Slab tearing and its signals in foreland basins controlled by passive margin strength

Abstract

Horizontal slab tearing, the lateral detachment of a subducting oceanic slab from continental lithosphere, is widely inferred from seismic tomography, yet its surface expressions in mountain belts and foreland basins remain ambiguous and, in many cases, contradictory. Existing geodynamic models commonly predict rapid horizontal tear propagation, implying that associated surface and stratigraphic signals should be too transient to be preserved in the geological record. In contrast, field observations, including lateral migration of foreland-basin depocenters and systematic basin thickening in the direction of inferred tear propagation, suggest more persistent and coherent surface responses. This discrepancy highlights a long-standing disconnect between geodynamic model based predictions and geological evidence. Here, we resolve this paradox by demonstrating that lateral variations in passive-margin strength exert a first-order control on the initiation, propagation, and surface expression of horizontal slab tearing. Using fully coupled three-dimensional thermo-mechanical and surface-process simulations, we show that passive-margin strength heterogeneity can substantially slow tear propagation and generate long-lived tectonostratigraphic signatures consistent with natural examples from the Alps, Carpathians, Zagros, and other orogenic belts. Our results bridge deep mantle dynamics and foreland-basin records, providing a unified framework for identifying, interpreting, and reconstructing slab tearing in orogenic systems worldwide.