Nappes of the southern Tien Shan

Abstract

parts of the area are shown. Nappes of the southern Tien Shan occur on a passive margin of the Paleozoic AlayTarim continent. The lower nappes are composed of the passive margin rocks; the upper, of the Paleozoic Turkestan oceanic crust rocks and of rocks of an accretionary prism that occurred nearby the Paleozoic Kazakh‐Kyrgyz microcontinent margin. The accretionary prism was formed during a long-term interval. In the Moscovian after the closure of the Turkestan oceanic basin and during the collision of the Alay-Tarim and Kazakh‐Kyrgyz terranes the accretionary prism rocks were overthrusted onto the Alay-Tarim continental margin. The oceanic crust subduction was followed by the Late Carboniferous and Early Permian subduction of the Alay-Tarim continental crust beneath the Kazakh‐Kyrgyz terrane. At that time a transverse shortening of the Alay-Tarim continental slope resulted in a tectonic decoupling of sediments and formation of the southern Tien Shan lower nappes. INDEX TERMS: 1209 Geodesy and Gravity: Tectonic deformation; 1212 Geodesy and Gravity: Earth’s interior: composition and state; 1213 Geodesy and Gravity: Earth’s interior: dynamics; KEYWORDS: Nappe, accretionary prism, Tien Shan, Turkestan oceanic basin.