Differences between autochthonous and allochthonous microorganisms
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The three terms refer to the origin of a sediment:
autochtonous refers to sediments that are native to its location (e.g. carbonat precipitation in a lacustrine facies),allochtonous refers to sediments originating from a place other than where it was found (e.g. glacial dropstones in marine sediments), andparaautochtonous refers to sediments of intermediate/mixed characteristics.
As such, these are very general terms and, as a consequence, there are no a priori characteristics which can be applied universally. In the field, you will have to analyze the facies under consideration and find out what specific lithological properties you would expect and what the depositional regime was. If you find clear deviations from these expectations, clear indications of (long distance) transport (e.g. well-rounded pebbles), biotics of different origin, etc., these may be good hints for allochtonous formation.
autochtonous refers to sediments that are native to its location (e.g. carbonat precipitation in a lacustrine facies),allochtonous refers to sediments originating from a place other than where it was found (e.g. glacial dropstones in marine sediments), andparaautochtonous refers to sediments of intermediate/mixed characteristics.
As such, these are very general terms and, as a consequence, there are no a priori characteristics which can be applied universally. In the field, you will have to analyze the facies under consideration and find out what specific lithological properties you would expect and what the depositional regime was. If you find clear deviations from these expectations, clear indications of (long distance) transport (e.g. well-rounded pebbles), biotics of different origin, etc., these may be good hints for allochtonous formation.
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