involving indentations and/or buttressing effects. The indentation of Hercynian Europe by a microplate or an African promontory during the Hercynian orogeny might be one of the principal causes for the secondary bending and the associated nappe rotations.