An Encyclopaedia of Indian Archaeology v1.c10.s6: 5.6 Thermoluminescent
An Encyclopaedia of Indian Archaeology v1.c10.s6
- Language
- English
5.6 Thermoluminescent
v1.c10.s6.1
Potsherds, bricks, fired earth, etc., gradually accumulate thermoluminescence (TL) due to internal and external irradiations. Internal irradiations are caused by impurities like uranium, thorium and potassium, and external ones are due to radioactive substances in the surrounding medium and from the cosmic rays. Once the sample is heated, say in the kiln, the accumulated TL then starts and will depend upon the amount of radioactive impurities present and the length of time since the sample was last fired. Through controlled heating the TL accumulated during the archaeological time (i.e. since a pot was fired) can be released and measured by a suitable photomultiplier detection system. A measurement of the radioactive impurity content enables one to calculate the rate of TL accumulation (TL/years). The total accumulated TL and TL/years then enable one to find out the archaeological age. So far only two laboratories have reported TL measurements on Indian archaeological material (table below)—the Research Laboratory for Archaeology at Oxford and the Health Physics Division of the Bhabha Atomic Research Centre, Bombay. Now the Physical Research Laboratory, Ahmedabad, is trying to install a TL-dating system of the same dimensions as its ¹⁴C project [5.3].
v1.c10.s6.2
Samples of the OCW [4. 12] from ATRANJIKHERA, LAL QILA, JHINJHANA and NASIRPUR, all in Uttar Pradesh, were assayed at Oxford by Aitken's group. Since all the pottery samples were from the OCW culture one expected the TL dates to give a time-spread of 200 to 300 years. Instead, the dates show a wide scatter of *c.* 1180-2650 B.C. At the moment the dates only indicate that the OCW culture is pre-1100 B.C. and thus a pre-Iron Age culture. The BARC group TL-dated a variety of samples ranging from the medieval to the pre-Harappa [4.8] times. The table shows that the few samples that have been TL-dated only indicate the dating potentiality of this method. There is not much of archaeological value that can be learnt from the dates so far available.
v1.c10.s6.3
Unlike the ¹⁴C method, which depends only upon carbonaceous material and is therefore difficult to come by in excavations, the TL technique can be applied to all sorts of baked earth material, which is always plentiful.
v1.c10.s6.4
Cairns, T., 1976, in *Analytical Chemistry*, 48, p. 266. Lal, B.B., 1972, in *Antiquity*, 46, p. 282 (for TL dates of OCW). Sasidharan, R., Nambi, K.V.S., & Parthasarthy, R., 1975, in Sunta, C.M., *et al*, ed, *Thermoluminescence & its Applications*, Kalpakkam. Sasidharan, R., Sunta, C.M., & Nambi, K.S.V., 1978, in Zimmerman, D.W., ed, *Ancient TL.*, 2, winter, 1978. Seeley, Mary-Ann, 1975, in *Jour of Arch. Science*, 2, p. 17. Tite, M.S., 1972, *Methods of Physical Examination*, London.—D.P. AGRAWAL
v1.c10.s6.5
THERMOLUMINESCENCE DATES
v1.c10.s6.6
| *Sample* | *Laboratory* | *Site* | *Material* | *TL age* B.C./B.P. | *Reference* |
| 111-C1 | RLA | ATRANJIKHERA | OCW [4.12] | 2280 B.C. | Lal, 1972 |
| 111-C2 | ” | ” | ” | 1250 B.C. | ” |
| 112-A1 | ” | LAL QILA | ” | 1730 B.C. | ” |
| 112-A2 | ” | ” | ” | 2030 B.C. | ” |
| 113-B1 | ” | JHINJHANA | ” | 1570 B.C. | ” |
| 113-B2 | ” | ” | ” | 2650 B.C. | ” |
| 114-A1 | ” | NASIRPUR | ” | 1500 B.C. | ” |
| 114-A2 | ” | ” | ” | 1180 B.C. | ” |
| P 1 | BARC | KALIBANGAN | Harappa [4.9] | 3000 B.P. | Sasidharan, *et al.*, 1975 |
| P 2 | ” | RAJGIR | NBPW [4.18.1] | 5000 B.P. | ” |
| P 3 | ” | HASTINĀPURA | PGW [4.15] | 1900 B.P. | ” |
| P 4 | ” | AHICCHATRĀ | ” | 2930 B.P. | ” |
| P 5 | ” | GILUND | ” | 2300 B.P. | ” |
| P 7 | ” | SANUR | Megalithic [4.17.9] | 1280 B.P. | ” |
| P 8 | ” | HASTINĀPURA | Medieval glazed ware | 10060 B.P. | ” |
| P 9 | ” | PURANA QILA | ” | 2320 B.P. | ” |
| P 10 | ” | KALIBANGAN | Pre-Harappa [4.8] | 4390 B.P. | ” |