A palynological investigation of the lower

peat in the province of ,

the

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 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 , 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 , now at Bogor the (Java), for identifications of the mosses. 264 J. VAN DONSELAAR AND F. P. JONKER

Harlingen)

(NW BARRADEEL

Fig. 3 THE LOWER PEAT IN THE PROVINCE OF FRIESLAND 265

have shown the the peat originally must same appearance as young In later and much (subatlantic) Sphagnum peat. a warmer period,

according to him the subboreal one, a decay set in which led to the that find in these formation of highly humified peat we now layers

FIRDGUM

Fig. 4

Here found marine sands (lit. 8, 9, 10). we a Sphagnum peat covered by by which already in the atlantic period the supply of air was cut off.

The peat consequently did not decay when the peat bog was over- flown the This that the atlantic by sea. suggests Sphagnum peat too may

originally have had the same appearance as the young Sphagnum peat and that the have taken in later Whether decay may place a period. transformation of Weber this requires a change climate, as assumed, is another undecided question.

Below the “Tjummarumer Miedpolder” (see diagram, fig. 5) we in found no peat, only a 13 cm thick layer of dark cover sand, rich humus. that the Palynological investigation showed layer was of

boreal and with the boreal sand that we found below age, corresponded SE the peat layer of Harlingen (fig. 1). The lowest spectrum of the

diagram, where the sand contained no humus, shows too much secon- dary pollen to be taken into consideration. The sand contained,just

as the sand below the peat layer SE of Harlingen, some microspores of Selaginella selaginoides. At this place the peat was probably swept the which that the latter have away by sea, means must worn out

a deep channel. Below the villages and Wynaldum, in the municipality 266 J. VAN DONSELAAR AND F. P. JONKER

of found either. Below the marine Barradeel, we no peat Wynaldum

sands of the tidal flats, by which the peat is usually covered, rested on the boulder This that all the have clay. means younger layers must been the Below the of swept away by sea. village Tjummarum we boreal found only a very thin layer of peat, which proved to be of

age. This means either that the top layers of the peat have been eroded

TJUMMARUMER MIEDPOLDER.

Fig. 5

that the by the sea or sea already broke in to this area before the

latter were formed.

Our investigations show that in the earlier part of the holocene the caused rise period a rise of sea level must have a of the ground level: reached the the water as soon as the ground water surface, area rich in was covered by plant growth (the dark sand, humus), and peat The formation begun. growth of the peat was made possible by a continuous rise of the ground water level but came to an end when the and the covered the the expanding sea reached area bog was by sands of the tidal flats. In the W part of the country the lower peat in developed a fresh water laguna and the environment therefore was eutrophous to mesotrophous. In our area the circumstances changed during the formation of the peat layers from eutrophous to more or less oligotrophous. The top layers of the lower peat from Firdgum THE LOWER PEAT IN THE PROVINCE OF FRIESLAND 267

even represent an oligotrophous raised bog, consisting chiefly of Sphagnum rubellum.

Peat been in layers of more recent date have not met with our unable borings. We are as yet to give an explanation of the highly varying depths at which the lower peat was met with; in places that were horizontally only a few kilometers apart, the depth at which the several peat was found, differs meters.

REFERENCES

1. holocene ANDEL,Tj.vAN,Pollenanalytische datering van een transgressie in in XI Noord-West Friesland; Geologic en Mijnbouw (1949), p. 171—173. Dr C. 2. Florschutz, F., Bespreking van het proefschrift van G. Vermeer-

Louman: Pollenanalytisch onderzoek van den West-Nederlandschen bodem; in Kon. Aardr. Genootsch. Tijdschr. (Nov. 1934), p. 1—8. 3. “veen Florschutz, F., Laagterras en op grootere diepte” onder Velzen; in Ned. Aardr. Genootsch. LXI Tijdschr. (1944), p. 25—33. 4. Duizend den FlorschOtz, F. en I. M. v. d. Vlerk, eeuwen geschiedenis van in De Maastunnel II bodem van Rotterdam; (1939), p. 1—6.

5. Godwin, H., Coastal peat beds of the British Isles and North Sea region; in XXXI Journ. of Ecology (1943), p. 199—247. 6. Coastal beds of Godwin, H., peat the North sea regions as indices of land- in The New and sea-level changes; Phytologist XLIV (1945), p. 29—69. 7. Vermeer-Louman, C. G., Pollenanalytisch onderzoek van den West-Neder- landschen Bodem; Thesis Amsterdam 1934. 8. Weber, C. A., Grenzhorizont und Klimaschwankungen; in Handel. 20e Nat. 260—261. Ned. Gen. Congr. (1925), p. 9. Weber, C. A., Grenzhorizont und Klimaschwankungen; in Abh. Nat.

wissensch. Bremen Ver. XXVI (1926), p. 98—106. 10. Weber, C. A., Grenzhorizont und altere Sphagnumtorf; in Abh. Nat. wiss.

Ver. XXVIII 57—65. Bremen (1930), p.