DATING METHODS IN ARCHAEOLOGY DATING METHODS IN ARCHAEOLOGY Archaeological investigations have no meaning unless the chronological sequence of the events are reconstructed faithfully. The real meaning of history is to trace the developments in various fields of the human past. Towards this end, while investigating the past cultures, archaeology depends on various dating methods. These dating methods can broadly be divided into two categories, i. These are mainly non-scientific dating methods. These methods were relied on especially prior to the introduction of scientific methods of dating. But, even when the scientific methods of absolute dating are available, this method of dating has not lost its importance, as many a time we have to depend solely on relative dating. Even when the absolute dates are available, we have to supplement the information with relative dating. The various methods of relative dating are; 1. Stratigraphical succession: 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. 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. Basing on this principle, the cultural assemblages found in different layers can be assigned a chronological personality. 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. This method, however, has some disadvantages. In practice it is found that the mounds are disturbed9+ by all sorts of pits and dumps. In such cases subjective element cannot be ruled out. But, for a single culture site the method is quite reliable. Synchronism: 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. For example, beads closely resembling those from the temple repositories at Cnoss and dating from C. C were found in a late context Period V at Harappa. 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. By noting the association of these beads it has been possible to trace a archaeological datum line across Indian sub-continent and Mesopotamia. Associations: 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. Once a type has been classified by the aid of its context further specimen of the same type, even when found in isolation, can be assigned their place in terms of dates. Association in simplicity can be illustrated by an example, at the port of Arikamedu near Pondicherry. 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. ASTRONOMICAL CHRONOLOGY: Sometimes dates are also obtained with the assistance of astronomy. Clay tablets found in West Asia contain inscriptional evidence with regard to the occurrence of a solar eclipse. Specialists in the field of astronomical research placed this solar eclipse as on 15 th June 763 B. The Almanac belonging to Maya culture of Central America helped in dating several important sites accurately on the basis of astronomy. 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. DIAGNOSTIC TRAILS AND DATING: 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. THICKNESS OF DEPOSIT AND DATING: 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. However this formula has not been accepted by many archaeologists. Further this formula has been disproved on many occasions. TYPOLOGY AND DATING: Pottery is probably the most abundantly available antique material in any archaeological site. The types and forms or shape of these pots and also the antiquities under go evolutionary changes in cource of time, and thus contribute towards our knowledge of the chronological asssignments. It is based on the simple fact that industrial and art forms and for that matter all objects are subject to evolutionary process. Typological evolution may take either the form of improvement or the form of devolution or degeneration. Working out these changes brought in during the evolutionary process helps us in fixing chronological slots for different shapes. Examples may be cited from Greek archaeology where even the shapes of the pots have been appropriately and approximately dated. Similarly the forms of the pots of the Maya culture and the shapes and decorations on the Chinese potteries have been so adequately dated that their relative dating value is immense. But in India though the variety of wares are satisfactorily dated the typological evolution is yet to be worked out. ARCHITECTURE AND DATING Houses, publica buildings and places of worship are also quite useful in providing relative dating. It is a common knowledge that the building and the building material of Harappan architecture are quite characteristic. Again the architectural feature of the building of th4e Sultanate period, Mughal period, Maratha period are quite distinct and have, therefore, accordingly been assigned different dates. Size of the bricks, shapes of the pillars, features of the capitals, pattersns of decorations and styles of paintings - all contribute towards relative datingin archaeological research. ABSOLUTE OR SCIENTIFIC DATING METHODS 1. RADIOCARBON OR C-14 DATING: This is one of the most important methods of dating the ancient objects which contain some carbon in them. This method was discovered by Prof. Libby in 1946, which won him Noble Prize in Chemistry. This method has achieved fame within a short time largely because it provides chronology for the prehistoric cultures, when we do not have written records. Scientific Explanation of this Therory : This method is based on the presence of radio-active carbon of atomic weight 14 in organic matter. Cosmic radiation produces in the upper atmosphere of the earth Neutron particles, some of which hit the atoms of ordinary Nitrogen. This is captured by the nucleus of the nitrogen atom, which gives off a proton and thus changing to Carbon-14. This Carbon-14 in turn is radio-active and by losing an electron reverts to nitrogen. This creation of new carbon atoms and then reverting to nitrogen has achieved a state of equilibrium in the long duration of the earths existence. C-14 along with the carbondioxide enter the living organisms in the process of photosynthesis, and all the radiocarbon atoms that disintegrate in living things are replaced by the C-14 entering the food chain. Thus the process of radio carbon present in the living organism is same as in the atmosphere. It is further assumed that all living animals derive body material from the plant kingdom, and also exhibit the same proportion of C-14 material. Therefore as soon as the organism dies no further radiocarbon is added. At that time the radioactive disintegration takes over in an uncompensated manner. The C-14 has a half-life of about 5730 years, i. In the disintegration process the Carbon-14 returns to nitrogen emitting a beta particle in the process. The quantity of the C-14 remaining is measured by counting the beta radiation emitted per minute per gram of material. Modern C-14 emits about 15 counts per minute per gram, whereas Carbon-14 which is 5700 years old, emits about 7. Specimens for C-14 Dating : 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 to C-14 dating. Quantity of Samples: Quantity of samples sent for radicarbon dating should be sufficient enough to give proper results. It has been found that a sample yielding five grams of pure carbon is generally sufficient. As quite a bit of sample is lost in the pre-pigmentation process one should try to collect as big sample as possible. Minimum Wood 10-30 3 Shell 50-100 5 Bone 100-500 200 Iron Cast iron 100-150 30 Iron Steel 300-500 150 Bones are generally affected by ground water carbonates and are therefore least reliable for dating. Charred bones are better preserved and are therefor
