J.P. Pals

A late holocene deposit under the Westfriese Zeedijk near Enkhuizen (Prov. of Noord-Holland, The Netherlands): Palaeoecological and archaeological aspects

A Late Holocene lake and peat deposit preserved under the sea dike near Enkhuizen was examined by means of an analysis of both microfossils and macroscopic remains of plants and animals. The hypothesis that the abandonment of Bronze Age settlements in eastern West-Friesland was caused by a rise of the water table was confirmed. This hydrological change was most probably concomitant with the shift towards a more oceanic climate at the Subboreal/Subatlantic transition. The local succession, from the time that the rising of the water table led to a shallow fresh-water pool (viz., ca. 2850 B.P.) until the formation of Sphagnum peat (at ca. 1900 B.P.), could be reconstructed in detail. The gyttja deposited in the initial phase of the section was formed in stagnant, shallow, eutrophic and alkaline water, as is indicated by the presence of some representatives of the Zygnemataceae, Cyanophyceae and Diatomeae. The invertebrates also point to shallow water with a dense stand of vegetation and eutrophic conditions, judging by the presence of Eurycercus lamellatus, Simocephalus sp. and Moina sp. (Cladocera). During the phase in which the open water was gradually filled in by vegetable litter, especially Carex riparia, Lycopus europaeus and Equisetum fluviatile played a prominent part. Subsequently the mesotraphentous Menyanthes trifoliata could settle. The peat deposition continued until the surface had been raised high enough in relation to the water table to permit the establishment of Salix, Thelypteris and Lychnis flos-cuculi. From the subsequent birch carr the succession proceeded to a Sphagnum bog in which Ericaceae played a part. Late Medieval habitation on the oligotrophic bog, which probably began in the eleventh or twelfth century A.D., is reflected, among other things, by the presence of pollen of Secale cereale and Centaurea cyanus and of seeds of Plantago major and some other weeds. The drainage required for habitation and agriculture will have caused subsidence and oxidation of the peat in West-Friesland. In combination with the continuing rise of the sea level during the Late Holocene, this resulted in an increased influence of the sea (in the section this is shown by the occurrence of Salicornia europaea, Puccinellia distans, Triglochin maritima and Foraminifera). A dike was built to protect the cultivated area. In addition to pollen and seeds, more than 100 taxa of other micro- and macrofossils were identified, of which 39 hitherto unrecognized or incompletely known “Types”, predominantly from the gyttja, are described and figured. Among the fossils described are fungal and algal spores, spores of Riccia cf, sorocarpa (Hepaticae), invertebrates, and some Types of unknown origin.

Paleoecological studies in the Klokkeweel bog near hoogkarspel (prov. of Noord-Holland)

The course of filling-in and subsequent bog development of a brackish eutrophic lake is analyzed by means of investigations of pollen, spores, algae, fungal remains, diatoms and plant macrofossils. Some unknown and/or not generally known micro- and macro-fossils are described and illustrated. 14C datings and ignition residue determinations have been made. The analysis was expected to provide information about both regional and local vegetational developments, but the picture presented by the micro- and macrofossils is mainly local. In the lake sediment, deposited on a subsoil of marine clay, and the overlying peat the following phases in the vegetational succession have been defined: (a) initial phase with small elodeids, dominated by Myriophyllum spicatum; (b) littoral phase, characterized by vegetation types of Callitricho-Batrachion; (c) floating mat phase: Cicuto-Caricetum pseudocyperi, followed by a Caricetum paniculatae; (d) willow scrub with undergrowth of Dryopteris; and (e) birch carr. Salinity, alkalinity and trophic degree decrease with the advancing succession. The vegetation shows traces of human influence, but apparently the local succession is not strongly affected. The phase with birch carr shows two periods of wetter conditions, dated ca. 750 B.C. and ca. 600 B.C., respectively. The final period may explain the widespread abandonment of prehistoric settlements in West Friesland. The pollen diagram shows a mysterious maximum of Pinus from ca. 750 to ca. 650 B.C.

An Upper Eemian lake deposit from Twente, eastern Netherlands

Abstract Study of micro- and macrofossils from a c. 80 cm thick organic deposit at Kamphuis (Twente, eastern Netherlands) provided information about vegetational succession in a lake and the surrounding marsh and forest. The deposit lies at the base of more than 20 m of predominantly sandy Weichselian sediments. The pollen diagram indicates an Upper Eemian (last Interglacial) age: zones E4b, E5 and E6a. The most abundant dry forest pollen types of zone E4b are Corylus, Taxus and Quercus. Zone E5 is mainly characterized by a rise of the pollen curves of Carpinus and Picea and zone E6 shows a pronounced maximum of Picea. The recorded changes in forest composition may have been related to soil development, but there are no palaeoecological indications of an acidification concomitant with the final dominance of Picea. The presence of Ilex and Hedera pollen in zone E6a possibly indicates that this Picea dominance was not related to a decline in mean temperature. The expansion of the midly parasitic fungus Ustulina deusta is apparently related to increasingly unfavourable conditions for the growth of deciduous forest elements. Macrofossils of local aquatic plants, marsh plants and invertebrates indicate a stagnant, eutrophic and base-rich aquatic environment. Some unknown and not generally known micro- and macrofossils are described and illustrated.

Weed and insect infestation of a grain cargo in a ship at the Roman fort of Laurium in Woerden (Province of Zuid-Holland)

Abstract Macroscopic plant remains, insect remains and pollen from a layer of waterlogged cereal grains in a Roman ship dated to the end of the 2nd century were analyzed. The deposit consisted of threshed emmer wheat (Triticum dicoccum). Weed and insect infestation allowed conclusions concerning origin, quality and storage conditions of the grain to be drawn.

Palaeoecological study of a Weichselian wetland site in the Netherlands suggests a link with Dansgaard-Oeschger climate oscillation

Botanical microfossils, macroremains and oribatid mites of a Weichselian interstadial deposit in the central Netherlands point to a temporary, sub-arctic wetland in a treeless landscape. Radiocarbon dates and OSL dates show an age between ca. 54.6 and 46.6 ka cal BP. The vegetation succession, starting as a peat-forming wetland that developed into a lake, might well be linked with a Dansgaard-Oeschger climatic cycle. We suggest that during the rapid warming at the start of a D-O cycle, relatively low areas in the landscape became wetlands where peat was formed. During the more gradual temperature decline that followed, evaporation diminished; the wetlands became inundated and lake sediments were formed. During subsequent sub-arctic conditions the interstadial deposits were covered with wind-blown sand. Apart from changes in effective precipitation also the climate-related presence and absence of permafrost conditions may have played a role in the formation of the observed sedimentological sequence from sand to peat, through lacustrine sediment, with coversand on top. The Wageningen sequence may correspond with D-O event 12, 13 or 14. Some hitherto not recorded microfossils were described and illustrated.