Een-Schipsloot - The geological-palynological investigation of a Tjonger site
In the very narrow watershed region of the valley systems of the Tjonger and Peizerdiep, that originated during the Pleniglacial, remains have been found of the Tjonger tradition. The site lies at a relatively high point of the somewhat undulating Allerød horizon, developed as a soil over the Younger Cover sand I. At the lower spots of this horizon a thin, sandy peat layer formed in the Betula phase of the Allerød.
At the beginning of the Late Dryas a permafrost was formed here; possibly in connection with this, round basins originated in the frozen soil, with a diameter of 1-3 m and a depth of 0.15 -1.00 m. The upward movement of ground-water under pressure probably played a role in this. In the basins open water was present; in the largest basin (basin I) peat formation took place. This is dated to 10,495 ± 60 B.P. (GrN-6341).
Precisely how the basins originated cannot be satisfactorily explained; it is possible that hearths of the Tjonger people weakened the permafrost to such an extent that the process of upward movement of ground-water was set in motion as a result. At the bottom of the basin filling a coarse sandy layer is present, like a crust, that continues against the wall of the basin practically as far as its periphery. The boundary between the wall of the basin and the crust-like sand layer is very sharply defined. Ultimately the basins dried up, after which they became filled up with Younger Cover sand II. This occurred still during the Late Dryas, possibly in connection with the disappearance of the permafrost.