Revision summary
TL measures light from trapped electrons when a mineral is heated. The clock starts at the last firing or sunlight bleach. Pottery, hearths, and burnt flint are the main archaeological samples. The age is equivalent dose divided by annual dose rate. Water, fading, and incomplete zeroing are the chief errors.
Model answer
Introduction
Thermoluminescence dating ages fired clay, burnt flint, and some sediments by measuring trapped electrons released as light when the sample is heated.
Body
Principle
- Ionising radiation from uranium, thorium, and potassium fills traps in the crystal. Heat or strong light empties them. The last firing or bleaching is the clock’s zero.
- In the laboratory the sample is heated, light is counted, and the equivalent dose is divided by the annual dose rate.
- Range is roughly a few hundred years to several hundred thousand years, useful where carbon is scarce.
Use in anthropology
- Pottery, hearths, and burnt flint at palaeolithic and Neolithic sites, including Near Eastern early farming contexts such as Jericho sequences when ceramics appear, can be dated.
- Indian applications include pottery and burnt clay at Harappan and later sites, and burnt flint in some palaeolithic debates.
- Limits: anomalous fading, incomplete zeroing, and water-content error. TL is a clock, not a culture name.
Flow diagram
flowchart TD RAD[Natural radiation] --> TR[Electron traps] HEAT[Firing or lab heat] --> L[Luminescence] L --> AGE[Equivalent dose / dose rate]
Conclusion
TL dates the last heating or bleaching of mineral grains. It is a workhorse for ceramics and burnt stone when the zero event is well understood.
Quick related
Students also ask
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Can TL date an unfired stone tool?
Only if the grain was bleached or heated. An unreset core gives a geological, not a knapping, age.
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Is TL more accurate than radiocarbon?
Not in the 14C window for good charcoal. It is the method of choice when organics are gone and minerals were fired.
PYQ trend
When UPSC asked this
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2025 · Q5(c) · Anthropology GS 1 · 10 marks
Fission track dating method and its applications. -
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Q5(c) · UPSC Mains 2025 · Anthropology GS 1 · 10 marks
Fission track dating method and its applications.
Principles of Prehistoric Archaeology. Chronology
Fission-track dating counts damage trails from uranium-238 fission in minerals or glass. Price, Walker and Fleischer developed the method. Zircon, apatite and volcanic glass are the usual materials. Applications include dating tephra at hominin sites, heated stone, and Himalayan or Siwalik thermal history. Heat can anneal tracks and reset the clock, so dates need stratigraphic and other radiometric checks. Different minerals do not share one single year-range.
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Principles of Prehistoric Archaeology. Chronology
Chronometric dating gives an age in years; relative dating only orders remains. Radiocarbon dates organic material to about 50,000 years and requires calibration. K–Ar/Ar–Ar dates volcanic layers associated with early hominins. TL dates last heating; OSL dates last light exposure. U-series and ESR extend the cave and tooth record. Every date belongs to a sample and event and must fit association and stratigraphy.
Q5(b) · UPSC Mains 2023 · Anthropology GS 1 · 10 marks
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Principles of Prehistoric Archaeology. Chronology
Rakhigarhi is a very large Harappan site in Haryana on the Ghaggar–Drishadvati belt. ASI and Deccan College excavations exposed town and cemetery. Craft and agriculture match the Indus urban economy. 2019 aDNA lacked a Steppe signal in the reported Mature Harappan genome. The site joins settlement archaeology to biological prehistory.
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