Tectonic Inversion and Geomorphic Evolution of the Algerian Margin Since Messinian Times: Insights From New Onshore/Offshore Analog Modeling Experiments

Tectonic inversion of passive margins is a common but poorly documented process preceding subduction inception. We perform here a comprehensive land-sea experimental modeling of this key process by reproducing the morphotectonic and sedimentary evolution of the central Algerian margin over the last 6 Myr. Our approach is based on scaled analog models integrating interactions between crustal shortening and surface processes, including erosion, water transport, sedimentation, gravitational instabilities, and base-level changes. A challenge was to simulate the effects of the Messinian Salinity Crisis (MSC) through a major sea-level oscillation and halite deposition. By using realistic boundary conditions, adapted analog material, and robust, first-order parameters for physiography setups, we successfully reproduce the morphotectonic domains and the time-dependent geometrical relationships between fluvio-deltaic sedimentary systems, erosional surfaces, and thrust faults as observed since Messinian times. Our results highlight (1) the key role played by the MSC sea-level oscillation on an ultra-fast building, destruction and re-sedimentation of fans and deltas from the upper slope to the abyssal plain; (2) the development of a large popup structure subparallel to the coastline, with progressive strain migration from the backthrust on land toward a frontal thrust of opposite vergence at mid-slope and the margin toe; and (3) the importance of lateral changes in initial wedge shape and strain distribution for determining the non-cylindrical geometry of the margin and progradation of piggy-back basins during tectonic inversion. Our results support that the central Algerian margin is witnessing the early building of an accretionary wedge combining thin-skinned and thick-skinned tectonic styles.

Automated summary

A comprehensive land-sea experimental modeling was conducted to reproduce the morphotectonic and sedimentary evolution of the central Algerian margin over the last 6 million years. The study highlighted the key role of the Messinian Salinity Crisis on the morphotectonic evolution, and identified the central Algerian margin as experiencing the early building of an accretionary wedge combining thin-skinned and thick-skinned tectonic styles.