Late Palaeozoic to Triassic evolution of the Turan and Scythian platforms: The pre-history of the Palaeo-Tethyan closure

A number of en échelon-arranged, southwest-facing arc fragments of Palaeozoic to Jurassic ages, sandwiched between two fairly straight east-northeast trending boundaries, constitute the basement of the Scythian and the Turan platforms located between the Laurasian and Tethyside units. They have until now largely escaped detection owing to extensive Jurassic and younger cover and the inaccessibility of the subsurface data to the international geological community. These units are separated from one another by linear/gently-curved faults of great length and steep dip. Those that are exposed show evidence of strike-slip motion. The arc units originally constituted parts of a single “Silk Road Arc” located somewhere south of the present-day central Asia for much of the Palaeozoic, although by the late Carboniferous they had been united into a continental margin arc south of the Tarim basin and equivalent units to the west and east. They were stacked into their present places in northern Afghanistan, Turkmenistan, Caucasus and the northern Black Sea by large-scale, right-lateral strike-slip coastwise transport along arc-slicing and arc-shaving strike-slip faults in the Triassic and medial Jurassic simultaneously with the subductive elimination of Palaeo-Tethys. This gigantic dextral zone (“the Silk Road transpression”) was a trans-Eurasian structure and was active simultaneously with another, similar system, the Gornostaev keirogen and greatly distorted Eurasia. The late Palaeozoic to Jurassic internal deformation of the Dniepr–Donets aulacogen was also a part of the dextral strain in southern Europe. When the emplacement of the Scythian and Turan units was completed, the elimination of Palaeo-Tethys had also ended and Neo-Tethyan arcs were constructed atop their ruins, mostly across their southern parts. The western end of the great dextral zone that emplaced the Turan and Scythian units horsetails just east of north Dobrudja and a small component goes along the Tornquist–Teisseyre lineament.