allochthon

[ uh-lok-thuh n, -thon ]
/ əˈlɒk θən, -θɒn /

noun Geology.

a geological formation not formed in the region where found and moved to its present location by tectonic forces. Compare autochthon(def 3).

Origin of allochthon

First recorded in 1940–45; back formation from allochthonous