1. FAULT SYSTEMS IN THE UPPER CRUST OF THE CENTRAL ASIAN FOLDING BELT
- Author
-
V. S. Burtman
- Subjects
тектонические разломы ,активные разломы ,тянь-шань ,алтай ,саяны ,Geology ,QE1-996.5 - Abstract
This article considers the disjunctive deformation of the upper crust in the Tien Shan and Altai-Sayan regions of the Central Asian folding belt. An analysis of the diagrams of fault directions constructed on the basis of information on more than 3000 faults revealed orthogonal fault system assemblages in these regions. Among them, a significant number of faults were functioning during two or more epochs of orogenic deformations. The direction of displacements was determined by the deformation field existing in that epoch, irrespective of the fault kinematics in the previous deformation epochs. The Tien Shan is a Paleozoic folded belt that experienced cover-folded deformations and orogenesis in the Paleozoic, as well as neotectonic orogenesis in the Late Cenozoic. The Paleozoic Tien Shan consists of the Caledonian and Variscan provinces, which underwent a different number of deformation epochs. Two deformation epochs — Late Paleozoic and Late Cenozoic — covered the entire Variscan province of the Tien Shan. Late Paleozoic deformations were associated with a collision of the Tarim and Kazakhstan paleocontinents. The Turkestan Ocean having separated these blocks was closed in the Late Carboniferous. The orogenesis having occurred during Permian was a late stage of that deformation epoch. Four or more orogenic epochs were characteristic of the Caledonian Northern Tien Shan. In the middle Ordovician, the Terskey Ocean, which had separated the Kokchetau-Issyk-Kul and Syrdarya microcontinents in the early Paleozoic, was closed. The collision of these blocks was accompanied by orogenic deformations and the formation of the Late Ordovician molasses. The distribution of the Late Devonian molasses in the region indicates orogenic processes having occurred at that time. Subsequently, the Caledonide territory, along with the entire Tien Shan, was covered by orogenesis in the Permian and Late Cenozoic. During the Late Cenozoic deformation, no fault systems appeared in the Variscan and Caledonian provinces of the Tien Shan; rather, a movement along the Paleozoic faults of a corresponding direction took place. Orogenic dislocations occurred in the different parts of the Altai-Sayan region in Cambrian, Ordovician, Silurian, Devonian, Late Paleozoic and Late Cenozoic. In this region, the Late Paleozoic assemblages of fault systems activated in the most recent epoch were identified, and the fault system assemblage in the Late Cenozoic was revealed.
- Published
- 2020
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