关键词: 古滑坡, 岩溶, 巫山县城, 三峡库区

Abstract: The former specified Xiufengsi landslide was extended as an ancient Xiufengsi-Dakuaizi landslide and its genetic process was probed by the author. The landslide is located between two trenches and shows as an irregular dumbbell. The slide body with a value of about 200×10⁴ m³ was generated from marly stone of the first member in Triassic Badong Formation(T₂b₁). The slide was developed under special geomorphologic and geologic environment, and controlled by karstification. All the rockmass of slide part, slide zone and slide bed suffered strong karstification and has complex structure. The genetic process is as follows: ① Wushan syncline was put forward by Yanshan movement, and Xiufengsi-Dakuaizi located at the steep-dipping NNW wing of the syncline;② Denudation occured on surface, corrosion and argillation occured in depth in neotectonic era, the soft strata slid on the limestone top and the gentle local fold zone was put forth along the water-table level;③ the mudstone was denuded, the fold zone was exposed in the trench, the marly stone continually slid, and the fold zone was sheared by the sliding body, so the landslide was throughout， and at the same time, the below limestone rockmass was deformed by desolation;④The landslide was fractured, divided and decreased in value by the further karstification and denudation, the limestone layer near Shiban trench dipped reversely, and the limestone top dropped, so the recent appearance was shaped. That type of landslide can be concluded as bedding traction-bed flat-slowdown landslide in karst process.

Key words: ancient landslide, karst, Wushan County town, Three Gorges reservoir region