MINUSINSKAYA KETTLE, KUZNETSKY ALATAU, KUZNETSKY TROUGH AT THE END OF THE MIDDLE (the givetian AGE) AND THE BEGINNING OF THE UPPER (the FRANCIAN AGE) DEVON
The work is devoted to the issues of paleogeographic reconstructions of the territory of the Minusinskiye kettles, Kuznetsk Alatau and Kuznetsk trough in the Givetian and Frasnian ages of the Middle and Upper Devonian. It is shown that on the border of the Middle and the Upper Devonian, territory of the southern margin of the Siberian Craton, attached to the ancient platform at the end of the Caledonian folding epoch, had experienced a sharp eustatic rise. An isolated lake reservoir appears in the Minusinskaya kettle, remains of which are represented by the Oydanovskaya (the Early Frasnian), the Kokhaiskaya (the Late Frasnian), and the Tubinskaya (the Famennian) formations. In zone of junction of the Siberian craton with the Kolyvan-Tomsk mobile zone, foothill trough is formed, a fragment of which is represented by the Kuznetsk coal basin in modern time slice. The boundary between cratonized area and the submountain trough is confined to a deep fault in the axial part of the mountain structure. The submountain trough has clearly pronounced asymmetry of relief; in areas adjacent to the mountains, a continental accumulative plain is formed, transferring to the northwest into the sea basin. In parts of it remote from the coast, on the border of continental slope, a chain of reefs had been formed in the Late Frasnian. Territory of the submountain trough in the Upper Devonian experienced gradual subsidence, which is expressed in gradual deepening of sea basin in the part adjacent to the mobile belt. In section of the Upper Devonian sediments of the trough, the fact of the Minusinsk paleolake waves breakthrough has been recorded, through the mountain structure into the submountain trough, with formation of thick alluvial fan (the Sergievskaya suite). As possible reason for such an event and drainage of the lake basin in the Kokhai time, increased seismic activity of the region is considered, traces of which have been recorded in form of seismic dislocations in the deposits of the Kokhai formation. Periodic damping of the Minusinsk lake reservoir may have caused the abrapt jump in evolution of cross-finned fish and the appearance of the first land animals (tetrapods).