A STEP fault in Central Betics, associated with lateral lithospheric tearing at the northern edge of the Gibraltar arc subduction system

作者：de Lis Mancilla Flor; Heit Benjamin; Morales Jose; Yuan Xiaohui; Stich Daniel; Molina Aguilera Antonio; Miguel Azanon Jose; Martin Rosa

来源：Earth and Planetary Science Letters, 2018, 486: 32-40.

DOI：10.1016/j.epsl.2018.01.008

• westernmost Mediterranean subduction system
• central Betics
• sharp Moho step
• STEP fault
• positive tectonic flower structure

We study the crustal and lithospheric mantle structure under central Betics in the westernmost Mediterranean region by migrating P-receiver functions along a dense seismic profile (similar to 2 km interstation distance). The profile, North-South oriented, probes the crustal structure of different geological units, from the Alboran domain in the south with metamorphic rocks, through the External Zones with sedimentary rocks to the Variscan terrains of the Iberian Massif in the north. From north to south, the Moho depth increases from similar to 30 km to similar to 46 km underneath the Guadix basin, due to the underthrusting of the Iberian crust below the Alboran crust, and suddenly shallows to similar to 30 km underneath the Internal Zones with a step of 17 km. This sharp Moho step correlates well with a lithospheric step of similar to 40 km, where the thickness of the lithosphere changes abruptly from similar to 100 km in the north to similar to 50 km in the south. We interpret this sharp and prominent lithospheric step as the termination of the Iberian lithosphere caused by a near-vertical STEP (Subduction-Transform-Edge-Propagator) fault that continues towards the surface as a positive flower tectonic structure of crustal scale. This STEP fault is located at the northern edge of the narrow Westernmost Mediterranean subduction system facilitating the slab rollback motion towards the west. The sharp termination of the Iberian lithosphere occurs under the contact between the Alpujarride and the Nevado-Filabride complexes of the Alboran domain in an ENE-WSW right-lateral transpressive shear zone. The thickest crust and lithosphere do not correlate with the highest topography along the profile suggesting that this high topography is a combined effect of the positive flower structure, and the push up of the asthenosphere produced by the removal of the Iberian lithosphere.

• 出版日期2018-3-15