Carbon dating tree buried in layers
They serve as ‘guiding fossils’ for dating (yes, early archaeologists borrowed this term from geology).
At Göbekli Tepe, we can differentiate two layers which are completely different in the type of architecture appearing in them.
Göbekli Tepe was abandoned after the middle PPN B, i.e. That is the time when agriculture finally is fully established; the demise of a hunter-gatherer site would thus fit in this general picture.
There are neither domesticated plants, nor animals at Göbekli Tepe.
During the refilling, objects that obviously had a great importance to PPN people were deposited in the filling [link].
However it seems that refilling was a relatively fast process.
Projectile points from Göbekli Tepe include PPN A types like el-Khiam, Helwan and Aswad points; regarding the PPNB, Byblos and Nemrik points are very frequent, Nevalı Çori points are rare.
A far better source of organic remains for the direct dating of architectural structures is the wall plaster used in the enclosures.
This wall plaster comprises loam, which also contains small amounts of organic material. Tables 1-4) taken from the wall plaster of Enclosure D gives a date of 9984 ± 42 14C-BP (9745-9314 cal BC at the 95.4% confidence level), thus placing the circle in the PPNA.
They clearly show that the site was in use beginning from the PPN A and into the PPN B.
A closer examination of the points reveals, however, that characteristic forms of the latest PPN B are missing.This problem can be avoided by sampling only the oldest calcium carbonate layer in a thin section: the result should be a date near the beginning of soil formation around the stone, i.e. Radiocarbon data are available from both the architecture of Layers III and II.