THE POLYCYCLIC TECTONIC THEORY AND THE EVOLUTION OF PETROLIFEROUS BASINS
多旋回构造运动与含油气盆地

Some of the author's opinions during the past years concerning the tectonic evolution of China's petroliferous basins are, bound up with or inspired by the polycyclic tectonic theory founded by Prof. Huang Jiqing. In this paper the following points are discussed: 1. The preparatory stages of the Protoplatform, including the aulacogens on some early-stabilized cratons(e. g. the Sino-Korean) and the sedimentary depressions on others whose mobility was persisted to a much later time(e. g. the Yangtze), were also developed polycyclicly and their potentiality of oil and gas resources could not be overlooked. 2. The Mongolian geosynclinal foldbelts are intercontinental geosynclines, different in tectonic essentials from marginal geosynclines. Though small "oceanic basins" had existed here and there when the Protoplatform was disintegrated at different periods, the cycle of appearing of the oceanic crust, however, was short in time and restricted in space (Miyashiro). The opening and closing of the geosynclines behaved accordion-like in each cycle; and the uplifting and subsiding of the platforms with transgressions and regressions of seas were in tune with the geosynclines. It is under this geosyncline-platform tectonic regime that many Paleozoic petroliferous basins were developed polycyclicly within the platform or bordering the geosyncline. The author has proposed a classification scheme for them. 3. Prof. Huang's Pal-Asia of the late Variscan cycle is also related to the global tectonic event of the formation of Pangea B of Morel. The tectonic development from Late Carboniferous through Permian to Early Triassic (sometimes even to Early Jurassic), called by the writer "the transitional stage", though relatively short in time-span and relatively calm in regard to orogenesis and taphrogenesis as Prof. Huang pointed out, was, however,marked by the major transcurrent movements and the paradigm change of global thermal regime. The development of collapse basins (of which the Junggar is an example) on the Variscan foldbelts and the relative transgressive and extensile features on their borderlands and on the platforms are important factors in the assessment of Late Paleozoic-Early Mesozoic oil and gas basins. 4. Prof. Huang has stated that the Tethys was also developed polycyclicly since the Late Paleozoic and has given a clear picture of the "suture lines" with ophiolites from the south of the Kunlun to the Himalayas and their correspondent features in the western parts of Sichuan and Yunnan. In Prof. Huang's scheme each suture line is accompanied by a foldbelt on its southern side and with successively younger age to the south. In the writer's opinion, the thick marine sediments of these foldbelts may represent the passive margins of the Tethys oceanic crust when it was spreading asymmetrically in each cycle of development. In this respect, they should not be excluded from the future targets of oil and gas prospecting, although their state of deformati