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Absolute Dating Methods in Archaeology.pptx
- 1. ABSOLUTE DATING METHODS IN ARCHAEOLOGY Unraveling the Timeline of Human History BY Dr. Rajiv Kumar Jaiswal Assistant Professor Dept. of AIHC & Archaeology Vasanta College for Women KFI, Rajghat Fort BHU, Varanasi
- 2. INTRODUCTION TO DATING METHODS The study of the past is to understand the human behavioural activities and cultural progress in a sequential order based on tangible and intangible evidences in a given socio-economic-cultural context. The Archaeological data has to be placed in a chronological order to understand this sequential cultural process. For this, various dating methods are being used in the archaeological investigations.
- 3. IMPORTANCE OF DATING METHODS IN ARCHAEOLOGY Dating in archaeology is crucial for several reasons: • Chronology Establishment: Dating allows archaeologists to establish the chronological order of artifacts, sites, and cultural phenomena. This chronological framework is essential for understanding the sequence of events in human history and the development of cultures. • Interpretation of Cultural Change: By dating artifacts and sites, archaeologists can track changes in material culture over time. This helps in interpreting shifts in technology, social organization, economy, and ideology, providing insights into how societies evolve and interact.
- 4. CONT…. • Contextual Understanding: Dating helps archaeologists place artifacts and sites within their historical and cultural context. • Cross-Cultural Comparisons: Dating methods enable archaeologists to compare the development of different cultures and regions. By establishing timelines, researchers can identify similarities, differences, and connections between various societies
- 5. DATING TECHNIQUES Dating techniques in archaeology are diverse, ranging from relative methods that provide a sequence of events without precise dates to absolute methods that assign specific chronological ages to artifacts and sites. Here's an introduction to some of the key dating techniques: 1. Relative Dating Methods 2. Absolute Dating Methods
- 6. DATING TECHNIQUES Relative Dating Techniques I. Stratigraphy II. Typology III. Pollen Analysis IV. Geo-chronology V. Fluorine Test VI. Nitrogen Test VII. Seriation VIII.Varve Absolute Dating Techniques I. Radio-carbon (C-14) II. Thermo-luminescence (TL) III. Potassium-Argon (K-Ar) IV. Dendro-chronology (Tree-ring) V. Obsidian Hydration VI. Fission-track VII. Electron spin resonance (ESR) VIII.Uranuim series
- 9. Absolute Dating Techniques I. Radio-carbon (C-14) II. Thermo-luminescence (TL) III.Potassium-Argon (K-Ar) IV.Dendro-chronology (Tree-ring) V. Obsidian Hydration VI.Fission-track VII.Electron Spin Resonance (ESR) VIII.Uranium series Absolute dating techniques fall under major four processes, namely radioactive processes, chemical processes, geological processes and biological processes. 1. Radiocarbon, potassium-argon, uranium-lead, thorium-lead, fission track, TL, OSL and ESR fall under radioactive processes. 2. Amino acid and obsidian hydration come under chemical processes. 3. Archaeo-magnetism come under geological processes. 4. Dendrochronology come under biological processes.
- 10. INTRODUCTION TO RADIOCARBON DATING The radiocarbon dating has changed the face of the archaeological research. It has made a revolutionary impact in the fields of archaeology and Quaternary science. Willard F. Libby developed this method in 1948 as spin-off from atomic research during second world war. Since then, it remains the most widely used dating techniques in modern archaeology. Half-life of C-14 is 5730±40. 10 Rajiv Kumar Jaiswal
- 11. FORMATION OF CARBON-14 Carbon-14 is a rare, radioactive isotope of carbon that forms in the upper atmosphere when cosmic rays collide with nitrogen atoms, producing carbon-14 atoms. These carbon-14 atoms then combine with oxygen to form carbon dioxide (CO2). Carbon-14 is incorporated into the cells of all living organisms through processes like photosynthesis (in plants) or consumption of plants and other animals (in animals). As long as an organism is alive and continues to consume food and exchange gases with the atmosphere, the ratio of carbon-14 to stable carbon isotopes (carbon- 12 and carbon-13) in its tissues remains relatively constant. Rajiv Kumar Jaiswal 11
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- 13. RECOMMENDED MINIMUM AMOUNT OF SAMPLE Rajiv Kumar Jaiswal 13
- 15. APPLICATIONS OF RADIOCARBON DATING IN ARCHAEOLOGY Rajiv Kumar Jaiswal 15 Radiocarbon dating has numerous applications in archaeology, offering invaluable insights into the timing and sequence of events in human history. Some of the key applications include: • Dating Organic Artifacts • Establishing Chronologies • Determining Site Occupation Periods • Dating Human Remains • Studying Cultural Evolution • Reconstructing Paleo-environments • Refining Historical Chronologies
- 16. ACCELERATOR MASS SPECTROMETRY (AMS) • Accelerator Mass Spectrometry (AMS) is a technique used for measuring the concentration of rare isotopes that cannot be detected with conventional spectrometers. • AMS is a highly sensitive method of counting atoms. It has the capacity to separate and measure rare isotopes from an abundant neighbouring mass. In the sense, it separate and measure the C-14 from C-12.
- 17. CONTRIBUTION OF C-14 IN INDIAN ARCHAEOLOGY Rajiv Kumar Jaiswal 17 Radiocarbon dating has been widely applied to Indian archaeological sites across various periods and regions, contributing to our understanding of India's rich cultural history. Several prominent Indian archaeological sites have been dated using radiocarbon dating methods, including sites associated with the Prehistoric sites like Chopani mando, Jhunsi, Koldihwa, Lahuradewa, Indus-Saraswati Civilization (such as Dholavira, Lothal, Rakhigarhi and Kalibangan), Early historic sites (such as Rajghat, Sarnath, Sanchi and Aktha), Megalithic sites, Rock art sites, Iron age sites (such as Malhar, Raja- Nal-ka Tila, Dadupur) and many others spanning different periods and cultural contexts.
- 18. C-14 labs in India Birbal Sahani Institute of Palaeobotany (BSIP) at Lucknow in Uttar Pradesh Physical Research Laboratory (PRL) at Ahmedabad, In Gujrat Institute of Physics at Bhubanehswar in Orissa National Geophysical Research Institute (NGRI) at Hyderabad in Telangana Inter University Accelerator Centre (IUAC) in New Delhi. Rajiv Kumar Jaiswal 18
- 19. THERMO-LUMINESCENCE DATING • Thermo-luminescence dating is a method used to determine the age of archaeological materials, primarily pottery or burnt flint, by measuring the amount of accumulated radiation-induced electrons trapped in the crystal lattice of minerals, such as quartz or feldspar, during their exposure to natural radiation in the environment. • How TL dating works: Radiation Exposure Heating Event Measurement of Light Emission Age Calculation
- 21. CONT…. • TL dating is particularly useful for dating pottery, ceramic objects, and burnt flint found at archaeological sites where organic materials for radiocarbon dating are not available or are not well-preserved. It provides valuable chronological information about human occupations, technological developments, and environmental changes in the past. • When the light (optic) is used instead of heat (thermo) to released the accumulated electrons, then it is called Optically Stimulated Luminescence (OSL).
- 22. POTASSIUM-ARGON (K-AR) DATING • Potassium-Argon (K-Ar) dating is a geochronological method used to determine the age of rocks and minerals based on the decay of radioactive potassium-40 (K-40) to argon-40 (Ar-40) within the mineral's crystal lattice. This method is particularly useful for dating volcanic rocks and minerals, as they often contain potassium-bearing minerals, such as micas, feldspars, and volcanic glass, suitable for K-Ar dating. • potassium-argon dating is a powerful geochronological tool that has significantly contributed to our understanding of Earth's history, the timing of geological events, and the processes of rock formation and alteration.
- 24. DENDRO-CHRONOLOGY • Dendrochronology is a dating method that uses the analysis of tree rings to determine the age of wooden objects, archaeological artifacts, and environmental changes over time. Here's how dendrochronology works: • Formation of Tree Rings: Each year, trees in temperate and boreal regions produce a new layer of growth, or tree ring. The width, density, and other characteristics of these rings are influenced by various factors, including climate, soil conditions, and tree physiology. • Pattern of Tree Rings: By analyzing the pattern of rings in a tree's growth, dendr- ochronologists can identify sequences of wide and narrow rings unique to each tree. • Dating Wooden Objects: Dendrochronology can be used to date wooden objects, such as archaeological artifacts, buildings, or artworks, by comparing their ring patterns to master chronologies. • Climate and Environmental Reconstruction: Dendrochronology provides valuable information about past climate and environmental conditions. By analyzing tree ring widths, isotopic composition, and other parameters, researchers can reconstruct past climate variability, including temperature, precipitation, and drought events.
- 25. CONT…. • In summary, dendrochronology is a powerful dating method that relies on the analysis of tree rings to establish precise chronologies and reconstruct environmental histories. Its ability to provide accurate dates and detailed environmental information makes it an invaluable tool for understanding past human societies and natural ecosystems.
- 27. OBSIDIAN HYDRATION • Obsidian hydration dating is a dating technique used to estimate the age of obsidian artifacts based on the thickness of the hydration rind that forms on their surface over time. Obsidian is a natural volcanic glass that was widely used by past societies for making tools, weapons, and ornaments due to its sharp edges and ease of shaping. • Hydration Process: When obsidian is exposed to air, water molecules gradually diffuse into its surface through a process known as hydration. • Thickness of Hydration Rind: The rate of hydration depends on factors such as temperature, humidity, and the chemical composition of the obsidian.
- 29. FISSION-TRACK DATING • The natural splitting (fission) of uranium-238 (U-238) atoms present in obsidian and other volcanic minerals leaves traces of called fission tracks. These fission tracks are erased once the mineral is heated above a critical temperature. • During volcanic eruption, all fission tracks present in the minerals are removed. This sets the clock to zero. However, the fission tracks again started appearing once the material cooled down. • The density of uranium-238 fission tracks is proportional to the time elapsed since the sample was last heated. The date is determined by calculating the presence of the fission tracks.
- 30. ELECTRON SPIN RESONANCE (ESR) • Electron spin resonance (ESR) dating is a geochronological method used to determine the age of materials containing unpaired electrons, such as tooth enamel, quartz, and fossilized shells, by measuring the accumulation of trapped electrons over time due to exposure to natural radiation. Here's how ESR dating works: • Trapping of Electrons: When minerals or materials containing unpaired electrons are exposed to natural radiation in the environment, electrons become trapped in defects or imperfections within the crystal lattice. These trapped electrons are typically free radicals or paramagnetic species. • Stable and Unstable Centers: Within the crystal lattice, trapped electrons may occupy both stable and unstable centers. Stable centers retain trapped electrons for long periods, while unstable centers release trapped electrons upon exposure to light or heat. • Accumulation of Trapped Electrons: Over time, additional trapped electrons accumulate in the material's crystal lattice due to ongoing exposure to natural radiation. The number of trapped electrons increases with the duration of exposure and is proportional to the age of the material.
- 32. URANIUM SERIES DATING • Uranium series dating is a radiometric dating method used to determine the age of calcium carbonate materials, such as speleothems (e.g., stalagmites, stalactites), corals, and mollusk shells, by measuring the radioactive decay of uranium isotopes and their daughter products within the mineral matrix. This dating method is particularly useful for dating materials that have formed in water-rich environments, such as caves, oceans, and lakes. Here's how uranium series dating works: • Uranium Decay Series: Uranium series dating relies on the radioactive decay of uranium isotopes (^238U, ^235U, and ^234U) and their subsequent decay products. Uranium-238 (^238U) decays through a series of radioactive decay steps to eventually form stable lead-206 (^206Pb). Similarly, uranium-235 (^235U) and uranium-234 (^234U) also undergo radioactive decay to form lead isotopes (^207Pb and ^230Th, respectively). • In summary, uranium series dating provides valuable chronological information about calcium carbonate materials and their formation history, contributing to our understanding of past environmental and geological processes.