RUSSIAN JOURNAL OF EARTH SCIENCES VOL. 10, ES1006, doi:10.2205/2007ES000223, 2008
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[3] By the early 1960s thrust faults that separated different facies of synchronous sediments were described in the Alay and Turkestan ranges, southern Tien Shan, on limbs of large synclines [Porshnyakov, 1960, 1962]. Studies of thrust faults in that and other southern Tien Shan regions suggest that they represent fragments of a multilayered Late Paleozoic nappe ensemble that covered a vast territory [Burtman, 1968, 1970; Burtman and Klishevich, 1971]. Nappes from different southern Tien Shan regions were described in books by Biske [1996], Biske et al. [1982, 1985], Burtman [1973, 1976, 2006a], Mukhin et al. [1991], and in many papers. Russian book by Burtman [2006a] and this paper discuss the nappe distribution throughout the southern Tien Shan.
[5] Geologic sections of the area include ten or more allochthonous thrust sheets. In multilayered tectonic ensembles the sheets formed by rocks of similar composition and genesis are repeated several times in the geologic section.
[6] In the proposed model of southern Tien Shan nappes we distinguish primary and secondary overthrust faults. Primary overthrust faults separate tectonic sheets composed of rocks that were formed in different, mainly adjacent tectonic environments, for instance, on shelf and continental slope. Primary overthrust faults represent unit boundaries. Secondary overthrust faults twin the sets of tectonic sheets in the geologic section. They complicate the nappe ensemble structure and internal structure of the units. Tectonic sheets composed of rocks of the same origin and age are referred to a single unit independently of their position in geologic sections that are commonly deformed by secondary overthrust faults. The reconstructed position of units, which they occupied prior to overthrusting, appears as a natural succession of facies zones on continental margins and in oceanic basins.
[7] Rocks of the structural units comprise tectonic sheets, windows, and sheet fragments of different origin: tectonic slices, klippes, tectonic mélange blocks, and olistoplaques and olistoliths in olistostromes. Position of these fragments is commonly a debated topic. On describing a complicated nappe structure in the Tien Shan the generalized term "oreade'' is convenient for designation of unit parts and fragments independently of their position and mode of setting apart (oreades are nymphs of mountains and rocks in ancient Greek myths).
[8] It is appropriate to begin the discussion of southern Tien Shan nappes from the western Tien Shan where they are better studied.
Citation: 2008), Nappes of the southern Tien Shan, Russ. J. Earth Sci., 10, ES1006, doi:10.2205/2007ES000223.
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