STRUCTURAL STYLE AND KINEMATIC EVOLUTION OF THE HIGH ZAGROS, IRAN

Abstract

The High Zagros in Iran, the most internal zone of the Zagros fold‐and‐thrust belt, is discontinuous and is only present in two mountainous areas located in the central and eastern parts of the belt respectively. Compared to other zones of the Zagros fold‐and‐thrust belt, the High Zagros has been relatively poorly studied. We present here new maps of these regions together with six new cross‐sections and two associated kinematic models. In addition to the well‐known basal décollement level located in the Upper Proterozoic Hormuz Formation, there is evidence for the existence of a deep intermediate décollement located within the Ordovician‐Silurian shale succession. From a geometric point of view, activation of this detachment and of the basal detachment has caused the development of duplexes which are confined within the cores of anticlines. From a kinematic point of view, a two‐phase history is suggested. During the first thin‐skinned phase, large detachment folds developed over the Hormuz salt and different intermediate décollements were activated together with fore‐ and back‐thrusts. This was followed by a thick‐skinned phase marked by the activation of major out‐of‐sequence basement thrusts, partly inherited from old basement faults. This final and still active phase of deformation is responsible for the exhumation of the Lower Palaeozoic succession. Finally, this kinematic model is integrated into a general tectonic scenario for the Zagros fold‐and‐thrust belt.