Tectonics
Tahmoores Yousefi; Kouros Yazdjerdi; Manouchehr Ghorashi; Alireza Shahidi
Abstract
The current form of the folded Zagros is the result of the oblique collision the Arabian and Iranian plates in Late Cenozoic. In this study, Cenozoic stress field changes in Zagros Simply folded belt and structural evolution after collision in Shiraz Area have been evaluated. The geological formations ...
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The current form of the folded Zagros is the result of the oblique collision the Arabian and Iranian plates in Late Cenozoic. In this study, Cenozoic stress field changes in Zagros Simply folded belt and structural evolution after collision in Shiraz Area have been evaluated. The geological formations under investigation are from Late Cretaceous to Neogene (Late Cenozoic). In this regard, geometry and kinematics of the faults, stylolites and other tectonic and stratigraphic evidence in geological formations outcrops in the study area at 30 stations were taken. The tension main axes (σ1, σ2, σ3) were calculated by Inversion Method for the categorized data. The results of the reconstruction of the paleo stress show compressional and Strike- Slip tectonic regime in Cenozoic. Moreover, anticlockwise rotation of the direction of compressive stress over time is about 60 degrees. As pre-folding compressional stress direction (σ1) is about N60E and its time is Miocene and before that. Whereas syn-folding stress direction is N35E and its age is equivalent to Pliocene that is the same age as old Bakhtiary formation. Stress changes in post-folding indicate N20E and its age equivalent to Pleistocene that is the same age as young Bakhtiary formation. At the present time, the maximum stress direction that is about N-S affects the area.
Tectonics
Tahmoores Yousefi; Kooros Yazdjerdi; 2Manouchehr Ghorash; Alireza Shahidi
Abstract
Abstract: The brittle tectonic history expresses different tectonic events in the Zagros Simply Folded Belt. Consequence of Mesozoic extension, rifting and the shortening derived from the Cenozoic Eurasia – Arabia collision. In order to reconstruction the ancient tensions in the Mesozoic deposits ...
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Abstract: The brittle tectonic history expresses different tectonic events in the Zagros Simply Folded Belt. Consequence of Mesozoic extension, rifting and the shortening derived from the Cenozoic Eurasia – Arabia collision. In order to reconstruction the ancient tensions in the Mesozoic deposits in the east and south-east of Shiraz, geometry and kinematics of the faults data simultaneously with sedimentation was investigated using the inversion method, to evaluated rifting time, the former of Neo-Tethys and its collisions in Cretaceous and Paleocene. In this regard 21 stations have been exposed in Khanekat to Pabdeh Formations. The resulted geometry and kinematics of the faults data were calculated situation main tension axes (σ1, σ2, σ3 ), tension ellipsoid figure or ratio of difference (ɸ). The results are as follows: from Triassic to upper Cretaceous (Mastrichtian) in Khanekat,Surmeh, Fahlian, Darian, Sarvak, Ilam, Gurpi, Tarbur Formations and Ghorban Member; extensional tectonic regime was dominant and having NE-SW direction (N052°) but in Pabdeh Formation with Paleocene age, tectonic regime has changed into compression with NE-SW compressional stress direction(N045°). So it was concluded that in simply folded Zagros of interior Fars, time of rifting and the forming of Neo-Tethyan basin was Triassic or older (Permian) with NE-SW extensional direction. The beginning of compressional tectonic regime with the same direction has been in Paleocene.
