AN APPROACH TO THE STUDY OF INVERSION POINTS AND TANGENCY-IN POINTS FOR OROGENY AND COUPLED/DECOUPLED BASIN DEVELOPMENT

The study of orogeny and coupled/decoupled basin development regarded orogeny and basin development as a whole and explored a uniform kinematic process and geodynamic mechanics between the both. The key of methodology for the study was to grasp, correctly and practically, inversion points and tangency-in points, the former representing obvious changes of tectonic patterns or styles, and the latter constituting a key link connecting basins with orogeny. For the inversion points, we should, first of all, understand the essential problems of orogeny and coupled/decoupled basin development in a given regional framework. In addition, the tectonic features of Chinese continent decided the difficulties and complexities of discerning inversion points, which supported, in turn, a wide platform for the study of tengency-in points. The tangency-in points might be decided by a poly-direction, poly-visual angle, poly-level and poly-aspect means, in which the orogenic types and structural styles should be the first important and necessary one. As the road one must take for the study of inversion points and tangency-in points, a combination of "normal succession" and "reversal succession" was emphasized, with stress on the study of "reversal succession". Namely, regional evolution and basin development should be worked from the ancient to the present, and the oil-gas accumulation analysed from the young structural layers to the older ones. The paper introduced some experiences to compile some profiles, perpendicular to the regional tectonic strike, across both an orogen and neighbouring basins. With the inversion points and tangency-in points being embodied in the basin research, the alternation of basin generations as well as tectonic patterns and structural styles in each generation should be correctly distinguished, particularly, to distinguish the basin generations changed in the periods of main tectono-thermal events. The prerequisite for understanding basin generations was to constrain a geohistorical phase and to stipulate a basin definition. The advances in the study of inversion points and tangency-in points for orogeny and coupled/decoupled basin development must open up a new prospect of the basin research, and then draw a new inspiration in the oil-gas exploration of relict marine basins.