[1] We present the first complete balanced cross section across the southeastern Zagros fold-thrust belt (ZFTB). The following main structural features emerge from this section: (1) In the south of the ZFTB, the Proterozoic-to-Recent sedimentary sequence has been decoupled from its Panafrican basement along the ductile basal evaporites and folded into a series of large detachment anticlines. Ongoing shortening of these structures has resulted in migration of the basal salt layers into the cores of the anticlines and propagation of forelimb thrusts. (2) In the north of the ZFTB, deep-seated ramps have folded the hanging wall rocks and produced imbrications and duplex structures within the higher levels of the sedimentary sequence. (3) Out-of-sequence thrusts, linked to major seismogenic basement faults, have cut through the structures in the cover of the ZFTB. A three-step incremental restoration of the section shows that two main phases of deformation can be separated in the tectonic evolution of the ZFTB: a MioPliocene thin-skinned phase, in the course of which most of the structures in the cover were generated, followed by a Pliocene to Recent thick-skinned phase, expressed as out-of-sequence faulting in the cover, which is currently underlined by the seismicity within the basement. In plan view, the initial structures of the southeastern ZFTB developed with a curved shape essentially controlled by the shape and thickness of the underlying Proterozoic salt basin (i.e., the ''Jura style''). In the following basement-involved phase, out-of-sequence thrusts cut at oblique angles through the preexisting structures of the cover. The total shortening absorbed in the cover amounts to at least 45 km, corresponding to a ratio of $22%. From thin-skinned to thick-skinned tectonics, Tectonics, 24, TC3007,

[1] We present the first P-T, deformation time, and kinematic constraints on the only known blueschist facies rocks (BS) present in the Zagros (Hajiabad area). The BS were underplated below the Sanandaj-Sirjan zone and crop out as kilometer-scale bodies within extensive colored melange units marking discontinuously the Neotethyan suture zone. P-T estimates point to high-pressure/low-temperature (HP-LT) conditions around 11 kbar and 520-530°C for the majority of BS, along a $15°C km À1 gradient. Some exotic blocks in matrix serpentinite reached 17-18 kbar at $500°C. In situ laser probe 40 Ar-39 Ar radiometric age constraints on phengite cluster between 85 and 95 Ma and suggest that (1) synconvergence exhumation of Zagros BS from 35-50 km to depths <15-20 km was accomplished before 80 Ma, (2) BS exhumation corresponded to a transient process with respect to the long-lived subduction beneath Iran ($150-35 Ma), and (3) age constraints for Zagros BS are 5-10 Myr older than for the nearby Oman HP-LT rocks and broadly coincide with obduction processes in the region (circa 95-70 Ma). We propose that the mechanical coupling across the Neotethyan subduction zone (NSZ) beneath Iran was modified by the large-scale plate rearrangement accompanying obduction, allowing for a short-lived exhumation of Zagros BS. Exhumation ceased at the end of obduction, when subduction of the Arabian continental margin stopped. Kinematic calculations suggest that convergence velocities across the NSZ likely doubled (to $5-6 cm yr À1 ) during the period 118-85 Ma, so that BS exhumation may have been promoted by a combination of obduction movements and increased convergence velocities.

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