Slab tearing and its surface signals controlled by passive margin strength

Article https://doi.org/10.1038/s41467-026-73963-8 Slab tearing and its surface signals controlled by passive margin strength Received: 4 November 2025 Accepted: 26 May 2026 1234567890():,; 1234567890():,; Check for updates Giridas Maiti 1 , Nevena Andrić-Tomašević Lucas H. J. Eskens1 & Taras Gerya2 1 , Attila Balázs 2 , 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 longstanding 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 surfaceprocess 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 deepmantle dynamics and surface geological records, providing a unified framework to identify and interpret slab tearing in orogenic systems worldwide. Mountain building at continental collision zones is profoundly influenced by subducting slab dynamics. Shortly after the onset of collision, the negatively buoyant oceanic slab typically detaches from the buoyant continental lithosphere in a process known as slab detachment or breakoff1,2. Seismic tomography reveals that this detachment usually migrates laterally along strike of collisional boundaries, a process termed in literature as slab tearing3,4. Slab tearing is therefore a fundamental geodynamic process in the early stages of orogeny and exerts first-order control on the evolution of mountain belts. Since its recognition, it has been invoked in nearly every major collisional orogen (Fig. 1a), including the Alps–Carpathians5,6, Apennines7–9, western Mediterranean4,10, Aegean–Anatolia–Zagros11, Caucasus12, and Himalaya13,14. Although seismic tomography data (Fig. 1b, c) supports these interpretations3,11,12,15, the surface expressions of slab tearing in orogens5,13,14 and adjacent foreland basins6,8,11 remain widely debated and largely speculated16. Existing geodynamic models provide important insights into the initiation and dynamics of slab tearing, but they consistently predict a rapid lateral tear-propagation velocity of 35–120 cm yr−1 17–23. These values are an order of magnitude faster than indirect estimates from geological proxies, which are typically <10 cm yr−1 6–8. Such rapid propagation in earlier models yields only short-lived surface signals, which are difficult to identify and separate from collisional overprints. Moreover, previous models largely ignore feedback between tectonics, erosion, and sedimentation that shape coupled mountain–basin systems. This leaves a critical gap in linking deeplithospheric process slab tearing to preserved surface records. Closing this gap is essential for reliably identifying slab tearing in surface 1 Institute of Applied Geosciences, Karlsruhe Institute of Technology, Karlsruhe, Germany. 2Institute of Geophysics, ETH, Zürich, Switzerland. e-mail: Nature Communications | (2026)17:4964 1 Article geological records and for reconstructing the spatial and temporal evolution of mountain building in collisional orogens worldwide. Foreland basins that form adjacent to growing mountain belts provide a key archive of slab-tearing’s surface signals. Their stratigraphy records the interplay between tectonic uplift driven by plate convergence and subduction dynamics, and sediment fluxes modulated by climate, lithology, and sea level24–27. Yet isolating slab-tearing signals in these basins is inherently challenging. Because tearing typically occurs just before or during the early stages of collision3,16,18,19, its imprints are often overprinted by subsequent collisional processes. In addition, features often attributed to slab tearing may also arise from alternative mechanisms, including oblique convergence28,29, lateral variations in lithospheric flexural rigidity30, or far-field eustatic effects31. Disentangling these competing signals requires models that capture both deep-lithospheric dynamics and surface processes. A likely reason for unrealistically fast tearing in previous models is the assumption of laterally uniform passive margins. In reality, passive margins are highly heterogeneous, with variations in oceanic age32, crustal structure, and the presence of microcontinental blocks separated by exhumed mantle or younger oceanic branches33,34. Because slab detachment localizes at the ocean–continent transition or along former passive margins1, these heterogeneities are expected to exert strong control on where tearing initiates, how it propagates, and how its signals are transmitted to the surface. Here, we emphasize that these heterogeneities translate into along-strike variations in passivemargin strength, which we define as integrated lithospheric yield strength governed by crustal thickness, thermal state, composition, and adjacent oceanic age. We therefore hypothesize that variations in passive-margin strength govern tear-propagation velocity and control the generation and preservation of diagnostic tectonostratigraphic signals in foreland basins adjacent to orogenic belts, which our models evaluate against the Northern Alpine Foreland Basin (NAFB) record. To test this hypothesis, we conduct state-of-the-art, fully coupled 3D thermo-mechanical and surface-process simulations that incorporate realistic passive-margin heterogeneity (Supplementary Fig. S1). The models simulate slab tearing beneath the Alps between ~30–20 Ma, when closure of the Piemont–Ligurian Ocean led to collision of the European passive margin with the Adriatic plate, triggering the Alpine orogeny4,5,35. Here, we show that along-strike variability in passive-margin structure, marked by the Briançonnais terrane36,37 and contrasting oceanic ages of the Valais and Piemont–Ligurian domains38,39, provides natural conditions for passive-margin strength heterogeneity. This heterogeneity controls the location of tear initiation and produces tear-propagation velocities comparable to geological estimates during Alpine collision. Our results reveal that slab tearing generates coeval but contrasting depositional environments in foreland (...truncated)