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Home/Anthropology/Mains PYQ/2021/Paper I/Prehistoric Archaeology
UPSC MainsAnthropology Optional Paper I 2021 10 Marks Model Answer Available

Thermoluminescence (TL) Dating — 2021 Paper I

Question · 2021 · Paper I · 10 Marks

Thermoluminescence (TL) dating

Model Answer

VAID ICS

Approach

  • Demand of Question: Explain the principle, working and archaeological significance of Thermoluminescence dating.
  • Structuring the Response: Define TL, explain the trapped-electron mechanism and age calculation, followed by applications and limitations.
  • Key Dimensions to Cover: Quartz/feldspar, natural radiation, heating/resetting, accumulated dose, annual dose, pottery and burnt materials.

Model Answer

Introduction

Thermoluminescence (TL) dating is an absolute/dosimetric dating technique used mainly for materials that were heated in the past. It measures the light released from radiation-induced trapped electrons in minerals such as quartz and feldspar when the sample is reheated.

Principle of TL Dating

Crystalline minerals contain imperfections or electron traps. Natural ionising radiation from uranium, thorium, potassium and cosmic/environmental sources gradually displaces electrons, some of which become trapped in the crystal lattice.

When an object such as pottery is strongly heated during manufacture, previously accumulated trapped electrons are released, effectively resetting the TL clock. After cooling and burial, electrons again accumulate in proportion to the radiation received over time.

Heating/zeroing → Burial → Natural radiation → Electron trapping → Laboratory reheating → Light emission → Age

Working

In the laboratory, a sample is gradually reheated. The trapped electrons acquire sufficient energy to escape and recombine, releasing energy as thermoluminescent light.

The intensity of this luminescence is used to estimate the accumulated or equivalent radiation dose since the last heating.

Age = Accumulated radiation dose / Annual radiation dose

Thus, TL determines essentially the time elapsed since the material was last sufficiently heated.

Development and Applications

A major archaeological demonstration was provided by M.J. Aitken, M.S. Tite and J. Reid in “Thermoluminescent Dating of Ancient Ceramics” (1964), where pottery samples extending back several thousand years were successfully investigated.

TL is particularly useful for:

  • Pottery and ceramics
  • Terracotta and bricks
  • Burnt clay
  • Heated stones and flint
  • Some other naturally or culturally heated mineral materials

It is especially valuable where radiocarbon dating cannot be directly applied, because TL can date heated inorganic material itself.

Limitations

  • The material must have been sufficiently heated/reset initially.
  • Accurate estimation of the annual environmental radiation dose is essential.
  • Changes in burial environment can affect dose-rate calculations.
  • Some minerals, particularly feldspars, may suffer anomalous fading, causing loss of stored signal and underestimation of age.
  • Sampling and laboratory preparation may be partly destructive.

Conclusion

TL dating provides archaeology and palaeoanthropology with an important chronological tool by converting stored radiation energy into elapsed time. Its particular strength lies in directly dating heated inorganic remains, especially pottery, thereby complementing radiocarbon and other absolute dating techniques.

2026 Discuss with examples, how general comparative analogy has been used in ethnoarchaeological studies in India. 2026 Make a critical appraisal of the mesolithic culture of Ganga basin with reference to artifacts, faunal and human skeletal remains excavated from different sites. 2026 Ethnoarchaeology and classical archaeology. 2026 Give the distribution of Palaeolithic sites around the Himalayan and Sub-Himalayan areas, highlighting the typo-technologies of the tools.

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UPSC Anthropology Optional 2021 — Paper I

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