Structural geometry in the eastern Pyrenees and western Gulf of Lion (Western Mediterranean)

• Published in: Journal of structural geology 2001-11, Vol.23 (11), p.1701-1726
• Main Authors: Mauffret, Alain, Durand de Grossouvre, Bernard, Tadeu Dos Reis, Antonio, Gorini, Christian, Nercessian, Alex
• Format: Article
• Language: English
• Subjects: Crustal thinning; Seismic lines; Tectonics
• ISSN: 0191-8141; 1873-1201
• DOI: 10.1016/S0191-8141(01)00025-6

We present new seismic data from the Gulf of Lion located east of the Pyrenees on the continental shelf of the Mediterranean Sea. The deep penetration LISA (Ligurian–Sardinia Sea) seismic lines, the shots of the LISA cruise recorded on land, and the high definition ELF seismic sections allow us to present a complete picture of the tectonics in this area from the surface to the Moho level, and also to document late Miocene–early Pliocene extensional tectonics in the area. Previous studies show a prominent thinning of the crust observed from the Pyrenees towards the Gulf of Lion. The Moho depth varies from 48 km beneath the Axial Range crust (thickened during the Pyrenean Eocene Orogeny) to 21 km below the Catalan Basin in the Gulf of Lion. This crustal thinning occurred mainly during the early Miocene extension of the Mediterranean Sea. Balanced reconstructed geological sections derived from reflection and refraction seismic data allow us to evaluate the stretching factors at the crustal level. A maximum extension of 25 km is computed for the Catalan Basin area. This extension is related to detachments that penetrate the crust as deep as 11 km to the base of the brittle crust. These intra basement detachments have been confused in the past with the Paleozoic acoustic basement. The detachments show a clear listric shape and the geometry of horst and grabens can be explained by a hanging wall and footwall configuration with isostatic rebound of the footwall. The uplift in the Eastern Pyrenees (Albères and Canigou Massifs), on the other hand, is related to the late Miocene–early Pliocene extension we mapped in the area. These elevated features, probably formed by isostatic rebound, are surrounded by deep basins such as the Roussillon and El Empordà depressions. A 1.7 km uplift during the late Miocene–early Pliocene is computed in the offshore part of the Albères Massif. The cause of this Late Miocene–early Pliocene extension is not well explained although an uplift related to the Messinian desiccation or a thermal anomaly in the mantle have been proposed. The relationship between the Eastern Pyrenees and the Gulf of Lion is governed by NE–SW transfer faults. These faults represent the southwestern limits of the Gulf of Lion basins. Although much seismicity is recorded in the Eastern Pyrenees, we do not see evidence of present tectonics in the Gulf of Lion as the extensional faults were active only until the early Pliocene. Therefore, the present stress is prob