Orogenic structure and topography track subduction singularities during slab delamination and detachment

Abstract

A new model of Alpine mountain-building based on state-of-the-art seismic imaging explains how slab delamination and detachment facilitated indentation and led to along-strike changes in orogenic structure, denudation and basin dynamics. After Adria-Europe plate collision (40–32 Ma), slab steepening and delamination of the European slab changed the taper angle of the orogenic wedge in the Central Alps as the subduction singularity migrated northward. This induced rapid exhumation and denudation of the Lepontine orogenic core, accompanied by waves of clastic deposition in the overfilled western foreland basin. In the Eastern Alps, the heavier part of the slab delaminated further northward, driving prolonged subsidence and marine sedimentation in the underfilled eastern foreland basin. At ~ 20 Ma, the slab segment beneath the Eastern Alps detached, facilitating fragmentation of the indenting northern edge of the Adriatic Plate. This offset the collisional edifice while reorganizing subduction singularities and bifurcating drainage divides. Slab detachment triggered rapid uplift and terrigenous filling of the eastern foreland basin, together with orogen-parallel extrusion of the rapidly exhuming Tauern orogenic core toward the Pannonian Basin. There followed a dramatic shift in thrust-activity and -vergence from northward to southward. Similar lateral variations are documented for other orogens experiencing slab delamination and detachment.