LOWER PALEOZOIC DEPOSITS IN THE STRUCTURE OF THE KAPKA-TASH RIDGE (NORTHERN TIEN-SHAN)

On the basis of Cambrian, Lower and Middle Ordovician fossils which ha ve been first collected and described, the widespread opinion on the R iphean age and simple monoclinic occurrence of the series of the Baidu la and Kapka-Tash Ridges is discarded. It is shown that the region str ucture corresponds to the structural paragenesis of a secondary tecton ic collage. The main tectonic units in the region are sublatitudinally striking blocks no wider than 20 km. In the south and in the north th ey border on Late Paleozoic strike-slip faults no less than 100 km in length. Within the blocks, Early (E-O(1)t) and Late (O(1)a-O-2) Caledo nian structural stages separated by regional discordance have been est ablished. They consist of different geodynamic complexes (island arcs, ophiolites, and shelf of the back-are basin). A wide variety of fossi ls have been found in Early Caledonian formations. Here ophiolites con tain conodonts, Radiolaria, and sponge spiculas, the island-are comple x is characterized by the presence of trilobites, brachiopods, chiolit es, chiolitotelmints, and conodonts, and shelf deposits contain bryozo ans, sponges, inarticulate brachiopods, and acritarchs. The age of Are nig-Llandeilo series is determined by graptolites.