EXTENSION VERSUS SHORTENING MODELS FOR HINTERLAND-DIRECTED MOTIONS INTHE SOUTHERN QUEBEC APPALACHIANS

In the Taconian internal zone of southern Quebec, structures related t o hinterland-directed motion are found on both limbs of the Sutton-Not re-Dame mountains anticlinorium (D-3West and D-3East structures) and a long the St-Joseph fault. These ductile to brittle-ductile structures were formed during upper- to mid-greenschist grade metamorphic events, thus suggesting that the area occupied a mid-crustal position during hinterland motion. Layer-extensional fabrics along the eastern limb of the Sutton-Notre-Dame mountains anticlinorium can be interpreted eith er as structures contemporaneous to backthrusting deformation rooted o n the western Limb of the anticlinorium or as structures formed during normal faulting along the St-Joseph fault. The study of layer-extensi onal structures found in the Taconian internal zone of the southern Qu ebec Appalachians shows that it is not obvious to infer wether normal- sense fabrics that occur in orogenic hinterlands are related to region al crustal extension or to local syn-collisional extensional faulting.