Abstract

This paper describes the orogenic evolution of the southeast Anatolian orogenic belt based mostly on new geologic data collected from its constituent tectonic units in the course of new mapping programs of the past decade.

The southeast Anatolian orogenic segment of the Alpides may be divided into three approximately east-west-trending zones. From south to north, they are the Arabian Platform, followed by a zone of imbrication, and then a zone of nappes. The Arabian Platform includes a mostly marine, sedimentary succession deposited from early Cambrian to middle Miocene time. The zone of imbrication is a narrow belt sandwiched between the Arabian Platform and the zone of nappes. It consists of imbricated thrust slices emplaced onto a Late Cretaceous to early Miocene sequence. The zone of nappes is the highest tectonic unit, consisting of two stacks of nappes simply designated the lower and upper nappes. The lower nappe is represented by the slices of a polyphase metamorpbic ophiolitic assemblage and the Maden Group. The upper nappe rests on the lower nappe and is represented by the Bitlis and Pötürge metamorphic massifs.

Southeastern Anatolia underwent two major episodes of Alpide deformation. The first occurred during the Late Cretaceous period, when ophiolite was emplaced on the Arabian Platform. This event was not the consequence of a continental collision. The ophiolite obduction onto the Arabian Platform was followed by a regionwide extension and a new marine transgression over the platform immediately after the ophiolite obduction. The second episode of deformation occurred during middle Eocene-Miocene time in two distinct stages as a result of the progressive elimination and complete closure of the ocean(s) which led to the collision between the zone of nappes located to the north (being a part of Eurasia) and the Arabian plate. The Maden marginal basin formed north of the subduction zone that eliminated the ocean between Eurasia and Arabia, along the southern margin of the Taurus belt, and abutted the Arabian Plate much later, during the final collision.

The second episode of deformation formed the present orogenic segment leading to the amalgamation of different tectonic units. These amalgamated nappes collided with the Arabian plate and welded onto it at the latest stage of the orogenic evolution during the Miocene epoch.

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