An Encyclopaedia of Indian Archaeology v1.c10.s3.2

v1.c10.s3.2

Suggestions for corrections to ¹⁴C dates are: (1) C = 1.26R—700 (Stuiver’s formula, 1970); (2) C = 112 + 0·690 R + 0·152 × 10 ³ R²—0·38 × 10⁻⁷ R³ (Wendland and Donley’s formula, 1971); and (3) MASCA factor (Ralph *et al*’s formula, 1973) (where C = corrected age and R = uncorrected radiocarbon age). Even these formulators have changed their own formulae several times. Ralph *et al*.’s formula is quite well-known as it has been very widely circulated in the *MASCA Newsletter*, 11, 1, of the Univ. Pennsylvania. They have given detailed tables where ¹⁴C dates from A.D. 1800 to 4140 B.C. can be converted into MASCA-corrected dates. Already several archaeologists have started using these corrections, perhaps a little too indiscreetly. Before the details of how these corrections affect Indian chronology are gone into, the basic problems involved may be reviewed. If there is a discrepancy between the ¹⁴C dates and dendrochronological dates there can be several alternative reasons for it: (1) variation in cosmic ray flux may have affected the ¹⁴C production; (2) changes in the magnetic field may have affected the ¹⁴C production; (3) the sequoi and bristlecone pine trees grow in California at heights of more than 3000 m and therefore there may have been *in situ* production of ¹⁴C; (4) there may have been radial diffusion of younger plant material into the older rings; and (5) geographical factors may be responsible for such observed variations. These technical controversies apart, a few facts may be pointed out. In New Zealand scientists have worked out a sequence of ¹⁴C dates for Kauri pine which contrasts strongly when compared to the Californian tree curve. ‘But the New Zealand dates recalibrated against the Kauri pine curves seem to make more archaeological sense than calibration with the bristlecone pine. Thus a local factor seems to be at play.’ Diffusion inwards of resin in the tree-rings has been reported by Rafter. Olsson pointed out 100% atomic bomb effect in pre-bomb (1954-50) tree-rings. Besides these uncertainties of radial diffusion of plant material there are significant differences in measurements between Arizona and La Jolla laboratories which range from 6% to 70%. It is to be noted that these measurements were made on the same tree-rings. We thus see that the calibration of the radiocarbon calendar is still beset with many uncertainties and problems, though the workers in the USA seem to be accepting tree-ring data for corrections.