Relative dating methods in archaeology
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.
Even when the absolute dates are available, we have to supplement the information with relative dating.
The various methods of relative dating are; This method depends on the common observation that the height of the habitational area increases as the people continue to live at the same place.
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.
It is nearly always association with other phenomena that gives a first clue as to the use, the age and chronological attribution of a potential datum, but age at least may sometimes be inferred from position in a geological deposit or a layer of peat.
Association in simplicity can be illustrated by an example, at the port of Arikamedu near Pondicherry.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.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.
Charred bones are better preserved and are therefore relatively more reliable.