The Southern Tian-Shan thrust tectonics controversy: Forming a basis for paradigm shift

Abstract

The reinterpretation of the Paleozoic Southern Tian-Shan (STS) orogen tectonics took place from the 1950s to the 1980s and was connected with the research activity of G. S. Porshniakov (1918–1993), professor of Leningrad University, as well as that of his colleagues and opponents. The main factors of this reinterpretation were i) extensive field investigations, including geological mapping and paleontological dating, and especially engaging young scientists to the study; ii) development of scientific schools and free competition between them; iii) welltimed change and evaluation of theoretic models while using global experience. G. S. Porshniakov gave a talk to present his own new tectonic model for the STS where the space shortening and top-to-the-south thrust movement were shown as the leading factor. In modern terms, it means the collision of the ancient Kazakhstan, Tarim and Gissar continents. The model emerged as a result of detailed paleontological dating, which showed different lithology of coeval formations. The thrust model by Porshniakov was defended in a controversy with the colleagues who insisted on the earlier “deep faults” ideas. It was then checked and verified by geological mapping of the vast territory from the Kyzylkum in the west up to Chinese Xinjiang. After some actualistic modernization, this conception agrees with new ideas in the Paleozoic history of the STS, such as ocean and continental margins development, internal arcs, intraplate (plum) magmatism and disposal of post-collisional granite intrusions.