Initiation of subduction at Atlantic‐type margins: Insights from laboratory experiments

Abstract

Abstract. We have performed scaled lithospheric experiments to simulate the behavior of a ocean-continent plate system subjected to compressional strain over a geological timescale. Experiments have been constructed using sand and silicone putty, representing the brittle upper crust and the ductile lower crust/upper mantle, respectively; the layers floated on glucose syrup simulating the asthenosphere. Compressional stress is achieved by displacing a piston at constant velocity perpendicular to the plate margin. We investigate the influence of four parameters: (1) the negative buoyancy of oceanic lithosphere, (2) the horizontal body forces between continent and ocean, and (3) the brittle and (4) the ductile strength of the passive margin. Two numbers express the importance of these parameters: the Argand number (Ar), representing the ratio between the body force of continent and its integrated strength, and the buoyancy number (F), representing the ratio between the buoyancy force of ocean and its ductile resistance. We obtain three scenarios. In experiments with Ar 3 and F < 1 the ocean deforms by distributed folds, resembling the undulations observed in the Indian Ocean. In experiments with Ar 7 and F >1 the continent collapses toward the ocean, producing back-arc extension and subduction, simulating the postAlpine Neogene evolution of the Mediterranean area. In experiments with Ar 3 and F > 1 the passive margin slowly evolves toward trench nucleation with the formation of a viscous mantle instability. We conclude that the latter model can be applied to the evolution of Atlantic-type margins, where there is evidence of this ongoing process.

Recent and active deformation pattern off the easternmost Algerian margin, Western Mediterranean Sea: New evidence for contractional tectonic reactivation

“…Two main forces must be overcome to allow subduction to develop: elastic plate flexure (bending stress) and frictional resistance across a pre-existing fault (McKenzie, 1977). In our case study, although the slow convergence rate is not favoring a spontaneous subduction nucleation at the continent-ocean transition ( [Faccenna et al, 1999] and [Stern, 2004]), the sediment loading acting on a young lithosphere may provide an effective mechanism to enhance this process (Cloetingh et al, 1982). Similar case studies of Plio-Quaternary inversion of a former backarc basin can be found in the Japan sea (e.g.…”

“…Therefore passive margins are good potential locations for such a process to occur (e.g. [Cloetingh et al, 1982], [Faccenna et al, 1999] and [Leroy et al, 2004]; and references therein). Two main forces must be overcome to allow subduction to develop: elastic plate flexure (bending stress) and frictional resistance across a pre-existing fault (McKenzie, 1977).…”

Some remarks on the earthquakes of Fennoscandia: A conceptual seismological model drawn from the perspective of hyperextension

“…A parallel implication of our observations and interpretations is that far-field forces may perhaps not be able to propagate very deeply into a hyperextended continental margin. The resolution of contrasting oceanward-directed continental and landward-directed oceanic GPE against the TB and the hyperextended distal domain may perhaps ultimately localize as oceanic-continent subduction (e.g., Masson et al, 1994;Faccenna et al, 1999;Péron-Pinvidic et al, 2008;Marques et al, 2013;Redfield & Osmundsen, 2013).…”

“…Consequently, much of the distal domain can potentially comprise a permanently weakened zone (Masson et al, 1994;Faccenna et al, 1999;Péron-Pinvidic et al, 2008Mohn et al, 2010;Lundin & Doré, 2011;Sutra & Manatschal, 2012;Redfield & Osmundsen, 2013; this paper).…”

New analogue materials for nonlinear lithosphere rheology, with an application to slab break-off

“…Davy and Cobbold (1988);Faccenna et al (1999); Guillaume et al (2009);Duarte et al (2013)). By adding fine iron powder (Funiciello et al, 2004;Schellart, 2008; sample h R σ r Newtonian Power-law rs Figure 3: Schematic rheometer setup, with gap height h and disk radius R, including a schematic depiction of shear stress σ variation as function of radial distance r for Newtonian and power-law materials, rs is the radial distance where the shear stress curves of Newtonian as well as power-law materials intersect (Carvalho et al, 1994).…”