Normal size grading is the only reliable criterionto interpret a deep-water sand as a turbid&. Thefollowing test can be administered to measure thevalidity of an interpretation of a deep-water sand as aturbidite. If an interpretation is based on observations, such as the presence of sharp basal contact,normal size grading, and gradational upper contact,then the sand may be reasonably interpreted as aturbidite (Fig. 3A,B). But if a turbidite interpretation is based on excuses, such as the normal grading is absent because of uniform grain size, or the normal grading is absent because of short distance of tranport, or the normal grading is absent because of sediment deformation, or the normal grading is absent because of bioturbation, or the gradational upper contact is absent because of possible erosion and so on, then it is not possible to demonstrate that it is a turbidite.