Some supergene deformation structures in marly limestone in the Three-Gorges region and their relation to geohazards

Abstract：Supergene deformation structure, whose mechanism is different from that of the endokinetic deformation structure, in marly limestone in the Three-Gorges region forms by karst dissolution in special geological, geomorphological and climatic conditions, and while endokinetic deformation is superimposed by supergene deformation, the structure would become very complex. Supergene deformation structure may fall into the continuous deformation structure type, discontinuous deformation structure type and transitional deformation structure type, of which the first type includes flying goose-shaped folds and bending layers, the second type includes the close-spaced joint zone and normal fault by dissolution, and the third type includes boudin structure by dissolution and turning-around blocks. They are widespread in the Three-Gorges region and form by dissolution of marly limestone. The process of supergene deformation is also the process of ground deformation and destruction. Many geohazards occurred frequently in the Three-Gorges region are related to the development of supergene deformation structure. Therefore the most effective measure to control geohazards is to keep water from infiltrating into the ground.