Relative dating in archaeology

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.

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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. 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 , 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 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.

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 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 has a half-life of about years, i. In the disintegration process the Carbon returns to nitrogen emitting a beta particle in the process. The quantity of the C remaining is measured by counting the beta radiation emitted per minute per gram of material.

Modern C emits about 15 counts per minute per gram, whereas Carbon which is years old, emits about 7. Specimens for C Dating: Specimens of organic material which can yield good amount of carbon can be collected for C dating.

Quantity of samples sent for radicarbon dating should be sufficient enough to give proper results. As quite a bit of sample is lost in the pre-pigmentation process one should try to collect as big sample as possible. Bones are generally affected by ground water carbonates and are therefore least reliable for dating. Charred bones are better preserved and are therefore relatively more reliable.

Charcoal is best material specially if derived from short live plants. How to collect samples: While collecting samples for radio carbon dating we should take utmost care, and should observe the following principles and methods. Sample should be collected from and undisturbed layer. Deposits bearing, pit activities and overlap of layers are not good for sampling.

Dating Techniques In Archaeology

The excavator himself should collect the sample from an undisturbed area of the site which has a fair soil cover and is free of lay water associated structures like ring wells and soakage pits. Samples which are in contact or near the roots of any plants or trees should not be collected because these roots may implant fresh carbon into the specimens. Handling with bare hands may add oil, grease, etc to the sample. Therefore, it is better to collect samples with clean and dry stainless steel sclapels or squeezers. It may also be collected with the help of glass. Stainless steel, glass, polythene and aluminium are free from carbonatious organic material.

Therefore sampling should be done with such material only. Samples should be sundried before pacing in aluminium thin foils and placed in a glass jar or secured safely in thick polythene covers. Before pacing the soil should be removed while it is wet at the site. Method of Sample Recording: Before removing the sample from the site we should note down the data or the environment of the sample.

We have to fill the data sheets, which should be done at the time of sampling and should be submitted along with the sample to the dating laboratory. These sheets require data on environment and stratigraphy of the sample, and archaeological estimates of its dating. This data help in obtaining and objective interpretation of dates. Limitation and Errors of C Dating: There are a number of technical difficulties inherent in this method of dating.

Relative Dating: Applications and Important Techniques Explained

The first difficulty is that the quantity required for a single determination is comparatively large. It will be difficult to obtain sufficient quantities of samples, especially in the case of valuable museum specimens. The second difficulty is that the radio active decay does not take place at a uniform rate but is a random process, and is therefore, governed by the laws of statistical probability. Another difficulty that has to be taken into serious consideration is the possibility of uneven distribution of radio carbon in organic matter. If the specimen is analyzed after having been exposed to contamination by carbon compounds of an age younger than its own, radio carbon age is liable to be reduced.

The best results can be obtained from specimens, which were preserved under very dry conditions, or even enclosed in rock tombs of the like.

How Carbon Dating Works

Very dangerous contamination is done, very often, by the growth of fungus and bacteria on the surface of the specimen which even when removed from the specimen may falsify its actual age. Though there are some drawbacks and technical difficulties, the radiocarbon method is a reliable, efficient and most useful method of dating the archaeological specimens. We are helpless in the case of contamination done by the natural agencies in the past, but we can overcome most of the difficulties by paying sufficient care and attention while collecting the samples.

It is the duty of an archaeologist to study with care the condition of preservation of specimens submitted for analysis and, in fact, to submit only specimens that can be regarded as fool-proof as is possible in the circumstances. Dendrochronology is a method that uses tree-ring analysis to establish chronology. A major application of dendrochronology in archaeology, as a tool for establishing dates from the samples of wood and articles made out of wood is not only in working out primary chronologies but also in cross checking the already known dates by other methods.

Often, the tree-ring analysis from a site can give strong clues about the length of occupation, certain periods of building or repair activities at the site. Another application of tree-ring analysis is the inference of past environmental conditions, which is extremely useful to the archaeologists. The modern science of dendrochronology was pioneered by A. Tree ring analysis is based on the phenomenon of formation of annual growth rings in many trees, such as conifers. These rings are shown by the trees growing in regions with regular seasonal changes of climate.

As a rule trees produce one ring every year. When growing season rainy season begins, sets of large, thinly-walled cells are added to the wood. This process repeats in the following years also. The formation of rings is affected by drought and prosperous seasons. In the years with unfavourable weather the growth rings will be unusually narrow. On the other hand, during years with exceptionally large amounts of rain the tree will form much wider growth rings. Most of the trees in a give area show the same variability in the width of the growth rings because of the conditions they all endured.

Thus there is co-relation between the rings of one tree to that of another. Further, one can correlate with one another growth rings of different trees of same region, and by counting backwards co-relating the inner rings of younger trees with the outer rings of older trees we can reconstruct a sequence of dates. By comparing a sample with these calendars or charts we can estimate the age of that sample.

Thus it is possible to know the age of the wood used for making furniture or in the construction work. The main disadvantage with the system is that, we require a sample showing at least 20 growth rings to make an objective estimation of its age. Hence smaller samples cannot be dated. This method can date the sample upto the time of cutting the tree, but not the date when it was actually brought into use. This method is based on the fact that the magnetic field of the earth is changing constantly in direction and proporationate intensity, and that these changes lead to measurable records. The magnetism present in the clay is nullified once the pottery, bricks or klins are heated above degree centigrade.

This implanted magnetism can be measured and the date of its firing estimated. The dating of ancient pottery by Thermoluminiscence measurements was suggested by Farrington Daniels of the University of Wisconsin in America Thermoluminescence is the release in the form of light of stored energy from a substance when it is heated. All ceramic material contain certain amounts of radioactive impurities uranium, thorium, potassium.

When the ceramic is heated the radioactive energy present in the clay till then is lost, and fresh energy acquired gradually depending on the time of its existence. Relative Dating In Archaeology Relative dating in archaeology presumes the age of an artefact in relation and by comparison, to other objects found in its vicinity. Limits to relative dating are that it cannot provide an accurate year or a specific date of use. The style of the artefact and its archaeology location stratigraphically are required to arrive at a relative date.

For example, if an artefact, say an oil lamp, is found co-located on the same floor of a governor's dwelling, and that floor can be dated in archaeology terms by reason of the patterns employed in the mosaic, then it is assumed that in relation to the floor that the lamp is of the same age. Stratigraphy As A Dating Technique The underlying principle of stratigraphic analysis in archaeology is that of superposition. This term means that older artefacts are usually found below younger items. When an archaeological site is excavated the sides of the unexcavated baulk reveals layering of subsequent settlements and activity.

Stratigraphic excavation is the recording and study of these different strata as they are removed from the area. Style Analysis As An Archaeology Dating Technique The shape and style of an artefact changes through time although its function may remain the same. The changing styles of pottery, glass, stoneware, and metal objects provide archaeology analysts with known progressive sequences.

Once an artefact is compared to its known development date then whenever that item reappears in the archaeological record, of that or any other site, it can quickly be dated.

Relative Dating: Applications and Important Techniques Explained

The Weakness of Relative Dating The potential flaws in relative dating in archaeology are obvious. Simply assuming that an artefact is older because it was found at a lower depth in the record is only subjective science. There are many instances of deep holes being dug for rubbish pits or to locate well water that protrude into the record of older strata injecting more modern material as they are filled in over time.

Landslides and slips can completely change the topography of an entire archaeology site burying what was once on top by that which is much older, hence reversing the strata layers. Absolute Dating As An Archaeology Dating Technique A more precise and accurate archaeology dating system is known as absolute dating and can in most circumstances provide a calendar year to the object. Since there has been a transformation in the dating techniques of archaeologists.

Absolute dating is highly dependant on laboratory analysis.


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There are a number of techniques that have come to archaeology through the nuclear research efforts during WW2.