Tectonic paleostress field and its impact on the geodynamic evolution of Central Iran, case study: the Shotori Mountain

The Shotori mountain range is located along the northern terminus of the Nayband fault on the eastern and western domains of the Tabas and Lut blocks, respectively. This range with NNW-SSE trending and approximately 120 km long includes a series of thrust faults approaching the right-lateral strike-slip Nayband fault. Since the Shotori range has experienced various geological events since the Triassic, our investigations suggest that the basement of the Central Iranian subcontinent of the Shotori range contains the early Triassic deep sedimentary with normal faults which confirms Triassic tensional tectonic stress regime in the region. After the middle Triassic, the mountain range has experienced thrust and strike-slip regimes. Therefore, in this study, we reconstruct the stress regimes for different geological periods using fault-slip data. The inversion of fault-slip data reveals drastic temporal changes in the maximum stress regime (σ1) over the Triassic, Jurassic, Cretaceous, Paleogene, Neogen, and Quaternary. The reconstruction of the stress field based on the age and direction of fault movement reveals that the direction of the maximum horizontal stress axis (σ1) under a tensional stress regime was approximately N129° in the Early Triassic. This stress regime is the cause of thinning and subsidence of the Shotori sedimentary basin. During the middle Triassic, the σ1 direction was about N81° and the upper Triassic, the σ1 direction was almost N115°. The middle Triassic and upper Triassic stress states exhibited two distinct strike-slip and compressive stress regimes. This stress regime led to the uplift of the Shotori sedimentary basin. During the Jurassic, the direction of the maximum horizontal stress axis (σ1) was ∼NW-SE under a compressive stress regime. During the Triassic, the σ1 direction was ∼N-S. This stress regime led to the formation of the high topography of the Shotori Mountain Range. In the Late Cretaceous, the direction of the maximum horizontal stress axis (σ1) under the extensional stress regime was ∼NE-SW. This stress regime led to the uplift of the Paleogen Dacite in eastern Iran. During the Neogene, the σ1 direction was ∼N6o°. The Quaternary tectonic regime is strike-slip and the σ1 direction is ∼N50°, consistent with the current convergence direction of the Arabia–Eurasia plates. Our paleostress analysis reveals four recognized stress in this area, which includes compressional, transtensional, transpressional, and strike-slip regimes. Our findings indicated that the crustal diversity of the tectonic regimes was responsible for the formation of various geological structures, such as folds, faults by different mechanisms, and the present-day configuration of the Shotori sedimentary basin.