Abstract: Trace fossils may be classified in a variety of ways, the more important of which are describtive （nongenetic）, preservational （toponomic） and behavioral （ethological）. Trace fossils are studied mainly by sedimentologists, palaeontologists and stratigrapher;each of these disciplines is concerned only with certain facets of ichnology, yet the three overlap in the areas of palaeoecology and environmental reconstruction. The most concernd and successful applications of ichnology to geological surveys are facies analyses and recongnization of depositional environments. The trace fossil assemblages or ichnofacies constitute the basis for the relative scale of paleobathymetry. Traces can make a major contribution toward interpretating conditions of sedimentation, especielly the relative rate of deposition. The study of Tace fossils and bioturbation can provide important Maferial lues for the interpretation of original substrate conditions