The study presents the types

characteristics and the forming process of the bedding decollement deformation domain in the Lower Paleozoic shales in southeast Chongqing via mechanical analysis based on the observation of shale outcrops and cores

and discusses its geological significances in combination with shale gas exploration practices.Two types of bedding decollement deformation domains

namely compression-type and gravity-type

are recognized.The compression-type is formed when horizontal compressive tectonic stress dominates and shale layers are under the action of reverse fault;on the contrary

the gravity-type is formed when the overburden pressure dominates and the shale layers are under the action of normal fault.Compared with the gravity-type

the compression-type is more intense in stratum deformation with larger scale of influence on shales.Burial depth and dip angles are the key geological factors that control the formation of bedding decollement deformation domain in the same shale layer in a certain area.The critical dip angles for the compression-type expand gradually with the shale burial depth increasing

whereas that for the gravity-type decreases gradually with the increasing burial depth.The gravity-type is destructive to the preservation of shale gas.The bedding crushed zones and net fracture systems resulted by compression-type in an anticline are interpreted as the main migration pathways and reservoir space for shale gas

while those in an syncline are the main pathways for shale gas migrating to adjacent anticlines or releasing in the atmosphere.