A Burdigalian age for extensional ductile tectonics in the Edough Massif (Kabylies, Algeria). 39Ar-40Ar radiometric data

The Edough massif (North Africa Alpine chain, NE Algeria) was affected by a strong synmetamorphic ductile deformation interpreted in terms of normal faulting that appears to have controlled exhumation and cooling of the metamorphic rocks. Mica dates (16-17 Ma) suggest a late Burdigalian age for extensional tectonics. 40Ar/39Ar amphibole (24.1 ± 1.4 Ma) and U-Pb monazite (18 ± 5 Ma) probably mark the end of the under-thrusting processes in the Edough massif and beginning of exhumation. These ages are compared with ages of post-nappe marine sediments and magmatism, which leads to 200-300 deg C/Ma cooling rate estimates and uplift rates in the range of 6-8 km/Ma. Within the geodynamical framework of the western Mediterranea, these new data could be associated with the opening of the south-balearic basins and crustal extension on their margins