n.
In geology, a large body or sheet of rock that has been moved by faulting or folding a distance of about 1 mi (1.5 km) or more from its original position.
A nappe may be the hanging wall of a low-angle thrust fault (a fracture in the rocks of the Earth's crust caused by contraction), or it may be a large recumbent fold (i.e., an undulation in the stratified rocks that have an essentially horizontal axial plane); both processes position older rocks over younger rocks.