Shale-related minibasins atop a massive olistostrome in an active accretionary wedge setting: Two-dimensional numerical modeling applied to the Iranian Makran

Abstract

Minibasins are sagging synformal depocenters surrounded by upsurging ductile material. They are traditionally related to salt tectonics. The onshore Iranian Makran accretionary wedge exhibits closed minibasins developed onto a regional-scale olistostrome with a shaly matrix. Two-dimensional numerical experiments were carried out to investigate whether the growth of such minibasins above a shale-dominated unit is feasible and how the presence of a regional, shale-dominated olistostrome may affect the structural evolution of active accretionary wedges. Model results indicate that rapid mass-flow emplacement triggers thickening of the rear of the wedge while minibasins grow in a more frontal, tectonically quiet region. Further wedge growth leads to a jump forward of frontal accretion. Compared to the case history, this jump would explain the structural characteristics of the Coastal Makran in Iran.