- Method of site survey, Scientific aids in exploration, Excavations: Horizontal, Vertical, etc., Stratigraphy: Relative and Absolute dating:
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The document discusses various methods for site surveys and scientific aids in archaeological exploration, detailing the objectives, methods, and tools used for locating and dating ancient sites. Key techniques include ethnographic studies, aerial photography, remote sensing, and different dating methods such as radiocarbon and thermoluminescence dating. The importance of local traditions, historical literature, and previous archaeological work in guiding explorations is emphasized.
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- Method of site survey, Scientific aids in exploration, Excavations: Horizontal, Vertical, etc., Stratigraphy: Relative and Absolute dating:
- 1. AVENUES OF DISCOVERIES METHOD OF SITE SURVEY SCIENTIFIC AIDS IN EXPLORATION EXCAVATIONS: HORIZONTAL, VERTICAL, ETC., STRATIGRAPHY: RELATIVE AND ABSOLUTE DATING: By Dr. ASHWANI ASTHANA
- 2. AVENUES OF DISCOVERIES 1. NATURE AND OBJECTIVES • Introduction: • Location of an ancient site or a buried monument or an artifact is one of the important first steps in archaeological investigation. • The discovery of site of Mari on the Euphrates was the result of a chance discovery by the local people. • Londoners discovered ancient Roman walls during the clearance done after the German raids in World War II. • Harappa (in Montgomery District of Punjab in 1921. ) and Raj-Ghat (Varanasi 1944) • An archaeologist has to take note of such discoveries and utilize the data in his field investigation, though he does not depend solely on them.
- 3. • Roll of Natural Agencies (flood and sea/river erosion) • The search for ancient sites and antiquarian remain • The process of locating, recording and study of archaeological sites on the basis of their surface features and without recourse to excavation is known in England as “Field archaeology”. Terms like “Site Survey” or “Reconnaissance” are used in the United States. • The term exploration is used in India to distinguish preliminary site survey form excavation. Crawford would call it “archaeology without digging”. • On the basis of surface exploration, many intersecting facts like the distribution pattern, interspacing of sites, factory sites and seasonal sites can also be identified. Introduction:
- 4. Objectives: 1. Survey of Pre-Historic Sites 2. Survey of Proto-Historic and Historical Sites 3. Survey for a specific problem 4. General Survey
- 5. •
- 6. METHOD OF SITE SURVEY • Map Reading: • Study of Physical Features – Hills – Passes – Lakes – Rivers – Rock, Minerals and Metals
- 7. Ethnographic Data • In undertaking exploration in pre-historic sites especially in areas were the hunter-gatherer and simple agricultural groups still exist, an ethnographic study of the local inhabitants may be necessary. • A study of their material equipment, social organization will be useful to known their settlement patterns and their traditions, for comparative study.
- 8. Historical Literature • Before exploring an area or an ancient city. The explorer would do well to acquaint himself as fully as possible with all the available historical literature about the site. • This data is not required for purely pre-historic exploration • The Buddhist literature is essential for undertaking exploration in the Buddhist sites.
- 9. • The location of the famous site of Troy was a matter of dispute until Schlieman identified it in the light of Homer’s lliad and Odyssey, local traditions and inscriptions and later confirmed by the excavations conducted there. • The foreign travelers or ancient geographers accounts help us to identify ancient towns. • The excavation done there has remarkably confirmed Megasthenes’ description of Pataliputra city.
- 10. • The accounts of the Chinese travelers Fahien (4th century A.D.) and Yuan Chuang (7th century A.D.) are of great use for archaeology of the Buddhist sites of India. • The royal edicts like those of Ashoka were often put up on the highways or junctions. • With there help we could locate the ancient trade routes of the Mauryan times. • Inscriptional data also helped in the identification of the Chola port-town of Kaveripumpattinam.
- 11. Previous Works • Archaeological work done in the area either in the form of the exploration of excavations. • A visit to the museums and examination of the antiquities found previously in the area would be of great help. • The explorer would do well to consult the old Annual Report of the Archaeological Survey of India and its successor Indian Archaeology – A Review • The publications by the state Government and the University departments of archaeology on the work done by them should also be consulted.
- 12. Local Tradition • Local traditions have their own value in reconstructing regional or local history. • They often preserve old memories of the long forgotten facts about cities or towns and even about some particulars landmarks within the town. • This memory may be preserved in the form of legends or folks songs, which would often be able to point out certain spots as the places where the ancient place or temple stood or as the place where a battle took place and the like.
- 13. • This would often the excavator to choose the spot of his excavation within a site. • It has been the experience of the author that the villagers would point to certain localities now under cultivation as the place where the old village stood..
- 14. SCIENTIFIC AIDS IN EXPLORATION • Apart from the physical methods of prospecting, some scientific aids like the magnetic and electricity resistivity methods are also found extremely useful. • They would register certain types of abnormal surface disturbances of anomalies indicating some disturbances or anomalies indicating some features below the earth, which cause them. • The presence of structures or metal objects below.
- 15. Magnetic Survey • The Proton-Magnetometer is a highly sensitive apparatus, which has been found useful in detecting buried iron kiln sites and certain kinds of soil. • The spots where the anomalies are registered can be taken up for excavations. • Disadvantage • Proton-magnetic survey of certain suspected areas covered with sand was done at Kaveripattinam and Madurai in South India
- 16. • It involves setting up of a line of electrodes a few inches into the ground at the intervals of 30 cms. • Anomalies between the electrodes can then be plotted. • A team of three people would normally suffice to cover several acres in a day.
- 17. Thermo- Remnant Magnetic Survey: • By this method, the existence of brunt clay artifacts, burnt brick structures and sites, which experienced extensive configuration, could be detected. • The objects cause magnetic disturbance, which are recorded.
- 18. Electricity Resistivity Survey: • The resistivity meter is based on the fact that the ground can conduct electricity. • Electrical conductivity of the soil depends on its nature. • The geologist used this method and civil Engineers to study the layer of the earth, but first applied to detect buried archaeological structures by R.J.C. Atkinson in 1946.
- 21. • The special instrument, the Megger Earth Tester, is used to record and plot and variations in resistivity in graph model. • If the soil is very wet or dry, the electrical resistance may be uniform throughout the strata and in such cases; the results of the Survey may not be satisfactory.
- 22. Probe Survey: • This is done with a simple apparatus of an iron bar with a tapered point and a T-handle and used as a probe across a suspected wall or pit at convenient intervals. • When the probe penetrates any stratum different in texture form top soil, this can both be felt as a difference in resistance and heard as a different sound.
- 23. Augur Survey: • Generally it is used by geologists. • Hand augurs are used to take out samples every 3 cms. • The strata accumulation over the bedrock and their content can be know. • Its use is rather limited in hard soil.
- 24. Drills: • In oil prospecting and geological survey, power driven augurs and drills are extensively used. • They can penetrate to great depths and reveal the nature of the strata below. • To probe the strata lying buried below flood deposits and sand accumulation.
- 25. • The Archaeological Survey of India used this in 1968 in and around Cranganore in Kerala • To find out if there were cultural strata below the huge sand accumulation deposited by the Periar River.
- 26. Exploration by Sound: • The soil or structure below, the sound from the natural or undisturbed soil would be different from that of the disturbed one or artificially accumulated one.
- 27. Geo-Chemical Method: • The soil of ancient settlements often contains high concentration of phosphates from organic refuse. • “In regions where the vegetations and terrain are helpful to air photography the method can be used with advantage to sample wide areas”
- 28. Aerial Survey and Photography: • As pointed out by Kathleen Kenyon, the value of air photography is of two folds. • The whole layout of the ancient cities, the criss-cross road and streets, the alignment of the houses, the fortifications, Stupas or Vihara complexes therein. • If it was a fortified city, the outline of the fortification or the defense wall surrounding the city can be identified as well as the entrance gateways and such other landmarks.
- 29. Shadow Marks:
- 32. Crop Marks: • Differences in vegetation and the consequent crop marks and colour contrasts are brought out clearly in photographs. • Aerial photography serve as good indicators of the buried buildings or ditches. • It was used for archaeological purposes as early as 1915 by Leon Rey in Macedonia and Lt. Col. G.A. Beazeley in Iraq in 1919.
- 33. • Father Poidebard made further technical improvements and surveyed the desert regions of Syria. • The method of horizontal lighting of the morning or evening exaggerates the undulating aided by the variations in the colour of the field. This method was perfected in 1930s. The buried runis of the frontier zone of the Roman Empire buried over a vast distance in Syrian desert could be plotted by air photographs. From 1939, stereoscopic examination of large areas was developed.
- 35. Photogrammetry: • The technique of transforming aerial photography into a scaled plan is an important and fruitful development that helps us to get a graphic and enlarged view of the site • “Aerial mapping can telescope year of work on foot into span of weeks”. • “the invention of air camera is as valuable to archaeology as that of the telescope to astronomy”.
- 36. Remote Sensing: • Remote sensing includes high and low level aerial photography and satellite imagery. Remote sensing is the science and technology of obtaining information or data about physical objects and the environments through the process of recording, measuring and interpreting photographic images and patterns of electronic radiant energy.
- 40. Radar: • This basic idea of the recent and promising techniques of ground penetrating radar is that, the materials with different electrical properties leads to different velocities of the radar beam. This technique directs a short burst of energy towards the object. A part of this energy is reflected back to the surface, where it is monitored and recorded as an ‘echo’.
- 41. Radar in use
- 42. • The calculation is done after measuring the time elapsed between sending and receiving pulse, i.e. the delay time. • Radar sees rocks, pavements, and foundations etc, soils with different material content and also metals. • It penetrates frozen ground without problems. • The equipment can be carried and surveyed out quickly. • The output is a depth profile, it very much resembles as seismograph, which is also based on delay times.
- 43. Under Water Survey: • To investigate the archaeological features buried in mud and of a few maters below the lakes surface, the high precision seismic reflection method has been developed. • Acoustic waves with properties between sonar (frequency 30 to 50 KHz corresponding to wavelength of 3 to 5 cm) and those used for oil prospect ion are selected for archaeological investigation. For this acoustic at a frequency of 5 KHz, corresponding to a wavelength of 30 cm. in water, they are suited both for partly penetrating into the seabed and for detecting objects.
- 44. • The waves are emitted in pulses by special land speakers (pingers) activated by a short discharge from the pinger, which is towed along or a aside a boat, the sound wave travels downwards, where part of its energy is reflected and part penetrates into the mud. • Assuming an object of clearly differing acoustic impedance is buried there, it will send back most of the remaining sound energy. A special underwater microphone (hydrophone) picks up the returning signals near the surface.
- 45. • The signals intensity and the time elapsed between the pulse leaving the pinger and the reflecting signals arriving at the hydrophone is measured for the archaeological reconnaissance.
- 51. Excavations: Horizontal, Vertical, etc., • Introduction: • Trial trenching or Sondages. • Regular trenching System or vertical excavation • Grid System or Horizontal Excavation • Open stripping • Quadrant Method
- 56. Huts Impression
- 62. STRATIGRAPHY: • Definition: • It is a branch of geology dealing with the classification, correlation and interpretation of stratified rocks. • Example: • Introduction: • This method was first used by William Smith also called “Strata Smith” in 1816 for geological stratifications with the help of fossils. • This was adopted for archaeological investigation also later on.
- 70. Disturbance to the Strata: • Pits: • Post-Hole: • Ghost wall or Robbers trench:
- 73. RELATIVE AND ABSOLUTE DATING: • Relative Dating: • Absolute Dating: • 1 Glacial Varve Chronology • 2 Radio Carbon Dating (Carbon- 14) • 3 Thermo luminescence Dating (T l. Dating) • 4 Archaeomagnetism • 5 Potassium-argon Dating • 6 Fluorine, Uranium And Nitrogen Dating Of Bones • 7 Fluorine Dating • 8 Uranium Dating
- 74. • 9 Nitrogen Or Collagen Dating • 10 Dendrochronology • Glacial Varve Chronology: • This Geological method of dating was evolved for the first time by Sir. Gerard De Geer. • Varve dating depends on the waters that flow down from the glaciated areas. • It deposits the rough material in the lakes, but later, in the autumn, drops only the finest silt until all deposition stops in winter and consequently the deposit is thin. • Each year a layer or varve is added.
- 76. • These are varied and laminated clays. These annual deposits or cycle of sedimentation are counted in a series of sections and a time scale is evolved for a region. • With the help of additional evidence from the study of moraines and other related features, varves from different regions are correlated for building up a chronology covering larger regions. • By this study of varved clays, De Geer arrived at a chronology for the end of the last Ice Age in Northern Europe as about 12,000 years ago. • In the lake deposits of Scandinavia and North America it has been possible to count back to the period immediately after the retreat of the glaciers.
- 77. RADIO CARBON DATING (CARBON- 14): • Willard F. Libby devised this method of C-14 dating in U.S.A. in 1948. • Carbon-14, which is radioactive heavy isotope of Carbon is present in the earth’s upper atmosphere. • The C-14, atoms combines with oxygen to form carbon dioxide and become mixed in the earth’s atmosphere and enter into all living organisms like plants and animals. • All living organisms absorb C-14 (the radio active carbon) and C-12 (ordinary carbon) in a constant proportion till the moment of death, after which the radiocarbon already absorbed, starts decaying at a rate determined only by the half-life of the isotope.
- 78. PRL-Radiocarbon Laboratory, showing the glass lines for producing CH 4 gas and C2 H6 liquid for Carbon-14 activity measurement.
- 79. • The Carbon-14 is reduced to half in 5568 + 30 years. It is possible to determine the age of an organic sample by ascertaining the specific Carbon 14 activity in the sample. • The amount of C-14, remaining in the dead organic matter as indicated by its radioactivity is proportional to the time elapsed since death. • The dating of an ancient organic sample results from the amount of disintegration that has occurred since death. • This dating is possible on the basis of the present day C-14 content of living matter and the known half-life of C-14. • “The laboratory procedure consists of burning the sample, reducing into pure carbon and measuring the radioactivity in a specially constructed radiation counter”.
- 82. • The material that are found suitable for this examination are: wood, charcoal, charred bone, textile piece, leather, hair, skin, antler, tusk, shell, dung, charred grains etc. • Sampling:
- 83. Sampling
- 84. • Documentation: • There are a number of centers in USA and U.K. having laboratory facilities for Carbon- 14, analysis. They are extensively used by the archaeologist. In India too, we have a few institutions undertaking these analysis, such as the Tata Institute of Fundamental Research, Bombay and the Birbal Sahni Institute of Palaeo-Botany, Lucknow and the Physical Science Laboratory, Ahmadabad.
- 85. Thermoluminescence Dating (Tl. Dating): • This method is helpful in dating the ancient clay objects like the pottery, bricks and the ceramics. • All clays contain crystalline constituents and also traces of radioactive materials the decay of which leads to the accumulation of energy at a constant rate within the materials. • This accumulated energy is released as a flash of light when the clay material is headed to a very high temperature.
- 86. • This phenomenon is called thermo-luminescence. The amount of light thus emitted is measured by sensitive photoelectric equipment when pottery is made and fired; the accumulated radiation in the clay is released as thermo-luminescence. • This method involves the measurements of the decay of the radioactive particles in baked clay by calculating the amount of damage to the crystal structure of the material. • Therefore, if one takes a sample of pottery and measures the amount of thermo-luminescence light emitted on heating, it should be possible to relate this to the time that has elapsed since the pottery was originally fired.
- 87. • There are certain practical difficulties in applying this method widely but attempts are being made to improve it for wider application. • It is still in the experimental stage. “Once the method is perfected it will give a valuable check on radio carbon dating for all periods of the past when pottery was in use”.
- 88. Archaeomagnetism: • This technique has been developed for dating backed structures such as kiln, hearths and burnt clay walls, if they have remained in situ. • The method is based on the behavior of iron particles in the clay when it is in plastic state prior to its hardening, during the process of firing or application of heat. • Any objects in which there are bits of magnetic iron is given magnetic power by earth’s magnetic field.
- 89. • When a clay object is heated above a certain temperature the magnetism is lost; but it regains when it is cooled. • While regaining it thus, the orientation and strength of the regained magnetism are determined by the earth’s magnetic field at the moment of their last cooling, and hence it is called archaeo or remnant magnetism. • “Let us take an example of an earthen jar that was hardened near London in a very hot stove and then was allowed to cool, centuries later, a scientist finds that jar and wants to date it. • If he can measure the direction of the remnant magnetic line in the pot and if he knows what year the magnetic lines of the earth pointed in this true direction, we can date the year when the jar was heated in the stove. We will then know how old the jar is
- 91. • The instrument for measuring the direction and strength of the remnant magnetism was designed by Profs. Cook and Balsha. It is called magnetometer. • With its help; the scientists search the true magnetic north record and discover in what century and almost in which year true magnetic north was pointing exactly in that direction. • Then they can arrive at the near date for the object. • The dates obtained by archaeomagnetic methods are very encouraging and agree with the known dates of the objects tested. This was tested on the objects from Roman sites in England and the dates obtained tally well with known dates.
- 92. Potassium-argon Dating: • This method resembles closely the Carbon-14, method. The earth’s crust contains potassium of which Isotope K 40 decays to Argon 40 at a known rate, its half-life being 1.300 million years. • The date of a sample is determined by measuring i.e., Potassium-40, and the Argon-40 present. Volcanic eruption serves as good samples for this method. • This method was applied to date samples of Early Pleistocene period in the Olduvai Gorge. This is useful for dating materials 23 to 26 million years old.
- 93. Fluorine, Uranium And Nitrogen Dating Of Bones: • The basis for this analysis in the words of Kenneth Oalley is “The Fluorine and Uranium content of the mineral matter of buried bones and teeth increases with the passage of time where as the organic (protein ) content measured as nitrogen decreases. • Thus, the comparison of the fluorine Uranium, and / or nitrogen content of bone or tooth of questionable age with the range of these elements in other bones or teeth of known age and in similar matrix at the same site, sometimes indicates clearly the relative antiquity of the specimen in question
- 94. Fluorine Dating: • The buried bones or teeth gradually absorb the fluorine that is present in the ground water. It replaces the hydroxyl content. • The greater the fluorine content of a bone, the greater is its antiquity, But the rate at which this absorption happens, depends on the fluorine in circulation, climate and similar factors and therefore, this method may not be useful in comparing the bones of different areas, or hydrological conditions.
- 95. • However, in a given area, the fluorine test will gives us the relative age of bones of different geological ages. • The test in combination with uranium content test and radiocarbon test has proved of great value notably in detecting the fake claim of the Piltdown man and also confirming the Acheulian age of the Swanscombe skull.
- 96. Uranium Dating: • Like fluorine, uranium is also present in the ground water and is absorbed by the mineral matter of bones and teeth. • This uranium content of the bones can be measured and the relative age of the bones determined. • The uranium content of the bones can be measured and the relative age of the bones is determined. • The uranium content is measured by the method known as radio-metric assay, which takes the form of exposing a sample to a Geiger counter and counting the radiations per minute.
- 97. • This test helps us to distinguish between fossil bones and the recently introduced bones in old gravels or sands.
- 98. Nitrogen Or Collagen Dating: • Bones basically consists of calcium phosphate, fat and bones protein or collagen. On death, the fats gradually disappear. • The collagen survives much longer though it decays at a uniform rate. This can be measured by nitrogen assay. • The rate of decay depends on physical, chemical and other factors and therefore, cannot be universal, but bones of different dates in a single deposit can be distinguished on the basis of nitrogen content.
- 99. • Nitrogen analysis is particularly useful for relative dating of bones of several ages (preserved in identical conditions) in cases where they are too recent to be within the range of fluorine or uranium methods. • It is very valuable as a means of cross- checking the results of uranium and fluorine analysis of the bones believed to be of the Pleistocene age on open sites.
- 100. DENDROCHRONOLOGY: • Sir. A.E. Douglass developed tree-ring counting or Dendrochronology in 1922. • All trees from ring each year but they vary in thickness according to the climatic conditions. • This would permit comparison and correlation of ring patterns found on cut surfaces of recent and ancient trees. • Douglas showed how the variations could be used to date archaeological material. He showed how in one restricted area in USA.
- 101. • Having the same climatic condition, he could build up a scale of ring pattern of timbers from the present back to pre-Colombian period. • Growth of rings can be clearly demarcated in trees growing in areas, which have regular seasonal climate changes. • Wet springs and summers produce thick rings whereas dry winters produce thinner rings. • Tree ring sequence show a rhythmic variation and such cycle are found to recur every eleven years coinciding with the sun spot cycle. • While useful results have been obtained in America, it has difficulties in Europe where seasonal variations are not so clear.
- 105. • Another difficulty is in some trees the same rings vary in thickness in different parts of their circumference. But despite these difficulties, this method has been extensively employed in USA, England and Scandinavia. • Attempts have been made to correlate the tree rings over long distance to links the climatic sequence of America, Europe and other continents. • The tree rings undoubtedly serve as indicators of climatic oscillations. The method has been successfully adopted for the dating of the prehistoric settlements in southwest USA.
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