Originating in a place other than where it is found. (adjective)
Buried or found in a place remote from the site of formation. (adjective)
Examples of word allochthonous
More generally, given that the magnitude and recurrence interval of water levels produced by ice jams often exceed those of open-water conditions, breakup is probably the main supplier of allochthonous organic material in cold-regions rivers .
The two methodologies give opposite results when accounting for the input of allochthonous (produced outside) organic matter to a particular ecosystem: CO2 flux measurement gives negative NEP due to increased CO2 emission from soil to atmosphere, while weighing gives a higher accumulation of organic carbon (C) in the soil.