Abstract:

Combineing closely the practical exploration and guided by multidisciplinary geological theory and technology, a comprehensive geological model has been set up to explain and restore paleogeomorphology unit attributes of the Ordovician weathering crust of eastern Ordos basin. Meanwhile, according to drilling and logging geologic data, authors also combine basin tectonic evolution with results of “impression method” organic integration and results of “residual thick method”, discuss the methods and thinking of Ordovician weathering crust paleogeomorphology restoration, and its ancient landscape development characteristics through in-depth analysis of the stratigraphic combination under and above Ordovician unconformity erosion surface, and explore a new method of palaeogeomorphologic reconstruction-“synthetic method”. The research results show that the stratigraphic combination, under and above Ordovician unconformity erosion surface in the eastern of Ordos basin, can be divide into four basic types including “up thin down thin”, “up thick down thick”, “up thick down thin”, “up thin down thick” , and eight sub models which were “up relative thickening down relative thinning”, “up relative thinning down relative thinning”, “up relative thinning down relative thickening”, “up relative thickening down relative thickening”, etc. The corresponding paleogeomorphology explanation includes three two-level paleogeomorphology units as karst highland, karst slope, karst basin,and eleven three-level paleogeomorphology units including monadnock, tableland, residual tableland, level terrace, cheuch, shallow depression,deep depression etc. The Karst highlands occurs restrictively in the southwestern research area.The Karst slope occupies most of the study area where the  main paleogeomorphology units were slope tableland and slope level terrace. The Karst basin is located in the eastern study area and the main paleogeomorphology units include basin shallow depression.

Key words: Ordos basin, Ordovician, weathering crust, karst palaeogeomorphology, comprehensive geological model