Neogene to Present paleostress field in Eastern Iran (Sistan belt) and implication for regional geodynamics
Résumé
We conducted a stress field analysis of the northern part of the ~700 km long north-south
trending, seismically active Sistan orogenic belt of Eastern Iran formed as a result of the closure of a
branch of the Neo-Tethys during the early Cenozoic. Fault kinematic data reveal drastic changes in the stress
regime of Eastern Iran during the late Cenozoic, with three successive directions of compression (σ
1
), from
90°N during the middle-
late Miocene to 60°N during the late Pliocene and 25°N during the Plio-Quaternary,
thereby evidencing a counterclockwise rotation of about 65° of σ
1
in less than 10 Myr. As shown by
compilation of paleostress data, Plio-Quaternary direction of compression in Sistan coincides with the one
recorded across the whole of Iran and with present-day Arabia-Eurasia convergence direction. This result
suggests effective stress transfer from the Zagros collision and that Sistan is at present mechanically coupled
and shortened along with the rest of the Iranian crust/lithosphere. By contrast, Miocene compression is
markedly different in the Iranian hinterland (e.g., Sistan, Central Iran, and Kopet Dagh) and in the Zagros
orogen. This could tentatively be related to the end of Sistan collision and/or to the imprint of active
deformation occurring further to the east. The intermediate late Pliocene compression (i.e., 60°N) could
correspond to the progressive reorientation of the stress regime, as Sistan gets mechanically coupled to the
Zagros collision
Domaines
Sciences de la TerreOrigine | Fichiers éditeurs autorisés sur une archive ouverte |
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