Geodynamic Evolution of the Tethyan Paleomargin of Iran: Comparison with Oman

Robin, Cecile¹, Philippe Razin², Spela Gorican³, François Guillocheau⁴, Gilles Dromart⁵ (1) University of Rennes, Rennes, France (2) Bordeaux University, Bordeaux, France (3) Ljubjana University, Ljubjana, Slovenia (4) Géosciences Rennes, Université de Rennes-1, Rennes, France (5) Université de Lyon 1, Lyon, France

In the frame of the MEBE program, a detailed sedimentological and stratigraphical (bios­tratigraphy on radiolarians and sequence stratigraphy) study of the Iran Tethyan paleomar­gin has been carried out. By comparison with Oman where only obduction occurred, those sediments were strongly deformed at the time of the Zagros collision (Miocene). The stud­ied area belongs to the Pichakun nappes, cropping out along the Crush zone. These Middle Jurassic to Lower Cretaceous sediments are mainly carbonates. They have been deposited on a deep-sea plain by various types of gravitational deposits, from debris flows to low-den-sity turbidity currents (most of the radiolarites). This deep-sea plain seems more narrow than the Oman’s one: deep-sea fans deposits looks like more as low efficency systems with no by-pass zone. No Triassic and Lower Jurassic sediments have been characterized in those tectonic units. Two cycles have been recognized with two most distal facies periods (clays deposition, time equivalent of maximum flooding surfaces) during Kimmeridgian and Early Cretaceous (Hauterivian or Early Aptian). At third order sequence scale, several differ­ences between Oman and Iran exist and will be discussed. By contrast with Oman, no defor­mation and truncation occurred during late Jurassic, at time of the Indian Ocean spreading. The paleogeographical consequences will be discussed at the southern Tethys margin scale, and more especially for the Late Jurassic (spatial deformation of the Arabian plate).