A palynological investigation of the lower peat in the province of Friesland, the Netherlands BY J. van Donselaar and F.P. Jonker (Utrecht) Received March 14th, 1952 till the lower of Up now deposits peat (in Dutch: veen-op-grotere- diepte = peat at greater depth) have been investigated in the Netherlands in the Western mainly part of the country, viz. in the provinces of Noord-Holland, Zuid-Holland and Zeeland. The analyses have shown that the development of this, now comparatively well known peat layer must have begun either in the second half of the boreal or else in the of the atlantic and that it period beginning one, of the must have come to an end in the first half latter. Among the earlier the investigators botanist Mrs Vermeer-Louman and some geologists had arrived at the conclusion that the sudden transgression of the North which made end the of sea an to formation peat, took in the boreal and that the place period, whole lower deposit of peat, of boreal This therefore, was age (lit. 7). opinion, however, was sufficiently disproved by Florschutz, and all subsequent analyses confirmed the have view that the peat formation must have stopped in the atlantic The conclusion early period (lit. 2, 3, 4). same was arrived at by Godwin as a result of his investigations of the lower peat found in SE England (lit. 5, 6) and by several German investi- result of their the lower in NW gators as a analyses of peat, found Germany. Only one analyses of the lower peat in the province of Friesland, in the Northern of the part Netherlands, has sofar been published. The Andel found 3.50 geologist van near Kiesterzijl, at a depth of only m He identified a thin layer of peat. it with the lower peat from the W of the part Netherlands which occurs several meters deeper. His show boreal two diagrams a age for the basal layers and an atlantic age for the top ones and they confirm therefore the conclusions,ob- W the tained in the part of country (lit. 1). month of During the June, 1950, a number of deep borings have been carried out on the territory of the large municipality of Barradeel in the province of Friesland. These borings have been made possible the Frisian the assistance by a grant from Academy at Leeuwarden, by of the department for the maintenance of dikes, roads, bridges and canals in the Province of Friesland and by that of the board of the 260 J. VAN DONSELAAR AND F. P. JONKER We wish here too'our Wieringermeer. to express deep-felt gratitude for their help. Some time before these borings were carried out, the second author visited a deep pit, excavated for the construction of a new sluice outside the of the near Harlingen, just territory municipality of Barradeel. Even at the bottom of this 10 meter deep pit the lower reached but there peat was not yet were a few lumps of peat, that had come to light when a number of poles had to be driven in. These lumps have been analysed by Mr K. B. A. Bodlaender. One of them showed boreal the other atlantic part spectra, part ones, which that there with means was a complete agreement the results, obtained by van Andel in Friesland, and by other investigators in Western Holland. The only discrepancy with the description given Andel is found in the difference in of the by van great depth This difference is the remarkable analysed layers. more as the localities the are situated only a few kilometers apart from each other and as surface flat. Our 1 of is quite fig. shows a pollen diagram a sample lower collected in the Barradeel that is situated SE of peat part of of Harlingen. The layer occurs at a depth of 4.30—4.80, is overlain and sand in by marine sand rests on a layer of cover that is rich humus. As the sand below the late-boreal cover peat shows typical spectra, the the in development of peat must have begun the neighbourhood of the transition between Boreal and Atlanticum. A remarkable feature are the high tops in the Corylus line, a boreal top of 283 % and the A a top at boreal-atlantic transition of even 1170 %. large the that time with part of area was apparently during covered Corylus bush, which must have ousted all the other trees and shrubs. As in contradistinction Betula and other Corylus to species was not included in the pollen sum of 150 tree pollen grains used for the construction of the caused rise the diagram, this abundance of Corylus pollen a of pollen percentage of Pinus and of some other trees. A second diagram after had been of the same layer (fig. 2) constructed Corylus included in the much better of the pollen sum, gives a impression pollen production of the forests by which the area must have been surrounded. it is still usual exclude from the this Though to Corylus pollen sum, shows that it is better included. This is the more desirable as Corylus all is not at confined to the shrub layer of the forests. However, a difference between the two diagrams becomes important only when the of is percentage Corylus pollen very high. the otherbotanical remains the With regard to we can give following particulars: the dark cover sand contained fragments of Phragmites and of The the rich in sand Cyperaceae. basal part of peat was drift and it contained fruits of Potamogeton, Carex and Betula, wood of Betula and remains and of The 10 of stems roots Cyperaceae. next cm (4.70 —4.60) still contained fruits of Potamogeton and Carex but in addition to these the remains of Eriophorum tufts and much Alnus wood. 4.40 the formed mixed with Carex Up to peat was by Eriophorum rests and with few leaves of In the of the a Sphaguum. upper part peat the quantity of Sphagnum remains increased considerably, but Erio- THE LOWER PEAT IN THE PROVINCE OF FRIESLAND 261 Harlingen) (SE BARRADEEL Fig. 1 262 DONSELAAR J. VAN AND F. P. JONKER BARRADEEL (SE Harlingen) Fig. 2 THE LOWER PEAT IN THE PROVINCE OF FRIESLAND 263 phorum remained an important component; seeds of Juncus were found and in the 10 the contained of fruits upper cm peat large quantities and seeds of Triglochin palustre. This shows that during the formation ofthe the environment peat changed from eutrophous to mesotrophous less the and that it became finally more or oligotrophous. During earlier part of the peat formation drift sand was swept into the bog, which shows that the sands even in Atlanticum the were not yet fixed by the vegetation. Barradeel that N Another profile we bored in the part of lies of The Harlingen (see diagram, fig. 3). peat here occurs at a depth of 590 The formation of the —525. peat begun in the latter part of the boreal period and here too the boreal-atlantic transition is marked by a slight indication of a Corylus top. The layer of sand rich in humus which the on peat rests, is here much thinner. The peat was formed in of this basal which a Carex-Sphagnum bog; on top peat layer contained found thick a good deal of fine sand, we a layer of Eriophorum peat, the mixed with of in upper part Sphagnum, which indicates a change the environment from the mesotrophous to a more or less oligotrophous condition. In the in middle of the peat layer we found immediate succession indications of two transgressions, each transgression sand dark characterized by the succession pale clay a clay that is rich in humus pale clay sand. These bands are of marine origin, for we found besides fruits of Potamogeton remains of Ostracoda and Foraminifera, spicula of Spongiae and shells of the molluscs Mytilus edulis, Retusa alba, and Macoma baltica. These two transgressions had The no influence on the percentages of tree pollen. percentage of Sphagnum spores, however, decreased considerably. The percentage of derived from increased from The spores Bryales 0 % to 60 %. possi- bility that the marine layers have been shoved in during a much later which the of from transgression by upper part the peat was separated the lower be the part, can not fully excluded. However, typical succession of thin sand and clay layers and the decrease in the number of make it that the Sphagnum spores probable transgression layers This in are autochthonous. means that a temporary breaking of the took sea place, and that at the end of that period peat formation was resumed. hamlet Fig. 4 shows the pollen diagram of the lower peat near the in the the of Firdgum, where peat formation began vicinity of transi- tion between Boreal and Atlanticum, recognizable i.a. once more by a of Corylus top. The layer is 26 cm thick and consists in the basal part forest formed in alder brook. The 6 cm is peat, an upper pure Sphag- mixed num peat consisting of excellently preserved Sphagnum rubellum * U / X i o # with Webera nutans and Aulacomnium palustre h This is the more remark- able as the atlantic Sphagnum peat (old moss peat) of our raised bogs is humified and shows remains always highly hardly any recognizable of Sphagnum plants. Carl Albert Weber, one of the founders of modern peat investigation, was of opinion that the atlantic Sphagnum 1 We are much indebted to Dr W. Mever from Amsterdam, now at Bogor the (Java), for identifications of the mosses.