EGS 1999

Christine SOUQUE*, Dominique FRIZON DE LAMOTTE*, Philippe ROBION* & Hugues FEINBERG**

*Université de Cergy-Pontoise, département des Sciences de la Terre (CNRS, ESA 7072), F95031 Cergy-Pontoise, France.
** Ecole Normale Supérieure, laboratoire de Géologie (CNRS, URA 1316), 24 rue Lhomond, F75005 Paris, France.

Structural, magnetic fabric and paleomagnetic evidences for vertical axis rotations in a duplex structure (La Cagalière, NE Pyrenees).

Abstract :

In order to constrain the tectonic evolution of the " La Cagalière " duplex structure building, we have performed and compared microtectonic, magnetic fabric and paleomagnetic studies. The Duplex is made up of four sheets of Illerdian limestones. The allochthonous roof of the duplex is the forelimb of the Lagrasse fold (Aude, France). Each sheet exhibit a distinct microtectonic and magnetic fabric signature. Magnetic fabric indicates the Layer paralell shortening orientation whilst microtectonic shows transport direction. Both support a rotation of tectonic transport direction (from N160 to N110) during building of the duplex. Such a change is also known region scale.
Nevertheless, paleomagnetic data indicate clockwise rotations of the sheets from few degrees for the last and lower sheet, to a maximum of 50° for the first and uppermost one. This suggests that the duplex has been built during the second tectonic event (N110) and that sheets suffered incremental clockwise rotation during their emplacement.