Slab tearing and its surface signals controlled by passive margin strength.

Abstract

Slab tearing, the lateral detachment of subducting oceanic slab from continental lithosphere, is widely inferred from seismic tomography, yet its surface expressions in mountain belts and adjacent foreland basins remain ambiguous and often contradictory. Existing geodynamic models predict that slab tearing propagates at unrealistically high velocities, implying its transient signatures unlikely to be preserved in surface or stratigraphic records. In contrast, geological observations, such as lateral migration of foreland basin depocenters and systematic basin thickening in the direction of tear propagation, indicate more persistent surface responses, highlighting a long-standing disconnect between models and field evidence. Here we resolve this paradox by showing that lateral variations in passive-margin strength fundamentally control the initiation, propagation, and surface imprint of slab tearing. Using fully coupled three-dimensional thermo-mechanical and surface-process simulations, we demonstrate that accounting for passive-margin heterogeneity significantly slows tear propagation and produces long-lived tectonostratigraphic signatures consistent with natural examples from the Alps, Carpathians, Zagros, and other orogenic belts. These results bridge deep-mantle dynamics and surface geological records, providing a unified framework to identify and interpret slab tearing in orogenic systems worldwide.