Bulk stable light isotopic ratios in archaeological birch bark tars

The authors report a preliminary study of the light stable isotopic (δD, δ13C and δ18O) values for bulk archaeological birch bark tars, over a geographical (e.g. Greece to Norway) and chronological (9500–3000 BP) range. For δ13C an increase in fractionation with increase in latitude is observed in samples from Greece which are less depleted than those from northern Europe. There is no clear difference between the samples from northern Europe. There is no apparent trend in δ13C value with the 14C age of the sample. Due to biosynthetic fractionation all the samples are significantly depleted in 2H and enriched in 18O relative to the global meteoric water line. This study indicates that archaeological birch bark tar from Greece can be distinguished from those of northern Europe; this separation is probably based on the extreme geographical range of the samples examined here. But this does provide evidence that the birch bark tars were probably made locally rather than traded.