A geological formation not formed in the region where it was found: Allochthon takes place when a geological structure is moved to its present location by tectonic forces.

An allochthon is a mass of rock that has been transported a great distance from its original place of deposition, usually by tectonic forces, such as overthrusting or gravity sliding.

Am allochthon can be a rock mass formed somewhere other than its present location and was transported by fault movements, large-scale gravity sliding, or similar processes.