Quite convincing dates are sometimes arrived at by importing parallels from other contemporaneous cultures.This parallelism is formed due to trade relations, particularly wehen trade followed in both directions.Basing on this principle, the cultural assemblages found in different layers can be assigned a chronological personality. In practice it is found that the mounds are disturbed9+ by all sorts of pits and dumps.For example, if the cultural contents of the lower deposit are Mauryan in character, appropriately this deposit may be assigned a date between 400-200 B. Similarly, if the cultural equipment of the upper deposit are of the Sunga period, this deposit has to placed between 200-73 B. Quite often, the archaeologist decided the change of stratum on the basis of the feed of the deposit.This closely agrees with the fact that the seals from Indus Valley style from Ur, Kish and Tell Asmar and other sites fall within the range of 2500-1500 B. When a group or type of objects are found together under circumstances suggesting contemporanity they are said to be associated.
The deposit thus occurring forms layers depending on the nature of the material brought in by the people inhabiting the area.
According to this method, the upper deposits are younger and the lower deposits are older.