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For example, beads closely resembling those from the temple repositories at Cnoss and dating from C.1600 B.
C were found in a late context (Period V) at Harappa. By noting the association of these beads it has been possible to trace a archaeological datum line across Indian sub-continent and Mesopotamia.
In such cases subjective element cannot be ruled out.
But, for a single culture site the method is quite reliable.
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.
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.Sir Flinders Petrie had worked out a formula for dating the finds on the basis of the thickness of the deposit.According to him a period of hundred years may be granted for the accumulation of a deposit of one and a half feet.Astronomical data have been applied in the study of geological ice ages by calculating the curves for major fluctuation of solar radiation.Consequently, the chronology worked out for the geological deposits helped in dating the prehistoric tools found in these deposits. There are certain antiquities and potteries which by themselves have acquired a dating value.Whenever and where ever such antiquities are found, associated finds are automatically dated.For example Mauryan terracottas, Roman amphorae, Harappan pottery, NBP , PGW,etc.Specimens of organic material which can yield good amount of carbon can be collected for C-14 dating.For example charcoal, wood, shell, paper, leaves, cloth, animal hair, bone, pollen, tooth, iron, prehistoric soot from the ceiling of the caves practically any material containing some carbon can be subjected Bones are generally affected by ground water carbonates and are therefore least reliable for dating.Antiquities and potteries of Roman origin were found in association with the finds of Indian origin.With the aid of these dated imports it was possible to date the associated Indian objects to the first two centuries A. Similarly NBP and PGW has helped in fixing the chronology of numerous sites. Sometimes dates are also obtained with the assistance of astronomy.