text: Most trace fossils are known from marine deposits. Essentially, there are two types of traces, either exogenic ones, which are made on the surface of the sediment (such as tracks) or endogenic ones, which are made within the layers of sediment (such as burrows).
  Surface trails on sediment in shallow marine environments stand less chance of fossilization because they are subjected to wave and current action. Conditions in quiet, deep-water environments tend to be more favorable for preserving fine trace structures.
  Most trace fossils are usually readily identified by reference to similar phenomena in modern environments. However, the structures made by organisms in recent sediment have only been studied in a limited range of environments, mostly in coastal areas, including tidal flats.