She observed a fundamental distinction in the ground plans of buildings – round constructions in the earlier PPN A, rectangular buildings in the later PPN B.
She further based her subdivision on differences in the material culture.
The general chronological division for the Early Neolithic was developed in the Southern Levant, by Kathleen Kenyon on the basis of the stratigraphy of Jericho.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.Although the observed archaeological stratigraphy is confirmed by the relative sequence of the data, absolute ages are clearly too young, with Layer III being pushed into the 9th millennium, and Layer II producing ages from the 8th or even 7th millennia cal BC.Radiocarbon data support the general archaeological dating (see below).So far so good, but there is a problem with this story.
A far better source of organic remains for the direct dating of architectural structures is the wall plaster used in the enclosures.