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Summary

A number of stratigraphical sections and four pollen diagrams have been constructed in an attempt to trace the history and development of the area.

Together, the pollen diagrams cover a period starting in zone I of the Late-glacial period and ending in zone VIII. The diagrams are generally of a western type but correspond more closely with the Somerset diagrams than with the Cardiganshire or Shropshire type.

Correlation between the stratigraphy and the pollen analysis show that the Common and its immediate surroundings began its development towards the end of the last glaci-ation when the irregular dumping of drift material led to the impounding of a long, shallow lake. By progressive deposition of material, at first mineral but later organic, the lake basin gradually became filled and the vegetation which covered it passed through the stages of a typical hydrosere to Spagnum bog and Callunetum. At about the time of the Boreal-Alantic transition the course of the succession, which had until then included Phragmites-Cladmm fen, became altered and the fen and reedswamp stages are now represented by an impoverished swamp dominated by species of Juncus and Carex.

The birchwood-with-Phragmites has developed from a lagg vegetation while the birchwood-with-Cflmv and the southern birchwood have been formed by the colonization of the bog communities, the former at a comparatively recent date.

The most recent of those deposits which have been investigated are the downwash clays which are correlated in the pollen diagram with zone VIII and were apparently produced as a result of forest clearance and increasing wetness of climate.