Abstract:

Using residual thickness method，paleoˉtectonic features during different periods are recovered in Ordos Basin.Taking karst reservoirs in the Ordovician as an example，this paper also discusses the influence of paleoˉtectonic evolutionary process on the development of karst reservoirs.In the Ordovician，the paleotectonics ofOrdos Basin features in one high between an eastern lowwith gentle slope and awestern lowwith steep slope.Dolom itewith gypsum deposited on the eastern gentle slope，and provided amaterial basis for the developmentof paleokarst reservoirs.After the Ordovician，there was a hiatus about1.3×10 12 years and the previous tectonics was inherited.From a paleogeomorphic pointofview，the eastern slope of the central paleohigh belongs to a karst slope where concentrated water flow and active throughflow provided favorable conditions for the development of karst reservoirs ofweathering crust type.From the Carboniferous Benxi period when deposition renewed to the Early-Middle Triassic，the erosion surface on top of the Ordovician keptprevious paleotectonic features.The paleohigh is believed to be favorable destinations for subsurface active fluids.The slope zones，which experienced karsitification ofweathering crusts earlier，are favorable for the development of burial karsitification.

Key words: dolom ite with gypsum, erosion surface, exposed weathering crust period, burial karstification, paleotectonics, Ordos Basin