CENOZOIC ROTATION OF MICROCONTINENTAL BLOCKS IN CENTRAL IRAN

The Lut Block (LB) is an N-S trending continental sliver that forms the eastern part of the East Central Iranian Microcontinent (CEIM), and belongs to a major tectonic domain at the interface between Eurasia, India and Arabia. The boundaries of the LB are defined by Mesozoic to Cenozoic ophiolitic and flysch belts. Previous paleomagnetic studies suggest that the CEIM and LB underwent 135° counter-clockwise rotation with respect to Eurasia since the Triassic. We present here key structural and tectonostratigraphic features in the LB and surrounding areas, which provide new constraints on the Cenozoic evolution of continental blocks in Central Iran. First, the Sanadaj-Sirjan Zone is situated on the SW side of the CEIM is currently disconnected from the LB and the direction of maximal elongation of these two continental slivers forms an angle of at least 90°. However, the Sanadaj-Sirjan Zone shares several tectonostratigraphic features with the LB suggesting that these continental slivers may have been originally connected. Second, the Doruneh Fault in a half-circle pattern extends along the northern margin of the LB surrounds the structures characterized by NE and NW curvature in the NE and NW edges of the LB, respectively. The Zeber Kuh Complex is one of these structures; it is characterized by a dextral compressional strike-slip duplex with a positive flower structure shape developed pre-Late Miocene between the Doruneh and Kalmard Faults. Third, similar indications of dextral shearing are given by compressional and extensional strike-slip duplexes in the NW Nehbandan area along the eastern margin of the LB. Structural patterns of the Nehbandan area can be followed towards the center of the LB and define an S-shape mega structure that connects to the western edge of the LB. Finally, a mega antiform with an NW-trending axial plane and similar plunging occurs in the Eocene flysch basin east of the LB. In conclusion, the presented features support anticlockwise rotation of the CEIM in the Late Paleogene-Early Neogene. Although the exact causes for the rotation of continental blocks in Central Iran remain unclear, we speculate that India-Eurasia collision and southwestward tectonic escape of the Afghan Block were the main controlling factors, which facilitated nucleation of continental faults along Neotethyan sutures.