Neogene to Present paleostress field in Eastern Iran (Sistan belt) and implications for regional geodynamics

Abstract

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 (σ1), 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 σ1 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.

The kinematics of the Dasht-e Bayaz earthquake fault during Pliocene-Quaternary: Implications for the tectonics of eastern Central Iran

“…Despite the coherency between our results and those obtained in the northern regions, the history of stress changes along the Dasht-e Bayaz fault differs from what is recently obtained along the Sistan Suture zone (Jentzer et al, 2017). Jentzer et al (2017) presented different sets of fault slip data related to three successive stress states indicating an anticlockwise rotation in the direction of maximum compression from a Late Miocene E-W directed σ1 to a late Pliocene to present-day maximum compression directed N026±8°E (see the section 6.2 for more details). Their anticlockwise rotation pattern is contrary to the history we found around the Dasht-e Bayaz and Abiz faults.…”

“…The recent study in the Sistan belt of eastern Iran (Jentzer et al, 2017), however, obtained three distinct deformation stages during late Cenozoic, including (1) an E-W (N087±5°E) direction of σ 1 probably in the Late Miocene, (2) a late Pliocene ENE-WSW (N059±8°E) direction of σ 1 and (3) a late Pliocene to present-day maximum compression (N026±8°E). The same authors proposed that during the last ~10-5 Ma, the direction of compression has rotated about 60° counterclockwise in Sistan.…”

“…We compared the pattern of kinematic changes along the Dasht-e Bayaz fault with similar studies in nearby regions in E and NE Iran (e.g. Shabanian et al, 2010;Farbod et al, 2011;Javidfakhr et al, 2011;Jentzer et al, 2017;Tadayon et al, 2017), which has allowed us to place our results in a larger geodynamic scale (see the discussion).…”

“…Iran is due to the stress transfer from the Arabia -Central Iran collision, or is influenced by the geometry 101 and relative motion of individual blocks in eastern Iran (e.g., Jentzer et al, 2017).…”

Multiphase Structural Evolution of a Continental Margin During Obduction Orogeny: Insights From the Jebel Akhdar Dome, Oman Mountains

“…Increasing convergence rates after 17 Ma (Figure ) match uplift of the Iranian Plateau interpreted to initiate between 15 and 12 Ma (Mouthereau et al, ). Likewise, directions of Arabian plate motion (Figure ) reflect paleostress interpretations interpreted for Eastern Iran: (1) E‐W compression during middle to late Miocene, (2) ENE‐WSW in the late Pliocene, and (3) NNE‐SSW during Plio‐Quarternary (Jentzer et al, ).…”