Meetings of the Royal Botanical Society of the Netherlands

According to some authors the sequence of transgressions and regressions in the Dutch coastal area (Calais and Dunkerque transgressions and Holland peat, respectively) and in South Sweden can be related to climatic oscillations. Fluctuations in the humidity of the ombrogenous peat-producing environment have generally been attributed to fluctuations in precipitation and/or temperature in Atlantic, Subboreal and Subatlantic periods. The question posed here is whether or not the climate is the direct determining agent in both the sedimentary rhythmics and the ombrogenous peat growth. Peat studies by B. van Geel in the Wietmarscher Moor and the Engbertsdijksveen have resulted in a detailed picture of local peat successions. In the period between c. 1600 and 500 B.C. (Subboreal/Subatlantic transition) the climatic deterioration, recognized throughout NW Europe, does not appear to be a single transition. There is a series of cyclic fluctuations in the effective precipitation with a tendency towards a quantitative increase, eventually resulting in the growth of “Younger Sphagnum peat" in the raised bogs. In the period between 2000 and 1200 B.C., relatively dry phases of ombrogenous peat growth seem to be synchronous with regression phases distinguished in the coastal area. There are hardly any recognizable parallel developments in the ombrogenous peat growth and in the transgressions and regressions from 1200 to 500 B.C.